Updated on 2021/11/09

写真a

 
SAKAMOTO Tatsuya
 
Organization
Natural Science and Technology Professor
Position
Professor
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Degree

  • Ph.D. ( The University of Tokyo )

Research Interests

  • Molecular Physiology of Adaptation

  • Comparative Endocrinology

  • Marine Biology

  • 適応生理学

  • 比較内分泌学

  • 海洋生物学

Research Areas

  • Life Science / Animal physiological chemistry, physiology and behavioral biology

  • Life Science / Aquatic bioproduction science

  • Life Science / Morphology and anatomical structure

Education

  • The University of Tokyo   理学系研究科   動物学

    - 1992

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    Country: Japan

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  • The University of Tokyo    

    - 1992

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  • The University of Tokyo   Faculty of Science  

    - 1987

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    Country: Japan

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  • The University of Tokyo    

    - 1987

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Research History

  • - 岡山大学自然科学研究科 教授

    2004

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  • - Professor,Graduate School of Natural Science and Technology,Okayama University

    2004

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Professional Memberships

  • 国際比較内分泌学会連合(International Federation of Comparative Endocrinological Societies)

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  • 日本比較内分泌学会

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  • 日本生理学会

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  • 日本動物学会

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Papers

  • The gastrin-releasing peptide/bombesin system revisited by a reverse-evolutionary study considering Xenopus International journal

    Asuka Hirooka, Mayuko Hamada, Daiki Fujiyama, Keiko Takanami, Yasuhisa Kobayashi, Takumi Oti, Yukitoshi Katayama, Tatsuya Sakamoto, Hirotaka Sakamoto

    Scientific Reports   11 ( 1 )   13315 - 13315   2021.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    <title>Abstract</title>Bombesin is a putative antibacterial peptide isolated from the skin of the frog, <italic>Bombina bombina</italic>. Two related (bombesin-like) peptides, gastrin-releasing peptide (GRP) and neuromedin B (NMB) have been found in mammals. The history of GRP/bombesin discovery has caused little attention to be paid to the evolutionary relationship of GRP/bombesin and their receptors in vertebrates. We have classified the peptides and their receptors from the phylogenetic viewpoint using a newly established genetic database and bioinformatics. Here we show, by using a clawed frog (<italic>Xenopus tropicalis</italic>), that GRP is not a mammalian counterpart of bombesin and also that, whereas the GRP system is widely conserved among vertebrates, the NMB/bombesin system has diversified in certain lineages, in particular in frog species. To understand the derivation of GRP system in the ancestor of mammals, we have focused on the GRP system in <italic>Xenopus</italic>. Gene expression analyses combined with immunohistochemistry and Western blotting experiments demonstrated that GRP peptides and their receptors are distributed in the brain and stomach of <italic>Xenopus</italic>. We conclude that GRP peptides and their receptors have evolved from ancestral (GRP-like peptide) homologues to play multiple roles in both the gut and the brain as one of the <italic>‘gut-brain peptide’</italic> systems.

    DOI: 10.1038/s41598-021-92528-x

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    Other Link: http://www.nature.com/articles/s41598-021-92528-x

  • Sexual Experience Induces the Expression of Gastrin-Releasing Peptide and Oxytocin Receptors in the Spinal Ejaculation Generator in Rats. International journal

    Takumi Oti, Ryota Ueda, Ryoko Kumagai, Junta Nagafuchi, Takashi Ito, Tatsuya Sakamoto, Yasuhiko Kondo, Hirotaka Sakamoto

    International journal of molecular sciences   22 ( 19 )   2021.9

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    Language:English   Publishing type:Research paper (scientific journal)  

    Male sexual function in mammals is controlled by the brain neural circuits and the spinal cord centers located in the lamina X of the lumbar spinal cord (L3-L4). Recently, we reported that hypothalamic oxytocin neurons project to the lumbar spinal cord to activate the neurons located in the dorsal lamina X of the lumbar spinal cord (dXL) via oxytocin receptors, thereby facilitating male sexual activity. Sexual experiences can influence male sexual activity in rats. However, how this experience affects the brain-spinal cord neural circuits underlying male sexual activity remains unknown. Focusing on dXL neurons that are innervated by hypothalamic oxytocinergic neurons controlling male sexual function, we examined whether sexual experience affects such neural circuits. We found that >50% of dXL neurons were activated in the first ejaculation group and ~30% in the control and intromission groups in sexually naïve males. In contrast, in sexually experienced males, ~50% of dXL neurons were activated in both the intromission and ejaculation groups, compared to ~30% in the control group. Furthermore, sexual experience induced expressions of gastrin-releasing peptide and oxytocin receptors in the lumbar spinal cord. This is the first demonstration of the effects of sexual experience on molecular expressions in the neural circuits controlling male sexual activity in the spinal cord.

    DOI: 10.3390/ijms221910362

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  • Immunoelectron Microscopic Characterization of Vasopressin-Producing Neurons in the Hypothalamo-Pituitary Axis of Non-Human Primates by Use of Formaldehyde-Fixed Tissues Stored at -25 °C for Several Years. International journal

    Akito Otubo, Sho Maejima, Takumi Oti, Keita Satoh, Yasumasa Ueda, John F Morris, Tatsuya Sakamoto, Hirotaka Sakamoto

    International journal of molecular sciences   22 ( 17 )   2021.8

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    Language:English   Publishing type:Research paper (scientific journal)  

    Translational research often requires the testing of experimental therapies in primates, but research in non-human primates is now stringently controlled by law around the world. Tissues fixed in formaldehyde without glutaraldehyde have been thought to be inappropriate for use in electron microscopic analysis, particularly those of the brain. Here we report the immunoelectron microscopic characterization of arginine vasopressin (AVP)-producing neurons in macaque hypothalamo-pituitary axis tissues fixed by perfusion with 4% formaldehyde and stored at -25 °C for several years (4-6 years). The size difference of dense-cored vesicles between magnocellular and parvocellular AVP neurons was detectable in their cell bodies and perivascular nerve endings located, respectively, in the posterior pituitary and median eminence. Furthermore, glutamate and the vesicular glutamate transporter 2 could be colocalized with AVP in perivascular nerve endings of both the posterior pituitary and the external layer of the median eminence, suggesting that both magnocellular and parvocellular AVP neurons are glutamatergic in primates. Both ultrastructure and immunoreactivity can therefore be sufficiently preserved in macaque brain tissues stored long-term, initially for light microscopy. Taken together, these results suggest that this methodology could be applied to the human post-mortem brain and be very useful in translational research.

    DOI: 10.3390/ijms22179180

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  • Estrogens influence female itch sensitivity via the spinal gastrin-releasing peptide receptor neurons International journal

    Keiko Takanami, Daisuke Uta, Ken Ichi Matsuda, Mitsuhiro Kawata, Earl Carstens, Tatsuya Sakamoto, Hirotaka Sakamoto

    Proceedings of the National Academy of Sciences   118 ( 31 )   e2103536118 - e2103536118   2021.8

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Proceedings of the National Academy of Sciences  

    There are sex differences in somatosensory sensitivity. Circulating estrogens appear to have a pronociceptive effect that explains why females are reported to be more sensitive to pain than males. Although itch symptoms develop during pregnancy in many women, the underlying mechanism of female-specific pruritus is unknown. Here, we demonstrate that estradiol, but not progesterone, enhances histamine-evoked scratching behavior indicative of itch in female rats. Estradiol increased the expression of the spinal itch mediator, gastrin-releasing peptide (GRP), and increased the histamine-evoked activity of itch-processing neurons that express the GRP receptor (GRPR) in the spinal dorsal horn. The enhancement of itch behavior by estradiol was suppressed by intrathecal administration of a GRPR blocker. In vivo electrophysiological analysis showed that estradiol increased the histamine-evoked firing frequency and prolonged the response of spinal GRP-sensitive neurons in female rats. On the other hand, estradiol did not affect the threshold of noxious thermal pain and decreased touch sensitivity, indicating that estradiol separately affects itch, pain, and touch modalities. Thus, estrogens selectively enhance histamine-evoked itch in females via the spinal GRP/GRPR system. This may explain why itch sensation varies with estrogen levels and provides a basis for treating itch in females by targeting GRPR.

    DOI: 10.1073/pnas.2103536118

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    Other Link: https://syndication.highwire.org/content/doi/10.1073/pnas.2103536118

  • Systemic effects of oxytocin on male sexual activity via the spinal ejaculation generator in rats. International journal

    Takumi Oti, Tatsuya Sakamoto, Hirotaka Sakamoto

    Communicative & integrative biology   14 ( 1 )   55 - 60   2021.3

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    Oxytocin is produced in the hypothalamus and stimulates uterine contraction and milk ejection. While many people consider oxytocin to be a female hormone, it is reported that, in men, the plasma oxytocin level increases markedly after ejaculation. However, this aspect of oxytocin physiology is poorly understood. The spinal ejaculation generator (SEG), which expresses the neuropeptide, gastrin-releasing peptide (GRP), can trigger ejaculation in rats. Therefore, we focused on systemic effects of oxytocin on the GRP/SEG neuron system in the lumbar spinal cord controlling sexual activity in male rats. We found that systemic administration of oxytocin significantly shortened the latency to the first mount, intromission and ejaculation during male copulatory behavior. In addition, the local oxytocin level in the lumbar cord was significantly higher in males than in females. Histological analysis showed that oxytocin-binding is apparent in spinal GRP/SEG neurons. We therefore conclude that oxytocin influences male sexual activity via the SEG.

    DOI: 10.1080/19420889.2021.1902056

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  • In Vivo Electrophysiology of Peptidergic Neurons in Deep Layers of the Lumbar Spinal Cord after Optogenetic Stimulation of Hypothalamic Paraventricular Oxytocin Neurons in Rats International journal

    Daisuke Uta, Takumi Oti, Tatsuya Sakamoto, Hirotaka Sakamoto

    International Journal of Molecular Sciences   22 ( 7 )   3400 - 3400   2021.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:MDPI AG  

    The spinal ejaculation generator (SEG) is located in the central gray (lamina X) of the rat lumbar spinal cord and plays a pivotal role in the ejaculatory reflex. We recently reported that SEG neurons express the oxytocin receptor and are activated by oxytocin projections from the paraventricular nucleus of hypothalamus (PVH). However, it is unknown whether the SEG responds to oxytocin in vivo. In this study, we analyzed the characteristics of the brain–spinal cord neural circuit that controls male sexual function using a newly developed in vivo electrophysiological technique. Optogenetic stimulation of the PVH of rats expressing channel rhodopsin under the oxytocin receptor promoter increased the spontaneous firing of most lamina X SEG neurons. This is the first demonstration of the in vivo electrical response from the deeper (lamina X) neurons in the spinal cord. Furthermore, we succeeded in the in vivo whole-cell recordings of lamina X neurons. In vivo whole-cell recordings may reveal the features of lamina X SEG neurons, including differences in neurotransmitters and response to stimulation. Taken together, these results suggest that in vivo electrophysiological stimulation can elucidate the neurophysiological response of a variety of spinal neurons during male sexual behavior.

    DOI: 10.3390/ijms22073400

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  • Oxytocin Influences Male Sexual Activity via Non-synaptic Axonal Release in the Spinal Cord. International journal

    Takumi Oti, Keita Satoh, Daisuke Uta, Junta Nagafuchi, Sayaka Tateishi, Ryota Ueda, Keiko Takanami, Larry J Young, Antony Galione, John F Morris, Tatsuya Sakamoto, Hirotaka Sakamoto

    Current biology : CB   31 ( 1 )   103 - 114   2021.1

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    Language:English   Publishing type:Research paper (scientific journal)  

    Oxytocinergic neurons in the paraventricular nucleus of the hypothalamus that project to extrahypothalamic brain areas and the lumbar spinal cord play an important role in the control of erectile function and male sexual behavior in mammals. The gastrin-releasing peptide (GRP) system in the lumbosacral spinal cord is an important component of the neural circuits that control penile reflexes in rats, circuits that are commonly referred to as the "spinal ejaculation generator (SEG)." We have examined the functional interaction between the SEG neurons and the hypothalamo-spinal oxytocin system in rats. Here, we show that SEG/GRP neurons express oxytocin receptors and are activated by oxytocin during male sexual behavior. Intrathecal injection of oxytocin receptor antagonist not only attenuates ejaculation but also affects pre-ejaculatory behavior during normal sexual activity. Electron microscopy of potassium-stimulated acute slices of the lumbar cord showed that oxytocin-neurophysin-immunoreactivity was detected in large numbers of neurosecretory dense-cored vesicles, many of which are located close to the plasmalemma of axonal varicosities in which no electron-lucent microvesicles or synaptic membrane thickenings were visible. These results suggested that, in rats, release of oxytocin in the lumbar spinal cord is not limited to conventional synapses but occurs by exocytosis of the dense-cored vesicles from axonal varicosities and acts by diffusion-a localized volume transmission-to reach oxytocin receptors on GRP neurons and facilitate male sexual function.

    DOI: 10.1016/j.cub.2020.09.089

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  • Prolactin

    Yoko Yamaguchi, Tatsuya Sakamoto

    Handbook of Hormones   203 - 205   2021

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    Publishing type:Part of collection (book)   Publisher:Elsevier  

    DOI: 10.1016/b978-0-12-820649-2.00054-1

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  • Growth hormone/prolactin family

    Yoko Yamaguchi, Tatsuya Sakamoto

    Handbook of Hormones   197 - 198   2021

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    Publishing type:Part of collection (book)   Publisher:Elsevier  

    DOI: 10.1016/b978-0-12-820649-2.00052-8

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  • Prolactin-releasing peptide

    Tetsuya Tachibana, Tatsuya Sakamoto

    Handbook of Hormones   33 - 36   2021

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    Publishing type:Part of collection (book)   Publisher:Elsevier  

    DOI: 10.1016/b978-0-12-820649-2.00008-5

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  • 異なる浸透圧におけるメダカの成長と体液調節・エネルギー代謝

    御輿 真穂, 坂本 竜哉

    比較内分泌学   38 ( 147 )   209 - 211   2012

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    Language:Japanese   Publisher:Japan Society for Comparative Endocrinology  

    DOI: 10.5983/nl2008jsce.38.209

    CiNii Article

    CiNii Books

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    Other Link: https://jlc.jst.go.jp/DN/JALC/10013529337?from=CiNii

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Books

  • "Growth Hormone/Prolactin Family." Handbook of Hormones: Comparative Endocrinology for Basic and Clinical Research

    Elsevier  2021 

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  • "Prolactin-Releasing Peptide." Handbook of Hormones: Comparative Endocrinology for Basic and Clinical Research

    Elsevier  2021 

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  • "Prolactin." Handbook of Hormones: Comparative Endocrinology for Basic and Clinical Research

    Elsevier  2021 

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  • Japanese Marine Life - A Practical Training Guide in Marine Biology.

    Springer Nature  2020 

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  • Evolution of calcium homeostasis and its hormonal regulation in vertebrates

    坂本 竜哉

    2012 

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  • Prolactin. B.E. Toth (ed.)

    坂本 竜哉

    2012 

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  • Recent Advances in Comparative Endocrinology

    2001 

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  • Growth and Growth Regulation in Fish

    American Fisheries Society  2000 

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  • Growth hormone endocrinology of Atlantic salmon during parr-smolt transformation.(共著)

    Growth and Growth Regulation in Fish American Fisheries Society 

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  • Growth hormone endocrinology of Atlantic salmon during parr-smolt transformation.(共著)

    Growth and Growth Regulation in Fish American Fisheries Society 

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  • Osamoregulatory roles of prolactin and growth hormone in teleosts(共著)

    Prolactin gene family and its receptors, Elsevier, Amsterdam 

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  • Hepatic growth hormone receptors in the eel and trout(共著)

    Hormones and environment. Hong Kong Univ. Press, Hong Kong 

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  • Roles of growth hormone and prolactin during adaptation of the gobies to various environments.(共著)

    Growth and Growth Regulation in Fish. American Fisheries Society 

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  • Hepatic growth hormone receptors in the eel and trout(共著)

    Hormones and environment. Hong Kong Univ. Press, Hong Kong 

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  • Roles of growth hormone and prolactin during adaptation of the gobies to various environments.(共著)

    Growth and Growth Regulation in Fish. American Fisheries Society 

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  • Osamoregulatory roles of prolactin and growth hormone in teleosts(共著)

    Prolactin gene family and its receptors, Elsevier, Amsterdam 

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MISC

  • Oxytocin Influences Male Sexual Activity via Non-synaptic Axonal Release in the Spinal Cord International journal

    Takumi Oti, Keita Satoh, Daisuke Uta, Junta Nagafuchi, Sayaka Tateishi, Ryota Ueda, Keiko Takanami, Larry J. Young, Antony Galione, John F. Morris, Tatsuya Sakamoto, Hirotaka Sakamoto

    Current Biology   2020.10

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    Language:English   Publisher:Elsevier BV  

    Oxytocinergic neurons in the paraventricular nucleus of the hypothalamus that project to extrahypothalamic brain areas and the lumbar spinal cord play an important role in the control of erectile function and male sexual behavior in mammals. The gastrin-releasing peptide (GRP) system in the lumbosacral spinal cord is an important component of the neural circuits that control penile reflexes in rats, circuits that are commonly referred to as the "spinal ejaculation generator (SEG)." We have examined the functional interaction between the SEG neurons and the hypothalamo-spinal oxytocin system in rats. Here, we show that SEG/GRP neurons express oxytocin receptors and are activated by oxytocin during male sexual behavior. Intrathecal injection of oxytocin receptor antagonist not only attenuates ejaculation but also affects pre-ejaculatory behavior during normal sexual activity. Electron microscopy of potassium-stimulated acute slices of the lumbar cord showed that oxytocin-neurophysin-immunoreactivity was detected in large numbers of neurosecretory dense-cored vesicles, many of which are located close to the plasmalemma of axonal varicosities in which no electron-lucent microvesicles or synaptic membrane thickenings were visible. These results suggested that, in rats, release of oxytocin in the lumbar spinal cord is not limited to conventional synapses but occurs by exocytosis of the dense-cored vesicles from axonal varicosities and acts by diffusion-a localized volume transmission-to reach oxytocin receptors on GRP neurons and facilitate male sexual function.

    DOI: 10.1016/j.cub.2020.09.089

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  • Variation of pro‐vasopressin processing in parvocellular and magnocellular neurons in the paraventricular nucleus of the hypothalamus: Evidence from the vasopressin‐related glycopeptide copeptin

    Natsuko Kawakami, Akito Otubo, Sho Maejima, Ashraf H. Talukder, Keita Satoh, Takumi Oti, Keiko Takanami, Yasumasa Ueda, Keiichi Itoi, John F. Morris, Tatsuya Sakamoto, Hirotaka Sakamoto

    Journal of Comparative Neurology   2020.9

  • Introducing the Amphibious Mudskipper Goby as a Unique Model to Evaluate Neuro/Endocrine Regulation of Behaviors Mediated by Buccal Sensation and Corticosteroids

    Yukitoshi Katayama, Kazuhiro Saito, Tatsuya Sakamoto

    International Journal of Molecular Sciences   21 ( 18 )   6748 - 6748   2020.9

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    Publisher:MDPI AG  

    Some fish have acquired the ability to breathe air, but these fish can no longer flush their gills effectively when out of water. Hence, they have developed characteristic means for defense against external stressors, including thirst (osmolarity/ions) and toxicity. Amphibious fish, extant air-breathing fish emerged from water, may serve as models to examine physiological responses to these stressors. Some of these fish, including mudskipper gobies such as Periophthalmodon schlosseri, Boleophthalmus boddarti and our Periophthalmus modestus, display distinct adaptational behaviors to these factors compared with fully aquatic fish. In this review, we introduce the mudskipper goby as a unique model to study the behaviors and the neuro/endocrine mechanisms of behavioral responses to the stressors. Our studies have shown that a local sensation of thirst in the buccal cavity—this being induced by dipsogenic hormones—motivates these fish to move to water through a forebrain response. The corticosteroid system, which is responsive to various stressors, also stimulates migration, possibly via the receptors in the brain. We suggest that such fish are an important model to deepen insights into the stress-related neuro/endocrine-behavioral effects.

    DOI: 10.3390/ijms21186748

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  • Transcriptomic Analysis of the Kuruma Prawn Marsupenaeus japonicus Reveals Possible Peripheral Regulation of the Ovary Invited Reviewed

    Naoaki Tsutsui, Yasuhisa Kobayashi, Kouichi Izumikawa, Tatsuya Sakamoto

    Frontiers in Endocrinology   11   2020.8

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    Publisher:Frontiers Media SA  

    DOI: 10.3389/fendo.2020.00541

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  • Vasopressin gene products are colocalised with corticotrophin‐releasing factor within neurosecretory vesicles in the external zone of the median eminence of the Japanese macaque monkey ( Macaca fuscata )

    Akito Otubo, Natsuko Kawakami, Sho Maejima, Yasumasa Ueda, John F. Morris, Tatsuya Sakamoto, Hirotaka Sakamoto

    Journal of Neuroendocrinology   32 ( 8 )   2020.8

  • Facilitated NaCl Uptake in the Highly Developed Bundle of the Nephron in Japanese Red Stingray Hemitrygon akajei Revealed by Comparative Anatomy and Molecular Mapping

    Naotaka Aburatani, Wataru Takagi, Marty Kwok-Sing Wong, Mitsutaka Kadota, Shigehiro Kuraku, Kotaro Tokunaga, Kazuya Kofuji, Kazuhiro Saito, Waichiro Godo, Tatsuya Sakamoto, Susumu Hyodo

    Zoological Science   37 ( 5 )   1 - 1   2020.7

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    Publisher:Zoological Society of Japan  

    DOI: 10.2108/zs200038

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  • Detection and Characterization of Estrogen Receptor Beta Expression in the Brain with Newly Developed Transgenic Mice

    Shoko Sagoshi, Sho Maejima, Masahiro Morishita, Satoshi Takenawa, Akito Otubo, Keiko Takanami, Tatsuya Sakamoto, Hirotaka Sakamoto, Shinji Tsukahara, Sonoko Ogawa

    Neuroscience   438   182 - 197   2020.7

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    Publisher:Elsevier BV  

    DOI: 10.1016/j.neuroscience.2020.04.047

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  • Ghrelin and food acquisition in wild and cultured Japanese eel (Anguilla japonica)

    Takashi Yada, Michihisa Abe, Kenzo Kaifu, Kazuki Yokouchi, Nobuto Fukuda, Sakie Kodama, Hiroshi Hakoyama, Maho Ogoshi, Hiroyuki Kaiya, Tatsuya Sakamoto, Shunsuke Moriyama, Katsumi Tsukamoto

    Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology   245   110700 - 110700   2020.7

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    Language:English   Publisher:Elsevier BV  

    To clarify the relationships between growth, endocrine status and habitat characteristics in Japanese eel (Anguilla japonica), plasma and stomach mRNA levels of ghrelin were examined in wild eels captured in the river and the bay, and in cultured eels during and after experimental fasting. Wild juvenile eels captured in freshwater habitats within the river showed significantly higher plasma and stomach mRNA levels of ghrelin than did fish obtained from brackish-water habitats within the bay. In cultured eels experimentally fasted for 4 weeks, plasma and stomach mRNA levels of ghrelin increased. After refeeding, the both parameters returned to the levels observed in continuously feeding control fish. In pigmented elvers, 2 months of feed restriction resulted in a significant increase in whole-body ghrelin mRNA. It is suggested that interaction between ghrelin and feeding is related to their habitats through differential food acquisition in fresh and brackish water environments.

    DOI: 10.1016/j.cbpa.2020.110700

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  • Current and Future Research at Japanese National Marine and Inland Water Stations

    Ocean Newsletter   2019.12

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  • Hormonal regulation of thirst in the amphibious ray-finned fish suggests the requirement for terrestrialization during evolution. International journal

    Yukitoshi Katayama, Yoshio Takei, Makoto Kusakabe, Tatsuya Sakamoto

    Scientific reports   9 ( 1 )   16347 - 16347   2019.11

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    Language:English  

    Thirst has evolved for vertebrate terrestrial adaptation. We previously showed that buccal drying induced a series of drinking behaviours (migration to water-taking water into the mouth-swallowing) in the amphibious mudskipper goby, thereby discovering thirst in ray-finned fish. However, roles of dipsogenic/antidipsogenic hormones, which act on the thirst center in terrestrial tetrapods, have remained unclear in the mudskipper thirst. Here we examined the hormonal effects on the mudskipper drinking behaviours, particularly the antagonistic interaction between angiotensin II (AngII) and atrial natriuretic peptide (ANP) which is important for thirst regulation in mammalian 'forebrain'. Expectedly, intracerebroventricular injection of ANP in mudskippers reduced AngII-increased drinking rate. ANP also suppressed the neural activity at the 'hindbrain' region for the swallowing reflex, and the maintenance of buccopharyngeal water due to the swallowing inhibition may attenuate the motivation to move to water. Thus, the hormonal molecules involved in drinking regulation, as well as the influence of buccopharyngeal water, appear to be conserved in distantly related species to solve osmoregulatory problems, whereas hormonal control of thirst at the forebrain might have been acquired only in tetrapod lineage during evolution.

    DOI: 10.1038/s41598-019-52870-7

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  • Sea Docking by Dual-eye Pose Estimation with Optimized Genetic Algorithm Parameters

    Khin Nwe Lwin, Myo Myint, Naoki Mukada, Daiki Yamada, Takayuki Matsuno, Kazuhiro Saitou, Waichiro Godou, Tatsuya Sakamoto, Mamoru Minami

    Journal of Intelligent & Robotic Systems   96 ( 2 )   245 - 266   2019.11

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  • Discussion about Reproductive Mechanism of Eel-Grass(Zostera marina)

    Tomio FUKUDA, Yasutoshi KOHDA, Masatoshi MIZUTANI, Tatsuya SAKAMOTO

    J Kibi Int Univ Res Inst Health Welfare. (29),1-20 (2019-03-22)   2019.3

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  • 'Central' Actions of Corticosteroid Signaling Suggested by Constitutive Knockout of Corticosteroid Receptors in Small Fish

    Sakamoto T, Sakamoto H

    Nutrients. 2019 Mar 13;11(3). pii: E611. doi: 10.3390/nu11030611   2019

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  • Hyperosmotic tolerance of adult fish and early embryos are determined by discrete, single loci in the genus Oryzias

    Taijun Myosho, Hideya Takahashi, Kento Yoshida, Tadashi Sato, Satoshi Hamaguchi, Tatsuya Sakamoto, Mitsuru Sakaizumi

    Scientific Reports   8 ( 1 )   2018.12

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    Publisher:Springer Science and Business Media LLC  

    DOI: 10.1038/s41598-018-24621-7

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    Other Link: http://www.nature.com/articles/s41598-018-24621-7

  • The Amphibious Mudskipper: A Unique Model Bridging the Gap of Central Actions of Osmoregulatory Hormones Between Terrestrial and Aquatic Vertebrates. Reviewed

    Katayama K, Sakamoto T, Takanami K, Takei Y

    Frontiers in Physiology,   9   1112   2018.8

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  • Characterization of distinct ovarian isoform of crustacean female sex hormone in the kuruma prawn Marsupenaeus japonicus

    Naoaki Tsutsui, Sayaka Kotaka, Tsuyoshi Ohira, Tatsuya Sakamoto

    COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY   217   7 - 16   2018.3

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    Language:English   Publisher:ELSEVIER SCIENCE INC  

    The eyestalk hormone, crustacean female sex hormone (CFSH), regulates the development of female secondary sexual characteristics in the blue crab Callinectes sapidus. After its discovery, several CFSH gene orthologs have been identified in some species of the suborder Pleocyemata as well. Similarly, in species of another suborder (Dendrobranchiata), an ortholog (Maj-CFSH) has been characterized as an eyestalk factor expressed in both females and males of the kuruma prawn, Marsupenaeus japonicus. In this study, another novel CFSH isoform was identified in the same species using cDNA cloning, expression analysis, and recombinant protein production. The isoform has "CFSH-family" structural characteristics but is dominantly expressed in the ovary, and was therefore designated as Maj-CFSH-ov. Its mRNA and protein levels in vitellogenic ovaries are higher than those in non-vitellogenic ovaries. In the vitellogenic ovary, both mRNA and protein expression of Maj-CFSH-ov are localized to oogonia and previtellogenic oocytes that occupy a small portion of vitellogenic ovaries, but not to the major developing oocytes. A vitellogenesis-inhibiting peptide of M. japonicus (Pej-SGP-I) reduced the expression of vitellogenin in incubated ovarian fragments, but not that of Maj-CFSH-ov. These results indicate that M. japonicus possesses two CFSH isoforms that are derived from distinct tissues, the central X-organ/sinus gland complex and peripheral ovaries. The expression profile of Maj-CFSH-ov suggests its involvement in some reproductive process other than vitellogenesis.

    DOI: 10.1016/j.cbpa.2017.12.009

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  • Analyzing the effects of co-expression of chick (Gallus gallus) melanocortin receptors with either chick MRAP1 or MRAP2 in CHO cells on sensitivity to ACTH(1–24) or ACTH(1–13)NH2: Implications for the avian HPA axis and avian melanocortin circuits in the hypothalamus

    Alexa L. Thomas, Fumihiko Maekawa, Takaharu Kawashima, Hirotaka Sakamoto, Tatsuya Sakamoto, Perry Davis, Robert M. Dores

    General and Comparative Endocrinology   256   50 - 56   2018.1

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    In order to better understand the roles that melanocortin receptors (cMCRs) and melanocortin-2 receptor accessory proteins (cMRAP1 and cMRAP2) play in the HPA axis and hypothalamus, adrenal gland and hypothalamus mRNA from 1 day-old white leghorn chicks (Gallus gallus), were analyzed by real-time PCR. mRNA was also made for kidney, ovary, and liver. Mrap1 mRNA could be detected in adrenal tissue, but not in any of the other tissues, and mrap2 mRNA was also detected in the adrenal gland. Finally, all five melanocortin receptors mRNAs could be detected in the adrenal gland
    mc2r and mc5r mRNAs were the most abundant. To evaluate any potential interactions between MRAP1 and the MCRs that may occur in adrenal cells, individual chick mcr cDNA constructs were transiently expressed in CHO cells either in the presence or absence of a chick mrap1 cDNA, and the transfected cells were stimulated with hACTH(1–24) at concentrations ranging from 10−13 M to 10−6 M. As expected, MC2R required co-expression with MRAP1 for functional expression
    whereas, co-expression of cMC3R with cMRAP1 had no statistically significant effect on sensitivity to hACTH(1–24). However, co-expression of MC4R and MC5R with MRAP1, increased sensitivity for ACTH(1–24) by approximately 35 fold and 365 fold, respectively. However, co-expressing of cMRAP2 with these melanocortin receptors had no effect on sensitivity to hACTH(1–24). Since the real-time PCR analysis detected mrap2 mRNA and mc4r mRNA in the hypothalamus, the interaction between cMC4R and cMRAP2 with respect to sensitivity to ACTH(1–13)NH2 stimulation was also evaluated. However, no effect, either positive or negative, was observed. Finally, the highest levels of mc5r mRNA were detected in liver cells. This observation raises the possibility that in one-day old chicks, activation of the HPA axis may also involve a physiological response from liver cells.

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  • Drinking by amphibious fish: convergent evolution of thirst mechanisms during vertebrate terrestrialization. International journal

    Yukitoshi Katayama, Tatsuya Sakamoto, Kazuhiro Saito, Hirotsugu Tsuchimochi, Hiroyuki Kaiya, Taro Watanabe, James T Pearson, Yoshio Takei

    Scientific reports   8 ( 1 )   625 - 625   2018.1

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    Thirst aroused in the forebrain by angiotensin II (AngII) or buccal drying motivates terrestrial vertebrates to search for water, whereas aquatic fish can drink surrounding water only by reflex swallowing generated in the hindbrain. Indeed, AngII induces drinking through the hindbrain even after removal of the whole forebrain in aquatic fish. Here we show that AngII induces thirst also in the amphibious mudskipper goby without direct action on the forebrain, but through buccal drying. Intracerebroventricular injection of AngII motivated mudskippers to move into water and drink as with tetrapods. However, AngII primarily increased immunoreactive c-Fos at the hindbrain swallowing center where AngII receptors were expressed, as in other ray-finned fish, and such direct action on the forebrain was not found. Behavioural analyses showed that loss of buccal water on land by AngII-induced swallowing, by piercing holes in the opercula, or by water-absorptive gel placed in the cavity motivated mudskippers to move to water for refilling. Since sensory detection of water at the bucco-pharyngeal cavity like 'dry mouth' has recently been noted to regulate thirst in mammals, similar mechanisms seem to have evolved in distantly related species in order to solve osmoregulatory problems during terrestrialization.

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  • Nemertean and phoronid genomes reveal lophotrochozoan evolution and the origin of bilaterian heads

    Yi-Jyun Luo, Miyuki Kanda, Ryo Koyanagi, Kanako Hisata, Tadashi Akiyama, Hirotaka Sakamoto, Tatsuya Sakamoto, Noriyuki Satoh

    Nature Ecology and Evolution   2 ( 1 )   141 - 151   2018.1

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    Nemerteans (ribbon worms) and phoronids (horseshoe worms) are closely related lophotrochozoans - a group of animals including leeches, snails and other invertebrates. Lophotrochozoans represent a superphylum that is crucial to our understanding of bilaterian evolution. However, given the inconsistency of molecular and morphological data for these groups, their origins have been unclear. Here, we present draft genomes of the nemertean Notospermus geniculatus and the phoronid Phoronis australis, together with transcriptomes along the adult bodies. Our genome-based phylogenetic analyses place Nemertea sister to the group containing Phoronida and Brachiopoda. We show that lophotrochozoans share many gene families with deuterostomes, suggesting that these two groups retain a core bilaterian gene repertoire that ecdysozoans (for example, flies and nematodes) and platyzoans (for example, flatworms and rotifers) do not. Comparative transcriptomics demonstrates that lophophores of phoronids and brachiopods are similar not only morphologically, but also at the molecular level. Despite dissimilar head structures, lophophores express vertebrate head and neuronal marker genes. This finding suggests a common origin of bilaterian head patterning, although different heads evolved independently in each lineage. Furthermore, we observe lineage-specific expansions of innate immunity and toxin-related genes. Together, our study reveals a dual nature of lophotrochozoans, where conserved and lineage-specific features shape their evolution.

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  • A sexually dimorphic peptidergic system in the lower spinal cord controlling penile function in non-human primates

    T. Ito, T. Oti, K. Takanami, K. Satoh, Y. Ueda, T. Sakamoto, H. Sakamoto

    Spinal Cord   56 ( 1 )   57 - 62   2018

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    Study design: Experimental animal study. Objectives: Although a population of gastrin-releasing peptide (GRP) neurons in the lumbar spinal cord has an important role in erection and ejaculation in rats, little information exists on this GRP system in primates. To identify the male-specific GRP system in the primate spinal cord, we studied the lumbosacral cord in macaque monkeys as a non-human primate model. Setting: University laboratory in Japan. Methods: To determine the gene sequence of GRP precursors, the rhesus macaque monkey genomic sequence data were searched, followed by phylogenetic analysis. Subsequently, immunocytochemical analysis for GRP was performed in the monkey spinal cord. Results: We have used bioinformatics to identify the ortholog gene for GRP precursor in macaque monkeys. Phylogenetic analysis suggested that primate prepro-GRP is separated from that of other mammalian species and clustered to an independent branch as primates. Immunocytochemistry for GRP further demonstrated that male-dominant sexual dimorphism was found in the spinal GRP system in monkeys as in rodents. Conclusion: We have demonstrated in macaque monkeys that the GRP system in the lower spinal cord shows male-specific dimorphism and May have an important role in penile functions not only in rodents but also in primates.

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  • Unique Model Bridging the Gap of Central Actions of Osmoregulatory Hormones

    Katayama Y, Sakamoto T, Takanami K, Takei Y

    Front Physiol. 2018 Aug 14;9:1112.   2018

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  • Effects of Sex Steroids on the Spinal Gastrin-Releasing

    Oti T, Takanami K, Ito S, Ueda T, Matsuda KI, Kawata M, Soh J, Ukimura O

    Endocrinology. 2018 Apr 1;159(4):1886-1896   2018

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  • Effects of Sex Steroids on the Spinal Gastrin-Releasing Peptide System Controlling Male Sexual Function in Rats. International journal

    Takumi Oti, Keiko Takanami, Saya Ito, Takashi Ueda, Ken Ichi Matsuda, Mitsuhiro Kawata, Jintetsu Soh, Osamu Ukimura, Tatsuya Sakamoto, Hirotaka Sakamoto

    Endocrinology   159 ( 4 )   1886 - 1896   2018

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    The gastrin-releasing peptide (GRP) system in the lumbosacral spinal cord controls male sexual function in rats. In contrast, in female rats, GRP neurons could scarcely be detected around puberty when circulating ovarian steroid hormones such as estradiol and progesterone levels are increasing. However, little information is available on feminizing or demasculinizing effects of ovarian steroids on the central nervous system in female puberty and adulthood. In this study, to visualize the spinal GRP neurons in vivo, we generated a GRP-promoter-Venus transgenic (Tg) rat line and studied the effects of the sex steroid hormones on GRP expression in the rat lumbar cord by examining the Venus fluorescence. In these Tg rats, the sexually dimorphic spinal GRP neurons controlling male sexual function were clearly labeled with Venus fluorescence. As expected, Venus fluorescence in the male lumbar cord was markedly decreased after castration and restored by chronic androgen replacement. Furthermore, androgen-induced Venus expression in the spinal cord of adult Tg males was significantly attenuated by chronic treatment with progesterone but not with estradiol. A luciferase assay using a human GRP-promoter construct showed that androgens enhance the spinal GRP system, and more strikingly, that progesterone acts to inhibit the GRP system via an androgen receptor-mediated mechanism. These results demonstrate that circulating androgens may play an important role in the spinal GRP system controlling male sexual function not only in rats but also in humans and that progesterone could be an important feminizing factor in the spinal GRP system in females during pubertal development.

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  • Visual Docking against Bubble Noise with Three-dimensional Perception Using Dual-eye Cameras

    Khin Lwin, Naoki Mukada, Myo Myint, Daiki Yamada, Akira Yanou, Takayuki Matsno, Kazuhiro Saitou, Waichiro Godou, Tatsuya Sakamoto, Mamoru Minami

    IEEE Journal of Oceanic Engineering DOI (identifier) 10.1109/JOE.2018.2871651   2018

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  • Robust Visual Servoing against Air Bubble Noise with

    Khin Lwin, Naoki Mukada, Myo Myint, Daiki Yamada, Akira Yanou, Takayuki Matsno, Kazuhiro Saitou, Waichiro Godou, Tatsuya Sakamoto, Mamoru Minami

    Journal of Advanced Mechanical Design, Systems, and Manufacturing   2018

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  • Molecular cloning and tissue distribution analysis of corticosteroid receptor genes in two cartilaginous fishes, catshark (Elasmobranchii) and elephant fish (Holocephali)

    Wataru Takagi, Tatsuya Sakamoto

    Data in Brief   7   2018

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  • A possible principal function of corticosteroid signaling that is conserved in vertebrate evolution: Lessons from receptor-knockout small fish

    Tatsuya Sakamoto, Susumu Hyodo, Wataru Takagi

    Journal of Steroid Biochemistry and Molecular Biology   2018

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    Corticosteroid receptors are critical for homeostasis maintenance, but understanding of the principal roles of the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) throughout vertebrates is limited. Lines of constitutive GR-knockout zebrafish and MR-knockout medaka have recently been generated as the first adult-viable corticosteroid receptor-knockout animals, in contrast to the lethality of these receptor knockouts in mice. Here, we describe behavioral and physiological modifications following disruption of corticosteroid receptor function in these animal models. We suggest these data point toward a potentially conserved function of corticosteroid receptors in integrating brain-behavior and visual responses in vertebrates. Finally, we discuss how future work in cartilaginous fishes (Chondrichthyes) will further advance understanding of the unity and diversity of corticosteroid receptor function, since distinct orthologs of GR and MR derived from an ancestral corticoid receptor appear in these basal jawed vertebrates.

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  • The mineralo-corticoid receptor knockout in medaka is further validated by glucocorticoid receptor compensation

    Tatsuya Sakamoto, Madoka Yoshiki, Hirotaka Sakamoto

    SCIENTIFIC DATA   4   924 - 928   2017.12

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    To study the critical role of mineralocorticoid signalling, we generated a constitutive mineralocorticoid receptor (MR)-knockout (KO) medaka as the first adult-viable MR-KO animal. This KO medaka displayed abnormal behaviours affected by visual stimuli. In contrast, the loss of MR did not result in overt phenotypic changes in osmoregulation, despite the well-known osmoregulatory functions of MR in mammals. Since glucocorticoid receptor (GR) has been suggested to compensate for loss of MR, we examined expression of duplicated GRs with markedly different ligand sensitivities, in various tissues. qRT-PCR results revealed that the absence of MR induced GR1 in the brain and eyes, but not in osmoregulatory organs. This reinforces the important functions of glucocorticoid signalling, but the minor role of mineralocorticoid signalling, in fish osmoregulation. Because both 11-deoxycorticosterone (DOC) and cortisol are ligands for MR, whereas GRs are specific to cortisol, GR1 signalling may compensate for the absence of cortisol-MR, rather than that of DOC-MR. Thus, this GR expression suggests that our MR-KO model can be used specifically to characterize DOC-MR signalling.

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  • MORPHOLOGICAL AND MOLECULAR EVOLUTIONAL ANALYSES OF ITCH FOCUSED ON THE GASTRIN-RELEASING PEPTIDE SYSTEM IN MAMMALS

    Keiko Takanami, Keita Satoh, Kazuyoshi Murata, Tatsuya Sakamoto, Hirotaka Sakamoto

    ACTA DERMATO-VENEREOLOGICA   97 ( 8 )   1049 - 1050   2017.9

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  • Identification of the sexually dimorphic gastrin-releasing peptide system in the lumbosacral spinal cord that controls male reproductive function in the mouse and Asian house musk shrew (Suncus murinus)

    Kei Tamura, Yasuhisa Kobayashi, Asuka Hirooka, Keiko Takanami, Takumi Oti, Takamichi Jogahara, Sen-ichi Oda, Tatsuya Sakamoto, Hirotaka Sakamoto

    JOURNAL OF COMPARATIVE NEUROLOGY   525 ( 7 )   1586 - 1598   2017.5

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    Several regions of the brain and spinal cord control male reproductive function. We previously demonstrated that the gastrin-releasing peptide (GRP) system, located in the lumbosacral spinal cord of rats, controls spinal centers to promote penile reflexes during male copulatory behavior. However, little information exists on the male-specific spinal GRP system in animals other than rats. The objective of this study was to examine the functional generality of the spinal GRP system in mammals using the Asian house musk shrew (Suncus murinus; suncus named as the laboratory strain), a specialized placental mammal model. Mice are also used for a representative model of small laboratory animals. We first isolated complementary DNA encoding GRP in suncus. Phylogenetic analysis revealed that suncus preproGRP was clustered to an independent branch. Reverse transcription-PCR showed that GRP and its receptor mRNAs were both expressed in the lumbar spinal cord of suncus and mice. Immunohistochemistry for GRP demonstrated that the sexually dimorphic GRP system and male-specific expression/distribution patterns of GRP in the lumbosacral spinal cord in suncus are similar to those of mice. In suncus, we further found that most GRP-expressing neurons in males also express androgen receptors, suggesting that this male-dominant system in suncus is also androgen-dependent. Taken together, these results indicate that the sexually dimorphic spinal GRP system exists not only in mice but also in suncus, suggesting that this system is a conserved property in mammals. J. Comp. Neurol. 525:1586-1598, 2017. (c) 2016 Wiley Periodicals, Inc.

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  • クルマエビの卵巣で発現するペプチドホルモン様因子

    筒井直昭, 坂本竜哉

    日本比較内分泌学会大会及びシンポジウムプログラム・講演要旨   42nd   43   2017

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  • Crystal structure of a crustacean hyperglycemic hormone (CHH) precursor suggests structural variety in the C-terminal regions of CHH superfamily members

    Naoaki Tsutsui, Tatsuya Sakamoto, Fumio Arisaka, Masaru Tanokura, Hiromichi Nagasawa, Koji Nagata

    FEBS JOURNAL   283 ( 23 )   4325 - 4339   2016.12

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    The crustacean hyperglycemic hormone (CHH) is one of the major hormones in crustaceans, and peptides belonging to the CHH superfamily have been found in diverse ecdysozoans. Although the basic function of CHH is to control energy metabolism, it also plays various roles in crustacean species, such as in molting and vitellogenesis. Here, we present the crystal structure of Pej-SGP-I-Gly, a partially active precursor of CHH from the kuruma prawn Marsupenaeus japonicus, which has an additional Gly residue in place of the C-terminal amide group of the mature Pej-SGP-I. The 1.6-angstrom crystal structure showed not only the common CHH superfamily scaffold comprising three a-helices, three disulfide bridges, and a hydrophobic core but also revealed that the C-terminal part has a variant backbone fold that is specific to Pej-SGP-I-Gly. The a-helix 4 of Pej-SGP-I-Gly was much longer than that of molt-inhibiting hormone (Pej-MIH) from the same species, and as a result, the following C-terminal helix, corresponding to a-helix 5 in MIH, was not formed. Unlike monomeric PejMIH, Pej-SGP-I-Gly forms a homodimer in the crystal structure via its unique a-helix 4. The unexpected dissimilar folds between Pej-SGP-I-Gly and Pej-MIH appear to be the result of their distinct C-terminal amino acid sequences. Variations in amino acid sequences and lengths and the resulting variety of backbone folds allow the C-terminal and sterically adjoining regions to confer different hormonal activities in diverse CHH superfamily members.

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  • Principal function of mineralocorticoid signaling suggested by constitutive knockout of the mineralocorticoid receptor in medaka fish

    Tatsuya Sakamoto, Madoka Yoshiki, Hideya Takahashi, Masayuki Yoshida, Yukiko Ogino, Toshitaka Ikeuchi, Tomoya Nakamachi, Norifumi Konno, Kouhei Matsuda, Hirotaka Sakamoto

    SCIENTIFIC REPORTS   6   2016.11

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    As in osmoregulation, mineralocorticoid signaling is implicated in the control of brain-behavior actions. Nevertheless, the understanding of this role is limited, partly due to the mortality of mineralocorticoid receptor (MR)-knockout (KO) mice due to impaired Na+ reabsorption. In teleost fish, a distinct mineralocorticoid system has only been identified recently. Here, we generated a constitutive MR-KO medaka as the first adult-viable MR-KO animal, since MR expression is modest in osmoregulatory organs but high in the brain of adult medaka as for most teleosts. Hyper-and hypo-osmoregulation were normal in MR-KO medaka. When we studied the behavioral phenotypes based on the central MR localization, however, MR-KO medaka failed to track moving dots despite having an increase in acceleration of swimming. These findings reinforce previous results showing a minor role for mineralocorticoid signaling in fish osmoregulation, and provide the first convincing evidence that MR is required for normal locomotor activity in response to visual motion stimuli, but not for the recognition of these stimuli per se. We suggest that MR potentially integrates brain-behavioral and visual responses, which might be a conserved function of mineralocorticoid signaling through vertebrates. Importantly, this fish model allows for the possible identification of novel aspects of mineralocorticoid signaling.

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  • High levels of plasma cortisol and impaired hypoosmoregulation in a mutant medaka deficient in P450c17I

    Hideya Takahashi, Tadashi Sato, Toshitaka Ikeuchi, Kazuhiro Saito, Mitsuru Sakaizumi, Tatsuya Sakamoto

    MOLECULAR AND CELLULAR ENDOCRINOLOGY   430 ( C )   25 - 32   2016.7

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    scl is a spontaneous medaka mutant deficient in P450c17I, which is required for production of sex steroids, but not of cortisol, the major role of which is osmoregulation in teleost fish. The scl mutant provides a new model to study the functions of these hormones. We first found that fish homozygous for this mutation have plasma cortisol constitutively at a high physiological level (1000 nM). Since we previously showed that this level reversed the seawater-type differentiation of the medaka gastrointestinal tract, hypoosmoregulation of the scl mutant was analyzed. Muscle water contents in freshwater were normal in scl homozygotes, but the contents were lower than those of the wild type (WT) after seawater transfer. There were no differences in gill mRNA levels of corticosteroid receptors or ion transporters between scl homozygotes and WT. In the intestine, expression of glucocorticoid receptors and Na+/K+/2Cl(-) cotransporter were induced in WT during seawater acclimation, but not in scl homozygotes. The high plasma cortisol may prevent hypoosmoregulation by inhibition of increased intestinal water absorption, essentially by the Na+/K+/2Cl(-) cotransporter, in seawater. (C) 2016 Elsevier Ireland Ltd. All rights reserved.

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  • Data for amino acid alignment of Japanese stingray melanocortin receptors with other gnathostome melanocortin receptor sequences, and the ligand selectivity of Japanese stingray melanocortin receptors

    Akiyoshi Takahashi, Perry Davis, Christina Reinick, Kanta Mizusawa, Tatsuya Sakamoto, Robert M. Dores

    Data in Brief   7   1670 - 1677   2016.6

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    This article contains structure and pharmacological characteristics of melanocortin receptors (MCRs) related to research published in "Characterization of melanocortin receptors from stingray Dasyatis akajei, a cartilaginous fish" (Takahashi et al., 2016) [1]. The amino acid sequences of the stingray, D. akajei, MC1R, MC2R, MC3R, MC4R, and MC5R were aligned with the corresponding melanocortin receptor sequences from the elephant shark, Callorhinchus milii, the dogfish, Squalus acanthias, the goldfish, Carassius auratus, and the mouse, Mus musculus. These alignments provide the basis for phylogenetic analysis of these gnathostome melanocortin receptor sequences. In addition, the Japanese stingray melanocortin receptors were separately expressed in Chinese Hamster Ovary cells, and stimulated with stingray ACTH, α-MSH, β-MSH, γ-MSH, δ-MSH, and β-endorphin. The dose response curves reveal the order of ligand selectivity for each stingray MCR.

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  • Characterization of melanocortin receptors from stingray Dasyatis akajei, a cartilaginous fish

    Akiyoshi Takahashi, Perry Davis, Christina Reinick, Kanta Mizusawa, Tatsuya Sakamoto, Robert M. Dores

    GENERAL AND COMPARATIVE ENDOCRINOLOGY   232   115 - 124   2016.6

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    Melanocortin (MC) systems are composed of MC peptides such as adrenocorticotropic hormone (ACTH), several molecular forms of melanocyte-stimulating hormones (MSHs) and MC receptors (MCRs). Here we demonstrated that the cartilaginous fish, Dasyatis akajei (stingray) expresses five subtypes of MCR genes-mc1r to mc5r-as in the case of teleost and tetrapod species. This is the first evidence showing the presence of the full repertoire of melanocortin receptors in a single of cartilaginous fish. Expression of respective stingray mcr cDNAs in Chinese hamster ovary cells revealed that Des-acetyl-alpha-MSH exhibited cAMP-producing activity indistinguishable to ACTH(1-24) on MC1R and MC2R, while the activity of Des-acetyl-alpha-MSH on MC3R, MC4R, and MC5R were similar to or slightly greater than that of ACTH(1-24). Notably, in contrast to the other vertebrates, MC2R did not require coexpression with a melanocortin receptor-2 accessory protein 1 (mrap1) cDNA for functional expression. One of the roles of MC system resides in regulation of the pituitary-interrenal (PI) axis-a homologue of tetrapod pituitary adrenal axis. In stingray, interrenal tissues were shown to express mc2r and mc5r as major MCR genes. These results established the presence of functional PI axis in stingray at the level of receptor molecule. While MC2R participates in adrenal functions together with MRAP1 in tetrapod species, the fact that sensitivity of MC5R to Des-acetyl-alpha-MSH and ACTH(1-24) were two order of magnitude higher than MC2R without coexpression with MRAP1 suggested that MC5R could play a more important role than MC2R to transmit signals conveyed by ACTH and MSHs if MRAP1 is really absent in the stingray. (C) 2016 Elsevier Inc. All rights reserved.

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  • Postnatal development of the gastrin-releasing peptide system in the lumbosacral spinal cord controlling male reproductive function in rats

    Nao Katayama, Takumi Oti, Keiko Takanami, Tatsuya Sakamoto, Hirotaka Sakamoto

    PROCEEDINGS OF THE JAPAN ACADEMY SERIES B-PHYSICAL AND BIOLOGICAL SCIENCES   92 ( 2 )   69 - 75   2016.2

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    A sexually dimorphic spinal gastrin-releasing peptide (GRP) system in the lumbosacral spinal cord, which projects to the lower spinal centers, controls erection and ejaculation in rats. However, little is known about the postnatal development of this system. In this study, we therefore examined the postnatal development of the male-dominant spinal GRP system and its sexual differentiation in rats using immunohistochemistry. Our results show that male-dominant expression of GRP is prominent from the onset of puberty and that sexually dimorphism persists into adulthood. These results suggest that androgen surge during male puberty plays an important role in the development and maintenance of the male-specific GRP function in the rat spinal cord.

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  • Perinatal testosterone exposure is critical for the development of the male-specific sexually dimorphic gastrin-releasing peptide system in the lumbosacral spinal cord that mediates erection and ejaculation

    Takumi Oti, Keiko Takanami, Nao Katayama, Tomoca Edey, Keita Satoh, Tatsuya Sakamoto, Hirotaka Sakamoto

    BIOLOGY OF SEX DIFFERENCES   7 ( 1 )   2016.1

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    Background: In rats, a sexually dimorphic spinal gastrin-releasing peptide (GRP) system in the lumbosacral spinal cord projects to spinal centers that control erection and ejaculation. This system controls the sexual function of adult males in an androgen-dependent manner. In the present study, we assessed the influence of androgen exposure on the spinal GRP system during a critical period of the development of sexual dimorphism.
    Methods: Immunohistochemistry was used to determine if the development of the spinal GRP system is regulated by the perinatal androgen surge. We first analyzed the responses of neonates administered with anti-androgen flutamide. To remove endogenous androgens, rats were castrated at birth. Further, neonatal females were administered androgens during a critical period to evaluate the development of the male-specific spinal GRP system.
    Results: Treatment of neonates with flutamide on postnatal days 0 and 1 attenuated the spinal GRP system during adulthood. Castrating male rats at birth resulted in a decrease in the number of GRP neurons and the intensity of neuronal GRP in the spinal cord during adulthood despite testosterone supplementation during puberty. This effect was prevented if the rats were treated with testosterone propionate immediately after castration. Moreover, treating female rats with androgens on the day of birth and the next day, masculinized the spinal GRP system during adulthood, which resembled the masculinized phenotype of adult males and induced a hypermasculine appearance.
    Conclusions: The perinatal androgen surge plays a key role in masculinization of the spinal GRP system that controls male sexual behavior. Further, the present study provides potentially new approaches to treat sexual disorders of males.

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  • Comparative Anatomy of Gastrin-releasing Peptide Pathways in the Trigeminal Sensory System of Mouse and the Asian House Musk Shrew Suncus murinus

    Keiko Takanami, Kaihei Inoue, Hiroki Mukai, Kei Tamura, Takamichi Jogahara, Sen-ichi Oda, Mitsuhiro Kawata, Tatsuya Sakamoto, Hirotaka Sakamoto

    ACTA HISTOCHEMICA ET CYTOCHEMICA   49 ( 6 )   181 - 190   2016

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    Gastrin-releasing peptide (GRP) has recently been identified as an itch-signaling molecule in the primary afferents and spinal cord of rodents. However, little information exists on the expression and localization of GRP in the trigeminal somatosensory system other than in rats. We examined the generality of the trigeminal GRP system in mammals using two distinct species, suncus as a model of specialized placental mammals known to have a well-developed trigeminal sensory system and mice as a representative small laboratory animal. We first analyzed the gross morphology of the trigeminal somatosensory system in suncus to provide a brainstem atlas on which to map GRP distribution. Immunohistochemical analyses showed that 8% of trigeminal ganglion neurons in suncus and 6% in mice expressed GRP. Expression was restricted to cells with smaller somata. The GRP-containing fibers were densely distributed in the superficial layers of the caudal part of the trigeminal spinal nucleus (Vc) but rare in the rostral parts, both in suncus and mice. Expression of GRP receptor mRNA and protein was also detected in the Vc of suncus. Taken together, these results suggest that the trigeminal GRP system mediating itch sensation is conserved in mammals.

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  • Three-dimensional visualization of multiple synapses in thick sections using high-voltage electron microscopy in the rat spinal cord

    Keita Satoh, Keiko Takanami, Kazuyoshi Murata, Mitsuhiro Kawata, Tatsuya Sakamoto, Hirotaka Sakamoto

    Data in Brief   4   566 - 570   2015.9

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    This data article contains complementary figure and movies (Supplementary Movies 1-3) related to the research article entitled, "Effective synaptome analysis of itch-mediating neurons in the spinal cord: a novel immunohistochemical methodology using high-voltage electron microscopy" [7]. It is important to show the synaptic connections at the ultrastructural level to understand the neural circuit, which requires the three-dimensional (3-D) analyses in the electron microscopy. Here, we applied a new sample preparation method, a high-contrast en bloc staining according to the protocol of the National Center for Microscopy and Imaging Research (NCMIR), University of California, San Diego, CA, USA to high-voltage electron microscopy (HVEM) tomography in order to examine the 3-D chemical neuroanatomy of the rat spinal cord. Pre-embedding immunoelectron microscopy was used in this study. HVEM has an excellent potential to directly visualize the ultrastructures in semi-thin sections (~5. μm thick), and we have successfully visualized many itch-mediating synaptic connections and neural networks in the spinal cord using "HVEM tomography". Moreover, the methodology used in this study is simple and can be applied in multiple ways. This is an important contribution to ultrastructural investigations of the central nervous system in the present post-genomic age.

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  • Mudskipper to general behavioral neuroendocrinology

    Tatsuya Sakamoto, Yukitoshi Katayama, Yasuhisa Kobayashi, Kazuhiro Saito, Yoshio Takei

    NIPPON SUISAN GAKKAISHI   81 ( 5 )   868 - 868   2015.9

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  • Osmotic/ionic status of body fluids in the euryhaline cephalopod suggest possible parallel evolution of osmoregulation

    Tatsuya Sakamoto, Satoshi Ogawa, Yudai Nishiyama, Chiaki Akada, Hideya Takahashi, Taro Watanabe, Hiroyuki Minakata, Hirotaka Sakamoto

    SCIENTIFIC REPORTS   5   2015.9

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    Acclimation from marine to dilute environments constitutes among the dramatic evolutionary transitions in the history of life. Such adaptations have evolved in multiple lineages, but studies of the blood/hemolymph homeostasis mechanisms are limited to those using evolutionarily advanced Deuterostome (chordates) and Ecdysozoa (crustaceans). Here, we examined hemolymph homeostasis in the advanced Lophotrochozoa/mollusc, the other unexplored taxa, and its possible regulation by the vasopressin/oxytocin superfamily peptides known to be implicated in fluid homeostasis in Chordata and Arthropoda. The hemolymph osmotic and ionic status in the euryhaline cephalopod (Octopus ocellatus) following transfer from 30-ppt normal seawater to 20 ppt salinity indicate hyperosmo- and hyperionoregulatory abilities for more than 1 week, as in crustaceans and teleost fish. While ventilation frequency decreased by 1 day, Na+/K+-ATPase activity, which has been generally implicated in ion transport, was induced in two of the eight posterior gills after 1 week. In addition, the octopuses were intravenously injected with 1 or 100 ng/g octopressin or cephalotocin, which are Octopus vasopressin/oxytocin orthologs. After 1 day, octopressin, but not cephalotocin, decreased the hemolymph osmolality and Ca concentrations, as well as urinary Na concentrations. These data provide evidence for possible parallel evolution in hyperionoregulatory mechanisms and coordination by conserved peptides.

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  • In vivo imaging of axonal transport of mitochondria in the diseased and aged mammalian CNS. International journal

    Yuji Takihara, Masaru Inatani, Kei Eto, Toshihiro Inoue, Alexander Kreymerman, Seiji Miyake, Shinji Ueno, Masatoshi Nagaya, Ayami Nakanishi, Keiichiro Iwao, Yoshihiro Takamura, Hirotaka Sakamoto, Keita Satoh, Mineo Kondo, Tatsuya Sakamoto, Jeffrey L Goldberg, Junichi Nabekura, Hidenobu Tanihara

    Proceedings of the National Academy of Sciences of the United States of America   112 ( 33 )   10515 - 20   2015.8

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    The lack of intravital imaging of axonal transport of mitochondria in the mammalian CNS precludes characterization of the dynamics of axonal transport of mitochondria in the diseased and aged mammalian CNS. Glaucoma, the most common neurodegenerative eye disease, is characterized by axon degeneration and the death of retinal ganglion cells (RGCs) and by an age-related increase in incidence. RGC death is hypothesized to result from disturbances in axonal transport and in mitochondrial function. Here we report minimally invasive intravital multiphoton imaging of anesthetized mouse RGCs through the sclera that provides sequential time-lapse images of mitochondria transported in a single axon with submicrometer resolution. Unlike findings from explants, we show that the axonal transport of mitochondria is highly dynamic in the mammalian CNS in vivo under physiological conditions. Furthermore, in the early stage of glaucoma modeled in adult (4-mo-old) mice, the number of transported mitochondria decreases before RGC death, although transport does not shorten. However, with increasing age up to 23-25 mo, mitochondrial transport (duration, distance, and duty cycle) shortens. In axons, mitochondria-free regions increase and lengths of transported mitochondria decrease with aging, although totally organized transport patterns are preserved in old (23- to 25-mo-old) mice. Moreover, axonal transport of mitochondria is more vulnerable to glaucomatous insults in old mice than in adult mice. These mitochondrial changes with aging may underlie the age-related increase in glaucoma incidence. Our method is useful for characterizing the dynamics of axonal transport of mitochondria and may be applied to other submicrometer structures in the diseased and aged mammalian CNS in vivo.

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  • Invivo processing and release into the circulation of GFP fusion protein in arginine vasopressin enhanced GFP transgenic rats: response to osmotic stimulation

    Keita Satoh, Takumi Oti, Akiko Katoh, Yoichi Ueta, John F. Morris, Tatsuya Sakamoto, Hirotaka Sakamoto

    FEBS JOURNAL   282 ( 13 )   2488 - 2499   2015.7

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    Arginine vasopressin (AVP) is a neurohypophysial hormone synthesized as a part of a prepropeptide precursor containing the signal peptide, AVP hormone, AVP-associated neurophysin II and copeptin in the hypothalamic neurosecretory neurons. A transgenic (Tg) rat line expressing the AVP-eGFP fusion gene has been generated. To establish the AVP-eGFP Tg rat as a unique model for an analysis of AVP dynamics invivo, we first examined the invivo molecular dynamics of the AVP-eGFP fusion gene, and then the release of GFP in response to physiological stimuli. Double immunoelectron microscopy demonstrated that GFP was specifically localized in neurosecretory vesicles of AVP neurons in this Tg rat. After stimulation of the posterior pituitary with high potassium we demonstrated the exocytosis of AVP neurosecretory vesicles containing GFP at the ultrastructural level. Biochemical analyses indicated that the AVP-eGFP fusion gene is subjected to invivo post-translational modifications like the native AVP gene, and is packaged into neurosecretory vesicles as a fusion protein: copeptin(1-14)-GFP. Moreover, GFP release into the circulating blood appeared to be augmented after osmotic stimulation, like native AVP. Thus, here we show for the first time the invivo molecular processing of the AVP-eGFP fusion gene and stimulated secretion after osmotic stimulation in rats. Because GFP behaved like native AVP in the hypothalamo-pituitary axis, and in particular was released into the circulation in response to a physiological stimulus, the AVP-eGFP Tg rat model appears to be a powerful tool for analyzing neuroendocrine systems at the organismal level.

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  • Effective synaptome analysis of itch-mediating neurons in the spinal cord: A novel immunohistochemical methodology using high-voltage electron microscopy

    Keita Satoh, Keiko Takanami, Kazuyoshi Murata, Mitsuhiro Kawata, Tatsuya Sakamoto, Hirotaka Sakamoto

    NEUROSCIENCE LETTERS   599   86 - 91   2015.7

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    Transmission electron microscopy (TEM) is used for three-dimensional (3-D) analysis of synaptic connections in neuroscience research. However, 3-D reconstruction of the synapses using serial ultrathin sections is a powerful but tedious approach requiring advanced technical skills. High-voltage electron microscopy (HVEM) allows examination of thicker sections of biological specimens due to the increased penetration of the more accelerated electrons, which is useful to analyze the 3-D structure of biological specimens. However, it is still difficult to visualize the neural networks and synaptic connections in 3-D using HVEM because of insufficient and non uniform heavy metal staining in the membranous structures in semi-thin sections. Here, we present the successful chemical 3-D neuroanatomy of the rat spinal dorsal horn at the ultrastructural level as a first step for effective synaptome analysis by applying a high-contrast en bloc staining method to immune-HVEM tomography. Our new approach made it possible to examine many itch-mediating synaptic connections and neural networks in the spinal cord simultaneously using HVEM tomography. This novel 3-D electron microscopy is very useful for the analysis of synaptic structure and the chemical neuroanatomy at the 3-D ultrastructural level. (C) 2015 Elsevier Ireland Ltd. All rights reserved.

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  • Neurohypophysial Hormones Regulate Amphibious Behaviour in the Mudskipper Goby

    Tatsuya Sakamoto, Yudai Nishiyama, Aoi Ikeda, Hideya Takahashi, Susumu Hyodo, Nao Kagawa, Hirotaka Sakamoto

    PLOS ONE   10 ( 7 )   2015.7

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    The neurohypophysial hormones, arginine vasotocin and isotocin, regulate both hydromineral balance and social behaviors in fish. In the amphibious mudskipper, Periophthalmus modestus, we previously found arginine-vasotocin-specific regulation of aggressive behavior, including migration of the submissive subordinate into water. This migration also implies the need for adaptation to dehydration. Here, we examined the effects of arginine vasotocin and isotocin administration on the amphibious behavior of individual mudskippers in vivo. The mudskippers remained in the water for an increased period of time after 1-8 h of intracerebroventricular (ICV) injection with 500 pg/g arginine vasotocin or isotocin. The 'frequency of migration' was decreased after ICV injection of arginine vasotocin or isotocin, reflecting a tendency to remain in the water. ICV injections of isotocin receptor antagonist with arginine vasotocin or isotocin inhibited all of these hormonal effects. In animals kept out of water, mRNA expression of brain arginine vasotocin and isotocin precursors increased 3- and 1.5-fold, respectively. Given the relatively wide distribution of arginine vasotocin fibres throughout the mudskipper brain, induction of arginine vasotocin and isotocin under terrestrial conditions may be involved also in the preference for an aquatic habitat as ligands for brain isotocin receptors.

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  • 07B01 瀬戸内海を題材とした小学校理科第6学年「生き物のくらしと環境」の授業開発 : Place-Based Educationの観点を参考にして(環境教育,一般研究発表(口頭発表))

    土屋 美和, 定金 なつみ, 藤井 浩樹, 田中 喜一郎, 筒井 直昭, 小林 靖尚, 坂本 竜哉

    日本理科教育学会全国大会要項   ( 65 )   199 - 199   2015

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  • Basic reproductive biology of daggertooth pike conger, Muraenesox cinereus: A possible model for oogenesis in Anguilliformes

    Kobayashi, Y, T. Mototani

    Zoological Letters 1(1): 1-7 (2015)   2015

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  • Hormonal Regulation of Body Fluid in Teleost Fishes

    SAKAMOTO, T

    Bulletin of the Society of Sea Water Science, Japan 69(4): 244-246 (2015)   2015

  • Artificial burrow sizes for capturing the North American invasive crayfish <i>Procambarus clarkii</i>.

    USHIMI Haruna, MIYATAKE Yuta, TSUTSUI Naoaki, SAKAMOTO Tatsuya, NAKATA Kazuyoshi

    Ecology and Civil Engineering   18 ( 2 )   79 - 86   2015

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    We conducted aquarium experiments of artificial burrow preference by the North American invasive crayfish <i>Procambarus clarkii</i> to clarify the artificial burrow sizes for capturing <i>P. clarkii</i> in invaded freshwater areas (e.g., paddy fields, agricultural channels, rivers, lakes, ponds, etc.). In the aquarium experiments, we observed the preference for internal diameters and lengths of artificial burrows by <i>P. clarkii</i>, which were made from straight polyvinyl chloride pipes. The relationship between the total length (TL)(X, mm) of <i>P. clarkii</i> and the preferred internal diameter (Y, mm) of artificial burrows was described by the significant linear regression: Y=0.58X+4.26( n=49, P<0.001). Among the artificial burrows of different lengths, TL×4 burrows were mainly preferred by <i>P. clarkii</i>. Based on these results, we propose artificial burrow sizes for use to eradicate <i>P. clarkii</i>.

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  • Effect of environmental salinity on expression of adrenomedullin genes suggests osmoregulatory activity in the medaka, Oryzias latipes.

    Ogoshi, M, K. Kato

    Zoological Letters 1(1): 1-7 (2015)   2015

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  • Requirement of vasotocin for being a winner in love triangle relationships (two males and one female) of medaka fish

    Yokoi S, Sakamoto, T

    AQUABIOLOGY 37(6) 591-597 2015   2015

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  • P4-12 AVP-eGFP TgラットにおけるインビボGFP動態(細胞生物・電子顕微鏡,ポスター発表,組織化学のモーダルシフト,第56回日本組織細胞化学会総会・学術集会)

    佐藤 慧太, 越智 拓海, 加藤 明子, 上田 陽一, Morris John F, 坂本 竜哉, 坂本 浩隆

    日本組織細胞化学会総会プログラムおよび抄録集   ( 56 )   72 - 72   2015

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    Other Link: http://search.jamas.or.jp/link/ui/2016046963

  • P8-03 霊長類ニホンザルの脊髄におけるgastrin-releasing peptide系の存在(脳機能,ポスター発表,組織化学のモーダルシフト,第56回日本組織細胞化学会総会・学術集会)

    伊藤 隆志, 高浪 景子, 越智 拓海, 小林 靖尚, 佐藤 慧太, 高橋 俊次, 上田 康雅, 坂本 竜哉, 坂本 浩隆

    日本組織細胞化学会総会プログラムおよび抄録集   ( 56 )   78 - 78   2015

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  • 卵黄形成抑制ホルモンの作用機序解明に向けたクルマエビ卵巣の遺伝子の網羅的解析

    筒井直昭, 小林靖尚, 泉川晃一, 坂本竜哉

    日本水産学会大会講演要旨集   2014   100   2014.9

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  • Distribution of Gastrin-Releasing Peptide in the Rat Trigeminal and Spinal Somatosensory Systems

    Keiko Takanami, Hirotaka Sakamoto, Ken Ichi Matsuda, Keita Satoh, Takashi Tanida, Shunji Yamada, Kaihei Inoue, Takumi Oti, Tatsuya Sakamoto, Mitsuhiro Kawata

    JOURNAL OF COMPARATIVE NEUROLOGY   522 ( 8 )   1858 - 1873   2014.6

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    Gastrin-releasing peptide (GRP) has recently been identified as an itch-specific neuropeptide in the spinal sensory system in mice, but there are no reports of the expression and distribution of GRP in the trigeminal sensory system in mammals. We characterized and compared GRP-immunoreactive (ir) neurons in the trigeminal ganglion (TG) with those in the rat spinal dorsal root ganglion (DRG). GRP immunoreactivity was expressed in 12% of TG and 6% of DRG neurons and was restricted to the small- and medium-sized type cells. In both the TG and DRG, many GRP-ir neurons also expressed substance P and calcitonin gene-related peptide, but not isolectin B-4. The different proportions of GRP and transient receptor potential vanilloid 1 double-positive neurons in the TG and DRG imply that itch sensations via the TG and DRG pathways are transmitted through distinct mechanisms. The distribution of the axon terminals of GRP-ir primary afferents and their synaptic connectivity with the rat trigeminal sensory nuclei and spinal dorsal horn were investigated by using light and electron microscopic histochemistry. Although GRP-ir fibers were rarely observed in the trigeminal sensory nucleus principalis, oralis, and interpolaris, they were predominant in the superficial layers of the trigeminal sensory nucleus caudalis (Vc), similar to the spinal dorsal horn. Ultrastructural analysis revealed that GRP-ir terminals contained clear microvesicles and large dense-cored vesicles, and formed asymmetric synaptic contacts with a few dendrites in the Vc and spinal dorsal horn. These results suggest that GRP-dependent orofacial and spinal pruriceptive inputs are processed mainly in the superficial laminae of the Vc and spinal dorsal horn. J. Comp. Neurol. 522:1858-1873, 2014. (c) 2013 Wiley Periodicals, Inc.

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  • Effects of Inorganic Mercury and Methylmercury on Osteoclasts and Osteoblasts in the Scales of the Marine Teleost as a Model System of Bone

    Koji Yachiguchi, Toshio Sekiguchi, Masaki Nakano, Atsuhiko Hattori, Megumi Yamamoto, Kei-ichiro Kitamura, Masahiro Maeda, Yoshiaki Tabuchi, Takashi Kondo, Hiromitsu Kamauchi, Hajime Nakabayashi, Ajai K. Srivastav, Kazuichi Hayakawa, Tatsuya Sakamoto, Nobuo Suzuki

    ZOOLOGICAL SCIENCE   31 ( 5 )   330 - 337   2014.5

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    To evaluate the effects of inorganic mercury (InHg) and methylmercury (MeHg) on bone metabolism in a marine teleost, the activity of tartrate-resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP) as indicators of such activity in osteoclasts and osteoblasts, respectively, were examined in scales of nibbler fish (Girella punctata). We found several lines of scales with nearly the same TRAP and ALP activity levels. Using these scales, we evaluated the influence of InHg and MeHg. TRAP activity in the scales treated with InHg (10(-5) and 10(-4) M) and MeHg (10(-6) to 10(-4) M) during 6 hrs of incubation decreased significantly. In contrast, ALP activity decreased after exposure to InHg (10(-5) and 10(-4) M) and MeHg (10(-)6 to 10(-4) M) for 18 and 36 hrs, although its activity did not change after 6 hrs of incubation. As in enzyme activity 6 hrs after incubation, mRNA expression of TRAP (osteoclastic marker) decreased significantly with InHg and MeHg treatment, while that of collagen (osteoblastic marker) did not change significantly. At 6 hrs after incubation, the mRNA expression of metallothionein, which is a metal-binding protein in osteoblasts, was significantly increased following treatment with InHg or MeHg, suggesting that it may be involved in the protection of osteoblasts against mercury exposure up to 6 hrs after incubation. To our knowledge, this is the first report of the effects of mercury on osteoclasts and osteoblasts using marine teleost scale as a model system of bone.

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  • 軟骨魚類アカエイの子宮内液に含まれるタンパク質の精製と解析

    筒井直昭, 小林靖尚, 坂本竜哉

    日本水産学会大会講演要旨集   2014   171   2014.3

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  • Androgen regulates development of the sexually dimorphic gastrin-releasing peptide neuron system in the lumbar spinal cord: Evidence from a mouse line lacking androgen receptor in the nervous system

    Hirotaka Sakamoto, Kazuhiro Saito, Clarisse Marie-Luce, Kalina Raskin, Takumi Oti, Keita Satoh, Kei Tamura, Tatsuya Sakamoto, Sakina Mhaouty-Kodja

    NEUROSCIENCE LETTERS   558   109 - 114   2014.1

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    Androgens including testosterone, organize the nervous system as well as masculine external and internal genitalia during the perinatal period. Androgen organization involves promotion of masculine body features, usually by acting through androgen receptors (ARs). We have recently demonstrated that the gastrin-releasing peptide (GRP) system in the lumbar spinal cord also mediates spinal centers promoting penile reflexes during male sexual behavior in rats. Testosterone may induce sexual differentiation of this spinal GRP system during development and maintain its activation in adulthood. In the present study, we examined the role of ARs in the nervous system regulating the development of the sexually dimorphic GRP system. For this purpose, we used a conditional mouse line selectively lacking the AR gene in the nervous system. AR foxed males carrying (mutants) or not (controls) the nestin-Cre transgene were castrated in adulthood and supplemented with physiological amounts of testosterone. Loss of AR expression in the nervous system resulted in a significant decrease in the number of GRP neurons compared to control littermates. Consequently, the intensity of GRP axonal projections onto the lower lumbar and upper sacral spinal cord was greater in control males than in mutant males. These results suggest that ARs expressed in the nervous system play a significant role in the development of the GRP system in the male lumbar spinal cord. The AR-deletion mutation may attenuate sexual behavior and activity of mutant males via spinal GRP system-mediated neural mechanisms. (C) 2013 Elsevier Ireland Ltd. All rights reserved.

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  • Okayama University's Approach in Spreading Marine Education:A Focus on Cross-Learning in Science and Literature based on a Local Community Linkage featuring "The Expedition of Japanese Eel"

    KOBAYASHI Yasuhisa, TSUTSUI Naoaki, SAITO Kazuhiro, SAKAMOTO Tatsuya, FUJII Hiroki

    JSSE Research Report   29 ( 3 )   79 - 82   2014

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  • Effects of fasting and refeeding on intestinal cell proliferation and apoptosis in hammerhead shark (Sphyrna lewini).

    H. Takahashi, S. Hyodo, T. Abe, C. Takagi, E.G. Grau, T. Sakamoto

    J Coast Life Med. 2 (2014) 253-258   2014

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  • Marine macrophyte (eelgrass, Zostera marina) bed creation base research for conservation (2) The function of coleoptile in the seed germination of the eelgrass: Factor recognising bottom mud surface.

    T. Fukuda, Y. Kohda, T. Sakamoto

    J Kibi Int Univ Res Inst Health Welfare. 15 (2014) 13-19.   2014

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  • Marine macrophyte (eelgrass, Zostera marina) bed creation base research for conservation (1) The seeding depth of the seed of eelgrass and the growth beginning of cotyledon.

    T. Fukuda, Y. Kohda, T. Sakamoto

    J Kibi Int Univ Res Inst Health Welfare. 15 (2014) 7-12.   2014

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  • Diverse hormonal control of osmoregulation in euryhaline teleosts

    Y. Takei, H. Takahashi, J. Hiroi, T. Sakamoto

    Am J Physiol Regul Integr Comp Physiol. 307 (2014) 778-792   2014

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  • Functions of two distinct "prolactin-releasing peptides" evolved from a common ancestral gene

    Tetsuya Tachibana, Tatsuya Sakamoto

    FRONTIERS IN ENDOCRINOLOGY   5   2014

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    Prolactin-releasing peptide (PrRP) is one of the RF-amide peptides and was originally identified in the bovine hypothalamus as a stimulator of prolactin (PRL) release. Independently, another RF-amide peptide was found in Japanese crucian carp and named Carassius-RFa (C-RFa), which shows high homology to PrRP and stimulates PRL secretion in teleost fish. Therefore, C-RFa has been recognized as fish PrRP. However, recent work has revealed that PrRP and C-RFa in non-mammalian vertebrates are encoded by separate genes originated through duplication of an ancestral gene. Indeed, both PrRP and C-RFa are suggested to exist in teleost, amphibian, reptile, and avian species. Therefore, we propose that non-mammalian PrRP (C-RFa) be renamed PrRP2. Despite a common evolutionary origin, PrRP2 appears to be a physiological regulator of PRL, whereas this is not a consistent role for PrRP itself. Further work revealed that the biological functions of PrRP and PrRP2 are not limited solely to PRL release, because they are also neuro-modulators of several hypothalamus pituitary axes and are involved in some brain circuits related to the regulation of food intake, stress, and cardiovascular functions. However, these actions appear to be different among vertebrates. For example, central injection of PrRP inhibits feeding behavior in rodents and teleosts, while it stimulates it in chicks. Therefore, both PrRP and PrRP2 have acquired diverse actions through evolution. In this review, we integrate the burgeoning information of structures, expression profiles, and multiple biological actions of PrRP in higher vertebrates, as well as those of PrRP2 in non-mammals.

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  • Potential roles of arginine-vasotocin in the regulation of aggressive behavior in the mudskipper (Periophthalmus modestus)

    Nao Kagawa, Yudai Nishiyama, Kanoko Kato, Hideya Takahashi, Yasuhisa Kobayashi, Hirotaka Sakamoto, Tatsuya Sakamoto

    General and Comparative Endocrinology   194   257 - 263   2013.12

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    The hypothalamic hormones, arginine-vasotocin (VT) and isotocin (IT), play central roles in osmoregulation and in the regulation of social behaviors including aggressive behavior in many vertebrates including fish. Here, we examined whether these hormones are associated with aggressive behavior in the mudskipper (Periophthalmus modestus). The mudskipper is an amphibious fish, which lives in the brackish water of river mouths and displays unique aggressive behavior. Upon introduction to each other in an experimental tank with aquatic and terrestrial areas, a pair of males can be classified as aggressive dominant or submissive subordinate based on the frequency of their aggressive acts, which is significantly higher in dominant male. Additionally, the length of stay in terrestrial area of dominant was longer than that of the subordinate. The latter remained in aquatic area almost throughout the period of behavioral observation. The expression of brain VT mRNA was significantly higher in subordinate than in dominant, whereas neither IT mRNA expression nor plasma cortisol level differed between subordinate and dominant male. On the other hand, an intracerebroventricular injection of VT increased aggressive behaviors in mudskippers. In addition to known roles of VT in mediation of aggressive behavior, these results may shed light on the role of endogenous VT toward water migration in submissive mudskippers. The amphibious fish is a valuable experimental model to observe the relationship between effects of central VT on the osmoregulation and social behavioral regulation in vertebrates. © 2013.

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  • Central administration of prolactin-releasing peptide shifts the utilities of metabolic fuels from carbohydrate to lipids in chicks

    Tetsuya Tachibana, Shunsuke Moriyama, Md Sakirul Islam Khan, Tatsuya Sakamoto

    PHYSIOLOGY & BEHAVIOR   120   40 - 45   2013.8

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    We have recently identified prolactin (PRL)-releasing peptides (PrRPs) and their stimulating effects on feeding behavior in chicks. To investigate further metabolic functions of PrRP, the present study was performed to clarify whether intracerebroventricular (ICV) injection of PrRP31, an active form of PrRP in chicks, affects heat production (HP), respiratory quotient (RQ) and plasma concentrations of metabolic fuels in chicks. The ICV injection of PrRP31 (94 and 375 pmol) did not affect HP but significantly lowered RQ. The change in RQ implies that PrRP31 shifted the utility of metabolic fuels in the body. This idea was confirmed by subsequent results in which ICV injection of PrRP31 significantly reduced glucose but increased non-esterified fatty acid concentrations in plasma. These shifts in blood metabolic fuels would not be through the increased plasma insulin, because the ICV injection of PrRP31 significantly decreased plasma insulin concentration. On the other hand, ICV injection of another orexigenic peptide, neuropeptide Y (NPY) also induced the insulin release and the metabolic effects were similar to those of PrRP31. Because ICV injection of PrRP31 increased NPY mRNA in the diencephalon, the NPY may mediate the metabolic functions of PrRP31. In summary, the present study suggests that central PrRP31 shifts the utilities of peripheral energy sources, which is not via hyperinsulinemia but via the diencephalon. (C) 2013 Elsevier Inc. All rights reserved.

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  • Static and Dynamic Hypergravity Responses of Osteoblasts and Osteoclasts in Medaka Scales

    Sachiko Yano, Kei-ichiro Kitamura, Yusuke Satoh, Masaki Nakano, Atsuhiko Hattori, Toshio Sekiguchi, Mika Ikegame, Hiroshi Nakashima, Katsunori Omori, Kazuichi Hayakawa, Atsuhiko Chiba, Yuichi Sasayama, Sadakazu Ejiri, Yuko Mikuni-Takagaki, Hiroyuki Mishima, Hisayuki Funahashi, Tatsuya Sakamoto, Nobuo Suzuki

    ZOOLOGICAL SCIENCE   30 ( 3 )   217 - 223   2013.3

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    Fish scales are a form of calcified tissue similar to that found in human bone. In medaka scales, we detected both osteoblasts and osteoclasts and subsequently developed a new scale assay system. Using this system, we analyzed the osteoblastic and osteoclastic responses under 2-, 3-, and 4-gravity (G) loading by both centrifugation and vibration. After loading for 10 min, the scales from centrifugal and vibration loading were incubated for 6 and 24 hrs, respectively, after which the osteoblastic and osteoclastic activities were measured. Osteoblastic activity significantly increased under 2- to 4-G loading by both centrifugation and vibration. In contrast, we found that osteoclastic activity significantly decreased under 2- and 3-G loading in response to both centrifugation and vibration. Under 4-G loading, osteoclastic activity also decreased on centrifugation, but significantly increased under 4-G loading by vibration, concomitant with markedly increased osteoblastic activity. Expression of the receptor activator of the NF-kappa B ligand (RANKL), an activation factor of osteoclasts expressed in osteoblasts, increased significantly under 4-G loading by vibration but was unchanged by centrifugal loading. A protein sequence similar to osteoprotegerin (OPG), which is known as an osteoclastogenesis inhibitory factor, was found in medaka using our sequence analysis. The ratio of RANKL/OPG-like mRNAs in the vibration-loaded scales was significantly higher than that in the control scales, although there was no difference between centrifugal loaded scales and the control scales. Accordingly, medaka scales provide a useful model by which to analyze bone metabolism in response to physical strain.

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  • The role of 'mineralocorticoids' in teleost fish: Relative importance of glucocorticoid signaling in the osmoregulation and 'central' actions of mineralocorticoid receptor

    Hideya Takahashi, Tatsuya Sakamoto

    GENERAL AND COMPARATIVE ENDOCRINOLOGY   181   223 - 228   2013.1

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    It has long been held that cortisol, a glucocorticoid in many vertebrates, performs glucocorticoid and mineralocorticoid actions in the teleost fish since it lacks aldosterone. However, in addition to the counterparts of tetrapod mineralocorticoid receptors (MRs), 11-deoxycorticosterone (DOC) has been recently identified as a specific endogenous ligand for the MRs in teleosts. Here, we point out the minor role of mineralocorticoid signaling (i.e., DOC-MR) in the osmoregulation compared with those of glucocorticoid signaling (i.e., cortisol-glucocorticoid receptor [GR]), and review the current findings on the physiological roles of the DOC-MR in teleosts. Cortisol promotes both freshwater and seawater adaptation via the GRs in the osmoregulatory organs such as gills and gastrointestinal tracts, but the expressions of MR mRNA are abundant in the brains especially in the key components of the stress axis and cerebellums. Together with the behavioral effects of intracerebroventricular injection with DOC, the MR is suggested to play an important role in the brain dependent behaviors. Since the abundant expression of central MRs has been reported also in higher vertebrates and the MR is thought to be ancestral to the GR, the role of MR in fish might reflect the principal and original function of corticosteroid signaling. Functional evolution of corticosteroid systems is summarized and areas in need of research like our on-going experiments with MR-knockout medaka are outlined. (C) 2012 Elsevier Inc. All rights reserved.

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  • Osmolality and ionic status of hemolymph and branchial Na+/K+-ATPase in adult mitten crab during seawater adaptation.

    T. Sakamoto, S. Ogawa, Y. Nishiyama, W, Godo, H. Takahashi

    HOAJ Biol. 2:5 (2013) 1-7.   2013

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  • Morphological responses of mitochondria-rich cells to hypersaline environment in the Australian mudskipper, Periophthalmus minutus (vol 29, pg 444, 2012)

    N. Itoki, T. Sakamoto, M. Hayashi, T. Takeda, A. Ishimatsu

    ZOOLOGICAL SCIENCE   29 ( 11 )   794 - 794   2012.11

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  • Three-dimensional evaluation of the spinal local neural network revealed by the high-voltage electron microscopy: a double immunohistochemical study

    Takumi Oti, Keita Satoh, Kazuhiro Saito, Kazuyoshi Murata, Mitsuhiro Kawata, Tatsuya Sakamoto, Hirotaka Sakamoto

    HISTOCHEMISTRY AND CELL BIOLOGY   138 ( 4 )   693 - 697   2012.10

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    Three-dimensional (3-D) analysis of anatomical ultrastructures is important in biological research. However, 3-D image analysis on exact serial sets of ultra-thin sections from biological specimens is very difficult to achieve, and limited information can be obtained by 3-D reconstruction from these sections due to the small area that can be reconstructed. On the other hand, the high-penetration power of electrons by an ultra-high accelerating voltage enables thick sections of biological specimens to be examined. High-voltage electron microscopy (HVEM) is particularly useful for 3-D analysis of the central nervous system because considerably thick sections can be observed at the ultrastructure level. Here, we applied HVEM tomography assisted by light microscopy to a study of the 3-D chemical neuroanatomy of the rat lower spinal cord annotated by double-labeling immunohistochemistry. This powerful methodology is useful for studying molecular and/or chemical neuroanatomy at the 3-D ultrastructural level.

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  • Growth, energetics and the cortisol-hepatic glucocorticoid receptor axis of medaka (Oryzias latipes) in various salinities

    Maho Ogoshi, Kanoko Kato, Hideya Takahashi, Toshitaka Ikeuchi, Tsukasa Abe, Tatsuya Sakamoto

    GENERAL AND COMPARATIVE ENDOCRINOLOGY   178 ( 2 )   175 - 179   2012.9

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    We examined growth of euryhaline Japanese medaka (Oryzias latipes) after transfer to freshwater or seawater from isotonic saline. Growth was unaffected by the different salinities for 1 week, but the body weight increase and BMI of fish kept in freshwater for 2-3 weeks were significantly higher than those in the isotonic controls. These results may reflect the usual habitat of this species. To assess the basis for the difference in growth, energetics and the hepatic stress axis were evaluated 1 week after the transfer. Unexpectedly, despite the higher growth rate, the rate of routine oxygen consumption was significantly higher in freshwater. Plasma cortisol levels in freshwater were significantly higher than those in seawater, and the mRNA levels of the glucocorticoid receptor (GR1) in the liver were significantly lower in freshwater and seawater, compared to that in isotonic saline. Branchial Na+/K+-ATPase activities were also reduced significantly in freshwater and seawater, compared to that in isotonic saline. The higher levels of hepatic GR1 expression and branchial Na+/K+-ATPase activity in isotonic salinity than those in freshwater and seawater for 1 week may account for the lower growth rate under the isotonic condition. After 3 weeks, however, the Na+/K+-ATPase activity in seawater was significantly higher than that in freshwater. No significant difference in growth rate between freshwater and seawater groups indicates that medaka is a good model for studies of hypo- and hyperosmotic adaptations, since osmoregulation is not strongly associated with size and growth. (C) 2012 Elsevier Inc. All rights reserved.

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  • Prostaglandin E-2 Increases Both Osteoblastic and Osteoclastic Activity in the Scales and Participates in Calcium Metabolism in Goldfish

    Katsunori Omori, Shigehito Wada, Yusuke Maruyama, Atsuhiko Hattori, Kei-Ichiro Kitamura, Yusuke Sato, Masayuki Nara, Hisayuki Funahashi, Koji Yachiguchi, Kazuichi Hayakawa, Masato Endo, Rei Kusakari, Sachiko Yano, Ajai K. Srivastav, Takashi Kusui, Sadakazu Ejiri, Wenxi Chen, Yoshiaki Tabuchi, Yukihiro Furusawa, Takashi Kondo, Yuichi Sasayama, Takumi Nishiuchi, Masaki Nakano, Tatsuya Sakamoto, Nobuo Suzuki

    ZOOLOGICAL SCIENCE   29 ( 8 )   499 - 504   2012.8

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    Using our original in vitro assay system with goldfish scales, we examined the direct effect of prostaglandin E-2 (PGE(2)) on osteoclasts and osteoblasts in teleosts. In this assay system, we measured the activity of alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) as respective indicators of each activity in osteoblasts and osteoclasts. ALP activity in scales significantly increased following treatment at high concentration of PGE(2) (10(-7) and 10(-6) M) over 6 hrs of incubation. At 18 hrs of incubation, ALP activity also significantly increased in the PGE(2) (10(-9) to 10(-6) M)-treated scale. In the case of osteoclasts, TRAP activity tended to increase at 6 hrs of incubation, and then significantly increased at 18 hrs of incubation by PGE(2) (10(-7) to 10(-6) M) treatment. At 18 hrs of incubation, the mRNA expression of osteoclastic markers (TRAP and cathepsin K) and receptor activator of the NF-kappa B ligand (RANKL), an activating factor of osteoclasts expressed in osteoblasts, increased in PGE(2) treated-scales. Thus, PGE(2) acts on osteoblasts, and then increases the osteoclastic activity in the scales of goldfish as it does in the bone of mammals. In an in vivo experiment, plasma calcium levels and scale TRAP and ALP activities in the PGE(2)-injencted goldfish increased significantly. We conclude that, in teleosts, PGE(2) activates both osteoblasts and osteoclasts and participates in calcium metabolism.

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  • Cloning of two members of the calcitonin-family receptors from stingray, Dasyatis akajei: Possible physiological roles of the calcitonin family in osmoregulation

    Nobuo Suzuki, Toshio Sekiguchi, Honoo Satake, Kanoko Kato, Yudai Nishiyama, Hideya Takahashi, Janine A. Danks, T. John Martin, Atsuhiko Hattori, Masaki Nakano, Makiko Kakikawa, Sotoshi Yamada, Maho Ogoshi, Susumu Hyodo, Yoko Yamaguchi, Vishwajit S. Chowdhury, Kazuichi Hayakawa, Hisayuki Funahashi, Tatsuya Sakamoto, Yuichi Sasayama

    GENE   499 ( 2 )   326 - 331   2012.5

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    In cartilaginous fish, two cDNAs encoding calcitonin-family receptors were isolated for the first time from the stingray brain. The open reading frame of one receptor cDNA coded a 525-amino acid protein. The amino acid identity of this receptor to human calcitonin-receptor-like receptor (CRLR) is 64.5%, frog CRLR is 64.7%, and flounder CRLR is 61.2% and this was higher than to human calcitonin receptor (CTR) (46.1%), frog CTR (54.7%), and flounder CTR (48.9%). We strongly suggested that this receptor is a ray CRLR based on phylogenetic analysis. In case of the second receptor, amino acid identity among CRLRs (human 50.5%, frog 50.7%, flounder 48.0%) and CTRs (human 43.2%, frog 49.1%, flounder 41.8%) was similar. From phylogenetic analysis of both CRLRs and CTRs, we believe that this receptor is ray CTR. The expression of ray CRLR mRNA was predominantly detected in the nervous system (brain) and vascular system (atrium, ventricle, and gill), which reflects the similar localization of CGRP in the nervous and vascular systems as mammals. It was observed that the second receptor was expressed in several tissues, namely cartilage, brain, pituitary gland, gill, atrium, ventricle, pancreas, spleen, liver, gall bladder, intestine, rectal gland, kidney, testis and ovary. This localization pattern was very similar to flounder CTR. Both receptor mRNAs were strongly expressed in the gill. This suggests that the calcitonin-family members are involved in the osmoregulation of stingray as this fish is known to be euryhaline. When a stingray was transferred to diluted seawater (20% seawater), the expression of both receptors significantly decreased in the gill. Similar results were obtained in the kidney of the stingray. Thus, our cloning and isolation of both receptors in the stingray will be helpful for elucidation of their physiological role(s) such as osmoregulation including calcium metabolism of cartilaginous fish. (C) 2012 Elsevier B.V. All rights reserved.

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  • Rapid signaling of steroid hormones in the vertebrate nervous system

    Hirotaka Sakamoto, Hideya Takahashi, Ken-Ichi Matsuda, Mayumi Nishi, Keiko Takanami, Maho Ogoshi, Tatsuya Sakamoto, Mitsuhiro Kawata

    FRONTIERS IN BIOSCIENCE-LANDMARK   17   996 - 1019   2012.1

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    Steroid hormones easily cross the blood-brain barrier because of their physicochemical lipid solubility. The hormones act through nuclear receptor-mediated mechanisms and modulate gene transcription. In contrast to their genomic actions, the non-genomic rapid action of steroid hormones, acting via various types of membrane-associated receptors, reveals pharmacological properties that are distinct from the actions of the intracellular nuclear receptors. As a result, non-genomic rapid actions have gained increased scientific interest. However, insight into the phylogenic and/or comparative actions of steroids in the brain is still poorly understood. In this review, we summarize recent findings concerning the rapid, non-genomic signaling of steroid hormones in the vertebrate central nervous system, and we discuss (using a comparative view from fish to mammals) recently published data regarding the mechanism underlying physiology and behavior.

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  • Prolactin inhibits osteoclastic activity in the goldfish scale: a novel direct action of prolactin in teleosts.

    H. Takahashi, N. Suzuki, C. Takagi, M. Ikegame, T. Yamamoto, A. Takahashi, S. Moriyama, A. Hattori, T. Sakamoto

    Zool Sci, Virtual Issue, (2012)   2012

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  • Comparative and general aspects of calcium homeostasis and its hormonal regulations.

    N. Suzuki, T. Sakamoto

    Zool Sci, Virtual Issue, (2012)   2012

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  • Hemolymph osmotic, ionic status, and branchial Na<sup>+</sup>/K<sup>+</sup>-ATPase activity under varying environmental conditions in the intertidal grapsid crab, Gaetice depressusd

    Takeshi Nanba, Hideya Takahashi, Tsukasa Abe, Waichirou Godo, Maho Ogoshi, Hirotaka Sakamoto, Naoaki Tsutsui, Tatsuya Sakamoto

    International Aquatic Research   4 ( 1 )   2012

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    © 2012, Nanba et al.; licensee Springer. Osmo- and ionoregulatory abilities were examined in the intertidal grapsid crab, Gaetice depressus, transferred from normal seawater (30 ppt) to low (10 ppt) or high (50 ppt) salinities for 2 and 10 days, in addition to animals kept out of water for 2 days. The results of the hemolymph osmotic and ionic status indicate that G. depressus is able to adapt for more than 10 days in these salinities and for 2 days under terrestrial conditions. Especially, the free Ca2+ concentration was relatively maintained compared with concentrations of monovalent ions and osmolality values in 10 and 50 ppt, partly using the complexed calcium (total minus free calcium) as an internal reserve in the hemolymph. In 10 ppt, complexed calcium disappeared from the hemolymph after 10 days, indicating that all the hemolymph calcium was ionized. In 50 ppt, free Ca2+ was regulated to lower levels than concentrations in the medium, while total calcium increased to higher levels after 2 days. Examination of Na+/K+-ATPase activity, which has been implicated in ion transport in many crustaceans, revealed that induction of high Na+/K+-ATPase activity varies among the posterior gills in response to salinities. Ten-ppt salinity induces activity in two of the posterior gills (gill numbers 6 and 7, eight in total), albeit with differing degrees of response. In contrast, 50-ppt salinity stimulates the activity primarily in gill number 8, suggesting that this gill may be associated specifically with ion excretion in G. depressus. As a euryhaline amphibious crab, this abundant species around Japan will serve as a model to study the osmotic/ionic regulatory mechanisms which operate in crustaceans.

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  • 異なる浸透圧におけるメダカの成長と体液調節・エネルギー代謝

    御輿 真穂, 坂本 竜哉

    比較内分泌学   38 ( 147 )   209 - 211   2012

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    Language:Japanese   Publisher:Japan Society for Comparative Endocrinology  

    DOI: 10.5983/nl2008jsce.38.209

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    Other Link: https://jlc.jst.go.jp/DN/JALC/10013529337?from=CiNii

  • Corticosteroids stimulate the amphibious behavior in mudskipper: Potential role of mineralocorticoid receptors in teleost fish

    Tatsuya Sakamoto, Chie Mori, Shogo Minami, Hideya Takahashi, Tsukasa Abe, Daisuke Ojima, Maho Ogoshi, Hirotaka Sakamoto

    PHYSIOLOGY & BEHAVIOR   104 ( 5 )   923 - 928   2011.10

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    It has long been held that cortisol, a glucocorticoid in many vertebrates, carries out both glucocorticoid and mineralocorticoid actions in teleost fish. However, 11-deoxycorticosterone (DOC) has been identified as a specific endogenous ligand for the teleostean mineralocorticoid receptor (MR). Furthermore, the expressions of MR mRNA are modest in the osmoregulatory organs, but considerably higher in the brain of most teleosts. These recent findings suggest that the mineralocorticoid system (DOC/MR) may carry out some behavioral functions in fish. To test this possibility, we examined the effects of cortisol and DOC administration in the amphibious behavior in mudskipper (Periophthalmus modestus) in vivo. It was found that mudskippers remained in the water for an increased period of time when they were immersed into 5 mu M DOC or cortisol for 8 h. Additionally, an exposure to 25 mu M DOC for 4 to 8 h caused a decreased migratory frequency of mudskippers to the water, reflected a tendency to remain in the water. It was further observed that after 8 h of intracerebroventricular (ICV) injection with 0.3 pmol DOC or cortisol the staying period in the water increased in fish. The migratory frequency was decreased after ICV DOC injection which indicated that fishes stayed in the water. Concurrent ICV injections of cortisol with RU486 [a specific glucocorticoid-receptor (GR) antagonist] inhibited only the partial effects of cortisol. Together with no changes in the plasma DOC concentrations under terrestrial conditions, these results indicate the involvement of brain MRs as cortisol receptors in the preference for an aquatic habitat of mudskippers. Although the role of GR signaling cannot be excluded in the aquatic preference, our data further suggest that the MR may play an important role in the brain dependent behaviors of teleost fish. (C) 2011 Elsevier Inc. All rights reserved.

    DOI: 10.1016/j.physbeh.2011.06.002

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  • Embryonic development and larval behavior of the kissing loach (Parabotia curta): adaptations to an ephemeral, hypoxic environment

    Tsukasa Abe, Tatsuya Sakamoto

    ICHTHYOLOGICAL RESEARCH   58 ( 3 )   238 - 244   2011.7

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    Many teleost fishes in lowland fresh waters spawn in ephemeral flooded areas, the bottoms of which are prone to hypoxia. Little is known about how embryos and larvae deal with these potentially hostile environments. This study examines the functional and behavioral ontogeny of one such species, the kissing loach (Parabotia curta). Kissing loach eggs are demersal and adhesive. Hatching occurs at 24.8 +/- A 0.1 h post-fertilization at 25A degrees C, much earlier than most fish species. The newly hatched larvae are precocious with no functional mouth, fins or eye pigmentation. Swimbladder inflation normally occurs at about 4 days posthatch, even before which the hatched larvae moved immediately toward the water surface to hang from water moss. Experiments with larvae 20 h after hatching showed that they spent significantly less time on the bottom in hypoxic water (2 mg/l) than in normoxic water, and suggest that hypoxia is a major directive factor in eliciting surfacing behavior. For the kissing loach, we have previously reported short-term spawning after the formation of flood areas as well as wide scattering of the spawned eggs in the temporal flooded areas. These traits with the present results of hatching at an early stage and the immediate upward movement of larvae are considered to be effective strategies for using ephemeral, hypoxic flooded areas for reproduction.

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  • Isolation and Characterisation of Prolactin-Releasing Peptide in Chicks and its Effect on Prolactin Release and Feeding Behaviour

    T. Tachibana, S. Moriyama, A. Takahashi, A. Tsukada, A. Oda, S. Takeuchi, T. Sakamoto

    JOURNAL OF NEUROENDOCRINOLOGY   23 ( 1 )   74 - 81   2011.1

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    Prolactin (PRL)-releasing peptides (PrRP) have been identified in mammals, amphibians and fishes, and these animals have several PrRPs that consist of different numbers of amino acids such as 20, 31 and 37. In the present study, we identified the cDNA encoding chicken prepro-PrRP, which can generate putative PrRPs, and cloned and sequenced it. Sequences for the coding region suggested the occurrence of putative PrRPs of 20, 31 and 32 amino acid residues. The amino acid sequence of chicken PrRP20 showed 100%, 95% and 70% identity with those of PrRP20s from teleosts, Xenopus laevis and mammals, respectively. On the other hand, chicken PrRP31 showed approximately 90% and 52-55% homology to PrRP31s of X. laevis and mammals, respectively. Native chicken PrRPs were purified from an acid extract of chick brain by a Sep-Pak C18 cartridge (Waters Corp., Milford, MA, USA), affinity chromatography using anti-salmon PrRP serum, and reverse phase high-performance liquid chromatography (HPLC) on an ODS-120T column (TOSOH, Tokyo, Japan). The existence of chicken PrRP20 and PrRP31 in the brain was demonstrated by comparing them with the synthetic peptides using HPLC and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. Chicken PrRP31 increased plasma PRL concentration when administered peripherally, whereas central administration decreased the concentration, suggesting that chicken PrRP31 has a distinct effect on PRL secretion between tissues in chicks. On the other hand, plasma growth hormone concentration decreased with both peripheral and central administrations of chicken PrRP31. Furthermore, central administration of chicken PrRP31 increased food intake in chicks compared to those observed in mammals and fishes. Taken together with the results indicating that chicken PrRP20 did not show endocrine and behavioural effects, we showed that chicken PrRP has a similar amino acid sequence to teleosts, Xenopus laevis and mammals, although the actions were variable among vertebrates.

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  • Dual in vitro effects of cortisol on cell turnover in the medaka esophagus via the glucocorticoid receptor

    Chiyo Takagi, Hideya Takahashi, Hiroki Kudose, Kanoko Kato, Tatsuya Sakamoto

    LIFE SCIENCES   88 ( 5-6 )   239 - 245   2011.1

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    Aims: Cortisol is a glucocorticoid in mammals, but has both gluco- and mineralocorticoid activities in teleost fish. Our previous in vivo studies on osmoregulatory esophagi of euryhaline fish showed that epithelial apoptosis for the simple epithelium in seawater and cell proliferation for the stratified epithelium in fresh water are both induced by cortisol. The aim of the present study was to examine the mechanism of these dual cortisol effects on esophageal cell turnover.
    Main methods: We developed a tissue culture method for the esophagus from euryhaline medaka (Oryzias latipes) and assessed cell proliferation and apoptosis in vitro in response to cortisol and 11-deoxycorticosterone (DOC), a recently identified agonist of the teleostean mineralocorticoid receptor.
    Key findings: Epithelial apoptosis, a well-established glucocorticoid function, was stimulated by treatment of the esophagus culture with 10 nM cortisol for 8 days, but no effects were seen at higher doses (100 and 1000 nM). In contrast, cell proliferation was induced by 1000 nM cortisol treatment for 8 days and this response was dose-dependent. Both effects were blocked by RU-486, a glucocorticoid receptor antagonist. DOC showed no significant effects at 10-1000 nM.
    Significance: In the esophageal epithelium in euryhaline fish, cortisol induces either apoptosis or cell proliferation via the glucocorticoid receptor, depending on the cortisol concentration. The glucocorticoid signaling may play a more important role than mineralocorticoid signaling in differentiation of the osmoregulatory esophagus in euryhaline fishes. (C) 2010 Elsevier Inc. All rights reserved.

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  • Detection and activity of iodine-131 in brown algae collected in the Japanese coastal areas

    Takami Morita, Kentaro Niwa, Ken Fujimoto, Hiromi Kasai, Haruya Yamada, Kou Nishiutch, Tatsuya Sakamoto, Waichiro Godo, Seiya Taino, Yoshihiro Hayashi, Koji Takeno, Tomokazu Nishigaki, Kunihiro Fujiwara, Hisamichi Aratake, Shingo Kamonoshita, Hiroshi Hashimoto, Takuya Kobayashi, Sigeyoshi Otosaka, Tetsuji Imanaka

    SCIENCE OF THE TOTAL ENVIRONMENT   408 ( 16 )   3443 - 3447   2010.7

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    Iodine-131 (physical half-life: 8.04 days) was detected in brown algae collected off the Japanese coast. Brown algae have been extensively used as bioindicators for radioiodine because of their ability to accumulate radionuclides in high concentration factors. The maximum measured specific activity of (131)I in brown algae was 0.37 +/- 0.010 Bq/kg-wet. Cesium-137 was also detected in all brown algal samples used in this study. There was no correlation between specific activities of (131)I and (137)Cs in these seaweeds. The specific activity of (137)Cs ranged from 0.0034 +/- 0.00075 to 0.090 +/- 0.014 Bq/kg-wet. Low specific activity and minimal variability of (137)Cs in brown algae indicated that past nuclear weapon tests were the source of (137)Cs. Although nuclear power stations and nuclear fuel reprocessing plants are known to be pollution sources of (131)I, there was no relationship between the sites where (131)I was detected and the locations of nuclear power facilities. Most of the sites where (131)I was detected were near big cities with large populations. Iodine-131 is frequently used in diagnostic and therapeutic nuclear medicine. On the basis of the results, we suggest that the likely pollution source of (131)I, detected in brown seaweeds, is not nuclear power facilities, but nuclear medicine procedures. (C) 2010 Elsevier B.V. All rights reserved.

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  • Concentration of iodine-131 in brown algae collected in Japanese coastal areas.

    Morita T, Niwa K, Fujimoto K, Kasai H, Yamada H, Nishiutch K, Sakamoto T

    KEK Proceedings   63 - 66   2009

  • Prolactin Inhibits Osteoclastic Activity in the Goldfish Scale: A Novel Direct Action of Prolactin in Teleosts

    Hideya Takahashi, Nobuo Suzuki, Chiyo Takagi, Mika Ikegame, Toshio Yamamoto, Akiyoshi Takahashi, Shunsuke Moriyama, Atsuhiko Hattori, Tatsuya Sakamoto

    ZOOLOGICAL SCIENCE   25 ( 7 )   739 - 745   2008.7

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    In teleosts, prolactin is involved in calcium regulation, but its role in scale/bone metabolism is unclear. Using the in-vitro system with goldfish scales developed recently, we explored the effects of teleost prolactin, growth hormone, and somatolactin on osteoclasts and osteoblasts. Addition of prolactin at concentrations of 0.01-100 ng/ml reduced osteoclastic activity, partly via osteoclast apoptosis, after 6-18 h incubation. Conversely, growth hormone and somatolactin at a concentration of 100 ng/ml increased osteoclastic activity after 18 h incubation, indicating the specificity of the inhibitory effect of prolactin on osteoclastic activity. On the other hand, these three hormones promoted osteoblastic activity at concentrations of 10-100 ng/ml. The results from this study are the first demonstration of direct effects of prolactin on scale/bone metabolism and osteoclastic activity in a teleost.

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  • Spawning Behavior of the kissing loach (Leptobotia curta) in temporary waters

    Tsukasa Abe, Ichiro Kobayashi, Masahiro Kon, Tatsuya Sakamoto

    ZOOLOGICAL SCIENCE   24 ( 8 )   850 - 853   2007.8

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    The natural spawning behavior of the kissing loach, an endangered species of Botiidae, was investigated in the wild in early June for two years in relation to several environmental factors. Kissing loaches spawned in temporary waters after elevation in water level. All spawnings observed (n=163) occurred within 3-5.5 hours from late afternoon to night after formation of the temporary water. These spawnings were performed by one female and one (71%) or two (29%) males in densely vegetated lentic waters. The female and following male(s) swam into dense grasses, where they vibrated to spawn intermittently. After the vibration continuing for 3-20 seconds, they moved to other parts of the dense grassy area and began vibration again. This sequence of spawning behavior was usually repeated several times, and the eggs were thus scattered widely. The spawning behavior and the rapid larval development of this species appear to be adaptations for the use of temporary waters as a spawning ground. The rise in water level and the consequent formation of temporary waters appear to be crucial triggers for reproduction of the kissing loach.

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  • Prolactin receptor and proliferating/apoptotic cells in esophagus of the Mozambique tilapia (Oreochromis mossambicus) in fresh water and in seawater

    Hideya Takahashi, Patrick Prunet, Takashi Kitahashi, Shingo Kajimura, Tetsuya Hirano, E. Gordon Grau, Tatsuya Sakamoto

    GENERAL AND COMPARATIVE ENDOCRINOLOGY   152 ( 2-3 )   326 - 331   2007.6

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    We have previously shown that esophageal epithelium of a euryhaline goby displays elevated cell proliferation in freshwater (FW) fish, but undergo apoptosis during seawater (SW) acclimation. Prolactin (PRL) injection into the goby induced the cell proliferation, whereas cortisol treatment stimulated the cell proliferation and apoptosis [Takahashi, H., Sakamoto, T., Narita, K., 2006a. Cell proliferation and apoptosis in the anterior intestine of an amphibious, euryhaline mudskipper (Periophthalmus modestus). J. Comp. Physiol. B 176, 463-468, 2006). In the euryhaline tilapia (Oreochromis mossambicus), the dynamics of changes in cortisol-glucccorticoid receptors (GR) during acclimation to different salinities also suggests a role for glucocorticoid signaling in the esophageal cell turnover, but the mode of PRL action remains largely unclear. In the present study, we report on effects in the tilapia esophagus that result from changes in environmental salinity. Specifically, we assessed: (1) mRNA expression of PRL receptor (PRLR) using quantitative real-time RTPCR; (2) esophageal cell proliferation and apoptosis, using immunohistochemistry of proliferating cells nuclear antigen (PCNA) and in situ nick end-labeling of genomic DNA (TUNEL); (3) the possible localization of immunoreactive PRLR on proliferating/apoptotic cells. Plasma PRL increased after FW acclimation; PRLR mRNA levels in the esophagus of FW fish were significantly higher than those in SW-acclimated fish. Cell proliferation was induced randomly throughout the esophageal epithelium after FW acclimation, while cell division and increased apoptosis were concentrated at the tips of esopliageal epithelial folds in SW-acclimated fish. Immunoreactive PRLR appeared to be localized at proliferating cells and at certain apoptotic cells, whereas immunoreactive GR was observed over the whole epithelium including the apoptotic/proliferating cells. Thus, PRL appears to affect cell turnover directly in the esophageal epithelium of the eurylialine tilapia. (c) 2007 Elsevier Inc. All rights reserved.

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  • Spawning behavior of kissing loach (Leptobotia curta) is limited after the formation of temporary waters

    Abe, T, I. Kobayashi, M. Kon, T. Sakamoto

    Zool. Sci.   24: 922-926   2007

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  • Molecular cloning and functional characterization of a prolactin-releasing peptide homol from Xenopus laevis

    Tatsuya Sakamoto, Aiko Oda, Kazutoshi Yamamoto, Miyoko Kaneko, Sakae Kikuyama, Akio Nishikawa, Akiyoshi Takahashi, Hiroshi Kawauchi, Kazuyoshi Tsutsui, Masaaki Fujimoto

    PEPTIDES   27 ( 12 )   3347 - 3351   2006.12

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    Amino acid sequences for identified prolactin (PRL)-releasing peptides (PrRPs) were conserved in mammals (&gt; 90%) or teleost fishes (100%), but there were considerable differences between these classes in the sequence (&lt; 65%) as well as in the role of PrRP. In species other than fishes and mammals, we have identified frog PrRP. The cDNA encoding Xenopus laevis prepro-PrRP, which can generate putative PrRPs, was cloned and sequenced. Sequences for the coding region showed higher identity with teleost PrRPs than mammalian homologues, but suggested the occurrence of putative PrRPs of 20 and 31 residues as in mammals. The amino acid sequence of PrRP20 was only one residue different from teleost PrRP20, but shared 70% identity with mammalian PrRP20s. In primary cultures of bullfrog (Rana catesbeiana) pituitary cells, Xenopus PrRPs increased prolactin concentrations in culture medium to 130-160% of the control, but PrRPs was much less potent than thyrotropin-releasing hormone (TRH) causing a three- to four-fold increase in prolactin concentrations. PrRP mRNA levels in the developing Xenopus brain peak in early prometamorphosis, different from prolactin levels. PrRP may not be a major prolactin-releasing factor (PRF), at least in adult frogs, as in mammals. (c) 2006 Elsevier Inc. All rights reserved.

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  • In vivo effects of thyroid honnone, corticosteroids and prolactin on cell proliferation and apoptosis in the anterior intestine of the euryhaline mudskipper (Periophthalmus modestus)

    Hideya Takahashi, Akiyoshi Takahashi, Tatsuya Sakamoto

    LIFE SCIENCES   79 ( 19 )   1873 - 1880   2006.10

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    We have previously shown that anterior intestinal epithelium of the euryhaline mudskipper (Periophthalmus modestus) undergoes apoptosis during seawater (SW) acclimation, whereas elevated cell proliferation was observed in freshwater (FW)-acclimated fish. To understand the possible endocrine regulation of the gastrointestinal cell turnover during salinity acclimation, we examined the ratios of apoptotic and proliferating cells in the anterior intestine of one-third SW-acclimated mudskipper treated with triiodothyronine (T-3) cortisol, 11-deoxycorticosterone (DOC, the putative teleostean mineralocorticoid), or prolactin (PRL). In situ nick end labeling of genomic DNA (TUNEL) and immunohistochemistry of proliferating cells nuclear antigen (PCNA) were used as indicators of apoptosis and cell proliferations, respectively. Cortisol significantly elevated apoptosis (P &lt; 0.05) in the epithelia and connective tissues and also stimulated the epithelial cell proliferation (P &lt; 0.05). PRL induced epithelial cell proliferation (P &lt; 0.05), but did not affect apoptotic status of the intestinal epithelium. Neither T-3 nor DOC had any impact on cell proliferation or apoptosis. Together, our results suggest a role for cortisol and PRL in the regulation of anterior intestinal epithelial turnover during salinity acclimation in this species. (c) 2006 Elsevier Inc. All rights reserved.

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  • Cell proliferation and apoptosis in the anterior intestine of an amphibious, euryhaline mudskipper (Periophthalmus modestus)

    H Takahashi, T Sakamoto, K Narita

    JOURNAL OF COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL SYSTEMIC AND ENVIRONMENTAL PHYSIOLOGY   176 ( 5 )   463 - 468   2006.6

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    In order to replace the diffusive loss of water to the surrounding environment, seawater (SW)-acclimated euryhaline fishes have gastrointestinal tracts with higher ion/water flux in concert with greater permeability, and contrast that to freshwater (FW)-acclimated fish. To understand the cellular basis for these differences, we examined cell proliferation and apoptosis in the anterior intestine of mudskipper transferred from one-third SW to FW or to SW for 1 and 7 days, and those kept out of water for 1 day. The intestinal apoptosis (indicated by DNA laddering) increased during seawater acclimation. TUNEL staining detected numerous apoptotic cells over the epithelium of SW-acclimated fish. Cell proliferation ([H-3]thymidine incorporation) in the FW fish was greater than those in SW 7 days after transfer. Labeling with a Proliferating cell nuclear antigen (PCNA) antibody indicated that proliferating cells were greater in number and randomly distributed in the epithelium of FW fish, whereas in SW fish they were almost entirely in the troughs of the intestinal folds. There were no changes in cell turnover in fish kept out of water. During acclimation to different salinities, modification of the cell turnover and abundance may play an important role in regulating the permeability (and transport capacity) of the gastrointestinal tract of fish.

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  • Prolactin-releasing peptide is essential to maintain the prolactin level and osmotic balance in freshwater teleost fish

    M Fujimoto, T Sakamoto, T Kanetoh, M Osaka, S Moriyama

    PEPTIDES   27 ( 5 )   1104 - 1109   2006.5

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    We administered prolactin-releasing peptide (PrRP) or anti-PrRP antiserum to goldfish in, fresh water and analyzed their effects on prolactin and osmoregulatory mechanisms. The pituitary mRNA level of prolactin increased by PrRP but decreased by anti-PrRP. The rate of water inflow in the gills decreased by PrRP and increased by anti-PrRP, showing that PrRP restricts branchial water permeability, as also restricted by prolactin. PrRP also expanded the mucous cell layers on the scales, which may restrict efficiently water inflow by the mucous system. Eventually, the plasma osmotic pressure decreased by anti-PrRP. We conclude that PrRP is essential to maintain prolactin levels and osmotic balance in fresh water. (c) 2006 Elsevier Inc. All rights reserved.

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  • Expression of glucocorticoid receptor in the intestine of a euryhaline teleost, the mozambique tilapia (Oreochromis mossambicus): Effect of seawater exposure and cortisol treatment

    H Takahashi, T Sakamoto, S Hyodo, BS Shepherd, T Kaneko, EG Grau

    LIFE SCIENCES   78 ( 20 )   2329 - 2335   2006.4

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    Cortisol plays an important role in controlling intestinal water and ion transport in teleosts possibly through glucocorticoid receptor (GR) and/or mineralocorticoid receptor. To better understand the role of GR in the teleost intestine, in a euryhaline tilapia, Oreochromis mossambicus, we examined (1) the intestinal localizations of GR; (2) the effects of environmental salinity challenge and cortisol treatment oil GR mRNA expression. The mRNA abundance of GR in the posterior intestinal region of tilapia was found to be higher than that in the anterior and middle intestine. In the posterior intestine, GR appears to be localized in the mucosal layer. GR mRNA levels in the posterior intestine were elevated after exposure of freshwater fish to seawater for 7 days following an increase in plasma cortisol. Similarly, cortisol implantation in freshwater tilapia for 7 days elevated the intestinal GR mRNA. These results indicate that seawater acclimation is accompanied by upregulation of GR mRNA abundance in intestinal tissue, possibly as a consequence of the elevation of cortisol levels. In contrast, a single intraperitoneal injection of cortisol into freshwater tilapia decreased intestinal GR mRNA. This downregulation of the GR mRNA by cortisol suggests a dual mode of autoregulation of GR expression by cortisol. (c) 2005 Elsevier Inc. All lights reserved.

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  • Chemical components in the pouch fluid of the seahorse, Hippocampus barbouri Jordan and Richardson 1908 and their uptake in embryos.

    Oconer,EP, CP Pascual, AA Herrera, T. Sakamoto, JT Wetzel

    Asia Life Sciences   2006

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  • Prolactin and growth hormone in fish osmoregulation

    Sakamoto, T, S. D. McCormick

    Gen. Comp. Endocrinol.   147: 24-30   2006

  • Primary structure of proopiomelanocortin in reptiles Reviewed

    Takahashi A, Sakamoto T, Lance VA, Kawauchi H

    Proc. Jpn. Soc. Comp. Endocrinol.   ( 20 )   48 - 48   2005.11

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  • High ambient ammonia promotes growth in a ureogenic goby, Mugilogobius abei

    K Iwata, T Sakamoto, Iwata, I, E Nishiguchi, M Kajimura

    JOURNAL OF COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL SYSTEMIC AND ENVIRONMENTAL PHYSIOLOGY   175 ( 6 )   395 - 404   2005.8

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    Mugilogobius abei has the ability to produce large amounts of urea when exposed to high ambient ammonia. Despite this metabolically costly approach, and reports of growth inhibition effects of ammonia on fish, M. abei exposed to ammonia shows no adverse effects on growth. To investigate this observation the growth of M. abei was measured at room temperatures for 8 weeks at a constant ration level under solitary and grouped conditions, in 20% SW with or without (control) 2 mM NH4Cl. Furthermore, pituitary mRNA levels of growth hormone, oxygen consumption, incorporation of external N-15-ammonia into amino acid and protein fractions as well as behavioral activities were also examined. The specific growth rates of ammonia-exposed fish under grouped condition over the 8 weeks were significantly higher than those of control, while those rates under solitary condition were not significantly different between the treatments. The pituitary of ammonia-exposed fish had higher growth hormone mRNA than in control fish. The use of N-15 isotope revealed that M. abei can actively use external ammonia as a supplementary nitrogen source. Oxygen consumption of ammonia-exposed fish was significantly lower than that of control fish. Locomotor activity and aggressive behavior under grouped condition were significantly reduced in ammonia-exposed fish as compared to those of control. These combined alterations in the ammonia-exposed fish may result in the higher growth rates.

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  • Expression of prolactin-releasing peptide and prolactin in the euryhaline mudskippers (Periophthalmus modestus): prolactin-releasing peptide as a primary regulator of prolactin

    T Sakamoto, M Amano, S Hyodo, S Moriyama, A Takahashi, H Kawauchi, M Ando

    JOURNAL OF MOLECULAR ENDOCRINOLOGY   34 ( 3 )   825 - 834   2005.6

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    Prolactin (PRL)-releasing peptide (PrRP) is a strong candidate stimulator of pituitary PRL transcription and secretion in teleosts. However, the role in control of extrapituitary PRL expression is unclear even in mammals. To study the possible presence of PrRP-PRL axes not only in the brain-pituitary but also in peripheral organs, the expression patterns of PrRP, PRL and growth hormone (GH) were characterized in amphibious euryhaline mudskippers (Periophthalmus modestus). PrRP mRNA is abundantly expressed not only in the brain but also in the liver, gut and ovary, while less abundant expression was also detected in the skin and kidney. Corresponding to the distribution of PrRP mRNA, PRL mRNA was also detectable in these organs. During adaptation to different environments, the changes in mRNA levels of PrRP paralleled those in PRL in the brain-pituitary, liver and gut in an organ-specific manner. Brain PrRP mRNA and the pituitary PRL mRNA increased under freshwater and terrestrial conditions (P &lt; 0.05); expression of PrRP and PRL in the gut of freshwater fish was higher (P &lt; 0.05) than those in sea-water fish although there were no changes in fish kept out of water; no significant change was seen in the liver. Expressions of GH were not correlated with PrRP. In the gut, PrRP and PRL appear to be co-localized in the mucosal layer, especially in the mucous cells. Thus, PrRP may also be a local modulator of extrapituitary PRL expression and the PrRP-PRL axes in various organs may play an organ-specific role during environmental adaptation.

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  • Prolactin: fishy tales of a primary regulator and function

    Sakamoto, T, A. Oda, H. Takahashi, T. Oda, K. Narita, J. Fujiwara

    Ann. NY Acad. Sci.   1040: 184-188   2005

  • Intra-arterial injection of prolactin-releasing peptide elevates prolactin gene expression and plasma prolactin levels in rainbow trout

    T Sakamoto, T Agustsson, S Moriyama, T Itoh, A Takahashi, H Kawauchi, BT Bjornsson, M Ando

    JOURNAL OF COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL SYSTEMIC AND ENVIRONMENTAL PHYSIOLOGY   173 ( 4 )   333 - 337   2003.6

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    Prolactin-releasing peptide (PrRP), recently isolated from the brain of mammals and teleosts, is a strong candidate for being a stimulatory hormone of pituitary prolactin secretion. The present study examined whether or not PrRP is capable of inducing prolactin gene expression and elevating plasma prolactin levels in vivo in cannulated rainbow trout. Following a single intra-arterial injection of chum salmon PrRP (40 nmol kg(-1)) through a dorsal aorta catheter, plasma prolactin levels increased (P&lt;0.05) rapidly (2 min and 30 min), and prolactin mRNA levels were elevated (P&lt;0.05) in pituitaries sampled 8 h after the injection. In contrast, plasma levels of somatolactin were decreased (P&lt;0.05) and growth hormone and somatolactin mRNA levels were not significantly affected by PrRP. Thus, PrRP appears to be a potent prolactin secretagogue as well as prolactin transcription inducer in vivo in the rainbow trout.

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  • Prolactin, somatolactin and growth hormone gene expression during parr-smolt transformation of Atlantic salmon

    Agustsson, T, K. Sundell, T. Sakamoto, M. Ando, B. Th, Bj嗷nsson

    Aquaculture   2003

  • Fishy tales of prolactin-releasing peptide

    Sakamoto, T, M. Fujimoto, M. Ando

    Int. Rev. Cytol   225: 91-130   2003

  • Isolation and characterization of a homologue of mammalian prolactin-releasing peptide from the tilapia brain and its effect on prolactin release from the tilapia pituitary

    AP Seale, T Itoh, S Moriyama, A Takahashi, H Kawauchi, T Sakamoto, M Fujimoto, LG Riley, T Hirano, EG Grau

    GENERAL AND COMPARATIVE ENDOCRINOLOGY   125 ( 3 )   328 - 339   2002.2

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    In the tilapia (Oreochromis mossambicus), as in many teleosts, prolactin (PRL) plays a major role in osmoregulation in freshwater. Recently, PRL-releasing peptides (PrRPs) have been characterized in mammals. Independently, a novel C-terminal RF (arginine-phenylalanine) amide peptide (Carrasius RF amide: C-RFa), which is structurally related to mammalian PrRPs, has been isolated from the brain of the Japanese crucian carp. The putative PrRP was purified from an acid extract of tilapia brain by affinity chromatography with antibody against synthetic C-RFa and HPLC on a reverse-phase ODS-120 column. The tilapia PrRP cDNA was subsequently cloned by polymerase chain reaction. The cDNA consists of 619 bp encoding a preprohormone of 117 amino acids. Sequence comparison of the isolated peptide and the preprohormone revealed that tilapia PrRP contains 20 amino acids and is identical to C-RFa. Incubation of the tilapia pituitary with synthetic C-RFa (100 nM) significantly stimulated the release of two forms of tilapia PRL (PRI188 and PRI177). However, the effect of C-RFa was less pronounced than the marked increase in PRL release in response to hyposmotic medium. The ability of C-RFa to stimulate PRL release appears to be specific, since C-RFa failed to stimulate growth hormone release from the pituitary in organ culture. In contrast, rat and human PrRPs had no effect on PRL release. C-RFa was equipotent with chicken GnRH in stimulating PRL release in the pituitary preincubated with estradiol 17beta. Circulating levels of PRL were significantly increased 1 h after intraperitoneal injection of 0.1 mug/g of C-RFa in female tilapia in freshwater but not in males. These results suggest that C-RFa is physiologically involved in the control of PRL secretion in tilapia. (C) 2002 Elsevier Science (USA).

    DOI: 10.1006/gcen.2001.7727

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  • Calcium ion triggeres the rapid morphological oscillation of chloride cells in the mudskipper

    Sakamoto, T, M. Ando

    J. Comp. Physiol. B   2002

  • Ureogenic function and periodic urea excretion in a gobiid fish, Mugilogobius abei.

    Iwata, K, M. Kajimura, T. Sakamoto

    Fish. Sci   2002

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  • Growth hormone and prolactin in expression during environmental adaptation of gobies

    Sakamoto, T, K. Iwata, M. Ando

    Fish. Sci.   2002

  • Differential display of skin mRNAs regulated during adaptation of mudskipper to different environments

    Sakamoto, T, H. Yasunaga, S. Yokota, M. Ando

    J. Comp. Physiol. B   2002

  • Medaka, Oryzias latipes, as a model for hypoosmoregulation of euryhaline fishes

    Sakamoto, T, T. Kozaka, A. Takahashi, H. Kawauchi, M. Ando

    Aquaculture   2001

  • Regulation of the ion-transporting mitochondrion-rich cell during adaptation of teleost fishes to different salinities

    Sakamoto, T, K. Uchida, S. Yokota

    Zool. Sci.   2001

  • Regulation of the ion-transporting mitochondrion-rich cell during adaptation of teleost fishes to different salinities

    Sakamoto, T, K. Uchida, S. Yokota

    Zool. Sci.,   18: 1163-1174   2001

  • Growth hormone endocrinology of Atlantic salmon (Salmo salar): pituitary gene expression, hormone storage, secretion and plasma levels during parr--smolt transformation

    Agustsson, T, K. Sundell, T. Sakamoto, M. Ando, B. Th, Bj嗷nsson

    J. Endocrinol.   2001

  • Rapid morphological oscillation of mitochondrion-rich cell in estuarine mudskipper following salinity changes

    Sakamoto, T, S. Yokota, M. Ando

    J. Exp. Zool.   2000

  • Functional ureogenesis in the gobiid fish, Mugilogobius abei

    Iwata, K, M. Kajimura, T. Sakamoto

    J. Exp. Biol.   2000

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  • Induction of mRNAs in response to acclimation of trout cells to different osmolalities

    Sakamoto, T, N. Ojima, M. Yamashita

    Fish. Physiol. Biochem.   2000

  • Functional ureogenesis in the gobiid fish, #IDBMugilogobius abei(/)-#IRDB.(共著)

    J. Exp. Biol.   203   3703 - 3715   2000

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  • Is the primitive regulation of pituitary prolactin (tPRL(177) and tPRL(188)) secretion and gene expression in the euryhaline tilapia (Oreochromis mossambicus) hypothalamic or environmental?

    BS Shepherd, T Sakamoto, S Hyodo, RS Nishioka, C Ball, HA Bern, EG Grau

    JOURNAL OF ENDOCRINOLOGY   161 ( 1 )   121 - 129   1999.4

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    We examined the effects of environmental salinity on circulating levels of the two prolactins (tPRL(177) and tPRL(188)) and levels of pituitary tPRL(177) and tPRL(188) mRNA in the euryhaline tilapia, Oreochromis mossambicus. Fish were sham-operated or hypophysectomized and the rostral pars distalis (RPD) autotransplanted onto the optic nerve. Following post-operative recovery in 1/4 seawater, tilapia were transferred to fresh water (FW), 1/4 seawater (SW) or SW. Serum tPRL(177) and tPRL(188) levels in sham-operated and RPD-autotransplanted fish were highest in FW and decreased as salinity was increased. tPRL(177) and tPRL(188) mRNA levels in RPD implants as well as in pituitaries from the sham-operated fish were also highest in FW and decreased with increasing salinity. Serum osmolality increased with salinity, with the highest levels occurring in die seawater groups. We conclude that some plasma factor (probably plasma osmolality), in the absence of hypothalamic innervation, exerts a direct regulatory action on prolactin release and gene expression in the pituitary of O. mossambicus. This regulation is in accord with the actions of the two prolactins in the freshwater osmoregulation of the tilapia.

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  • Development of the myotomal neuromuscular system in embryonic and larval angelfish, Pterophyllum scalare

    Sakamoto, H, M. Yoshida, T. Sakamoto, K. Uematsu

    Zool. Sci.   1999

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  • Novel [3H]clonidine binding sites in the intestine of the eel acclimated to sea water

    Hung Tae Kim, Tatsuya Sakamoto, Masaaki Ando

    Zoological Science   15 ( 2 )   205 - 212   1998

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    Novel clonidine binding sites were characterized in the intestinal membrane isolated from seawater eels. The specific clonidine binding sites consisted of at least two classes, high affinity (Kd = 1.4 ± 0.3 nM, n = 5) and low affinity (Kd = 175 ± 34 nM, n = 5) sites. The specific binding of 2 nM [3H]clonidine was most enhanced at 20°C and at pH 7.5, and reversed by unlabelled clonidine. Such binding was hardly inhibited by adrenaline, yohimbine or rauwolscine, indicating that most binding sites are distinct from α2-adrenoceptor. The specific clonidine binding was inhibited by various imidazoline/guanidinium drugs, indicating existence of imidazoline/guanidinium receptive sites (IGRS) or imidazoline receptors in the eel intestine. Competition experiments revealed that rank order to displace 2 nM [3H]clonidine from their binding sites was as follows: guanabenz &gt
    cirazoline = naphazoline = UK14304 = ST587 ≥ clonidine ≥ idazoxan = RX821002 = tolazoline &gt
    ST93 = oxymetazoline = amiloride = ST91 &gt
    yohimbine = efaroxan = rauwolscine ≥ adrenaline = ST567 = histamine = agmatine. The rank order was different from those in I1 or I2 sites of IGRS reported in various mammalian tissues, suggesting existence of new IGRS, non I1 and non I2 sites, in the eel intestine. In addition, structure-affinity relationships are discussed from the results of competition experiments. Although physiological role of IGRS is not clear yet even in mammalian cells/tissues, eel intestine may be a good model to elucidate how the IGRS act in the cell and to decide what is the endogenous ligand for the IGRS, since eel intestine contains great amount of IGRS and it responds to guanabenz, an exogenous clonidine derivative.

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  • Novel [3H]clonidine binding sites in the intestine of the eel acclimated to sea water

    Hung Tae Kim, Tatsuya Sakamoto, Masaaki Ando

    Zoological Science   15 ( 2 )   205 - 212   1998

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    Novel clonidine binding sites were characterized in the intestinal membrane isolated from seawater eels. The specific clonidine binding sites consisted of at least two classes, high affinity (Kd = 1.4 ± 0.3 nM, n = 5) and low affinity (Kd = 175 ± 34 nM, n = 5) sites. The specific binding of 2 nM [3H]clonidine was most enhanced at 20°C and at pH 7.5, and reversed by unlabelled clonidine. Such binding was hardly inhibited by adrenaline, yohimbine or rauwolscine, indicating that most binding sites are distinct from α2-adrenoceptor. The specific clonidine binding was inhibited by various imidazoline/guanidinium drugs, indicating existence of imidazoline/guanidinium receptive sites (IGRS) or imidazoline receptors in the eel intestine. Competition experiments revealed that rank order to displace 2 nM [3H]clonidine from their binding sites was as follows: guanabenz &gt
    cirazoline = naphazoline = UK14304 = ST587 ≥ clonidine ≥ idazoxan = RX821002 = tolazoline &gt
    ST93 = oxymetazoline = amiloride = ST91 &gt
    yohimbine = efaroxan = rauwolscine ≥ adrenaline = ST567 = histamine = agmatine. The rank order was different from those in I1 or I2 sites of IGRS reported in various mammalian tissues, suggesting existence of new IGRS, non I1 and non I2 sites, in the eel intestine. In addition, structure-affinity relationships are discussed from the results of competition experiments. Although physiological role of IGRS is not clear yet even in mammalian cells/tissues, eel intestine may be a good model to elucidate how the IGRS act in the cell and to decide what is the endogenous ligand for the IGRS, since eel intestine contains great amount of IGRS and it responds to guanabenz, an exogenous clonidine derivative.

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  • Novel [3H]clonidine binding sites in the intestine of the eel acclimated to sea water

    Kim, H. T, T. Sakamoto, M. Ando

    Zool. Sci   1998

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  • Physiological and respiratory responses of the Mozambique tilapia (Oreochromis mossambicus) to salinity acclimation

    John D. Morgan, Tatsuya Sakamoto, E. Gordon Grau, George K. Iwama

    Comparative Biochemistry and Physiology - A Physiology   117 ( 3 )   391 - 398   1997.7

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    We have examined several physiological variables related to salinity acclimation in the euryhaline tilapia, Oreochromis mossambicus. Tilapia reared in fresh water (FW) were transferred to FW, isosmotic salinity (ISO, 12‰%) and 75% seawater (SW, 25‰). Oxygen consumption, plasma levels of cortisol, growth hormone (GH), prolactins (tPRL177 and tPRL188), glucose, ions (Na+, K+, Cl-), and gill Na+,K+-ATPase activities were measured for up to 4 days in each salinity treatment. Plasma Na+ and Cl- concentrations were elevated 1 day after transfer to SW, but returned to FW values on day 4. Plasma cortisol and glucose levels were higher in FW and ISO than in SW 1 day after transfer. Plasma GH levels of tilapia in SW increased above FW and ISO values after 4 days, whereas plasma PRL levels decreased in ISO and SW compared to FW at 4 days. These results are consistent with the possible osmoregulation roles of GH and PRL in SW and FW, respectively. Gill Na+,K+-ATPase activity of tilapia in SW increased more than 2-fold over the FW value after 4 days, but activity of this enzyme did not change in ISO. Oxygen consumption rates of tilapia in SW were significantly elevated 4 days after transfer compared to FW and ISO. The results of this study indicate that the physiological changes associated with SW acclimation in tilapia represents a significant short-term energetic cost, and may account for as much as 20% of total body metabolism after 4 days in SW.

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  • Physiological and respiratory responses of the Mozambique tilapia (Oreochromis mossambicus) to salinity acclimation

    John D. Morgan, Tatsuya Sakamoto, E. Gordon Grau, George K. Iwama

    Comparative Biochemistry and Physiology - A Physiology   117 ( 3 )   391 - 398   1997.7

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    We have examined several physiological variables related to salinity acclimation in the euryhaline tilapia, Oreochromis mossambicus. Tilapia reared in fresh water (FW) were transferred to FW, isosmotic salinity (ISO, 12‰%) and 75% seawater (SW, 25‰). Oxygen consumption, plasma levels of cortisol, growth hormone (GH), prolactins (tPRL177 and tPRL188), glucose, ions (Na+, K+, Cl-), and gill Na+,K+-ATPase activities were measured for up to 4 days in each salinity treatment. Plasma Na+ and Cl- concentrations were elevated 1 day after transfer to SW, but returned to FW values on day 4. Plasma cortisol and glucose levels were higher in FW and ISO than in SW 1 day after transfer. Plasma GH levels of tilapia in SW increased above FW and ISO values after 4 days, whereas plasma PRL levels decreased in ISO and SW compared to FW at 4 days. These results are consistent with the possible osmoregulation roles of GH and PRL in SW and FW, respectively. Gill Na+,K+-ATPase activity of tilapia in SW increased more than 2-fold over the FW value after 4 days, but activity of this enzyme did not change in ISO. Oxygen consumption rates of tilapia in SW were significantly elevated 4 days after transfer compared to FW and ISO. The results of this study indicate that the physiological changes associated with SW acclimation in tilapia represents a significant short-term energetic cost, and may account for as much as 20% of total body metabolism after 4 days in SW.

    DOI: 10.1016/S0300-9629(96)00261-7

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  • Somatotropic actions of the homologous growth hormone(tGH)and prolactin(tPRL177)in the euryhaline teleost, the tilapia, Oreochromis mossambicus(共著)

    Proc. Natl. Acad. Sci. USA   94   2068 - 2072   1997

  • Somatotropic actions of the homologous growth hormone(tGH)and prolactin(tPRL177)in the euryhaline teleost, the tilapia, Oreochromis mossambicus

    Proc. Natl. Acad. Sci. USA   94   2068 - 2072   1997

  • Induction of proteins in response to cold acclimation of rainbow trout cells

    Michiaki Yamashita, Nobuhiko Ojima, Tatsuya Sakamoto

    FEBS Letters   382 ( 3 )   261 - 264   1996.3

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    The in vitro translation of poly(A)-RNA isolated from control and cold-treated cells showed that low temperatures induced changes in the population of translatable mRNAs. When cellular proteins extracted from cold-treated cells were subjected to two-dimensional gel electrophoresis, the 70 kDa protein was found to be synthesized during the cold treatment. N-terminal sequence analysis showed that the 70 kDa cold-inducible protein was a homolog of the mammalian valosin-containing protein and yeast CDC48p. The changes in mRNA and protein contents during cold acclimation may result from the expression of genes involved in the adjustment of cellular metabolism to low temperature or the induced proteins may be directly involved in the cold acclimation.

    DOI: 10.1016/0014-5793(96)00172-X

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  • Molecular cloning and cold-inducible gene expression of ferritin H subunit isoforms in rainbow trout cells

    Michiaki Yamashita, Nobuhiko Ojima, Tatsuya Sakamoto

    Journal of Biological Chemistry   271 ( 43 )   26908 - 26913   1996

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    Cold acclimation of rainbow trout cells is considered to be mediated by alterations in the mRNAs and proteins present in cold-treated cells. A subtracted cDNA library from cold-treated rainbow trout RTG-2 cells was constructed and screened to isolate cDNA induced in the cold-treated cells in order to elucidate which genes are induced by cold acclimation. A set of cDNA clones encoding three members of ferritin H isoforms was isolated as cold- inducible genes. Northern blot analysis and nuclear run-on transcription assay showed that the transcription and accumulation of the ferritin H isoforms mRNA were enhanced by cold acclimation. Furthermore, the ferritin level in the trout cells increased on cold acclimation in response to a temperature shift from 22 °C to 4 °C. When the trout cells were subjected to 4 °C under the condition of a decreased ferritin H level obtained by the addition of an antisense oligonucleotide, cell growth was apparently inhibited. These findings indicate an association between the induction of ferritin H and cellular mechanisms during cold acclimation of trout cells.

    DOI: 10.1074/jbc.271.43.26908

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  • Expression of insulin-like growth factor I gene in osmoregulatory organs during seawater adaptation of the salmonid fish : Possible mode of osmoregulatory action of growth hormone(共著)

    Proc. Natl. Acad. Sci. USA   90   1912 - 1916   1993

  • Expression of insulin-like growth factor I gene in osmoregulatory organs during seawater adaptation of the salmonid fish : Possible mode of osmoregulatory action of growth hormone

    Proc. Natl. Acad. Sci. USA   90   1912 - 1916   1993

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Awards

  • 日本動物学会奨励賞

    坂本 竜哉

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  • Dodd Memorial Prize

    SAKAMOTO Tatsuya

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  • Marine Biology (2020academic year) Late  - 金1,金2

  • Seminar in Chemical Correlation and Control (2020academic year) Year-round  - その他

  • Marine Biology (2020academic year) Summer concentration  - その他

  • Marine Course 1 (2020academic year) 1st semester  - その他

  • Marine Course 3 (2020academic year) Second semester  - その他

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