研究者詳細 - 坂本　竜哉

MISC - 坂本　竜哉

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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年1月

記述言語：英語出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

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.

DOI： 10.1016/j.lfs.2010.11.017

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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年7月

記述言語：英語出版者・発行元：ELSEVIER SCIENCE BV

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.

DOI： 10.1016/j.scitotenv.2010.04.001

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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年

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年7月

記述言語：英語出版者・発行元：ZOOLOGICAL SOC JAPAN

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.

DOI： 10.2108/zsj.25.739

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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年8月

記述言語：英語出版者・発行元：ZOOLOGICAL SOC JAPAN

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.

DOI： 10.2108/zsj.24.850

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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年6月

記述言語：英語出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE

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.

DOI： 10.1016/j.ygcen.2007.02.021

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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年

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年12月

記述言語：英語出版者・発行元：ELSEVIER SCIENCE INC

Amino acid sequences for identified prolactin (PRL)-releasing peptides (PrRPs) were conserved in mammals (> 90%) or teleost fishes (100%), but there were considerable differences between these classes in the sequence (< 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.

DOI： 10.1016/j.peptides.2006.08.003

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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年10月

記述言語：英語出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

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 < 0.05) in the epithelia and connective tissues and also stimulated the epithelial cell proliferation (P < 0.05). PRL induced epithelial cell proliferation (P < 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.

DOI： 10.1016/j.lfs.2006.06.021

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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年6月

記述言語：英語出版者・発行元：SPRINGER

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.

DOI： 10.1007/s00360-006-0067-x

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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年5月

記述言語：英語出版者・発行元：ELSEVIER SCIENCE INC

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.

DOI： 10.1016/j.peptides.2005.06.034

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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年4月

記述言語：英語出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

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.

DOI： 10.1016/j.lfs.2005.09.050

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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年

Prolactin and growth hormone in fish osmoregulation

Sakamoto, T, S. D. McCormick

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

Prolactin inhibits osteoclastic activities in the scales of goldfish

Nobuo Suzuki, Tatsuya Sakamoto, Mika Ikegame, Toshio Yamamoto, Akiyoshi Takahashi, Shunsuke Moriyama, Hiroshi Kawauchi, Atsuhiko Hattori

ZOOLOGICAL SCIENCE 22 ( 12 ) 1498 - 1498 2005年12月

Primary structure of proopiomelanocortin in reptiles 査読

Takahashi A, Sakamoto T, Lance VA, Kawauchi H

Proc. Jpn. Soc. Comp. Endocrinol. ( 20 ) 48 - 48 2005年11月

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年8月

記述言語：英語出版者・発行元：SPRINGER

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.

DOI： 10.1007/s00360-005-0001-7

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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年6月

記述言語：英語出版者・発行元：SOC ENDOCRINOLOGY

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 < 0.05); expression of PrRP and PRL in the gut of freshwater fish was higher (P < 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.

DOI： 10.1677/jme.1.01768

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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年

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年6月

記述言語：英語出版者・発行元：SPRINGER-VERLAG

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<0.05) rapidly (2 min and 30 min), and prolactin mRNA levels were elevated (P<0.05) in pituitaries sampled 8 h after the injection. In contrast, plasma levels of somatolactin were decreased (P<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.

DOI： 10.1007/s00360-003-0340-1

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