Faculty Profiles - SAKAMOTO Tatsuya

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A finally identified prolactin releasing factor from a mammal and a fish.

KAGAKU TO SEIBUTSU 36 ( 12 ) 798 - 799 1998

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

Language：English

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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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

Language：English

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

Osmoregulatory actions of growth hormone and prolactin in an advanced teleost(共著)

SAKAMOTO T

Gen. Comp. Endocrinol 106 95 - 101 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

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

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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