Tetsuya Hirano

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Osmoregulatory actions of growth hormone (GH) and its mode of action in salmonids are reviewed. We present evidence suggesting that insulin-like growth factor I (IGF-I) mediates some of the actions of GH on seawater acclimation. Plasma concentration and turnover of GH rise following exposure to seawater. Exogenous GH (in vivo) increases gill Na+,K+-ATPase(More)
We have identified ghrelin and cDNA encoding precursor protein from the stomach of a euryhaline tilapia, Oreochromis mossambicus. The sequence of 20-amino acid tilapia ghrelin is GSSFLSPSQKPQNKVKSSRI. The third serine residue was modified by n-decanoic acid. The carboxyl-terminal end of the peptide possessed an amide structure. RT-PCR analysis revealed high(More)
The Mozambique tilapia, Oreochromis mossambicus, is capable of surviving a wide range of salinities and temperatures. The present study was undertaken to investigate the influence of environmental salinity and temperature on osmoregulatory ability, organic osmolytes and plasma hormone profiles in the tilapia. Fish were acclimated to fresh water (FW),(More)
The ontogeny of pituitary cell-types, hypothalamic neurons and their fibers, was studied immunocytochemically during development of chum salmon. Five weeks after fertilization (eyed stage embryos), 5 cell-types were detected in the adenohypophysial (AHP) anlage; prolactin (PRL)-, growth hormone (GH)-, adrenocorticotropin (ACTH)-, melanotropin (α-MSH)-, and(More)
Morphological changes in the chloride cells (CCs) in the yolk-sac membrane of euryhaline tilapia (Oreochromis mossambicus) embryos and larvae were examined in relation to environmental salinity. Half of a brood of embryos spawned in fresh water (FW) were transferred directly to seawater (SW) 1 day before hatching; the other half was maintained in FW. The(More)
To clarify the hormonal regulation of metamorphosis of the conger eel (Conger myriaster), changes in whole body concentrations of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), and cortisol during metamorphosis were examined, as well as the changes in the histological activity of the thyroid gland. In larvae before metamorphosis, T4 and T3(More)
Two PRL-releasing peptides (PrRP20 and PrRP31) were recently identified from mammalian hypothalamus by an orphan receptor strategy, and a C-terminal RF (arginyl-phenylalamyl-) amide peptide (RFa), structurally related to mammalian PrRP, was also identified from the brain of the Japanese crucian carp (C-RFa) by an intestine-contracting assay. However, to(More)
Plasma somatolactin (SL) concentrations were examined in chum salmon in relation to gonadal maturation; immature salmon in the Bering Sea at various stages of maturation, and mature salmon during upstream migration caught at the ocean, bay and river. Plasma SL concentrations as well as plasma prolactin (PRL) and growth hormone (GH) levels in the immature(More)
Thyroid hormone concentrations in unfertilized eggs of 26 species of various freshwater, marine and diadromous teleosts were examined, together with changes in their concentrations during egg development in some species. Significant quantities of both thyroxine (T4) and triiodothyronine (T3) were found in eggs of all species examined. Mean T4 and T3(More)
To clarify the role of growth hormone (GH) in salmonids during seawater (SW) adaptation, we examined GH kinetics in chronically cannulated rainbow trout, weighing about 1 kg. When trout were transferred from fresh water (FW) to 75% SW, plasma chloride concentration was normalized within 1 week. Plasma GH concentration increased significantly 2 days after(More)