title: Gonadotrophic cells and gonadal sex differentiation in medaka: Characterization of several northern and southern strains.
abstract: Gonadotropins play an important role in gametogenesis and reproduction in vertebrates. Their localization in the pituitary during gonadal sex differentiation has been studied mainly in southern (Oryzias latipes) strains of medaka fish, with that in northern medaka (O. sakaizumii) remaining poorly understood. Hence, in this study, we characterized gonadal differentiation and gonadotrophic cells during sex differentiation in two northern strains (HNI and Kaga) and two southern strains (Hd-rR and d-rR/Tokyo). All strains exhibited similar sex differentiation at hatching, such as (1) sex difference in germ cell number (XX > XY), and (2) the transition of XX germ cells into meiosis, and (3) presence of glycoprotein-α (Gpa)-positive cells. However, follicle-stimulating hormone-β (Fshb)-positive cells were first detected in the pituitary 1 day post-hatching in HNI. Exposure to high-temperature conditions and to cortisol in a dose dependent manner resulted in the localization of Fshb cells in the pituitary at hatching. This study demonstrates differences in gonadotropin subunit expression between northern and southern strains of medaka, and suggests that Fsh is not involved in early gonadal sex differentiation, such as the sex difference in germ cell number, and that high-temperature induce Fshb expression via cortisol production in medaka.
authors: Laboratory of Molecular Reproductive Biology, Graduate School of Integrated Pharmaceutical and Nutritional Sciences, University of Shizuoka, Shizuoka, Japan.
authors: Yoshifumi
authors: Y
authors: Horie
authors: Laboratory of Molecular Reproductive Biology, Institute for Environmental Sciences, University of Shizuoka, Shizuoka, Japan.|Laboratory of Molecular Reproductive Biology, Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka, Shizuoka, Japan.
authors: Tohru
authors: T
authors: Kobayashi
mesh_terms: D000818:Animals; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D006066:Gonads / Q000166:cytology / Q000254:growth & development*; D006358:Hot Temperature; D006854:Hydrocortisone / Q000494:pharmacology; D007564:Japan; D008297:Male; D009990:Oryzias / Q000235:genetics / Q000502:physiology*; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism; D012733:Sex Differentiation; D013045:Species Specificity
chemical_list: D005640:Follicle Stimulating Hormone; D006854:Hydrocortisone