title: Two states of active spermatogenesis switch between reproductive and non-reproductive seasons in the testes of the medaka, Oryzias latipes.
abstract: Seasonal change in spermatogenesis was examined in the restricted spermatogonium-type testes of a teleost, Oryzias latipes. Histological observation revealed that the number of each stage of germ cells during most of the non-reproductive season, from October to January (O-J period) was nearly half of that during the reproductive season, from May to July (M-J period), except for type B spermatogonia (B-gonia), which was actually equal. As a result, the ratio of primary spermatocytes (P-cytes) to B-gonia was remarkably small in the O-J period. Despite the differences between both time periods, the proliferative activity of type A spermatogonia (A-gonia), B-gonia, or P-cytes was at a similar level in both periods. Moreover, in cultured testes treated with bromodeoxyuridine as a cell-lineage tracer, P-cytes differentiated to spermatids in 11-15 days in both M-J and O-J periods. These indicate that spermatogenesis is active in each period at a different state. In the spermatogenic testis, A-gonial proliferation was maintained by human follicle stimulating hormone/luteinizing hormone in culture. Whereas cell death of B-gonia and/or P-cytes gradually increased in the M-J period in spite of those cells being constant in population sizes. In transition to the O-J period, A-gonia and P-cytes first decreased, which was accompanied by a decrease in proliferative activity of A-gonia and relative increase of dead cells from B-gonia and/or P-cytes against live P-cytes. These suggest that A-gonial proliferation and cell death of B-gonia and/or P-cytes that is induced coordinately with B-gonial differentiation are critical for the spermatogenic control.
authors.affiliation: Department of Biology, Faculty of Science, Yamagata University, 1-4-12 Kojirakawa, Yamagata 990-8560, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Iwasaki
authors.forename: Keiko
authors.initials: K
authors.lastname: Ohkawa
authors.forename: Hisato
authors.initials: H
authors.lastname: Sadakata
authors.forename: Akiko
authors.initials: A
authors.lastname: Kashiwadate
authors.forename: Eriko
authors.initials: E
authors.lastname: Takayama-Watanabe
authors.forename: Kazuo
authors.initials: K
authors.lastname: Onitake
authors.forename: Akihiko
authors.initials: A
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D001973:Bromodeoxyuridine / Q000008:administration & dosage; D016923:Cell Death; D049109:Cell Proliferation / Q000187:drug effects; D005640:Follicle Stimulating Hormone / Q000494:pharmacology / Q000502:physiology; D007986:Luteinizing Hormone / Q000494:pharmacology; D008297:Male; D009924:Organ Culture Techniques; D009990:Oryzias / Q000502:physiology*; D012621:Seasons; D013087:Spermatids / Q000166:cytology / Q000502:physiology; D013090:Spermatocytes / Q000166:cytology / Q000502:physiology*; D013091:Spermatogenesis; D013093:Spermatogonia / Q000166:cytology / Q000502:physiology*; D013737:Testis / Q000166:cytology / Q000502:physiology
chemical_list: D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D001973:Bromodeoxyuridine