title: Abnormal spermatogenesis at low temperatures in the Japanese red-bellied newt, Cynops pyrrhogaster: possible biological significance of the cessation of spermatocytogenesis.
abstract: In newt testis, spermatocytes never appear during winter, because secondary spermatogonia die by apoptosis just before meiosis. In the current study, we examined the effect of low temperatures on spermatogenesis. Incubation of newts at low temperatures (8, 12, 15 degrees C) induced defects in spermatogenesis in a temperature-dependent manner. At 8 degrees C, multinucleated giant cells (MGCs) were observed in spermatocytes and spermatogenesis never proceeded beyond meiosis. Although spermatocytes completed meiotic divisions at 12 degrees C, severe cell death was observed in the spermatids. At 15 degrees C both normal and abnormal spermiogenesis were observed. Under these conditions, impaired meiotic synapsis/recombination and down-regulation of the expression of the DMC1 protein, which play pivotal roles in meiotic pairing in eukaryotes, were also observed. Furthermore, to examine the quality of the sperm produced at low temperature for supporting development, artificial insemination was performed. The eggs inseminated with spermatozoa derived from newts kept at 15 degrees C demonstrated a restricted developmental capacity, even though these spermatozoa had an equal capacity for carrying out fertilization to those kept at 22 degrees C. These results suggest that meiosis at low temperatures cause the production of abnormal spermatozoa. Conservation and the significance of this phenomenon in poikilothermic vertebrates living in the temperate zones are also discussed.
authors.affiliation: Department of Biochemistry, Fukui Medical University, Shimoaizuki, Matsuoka, Fukui, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yazawa
authors.forename: Yuki
authors.initials: Y
authors.lastname: Nakayama
authors.forename: Kenta
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Matsuda
authors.forename: Keisuke
authors.initials: K
authors.lastname: Abe
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kitano
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Abé
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamamoto
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics; D002869:Chromosome Aberrations; D002875:Chromosomes; D003080:Cold Temperature; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D007315:Insemination, Artificial; D008297:Male; D008540:Meiosis / Q000502:physiology; D012455:Salamandridae / Q000502:physiology*; D013091:Spermatogenesis / Q000502:physiology*; D013093:Spermatogonia / Q000502:physiology; D013094:Spermatozoa / Q000002:abnormalities; D013737:Testis / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins