@inproceedings{oai:jaxa.repo.nii.ac.jp:00013919,
 author = {渡辺, 明彦 and 鬼武, 一夫 and Watanabe, Akihiko and Onitake, Kazuo},
 book = {宇宙利用シンポジウム　第19回　平成14年度, Space Utilization Research: Proceedings of the Nineteenth Space Utilization Symposium},
 month = {Feb},
 note = {Spermatogenesis progresses under the influences of hormonal control through blood flow in vertebrates. In testes, germ cells at every stage interact with somatic cells and those interactions regulate the progress of spermatogenesis. While, germ cell differentiation autonomously progresses in some processes. Those controls cooperate with each other and enable the testis to provide the adequate amount of sperm in the species-specific reproductive period. Thus, it was significant for understanding the mechanism of spermatogenetic control in vertebrates to elucidate the effect of the three distinct controlling systems independently. In the medaka fish, Oryzias latipes, primary spermatocytes autonomously differentiate into fertilizable sperm in cell culture. On the other hand, all the spermatogenetic process is suggested to progress orderly in the cultured testis. Because the spermatogenesis in the cell culture progresses without the hormonal control and germ-somatic cell interaction and that in the organ culture does without the hormonal control, it is possible to elucidate the effect of each controlling system on spermatogenesis by comparing the spermatogenesis in vivo. In this study, to elucidate the effect of hypergravity on the control of spermatogenesis, male fish, organ culture of the medaka testis or cell culture of the medaka germ cells was centrifuged at 5 G for 5 or 10 days. In the medaka testis, both in vivo and in vitro, the percentages of each stage of germ cells did not change significantly. However, the percentage of apoptotic germ cells decreased in the testis of the medaka fish at 5 G. On the other hand, no difference was observed in the cultured testis. These results suggest that hormonal control were influenced by the hypergravity that resulted in the suppression of germ cell apoptosis. In organ culture, germ cell apoptosis was suppressed by gonadotropin, suggesting that it may involve in the suppression of germ cell apoptosis in the hypergravitational condition. While, mitochondria localization was significantly suppressed in spermatids that underwent spermiogenesis in cell culture at 5 G. This result suggests that autonomous control of spermiogenesis was influenced by the hypergravitational condition. The results of the present study demonstrate that medaka fish is available to elucidate the effect of hypergravity on the mechanisms for controlling spermatogenesis. This indicates that the medaka fish is one of the suitable animals to investigate the influences of the space environment on the spermatogenesis in vertebrates because the basic mechanism for controlling spermatogenesis is common in vertebrates., 資料番号: AA0045438012},
 pages = {36--38},
 publisher = {宇宙科学研究所, The Institute of Space and Astronautical Science (ISAS)},
 title = {過重力環境がメダカの精子形成とその調節機構に及ぼす影響の解析},
 year = {2003}
}