REGULAR ARTICLES

Cell Research (2003); 13(6):491-497

Karyotype differentiation and reproductive isolation among natural populations of Drosophila lacertosa

Li Ping HE ^1,4, Hide Aki WATABE^{3, *}, Ya Ping ZHANG^{1, 2, *}, Tadashi AOTSUKA⁵

¹Laboratory of Molecular Biology of Domestic Animals, and Cellular and Molecular Evolution, Kunming,
Institute of Zoology, the Chinese Academy of Sciences,Kunming,Yunnan 650019,China. E-mail: zhangyp@public.km.yn.cn

²Laboratory for Conservation and Utilization of Bio-resource, Yunnan University, Kunming, Yunnan 650223, China

³Biological Laboratory, Sapporo College, Hokkaido University of Education, Sapporo 002-8502, Japan. E-mail: watabe@sap.hokkyodai.ac.jp

⁴Graduate School of the Chinese Academy of Sciences, Beijing, China.

⁵Department of Biology, Tokyo Metropolitan University, Hachioji-shi 192-0397, Japan.

Received May-14-2003 Revised July-9-2003 Accepted July-25-2003

Correspondence: Dr. Ya Ping Zhang, Fax: 0871-5195430;Tel: 0871-5190761, E-mail: zhangyp@public.km.yn.cn,and Dr. Hide-aki WATABE, E-mail: watabe@sap.hokkyodai.ac.jp, Tel: 0081-11-778-0342, Fax: 0081-11-778-8822.

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Abstract

Hindlimb unloading (HU) in rodent is a well-accepted ground-based model used to simulate some of the conditions of space flight and reproduce its deleterious effects on the musculoskeletal, cardiovascular and immune systems. In this study, the effects of HU on lymphocyte homeostasis in the spleen and thymus of mice were examined. HU was found to drastically deplete various cell populations in the spleen and thymus. These changes are likely to be mediated by apoptosis, since DNA strand breaks indicative of apoptosis were detected by terminal deoxynucleotidyl transferase-mediated nick end-labeling in both splenocytes and thymocytes. Surprisingly, administration of opioid antagonists or interference with the Fas-FasL interaction was able to block HU-induced reductions of splenocytes, but not thymocytes. On the other hand, steroid receptor antagonists blocked the reduction of lymphocyte numbers in both spleen and thymus. Therefore, the effects of HU on the homeostasis of splenocytes and thymocytes must be exerted through distinct mechanisms.
Key words: hindlimb unloading, apoptosis, stress, lymphocytes.