1. Departments of Reroduction,Nippon Veterinary and Animal Science University,7-1 Kyonan-cho 1 chome,Musashino-shi,Tokyo180-8602,Japan
2. Departments of Radiology,Nippon Veterinary and Animal Science University,71 Kyonan-cho 1 chome,Musashino-shi,Tokyo 180-8602,Japan
3. International Space Radiation Lab.and Division of Radiotoxicology and Protection,National Institute of Radiological Science,4-9-1 Anagawa,Inage-ku,Chiba 263-8555,Japan