1. Laboratory of Animal Genetics and Breeding, Faculty of Agriculture, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-Ku, Tokyo 156, Japan
2. Department of Blood Typing, Laboratory of Racing Chemistry, 4-37-6 Kamiyouga, Setagaya-Ku, Tokyo 158, Japan
3. Laboratory of Animal Resources, Faculty of Bioindustry, Tokyo University of Agriculture, 099-24 Aza-yasaka, Abashiri-shi, Hokkaido 196, Japan
4. Stromont Laboratory, 1237 East Beamer Street, Suite D, Woodland, California 95776, USA