1. Department of Comparative Pathophysiology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113, Japan
2. Equine Research Institute, Japan Racing Association, 321-4 Togami-cho, Utsunomiya, Tochigi 320, Japan
3. Hidaka Nosai, 2-5-5 Urakawa-cho, Sakaimachi Higashi, Urakawa-gun, Hokkaido 057, Japan