1. Department of Laboratory Animal Science. Nippon Medical School, 1-1-5. Sendagi, Bunkyo-ku, Tokyo 113, Japan; Department of Medical Zoology, Faculty of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo
113, Japan
2. Department of Laboratory Animal Science. Nippon Medical School, 1-1-5. Sendagi, Bunkyo-ku, Tokyo 113, Japan; Department of Medical Zoology, Faculty of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113,
Japan
3. Department of Medical Zoology, Faculty of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113, Japan