1. Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
2. Laboratory of Cell Biology and Morphology, School of Bioresources Hiroshima Prefectural University, Shoubara-shi, Hiroshima 727-0023, Japan
3. Laboratory of Veterinary Pharmacology, School of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino, Tokyo 180-8602, Japan
4. Japan Food Research Laboratories, 6-11-10 Nagayama, Tama, Tokyo 206-0025, Japan