1. Department of Surgery 1, School of Veterinary Medicine, Azabu University, 1–17–71 Fuchinobe, Chuo-ku, Sagamihara-shi, Kanagawa 252-5201, Japan
2. Research Fellow of the Japan Society for the Promotion of Science, 5–3–1 Kojimachi, Chiyoda-ku, Tokyo 102-0083, Japan