1. Department of Laboratory Animal Medicine, Central Institute for Experimental Animals, 1430 Nogawa, Miyamae, Kawasaki 216, Japan
2. Taiho Pharmaceutical Co., Research Institute, 224-2 Hiraishi, Kawauchi, Tokushima, 771-01, Japan
3. Department of Laboratory Animal Science, School of Hygienic Sciences, Kitasato University, Kitasato, Sagamihara 228, Japan
4. Department of Laboratory Animal Science, School of Hygienic Sciences, Kitasato University, Kitasato, Sagamihara 228, Japan; Wakamoto Pharmaceutical Co., Ltd, 378 Kanade, Ohi-machi, Ashigarakami-gun, Kanagawa 258, Japan