1. Laboratory of Laboratory Animal Science and Medicine, School of Veterinary Medicine, Kitasato University, 35-1 Higashi-23, Towada, Aomori 034-8628, Japan
2. Department of Laboratory Animal Medicine, Section of Animal Models, Research Institute, National Center for Global Health and Medicine, Koyama 1-21-1, Shinjuku, Tokyo 162-8655, Japan
3. Laboratory of veterinary pathology, School of Veterinary Medicine, Kitasato University, 35-1 Higashi-23, Towada, Aomori 034-8628, Japan
4. Laboratory of Biomedical Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan