1. Laboratory of Pathology, Toxicology Division, The Institute of Environmental Toxicology, 4321 Uchimoriya-machi, Joso, Ibaraki 303-0043, Japan
2. Safety Science Research Laboratory, Central Research Institute, Ishihara Sangyo Kaisha, Ltd., 2-3-1 Nishi-shibukawa, Kusatsu-shi, Shiga 525-0025, Japan