1. Research Department, Research and Development Division, Hokuriku Seiyaku Co., Ltd., 37-1-1 Inokuchi, Katsuyama, Fukui 911-8555, Japan
2. Department of Hygiene and Preventive Medicine, Niigata University School of Medicine, Asahimachi-dori 1-757, Niigata City, Niigata 951-8510, Japan