1. Department of Cell Physiology, Hokkaido University Graduate School of Medicine, N15 W7, Kita-ku, Sapporo, Japan
2. Graduate School of Pharmaceutical Sciences, Hokkaido University, N12 W6, Kita-ku, Sapporo, Japan
3. Department of Microbiology, Shimane University Faculty of Medicine, 89-1, Enya-cho, Izumo, Shimane, Japan