1. Graduate School of Medicine, Hokkaido University, N15, W7, Kita-ku, Sapporo 060-8638, Japan
2. Graduate School of Medicine, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan
3. Faculty of Medicine, Hokkaido University, N15, W7, Kita-ku, Sapporo 060-8638, Japan
4. Graduate School of Life Science, Hokkaido University, N10, W8, Kita-ku, Sapporo 060-0810, Japan
5. Faculty of Advanced Life Science, Hokkaido University, N10, W8, Kita-ku, Sapporo 060-0810, Japan