1. Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo
060-0815, Japan
2. Watanabe Oyster Laboratory Company Limited, 490-3,
Shimo-ongata-cho, Hachioji, Tokyo 190-0154, Japan
3. Faculty of Health Sciences, Hokkaido University, Kita-12, Nishi-5,
Kita-ku, Sapporo 060-0812, Japan