1. Department of Biochemistry, Hokkaido University Graduate School of Medicine, Kita-ku, Kita 15, Nishi 7, Sapporo 060-8638, Japan
2. Department of Obstetrics and Gynecology, Hokkaido University Graduate School of Medicine, Kita-ku, Kita 15, Nishi 7, Sapporo 060-8638, Japan