1. Graduate School of Health Sciences, Hokkaido University, Kita-12, Nishi-5, Kita-ku, Sapporo 060-0812, Japan
2. Biological Research, Education and Instrumentation Center, Sapporo Medical University, Minami-1, Nichi-17, Chuo-ku, Sapporo 060-8556, Japan
3. Faculty of Health Sciences, Hokkaido University, Kita-12, Nishi-5, Kita-ku, Sapporo 060-812, Japan