1. Institute for Immunology/Genetic Medicine (retired); Hokkaido University; Sapporo Hokkaido 060-0815 Japan
2. Environmental Molecular Biology, Division of Bioscience, Graduate School of Environmental Earth Science; Hokkaido University; Sapporo Hokkaido 060-0815 Japan
3. Isotope Center (retired); Hokkaido University; Sapporo Hokkaido 060-0815 Japan