1. Meat Science Laboratory, Dept. of Animal and Food Hygiene; Obihiro Univ. of Agriculture and Veterinary Medicine; Nishi2-11, Inada-cho Obihiro Hokkaido 080-8555 Japan
2. Muscle Biology and Meat Science Laboratory, Graduate School of Agriculture; Hokkaido Univ; N-9, W-9, Kita-ku Sapporo Hokkaido 060-8589 Japan
3. Electron Microscope Laboratory, Research Faculty of Agriculture; Hokkaido Univ; N-9, W-9, Kita-ku Sapporo Hokkaido 060-8589 Japan