1. Department of Chemical and Biological Sciences; Japan Women's University; 8-1, Mejirodai 2-chome Tokyo 112-8681 Japan
2. Laboratory of Electron Microscopy; Japan Women's University; 8-1, Mejirodai 2-chome Tokyo 112-8681 Japan
3. Marine Mammals Research Group; Institute of Marine Research; P.O. Box 1870 Nordnes, N-5817 Bergen Norway