1. Department of Physiology, Nippon Medical School, Sendagi 1-1-5, Bunkyo-ku, Tokyo 113, Japan
2. Division of Biochemistry, Institute of Medical Science, The Jikei University School of Medicine, Tokyo, Japan
3. Department of Neurology, Faculty of Medicine, Kyoto University, Kyoto, Japan
4. Laboratory of Chemical Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA