1. Research Institute for Diseases of Old Age, Juntendo University School of Medicine; Tokyo 113-8421 Japan
2. Department of Clinical Biochemistry, School of Pharmacy; Tokyo University of Pharmacy and Life Sciences; 1432-1 Horinouchi Tokyo 192-0392 Japan
3. Department of Biochemistry and Biophysics, Graduate School of Health Care Sciences; Tokyo Medical and Dental University; Tokyo 113-8510 Japan
4. Laboratory of Cell and Developmental Biology; National Institute of Dental and Craniofacial Research, National Institutes of Health; Bethesda MD 20814