1. Department of Cytology and Histology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan
2. Research Fellow of Japan Society for the Promotion of Science, Tokyo 102-0083, Japan
3. Department of Cytology and Histology, Okayama University Medical School, Okayama 700-8558, Japan
4. Department of Physiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
5. Department of Oral and Maxillofacial Pathology, Osaka University Graduate School of Dentistry, Osaka 565-0871, Japan
6. Department of Rehabilitation for Orofacial Disorders, Osaka University Graduate School of Dentistry, Osaka 565-0871, Japan
7. Department of Cytology and Histology, Faculty of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8558, Japan