1. Sakamachi Hospital, Arakawamachi, Niigata 959-31, Japan
2. Department of Immunology, Niigata University School of Medicine, Niigata 951, Japan
3. Third Department of Anatomy, Niigata University School of Medicine, Niigata 951, Japan
4. Department of Diagnostics, Niigata University School of Medicine, Niigata 951, Japan