1. Department of Gastroenterology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-Ku, Tokyo 113-8421, Japan
2. Department of Life Science, Faculty of Engineering and Resource Science, Akita University, Akita 010-8502, Japan
3. Department of Gastroenterology, Yokote Municipal Hospital, Akita 013-8602, Japan