1. Department of Gastroenterology and Hepatology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki 852-8501, Japan
2. Department of Endoscopy, Nagasaki University Hospital, Nagasaki 852-8501, Japan
3. Department of Histology and Cell Biology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki 852-8523, Japan
4. Medical Education Development Center, Nagasaki University Hospital, Nagasaki 852-8501, Japan