1. Department of Pathology, Showa University School of Medicine , 1-5-8, Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
2. Hitachi High-Tech Corporation , 882, Ichige, Hitachinaka-shi, Ibaraki 312-8504, Japan
3. Department of Anesthesia, Showa University Graduate School of Dentistry , 2-1-1, Kitasenzoku, Ota-ku, Tokyo 145-8515, Japan
4. Department of Anatomy, Showa University School of Medicine , Tokyo 142-8555, Japan
5. Digestive Disease Center, Showa University Northern Yokohama Hospital , 35-1, Chigasakityuou, Tuzuki-ku, Yokohama-shi, Kanagawa 224-8503, Japan
6. Center for Electron Microscopy, Showa University , Tokyo 142-8555, Japan