1. Department of Gastroenterological Surgery; Yokohama City University Graduate School of Medicine; 3-9 Fukuura, Kanazawa-ku Yokohama 236-0004 Kanagawa Japan
2. Department of Biostatistics; Yokohama City University; Yokohama Kanagawa Japan
3. Laboratory of Animal Biological Responses; Department of Veterinary Science; School of Veterinary Medicine; Rakuno Gakuen University; Ebetsu Hokkaido Japan