1. Division of Gastroenterology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, P.R. China
2. Division of Science and Technology, Beijing Normal University-Hong Kong Baptist University United International College, Zhuhai, P.R. China
3. Division of Gastroenterology, The First Affiliated Hospital, Sun Yat-sen University, 58 Zhongshan Road 2, Guangzhou 510080, P.R. China