1. *Department of Medicine, Palo Alto Veterans Affairs Medical Center, Palo Alto, CA 94304;
2. Stanford University Digestive Disease Center, Stanford, CA 94305;
3. Division of Gastroenterology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, People's Republic of China; and
4. Biosciences, Department of Biology, Abo Akademi University, FI-20520, Turku, Finland