1. Institute for Biomedical Sciences, Digestive Disease Research Group, Georgia State University, Atlanta, GA 30303, USA
2. Research, Atlanta Veterans Affairs Medical Center, Decatur, GA 30302, USA
3. Department of Medicine, Division of Gastroenterology & Hepatology, Indiana University School of Medicine, Indianapolis, IN 46220, USA
4. Research, Richard L. Roudebush VA Medical Center, Indianapolis, IN 46202, USA
5. Department of Medical Physiology, Texas A&M University School of Medicine, Bryan, TX 77807, USA