1. Department of Internal Medicine, Oklahoma University Health Sciences Center, Williams Pavilion 1130, P.O. Box 26901, Oklahoma City, OK 73104, USA
2. Dow Medical College, Mission Road, Karachi 74200, Pakistan
3. Section of Digestive Diseases and Nutrition, Oklahoma University Health Sciences Center, Williams Pavilion 1345, 920 SL Young Boulevard, Oklahoma City, OK 73104, USA