[1] Univ N Carolina, Sch Med, Ctr Esophageal Dis & Swallowing, Chapel Hill, NC 27599 USA
[2] Univ N Carolina, Sch Med, Ctr Gastrointestinal Biol & Dis, Chapel Hill, NC 27599 USA
[3] Univ N Carolina, Sch Med, Div Gastroenterol & Hepatol, Dept Med,Dept Pathol & Lab Med, Chapel Hill, NC 27599 USA