[1] Kings Coll London, Dept Clin & Mol Genet, London WC2R 2LS, England
[2] Univ Kiel, Inst Clin & Mol Biol, Kiel, Germany
[3] Univ Newcastle, Dept Gastroenterol & Hepatol, Newcastle Upon Tyne, Tyne & Wear, England
[4] Kings Coll London, Dept Gastroenterol, London, England
[5] UCL, Inst Digest Dis, London, England
[6] Univ Kiel, Dept Med, Kiel, Germany