[1] HARVARD UNIV, SCH MED, BOSTON, MA 02115 USA
[2] WASHINGTON UNIV, SCH MED, DEPT MED, ST LOUIS, MO 63110 USA
[3] WASHINGTON UNIV, SCH MED, DEPT SURG PATHOL, ST LOUIS, MO 63110 USA
[4] CHARLES A DANA RES INST, DEPT MED, DIV GASTROENTEROL, BOSTON, MA USA
[5] CHARLES A DANA RES INST, DEPT PATHOL, BOSTON, MA USA