[1] LOUISIANA STATE UNIV, SCH MED, DEPT PHYSIOL, NEW ORLEANS, LA 70119 USA
[2] CHU VAUDOIS, DEPT CHIRURG EXPTL, CH-1011 LAUSANNE, SWITZERLAND
[3] FREE UNIV BERLIN, KLINIKUM STEGLITZ, INNERE MED SCHWERPUNKT GASTROENTEROL ABT, D-1000 BERLIN 45, FED REP GER