1. H. Mashimo, D.-C. Wu, D. K. Podolsky, Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease, Jackson 7, Massachusetts General Hospital, Fruit Street, Boston, MA 02114, USA.
2. M. C. Fishman, Cardiovascular Research Center, Massachusetts General Hospital East, 149 13th Street, Charlestown, MA 02129, USA.