1. Hematology-Oncology Division, Beth Israel Hospital, Harvard Medical School, Boston, MA 02215.
2. Gastroenterology Division, Robert Wood Johnson Medical School, New Brunswick, NJ 08903.
3. Gastroenterology Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115.
4. Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115.