The purpose of this project is to seek better understanding of the structure and function of the human gastrointestinal mucosa in health and in disease. The effects of laxatives on intestinal mucosa, the synthesis of chylomicrons by human jejunal mucosa, and mechanisms of intestinal oxalate absorption are being studied. We are continuing to investigate the pathogenesis of a variety of diseases which involve the gastrointestinal tract such as idiopathic intestinal pseudoobstruction, erosive gastritis, and celiac sprue. The diagnostic usefulness of peroral and rectal suction biopsies in inflammatory bowel diseases is being investigated. BIBLIOGRAPHIC REFERENCES: Silverstein FE, Rubin CE: Chapter on "Gastrointestinal Endoscopy" in Harrison's Principles of Internal Medicine, 1977 edition, in press. MacDonald WC, Rubin CE: Chapter on "Tumors, Gastritis, and Other Diseases of the Stomach" in Harrison's Principles of Internal Medicine, 1977 edition, in press.