John P Geibel DSc, MD, MSc
Professor of Surgery (Gastrointestinal) and of Cellular and Molecular Physiology; Vice Chair, Surgery; Director, Surgical Research
Gastric Acid Secretion; Colonic Fluid Transport; Renal Physiology; Intracellular Ion Activity Measurements; Calcium Sensing Receptor; Diarrheal disease, electrophysiology; CFTR; AMPKinase volume regulation
Current ProjectsWe are focused on 3 main areas; gastric ion transport in health and disease, intestinal ion transport in health and disease, and renal physiology. For gastric ion transport we are focusing on means to modulate acid secretion and reverse erosion. We use a combination of natural products and biochemical modifications to treat acid disease at the cellular level. For studies of intestinal ion transport, we are focusing on how the calcium sensing receptor(CaSR) can modulate fluid transport during toxin induced diarrhea. In addition we are investigating means to prevent ischemic injury by activating ionic pathways using the AMPKinase. Finally we are trying to prevent IBD/IBS associated epithelial injury in the gut by Casr activation . For the renal studies we are interested in acid base homeostasis along the nephron, and are now investigating the role of the CaSR in modulating fluid secretion and renal stone formation.
Our primary focus is on real time monitoring of ion transport mechanisms in epithelia, using high-resolution microscopy. One of the crucial problems facing all epithelial cells is the control of the intracellular milieu. In an effort to maintain ionic homeostasis, epithelial cells have devised a variety of ion channels, transport proteins, and carriers to regulate and maintain the intracellular ionic concentrations. To further understand how ions are transported in epithelial cells, we have developed a variety of optical techniques to continuously monitor intracellular ionic concentrations in real time. Using high-resolution video or confocal microscopy we are presently able to monitor intracellular Ca2+, Na+, K+, Cl-, pH, and membrane potential. We are currently investigating various aspects of renal tubule and gastric tissue ion transport in intact renal tubules and gastric glands. We also are characterizing the secretory and reabsorptive properties of the colonic crypt, with a special focus on diarrheal disease.