Dan R. Halm

Biography

Education History: Ph.D., University of Iowa, 1981 Associate Professor, Neuroscience Cell Biology, & Physiology  , works in Biological Sciences Bldg II 149, 3640 Colonel Glenn Hwy, Dayton, OH 45435-0001

Research Interest

Current research interests in his lab focus on the response of intestinal epithelial cells to stimulation from neural and hormonal stimuli [4]. Epithelial tissues form the barrier between the body interior and the external environment; and during digestion, intestinal epithelial cells secrete fluid to promote luminal enzyme action and motility, followed by reabsorption of this fluid to limit water loss from the body. Cells making up the epithelium produce fluid by secreting ions, such as Cl-, K+ and H+, into the lumen [15]. Macromolecular secretions amend the composition of this fluid by adding digestive enzymes, mucus, immunoglobulins and other molecules that support the health of the digestive tract [13]. Ion secretory mechanisms involve the action of specific ion transport proteins, such as Na+/K+-ATPase, Na+/K+/2Cl--cotransporter, K+ channels, and Cl- channels, which guide flow from the interstitium into the lumen. Regulation of these transport proteins allows for an orderly production of fluid as circumstances change during the day. Measurement of ion flow is a central activity in the lab, including patch-clamp recording of currents in epithelial cells as well as transepithelial currents. Biochemical assays complement these physiologic measurements by allowing detection of ion channel expression with RT-PCR, immunoblot and immunohistologic methods as well as quantifying changes in signaling molecules of specific regulatory pathways. In addition, imaging of epithelial structures permits visualization of morphological changes occurring during secretion, with incorporation of fluorescent dyes permitting detection of cellular ion composition (pH, Ca++, Cl-) during the time course of secretory activation. Together these techniques contribute to understanding the normal and pathophysiologic operation of epithelia.