P.hd in Insect physiology

P.hd in Insect physiology

We study the mechanisms of transport of small solutes and water molecules across cell membranes. Our primary interest lies in the physiology of epithelial cells, the cells that line surfaces of the body and are the key transporting cells of organs like the intestine, kidneys and eyes. In many of these epithelial cell systems, it is still not clear as to what the driving forces for water absorption and secretion are. The technical challenge of working with small living structures in vitro requires experimental models dedicated to each cell system and the parameters being measured. Where information is sought at a single membrane level we use artificial planar bilayer membranes with model channels like the antibiotic gramicidin inserted in them.

The primary research interest of the Membrane Biophysics Laboratory is the study of transport processes in cell membranes, particularly the coupled transport of solutes and water molecules. We investigate cellular and molecular mechanisms that underlie physiological processes in epithelial cells, cell layers and artificial planar bilayer membranes with model channels inserted in them using three or four techniques:

Microperfusion electrophysiology of tubular insect epithelial cells, e.g. the Drosophila midgut; analysis of ion-currents and ion-water interactions in ion channels in artificial bimolecular lipid membranes; capacitance probe measurement of transepithelial water transport and fluid transport in insect epithelia using the Ramsay technique

The Drosophila midgut has recently been shown to have progenitor cells that determine the architecture of the midgut of the fly with a plan strikingly similar to the development of the mammalian gut. However, very little is known of the physiology of the Drosophila midgut. As the gut is segmented, we perfuse individual segments in vitro, and test epithelial transport models with a defined number of cells and negligible barriers. Complete ultrastructural stereology has been done of all relevant membrane areal and volume densities. With excellent control of transepithelial voltage, pressure and solute composition gradients, we have identified a V-H+-ATPase present predominantly or exclusively on the basolateral membranes that is a powerful transporter for acid-base regulation. We are now analyzing the larval and adult epithelium to understand the role of the carbonic anhydrase catalysed intracellular H+ transport pool, and the localisation and other transporters involved in transepithelial H+ transport.