A great deal has been learned about the way the microcirculation responds to its environment, including responses to pressure, flow and oxygen, by using microscopic investigation and physiological transducers. We also are beginning to understand the pharmacologies of arteriolar smooth muscle and endothelial cells, including cell surface receptors, ion channels, second messenger macromolecules, and electrical behavior, and the anatomical structures, including ap junctions between different cell types which may provide communications. We have learned relatively less about how cellular mechanisms control vascular function. Electrical communication is hypothesized to play a fundamental role in coupling responses along arteriolar networks; recordings of such communication will reveal much about cellular control of microvessel function. Dr. Beach proposes studies of arteriolar signaling mechanisms in the Department of Biomedical Engineering at the University of Virginia, using novel instrumental and spectroscopic methods to extend the use of voltage sensitive dyes and calcium indicators. He proposes to investigate the spread of electrical activity and changes in intracellular calcium, which signal conducted vasomotor responses along resistance arterioles, and to establish the correlations between membrane potential changes, calcium changes and vasomotor activity. He will use localized stimulation with vasoactive agonists to initiate conducted responses, while recording images of the change in membrane potential and in calcium during the time between stimulation and the fully developed vasomotor response. A specialized camera and controller will be developed enabling small optical signals to be imaged in real-time. Changes in emission spectra of electrochromic voltage sensitive dyes will be exploited to measure the 10-20mV changes in membrane potential which are estimated to occur in cells of the arterioles of the cheek pouch, and to record electrical changes during the motion of conducted vasomotor responses. A prism spectrograph will be employed to perform spectral analysis of optical signals along microvessel segments. Evidence for electrotonic conduction pathways will be sought by investigating electrical and calcium responses occurring along the endothelial and smooth muscle cell layers of arterioles. These observations are needed to better understand how electrical and chemical signaling operate in microvessels. Dr. Beach's long term goal is to use his combined training in engineering and physiology to study aspects of vascular function which for which data remain inaccessible with conventional chemical and electrophysiological methods.
| Kao, W Y; Davis, C E; Kim, Y I et al. (2001) Fluorescence emission spectral shift measurements of membrane potential in single cells. Biophys J 81:1163-70 |
| Beach, J M; McGahren, E D; Duling, B R (1998) Capillaries and arterioles are electrically coupled in hamster cheek pouch. Am J Physiol 275:H1489-96 |
| Beach, J M; McGahren, E D; Xia, J et al. (1996) Ratiometric measurement of endothelial depolarization in arterioles with a potential-sensitive dye. Am J Physiol 270:H2216-27 |
