Lee D. Peachey, Ph. D. Professor of Biology Ph.D., Rockefeller University, 1959 309 Leidy Laboratories Department of Biology University of Pennsylvania Philadelphia, PA 19104 USA V +1 215 898.5788 F +1 215 898.8780 E lpeachey@sas.upenn.edu

research : publications

neurobiology and cell biology The long-range interest in this laboratory is understanding how cell structures are formed and how these structures underlie cell functions. A major specific interest is how skeletal muscle cells are controlled with respect to activation and relaxation. Early EM studies in this laboratory contributed structural information on T-system and SR (sarcoplasmic reticulum) membranes and helped to outline how these two membrane systems are involved in the process of coupling surface excitation to the initiation of intracellular contraction. Later, quantitative structural information was obtained, related to electrophysiological measurements of fiber capacitance, and incorporated into electrophysiological models of electrical activity of the T-system. This, in turn, led to experimental studies that showed that the T-system carries excitation into the depth of the muscle fiber by an action potential mechanism. Presently, high voltage electron microscopy is being used in the laboratory to obtain three-dimensional structural information on both T-system and SR, using selective stains and stereoscopic EM methods. Relatively thick slices (1-2 micrometers) of plastic embedded tissues are examined in a transmission electron microscope at 400 kV. Stereoscopic micrographs allow direct three-dimensional visualization of membrane networks and rapid structural analysis is accomplished in this way. Two results to come from this work are the discovery of helicoidal arrangements in the membrane systems and fibrillar striations of skeletal muscle cells, and a classification of subregions of the T-system membranes into tubular, noncontact regions and flattened regions that form contacts with SR. We also have developed methods for doing quantitative EM (stereology) using a digital planimeter coupled with a computer. An extension of this is the development of a computer graphic system for three-dimensional reconstruction and display of data from stereoscopic and multiple-tilt electron micrographs, yielding quantitative 3D information on the structures reconstructed. Confocal scanning laser microscopes are used to study muscle cells and other types of cells in culture. Recently techniques have been developed for sequential viewing of the same cells by confocal fluorescence microscopy and high voltage electron microscopy, combining and correlating the best advantages of each instrument on the same sample. For example, fluorescent-tagged antibodies, localized in 3D by confocal fluorescence microscopy, can directly be related to fine structures seen in the same cells in whole mounts in the high voltage electron microscope.

selected publications Holleran, E.A., Gray-Board, G., Holzbaur, E.L.F. and Peachey, L.D. 1996. Fluorescence, confocal, and intermediated voltage electron microscopy of centractin localization in transfected PtK2 cells. 53rd Ann. Proc. Microscopy Soc. Amer., Minneaplois, MN (G.WW. Bailey and A.J. Garret-Reed, eds.) 28-29 Murakami, T., Ishikawa, H., and Peachey, L.D. 1994. Confocal microscopic 3D visualization of membranous organelles in living cultured fibroblasts. Bioimages 2:21-28. Fujimaki, N., Peachey, L.D., Murakami, T, and Ishikawa, H. 1993. Three-dimensional visualization of the T-system in fixed and embedded frog skeletal muscle fibers by confocal laser scanning reflection microscopy. Bioimages 1:167-174. Huang, C.L-H. and Peachey, L.D. 1992. A reconstruction of charge movements during the action potential in frog skeletal muscle. Biophys. J. 61:1133-1146. Huang, C.L-H. and Peachey, L.D. 1989. The anatomical distribution of voltage-dependent membrane capacitance in frog skeletal muscle fibers. J. Gen. Physiol. 93:565-584. Heath, J.P. and Peachey, L.D. 1989. Morphology of fibroblasts in collagen gels: a study using 400 kV electron microscopy and computer graphics. Cell Motility and the Cytoskeleton 14:382-392. Sundell, C.L., Goldman, Y.E., and Peachey, L.D. 1986. Fine structure in near-field and far-field laser diffraction patterns from skeletal muscle fibers. Biophys. J. 49:521-530.