The purpose of this shared instrumentation grant is to obtain funds to purchase a Philips EM 410G Transmission Electron Microscope to be housed in a core electron microscopy unit in the Department of Cell Biology at the Baylor College of Medicine. This facility currently houses two electron microscopes, a Siemens 102 (purchased in 1972) and a JEOL 100XC scanning/transmission electron microscope (purchased in 1976). These two electron microscopes are the only instruments currently serving the needs of a Department of Cell Biology which includes 44 full-time faculty members. The Philips EM 410G is being requested specifically to replace the Siemens 102 which is over ten years old and frequently not available for use because of disrepair. The acquisition of the Philips EM 410G to replace the Siemens 102 will provide the appropriate stable and high resolution instrumentation needed to carry on the electron microscopy-related research activities of the major research group, as well as other members of the Department of Cell Biology.