In the early eighties, the PI received funds from the NCRR program to purchase an electron microscope, and at that time we bought the JEOL 1200EX. This microscope, operated by the Department of Cell Biology, has served as a shared resource at our Medical Center. Unfortunately, the microscope has been very unreliable in recent years and indeed for the past six months it has only worked sporadically due to extensive water damage resulting from a ceiling flood. Although both the condenser and objective lenses are being replaced, JOEL cannot rule out continued problems as a result of the initial water damage. It is therefore essential that we obtain a replacement EM as soon as possible since a number of faculty members at Georgetown have research projects that depend upon high quality electron microscopy. We wish to purchase the Hitachi Model H-7600-1; this microscope has many advantages and improvements over our aging JEOL 1200EX that would significantly enhance our ability to carry out the projects described in this grant proposal. Included among these advantages are greater reliability, ease of operation, digital imaging of sections, increased specimen stability in the electron beam, increased number of specimens which can be evaluated at one time, enhanced use for morphometric analysis, montage collection, ease of surveying of samples, and ability to identify and return to specific regions on specimen grids. The ability to have computerized alignment together with maintenance of such important viewing factors as consistent brightness regardless of operating Kv or magnification facilitates the ease of surveying samples and the taking of electron micrographs. Finally, the user-friendly operation and ease of control manipulation significantly reduces user fatigue and facilitates multi-user usage. We believe that it is important that this microscope be procured as soon as possible to enable us to continue to meet the commitments to the research projects as outlined in our grants.