The purpose of this submission is to request funding to purchase a Mark I Model 68A rodent cesium (137Cs) irradiator for use by several PHS funded scientists that require this item of specialized equipment to irradiate mice or cell lines as a critical component of their research. The irradiation of transgenic mice by these scientists is a pre-requisite to bone marrow transplantation in immune competent mice when the intent of the research is to: 1. Study the contribution of specific bone marrow cells populations to the progression of lesion development in atherosclerosis or myocardial infarction 2. Study the biomechanical contribution of various adhesion molecules in the normal trafficking and migration of inflammatory cells in atherosclerosis and myocardial infarction where the double or triple gene knockouts would normally be lethal to the mice. 3. To introduce thymic precursors that engineered to delete the gene encoding c-myb in developing thymocytes after introduction into irradiated hosts. This is done in order to test the role of c-myb during positive and negative selection in the thymus more efficiently than breeding the targeted c-myb locus, along with the necessary Cre transgenes onto a variety of mouse backgrounds 4. Investigate the contribution of clonal populations T-lymphocytes to the induction of pulmonary damage in mouse models of influenza and respiratory syncytial virus infection 5. Induce damage to the intestinal mucosa in a manner that is reproducible to investigate the role of various cytokines and growth factors in mucosal inflammation and repair. The irradiation of cell lines is necessary in the following types of studies: 1. Produce feeder cells for maintaining cultures a fastidious cell lines such as embryonic stem cells 2. Induce defined DNA damage to cell lines to study the sensitizing effects of various treatments to induce radiation sensitivity for the development of novel cancer therapeutic strategies This irradiator will replace an existing unit Nordion Gamma Cell 40 purchased in 1984 and for which repair parts are no longer commercially available. [unreadable] [unreadable]