The long term objectives of these studies are to examine at the molecular level the mechanisms by which rat virus produces cranio-facial disturbances. The specific aims of this pilot project are to examine the ability of the virus to replicate in calvaria of newborn animals; examine the morphological effects of the virus on the bones and determine degree and site of infection; initiate studies on the effects of the virus on extracellular matrix components; and determine if the virus replicates in the different cell types of the growing calvaria. Calvaria will be infected in vitro with virus and the overall ability of the virus to replicate will be examined by isolation and titration. The specific sites where virus are present will be determined histologically and by the use of specific DNA probes. The ability of the cells to produce mucopolysaccharides and collagen will be determined using radioisotope labeling and extraction. The different cell types present in calvaria will be separated and grown in culture and the ability of virus to replicate in them will be measured.