title: Comparative studies on Visna, progressive pneumonia, and Rous sarcoma viruses by electron microscopy.
mesh_terms: D000818:Animals; D001358:Avian Sarcoma Viruses / Q000145:classification / Q000472:pathogenicity; D002478:Cells, Cultured; D002642:Chick Embryo; D008854:Microscopy, Electron; D011328:Prions; D012608:Scrapie / Q000382:microbiology; D012756:Sheep; D012897:Slow Virus Diseases / Q000382:microbiology*; D014713:Viruses, Unclassified / Q000472:pathogenicity
chemical_list: D011328:Prions