An ultrastructural study of the formation of "dark" and "light" cytoplasmic inclusions by murine cytomegalovirus in mouse submandibular gland.

Electron micrographs of acinar cells of the submandibular glands of CFW mice infected with murine cytomegalovirus, Smith strain, were studied. The resulting viral intracytoplasmic inclusion bodies were classified into two groups termed "light" (relatively electron-lucent) and "dark" (relatively electron-dense). It appeared that the "dark" type was the late stage of inclusion body maturation.

Interferon production by mammalian cells grown in a serum-free medium.

Interferon, produced by rabbit heart cells grown in a serum-free medium, failed to protect rabbit heart serum-free cells, but protected rabbit heart serum-containing-medium cells against vaccinia and vesicular stomatitis virus. Interferon produced in serum-free cells had a greater species specificity than that produced in serum-containing media. The difference in activity was shown to be due to lack of adsorption by serum-free-medium cells.