Morphologic Aspects of Rous Sarcoma Virus Elaboration2

Abstract

In ultrastructural studies of 7 avian tumors induced by the Bryan strain of the Rous sarcoma agent, we observed virus elaboration and elimination from the cell by budding of the cytoplasmic membrane in about 5 percent of the cells of 5 growths. The process could be traced from the earliest stages of budding to separation of the particle from the pedicel of the cell membrane. Newly formed particles exhibited a central region of low density, and the electron-dense nucleoid, typical of the “mature” virus, developed after separation of the particle from the cell. Nonviral bodies, “mucoastrosomes,” of approximately the same size as virus particles were present in the intercellular material. The probable origin of the structures from cytoplasmic membrane is discussed.