Viruses and renal carcinoma of Rana pipiens: II. Ultrastructural studies and sequential development of virus isolated from normal and tumor tissue

Abstract

The sequential development of a virus (FV 1) isolated from cultured frog kidney cells has been studied by electron microscopy in fathead minnow (FHM) and baby hamster kidney (BHK 21/13) cells. Regions of virus synthesis were first seen in the cell cytoplasm at 7 and 10 hours after infection of FHM and BHK 21/13 cells, respectively. These sites contained virus particles in all stages of development from partial capsids to complete capsids with nucleoids. The virus was hexagonal and measured approximately 120 by 130 mμ. At 12 hours after infection, virus was seen budding from the cytoplasmic membrane, thus acquiring an envelope. This process continued throughout the course of the infection. Late in the infection (24–48 hours) one or more virus crystals were regularly seen in the cytoplasm of FHM cells and occasionally in BHK 21/13 cells. FV 1 replication in adult and embryonic frog cell monolayers, cultured Lucké tumor cells, and chick embryo monolayers was identical to that seen in FHM and BHK 21/13 cells. Eleven additional isolates from both normal and tumor (Lucké) frog tissue were examined in FHM cells. The morphology and site of synthesis of these isolates were identical to FV 1 and contrasted with the nuclear site of synthesis of virus seen in the Lucké tumor.