Abstract
Reverse transcriptase activity was detected in the supernatants of rat embryo fibroblast cell cultures transformed by HSV types 1 and 2 at either the sub-optimal temperature of 20 °C or the supra-optimal temperature of 42 °C. Rat cell clones which had been transformed at 20 °C contained higher levels of C-type virus DNA polymerase than did cell clones which had been transformed at 42 °C. Syncytia formation typical for C-type RNA viruses occurred at passages higher than 24. The activation of endogenous C-type RNA viruses was independent of the virus and transformation method used.