[A thermosensitive characteristic of the Schmidt Rupin strain ...

Quail embryo skin fibroblasts infected with wild type Rous sarcoma virus SR-RSV grow, at 36 or 41 degrees C, twice as fast (30 hours. mean division time) as the uninfected controls or the cells infected with RAV-1 virus. At 36 degrees C the SR-RSV infected cells stop growing after the same delay as the controls, thus having undergone twice as many doublings, (38 to 40 instead 18 to 20). However, at 41 degrees C, SR-RSV infected cells stop 5 to 6 divisions earlier. This cannot be reversed by shifting the cultures to 36 degrees C. Rising to 41 degrees C those cultures which grew previously at 36 degrees C reduce the number of residual divisions. No such effect is observed with NYts68 or PA101 viruses which display a reduced level of pp60v-src activity at 41 degrees C.