Age response to x-radiation of murine lymphoma cells synchronized in vivo

Cells of a transplantable murine lymphoma line were partially synchronized in vivo by administration of a single dose of 0.5 mg of hydroxyurea per lymphoma-bearing mouse. At various times after administration of hydroxyurea, the femurs of the lymphomatous mice were X-irradiated, and the number of lymphoma colony-forming units per femur were then assayed by the spleencolony technique. A well-defined age response to irradiation of the lymphoma cells in vivo, similar to that of HeLa cells in vitro, was observed.