[Ultrastructural characterization of a retrovirus of mice (BL/F) producing leukemia in rats].

Two distinct leukemogenic viral subpopulations, BL/F (EL) and BL/F (SL) were derived from RadLV-Rs by propagation in rats. They were purified from the serum and studied by thin section and negative stain electron microscopy. Their ultrastructural organizations were not found to differ significantly from each other or from other murine leukemia viruses for which a detailed model now exists. Our work constitutes to our knowledge a first indepth study of viruses associated with radiation leukemia. It confirms the MuLV model built hitherto exclusively on observations from in vitro grown viruses.