SUMMARY : Three cell lines persistently infected with Friend leukemia virus were obtained by treating MLg cells with a homogenate of Friend leukemia virusinfected mouse spleens. Two of them were highly leukemogenic and the other was low leukemogenic.The virus titer of the culture fluid of the highly leukemogenic cell lines was about 103 ID50/0.2 ml or more and the undiluted culture fluid induced leukemia in young adult mice within one or two weeks. Virus particles in the low leukemogenic cell line revealed by electronmicroscopy were morphologically indistinguishable from and not fewer than those found in one of the former two cell lines. The persistently infected cell lines could be stored at -70 C without impairing the virus production from the cells.
A non-leukemogmic strain of Friend leukemia virus ( F L V ) propagated in vitro interfered with infection by murine sarcoma virus (Moloney) ( M S V ) and acted as a helper of defective MSV. This suggests that the non-leukemogenic strain of FLV is infectious. After prolonged propagation in vitro, the Ieukemogenicity of a highly leukemogenic strain of FL V gradually decreased, while the infectivity assayed by iriterference with MS V infection remained unchanged.
Murine sarcoma virus (Moloney) ( M S V ) transformed C3H2K cells originating Bassin et al., 1968;Bather et al., 1968) and rat cells (Ting, 1966;Bernard et al., 1967). The titration pattern of murine sarcoma virus (Moloney) (MSV) indicated that MSV was defective and simultaneous infection with a murine leukemia virus was required for MSV focus formation (Hartley and Rowe, 1966;O'Connor and Fischinger, 1968;Guillemain et al., 1968). The hamster tumors induced by MSV were free from infectious MSV, and the virus was rescued by the inoculation of the tumor cells into mouse cell cultures followed by infection with murine leukemia viruses (Huebner et al., 1966; Bassin ct a/., 1968).In our paper, the titration pattern of MSV, the interference between Friend leukemia virus (FLV) and MSV, and the focus formation in synchronized cultures will be presented. The purpose of these experiments was to examine whether any similarities exist between murine and avian sarcoma viruses.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.