| Abstract: | Examination of various normal and neoplastic tissues reveals the presence of intracisternal A-particles in five strains of mice and their hybrids. Cell types derived from all three embryonic germ layers contain these particles, and their presence in gonadal tissue of both sexes suggests that vertical transmission can take place. Intracisternal A-particles are found in most of the tissues known to support the replication of mouse leukemia viruses and mammary tumor virus. Further, they have been shown to coexist in the same cell with C particles and intracytoplasmic A-particles (mammary tumor virus precursors). Although it has not been possible to demonstrate biological activity associated with intracisternal A-particles, there is the possibility that they represent the partial gene expression of one of the known oncogenic RNA viruses, and as such serve as a marker for an incomplete replication cycle. |
