Hiromitsu Okano

Time Cycle for Intracellular Synthesis of Murine Leukaemia Virus

MURINE leukaemia provides an effective model system for the study of both the disease process and the specific cell–virus interactions that elicit the leukaemic response1. In spite of numerous ultrastructural studies2, there is no information about the nature, site and duration of the intracellular cycle for this group of RNA viruses.

Distribution of viral antigen in mouse mammary tumor cells as revealed by ferritin antibody conjugate technique.

Rabbit antiserum against purifled type B particles from spontaneous mouse mammary tumor tissue was conjugated with ferritin for immunoelectron microscopy in order to demonstrate a relationship between type A and B particles. Ferritin granules were found deposited on type B particles and on budding A particles; some were also found similarly deposited on the naked cytoplasmic A particles. These observations suggest that type A particles contain material which is common in antigenic property to that contained in type B particles. The flndings may support the view that the naked cytoplasmic A particles are a precursor of B particles.

Inoculation of Chicken Sarcoma Virus into Chicken Thymus. An Electron Microscopy

Summary Intra-thymic inoculation of virus suspension is introduced as a method for electron microscopic study of chicken sarcoma of Chiba strain. In the tumor produced in the thymus, a significantly larger number of virus particles attached to the tumor cell was observed than in those produced at other sites. The virus particles were detected chiefly on the cell surface, in cytoplasmic vacuoles and in peculiar intracellular spaces.

Establishment and characterization of cell lines from gross virus-induced rat leukemia

Cells from thymus and/or bone marrow tissues of either normal or Gross virus-infected W/Fu rats were cultivated individually or mixed. Four continuous cell lines were obtained: 1) individual cultivation of the cells from thymic lymphoma, 2) combined cultivation of cells from thymic lymphoma and normal bone marrow, 3) bone marrow of a leukemic rat and normal thymus, and 4) bone marrow of a leukemic rat supplemented with cell-free extracts of normal thymus homogenates. The morphological features were similar in these 4 cell lines. The cells correspond morphologically to lymphoblasts, grow rapidly in suspension, and are transplantable in newborn rats. The cells release abundant Type-C virus particles. The inoculation of cell-free culture fluid into newborn rats resulted, after 7–9 weeks, in the development of thymic lymphoma in high incidence.