Richard Siegler

Direct transformation of 3T3 cells by Abelson murine leukaemia virus.

MURINE leukaemia viruses (MLV) cause tumours of haemopoietic origin in vivo1,2, but although they replicate in vitro, they generally do not transform cells. MLV provides helper activity3 for the replication of defective murine sarcoma virus (MSV)4 which possess a transforming activity5. Abelson and Rabstein6 isolated an agent in association with Moloney leukaemia virus (MLV-M) which causes a rapidly progressive lymphoblastic leukaemia of bone-marrow-derived lymphocytes (B cells)7. In addition, this Abelson virus (MLV-A) in conjunction with MLV-M causes rapid appearance of immunoglobulin-producing plasmacytomas in BALB/c mice primed with oil8. We now report that MLV-A can be defective for virus replication and show that this agent directly transforms 3T3 cells in vitro. A quantitative transformation assay is described.

Chromosome Aberrations: Their Role in the Etiology of Murine Leukemia

If the association between chromosome aberrations and leukemia is a causal one, the aberrations should be present before the appearance of tumor. In a virus-induced murine leukemia in which the pre- and early leukemic stages were defined, aneuploidy was observed only during the later stages of the disease. This suggests that the chromosome alteration results from, rather than initiates, the neoplastic transformation.

Studies on the Mechanism of Action of Thymic Leukemogenic Virus.

Summary Murine Leukemia virus (Rich) was inoculated into only one of the 2 thy-muses of infant mice which were sacrificed 2 months later. The animals were analyzed to compare the incidence of lymphoma evolving in the inoculated thymus with the incidence of lymphoma evolving in the uninocu-lated thymus. It was found that of 30 animals suitable for analysis, in 90% of cases the tumor arose in the inoculated thymus, supporting the view that the mechanism of viral leukemogenesis is direct.

ARTIFICIAL RESPIRATION IN MICE DURING THORACIC SURGERY: A SIMPLE INEXPENSIVE TECHNIC.

During experiments designed to determine the effect of unilateral thymectomy on the unilateral development of thymic lymphoma in mice (1,2) an apparatus for artificial respiration with positive pressure oxygen in mice was developed. Use of the device permits wide surgical exposure of the thorax and approximates the conditions accomplished by modern anesthesia machines. Because the device decreases the hazard of pneumothorax during experimental surgery on mice and is inexpensive to construct, the apparatus is presented for possible interest to other investigators. The apparatus consists of 3 parts: 1) a flow valve, bubble meter, and high pressure limit assembly; 2) a valve to provide intermittent oxygen flow, and 3) an endotracheal catheter (Fig. 1.) 1. Flow valve, bubble meter, and high pressure limit assembly. The regulation of small amounts of oxygen is accomplished by use of a screw clamp on the oxygen supply rubber tubing which leads directly from the reducing valve of a standard oxygen tank. The rate of flow of oxygen is visually observed by bubbling the gas through water. By means of a “T” tube, the high pressure limit tube is connected to the metered gas flow. This last device consists of a length of glass tubing immersed in a column of water. The height of water above the open lower end of the tube determines the pressure at which excess oxygen will blow off. The upper end of the pressure limit tube is twice as high as the water column to prevent water from rebounding into the supply line. 2.“Finger valve.” The intermittent flow of positive pressure oxygen is controlled by a manually operated open-type valve. This device is constructed by cutting a 2 cm round hole in a 4 inch length of 3/4′ polyethylene drying tube.

Significance of Increased Alkaline Phosphatase Activity in Viral-Induced Thymic Lymphoma.

Summary Mice inoculated with a leukemogenic virus (Rich) were studied to determine when alkaline phosphatase appears in thymic cells relative to the developing thymic lymphoma. The findings indicated that the enzyme increase occurs only after the tumor is definitely established, hence this change cannot be causally related to the neoplasm.