Biomedical subjects
Publications and source records attributed to C J Larsen.
Murine cells continuously producing Friend viral complex were synchronized by Ficoll gradient centrifugation. Cells were isolated from different parts of the gradient and counts of budding particles were performed on ultra-thin sections. No significant differences were noticed, suggesting that viral release is not related to cell cycle.
Molecular hybridization techniques were used for searching nucleic acid sequences homologous to murine and simian oncornaviral genomes in the RNA of various categories of human leukaemic cells. We report attempts to characterize the sequences that were detected in defined categories of leukemias. It is shown that: i) although there is some correlation between the two probes used in our study with regard to the positivity or the negativity of the tests for the same leukaemic cases, there are also some discrepancies since some of the cases are positive with one probe and negative with the other; ii) the common sequences of the two probes when isolated, were ineffective to detect any complementary sequences in leukemic cases which were scored as positive when the entire probes were used; iii) the complementary sequences detected in three positive cases of acute myelogenous leukemias by a recycled probe are additive and therefore most probably distributed along the viral genome.
Oncornaviral particles on the way of their synthesis have been isolated from cytoplasm of a Friend virus-producing murine cell line. By use of electron microscopy and retrotranscriptase assay, it was found that the majority of the viral structures is pelleted by sedimentation at 90.000 g. The Poly (A) RNA of this pellet contains principally 70S and 35S RNA species which, as judged by size determination and hybridization with Friend-virus c-DNA are the species embedded into the virions. We verified that conditions which were used in the course of isolation, effectively dissociate polysomes and prevent them from co-sedimenting with viruses.
This review tentatively recaptitulates most of the known data concerning the genome of oncornaviruses (Retroviruses). The first part deals with the structural features of the 60-70S RNA and its constituting subunits and other cellular RNAs which are present inside the viruses. The second part describes the viral RNA species which have been found in various cell systems including infected producer cells, transformed and non producer cells, normal and inductible cells. A special part is devoted to viral RNAs isolated from human cancer cells.
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The presence of viral-like sequences in the RNA of various types of leukemic cells was investigated by hybridizing cellular poly(A)-containing RNA with cDNA synthesized in an endogenous system of purified Moloney murine sarcoma virus [M-MSV-(MLV)]. Poly(A)-RNA-cDNA hybrids were detected by assaying their resistance to S1 nuclease. Hybrids were found in 22 out of the 46 leukemias that were tested. None of the controls, including material obtained from buffy coats, bone marrow cells, and a continuous human cell line, was positive. Positive cases were found in all the different categories of leukemias with the exception of chronic myelogenous leukemias. There was no definite corelation between the category of leukemia and positivity. A few cases contained a very high proportion of poly(A)-RNA-cDNA hybrid.
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The two 8S A and B RNAs of the Mouse Sarcoma Virus (Moloney) can be converted by heating into a homogeneous population. After digestion with T(1) RNAse, they give identical fingerprints. It is concluded that these two molecules represent conformational isomers of the same molecular species.
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Several low-molecular-weight RNAs were released from mouse leukemia sarcoma virus 70S RNA under conditions of thermal denaturation. One of them, the 70S-associated 8S RNA, exhibits a number of structural properties characteristic of a previously described free viral 8S RNA. This similarity was revealed by polyacrylamide gel electrophoresis and nucleotide composition.
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