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Biomedical subjects

R R Friis

Publications and source records attributed to R R Friis.

At least 73 records · Page 4Linked to original sources
PubMed1978

Comparison of the RNA-dependent DNA polymerase of an endogenous avian leukosis virus to the polymerase of an exogenous avian leukosis virus.

RNA-dependent DNA polymerases from Rous-associated virus-O and avian myeloblastosis virus were partially purified by affinity chromatography and compared to each other. The enzymes are indistinguishable in the immunoglobulin inhibition test and by several enzymological criteria, such as optimum curves for the concentrations of Mg2+, K+, H+; monophasic Lineweaver-Burk plot for dTTP and biphasic Lineweaver-Burk plot for dGTP. In thermal inactivation studies a small difference can be observed, suggesting a minor difference in the physical structures of the enzymes. Our findings are consistent with the idea that the RNA-dpendent DNA polymerases of endogenous and exogenous avian leukosis viruses are very closely related to each other and therefore may be regarded as one group of polymerases.

Antigen-Antibody Reactions↗
PubMed1978

Purification and characterization of particles containing RNA-dependent DNA polymerase, in the allantoic fluid of uninfected leukosis virus-free chicken eggs.

The allantoic fluid of embryonated chicken eggs regularly contains particle-associated RNA-dependent DNA polymerase, as shown by its reaction with homopolymeric and heteropolymeric RNA and by the characterization of the products. The purification of the particles is described. The purified particles are different from the known avian RNA tumor viruses in their protein composition and their sedimentation constant. They do not exhibit biological properties typical for RNA tumour viruses, such as helper activity, interfering properties or infectivity and do not show endogenous DNA synthesis. The particles are discussed as non-viral elements.

Allantois↗
PubMed1978

Polyethylene glycol-mediated infection with avian sarcoma viruses.

In this communication we report that fusion of viral and cellular membranes by polyethylene glycol is a convenient approach to overcoming genetically determined resistance to infection. Using this method, avian sarcoma virus-transformed mammalian cells have been produced which serve as useful model systems for the study of Rous sarcoma virus-specific tumor antigens.

Animals↗
PubMed1978

Immunogenicity of the envelope glycoprotein of avian sarcoma virus.

The expression of type E-specific glycoprotein in chick-helper factor-positive [chf(+)] chickens is not restricted to a certain stage of embryogenesis but persists in postembryonic life. This finding prompted an investigation of the immunogenicity of the viral envelope glycoprotein of exogenous avian sarcoma virus in chf(+) and chf(-) chickens. Sensitization of both classes of chickens resulted in the induction of detectable antibody reactivity to determinants of the glycoprotein that were type-specific as well as group-specific. Because group-specific determinants are present on type E-specific glycoprotein, these results link immunity to exogenous viral envelope glycoprotein in chf(+) chickens with autoreactivity. A model is proposed to rationalize the induction of reactivity in this system.

Alpharetrovirus↗
PubMed1978

Binding of tryptophanyl-tRNA to the reverse transcriptase of replication-defective avian sarcoma viruses.

The ability of reverse transcriptase to bind to [3H]tryptophanyl-tRNA and to function as DNA polymerase was compared for five temperature-sensitive mutants of avian sarcoma virus. Both activities of the reverse transcriptase were found to be heat labile in LA 335 and LA 336 as compared with the wild-type parents. For the other mutant viruses, LA 338, LA 343, and LA 672, grown at the permissive temperature, the reverse transcriptase was nearly as heat stable as for the wild-type parents in terms of tRNA binding and DNA polymerase. LA 338, LA 343, and LA 672 showed characteristic defects in their reverse transcriptase when propagated at the nonpermissive temperature; namely, tryptophanyl-tRNA binding and DNA polymerase activities were coordinately decreased in these virions. The reduced enzymatic activities were not entirely due to an inactive reverse transcriptase present in the virions, however, but rather lower amounts of enzyme protein incorporated into the virions contributed to the effect, according to assays of reverse transcriptase antigen by radioimmune competition.

Animals↗
PubMed1977

Quantitative determination of myoinositol, inositol 1-phosphate, inositol cyclic 1 : 2-phosphate and glycerylphosphoinositol in normal and Rous-sarcoma-virus-transformed quail fibroblasts under different growth conditions.

Myoinositol and its phosphorylated derivatives have been quantitatively determined in normal and Rous-sarcoma-virus-transformed quail cells under various growth conditions using [2-(3)H]myoinositol at isotope equilibrium conditions. The following amounts were determined (nmol/mumol phospholipid, as a unit of cell mass): exponentially growing normal and tumor cells contained 25--40 nmol free inositol, 0.40--0.45 nmol myoinositol 1-phosphate, 0.30--0.50 nmol glycerylphosphoinositol, and 0.03--0.04 nmol myoinositol cyclic 1 : 2-phosphate. At high cell populations in the absence of serum, conditions which result in cessation of growth by normal but not by tumor cells, changed levels were found for glycerylphosphoinositol and free inositol. In tumor cells the levels of these two compounds increased to 0.64 nmol and 64 nmol, respectively. In normal cells glycerylphosphoinositol increased to 0.95 nmol and free inositol showed highly elevated levels of 144 nmol. At short pulses the specific activities of inositol 1-phosphate and inositol cyclic 1 : 2-phosphate were found to be higher than that of phosphatidylinositol. This was not the case for glycerylphosphoinositol.

Animals↗
PubMed1977

Influence of defective virion core proteins on RNA maturation with an avian sarcoma virus.

The RNA of the avian sarcoma virus B77 temperature-sensitive mutant LA334 was investigated using electrophoretic analysis. The RNA from mutant virus grown at the nonpermissive temperature (42degrees C) showed a heterogeneous peak between 80 and 125S, and another at about 35S. The RNA of the mutant virus grown at the permissive temperature (35 degrees C) behaved like wild-type B77 virus RNA, exhibiting a major peak at 70S. The homology between the various RNA fractions and virus-specific DNA probe was determined, indicating that mutant virus grown at the nonpermissive temperature contains relatively large amounts of nonviral-specific RNA.

Avian Sarcoma Viruses↗
PubMed1977

Changes in phosphatidylinositol metabolism correlated to growth state of normal and Rous sarcoma virus-transformed Japanese quail cells.

Second-passage Japanese quail embryo cell cultures, normal or quantitatively transformed by Rous sarcoma virus, were investigated for phospholipid composition and metabolism. Cells cultivated at low and high population density as well as in the presence or absence of serum, have been compared by chemical analysis and in pulse-chase experiments. No differences in the lipid compositions between the normal and the tumor cells or between cells under different culture conditions were detected. In no case was the metabolism of phosphatidylserine or sphingomyelin affected by culture conditions. The metabolism of the choline and ethanolamine glycerophospholipids, however, differed according to culture conditions, whether cells were normal or transformed. Significantly, in normal cells, the breakdown of [32P]phosphate-labeled phosphatidylinositol was slowed when cell growth was restricted, i.e., at high population density or in medium without serum. This effect was not observed in tumor cells under such culture conditions, and cells were not growth inhibited. Hence, release of [32P]phosphate from phosphatidylinositol is the only parameter in the metabolism of phospholipids observed to correlate with growth.

Animals↗
PubMed1976

The effect of transformation-defective avian oncornavirus mutants on tumor antigen expression.

The recent isolation of conditional (temperature sensitive) and nonconditional transformation-defective mutants of avian sarcoma virus strains has facilitated the investigation of the effect of virus transformation on the cell's phenotype, e.g., with respect to morphology, growth pattern, or cell surface antigenicity. Special emphasis was laid on elucidating the correlation between transformed phenotype and tumor antigen expression. All of the tested nontransforming deletion mutants and the majority of the temperature-sensitive mutants were unable to induce tumor antigens in phenotypically untransformed cells. However, 3 temperature-sensitive mutants were found which were able to support the expression of tumor specific surface antigens even at restrictive temperature, when cells otherwise exhibited a normal phenotype. The theoretical and practical implications of this association between normal phenotype and tumor antigen expression are discussed.

Agglutination↗
PubMed1976

Viral glycoprotein synthesis studies in an established line of Japanese quail embryo cells infected with the Bryan high-titer strain of Rous sarcoma virus.

Although a glycoprotein with an approximate molecular weight of 43,000 is associated with purified virions of the Bryan high-titer strain of Rous sarcoma virus propagated on R(-)Q cells, these virions lack gp85, the major glycoprotein of the avian tumor virus envelope. As measured by immune precipitation with a specific antiserum, gp85 does not accumulate to detectable levels in R(-)Q cells.

Animals↗