PubMed Health⌕ Search

Biomedical subjects

M T Borrás

Publications and source records attributed to M T Borrás.

7 recordsLinked to original sources
PubMed1982

Inability to transmit scrapie by transfection of mouse embryo cells in vitro.

Infectivity of nucleic acid from highly infectious mouse scrapie brains was studied by transfecting the nucleic acid in vitro prior to inoculation into animals. Foetal mouse brain and whole mouse embryo cultures were chosen as the cells used for the transfection. As an internal control, infectious nucleic acid was recovered from bacteriophage phi X174 and whole virus particles were obtained when cultures were transfected with herpes simplex virus DNA. In contrast, none of the animals inoculated with nucleic acid preparations derived from scrapie-infected tissues developed scrapie disease either with or without transfection procedures. These findings (i) show transfection techniques fail to elicit evidence of a scrapie-specific infectious nucleic acid and (ii) confirm the observation that scrapie is not a viroid.

Animals↗
PubMed1973

Difference between functional and structural integrity of messenger RNA.

Messenger RNA molecules that are structurally stable, as measured by their ability to hybridize to DNA, may nevertheless be considerably less stable in retaining their ability to function in protein synthesis. The structure of the majority of the mRNA of phage S13 decays with a half-life of 10.6 +/- 0.5 min. In contrast, much of the function of the mRNA that is involved in synthesis of a capsid protein (product of the F gene) decays rapidly with a half-life of 1.4 +/- 0.8 min; a residual amount of function decays with a half-life of 14.0 +/- 4.0 min. The measurements were made in the presence of rifampicin, which was used to prevent the formation of new mRNA. A proposed model for the functional decay is based on the polycistronic nature of the mRNA. Degradation of the mRNA would proceed in two steps: the first step would be a fast attack at a region near the 5'-terminus of each molecule that would eliminate the function of the proximal message; the second step would be a slow attack on the remaining messenger molecule precipitating a subsequent rapid degradation of the physical structure.

Carbon Isotopes↗
PubMed1971

Superinfection in bacteriophage S13 and determination of the number of bacteriophage particles which can function in an infected cell.

Bacteriophage S13 shows exclusion of superinfecting homologous phage, but the exclusion is only partial. The superinfecting phage can form infectious replicative form deoxyribonucleic acid (RF), can direct protein synthesis, and can form progeny particles even at a superinfection time as late as 60 min after the first infection. Exclusion is also only partial for the closely related phage phiX174. Seven min after the first infection, the exclusion mechanism begins to operate, requiring continuous phage-specified protein synthesis. The gene A protein (required for synthesis of progeny RF) appears to be involved in the exclusion mechanism. In superinfection experiments, it was found that at least 40 phage particles per cell can replicate and can carry out protein synthesis, though the number of sites for binding of RF to the membrane is only about 15 per cell. The results suggest that attachment of RF to a binding site is not required for protein synthesis. Evidence is presented that non-attached parental RF can serve as a template for single-stranded deoxyribonucleic acid synthesis.

Binding Sites↗