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Biomedical subjects

J W Watts

Publications and source records attributed to J W Watts.

35 records · Page 2Linked to original sources
PubMed1981

The mechanism of entry of viruses into plant protoplasts.

Plant protoplasts may be efficiently infected with viruses. Attachment to the plasmalemma is a critical step in infection; positively charged viruses readily adhere and infect but negatively charged viruses require the presence of a polycation (e.g. poly-L-ornithine) before infection can occur. The role of the polycation appears to be twofold: to modify the charge of the virus and to damage the surface of the protoplast. Virus probably enters the protoplast during repair of damaged regions of the plasmalemma. Pinocytosis does not appear to play a significant part in inoculation.

Adhesiveness↗
PubMed1969

The loss of rapidly labelled ribonucleic acid from isolated HeLa cell nuclei.

1. The loss of nucleic acids and protein from isolated HeLa-cell nuclei was studied. During 4hr. incubation at 37 degrees DNA was conserved, but appreciable amounts of RNA and protein were lost. 2. Two classes of nuclear RNA were distinguished: at least 75% of the RNA was lost from the nuclei relatively slowly through degradation to acid-soluble fragments; the rest of the RNA was lost much more rapidly, not only through degradation to acid-soluble fragments but also through diffusion of RNA out of the nuclei into the incubation medium. 3. The RNA that was preferentially lost was the fraction of nuclear RNA that was rapidly labelled when intact HeLa cells were grown in a medium containing radioactive precursors of RNA. 4. The RNA appearing in the incubation medium was apparently partially degraded and had a sedimentation coefficient of about that of transfer RNA. 5. Both the degradation of RNA and the loss of RNA from the nuclei were sensitive to bivalent cations. Low concentrations of Mg(2+) and Mn(2+) greatly increased the rate of degradation of the rapidly labelled RNA to acid-soluble fragments, and produced a corresponding decrease in the amount of RNA diffusing into the medium. At higher concentrations they suppressed both degradation and diffusion of RNA. The cations Ca(2+), Cu(2+), Zn(2+) and Ni(2+) all progressively inhibited both forms of loss of RNA. 6. Salts of univalent cations produced appreciable effects only at ionic strengths of about 0.2, when degradation to acid-soluble fragments was preferentially inhibited. 7. Both ADP and ATP inhibited loss of RNA at about 30mm. 8. It was concluded that the diffusion of rapidly labelled RNA out of the isolated nuclei was not related to the movement of RNA from nucleus to cytoplasm in vivo, but reflected the ease with which the rapidly labelled RNA detached from the chromatin and the permeability of the membranes of isolated nuclei.

Adenine Nucleotides↗
PubMed1969

Stimulation of incorporation of nucleic acid precursors into HeLa cells caused by proflavine.

1. The effect of proflavine and other acridines on the incorporation of precursors into the nucleic acids of HeLa cells was examined. 2. Relatively low concentrations (50mum) of proflavine completely inhibited incorporation of precursors into DNA, but allowed a small extent of incorporation into RNA. 3. Acridine-resistant incorporation into RNA was unaffected by actinomycin D at 2mug./ml. and persisted even at high concentrations (500mum) of many acridines. 4. A few combinations of acridine and precursor, notably 250mum-proflavine and [(14)C]adenine, caused a stimulation of incorporation. 5. The proflavine-stimulated incorporation was into alkali-stable di- and tri-nucleotides. 6. It was concluded that the effect was due to the preferential inhibition of degradation of a fraction of RNA that normally turned over, thus allowing small radioactive oligonucleotides to accumulate in the cells.

Acridines↗
PubMed1966

The effect of proflavine on HeLa cells.

1. The effect of proflavine on the metabolism of RNA, DNA and protein of HeLa cells was studied. 2. The synthesis of RNA, DNA and protein was progressively inhibited by concentrations of proflavine up to 43mum. 3. There was no simple relationship between the degrees of inhibition of synthesis of RNA, DNA and protein by increasing concentrations of proflavine: the synthesis of RNA was most readily inhibited, and the synthesis of protein was relatively insensitive. 4. A concentration of 22mum-proflavine inhibited synthesis of RNA and DNA and caused a progressive loss of RNA from both nucleus and cytoplasm without any accompanying loss of DNA or dry weight from the cells. 5. The rapidly labelled RNA in the nucleus was preferentially degraded and was not transferred in a stable form to the cytoplasm.

Acridines↗
PubMedDate not supplied

A method for the purification of large quantities of biologically active ribonucleic acid components from cowpea chlorotic mottle virus, a multicomponent plant virus.

Cowpea chlorotic mottle virus RNA has been prepared in comparatively high yield (at least 50%) by a modified phenol extraction method. The preparation, which has high biological activity, has been resolved into four components by zonal centrifugation on a 15-40% (w/v) sucrose density gradient. The components obtained have been tested for biological activity against whole plants and plant protoplasts. Each of the two largest components RNA 1 and RNA 2 was by itself infective (50-90% of the specific infectivity of the whole genome) and produced virus-specific proteins (coat protein and P2) and RNAs ("RNA 3" and "RNA 4"). Contamination by small proportions (less than 10%) of neighbouring RNAs is presumed to be involved in this infectivity. The two smallest components were obtained in an almost pure form.

Electrophoresis, Polyacrylamide Gel↗