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Volume 23,
Issue 1,
1974
Volume 23, Issue 1, 1974
- Articles
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Virus Resistance Induced in Plants by Polyacrylic Acid
More LessSUMMARYPolyacrylic acid (PA) injected into tobacco cv. Xanthi-nc induced complete resistance to infection with TMV or tobacco necrosis virus but only partial resistance to potato virus X. The effect was maximal when the injection was made 2 to 3 days before inoculation. The lesion size was limited when the injection was made after inoculation. Using PA of 3500, 27000, 76000, 230000 and 1 × 106 mol. wt. the resistance decreased with increasing size of the polymer. In plants younger than 7 weeks, only the smallest polymer was active and evidence suggested that cell permeability to the larger polymers might increase with age of plant. The PA-induced resistance disappeared when plants were kept at 32 °C, but the effect of temperature was reversible. Polyacrylamide failed to induce resistance suggesting that the polyanionic structure of the acid polymers is responsible for the phenomenon.
Disc-electrophoresis in 10% polyacrylamide gels showed that three additional soluble proteins appeared in PA-injected leaves, but only in conditions in which resistance to infection was induced. These new proteins co-electrophoresed with three out of four proteins produced in TMV-infected leaves of cv. Xanthi plants that also are resistant to infection and may be the cause of resistance.
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A Possible Explanation of the Resistance of Virus-infected Tobacco Plants to Second Infection
More LessSUMMARYLeaves of tobacco plant cv. Xanthi-nc inoculated or systemically infected with potato virus Y, cucumber mosaic virus, potato virus X, potato aucuba mosaic virus or alfalfa mosaic virus showed varying degrees of resistance to infection with tobacco mosaic virus. The resistance was correlated with the appearance of at least three proteins not present in healthy plants. These were the proteins that appear in leaves injected with polyacrylic acid. Both the resistance to second infection and proteins decreased when the plants were kept for 2 days before inoculation at 32 °C.
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Group G Chromosomes and the Susceptibility of Cells of Human Origin to Coxsackie B Viruses
More LessSUMMARYComparative karyological studies have been made on the J-96 line of human leukaemic cells, which are susceptible to enteroviruses, and on cell strains derived from this line which are persistently infected with Coxsackie B5 virus or free from infective virus but possessing high specific resistance to Coxsackie B3 or B5 viruses. It was shown that the karyotypes of these cell strains were characterized by reduced numbers of small acrocentric chromosomes of group G. It is suggested that group G chromosomes in cells of human origin incorporate genes which control alkaline phosphatase activity and the production of specific substances essential to adsorption and intracellular development of Coxsackie B viruses.
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Electrophoretic Characterization of Purified Mouse L Cell Interferon of High Specific Activity
More LessSUMMARYL cell interferon was purified by precipitation with zinc acetate and chromatography on DEAE- and CM-Sephadex, to a maximum sp. act. of 2 × 108 international units per mg protein. As analysed by polyacrylamide gel electrophoresis, such preparations contained large amounts of contaminating proteins, some of which coincided in mobility with components in the corresponding material from uninduced L cell cultures. However, at the position of the dominant, sharp interferon peak, a protein band was discernible which was not apparent in the control material. The sp. act. of the electrophoretic peak interferon must be 3 × 108 units, or more, per mg protein, and it appears that only several molecules, at the most, of interferon need be bound to a cell to exert a demonstrable antiviral action.
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Studies in Genetic Resistance to RSV (RAV-O)
More LessSUMMARYEmbryos of the highly inbred Reaseheath W line were found to be resistant to RSV (RAV-O), a subgroup E virus. The results of test-cross matings between this line and the inbred Reaseheath I and C lines confirmed the two-loci genetic model reported previously by us for inheritance of response of fowl to RSV (RAV-O). Two loci were postulated in this model. Inhibitor e , with resistance Ie allele dominant over ie , and tumour virus e (tve), with susceptibility allele es dominant over resistance allele er . Ie is epistatic to es , inhibiting its expression. The genotype of the W line was typified as IeIeerer , a third type of resistance (Type III), and the first two types, IeIeeses and ieieerer , were reported in our previous communication for the I and C lines, respectively.
It was found in certain crosses that embryos resistant to subgroup B virus were also resistant to RSV (RAV-O), but embryos susceptible to subgroup B virus were found segregating for resistance to subgroup E virus. This type of segregation failed to support the concept advanced by other workers that the association between the two types of resistance was dependent on genes at the tvb locus.
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On the Nature of Poliovirus Genetic Recombinants
More LessSUMMARYRecombinant and parental poliovirus particles were indistinguishable by ratezonal and isopycnic sedimentation, and by u.v. inactivation. Sensitive selective procedures, applied to ts + recombinants to detect genetic segregation of one parent, failed to reveal any. Poliovirus genetic recombinant particles thus appear to be conventional virus particles; their significance for recombination mechanisms is discussed. Sensitivity to the growth inhibitor 2-(3-chloro-p-tolyl)-5-ethyl-1,3,4-oxadiazole is shown to depend on a product of the structural protein gene.
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The Appearance of Hordeum Mosaic Virus in Wheat Leaf Cells after Fixation in Glutaraldehyde or Chromate
More LessSUMMARYOnly aggregates of hordeum mosaic virus were encountered in cytoplasm of cells fixed in a fixative containing chromate (pH 7.2) and post-fixed in osmic acid. In contrast, hordeum mosaic virus inclusions in wheat leaf cells appeared after glutaraldehyde and osmic acid fixation as aggregates in well-fixed dense cytoplasm, as partly disrupted inclusions, or as loosely occurring virus in incompletely fixed cytoplasm. The results showed that use of more than one fixative in an investigation of plant virus infected tissue is useful for extending and interpreting ultrastructural observations.
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Inhibition of the Particle-associated RNA-dependent RNA Polymerase Activity of Influenza Viruses by Chelating Agents
More LessSUMMARYApproximately 0.05 mm concentrations of the chelating agents bathocuproine and bathophenanthroline disulphonic acid disodium salts, which form very stable complexes with ‘soft’ heavy-metal ions such as zinc, inhibited in vitro the RNA-dependent RNA polymerase activity associated with influenza B/LEE/40 and A/RI-5+ (H2N2) viruses in the presence of a large molar excess of Mn(II) and Mg(II). Certain heterocyclic thiosemicarbazones also inhibited influenza RNA polymerase activity, although complete inhibition was not detected even with high concentrations (0.1 mm) of the compounds. Analogues of the active heterocyclic thiosemicarbazones, such as isatin 3-semicarbazone, which have reduced chelating activities for zinc, also had reduced inhibitory effects on influenza virus associated RNA polymerase activity. However, inhibition of influenza RNA polymerase activity by 0.1 mm-bathocuproine or 0.1 mm-isatin 3-thiosemicarbazone was not reversed by the addition of molar equivalent or excess concentrations of zinc. Relatively high concentrations of the chelating agents had no detectable effect on the haemagglutinin, neuraminidase or infectivity titres of influenza B/LEE/40 virus. The chelating agents may inhibit influenza virus-associated RNA polymerase activity by the formation of a ternary complex of enzyme-metal-ligand.
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Retarded Growth of Poliovirus in Contact Inhibited Cells
More LessSUMMARYCV1, BSC1, Vero, and primary monkey kidney cells were seeded either at low cell density and infected with poliovirus while growing, or at high cell density and infected under conditions of contact inhibition. Virus RNA synthesis and virus production were delayed in the cells seeded at high cell density, although neither adsorption nor uncoating of the parental virus particles were altered. In spite of the delay, however, virus RNA synthesis, once initiated, proceeded in the same fashion and at the same rate in both growing and resting cells. This implies that one of the first events following uncoating of the infecting virus was temporarily retarded in resting cells. There are indications that this delay might be due to a lag in the formation of parental virus polyribosomes.
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Relationship of Cytotoxicity and Interferon-inducing Activity of Polyriboinosinic Acid. Polyribocytidylic Acid to the Molecular Weights of the Homopolymers
More LessSUMMARYThe molecular size of poly I.poly C required for lysis of interferon-treated L cells was the same as the size required for induction of interferon in these cells. The size requirement for both interferon induction and toxicity for interferon-treated L cells resided in the poly I strand, while variations of the poly C strand size were without effect on interferon induction or cell lysis.
The size of poly I.poly C required to induce interferon in primed L cells or primed primary rabbit kidney cells was the same as the size required to induce interferon in normal L cells or normal rabbit kidney cells. Again, these requirements proved more stringent for the poly I strand than for the poly C strand. These data suggest that both primed and normal cells recognize the same molecular ‘trigger’ for interferon induction.
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The Flaviviruses (Group B Arboviruses): a Cross-neutralization Study
More LessSUMMARYCross-neutralization studies on 42 flaviviruses and their respective antisera were performed by a plaque assay in a line of pig kidney cells. Six tick-borne viruses fell into one subgroup; seven viruses associated with bats and small rodents and a further tick-borne virus fell into a second subgroup. Twenty-two mosquito-borne viruses fell into one major and four minor subgroups. Four mosquito-borne, one tick-borne and one bat virus showed no relationship to any other flavivirus.
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A Temperature-sensitive Mutant of Vesicular Stomatitis Virus with Two Abnormal Virus Proteins
More LessSUMMARYMutant ts D1 is the only member of complementation group D of vesicular stomatitis virus (VSV), New Jersey serotype (Pringle, Duncan & Stevenson, 1971). At the non-permissive temperature (39 °C) both virus RNA and structural proteins are synthesized in BHK-21 cells infected with this mutant (Wunner & Pringle, 1972b).
Comparison of virus particle and intracellular proteins have shown that polypeptides G and N of ts D1 grown at 31 °C, and intracellular proteins at 39 °C, have altered electrophoretic mobilities in 10% SDS-polyacrylamide gel corresponding to mol. wt. differences of 3500 and 1000 respectively, yet viability at the permissive temperature was unimpaired. The differences were evident by both continuous and discontinuous SDS-polyacrylamide gel electrophoresis.
Reversion of the ts phenotype to wild type was accompanied by a restoration of normal mobility to polypeptide N, whereas G retained the abnormal mobility of the mutant. Thus the ts phenotype is directly related to the altered mobility of N.
The extent of glycosylation of G in mutant ts D1 appeared to be different from that of group C ts mutants and wild type.
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The Rapid Isolation of Plant Virus RNAs using Sodium Perchlorate
J. Wilcockson and R. HullSUMMARYRNAs prepared from particles of ten plant viruses by a new procedure in which detergent and sodium perchlorate were used were compared with RNAs obtained by the standard two-phase phenol technique. On the basis of u.v. extinction spectra, yield, component composition and infectivity of the RNAs, the NaClO4 method was judged to be as good as and often considerably better than, the phenol method. Moreover, the NaClO4 method is simpler and faster, and it gives good yields of RNA from viruses from which it is usually difficult to isolate RNA by the phenol method.
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Human Serum Lipoproteins as Inhibitors of Haemagglutination for Selected Togaviruses
More LessSUMMARYHuman serum was fractionated by ultracentrifuging and the non-specific inhibitory activity for the togaviruses, Japanese encephalitis virus and rubella virus, was found chiefly in the very low density lipoprotein (VLDL) and low density lipoprotein (LDL) fractions. The specific inhibitory activity per mg protein or lipid of each lipoprotein fraction was greater for Japanese encephalitis virus. Japanese encephalitis virus was significantly more sensitive to VLDL than LDL whereas rubella virus was equally sensitive to either.
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