- Volume 14, Issue 2, 1972
Volume 14, Issue 2, 1972
- Articles
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Some Properties of Potato Mop-Top Virus and its Serological Relationship to Tobacco Mosaic Virus
More LessSUMMARYPotato mop-top (PMTV) and tobacco mosaic (TMV) viruses are serologically related, but only slightly. An antiserum with a titre of 1600 against TMV had a titre of only 5 against PMTV. Similarly, an antiserum with a titre of 2048 against PMTV had a titre of only 8 against TMV; when diluted in saline this antiserum did not precipitate TMV, but did when diluted in 0.1 m EDTA pH 7.7. Particles of PMTV were of many lengths, with peaks in the distribution of lengths at 250 to 300 nm. and 100 to 150 nm. Only the longest particles were infective. They had the same width and pitch of the protein helix as TMV particles. Sap from infected leaves contained only few particles, many of which were defective; the main defect was the uncoiling of the protein from one end. Plants infected with TMV are partially protected against infection by PMTV.
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Electrophoretic Analysis of Membrane Glycoproteins in Normal and Polyoma Virus Transformed BHK21 Cells
More LessSUMMARYBHK21 cells transformed by polyoma virus have been shown to release protein into the medium which is more glycosylated than that released by normal BHK21 cells. Correspondingly the residual protein in all membrane fractions (particularly plasma and smooth reticulum membranes) has a lower degree of glycosylation in transformed cells. The glycoproteins in these fractions and in saline washes of normal and transformed cells have been compared by electrophoresis in acrylamide gels. The washes from transformed cells contain a component of molecular weight about 135,000 which is more highly glycosylated than the corresponding component of normal cells. The corresponding membrane fractions of transformed cells are much less glycosylated. It is suggested that transformation by polyoma virus is accompanied by defects in the synthesis or assembly into the membranes of a large component with a high aminosugar to amino acid content.
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Polyoma Virus Basic Proteins
More LessSUMMARYPolyoma virus particles contain three small basic polypeptides. These appear to be host cell histones which can be synthesized in mouse cells before infection. Comparison of peptides of polypeptides derived from [35S]-methionine labelled virus with those from mouse cell histones showed correspondence of two major and several minor peptides. It is concluded that these polypeptides are therefore not virus coded.
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A New Transducing Phage Related to P22 of Salmonella typhimurium
More LessSUMMARYProperties of a new general transducing phage, PSA68, isolated from a commercial digestive are described in comparison with other transducing phages, L, MG40, and P22. The morphology, the latent period, and the average burst size of PSA68 were indistinguishable from those of P22. This phage most resembled L serologically and MG40 in immunity properties; P22 was dominant over the other three phages, and PSA68 and MG40 over L. The buoyant density of PSA68 was 1.510 g./cm.3, identical to L and MG40, that of P22 being 1.520 g./cm3. The relative number of abortive transductants produced by the nonmotile double mutants was not significantly different among the four phages, though the transduction frequencies per p.f.u. were different from each other, implying the presence of genetically identical lengths of chromosome fragments.
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Virus Particles in Aspergillus foetidus: a Multicomponent System
G. Ratti and K. W. BuckSUMMARYTwo electrophoretically distinct classes of virus particles, designated fast (AfV-F) and slow (AfV-S) according to their relative electrophoretic mobilities, were isolated from the mycelium of Aspergillus foetidus, strain imi 41871. They were almost completely separated by dialysis against 0.03m-phosphate buffer, pH 7.6, in which F particles remained in suspension, while S particles precipitated, and were further purified by caesium chloride density gradient centrifugation. Electron microscopy showed that both classes were composed of isometric particles of similar diameter.
RNA, prepared from both AfV-F and AfV-S, was double-stranded. In polyacrylamide gel electrophoresis AfV-F RNA was resolved into four main components with molecular weights of 2.31, 1.87, 1.70 and 1.44 × 106, while AfV-S RNA gave two components with molecular weights of 2.76 and 2.24 × 106.
Both AfV-F and AfV-S could be separated by centrifugation in caesium chloride gradients into a number of fractions containing particles with different buoyant densities. Electrophoretic analysis of the RNA prepared from the virus fractions indicated that the multiple RNA components are not fragments released from a single virus particle, but are separately encapsidated in different particles.
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Determinants of Lymphocytic Choriomeningitis Interference
More LessSUMMARYA plaque assay is described in which cytolytic activity of lymphocytic choriomeningitis virus (LCMV) is observed at low but not at high concentrations of infecting virus. Quantitation of the interference at high virus concentrations is detailed. Use of this assay during the course of the LCMV infection in L cells has shown that an interfering component is produced in abundance after the initial peak in infectivity in the medium has been reached. Thereafter the ability of the virus stock to form infective centres declines while the interference activity rises. Coinfection of L cells with high concentrations of one LCMV strain and low concentrations of any other tested strain prevents cellular destruction. When small virus inocula are used interference can be observed within single ‘bull’s eye’ plaques which exhibit concentric rings of lysed and intact cells. Simultaneous infection of L cells with an auto-interfering concentration of LCMV does not interfere significantly with plaque formation by mengo, vaccinia, and vesicular stomatitis viruses, but reduces four- to fivefold the number of plaques formed by the Amapari and Parana viruses related to LCVM. Interferon does not play a role in the system described. The physical and the immunological data on the interfering substance are consistent with the hypothesis that defective-interfering virus particles are present in LCMV tissue culture stocks.
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Herpes Simplex Virus Latency in Cultured Human Cells Following Treatment with Cytosine Arabinoside
More LessSUMMARYTreatment of human cell cultures infected with herpes simplex virus type 2 (HSV-2) with cytosine arabinoside resulted in the prevention of both virus cytopathology and synthesis of detectable infectious virus. Following removal of the inhibitor infectious HSV-2 reappeared and the cultures were destroyed. However, there was a delay of at least 5 to 6 days following inhibitor removal before infectious virus could be detected. The reappearance of infectious HSV-2 was paralleled by virus cytopathology. The period between the disappearance and reappearance of infectious virus is defined as the latent period. Cultures during this period were as sensitive as control cultures to superinfection with HSV-2 or vesicular stomatitis virus. Infectious centre assays performed with cultures during the latent period indicated that as many as 1 in 800 cells were capable of ultimately synthesizing infectious virus. Attempts to prevent the reappearance of infectious HSV-2 by treating infected cultures with cytosine arabinoside for up to 22 days were unsuccessful, thus indicating that HSV-2 can remain associated with the cells in a non-infectious form for an extended period without being degraded.
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The Structure of Tobacco Rattle Virus Ribonucleic Acids: Nature of the 3′-Terminal Nucleosides
G. Darby and A. C. MinsonSUMMARYThe two species of RNA have been purified from the long and short particles of the multicomponent plant virus, tobacco rattle isolate CAM. 3′-End-group analysis, using the technique of periodate oxidation followed by reduction with [3H]-borohydride, showed that both species of RNA had an unphosphorylated cytidine residue at the 3′ end.
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