- Volume 31, Issue 2, 1976
Volume 31, Issue 2, 1976
- Articles
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Comparative Ultrastructural Studies of Insect Granulosis and Nuclear Polyhedrosis Viruses
More LessSUMMARYOptical diffraction studies indicated that the periodic lattice structure in electron micrographs of the capsids of two granulosis and two nuclear polyhedrosis viruses were indistinguishable. The capsid is composed of stacked rings spaced 4.5 nm apart.
Comparison of the intracellular forms of Bombyx mori nuclear polyhedrosis virus with negatively stained virus particles leads us to encourage the more general use of the term ‘capsid’ instead of ‘intimate membrane’ and the term ‘virus membrane’ in place of ‘developmental membrane’. These terms are consistent with those currently used for most animal and plant viruses.
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Cleavage of T4-Induced Proteins During Phage Morphogenesis: Characterization of Peptides
More LessSUMMARYPolypeptides of low mol. wt. have been extracted from T4 coliphages and from Escherichia coli B cells infected with a wild type and various amber mutants of bacteriophage T4. Six peptides were fractionated by chromatography on phospho-cellulose: three of them were cleaved from proteins synthesized late in infection and related to phage head. The remaining three peptides have been shown to arise from early-labelled phage-induced proteins. Two of these six small petide fragments were found in the head of the T4 phage.
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Permissiveness of Mouse, Monkey and Hybrid Cells to Encephalomyocarditis (EMC) Virus
More LessSUMMARYEncephalomyocarditis (EMC) virus replicates to high titre in permissive mouse kidney (MKS) cells but poorly in monkey kidney (CV1) cells. The permissiveness of monkey-mouse hybrid cells varies according to their chromosomal content.
In monkey cells, the synthesis of both single-stranded and double-stranded virus RNA is restricted; in semi-permissive hybrid clones, the double-stranded RNA is synthesized normally, whereas the synthesis of the single-stranded RNA is inhibited. Thus, it seems that more than one restrictive event is responsible for the low permissiveness of monkey cells to EMC virus.
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Morphological Components of Herpesvirus.
More LessSUMMARYThe disruption of envelopes and the fragmentation of capsids of equine herpesvirus type 1 observed in negatively stained samples were attributed to viral dehydration on carbon films during preparation for electron microscopy. Prior fixation of virus with OsO4 or glutaraldehyde and subsequent application of negative stain before drying minimized envelope disruption and virtually eliminated the occurrence of capsomere sheets and broken capsids. This simple procedure significantly improves electron microscopic evaluation of herpesvirus samples.
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Enhancement of Polysome Formation and Protein Synthesis in Sendai Virus-Infected Cells
More LessSUMMARYA considerable stimulation of total protein synthesis in Sendai virus-infected chicken fibroblasts occurred 18 h after infection. The stimulation of synthesis was shown to be due mainly to the synthesis of virus-specific proteins; the synthesis of host proteins was either unchanged or slightly enhanced. The level of functional polyribosomes in virus-infected cells was also increased as compared to that in mock-infected control while the number of free 80S ribosomes was proportionally decreased.
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In vivo and In vitro Effects on the Electrophoretic Forms of Particles of Broad Bean True Mosaic Virus
More LessSUMMARYPreparations of broad bean true mosaic virus (BBTMV) contained three centrifugal components: top, middle, and bottom. These had sedimentation coefficients of 59, 95, and 116S. Top component was only found when a reducing agent was used during all stages of purification and subsequent storage. When electrophoresed on acrylamide gels, particles of BBTMV migrated as two, and sometimes three, electrophoretic forms. In new infections a slower migrating form predominated; in older infections a faster migrating form predominated. The relative migration rates of the electrophoretic forms depended on the kind of infected leaf sampled, the environmental conditions during infection, the method of purification, and the period of storage after purification. The changes in mobility of the various forms are ascribed to limited proteolysis, which increased the negative charge of the virus particle by altering the charge of the coat protein. The coat protein is made up of two polypeptides, of mol. wt. 37500 and 20000 to 24500, respectively. The change in charge resulted from a decrease in size, and possibly a change in conformation, of the smaller polypeptide.
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Preparation and Characterization of Influenza Virus Cores
More LessSUMMARYLipid-free influenza virus cores have been obtained by a three step procedure consisting of (a) treatment with proteolytic enzyme, (b) fixation with formaldehyde and (c) delipidization with saponin or deoxycholate.
Several reagents proved efficient in removing the virus lipids as judged by morphological features and increased buoyant density, but only cores prepared by means of sodium deoxycholate have been characterized closely. Ultrathin sections revealed round bodies (about 65 nm in diam.) delineated by a single dense track and with an internal structure very similar to that of the complete virus particles. They contained both the nucleoprotein and the M-protein and no lipids.
It is proposed to call the limiting structure which appears (3 to 4 nm thick in ultrathin sections) the core shell.
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Ribonucleotides in Infectious Bovine Rhinotracheitis Virus DNA
More LessSUMMARYInfectious bovine rhinotracheitis (IBR) virus was grown in the presence of 5-3H-uridine in a continuous line of bovine kidney cells. 5-3H-uridine was found to be associated with viral nucleocapsids. Furthermore, purification of the viral nucleic acid present in nucleocapsids illustrated that 5-3H-uridine was part of the viral nucleic acid. Purification of viral DNA from infected cells also indicated that 5-3H-uridine was associated with viral nucleic acid possibly as ribonucleotides. The label was identified as RNA by measuring its susceptibility to RNase and analysis of the bases. Short pulses with 5-3H-uridine, resulted in labelled nucleic acid which was extremely sensitive to RNase and alkali but resistant to DNase. Nucleotide analysis indicated that after short pulses all the radioactivity was associated with the base uracil whereas upon longer labelling periods a large percentage of the label was associated with cytosine. However even if viral DNA was isolated from nucleocapsids there was still some radioactivity associated with uracil. Sedimentation of heat denatured 5-3H-uridine label viral nucleic acid in Cs2SO4 indicated that the label sedimented at a density of single stranded DNA suggesting that the ribonucleotides are covalently linked to the viral DNA.
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Comparison of Swine Vesicular Disease Virus and Coxsackie B5 Virus by Serological and RNA Hybridization Methods
More LessSUMMARYThe relatedness of swine vesicular disease virus (SVDV) and Coxsackie B5 virus has been studied by virus neutralization and immunodiffusion tests and by hybridization of the virus RNAs. Clearly defined differences between the two viruses were found by the three methods. Isolates of SVDV from several countries were very closely related but could be differentiated. Recent isolates of Coxsackie B5 virus also appeared to be similar but clear differences could be detected between these and the prototype (Faulkner) strain of the virus. The SVDV isolates were more closely related to the Faulkner strain than to the recent isolates of Coxsackie B5 virus. Perhaps of more importance, the Faulkner strain was more closely related to SVDV than it was to the recent Coxsackie B5 isolates. The significance of these observations in relation to the recent emergence of swine vesicular disease is discussed.
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Rescue of a Rat Tropic Rat Hepatoma Virus Pseudotype Kirsten Sarcoma Virus by Co-Cultivation of Hepatoma Tissue Culture Cells with K-NRK Cells
More LessSUMMARYA rat tropic rat hepatoma virus pseudotype Kirsten sarcoma virus has been rescued from a co-culture of rat hepatoma tissue culture cells, HTC-H1, with Kirsten murine sarcoma transformed non-producer rat kidney cells (K-NRK). The virus complex, RHHV-KiMSV, released from the co-culture exhibited cell transformation ability on normal rat kidney (NRK) cells and showed a restricted host range limited to rat embryo fibroblasts and other normal rat cell lines. Evidence derived from indirect immunofluorescence assays demonstrated the association of rat helper virus specific gs-1 and gs-3 antigens with RHHV-KiMSV transformed cells. RHHV-KiMSV is currently being cultured at a titre as high as 104 f.f.u./ml in tissue culture, and thus offering opportunity for biochemical studies of rat viruses.
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Characterization of Two Particle Types of Calf Rotavirus
More LessSUMMARYTwo distinct types of rotavirus particle were isolated in caesium chloride density gradients. The higher density particle banded at 1µ38 g/ml and measured 55 ± 0µ4 nm in diameter while the less dense particle banded at 1µ36 g/ml, measured 66 ± 0µ4 nm in diameter and appeared to possess an extra outer capsid layer. Some forms intermediate between the two types were seen. Since the two particles had a similar but not identical morphology and polypeptide composition, they were considered to be different forms of the same virus. Infectivity was associated with the larger particle which contained one more polypeptide than the smaller particle.
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Human Fibroblast and Leukocyte Interferons Show Different Dose-Response Curves in Assay of Cell Protection
More LessSUMMARYPreparations of human fibroblast and leukocyte interferons of similar potency show markedly different dose-response curves in an assay which measures the degree of protection of tissue cultures against virus c.p.e. The effect is observed with both vesicular stomatitis virus (VSV) and Mengovirus, and is not altered by purification of the interferons.
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Influence of pH and Divalent Anions on the Buoyant Density of Maize Dwarf Mosaic Virus in CsCl
More LessSUMMARYThe buoyant density of particles of maize dwarf mosaic virus (MDMV) in CsCl was influenced by pH and divalent anion concentration. Particle density increased with increasing pH at low buffer molarity; it decreased with increasing divalent anion concentration. The density shifts induced by divalent anions and acid pH were reversible, but those occurring at alkaline pH were irreversible. Of the strains examined, all behaved identically except 13B (MDMV-B), which was denser under all conditions and so could be physically separated from MDMV-A.
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Variants of the HR Strain of Sindbis Virus Lethal for Mice
L. R. Boone and A. BrownSUMMARYWe have selected two similar variants of Sindbis HR virus which are lethal for mice. Consecutive brain to brain passage series were conducted in suckling and weanling mice. Specific anti-Sindbis HR neutralization tests and protection tests demonstrate that these viruses are derived from the parent Sindbis HR.
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Electron Microscopy of Tobacco Mosaic Virus Prepared with the Aid of Negative Staining-Carbon Film Techniques
More LessSUMMARYThe negative staining-carbon technique has been applied to suspensions of freshly prepared type strain tobacco mosaic virus particles in high concentrations. Electron microscope images show that paracrystalline arrays of the virus were formed, in which large areas of rods could be viewed along their long axes and in parallel arrays in horizontal positions. High-resolution micrographs showed the protein structure units in rods photographed in both vertical and horizontal orientations.
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Requirement of an Adenylic Acid-Rich Segment for the Infectivity of Encephalomyocarditis Virus RNA
More LessSUMMARYAbout 80% of the RNA molecules extracted from encephalomyocarditis (EMC) virus were bound by oligo(dT)-cellulose under conditions which bind poly(A) but not poly(C) nor ribosomal RNA. This shows that most EMC virus RNA molecules contain a poly(A) tract. Both bound and unbound fractions contained RNA molecules of apparently the same size when examined by sucrose gradient sedimentation, but the bound fraction contained an adenylic acid-rich segment of about 20 nucleotides long, whereas the unbound RNA did not. The bound RNA had 200 times the specific infectivity of the unbound RNA which suggests that the poly(A) tract present in EMC virus RNA is required for infectivity.
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Genes 46 and 47 of Phage T4: Possible Compensation for Loss of their Function
More LessSUMMARYThe gene 46 and 47 functions of phage T4 are required for normal DNA replication, recombination, u.v. repair and host DNA breakdown, and yet am mutants defective in these genes characteristically form tiny plaques on Escherichia coli strains lacking an am suppressor. Our results imply that this limited growth is not due to misreading of am codons or partial function of nearly complete polypeptides terminated at the am mutation. Thus it appears that genes 46 and 47 are not entirely essential, perhaps because other phage or host products can partially compensate for their loss.
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