- Volume 29, Issue 3, 1975
Volume 29, Issue 3, 1975
- Articles
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An Image Analysis Study of Adenovirus Type 5-induced Crystalline Inclusions
More LessSummaryA combined electron microscopic and optical diffractometric study of Ad5-induced non-virion protein crystals found in the nuclei of infected KB cells at late times (48 to 72 h p.i.) after infection has been carried out. Data obtained have indicated that the unit cell of the crystal is rectangular and not hexagonal as previously presumed.
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Polyamino Acid Induced Aphid Transmission of Plant Viruses
More LessSummaryAphids transmitted poly-l-ornithine (PLO)-treated tobacco mosaic virus (TMV) when given acquisition and inoculation access periods as brief as 30 s and 2 min, respectively; the ability to transmit was lost within 90 min. Aphids without claws were able to transmit the virus. Transmission thus seems similar to that of non-persistent viruses.
The ratio of virus to polyamino acid, as well as the KCl concentration, markedly affected transmission. Transmission was best from mixtures which contained 250 μg/ml TMV, 2.5 μg/ml PLO (mol. wt. 120000) and 0.6 m-KCl. A similar mixture favoured transmission when poly-l-lysine (mol. wt. 85000) was substituted for PLO, but with poly-l-lysine (mol. wt. 30000) it was necessary to decrease the KCl to 0.3 m to obtain transmission. Less KCl (0.08 to 0.24 m) also favoured aphid transmission of PLO-treated potato virus X and tobacco rattle virus. PLO-treated TMV ultracentrifuged in the presence of, and resuspended in, 0.6 m-KCl remained aphid transmissible while PLO-treated virus in 2 m-KCl, which favours greater dissociation of the virus-PLO complex, was transmissible neither before nor after sedimentation by ultracentrifuging, and resuspension in 0.6 m-KCl. These results show that transmissibility is not due to a permanent alteration of the virus by PLO and indicate that the formation of a TMV-PLO complex is required for transmission. Sequential acquisition experiments suggest that PLO may act by binding TMV to receptor sites in aphids. However, the possibility that PLO affects the infection process was not ruled out.
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Disruption of Vi Bacteriophage III and Localization of its Deacetylase Activity
More LessSummaryIt has been shown that particles of Vi bacteriophage III catalyse deacetylation of O-acetyl pectic (polygalacturonic) acid, a structural analogue of Vi poly-saccharide (Vi antigen). Using this substrate, and determining the acetic acid liberated by gas-liquid chromatography, a method for the estimation of Vi phage deacetylase activity has been developed.
Purified particles of Vi phage III were exposed to a variety of mildly dissociative reagents and conditions, and then tested for plaque-forming and for deacetylase activity. They have also been inspected under the electron microscope. Osmotic shock, and incubation in the presence of ethylenediaminetetraacetic acid (≥ 0.01 m), or of l-arginine (0.25 m), were found to cause disintegration of the virions into empty head capsids, deoxyribonucleic acid, and base plates still carrying the spikes. The mixtures of viral fragments exhibited an increased deacetylase activity.
Using zonal sedimentation and ion exchange chromatography, the phage fragments obtained by treatment with ethylenediaminetetraacetic acid have been fractionated and the base plates isolated. Amongst the viral components, these structures showed the highest specific deacetylase activity. They had the shape of six-pointed stars (about 9.5 nm inner, and 14.5 nm outer diam.) with a central hole or plug (∼3 nm), carrying six spikes, roughly cylindrical organelles of approx. 11 × 4 nm, one at each of the points. Of the polypeptides of six sizes (P.1, about 153000 daltons; P.2, 91000; P.3, 71000; P.4, 56500; P.6, 22000), detected in whole Vi phage III virions by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, only two, P.2 and P.3, were found in the base plates.
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On the Mechanism of Neurotropism of Vesicular Stomatitis Virus in Newborn Hamsters. Studies with Temperature-sensitive Mutants
More LessSummaryThe virulence of temperature-sensitive mutants of vesicular stomatitis virus (VSV) injected subcutaneously into newborn hamsters was positively correlated with their tendency to generate revertants and with their leakiness in cultured hamster embryo fibroblasts maintained at 37 °C, the measured body temperature of the animals under our experimental conditions. The complementation group of the mutants seemed important only in that it tended to determine reversion frequency and leakiness. One non-reverting group I mutant (T1026), however, was much less virulent than would be expected from its extreme eakiness at body temperature.
The disease produced by the less virulent mutants was characterized by neurological symptoms and led to delayed death, unlike the rapid death produced by virulent mutants. Infectious virus could be found in higher titres in the brains than in peripheral organs of such animals (with ratios as high as 108). This neurotropism was not correlated with the complementation group of themutant but was shown to be the consequence of survival for more than 3 days after injection. Age was not responsible for the effect. Animals injected at birth with T1026 were completely resistant to subcutaneous superinfection with the highly virulent wild-type virus HR at 3 to 4 days, though non-T1026-protected animals were completely sensitive. When HR was injected intracerebrally at 3 to 4 days, the T1026-protected animals allowed replication to high titres in the brain but not in peripheral organs, whereas non-T1026-protected animals allowed replication to high titres in both brain and in peripheral organs.
We suggest from these results that the observed neurotropism is produced by a resistance mechanism operative in peripheral organs but not in the brain; this resistance develops rapidly in newborn animals on exposure to virus and clears virus from the peripheral organs leaving it in the brain. It is possible that our effect represents a controlled and accelerated induction of the classical peripheral resistance of animals to various viruses which normally develops with age.
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Interferon Induction by Viruses and Polynucleotides: A Differential Effect of Camptothecin
More LessSummaryThe plant alkaloid camptothecin inhibits interferon production induced by Newcastle disease virus (NDV) or ultraviolet-irradiated NDV in chick and human cells, and by Sindbis virus in chick cells. It has no effect on interferon production induced by poly(rI).poly(rC) in chick and human cells. No effect of camptothecin could be detected on the multiplication of NDV, and it is concluded that the inhibition reflects a difference between interferon induction by viruses and by polynucleotides.
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Characteristics of the Major Internal Protein and RNA-Dependent DNA Polymerase of Bovine Leukaemia Virus
SummaryA virus designated bovine leukaemia virus (BLV), associated with leukaemia in cattle and previously demonstrated to induce the disease in sheep, was purified from chronically infected sheep cell cultures. Electrophoretic analysis showed a major protein of mol. wt. about 24000 (p24) which reacted in gel diffusion and complement-fixation tests with sera from naturally infected cattle, experimentally infected sheep, and guinea pigs immunized with p24. BLV p24 has an isoelectric point of 8.6. Interspecies antigenic reactivities characteristic of mammalian Type C virus p30s were not detected in disrupted BLV or on p24. Sheep and guinea pig antisera to BLV, reactive withp 24, also did not precipitate several Type C virus p30s in radioimmunoassays. BLV is also distinguished from Type C viruses and resembles mouse mammary tumour virus and Mason-Pfizer virus in having an RNA-dependent DNA polymerase which is preferentially active in the presence of Mg++ when synthetic templates are used. Along with previously published morphological data, the above indicates that BLV is not a Type C virus as classically defined. Four hundred and forty one human sera from cancer patients and matched controls were non-reactive with disrupted BLV, BLV infected cells, and BLV p24 in complement-fixation tests.
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Inhibition of Interferon Action by Vitamin A
More LessSummarySimultaneous treatment of mouse cells with interferon and vitamin A (retinoic acid) resulted in an inhibition of interferon action. Increasing concentrations of calf serum decreased the inhibitory effect of retinoic acid on interferon action. Treatment of interferon with retinoic acid prior to the assay for interferon activity also resulted in a loss of interferon activity. Since the residual retinoic acid present after dilution of the interferon for assay was not sufficient to interfere with the assay, it is presumed that interferon and retinoic acid must interact in some fashion to inhibit interferon activity. Calf serum prevented the apparent interaction of retinoic acid and interferon.
The loss of interferon activity which resulted from treatment of interferon with retinoic acid was dependent on temperature and time of incubation. Retinyl acetate (acetate ester of vitamin A) and retinal (vitamin A aldehyde) only slightly inhibited interferon activity, while retinoic acid (vitamin A acid) and retinol (vitamin A alcohol) were similarly effective at inhibiting interferon activity. Another fat soluble vitamin, vitamin K1, did not inhibit interferon activity.
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A Double-helical Structure for Re-aggregated Protein of Narcissus Mosaic Virus
More LessSummaryIsolated protein subunits of narcissus mosaic virus have been assembled without RNA into rod-like structures of similar diameter to the intact virus. Optical diffraction patterns from electron micrographs of these particles show that the subunits are in a double-helical arrangement.
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Optical Diffraction from Particles of Narcissus Mosaic Virus
More LessSummaryOptical diffraction studies of negatively stained particles of narcissus mosaic virus confirm that the protein subunits are arranged on a helix of pitch 36 Å, with a repeat period of five times the pitch, and suggest that there are 6.8 subunits per turn of the helix.
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Unique Virus-related DNA Sequences in Sheep Progressive Pneumonia Lung
More LessSummaryHybridization studies with [3H]-cDNA of progressive pneumonia, maedi and visna viruses demonstrate that lung DNA from sheep afflicted with progressive interstitial pneumonia possesses virus-related sequences not present in normal sheep lung DNA.
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