- Volume 7, Issue 2, 1970
Volume 7, Issue 2, 1970
- Articles
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Replication of Rous Sarcoma Virus in Synchronized Cells
More LessSUMMARYWhen synchronized chicken embryo cells were infected with Rous sarcoma virus in the the G-1 period of the cell cycle, virus replication was delayed by several hours compared with cells infected in the S period, and virus release began only after mitosis. The delay in replication was not due to a change in the rate of virus adsorption and penetration. There was no delay in replication of Newcastle disease virus, indicating that the cells in G-1 were able to support replication of other RNA viruses. The shortest latent period for RSV (12 to 14 hr) occurred when cells were infected between S and mitosis. The latent period increased for cells infected after the maximum of mitosis. Cells which had been in culture for more than 15 hr rapidly lost their susceptibility to infection by RSV.
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Vesicular Stomatitis Virus Maturation Sites in Six Different Host Cells
More LessSUMMARYSix different cell types, L, Vero, HeLa, BHK21, PK(H13) and CF, were infected with vesicular stomatitis virus. A minimum of 100 individual virus-containing cells of each type was scored for the sites of viral maturation as observed by electron microscopy of thin sections. The principal site of viral maturation was the intracytoplasmic vacuolar membranes for PK(H13) and the plasma membrane for L and Vero cells. Both types of membranes served as sites for HeLa and BHK21 cells.It is concluded that the site of maturation of vesicular stomatitis virus is a host-dependent phenomenon.
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Purification and Characterization of Bovine Enteroviruses
More LessSUMMARYThree serologically distinct bovine enteroviruses (VG-5–27; vc-65–182; vp-7–19) grew in BHK21 cells to concentrations of approximately 5 × 108 p.f.u./ml. A purification procedure was used which involved sedimentation and gel-filtration through a Sepharose 2B column. The virus particles were spherical (diameter of 27 nm.), had a buoyant density of 1·34 g./ml. in CsCl and a sedimentation coefficient of approximately 165 s. The RNA of each of the virus types had a sedimentation coefficient of 35 s in sucrose-gradients and the base compositions were similar, being characterized by high A (30 %) and low U (21 %).
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Demonstration of Three Specific Sites on the Surface of Foot-and-Mouth Disease Virus by Antibody Complexing
F. Brown and C. J. SmaleSUMMARYThe reactions of foot-and-mouth disease virus with IgG and IgM have been studied by agar precipitin tests and by electron microscopy. The 140s component produces a precipitin band with each antibody class. It also produces a band with IgG which has been absorbed with 12s virus protein sub-units or trypsin-treated virus, providing evidence for the presence of more than one type of combining site. Trypsin-treated virus also gives a band with IgG and with IgG absorbed with 12s protein sub-units, indicating the presence of a third site. Electron microscopy shows that IgG reacts with the entire surface of the virus particle, producing complexes in which the outline of the virus particles is obscure. In contrast, IgM or IgG which has been absorbed with 12s protein sub-units or trypsin-treated virus forms complexes in which attachment is at regularly spaced sites on the virus surface. Trypsin-treated virus also produces complexes of this type with IgG absorbed with 12s protein sub-units. The virus thus appears to possess at least three types of combining site, one on the faces of the particle and the others at regularly spaced intervals, probably at the vertices.
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Electron Microscopic Study of Tissue Cultures Infected with Simian Haemorrhagic Fever Virus
More LessSUMMARYThe morphology and development of simian haemorrhagic fever virus was studied in tissue cultures infected with low multiplicities of virus. Early cytoplasmic lesions which were observed 24 hr after infection consisted of increased concentrations of polysomes and small vesicles 100 nm. in diameter filled with densely staining fibrillar material. As the lesions progressed, thickened membranous structures developed at the periphery of the vesicles. The membranes appeared to lengthen and thicken by a process of end-to-end and side-to-side fusion. Serial sections demonstrated that the fused, thickened structures were lamellae. Their role in the morphogenesis of simian haemorrhagic fever virus is not presently known.
Spherical virus particles measuring 40 to 45 nm. in diameter appeared in cells by 72 hr after infection. Infected cells contained vacuoles which enclosed accumulations of enveloped spherical particles. Some particles appeared to be budding into vacuoles.
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Leakage of β-Galactosidase from Phage-infected Escherichia coli: A Re-evaluation
More LessSUMMARYInfection of Escherichia coli by bacteriophage T4 is not accompanied by leakage of β-galactosidase. Liberation of the enzyme, soon after infection, results from lysis from without. The nature of the lytic enzyme systems responsible for lysis from without is discussed.
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Light and Electron Microscopy of Cells Infected with Tobacco Necrosis and Satellite Viruses
More LessSUMMARYFrench-bean leaves inoculated with the stipple streak strain of tobacco necrosis virus alone or mixed with the satellite virus were examined microscopically. Light microscopy showed two types of inclusion in some living epidermal cells, one hyaline, the other granular and containing small crystals. Some cells also contained crystals different in form from those in the inclusions. Light microscopy of parenchymatous cells fixed and stained for electron microscopy showed only one type of inclusion, with smooth appearance. The crystals seen in the living cells were not found, but some cells from leaves infected with the mixture had areas containing both heavily stained amorphous material and bodies 1 to 2 ¼m. across.
Electron microscopy of thin sections of the same fixed and stained material showed some cells to contain a structureless, electron-dense material, prominent cytoplasmic membranes and many vesicles, especially from leaves inoculated with the mixture. The electron-dense material often contained satellite virus in crystalline arrays and sometimes rhombic plates 1 to 2 ¼m. long. Whenever satellite virus was identified, tobacco necrosis virus occurred near to it. Cells infected with tobacco necrosis virus alone had well-defined areas in which the virus was concentrated and apparently uncontaminated. These areas corresponded to the inclusions seen in the light microscope. The relative frequency with which particles of the two viruses were detected by electron microscopy of leaf sections differed from the relative concentration of the two estimated by serological assays on sap extracted from leaves inoculated with the mixture.
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Rescue of Heat-inactivated Adenovirus Types 1 and 6 by Ultraviolet-irradiated Adenovirus Type 8
More LessSUMMARYHeating human adenovirus types 1 and 6 at 56° reduced infectivity very rapidly. A treatment for 10 to 15 min. usually completely destroyed the infectivity. However, the rescue of heated virus occurred when HEp-2 cells were inoculated simultaneously with heat-inactivated type 1 or 6 and u.v.-irradiated type 8.
Rescue was dependent upon the length of heat treatment, as viruses heated at 56° for more than 20 min. could not be rescued. On the other hand, the rescue of heat-inactivated type 6 was related to theu.v. dose employed, i.e. type 8 unirradiated or irradiated for 20 min. was not suitable for rescue.
The possible mechanism of rescue observed with heat-inactivated adenovirus types 1 and 6 by u.v.-irradiated type 8 is discussed.
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Tubular Inclusion Bodies in Plants Infected with Viruses of the NEPO Type
More LessSUMMARYTubular inclusion bodies containing single rows of virus particles were observed by electron microscopy in hosts infected with three NEPO viruses. When Nicotiana rustica L. plants were inoculated with cherry leaf roll virus tubules were found in axillary buds 4 days later and reached a maximum concentration after 2 to 3 weeks. Tubules were also found in root tips, pollen, ovules and mature seeds of these plants, but not in the leaf tissue.
Sections through cherry leaf roll virus infected tissue showed the tubules to be most frequent in the cytoplasm of undifferentiated cells. They occurred singly or in bundles and appeared to pass between cells. The tubule wall usually consisted of a single layer forming a complete tube in cross section.
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Volume 1 (1967)