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Biomedical subjects

B N Fields

Publications and source records attributed to B N Fields.

At least 163 records · Page 9Linked to original sources
PubMed1977

Molecular basis of reovirus virulence: role of the S1 gene.

A genetic approach has been used to define the molecular basis for the different patterns of virulence and central nervous system cell tropism exhibited by reovirus types 1 and 3. Intracerebral inoculation of reovirus type 3 into newborn mice causes a necrotizing encephalitis (without ependymal damage) that is uniformly fatal. Animal inoculated with reovirus type 1 generally survive and may develop epedymal cell damage (without neuronal necrosis) and hydrocephalus. Using recombinant clones derived from crosses between reovirus types 1 and 3, we have been able to determine that the S1 genome segment is responsible for the differing cell tropism of reovirus serotypes and is the major determinant of neurovirulence. The type 1 S1 genome segment is responsible for ependymal damage with subsequent hydrocephalus; the type 3 S1 genome segment is responsible for neuronal necrosis and neurovirulence. We postulate that these differences are due to the specific interaction of the sigma1 outer capsid polypeptide (the protein coded for by the S1 genome segment) with receptors on the surface of either ependymal cells or neuronal cells.

Animals↗
PubMed1977

Genome RNAs and polypeptides of reovirus serotypes 1, 2, and 3.

The virus-specific double-stranded genome RNA and polypeptides present in virions and cells infected with the three mammalian reovirus serotypes have been examined by co-electrophoresis in several different polyacrylamide gel systems. The double-stranded RNA and polypeptide species previously described for type 3 Dearing were found to have corresponding species in the other serotypes examined. In each serotype several RNA and polypeptide species were found to have different electrophoretic mobilities from the corresponding RNA or polypeptide species of type 3 Dearing. The combination of electrophoretic variants among the RNAs and polypeptides of the reovirus serotypes gave electrophoretic markers in all 10 of the reovirus genes. The usefulness of these electrophoretic markers in "mapping" the reovirus genome is discussed.

L Cells↗
PubMed1976

Host restriction of Friend Leukemia virus coat protein synthesis.

Fv-1 gene-mediated host restriction of Friend leukemia virus replication was investigated in terms of coat protein synthesis. By using the assay of pseudotype formation with vesicular stomatitis virus. it was shown that under restricting growth conditions the availablity of leukemia virus coat protein for pseudotype formation was decreased. These studies appear to eliminate a pure assembly defect as the mechanism of Fv-1 host restriction.

Cell Line↗
PubMed1976

Fate of input oncornavirion RNA--biological studies.

The fate of input Friend leukemia virus RNA was studied using labeled input virus. The appearance of nuclear RNA-DNA hybrid molecules and the apparent integration of input virion RNA with host cell DNA was studied using a series of inhibitors of DNA or protein synthesis, cell growth conditions, and an intercalating agent. Under all these conditions of infection, little to no viral-specific RNA-DNA hybrid molecules were formed. These data demonstrate that the formation of such RNA-DNA hybrid structures requires conditions of infection that allow provirus synthesis and integration. Furthermore, they suggest that at least a fraction of input virion RNA may transiently become integrated with host cell DNA.

Adsorption↗
PubMed1976

Reovirus-specific polypeptides: analysis using discontinuous gel electrophoresis.

The electrophoretic analysis of reovirus-specific polypeptides in infected cells using a discontinuous gel system has allowed the resolution of additional viral-specific polypeptides, including one large-sized gamma3 and two (or possibly three) medium-sized (mu3, mu4, mu5(?)) species. The proteins designated mu0, sigma1, and sigma2 based on electrophoretic mobility in gel systems containing phosphate-urea correspond to mu4, sigma2, and sigma1, respectively, when analyzed in systems containing Tris-glycine. It is likely that protein modifications (phosphorylation and glycosylation) are responsible for at least some of these differences.

Acetone↗
PubMed1974

Neurotropic virus-host relationship alterations due to variation in viral genome as studied by electron microscopy.

A series of experiments has been described in which litters of suckling rats were inoculated either with wild-type reovirus type III or one of two of its temperature-sensitive (ts) mutants. While the wild-type virus produced an acute, fatal syndrome, the ts mutants were substantially less neurovirulent. Of the ts mutant-inoculated animals, a large percentage of the surviving (chronic) animals given ts mutant B showed an unobstructive hydrocephalus ex vacuo whereas chronic ts mutant C animals showed no visible nervous system disease. The ts mutants persisted within the central nervous system (CNS) for 6 to 8 weeks, after which they could not be detected either virologically, immunologically or morphologically. In another set of experiments, organized CNS explants were studied following infection with either measles virus or the neuroadapted Mantooth strain of SSPE virus, a variant of measles. Wild measles (Edmonston strain) exerted an acute destructive effect, but SSPE virus had a tendency to enter into coexistence with the tissue without destroying its organotypic nature. These relationships are somewhat reminiscent of the neuropathologic conditions caused by these two viruses in man. Since the reovirus type III ts mutants possess both genetic and morphologic defects and in many instances cause CNS conditions different from that induced by the wild-type virus, it has been proposed that a comparable situation may exist after measles and SSPE virus infection. SSPE virions of the strain studied were found to be defective in certain viral components which may have contributed to the lower neurovirulence and its entering into a chronic relationship with the CNS, in contrast to the acute destructive nature of measles infection. The findings are discussed in terms of relevance to other chronic CNS diseases, particularly multiple sclerosis, in which the possiblity exists that a mutant virus is operative.

Animals↗
PubMed1973

Purification of oncornaviruses by agglutination with concanacalin A (murine leukemia virus-phytohemagglutinin-friend virus).

Concanavalin A (Con A) has been used to rapidly and selectively agglutinate murine and avian oncornavirions from culture medium or plasma. The agglutinated virus was concentrated rapidly and gently by low-speed centrifugation and solubilization with alpha-methyl mannoside. Infectious virus was purified 2.3 times with respect to nucleic-acid content, and more than 60% of its infectivity was recovered. Infectious particles of densities 1.18 and 1.16 g/cm(3) were found in mouse cells infected with Friend virus. Con A reacted only with particles of density 1.16 g/cm(3), indicating heterogeneity with respect to carbohydrate content or structure as well as buoyant density. Electron microscopy of virus agglutinated with Con A showed a zone of Con A-glycoprotein complexes averaging 12-15 nm in thickness.

Agglutination↗
PubMed1973

Host restriction of Friend leukemia virus. Role of the viral outer coat.

Host restriction of oncogenesis of RNA tumor viruses in vivo is associated with several gene loci. One of these genes, the Fv-1 locus in mice, is expressed in vitro and may be studied in mouse-embryo cultures that are restrictive or permissive for replication of Friend leukemia virus. Two strains of Friend leukemia virus, N-or B-tropic, show reciprocal ability to replicate successfully in either NIH Swiss (N-type) or BALB/c (B-type) cells that differ at the Fv-1 locus. These two strains of virus and two cell lines form a system to measure host restriction in vitro. Measurement of adsorption of Friend leukemia virus to permissive or restrictive cells reveals no difference in rate or total amount of virus bound. Furthermore, studies with virions of vesicular stomatitis virus phenotypically mixed within an envelope containing Friend leukemia virus protein show no differences in penetration or replication of vesicular stomatitis virus. These results strongly suggest that host restriction of Friend leukemia virus is due to an intracellular event in the viral replication cycle.

Animals↗