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Biomedical subjects

S Schlesinger

Publications and source records attributed to S Schlesinger.

At least 91 records · Page 5Linked to original sources
PubMed1980

Establishment and maintenance of persistent infection by Sindbis virus in BHK cells.

We have established a persistent infection of BHK cells with a preparation of Sindbis virus heavily enriched in defective interfering (DI) particles. The small fraction of cells that survived the initial infection grew out to form a stable population of cells [BHK(Sin-1) cells], most of which synthesized viral RNA and viral antigens. The presence of DI particles in this virus stock was required to establish this persistent state. BHK(Sin-1) cells released a small-plaque, temperature-sensitive virus (Sin-1 virus) as well as DI particles containing DI RNAs larger than those present in the original stock used to establish the persistent state. A cloned stock of Sin-1 virus, free of detectable DI particles, was able to initiate a persistent infection more quickly and with greater cell survival than the original stock of Sindbis virus containing DI particles. About 2 weeks after the Sin-1 virus-infected cells were cultured, DI RNAs arose and soon became the dominant viral RNA species produced by these cells.

Animals↗
PubMed1980

[Quantitative shifting of intra and peritumoral cell populations after intratumoral BCG-cell-wall therapy in squamous epithelial mouth neoplasms].

A qualitative histologic examination of squamous cell carcinoma of the buccal cavity was made before and after the injection of BCG cell walls directly into the tumor. The density of the inflammatory infiltrate in and at the tumor site differed significantly. The distribution pattern of the cells involved in the infiltrate showed an increased number of lymphocytes and histiocytes. Lymphocytes, the largest cell group represented, were more frequently demonstrated in the tumor than outside it. The injection of BCG cell walls directly into the tumor primarily causes a shift in the total number of cells and only secondarily an alteration in the distribution pattern of the cells involved in the infiltrate.

Administration, Topical↗
PubMed1979

Restricted replication of two alphaviruses in ricin-resistant mouse L cells with altered glycosyltransferase activities.

Two mouse L cell variant lines (CL 3 and CL 6) selected for resistance to the toxic plant lectin ricin were restricted in their ability to replicate the two alphaviruses Sindbis virus and Semliki Forest virus. CL 3 cells have been shown to exhibit increased CMP-sialic acid:glycoprotein sialyltransferase and GM3 synthetase activities, whereas CL 6 cells have been shown to contain decreased UDPgalactose:glycoprotein galactosyltransferase and UDP-N-acetylglucosamine:glycoprotein N-acetylglucosaminyltransferase activities. The adsorption of Sindbis virus to CL 6 cells was considerably reduced, suggesting that the loss or inaccessibility of the receptors for Sindbis virus accounted for a major defect in virus production in these cells. In contrast, CL 3 synthesized Sindbis viral RNA and proteins but were unable to convert the precursor glycoprotein PE2 to the structural protein E2. The cleavage of PE2 to E2 was also blocked in both CL 3 and CL 6 cells infected with Semliki Forest virus.

Galactosyltransferases↗
PubMed1978

Proliferative capacity of mouse peritoneal macrophages in vitro.

Thioglycolate-stimulated mouse peritoneal macrophages cultured in the presence of macrophage growth factor (MGF) will continue to proliferate when they are removed from culture dishes with the local anesthetic lidocaine and subcultured. The number of times the cells can be subcultured and remain in a proliferative state is dependent on the number of previous cell divisions. One precursor cell (colony-forming cell) yields about 2.6 X 10(4) daughter cells. When MGF is removed from actively proliferating macrophages, they leave the cell cycle and enter a "resting" condition. When MGF is readded, cells reenter the cell cycle and proliferate with the same doubling time as if MGF had not been removed. Membrane 5'-nucleotidase activity was used as a probe to identify the state of macrophage activation. Proliferating macrophage populations had significantly higher enzyme levels than stimulated macrophages cultured without MGF. These enzymes levels were, however, lower than those found for resident (unstimulated) macrophages.

Animals↗
PubMed1978

Synthesis and infectivity of vesicular stomatitis virus containing nonglycosylated G protein.

The replication of vesicular stomatitis virus (VSV) is inhibited by tunicamycin (TM), an antibiotic that blocks the formation of N-acetylglucosaminelipid intermediates. We had shown previously that the viral glycoprotein (G) synthesized in cells treated with TM is not glycosylated and is not found on the outer surface of the cell plasma membrane. In this report, we shown that cells exposed to TM produce a low yield of infectious particles. The yield is increased when the temperature during infection is lowered from 37 to 30 degrees C. At 30 degrees C in the presence of TM, both wild-type VSV and the temperature-sensitive mutant ts045 produce particles that do not bind to concanavalin A Sepharose and contain only the nonglycosylated form of G. These particles have a specific infectivity (pfu/cpm) comparable to that of VSV containing glycosylated G.

Anti-Bacterial Agents↗
PubMed1977

Impaired intracellular migration and altered solubility of nonglycosylated glycoproteins of vesicular stomatitis virus and Sindbis virus.

Tunicamycin, an antibiotic which prevents the glycosylation of newly synthesized proteins, inhibits the replication of both vesicular stomatitis virus and Sindbis virus. In tunicamycin-treated infected cells, all of the viral proteins are synthesized but the glycoproteins are devoid of carbohydrate. The nonglycosylated glycoproteins could not be detected on the outside of the plasma membrane by lactoperoxidase labeling, indirect immunofluorescence staining, or chymotrypsin treatment of intact cells, whereas the glycosylated glycoproteins were readily detected by all three methods. These results indicate that the bulk of the nonglycosylated glycoproteins are unable to undergo the normal migration to the cell surface. In contrast to the normal glycosylated viral glycoproteins, the nonglycosylated glycoproteins were insoluble in nonionic detergents such as Triton X-100. The nonglycosylated glycoprotein of vesicular stomatitis virus could be solubilized using a combination of 6 M guanidine hydrochloride and 0.2% Triton X-100, but precipitated when the 6 M guanidine was removed by dialysis. These results suggest that the lack of carbohydrate alters the properties of the glycoproteins, which may explain their impaired mobility through the intracellular membranous system.

Anti-Bacterial Agents↗
PubMed1977

Tunicamycin inhibits glycosylation and multiplication of Sindbis and vesicular stomatitis viruses.

Tunicamycin (TM), an antibiotic that inhibits the formation of N-acetylglucosamine-lipid intermediates, thereby preventing the glycosylation of newly synthesized glycoproteins, inhibits the growth of Sindbis virus and vesicular stomatitis virus in BHK cells. At 0.5 mug of TM per ml, the replication of both viruses is inhibited 99.9%. Noninfectious particles were not detected. All the viral proteins were synthesized in the presence of TM, but the glycoproteins were selectively altered in that they migrated faster than normal viral glycoproteins when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, suggesting defective glycosylation. Within 1 h after TM addition, [14C]glucosamine incorporation into glycoproteins was inhibited 20%, whereas [35S]methionine incorporation was unaffected. By 2 to 3 h after TM addition, glucosamine incorporation had fallen to 15% of control value, with methionine incorporation being 60% of normal. TM did not affect the growth of the nomenveloped encephalomyocarditis virus in BHK cells, demonstrating that TM is not a general inhibitor of protein synthesis. These data demonstrate that TM specifically inhibits the glycosylation of viral glycoproteins and that glycosylation may be essential for the normal assembly of enveloped viral particles.

Anti-Bacterial Agents↗
PubMed1976

Enveloped virus acquires membrane defect when passaged in fibroblasts from I-cell disease patients.

Sindbis virus obtained after passage on human fibroblasts from patients with I-cell disease (mucolipidosis II) and called I-cell virus differed from Sindbis virus obtained from chick fibroblasts or from normal human fibroblasts in two ways: (1) The I-cell virus was extremely unstable to freezing and thawing, (2) The I-cell virus showed greatly exaggerated sensitivity to inactivation by Triton X-100. Sindbis virus from fibroblasts from two patients with mucolipidosis III, a milder form of I-cell disease, showed similar, though milder, freeze-sensitivity. When freeze-sensitive I-cell virus was passaged once in mouse L-cells or normal human fibroblasts, the virus was no longer abnormal. The viral glycoproteins of I-cell virus were not distinguishable from viral glycoproteins of controls by sodium dodecyl sulfate gel electrophoresis. Gel filtration of the glycopeptides suggested small differences in two of the four glycopeptides. These findings indicate that Sindbis virus is phenotypically altered when grown on I-cell fibroblasts. These alterations must be attributed to viral envelope components derived from the host plasma membrane (membrane lipids) or to alterations in viral envelope glycoproteins. In either case, the alterations appear related to the genetic defect in I-cell fibroblasts. From these results it is clear that enveloped viruses can be useful to demonstrate and to analyze membrane defects in certain human diseases. The phenotypically altered viruses may, in turn, provide probes for studying the functional relationships of virus membrane components.

Cell Membrane↗
PubMed1976

Defective interfering passages of Sindbis virus: nature of the defective virion RNA.

Defective interfering particles of Sindbis virus contain 20S RNA identical to that found in BHK cells co-infected with standard and defective virions. We have characterized these RNAs by their oligonucleotide fingerprints. Most of the oligonucleotides were identical to those found in the mRNA (26S RNA) that codes for the virion structural proteins. Three oligonucleotides found in 20S RNA were absent from the 26S RNA pattern and may represent sequences from the 5' end of the virion RNA. Previous difficulties in describing the nature of the defective virion RNA were due to the aggregated state of the RNA. Nucleocapsids obtained from standard and defective virions were essentially the same size and had about the same density, suggesting that defective particles contain more than a single molecule of 20S RNA.

Base Sequence↗