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Biomedical subjects

R R Dourmashkin

Publications and source records attributed to R R Dourmashkin.

At least 19 recordsLinked to original sources
PubMed1988

Interactions of a nonneutralizing IgM antibody and complement in parainfluenza virus neutralization.

While many viruses activate the complement cascade directly, this is generally not a neutralizing event in the absence of antibody. We used a nonneutralizing IgM monoclonal antibody to parainfluenza virus type 3 (PIV3) hemagglutinin-neuraminidase (HN) to explore the role of antibody in complement-dependent neutralization of PIV3. Neither the antibody nor nonimmune guinea pig serum (GPS) neutralized PIV3 significantly, but a more than 100-fold reduction in titer was found when antibody and GPS were combined. Heat-inactivated GPS or GPS lacking either of two different complement proteins were all inactive with or without antibody. Specific repletion of the deficient sera with highly purified complement proteins restored neutralizing activity, indicating an absolute requirement for the classical pathway of complement activation and lytic terminal complement components, and viral lysis was confirmed by electron microscopy. The presence of antibody before complement activation was essential; later addition had no effect. Spontaneous complement activation by PIV3 occurred via the classical pathway in the absence of antibody. Addition of antibody did not alter the overall rate or extent of complement component C3 binding to PIV3 in these experiments. We conclude that certain nonneutralizing antibodies may support complement-dependent PIV3 neutralization by facilitating viral lysis. This process does not, however, involve enhanced activation through the C3 step. Lysis may require antibody-dependent localization of the membrane attack complex or reorganization of the viral envelope structures to facilitate attack complex insertion and lysis.

Antibodies, Monoclonal↗
PubMed1983

Epithelial patchy necrosis in Crohn's disease.

Electron and light microscopic studies of the intestinal epithelium in Crohn's disease demonstrated localized areas of damage to the superficial epithelium, occurring without accompanying acute inflammation. In a blind study of rectal biopsy specimens from seven patients with Crohn's disease, four with ulcerative colitis, and four normal controls, this finding of patchy necrosis without acute inflammation was observed exclusively in four of the seven cases of Crohn's disease.

Biopsy↗
PubMed1982

Ultrastructure of a hyaluronic acid matrix.

Freeze-etch replicas of a hylauronic acid matrix were visualized by electron microscopy. In water a coarse branching fibrillar network of hyaluronic acid aggregates was seen. The high solvent permeability of this matrix suggests that the spaces observed are relatively devoid of unaggregated polymer. Addition of calcium disordered the matrix, resulting in a more dispersed felt of polymer.

Extracellular Space↗
PubMed1981

Ribonucleoprotein of avian infectious bronchitis virus.

The ribonucleoprotein (RNP) of avian infectious bronchitis virus (IBV) was examined by electron microscopy after shadowing with carbon/platinum. Linear RNP strands up to 6.7 microns in length, from three IVB strains, were sensitive to both pancreatic RNase and to proteases. These strands were obtained from spontaneously disrupted complete particles but not from disrupted incomplete particles that lacked RNP. They were also released from Nonidet P40-disrupted particles and could be isolated on sucrose density gradients at a density of 1.27 g/ml. In some cases, helical RNP complexes associated with virus particles were observed that were similar to RNPs of human coronavirus strain 229E and mouse hepatitis virus strain 3.

Centrifugation, Density Gradient↗
PubMed1980

Electron microscopic demonstration of lesions in target cell membranes associated with antibody-dependent cellular cytotoxicity.

To test the hypothesis that complement-mediated cell lysis and cell-mediated cytotoxicity operate by analogous mechanisms, cell membranes from two antibody-dependent cytotoxicity systems were examined by electron microscopy after negative staining. Ring-shaped membrane lesions generally similar to, but larger than, those previously described for complement lysis were observed. These findings are in agreement with recent measurements of larger functional pores for ADCC than complement.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1979

Studies on the mechanism of influenza virus entry into cells.

Inhibitors of glycolysis, oxidative phosphorylation, protein synthesis, membrane Na&-K& transport and microfilament and microtubule function have been employed to elucidate the mechanism of influenza virus uptake by CAM and CEF cells. Electron microscopy demonstrated uptake of virus by viropexis in the presence of all these inhibitors. Utilizing a pulse labelling technique, virus entering CEF cells in the presence of inhibitors was shown to initiate specific virus polypeptide synthesis after neutralization of remaining extracellular virus and removal of the inhibitors. As a consequence of these findings an energy independent mechanism of viropexis has been proposed.

Animals↗
PubMed1979

Interaction of Mycoplasma pneumoniae with human lung fibroblasts: characterization of the in vitro model.

The interaction of pathogenic Mycoplasma pneumoniae and host cells was studied in cell cultures of MRC-5 human lung fibroblasts. A comparison of results obtained with fibroblasts in a monolayer format and with hamster tracheal explant cultures indicated that the former can bind significantly larger numbers of mycoplasmas. In addition, the attachment was 96% specific, that is, mediated through a neuraminidase-sensitive receptor on the host cell. Uptake of mycoplasmas was directly related to the number of mycoplasma cells present in the inoculum, and attachment was virtually complete within a 30-min period at 37 degrees C. High doses of M. pneumoniae induced a marked cytopathic effect, whereas doses of less than or equal to 10(6) colony-forming units per ml produced grossly observable cell damage that was moderate and variable. Transmission electron microscopy studies indicated that attachment of M. pneumoniae to the surface of lung fibroblasts occurred with the specialized terminal structure or binding site oriented closest to the epithelial cell surface. The filamentous mycoplasma cells were spatially arranged in several configurations and were not limited to a vertical orientation. The advantages and disadvantages of human lung fibroblast monolayer cultures, in reference to other in vitro models are discussed. A new mycoplasma agar medium (G-200 agar) with a defined tissue culture base and 10% horse serum is also described.

Binding Sites↗
PubMed1979

A year's experience of the rotavirus syndrome and its association with respiratory illness.

In a hospital study rotavirus was identified in 51% of 152 children with diarrhoea. These patients showed a clinical pattern that was distinct from patients in whom the diarrhoea was associated with bacteria, other viruses, or no pathogens. A respiratory illness was described in 66% of rotavirus patients and usually preceded the gastrointestinal symptoms. Vomiting lasted between one and 3 days and was curtailed by substituting the normal diet with clear fluids. Watery diarrhoes continued for 4 or 5 days, even when rehydration was by the intravenous rather than the oral route. Prolonged diarrhoea was rare. Most children infected with rotavirus were under 2 years of age, but dehydration was most severe in infants aged between 12 and 18 months. A clinician can thus recognise the rotavirus syndrome and expect spontaneous recovery if adequate rehydration is maintained for a critical few days.

Adolescent↗
PubMed1979

Growth and effect of chlamydiae in human and bovine oviduct organ cultures.

Organ cultures of 10 Fallopian tubes were inoculated with a genital strain of Chlamydia trachomatis and seven were infected. Infection was enhanced by centrifuging the organisms on to the tissues, larger numbers of organisms being reisolated from the tissues after this procedure. There was evidence of chlamydial multiplication because the number of organisms which were recovered from the tissues three to five days after inoculation had increased. Recovery was rare, however, after the sixth day, thus suggesting a self-limiting infection. Organ cultures of two bovine oviducts were infected with the bovine abortion strain of Chlamydia psittaci, but in these experiments centrifugation of the inocula did not enhance infection. The organisms were found in both the tissue and medium of cultures up to 18 days after inoculation and in much greater numbers than in the C. trachomatis-infected Fallopian cultures. Chlamydial infection was not entirely host-tissue specific, because C. trachomatis organisms were isolated from bovine oviduct cultures. Inclusions, however, were not detected histologically or electron microscopically in the epithelium of C. trachomatis-infected cultures, but they were detected by these means in C. psittaci-infected bovine cultures. All the elements of the chlamydial growth cycle were seen by electron microscopy, organisms being found in ciliated and possibly non-ciliated cells, and shedding of some infected epithelial cells was observed. No evidence of extensive epithelial cell damage was observed, however, and no loss of ciliary activity was detected in cultures infected with either C. trachomatis or C. psittaci when compared with uninoculated cultures. Thus acute salpingitis, when caused by chlamydial infection, is probably immunologically mediated.

Animals↗
PubMed1978

The structural events associated with the attachment of complement components to cell membranes in reactive lysis.

Electron microscopic study of the events occurring at the cell membrane during reactive lysis by complement, showed that a foliaceous particle was formed at the C5b-7 stage, that enlarged to a particle with a variable number of arms at the C5b-8 stage. Up to this point, no typical complement lesions were found. At the C5b-9 stages, the particles were completely converted to typical complement lesions, i.e. hollow cylinders projecting from the cell membrane and partly penetrating it. C5b-9 complexes assembled in the fluid phase did not show the typical structure of the lesions, but were amorphous masses of fibres.

Complement C5↗
PubMed1977

Relationship of pili to colonial morphology among pathogenic and nonpathogenic species of Neisseria.

Growth in colonies with type 1 morphology and the presence of pili are characteristics that have been associated with virulence of gonococci for humans. To determine whether the presence of pili per se might be responsible for colony type 1 morphology, the relationship of pili to colony type was examined in various species of Neisseria. Short pili (175 to 210 nm in length) were seen only on nonpathogenic neisseria, whereas long pili (up to 4,300 nm) were seen on organisms of both nonpathogenic and pathogenic species. Although long pili, similar to those found on organisms from high-domed, type 1 colonies of gonococci, were observed on organisms from high-domed, type 1 colonies of nonpathogenic Neisseria species, they were also observed on low-convex, type 4 colonies of meningococci and nonpathogenic neisseria. Among meningococci there was no difference in the morphology of colonies consisting of organisms with many long pili and colonies consisting of organisms that completely lacked pili. Thus, there was no consistent relationship of pili to colonial morphology. Unless the pili of N. gonorrhoeae are unique among Neisseria species in their influence on colonial morphology, it is likely that factors other than pili determine colony type 1 morphology of gonococci. Whether these same factors, either alone or in conjunction with pili, are also responsible for gonococcal virulence warrants further investigation.

Neisseria↗