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Biomedical subjects

S J Armstrong

Publications and source records attributed to S J Armstrong.

At least 55 records · Page 3Linked to original sources
PubMed1990

Mechanisms of neutralization of influenza virus in tracheal epithelial and BHK cells vary according to IgG concentration.

The interaction of IgG-neutralized type A influenza virus with differentiated epithelial cells of mouse trachea, BHK cells, and chicken erythrocytes was studied using three mouse monoclonal antibodies (IgG2a) each directed against a different antigenic site on the hemagglutinin. At high HIU:HAU ratios virus was neutralized greater than 99%, monodisperse, and attached to tracheal epithelial and BHK cells in normal amounts. The majority (70-80%) of neutralized virus failed to attach to erythrocytes. At low HIU:HAU ratios the virus was aggregated by each of the antibodies, and attachment to tracheal epithelial and BHK cells was inhibited by up to 75%. Combined aggregation and inhibition of attachment could theoretically account for up to 96% loss of infectivity but this corresponded with the observed degree of neutralization with only one of the antibodies. With increasing antibody:virus ratios, aggregation and inhibition of attachment contributed ever diminishingly to the observed neutralization and eventually not at all. Both neutralized and infectious virus attached to neuraminidase-sensitive receptors. After attachment neutralized virus became increasingly resistant to removal by neuraminidase suggesting that it had been internalized by the cell.

Animals↗
PubMed1990

Morphological studies of the neutralization of influenza virus by IgM.

Quantitative relationships between neutralization, aggregation and attachment to monolayers of chick embryo fibroblast (CEF) cells have been studied using a constant amount of influenza A/fowl plague virus/Rostock/34 (H7N1) and varying amounts of purified mouse polyclonal IgM directed against the haemagglutinin, the major viral neutralization antigen. There are two major types of interaction. (i) At low concentrations of IgM there is aggregation of virus, but no neutralization provided that the aggregates are dispersed by vortexing and dilution. Maximum aggregation occurs at less than seven molecules of IgM per virion and the IgM is probably bound in the 'staple' or 'crab' conformation at these concentrations. (ii) At higher concentrations there is neutralization and this coincides with inhibition of attachment of virus to CEF cells. Neutralization of 50% infectivity requires about 35 molecules of IgM per virion. The maximum neutralization observed was only 87%. Quantitative data and electron microscopy observations suggest that molecules of IgM at the higher concentrations adopt a planar stance approximately perpendicular to the viral surface. It appears that IgM neutralizes fowl plague virus in vitro primarily by interfering with its attachment to cells; the fraction of neutralized virus that does attach is known not be internalized.

Antibodies, Viral↗
PubMed1989

The relationship between number of interphase nors and nor-bearing chromosomes in non-Hodgkin's lymphoma.

The ribosomal genes (located on the acrocentric chromosomes 13-15, 21-22) may be identified by their silver stained gene products, i.e. NOR related proteins. The NOR bearing chromosome activity can be observed at metaphase with the potential for all ten chromosomes to be positively stained. On the other hand, during interphase they fuse so that eventually only a single silver positive structure is seen in resting normal cells. Investigations of histopathological sections of non-Hodgkin's lymphoma (NHL) have demonstrated a correlation between the numbers of interphase NORs and the grade of tumour. There is generally a higher number of interphase in high-grade, and a lower number in low-grade tumours. This histopathological and cytogenetic study of 13 patients with NHL shows that the higher numbers of interphase NORs in the high-grade tumours is not necessarily a reflection of increased numbers of NOR-bearing chromosomes. Examples were found of high-grade neoplasms, showing the expected high numbers of interphase NORs, but not an increased number of NOR-bearing chromosomes. Conversely, some low-grade tumours, with the expected low number of interphase NORs, had increased numbers of NOR-bearing chromosomes. Our conclusion is that the interphase NOR number is related to factors other than chromosome numbers. We suggest that NOR numbers at interphase may be related to cell turnover. This is supported by previous investigations using DNA flow cytometry and the monoclonal antibody Ki67.

Chromosomes, Human↗
PubMed1989

Ventricular fibrillation in coronary angiography: what is the role of contrast medium?

A retrospective review of patients with coronary angiography was undertaken to establish the incidence of ventricular fibrillation and other serious arrhythmias and to identify possible causative factors, in particular whether the use of non-ionic contrast medium increased the risk of a serious arrhythmia. Out of 3660 patients reviewed there were 10 cases of ventricular fibrillation. In all cases, there were identifiable technical factors thought to have accounted for the arrhythmia. There were no cases of ventricular fibrillation complicating a technically satisfactory injection of ionic or non-ionic contrast medium. There was no significant difference in the incidence of serious arrhythmias between patients given ionic and those given non-ionic contrast medium.

Angiocardiography↗
PubMed1988

One defective interfering particle per cell prevents influenza virus-mediated cytopathology: an efficient assay system.

The titre of defective interfering (DI) influenza virus measured by an assay based on the inhibition of cytopathology caused by A/WSN (H1N1) influenza virus in MDCK cells was 320,000-fold greater than titres measured by inhibition of infectious centre formation. Interference was less in other types of cell. By electron microscopy, we have shown that the ratio between physical particles and DI units in preparations of the DI virus was approximately unity, which suggested that one or few DI particles is/are required to confer resistance of a MDCK cell to viral cytopathology. This human DI virus interfered heterotypically with an avian H7N1 influenza virus.

Animals↗
PubMed1987

Quantitative relationships between an influenza virus and neutralizing antibody.

In this quantitative study of the interaction of influenza virus with neutralizing antibody we have determined the maximum number of antibody molecules which can bind to the haemagglutinin (HA) of native influenza A/FPV/Rostock/34 (H7N1) particles in aqueous suspension and the minimum number which is required to cause neutralization. Using radiolabelled immunoglobulins approximately one IgG molecule, whether of monoclonal or polyclonal origin, binds per HA spike under conditions of antibody saturation. In the same manner, we have determined that when infectivity is neutralized by 63% (1/e) about 70 molecules of monoclonal IgGs HC2 and HC10 were bound per virus particle and this is supported by independent evidence from electron microscopy. However, the kinetics of neutralization were single-hit or at most, under critical conditions of low temperature (4 degrees) and minimal neutralizing concentrations of antibody, two-hit. This apparent conflict is reconciled by a hypothesis which proposes that neutralization occurs only when antibody binds to certain "neutralization relevant" HA spikes which are in the minority. It is suggested that these only differ from the majority of "neutralization irrelevant" HA spikes by their transmembrane interaction with the core of the virion.

Antibodies, Monoclonal↗
PubMed1983

Reverse transcriptase activity and particles of retroviral density in cultured canine lymphosarcoma supernatants.

Lymphoid tissue from 43 cases of canine lymphosarcoma and from 40 clinically normal dogs have been examined for markers of retrovirus infection. From 69-76% of culture supernatants from lymphosarcomas were shown to contain particles of retroviral density and to possess poly rC-oligo dG templated polymerase (reverse transcriptase) activity compared with 17-24% of culture supernatants from normal canine lymphoid cells. In 6 culture supernatants from cases of lymphosarcoma, high molecular weight 60-70S RNA was detected and shown to be found in association with this particulate reverse transcriptase activity. No such RNA was detected in 6 culture supernatants from normal canine lymphoid cells.

Animals↗
PubMed1983

Reverse transcriptase activity in a case of ovine lymphoblastic leukaemia.

Tissues taken post mortem from a sheep suffering from lymphoblastic leukaemia were examined for retroviral reverse transcriptase (RT) activity and for particles of retroviral density. Cultured bone marrow and lymph node cells were found to release into the medium particles of 1.16 and 1.21 g/ml density, and poly rC-oligo dG templated activity could be detected in cell-free supernatants. Tissues from two normal sheep were not found to exhibit these characteristics. Electron microscopic observation failed to reveal any retrovirus-like particles in the RT positive tissues. In vitro transmission studies indicated that the RT activity could not be transmitted to either sheep choroid plexus or lamb trachea cells, but was transmitted, at low efficiency, to both bovine kidney and mink lung cells.

Animals↗
PubMed1972

Inhibition of influenza virus replication by -amanitin: mode of action.

The replication of influenza virus in chick embryo fibroblast cells is inhibited by alpha-amanitin added during the first 2 hr of infection at concentrations similar to those required to inhibit cellular DNA-dependent RNA polymerase form II in vivo. Of two periods of increased RNA synthesis observed in cells infected with influenza virus, only the first, occurring from 0 to 2 hr after infection, is sensitive to alpha-amanitin. During this early period, there is a stimulation of the activity of DNA-dependent RNA polymerase II of nuclei isolated from infected cells. The data suggest that DNA transcription mediated by polymerase II is essential for influenza virus replication.

Animals↗