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Biomedical subjects

H M Keir

Publications and source records attributed to H M Keir.

At least 19 recordsLinked to original sources
PubMed1989

In vitro enhancement of respiratory syncytial virus infection of U937 cells by human sera.

Human sera containing respiratory syncytial (RS) virus-specific antibodies enhance RS virus infection of the U937 macrophage cell line. There was an increase in the number of cells expressing virus antigen when U937 cells were infected with RS virus in the presence of human serum compared to cells infected in the absence of human serum. Human sera enhanced virus yield, as measured by the cell-released infectious virus, by an average of 50-fold compared to virus infection in the absence of human serum. The comparison of the enhancing activities of paired acute and convalescent human sera showed that the titre of enhancing antibody increased in parallel with the titre of RS virus-specific antibody measured by complement fixation and virus neutralization. An RS virus-specific neutralizing monoclonal antibody directed to the virus F protein enhanced virus infection of U937 cells. A non-neutralizing monoclonal antibody directed to the virus nucleoprotein did not enhance virus infection. The possible role of enhancing antibodies in vivo is discussed.

Aged↗
PubMed1987

Immunoblot analysis of the human antibody response to respiratory syncytial virus infection.

The protein specificities of the antibodies induced during natural respiratory syncytial (RS) virus infection in humans were investigated using immunoblotting of human sera against virus proteins resolved by gel electrophoresis. Sera from 33 patients, who had complement-fixing antibodies against RS virus, were analysed. All the patients showed a response against the virus nucleoprotein (VPN41) and glycoprotein (VGP48). Antibodies against the virus proteins GP90, VPP32, VPM27 and two proteins of molecular weights 24,800 and 23,700 were also demonstrated. The spectrum of protein specificities of the antibodies varied among patients. There was an increase in the level of antibody for these virus proteins between the acute and convalescent serum samples from five patients. The protein specificities of the IgG and IgM antibodies were determined for five patients; VPN41, VPP32 and VPM27 induced IgG and IgM in all of these sera. Two of the five patients had detectable IgG but not IgM antibodies against VGP48, whereas the remaining three sera had detectable VGP48-specific IgG and IgM antibodies.

Antibodies, Viral↗
PubMed1986

Factors affecting polyamine excretion from mammalian cells in culture. Inhibitors of polyamine biosynthesis.

Canavanine, diaminopropane, alpha-methylornithine and methylglyoxal bis(guanylhydrazone) decreased the intracellular polyamine concentrations in growing baby hamster kidney cells. Each of the inhibitors also prevented polyamine efflux into the extracellular medium. Concomitant with the decrease in polyamine excretion was a change in the distribution of polyamines in the extracellular medium. In each case there was a decrease in the amount of radioactivity present as free spermidine and an increase in that found as acetyl polyamines. The magnitude of this shift correlated with the degree of inhibition of excretion. It may be that acetyl polyamines play a role in the regulation of polyamine excretion.

Acetylation↗
PubMed1986

Antigenic variation between human respiratory syncytial virus isolates.

Three hybridoma antibodies, prepared against the RSN-2 strain of human respiratory syncytial (RS) virus, have been used to identify antigenic variation between 41 isolates of RS virus collected from widely separated geographical regions over a period of 29 years. One antibody was directed against an antigenic site on the virus fusion protein, VP70. This site was shared by 21 virus isolates tested and its recognition by the antibody was sensitive to the presence of 2-mercaptoethanol. The remaining two antibodies used react against the virus phosphoprotein, VPP32. Two independent sites were recognized on VPP32 by these antibodies. One antibody reacted with all of the virus isolates screened while the second reacted with only 21 out of the 41 virus isolates. On the basis of the variable epitope, two antigenic types of human RS virus were identified. The distribution of each antigenic group among 28 RS virus isolates from the Grampian Region, north-east Scotland, collected between 1982 and 1984 was determined. The reactivity of these antibodies was examined using immunofluorescence staining and by immunoblotting; the latter technique also revealed that the electrophoretic mobility of VPP32 varied in parallel with the variable antigenic site.

Animals↗
PubMed1979

Polyamine replacement by magnesium ions in BHK-21/C13 cells.

Cultures of BHK-21/C13 cells, whose growth was inhibited by deprivation of serum, were stimulated to grow by addition of serum to the culture medium. Addition of MgCl(2) to the medium, to increase the concentration of Mg(2+) ions by 15mm, 30min before addition of serum, had no effect on the stimulation of cell growth, but inhibited the accumulation of cellular spermidine, so that the spermidine/spermine molar ratio was lower in these cultures than in cultures that had received no additional cations. The increase in the activity of ornithine decarboxylase that occurs 4-5h after serum ;step-up' was substantially diminished by increasing the concentration of Mg(2+) ions, but not of Na(+) or K(+) ions, in the medium by 30mm, 30min before addition of serum, and this inhibition was maintained for at least 24h. Methylglyoxal bis(guanylhydrazone), added to serum-deprived cultures to a concentration of 20mum, 30min before addition of serum, severely inhibited the increase in cell growth. The inhibitory effects of the drug were prevented by simultaneous addition of spermidine to the medium (to 100mum), and were partly prevented by the simultaneous addition of Mg(2+) ions (to 30mm). Mg(2+) ions were particularly effective in overcoming the inhibitory effect of methylglyoxal bis(guanylhydrazone) on the synthesis of DNA. Thus although a certain lack of specificity for cations exists in BHK-21/C13 cells, in that Mg(2+) ions can be substituted for polyamines, particularly spermidine, to some extent, there are cellular processes for which the requirement for polyamines as cations is specific.

Animals↗
PubMed1979

Effect of amino acid deprivation on DNA synthesis in BHK-21/C13 cells.

Removal of serum from BHK-21/C13 cells in culture results in a decline in thymidine incorporation extending over five days. Additional removal of any of several amino acids results in a rapid decrease in incorporation of thymidine to negligible levels by 24 hours. Replacement by complete medium then provokes a synchronous wave of DNA synthesis after only ten hours with DNA synthesis first increased at six hours. Starvation for glutamine results in a rapid decline in protein synthesis over the 24 hour period when DNA synthesis is falling. However, there is considerable degradation of total protein during this period, and RNA degradation is also greatly increased. Concurrently, synthesis of RNA falls to less than 10% of that in control cells.

Amino Acids↗
PubMed1978

Onset of ribosome degradation during cessation of growth in BHK-21/C13 cells.

When BHK-21/C13 cells growing exponentially in 10% serum are transferred to a medium containing only 0.25% serum, cell growth is decreased. After initial changes in RNA synthesis and degradation, protein content of the cultures reaches a plateau and eventually DNA synthesis is arrested. rRNA is relatively stable in exponentially growing cells. Immediately after 'step-down' rRNA degradation commences, but poly(A)-containing RNA does not appear to be degraded any faster than in control cells. Reutilization of RNA precursors has been independently measured and amounts to less than 1%/h for rRNA, insufficient to influence the conclusion that rRNA degradation begins almost immediately after 'step-down'. The degree of reutilization of uridine is much greater for poly(A)-containing RNA than for poly(A)-free RNA.

Animals↗
PubMed1978

Diminished excretion of polyamines from BHK-21/C13 cells exposed to methylglyoxal bis(guanylhydrazone).

Methylglyoxal bis(guanylhydrazone) (1,1'-[methylethanediylidine)dinitrilo]diguanidine) inhibited the growth of BHK-21/C13 cells in monolayer cultures. Accumulation of spermidine and spermine was inhibited, whereas the accumulation of putrescine was increased. The intracellular spermidine/spermine molar ratio decreased conly slightly after exposure of the cells to 20 micrometer-methylglyoxal bis(guanylhydrazone) for 1 day. Cells incubated in the presence of the drug released less polyamine into the culture medium that did control cells, the polyamine released consisting almost exclusively of spermidine, both free and as a conjugated form.

Cell Division↗
PubMed1978

Incorporation of 6-thioguanosine and 4-thiouridine into RNA. Application to isolation of newly synthesised RNA by affinity chromatography.

Isolation of newly synthesised RNA can be achieved by treatment of cells in culture with 6-thioguanosine or 4-thiouridine followed by separation of thiol-containing RNA by affinity chromatography on mercurated cellulose columns. After short periods of treatment with 6-thioguanosine the proportion of RNA retained on mercurated cellulose is the same for both poly(A)-containing and poly(A)-free RNA, indicating similar incorporation of the drug into mRNA and rRNA. However, after longer periods of exposure, the cytotoxic effect of 6-thioguanosine results in diminished incorporation of radioactive uridine into RNA and of radioactive leucine into protein; this suggests that synthesis of both RNA and protein are impaired. On the other hand, even after long exposure to high concentrations of 4-thiouridine, the syntheses of RNA and protein are not significantly affected. Proteins synthesised after treatment of cells with 6-thioguanosine are less stable than proteins synthesised after treatment of cells with 4-thiouridine.

Animals↗
PubMed1978

Excretion of spermidine from BHK-21/C13 cells exposed to 6-thioguanosine.

The growth of BHK-21/C13 cells in monolayer cultures was inhibited by 6-thioguanosine. Accumulation of putrescine, spermidine, and spermine was inhibited by 6-thioguanosine, and cells incubated in the presence of the drug had a decreased content of polyamines relative to control cells. These effects were more marked for spermidine than for spermine or putrescine. Consequently, the intracellular spermidine:spermine molar ratio was decreased in cells exposed to the drug. Cells, the polyamines of which had been labeled with [3H]putrescine, were incubated in the presence or absence of 6-thioguanosine. More polyamines were lost from cells exposed to the drug than from control cells. The radioactive material excreted was predominantly spermidine, both as its free form and in a conjugated form, even when the cells contained large amounts of labeled spermine. This release of spermidine from BHK-21/C13 cells into the culture medium was a specific response of the cells to alterations in growth potential rather than a consequence of leakage due to cell lysis.

Cell Division↗