Search PubMed⌕ Search

Biomedical subjects

M R Thompson

Publications and source records attributed to M R Thompson.

At least 55 records · Page 3Linked to original sources
PubMed1985

Characterization of human beta-interferon-binding sites on human cells.

Radioiodinated recombinant human beta-interferon (rHuIFN beta Ser), with almost full (greater than 90%) biological activity, was used to study the binding of human beta-interferon to Daudi cells. Specific binding was not observed with less biologically active (less than or equal to 10%) radioiodinated interferon. The bound radioiodinated interferon was shown to compete with human beta-interferon (HuIFN beta), rHuIFN beta Ser, human alpha-interferon (HuIFN alpha) and with human gamma-interferon (HuIFN gamma). Scatchard plot analyses suggest the presence of about 10,000 binding sites for HuIFN beta/Daudi cell. About 6,600 of these sites can be blocked by HuIFN alpha and 3,700 sites can be blocked by HuIFN gamma. The apparent Kd for HuIFN beta is 2.7 nM. The apparent Kd values for HuIFN alpha and HuIFN gamma are 3.7 and 1.1 nM, respectively. It was possible to demonstrate the cross-linking of HuIFN beta to two macromolecular components of Mr = 128,000 and 103,000. We propose the existence of at least two binding sites for HuIFN beta in Daudi cells, one site recognizing both HuIFN beta and HuIFN gamma, the other site recognizing both HuIFN beta and HuIFN alpha. Each site is capable of recognizing only HuIFN gamma or HuIFN alpha.

Binding, Competitive↗
PubMed1985

Biological and immunological characteristics of 125I-4Tyr and -18Tyr Escherichia coli heat-stable enterotoxin species purified by high-performance liquid chromatography.

A rapid procedure for the separation of Escherichia coli heat-stable enterotoxin iodination products is described. A two-step procedure using reverse-phase chromatography results in the separation of native, noniodinated heat-stable enterotoxins from several distinctly iodinated species which differ in their ability to bind to brush border receptors. Sequence analysis of the radioligands demonstrated mutually exclusive labeling at the 4Tyr and 18Tyr residues. These tracers have been immunologically and biologically characterized and have been shown to be antigenically similar but to differ in their toxicity for suckling mice. The radioligands separated by this procedure demonstrate stable behavior for a period of months.

Amino Acid Sequence↗
PubMed1985

Septal driving of hippocampal theta rhythm: role of gamma-aminobutyrate-benzodiazepine receptor complex in mediating effects of anxiolytics.

In free-moving male rats, when the hippocampal theta rhythm is artificially driven by stimulation in the septum at frequencies between 5 and 10 Hz, the function relating frequency to the threshold current required to drive the theta rhythm has a minimum at 7.7 Hz. This minimum is eliminated by anxiolytic drugs. Dose-response curves for this effect are reported for chlordiazepoxide, diazepam and meprobamate. The effect of meprobamate was reversed by two gamma-aminobutyrateA antagonists, picrotoxin and bicuculline, which have previously been shown to be without effects of their own. The gamma-aminobutyrateB agonist, baclofen, also without effect on its own, blocked the elimination of the 7.7-Hz minimum caused by the gamma-aminobutyrateA agonist, muscimol. The beta-carboline, ethyl-beta-carboline-3-carboxylate, had mixed agonist/antagonist properties, blocking the effects of chlordiazepoxide, diazepam and muscimol (though not sodium amylobarbitone) but itself acting like a benzodiazepine. Coupled with earlier data, these findings support a role for gamma-aminobutyrate receptors in mediating the effects of anxiolytic drugs.

Animals↗
PubMed1985

Revised amino acid sequence for a heat-stable enterotoxin produced by an Escherichia coli strain (18D) that is pathogenic for humans.

The amino acid sequence of heat-stable enterotoxin produced by enterotoxigenic Escherichia coli 18D has been revised. Amino acids originally assigned to positions 11 and 18, i.e., Tyr and Asn, respectively, were found to occupy positions 18 and 11, respectively. Thus all heat-stable enterotoxins composed of 18 amino acids sequenced to date from human, porcine, and bovine isolates of E. coli have identical primary structures, i.e., Asn-Thr-Phe-Tyr-Cys-Cys-Glu-Leu-Cys-Cys-Asn-Pro-Ala-Cys-Ala-Gly-Cys-Tyr. Furthermore, all 18- and 19-amino-acid heat-stable enterotoxins from E. coli share an almost identical core sequence, i.e., 14 of the 15 carboxy-terminal amino acid residues are identical.

Amino Acid Sequence↗
PubMed1984

Rapid screening assay for toxic shock syndrome toxin production by Staphylococcus aureus.

A rapid immunoblot assay (TST-blot) was developed and used to screen Staphylococcus aureus isolates for toxic shock syndrome toxin (TST) production. Growth from an 18-h stab inoculum of S. aureus on brain heart infusion agar was transferred directly to a nitrocellulose sheet. Nonspecific protein binding sites were blocked with bovine serum albumin, and the nitrocellulose sheet was incubated with affinity-purified antibody to TST, followed by incubation with horseradish peroxidase-conjugated protein A. Toxin was visualized by detection of the peroxidase-conjugated protein A-anti TST-TST complex with 4-chloro-1-napthol. The sensitivities and specificities of the TST-blot and Ouchterlony microslide immunodiffusion assay were compared by screening 141 S. aureus isolates for TST production. In both assays, 53 of 141 isolates produced detectable levels of TST, whereas 88 isolates produced no toxin. A 100% concordance was found between the two assays. The TST-blot yielded the same results in less than 24 h as those yielded by the 3-day immunodiffusion assay. Thus, this rapid method for detection of TST in multiple samples appears to be well suited for diagnostic and epidemiological studies. Furthermore, it would appear to be ideal for use in TST genetics research.

Bacterial Toxins↗
PubMed1984

Simple and reliable enzyme-linked immunosorbent assay with monoclonal antibodies for detection of Escherichia coli heat-stable enterotoxins.

We have developed a sensitive and specific competitive enzyme-linked immunosorbent assay for Escherichia coli heat-stable enterotoxins consisting of methanol-soluble, suckling mouse active peptides with similar core sequences (STa) by using monoclonal antibodies prepared against STa purified from a human isolate. The assay can detect 3 to 20 pg of purified STa, depending on the monoclonal antibody used in the assay. The assay is rapid, requiring ca. 1 h to complete. With this competitive enzyme-linked immunosorbent assay, we measured STa production by enterotoxigenic E. coli directly in Casamino Acid-yeast extract culture supernatants. The assay was suitable for measuring STa in culture supernatants from human, bovine, and porcine E. coli isolates. No cross-reactivity was observed with heat-labile enterotoxin, cholera toxin, or heat-stable enterotoxin STb, which is a methanol-insoluble peptide(s) active in the ligated pig jejunal loop test. A 100% correlation of toxin production was found by comparing the enzyme-linked immunosorbent assay with the previously established radioimmunoassay for STa and with suckling mouse activity.

Animals↗
PubMed1982

Production of Shigella dysenteriae type 1-like cytotoxin by Escherichia coli.

Strains of Escherichia coli previously implicated or proven to be causes of diarrhea were examined for production of a toxin similar to that of Shigella dysenteriae type 1 (Shiga). Organisms grown in an iron-depleted broth were lysed by pressure disruption followed by ultracentrifugation. Saline-dialyzed extracts were tested for cytotoxic effects on HeLa cells that were neutralizable with antiserum to Shiga toxin. Among the 13 E. coli strains so analyzed, 11 made a Shiga-like cytotoxin in levels ranging from trace (two avirulent isolates) to amounts equivalent to S. dysenteriae type 1 (two noninvasive strains that did not make E. coli heat-labile or -stable enterotoxins but were isolated from infants with diarrhea). As with extracts of Shiga toxin, lysates of these E. coli strains that produced high levels of Shiga-like toxin were enterotoxic for rabbits, paralytic and lethal for mice, and inhibited protein synthesis in HeLa cells. Thus, these data suggest that Shiga-like toxin may be another heretofore undiscovered factor in the pathogenesis of diarrhea caused by some E. coli strains.

Animals↗
PubMed1980

Characterization of Shigella dysenteriae 1 (Shiga) toxin purified by anti-Shiga toxin affinity chromatography.

Shigella dysenteriae 1 (Shiga) toxin was purified from whole-cell lysates by antitoxin affinity column chromatography, radioiodination, and Sephacryl S-200 gel filtration of 125I-labeled affinity column eluates. Two chromatographic peaks were observed. The percentage of radioactivity in peak I samples immunoprecipitated with antitoxin ranged from 95 to 100%. A pool of samples from this first peak contained over 90% of the HeLa-cell-cytotoxic units applied to the column and was enterotoxic for rabbit ileal loops and lethal for rabbits. This radiolabeled material migrated as a single cytotoxic band after nondenaturing polyacrylamide gel electrophoresis, but formed three bands, of 33,000, 29,000, and 4,000 to 7,000 daltons, after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In addition, material estimated as 7,000 daltons by Bio-Gel P-10 chromatography could be generated by treatment of S-200 peak I samples with 8 M urea. Pooled fractions from the second S-200 peak were separable into several low-molecular-weight peaks on a P-10 column. One of these P-10 peaks (7,000 daltons) was 27% immunoprecipitable with antitoxin. These data indicate that three of the known biological activities of Shiga toxin are associated with a 33,000-dalton substance which can be dissociated into 29,000- and 4,000- to 7,000-dalton components.

Animals↗
PubMed1980

Surgical presentation of small bowel lymphoma in adult coeliac disease.

A case of perforation of a small bowel lymphoma in a patient with coeliac disease is reported. Postoperative management was complicated by a large protein and fluid loss from the small bowel, rapidly controlled by treatment with corticosteroids. Attention is drawn, by briefly reviewing 11 other cases, to the ways in which small bowel lymphoma in patients with coeliac disease may present to the surgeon. Most patients who develop this complication of coeliac disease will die within 6 months of the diagnosis of small bowel lymphoma. Attention is drawn in this case to the rapidity with which the tumour grew and became disseminated.

Celiac Disease↗
PubMed1979

Shigellosis and Escherichia coli diarrhea: relative importance of invasive and toxigenic mechanisms.

Shigellae and dysentery-like Escherichia coli must invade the epithelium of the colon to cause disease which can present as dysentery, diarrhea, or both. This paper addresses the possible role of a Shigella dysenteriae-like (Shiga-like) toxin in the pathogenesis of shigellosis and E. coli diarrheal diseases. The possibility for such a role is suggested by the following observations: 1) diarrhea, considered to be a result of secretion of water by the small bowel, is frequently observed in shigellosis, a large bowel disease. 2) Even though shigellae do not invade the jejunum of monkeys fed Shigella flexneri, jejunal secretion is seen in animals with diarrhea. 3) The Shiga toxin of S. dysenteriae has enterotoxic activity and other serotypes of shigellae produce Shiga-like toxins. 4) E. coli 015 RDEC-1 causes a diarrheal disease and frequently death in young rabbits. This organism neither produces E. coli enterotoxins nor is it invasive, but it may produce low levels of a Shiga-like toxin.

Animals↗
PubMed1979

Production of exoenzyme S during Pseudomonas aeruginosa infections of burned mice.

Antisera which distinguished between Pseudomonas aeruginosa exoenzyme S and toxin A neutralized the adenosine diphosphate ribosyl transferase activity of the homologous, but not the heterologous, enzyme. Skin extracts and sera from burned mice infected with the exoenzyme S-producing strain P. aeruginosa 388 contained adenosine diphosphate ribosyl transferase activity that was not found in skin extracts or sera from uninfected mice. On the basis of immunological reactivity and enzymatic properties, the adenosine diphosphate ribosyl transferase activity present in skin extracts and sera from P. aeruginosa 388-infected mice was identified as exoenzyme S. Active elongation factor 2 levels in tissues from strain 388-infected mice were normal at 24 h postinfection, indicating that strain 388 does not produce detectable amounts of toxin A in vivo. An unexpected finding in this investigation was the presence of exoenzyme S-inactivating activity in the sera from some nonimmunized animals.

Animals↗