Biomedical subjects
B Marshall
Publications and source records attributed to B Marshall.
Most anti-human CD3 monoclonal antibodies are directed to the CD3 epsilon subunit.
The T cell receptor is a molecular complex compriSed of a clonally-restricted heterodimer (Ti) responsible for specific antigen recognition and a set of invariant CD3 peptides termed gamma, delta, epsilon, zeta and eta. The latter are believed to be involved in transmembrane signaling events given that monoclonal antibodies (mAb) directed to the native CD3 structure can trigger T cell activation. We show here that the vast majority of anti-human CD3 mAb are directed to an epitope(s) encoded in part or in total by the epsilon subunit since 15 of 18 independent mAb specifically react with a murine T cell line expressing the human CD3 epsilon chain at its cell surface. The WT31 mAb is also reactive with this cell line showing that its target epitope, originally assigned to the Ti structure, rather maps to the CD3 epsilon subunit. These findings suggest that the CD3 epsilon subunit is the most exposed of the native CD3 structures which are immunogenic and that cross-linking of the CD3 epsilon chain by mAb mediates the subsequent T cell activation via the T cell receptor complex.
High frequency of antimicrobial resistance in human fecal flora.
The frequency of resistance to seven different antimicrobial agents was examined in the aerobic gram-negative gut flora of over 600 individuals from hospitals, from laboratories where antibiotics were used, and from urban and rural communities. In a majority (62.5%) of fecal samples from people without a recent history of taking antibiotics, 10% or more of the total organisms were resistant to at least one of the antibiotics. In about 40% of the samples, resistance to more than one drug was present at this level. More than one-third of the samples contained resistant organisms comprising 50% or more of the total flora examined. Organisms with coresistance to multiple drugs were found frequently. Individuals taking antibiotics produced more samples with a higher proportion (greater than 50%) of resistant bacteria, and these samples also had a significantly greater number of different resistance determinants. This extensive study revealed a high prevalence of resistant bacteria in the gut flora of ambulatory and hospitalized individuals whether or not they were taking antibiotics.
Survival of Escherichia coli with and without ColE1::Tn5 after aerosol dispersal in a laboratory and a farm environment.
The survival of a laboratory strain and a naturally occurring fecal strain of Escherichia coli, with and without a Tn5-containing derivative of ColE1, was examined after aerosol dispersal in a laboratory office and a barn under ambient temperature and humidity conditions. Following the release of paired strains, air and diverse types of surfaces were assayed for the test organisms. In both environments, the number of airborne bacteria declined rapidly within the first 2 h. Longer survival was found on surfaces and varied with surface type: recovery was greatest from wood products. Organisms persisted for 1 day in the office and for up to 20 days in the barn. Survival of the fecal strain was better than that of the laboratory strain in both test environments. In general, plasmid-bearing strains fared similarly to their plasmidless parents, but in several comparisons the ColE1::Tn5-containing strain showed enhanced survival. These studies have implications for the present and proposed release of genetically engineered organisms with and without plasmid vectors.
Enzyme-linked immunosorbent assay for Campylobacter pyloridis: correlation with presence of C. pyloridis in the gastric mucosa.
Antibody to Campylobacter pyloridis was measured by ELISA in the sera of 160 patients from whom gastric biopsy specimens were also obtained. The antigen was an acid-glycine extract of C. pyloridis, and titers ranged from 80 to 22,000 ELISA units (EU). Of 117 patients in whom C. pyloridis was detected microbiologically or histologically, 87 (74%) had a titer greater than or equal to 300 EU, and only one had a titer less than 150 EU. Of 43 patients in whom C. pyloridis was not detected, only two (5%) had a titer greater than 300 EU. Thus, for a titer of 300 EU the ELISA test had a specificity of 97% and a sensitivity of 81%. At 150 EU the specificity was 78%, and the sensitivity was 99%. Histological diagnosis of active chronic gastritis was associated with a high median ELISA titer (485 E), chronic gastritis with a much lower titer (150 EU), and normal histology with a titer of 110 EU. Discriminating use of this serological test could be of assistance to detect C. pyloridis in the gastric mucosa.
Liaison between the community and an acute hospital for the elderly.
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A new tetracycline-resistance determinant, class E, isolated from Enterobacteriaceae.
A fifth tetracycline(Tc)-resistance determinant, designated class E, has been identified on a transferable plasmid found in a fecal strain of Escherichia coli. This determinant does not show homology by DNA-DNA hybridization at high stringency with any of four other Tc resistance determinants (classes A, B, C and D) previously described among the Enterobacteriaceae. Resistance is inducible by 1 microgram Tc/ml and increases the minimum inhibitory concentration 130-fold for Tc and 3.5-fold for minocycline. The mechanism, like that of the other four determinants examined, appears to involve an active efflux of the drug. Using a 32P-labeled cloned fragment containing the resistance determinant, we have found the determinant in Aeromonas, but not in any of over 200 other E. coli strains tested.
The mechanism of action of mAMSA.
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Antibiotic-resistant bacteria in wild primates: increased prevalence in baboons feeding on human refuse.
We examined three groups of wild baboons (Papio cynocephalus) in Amboseli National Park, Kenya, to determine the prevalence of aerobic antibiotic-resistant fecal bacteria in nonhuman primates with and without contact with human refuse. Using standard isolation and replica plating techniques, we found only low numbers of antibiotic-resistant gram-negative enteric bacteria in two groups of baboons leading an undisturbed existence in their natural habitat and having limited or no contact with humans. However, resistance was significantly higher among enteric bacteria from the third group of baboons living in close proximity to a tourist lodge and having daily contact with unprocessed human refuse. Conjugation studies and analysis of the cell DNA by gel electrophoresis showed that in many cases resistance was plasmid-borne and transferable. These data suggest that wild nonhuman primates in frequent contact with human debris have a higher proportion of antibiotic-resistant enteric bacteria than do conspecifics without this contact. The findings further suggest that such groups of wild animals may constitute a heretofore overlooked source of antibiotic resistance in the natural environment.
Homogeneity of transferable tetracycline-resistance determinants in Haemophilus species.
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Transposon Tn10-like tetracycline resistance determinants in Haemophilus parainfluenzae.
Tetracycline resistance (Tcr) determinants from three different strains of Haemophilus parainfluenzae expressed 10-fold higher levels of resistance when mated into Escherichia coli. No plasmid was found in any of the E. coli recipients, even in matings in which a plasmid was identified in the donor Haemophilus sp. The Tcr determinant from Haemophilus sp. caused instability of resident plasmids in the recipient E. coli: all plasmids were lost within 30 generations in antibiotic-free media. However, by serial subculture in antibiotics, stable resident plasmids were obtained which carried the Tcr determinant from Haemophilus sp. and were transferable by conjugation and transformation among E. coli strains. All Haemophilus determinants hybridized with a probe for the Tcr determinant on Tn10, which bears inducible Tcr. However, Haemophilus determinants were constitutively resistant to tetracycline in the Haemophilus donors and in the E. coli recipients. This constitutive expression was recessive to wild-type Tn10 in the same cell, indicating that the constitutive phenotype resulted from the absence of an active repressor. Restrictive enzyme analysis of various E. coli plasmid derivatives bearing a Tcr determinant from Haemophilus sp. demonstrated that the inserted DNA was of similar size (8.95 to 9.35 kilobases), close to that of Tn10. Heteroduplex analysis and DNA:DNA hybridization confirmed that the Tcr determinant from Haemophilus sp. had greater than 90% homology with the Tn10 determinant, including the DNA sequence for the repressor.
Evidence that mAMSA induces topoisomerase action.
Evidence is presented that the topoisomerase inhibitors novobiocin and coumermycin inhibit the production of double-strand breaks in mouse mastocytoma cell nuclear DNA by the anticancer drug 4'[(9-acridinyl)amino]-methanesulphon-m-anisidide (mAMSA). Novobiocin did not inhibit resealing of DNA breaks induced by mAMSA. It is suggested that mAMSA intercalation into DNA induces the action of a type II topoisomerase. mAMSA and oAMSA were equally effective in breaking the DNA in isolated nuclei.
Blocked 5'-termini in the fragments of chromosomal DNA produced in cells exposed to the antitumor drug 4'-[(9-acridinyl)-amino]methanesulphon-m-anisidide (mAMSA).
Comparison of the sensitivity of DNA isolated from untreated and mAMSA-treated PY815 mouse mastocytoma cells to hydrolysis by E.coli 3'-exonuclease III and phage lambda or phage T7 5'-exonucleases show that the fragments of chromosomal DNA produced by mAMSA treatment have free 3'-OH termini and blocked 5'-termini.
Unidentified curved bacilli on gastric epithelium in active chronic gastritis.
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Frequency of tetracycline resistance determinant classes among lactose-fermenting coliforms.
Using colony hybridization techniques and DNA probes derived from four distinct tetracycline resistance determinants, we have examined the frequency of these determinants among 225 lactose-fermenting coliforms isolated from fecal samples of both humans and animals. The class B, or Tn10-type determinant, occurred most frequently at 73.3%, followed by class A (on RP1) at 21.7%, and class C (on pSC101) at 8%; 3.5% of isolates harbored two of these determinants. Hybridization to class D, carried by plasmid RA1, was not found among any of the isolates. One isolate failed to hybridize to any of the probes and represents a fifth class of determinant. No dramatic differences were observed in the frequencies of these determinants among four populations examined: hospital, urban, rural, and laboratory. At low stringency conditions of hybridization we were able to demonstrate cross-hybridization of determinant A with class C DNA and limited reaction with class B DNA, but no reaction with class D DNA.
Site and sensitivity for stimulation of hypoxic pulmonary vasoconstriction.
Rat lungs were perfused in an in vitro circuit with separate control of alveolar and pulmonary arterial O2 tension. With perfusion flow constant, the hypoxic pulmonary vasoconstrictor (HPV) response was measured as changes of perfusion pressure. HPV was a function of both alveolar O2 tension (PvO2) and was described by a double sigmoid response surface. Where RA-v is this pressure response expressed as a percent of the maximum, the linearized form of the response surface is given by log [RA-v/(100-RA-v)] = 3.93 - 1.029 (log PvO2) - 1.623 (log PAO2). From this relationship it was concluded that 1) HPV is determined by PAO2 and PvO2; 2) the fundamental stimulus-response relationship is a sigmoid with a 50% response when both PAO2 and PvO2 are 30.3 Torr; 3) PAO2 has a greater effect than PvO2 due in part to the geometry of the vascular wall but principally due to O2 exchange between alveolar gas and blood in small pulmonary arteries; 4) there is not a localized sensor for HPV (the response is accounted for by each smooth muscle cell in the pulmonary arterial wall responding to the O2 tension in its vicinity); and 5) the characteristics of the response suggest that the cell sensor resembles a cytochrome.
Computerised patient administration system--second generation.
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A simple method for detecting drug effects on the DNA of mammalian cells.
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