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Biomedical subjects

G D Wright

Publications and source records attributed to G D Wright.

At least 91 records · Page 5Linked to original sources
PubMed1993

Purification and characterization of VanR and the cytosolic domain of VanS: a two-component regulatory system required for vancomycin resistance in Enterococcus faecium BM4147.

Resistance to the glycopeptide antibiotic vancomycin requires five genes. Two of these, vanR and vanS, have sequence homology to cytoplasmic response regulatory (VanR) and transmembrane sensory (VanS) proteins of two-component regulatory systems used to sense and transduce environmental signals. We report the overproduction and purification to homogeneity of VanR (27 kDa) and of a fusion protein of VanS (residues 95-374, the cytosolic domain) to the maltose binding protein (MBP), yielding a MBP-VanS protein of 76 kDa. The MBP-VanS fusion protein displayed an ATP-dependent autophosphorylation on a histidine residue with a rate of 0.17 min-1 and a phosphorylation stoichiometry of 10-15%. 32P-PhosphoMBP-VanS transferred the phosphoryl group to VanR. 32P-Phospho VanR showed chemical stability anticipated for an aspartyl phosphate and was relatively stable to hydrolysis (t1/2 = 10-12 h). Thus, the vancomycin resistance operon appears to have collected and specifically tailored the His kinase and Asp phosphoryl receptor of two-component signal transduction logic for sensing extracellular vancomycin and turning on structural genes, vanA and vanH, to make altered peptidoglycan structures such that vancomycin does not bind.

ATP-Binding Cassette Transporters↗
PubMed1993

Needle covers reduce needlestick injury.

The objective of the study, conducted in the general wards of Flinders Medical Center in South Australia, was to determine whether the risk of needlestick injuries from hypodermic needles could be reduced by the use of needle covers that are applied with a one-handed technique immediately after use of the needle. Baseline rates of needlestick injury were collected for a year prior to the use of needle covers, and incident cases of needlestick injury were collected after needle covers were introduced. The odds ratio, derived from pre- and post-intervention data, for injuries over which the use of needle covers could have had no influence, was used to show that the net effect of other influences on needlestick rates was not significant. The use of needle covers was associated with a significant reduction in needlestick injuries to nurses. The odds ratio for needlestick injury for nurse injuries that needle covers could not have prevented was 0.92. (95% CI 0.40-2.03). The odds ratio for needlestick injury for nurse injuries that needle covers could have prevented was 0.40 (95% CI 0.18-0.82). Although the odds of ratio for needlestick injury to cleaners was 0.19, the 95% exact confidence interval was 0.00-1.64.

Accidents, Occupational↗
PubMed1993

Acute urinary retention: an unusual presentation of appendiceal abscess.

Emergency physicians frequently encounter patients with acute urinary retention. Although most common among the elderly, pediatric and young adult patients occasionally may present with this complaint. The differential diagnosis and emergency department work-up must be age specific. We discuss the case of a young man who presented with acute urinary retention, subsequently found to be caused by undiagnosed appendicitis with appendiceal abscess formation. Only nine such cases have been reported in the literature thus far, with only one occurring in the nonpediatric population. This case represents the second such case to be reported. The importance of a thorough history, physical examination, and diagnostic work-up of patients who present with acute urinary retention, particularly those in the younger age group, is emphasized.

Abscess↗
PubMed1993

Autosomal dominant polycystic kidney disease with minimal clinical expression unlinked to the PKD1 locus.

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations at the PKD1 locus in most families. This locus has been assigned to the short arm of chromosome 16 by linkage analysis. It has been estimated that approximately 5% of families have a disease that does not map to this locus and most of these families have clinical features indistinguishable from the disease caused by PKD1 mutations. We report a large three-generation Caucasian family from Northern Ireland with ADPKD in whom all affected individuals (age range 22-68) were normotensive and only the two eldest had mild renal impairment. Linkage was excluded between the disease and both the alpha-globin gene complex and the microsatellite marker D16S283. This family confirms that phenotypic heterogeneity exists between unlinked families and that certain non-PKD1 mutations cause mild disease expression. Many such individuals may therefore remain undetected and the incidence of families with ADPKD who have non-PKD1 mutations may be greater than previously estimated.

Adolescent↗
PubMed1993

CT of the spine: value of reformatted images.

Recent improvements in CT software allow rapid and high-quality two-dimensional reformatting of scans of the spine. Reformatting involves computer interpolation of two-dimensional multislice images acquired during routine axial CT scanning in order to generate a three-dimensional volume of data. From this block of data, new images are created and displayed in any desired plane. Reformatted images are acquired within minutes following axial CT scanning.

Humans↗
PubMed1993

Genetic linkage analysis, clinical features and prognosis of autosomal dominant polycystic kidney disease in Northern Ireland.

Fifteen families with autosomal dominant polycystic kidney disease were analysed for coinheritance of the disease and DNA markers flanking the PKD1 locus. Eleven families demonstrated linkage to PKD1 markers. Two families were unlinked to the PKD1 locus (non-PKD1) and in two families the markers were uninformative. The clinical features and prognosis of 49 subjects with a PKD1 genotype were compared with 17 non-PKD1 subjects. The age at diagnosis in non-PKD1 subjects (37 +/- 11 years) was significantly later than PKD1 subjects (25 +/- 13 years, p < 0.001). Only two (12%) non-PKD1 subjects presented initially with clinical features of autosomal polycystic kidney disease compared to 27 (55%) of PKD1 subjects (p < 0.002). Hypertension was more common in PKD1 compared to non-PKD1 subjects (29% vs. 12%), as was stage renal failure (25% vs. 6%). Seventy-five percent of non-PKD1 subjects had not developed end-stage renal failure by the age of 54 years compared to only 35% of PKD1 subjects. Most families with autosomal polycystic kidney disease in this population have disease due to mutations at the PKD1 locus. However, the proportion of non-PKD1 families appears to be higher than estimates for other populations. This study also confirms initial reports that subjects with a non-PKD1 genotype have a milder disease with a better prognosis than those with a PKD1 genotype.

Adult↗
PubMed1992

Evidence for in vivo incorporation of D-lactate into peptidoglycan precursors of vancomycin-resistant enterococci.

The VanA ligase encoded by the vancomycin resistance plasmid pIP816 of Enterococcus faecium BM4147 condenses D-alanine with various D-2-hydroxy and D-2-amino acids in vitro. D-Lactate added to the culture medium restored the vancomycin resistance of a strain that does not produce the VanH dehydrogenase and therefore appears to be a substrate of VanA in vivo.

Drug Resistance, Microbial↗
PubMed1992

Characterization of vanY, a DD-carboxypeptidase from vancomycin-resistant Enterococcus faecium BM4147.

VanY is a protein with a molecular mass of 34.8 kDa encoded by vanY, a member of the high-level vancomycin resistance gene cluster found on plasmid pIP816 in Enterococcus faecium BM4147. Extracts from Escherichia coli JM83 bearing plasmid pAT383, which contains the vanY gene, were examined for enzymatic hydrolysis of peptidoglycan precursors. VanY was associated with the cell membranes and cleaved the C-terminal D-alanine residue of UDP-muramyl-pentapeptide but did not display transpeptidase or beta-lactamase activities. The DD-carboxypeptidase activity was not inhibited by beta-lactam antibiotics. VanY released the C-terminal D-hydroxy acid from depsipeptides produced by the vancomycin resistance protein VanA. These results demonstrate that VanY should contribute in vivo to the hydrolysis of both the D-alanyl-D-alanine- and the depsipeptide-containing peptidoglycan precursors.

Carboxypeptidases↗
PubMed1991

Molecular basis for vancomycin resistance in Enterococcus faecium BM4147: biosynthesis of a depsipeptide peptidoglycan precursor by vancomycin resistance proteins VanH and VanA.

Vancomycin resistance in Enterococcus faecium BM4147 is mediated by vancomycin resistance proteins VanA and VanH. VanA is a D-alanine:D-alanine ligase of altered substrate specificity [Bugg, T. D. H., Dutka-Malen, S., Arthur, M., Courvalin, P., & Walsh, C. T. (1991) Biochemistry 30, 2017-2021], while the sequence of VanH is related to those of alpha-keto acid dehydrogenases [Arthur, M., Molinas, C., Dutka-Malen, S., & Courvalin, P. (1991) Gene (submitted)]. We report purification of VanH to homogeneity, characterization as a D-specific alpha-keto acid dehydrogenase, and comparison with D-lactate dehydrogenases from Leuconostoc mesenteroides and Lactobacillus leichmanii. VanA was found to catalyze ester bond formation between D-alanine and the D-hydroxy acid products of VanH, the best substrate being D-2-hydroxybutyrate (Km = 0.60 mM). The VanA product D-alanyl-D-2-hydroxybutyrate could then be incorporated into the UDPMurNAc-pentapeptide peptidoglycan precursor by D-Ala-D-Ala adding enzyme from Escherichia coli or by crude extract from E. faecium BM4147. The vancomycin binding constant of a synthetic modified peptidoglycan analogue N-acetyl-D-alanyl-D-2-hydroxybutyrate (Kd greater than 73 mM) was greater than 1000-fold higher than the binding constant for N-acetyl-D-alanyl-D-alanine (Kd = 54 microM), partly due to the disruption of a hydrogen bond in the vancomycin-target complex, thus providing a molecular rationale for high-level vancomycin resistance.

Amino Acid Sequence↗
PubMed1991

Induction and substrate specificity of the lanosterol 14 alpha-demethylase from Saccharomyces cerevisiae Y222.

The potential inducibility of the lanosterol 14 alpha-demethylase (P-45014DM) from Saccharomyces cerevisiae Y222 by xenobiotics was investigated. This enzyme and NADPH-cytochrome P-450 reductase were unaffected by a number of compounds known to induce mammalian and some yeast cytochrome P-450 monooxygenases. Furthermore, dibutyryl cyclic AMP did not affect P-45014DM or P-450 reductase levels, while growth at 37 degrees C resulted in a slight decrease. P-45014DM was found to be specific for lanosterol and did not metabolize a number of P-450 substrates including benzo[a]pyrene.

Benzo(a)pyrene↗
PubMed1990

Non-sterol structural probes of the lanosterol 14 alpha-demethylase from Saccharomyces cerevisiae.

A number of non-sterol iron-liganding molecules were used to probe the active site of the lanosterol 14 alpha-demethylase from Saccharomyces cerevisiae. Simple bi- and tricyclic aromatic amines were found to exhibit Type II binding spectra with the demethylase. Stereochemical and positional effects appear to play critical roles in the binding of these compounds to the demethylase. These compounds have been used to generate additional active-site structural information on this enzyme, currently a target for the development of new antifungal agents.

Amines↗
PubMed1990

HIV testing of hospital patients.

This article sets out the issues involved in the development of hospital policy that will allow or require human immunodeficiency virus (HIV) testing of patients in hospital. It considers the shared and competing interests of patients and staff, and the obligations of employers to worker health and safety. It shows that hospitals are in a position to influence the definition of the public interest in this matter.

AIDS Serodiagnosis↗
PubMed1989

Effects of iron binding agents on Saccharomyces cerevisiae growth and cytochrome P450 content.

The yeast Saccharomyces cerevisiae Y222 was studied in the presence of the following iron-binding agents: Desferal, dipyridyl, and human and bovine transferrins. We report that cell growth and lanosterol 14 alpha-demethylase cytochrome P450 are not affected by Desferal but that dipyridyl and serum transferrins decrease the cytochrome P450 content of the yeast. Paradoxically, while both human and bovine transferrins reduce cytochrome P450 content, only bovine transferrin appears to affect cell growth in this strain. No evidence for siderophore production by this strain was found under low iron conditions.

2,2'-Dipyridyl↗
PubMed1988

An adult onset metachromatic leukodystrophy with dominant inheritance and normal arylsulphatase A levels.

A family with a variant of adult onset metachromatic leukodystrophy is presented. Clinical details from three affected members are given. The neurophysiological and neuroradiological data on the two brothers who have been recently studied are included. One of these died and the post-mortem findings are discussed along with those from a cousin who died some years ago. Arylsulphatase A levels were normal in both brothers yet the histological findings in the one who died are of a metachromatic leukodystrophy and thin-layer chromatography confirms an excess of sulphatides in the white matter of his brain. Disabling hypotension was a striking feature in both brothers but adrenal function was shown to be intact and autonomic neuropathy seemed the likely cause. Study of the family suggests a dominant mode of inheritance.

Cerebroside-Sulfatase↗