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Biomedical subjects

R Feeney

Publications and source records attributed to R Feeney.

11 recordsLinked to original sources
PubMed2000

On-site analysis of arsenic in groundwater using a microfabricated gold ultramicroelectrode array

Rapid on-site analysis of arsenic in groundwater was achieved with a small battery-powered unit in conjunction with a microfabricated gold ultramicroelectrode array (Au-UMEA). The sensor, consisting of 564 UME disks with a unique gold surface created by electron beam evaporation, was demonstrated to be highly sensitive to low-ppb As3+ using square wave anodic stripping voltammetry. The influence of the square wave frequency, pulse amplitude, and deposition potential on the arsenic peak stripping current was investigated. Varying those theoretical parameters yielded results surprisingly similar to those for the thin Hg film case. The performance of the Au-UMEA was evaluated for reproducibility and reliability. Three stability tests showed an average relative standard deviation of 2.5% for 15 consecutive runs. Limits of detection were investigated, and 0.05 ppb As3+ could be measured while maintaining a S/N of 3:1. Interference studies were performed in the presence of 50-500 ppb of Cu2+, Hg2+, and Pb2+. On-site analysis of groundwater containing arsenic was performed with a small battery-powered potentiostat. Quantification was done through standard additions, and these results were compared to the standard EPA methodology.

Journal Article↗
PubMed1997

Health care resource utilization and antimicrobial use in elderly patients with community-acquired lower respiratory tract infection who develop Clostridium difficile-associated diarrhoea.

We conducted a prospective observational study on the medical management and health service resource utilization associated with the hospital care of patients with community-acquired lower respiratory tract infection. Between January 1994 and June 1995, 28 such patients developed Clostridium difficile-associated diarrhoea; these 28 patients were matched with 56 age-matched patients, who were used as a control group in a comparative study. Progress during the first week after admission was similar as measured by fever days and pathology or radiology use. The use of iv cephalosporins (g/day) during the first week was greater in the group who developed C. difficile-associated diarrhoea than in controls. The length of hospital stay was 36.4 +/- 21.6 days in patients with C. difficile-associated diarrhoea compared with 19.8 +/- 13.3 days in controls. Cases also required more pathological and radiological tests and greater use of antimicrobials and other drugs; however, if pathology and radiology use was calculated per day of patient stay there was no difference between the two groups. When antimicrobial use was compared, controlling for the time taken until found to be C. difficile toxin positive, patients with C. difficile infection received more iv cefuroxime as well as more total cephalosporins, beta-lactams and macrolides measured in g/day. Interestingly, in this study we could not show an increased mortality associated with C. difficile diarrhoea despite obvious evidence of morbidity. The development of C. difficile-associated diarrhoea substantially increases health care resource utilization for individual patients who are admitted to hospital with lower respiratory tract infection.

Aged↗
PubMed1994

Cloning of a non-catalytic form of human trkB and distribution of messenger RNA for trkB in human brain.

A truncated form of the human trkB gene has been cloned and sequenced. This gene is related to the trk family of tyrosine kinases, the products of which act as receptors for the neurotrophins. Of these, brain-derived neurotrophic factor and mammalian neurotrophin-4 are the known ligands for the TrkB receptor. Catalytic and non-catalytic (or truncated) forms of the trkB gene have been cloned for rat and mouse. In this study, using in situ hybridization, we describe the distribution of trkB messenger RNA in fetal and adult human brain.

Amino Acid Sequence↗
PubMed1992

Duck liver 'malic' enzyme. Expression in Escherichia coli and characterization of the wild-type enzyme and site-directed mutants.

A cDNA for duck liver 'malic' enzyme (EC 1.1.1.40) was subcloned into pUC-8, and the active enzyme was expressed in Escherichia coli TG-2 cells as a fusion protein including a 15-residue N-terminal leader from beta-galactosidase coded by the lacZ' gene. C99S and R70Q mutants of the enzyme were generated by the M13 mismatch technique. The recombinant enzymes were purified to near homogeneity by a simple two-step procedure and characterized relative to the enzyme isolated from duck liver. The natural duck enzyme has a subunit molecular mass of approx. 65 kDa, and the following kinetic parameters for oxidative decarboxylation of L-malate at pH 7.0: Km NADP+ (4.6 microM); Km L-malate (73 microM); kcat (160 s-1); Ka (2.4 microM) and Ka' (270 microM), dissociation constants of Mn2+ at 'tight' (activating) and 'weak' metal sites; and substrate inhibition (51% of kcat. at 8 mM-L-malate). Properties of the E. coli-derived recombinant wild-type enzyme are indistinguishable from those of the natural duck enzyme. Kinetic parameters of the R70Q mutant are relatively unaltered, indicating that Arg-70 is not required for the reaction. The C99S mutant has unchanged Km for NADP+ and parameters for the 'weak' sites (i.e. inhibition by L-malate, Ka'); however, kcat. decreased 3-fold and Km for L-malate and Ka each increased 4-fold, resulting in a catalytic efficiency [kcat./(Km NADP+ x Km L-malate x Ka)] equal to 3.7% of the natural duck enzyme. These results suggest that the positioning of Cys-99 in the sequence is important for proper binding of L-malate and bivalent metal ions.

Amino Acid Sequence↗
PubMed1991

Normal beta-NGF content in Alzheimer's disease cerebral cortex and hippocampus.

Nerve growth factor (beta-NGF) is known to have beneficial effects on cholinergic cell survival and to function both in vivo and in vitro. It has been speculated that this protein, or the lack of it, may be involved in the aetiology of Alzheimer's disease (AD). We describe the measurement of beta-NGF content in 4 regions of the cerebral cortex and the hippocampus in AD brain compared with brain tissue from age-matched normal subjects using a sensitive sandwich immunoassay (ELISA). There was no difference in beta-NGF content in any region examined in AD compared with normal values despite the marked loss of cortical cholinergic function.

Aged↗
PubMed1990

A single amino acid substitution in lactate dehydrogenase improves the catalytic efficiency with an alternative coenzyme.

Using site-directed mutagenesis, the NADH-linked lactate dehydrogenase from Bacillus stearothermophilus has been specifically altered at a single residue to shift the coenzyme specificity towards NADPH. The single change is at position 53 in the amino acid sequence where a conserved aspartate has been replaced by a serine. This substitution was made to reduce steric hindrance on binding of the extra phosphate group of NADPH and to remove the negative charge of the aspartate group. The resultant mutant enzyme is 20 times more catalytically efficient than the wild-type enzyme with NADPH.

Amino Acid Sequence↗
PubMed1988

A specific, highly active malate dehydrogenase by redesign of a lactate dehydrogenase framework.

Three variations to the structure of the nicotinamide adenine dinucleotide (NAD)-dependent L-lactate dehydrogenase from Bacillus stearothermophilus were made to try to change the substrate specificity from lactate to malate: Asp197----Asn, Thr246----Gly, and Gln102----Arg). Each modification shifts the specificity from lactate to malate, although only the last (Gln102----Arg) provides an effective and highly specific catalyst for the new substrate. This synthetic enzyme has a ratio of catalytic rate (kcat) to Michaelis constant (Km) for oxaloacetate of 4.2 x 10(6)M-1 s-1, equal to that of native lactate dehydrogenase for its natural substrate, pyruvate, and a maximum velocity (250 s-1), which is double that reported for a natural malate dehydrogenase from B. stearothermophilus.

Binding Sites↗