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Biomedical subjects

I D Wilson

Publications and source records attributed to I D Wilson.

At least 109 records · Page 6Linked to original sources
PubMed1993

Cloning and characterization of avocado fruit mRNAs and their expression during ripening and low-temperature storage.

Differential screening of a cDNA library made from RNA extracted from avocado (Persea americana Mill cv. Hass) fruit stored at low temperature (7 degrees C) gave 23 cDNA clones grouped into 10 families, 6 of which showed increased expression during cold storage and normal ripening. Partial DNA sequencing was carried out for representative clones. Database searches found homologies with a polygalacturonase (PG), endochitinase, cysteine proteinase inhibitor and several stress-related proteins. No homologies were detected for clones from six families and their biological role remains to be elucidated. A full-length cDNA sequence for avocado PG was obtained and the predicted amino acid sequence compared with those from other PGs. mRNA encoding PG increased markedly during normal ripening, slightly later than mRNAs for cellulase and ethylene-forming enzyme (EFE). Low-temperature storage delayed ripening and retarded the appearance of mRNAs for enzymes known to be involved in cell wall metabolism and ethylene synthesis, such as cellulase, PG and EFE, and also other mRNAs of unknown function. The removal of ethylene from the atmosphere surrounding stored fruit delayed the appearance of the mRNAs encoding cellulase and PG more than the cold storage itself, although it hardly affected the expression of the EFE mRNA or the accumulation of mRNAs homologous to some other unidentified clones.

Amino Acid Sequence↗
PubMed1993

Coupling of HPLC with 19F- and 1H-NMR spectroscopy to investigate the human urinary excretion of flurbiprofen metabolites.

Results of an on-line HPLC-NMR analysis of human urine from a volunteer administered the anti-inflammatory drug flurbiprofen are reported. The two major human urinary metabolites, namely the glucuronides of flurbiprofen and of 4'-hydroxyflurbiprofen, have been identified using 1H- and 19F-NMR spectroscopy. In vivo conjugation of the racemic drug and its metabolites with D-glucuronic acid results in diastereomeric molecules which give resolved NMR spectra thereby permitting the diastereomeric proportions to be evaluated. The cause of the observed deviation from equal proportions is discussed. This study represents the first use of both 19F- and 600 MHz 1H-NMR spectroscopy coupled to HPLC.

Chromatography, High Pressure Liquid↗
PubMed1993

An investigation of the effects of carbon loading and endcapping on the solid-phase extraction of beta-blockers onto C18 bonded silica gel.

The effects of carbon loading and endcapping on the solid-phase extraction onto C18 bonded silica gel of a range of beta-blockers from aqueous buffer and from dog plasma has been investigated. The highest extraction efficiencies were obtained for those phases with carbon loadings of between 5 and 16% for phases without endcapping or 10.5-14% for endcapped material. With carbon loadings of 18 and 22% (plus endcapping) poor extractions from the matrix were obtained combined with further losses at the wash steps. Matrix effects were observed with dog plasma which accentuated the effects seen with buffer. These results are best explained by assuming that a cationic interaction of the secondary amino group present in the analytes with residual silanols on the silica surface is primarily responsible for the extraction of these analytes.

Adrenergic beta-Antagonists↗
PubMed1993

Apple ripening-related cDNA clone pAP4 confers ethylene-forming ability in transformed Saccharomyces cerevisiae.

The apple ripening-related cDNA insert of clone pAP4 (G.S. Ross, M.L. Knighton, M. Lay-Yee [1992] Plant Mol Biol 19: 231-238) has previously been shown to have considerable nucleic acid and predicted amino acid sequence similarity to the insert of a tomato ripening-related cDNA clone (pTOM13) that is known to encode the enzyme 1-aminocyclopropane-1-carboxylate (ACC) oxidase (A.J. Hamilton, G.W. Lycett, D. Grierson [1990] Nature 346: 284-287; A.J. Hamilton, M. Bouzayen, D. Grierson [1991] Proc Natl Acad Sci USA 88: 7434-7437). The cDNA insert from the clone pAP4 was fused between the galactose-inducible promoter and the terminator of the yeast expression vector pYES2. Transformation of Saccharomyces cerevisiae strain F808- with this DNA construct and incubation of the yeast in the presence of D[+]-galactose allowed these cells to convert ACC to ethylene. The transformed yeast converted 1-amino-2-ethylcyclopropane-1-carboxylate isomers to 1-butene with the same 1R,2S-stereoselectivity as achieved by the native ACC oxidase from applies. Both ascorbate and Fe2+ ions stimulated the rate of the production of ethylene from ACC by the transformed yeast, whereas Cu2+ and Co2+ were strongly inhibitory; these are features of ACC oxidase. Northern analysis of the total RNA from nontransformed and transformed yeast showed that the ability to convert the ACC to ethylene was correlated with the synthesis and accumulation of a novel 1.2-kb mRNA that hybridized to the cDNA clone pAP4. We conclude that the cDNA sequence of the clone pAP4 encodes ACC oxidase.

Cloning, Molecular↗
PubMed1992

Quantitative structure-metabolism relationships for substituted benzoic acids in the rat. Computational chemistry, NMR spectroscopy and pattern recognition studies.

An extensive set of computed molecular properties, both steric and electronic, have been calculated using molecular orbital and empirical methods for benzoic acid (1) and a congeneric series of substituted benzoic acids, i.e. 2-, 3- and 4-fluorobenzoic acids (2-4), 2-, 3- and 4-trifluoromethyl benzoic acids (5-7), 2-, 3- and 4-methylbenzoic acids (8-10), 4-amino benzoic acid (11), 2-fluoro-4-trifluoromethyl benzoic acid (12), 4-fluoro-2-trifluoromethyl benzoic acid (13), 3-trifluoromethyl-4-fluorobenzoic acid (14). We have monitored the urinary excretion profiles and determined the metabolic fate of compounds 2-7, 12-14 in the rat using high resolution 1H and 19F NMR spectroscopy. Corresponding data for compounds 1,8-11 are taken from the literature. In all cases phase II glucuronidation or glycine conjugation reactions dominated the metabolism of these compounds. Compounds 5, 7, 12, 13 have ester glucuronides as their major metabolites; the rest primarily form glycine conjugates. Compounds (1-12) have been classified according to their calculated physicochemical properties using pattern recognition methods and principal components maps have been used as a novel type of structure-metabolism diagram. The maps of compounds in the physicochemical property space served to separate the compounds into the two major classes which related to their principal metabolic fate in vivo, namely glucuronidation versus glycine conjugation. Compounds 13 and 14 were used as further probes of the property space, and dominant metabolic fates of glucuronidation and glycine conjugation, respectively, were predicted from the previous "training set map". The metabolic fate of compounds 1-14 can thus be classified according to a simple set of physicochemical rules. Investigation of the physicochemical properties which are important in distinguishing the metabolic fate of the compounds may give insight into key features of the drug-metabolizing enzyme active sites and hence provide information on basic mechanisms of benzoate metabolism.

Animals↗
PubMed1992

1H-NMR spectroscopy as a means of monitoring nephrotoxicity as exemplified by studies with cephaloridine.

1. Male albino rats were dosed intravenously with either 0.9% saline or cephaloridine in saline at doses of 650, 750 or 950 mg kg-1 d-1 for 7 d. 2. Urine analysis on day 3, after two doses of cephaloridine showed dose-related increases in glucose, total protein, N-acetyl beta-D-glucosaminidase, gamma-glutamyltranspeptidase, alkaline phosphatase and lactate dehydrogenase. 1H-NMR spectroscopy showed corresponding disturbed profiles of products of intermediary metabolism indicative of a disruption of renal function. 3. By day 6, after five doses of cephaloridine, analysis by both 1H-NMR and conventional methods showed that all indices had returned to normal. 1H-NMR was demonstrated to provide useful complementary information to conventional techniques on the time course of the onset of the nephrotoxicity and the recovery phase, and was at least as sensitive as conventional urine analysis.

Animals↗
PubMed1991

beta-Hydroxybutyrate: a urinary marker of imipenem induced nephrotoxicity in the cynomolgus monkey detected by high field 1H NMR spectroscopy.

The use of 1H NMR as a complement to conventional clinical chemistry and histopathology resulted in the detection of hitherto unsuspected changes in urine composition as a result of imipenem induced nephrotoxicity. Large quantities of beta-hydroxybutyrate, as well as other ketone bodies were detected, indicating a disruption of energy metabolism. beta-Hydroxybutyrate may provide a useful non-invasive marker for imipenem toxicity.

3-Hydroxybutyric Acid↗
PubMed1991

NMR-monitored solid-phase extraction of phenolphthalein glucuronide on phenylboronic acid and C18 bonded phases.

Preliminary studies have been undertaken to evaluate the potential of immobilized phenylboronic acid (PBA) for the solid-phase extraction (SPE) of glucuronide metabolites from urine. These studies have demonstrated that immobilized PBA can be used to specifically extract phenolphthalein glucuronide (5 mM) from urine. Urine samples were loaded onto the PBA SPE column in glycine buffer (pH 8.5) and were eluted using methanol-1% HCl (90:10, v/v). The overall recoveries of the phenolphthalein glucuronide for this procedure were high (99%), which compared well with similar studies carried out concomitantly on C18 bonded columns (93%).

Boronic Acids↗
PubMed1990

19F and 1H magnetic resonance strategies for metabolic studies on fluorinated xenobiotics: application to flurbiprofen [2-(2-fluoro-4-biphenylyl)propionic acid].

Strategies for the use of 1H and 19F nuclear magnetic resonance (NMR) spectroscopy as an aid to the study of the metabolic fate of fluorinated drugs are discussed with reference to the application of these methods to flurbiprofen metabolism in man. 1H and 19F NMR analysis of untreated urine enabled the detection of two major and eight minor metabolites of the drug. The two major metabolites were identified using a combination of NMR spectroscopy, solid-phase extraction chromatography with 19F and 1H NMR detection and chemical hydrolysis to a flurbiprofen glucuronide and the glucuronide of the 4-hydroxy metabolite. 1H-19F 2D shift correlated spectroscopy and spin-echo difference experiments are discussed in relation to their use in the structural identification of drug metabolites.

Fluorine↗
PubMed1989

The use of graphitized carbon black in solid phase extraction: comparison with C18 bonded silica gel.

Preliminary studies on the properties of a commercially available graphitized carbon black for the solid-phase (or liquid-solid) extraction of drugs and metabolites from biological fluids such as urine and plasma are described. A variety of basic drugs, all of the beta-blocker type, were efficiently extracted from dog plasma and subsequently recovered from the adsorbent using chloroform-methanol mixtures. Similarly metabolites of the non-steroidal anti-flammatory drug ibuprofen also were efficiently extracted from human urine. The proportions of methanol and chloroform used for elution were found to be critical to ensure complete recoveries of adsorbed material. Proton NMR studies of the column eluates from both carbon and C18 bonded silica gel extraction cartridges revealed differences in capacity and selectivity following the application of ibuprofen containing metabolite samples.

Adrenergic beta-Antagonists↗
PubMed1988

Ion-pair reversed-phase thin-layer chromatography of basic drugs using sulphonic acids.

The use of sulphonic acid ion-pair reagents in the thin-layer chromatography of four basic drugs (all secondary amines) on C18-bonded silica gel, paraffin coated silica gel and silica gel itself has been investigated. Effects of the ion-pair reagents were only obtained on C18-bonded silica gel, and only then when the reagents were pre-coated onto the stationary phase. In general the largest reductions in the RF values of the test compounds occurred when sodium dodecylsulphate was coated onto the plates.

Chromatography, Thin Layer↗