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Biomedical subjects

D J Best

Publications and source records attributed to D J Best.

14 recordsLinked to original sources
PubMed1991

The screening of selected microorganisms for use as models of mammalian drug metabolism.

Fifty fungi and two Streptomyces species were screened for their ability to metabolise the probe substrates aminopyrine, diazepam, testosterone, theophylline and warfarin. The metabolism of the 14C-labelled substrates by whole growing cells was compared with that by rat liver microsomes using TLC-autoradiography. Testosterone, warfarin and diazepam were readily metabolised by most microorganisms, and aminopyrine and theophylline were only metabolised by a few. A relationship between substrate lipophilicity and number of microorganisms able to biotransform the substrate was observed, lipophilic substrates being favoured for metabolism, analagous to mammalian cytochrome P-450. A wide variety of metabolites were produced by the screened cultures, with a significant number co-chromatographing with mammalian metabolites. Most microorganisms appeared to exhibit cytochrome P-450-type oxidative reactions such as hydroxylation and N-demethylation, similar to mammalian hepatic microsomal cytochrome P-450 systems.

Animals↗
PubMed1991

Disease clustering in time.

Tango (1984, Biometrics 40, 15-26) proposed a clustering index for testing for clusters of disease in time. A test based on this clustering index was shown to compare favourably with other statistical tests. In this article we show that Pearson's X2 and its components perform well in testing for clusters of disease in time. The rth of these components identifies a departure from uniformity in moments up to the rth and so helps describe the alternative, if any, to uniformity.

Biometry↗
PubMed1990

Aryl acylamidase from Rhodococcus erythropolis NCIB 12273.

A Rhodococcus erythropolis strain was isolated from soil on the basis of its ability to use acetaminophen as the sole source of both carbon and energy for growth. When grown in a complex medium containing an anilide inducer compound, the bacterium exhibited aryl acylamidase (EC 3.5.1.13) activity. This activity was not subject to carbon or nitrogen repression by the growth medium constituents as the enzyme was present throughout the exponential growth phase. The anilide was converted to the corresponding aniline, which was not further degraded. The enzyme was partially purified by a variety of methods including a batch ion exchange procedure, column ion exchange chromatography and hydrophobic interaction chromatography. The enzyme had a maximum activity at around pH 8.0 and had a Km for acetaminophen of 0.11 mM. Electrochemical assays of aryl acylamidase activity are described. The enzyme is suitable for use as a reagent in the clinical diagnostic measurement of acetaminophen.

Acetaminophen↗
PubMed1990

Optimal determination of most probable numbers.

Choosing the design of a dilution series experiment on the basis of availability of most probable number tables can result in a non-optimal design. Similarly, certain tables and/or rules for declaring dilution series results 'improbable' do not always give optimal decisions. Further, tables of most probable number confidence intervals are not all based on the same assumptions and give different intervals--which should be used? The aim of this article is to draw microbiologists' attention to these issues and to suggest practical solutions.

Bias↗
PubMed1987

Purification, crystallisation and preliminary X-ray diffraction characterisation of methanol dehydrogenase from Methylosinus trichosporium OB3b.

Methanol dehydrogenase was purified from the obligate methanotroph, Methylosinus trichosporium OB3b, in two steps from disrupted biomass by aqueous two-phase partition and ion-exchange chromatography. Copartitioning of a cytochrome c was dependent upon the pH at which aqueous partition was carried out. The native enzyme has a Mr of 120,000, as determined by gel filtration chromatography, and consists of two identical subunits. The purified enzyme contained four electrophoretically distinct isoenzymes, with pI values of 6.3, 6.58, 6.63 and 6.88. The native enzyme has been crystallised in a form suitable for high-resolution X-ray crystallographic studies. The crystals diffract to better than 0.19 nm spacing and are relatively stable to irradiation with X-rays. The space group is P6(1)22 (or P6(5)22) with cell dimensions a = b = 10.21 nm, c = 29.32 nm and the crystal probably contains a single monomer in the asymmetric unit.

Alcohol Oxidoreductases↗
PubMed1986

Studies on 6 alpha-substituted penicillins. II. Synthesis and structure-activity relationships of 6 beta-(2-aryl-2-sulfoacetamido)-6 alpha-methoxy penicillanic acids.

The synthesis and antibacterial activity of 6 alpha-methoxysulbenicillin analogues (2) are described. Structure-activity studies of these derivatives bearing hydrophilic substituents in the phenyl ring led to the identification of disodium 6 beta-[D-2-(3,4-dihydroxyphenyl)-2-sulfoacetamido]-6 alpha-methoxypenicillanate (2m) as a compound with potent activity against Pseudomonas aeruginosa including beta-lactamase producing strains. Additional substitution of 2m gave derivatives 2p, 2q, 2r, with a further improvement in activity against Gram-negative bacteria.

Chemical Phenomena↗
PubMed1985

Preparation and structure-activity relationships of some 6 alpha-substituted penicillins.

The influence on the antibacterial activity of introducing a 6 alpha-methoxy group into carbenicillin, and various 6 alpha-substituents into sulbenicillin and piperacillin was examined. Further variations of the side chain aryl group were examined in the 6 alpha-methoxy substituted series. This led to the identification of disodium 6 beta-(D,L-2-carboxy-2-thien-3-ylacetamido)-6 alpha-methoxypenicillanate (5b) as a beta-lactamase stable derivative with useful activity against Enterobacteriaceae, and disodium 6 beta-[D-2-(4-aminophenyl)-2-sulfoacetamido]-6 alpha-methoxypenicillanate (6e) with slightly lower activity against the Enterobacteriaceae but more active against Pseudomonas aeruginosa.

Enterobacteriaceae↗
PubMed1984

Insulin responsiveness in non-fa/fa and fa/fa Zucker rats: effects of adipocyte size.

Epididymal adipose tissue from non-fa/fa (lean) and fa/fa (obese) 14.5-week-old Zucker rats was used to study the influence of insulin and genotype on uptake of glucose and palmitate into adipocytes of different sizes. After incubation with radioactive substrate, adipocytes were inactivated and fixed by addition of osmium tetroxide; fixed adipocytes were isolated and separated by screening on the basis of size. Rates of substrate uptake into triacylglycerols were measured in adipocytes of each of ten size categories. Uptake rates of both glucose and palmitate increased as adipocyte size increased. Insulin had no effect on glucose uptake per adipocyte for fa/fa rats but had a highly significant (P less than 0.01) stimulatory effect on that for non-fa/fa rats. This stimulation became significantly greater with increasing adipocyte size. When insulin was included in the incubation media, glucose uptake rates were similar between similar sizes of adipocytes from non-fa/fa and fa/fa rats. Absence of insulin from the incubation media, however, resulted in lower rates of glucose uptake by adipocytes from non-fa/fa rats. Glucose uptake was maximal in adipocytes from fa/fa rats, even in the absence of insulin. Net uptake of palmitate into triacylglycerols was not influenced by insulin; a significant interaction was observed, however, between adipocyte size and genotype. Large adipocytes from fa/fa rats had greater rates of palmitate uptake than did adipocytes of similar size from non-fa/fa rats. The reverse was true for adipocytes less than 125 micron in diameter. The results of this study show that response to insulin of adipocytes of difference sizes varies with adipocyte size and with genotype.

Adipose Tissue↗
PubMed1980

New findings in methane-utilizing bacteria highlight their importance in the biosphere and their commercial potential.

Recent results, showing that the ubiquitous methane-utilizing bacteria (methanotrophs) can partially oxidize and, in some cases, extensively metabolize complex organic compounds, call for a reappraisal of their role in the cycling of elements in the biosphere. Possible environmental implications and opportunities for industrial exploitation are discussed.

Biological Evolution↗
PubMed1978

beta-lactam antibiotics. II. Structure-activity relationships of 6-[alpha-(alpha'-ureido-acylamino) acylamino] penicillanic acids.

The influence on the structure-activity relationships (S.A.R.) of the stereochemistry and various alkyl, aryl, aralkyl and heterocyclic substituents at the two chiral centres in the dipeptide side-chain of a new series of penicillins was examined. In many cases the effects of these changes had a pronounced influence on the degree of activity against Gram-positive and especially Gram-negative bacteria. Several compounds indicated that the size, shape and spatial disposition of a substituent were the parameters of importance in influencing activity, rather than it lipophilic or electronic character. The most active homologues in the series provided broad-spectrum penicillins which in terms of their in vitro antibacterial properties showed improvements over certain of the marketed penicillins. Thus 6-[D-alpha(alpha'-ureidoacyl-amino)acylamino]penicillanic acids were found which had a carbenicillin-like profile, with improvements against Pseudomonas aeruginosa, Klebsiella aerogenes, sensitive and beta-lactamase-producing Gram-positive cocci.

Bacteria↗