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Biomedical subjects

E Bailey

Publications and source records attributed to E Bailey.

At least 109 records · Page 6Linked to original sources
PubMed1988

2-Hydroxyethylation of haemoglobin in man.

Exposure of humans to 2-hydroxyethylating agents, such as ethylene oxide, results in the formation of N-(2-hydroxyethyl)valine (HOEtVal) at the N-terminal amino acid of haemoglobin. A novel method using gas chromatography-mass spectrometry (GC-MS) has been used to monitor the presence of this adduct in smokers and control subjects, and dose-response relationships were investigated between HOEtVal in haemoglobin, number of cigarettes smoked per day and plasma cotinine levels.

Cotinine↗
PubMed1987

Improved method for the determination of the major neutral steroids and unconjugated bile acids in human faeces using capillary gas chromatography.

An improved method has been developed for the determination of the major neutral steroids (cholesterol and 5 beta-cholestan-3 beta-ol) and unconjugated bile acids (deoxycholic acid and lithocholic acid) in human faeces, using capillary gas chromatography with flame ionization detection. The freeze-dried faecal sample was subjected to a two-stage Soxhlet extraction followed by an aqueous alkali-organic solvent partition step to separate neutral steroids from bile acids. The neutral steroids were analysed as their trimethylsilyl ether derivatives on an OV-1 capillary column. The bile acids were further purified on a Sep-Pak C18 cartridge and then fractionated on a Sep-Pak SIL cartridge. Unconjugated bile acids were analysed as their methyl ester-trimethylsilyl ether derivatives also on an OV-1 capillary column. Quantitation of neutral steroids and unconjugated bile acids was achieved by reference to appropriate internal standards, added to the faecal extract immediately after the Soxhlet extraction stage. The method is being used in a study of the effect of diet on the metabolic activity of human gut flora.

Animals↗
PubMed1987

Analytical methodology to determine stable isotopically labelled and unlabelled theophylline in human plasma using capillary gas chromatography-mass spectrometry.

A method is described for the simultaneous determination of [1,3-15N] theophylline and unlabelled theophylline in human plasma using gas chromatography-mass spectrometry. Plasma samples were subjected to extractive alkylation and the stable isotopically labelled and unlabelled forms of the drug were analysed as their N-pentafluorobenzyl derivatives on an SE-52 fused-silica capillary column. Quantitation was made by selected-ion monitoring employing as the internal standard 3-isobutyl-1-methylxanthine. The method has been used to study the absorption kinetics and bioavailability of a sustained release formulation of the drug when co-administered to human volunteers with a conventional formulation of the drug labelled with the stable isotope.

Adult↗
PubMed1987

Crystallization of an NADP+-dependent malic enzyme from rat liver.

Crystals of a tetrameric NADP+-dependent malic enzyme from rat liver have been grown in the presence of NADP+ using the hanging-drop method of vapour diffusion with ammonium sulphate as the precipitant. Measurement of the crystal density and calculation of the values of Vm for different numbers of polypeptide chains in the unit cell indicate that the asymmetric unit of the crystal contains a complete tetramer, allowing the application of non-crystallographic symmetry to the determination of the molecular structure of this enzyme. This structure would provide only the second example for an enzyme involved in oxidative decarboxylation, the other being 6-phosphogluconate dehydrogenase. In addition, then, to providing an insight into the structure-function relationship in malic enzyme, the successful structure determination would permit valuable comparisons to be made between these two and other enzymes with this catalytic activity.

Animals↗
PubMed1987

Estimation of exposure to alkylating carcinogens by the GC-MS determination of adducts to hemoglobin and nucleic acid bases in urine.

Many carcinogens and mutagens are electrophilic in nature and will react with nucleophilic sites in protein and nucleic acid. Determination of the extent of formation of these adducts of genotoxic agents with protein provides a practical method of monitoring human exposure and of determining the possible risk associated with the exposure. Proteins are predominantly attacked on the cysteine, histidine and N-terminal amino acids. Hemoglobin is the most suitable protein for dose monitoring due to its ready availability and its long lifetime. Methods have been developed using capillary gas chromatography with mass spectrometry for determining S-methylcysteine, Nr-[2-hydroxyethyl]histidine and Nr-[2-hydroxypropyl]histidine in hemoglobin, allowing the monitoring of in vivo exposure of laboratory animals and humans to methylating agents, ethylene oxide and propylene oxide, respectively. A method for monitoring exposure to acrylamide has also been devised based on the determination by gas chromatography-mass spectrometry of the adduct formed with cysteine residues in hemoglobin. An alternative method of dose monitoring of some methylating agents by the measurement of the urinary N-7-methylated guanine derived from alkylated DNA breakdown products has also been investigated.

Acrylamide↗
PubMed1987

Analysis of the equine lymphocyte antigen system by Southern blot hybridization.

Fourteen Standardbred horses homozygous for one of six equine lymphocyte antigen (ELA) specificities (A1, A3, A4, A5, A6, or A10) were analyzed by Southern blot hybridization using DNA probes derived from the mouse major histocompatibility complex (MHC). Total genomic DNA from peripheral lymphocytes was digested with the restriction enzymes Hind III, Pvu II, or Eco RI. Twenty-three to thirty-three bands were generated for individual horses with the class I cDNA probe. The resulting band patterns revealed 12-14 nonpolymorphic fragments, which is consistent with the highly conserved Qa/Tla genes seen in other species. The remaining 10-19 bands displayed significant polymorphism; no two animals had identical band patterns when studied with all three enzymes. The polymorphism was markedly decreased between animals of the same ELA serotypes. Unique bands were identified in both A1 horses and all four A6 animals. Pvu II digestions of lymphocyte DNA were hybridized with mouse MHC class II probes. A cDNA probe for the E alpha gene revealed only a single nonpolymorphic band. In contrast, a cDNA probe for the H-2 A alpha locus displayed three to five strong bands in each animal with polymorphism that was most pronounced between horses of different ELA serotypes. Genomic DNA probes for A beta and E beta genes both revealed multiple polymorphic bands. However, cross-hybridization between these two probes prevented distinction between A beta and E beta equivalent loci. The reduced polymorphism evident within ELA specificities is consistent with the concept that the equine lymphocyte antigen system includes two families of closely linked MHC genes.

Animals↗
PubMed1987

The determination of urinary 3-methyladenine in humans as a potential monitor of exposure to methylating agents.

The determination of urinary 3-methyladenine has been explored as a potential monitor of exposure to methylating carcinogens. A method based on the use of high resolution gas chromatography--mass spectrometry has been developed for measuring this methylated base in human urine. Urine is extracted by XAD-2 column chromatography and the extract purified by reverse phase C18 h.p.l.c. Derivatization with N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide yields the mono-tert-butyldimethylsilyl derivative of 3-methyladenine which has good gas chromatographic properties and is stable towards hydrolysis. The gas chromatographic separation was carried out using an SE-52 capillary column and quantitation made by electron impact selective ion monitoring mass spectrometry employing deuterium-labelled 3-methyladenine added initially to the urine as internal standard. Measurable levels (4.50-16.07 micrograms/24 h) of the methylated base have been found in control (i.e. nominally unexposed) human urines.

Adenine↗
PubMed1987

Evidence of a second polymorphic ELA class I (ELA-B) locus and gene order for three loci of the equine major histocompatibility complex.

Two antisera, B-442 and R-2046, were produced by immunizing offspring with purified peripheral blood lymphocytes from a parent matched for the ELA-A specificity carried on the unshared haplotype. Absorption analysis demonstrated that these antisera contained at least two families of cytotoxic antibodies, one directed against antigens present on T and B cells, and a second directed preferentially against antigens present on surface Ig positive cells. Immunoprecipitation studies using these antisera demonstrated that both antisera contain antibodies specific for glycoproteins with molecular weights characteristic of class I and class II MHC antigens. In lymphocyte typing tests of unfractionated lymphocytes, only the class I activity was readily detectable since the class II activity killed less than 25% of the cells. Family studies demonstrated that these antisera recognize products of genes linked to the ELA system. Based on two recombinants in an extended family it became apparent that the specificities detected by B-442 and R-2046 are not products of the ELA-A locus, but rather they are products of at least one other locus, defined in this paper as ELA-B. In this family a third recombinant was found between the A blood group system and the ELA-A locus. Based on these three recombinants, the most probable linear relationship of the following genes is: A blood group system/ELA-A/ELA-B.

Animals↗
PubMed1987

Genetic differentiation associated with gait within American standardbred horses.

American Standardbred horses are divided into two groups based upon gait: the trot and the pace. The tendency to trot (diagonally opposite legs moving forward together) or pace (the two legs on the same side of the body moving forward together) appears to be genetically determined, although no formal genetic analysis has been undertaken. There is nearly complete assortative mating for gait; however, about 20% of the offspring sired by trotters are registered as pacers, while fewer than 1% of those sired by pacers are registered as trotters. Electrophoretically detectable genic variation at 13 protein loci has been analysed for 371 trotters and 856 pacers, and 10 blood group loci have been examined for 600 trotters and 1227 pacers. Trotters and pacers shared common alleles at 20 of the 23 loci; however, there were significant differences in allele frequencies at 21 of the 23 loci. Highly significant fixation indices (FSTS) were observed for 17 of the loci. The extent of genetic difference between Standardbred trotters and pacers was as great as or greater than that seen between some distinct horse breeds.

Alleles↗
PubMed1987

Changes in immunoreactive malic enzyme in liver and brown adipose tissue during development of the rat.

There is a good correlation between changes in malic enzyme activity and immunoreactive protein in both hepatic and brown adipose tissue during postnatal development of the rat. Furthermore, the previously observed premature appearance of hepatic malic enzyme during the suckling period, in response to triiodothyronine, can also be achieved through dichloroacetate administration. A combination of triiodothyronine and dichloroacetate induces malic enzyme activity and immunoreactive protein in a synergistic manner, indicating different sites of action in the control of synthesis of hepatic malic enzyme although neither agent was found to affect the level of malic enzyme in brown adipose tissue. There is evidence to suggest that changes in the ability of the liver to express malic enzyme in response to triiodothyronine administration occur early in postnatal life.

Adipose Tissue, Brown↗
PubMed1987

Excretion of methylated nucleic acid bases as an indicator of exposure to nitrosatable drugs.

Urinary excretion of 3-methyladenine (3-meA) may be a valuable monitor of exposure to methylating carcinogens. In rats, the compound is known to be liberated from DNA following its formation, is not metabolized and is excreted intact in the urine. Studies with rats administered d3-methylating agents [e.g., a mixture of d6-aminopyrine (d6-AP) and nitrite which liberates d3-N-nitrosodimethylamine (NDMA) intragastrically] have confirmed that d3-3-meA is excreted in a dose-related manner. Although low levels of 'background' 3-meA have been found in rat and human urine, these are about 1000-fold lower than those of 7-methylguanine (7-meG). Thus, despite the fact that 3-meA is known to be formed at 10% of the level of 7-MeG in DNA following exposure of rats to methylating agents, the low 'background' that we have observed indicates that urinary 3-meA should be a more sensitive indicator of methylation than 7-meG.

Adenine↗
PubMed1986

Sex-linked changes in immunoreactive glucose-6-phosphate dehydrogenase in rat liver.

The level of hepatic immunoreactive glucose-6-phosphate dehydrogenase protein was found to correlate well with the enzyme activity in adult rats fed the stock laboratory diet in a variety of hormonal conditions. The amount of immunoreactive protein and enzyme activity was 2-fold greater in sexually mature female rats compared with aged matched male animals. However, this difference was absent in diabetic animals, and furthermore although triiodothyronine administration to the diabetic male rat could restore the level of enzyme activity to that of the normoglycaemic animal, it was much less effective in the female animal. In contrast, administration of insulin to the normoglycaemic animal increased the level of glucose-6-phosphate dehydrogenase in the female, but was without effect in the male. These results are discussed in relation to the possible role of thyroid status and steroid sex hormones in the regulation of hepatic glucose-6-phosphate dehydrogenase.

Animals↗
PubMed1986

Metabolic activation of olefins. Conversion of 1-octene to a putative reactive intermediate 1-octen-3-one: an alternative pathway to epoxidation.

The enzymic activation of a model olefin oct-1-ene was studied in rat liver microsomal systems in vitro. An active metabolite was trapped using N-acetylcysteine and identified by means of capillary GLC/mass spectrometry and 360 MHz 1H NMR as S-3-oxo-octyl-N-acetylcysteine. A two step pathway for the formation of this adduct was proposed involving first the production of oct-1-en-3-ol by NADPH dependent mixed function oxidases and secondly a NADP or NAD linked oxidation, independent of cytochrome P-450, to yield the putative reactive intermediate oct-1-en-3-one. Under physiological conditions, oct-1-en-3-one, prepared chemically, reacted non-enzymically with N-acetylcysteine with a t1/2 of about 6 sec. Enzymes catalysing the NADP-dependent oxidation of octen-3-ol were present in microsomal preparations from a number of organs apart from the liver, those from adrenal and intestinal epithelia showing the next highest levels of activity. Unlike the activation of octene, rates of hepatic activation of octen-3-ol were not induced by pretreatment of rats with phenobarbitone or 3-methylcholanthrene. Using 1-octene as the substrate, comparisons were made of alternative routes of hepatic metabolism activation. Relative to the rate of formation of the 3-oxo intermediate trapped with N-acetylcysteine, epoxidation of octene and subsequent hydrolysis to octane-1,2-diol was over 40 times more rapid. The rate of formation of a presumptive oxirane precursor trapped with the haem of cytochrome P-450 as N-(2-hydroxyoctyl)protoporphyrin IX was about 17-fold lower.

Alkenes↗
PubMed1986

Determination of methyl- and ethylmercury in rat blood and tissue samples by capillary gas chromatography with electron-capture detection.

A precise and accurate method has been developed for the determination of either methyl- or ethylmercury in the blood and tissue of rats using capillary gas chromatography with electron-capture detection. The biological sample was spiked with an internal standard (methyl- or ethylmercury chloride) and after treatment with sodium thiosulphate and cupric bromide the alkylmercurials were extracted into benzene as their bromide derivatives and analysed on an OV-275 glass capillary column. The sensitivity and selectivity of the method enabled determinations to be made on small volumes of blood and tissue homogenates. The method has been applied to a pharmacokinetic study in rats dosed orally with 8 mercury as methylmercury chloride or ethylmercury chloride.

Animals↗
PubMed1986

Segregation distortion within the equine MHC; analogy to a mouse T/t-complex trait.

Segregation distortion was found for a haplotype of the equine lymphocyte antigen (ELA) system in an extended family of American Standardbred horses. In one sire family, consisting of a stallion and his 17 sons and grandsons, the gene for ELA-A10 (A10) was transmitted to 57.7% of 638 offspring scored (P = 0.001). Significant segregation distortion was not seen for mares or for unrelated stallions, regardless of the ELA markers they possessed. Since the effect was seen for this one sire family and not seen for other stallions with A10, it is unlikely that the gene for A10 is the cause of this phenomenon, but rather A10 is linked to another major histocompatibility complex (MHC) gene causing this trait. This trait appeared analogous to the segregation distortion observed for the T/t complex of the mouse. Since segregation distortion involving MHC genes has been seen in other species, genes for this trait may be a general feature of the MHC.

Animals↗
PubMed1986

Monitoring exposure to acrylamide by the determination of S-(2-carboxyethyl)cysteine in hydrolyzed hemoglobin by gas chromatography-mass spectrometry.

Acrylamide is a potent cumulative neurotoxin in animals and man. In vivo exposure to this electrophile results in the formation of a covalently bound reaction product with cysteine residues in hemoglobin. This adduct yields on acid hydrolysis S-(2-carboxyethyl)cysteine which has been analyzed by capillary gas chromatography with mass spectrometry. Globin isolated from the blood of rats exposed to acrylamide was spiked with an internal standard (globin treated in vitro with d3-acrylamide) and was then hydrolyzed with 6 N HCl. The protein hydrolysate was fractionated on a Dowex 50W H+ ion exchange column and the amino acids in the partially purified extract were determined as N-heptafluorobutyryl methyl esters using an OV-1701 fused silica capillary column. Quantitation was made by chemical ionization (isobutane) selective ion monitoring in which the ions m/z 386 (M-OCH3)+ derived from derivatized S-(2-carboxyethyl)cysteine in the sample and the corresponding ion m/z 389 from the added deuterium-labeled internal standard were monitored. The dose-response relationship between production of hemoglobin adduct and dose of acrylamide (0.1 mg/kg-5 mg/kg) is curved, showing an increasing slope with increasing doses of acrylamide.

Acrylamide↗