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Biomedical subjects

A Weston

Publications and source records attributed to A Weston.

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

Dosimeters of human exposure to carcinogens: polycyclic aromatic hydrocarbon-macromolecular adducts.

The metabolic activation of polycyclic aromatic hydrocarbons (PAH), for example benzo[a]pyrene, leads to the formation of carcinogen-macromolecular adducts. Methods that make it possible to detect low levels of these adducts in human peripheral blood samples should be useful in the dosimetry of human exposure to carcinogens. We demonstrated previously the usefulness of enzyme immunoassays and of synchronous fluorescence spectroscopy (SFS) for detecting and characterizing low levels of PAH-macromolecular adducts present in synthetic adduct mixtures. These methods have now been refined and applied to the analysis of samples of peripheral blood collected from occupationally exposed individuals (coke-oven workers) and from people attending smoking cessation clinics. The results of both immunoassays and SFS show the presence of benzo[a]pyrene diol epoxide (BPDE)-DNA, BPDE-haemoglobin and other putative PAH-macromolecular adducts in peripheral blood samples from certain individuals.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1987

Biochemical and molecular epidemiology of human cancer: indicators of carcinogen exposure, DNA damage, and genetic predisposition.

The primary goal of biochemical and molecular epidemiology is to identify individuals at high cancer risk by obtaining evidence of high exposure to carcinogens, leading to pathobiological lesions in target cells, and/or increased oncogenic susceptibility due to either inherited or acquired host factors. This emerging and multidisciplinary area of cancer research combines epidemiological and laboratory approaches. Because DNA is considered to be an important target for modification by mutagens and carcinogens, damage to DNA can be used as an internal, molecular dosimeter of carcinogen exposure. The reactive species of these carcinogens may directly bind to DNA to form adducts and may indirectly cause secondary DNA lesions, e.g., via induction of free radicals and aldehydes. Highly sensitive and specific methods have been developed to measure the minute amounts of DNA lesions and DNA repair products found in biological specimens from humans exposed to carcinogens. For example, DNA adducts have been measured in cells and tissues from people occupationally exposed to carcinogenic polycyclic aromatic hydrocarbons. Antibodies recognizing carcinogen-DNA adducts have also been detected in human sera. Inherited predisposition to cancer has been revealed by recent advances in molecular genetics, including restriction-fragment-length polymorphism. For example, the hypothesis that rare alleles of the Ha-ras proto-oncogene are associated with an increased risk of lung cancer is currently being tested. These approaches afford the potential of biochemical and molecular epidemiology to predict disease risk for individual persons, instead of for populations, and before the onset of clinically evident disease.

Animals↗
PubMed1985

Comparative studies of the metabolic activation of chrysene in rodent and human skin.

Metabolism and activation of chrysene was examined in mouse, rat and human skin using a short-term organ culture technique. Mouse skin released larger quantities of free dihydrodiols into the culture medium than either rat or human skin and greater quantities of chrysene metabolites became covalently bound to the DNA of mouse skin. The stereochemistry of the chrysene-1,2-diol that was formed by each skin type was examined using high-performance liquid chromatography (HPLC) with a chiral stationary phase to resolve the enantiomers. It was found that in each case the (-)-enantiomer predominated. When hydrolysates of DNA extracted from rodent or human skin that had been treated with 3H-labelled chrysene were chromatographed on Sephadex LH-20 columns, the elution profiles of the hydrocarbon-DNA adducts were found to vary between the species studied. Further examination using HPLC showed that some of the adducts formed in skin had the chromatographic characteristics of adducts formed when the anti-isomer of the 'bay-region' diol-epoxide of chrysene (r-1,t-2-dihydroxy-t-3,4-oxy-1,2,3,4-tetrahydrochrysene) reacted with DNA and that others had the characteristics of triol-epoxide adducts.

Animals↗
PubMed1985

Alterations in the metabolism of 7,12-dimethylbenz[a]anthracene and various xenobiotics by rat hepatic microsomes following Sudan III treatment in vivo.

Sudan III treatment of Long-Evans rats results in increased hepatic monooxygenase activity using ethoxycoumarin and aniline as substrates. Monooxygenase activity towards amino-pyrine and nitrosodimethylamine is not affected. Sudan III treatment results in increased microsomal cytochrome P448 and increased amounts of a protein band which comigrates with purified cytochrome P448 during SDS polyacrylamide gel electrophoresis. The proportions of the different dihydrodiols formed during the incubation of 7,12-dimethylbenz[a]anthracene with microsomes vary between untreated and treated animals. Thus, extracts of microsomes from untreated rats were found to contain materials with chromatographic properties identical to those of the 3,4-dihydrodiol and the 5,6-dihydrodiol when examined on two different h.p.l.c. systems. Extracts of microsomes from Sudan III treated animals were found to contain materials with chromatographic properties identical to those of the 5,6-dihydrodiol and the 8,9-dihydrodiol when similarly examined. These findings suggest that the protective effect of Sudan III against DMBA induced leukaemia is mediated by an alteration in monooxygenase activity.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1983

Metabolic activation of benzo[a]pyrene in human skin maintained in short-term organ culture.

The metabolic activation of benzo[a]pyrene (BP) was examined in six samples of human skin after topical application of the hydrocarbon to the skin in short-term organ culture. The results show that all of the samples were capable of metabolizing BP to water-soluble products and to ether-soluble products that included the 4,5-, 7,8- and 9,10-dihydrodiols and a product which had chromatographic properties identical with those of authentic trans-11,12-dihydro-11,12-dihydroxybenzo[a]pyrene (BP-11,12-diol). The major BP-deoxyribonucleoside adduct detected in each skin sample appeared to be formed from the reaction of r-7,t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BP-7,8-diol 9,10-oxide) with deoxyguanosine residues in DNA.

Benzo(a)pyrene↗
PubMed1983

Formation of the 1,2-diol as a metabolite of 7,12-dimethylbenz[a]-anthracene by rodent and human skin.

Rodent and human skin maintained in short-term organ culture was treated with 3H-labelled 7,12-dimethylbenz[a]-anthracene. Extracts of the rodent tissue and culture fluid in which either mouse, rat or human skin had been maintained were found to contain radioactive material that possessed the chromatographic characteristics of trans-1,2-dihydro-1,2-dihydroxy-7,12-dimethylbenz[a]anthracene when it was examined in two different h.p.l.c. systems. When the metabolite was treated with hot mineral acid, the two radioactive products formed co-chromatographed with the phenols that were formed when the reference dihydrodiol was similarly treated. Acetylation of the isolated metabolite yielded a single product that had chromatographic properties identical to those of the diacetate of the reference dihydrodiol. Taken together these data show that the 1,2-dihydrodiol of 7,12-dimethylbenz[a]anthracene is formed as a metabolite of this hydrocarbon by rodent and human skin maintained in short-term organ culture.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1983

Metabolic activation of chrysene in mouse skin: evidence for the involvement of a triol-epoxide.

All three possible dihydrodiols of chrysene and a chrysene triol, formed from the further metabolism of the chrysene-1,2-diol, were detected when ether extracts of mouse skin that had been treated with 3H-labelled chrysene were examined by h.p.l.c. The major deoxyribonucleoside-hydrocarbon adducts present in hydrolysates of DNA isolated from the mouse skin were examined by chromatography on Sephadex LH20 and by h.p.l.c. on Zorbax ODS. One adduct had chromatographic properties identical to those of the major adduct formed when r-1,t-2-dihydroxy-t-3,4-oxy-1,2,3,4-tetrahydrochrysene reacts with DNA. A second major adduct was present that had chromatographic properties that were indistinguishable from those of an adduct that was formed when either chrysene-1,2-diol or 3-hydroxychrysene were incubated with DNA in a rat liver microsomal metabolising system. The results provide evidence that this new adduct is formed via the reaction of a 'triol-epoxide', that appears to be 9-hydroxy-chrysene-1,2-diol 3,4-oxide, with DNA in mouse skin.

Animals↗
PubMed1982

Metabolism and activation of benzo[a]pyrene by mouse and rat skin in short-term organ culture and in vivo.

The metabolic activation of BP was examined in mouse and rat skin in vivo and in short-term organ culture. In mouse skin, larger quantities of ether- and water-soluble metabolites were formed and more BP became bound covalently to DNA and protein than in rat skin. Qualitative differences in the formation of dihydrodiol metabolites and of BP-deoxyribonucleoside adducts between mouse and rat skin were also observed. Organ culture techniques may not provide a true model of metabolic activation in vivo because it was found that the covalent binding of BP to DNA and protein was reduced in skin maintained in culture despite an accumulation of dihydrodiol and other ether-soluble metabolites. In addition, the proportions of the syn- and anti-isomers of BP-7,8-diol 9,10-oxide involved in the formation of adducts with deoxyguanosine differed between skin treated in organ culture and in vivo.

Administration, Topical↗
PubMed1981

Transformation of Escherichia coli with plasmid deoxyribonucleic acid: calcium-induced binding of deoxyribonucleic acid to whole cells and to isolated membrane fractions.

Plasmid deoxyribonucleic acid (DNA) was tightly bound to cells of Escherichia coli at 0 degrees C in the presence of divalent cations. During incubation at 42 degrees C, 0.1 to 1% of this DNA became resistant to deoxyribonuclease. Deoxyribonuclease-resistant DNA binding and the ability to produce transformants became saturated when transformation mixtures contained 1 to 2 micrograms of plasmid NTP16 DNA and about 5 X 10(8) viable cells. Under optimum conditions, between 1 and 2 molecule equivalents of 3H-labeled NTP16 DNA per viable cell became deoxyribonuclease resistant. Despite this, only 0.1 to 1% of viable cells became transformed by saturating amounts of the plasmid. The results suggest that transport of DNA across the inner membrane is a limiting step in transformation. After transformation the bulk of labeled plasmid DNA remained associated with outer membranes. However, in vitro assays indicated that plasmid DNA would bind equally well to preparations of inner or outer membranes provided divalent cations were present to preparations of inner or outer membranes provided divalent cations were present. Divalent cations promoted differing levels of binding to isolated inner and outer membranes in the order Ca2+ much greater than Ba2+ greater than Sr2+ greater than Mg2+. This parallels their relative efficiencies in promoting transformation. Binding of plasmid DNA was greatly reduced when outer membranes were treated with trypsin; this suggests that protein components may be required for the binding or transport of DNA (or both) during transformation.

Biological Transport↗
PubMed1976

Chemical ionization and field desorption mass spectrometry of the gentamicins.

Gentamicin sulphate employed in therapeutics consists of a mixture of three major aminoglycoside components, the gentamicins C1, C1a and C2. In the electron impact mass spectra of these components weak parent ions may be observed but they are of no diagnostic value in the commercial mixture. Chemical ionization and field desorption spectra of individual gentamicin components and commercial mixtures are reported and discussed. Isobutane chemical ionization spectra exhibit some fragmentation, but under optimum field desorption conditions little glycosidic cleavage is observed and [M + H]+ ions dominate the spectra.

Amines↗