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Biomedical subjects

D H Phillips

Publications and source records attributed to D H Phillips.

190 records · Page 11Linked to original sources
PubMedDate not supplied

DNA adducts in cervical tissue of smokers and non-smokers.

Cervical biopsy samples were taken from 40 women, aged between 31 and 72, undergoing hysterectomies. Twenty-two of the women were smokers, four were ex-smokers and 14 were non-smokers. DNA was isolated and analysed using 32P-postlabelling, after butanol extraction or nuclease P1 digestion enhancement of the adducts. Resolution of the adducts was by thin-layer chromatography on polyethyleneimine (PEI)-cellulose. The pattern of adducts seen was similar to smoking-related adducts detected in other tissues and consisted mainly of a diagonal zone of radioactivity. With the butanol extraction enrichment method, the levels of adducts in DNA from the 22 smokers ranged from 1.65 to 6.04 adducts/10(8) nucleotides (mean = 3.70, SD = 1.36), in DNA from non-smokers from 1.16 to 3.98 (mean = 2.04, SD = 0.77) and in samples from ex-smokers from 2.57 to 3.35 (mean = 2.86, SD = 0.37). The increase in adduct levels in smokers compared with non-smokers was highly significant (Mann-Whitney test p = 0.0005, two-tailed). When analysed by the nuclease P1 digestion enhancement method, total adduct levels in samples from smokers (mean = 2.95, SD = 1.77) were not significantly different (p = 0.3, two-tailed) from levels in non-smokers (mean = 2.34, SD = 0.96). However, the level of a minor discrete adduct spot was significantly lower (p = 0.02, two-tailed) in smokers (mean = 0.19, SD = 0.36) than in non-smokers (mean = 0.39, SD = 0.41). The results indicate that some of the DNA adducts detected in cervical epithelium correlate with tobacco smoking and support the hypothesis that smoking-related cervical cancer results from exposure to genotoxic components of cigarette smoke that become activated to DNA-binding products in this tissue.

Adult↗
PubMedDate not supplied

In vitro mechanistic differences in benzo[a]pyrene-DNA adduct formation using fish liver and mussel digestive gland microsomal activating systems.

Turbot (Scophthalmus maximus) and mussel (Mytilus edulis) microsomes were incubated with DNA to examine if microsomal in vitro metabolism of BaP could result in DNA adducts detected by 32P-postlabelling. Turbot DNA was incubated with benzo[a]pyrene (BaP), NADPH and microsomal activating systems prepared from either livers of unexposed turbot, turbot exposed to BaP or beta-naphthoflavone (beta-NF) or digestive glands from mussels. The beta-NF activating system generated the highest levels of DNA adducts detected in this study (451.7 adducts per 10(8) nucleotides) and were distributed in three discrete adduct TLC spots, one of which (97% of the total adducts) co-migrated with the 32P-postlabelled BaP 7,8-diol, 9,10-epoxide-N2-guanine adduct. Fewer adducts (P < 0.05) were generated by BaP-induced microsomes (9.4-30.6 adducts per 108 nucleotides) but levels were higher (P <0.05) than those generated from untreated fish (3.5 adducts per 10(8) nucleotides). Co-incubation with 500 microM alpha-naphthoflavone (alpha-NF) resulted in 97-99% inhibition in adduct formation implicating cytochrome P450-dependent (CYP) bioactivation however there was some evidence for carry over of BaP in the liver microsomal preparations from BaP injected fish. In contrast to the fish activating systems, no DNA adducts were observed when mussel microsomes were incubated with BaP, DNA and NADPH.

Animals↗
PubMedDate not supplied

Correlative changes in metabolism and DNA damage in turbot (Scophthalmus maximus) exposed to benzo[a]pyrene.

Juvenile turbot (Scophthalmus maximus) were injected intraperitoneally with either corn oil or 5 mg/kg benzo[a]pyrene (BaP) dissolved in corn oil and sampled I and 3 days after injection. After 1 day, no elevation of 7-ethoxyresorufin O-deethylase (EROD) activity was observed, however bile metabolites (BaP-7,8 dihydrodiol representing 70% of the total metabolites) and a single hepatic DNA adduct spot (0.47 adducts/10(8) nucleotides) identified by 32P-postlabelling were formed. No BaP metabolites or DNA adducts were observed in either control or carrier control fish. Fish sampled after 3 days reported 5-fold higher (P < 0.05) levels of EROD activity, a shift in the bile metabolite profile towards BaP phenol formation (1OH and 30H BaP comprising up to 60% of total metabolites detected) and the formation of two adduct spots (0.86 and 0.71 adducts/10(8) nucleotides). These results show that BaP can be metabolised and form hydrophobic DNA adducts in turbot without EROD elevation. Following EROD elevation, a shift in the profile of both BaP metabolites and BaP metabolite-DNA interactions occurs indicative of other oxidative processes.

Animals↗
PubMedDate not supplied

Evidence of involvement of multiple sites of metabolism in the in vivo covalent binding of dibenzo[a,h]pyrene to DNA.

The in vivo formation of dibenzo[a,h]pyrene-DNA adducts in mouse skin was assessed by laser-excited fluorescence spectroscopy at 77 and 4.2 K. Two adducts were identified with fluorescence origin bands at approximately 383.5 and 407.2 nm, and these were shown to possess pyrene and benzo[a]pyrene (B[a]P) chromophores, respectively. Both DNA-bound chromophores displayed considerable electron-phonon coupling and likely assume a highly base-stacked or quasi-intercalated configuration within DNA duplexes. The presence of B[a]P and pyrene aromatic systems indicates that two-electron or monooxygenation metabolism occurred on either the a or h benzo moieties (which are equivalent) in the former case, and on both these rings in the latter case. The presence of two adduct species agrees with 32P-postlabeling analysis of the DNA, which showed the presence of two major adducts in both thin-layer and high-performance liquid chromatographic separations.

Animals↗
PubMedDate not supplied

Activation of c-Ha-ras-1 proto-oncogene by in vitro modification with a chemical carcinogen, benzo(a)pyrene diol-epoxide.

Chemical carcinogenesis generally proceeds via the formation of strongly electrophilic reactants, termed ultimate carcinogens. The observation that many ultimate carcinogens are potent mutagens and the results of studies on the covalent binding of carcinogens to cellular macromolecules suggest that tumour initiation results from mutations arising from the binding of ultimate carcinogens to DNA. Recently, gene transfer experiments have shown that some tumours contain activated oncogenes which are members of the ras gene family (reviewed in refs 6. 7) and which differ by single base pair substitutions from their non-transforming counterparts, the proto-oncogenes (see, for example, refs 8-11). Here we have used clones of the c-Ha-ras-1 proto-oncogene to show that reaction in vitro with an ultimate carcinogen generates a transforming oncogene when the modified DNA is introduced into NIH 3T3 cells. As DNA is the only cellular macromolecule present in the reactions, our experiments also show that reaction of an ultimate carcinogen with DNA alone can lead to the induction of mutations in mammalian cells.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMedDate not supplied

Correlation of DNA adduct levels in human lung with cigarette smoking.

Lung cancer is the most common cancer in men in the United Kingdom and the second most common in women, accounting for between 25 and 40% of all cancer deaths. Cigarette smoking is widely accepted as the major cause of lung cancer and linear relationships have been established between the number of cigarettes smoked and lung cancer risk. Although approximately 50 carcinogenic chemicals have been identified in cigarette smoke, a causal link between specific compounds and lung cancer has yet to be made. Studies on cigarette smokers' urine, blood and placenta have provided indications of carcinogen exposure, and although the presence of covalently-bound adducts in human DNA provides evidence of exposure to carcinogens, there have been no reports of systematic studies on the levels of DNA adducts in human lung. We report here, using the 32P-post-labelling technique, that cigarette smokers have higher adduct levels than non-smokers, that there is a linear relationship between adduct levels and daily or lifetime cigarette consumption, and that people who have given up smoking for at least five years have adduct levels similar to those of non-smokers.

Aged↗
PubMedDate not supplied

Impact of sample preparation on mineralogical analysis of zero-valent iron reactive barrier materials.

Permeable reactive barriers (PRBs) of zero-valent iron (Fe(0)) are increasingly being used to remediate contaminated ground water. Corrosion of Fe(0) filings and the formation of precipitates can occur when the PRB material comes in contact with ground water and may reduce the lifespan and effectiveness of the barrier. At present, there are no routine procedures for preparing and analyzing the mineral precipitates from Fe(0) PRB material. These procedures are needed because mineralogical composition of corrosion products used to interpret the barrier processes can change with iron oxidation and sample preparation. The objectives of this study were (i) to investigate a method of preparing Fe(0) reactive barrier material for mineralogical analysis by X-ray diffraction (XRD), and (ii) to identify Fe mineral phases and rates of transformations induced by different mineralogical preparation techniques. Materials from an in situ Fe(0) PRB were collected by undisturbed coring and processed for XRD analysis after different times since sampling for three size fractions and by various drying treatments. We found that whole-sample preparation for analysis was necessary because mineral precipitates occurred within the PRB material in different size fractions of the samples. Green rusts quickly disappeared from acetone-dried samples and were not present in air-dried and oven-dried samples. Maghemite/magnetite content increased over time and in oven-dried samples, especially after heating to 105 degrees C. We conclude that care must be taken during sample preparation of Fe(0) PRB material, especially for detection of green rusts, to ensure accurate identification of minerals present within the barrier system.

Chemical Precipitation↗
PubMedDate not supplied

Mineralogical characteristics and transformations during long-term operation of a zerovalent iron reactive barrier.

Design and operation of Fe0 permeable reactive barriers (PRBs) can be improved by understanding the long-term mineralogical transformations that occur within PRBs. Changes in mineral precipitates, cementation, and corrosion of Fe0 filings within an in situ pilot-scale PRB were examined after the first 30 months of operation and compared with results of a previous study of the PRB conducted 15 months earlier using X-ray diffraction and scanning electron microscopy employing energy dispersive X-ray and backscatter electron analyses. Iron (oxy)hydroxides, aragonite, and maghemite and/or magnetite occurred throughout the cores collected 30 mo after installation. Goethite, lepidocrocite, mackinawite, aragonite, calcite, and siderite were associated with oxidized and cemented areas, while green rusts were detected in more reduced zones. Basic differences from our last detailed investigation include (i) mackinawite crystallized from amorphous FeS, (ii) aragonite transformed into calcite, (iii) akaganeite transformed to goethite and lepidocrocite, (iv) iron (oxy)hydroxides and calcium and iron carbonate minerals increased, (v) cementation was greater in the more recent study, and (vi) oxidation, corrosion, and disintegration of Fe0 filings were greater, especially in cemented areas, in the more recent study. If the degree of corrosion and cementation that was observed from 15 to 30 mo after installation continues, certain portions of the PRB (i.e., up-gradient entrance of the ground water to the Fe0 section of the PRB) may last less than five more years, thus reducing the effectiveness of the PRB to mitigate contaminants.

Calcium Carbonate↗
PubMedDate not supplied

Carcinogen-DNA adducts in human breast tissue.

Breast cancer is the second leading cause of cancer death among American women. Known risk factors account for only approximately one-third of the 182,000 new cases diagnosed each year in the United States. There is both concern and debate over the contribution of environmental exposures related to lifestyle, occupation, and ambient pollution, particularly in high risk areas such as Long Island, NY and the rest of the northeastern United States. Biomarkers such as carcinogen-DNA adducts can help to explore the role of environmental risk factors for breast cancer by documenting DNA damage from specific carcinogens directly in human tissue. In this pilot study, a total of 31 breast tissue samples were analyzed by the 32P-postlabeling method for carcinogen-DNA adducts characteristic of complex mixtures of aromatic compounds (such as polycyclic aromatic hydrocarbons) and tobacco smoke. The samples included tumor and tumor-adjacent tissues from 15 women with breast cancer and normal tissue samples from 4 women undergoing breast reduction. Among the breast cancer cases, the mean aromatic/hydrophobic-DNA adduct level in all tissues assayed was 5.3 +/- 2.4 (SD) adducts/10(8) nucleotides compared to 2.3 +/- 1.5 among the samples from the noncancer patients. Breast tissue (tumor and/or nontumor) from 30% (5 of 15) of women with breast cancer displayed a pattern of adducts (referred to as a diagonal zone of radioactivity) associated previously, in studies of other tissues, with exposure to tobacco smoke. The 5 positive samples were from current smokers; tissue samples from the 8 nonsmoking cases did not show this characteristic pattern (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗