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Biomedical subjects

K Hemminki

Publications and source records attributed to K Hemminki.

At least 235 records · Page 13Linked to original sources
PubMed1996

DNA adduct formation in the human nasal mucosa as a biomarker of exposure to environmental mutagens and carcinogens.

Human exposure to chemical compounds, often termed xenobiotics, has been linked to a number of enhanced incidences of various neoplasias. A majority of these enter the human body through inhalation. Most xenobiotics are metabolized in the body to more hydrophilic metabolites before excretion in the urine and bile. During this process, promutagens and procarcinogens could be activated and could interact with proteins as well as DNA to form adducts. DNA adducts formed by chemical carcinogens can, therefore, be used as biomarkers of exposure and other host factors. This study that DNA adduct analysis can be performed on cells from human nasal mucosa. Using the nasal lavage procedure performed on 20 healthy volunteers, 5 x 10(5) to 5 x 10(6) cells were obtained from which 5 to 40 micrograms DNA was isolated. DNA adducts were analyzed by the 32-P-postlabeling assay. The DNA adduct levels ranged between 1.4 and 6 adducts/10(8) nucleotides. In addition to its simplicity, the nasal lavage procedure is an inexpensive, noninvasive procedure that requires no anesthetics or special equipment. Moreover, the cells obtained are the first to come in contact with air pollutants. DNA adduct analysis from human nose mucosa cells could therefore be used to develop a technique suitable for the assessment of exposure to chemical carcinogens through inhalation.

Adult↗
PubMed1996

In vitro characterization of DNA adducts formed by foundry air particulate matter.

This study is part of an ongoing investigation of biomarkers in iron foundry workers exposed to polycyclic aromatic compounds. Foundry workers with the highest exposures had elevated levels of DNA adducts in their white blood cells in previous studies. The purpose of this study was to characterize the nature of DNA reactive chemicals in foundry air samples through incubating the foundry filter extract with DNA and activation enzymes. Calf thymus DNA was incubated with foundry filter extract and activated by either rat liver activation mixture (S9 mix) or xanthine oxidase. A complex pattern of adducts was observed on thin-layer chromatography (TLC) by the 32P-postlabeling assay. Two selected polycyclic aromatic hydrocarbons (PAHs)--1-NP-and anti(+/-)benzo[a]pyrene-trans-7,8-dihydrodiol-9,10-epoxide [anti(+/-) BPDE]-DNA adducts--were used as marker compounds in characterizing the postlabeled DNA adducts by TLC combined with high-performance liquid chromatography (HPLC). After an initial separation of DNA adducts by TLC, individual spots were isolated and separated further on HPLC. HPLC analysis and spiking with anti(+/-)BPDE-DNA standard confirmed the co-migration of the anti(+/-)BPDE-DNA standard with one PAH adduct formed by the S9 mix-activated DCM extract in calf thymus DNA.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1996

DNA adducts in environmental, occupational and life-style studies in human biomonitoring.

The importance of DNA adducts in carcinogenesis had been discussed. The 32P-postlabelling method was developed as a quantitative technique to measure the level of different DNA adducts including adducts in human DNA. The elevated level of DNA adducts was found in white blood cells in persons exposed environmentally and occupationally to high concentrations of PAHs (polycyclic aromatic hydrocarbons) in the ambient air. Tobacco also generated higher level of DNA adducts both in lymphocytes and laryngeal tissues of smokers. Exposure to styrene has been of interest world-wide because of the very high exposure and persistence of adducts in DNA of lamination workers.

Air Pollutants↗
PubMed1995

DNA and protein adducts.

Application of methods for the measurement of DNA and protein adducts in environmental studies was surveyed. The methods included the 32P-postlabelling assay, immunoassay and synchronous fluorescence spectroscopy for DNA adducts. Additionally, methods for detecting excreted urinary RNA and DNA adducts were discussed. The protein adduct techniques included both immunological and chemical assays. The techniques have been applied in occupational and environmental studies, but usually one assay at a time. As specific DNA adducts can now be assayed for, it would be important to use these methods and specific protein adduct assays in the same studies. It is important to develop further specific adduct tests. This can be done with the help of standard compounds, which also allow quantitation in the assays. An international bank of standard compounds would be a major advancement to human biomonitoring.

Biomarkers↗
PubMed1995

N-nitrosodimethylamine and 7-methylguanine DNA adducts in tissues of rats fed Chinese salted fish.

Previous studies have demonstrated that rats fed Chinese salted fish developed carcinomas of the nasopharynx and nasal cavity. In the present work the contents of nitrosamines in salted fish from the city of Guangzhou, southern China, and the contents of nitrosamines and possible nitrosamine-induced DNA adducts in organs of rats fed the fish were analysed. Similar levels of N-nitrosodimethylamine (NDMA) were detected in tough and soft salted fish. The NDMA content in steamed fish was higher than in raw fish. In vitro incubation of salted fish with gastric juice significantly increased the level of NDMA. NDMA was found in liver and kidney from rats fed salted fish for 2 years, but no dose-dependence was found between salted fish treatment and NDMA content. The level of 7-methylguanine in rat liver DNA was found to be slightly higher than in DNA from nasopharynx. However, there were no significant differences in the level of 7-methylguanine in DNA samples from rats fed salted fish and rats fed standard diet.

Animals↗
PubMed1995

Reduced fertility among women exposed to organic solvents.

A retrospective time-to-pregnancy study was performed among women biologically monitored for exposure to organic solvents. The women were participants in a previous study on spontaneous abortion. They were classified into exposure categories on the basis of work description and the use of solvents as reported in the questionnaires and on biological exposure measurements. Daily or high solvent exposure, adjusted for potential confounders, was significantly associated with reduced fecundability in the discrete proportional hazards analysis (incidence density ratio of clinical pregnancies 0.41; 95% confidence interval [CI] 0.27-0.62). The incidence density ratios were decreased also among workers who were exposed to organic solvents in shoe factories (0.28; CI 0.11-0.71), dry cleaning shops (0.44; CI 0.22-0.86), and in the metal industry (0.58; CI 0.34-0.98). The possible effects of various biases are discussed. The results of the study support the hypothesis that daily or high exposure to organic solvents is associated with reduced fertility. There is a need for safer working methods in industries where organic solvents still are used.

Abortion, Spontaneous↗
PubMed1995

Coffee consumption not associated with risk of pancreas cancer in Finland.

BACKGROUND: Coffee consumption has been brought to focus as a possible risk factor for pancreas cancer. After having reviewed the available evidence, an International Agency for Research on Cancer working group concluded in 1991 that the evidence in humans that coffee drinking is carcinogenic in the pancreas is "inadequate," since the available data were considered suggestive of a weak relationship with high levels of coffee consumption, but the possibility that this was due to bias or confounding was judged tenable. METHODS: The association between coffee consumption and pancreas cancer risk was examined in a case-referent study in Finland. Data on coffee consumption 20 years prior to the diagnosis of cancer were obtained from the next of kin of 662 cases of pancreas cancer and 1,770 referent (stomach, colon, and rectum) cancers. The results were expressed as crude and age-, gender-, and tobacco smoking-adjusted odds ratios and 95% confidence intervals for three daily coffee dose categories 20 years prior to cancer diagnosis. RESULTS: The data failed to demonstrate any association between coffee consumption and risk for pancreas cancer. The crude odds ratios varied between 0.7 (95% confidence interval 0.3-1.5) and 1.3 (0.7-2.6), the adjusted ones between 0.5 (0.2-1.2) and 1.1 (0.6-2.1) in the different daily dose categories of coffee and between contrasts with the three referent cancers. The highest odds ratios were associated with the contrast between pancreas and colon cancer, the lowest between pancreas and rectum cancer. Adjustment for gender, age, and tobacco smoking slightly decreased the values of the odds ratios. The power of the study was low, however, to detect possible weak increases associated with coffee consumption. CONCLUSIONS: The results are unlikely to be negatively biased, and are compatible with the majority of epidemiologic results advanced, suggesting no positive association between coffee consumption and the risk of pancreas cancer.

Case-Control Studies↗
PubMed1995

Styrene: from characterisation of DNA adducts to application in styrene-exposed lamination workers.

Styrene oxide, a metabolite of styrene, reacts with many centres in nucleosides but in DNA N-7-, N2- and O6-guanine are the main sites. A 32P-postlabelling method was developed for the detection of O6-styrene oxide DNA adducts from white blood cells. The method involved use of nuclease P1 and magnet transfer. The O6 adducts were detected at a fmol range with about 10% labelling efficiency. In lamination workers the O6 adducts, adjusted for adduct recovery, were detected at a level of 5 adducts/10(8) nucleotides.

DNA Adducts↗
PubMed1995

DNA adducts in biomonitoring.

The types of occupational groups studied by postlabelling include foundry, coke oven and aluminium workers, roofers, garage and terminal workers, car mechanics and chimney sweeps. There does not seem to be a direct relationship between the exposure and adduct levels. However, the postlabelling assay is sensitive enough to show adducts in apparently unexposed individuals. The origin of such adducts is unknown; in the case of aromatic adducts, the origin is likely to be environmental and/or dietary.

Benzo(a)pyrene↗
PubMed1995

Analysis of UV-induced DNA photoproducts by 32P-postlabelling.

UV-induced cyclobutane dimers and 6-4 photoproducts, containing an unmodified nucleotide at the 5'-position were released from DNA by means of digestion with DNase I, snake venom phosphodiesterase and prostatic acid phosphatase. The enzymes were deactivated by proteinase K followed by ethanol precipitation. The products were phosphorylated by polynucleotide kinase and [gamma-32P]ATP. The TLC system used for the analysis enables separation of the different photoproducts and detection at a fmol level. T4 endonuclease treatment was applied to confirm the positions of cyclobutane dimers.

Animals↗
PubMed1995

Styrene oxide-induced HPRT mutations, DNA adducts and DNA strand breaks in cultured human lymphocytes.

Styrene-7,8-oxide (SO) is the major in vivo metabolite of styrene, a widely used plastic monomer. SO has been classified as probably carcinogenic to humans. We studied the genotoxic effects of SO in human peripheral blood lymphocytes (PBL) in vitro. SO-treatment in the range of 0.05-0.6 mM for 24 h resulted in a dose-dependent decrease of cell survival and increase of HPRT mutation, O6-guanine DNA adducts and DNA strand breaks, whereas higher concentrations caused pronounced cell death. SO was a weak mutagen, inducing at most 10-20 mutants per 10(6) clonable cells (approximately 4-fold over the background) after treatment with 0.2-0.4 mM for 24 h or 6 days. The levels of DNA adducts in treated cells correlated with SO-concentrations, but only four adducts per 10(8) nucleotides were detected at the highest treatment concentrations. Yet, adducts were still detectable in cells that had been cultured for 6-8 days after treatment. SO-induced DNA strand breaks, measured with the Comet assay, were detectable after 1 h exposure to 0.05-0.1 mM. Post-treatment incubation for 24 h decreased the level of DNA strand breaks to the control level. There was no correlation between the levels of DNA adducts and frequency of HPRT mutation. The present results indicate that SO is relatively inefficient in inducing HPRT mutation and O6-guanine DNA adducts in human lymphocytes in vitro, which may be related to its pronounced cytotoxicity at concentrations above 0.4 mM. A comparison with previous in vivo data obtained by the same assays in T-lymphocytes of styrene-exposed workers suggests that chronic, low dose exposure to styrene in the work environment may be more efficient in inducing persistent DNA adducts and HPRT mutation than acute, short-term exposure.

Animals↗
PubMed1995

Separation of transforming amino acid-substituting mutations in codons 12, 13 and 61 the N-ras gene by constant denaturant capillary electrophoresis (CDCE).

We used high fidelity PCR and constant denaturant capillary electrophoresis (CDCE) [Khrapko et al. (1994) Nucleic Acids Res., 22, 364-369] to separate wild type and different mutant N-ras exon 1 and 2 sequences. The set of plasmids containing N-ras cDNA, wild type or mutant sequences representing all transforming amino acid-substituting single base pair changes in codons 12, 13 (exon 1) and 61 (exon 2), were amplified using Pfu polymerase in a limited cycle polymerase chain reaction. One of the primers used for the amplification of each exon included a 40 nucleotide GC rich sequence that created high and low melting domains. The amplified fragments 151 bp (exon 1) and 150 bp (exon 2) were run on the CDCE with the 'denaturant zone' temperature of the capillary corresponding to the melting temperature of 111 bp (exon 1) and 110 bp (exon 2) low melting domains. The separation was achieved between wild type and mutant sequences as homoduplexes in 15 out of 19 cases, as a single base substitution alters the electrophoretic mobility of a partially melted double stranded fragment. The denaturation and reannealing of wild type and mutant fragments together created wild type/mutant heteroduplexes. All the heteroduplexes were well resolved from wild type homoduplex. In the current form mutant sequences were detected at a frequency of 10(-3) in the presence of wild type. This study has resulted in obtaining electrophoretic spectrum of different N-ras mutants on CDCE as homoduplexes as well as heteroduplexes.

Base Sequence↗
PubMed1995

UV-induced photoproducts in human skin explants analysed by TLC and HPLC-radioactivity detection.

The objective of this study was to apply the 32P-postlabelling method for the detection of UV-induced dipyrimidine photoadducts in human skin explants. [32P]TLC and [32P]HPLC analysis were used. These techniques allow detection of different combinations of cyclobutane dimers and 6-4 photoproducts in human skin at low doses of irradiation. Detection limit of the present method for some dinucleotide adducts is < 1 adduct per 10(7) normal nucleotides. Reaction of photochemical reversion of the cyclobutane dimers was performed to confirm the nature of the products detected in human skin explants.

Chromatography, High Pressure Liquid↗
PubMed1995

32P-postlabelling method for the detection of 7-alkylguanine adducts formed by the reaction of different 1,2-alkyl epoxides with DNA.

A 32P-postlabelling method is reported for the detection of 7-alkylguanines, the major adducts formed by the reaction of 1,2-alkylepoxides with DNA. Calf thymus DNA was reacted in vitro with different epoxides (ethylene oxide through octylene oxide) and digested with micrococcal nuclease and spleen phosphodiesterase to 3'-nucleotides. The adduct enrichment was carried out by an ion-exchange method and adducts were labelled with [gamma-32]ATP in a T4-polynucleotide kinase-mediated reaction. The labelled adducts, prior to resolution by two-dimensional TLC, were treated with nuclease P1. The recoveries of adducts formed by different epoxides ranged from 3 to 10%, tending to increase with the increase in the chain length of the substitutions. The 32P-postlabelled adducts were also analysed by HPLC coupled with a radioisotope detector. This method has been applied for the detection of 7-alkylguanine adducts in rats exposed to different alkenes. The method has potential for use in measuring human exposure to alkenes or their corresponding epoxides as well as the endogenously formed 7-alkylguanine adducts.

Animals↗
PubMed1995

Biomarkers of styrene exposure in lamination workers: levels of O6-guanine DNA adducts, DNA strand breaks and mutant frequencies in the hypoxanthine guanine phosphoribosyltransferase gene in T-lymphocytes.

Occupational exposure to styrene was studied in nine workers of a hand lamination plant in Bohemia. Personal dosimeters were used to monitor the styrene workplace exposure, and the levels of styrene in blood and mandelic acid in urine were measured. Blood samples were taken at four occasions during a 7 month period to determine styrene-specific O6-guanine DNA adducts in lymphocytes and granulocytes, DNA strand breaks and hypoxanthine guanine phosphoribosyltransferase (HPRT) mutant frequency in T-lymphocytes. Seven administrative employees in the same factory (factory controls) and eight persons in a research laboratory (laboratory controls) were used as referents. DNA adduct levels determined by the 32P-postlabelling method in lymphocytes of laminators were remarkably constant and significantly higher (P < 0.0001) than in factory controls at all four sampling times. HPRT mutant frequencies (MF) measured by the T-cell cloning assay were higher in the laminators (17.5 x 10(-6), group mean) than in the factory controls (15.7 x 10(-6), group mean) at three of the four sampling times, but the differences were not statistically significant. However, a statistically significant (P = 0.021) difference between MF in the laminators (18.0 x 10(-6), group mean) and laboratory controls (11.8 x 10(-6), group mean) was observed at sampling time 4 (the only sampling time when this latter group was studied). This result indicates that styrene exposure may induce gene mutation in T-cells in vivo. DNA strand breaks were studied by the 'Comet assay' at the fourth sampling time. The laminators were found to have significantly higher levels of DNA strand breaks than the factory controls (P = 0.032 for tail length, TL; P = 0.007 for percentage of DNA in tail, T%; and P = 0.020 for tail moment, TM). A statistically significant correlation was also found between the levels of lymphocyte DNA adducts and all three DNA strand break parameters (TL P = 0.046; T% P = 0.026 and TM P = 0.034). On the contrary, no significant correlations were found between DNA adduct levels and the HPRT mutant frequencies or between the mutant frequencies and DNA strand breaks. Taken together, these results add further support to the genotoxic and possibly mutagenic effects of styrene exposure in vivo. However, no simple quantitative relationship seems to exist between the levels of styrene-induced DNA damage and frequency of HPRT mutation in T-lymphocytes.

Adult↗
PubMed1995

Uptake, distribution, and formation of hemoglobin and DNA adducts after inhalation of C2-C8 1-alkenes (olefins) in the rat.

Absorption, distribution, elimination and hemoglobin and DNA adduct formation were studied in the rat after inhalation of individual C2-C8 1-alkenes (olefins) at 300 p.p.m., 12 h a day for 3 consecutive days. The concentrations of olefins were measured in blood, lung, brain, liver, kidney and perirenal fat immediately after each exposure and 12 h after the third exposure. DNA adducts were determined by 32P-postlabeling in liver, and lymphocytes sampled immediately after the last exposure. Hemoglobin adducts were determined by GC/MS and GC/MS/MS in erythrocytes sampled immediately after the last exposure. Concentrations of 1-alkenes in blood and organs reached a steady-state level after the first 12 h exposure, and the concentrations 12 h after the last exposure were generally low, except in fat tissue. Concentrations of 1-alkenes in blood and the different tissues increased with increasing number of carbon atoms. In contrast, levels of hemoglobin and DNA adducts decreased with increasing number of carbon atoms. The decrease was most pronounced from C2 to C3. The decrease through the whole homologous series from ethene to 1-octene was most pronounced for hemoglobin adducts followed by the DNA adducts in the lymphocytes. All 1-alkenes caused formation of detectable levels of hemoglobin and DNA adducts, although the levels of hemoglobin adducts after C4-C8 exposure were low. The project illustrates important aspects of the use of biomarkers. The structure-activity approach gives possibilities for extrapolation within the homologous series.

Absorption↗