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Biomedical subjects

H M Bolt

Publications and source records attributed to H M Bolt.

At least 55 records · Page 3Linked to original sources
PubMed1999

Determination of urinary thymidine glycol using affinity chromatography, HPLC and post-column reaction detection: a biomarker of oxidative DNA damage upon kidney transplantation.

Reactive oxygen species are generated during ischaemia-reperfusion of tissue. Oxidation of thymidine by hydroxyl radicals (HO) leads to the formation of 5,6-dihydroxy-5,6-dihydrothymidine (thymidine glycol). Thymidine glycol is excreted in urine and can be used as biomarker of oxidative DNA damage. Time dependent changes in urinary excretion rates of thymidine glycol were determined in six patients after kidney transplantation and in six healthy controls. A new analytical method was developed involving affinity chromatography and subsequent reverse-phase high-performance liquid chromatography (RP-HPLC) with a post-column chemical reaction detector and endpoint fluorescence detection. The detection limit of this fluorimetric assay was 1.6 ng thymidine glycol per ml urine, which corresponds to about half of the physiological excretion level in healthy control persons. After kidney transplantation the urinary excretion rate of thymidine glycol increased gradually reaching a maximum around 48 h. The excretion rate remained elevated until the end of the observation period of 10 days. Severe proteinuria with an excretion rate of up to 7.2 g of total protein per mmol creatinine was also observed immediately after transplantation and declined within the first 24 h of allograft function (0.35+/-0.26 g/mmol creatinine). The protein excretion pattern, based on separation of urinary proteins on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), as well as excretion of individual biomarker proteins, indicated nonselective glomerular and tubular damage. The increased excretion of thymidine glycol after kidney transplantation may be explained by ischaemia-reperfusion induced oxidative DNA damage of the transplanted kidney.

Adult↗
PubMed1999

Differential substrate behaviours of ethylene oxide and propylene oxide towards human glutathione transferase theta hGSTT1-1.

The transformation of ethylene oxide (EO), propylene oxide (PO) and 1-butylene oxide (1-BuO) by human glutathione transferase theta (hGSTT1-1) was studied comparatively using 'conjugator' (GSTT1 + individuals) erythrocyte lysates. The relative sequence of velocity of enzymic transformation was PO > EO >> 1-BuO. The faster transformation of PO compared to EO was corroborated in studies with human and rat GSTT1-1 (hGSTT1-1 and rGSTT1-1, respectively) expressed by Salmonella typhimurium TA1535. This sequence of reactivities of homologous epoxides towards GSTT1-1 contrasts to the sequence observed in homologous alkyl halides (methyl bromide, MBr; ethyl bromide, EtBr; n-propyl bromide, PrBr) where the relative sequence MeBr >> EtBr > PrBr is observed. The higher reactivity towards GSTT1-1 of propylene oxide compared to ethylene oxide is consistent with a higher chemical reactivity. This is corroborated by experimental data of acid-catalysed hydrolysis of a number of aliphatic epoxides, including ethylene oxide and propylene oxide and consistent with semi-empirical molecular orbital modelings.

Animals↗
PubMed1999

Pathological excretion patterns of urinary proteins in renal cell cancer patients exposed to trichloroethylene.

A study was carried out to investigate urinary protein excretion patterns by means of SDS-polyacrylamide-gel-electrophoresis (SDS-PAGE) in renal cell cancer patients who had previously been exposed to high levels of trichloroethylene. Thirty-eight out of 41 (93%) renal cell cancer patients investigated had former extensive trichloroethylene exposure, but only 23 out of 50 (46%) renal cell cancer patients without a history of occupational exposure to trichloroethylene revealed urinary protein patterns indicative of toxic effects on the tubular system. One hundred controls without histories of overt renal disease and not occupationally exposed to trichloroethylene were examined in the same way; only 11 (11%) of them displayed protein excretion patterns indicative of damage to the renal tubule. These results are supported by alpha 1-microglobulin excretion data. The following conclusions are drawn: (1) Substantially more cases of tubular damage are found amongst renal cell carcinoma patients having been exposed to substantial levels of trichloroethylene over many years as compared with renal cell carcinoma patients not exposed to trichloroethylene. (2) The results support the view that chronic tubular damage is a precondition for the nephrocarcinogenic effect of trichloroethylene. (3) The findings indicate that urine protein patterns, on the basis of the SDS-PAGE methodology, represent a 'biological effect parameter' for the medical surveillance of persons occupationally exposed to trichloroethylene.

Aged↗
PubMed1999

Occurrence of urinary tract tumors in miners highly exposed to dinitrotoluene.

Between 1984 and 1997, six cases of urothelial cancer and 14 cases of renal cell cancer occurred in a group of 500 underground mining workers in the copper-mining industry of the former German Democratic Republic, with high exposures to explosives containing technical dinitrotoluene. Exposure durations ranged from 7 to 37 years, and latency periods ranged from 21 to 46 years. The incidences of both urothelial and renal cell tumors in this group were much higher than anticipated on the basis of the cancer registers of the German Democratic Republic by factors of 4.5 and 14.3, respectively. The cancer cases and a representative group of 183 formerly dinitrotoluene-exposed miners of this local industry were interviewed for their working history and grouped into four exposure categories. This categorization of the 14 renal cell tumor cases revealed no dose-dependency concerning explosives in any of the four exposure categories and was similar to that of the representative group of employees, whereas the urothelial tumor cases were predominantly confined to the high-exposure categories. Furthermore, all identified tumor patients were genotyped by polymerase chain reaction, using lymphocyte DNA, regarding their genetic status of the polymorphic xenobiotic metabolizing enzymes, including the N-acetyltransferase 2 and the glutathione-S-transferases M1 and T1. This genotyping revealed remarkable distributions only for the urothelial tumor cases, who were exclusively identified as "slow acetylators." This points to the possibility of human carcinogenicity of dinitrotoluene, with regard to the urothelium as the target tissue.

Aged↗
PubMed1998

Modulation of prostaglandin H synthase-2 mRNA expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin in mice.

Prostaglandin endoperoxide H synthases (PGHS-1 and PGHS-2) catalyze an intermediate step in the biosynthesis of prostaglandins and thromboxanes. Recently, it was observed that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) modulates the expression of PGHS-2 mRNA in different cell lines. The main aim of this study was to examine whether PGHS-2 mRNA expression can be changed by acute TCDD in vivo and, second, we were also interested in whether modulation of PGHS-2 is mediated by the aryl hydrocarbon receptor (AhR) which is known to be involved in the transcriptional control of TCDD-induced phase 1 and phase 2 enzymes. Initially C57BL/6J mice were treated with a single dose of 10,000 ng TCDD/kg and the PGHS-1 and PGHS-2 mRNAs were analyzed in liver, lung, thymus, kidney, and spleen. In all tissues examined the expression of PGHS-1 mRNA was not affected by TCDD. However, TCDD treatment enhanced the PGHS-2 mRNA levels in lung and spleen. No effect of TCDD on PGHS-2 expression was found in liver and kidney. For dose-response studies C57BL/6J and DBA/2J mice were treated for 24 h with various doses of TCDD (1-50,000 ng/kg) and the PGHS-2 mRNA increases were analyzed in lungs and spleens. A significant increase of PGHS-2 mRNA in lungs of C57BL/6J mice was found at a dose of 100 ng TCDD/kg, whereas a nearly 100-fold higher TCDD dose was needed to increase PGHS-2 in DBA/2J mice. A similar dose-dependent induction of PGHS-2 was found in spleens of C57BL/6J mice; however, no significant increase of PGHS-2 was found in spleens of DBA/2 mice. These results indicate an involvement of AhR in TCDD-mediated changes of PGHS-2 expression. This suggestion is supported by studies in AhR-deficient animals which showed that TCDD had no effect on PGHS-2 mRNA. When changes of PGHS-2 mRNA expression are compared with those of CYP1A1 between 4 and 72 h after TCDD, it is noteworthy that TCDD led to a delayed and more transient increase of PGHS-2. These data suggest that the mechanism of modulation of both genes by TCDD may be different.

Animals↗
PubMed1998

Mutagenic properties of 1,2,3,4-tetrahydronaphthaline-1-hydroperoxide, a model compound for organic peroxides in Diesel exhaust.

The genotoxicity of the organic peroxide 1,2,3,4-tetrahydronaphthaline-1-hydroperoxide (or tetraline-1-hydroperoxide, THP) was investigated in the Ames assay without a metabolic activating system using Salmonella typhimurium strains TA 98, TA 100, and TA 102. THP served as a model compound for higher organic peroxides, which can arise from autoxidation of hydrocarbons, e.g. in Diesel exhaust. While THP induced no mutagenic response in S. typhimurium TA 98, it was directly mutagenic in strains TA 100 and TA 102. These data, along with findings on mutagenic properties of other alkyl hydroperoxides, suggest that such compounds deserve further investigation regarding their genotoxic potential and occurrence in the environment.

Models, Chemical↗
PubMed1998

Glutathione transferase T1 and M1 genotype polymorphism in the normal population of Shanghai.

Glutathione transferases are known to be important enzymes in the metabolism of xenobiotics. In humans genetic polymorphisms have been reported for the hGSTM1 and hGSTT1 genes leading to individual differences in susceptibility towards toxic effects, such as cancer. This study describes the distribution of the two polymorphisms of hGSTT1 and hGSTM1 in the normal Chinese population of Shanghai. Out of 219 healthy individuals having been genotyped for GSTT1 and GSTM1, 108 (49%) were identified to be homozygously deficient for the GSTT1 gene and 107 (49%) for the GSTM1 gene.

Adult↗
PubMed1998

Determination of glutathione transferase (GSTT1-1) activities in different tissues based on formation of radioactive metabolites using 35S-glutathione.

A new system has been developed to determine enzyme activities of glutathione transferase theta (GSTT1-1) based on radiometric product detection resulting from the enzymic reaction of methyl chloride with 35S-labelled glutathione. In principle, the method is universally applicable for determination of glutathione transferase activities towards a multiplicity of substrates. The method distinguishes between erythocyte GSTT1-1 activities of human 'non-conjugators', 'low conjugators' and 'high conjugators'. Application to cytosol preparations of livers and kidneys of male and female Fischer 344 and B6C3F1 mice reveals differential GSTT1-1 activities in hepatic and renal tissues. These ought to be considered in species-specific modellings of organ toxicities of chlorinated hydrocarbons.

Animals↗
PubMed1998

Renal cell cancer correlated with occupational exposure to trichloroethene.

A previous cohort-study in a cardboard factory demonstrated that high and prolonged occupational exposure to trichloroethene (C2HCl3) is associated with an increased incidence of renal cell cancer. The present hospital-based case/control study investigates occupational exposure in 58 patients with renal cell cancer with special emphasis on C2HCl3 and the structurally and toxicologically closely related compound tetrachloroethene (C2Cl4). A group of 84 patients from the accident wards of three general hospitals in the same area served as controls. Of the 58 cases, 19 had histories of occupational C2HCl3 exposure for at least 2 years and none had been exposed to C2Cl4; of the 84 controls, 5 had been occupationally exposed to C2HCl3 and 2 to C2Cl4. After adjustment for other risk factors, such as age, obesity, high blood pressure, smoking and chronic intake of diuretics, the study demonstrates an association of renal cell cancer with long-term exposure to C2HCl3 (odds ratio 10.80; 95% CI: 3.36-34.75).

Aged↗
PubMed1997

[Clinical relevance of acetylator phenotyping in 196 urothelial tumor patients].

A total of 196 patients with urothelial tumours were phenotyped for N-acetyltransferase 2 by the molar ratio of two caffeine metabolites excreted in urine. The proportion of "slow" acetylators, who are genetically predisposed to urothelial tumours if they have been exposed to aromatic amines in the past, in the entire group was 55%, within the range in a normal population. Among 40 patients with assumed former occupational exposure to aromatic amines, 65% were "slow" acetylators. Invasiveness, histopathological grading of the urothelial tumour at the time of first diagnosis, and course were not related to acetylator phenotype.

Acetylation↗
PubMed1997

Influence of polymorphisms of GSTM1 and GSTT1 for risk of renal cell cancer in workers with long-term high occupational exposure to trichloroethene.

Suspected nephrocarcinogenic effects of trichloroethene (TRI) in humans are attributed to metabolites derived from the glutathione transferase (GST) pathway. The influence of polymorphisms of GSTM1 and GSTT1 isoenzymes on the risk of renal cell cancer in subjects having been exposed to high levels of TRI over many years was investigated. GSTM1 and GSTT1 genotypes were determined by internal standard controlled polymerase chain reaction. Fourty-five cases with histologically verified renal cell cancer and a history of long-term occupational exposure to high concentrations of TRI were studied. A reference group consisted of 48 workers from the same geographical region with similar histories of occupational exposures to TRI but not suffering from any cancer. Among the 45 renal cell cancer patients, 27 carried at least one functional GSTM1 gene (GSTT1 +) and 18 at least one functional GSTT1 gene (GSTT1 +). Among the 48 reference workers, 17 were GSTM1 + and 31 were GSTT1 +. Odds ratio for renal cell cancer were 2.7 for GSTM1 + individuals (95% CI, 1.18-6.33; P < 0.02) and 4.2 for GSTT1 + individuals (95% CI, 1.16-14.91; P < 0.05), respectively. The data support the present concept of the nephrocarcinogenicity of TRI.

Aged↗
PubMed1997

A note on the physiological background of the ethylene oxide adduct 7-(2-hydroxyethyl)guanine in DNA from human blood.

A newly developed high-performance liquid chromatography (HPLC) method involves derivatization with phenylglyoxal and fluorescence detection, using 7-methylguanine as internal standard. The physiological background of the adduct 7-(2-hydroxyethyl)guanine in DNA isolated from human blood was determined by this method. In five persons the range of the adduct was between 2.1 and 5.8 pmol/mg DNA (mean 3.2). This finding is consistent with previous data obtained by others, using different analytical methods, and points to an intrinsic carcinogenic risk due to endogenous ethylene oxide.

Chromatography, High Pressure Liquid↗
PubMed1996

Differential reactivities of the mono- and di-epoxide of 1,3-butadiene.

The acid-catalysed (perchloric acid) hydrolysis of 1,2-epoxybutene-3 (EB) and of 1,2:3,4-diepoxybutane (DEB), two reactive epoxide metabolites of 1,3-butadiene (BD), was determined based on reaction of unchanged epoxide with 1-nitro-4-pyridyl-benzene (NBP). Related to different epoxide concentrations, both reactions were of first order. Related to different proton concentrations, second-order rate constants were obtained (approximately 10 s-1 M-1 perchloric acid for EB; approximately 0.01 s-1 M-1 perchloric acid for DEB). These data show a much higher chemical stability of DEB compared to EB. Moreover, EB and DEB were reacted at pH 7.2 in 10 mM TRIS buffer with deoxyguanosine (dG), guanosine (G) or calf thymus DNA. The unreacted epoxides (EB or DEB) present in the incubation mixtures with time were determined by gas chromatography. Consistent with the results of the acid-catalysed hydrolysis, the second-order rate constants for reaction with dG, G or DNA were more than 10-fold higher with EB, compared to those with DEB.

Carcinogens↗
PubMed1996

Biological formation of the 1,3-butadiene DNA adducts 7-N-(2-hydroxy-3-buten-1-yl)guanine, 7-N-(1-hydroxy-3-buten-2-yl)guanine and 7-N-(2,3,4-trihydroxy-butyl)guanine.

Male mice (B6C3F1) and male Wistar rats were exposed to [1,4-(14)C] butadiene in a closed all-glass desiccator jar system, and liver DNA was obtained. After acid hydrolysis and HPLC chromatography radioactive 7-N-(1-hydroxy-3-buten-2-yl)guanine and 7-N-(2,3,4-trihydroxybutyl)guanine were identified as radioactive DNA adducts. The same DNA adducts were identified upon incubation of calf thymus DNA, rat liver microsomes, [1,4-(14)C]butadiene and an NADPH-regenerating system. In this system, a third radioactive adduct was found which was identified as 7-N-(2-hydroxy-3-buten-yl)guanine.

Animals↗
PubMed1996

Butadiene and isoprene: future studies and implications.

Based on the symposium on 1,-3-butadiene and isoprene at Blaine, WA, the following areas need special attention for future research: (1) discrepancies in PBPK modelling by different groups should be solved; (2) potential human target tissues (bone marrow, lymphatic tissues) should be better integrated into PBPK models; (3) the present rapid development in research on human genetic interindividual differences in 1,3-butadiene metabolism and toxicity should be supported, with the intention to determine human subgroups of differential susceptibility and to integrate this into epidemiological research; (4) further validation of past exposures in the epidemiologically studied corhorts is very desirable; (5) the question of possibly differential effects in 1,3-butadiene monomer workers and styrene-butadiene-rubber workers (lymphosarcoma?, reticulosarcoma?, leukemia?) should be resolved in future epidemiological studies; (6) potential human target tissues (bone marrow, lymphatic tissues) should be better integrated into PBPK modelling; (7) risk assessment of isoprene and, by quantitative comparison, of 1,3-butadiene in humans should consider the physiological background of endogenous isoprene production; and (8) future research on biomarkers should establish practical tools for medical surveillance of presently exposed persons.

Animals↗
PubMed1996

Quantification of endogenous carcinogens. The ethylene oxide paradox.

Although ethylene oxide is a proven genotoxic carcinogen in experimental animals, its human carcinogenicity is still being debated. Alkylations (hydroxyethylation) of DNA and proteins by ethylene oxide are well established. Ethylene oxide is metabolically formed from ethylene, which is a natural body constituent. Thus, endogenous sources of ethylene/ethylene oxide contribute to background alkylations of physiological macromolecules. There are now experimentally well established data sets on the background hydroxyethylations of the N-terminal valine of hemoglobin and of the 7-N position of guanine in DNA, in laboratory animals as well as in humans: A review of these data leads to the conclusion that these background levels display remarkable consistency between the different species studied and, as far as DNA adducts are concerned, also between different tissues. From the existing database it can be deduced that in rats a hemoglobin alkylation, equivalent to the level of normal background, would be caused by repetitive external atmospheric exposures to ethylene oxide (6 hr/day, 5 days/week for several weeks) of about 30 ppb. On the contrary, in the same species, a DNA alkylation, equivalent to the level of normal background, would be caused by similar repetitive exposures to ethylene oxide at about 1-2 ppm. This paradox is unresolved. It points, however, to the biological importance of endogenous DNA alkylations and questions current regulatory procedures of assessing the risk of minute doses of exogenous carcinogens.

Animals↗