Helmut Bartsch

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Journal of Cancer Research and Clinical Oncology, 1991

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Zur Chemie des Phorbols, VI

Zeitschrift für Naturforschung B, 1968

Oxidation of the secondary hydroxyl in phorbol-13,20-diacetate with chromium-trioxide/pyridine yi... more Oxidation of the secondary hydroxyl in phorbol-13,20-diacetate with chromium-trioxide/pyridine yields the diketone phorbol-12-on-13,20-diacetate. The newly introduced carbonyl group is sterically hindered thus allowing for selective reduction of the α„β-unsaturated ketone to give neophorbol-13,20-diacetate, a positional isomer of phorbol-13,20-diacetate in respect to the carbonyl group. By addition of the circular dichroismus of phorbol-13,20-diacetate and neophorbol-13,20-diacetate the dichroism of phorbol-12-on-13,20-diacetate was calculated, indicating that the electronic system of the two carbonyl functions in the latter do not interact. This excludes the existence of the structural unit of an 1,2-diketone in phorbol-12-on-13,20-diacetate. UV-absorption and circular dichroic spectra of derivatives of phorbol esterified or etherified in the 4-position suggest strongly the presence of a tertiary 1,2-ketol group in phorbol. By investigations of the UV-absorption below 200 nm of tet...

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Role of lime in the generation of reactive oxygen species from betel-quid ingredients

Environmental Health Perspectives, 1992

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Mechanisms of fat-related modulation of N-nitrosodiethylamine-induced tumors in rats: organ distribution, blood lipids, enzymes and pro-oxidant state

Carcinogenesis, 1991

Groups of rats, either dosed with N-nitrosodiethylamine (NDEA) for 10 weeks (from the age of 7 to... more Groups of rats, either dosed with N-nitrosodiethylamine (NDEA) for 10 weeks (from the age of 7 to 17 weeks) or untreated, were fed diets containing either 2% (low fat, LF) or 30% polyunsaturated fat (high fat, HF) on an equicaloric basis from 5 weeks until rats were 43 weeks old. Biochemical parameters were measured during and at the end of the experiment in various organs, blood, urine and exhaled air, for correlation with the presence or absence of tumors. The HF diet tended to increase the number of hepatic tumors induced by NDEA, while the number of extrahepatic tumors was higher in rats fed on the LF diet; also the overall tumor incidence was higher in the LF group. In the HF/NDEA group, only two benign extrahepatic tumors were found. Plasma total and free cholesterol and triglyceride concentrations were lower in the HF than the LF group without NDEA treatment. In animals bearing liver and/or extrahepatic tumors all plasma lipid concentrations were lower than in tumor-free animals. Only minor or no changes were detected in blood catalase activity, malondialdehyde level, reduced glutathione (GSH) level or GSH-related enzymes and excretion of thioethers in the urine due to dietary modulation or NDEA. Changes in the liver that were associated with the HF diet were: (i) increased amounts of some polyunsaturated fatty acids and of total phospholipids in liver microsomes; (ii) an enhanced level of lipid peroxidation in liver; (iii) a decrease in liver glutathione levels during NDEA treatment, with a simultaneous adaptive increase in superoxide dismutase levels, and a decrease in renal glutathione levels in both treated and untreated groups; (iv) enhanced microsomal induction of aminopyrine N-demethylase and epoxide hydrolase activities by NDEA, and (v) decreased hexose monophosphate shunt (HMS) activity. All mono-oxygenase activities were lower, and the activities of epoxide hydrolase, UDP-glucuronosyltransferase and HMS were higher, in liver tumors than in non-tumorous liver of similarly-treated rats. Neither diet nor NDEA had a major effect on drug-metabolizing enzyme activities in lung and kidney. HF diet significantly increased ethane exhalation (an indicator of the whole-body pro-oxidant state) over those on the LF diet: in rats on either diet, it was further increased when NDEA was given. Ethane exhalation was still elevated 30 weeks after the cessation of NDEA treatment. Our results suggest an association between the observed changes in biochemical parameters, notably oxidative stress, due to dietary modulation and the altered tumor incidence and organ distribution of tumors induced by NDEA.

Evaluation of DNA damage by the alkaline elution technique in liver, kidneys and lungs of rats and hamsters treated with N-nitrosodialkyl-amines

Carcinogenesis, 1983

Induction of single-strand breaks in the DNA of three organs of BD-VI rats and Syrian golden hams... more Induction of single-strand breaks in the DNA of three organs of BD-VI rats and Syrian golden hamsters was examined 4 h after a single i.p. dose of N-nitrosodimethylamine (DMN) or N-nitrosodiethylamine (DEN). Damage was monitored in vivo by the alkaline elution method, in which DNA is dosed fluorometrically. DNA damage was induced by DMN in the liver and kidneys of rats and in the liver and lungs of hamsters, and by DEN in rat and hamster liver. High doses of the hepatocarcinogen and hepatotoxic compound carbon tetrachloride, did not induce DNA damage in rat liver. A correspondence between DNA fragmentation (our study) and tumour induction (reported in the literature) was found in the following organs: rat and hamster liver (DMN, DEN), rat kidney (DMN), rat lung (DMN, DEN), hamster kidney (DMN, DEN). In contrast, no such correlation was observed in rat kidney and hamster lung following DEN-treatment and in hamster lung following DMN-treatment. Thus, the in vivo alkaline elution assay would appear to be most useful for detecting DNA damage by chemicals that are activated metabolically in the liver and that bind to hepatic DNA.

Genetically based N-acetyltransferase metabolic polymorphism and low-level environmental exposure to carcinogens

Nature, 1994

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Immunohistochemical detection of pulmonary cytochrome P450IA and metabolic activities associated with P450IA1 and P450IA2 isozymes in lung cancer patients

Environmental Health Perspectives, 1992

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Studies on the efficiency of the Salmonella /rat hepatocyte assay for the detection of carcinogens as mutagens: activation of 1,2-dimethyl-hydrazine and procarbazine into bacterial mutagens

Carcinogenesis, 1983

Aflatoxin B1, benzo[a]pyrene, N-nitrosomorpholine, procarbazine (PC) and 1,2-dimethylhydrazine (D... more Aflatoxin B1, benzo[a]pyrene, N-nitrosomorpholine, procarbazine (PC) and 1,2-dimethylhydrazine (DMH) were used to investigate the efficiency of the Salmonella/rat hepatocyte assay for detecting carcinogens as mutagens. In this assay, bacteria and the test compound were co-incubated with freshly isolated rat hepatocytes and then plated onto minimal glucose agar. Factors for optimal mutagenicity, including the number of hepatocytes and the number of bacteria, the type of assay medium and the length of incubation in liquid medium were investigated. All the compounds were metabolized into bacterial mutagens. Mediation of the mutagenicity of PC and DMH by rat hepatocytes indicates that freshly isolated cells of this type are a useful alternative metabolic activation system for use in screening chemicals found to be non-mutagenic in the Salmonella/microsome assay.

Metabolism and urinary excretion of mutagenic metabolites of benzo[a]pyrene in C57 and DBA mice strains

Carcinogenesis, 1984

Groups of C57Bl/6 (B6) mice (responsive) and DBA/2 (D2) (non-responsive) mice received an i.p. do... more Groups of C57Bl/6 (B6) mice (responsive) and DBA/2 (D2) (non-responsive) mice received an i.p. dose of benzo[a]pyrene (BP) (100 mg/kg body weight) with or without pretreatment with beta-naphthoflavone (BNF), an inducer of monooxygenases. The amount of mutagenic BP metabolites in the urine was determined by the Salmonella/microsome assay (strain TA100) and excretion of BP metabolites was quantified by h.p.l.c. After inducer treatment, the responsive mice excreted more mutagens and total oxidized BP metabolites in the urine than did the non-responsive strain. The ratio of BP diols:total oxidized metabolites was 0.42 in B6 mice and 0.72 in D2 mice and was not affected by inducer treatment. After a dose of [14C]BP, radioactivity was measured in the faeces for up to 7 days. The half-life of [14C]BP in the non-responsive D2 mice was about twice that in the responsive B6 mice. Our results agreed with a previously proposed model of the risk factors for toxic effects and/or the development of tumours after exposure to polycyclic aromatic hydrocarbons in responsive and non-responsive mouse strains.

DNA adducts in urothelial cells: Relationship with biomarkers of exposure to arylamines and polycyclic aromatic hydrocarbons from tobacco smoke

International Journal of Cancer, 1996

Markers of exposure to polycyclic aromatic hydrocarbons (urinary 1-hydroxypyrene-glucuronide) and... more Markers of exposure to polycyclic aromatic hydrocarbons (urinary 1-hydroxypyrene-glucuronide) and aromatic amines (4-aminobiphenyl-hemoglobin adducts), as well as urinary mutagenicity, were measured in 47 healthy smokers and 50 nonsmokers. DNA adducts were determined by P32-postlabeling in the exfoliated bladder cells of 39 healthy subjects. Both 1-hydroxypyrene-glucuronide (1-OHPG) and 4-aminobiphenyl adducts (4-ABP-Hb) were associated with smoking habits, but only 4-ABP-Hb adducts were associated with consumption of black, air-cured tobacco. The levels of 2 DNA adducts (numbers 2 and 4) in urothelial cells were clearly associated with 4-ABP-Hb adducts, in all subjects and in smokers. Levels of one of these DNA adducts (number 2) were also associated with 1-hydroxypyrene-glucuronide in urines, but in smokers the association was not statistically significant. Overall, these observations constitute further evidence of a role of arylamines in tobacco-induced bladder cancer.

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Encyclopedia of Cancer, 2011

Modulation by Polyunsaturated Lipid Diets of Nitrosamine-Induced Cancers in Rats: Effects on Prooxidant State and Drug Metabolism

Chemical Carcinogenesis, 1988

Dietary lipids are associated with increased risks for certain types of cancer, especially those ... more Dietary lipids are associated with increased risks for certain types of cancer, especially those of the breast and colon. This enhancing effect has been documented in humans by epidemiological studies1,2,3, as well as by studies in experimental animals4,5,6,7,8. Although the association between dietary lipids and carcinogenesis has been known for a long time, the molecular mechanism by which lipids modulate tumor development remains largely unknown.

Cytochrome P-450 Isozyme Pattern Is Related to Individual Susceptibility to Diethylnitrosamine-induced Liver Cancer in Rats

Japanese Journal of Cancer Research, 1991

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Influence of dietary fatty acid, vegetable, and vitamin intake on etheno-DNA adducts in white blood cells of healthy female volunteers: a pilot study

Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology, 2001

Etheno-DNA adducts such as 1,N(6)-ethenodeoxyadenosine (epsilondA) and N(2),3-ethenodeoxycytidine... more Etheno-DNA adducts such as 1,N(6)-ethenodeoxyadenosine (epsilondA) and N(2),3-ethenodeoxycytidine (epsilondC) are formed as result of oxidative stress and lipid peroxidation via reactive alkenals (J. Nair et al., Mutat. Res., 424:59-69, 1999). High pi-6 polyunsaturated fatty acid intake markedly increased levels of WBCs in female volunteers on a controlled diet (J. Nair et al., Cancer Epidemiol. Biomark. Prev., 6:591-601, 1997). In healthy female volunteers we investigated possible correlations between dietary fatty acid intake (by questionnaire), concentration of linoleic acid (LA) and oleic acid (OA) in serum (n = 34), and etheno-DNA adduct levels in WBC (n = 42). Two groups of samples were selected according to dietary intake >15 g (group A) or <5 g (group B) LA/day. Serum samples were analyzed for free OA and LA by gas chromatography-mass spectroscopy and WBC-DNA for epsilondA and epsilondC adducts by immunoaffinity (32)P postlabeling. On a group level, serum LA and OA con...

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Glutathione S -transferase M1 and T1 null genotypes and the risk of gastric and colorectal cancers

Cancer Letters, 2001

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Vinylidene chloride linked to cancer

Chemical & Engineering News, 1977

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Präventive Onkologie — das Endziel der Bekämpfung bösartiger Erkrankungen

Heidelberger Jahrbücher

Evaluation of the carcinogenicity of chemicals: a review of the Monograph Program of the International Agency for Research on Cancer (1971 to 1977)

Cancer research, 1978

In 1971 the International Agency for Research on Cancer initiated a program on the evaluation of ... more In 1971 the International Agency for Research on Cancer initiated a program on the evaluation of the carcinogenic risk of chemicals to humans, which concentrated on the production of monographs on individual chemicals. A review of this ongoing program is presented here as a contribution to the discussion of primary prevention of cancer. A total of 368 chemicals were evaluated in the first 16 volumes of the International Agency for Research on Cancer monographs. For 26 chemicals (or industrial processes), a positive association between exposure and the occurrence of cancer in humans was observed. For 221 chemicals, some evidence of carcinogenicity was found in at least one species of experimental animals. However, no evaluation of the carcinogenic risk of these chemicals to humans was made, either because no epidemiological studies or case reports were available or because the results of available human studies were inconclusive. For the remaining 121 chemicals, the available data we...

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Nucleophilic selectivity and reaction kinetics of chloroethylene oxide assessed by the 4-(p-nitrobenzyl)pyridine assay and proton nuclear magnetic resonance spectroscopy

Chemico-Biological Interactions, 1990

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Anti-benzo[a]pyrene diolepoxide—DNA adduct levels in peripheral mononuclear cells from coke oven workers and the enhancing effect of smoking

Carcinogenesis, 1995

The level of (+/-)-r-7,t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) bou... more The level of (+/-)-r-7,t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) bound to DNA of lymphocytes plus monocytes in 39 coke oven workers exposed to polycyclic aromatic hydrocarbons (PAH) and 39 non-exposed persons (controls) were investigated, each of the groups consisting of smokers and non-smokers. The adduct level was measured by an improved HPLC/fluorescence method (Rojas, M., Alexandrov, K., van Schooten, F. J., Hillebrand, M., Kriek, E. and Bartsch, H., Carcinogenesis, 15, 557-560, 1994) through the release of the corresponding benzo[a]pyrene (B[a]P) tetrols. The anti-BPDE-DNA adduct was detected in 51% of coke oven workers exposed to PAH and in 18% of the non-exposed (control) subjects. The mean level of anti-BPDE-DNA adducts/10(8) nucleotides in coke oven workers (15.7 +/- 37.8) was approximately 8 times higher than in non-exposed subjects (2.0 +/- 8.7). The interindividual variation of adduct levels was approximately 100-fold in coke oven workers and approximately 50-fold in controls respectively. Smokers in the exposed group had 3.5 times more DNA adducts than non-smokers. With the exception of one non-smoker with very high adduct levels (52.8 adducts/10(8)), the control subjects showed the presence of barely detectable adducts in only 16% of the samples examined. The increased in vivo formation in some smokers and high variability of anti-BPDE-DNA adducts in coke oven workers suggests variations in genetically controlled activation/inactivation reactions of PAH metabolism.

Absract

Journal of Cancer Research and Clinical Oncology, 1991

Download

Zur Chemie des Phorbols, VI

Zeitschrift für Naturforschung B, 1968

Download

Role of lime in the generation of reactive oxygen species from betel-quid ingredients

Environmental Health Perspectives, 1992

Download

Mechanisms of fat-related modulation of N-nitrosodiethylamine-induced tumors in rats: organ distribution, blood lipids, enzymes and pro-oxidant state

Carcinogenesis, 1991

Evaluation of DNA damage by the alkaline elution technique in liver, kidneys and lungs of rats and hamsters treated with N-nitrosodialkyl-amines

Carcinogenesis, 1983

Genetically based N-acetyltransferase metabolic polymorphism and low-level environmental exposure to carcinogens

Nature, 1994

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Immunohistochemical detection of pulmonary cytochrome P450IA and metabolic activities associated with P450IA1 and P450IA2 isozymes in lung cancer patients

Environmental Health Perspectives, 1992

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Studies on the efficiency of the Salmonella /rat hepatocyte assay for the detection of carcinogens as mutagens: activation of 1,2-dimethyl-hydrazine and procarbazine into bacterial mutagens

Carcinogenesis, 1983

Metabolism and urinary excretion of mutagenic metabolites of benzo[a]pyrene in C57 and DBA mice strains

Carcinogenesis, 1984

DNA adducts in urothelial cells: Relationship with biomarkers of exposure to arylamines and polycyclic aromatic hydrocarbons from tobacco smoke

International Journal of Cancer, 1996

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Encyclopedia of Cancer, 2011

Modulation by Polyunsaturated Lipid Diets of Nitrosamine-Induced Cancers in Rats: Effects on Prooxidant State and Drug Metabolism

Chemical Carcinogenesis, 1988

Cytochrome P-450 Isozyme Pattern Is Related to Individual Susceptibility to Diethylnitrosamine-induced Liver Cancer in Rats

Japanese Journal of Cancer Research, 1991

Download

Influence of dietary fatty acid, vegetable, and vitamin intake on etheno-DNA adducts in white blood cells of healthy female volunteers: a pilot study

Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology, 2001

Download

Glutathione S -transferase M1 and T1 null genotypes and the risk of gastric and colorectal cancers

Cancer Letters, 2001

Download

Vinylidene chloride linked to cancer

Chemical & Engineering News, 1977

Download

Präventive Onkologie — das Endziel der Bekämpfung bösartiger Erkrankungen

Heidelberger Jahrbücher