36 results on '"Vock E"'
Search Results
2. Chicken egg fetal liver DNA and histopathologic effects of structurally diverse carcinogens and non-carcinogens
- Author
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Iatropoulos, M.J., Kobets, T., Duan, J.-D., Brunnemann, K.D., Vock, E., Deschl, U., and Williams, G.M.
- Published
- 2017
- Full Text
- View/download PDF
3. Letter to the editor
- Author
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Zeller, A., Czich, A., Guérard, M., Honarvar, N., Martus, H.-J., Pfuhler, S., Vock, E., and Kirkland, D.
- Published
- 2022
- Full Text
- View/download PDF
4. Towards the Management of the Development of Product-Service Systems in Business Ecosystems - State-of-the-Art
- Author
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Humbeck, P., primary, Vock, E., additional, and Bauernhansl, T., additional
- Published
- 2019
- Full Text
- View/download PDF
5. 32P-Postlabeling of a DNA adduct derived from 4,4′-methylenedianiline, in the olfactory epithelium of rats exposed by inhalation to 4,4′-methylenediphenyl diisocyanate
- Author
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Vock, E H, Hoymann, H-G, Heinrich, U, Lutz, W K, University of Zurich, and Vock, E H
- Subjects
610 Medicine & health ,1306 Cancer Research ,142-005 142-005 - Abstract
Tissues obtained from female Wistar rats exposed to a 0.9 μm aerosol of 4,4′-methylenediphenyl diisocyanate (MDI) for 17 h per day, 5 days per week, for one year, at levels of 0, 0.3, 0.7 and 2.0 mg/m3, were analyzed for DNA adducts. A 32P-postlabeling method was used to detect (i). adducts formed by the reaction of the isocyanate group(s) of MDI with DNA; and a 32P-postlabeling method was adapted to detect (ii), a DNA adduct formed by 4,4′-methylenedianiline (MDA), a hydrolysis/decarboxylation product of MDI. In the lung, neither isocyanate adducts nor the arylamine adduct were detectable. The same negative result was seen in the liver, the bladder, the kidney, the respiratory epithelium and in peripheral lymphocytes. In the olfactory epithelium, on the other hand, the aryl-amine-derived DNA adduct was detected, at the very low levels of 5, 9 and 10 adduct-nucleotides per 1010 nucleotides, for the three dose groups, respectively. The adduct co-chromatographed with the one formed in the liver of rats after oral gavage of MDA. The results are discussed in terms of the importance of genotoxic versus nongenotoxic aspects of carcinogenesis
- Published
- 2017
6. BioCelerate Toxicology Data Sharing initiative: Development of a centralized, searchable Preclinical Data Repository for the Biopharmaceutical Industry
- Author
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Bjerregaard, T.G., primary, Graziano, M., additional, Vock, E., additional, Kahlbaugh, G., additional, Houser, W., additional, Page, T., additional, Mera, K., additional, Fukushima, T., additional, Kuzumoto, M., additional, and Frahm, S., additional
- Published
- 2018
- Full Text
- View/download PDF
7. Legacy data sharing to improve drug safety assessment
- Author
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Sanz, F., Pognan, F., Steger-Hartmann, T., Díaz, C., Cases, M., Pastor, M., Marc, P., Wichard, J., Briggs, K., Watson, D.K., Kleinöder, T., Yang, C., Amberg, A., Beaumont, M., Brookes, A.J., Brunak, S., Cronin, M.T.D., Ecker, G.F., Escher, S., Greene, N., Guzmán, A., Hersey, A., Jacques, P., Lammens, L., Mestres, J., Muster, W., Northeved, H., Pinches, M., Saiz, J., Sajot, N., Valencia, A., Lei, J. van der, Vermeulen, N.P.E., Vock, E., Wolber, G., Zamora, I., and Publica
- Abstract
The sharing of legacy preclinical safety data among pharmaceutical companies and its integration with other information sources offers unprecedented opportunities to improve the early assessment of drug safety. Here, we discuss the experience of the eTOX project, which was established through the Innovative Medicines Initiative to explore this possibility.
- Published
- 2017
8. Pointwise bounds on eigenfunctions and wave packets inN-body quantum systems IV
- Author
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Deift, P., Hunziker, W., Simon, B., and Vock, E.
- Published
- 1978
- Full Text
- View/download PDF
9. Stability of Schrödinger eigenvalue problems
- Author
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Vock, E. and Hunziker, W.
- Published
- 1982
- Full Text
- View/download PDF
10. Discrimination between genotoxicity and cytotoxicity for the induction of DNA double-strand breaks in cells treated with aldehydes and diepoxides
- Author
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Vock E., Lutz W., Ilinskaya O., and Vamvakas S.
- Subjects
Aldehyde ,Double-strand break ,Diepoxide - Abstract
The time-dependent dose-response relationships for the induction of DNA double-strand breaks (DSB) assessed by pulsed-field gel electrophoresis (PFGE) and for viability (evaluated by the MTT cytotoxicity test) were investigated in order to discriminate between genotoxic and cytotoxic mechanisms of DNA fragmentation. Cultured human lung epithelial cells (A549) were treated (i) with the aldehydes formaldehyde or glutaraldehyde and (ii) with the DNA-DNA interstrand crosslinkers melphalan, diepoxybutane or diepoxyoctane. Induction of DSB by formaldehyde and glutaraldehyde was seen only after cell viability was reduced to less than about 60% of the control values, indicating that DSB were the consequence of extragenomic damage and viability loss. Melphalan, diepoxybutane and diepoxyoctane induced DSB by a genotoxic mode with concentrations that did not affect cell survival: 8 h after treatment initiation both heat-labile crosslinks and DSB could be detected. Cells were not able to repair the crosslinks induced by diepoxybutane, the crosslinker with the shortest chain length. In contrast, with melphalan and diepoxyoctane, which have a longer crosslinking property considerable repair of crosslinks was observed. The molecular size distribution of the produced DNA fragments supported this mechanistic distinction. The DNA fragments generated by diepoxides were initially large, their concentration decreasing monotonously from 7 Mbp to less than 1 Mbp and were converted to smaller fragments by 72 h in the course of cell death. In contrast, DNA fragments induced by formaldehyde peaked below 1 Mbp, implicating activation of DNA-degrading enzymes. Copyright (C) 1999 Elsevier Science B.V.
- Published
- 1999
11. Investigation of the Induction of DNA Double-Strand Breaks by Methylenediphenyl-4,4′-diisocyanate in Cultured Human Lung Epithelial Cells
- Author
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Vock, E, primary
- Published
- 1998
- Full Text
- View/download PDF
12. Anaerobic Desulfonation of 4-Tolylsulfonate and 2-(4-Sulfophenyl) Butyrate by a Clostridium sp
- Author
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Denger, K, primary, Kertesz, M A, additional, Vock, E H, additional, Schon, R, additional, Magli, A, additional, and Cook, A M, additional
- Published
- 1996
- Full Text
- View/download PDF
13. Pointwise bounds on eigenfunctions and wave packets in N-body quantum systems IV.
- Author
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Deift, P., Hunziker, W., Simon, B., and Vock, E.
- Abstract
We describe several new techniques for obtaining detailed information on the exponential falloff of discrete eigenfunctions of N-body Schrödinger operators. An example of a new result is the bound (conjectured by Morgan) $$\left| {\psi (x_1 \ldots x_N )} \right| \leqq C\exp ( - \sum\limits_1^N {\alpha _n r_n )}$$ for an eigenfunction ω of with energy E. In this bound r r... r are the radii | x| in increasing order and the α's are restricted by α<( E− E), where E, for n=0, 1,..., N−1, is the lowest energy of the system described by H. Our methods include subharmonic comparison theorems and 'geometric spectral analysis'. [ABSTRACT FROM AUTHOR]
- Published
- 1978
- Full Text
- View/download PDF
14. Trans- and cis-DNA adduct concentration in epidermis from mouse and rat skin treated ex vivo with benzo[a]pyrene diol epoxide and its corresponding chlorohydrin
- Author
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Vock, E. H., Wolfe, A. R., and Meehan, T.
- Published
- 2001
- Full Text
- View/download PDF
15. Distribution and DNA adduct formation of radiolabeled methylenediphenyl-4,4'-diisocyanate (MDI) in the rat after topical treatment
- Author
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Vock, E. H. and Lutz, W. K.
- Published
- 1997
- Full Text
- View/download PDF
16. 32P-postlabeling of a DNA adduct derived from 4,4'-methylenedianiline, in the olfactory epithelium of rats exposed by inhalation to 4,4'-methylenediphenyl diisocyanate.
- Author
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Vock, E H, Hoymann, H G, Heinrich, U, and Lutz, W K
- Abstract
Tissues obtained from female Wistar rats exposed to a 0.9 microm aerosol of 4,4'-methylenediphenyl diisocyanate (MDI) for 17 h per day, 5 days per week, for one year, at levels of 0, 0.3, 0.7 and 2.0 mg/m(3), were analyzed for DNA adducts. A 32P-postlabeling method was used to detect (i), adducts formed by the reaction of the isocyanate group(s) of MDI with DNA; and a 32P-postlabeling method was adapted to detect (ii), a DNA adduct formed by 4,4'- methylenedianiline (MDA), a hydrolysis/decarboxylation product of MDIV. In the lung, neither isocyanate adducts nor the arylamine adduct were detectable. The same negative result was seen in the liver, the bladder, the kidney, the respiratory epithelium and in peripheral lymphocytes. In the olfactory epithelium, on the other hand, the arylamine-derived DNA adduct was detected, at the very low levels of 5,9 and 10 adduct-nucleotides per 10(10) nucleotides, for the three dose groups, respectively. The adduct co-chromatographed with the one formed in the liver of rats after oral gavage of MDA. The results are discussed in terms of the importance of genotoxic versus nongenotoxic aspects of carcinogenesis.
- Published
- 1996
- Full Text
- View/download PDF
17. Pointwise bounds on eigenfunctions and wave packets in $N$-body quantum systems. IV
- Author
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Deift, P., Hunziker, W., Simon, B., and Vock, E.
- Subjects
81C05 ,35P15 ,81H10 - Published
- 1978
18. ^3^2P-Postlabeling analysis of DNA adducts formed in vitro and in rat skin by methylenediphenyl-4,4'-diisocyanate (MDI)
- Author
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Vock, E. H., Cantoreggi, S., Gupta, R. C., and Lutz, W. K.
- Published
- 1995
- Full Text
- View/download PDF
19. In Silico Prediction of Oral Acute Rodent Toxicity Using Consensus Machine Learning.
- Author
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Schieferdecker S, Rottach F, and Vock E
- Subjects
- Animals, Administration, Oral, Toxicity Tests, Acute, Rodentia, Rats, Mice, Machine Learning, Computer Simulation
- Abstract
Acute oral toxicity (AOT) is required for the classification and labeling of chemicals according to the global harmonized system (GHS). Acute oral toxicity studies are optimized to minimize the use of animals. However, with the advent of the three R
s principles and machine learning in toxicology, alternative in silico methods became a reasonable alternative approach for addressing the AOT of new chemical matter. Here, we describe the compilation of AOT data from a commercial database and the development of a consensus classification model after evaluating different combinations of molecular representations and machine learning algorithms. The model shows significantly better performance compared to publicly available AOT models. Its performance was evaluated on an external validation data set, which was compiled from the literature, and an applicability domain was deduced.- Published
- 2024
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- View/download PDF
20. Mechanisms of Nitrosamine Mutagenicity and Their Relationship to Rodent Carcinogenic Potency.
- Author
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Snodin DJ, Trejo-Martin A, Ponting DJ, Smith GF, Czich A, Cross K, Custer L, Elloway J, Greene N, Kalgutkar AS, Stalford SA, Tennant RE, Vock E, Zalewski A, Ziegler V, and Dobo KL
- Subjects
- Humans, Animals, Mutagens toxicity, Rodentia metabolism, Carcinogenesis, Carbon, Mutagenicity Tests, Carcinogens toxicity, Nitrosamines toxicity, Nitrosamines metabolism
- Abstract
A thorough literature review was undertaken to understand how the pathways of N -nitrosamine transformation relate to mutagenic potential and carcinogenic potency in rodents. Empirical and computational evidence indicates that a common radical intermediate is created by CYP-mediated hydrogen abstraction at the α-carbon; it is responsible for both activation, leading to the formation of DNA-reactive diazonium species, and deactivation by denitrosation. There are competing sites of CYP metabolism (e.g., β-carbon), and other reactive species can form following initial bioactivation, although these alternative pathways tend to decrease rather than enhance carcinogenic potency. The activation pathway, oxidative dealkylation, is a common reaction in drug metabolism and evidence indicates that the carbonyl byproduct, e.g., formaldehyde, does not contribute to the toxic properties of N -nitrosamines. Nitric oxide (NO), a side product of denitrosation, can similarly be discounted as an enhancer of N -nitrosamine toxicity based on carcinogenicity data for substances that act as NO-donors. However, not all N -nitrosamines are potent rodent carcinogens. In a significant number of cases, there is a potency overlap with non- N -nitrosamine carcinogens that are not in the Cohort of Concern (CoC; high-potency rodent carcinogens comprising aflatoxin-like-, N -nitroso-, and alkyl-azoxy compounds), while other N -nitrosamines are devoid of carcinogenic potential. In this context, mutagenicity is a useful surrogate for carcinogenicity, as proposed in the ICH M7 (R2) (2023) guidance. Thus, in the safety assessment and control of N -nitrosamines in medicines, it is important to understand those complementary attributes of mechanisms of mutagenicity and structure-activity relationships that translate to elevated potency versus those which are associated with a reduction in, or absence of, carcinogenic potency.
- Published
- 2024
- Full Text
- View/download PDF
21. eTRANSAFE: data science to empower translational safety assessment.
- Author
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Sanz F, Pognan F, Steger-Hartmann T, Díaz C, Asakura S, Amberg A, Bécourt-Lhote N, Blomberg N, Bosc N, Briggs K, Bringezu F, Brulle-Wohlhueter C, Brunak S, Bueters R, Callegaro G, Capella-Gutierrez S, Centeno E, Corvi J, Cronin MTD, Drew P, Duchateau-Nguyen G, Ecker GF, Escher S, Felix E, Ferreiro M, Frericks M, Furlong LI, Geiger R, George C, Grandits M, Ivanov-Draganov D, Kilgour-Christie J, Kiziloren T, Kors JA, Koyama N, Kreuchwig A, Leach AR, Mayer MA, Monecke P, Muster W, Nakazawa CM, Nicholson G, Parry R, Pastor M, Piñero J, Oberhauser N, Ramírez-Anguita JM, Rodrigo A, Smajic A, Schaefer M, Schieferdecker S, Soininen I, Terricabras E, Trairatphisan P, Turner SC, Valencia A, van de Water B, van der Lei JL, van Mulligen EM, Vock E, and Wilkinson D
- Subjects
- Humans, Data Science, Translational Research, Biomedical
- Published
- 2023
- Full Text
- View/download PDF
22. Acceptable intakes (AIs) for 11 small molecule N-nitrosamines (NAs).
- Author
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Bercu JP, Masuda-Herrera M, Trejo-Martin A, Sura P, Jolly R, Kenyon M, Thomas R, Ponting DJ, Snodin D, Tuschl G, Simon S, De Vlieger K, Hutchinson R, Czich A, Glowienke S, Reddy MV, Johanssen S, Vock E, Claude N, and Weaver RJ
- Subjects
- Animals, Carcinogens, Structure-Activity Relationship, Pharmaceutical Preparations, Nitrosamines toxicity
- Abstract
Low levels of N-nitrosamines (NAs) were detected in pharmaceuticals and, as a result, health authorities (HAs) have published acceptable intakes (AIs) in pharmaceuticals to limit potential carcinogenic risk. The rationales behind the AIs have not been provided to understand the process for selecting a TD
50 or read-across analog. In this manuscript we evaluated the toxicity data for eleven common NAs in a comprehensive and transparent process consistent with ICH M7. This evaluation included substances which had datasets that were robust, limited but sufficient, and substances with insufficient experimental animal carcinogenicity data. In the case of robust or limited but sufficient carcinogenicity information, AIs were calculated based on published or derived TD50 s from the most sensitive organ site. In the case of insufficient carcinogenicity information, available carcinogenicity data and structure activity relationships (SARs) were applied to categorical-based AIs of 1500 ng/day, 150 ng/day or 18 ng/day; however additional data (such as biological or additional computational modelling) could inform an alternative AI. This approach advances the methodology used to derive AIs for NAs., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:There are authors and co-authors employed by pharmaceutical companies., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)- Published
- 2023
- Full Text
- View/download PDF
23. Development of Pharmacophore Models for the Important Off-Target 5-HT 2B Receptor.
- Author
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Schieferdecker S and Vock E
- Subjects
- Molecular Dynamics Simulation, Serotonin 5-HT2 Receptor Agonists pharmacology, Serotonin 5-HT2 Receptor Agonists chemistry, Catalytic Domain, Receptor, Serotonin, 5-HT2B, Serotonin, Pharmacophore
- Abstract
Toxicity is a major cause of attrition in the development of pharmaceuticals, and the off-target effects are a frequent contributor. The 5-HT
2B receptor agonism is known to be responsible for a variety of safety concerns including valvular heart disease which was the cause for the withdrawal of several compounds from the market. An early detection of potential binding to this receptor is thus desirable. Herein, we present the identification of key amino acid residues in the active site of 5-HT2B by molecular dynamics simulations, the development of pharmacophore models and their performance on in-house data, and a structurally highly diverse subset of Enamine REAL labeled for 5-HT2B activity by a machine learning model. These models may be used as filters employed on screening compound sets for the early filtration of compounds with potential 5-HT2B off-target liabilities.- Published
- 2023
- Full Text
- View/download PDF
24. Evaluation of Pharmaceuticals for DNA Damage in the Chicken Egg Genotoxicity Assay (CEGA).
- Author
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Kobets T, Duan JD, Vock E, Deschl U, and Williams GM
- Subjects
- Animals, Comet Assay methods, DNA Adducts, Humans, Mutagenicity Tests methods, Mutagens toxicity, Pharmaceutical Preparations, Chickens, DNA Damage
- Abstract
DNA damage is an established initiating event in the mutagenicity and carcinogenicity of genotoxic chemicals. Accordingly, assessment of this endpoint is critical for chemicals which are being developed for use in humans. To assess the ability of the Chicken Egg Genotoxicity Assay (CEGA) to detect genotoxic pharmaceuticals, a set of 23 compounds with different pharmacological and reported genotoxic effects was tested for the potential to produce nuclear DNA adducts and strand breaks in the embryo-fetal livers using the
32 P-nucleotide postlabeling (NPL) and comet assays, respectively. Due to high toxicity, two aneugens, colchicine and vinblastine, and an autophagy inhibitor, hydroxychloroquine, could not be evaluated. Out of the 20 remaining pharmaceuticals, 10 including estrogen modulators, diethylstilbestrol and tamoxifen, antineoplastics cyclophosphamide, etoposide, and mitomycin C, antifungal griseofulvin, local anesthetics lidocaine and prilocaine, and antihistamines diphenhydramine and doxylamine, yielded clear positive outcomes in at least one of the assays. The antihypertensive vasodilator hydralazine and antineoplastics streptozotocin and teniposide, produced only DNA strand breaks, which were not dose-dependent, and thus, the results with these 3 pharmaceuticals were considered equivocal. No DNA damage was detected for 7 compounds, including the purine antagonist 6-thioguanine, antipyretic analgesics acetaminophen and phenacetin, antibiotic ciprofloxacin, antilipidemic clofibrate, anti-inflammatory ibuprofen, and sedative phenobarbital. However, low solubility of these compounds limited dosages tested in CEGA. Overall, results in CEGA were largely in concordance with the outcomes in other systems in vitro and in vivo, indicating that CEGA provides reliable detection of DNA damaging activity of genotoxic compounds. Further evaluations with a broader set of compounds would support this conclusion.- Published
- 2022
- Full Text
- View/download PDF
25. Genotoxicity Assessment of Drug Metabolites in the Context of MIST and Beyond.
- Author
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Zeller A, Brigo A, Brink A, Guerard M, Lang D, Muster W, Runge F, Sutter A, Vock E, Wichard J, and Schadt S
- Subjects
- Amines metabolism, Animals, Drug-Related Side Effects and Adverse Reactions, Humans, Pharmacokinetics, Risk Assessment, Carcinogens metabolism, Drug Development, Mutagens metabolism, Pharmaceutical Preparations metabolism
- Abstract
While there are dedicated guidelines for industry regarding the assessment of the genotoxic potential of new pharmaceuticals and impurities, and the general safety assessment of major drug metabolites, only limited guidance exists on the assessment of potential genotoxic minor drug metabolites. In this Perspective, we discuss challenges associated with assessing the genotoxic potential of human metabolites and share five case studies within the context of an "aware-avoid-assess" paradigm. A special focus is on a class of potentially genotoxic carcinogens, aromatic amines (arylamines and anilines). This compound class is frequently used as building blocks and may show up as impurities, metabolites, or degradants in pharmaceuticals. We propose several recommendations that should help project teams at different stages of pharmaceutical development. In most cases, proactive interactions with the relevant health authority should be considered to endorse the proposed genotoxicity assessment strategy for minor drug metabolites.
- Published
- 2020
- Full Text
- View/download PDF
26. DNA-damaging activities of twenty-four structurally diverse unsubstituted and substituted cyclic compounds in embryo-fetal chicken livers.
- Author
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Kobets T, Duan JD, Brunnemann KD, Vock E, Deschl U, and Williams GM
- Subjects
- Animals, Comet Assay, DNA Adducts analysis, DNA Breaks, Single-Stranded, Liver chemistry, Liver drug effects, Liver embryology, Molecular Structure, Mutagenicity Tests methods, Specific Pathogen-Free Organisms, Structure-Activity Relationship, Chick Embryo drug effects, DNA Damage, Hydrocarbons, Cyclic toxicity
- Abstract
DNA-damaging activities of twenty-four structurally diverse unsubstituted and substituted cyclic compounds were assessed in embryo-fetal chicken livers. Formation of DNA adducts and strand breaks were measured using the nucleotide
32 P-postlabelling (NPL) and comet assays, respectively. Unsubstituted monocyclic benzene, polycyclic fused ring compound naphthalene, covalently connected polycyclic ring compound biphenyl, and heterocyclic ring compound fluorene did not produce DNA damage. Amino-substituted monocyclic compounds, aniline and p-phenylenediamine, as well as polycyclic 1-naphthylamine were also negative. In contrast, carcinogenic monocyclic methyl-substituted anilines: o-toluidine, 2,6-xylidine, 3,4-dimethylaniline, 4-chloro-o-toluidine; 2 methoxy-substituted methylaniline: p-cresidine; 2,4 and 2,6 diamino- or dinitro- substituted toluenes all produced DNA damage. Genotoxic polycyclic amino-substituted 2-naphthylamine, 4-aminobiphenyl, benzidine, methyl-substituted 3,2'-dimethyl-4-aminobiphenyl and 4-dimethylaminoazobenzene as well as amino- and nitro- fluorenes substituted at the 1 or 2 positions also were positive in at least one of the assays. Overall, the DNA damaging activity of cyclic compounds in embryo-fetal chicken livers reflected the type and position of the substitution on the aromatic ring. Additionally, substituted polycyclic compounds exhibited higher DNA-damaging potency compared to monocyclic chemicals. These results are congruent with in vivo findings in other species, establishing chicken eggs as a reliable system for structure-activity assessment of members of groups of related chemicals., (Copyright © 2019 Elsevier B.V. All rights reserved.)- Published
- 2019
- Full Text
- View/download PDF
27. Expression of Genes Encoding for Xenobiotic Metabolism After Exposure to Dialkylnitrosamines in the Chicken Egg Genotoxicity Alternative Model.
- Author
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Kobets T, Iatropoulos MJ, Duan JD, Brunnemann KD, Iacobas DA, Iacobas S, Vock E, Deschl U, and Williams GM
- Subjects
- Animals, Biotransformation, In Vitro Techniques, Mutagenicity Tests, Nitrosamines chemistry, Nitrosamines metabolism, Ovum metabolism, Xenobiotics chemistry, Xenobiotics metabolism, Animal Testing Alternatives, Chickens, Nitrosamines toxicity, Ovum drug effects, Transcriptome drug effects, Xenobiotics toxicity
- Abstract
The Chicken Egg Genotoxicity Assay (CEGA) demonstrated responsiveness to various DNA-reactive chemicals requiring metabolic activation, which implies broad bioactivation capability. To assess potential metabolic competence, expression profiles of metabolic genes in the embryo-chicken fetal liver were determined using microarray technology. Fertilized chicken eggs were injected under the CEGA protocol with vehicle (deionized water [DW]), the activation-dependent carcinogens, diethylnitrosamine (DEN), and N-nitrosodiethanolamine (NDELA) at doses producing no effect on survival. Previously in CEGA, DEN produced DNA damage, whereas NDELA did not. Expressions of 463 genes known to encode for phase I and II of endo- and xenobiotic metabolism were detected on the array. DW did not affect the expression of the selected genes, deregulating less than 1% of them. In contrast, DEN at 2 mg/egg and NDELA at 4 mg/egg produced significant transcriptomic alterations, up-regulating up to 41% and down-regulating over 31% of studied genes. Both nitrosamines modulated the majority of the genes in a similar manner, sharing 64 up-regulated and 93 down-regulated genes with respect to control group, indicating similarity in the regulation of their metabolism by avian liver. Differences in gene expression between DEN and NDELA were documented for several phase I CYP 450 genes that are responsible for nitrosamine biotransformation, as well as for phase II genes that regulate detoxication reactions. These findings could underlie the difference in genotoxicity of DEN and NDELA in CEGA. In conclusion, the analysis of gene expression profiles in embryo-chicken fetal liver dosed with dialkylnitrosamines demonstrated that avian species possess a complex array of inducible genes coding for biotransformation.
- Published
- 2018
- Full Text
- View/download PDF
28. Legacy data sharing to improve drug safety assessment: the eTOX project.
- Author
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Sanz F, Pognan F, Steger-Hartmann T, Díaz C, Cases M, Pastor M, Marc P, Wichard J, Briggs K, Watson DK, Kleinöder T, Yang C, Amberg A, Beaumont M, Brookes AJ, Brunak S, Cronin MTD, Ecker GF, Escher S, Greene N, Guzmán A, Hersey A, Jacques P, Lammens L, Mestres J, Muster W, Northeved H, Pinches M, Saiz J, Sajot N, Valencia A, van der Lei J, Vermeulen NPE, Vock E, Wolber G, and Zamora I
- Subjects
- Humans, Risk Assessment methods, Drug Evaluation, Preclinical methods, Drug Industry methods, Drug-Related Side Effects and Adverse Reactions, Information Dissemination
- Abstract
The sharing of legacy preclinical safety data among pharmaceutical companies and its integration with other information sources offers unprecedented opportunities to improve the early assessment of drug safety. Here, we discuss the experience of the eTOX project, which was established through the Innovative Medicines Initiative to explore this possibility.
- Published
- 2017
- Full Text
- View/download PDF
29. Chicken fetal liver DNA damage and adduct formation by activation-dependent DNA-reactive carcinogens and related compounds of several structural classes.
- Author
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Williams GM, Duan JD, Brunnemann KD, Iatropoulos MJ, Vock E, and Deschl U
- Subjects
- Animals, Chick Embryo, Comet Assay, DNA Adducts drug effects, Dose-Response Relationship, Drug, Liver embryology, Liver pathology, Single-Cell Analysis, Structure-Activity Relationship, Carcinogens chemistry, Carcinogens toxicity, DNA Damage, Liver drug effects
- Abstract
The chicken egg genotoxicity assay (CEGA), which utilizes the liver of an intact and aseptic embryo-fetal test organism, was evaluated using four activation-dependent DNA-reactive carcinogens and four structurally related less potent carcinogens or non-carcinogens. In the assay, three daily doses of test substances were administered to eggs containing 9-11-day-old fetuses and the fetal livers were assessed for two endpoints, DNA breaks using the alkaline single cell gel electrophoresis (comet) assay and DNA adducts using the (32)P-nucleotide postlabeling (NPL) assay. The effects of four carcinogens of different structures requiring distinct pathways of bioactivation, i.e., 2-acetylaminofluorene (AAF), aflatoxin B1 (AFB1), benzo[a]pyrene (B[a]P), and diethylnitrosamine (DEN), were compared with structurally related non-carcinogens fluorene (FLU) and benzo[e]pyrene (B[e]P) or weak carcinogens, aflatoxin B2 (AFB2) and N-nitrosodiethanolamine (NDELA). The four carcinogens all produced DNA breaks at microgram or low milligram total doses, whereas less potent carcinogens and non-carcinogens yielded borderline or negative results, respectively, at higher doses. AAF and B[a]P produced DNA adducts, whereas none was found with the related comparators FLU or B[e]P, consistent with comet results. DEN and NDELA were also negative for adducts, as expected in the case of DEN for an alkylating agent in the standard NPL assay. Also, AFB1 and AFB2 were negative in NPL, as expected, due to the nature of ring opened aflatoxin adducts, which are resistant to enzymatic digestion. Thus, the CEGA, using comet and NPL, is capable of detection of the genotoxicity of diverse DNA-reactive carcinogens, while not yielding false positives for non-carcinogens., (© The Author 2014. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)
- Published
- 2014
- Full Text
- View/download PDF
30. Use of in silico systems and expert knowledge for structure-based assessment of potentially mutagenic impurities.
- Author
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Sutter A, Amberg A, Boyer S, Brigo A, Contrera JF, Custer LL, Dobo KL, Gervais V, Glowienke S, van Gompel J, Greene N, Muster W, Nicolette J, Reddy MV, Thybaud V, Vock E, White AT, and Müller L
- Subjects
- Computer Simulation, DNA Damage, Drug Contamination, Drug Industry methods, Quantitative Structure-Activity Relationship, Mutagenicity Tests methods, Mutagens chemistry, Mutagens toxicity
- Abstract
Genotoxicity hazard identification is part of the impurity qualification process for drug substances and products, the first step of which being the prediction of their potential DNA reactivity using in silico (quantitative) structure-activity relationship (Q)SAR models/systems. This white paper provides information relevant to the development of the draft harmonized tripartite guideline ICH M7 on potentially DNA-reactive/mutagenic impurities in pharmaceuticals and their application in practice. It explains relevant (Q)SAR methodologies as well as the added value of expert knowledge. Moreover, the predictive value of the different methodologies analyzed in two surveys conveyed in the US and European pharmaceutical industry is compared: most pharmaceutical companies used a rule-based expert system as their primary methodology, yielding negative predictivity values of ⩾78% in all participating companies. A further increase (>90%) was often achieved by an additional expert review and/or a second QSAR methodology. Also in the latter case, an expert review was mandatory, especially when conflicting results were obtained. Based on the available data, we concluded that a rule-based expert system complemented by either expert knowledge or a second (Q)SAR model is appropriate. A maximal transparency of the assessment process (e.g. methods, results, arguments of weight-of-evidence approach) achieved by e.g. data sharing initiatives and the use of standards for reporting will enable regulators to fully understand the results of the analysis. Overall, the procedures presented here for structure-based assessment are considered appropriate for regulatory submissions in the scope of ICH M7., (Copyright © 2013 Elsevier Inc. All rights reserved.)
- Published
- 2013
- Full Text
- View/download PDF
31. Collaborative study on fifteen compounds in the rat-liver Comet assay integrated into 2- and 4-week repeat-dose studies.
- Author
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Rothfuss A, O'Donovan M, De Boeck M, Brault D, Czich A, Custer L, Hamada S, Plappert-Helbig U, Hayashi M, Howe J, Kraynak AR, van der Leede BJ, Nakajima M, Priestley C, Thybaud V, Saigo K, Sawant S, Shi J, Storer R, Struwe M, Vock E, and Galloway S
- Subjects
- Animals, Carcinogens toxicity, Comet Assay methods, Dose-Response Relationship, Drug, Drug Administration Schedule, Liver drug effects, Male, Micronucleus Tests methods, Rats, Rats, Wistar, Toxicity Tests, Mutagens toxicity
- Abstract
A collaborative trial was conducted to evaluate the possibility of integrating the rat-liver Comet assay into repeat-dose toxicity studies. Fourteen laboratories from Europe, Japan and the USA tested fifteen chemicals. Two chemicals had been previously shown to induce micronuclei in an acute protocol, but were found negative in a 4-week Micronucleus (MN) Assay (benzo[a]pyrene and 1,2-dimethylhydrazine; Hamada et al., 2001); four genotoxic rat-liver carcinogens that were negative in the MN assay in bone marrow or blood (2,6-dinitrotoluene, dimethylnitrosamine, 1,2-dibromomethane, and 2-amino-3-methylimidazo[4,5-f]quinoline); three compounds used in the ongoing JaCVAM (Japanese Center for the Validation of Alternative Methods) validation study of the acute liver Comet assay (2,4-diaminotoluene, 2,6-diaminotoluene and acrylamide); three pharmaceutical-like compounds (chlordiazepoxide, pyrimethamine and gemifloxacin), and three non-genotoxic rodent liver carcinogens (methapyrilene, clofibrate and phenobarbital). Male rats received oral administrations of the test compounds, daily for two or four weeks. The top dose was meant to be the highest dose producing clinical signs or histopathological effects without causing mortality, i.e. the 28-day maximum tolerated dose. The liver Comet assay was performed according to published recommendations and following the protocol for the ongoing JaCVAM validation trial. Laboratories provided liver Comet assay data obtained at the end of the long-term (2- or 4-week) studies together with an evaluation of liver histology. Most of the test compounds were also investigated in the liver Comet assay after short-term (1-3 daily) administration to compare the sensitivity of the two study designs. MN analyses were conducted in bone marrow or peripheral blood for most of the compounds to determine whether the liver Comet assay could complement the MN assay for the detection of genotoxins after long-term treatment. Most of the liver genotoxins were positive and the three non-genotoxic carcinogens gave negative result in the liver Comet assay after long-term administration. There was a high concordance between short- and long-term Comet assay results. Most compounds when tested up to the maximum tolerated dose were correctly detected in both short- and long-term studies. Discrepant results were obtained with 2,6 diaminotoluene (negative in the short-term, but positive in the long-term study), phenobarbital (positive in the short-term, but negative in the long-term study) and gemifloxacin (positive in the short-term, but negative in the long-term study). The overall results indicate that the liver Comet assay can be integrated within repeat-dose toxicity studies and efficiently complements the MN assay in detecting genotoxins. Practical aspects of integrating genotoxicity endpoints into repeat-dose studies were evaluated, e.g. by investigating the effect of blood sampling, as typically performed during toxicity studies, on the Comet and MN assays. The bleeding protocols used here did not affect the conclusions of the Comet assay or of the MN assays in blood and bone marrow. Although bleeding generally increased reticulocyte frequencies, the sensitivity of the response in the MN assay was not altered. These findings indicate that all animals in a toxicity study (main-study animals as well as toxicokinetic (TK) satellite animals) could be used for evaluating genotoxicity. However, possible logistical issues with scheduling of the necropsies and the need to conduct electrophoresis promptly after tissue sampling suggest that the use of TK animals could be simpler. The data so far do not indicate that liver proliferation or toxicity confound the results of the liver Comet assay. As was also true for other genotoxicity assays, criteria for evaluation of Comet assay results and statistical analyses differed among laboratories. Whereas comprehensive advice on statistical analysis is available in the literature, agreement is needed on applying consistent criteria., (Copyright © 2010 Elsevier B.V. All rights reserved.)
- Published
- 2010
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32. Discrimination between genotoxicity and cytotoxicity for the induction of DNA double-strand breaks in cells treated with aldehydes and diepoxides.
- Author
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Vock EH, Lutz WK, Ilinskaya O, and Vamvakas S
- Subjects
- Alkylating Agents toxicity, Carcinogenicity Tests, Cell Line, Cell Survival drug effects, Electrophoresis, Gel, Pulsed-Field methods, Epithelial Cells drug effects, Formaldehyde toxicity, Glutaral toxicity, Humans, Lung, Lung Neoplasms, Melphalan toxicity, Mutagenicity Tests, Tumor Cells, Cultured, Aldehydes toxicity, Carcinogens toxicity, DNA Damage, Epoxy Compounds toxicity, Mutagens toxicity
- Abstract
The time-dependent dose-response relationships for the induction of DNA double-strand breaks (DSB) assessed by pulsed-field gel electrophoresis (PFGE) and for viability (evaluated by the MTT cytotoxicity test) were investigated in order to discriminate between genotoxic and cytotoxic mechanisms of DNA fragmentation. Cultured human lung epithelial cells (A549) were treated (i) with the aldehydes formaldehyde or glutaraldehyde and (ii) with the DNA-DNA interstrand crosslinkers melphalan, diepoxybutane or diepoxyoctane. Induction of DSB by formaldehyde and glutaraldehyde was seen only after cell viability was reduced to less than about 60% of the control values, indicating that DSB were the consequence of extragenomic damage and viability loss. Melphalan, diepoxybutane and diepoxyoctane induced DSB by a genotoxic mode with concentrations that did not affect cell survival: 8 h after treatment initiation both heat-labile crosslinks and DSB could be detected. Cells were not able to repair the crosslinks induced by diepoxybutane, the crosslinker with the shortest chain length. In contrast, with melphalan and diepoxyoctane, which have a longer crosslinking property considerable repair of crosslinks was observed. The molecular size distribution of the produced DNA fragments supported this mechanistic distinction. The DNA fragments generated by diepoxides were initially large, their concentration decreasing monotonously from 7 Mbp to less than 1 Mbp and were converted to smaller fragments by 72 h in the course of cell death. In contrast, DNA fragments induced by formaldehyde peaked below 1 Mbp, implicating activation of DNA-degrading enzymes., (Copyright 1999 Elsevier Science B.V.)
- Published
- 1999
- Full Text
- View/download PDF
33. Investigation of the induction of DNA double-strand breaks by methylenediphenyl-4-4'-diisocyanate in cultured human lung epithelial cells.
- Author
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Vock EH, Vamvakas S, Gahlmann R, and Lutz WK
- Subjects
- Aniline Compounds toxicity, Carcinogens toxicity, Cell Nucleus drug effects, Cell Nucleus ultrastructure, Cell Survival drug effects, Cells, Cultured, DNA Fragmentation drug effects, Electrophoresis, Polyacrylamide Gel, Humans, Lung cytology, Melphalan toxicity, Molecular Weight, Octoxynol toxicity, DNA drug effects, DNA Damage drug effects, Epithelial Cells drug effects, Isocyanates toxicity, Lung drug effects
- Abstract
The question was addressed whether methylenediphenyl-4,4'-diisocyanate (MDI), a bifunctional electrophile, can induce DNA double-strand breaks (DSB) by repair of interstrand DNA crosslinks or whether DSB are the result of cell death. Cultured human lung epithelial cells (A549) were treated with MDI, methylene-4,4'-dianiline (MDA; a potential hydrolysis product of MDI), the nitrogen mustard melphalan, and the detergent Triton X-100. All chemicals were dissolved in ethylene glycol dimethyl ether which was added to a cell monolayer covered with phosphate-buffered saline. After 2 h, the treatment solution was exchanged against medium, and 8, 24, and 72 h after treatment initiation, the induction of DNA double-strand breaks was assessed by pulsed-field gel electrophoresis. At the same time, the viability was determined with the MTT test (intracellular reduction of the tetrazolium dye MTT). At the 8-h time point, 1 and 10 microM melphalan induced DSB without concomitant effect on cell viability. With all other chemicals, the dose-response curves for DNA fragmentation and viability were mirror images. Approximate 50% lethal concentrations were 200, 3000, and 100 microM for MDI, MDA, and Triton X-100, respectively. For these chemicals, the observed DSB were the consequence of extragenomic damage in the course of cell death rather than of an interaction with DNA. The mechanistic difference of melphalan was supported by analysis of nuclear morphology. Apoptotic bodies were observed only after melphalan treatment, whereas MDI and Triton X-100 produced only irregular clumping of chromatin (72-h time point). DNA fragment length analysis showed a time-independent pattern, with sizes between 1 and 4 Mbp for melphalan, while MDI, and Triton X-100 induced smaller DNA fragments in a time-dependent manner. It is concluded that DSB observed in cells treated with MDI are unlikely the result of DNA crosslink formation.
- Published
- 1998
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34. Discrimination between genotoxicity and cytotoxicity in the induction of DNA double-strand breaks in cells treated with etoposide, melphalan, cisplatin, potassium cyanide, Triton X-100, and gamma-irradiation.
- Author
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Vock EH, Lutz WK, Hormes P, Hoffmann HD, and Vamvakas S
- Subjects
- Cell Line, Cisplatin toxicity, DNA Fragmentation, Electrophoresis, Gel, Pulsed-Field, Etoposide toxicity, Gamma Rays, Humans, Melphalan toxicity, Octoxynol toxicity, Potassium Cyanide toxicity, Antineoplastic Agents toxicity, DNA Damage, Mutagens toxicity
- Abstract
The dose-response relationships for DNA fragmentation (assessed by pulsed-field gel electrophoresis, PFGE) and for viability (evaluated by measuring the reduction of MTT dye which can be accomplished by viable cells only) were investigated in order to discriminate between genotoxicity and cytotoxicity in the pathogenesis of DNA double-strand breaks (DSB). Cultured human lung epithelial cells (A549) were treated with the DNA-intrastrand crosslinker cisplatin, the DNA-interstrand crosslinker melphalan and the topoisomerase II inhibitor etoposide. The cytotoxic mode of DSB induction was investigated by using the mitochondrial respiratory chain toxin potassium cyanide (KCN) and the detergent Triton X-100. gamma-Irradiation induced a linear dose response for DSB which were efficiently repaired and did not cause reduction in cell survival over a period of 72 h. With etoposide and melphalan a significant increase in DSB was seen 8 h after treatment initiation with concentrations that did not affect cell survival, implicating genotoxicity as the causal event. In contrast, induction of DSB by KCN and Triton X-100, and also by cisplatin, was seen only after cell viability was reduced to less than about 60%, indicating that DSB were the consequence of extragenomic damage. This mechanistic distinction of the two classes was supported by DNA fragment length analysis. In line with a genotoxic mechanism and absence of additional cytotoxic effects, the DNA fragments generated by gamma-irradiation as well as by etoposide and melphalan displayed a distribution between 1 and 4 Mbp with a peak around 2 Mbp. In contrast, DNA fragments induced by Triton X-100 and KCN peaked below 0.5 Mbp, implicating activation of DNA-degrading enzymes. This type of investigation is suggested for the study of chemicals for potential DNA interstrand crosslinking, an important promutagenic type of DNA damage. To avoid false positive results in genetic toxicity testing it is suggested that all assays include a dose-response relationship for both genotoxicity and viability.
- Published
- 1998
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35. On the role of DNA double-strand breaks in toxicity and carcinogenesis.
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Vamvakas S, Vock EH, and Lutz WK
- Subjects
- Animals, Cell Death genetics, Chromosome Aberrations genetics, DNA genetics, DNA radiation effects, DNA Repair genetics, DNA Repair physiology, DNA Topoisomerases, Type I genetics, DNA Topoisomerases, Type I metabolism, Electrophoresis, Homeostasis, Humans, Incidence, Neoplasms chemically induced, Neoplasms epidemiology, Reactive Oxygen Species, Transcription, Genetic drug effects, Transcription, Genetic genetics, Xenobiotics toxicity, Cell Transformation, Neoplastic genetics, DNA drug effects, DNA Damage, Neoplasms genetics
- Abstract
DNA double-strand breaks are associated with various endogenous processes, such as transcription, recombination, replication, and with the process of active cell death, which aims to eliminate cells. In addition, DNA double-strand breaks can be induced by irradiation, exposure to chemicals, increased formation of reactive oxygen species, and, indirectly, during repair of other types of DNA damage or as a consequence of extranuclear lesions. In addition to the neutral filter elution of DNA, the recently introduced pulsed-field gel electrophoresis is capable of determining DNA double-strand breaks with higher accuracy and sensitivity and is expected to increase our knowledge on the frequency and the role of DNA breakage. Parallel determination of parameters for cytotoxicity is necessary to elucidate the causal primary lesion. Although the repair of DNA double-strand breaks is a complex task, cells are capable of repairing--with or without errors and up to a certain extent--and surviving this DNA lesion. Gene translocations, rearrangements, amplifications, and deletions arising during repair and misrepair of double-strand breaks may contribute to cell transformation and tumor development.
- Published
- 1997
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36. 32P-postlabeling analysis of DNA adducts formed in vitro and in rat skin by methylenediphenyl-4,4'-diisocyanate (MDI).
- Author
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Vock EH, Cantoreggi S, Gupta RC, and Lutz WK
- Subjects
- Animals, Autoradiography, Female, In Vitro Techniques, Phosphorus Radioisotopes, Rats, Rats, Wistar, DNA Adducts analysis, Isocyanates metabolism, Skin metabolism
- Abstract
The 32P-postlabeling method was adapted for the detection of DNA adducts formed by methylenediphenyl-4,4'-diisocyanate (MDI). Incubation of the 3'-phosphates of the deoxyribosides of cytosine (C), adenine (A), guanine (G) and thymine (T) with MDI in Tris buffer resulted in the formation of 5, 7, 8, and 2 reaction products, respectively. Incubation of DNA with MDI resulted in detectable levels of 5, 2, and 1 adducts attributable to C, A, and G. Analysis of DNA isolated from the epidermis of rats treated dermally with 9 mg MDI showed an adduct pattern similar to the one seen in the in vitro DNA incubation. A total adduct level of 7 per 10(8) nucleotides was measured, the limit of detection was 2 adducts per 10(10) nucleotides. The data indicate that a minute fraction of MDI can reach DNA in vivo in a chemically reactive form. In comparison with the genotoxic skin carcinogen 7,12-dimethylbenz[a]anthracene on the other hand, the DNA-binding potency of MDI was more than 1000-fold lower.
- Published
- 1995
- Full Text
- View/download PDF
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