Age-related increases of 8-hydroxy-2'-deoxyguanosine and DNA-protein crosslinks in mouse organs.

Experimental data suggest a possible role of DNA damage in aging, mainly related to oxidative lesions. With the objective of evaluating DNA lesions as molecular biomarkers of aging, we measured 8-hydroxy-2'-deoxyguanosine (8-OH-dG) and DNA-protein crosslinks (DPXL) levels in different organs of mice aged 12 and 24 months. 8-OH-dG was detected by 32P postlabelling after removing unmodified dG by trifluoracetic acid, which prevented the artificial formation of 8-OH-dG during 32P labelling procedures.

Drug metabolism polymorphisms as modulators of cancer susceptibility.

Recently, several molecular genetic bases of polymorphic enzyme activities involved in drug activation and detoxification have been elucidated. Many molecular epidemiology studies based on these premises have sought to gather information on the association of genetically determined metabolic variants with different risks of environmentally induced cancer. While rare alterations of tumor suppressor genes dramatically raise cancer risk for the single affected subjects, far more common and less dramatic differences in genes encoding for drug metabolism enzymes can be responsible for a relatively small, but rather frequent increase of cancer risk at the population level.

Computer-aided analysis of mutagenicity and cell transformation data for assessing their relationship with carcinogenicity.

Using a computer-aided approach, the tests for Salmonella mutagenicity and transformation in established cell lines were compared for the qualitative bases of their carcinogenicity predictions. For this purpose, a database of 145 chemicals was prepared in which rodent carcinogenicity data and results of the Ames' and transformation tests were available. Using a software program for connectivity analysis (previously developed and validated by us), we assayed the molecular structures of these chemicals for the presence of fragments relatable to their positive (i.

Electronic biomedical journals: how they appear and what they offer.

This study, prompted by a number of articles presaging the imminent demise of biomedical journals due to the rise of their electronic spread, analysed 54 Web sites of the journals included in the Oncology section of the Science Citation Index, Journal Citation Reports (1994) and the sites of 10 other leading digitised biomedical journals. The aim was to determine quantitative and qualitative differences in terms of information content existing between the two media. The analysis confirmed that there are limits to the information contained in the scientific journals currently on the Internet and upholds the authors' conclusion that, in the oncology field, the printed journal will continue to have an important role for most individual users for some time.

Methods for predicting carcinogenic hazards: new opportunities coming from recent developments in molecular oncology and SAR studies.

Without epidemiological evidence, and prior to either short-term tests of genotoxicity or long-term tests of carcinogenicity in rodents, an initial level of information about the carcinogenic hazard of a chemical that perhaps has been designed on paper, but never synthesized, can be provided by structure-activity relationship (SAR) studies. Herein, we have reviewed the interesting strategies developed by human experts and/or computerized approaches for the identification of structural alerts that can denote the possible presence of a carcinogenic hazard in a novel molecule. At a higher level of information, immediately below epidemiological evidence, we have discussed carcinogenicity experiments performed in new types of genetically engineered small rodents.

A computerized connectivity approach for analyzing the structural basis of mutagenicity in Salmonella and its relationship with rodent carcinogenicity.

We have applied a new software program, based on graph theory and developed by our group, to predict mutagenicity in Salmonella. The software analyzes, as information in input, the structural formula and the biological activities of a relatively large database of chemicals to generate any possible molecular fragment with size ranging from two to ten nonhydrogen atoms, and detects (as predictors of biological activity) those fragments statistically associated with the biological property investigated. Our previous work used the program to predict carcinogenicity in small rodents.

Lack of significant promoting activity by benzene in the rat liver model of carcinogenesis.

The promoting activity of benzene on rat liver carcinogenesis was investigated. The chemical was tested for its ability to enhance the growth of preneoplastic foci, as detected by gamma-glutamyl transpeptidase (GGT) staining in diethylnitrosamine (DENA) initiated hepatocytes. Two weeks after receiving a single ip dose of 200 mg/kg DENA, F344 rats were given daily oral doses of 400 mg/kg benzene (5 d/wk) for 6 wk.

Molecular fragments associated with non-genotoxic carcinogens, as detected using a software program based on graph theory: their usefulness to predict carcinogenicity.

We assembled 390 chemicals with a structure non-alerting to DNA-reactivity (145 carcinogens and 245 non-carcinogens) for which rodent carcinogenicity data were available. These non-alerting chemicals were defined by the absence in their molecules of DNA-reactive (directly or after metabolic activation) alerting structures, as described by Ashby and coworkers (Mutat. Res.

Genotoxic and non-genotoxic activities of 2,4- and 2,6-diaminotoluene, as evaluated in Fischer-344 rat liver.

Among aminoaromatics, 2,4-diaminotoluene (2,4-DAT) and 2,6-diaminotoluene (2,6-DAT) represent a conflicting couple of isomers; despite showing the same structural alert to DNA reactivity (and thus potential genotoxicity), they are different in terms of carcinogenicity. Of the two, 2,4-DAT alone is a potent rodent carcinogen, the liver being its major target. According to the literature, assays using various short-term genotoxicity tests have not discriminated satisfactorily between the carcinogenic and non-carcinogenic isomer, both chemicals producing overall positive results.

Lack of alachlor induced DNA damage as assayed in rodent liver by the alkaline elution test.

Alachlor was studied in vivo for its capability to induce DNA damage, as evaluated by the alkaline elution test. The experiments were performed in mouse and rat liver after acute or subacute intraperitoneal or per os administrations of the chemical at sublethal dosages. Rat liver was also studied for DNA damage after administration of 2,6-diethylaniline, one of alachlor's major metabolites.

A genotoxicity study on N-acryloyl-N'-phenylpiperazine: implications of aneugenic effects in risk evaluations.

Further to a previous genotoxicity study, we analyzed sister-chromatid exchange (SCE) and DNA-repair induction (V79 and EUE cells in vitro) and DNA damage (rat liver in vivo) with regard to N-acryloyl-N'-phenylpiperazine (AcrNPP), a chemical proposed for biomaterial polymerization which contains an aromatic tertiary amine function in a piperazine cycle. This chemical induced SCEs in a dose-dependent fashion (up to approximately 3.7 times the control value), while it was negative for DNA-repair induction and weakly yet significantly positive for in vivo DNA damage (maximum increase approximately 1.

Genotoxicity analysis of N,N-dimethylaniline and N,N-dimethyl-p-toluidine.

N,N-Dimethylaniline (DMA, CAS No. 121-69-7) and N,N-dimethyl-p-toluidine (DMPT, CAS No. 99-97-8) belong to the N-dialkylaminoaromatics, a chemical class structurally alerting to DNA reactivity.

Non-genotoxic factors in the carcinogenetic process: problems of detection and hazard evaluation.

In the classical two-stage models of carcinogenesis, initiation has been usually related to a DNA-damage/gene-mutation event, while promotion has been related to the non-genotoxic effects of clonal expansion of preneoplastic cells and/or modulation of cell differentiation. It is now clear that the process of carcinogenesis is linked to more than one irreversible alteration in the genome. Likewise, we can envisage that non-genotoxic events can take place after perhaps 0, 1, 2 or more irreversible alterations in the genome.

Genotoxicity of N-acryloyl-N'-phenylpiperazine, a redox activator for acrylic resin polymerization.

N-Acryloyl-N'-phenylpiperazine is a promoter of redox reactions synthesized recently, and proposed as an activator for the polymerization of acrylic resins for biomedical use. The chemical was analyzed for different genotoxicity endpoints, to obtain both information on its possible mutagenic/carcinogenic potential and a model analysis of a tertiary arylamine, which belongs to a class of chemicals commonly used as polymerization accelerators in the biomaterial field. The genotoxicity endpoints considered were: gene mutation in the Salmonella test; structural and numerical chromosome alterations in Chinese hamster V79 cells, evaluated by the micronucleus test together with an immunofluorescent staining specific for kinetochore proteins; in vitro and in vivo DNA damage, evaluated in V79 cells and in mouse liver by the alkaline DNA elution technique.

Examples of uses of databases for quantitative and qualitative correlation studies between genotoxicity and carcinogenicity.

In this paper we give some examples of using databases of genotoxicity and carcinogenicity for quantitative and qualitative correlation studies between short-term tests and carcinogenicity. The quality of the databases is obviously important, but one of the major deficiencies of present databases is that they are too small. Using relatively small, different databases, different results can be obtained.

Are genotoxic carcinogens more potent than nongenotoxic carcinogens?

In this report we have raised the question whether genotoxic carcinogens are more potent than nongenotoxic carcinogens when studied in long-term carcinogenicity assays in rodents. To build a large database of compounds for which both carcinogenicity and genotoxicity had been investigated, we have used a database produced by Gold and co-workers for carcinogenic potency data (975 chemicals) and a database produced by Würgler for genotoxicity data (2834 chemicals). Considering compounds positive or negative in at least three short-term tests and in at least 75% of available tests, we could define 67 genotoxic carcinogens and 46 nongenotoxic carcinogens.

Lack of correlation between alkaline DNA fragmentation and DNA covalent binding induced by polychloroethanes after in vivo administration. Problems related to the assessment of a carcinogenic hazard.

The DNA-damaging activity of polychloroethanes was tested in mouse liver by the fluorometric assay of DNA unwinding. With the exception of 1,2-dichloroethane, all components of this chemical class had negative results. The failure of the parameter alkaline "DNA fragmentation" to detect the DNA-damaging activity of polychloroethanes is in sharp contrast with the measurement of DNA covalent binding, another short-term parameter of genotoxicity.

A rapid method for detecting DNA strand breaks in Mytilus galloprovincialis Lam. induced by genotoxic xenobiotic chemicals.

1. In this study, DNA from haemolymph cells of Mytilus galloprovincialis Lam., as well as from L1210 (murine leukemia) mouse cells was investigated utilizing the technique of the alkaline unwinding of the double stranded DNA molecule.

In vitro transformation of BALB/c 3T3 cells by 1,1,2,2-tetrachloroethane.

1,1,2,2-Tetrachloroethane (1,1,2,2-TTCE) was shown to be capable of inducing in vitro transformation of BALB/c 3T3 cells (clone A-31) either in the presence or in the absence of S9 activating system using an amplification-transformation (level-II) assay by reseeding confluent cells from each treatment and allowing additional rounds of cell replication. In the absence of metabolic activation, the highest assayed dose (1000 micrograms/ml), exerting the highest toxicity, was the only transforming dose. Lower doses of 1,1,2,2-TTCE were capable of transforming BALB/c cells in the presence of S9 activating system, the dose of 500 micrograms/ml exerting the highest transforming activity.

Negative results of short-term genotoxicity tests with 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene.

The phenobarbital-like enzyme inducer and tumor promoter of murine hepatocarcinogenesis, 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene has been assayed in short-term genotoxicity tests, i.e. the Salmonella mutagenicity test, micronucleus and chromosomal aberrations analysis in mouse bone marrow cells in vivo, DNA alkaline elution and DNA unwinding assays in mouse liver in vivo.

Lack of DNA alterations induced by orotic acid in rat liver as evaluated with two DNA unwinding methods.

One percent orotic acid supplemented diet is a promoting treatment in the rat model of liver carcinogenesis. After treatment with this type of diet, DNA alterations were observed using alkaline sucrose gradients and alkaline elution methods. In this work we have utilized two unwinding methods for the detection of DNA fragmentation.

Quantitative predictability of carcinogenicity of the covalent binding index of chemicals to DNA: comparison of the in vivo and in vitro assays.

The capability of covalent binding to DNA to predict the initiating potential of chemical carcinogens was compared for the assays performed in vivo (rodent liver DNA) and in vitro (purified DNA incubated in the presence of mouse and rat liver microsomes). A quantitative correlation between DNA adducts and carcinogenic potency was investigated. The in vivo assay appeared slightly, but not significantly, more predictive than the in vitro assay.

Mutagenicity in V79 cells does not correlate with carcinogenity in small rodents for 12 aromatic amines.

The aim of this investigation was to study the correlation between carcinogenicity in small rodents and mutagenic potency of aromatic amines, as measured by the induction of 6-thioguanine resistance in V79 Chinese hamster cells. It has been previously shown that the carcinogenic potency of these compounds is not correlated to their ability to induce DNA breakage, SCEs, or point mutations in bacteria, but a correlation exists with autoradiographic DNA repair test (in primary hepatocyte cultures). Twelve aromatic amines were tested and the rat liver S9 fraction was routinely incorporated in the mutation assay; mouse liver and hamster liver S9 fractions were also used as metabolizing systems.