Mutagenic Impact Research Articles

Study on the impact of mutagenic treatment on pollen and spikelet fertility and its relationship in rice (Oryza sativa L.)

The present study was conducted to study the impact of different mutagens on pollen and spikelet fertility. Pollen fertility and spikelet fertility per cent was found to be inversely proportional to increasing dose of the mutagen in all the treatments viz., gamma rays, EMS and its combination treatment. The range of per cent reduction in pollen fertility was observed from 16.67 per cent (100 Gy) to 26.62 per cent (300 Gy) in gamma rays treatment of the seeds. Reduction in pollen fertility due to EMS treatment and its combination treatment ranged from 13.57 per cent reduction (10 mM) to 24.16 per cent reduction (30 mM) and 20.62 per cent reduction (100 Gy + 30 mM) to 31.43 per cent reduction (300Gy + 30 mM) respectively. Spikelet fertility also showed similar relationship in all the treatments. The correlation coefficient between pollen and spikelet fertility was found to be positive and significant. The optimum dose of mutagen was also determined by using pollen and spikelet fertility per cent. The optimum dose was found to be 300 Gy, and 173 Gy + 30 mM for gamma rays and combination treatment respectively. Hence, this proves to be an easy method for determining optimum dose of mutagen.

Impact of RAS mutation subtype on clinical outcome-a cross-entity comparison of patients with advanced non-small cell lung cancer and colorectal cancer.

Mutated RAS onco-proteins are key drivers across many cancers. The distribution of somatic RAS mutations varies between cancer entities. Retrospective analyses have associated some RAS mutations with distinct clinical outcomes. However, the clinical impact of the full spectrum of RAS mutations in their disease contextuality remains to be defined. To improve upon this situation, we studied genomically and clinically annotated, prospectively recruited cohorts of patients with RAS-mutated metastatic lung cancer and colorectal cancer. Mutational spectra were compared with predictions derived from analyzing the mutagenic impact at the genome level for each entity. Interestingly, we found concordance of predicted signatures with those actually observed in our patients. Thus, composition of the functionally active RAS mutational subtypes is primarily determined by the mutagenic context. Most RAS mutations seemed dominant oncogenic drivers with entity-dependent clinical outcomes. RAS comutations were enriched in tumors harboring class 2/3 BRAF mutations, highlighting the functional dependency of some mutated BRAF isoforms on RAS. With our dataset, we established a probabilistic model for cross-entity comparison of the prognostic impact of specific RAS mutational subtypes. The resulting prognostic clusters showed largely consistent clinical categorizations in both entities. This suggests mutant subtype-specific functional properties leading to similar clinical effects. A notable exception is KRAS G12C, which imparted an adverse prognosis only in colorectal cancer. Our findings provide a framework for risk stratification of specific RAS mutations across several cancer entities, which is required to guide the analysis of clinical findings in patients treated with direct RAS inhibitors or agents targeting downstream pathways.

Impact of Mutagens on DNA Replication in Barley Chromosomes.

Replication errors that are caused by mutagens are critical for living cells. The aim of the study was to analyze the distribution of a DNA replication pattern on chromosomes of the H. vulgare ‘Start’ variety using pulse 5-ethynyl-2′-deoxyuridine (EdU) labeling, as well as its relationship to the DNA damage that is induced by mutagenic treatment with maleic hydrazide (MH) and γ ray. To the best of our knowledge, this is the first example of a study of the effects of mutagens on the DNA replication pattern in chromosomes, as well as the first to use EdU labeling for these purposes. The duration of the cell cycle of the Hordeum vulgare ‘Start’ variety was estimated for the first time, as well as the influence of MH and γ ray on it. The distribution of the signals of DNA replication along the chromosomes revealed relationships between DNA replication, the chromatin structure, and DNA damage. MH has a stronger impact on replication than γ ray. Application of EdU seems to be promising for precise analyses of cell cycle disturbances in the future, especially in plant species with small genomes.

Ethyl methane sulphonate induced changes in cyto-morphological and biochemical aspects of Coriandrum sativum L.

Abstract Induced mutagenesis plays a pivotal role in inducing variability among crops where hybridization is too hectic. However, efficiency of mutagen can be estimated by determining its effectiveness in inducing desirable characteristics in a short period in crops having narrow genetic base. Hence, present study has been done to assess the mutagenic impact of Ethyl Methane Sulphonate (EMS) on cytological, morphological and biochemical constituents of Coriandrum sativum L. The results revealed that the higher concentration and treatment duration are toxic in nature whereas lower concentrations of mutagen were quite beneficial in inducing positive characteristics with less toxicity. There was a progressive elevation in the chromosomal aberrations along with variations in morphological traits. The biochemical constituents (photosynthetic pigments and proline) are greatly affected by higher concentrations and durations of EMS treatment. The prominent chromosomal aberrations were stickiness and precocious movement at metaphase and bridges at anaphase while unorientation, scattering, c-metaphase laggards and disturbed polarity were also reported.

Antioxidant and antimicrobial activity of bacteriocin-producing strains of lactic acid bacteria isolated from the human gastrointestinal tract

Background: cancer patients require special attention to maintenance therapy of their organism vital activity. Distribution of nutritional deficiency in cancer patients not only limits the possibilities of application of modern treatment methods, but can also be the direct cause of life-threatening complications and premature death. Objective: to study the use of bioactive peptide complexes with low molecular weight and probiotic strains isolated from the human gastrointestinal tract in food products intended for patients with cancer during their treatment and rehabilitation. Material and Methods: 14 strains of lactic acid bacteria were pre-selected and identified for this study. They were allocated from the gastrointestinal tract of 500 healthy people and people with cancer, who presented different age groups. The study of antagonistic activity of lactic acid bacteria was carried out by using the MRS medium and Lysogeny broth (LB). Biocompatibility study was performed through the co-culture method on solid MRS medium. Results: Research results proved that the isolated metabolites belonged to bacteriocins, as the studied microorganisms were resistant both to their inhibitors and mutually resistant to the single-type synthesized substances. Conclusions. Probiotics have a positive effect on the immune system, as the gastro-intestinal flora they reduce the impact of mutagens and carcinogens.

RESIDENTS OF INDUSTRIAL REGIONS: LONG TERM DYNAMICS OF SPONTANEOUS MUTAGENESIS

The studies shows results of the 10-years research related to the frequency of chromosome aberrations in peripheral blood lymphocytes of North Ossetia inhabitants. The study of cytogenetic indexes in the blood of healthy individuals showed an increase in the average frequency of chromosome aberrations as time passed. The long-term cytogenetic study of North Ossetia residents’ blood showed the growth of medium frequency of aberrant metaphases from 2.07 ± 0.37 to 3.04 ± 0.16 in the group of adults and from 0.5 ± 0.25 to 1.9 ± 0.2 in the groups of children. The most significant increase among all studied cytogenetic indexes in groups of North Ossetia adults and children was in 2009 due to accidental release at one of the metallurgical enterprises in the capital city. All studied groups were characterized by prevailed acentric fragments among chromosome disorders, with an increase of all types of aberrations as time passed. There was a growth in the proportion of chromosome aberrations (adults had an increase of double fragments from 0.20 ± 0.11 to 0.60 ± 0.15 and chromosome exchanges from 0.27 ± 0.15 to 0.64 ± 0.13, children: from 0.13 ± 0.13 to 0.26 ± 0.12 and from 0 to 0.26 ± 0.20 respectively). Sex and smoking factors had no significant effect on the studied samples during the observation period. The 10-year (2002-2011) dynamics analysis of cytogenetic disorders has shown an intensification of mutagenic effects on residents of the republic, which were the most severe after accidental releases in 2009. The results of cytogenetic studies suggest that a mutagenic impact of chemical and radioactive nature takes place.

Enhanced tolerance of Deschampsia antarctica Desv. to the mutagenic effect of cadmium ions

Aim. To study the potential effects of different concentrations of cadmium ions on antarctic plant D. antarctica using PCR analysis. Methods. Plants were grown in vitro on B5 Gamborg and Eveleigh agar medium supplemented with CdCl2. Genetic rearrangements were studied by PCR-analysis using ISSR- and IRAP-primers. Results. Genetically identical plants of D. antarctica obtained by microclonal propagation in vitro were used for the study of mutagenic effect of cadmium ions. The influence of Cd2+ was investigated within the concentration ranging from 0.1 to 10 mM. The results of cultivation of D. antarctica plants in the presence of cadmium ions for 63 days allow to determine the concentration range that does not inhibit the growth of the plants in vitro, and it was up to 1 mM. It was found that toxicant concentrations of 0.1 and 0.2 mM did not cause changes in the profiles of PCR products. After growing the plants with 0.2–1 mM CdCl2 for 17 days, the changes in the profiles of PCR products, indicating the mutagenic impact, were observed at concentrations of 0.6 mM or above; moreover, the number of changes increased in dependence on the concentration of heavy metal. Prolonged influence (140-265 days) of cadmium ions in relatively low concentrations (0.1 mM and 0.4 mM) did not cause detectable mutations. Conclusions. D. antarctica, a plant extremophile, which has evolved mechanisms of resistance to a variety of extreme conditions as a result of adaptation to the existence in the harsh conditions of Antarctica, shows enhanced resistance to cadmium ions in comparison with other species of vascular plants. Inhibition of growth occurs at Cd2+ concentrations of 0.1 mM or above, whereas concentrations of 1 mM or above cause cessation of growth and death of plants. Mutagenic effect on D. antarctica was observed at Cd2+ concentrations of above 0.4 mM. After prolonged growth of plants (for 3–8 months) at cadmium ions concentrations of 0.1–0.4 mM, genetic changes was not found.Keywords: Deschampsia antarctica Desv., plants in vitro obtained by microclonal propagation, cadmium ions, mutagenic effect, PCR-analysis.

A comprehensive survey of the mutagenic impact of common cancer cytotoxics.

BackgroundGenomic mutations caused by cytotoxic agents used in cancer chemotherapy may cause secondary malignancies as well as contribute to the evolution of treatment-resistant tumour cells. The stable diploid genome of the chicken DT40 lymphoblast cell line, an established DNA repair model system, is well suited to accurately assay genomic mutations.ResultsWe use whole genome sequencing of multiple DT40 clones to determine the mutagenic effect of eight common cytotoxics used for the treatment of millions of patients worldwide. We determine the spontaneous mutagenesis rate at 2.3 × 10–10 per base per cell division and find that cisplatin, cyclophosphamide and etoposide induce extra base substitutions with distinct spectra. After four cycles of exposure, cisplatin induces 0.8 mutations per Mb, equivalent to the median mutational burden in common leukaemias. Cisplatin-induced mutations, including short insertions and deletions, are mainly located at sites of putative intrastrand crosslinks. We find two of the newly defined cisplatin-specific mutation types as causes of the reversion of BRCA2 mutations in emerging cisplatin-resistant tumours or cell clones. Gemcitabine, 5-fluorouracil, hydroxyurea, doxorubicin and paclitaxel have no measurable mutagenic effect. The cisplatin-induced mutation spectrum shows good correlation with cancer mutation signatures attributed to smoking and other sources of guanine-directed base damage.ConclusionThis study provides support for the use of cell line mutagenesis assays to validate or predict the mutagenic effect of environmental and iatrogenic exposures. Our results suggest genetic reversion due to cisplatin-induced mutations as a distinct mechanism for developing resistance.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-016-0963-7) contains supplementary material, which is available to authorized users.

Genomic mutational analysis of the impact of the classical strain improvement program on β-lactam producing Penicillium chrysogenum.

BackgroundPenicillium chrysogenum is a filamentous fungus that is employed as an industrial producer of β–lactams. The high β–lactam titers of current strains is the result of a classical strain improvement program (CSI) starting with a wild-type like strain more than six decades ago. This involved extensive mutagenesis and strain selection for improved β–lactam titers and growth characteristics. However, the impact of the CSI on the secondary metabolism in general remains unknown.ResultsTo examine the impact of CSI on secondary metabolism, a comparative genomic analysis of β-lactam producing strains was carried out by genome sequencing of three P. chrysogenum strains that are part of a lineage of the CSI, i.e., strains NRRL1951, Wisconsin 54-1255, DS17690, and the derived penicillin biosynthesis cluster free strain DS68530. CSI has resulted in a wide spread of mutations, that statistically did not result in an over- or underrepresentation of specific gene classes. However, in this set of mutations, 8 out of 31 secondary metabolite genes (20 polyketide synthases and 11 non-ribosomal peptide synthetases) were targeted with a corresponding and progressive loss in the production of a range of secondary metabolites unrelated to β–lactam production. Additionally, key Velvet complex proteins (LeaA and VelA) involved in global regulation of secondary metabolism have been repeatedly targeted for mutagenesis during CSI. Using comparative metabolic profiling, the polyketide synthetase gene cluster was identified that is responsible for sorbicillinoid biosynthesis, a group of yellow-colored metabolites that are abundantly produced by early production strains of P. chrysogenum.ConclusionsThe classical industrial strain improvement of P. chrysogenum has had a broad mutagenic impact on metabolism and has resulted in silencing of specific secondary metabolite genes with the concomitant diversion of metabolism towards the production of β–lactams.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2154-4) contains supplementary material, which is available to authorized users.

Mutagenic Effects of Iron Oxide Nanoparticles on Biological Cells

In recent years, there has been an increased interest in the design and use of iron oxide materials with nanoscale dimensions for magnetic, catalytic, biomedical, and electronic applications. The increased manufacture and use of iron oxide nanoparticles (IONPs) in consumer products as well as industrial processes is expected to lead to the unintentional release of IONPs into the environment. The impact of IONPs on the environment and on biological species is not well understood but remains a concern due to the increased chemical reactivity of nanoparticles relative to their bulk counterparts. This review article describes the impact of IONPs on cellular genetic components. The mutagenic impact of IONPs may damage an organism’s ability to develop or reproduce. To date, there has been experimental evidence of IONPs having mutagenic interactions on human cell lines including lymphoblastoids, fibroblasts, microvascular endothelial cells, bone marrow cells, lung epithelial cells, alveolar type II like epithelial cells, bronchial fibroblasts, skin epithelial cells, hepatocytes, cerebral endothelial cells, fibrosarcoma cells, breast carcinoma cells, lung carcinoma cells, and cervix carcinoma cells. Other cell lines including the Chinese hamster ovary cells, mouse fibroblast cells, murine fibroblast cells, Mytilus galloprovincialis sperm cells, mice lung cells, murine alveolar macrophages, mice hepatic and renal tissue cells, and vero cells have also shown mutagenic effects upon exposure to IONPs. We further show the influence of IONPs on microorganisms in the presence and absence of dissolved organic carbon. The results shed light on the transformations IONPs undergo in the environment and the nature of the potential mutagenic impact on biological cells.

Exposure to estrogen and ionizing radiation causes epigenetic dysregulation, activation of mitogen-activated protein kinase pathways, and genome instability in the mammary gland of ACI rats

The impact of environmental mutagens and carcinogens on the mammary gland has recently received a lot of attention. Among the most generally accepted carcinogenic agents identified as factors that may increase breast cancer incidence are ionizing radiation and elevated estrogen levels. However, the molecular mechanisms of mammary gland aberrations associated with radiation and estrogen exposure still need to be further elucidated, especially the interplay between elevated hormone levels and radiation. Therefore, in the present study, we investigated molecular changes induced in rat mammary gland tissue by estrogen, ionizing radiation, and the combined action of these two carcinogens using a well-established ACI rat model. We found that continuous exposure of intact female ACI rats to elevated levels of estrogen or to both estrogen and radiation resulted in significant hyperproliferative changes in rat mammary glands. In contrast, radiation exposure alone did not induce hyperplasia. Interestingly, despite the obvious disparity in mammary gland morphology, we did not detect significant differences in the levels of genomic methylation among animals exposed to estrogen, radiation, or both agents together. Specifically, we observed a significant global genomic hypomethylation at 6 weeks of exposure. However, by 12 and 18 weeks, the levels of global DNA methylation returned to those of age-matched controls. We also found that combined exposure to radiation and estrogen significantly altered the levels of histone H3 and H4 methylation and acetylation. Most importantly, we for the first time demonstrated that estrogen and radiation exposure caused a significant induction of p42/44 MAPK and p38 pathways that was paralleled by elevated levels of H3S10 phosphorylation, a well-established biomarker of genome and chromosome instability. The precise role of MAPK pathways and their inter-relationship with H3S10 phosphorylation and genome instability in mammary gland tissues needs to be explored further.

Impact of Meat Consumption, Preparation, and Mutagens on Aggressive Prostate Cancer

BackgroundThe association between meat consumption and prostate cancer remains unclear, perhaps reflecting heterogeneity in the types of tumors studied and the method of meat preparation—which can impact the production of carcinogens.MethodsWe address both issues in this case-control study focused on aggressive prostate cancer (470 cases and 512 controls), where men reported not only their meat intake but also their meat preparation and doneness level on a semi-quantitative food-frequency questionnaire. Associations between overall and grilled meat consumption, doneness level, ensuing carcinogens and aggressive prostate cancer were assessed using multivariate logistic regression.ResultsHigher consumption of any ground beef or processed meats were positively associated with aggressive prostate cancer, with ground beef showing the strongest association (OR = 2.30, 95% CI:1.39–3.81; P-trend = 0.002). This association primarily reflected intake of grilled or barbequed meat, with more well-done meat conferring a higher risk of aggressive prostate cancer. Comparing high and low consumptions of well/very well cooked ground beef to no consumption gave OR's of 2.04 (95% CI:1.41–2.96) and 1.51 (95% CI:1.06–2.14), respectively. In contrast, consumption of rare/medium cooked ground beef was not associated with aggressive prostate cancer. Looking at meat mutagens produced by cooking at high temperatures, we detected an increased risk with 2-amino-3,8-Dimethylimidazo-[4,5-f]Quinolaxine (MelQx) and 2-amino-3,4,8-trimethylimidazo(4,5-f)qunioxaline (DiMelQx), when comparing the highest to lowest quartiles of intake: OR = 1.69 (95% CI:1.08–2.64;P-trend = 0.02) and OR = 1.53 (95% CI:1.00–2.35; P-trend = 0.005), respectively.DiscussionHigher intake of well-done grilled or barbequed red meat and ensuing carcinogens could increase the risk of aggressive prostate cancer.

Families of transposable elements, population structure and the origin of species

BackgroundEukaryotic genomes harbor diverse families of repetitive DNA derived from transposable elements (TEs) that are able to replicate and insert into genomic DNA. The biological role of TEs remains unclear, although they have profound mutagenic impact on eukaryotic genomes and the origin of repetitive families often correlates with speciation events. We present a new hypothesis to explain the observed correlations based on classical concepts of population genetics.Presentation of the hypothesisThe main thesis presented in this paper is that the TE-derived repetitive families originate primarily by genetic drift in small populations derived mostly by subdivisions of large populations into subpopulations. We outline the potential impact of the emerging repetitive families on genetic diversification of different subpopulations, and discuss implications of such diversification for the origin of new species.Testing the hypothesisSeveral testable predictions of the hypothesis are examined. First, we focus on the prediction that the number of diverse families of TEs fixed in a representative genome of a particular species positively correlates with the cumulative number of subpopulations (demes) in the historical metapopulation from which the species has emerged. Furthermore, we present evidence indicating that human AluYa5 and AluYb8 families might have originated in separate proto-human subpopulations. We also revisit prior evidence linking the origin of repetitive families to mammalian phylogeny and present additional evidence linking repetitive families to speciation based on mammalian taxonomy. Finally, we discuss evidence that mammalian orders represented by the largest numbers of species may be subject to relatively recent population subdivisions and speciation events.Implications of the hypothesisThe hypothesis implies that subdivision of a population into small subpopulations is the major step in the origin of new families of TEs as well as of new species. The origin of new subpopulations is likely to be driven by the availability of new biological niches, consistent with the hypothesis of punctuated equilibria. The hypothesis also has implications for the ongoing debate on the role of genetic drift in genome evolution.ReviewersThis article was reviewed by Eugene Koonin, Juergen Brosius and I. King Jordan.

Mutagenic impact on fish of runoff events in agricultural areas in south-west France

When heavy rainfall follows herbicide application, the intense surface runoff causes stream water contamination. Aquatic organisms are then briefly exposed to a complex mixture of contaminants. The aim of the present study is to investigate the genotoxic impact of such events on fish. A model fish, the Crucian carp ( Carassius carassius) was exposed in controlled conditions, for 4 days, to water sampled daily in the Save River (France). The watershed of this stream is representative of agricultural areas in south-west France. Three hydrological conditions were compared: basal flow, winter flood, and spring flood. Chemical analysis of the water samples confirmed the higher contamination of the spring flood water, mainly explained by a peak of metolachlor. Genotoxicity was evaluated by micronucleus (MN) test and comet assay in peripheral erythrocytes. A significant increase in DNA breakdowns compared to controls was detected by the comet assay for all conditions. Exposure to spring flood water resulted in the highest damage induction. Moreover, induced chromosomal damage was only detected in this condition. In addition, fish were exposed, for 4 days, to an experimental mixture of 5 herbicides representative of the spring flood water contamination. Fish exhibited moderate DNA damage induction and no significant chromosomal damage. The mutagenicity induced by field-collected water is then suspected to be the result of numerous interactions between contaminants themselves and environmental factors, stressing the use of realistic exposure conditions. The results revealed a mutagenic impact of water contamination during the spring flood, emphasizing the need to consider these transient events in water quality monitoring programs.

Genotoxic and Mutagenic Potential of Agricultural Soil Irrigated with Tannery Effluents at Jajmau (Kanpur), India

It is a common practice in India to irrigate agricultural fields with wastewater originating from industries and domestic sources. At Jajmau (Kanpur), India, tannery effluent is used for irrigation purposes. This practice has been polluting the soil directly and groundwater and food crops indirectly. This study is aimed at evaluating the mutagenic impact of soil irrigated with tannery effluent. Soil extracts were prepared using four organic solvents (dichloromethane, methanol, acetonitrile, and acetone) and tested with Ames Salmonella/microsome test and DNA repair-defective E. coli k-12 mutants. Gas Chromatography-mass spectrometric analysis of soil samples revealed the presence of a large number of organic compounds including bis(2-ethylhexyl)phthalate, benzene, 1,3-hexadien-5-yne, 2,4-bis(1,1-dimethyl)phenol, Docosane, 10-methylnonadecane, and many higher alkanes. The soil extracts exhibited significant mutagenicity with Ames tester strains. TA98 was found to be the most sensitive strains to all the soil extracts, producing maximum response in terms of mutagenic index of 14.2 (-S9) and 13.6 (+S9) in the presence of dichloromethane extract. Dichloromethane-extracted soil exhibited a maximum mutagenic potential of 17.3 (-S9) and 20.0 (+S9) revertants/mg soil equivalent in TA100. Methanol, acetonitrile, and acetone extracts were also found to be mutagenic. A significant decline in the survival of DNA repair-defective E. coli K-12 mutants was observed compared to their isogenic wild-type counterparts when treated with different soil extracts. PolA mutant was found to be the most sensitive strain toward all four soil extracts.

Comparing the mutagenicity of toxaphene after aging in anoxic soils and accumulating in fish

A test program was conducted to evaluate the mutagenicity of toxaphene residuals extracted from aged soils and from fish collected in creeks near a toxaphene-contaminated site. The ultimate objective was to determine if the residual toxaphene congeners were more or less mutagenic than those in technical-grade toxaphene. The study showed that the mutagenicity of the bioaccumulated toxaphene congeners in fish, expressed as colony revertants per μg of residual toxaphene, was no greater than that of technical-grade toxaphene. The mutagenic impact of the toxaphene residuals in aged soil statistically was less than that for technical-grade toxaphene. Two specific congeners, a hexachlorobornane (labeled Hx-Sd) and a heptachlorobornane (labeled Hp-Sd), were found to accumulate over time in both soil and fish extracts, but did not show increased mutagenic impacts relative to that produced by technical-grade toxaphene.

Genotoxic effects of myosmine in human lymphocytes and upper aerodigestive tract epithelial cells.

Myosmine, 3-(1-pyrroline-2-yl)pyridine, is an alkaloid found in tobacco plants. Recently, it was also detected in various edibles and staple foods. Whereas other tobacco alkaloids such as nicotine and nornicotine and their nitrosation products, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN), have been widely discussed, the mutagenic impact of myosmine has not been investigated in detail. In the present study, possible genotoxic effects of myosmine were studied in human lymphocytes and nasal mucosal cells using the alkaline single cell microgel electrophoresis (Comet) assay. DNA single strand breaks, alkali labile sites and incomplete excision repair sites were expressed using the Olive tail moment (OTM). One hour incubation with myosmine at 0, 5, 10, 25 and 50 mM induced a low but significantly dose-dependent increase of DNA migration from 1.29 +/- 0.13 to 18.25 +/- 1.59 (OTM, mean +/- S.E., N=11) in lymphocytes. In nasal mucosal cells a similar although somewhat less extensive DNA damage from 1.17 +/- 0.12 to 21.67 +/- 2.97 (OTM, mean +/- S.E., N=10-11) was obtained after 1 h incubation with myosmine at 0, 10, 25, 50 and 100 mM. After prolonged incubation of human lymphocytes with 10mM myosmine for 1, 3, 6, and 24 h, a significant time-dependent increase of DNA migration from 3.45 +/- 0.43 to 57.77 +/- 8.24 (OTM, mean +/- S.E., N=4) was observed. Our data indicate that myosmine expresses significant genotoxic effects in human target cells of carcinogenesis. This result warrants further investigations on the impact of this dietary component on human health.

Evaluation of the genotoxic and teratogenic potential of a municipal sludge and sludge-amended soil using the amphibian Xenopus laevis and the tobacco: Nicotiana tabacum L. var. xanthi Dulieu

The toxic, genotoxic and teratogenic potential of a municipal sewage sludge was assessed using the micronucleus assay on the larvae of the amphibian Xenopus laevis and with the tobacco somatic mutation test using the yellow–green xanthi Dulieu mutant a 1 +/ a 1 a 2 +/ a 2. The teratogenic potential was assessed by means of the Frog Embryo Teratogenesis Assay-Xenopus (FETAX). Various doses of the pasty sludge added to a crop soil were tested using the three bioassays. The test systems were performed either directly with sludge or sludge-amended soil samples (plant model) or with aqueous extracts (aquatic animal model). Using the tobacco model, we found no mutagenic impact of the soil amended with the sludge, perhaps because the clay-like nature of the soil, with its high adsorption capacity, may have prevented the contaminants from reaching the target. All leachates of amended soils produced a significant size reduction in Xenopus embryos. Depending on the soil/sludge ratio, some leachates were found to be genotoxic but were never teratogenic. This battery of in vivo test systems enabled us to estimate the global long-term effects under agricultural conditions with various genetic endpoints on ecologically relevant organisms characteristic of the aquatic and terrestrial compartments.

Coupling of enhancer and insulator properties identified in two retrotransposons modulates their mutagenic impact on nearby genes.

We recently reported a novel transposition system in which two retroelements from Drosophila melanogaster, ZAM and Idefix, are highly mobilized and preferentially insert within intergenic regions. Among the loci where new copies are detected, a hot spot for their insertion was identified at the white locus, where up to three elements occurred within a 3-kb fragment upstream of the transcriptional start site of white. We have used these insertions as molecular entry points to throw light on the mutagenic effect exerted by multiple insertions of retrotransposons within intergenic regions of a genome. Analysis of the molecular mechanisms by which ZAM and Idefix elements interfere with the regulation of the white gene has shown that ZAM bears cis-acting regulatory sequences able to enhance transcription of the white gene in the eyes of the flies. This activation may be counteracted by Idefix, which acts as an insulator able to isolate the white gene from the upstream ZAM enhancer. In addition to revealing a novel insulator sequence with its own specific features, our data clearly illustrate how retroelements can act as epigenetic factors able to interfere with the transcriptional regulation of their host.

Analysis of point mutations in the hprt gene of cancer patients treated with radioimmunoglobulin therapy.

The mutagenic impact of various environmental and therapeutic agents can now be directly assayed in humans by the T-lymphocyte cloning assay. We have previously reported that following radioimmunoglobulin therapy, cancer patients exhibited increased mutant frequency of the hprt locus and an increased yield of large intergenic deletions compared to unexposed controls. Here we report the results of the analysis of 26 independent hprt mutations in nine cancer patients who underwent radioimmunoglobulin therapy. The majority of mutations (52%) had lost exon sequences from the mRNA. The remaining mutations were 20% small deletions and frameshifts and 28% base substitutions. The type of mutations observed were similar to those seen in unexposed controls. The site distribution of the mutations, however, indicates that some sequence contexts may be more sensitive to radiation mutagenesis than others.