Biomedical subjects

R Marcos

Publications and source records attributed to R Marcos.

At least 37 records · Page 2Linked to original sources

PubMed2000

Use of the Drosophila wing spot test in the genotoxicity testing of different herbicides.

Four herbicides, namely propanil, maleic hydrazide, glyphosate, and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), were investigated for genotoxicity in the wing spot test of Drosophila melanogaster. The herbicides were administered by chronic feeding to 3-day-old larvae. Two different crosses, a standard (ST) and a high-bioactivation (HB) cross, involving the flare-3 (flr(3)) and the multiple wing hairs (mwh) markers, were used. The HB cross uses flies characterized by an increased cytochrome P-450-dependent bioactivation capacity, which permits a more efficient biotransformation of promutagens and procarcinogens. In both crosses, the wings of the two types of progeny, which are inversion-free marker heterozygotes and balancer heterozygotes, were analyzed. Maleic hydrazide and glyphosate proved to be more genotoxic in the ST cross, whereas propanil appeared to be slightly more genotoxic in the HB cross. On the other hand, the herbicide 2,4,5-T increased the mutation frequency for only the small single spots in the ST cross.

2,4,5-Trichlorophenoxyacetic Acid↗

PubMed1999

Genotoxicity and radioresistance in electroplating workers exposed to chromium.

A biomonitoring study was carried out to investigate the genetic risk associated to occupational exposure to chromium. The induction of genetic damage was measured by analysing the frequency of micronuclei (MN) in peripheral blood lymphocytes. In addition to the 40 electroplater exposed workers who participated in the study, a group constituted by 18 volunteer donors, without exposure to chromium, was analysed as a control group. Measures of chromium levels at working place and in erythrocytes and urine were obtained, as indicators of exposure. The results from this study indicate that the blood from exposed workers contained higher levels of chromium, when compared with those obtained in the control group, and that a significant increase in the frequency of both the total number of MN and the number of binucleated cells carrying MN (BNMN) was detected. Furthermore, a good direct relationship was obtained between the amount of chromium present in air, erythrocytes or urine and the frequency of MN. To determine the existence of radioresistance as consequence of chromium exposure, the response of lymphocytes to the in vitro gamma-radiation was studied. The results of this experiment show a lower induction in the increase of the frequency of MN after challenge irradiation in the lymphocytes of chromium exposed workers, which should be indicative of an adaptive response.

Adaptation, Physiological↗

PubMed1999

Analysis of genomic damage in the mutagen-sensitive mus-201 mutant of Drosophila melanogaster by arbitrarily primed PCR (AP-PCR) fingerprinting.

DNA repair mechanisms are important to maintain the stability of the genome. In Drosophila melanogaster, the mus-201 gene is required in the excision repair process. To study the contribution of the mus-201 gene in the stability of the Drosophila genome, we have used the arbitrarily primed PCR fingerprinting method (AP-PCR). We have analysed the changes in the genomic DNA fingerprints from the progeny of wild-type males crossed with mus-201 repair-deficient or repair-proficient females. After induction of DNA damage with 2-acetylaminofluorene (2-AAF) in the wild-type parental males, quantitative and qualitative differences in the AP-PCR fingerprints were detected between the two crosses, and the estimate of the genomic damage detected by AP-PCR has clearly shown that the mus-201 repair deficiency is associated with an increase of genomic damage. The predominant type of alterations detected by AP-PCR under the mus-201 repair-deficient conditions agree with the results obtained in microsatellite PCR analysis, suggesting that the role of the mus-201 gene, necessary in excision repair, is not associated to the mismatch repair process. The work reported here demonstrates that the AP-PCR is a suitable technique to analyse genetic alterations in D. melanogaster and, consequently, can be used to compare the susceptibility to genomic damage of different DNA repair mutants.

2-Acetylaminofluorene↗

PubMed1999

Evaluation of DNA damage by the Comet assay in shoe workers exposed to toluene and other organic solvents.

The alkaline single-cell gel electrophoresis (or Comet) assay was applied to evaluate DNA damage in cryopreserved peripheral blood mononuclear leukocytes from 34 female shoe workers exposed to organic solvents and a group of 19 non-exposed women. We also investigated whether the polymorphisms of glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) genes affect individual level of DNA damage possibly induced by the solvent exposure. Chemical measurements of workplace air in the two factories studied showed that the workers were exposed to acetone, gasoline, and toluene in both factories and to ethylacetate and diisocyanate in one factory. In the exposed workers, the average level of blood hemoglobin was lower and that of urinary hippuric acid higher than in the non-exposed individuals. However, the occupational exposure to organic solvents did not affect the Comet values. Neither did age, smoking, or the GSTM1 genotype have any effect on the outcome of this assay. The low prevalence of the GSTT1-null genotype precluded conclusions on the influence of GSTT1 polymorphism.

Acetates↗

PubMed1999

Genotoxic evaluation of the antimicrobial drug, trimethoprim, in cultured human lymphocytes.

The antimicrobial drug, trimethoprim, was evaluated for genotoxicity in human peripheral blood lymphocyte cultures set-up from two healthy donors. Sister-chromatid exchanges (SCE) and micronuclei (MN) were scored as genetic endpoints. The treatment was done using different trimethoprim concentrations ranging from 1 to 100 microg/ml. From our results, we can conclude that this drug is able to induce both cytotoxic and moderate genotoxic effects, as revealed by the increases seen in SCE and MN frequencies in cultures from the two donors and, at least, at one of the concentrations tested.

Anti-Infective Agents, Urinary↗

PubMed1999

Low persistence of radiation-induced centromere positive and negative micronuclei in cultured human cells.

The micronucleus (MN) assay is widely used both in genetic toxicology and in the biomonitoring of human populations. Lymphocytes, cell lines, and bone marrow and epithelial cells are usually employed as target systems in such studies. However, little effort has been done to assess the persistence of MN in highly proliferative cells. To study the behaviour of MN containing whole chromosomes or acentric fragments, we have performed a time course experiment on the persistence of gamma-ray (3 Gy) induced MN in a human lymphoblastoid cell line. The frequency and content of MN were analyzed 1, 3, 7, 14, and 56 days after irradiation by pancentromeric fluorescence in situ hybridization (FISH). We observed a clear induction of both centromere positive and negative MN at completion of the first mitotic division. The frequency of both types of MN drastically declined to basal levels 7 days after irradiation with an identical kinetics. We therefore conclude that centromere positive and negative MN are highly unstable upon cell division, indicating that the MN assay could not be a good biomarker of DNA damage induced by acute treatments in highly proliferative cells. The implication of our findings in biomonitoring and in genotoxicity studies is discussed.

Apoptosis↗

PubMed1999

Examination of various biomarkers measuring genotoxic endpoints from Barcelona airport personnel.

Three different biomarkers: sister-chromatid exchanges (SCE), micronuclei (MN), and the Comet assay, were used to evaluate different kinds of genetic damage in peripheral blood lymphocytes from 34 male workers at Barcelona airport, exposed to low levels of hydrocarbons and jet fuel derivatives. The control group consisted of 11 unexposed men. We also investigated the ras p21 protein levels in plasma, in order to evaluate whether the ras gene could serve as a suitable potential marker of carcinogenic pollution in occupationally exposed cohorts. SCE and MN analyses failed to detect any statistically significant increase in the airport workers when compared with the controls, and in fact, the frequency of binucleated cells with MN in the exposed group was significantly lower than that obtained in the control. However, slight but significant differences in the mean comet length and genetic damage index were observed between the exposed and control groups when using the Comet assay. There were no statistically significant differences between both groups in p21 plasma levels. Smoking was shown to affect significantly both SCE and high frequency cells (HFC) in the exposed group.

Air Pollutants↗

PubMed1999

Analysis of bleomycin- and cytosine arabinoside-induced chromosome aberrations involving chromosomes 1 and 4 by painting FISH.

The genomic frequency of chromosomal aberrations obtained by chromosome painting is usually extrapolated from the observed frequency of aberrations by correcting for the DNA content of the labelled chromosomes. This extrapolation is based upon the assumption of random distribution of breakpoints from which aberrations are generated. However, the validity of this assumption has been widely questioned. While extensive investigations have been performed with ionizing radiation as chromosome breaking agent, little efforts have been done with chemical clastogens. In order to investigate interchromosomal differences in chemically-induced chromosome damage, we have used multicolour chromosome painting to analyse bleomycin-induced aberrations involving chromosomes 1 and 4, two chromosomes that differ in gene density. In addition, we have measured the effect of cytosine arabinoside upon the repair of bleomycin-induced DNA damage in chromosomes 1 and 4. Our results show that these chromosomes are equally sensitive to the clastogenic effect of bleomycin with a similar linear dose-effect relationship. However, the high gene density chromosome 1 appeared to be more sensitive to repair inhibition by Ara-C than chromosome 4. This enhanced sensitivity to repair inhibition in chromosome 1 could be mediated by preferential repair of open chromatin and actively transcribed regions.

Adult↗

PubMed1999

Genotoxic activity of different chromium compounds in larval cells of Drosophila melanogaster, as measured in the wing spot test.

Two chromium(VI) compounds (potassium chromate and potassium dichromate) and one chromium(III) compound, chromium chloride, were evaluated for genotoxic effects in the wing spot test of Drosophila melanogaster following standard procedures. This assay detects both somatic recombination and mutational events. The genotoxic effects were determined from the appearance of wing spots in flies transheterozygous for the third chromosome recessive markers multiple wing hairs (mwh) and flare-3 (flr(3)), as well as in flies heterozygous formwh and the multiply inverted TM3 balancer chromosome. Genetic changes induced in somatic cells of the wing's imaginal discs lead to the formation of mutant clones on the wingblade. Single spots are due to different genotoxic mechanisms: point mutation, deletion, chromosome breakage, and mitotic recombination; while twin spots are produced only by mitotic recombination. From our results it appears that both chromium(VI) compounds clearly increase the incidence of mutant clones by inducing high increases in the frequency of all types of clones recorded. On the contrary, chromium(III) did not increase the frequency of mutant clones. A high proportion of the total spot induction was due to mitotic recombination, confirming previously reported data on the strong recombinogenic activity of chromium(VI) compounds.

Animals↗

PubMed1999

Genotoxicity studies on the phenoxyacetates 2,4-D and 4-CPA in the Drosophila wing spot test.

The phenoxyacetates 2,4-D and 4-CPA were evaluated for genotoxicity using the Drosophila melanogaster wing spot test, which assesses for somatic mutation and recombination events. Third-instar larvae trans-heterozygous for two recessive mutations affecting the expression of wing trichomes, multiple wing hairs (mwh), and flare (flr) were treated by chronic feeding with different concentrations of the two chemicals. Feeding lasted until pupation of the surviving larvae and the genotoxic effects induced were evaluated in adults for the appearance of wing-blade cell clones with the mwh, flr, or mwh-flr phenotypes. Exposure to 2,4-D, at the highest concentration evaluated (10 mM), induced a weak but significant increase in the frequency of two of the categories of recorded spots: large single and total spots; in contrast, the 4-CPA treatments failed to induce any significant increase in the frequency of evaluated spots. When the heterozygous larvae for mwh and the multiple inverted TM3 balancer chromosome were treated with the chemicals, no increases were detected, either after the 2,4-D nor the 4-CPA treatments.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1999

Cytogenetic damage after 131-iodine treatment for hyperthyroidism and thyroid cancer. A study using the micronucleus test.

To detect the incidence and persistence of potential chromosome damage induced by iodine-131 therapy, we applied the cytokinesis-block micronucleus assay to peripheral blood lymphocytes from hyperthyroidism and thyroid cancer patients treated with 131I. Two groups of patients were evaluated in a longitudinal study; one group was composed of 47 hyperthyroid patients and the other of 39 thyroid cancer patients. In the hyperthyroidism group, the micronuclei frequency was determined before 131I therapy and 1 week, 1 month and 3 months after it. Furthermore, an additional sample was taken from a subgroup of 17 hyperthyroidism patients 6 months after treatment. In the thyroid cancer group, the analysis was also conducted over time, and four samples were studied: before treatment and 1 week, 6 months and 1 year later. Simultaneously, a cross-sectional study was performed with 70 control subjects and 54 thyroid cancer patients who had received the last therapeutic dose 1-6 years before the present study. In the hyperthyroidism group a significant increase in the micronuclei average was found over time. In the sample obtained 6 months after therapy, the micronuclei mean frequency was practically the same as in the sample taken 3 months before. In the thyroid cancer group a twofold increase in the frequency of micronuclei was seen 1 week after therapy. Although this value decreased across time, the micronuclei frequency obtained 1 year after 131I therapy remained higher than the value found before it. Concerning the data from the cross-sectional study, a significant increase in the frequency of micronuclei was detected in the subgroup of thyroid cancer patients treated between 1 and 3 years before the current study. These results indicate that exposure to 131I therapy induces chromosome damage in peripheral lymphocytes and that the cytokinesis-block micronucleus assay is sensitive enough to detect the genetic damage by exposure to sufficiently high levels of radiation from internal radioactive sources.

Adolescent↗

PubMed1999

Accelerated telomere shortening in the human inactive X chromosome.

Telomeres are nucleoprotein complexes at the end of eukaryotic chromosomes, with important roles in the maintenance of genomic stability and in chromosome segregation. Normal somatic cells lose telomeric repeats with each cell division both in vivo and in vitro. To address a potential role of nuclear architecture and epigenetic factors in telomere-length dynamics, the length of the telomeres of the X chromosomes and the autosomes was measured in metaphases from blood lymphocytes of human females of various ages, by quantitative FISH with a peptide nucleic-acid telomeric probe in combination with an X-chromosome centromere-specific probe. The activation status of the X chromosomes was simultaneously visualized with antibodies against acetylated histone H4. We observed an accelerated shortening of telomeric repeats in the inactive X chromosome, which suggests that epigenetic factors modulate not only the length but also the rate of age-associated telomere shortening in human cells in vivo. This is the first evidence to show a differential rate of telomere shortening between and within homologous chromosomes in any species. Our results are also consistent with a causative role of telomere shortening in the well-documented X-chromosome aneuploidy in aging humans.

Acetylation↗

PubMed1999

FISH analysis of 1cen-1q12 breakage, chromosome 1 numerical abnormalities and centromeric content of micronuclei in buccal cells from thyroid cancer and hyperthyroidism patients treated with radioactive iodine.

One of the health consequences of the Chernobyl nuclear power plant accident was a radioactive iodine-related increase in the incidence of thyroid cancer in exposed children. This radioisotope is used in the treatment of thyroid cancer and hyperthyroidism patients providing a convenient opportunity to study cytogenetic damage induced by known doses of radioactive iodine in treated patients. We used pancentromeric FISH on micronuclei and chromosome 1 tandem labelling FISH to monitor overall chromosome breakage and loss, 1q12 breakage and decondensation and chromosome 1 numerical abnormalities in buccal cells from 31 radioactive iodine-exposed hyperthyroidism and thyroid cancer patients. The overall outcome of the study, with 250,000 buccal cells analysed, is that there was no radioactive iodine-related increase in the frequency of micronuclei, 1q12 breakage, 1q12 decondensation or chromosome 1 numerical abnormalities. In addition, neither age nor gender, health status nor radioactive iodine dose modulated the frequency of the above cytogenetic end points. Although several uncertainties of these emerging molecular cytogenetic methodologies will require further experimentation, we conclude that, at the reported exposure levels, radioactive iodine did not induce detectable chromosome damage in buccal cells from treated patients.

Adult↗

PubMed1999

Molecular analysis of mutants obtained by treatment with alkylating agents in a quadruplicated white-ivory strain of Drosophila melanogaster.

The use of a white-ivory (wi) strain of Drosophila melanogaster carrying four copies of this allele, (wi)4, has proved to be useful in detecting somatic mutation in genotoxicity testing. Nevertheless, until now very little information exists about the nature of the genetic effects detected in such a strain. This work presents molecular data on the changes that have taken place in different germinal mutants obtained after treatment with alkylating agents. Three different phenotypes were obtained: wild-type red eyes, dark red eyes and eyes lighter than (wi)4. Our results show that, in at least one of the four copies of the allele, the wild-type red eye phenotypes are due to a precise excision of the 2.96 kb duplicated region characteristic of the wi allele. These data agree with previous results obtained in a strain carrying only a single copy of the wi allele. The dark red eye mutants analysed seemed to be generated as a cluster and all proved to be caused by deletions at the 3'-end of the duplicated wi region in two of the copies of the (wi)4 genome. Finally, the light eye mutants (obtained at high frequencies) failed to show alterations at the molecular level, although we cannot discard the possibility that they might have originated by the loss of some of the wi copies of the (wi)4 strain.

Alkylating Agents↗

PubMed1999

Low sensitivity of the sister chromatid exchange assay to detect the genotoxic effects of radioiodine therapy.

To assess the genotoxic risk associated with 131I therapy, sister chromatid exchanges (SCEs) and cells with unusually high SCE counts (HFC) were determined in a follow-up study performed with 46 hyperthyroidism and 39 thyroid cancer patients treated with 131I. In addition, a cross-sectional study was also carried out with 78 control persons and 51 thyroid cancer patients that had completed radioiodine therapy from 1 to 6 years prior to the current investigation. In the follow-up analysis, the study was conducted over time and four blood samples were drawn from each patient: the first one prior to the radioiodine treatment, with the remaining three taken sequentially over the year after therapy. Concerning the results obtained for the whole population in the follow-up study, the SCE and HFC values found after radioiodine therapy did not show any significant increase, neither in the hyperthyroidism nor thyroid cancer groups. Unlike the results mentioned above, when the effect of smoking habit was considered, there was a slight but significant increase in SCE in the samples taken 3 months and 1 week after 131I therapy in the hyperthyroidism and thyroid cancer non-smokers, respectively. The data obtained in the cross-sectional study did not show differences in SCE and HFC between the control group and the cancer group treated with 131I. It is noteworthy that among the different parameters analysed, smoking habit is the only factor that showed a direct relationship with SCE and HFC and, as a consequence, smokers had significantly more SCE and HFC than non-smokers. Taking into account our previous investigations showing a highly significant increase in the frequency of micronuclei for the same patients and sampling times, the outcomes obtained would suggest that the eventual genotoxic effect of 131I therapy could not be clearly detected by the SCE assay. This would reinforce the view that ionizing radiation appears to be a poor inducer of SCEs.

Adult↗

PubMed1999

Equal induction and persistence of chromosome aberrations involving chromosomes with heterogeneous lengths and gene densities.

Little is known about the factors modulating the initial induction and persistence of chromosome aberrations. Chromosome length and gene density have been proposed to play a significant role. We have therefore analyzed the induction and persistence of gamma-ray-induced aberrations involving four human chromosomes (1, 4, 18, and 19) with highly heterogeneous lengths and gene densities. Multicolor FISH was performed on a wild-type lymphoblastoid cell line 1, 3, 7, 14, 28, 42, and 56 d after gamma-irradiation. The frequency of induced chromosomal aberrations was proportional to the length of the chromosomes. Complex aberrations, dicentrics, and fragments were highly unstable and disappeared during the first week after treatment and with similar kinetics for all four chromosomes. The frequency of translocations decreased with time and followed an exponential decline. Thirty percent of the gamma-ray-induced translocations were stable over the entire study period, irrespective of the length and the gene density of the chromosome involved. Accordingly, we concluded that the induction of chromosome aberrations is proportional to the length of the chromosome, that gene density makes no measurable contribution to induction, and that neither length nor gene density influences the persistence of chromosome aberrations.

Cell Line↗

PubMed1998

Biomonitoring of workers exposed to lead. Genotoxic effects, its modulation by polyvitamin treatment and evaluation of the induced radioresistance.

A population monitoring study was performed, by using the micronucleus (MN) assay in human peripheral lymphocytes, to investigate whether occupational exposure to lead is genotoxic to workers. In addition to the exposed workers group, two more groups were studied, an external group from a factory without exposure to lead and an internal control group, from the same factory as the exposed workers, but that were not directly exposed to lead. Measures of lead levels at working place and in blood were calculated, and blood samples were collected to carry out a MN study. The results from these studies indicate that the blood from workers directly exposed contained high levels of lead, compared with the other groups, and a significant increase in the frequency of both the total number of MN and the number of binucleated cells carrying MN appeared. In addition, a study on the antimutagenic effects of a polyvitamin rich diet was conducted by measuring the frequency of MN after the workers had a four month daily intake of a polyvitamin-polymineral complex. These results clearly show a significant reduction of the MN frequency evaluated after this treatment, obtaining values that were even lower than those obtained in the internal control group. Finally, a challenge assay was carried out to determine response to gamma-radiation as indication of any kind of radiosensitivity or radioresistance. The results of this experiment did not show any significant variation in the increase of the frequency of MN after challenge irradiation in the lead exposed workers; nevertheless this increase was significantly reduced in the sample obtained after the polyvitamin treatment indicating a radioresistance response.

Adult↗

PubMed1998

Lack of genotoxicity of the herbicide atrazine in cultured human lymphocytes.

The widely used herbicide atrazine was evaluated for genotoxicity in cultured human peripheral blood lymphocytes. Sister-chromatid exchanges (SCE), chromosome aberrations (CA) and micronuclei (MN) were scored as genetic endpoints. To detect eventual metabolic modification in the genotoxicity of this herbicide, the cultures of SCE and MN demonstration were also treated with S9 microsomal fraction. From our results we can conclude that atrazine was able to exert a weak cytotoxic effect. However, the overall evaluation of the genotoxicity data indicate that this herbicide is not effective in the three assays conducted, irrespective of the presence of metabolic activation, which would mean a general lack of effectiveness of atrazine to induce clastogenic and aneugenic damage in cultured human lymphocytes.

Animals↗