Mean Number Of Sister Chromatid Exchanges Research Articles

Genotoxic effects of Roundup Full II® on lymphocytes of Chaetophractus villosus (Xenarthra, Mammalia): In vitro studies.

In Argentina, Chaetophractus villosus has a wide distribution that overlaps with agricultural areas where soybean is the predominant crop. In such areas the pesticide Roundup Full II® (RU) is widely applied. The genotoxic effect of its active ingredient glyphosate (RU is 66.2% glyphosate) on the peripheral blood lymphocytes of C. villosus was tested over a range of concentrations (280, 420, 560, 1120 μmol/L). Culture medium without glyphosate served as negative control, while medium containing mitomycin C served as positive control. Genetic damage was characterized in terms of the percentage of cells with chromosome aberrations (CA), the mean number of sister chromatid exchanges (SCE) per cell, and the modification of cell proliferation kinetics via the calculation of the replication index. Significant increases (p < 0.0001) were seen in the CA frequency and the mean number of SCEs per cell compared to negative controls at all the RU concentrations tested. Chromatid breaks, the only form of CA observed, under the 560 μmol/L RU conditions and in presence of mitomycin C were four to five times more common than at lower concentrations, while no viable cells were seen in the 1120 μmol/L treatment. The mean number of SCEs per cell was significantly higher under the 280 μmol/L RU conditions than the 420 or 560 μmol/L RU conditions; cells cultivated in the presence of MMC also showed significantly more SCEs. All the RU concentrations tested (except in the 1120 μmol/L RU treatment [no viable cells]) induced a significant reduction in the replication index (p < 0.0001). The present results confirm the genotoxic effects of RU on C. villosus lymphocytes in vitro, strongly suggesting that exposure to RU could induce DNA damage in C. villosus wildlife.

Permanent embryonic germ cell lines of BALB/cJ mice — an in vitro alternative for in vivo germ cell mutagenicity tests

To offer a sensitive and predictive in vitro method to assess germ cell mutagenicity, we established primordial germ (PG) cell-derived permanent female and male embryonic germ (EG) cell lines of the mouse (strain BALB/cJ). The differences in developmental sensitivity of EG cells and differentiated fibroblast cells of the mouse cell line 3T3 to genotoxicants were tested comparatively under identical test conditions. Cytotoxicity assay was measured by the MTT test and genotoxic effects were determined by sister chromatid exchanges (SCE) rates induced by standard reference mutagens. Both methods are used to assign the chemicals to two classes of in vivo reproductive toxicity, non- and strongly genotoxic to germ cells. Applying linear discriminant analysis, a biostatistical prediction model (PM) was developed for the female cell line EG 3. This procedure identified a single variable, the Ig(SCE 200EG 3) as the statistically significant concentration related increase of 200% in the mean number of SCEs per metaphase spread after 3 h of exposure to be sufficient for separation into the classes: non- and strongly genotoxic to germ cells. Applying this PM to the training set of five genotoxic and three non-genotoxic test chemicals, 100% correct classifications were obtained.

Trans-stilbene oxide-induced sister chromatid exchange in cultured human lymphocytes: influence of GSTM1 and GSTT1 genotypes.

About 50% and 15% of Caucasians lack the glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) genes and the corresponding enzyme activity, respectively. Both of these polymorphisms have been shown to affect the genotoxicity of some epoxides in cultured human lymphocytes. Especially GSTT1 appears to be important in whole-blood cultures, probably because GSTT1 activity is high in erythrocytes. The in vitro genotoxicity of trans-stilbene oxide (TSO), a model substrate for GSTM1, has been shown to depend on individual GSTM1 activity. The potential role of GSTM1 genotype, and the possible interference of GSTT1 genotype, has not previously been examined in this context. We have studied TSO-induced sister chromatid exchanges (SCEs) in 72 h whole-blood lymphocyte cultures from 24 healthy human donors, representing different combinations of GSTM1 and GSTT1 positive and null genotypes. TSO clearly increased SCEs in cultures of all donors. The mean number of SCEs per cell induced by 75 and 150 microM TSO was, respectively, 1.5- and 1.3-times higher in cultures of GSTM1 null than GSTM1 positive donors. In another experiment, GSTM1 null individuals showed, in comparison with GSTM1 positive subjects, a 1.8-fold SCE induction by 50 microM TSO. GSTT1 genotype did not have an unequivocal effect. Our findings suggest that the lack of the GSTM1 gene, resulting in reduced detoxification capacity, increases individual sensitivity to the genotoxic effects of TSO.

Repeated analysis of sister chromatid exchange induction by diepoxybutane in cultured human lymphocytes: effect of glutathione S-transferase T1 and M1 genotype

Spontaneous and diepoxybutane (DEB)-induced sister-chromatid exchanges (SCEs) were examined in whole-blood lymphocyte cultures of 3 men and 4 women. A strong increase in mean number of SCEs per cell with increasing DEB concentrations (0, 2 and 4 μM) was observed in cultures of all subjects, but 3 of the donors were clearly more sensitive than the others. The SCE measurements were repeated 2–6 times per donor over a period of 55 months to assess the stability of the individual SCE response. The results showed that SCE induction by DEB was steady in the individuals during the follow-up at each DEB dose, with no significant differences among the repeated experiments. At 4 μM DEB, the DEB-sensitive and -resistant donors could reliably be differentiated from each other in all trials. As DEB-sensitivity has been suggested to be due to the lack of glutathione S-transferase (GST) T1, the donors were genotyped for the presence of GSTT1 and GSTM1 genes. The 3 individuals found to be DEB-sensitive were all of the GSTT1 null genotype, whereas the 4 DEB-resistant donors were GSTT1 positive, which supported the role of the GSTT1 gene in determining DEB-sensitivity. Three of the DEB-resistant and none of the DEB-sensitive had the GSTM1 null genotype. Thus, the lack of the GSTM1 gene was not associated with the DEB-sensitivity trait. In conclusion, the present findings show that individual SCE responses to treatment of cultured human lymphocytes with DEB can reliably be reproduced in repeated trials. The results confirm that the GSTT1 gene but not the GSTM1 gene is important in determining individual sensitivity to the in vitro genotoxicity of DEB.

Sister chromatid exchanges in lymphocytes of nurses handling antineoplastic drugs

The effects of handling antineoplastic drugs were examined in a group of 23 nurses working in the hematology and oncology departments of different university hospitals in Ankara and in a group of 50 unexposed controls. The cytogenetic repercussions of exposure were assessed by examining sister chromatid exchanges (SCEs) in circulating lymphocytes which result from the breakage and rejoining of DNA at apparently homologous sites on the 2 chromatids of a single chromosome. A significant increased frequency of SCE is observed in nurses in daily contact with antineoplastics ( n = 23, mean SCEs/cell ± SE 6.5 ± 0.2) as compared to a group of controls ( n = 50, mean SCEs/cell 5.2 ± 0.2). The nurses who smoked also had a higher SCE frequency ( n = 15, mean SCEs/cell 7.0 ± 0.3) than non-smokers, ( n = 8, mean SCEs/cell 5.5 ± 0.3). A significant increase ( P < 0.001) in the mean number of SCE was found for non-smoking nurses as compared to non-smoking controls ( n = 27, mean SCEs/cell 4.1 ± 0.2).

Effects of auxin and cytokinin on induction of sister chromatid exchanges in cultured cells of wheat (Triticum aestivum L.)

In order to know the mutagenic effects of synthetic auxins (NAA, 2,4-D, and 2,4,5-T) and a cytokinin (kinetin) in vitro, sister chromatid exchanges (SCEs) were analyzed in cultured cells of a hexaploid wheat (Triticum aestivum L.). In the MS medium supplemented with 2.0 mg/l 2,4-D, the mean number of SCEs per cell was 15.2, and per pg of DNA, 0.42. No significant effect was found in the treatments of NAA or 2,4-D at concentrations of 0.5-10.0 mg/l, whereas more than 2.0 mg/l of 2,4,5-T induced dramatic increases of SCEs. Kinetin itself had no significant effect on SCE induction, but there was a tendency that SCEs induced by 2,4,5-T were suppressed by kinetin.

Studies on sister chromatid exchanges and chromosomal aberrations in tonsillar lymphocytes caused by several factors (author's transl)

Using primarily and continuously cultured lymphocytes from tonsils, various factors causing the changes of occurrence in sister chromatid exchanges (SCE) together with the chromosomal aberrations (CA) were examined. The most optimal culture conditions for the SCE observation were studied in primary tonsillar lymphocytes and determined as follows: The number of cells at initiation was; 2 X 106 cells/ml, the culture medium was RPMI-1640 containing 20% fetal calf serum, 15pg/ml of phytohemagglutinin-P and 1011g/ml of 5-bromodeoxyuridine (BUdR) ; the incubation period was 72 hours at 37-C. During 72 hours, the most of cells performed two rounds of DNA replication and showed the metaphases in which each chromosome had one chromatid unifilarly substituted with BUdR and one bifilarly. These cells were submitted to the fluorescence plus Giemsa technique (FPG) for the SCE observation following the usual procedures for chromosomal analysis (flame-drying method). The mean number of SCE in primary tonsillar lymphocytes from 13 patients showing tonsillar hypertrophy or recurrent tonsillitis without inflammatory signs was 5. 134-0.16 SCEs/cell, while 6.57-0. 15 SCEs/cell in 14 patients with chronic inflammatory tonsils. No significant changes of the SCE scores related to the ages, the grades of hypertrophy and the mitotic indices were observed. In the case of tonsillar lymphocytes infected by Epstein-Barr virus (EBV), the SCE scores showed the similar values to those in the chronic tonsillitis. The treatment of these cells with an antitumor drug (mitomycin C), u chemical mutagen (4-nitroquinoline 1-oxide) and the irradiation with ultraviolet light induced significantly the increases of SCE scores before the chromatid breaks occured. Caffein known as the specific inhibitor for DNA repair enzyme increased the breaks without the SCE changes. Nicotine which seems to be related to generation of lung cancer did not show any effects on the SCE or break changes even at 10-3 M. The infection by several DNA-viruses (adeno type 5 and 12, cowpox) or RNA-viruses (rubella, Sendai and Coxsackie B-5), which induced oral or upper respiratory tract infection did not cause the significant changes of SCE scores. However, it resulted in the increases of the breaks before the viral cytopathogenic effect was appeared. These results seem to indicate that the analysis of SCE and CA in tonsillar lymphocytes may be a useful procedure for the follow-up of the minor action of chemical mutagens and the initial change by viral infection with the other cellular responses.

Sister chromatid exchanges in balanced translocation carriers and in patients with unbalanced karyotypes.

Sister chromatid exchanges (SCEs) were studied in peripheral human leukocytes from 16 patients with balanced translocations or with unbalanced karyotypes, and from 4 controls. No difference was seen between these two groups of people in the mean number of SCEs per cell, or in the total number of SCEs observed for each pair of autosomes involved in the translocations studied. With this last number no difference from the expected number of SCEs, if one supposes that SCEs follow a random distribution, was seen.

Increased sister chromatid exchange events in the human late replicating X.

Human female blood cultures were labeled with BrdU for detecting sister chromatid exchanges (SCEs) by the Hoechst 33258 fluorescence technique. Late labeling with 3H-thymidine and autoradiography allowed the identification of the late replicating X. The mean number of SCEs in the cells was 13. The isopycnotic X showed an exchange frequency according to its relative length in the karyotype; in the late replicating X a doubled number of SCE events was observed.