Frequency Of Sister Chromatid Exchanges Research Articles

Characterization of a Novel Mechanism of Genomic Instability Involving the SEI1/SET/NM23H1 Pathway in Esophageal Cancers

Amplification of 19q is a frequent genetic alteration in many solid tumors, and SEI1 is a candidate oncogene within the amplified region. Our previous study found that the oncogenic function of SEI1 was associated with chromosome instability. In this study, we report a novel mechanism of genomic instability involving the SEI1-SET-NM23H1 pathway. Overexpression of SEI1 was observed in 57 of 100 of esophageal squamous cell carcinoma cases. Functional study showed that SEI1 had strong tumorigenic ability, and overexpression of SEI1 could induce the genomic instability by increasing micronuclei formation and reducing the number of chromosomes. Further study found that SEI1 was able to upregulate SET expression and subsequently promote the translocation of a small amount of NM23H1 from the cytoplasm to the nucleus. Nuclear NM23H1 can induce DNA damage through its DNA nick activity. Unlike CTL attack, only a small amount of NM23H1 translocated into the nucleus (<10%) induced by the overexpression of SEI1. Further study found that the small amount of NM23H1 only induced minor DNA damage and subsequently increased genomic instability, rather than inducing irreparable DNA damage and initiating apoptosis by CTL attack. Sister chromatid exchange experiment found that the translocation of small amount of NM23H1 into the nucleus induced by the overexpressions of SEI1/SET could increase the frequency of sister chromatid exchange. In addition, overexpression of SEI1 was associated with poor prognosis of esophageal squamous cell carcinoma. Taken together, these findings define a novel mechanism of genomic instability and malignant progression in esophageal cancers, a deadly disease of increasing incidence in developed countries.

In vitro and in vivo Cytogenetic Effects of Recombinant Human Erythropoietin on the Frequency of Sister Chromatid Exchanges Alone or in Combination with Mitomycin C

Background: Erythropoietin (EPO) is a glycoprotein which has a main property, erythropoiesis, but its range of action in the human body is very wide. It has been suggested that EPO acts cytoprotectively for many cell lines against many toxic causes in vitro and in vivo. Our aim was to study the action of EPO on DNA of two cell types, human lymphocytes in vitro and on P388 ascites tumor cells inoculated in BDF1 mice in the presence and absence of the genotoxic agent mitomycin C (MMC). Method: The sister chromatid exchange (SCE) assay was used as it is a very sensitive, simple and rapid method for detecting DNA damage. Proliferation rate indices (PRI) and mitotic indices (MI) were also counted. Results: EPO did not alter the SCE level when it acted alone on both cell lines. MMC as a potent genotoxic agent increased SCE levels in vitro and in vivo. EPO used in combination with MMC significantly decreased SCE levels and increased PRI and MI values induced by MMC alone both in vitro and in vivo. Conclusions: EPO acts protectively against the genotoxic potential of MMC, and this action may have clinical implications.

Roles of &lt;I&gt;REV3&lt;/I&gt; in proliferation and genomic stability of colon carci-noma cells

To investigate the roles of human REV3 gene in proliferation and genomic stability, we experimentally suppressed the REV3 expression in human colon cancer cells (SW480) by the interference RNA technology (RNAi) as monitored by real-time RT-PCR. Compared to untreated or mock-treated cells, ablation of REV3 significantly reduced cell growth rate, micronucleus formation and the frequency of sister chromatid exchange. Whereas the differences between untreated and mock-treated controls were insignificant. Indicators of cell cycle, proliferation and the expression of genetic information in cells of case group, which displayed lower-level expression of REV3, were extremely lower than the control group, and the difference was significant (P<0.05). Differences in the two control groups were not significant. This suggested that the reduced expression of REV3 may affect the growth and proliferation of colon cancer cells (SW480), and, to some extent, contribute to suppression of the genetic instability occurred in micronuclei and sister chromatids. Based on the results from this study, REV3 plays an important role in different cellular growth periods and physiological conditions, and its differential expression directly affects the development of human colon cancer cells.

Abstract 1310: ATR checkpoint kinase suppression in combination with oncogenic Ras expression synergistically increases genomic instability and potentiates tumorigenesis in mice

Abstract Oncogenic stress, such as that induced by expression of constitutively active forms of Ras, leads to the activation of the ATR-Chk1 pathway. The ATR-Chk1 signaling network is responsible for maintaining genome stability during S phase by preventing replication fork collapse into DNA double strand breaks (DSB). We asked whether oncogenic Ras expression increases the reliance on the ATR pathway for genome maintenance. Here, we report that activation of the ATR-Chk1 pathway functions prominently in suppressing genomic instability following oncogenic Ras expression and limits progression to malignancy in vivo. Independently derived isogenic mouse fibroblasts cultures expressing multiple copies of H-RasG12V or a single copy K-RasG12D exhibited significantly elevated levels of ATR-dependent Chk1 phosphorylation in comparison to untransformed controls. Consistent with a critical function for the ATR-Chk1 pathway in maintaining genome stability under oncogenic stress, H2AX phosphorylation and the frequency of sister chromatid exchange were increased to significantly higher levels by partial ATR suppression or Chk1 inhibition in H-RasG12V-transformed cells than in untransformed counterparts. The effect of combining ATR-Chk1 pathway suppression with H-RasG12V expression on genomic instability was greater than that observed following ATR-Chk1 pathway suppression or H-RasG12V expression alone and was not due to increased S phase representation. These results indicate that ATR limits genomic instability following oncogenic Ras expression and putatively provides an important barrier to further genetic alterations that contribute to malignant progression in vivo. To test this model, endogenous levels of K-RasG12D were conditionally induced via mosaic cre/lox activation of the K-RasG12D-LSL allele in ATR wild-type and haploinsufficient mice. We demonstrate that ATR haploinsufficiency synergizes with K-RasG12D expression to cause significantly increased incidences of lung adenocarcinoma, thymic lymphoma and spindle cell sarcoma. Notably, increased tumor incidence in ATR haploinsufficient mice was associated with elevated p53 LOH, consistent with a greater reliance on ATR for maintaining genomic stability under conditions of oncogenic stress. These data indicate that single copy loss of ATR or, potentially, other members of the ATR-Chk1 pathway (&amp;gt;20) may accelerate the malignant progression cancers induced by oncogenic forms of Ras in humans. Genetic alterations such as these may provide selectivity for therapeutic strategies that involve further suppression of ATR-Chk1 pathway activity to levels that are incompatible with continued cellular proliferation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1310.

Abstract 3638: DNA strand breaks induced by 2′-C-cyano-2′-deoxy-nucleoside analogs are repaired by homologous recombination

Abstract CNDAC [2′-C-cyano-2′-deoxy-1-β-D-arabino-pentofuranosyl-cytosine], which is undergoing clinical trials, and its congener CNDAG [9-(2-C-cyano-2-deoxy-1-β-D-arabino-pentofuranosyl) guanine] likely share the unique action mechanism of inducing single strand breaks (SSBs) through β-elimination which generates the chain-terminating analog CNddC(G) following incorporation into DNA. We postulate that subsequent processing or DNA replication across the unrepaired nicks would generate double strand breaks (DSBs). Cellular responses to these 2′-C-cyano-2′-deoxy-nucleoside analogs are concentration dependent. Cells were arrested in G2 or S- phase when exposed to high concentrations of CNDAC(G), while at lesser concentrations cells could progress into a second S-phase. This study used cytogenetic approaches to define the mechanisms of DSB formation and damage repair in the above biological context. First, metaphase chromosomal aberrations (including breaks and gaps) were measured in Chinese hamster ovary line AA8 and its mutant UV41, which is sensitized to CNDAC(G) due to lack of XPF, a key endonuclease in the nucleotide excision repair (NER) pathway. The mean values of chromosomal aberrations increased 6(7)-fold and &amp;gt; 6(3)-fold in AA8 and UV41 cells, respectively, after exposure to CNDAC(G) for two population doubling times, compared to those treated for only one population doubling time (n&amp;gt;50). These data clearly demonstrate that SSBs induced by CNDAC(G) in the first S-phase can be converted into one-ended DSBs during the second S-phase when replication forks encountering unrepaired SSBs. Second, the frequencies of sister chromatid exchanges (SCEs) in AA8 cells incubated with CNDAC(G) for two cell cycles (mean 14.2-17.6 per metaphase) were 2-fold of those exposed for one cell cycle (mean 7.4-8.4 per metaphase, n&amp;gt;20, p&amp;lt;0.001), the latter greater than control (mean 6 per metaphase, p&amp;lt;0.05). Since homologous recombination (HR) is considered the mechanism for SCE, these results indicate that CNDAC(G)-caused DNA damage is repaired by HR. Third, spontaneous chromosomal alterations in UV41 cells were 7-fold greater than those in parental AA8 cells, suggesting genetic instability conferred by XPF deficiency. The increase in chromosomal aberrations after CNDAC(G) exposure, regardless of length of time, was greater in UV41 cells compared to the wild-type. This suggests that XPF is likely needed to remove CNddC(G) preceding HR in the first cell cycle. Thus, NER and HR may work in concert to repair CNDAC(G)-induced damage. In addition, UV41 cells presented greater incidence of SCE after treatment with CNDAC for one population doubling time (n=30, p&amp;lt;0.01), suggesting nuclease(s) other than XPF may function in removal of CNddC. Together these results demonstrate that HR is responsible for repair of CNDAC(G)-induced DSBs generated during the second replication across initial SSBs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3638.

Genetic interactions between HNT3/Aprataxin and RAD27/FEN1 suggest parallel pathways for 5′ end processing during base excision repair

Mutations in Aprataxin cause the neurodegenerative syndrome ataxia oculomotor apraxia type 1. Aprataxin catalyzes removal of adenosine monophosphate (AMP) from the 5′ end of a DNA strand, which results from an aborted attempt to ligate a strand break containing a damaged end. To gain insight into which DNA lesions are substrates for Aprataxin action in vivo, we deleted the Saccharomyces cerevisiae HNT3 gene, which encodes the Aprataxin homolog, in combination with known DNA repair genes. While hnt3Δ single mutants were not sensitive to DNA damaging agents, loss of HNT3 caused synergistic sensitivity to H 2O 2 in backgrounds that accumulate strand breaks with blocked termini, including apn1Δ apn2Δ tpp1Δ and ntg1Δ ntg2Δ ogg1Δ. Loss of HNT3 in rad27Δ cells, which are deficient in long-patch base excision repair (LP-BER), resulted in synergistic sensitivity to H 2O 2 and MMS, indicating that Hnt3 and LP-BER provide parallel pathways for processing 5′ AMPs. Loss of HNT3 also increased the sister chromatid exchange frequency. Surprisingly, HNT3 deletion partially rescued H 2O 2 sensitivity in recombination-deficient rad51Δ and rad52Δ cells, suggesting that Hnt3 promotes formation of a repair intermediate that is resolved by recombination.

Cytogenetic analysis of peripheral blood lymphocytes of hospital staff occupationally exposed to low doses of ionizing radiation

Ionizing radiation is known to induce mutations and cell transformations, predominantly by causing single-strand and double-strand DNA breakage, thereby leading to chromosome instability and carcinogenesis. The aim of this study was to evaluate genotoxic effects in hospital staff exposed to low-dose ionizing radiation in comparison with a selected control group, by using the cytokinesis-blocked micronucleus (CBMN) and sister chromatid exchange (SCE) tests in peripheral blood lymphocytes. The study included 40 exposed radiology staff and 30 control subjects. The frequency of micronuclei (MN) was significantly increased in radiation-exposed groups compared with control persons (p < 0.05). The frequency of SCE did not show any significant difference in the exposed individuals in comparison to the controls. Our results showed that low-level chronic occupational exposure to ionizing radiation causes an increase of MN frequency in chromosomes, even though the absorbed doses were below the permissible limits. Our studies indicate that the CBMN assay is considered to be sensitive test in contrast to SCE analysis to evaluate chromosomal damage induced by ionizing radiation.

The role of ascorbic acid on titanium dioxide-induced genetic damage assessed by the comet assay and cytogenetic tests

Titanium dioxide (TiO 2) is used in several commercial products such as cosmetics, sunscreen, toothpaste and pharmaceuticals. However, some recent investigations have revealed that titanium particles generate potential harmful effects on the environment and humans. Because of its strong antioxidant activity, ascorbic acid (AA) is admitted to act as an anti-mutagenic agent. The present study was undertaken to investigate the protective effect of AA against TiO 2-induced genotoxicity. Sister chromatid exchange (SCE), micronucleus (MN) and the comet assays were used to assess TiO 2-induced genotoxicity and to establish the protective effects of AA. There were significant increases ( P<0.05) in both SCE and MN frequencies of cultures treated with TiO 2 as compared to controls. However, co-application of AA (4.87 and 9.73 μM) and TiO 2 resulted in decreases of SCE and MN rates as compared to the group treated with titanium alone. Besides, significant reductions of primary DNA damage (comet assay) were determined when the AA was added to the cell culture medium simultaneously with TiO 2. In conclusion, the preventive role of AA in alleviating TiO 2-induced DNA damage was indicated for the first time in the present study.

Formaldehyde-induced chromosomal aberrations and apoptosis in peripheral blood lymphocytes of personnel working in pathology departments

Peripheral blood lymphocytes (PBL) of 37 formaldehyde-exposed women from four pathology departments in Hungary were investigated to collect data on the effects of occupational exposures to formaldehyde and to find a possible relationship between in vivo formaldehyde-induced apoptosis and genotoxic effects. The subjects were divided into two groups: 16 donors exposed to formaldehyde together with various organic solvents, and 21 subjects exposed mainly to formaldehyde. The results were compared with 37 controls (all women) without known occupational exposure. Ambient air concentrations of formaldehyde were measured in three work places, and ranged from 0.23 to 1.21mg/m(3) (mean 0.9mg/m(3)). Measures of genotoxicity included the determination of the frequencies of chromosomal aberrations (CA), sister-chromatid exchange (SCE), HPRT mutations (variant frequency, VF) and the measurement of UV-induced unscheduled DNA-repair synthesis (UDS). The percentages of premature centromere division (PCD) and of cells with a high frequency of SCE (HF/SCE) were also scored. Apoptosis and cell proliferation were determined by flow cytometry. In both formaldehyde-exposed groups, the apoptotic activity and the CA levels in PBLs were significantly higher than in controls. The CA were mostly breaks of the chromatid type. In the second group, which was mainly exposed to formaldehyde, CA were slightly lower in comparison with the group exposed to formaldehyde and solvents, which may be attributed to a different rate of elimination of damaged lymphocytes as a consequence of formaldehyde-induced apoptotic activity. In the second group, a significant decrease of VF and a non-significant increase in HF/SCE were found compared with the control and the other group. In conclusion, the results demonstrate that exposure to formaldehyde induces apoptosis and CA, indicating an excess cancer risk among subjects occupationally exposed to formaldehyde. The results also emphasize the importance of the measurement of occupational air pollutants, such as formaldehyde, in order to avoid genotoxic effects in the workers.

Chromosome Instability in Patients with Chronic Renal Failure

The aim of this study was to investigate the frequency of sister chromatid exchanges (SCEs), the presence of cytostaticity, cytotoxicity, and therefore, the possible genetic instability in patients with chronic renal failure (CRF) in human cultured peripheral blood lymphocytes. Peripheral blood lymphocytes were cultured from 32 patients with CRF (average 55.2 years) and 18 healthy blood donors (average 44.6 years), and the SCE method was applied afterward. The increase in SCE frequency was evaluated as an immediate DNA damage index, while the reduction in the values of the proliferating rate indices was evaluated as a cytostatic index and the mitotic indices as a cytotoxic index was also measured. A significant increase in the SCE frequencies along with a significant reduction in mitotic indices was observed in patients with CRF compared with the controls. It is notable that there was no significant difference in SCE levels among patients with CRF and cancer, and patients with CRF alone. This study illustrates increased genetic instability in patients with CRF. These results could also be of a great importance in early diagnosis to prognosticate a possible generation of neoplasm in the future.

SOD1 Is Essential for the Viability of DT40 Cells and Nuclear SOD1 Functions as a Guardian of Genomic DNA

Reactive oxygen species (ROSs) are produced during normal cellular metabolism, particularly by respiration in mitochondria, and these ROSs are considered to cause oxidative damage to macromolecules, including DNA. In our previous paper, we found no indication that depletion of mitochondrial superoxide dismutase, SOD2, resulted in an increase in DNA damage. In this paper, we examined SOD1, which is distributed in the cytoplasm, nucleus, and mitochondrial intermembrane space. We generated conditional SOD1 knockout cells from chicken DT40 cells and analyzed their phenotypes. The results revealed that SOD1 was essential for viability and that depletion of SOD1, especially nuclear SOD1, increased sister chromatid exchange (SCE) frequency, suggesting that superoxide is generated in or near the nucleus and that nuclear SOD1 functions as a guardian of the genome. Furthermore, we found that ascorbic acid could offset the defects caused by SOD1 depletion, including cell lethality and increases in SCE frequency and apurinic/apyrimidinic sites.

Differences in chemical structure result in opposite cytogenetic behavior of benzodiazepines

Event Abstract Back to Event Differences in chemical structure result in opposite cytogenetic behavior of benzodiazepines Maria T. Ekonomopoulou1*, Maria Argyraki1, Doxakis Anestakis1 and Zafiroula Iakovidou-Kritsi1 1 Aristotle University of Thessaloniki, Laboratory of General Biology and Genetics, Greece Introduction. Benzodiazepines (BDZs) belong to the most commonly prescribed drugs for the treatment of a variety of psychological and physical diseases. Especially some of 1,4-BDZs possess a leading role as anxiolytic, sedative, hypnotic, anticonvulsant and muscle relaxant drugs. 1,4-BDZs have an aromatic benzene ring fused to 1,4-diazepine ring with various substituents. Despite their extended use in therapy, they present widely varying pharmacokinetic behavior and the majority of them do not have retrievable genotoxicity or carcinogenicity data. 1,5-BDZs is a group of polycyclic compounds with characteristic seven-membered heterocyclic rings. Though some members of them have important biological properties, there is lack of information on their effect on DNA. Materials and methods. We studied the cytogenetic effects of four of the most widely used 1,4-BDZs, alprazolam (AZ), bromazepam (BZ), diazepam (DZ) and lorazepam (LZ) in normal human lymphocyte cultures, using an expanded sample set, administering them at final concentrations equivalent to oral dosage. Then, we synthesized four 1,5-BDZs with small structural differences and investigated their cytogenetic activity in normal human lymphocyte cultures at concentrations equivalent to the per os doses of the 1,4-BDZs. Sister chromatid exchanges (SCEs) have been used as one of the most sensitive index of cytotoxic activity reflecting instability of DNA or/and a deficiency in DNA repair mechanisms. Proliferation rate index (PRI) has been estimated as a valuable marker of cytostaticity. Results. All four 1,4-BDZs caused a concentration-dependent, statistically significant increase of SCE frequency (p<0.001) followed by a statistically significant decrease of PRI (p<0.001) of lymphocytes. Three of the newly synthesized 1,5-BDZs exhibited positive cytogenetic activity (statistically significant reduction of SCEs, p<0,01 t-test), without showing cytostatic properties. Conclusion. The observed unexpected decrease of SCE frequency of the cultured lymphocytes due to 1,5-BDZs’ activity, in contrast to the genotoxic and cytostatic behavior of the 1,4-BDZs, is remarkable and requires further investigation in the effort to improve pharmacological effects. Keywords: cytogenetic effects, DNA, Benzodiazepines Conference: 8th Southeast European Congress on Xenobiotic Metabolism and Toxicity - XEMET 2010, Thessaloniki, Greece, 1 Oct - 5 Oct, 2010. Presentation Type: Oral Topic: Xenobiotic toxicity Citation: Ekonomopoulou MT, Argyraki M, Anestakis D and Iakovidou-Kritsi Z (2010). Differences in chemical structure result in opposite cytogenetic behavior of benzodiazepines. Front. Pharmacol. Conference Abstract: 8th Southeast European Congress on Xenobiotic Metabolism and Toxicity - XEMET 2010. doi: 10.3389/conf.fphar.2010.60.00118 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 28 Oct 2010; Published Online: 04 Nov 2010. * Correspondence: Dr. Maria T Ekonomopoulou, Aristotle University of Thessaloniki, Laboratory of General Biology and Genetics, Thessaloniki, Greece, biomary@med.auth.gr Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Maria T Ekonomopoulou Maria Argyraki Doxakis Anestakis Zafiroula Iakovidou-Kritsi Google Maria T Ekonomopoulou Maria Argyraki Doxakis Anestakis Zafiroula Iakovidou-Kritsi Google Scholar Maria T Ekonomopoulou Maria Argyraki Doxakis Anestakis Zafiroula Iakovidou-Kritsi PubMed Maria T Ekonomopoulou Maria Argyraki Doxakis Anestakis Zafiroula Iakovidou-Kritsi Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Comparative study of the cytotoxic and genotoxic effects of titanium oxide and aluminium oxide nanoparticles in Chinese hamster ovary (CHO-K1) cells

The aim of this study was to analyze the cytotoxicity and genotoxicity of titanium oxide (TiO 2) and aluminium oxide (Al 2O 3) nanoparticles (NPs) on Chinese hamster ovary (CHO-K1) cells using neutral red (NR), mitochondrial activity (by MTT assay), sister chromatid exchange (SCE), micronucleus (MN) formation, and cell cycle kinetics techniques. Results showed a dose-related cytotoxic effect evidenced after 24 h by changes in lysosomal and mitochondrial dehydrogenase activity. Interestingly, transmission electronic microscopy (TEM) showed the formation of perinuclear vesicles in CHO-K1 cells after treatment with both NPs during 24 h but no NP was detected in the nuclei. Genotoxic effects were shown by MN frequencies which significantly increased at 0.5 and 1 μg/mL TiO 2 and 0.5–10 μg/mL Al 2O 3. SCE frequencies were higher for cells treated with 1–5 μg/mL TiO 2. The absence of metaphases evidenced cytotoxicity for higher concentrations of TiO 2. No SCE induction was achieved after treatment with 1–25 μg/mL Al 2O 3. In conclusion, findings showed cytotoxic and genotoxic effects of TiO 2 and Al 2O 3 NPs on CHO-K1 cells. Possible causes of controversial reports are discussed further on.

Consequences of methemoglobinemia in pregnancy in newborns, children, and adults: issues raised by new findings on methemoglobin catabolism

Objective. The aim of this review is to warn about the effects of methemoglobin and its catabolic products and the toxic effects caused by environmental oxidants that cause high-risk pregnancy and may later impair the health of newborns, children and adolescents.Methods. In our study of pregnant women (n = 36) whose methemoglobin level was >1.5 g/l, we took blood samples from their newborns to determine the frequency of sister chromatid exchange (SCE) by cultivating lymphocytes. The research took place at the Department of Biology and Medical Genetics of the School of Medicine in Rijeka (Croatia).Results. The results have shown that no deviation in the SCE frequency was found in either case (1990). We examined data on the health of newborns collected at perinatal hospital departments in Rijeka (Croatia), the preschool office and school service at the Labin Health Center and continued until they were 18 years of age (2008). The statistics obtained by applying the chi-square test show that the incidences of neonatal jaundice (p = 0.034), heart murmur at a later age (p = 0.011) and dyslalia and learning/memory impairments (p = 0.002) were significantly higher than in children of control mothers (n = 19).Conclusion. Depending on the mother's exposure to environmental oxidants, during its development the fetus is more likely to be affected by methemoglobin and hemolysis. Oxidants affect the vascular endothelium of kidneys, brain and other vital organs, because they have the capacity to cross the damaged fetomaternal placental barrier. ‘Fetal preeclampsia’ is an expected manifestation of the condition. Our research proves our thesis on the pathophysiological relationship between methemoglobinemia and unexplained jaundice and hyperbilirubinemia, heart murmur at a later age, dyslalia and learning and memory impairments that have not exactly been demonstrated yet.

Genotoxic and antigenotoxic effects of Hemidesmus indicus R. Br. root extract in cultured lymphocytes

Aim of the study The genotoxic and antigenotoxic potential of the ethanolic extract of Hemidesmus indicus roots were evaluated in cultured human lymphocytes using cisplatin as the positive mutagen. Materials and methods Cytogenetic damage and cytotoxicity were determined in cells exposed to different doses of the extract, ranging from 2 to 32 μg/ml of culture medium, either alone or together with cisplatin. Results There was a significant reduction in cisplatin-induced frequencies of sister chromatid exchanges, chromosome aberrations and micronucleated binucleate cells at the lower concentrations of 4 and 8 μg/ml ( P < 0.05). However, the extract by itself reduced the proliferative rate index, mitotic index and cytokinesis-block proliferative index ( P < 0.05). Further, a significant increase in the percentage of chromosome aberrations was noticed at the higher concentrations. Conclusion Hemidesmus indicus root extract possesses significant genoprotective effect at the lower concentrations although it is cytotoxic and probably genotoxic at higher doses.

Evaluation of genotoxic effects of semicarbazide on cultured human lymphocytes and rat bone marrow

Semicarbazide (SEM) belongs to the hydrazine family of chemicals, some members of which are known to possess carcinogenic potential. Information on the potential hazard of SEM itself is incomplete and the possibility that it is genotoxic cannot be ruled out. SEM is widely used as a residue marker for the banned veterinary drug nitrofurazone. Also, it occurs as a break-down product of azodicarbonamide (ADC), a chemical used as a flour treatment. Furthermore, it may form as a reaction product of hypochlorite action on food additives. In the present study, we investigated the possible genotoxic effects of SEM with respect to the following cytogenetic end-points: (1) in vitro micronucleus (MN) formation and sister-chromatid exchange (SCE) induction in human lymphocytes and (2) in vivo micronucleus induction on rat bone marrow polychromatic erythrocytes (PCEs). Comparing MN and SCE frequencies on control and examined concentrations (0.5, 2.5, 5, 10 and 20 μg ml −1) did not reveal statistically significant differences except, marginally, the highest concentration (20 μg ml −1) in SCE analysis. On the other hand, oral administration of 50, 100 and 150 mg kg −1 b.w. of SEM showed a statistically significant effect in MN frequencies on Wistar rats’ bone marrow PCEs, with no dose–response pattern.

The manuscripts for these Proceedings were received by the Publisher: end of June 2009

Pesticides are widely used throughout the world in agriculture to protect crops and in public health to control diseases. Nevertheless, exposure to pesticides represents a potential risk to humans. This paper describes a study of possible genetic damage in the people living in regions contaminated with complex mixture of pesticides in Göksu Delta. In this study, used methods were chromosomal aberration (CA), sister chromatid exchange analysis (SCE) in the peripheral blood lymphocytes, and micronucleus (MN) assay in the buccal epithelial cells. In the present investigation, 32 affected subjects consist of 16 smoking and 16 non-smokings and an equal number of control subjects were assessed for genome damage. Micronucleus (MN), Broken egg (BE), Karyorrhexis (KR), Karyolysis (KL) and Binucleus (BN) frequencies were higher in affected subjects than in controls. Smoking had a statistically significant effect on the Micronucleus, Karyorrhexis and Binucleus frequencies for both the control and the exposed group. Also smoking and exposure affected the frequency of sister chromatid exchange and chromosomal aberrations compared with control groups.

Sister chromatid exchanges and chromosomal aberrations in Chinese hamster ovary (CHO-K1) cells treated with the insecticide pirimicarb

Pirimicarb and its formulation Aficida ® (50% pirimicarb) effects were studied on CHO-K1 cells employing sister chromatid exchange (SCE), chromosomal aberrations (CA), cell-cycle progression and mitotic index analyses. Continuous treatments were performed within 10–300 μg/ml concentration-range. Pirimicarb, but not Aficida ®, induced a concentration-dependent increase of abnormal cells. Pirimicarb induced a greater frequency of chromatid/isochromatid breaks than Aficida ® did. Regression analyses showed a concentration-dependent increase in the frequency of chromatid-type breaks for both compounds whereas only the frequency of isochromatid-type breaks did in those pirimicarb-treated cultures. SCEs in pirimicarb- or Aficida ®-treated cultures were significantly higher than control values with concentrations of 100–200 μg/ml. Both test compounds induced equivalent frequency of SCEs. A delay in cell-cycle kinetics was observed for pirimicarb and Aficida ® within 100–300 and 200–300 μg/ml concentration-range, respectively. An inhibition of MI was observed for both chemicals regardless of tested concentrations. Finally, the CAs appears to be a higher sensitive bioassay to detect DNA damage at lower concentrations of pirimicarb than SCEs does. The results demonstrated that pirimicarb and Aficida ® exert geno-cytotoxicity, at least in CHO-K1 cells.

Micronuclear and sister chromatid exchange analyses in peripheral lymphocytes of patients with oral lichen planus – a pilot study*

The purpose of this study was to determine the genetic instability of peripheral blood lymphocytes from patients diagnosed with oral lichen planus (OLP) by investigation of frequencies of micronuclei (MN) and sister chromatid exchange (SCE). A total of 22 newly diagnosed and untreated patients with OLP of same severity scores and twenty healthy controls participated in this study. They were all non-smokers with no previous history or family history of cancer. The periodontal status, flow rate and buffering capacity of whole mouth saliva were recorded. SCE and MN analyses were performed on peripheral blood lymphocytes of OLP patients and healthy controls. The frequencies of MN (50.00 +/- 22.36) and SCE (6.89 +/- 1.48) in OLP patients were found to be significantly elevated compared with that in normal individuals (25.20 +/- 9.52 and 5.93 +/- 1.31; z = 3.946, P = 0.0001; z = 2.346, P = 0.019). There were no significant differences in the MN frequency and SCE between the two subgroups with reticular or erosive types of OLP. These pilot data indicate an increased genomic instability in peripheral blood lymphocytes of a cohort of Turkish patients diagnosed with oral lichen planus as compared with that of healthy individuals. As patients with OLP may have an increased or potential risk for oral malignancy, these assays could be used in translational research to monitor beneficial effects of interventions and long-term prognosis.

ING2 controls the progression of DNA replication forks to maintain genome stability

Inhibitor of growth 2 (ING2) is a candidate tumour suppressor gene the expression of which is frequently lost in tumours. Here, we identified a new function for ING2 in the control of DNA replication and in the maintenance of genome stability. Global replication rate was markedly reduced during normal S-phase in small interfering RNA (siRNA) ING2 cells, as seen in a DNA fibre spreading experiment. Accordingly, we found that ING2 interacts with proliferating cell nuclear antigen and regulates its amount to the chromatin fraction, allowing normal replication progression and normal cell proliferation. Deregulation of DNA replication has been previously associated with genome instability. Hence, a high proportion of siRNA ING2 cells presented endoreduplication of their genome as well as an increased frequency of sister chromatid exchange. Thus, we propose for the first time that ING2 might function as a tumour suppressor gene by directly maintaining DNA integrity.