Evaluation of cisplatin + 5-FU, carboplatin + 5-FU, and ifosfamide + epirubicine regimens using the micronuclei test and nuclear abnormalities in the buccal mucosa

In the present work, the micronuclei (MN) test was performed in buccal mucosal samples from patients with cancer, with (pre- and post-treatment) and without genotoxic chemotherapy (GC), identified micronucleated cells (MNC) and nuclear abnormalities (binucleated cells (BN), pycnosis (PN), "broken-egg" (BE), condensed chromatin (CC), karyorrhexis (KR), and karyolysis (KL). The objective was to evaluate the genotoxicity of cisplatin + 5-Fluorouracil (5-FU), carboplatin (CBP) + 5-Fluorouracil, and ifosfamide (IFO) + epirubicine (EPI) regimens. The ifosfamide + epirubicine regimen described here produced a micronucleogenic effect, whereas the regimens using platinum compounds were cytotoxic for buccal mucosal cells, which probably explain the absence of increase of micronucleated cells in these samples compared with basal levels. In patients with cancer (with and without genotoxic chemotherapy), the numbers of MNC, PN, KR, total nuclear abnormalities and KL increased, together with a decrease in BN cells and CC. On the other hand, as consequence of the cytotoxicity of the drugs, the number of binucleated cells decreased and the number of karyolytic cells increased. These results could be used as a cytotoxicity marker in the future studies for different drugs.     

Evaluation of genotoxic effects induced by exposure to antineoplastic drugs in lymphocytes and exfoliated buccal cells of oncology nurses and pharmacy employees

The continuous introduction of new antineoplastic drugs and their use as complex mixture emphasize the need to carry out correct health risk assessment. The aim of this study was to evaluate genotoxic effects of antineoplastic drugs in nurses (n=25) and pharmacy technicians (n=5) employed in an oncology hospital. The nurses administered antineoplastic drugs in the day-care hospital (n=12) and in the wards (n=13), and pharmacy technicians prepared the drugs in the central pharmacy. We performed the micronucleus (MN) test with lymphocytes and exfoliated buccal cells and conducted traditional analysis of chromosomal aberrations (CA). Thirty healthy subjects were selected as controls. Monitoring of surface contamination with cyclophosphamide, 5-fluorouracil, ifosfamide, cytarabine, and gemcitabine showed the presence of detectable levels only for cyclophosphamide, 5-fluorouracil and ifosfamide. In addition, we measured the 5-fluorouracil metabolite alpha-F-betaalanine in the urine of all subjects and found significant concentrations only in 3 out of 25 nurses. The micronucleus assay with lymphocytes did not show significant differences between exposed and control groups, while the same test with exfoliated buccal cells found higher values in nurses administering antineoplastic drugs than in pharmacy employees. In the CA analysis, we detected in exposed groups a significant increase (about 2.5-fold) of structural CA, particularly breaks (up to 5.0-fold). Our results confirm the genotoxic effect of antineoplastic drugs in circulating blood lymphocytes. Moreover, in exfoliated buccal cells the data show more consistent genetic damage induced during administration of the antineoplastic drugs than during their preparation. The data also stress the use of this non-invasive sampling, to assess occupational exposure to mixture of chemicals at low doses.     

Cytogenetic biomonitoring of carpet fabric workers using micronucleus frequency, nuclear changes, and the calculation of risk assessment by repair index in exfoliated mucosa cells

The micronucleus (MN) assay in exfoliated buccal cells is a minimally invasive method for monitoring genetic damage in human populations and is used as an indicator of genotoxic exposition, as it is associated with chromosome aberrations. In this study, we evaluated MN frequencies and other nuclear changes (NCs), such as karyorrhexis (KR), karyolysis (KL), broken egg (BE), and binucleus in buccal mucosa cells of 50 carpet fabric workers (25 smokers and 25 nonsmokers) and 50 healthy control subjects (25 smokers and 25 nonsmokers). Microscopic observation of 2000 cells per individual was performed in both workers and control subjects. In both the control group and the exposed group, for each person a repair index (RI) was calculated via the following formula: (KR+KL)/(BE+MN). The results showed a statistically significant increase in the frequency of MN in buccal epithelial cells of exposed group compared with control group. There is a significant difference between worker and control groups (p<0.001) for RI. We believe that the calculation of RI values, in addition to nuclear changes, presents a new approach in risk assessment in relation to occupational exposure.     

The extent of chromosomal aberrations induced by chemotherapy in non-human primates depends on the schedule of administration

We utilized a non-human primate model, the rhesus monkey (Macaca mulatta), to quantitate the extent of chromosomal damage in bone marrow cells following chemotherapy. Thiotepa, etoposide, and paclitaxel were chosen as the chemotherapy agents due to their distinct mechanisms of action. Chromosomal aberrations were quantitated using traditional Giemsa stain. We sought to evaluate the extent to which genotoxicity was dependent on the schedule of administration by giving chemotherapy as either a bolus or a 96 h continuous infusion. Neutropenia and areas under the concentration curve (AUCs) were monitored to ensure comparable cytotoxicity and dose administered. At least 100 metaphases were scored in each marrow sample by an investigator unaware of the treatment history of the animals. All three drugs produced a statistically significant higher percentage of abnormal metaphases following bolus chemotherapy (p<0.0001, p=0.0015 and p<0.0001 for thiotepa, etoposide and paclitaxel, respectively). We conclude that infusional administration of thiotepa, etoposide and paclitaxel is less genotoxic to normal bone marrow cells than is bolus administration. These results suggest infusional regimens may be considered where there are concerns about long-term genotoxic sequelae, including secondary cancer, teratogenicity, or possibly the development of drug resistance. We believe this approach provides a reproducible model in which drugs and eventually, regimens can be compared.     

Positive interaction between 5-FU and FdUMP[10] in the inhibition of human colorectal tumor cell proliferation.

Interaction between 5-fluorouracil (5-FU) and FdUMP[10], a novel pro-drug formulation of the thymidylate synthase (TS) inhibitory nucleotide 5-fluoro-2'-deoxyuridine-5'-O-monophosphate (FdUMP), was investigated to evaluate the feasibility of using these two forms of fluorinated pyrimidine in combination chemotherapy regimens. 5-FU and FdUMP[10] are expected to differ in their relative intracellular distribution of active metabolites, and their combined administration may result in either a positive or a negative interactive effect. The dose-response behaviors of 5-FU and FdUMP[10] toward H630 and H630-10 (human colorectal tumor) cells were first investigated separately. Effects on cell viability were measured using an assay for 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), while cytotoxicity and apoptosis were investigated using clonogenic and TUNEL assays, respectively. Exposure of H630 cells to concentrations of FdUMP[10] insufficient to inhibit cell proliferation as a single agent markedly increased the cytotoxicity of 5-FU. The results indicate that 5-FU and FdUMP[10] interact in a positive manner, and that combining these two forms of fluorinated pyrimidine may be clinically beneficial.     

Chromosome damage and cytotoxicity in oral mucosa cells after 2 months of exposure to anabolic steroids (decadurabolin and winstrol) in weight lifting

The aim of the present study was to evaluate DNA damage (micronucleus) and cellular death (pyknosis, karyolysis and karyorrhexis) in exfoliated buccal mucosa cells from anabolic steroid users after 2 months of exposure. Two experimental groups consisting of 15 adult males who practise weight lifting and are anabolic steroid users or 15 adult males who practise weight lifting, but are non-anabolic steroid users, were recruited. In addition, 20 sedentary males, who do not practise any physical activity regularly, were matched by age with experimental groups. No significant statistical differences (p > 0.05) were noticed in individuals who practise physical activity only. On the other hand, an increase of micronucleated cells (MNCs) in anabolic steroid (decadurabulin and Winstrol) users was observed. Regarding cytotoxic parameters, the same observation has occurred, that is, significant statistical differences (p < 0.05) were noticed in the group exposed to anabolic steroids when compared with other controls, as depicted by high frequencies of pyknosis, karyolysis and karyorrhexis. Taken together, our results suggest that genomic instability and cytotoxicity are induced by anabolic steroid administration in oral mucosa cells as assessed by the micronucleus test.     

Genetic damage in exfoliated cells from oral mucosa of individuals exposed to X-rays during panoramic dental radiographies

The genotoxic effects of X-ray emitted during dental panoramic radiography were evaluated in exfoliated cells from oral epithelium through a differentiated protocol of the micronucleus test. Thirty-one healthy individuals agreed to participate in this study and were submitted to this procedure for diagnosis purpose after being requested by the dentist. All of them answered a questionnaire before the examination. Cells were obtained from both sides of the cheek by gentle scrapping with a cervical brush, immediately before the exposure and after 10 days. Cytological preparations were stained according to Feulgen-Rossenbeck reaction and analyzed under light and laser scanning confocal microscopies. Micronuclei, nuclear projections (buds and broken eggs) and degenerative nuclear alterations (condensed chromatin, karyolysis and karyorrhexis) were scored. The frequencies of micronuclei, karyolysis and pycnosis were similar before and after exposure (P > 0.90), whereas the condensation of the chromatin and the karyorrhexis increased significantly after exposure (P < 0.0001). In contrast, both bud and broken egg frequencies were significantly higher before the examination (P < 0.005), suggesting that these structures are associated to the normal epithelium differentiation. The results suggest that the X-ray exposure during panoramic dental radiography induces a cytotoxic effect by increasing apoptosis. We also believe that the score of other nuclear alterations in addition to the micronucleus improves the sensitivity of genotoxic effects detection.     

Induction of micronuclei by Zearalenone in Vero monkey kidney cells and in bone marrow cells of mice: protective effect of Vitamin E

Zearalenone (ZEN) is a non-steroidal estrogenic mycotoxin mainly produced by Fusarium graminaerum, found as a world-wide contaminant mainly of corn and wheat. Previous studies have demonstrated that among several other effects on animals and humans, ZEN also displays hepatotoxicity, immunotoxicity and nephrotoxicity. ZEN is mainly known as a hormonal disrupter due to its estrogenic activities and consequent toxicity for reproduction. Furthermore, mutagenic and genotoxic proprieties of ZEN were disclosed recently, the molecular mechanisms of which are not yet well understood. In the present study, the genotoxic potential of ZEN was evaluated using genotoxicity tests: the 'cytokinesis block micronucleus assay' in Vero monkey kidney cells and the 'in vivo mouse bone marrow micronucleus assay'. In cultured cells treated with 5, 10 and 20 microM ZEN, the frequency of binucleated micronucleated cells (BNMN) was assessed in 1000 binucleated cells and in mice given oral doses of 10, 20 and 40 mg/kg bw, the frequency of polychromatic erythrocytes micronucleated (PCEMN) in bone marrow cells was assessed in 2000 polychromatic erythrocytes (PCE). The potential prevention of ZEN-induced effects by 25 microM Vitamin E (Vit E) was also evaluated.In vivo, doses of 10, 20 and 40 mg/kg bw ZEN representing, respectively 2, 4 and 8% of the LD50 (LD50 of ZEN in mice is 500 mg/kg bw), were administered to animals either with or without pre-treatment with Vit E (216.6 mg/kg bw) in order to evaluate its preventive potential.ZEN was found to induce micronuclei (MN) in a dose-dependent manner in cultured Vero cells as well as in mouse bone marrow cells. The present data emphasise the likely clastogenic pathway among the molecular mechanisms that underlay the ZEN-induced genotoxicity. Vit E was found to prevent partially-from 30 to 50%-these toxic effects, most likely acting either as a structural analogue of ZEN or as an antioxidant.     

Sensitivity and specificity of the micronucleus test in hypotonic-swollen mononuclear leukocytes compared to the micronucleus test in binucleated lymphocytes to assess chromosomal breaks

OBJECTIVE: To examine the sensitivity and specificity of the micronucleus (MN) test on swollen mononuclear cells compared to that in binucleated lymphocytes. STUDY DESIGN: This is a cross-sectional experimental study. Samples were taken from patients who had a malignancy who were scheduled to receive chemotherapy; samples were taken before and after the chemotherapy regimen began. The MN tests on swollen mononuclear cells and binucleated lymphocytes were performed on every sample. Proportions of micronucleated cells/cells screened were noted and interpreted as positive or negative results. The results of both tests were compared to get the sensitivity and specificity of the MN test on swollen mononuclear cells. RESULTS: Of 59 samples obtained, 54 were included in this study. The results showed that the sensitivity of the MN test on swollen mononuclear cells compared to that on binucleated lymphocytes was 89% and specificity was 78%. CONCLUSION: The MN test on swollen mononuclear cells was able to detect chromosomal breaks caused by chronic clastogen exposure.     

Checkpoint signaling, base excision repair, and PARP promote survival of colon cancer cells treated with 5-fluorodeoxyuridine but not 5-fluorouracil

The fluoropyrimidines 5-fluorouracil (5-FU) and FdUrd (5-fluorodeoxyuridine; floxuridine) are the backbone of chemotherapy regimens for colon cancer and other tumors. Despite their widespread use, it remains unclear how these agents kill tumor cells. Here, we have analyzed the checkpoint and DNA repair pathways that affect colon tumor responses to 5-FU and FdUrd. These studies demonstrate that both FdUrd and 5-FU activate the ATR and ATM checkpoint signaling pathways, indicating that they cause genotoxic damage. Notably, however, depletion of ATM or ATR does not sensitize colon cancer cells to 5-FU, whereas these checkpoint pathways promote the survival of cells treated with FdUrd, suggesting that FdUrd exerts cytotoxicity by disrupting DNA replication and/or inducing DNA damage, whereas 5-FU does not. We also found that disabling the base excision (BER) repair pathway by depleting XRCC1 or APE1 sensitized colon cancer cells to FdUrd but not 5-FU. Consistent with a role for the BER pathway, we show that small molecule poly(ADP-ribose) polymerase 1/2 (PARP) inhibitors, AZD2281 and ABT-888, remarkably sensitized both mismatch repair (MMR)-proficient and -deficient colon cancer cell lines to FdUrd but not to 5-FU. Taken together, these studies demonstrate that the roles of genotoxin-induced checkpoint signaling and DNA repair differ significantly for these agents and also suggest a novel approach to colon cancer therapy in which FdUrd is combined with a small molecule PARP inhibitor.     

Genotoxic effects of doxorubicin in cultured human lymphocytes with different glutathione S-transferase genotypes

Doxorubicin (Dox) is a widely used drug in oncology with a broad spectrum of interactions with various cellular components; therefore, it is likely to act through different mechanisms. In clinical practice there is inter-individual variability in cytotoxic drug response and in the occurrence of adverse reactions. Glutathione S-transferases (GSTM1, GSTT1 and GSTP1) are thought to be involved in the detoxification of endogenous and exogenous genotoxicants. The aim of this work is the assessment of a possible influence of polymorphisms in GSTs on the levels of genetic damage induced in vitro by Dox in cultured human lymphocytes. For this purpose, whole blood cultures from individuals with different genotypes for GSTM1, GSTT1 and GSTP1 were exposed to Dox and the cytokinesis-blocked micronucleus (CBMN) assay was used as the endpoint for chromosomal damage in the lymphocytes. Genotyping of GSTM1 and GSTT1 was carried out by multiplex PCR and the GSTP1-Ile105Val polymorphism was determined by PCR/RFLP. The total number of micronuclei present in 1000 binucleated cells and the frequency of micronucleated binucleated lymphocytes in the different individuals were analyzed considering the GSTM1, GSTT1 and GSTP1 genotypes. The results obtained suggest that GSTM1 and GSTT1 deletion polymorphisms do not modify significantly the genotoxic potential of Dox. However, the GSTP1 Ile105Val polymorphism was associated with an increase of micronucleated binucleated cells induced by Dox. Lymphocytes from homozygous individuals for the variant form (Val/Val) presented a significant increase in micronucleated binucleated cells (approximately 1.5-fold; p<0.05) when compared with individuals with at least one wild-type allele. These results suggest a possible role for GSTP1 on the modulation of the genotoxicity induced by Dox, which may be considered in cancer therapy.     

A forward genetic approach for analyzing the mechanism of resistance to the anti-cancer drug, 5-fluorouracil, using Caenorhabditis elegans

Pyrimidine antagonists including 5-Fluorouracil (5-FU) have been used in chemotherapy for cancer patients for over 40 years. 5-FU, especially, is a mainstay treatment for colorectal cancer. It is a pro-drug that is converted to the active drug via the nucleic acid biosynthetic pathway. The metabolites of 5-FU inhibit normal RNA and DNA function, and induce apoptosis of cancer cells. One of the major obstacles to successful chemotherapy is the resistance of cancer cells to anti-cancer drugs. Therefore, it is important to elucidate resistance mechanisms to improve the efficacy of chemotherapy. We have used C. elegans as a model system to investigate the mechanism of resistance to 5-FU, which induces germ cell death and inhibits larval development in C. elegans. We screened 5-FU resistant mutants no longer arrested as larvae by 5-FU. We obtained 18 mutants out of 72,000 F1 individuals screened, and mapped them into three complementation groups. We propose that C. elegans could be a useful model system for studying mechanisms of resistance to anti-cancer drugs.     

Occupational exposure of workers to pesticides: Toxicogenetics and susceptibility gene polymorphisms

Farm workers are often exposed to pesticides, which are products belonging to a specific chemical group that affects the health of agricultural workers and is mostly recognized as genotoxic and carcinogenic. The exposure of workers from Piauí, Brazil, to these hazardous chemicals was assessed and cytogenetic alterations were evaluated using the buccal micronucleus assay, hematological and lipid parameters, butyrylcholinesterase (BChE) activity and genetic polymorphisms of enzymes involved in the metabolism of pesticides, such as PON1, as well as of the DNA repair system (OGG1, XRCC1 and XRCC4). Two groups of farm workers exposed to different types of pesticides were evaluated and compared to matched non-exposed control groups. A significant increase was observed in the frequencies of micronuclei, kariorrhexis, karyolysis and binucleated cells in the exposed groups (n = 100) compared to controls (n = 100). No differences were detected regarding the hematological parameters, lipid profile and BChE activity. No significant difference was observed either regarding DNA damage or nuclear fragmentation when specific metabolizing and DNA repair genotypes were investigated in the exposed groups.     

Micronucleus investigation of alcoholic patients with oral carcinomas

The micronucleus test (MN) is used as an indicator of genotoxic exposition, since it is associated with chromosome aberrations. An increased mutation rate in oral squamous cells, indicated by an increased MN frequency, is also related to the development of oral carcinomas. We evaluated the frequencies of MN and other metanucleated anomalies in the buccal squamous cells of 30 alcoholics with oral or oropharyngeal carcinomas, and compared them to a control group of abstinent health individuals. Microscopic examination was made of 2000 cells per individual from each of three distinct areas of the mouth: around the lesion (A), opposite to the lesion (B) and in the upper gingival-labial gutter (C); C was used as a control region because of low tumor frequency. There was a seven-fold increase in MN frequency in region B, a three-fold increase in region A and a two-fold, though nonsignificant, increase in C; indicating a gradient of frequencies towards carcinogenesis: C --> A --> B. Comparisons of frequencies of various types of metanucleated cells: binucleated, karyorrhexis (KR), karyolysis (KL) and broken egg (BE) in patients and controls showed, with few exceptions, highly significant differences. This gave us a better understanding of the dynamics of this squamous epithelium, supporting a more efficient biomonitor based on these various metanucleated anomalies: the repair index RI=(KL+KR)/(MN+BE). Also, the apparently contradictory results from regression analysis revealed that the MN frequency decreased with age and alcohol consumption, probably because of slow cell proliferation, and consequently led to a loss of homeostasis due to aging. In addition, in the analysis of nonparametric variables only one CAGE question was significant, confirming the effect of alcohol. In conclusion, the MN test and the repair index could be used for monitoring clinical evolution, by means of intra- and inter-individual cellular comparisons, in subjects with healed or surgically removed tumors or leukoplastic lesions, after chemo- or radiotherapeutic treatments.     

Increased frequency of micronucleated exfoliated cells among humans exposed in vivo to mobile telephone radiations

The health concerns have been raised following the enormous increase in the use of wireless mobile telephones throughout the world. This investigation had been taken, with the motive to find out whether mobile phone radiations cause any in vivo effects on the frequency of micronucleated exfoliated cells in the exposed subjects. A total of 109 subjects including 85 regular mobile phone users (exposed) and 24 non-users (controls) had participated in this study. Exfoliated cells were obtained by swabbing the buccal-mucosa from exposed as well as sex-age-matched controls. One thousand exfoliated cells were screened from each individual for nuclear anomalies including micronuclei (MN), karyolysis (KL), karyorrhexis (KH), broken egg (BE) and binucleated (BN) cells. The average daily duration of exposure to mobile phone radiations is 61.26 min with an overall average duration of exposure in term of years is 2.35 years in exposed subjects along with the 9.84+/-0.745 micronucleated cells (MNCs) and 10.72+/-0.889 total micronuclei (TMN) as compared to zero duration of exposure along with average 3.75+/-0.774 MNC and 4.00+/-0.808 TMN in controls. The means are significantly different in case of MNC and TMN at 0.01% level of significance. The mean of KL in controls is 13.17+/-2.750 and in exposed subjects is 13.06+/-1.793. The value of means of KH in exposed subjects (1.84+/-0.432) is slightly higher than in controls (1.42+/-0.737). Mean frequency of broken egg is found to be more in exposed subjects (0.65+/-0.276) as compared to controls (0.50+/-0.217). Frequency of presence of more than one nucleus in a cell (binucleated) is also higher in exposed (2.72+/-0.374) in comparison to controls (0.67+/-0.231). Although there is a slight increase in mean frequency of KH, BE and BN in exposed subjects but the difference is not found statistically significant. Correlation between 0-1, 1-2, 2-3 and 3-4 years of exposure and the frequency of MNC and TMN has been calculated and found to be positively correlated.     

Micronucleus induction and FISH analysis in buccal cells and lymphocytes of nurses administering antineoplastic drugs

A genotoxic effect for antineoplastic drugs, in particular micronucleus induction, has been shown in several studies. The aim of our study was to assess genotoxic effects in nurses administering different mixtures of antineoplastic drugs in an oncology hospital by evaluating the frequency of micronuclei in exfoliated buccal cells and blood lymphocytes by use of the standard micronucleus (MN) test and by identifying, by means of FISH analysis with centromeric probes, the mechanism of micronucleus induction (clastogenic or aneugenic). The study group comprised 23 nurses, 10 of whom worked in the day-care hospital and 13 in the ward. Twenty healthy subjects were selected as controls. Pan-centromeric FISH analysis was performed on lymphocytes from a selected group of nurses (12/23 subjects) characterized by higher MN frequencies as observed by standard Giemsa staining. A significant increase of micronucleus frequency compared with controls was found in exfoliated buccal cells of both groups of nurses: day-care hospital nurses 0.92 versus 0.45 (p=0.034) and ward nurses 0.94 versus 0.45 (p=0.051). An increase, although not statistically significant, of mean MN frequency was also found by the MN standard test on lymphocytes of the day-care hospital nurses (10.9 versus 7.5; p=0.056), while no differences were found in ward nurses (8.15 versus 7.5; p=0.56). We found that the administration of antineoplastic drugs by nurses in ward units induced a higher frequency of FISH MN+ (43% of subjects) than in the day-care hospital (20%). This was associated with the micronucleus size percentage. This finding could be correlated with the different compositions of administered mixtures of antineoplastic drugs: in ward units the mixtures contained drugs, such as vinorelbine, that were absent in the mixtures administered in the day-care hospital. Our results show genetic damage induced by administration of antineoplastic drugs, particularly in exfoliated buccal cells. This result suggests the useful application of this non-invasive sampling to evaluate genotoxic effects of occupational exposure to mixtures of inhalable chemicals at low doses.     

Exposure of thermoelectric power-plant workers to volatile organic compounds from fuel oil: genotoxic and cytotoxic effects in buccal epithelial cells

Thermoelectric power-plant workers are constantly exposed to high levels of potentially genotoxic gaseous substances, such as volatile organic compounds (VOCs) from the combustion of fuel oil or the processing of naphtha. The aim of the present study was to estimate the association between such occupational exposure and the frequency of micronucleated cells and cells with other nuclear anomalies. Buccal epithelial cells were collected from a total of 44 power-plant workers (exposed group) and 47 administrative workers (non-exposed group), and examined for the frequency of micronucleated cells (MNC) and of cells with other nuclear anomalies (ONA: pyknosis, karyolysis, and karyorrhexis) by means of the micronucleus assay. The frequencies of MNC and ONA per 1000 cells in the exposed group (1.8‰ and 82.4‰, respectively) were significantly higher than in the non-exposed group (0.2‰ and 58.3‰, respectively). The exposed group had a twelve-fold increase in risk for formation of MNC compared with non-exposed individuals (RR=12.1; 95% CI, 5.0-29.2; P<0.001). The confounding factors analyzed (age, smoking status, alcohol consumption, and mouthwash use) did not show any significant association with the frequency of MNC or ONA. The findings of this study show that workers from power plants exposed to VOCs have a significantly elevated risk for DNA damage. Therefore, bio-monitoring of DNA damage is recommended for this group of workers.     

Combinations of 5-fluorouracil with UCN-01 or staurosporine

The action of 5-Fluorouracil (5-FU) is mediated by inhibition of thymidylate synthase (TS), which is regulated by cell cycle proteins controlled by protein phosphorylation. We studied the effects of staurosporine and its analogue UCN-01, inhibitors of protein kinase C (PKC) on 5-FU cytotoxicity in Lovo colon cancer cells. Each drug contributes equally to the cell cycle effects of the 5-FU combinations. In sequential drug administration, the cell cycle distribution was determined by the first drug. Simultaneous 5-FU combinations induced additive effects in induction of apoptosis. When staurosporine was used as the second drug, induction of apoptosis was 2-fold higher than the sum of both drugs alone. Based on induction of apoptosis 5-FU addition prior to the PKC inhibitors seemed preferable.     

The cell composition in the lymphocyte population and the radiation adaptive response

Using lymphocytes of 5 healthy individuals the ability to adaptive response (AR), cell composition of population after PHA stimulation, changes in cell composition population after irradiation in the dose of 1.0 Gy and after irradiation in adaptive (0.05 Gy) and challenge (1.0 Gy) doses have been studied. AR observed in 2 of the 5 individuals only. After PHA stimulation the persons with AR have the total amount of cells after mitosis or during mitosis (the number of binucleated cells + the number of multinucleated cells + the whole cells with micronuclei + the number of mitotic cells) on average is higher than in persons without AR. In individuals with AR the linear correlation between the number of binucleated cells with micronuclei (on the 1000 scored binucleated cells) and the part of binucleated cells in the population is observed with coefficients of correlation -0.89 and -0.91. In the humans without AR this correlation is absent. The correlation observed permits to suppose that AR may occur at the expense of not only the decrease in number of damaged lymphocytes, but also the increase in the share of not damaged binucleated cell with the stable number of damaged cells.