Sister-chromatid exchanges and their distribution in human lymphocytes in relation to age, sex and smoking

Assessment of genome stability in various breeds of cattle

Chromosomal instability is a type of genome instability involving changes in genetic information at the chromosomal level. The basic tests used to identify this form of instability are sister chromatid exchange (SCE) tests and identification of fragile sites (FS). SCE is the process by which sister chromatids become fragmented as a result of DNA strand breakage and reassembly, followed by exchange of these fragments. FS can be observed in the form of breaks, gaps or constrictions on chromosomes, which often result from multiple nucleotide repeats in DNA that are difficult to replicate. The research material was the peripheral blood of ten breeds of cattle raised in Poland, including four native breeds covered by a genetic resources conservation programme, i.e. Polish Red, Polish Red-and-White, White-Backed, and Polish Black-and-White, as well as Polish Holstein-Friesian, Simmental, Montbéliarde, Jersey, Limousine and Danish Red. Two tests were performed on chromosomes obtained from in vitro cultures: SCE and FS. The average frequency of SCE was 5.08 ± 1.31, while the incidence of FS was 3.45 ± 0.94. Differences in the incidence of SCE and FS were observed between breeds. The least damage was observed in the Polish Red and White-Backed breeds, and the most in Polish Holstein-Friesians. The most damage was observed in the interstitial part of the chromosomes. Age was shown to significantly affect the incidence of SCE and FS. Younger cows showed less damage than older ones (SCE: 4.84 ± 1.25; 5.34 ± 1.24; FS: 3.10 ± 0.88, 3.80 ± 0.92).

Spontaneous sister chromatid exchange in mitotic chromosomes of the chinchilla (Chinchilla lanigera)

Kuchta-Gładysz, M., Wójcik, E., Szeleszczuk, O., Niedbała, P. and Tyblewska, K. 2015. Spontaneous sister chromatid exchange in mitotic chromosomes of the chinchilla (Chinchilla lanigera). Can. J. Anim. Sci. 95: 543–550. The sister chromatid exchange (SCE) test is a cytogenetic tool with applications as a short-term screen. It is used to assess the influence of physical and chemical factors with potential mutagenic and genotoxic properties on the animal organism. The test results make it possible to eliminate mutagens, as well as helping to predict possible genetic consequences in animal cells and assess animal resistance. The mitotic chromosomes were obtained from an in vitro culture of peripheral blood lymphocytes with added bromodeoxyuridine (BrdU), at five different concentrations: 0.25, 0.5, 1.0, 2.5, and 5.0 µg mL−1. The chromosomes were stained according to the FPG method. Our analyses revealed the spontaneous SCE level in the chinchilla at the concentration of 0.5 µg mL−1. Higher concentrations of this substance have a genotoxic effect and cause damage to the DNA structure of the chromosomes by inducing additional SCEs in the chromosomes of this species. The mean SCE/cell incidence in the chinchilla population was 4.34±1.28. We investigated the effects of age on the incidence of SCE and found it significantly affected this phenomenon in both sexes.

Sister chromatid exchange, (SCE), High-Frequency Cells (HFCs) and SCE distribution patterns in peripheral blood lymphocytes of Spanish adult smokers compared to non-smokers

According to the International Agency for Research on Cancer, smoking tobacco is a major cause of cancer in humans. It causes about half of all male cancer deaths and an ever increasing number of cancer deaths in females. The aim of this study was to establish whether cigarette smoking increases sister chromatid exchanges (SCEs) in peripheral blood lymphocytes in two Spanish population groups; light and heavy smokers. The mean number of High-Frequency Cells (HFCs) was determined and, the SCE distribution pattern among the chromosomes was analysed represented by a ratio described below. A local sample of 101 adult smokers (n=48) and non-smokers (n=53), aged from 18 to 49 years, was studied using SCE levels in peripheral lymphocytes. Heavy smoking (≥ 10 cigarettes per day) increased significantly the SCE frequency and the HFC parameters. Neither age nor sex significantly influenced the frequencies in the groups studied.

Sister chromatid exchanges in smokers and smokers with alcohol habit

Aim:

Sister chromatid exchange (SCE) test is a sensitive, biomarker of genotoxic substances. The present study was conducted to observe the frequency of SCEs in peripheral blood lymphocytes of 30 males with and without the habit of cigarette smoking and alcohol consumption.

Materials and Methods:

Subjects for this study were males aged between 25-50 years and were selected from the students, employees and the patients attending the outpatient department of Ragas dental college and Hospital, Chennai.

Results:

Controls, smokers, and smokers with alcohol habit were divided into two age groups as ≤30 years and ≥30 years. In controls the mean frequency of SCEs/cell in ≤30 years and ≥30 year's age group was 5.80 and 6.05, respectively. In Smokers SCEs/cell in ≤30 years and ≥30 year's age group was 7.7 and 8.8, respectively. In Smokers with alcohol habit SCEs/cell in ≤30 years and ≥30 years age group was 10.1 and 12.8, respectively.

Conclusions:

In this study, the duration of the smoking habit has shown a positive correlation with the mean SCE frequency. Whereas, frequency of the habit did not show any influence on the SCE levels. In smokers with alcohol habit, both the duration and frequency of their smoking habit has shown a significant effect on the SCE levels suggesting a synergistic effect of alcohol and smoking leading to excessive DNA damage.

Sister chromatid exchange in Greenleg Partridge and Polbar hens covered by the gene-pool protection program for farm animals in Poland

A basic assay that detects genotoxic DNA damage disrupting DNA replication and repair mechanisms is the sister chromatid exchange test. The frequency of sister chromatid exchanges was analyzed in chromosomes of the following hen breeds: Greenleg Partridge and Polbar. Chromosome preparations were obtained from our in vitro culture of peripheral blood lymphocytes stained using the fluorescence plus Giemsa (FPG) technique. The sister chromatid exchange (SCE)/cell mean of the hens under analysis was 7.83 ± 1.76 (7.22 ± 1.70 in the Greenleg Partridge and 8.43 ± 1.61 in the Polbar population). Statistically significant differences were identified between the hen breeds. A higher mean number of SCE/cell was observed in the group of hens producing fewer eggs (8.55 ± 1.51) compared with the group with a better egg yield (7.10 ± 1.65). The differences were statistically significant. Additionally, SCE frequency in the first, second, and third chromosome was analyzed in detail. The highest number of SCE was observed in the first and the lowest in the third chromosome. The SCE distribution in the particular regions of the analyzed chromosomes was also studied. The most numerous exchanges were observed in the proximal region, followed by the interstitial and distal areas.

DNA damage and susceptibility assessment in industrial workers exposed to styrene

Styrene is a widely used chemical in the manufacture of synthetic rubber, resins, polyesters, and plastics. The highest levels of human exposure to styrene occur during the production of reinforced plastic products. The objective of this study was to examine occupational exposure to styrene in a multistage approach, in order to integrate the following endpoints: styrene in workplace air, mandelic and phenylglyoxylic acids (MA + PGA) in urine, sister chromatid exchanges (SCE), micronuclei (MN), DNA damage (comet assay), and genetic polymorphisms of metabolizing enzymes (CYP2E1, EPHX1, GSTM1, GSTT1, and GSTP1). Seventy-five workers from a fiberglass-reinforced plastics factory and 77 unexposed controls took part in the study. The mean air concentration of styrene in the breathing zone of workers (30.4 ppm) and the mean concentration of urinary metabolites (MA + PGA = 443 ± 44 mg/g creatinine) exceeded the threshold limit value (TLV) and the biological exposure index (BEI). Significantly higher SCE frequency rate and DNA damage were observed in exposed workers, but MN frequency was not markedly modified by exposure. With respect to the effect of genetic polymorphisms on different exposure and effect biomarkers studied, an increase in SCE levels with elevated microsomal epoxide hydrolase activity was noted in exposed workers, suggesting a possible exposure-genotype interaction.

Antineoplastic Drugs as a Potential Risk Factor in Occupational Settings: Mechanisms of Action at the Cell Level, Genotoxic Effects, and Their Detection Using Different Biomarkers

U članku je prikazana osnovna podjela antineoplastičnih lijekova prema mehanizmima djelovanja na razini stanice. Objašnjeni su mehanizmi genotoksičnosti najvažnijih vrsta lijekova koji se primjenjuju u okviru uobičajenih protokola za liječenje zloćudnih novotvorina. Navedena je važeća klasifikacija antineoplastika prema kancerogenom potencijalu, podaci o mutagenom potencijalu te je prikazana njihova podjela u skladu s anatomsko-terapijsko-kemijskim sustavom klasifikacije. Sustavno su prikazani najvažniji rezultati svjetskih i hrvatskih istraživanja na populacijama radnika izloženih antineoplasticima, provedenih u razdoblju 1980.-2009. s pomoću četiri najčešće primjenjivane metode: analize izmjena sestrinskih kromatida, analize kromosomskih aberacija, mikronukleus-testa i komet-testa. Objašnjena su osnovna načela navedenih metoda te raspravljene njihove prednosti i nedostaci. Biološki pokazatelji daju važne podatke o individualnoj osjetljivosti profesionalno izloženih ispitanika koji mogu poslužiti unaprjeđenju postojećih uvjeta rada i upravljanju rizicima pri izloženosti genotoksičnim agensima. Na osnovi prednosti i nedostataka citogenetičkih metoda zaključeno je da je mikronukleus-test, koji podjednako uspješno dokazuje klastogene i aneugene učinke, jedna od najboljih metoda dostupnih za otkrivanje štetnih djelovanja antineoplastičnih lijekova koji su u aktivnoj primjeni.

Biomonitoring of human exposure to prestige oil: effects on DNA and endocrine parameters

Since 1960, about 400 tankers spilled more than 377765 tons of oil, with the Prestige accident (Galician coast, NW Spain, November 2002) the most recent. Taking into account the consistent large number of individuals exposed to oil that exists all over the world, it seems surprising the absence in the literature of studies focused on the chronic effects of this exposure on human health. In this work we evaluated the level of DNA damage by means of comet assay, and the potential endocrine alterations (prolactin and cortisol) caused by Prestige oil exposure in a population of 180 individuals, classified in 3 groups according to the tasks performed, and 60 controls. Heavy metals in blood were determined as exposure biomarkers, obtaining significant increases of aluminum, nickel and lead in the exposed groups as compared to controls. Higher levels of genetic damage and endocrine alterations were also observed in the exposed population. DNA damage levels were influenced by age, sex, and the use of protective clothes, and prolactin concentrations by the last two factors. Surprisingly, the use of mask did not seem to protect individuals from genetic or endocrine alterations. Moreover, polymorphisms in genes encoding for the main enzymes involved in the metabolism of oil components were analyzed as susceptibility biomarkers. CYP1A1-3'UTR and EPHX1 codons 113 and 139 variant alleles were related to higher damage levels, while lower DNA damage was observed in GSTM1 and GSTT1 null individuals.

Evaluation of micronucleus frequencies in blood lymphocytes from smelting plant workers exposed to arsenic

Arsenic is a world health problem due to the seriousness of its effects, mainly related with the increase of cancer. In Chile, the geological characteristics of the northern region, associated with the development of the copper mining and smelting activities, have contributed to increase the environmental levels of arsenic. This study has been conducted to investigate the relationship between arsenic occupational exposure and genotoxic effects in smelting plant workers. To determine the genotoxic risk related to the increase of cancer among the chronically exposed population, the frequency of micronuclei in blood (BNMN) has been evaluated. The study was carried out in a total of 207 men, divided into three groups: an exposed group of 105 individuals working in a smelting plant, an internal reference group with 52 employees at the same mine but in the administrative area, and an external reference group of 50 workers from another copper mine where no significant levels of arsenic were detected. As expected, differences between arsenic levels in urine have been detected between groups, with the exposed group being the one with a higher level of total arsenic in urine, followed by the internal reference group. Despite that, no significant differences in micronuclei frequencies in lymphocytes were detected among these groups.

Relationship between blood concentrations of heavy metals and cytogenetic and endocrine parameters among subjects involved in cleaning coastal areas affected by the 'Prestige' tanker oil spill

The sinking of the 'Prestige' oil tanker in front of the Galician coast (NW of Spain) in November 2002 offered a unique opportunity to analyze intermediate cytogenetic and endocrine effects among people exposed to the complex mixture of substances that oil constitutes, including several toxic heavy metals. In this work we evaluated the relationship between exposure to heavy metals (blood concentrations of aluminium, cadmium, nickel, lead and zinc) and genotoxic parameters (sister chromatid exchanges, micronucleus test and comet assay) or endocrine parameters (plasmatic concentrations of prolactin and cortisol) in subjects exposed to 'Prestige' oil during cleaning tasks developed after the spillage. Concentrations of lead were significantly related to the comet assay even after adjusting by age, sex and smoking. Cortisol concentrations were significantly influenced by aluminium, nickel (both, inversely) and cadmium (positively). Women had clearly higher concentrations of prolactin and cortisol, even when adjusting by age, smoking, cadmium, aluminium or nickel. Plasmatic cortisol was jointly influenced by gender, smoking and aluminium or nickel (all p<0.05). In women there was a strong relationship between concentrations of cadmium and prolactin (beta=0.37, p=0.031). When the effects of cadmium, aluminium and nickel on cortisol were simultaneously assessed, only the latter two metals remained statistically significant. Among parameters analysed, cortisol appeared to be the most sensitive to the effects of metal exposure. Plasma levels of cortisol deserve further evaluation as a potentially relevant biomarker to assess the effects of exposure to heavy metals.

Cell proliferation kinetics and genotoxicity in lymphocytes of smokers living in Mexico City

Genotoxicity caused by tobacco smoke was assessed in peripheral blood lymphocytes of smokers living in Mexico City by determining sister chromatid exchange (SCE), cell proliferation kinetics (CPK), replication index (RI) and mitotic index (MI). Nicotine levels, and its major metabolite cotinine, were also estimated in urine samples using gas-chromatography-mass spectrometry to quantify smoking intensity. The outcome of the analysis and the comparison of the 77-smoker group with a non-smoking control group showed that moderate and heavy smokers exhibited significant differences (P < 0.001 and P < 0.05, respectively) in CPK, with an underlying delay in the cellular cycle; similarly, RI was significantly different in these groups (P < 0.001 and P < 0.0001, respectively). There were significant correlations (P < 0.05) between age and number of years the subject had been smoking, as well as between RI and nicotine and cotinine levels and between CPK (M1, M2 and M3) and nicotine and cotinine levels. Smokers were classified for the analysis according to the nicotine levels (it is in relation to number of cigarettes smoked per day) found in urine (ng/mL) as: light (10-250), moderate (251-850) and heavy (851-4110). Significant differences in CPK were found (P < 0.05) between moderate and heavy smokers and non-smokers. Significant differences in RI were found between moderate (P < 0.001) and heavy smokers (P < 0.0001) and non-smokers, but not for the light smoking group. MI was determined in 57 of the smokers, whereas SCE frequency was only recorded in 34 smokers. Both parameters yielded no significant differences, nor correlations with any of the assessed variables. In conclusion, cytokinetic and cytostatic effects were mainly detected in heavy and moderate smokers. Cell cycle delay and RI decrease were found in all ;healthy' smokers. The nicotine and cotinine exposure (causing oxidative damage to DNA) may have implications in the decrease in cell replication due to direct damage to DNA and/or a decrease in the DNA repair mechanisms. Alternatively, nicotine and cotinine may possibly induce apoptosis.

Initial study on the effects of Prestige oil on human health

The big oil tanker Prestige wrecked at 130 miles from the coast of Galicia, on the Northwest of Spain, in November 19, 2002. During the accident over 40,000 tons of oil were spilled, and along the next weeks 22,000 more reached the shore in the way of three black tides. A great number of people participated in the cleaning tasks. The objective of this study was to initially evaluate the damage caused by Prestige oil in exposed individuals both from the cytogenetic and the endocrine points of view. Exposure level was determined by analysing volatile organic compounds in the environment and heavy metals in blood. Cytogenetic damage was determined by sister chromatid exchanges (SCE), and plasmatic prolactin and cortisol levels were used as biomarkers of endocrine toxicity. Finally we have determined the possible influence of GST genetic polymorphisms (GSTM1 and GSTT1 deletion polymorphisms, GSTP1 Ala105Val) on the evaluated effects. The exposed population was classified according to the performed cleaning tasks in three groups: volunteers that collaborated for 1 week (N=25), hired manual workers (N=20) and hired high-pressure cleaner workers (N=23). The control population consisted of 42 individuals. Exposure to Prestige oil caused cytogenetic damage in exposed individuals, being its effect influenced by age, sex, tobacco consumption and GSTM1 polymorphism. With regard to endocrine toxicity, our results showed that xenobiotics present in Prestige oil induced alterations in hormonal status, and thus it may be considered as an endocrine disruptor. Therefore, the selected parameters have shown to be good indicators of toxicity related to exposure to Prestige oil. In addition, data obtained point to the importance of using protective devices in preventing the effects related to the exposure.

Genotoxicity of tobacco smoke and tobacco smoke condensate: a review

This report reviews the literature on the genotoxicity of mainstream tobacco smoke and cigarette smoke condensate (CSC) published since 1985. CSC is genotoxic in nearly all systems in which it has been tested, with the base/neutral fractions being the most mutagenic. In rodents, cigarette smoke induces sister chromatid exchanges (SCEs) and micronuclei in bone marrow and lung cells. In humans, newborns of smoking mothers have elevated frequencies of HPRT mutants, translocations, and DNA strand breaks. Sperm of smokers have elevated frequencies of aneuploidy, DNA adducts, strand breaks, and oxidative damage. Smoking also produces mutagenic cervical mucus, micronuclei in cervical epithelial cells, and genotoxic amniotic fluid. These data suggest that tobacco smoke may be a human germ-cell mutagen. Tobacco smoke produces mutagenic urine, and it is a human somatic-cell mutagen, producing HPRT mutations, SCEs, microsatellite instability, and DNA damage in a variety of tissues. Of the 11 organ sites at which smoking causes cancer in humans, smoking-associated genotoxic effects have been found in all eight that have been examined thus far: oral/nasal, esophagus, pharynx/larynx, lung, pancreas, myeoloid organs, bladder/ureter, uterine cervix. Lung tumors of smokers contain a high frequency and unique spectrum of TP53 and KRAS mutations, reflective of the PAH (and possibly other) compounds in the smoke. Further studies are needed to clarify the modulation of the genotoxicity of tobacco smoke by various genetic polymorphisms. These data support a model of tobacco smoke carcinogenesis in which the components of tobacco smoke induce mutations that accumulate in a field of tissue that, through selection, drive the carcinogenic process. Most of the data reviewed here are from studies of human smokers. Thus, their relevance to humans cannot be denied, and their explanatory powers not easily dismissed. Tobacco smoke is now the most extreme example of a systemic human mutagen.

Differential mutagen sensitivity of peripheral blood lymphocytes from smokers and nonsmokers: effect of human cytomegalovirus infection

We used the mutagen sensitivity assay to test the hypothesis that human cytomegalovirus (HCMV) infection modifies the sensitivity of cells to genetic damage from genotoxic agents. Chromosome aberration (CA) frequency in peripheral blood lymphocytes (PBLs) from 20 smokers who were matched with 20 nonsmokers by age (+/- 5 years), sex, and ethnicity was evaluated following in vitro exposure to bleomycin and/or HCMV infection. Bleomycin induced significant (P < 0.05) concentration-dependent increases in the frequency of aberrant cells, chromatid-type damage (breaks), and chromosome-type aberrations (deletions, rearrangements) in PBLs. The baseline (background) CA frequency was similar in both smokers and nonsmokers. Significantly higher frequencies of aberrant cells (P < 0.05) were observed in PBLs from smokers compared to nonsmokers at all bleomycin concentrations tested (10, 30 and 100 microg/ml). Infection of PBLs with HCMV induced a significant (P < 0.05) twofold increase in the frequency of CA (primarily chromatid breaks) in PBLs, regardless of the smoking status. PBLs from smokers and nonsmokers infected with HCMV prior to challenge with bleomycin demonstrated significant (P < 0.05) concentration-dependent increases in the levels of aberrant cells, chromatid-type damage (breaks), and chromosome-type aberrations (deletions, rearrangements) compared to noninfected cells challenged with bleomycin. The frequency of induced CA was consistently higher for PBLs derived from smokers relative to nonsmokers (P = 0.06 and 0.002). These data indicate that, individually, both smoking and HCMV infection significantly enhance the sensitivity of PBLs to bleomycin-induced genetic damage. More importantly, the data also suggest that smoking and HCMV infection interact synergistically to enhance the sensitivity of PBLs to such damage.

Evaluation of genotoxic effects in a group of workers exposed to low levels of styrene

Occupational exposure to styrene was studied in a group of workers engaged in the production of fiberglass-reinforced plastics. Sister-chromatid exchanges (SCE), micronuclei (MN), and DNA damage (evaluated by means of comet assay) were measured in peripheral blood cells from the exposed workers and from a control population. Mandelic acid concentration, an indicator of styrene exposure level, was measured in urine samples collected at the end of the work shift. Average estimated values for styrene exposure were slightly below the threshold limit value (TLV) of 20 ppm recommended by the American Conference of Governmental Industrial Hygienists. Significant increases (P< or =0.01) have been found for SCE and MN frequencies and comet tail length among exposed individuals, as well as significant decreases (P< or =0.01) in the proliferation indices, as compared with control population. High correlation has been obtained between endpoints evaluated and exposure length, and increased values of SCE and MN frequencies and comet tail length have been found among smokers only in the exposed population. The high correlation obtained among SCE and MN frequencies and comet tail length, and the increase of these parameters in the exposed group with regard to control group justify the use of these three biomarkers in the evaluation of genotoxic effects in human populations exposed to styrene.

Sex chromosome loss, micronuclei, sister chromatid exchange and aging: a study including 16 centenarians

In the present study we analysed the possible effect of age, sex and smoking on the mean values of micronucleus (MN) and sister chromatid exchange (SCE) frequencies on peripheral blood obtained from 38 subjects ranging in age from 16 to 63 years and 16 centenarians. The mean number of binucleated cells with micronuclei varied in function of age and sex (as demonstrated by the analysis of covariance (F=13.13; P<0.001), particularly evident was the increment observed in women with increasing age (interaction age/sex: F=5.53; P<0.05). Smoking habits had no effects on MN frequency (F=0.36; P>0.05). Sex (F=4.18; P<0.05) and smoking habits (F=14.64; P<0.001) influenced significantly SCE per cell frequencies, but age had no effects on them (F=2.45; P>0.05). The age-associated increase of sex chromosome loss was studied using fluorescence in situ hybridisation (FISH) on interphase nuclei. The loss of Y signals was observed in approximately 10% of interphase cells from the centenarians males, that is six times more often than in the younger control men (approximately 1.6%). The frequency of X signal loss (approximately 1.7%) in young women was similar to that observed in male controls of the same age but the incidence of the X chromosome aneuploidy in centenarian females was appreciably higher (approximately 22%) than that found for the Y chromosome in males. These results were correlated with the data on MN formation and a positive correlation between the percentage of aneuploid cells (FISH) and MN values was observed (r=0.50; P<0.05).

Micronuclei in peripheral blood lymphocytes and buccal epithelial cells of Polish farmers exposed to pesticides

In this biomonitoring study, we investigated whether an occupational exposure to a complex mixture of chemical pesticides produced a significant increase of micronuclei (MN) in both peripheral blood lymphocytes and buccal cells. Forty-nine male workers exposed to pesticides, from an agricultural area of Malopolska Region in Southern Poland, together with 50 men from the same area without indication of exposure to pesticides that served as controls, were used in this investigation. No statistically significant differences in the frequencies of cytogenetic damage were detected between exposed and control individuals, for either type of cells. The multiple linear regression analysis in the case of lymphocytes indicated that the studied cytogenetic endpoints were inversely influenced by alcohol; whilst a negative binomial regression, in the case of buccal cells, indicated that the MN values were directly influenced by the ingestion of red meat. An inverse negative relationship between the cytokinesis-block proliferation index and age, and a significant increase of miscarriages due to the exposure to pesticides were also observed.

Chromosomal aberrations and sister-chromatid exchanges in Lithuanian populations: effects of occupational and environmental exposures

Cytogenetic analysis of chromosomal aberrations (CA) in 175,229 cells from 1113 individuals, both unexposed and occupationally or environmentally exposed to heavy metals (mercury and lead), organic (styrene, formaldehyde, phenol and benzo(a)pyrene) and inorganic (sulfur and nitrogen oxides, hydrogen and ammonium fluorides) volatile substances and/or ionizing radiation was performed. In addition, 11,250 cells from 225 individuals were scored for the frequency of sister-chromatid exchanges (SCE). Increased frequencies of CA were found in all occupationally exposed groups. A principal difference between the exposure to heavy metals and organic substances was found: increase in the CA frequency was dependent on duration of exposure to mercury but not dependent on duration of exposure to styrene, formaldehyde and phenol. A higher CA incidence was found in lymphocytes of children living in the vicinity of a plant manufacturing phosphate fertilizers. This indicates that children are a sensitive study group for the assessment of environmental exposure. However, the results of SCE analysis in these children were inconclusive. Exposure to ionizing radiation was found to cause chromosome breaks and chromatid exchanges in Chernobyl clean-up workers and chromatid breaks, chromatid exchanges, dicentric chromosomes and chromosome translocations in workers from the Ignalina Nuclear Power Plant. The increased frequency of chromatid exchanges in individuals exposed to ionizing radiation was quite unexpected. This may be attributed to the action of some unrecognized life-style or occupational factors, or to be a result of radiation-induced genomic instability. Also an increased SCE frequency was found in lymphocytes of Chernobyl clean-up workers.

Spontaneous sister chromatid exchange and chromosome aberration frequency in humans: the familial effect

The possible effects of environmental and genetic factors on spontaneous frequencies of sister chromatid exchanges (SCEs) and cells with chromosome aberrations (CAs) in human lymphocytes were investigated by analysing 177 completed families (mother, father and at least one child). After removing the effects of methodological, biological and life-style factors by the use of multifactor analysis of variance (MANOVA), SCEs and CAs residuals were analysed by simple correlation analysis and principal component analysis. SCEs and CAs inter-familiar variability was higher than that found within families. A significant correlation was found between the average SCE frequencies shared by parents (the so-called 'midpoint parents', or 'midparent') and offspring (linear slope b=0.26+/-0.07, p<0.05), but also between mother and father (b=0.23+/-0.11, p<0.05) suggesting the presence of an effective environmental factor. The midparent-offspring correlation was found to be sustained by the mother-offspring relationship (b=0.28+/-0.08, p<0.05), being the father-offspring correlation not significant (b=0.16+/-0.11, p0.05). Concerning CAs, no statistically significant correlation between parents was found, but the strong relationship between mother and offspring was confirmed (b=0.468+/-0.11, p<0.001). The SCEs correlation between mother vs. offspring disappeared for older offspring (over 23 years old). The obtained findings strongly showed that the genetic make-up is barely detectable in the presence of domestic environment factors which are shown to play the major role in determining the interfamilial variability of SCE and CA in a general population. These results strengthen the suitability of the use of SCEs and CAs analysis in human cytogenetic surveillance for the detection of effective environmental factors.

Sister chromatid exchange and micronucleus frequency in human lymphocytes of 1,650 subjects in an Italian population: I. Contribution of methodological factors

The influence of several methodological factors on mean values of sister chromatid exchanges (SCEs) and micronuclei (MN) in peripheral lymphocytes of 1,650 subjects was analyzed. Donors belonged to a general healthy population living in Pisa and in two nearby small cities: Cascina and Navacchio (Ca-Na). Blood samples were collected over a period of 29 months and processed in three different laboratories of the some institute. Slides were analyzed by several scorers. Our data showed that lymphocyte proliferation indexes (PIs) and baseline mean values of SCEs were affected mainly by sampling period. This factor accounted for a percentage ranging from roughly 10% (Pisa) to 20% (Ca-Na) of total SCE variance and from roughly 10% (Pisa) to 13% (Ca-Na) of total PIs variance. A marginal effect was attributable to the different laboratories involved (maximum 3% for SCEs and 7% for PIs). The sampling period variable included many sources of variability such as culture media batches, fetal calf serum, PHA, BrdUrd, and seasonality. MN counts revealed a more marked dependence on processing laboratories. This factor accounted for a percentage of roughly 10% (Pisa and Ca-Na) of total variance, while the sampling period was marginally effective (about 1-4% of total variability). Because laboratories were equipped and supplied with the same materials and consumables and technicians were rotated constantly, the only variable ascertained was represented by the three different models of CO2 incubators used for lymphocyte culturing. When "month" and "incubator" variables were considered jointly, experimental variability accounted for 15-20% of total variance, both for PIs and mean values SCEs and MN. The variability due to slide scoring was reduced by assigning each slide to five different scorers and matching low with high scorers in each group. Present data show that when the study is performed under these controlled conditions, about 20% of total interdonor variability can be explained by experimental or seasonal factors.

Sister chromatid exchange and micronucleus frequency in human lymphocytes of 1,650 subjects in an Italian population: II. Contribution of sex, age, and lifestyle

Sister chromatid exchange (SCE) and micronuclei (MN) analysis was carried out on 1,650 healthy individuals living in Pisa and in two nearby small cities, Cascina and Navacchio (Ca-Na). The effect of smoking on SCEs was linearly correlated with the number of cigarettes per day, and an increase of 7.3% SCEs was detectable for as few cigarettes as 1-10/day. Ex-smokers showed intermediate mean values of SCEs (8.09 +/- 1.88) in comparison with never smokers (7.54 +/- 1.61) and current smokers (8.45 +/- 1.94). Mean values of SCEs of ex-smokers decreased linearly with time of smoking cessation, reaching the mean values of never smokers within 8 years. The extent of SCE decrease was inversely proportional to the number of cigarettes previously smoked. No interaction between smoking habits and coffee or alcohol drinking on SCEs was observed. A borderline (P = 0.053) increase in mean SCE values in coffee drinkers (more than 3 cups/day) was found. The age effect on SCEs was remarkable in Ca-Na, but not in Pisa donors. Job type was not associated with significant modification of mean values of SCEs. Multiple logistic regression analysis revealed a statistically significant association between the proportion of high frequency cells (HCF) outliers and coffee consumption. Age and sex appeared to be by far the most important variables associated with modifications in MN frequency, which increased by 0.04 per thousand and 0.02 per thousand per year in males and females, respectively. Children and young donors (age < or = 40 years) showed lower MN frequency regardless of sex, whereas sex appeared to determine a significantly higher increase of MN only in females older than 40 years. In contrast, in males the MN rate by age tended to level off after the age of 30-50. MN frequencies of Pisa blue- and white-collar workers were statistically significantly higher than in students (+0.71 and +0.55 per thousand, respectively). Smoking did not determine any increase of MN frequency. A total lack of correlation (P = 0.913) between MN and SCEs was observed.

Sister chromatid exchange analysis in workers exposed to noise and vibration

Workers chronically exposed to whole-body vibration and noise are known to develop pathophysiological and psychological disturbances. The frequencies of sister chromatid exchanges (SCEs) and of cells with high frequencies of SCEs (HFCs) were analyzed in lymphocytes of 50 workers occupationally exposed to vibration and noise and of 34 controls. The exposed group included: individuals operating hand-vibrating tools (group 1), 'test-cell operators' (group 2) and 'run-up' operators (group 3) from an air base and helicopter pilots (group 4). The statistical analysis of the mean SCE count per cell was carried out by multiple regression analysis, comparing various predictor variables: exposure group, duration of exposure, age and cigarette consumption. Only cigarette consumption and exposure group were found to be significantly correlated with the mean SCE frequency. After allowing for the effects of smoking, the analysis indicates that: (1) there was no significant difference between group 1 and controls (p > 0.05); (2) the differences between group 2 and group 0, group 3 and group 0 and group 4 and group 0 were all highly significant (p < 0.001); (3) there was no significant difference between groups 2 and 3 (p > 0.05), nor between groups 2 and 3 combined and group 4 (p > 0.05); (4) exposure groups 2, 3 and 4 combined, had a significantly elevated mean SCE frequency compared to the control group (p < 0.0001). Statistical analysis of the proportion of HFCs was consistent with these results. Our data suggest that chronic exposure to whole-body vibration and noise may lead to an increase in the level of SCEs in man. The observed effects may not reflect a direct action of these physical agents on DNA. Alternative explanations may include some of the whole-body vibration and noise-induced or stress-induced pathophysiological alterations which may indirectly induce SCE formation.

Cytogenetic monitoring of a group of Italian floriculturists: no evidence of DNA damage related to pesticide exposure

The induction of sister chromatid exchanges (SCE), structural chromosome aberrations (CA) or micronuclei (MN) was investigated in peripheral lymphocytes of a group of Italian floriculturists exposed to a mixture of pesticides. No statistically significant difference in the frequencies of cytogenetic damage was detected between exposed and control subjects. Assessment of the effect of confounding factors indicated that smoking affected both SCE and CA frequencies. Multiple regression analysis showed that in heavy smokers (> or = 20 cigarettes/day), SCE and CA levels increased significantly by 17% and 54%, respectively, as compared to non-smokers.

The effects of age and lifestyle factors on the accumulation of cytogenetic damage as measured by chromosome painting

Individual responses to the aging process are variable and are affected by genetic as well as environmental factors. Fluorescent in situ hybridization with whole chromosome probes ('chromosome painting') provides an efficient approach for detecting structural chromosome aberrations in human lymphocytes. This rapid and sensitive technique is an effective tool for quantifying chronic exposure to environmental agents which may result in an accumulation of cytogenetic damage with age. We have applied this technology to a normal, putatively unexposed, population to document the relationship between age and the accumulation of cytogenetic damage, as well as to establish a baseline frequency of stable aberrations. Using probes for chromosomes 1, 2 and 4 simultaneously, the equivalent of 1000 metaphases was scored for stable and unstable aberrations from each of 91 subjects ranging in age from newborns (umbilical cord bloods; n = 14) to adults aged 19 to 79 years. Each subject (or one parent of each newborn) completed an extensive questionnaire to identify possible lifestyle factors that may influence the frequency of cytogenetic damage. Our findings show a significant increase in stable aberrations (translocations and insertions) with age (p < 0.0001). We also observed age-related increases with dicentrics (p < 0.0001) and acentric fragments (p < 0.0001). Relative to the frequencies observed in cord bloods, the frequencies of stable aberrations, dicentrics, and acentric fragments in adults aged 50 and over were elevated 10.6-fold, 3.3-fold, and 2.9-fold, respectively. Nine variables other than age are significantly associated with the frequency of stable aberrations; these are: smoking (two variables), consumption of diet drinks and/or diet sweeteners (4 variables), exposure to asbestos or coal products (1 variable each), and having a previous major illness (1 variable). Newborns whose mothers smoked during pregnancy had a 1.5-fold increase in stable aberrations (p = 0.029). Repeat samples from a subset of the adults indicate that for most subjects there is little change in individual translocation frequencies over a period of two to three years. These results support the hypothesis that stable chromosome aberrations show a greater accumulation with age than do unstable aberrations and suggest that lifestyle factors contribute to the accumulation of cytogenetic damage.

SCE analysis in human lymphocytes of a Spanish control population

SCE (sister-chromatid exchanges), HFC (high frequency cells) and PRI (proliferative rate index) were studied in the peripheral blood lymphocytes of 154 healthy male volunteers, from Barcelona (Spain). SCE, HFC and PRI variability between and/or within individuals was estimated by means of a mixed linear model. This model allows a determination of the relationship between confounding factors (demographics, life style, work exposure and medical history) and the cytogenetic and cytokinetic parameters analyzed. The results obtained indicate the existence of an important intra-individual heterogeneity in SCE rates, as well as in HFC and PRI values. Although age did not seem to affect either the SCE frequency or the HFC percentage, it showed a significant positive association with the presence of cells with higher SCE frequencies. With respect to the confounding factors, only cigarette smoking increased the SCE rates and the HFC values. On the other hand, PRI mean showed significant differences dependent on age and was inversely correlated with alcohol consumption and X-ray exposure.

Baseline and mitomycin C (MMC)-induced sister-chromatid exchanges in XX and XY cells of Callithrix jacchus chimeric twins

Lymphocytes from chimeric individuals of the species Callithrix jacchus (Primates) were examined to evaluate differences in the frequency of sister chromatid exchanges (SCE) between XX and XY cells. The aim was to discover whether SCE differ according to genetic sex and whether XX and XY cells show a different sensitivity to SCE inducing agents. This experimental model has enabled us to eliminate the possible differences caused by environmental factors. The results obtained do not reveal significant differences between male and female cells, in either the baseline SCE frequency or that induced by mitomycin C at concentrations of 0.01 and 0.03 microgram/ml. No significant differences were observed in the distribution of high SCE frequency cells (HFC), even if it is possible to observe a higher level of exchanges in XX cells in each trial. With regard to the phenotypic sex, there appears to be a trend towards slightly higher SCE rates in females, even if results are not statistically significant.

Increased frequency of sister chromatid exchanges in lymphocytes of Chernobyl clean-up workers

Sister chromatid exchanges (SCEs) were analysed in lymphocytes from 12 control persons and 33 Chernobyl clean-up workers. The group of Chernobyl clean-up workers consisted of civilians who were forced to go to Chernobyl to clean up environmental contamination caused by Chernobyl disaster. On average, they received 0.13 (range 0.04-0.249) Gy of external irradiation before returning to home. Cytogenetic analyses were performed 6-8 years after the irradiation. Standard cytogenetic techniques were used. Mean SCE frequency was 7.45 +/- 0.69 SCE/cell in controls and 10.30 +/- 0.31 SCE/cell in clean-up workers (p < 0.05). Analysis of variance showed that exposure to radiation explained 19.6%, occupational exposure to various chemical substances, 11.9%, coffee consumption, 8.3%, smoking, 4.2%, interaction between smoking and coffee consumption, 3.6%, and alcohol abuse, 3.4% of total variation in SCE frequency. Effects of all above confounding factors were significant (p < 0.05). In addition, increased frequencies of chromosome aberrations due to exposure at Chernobyl and alcohol consumption were observed. However, there was no correlation between external dose of irradiation and the frequency of chromosome aberrations. Thus, even 6-8 years after the irradiation, cytogenetic effects in lymphocytes of Chernobyl clean-up workers are still significant.