Sister Chromatid Exchange Studies Research Articles

A study of sister chromatid exchange in patients with dental amalgam restorations.

Dental amalgam is still widely used as a restorative material in developing countries due to its low cost and ease of manipulation. The health risks associated with the components of this restorative material has always been a matter of concern. Our study was designed to address this question regarding dental amalgam. To study sister chromatid exchange (SCE) as an indicator of systemic genotoxicity, due to the exposure from the components of amalgam restorations during its placement and chronic use. Systemic genotoxicity in subjects exposed to amalgam during its placement (Group II; n=5) and subjects with chronic exposure to amalgam (Group III; n=5) were compared with controls (Group I; n=5) by SCE assay in cultured peripheral blood lymphocytes. Subjects exposed to amalgam during its placement and subjects having chronic exposure to amalgam showed an increase in the frequency of SCE, but the change was not statistically significant (P=0.84, P=0.123 respectively). Systemic genotoxicity was not observed due to the components of amalgam restorations released during its placement and chronic use. The findings of this study can be considered as preliminary information on the systemic toxicity due to the components of amalgam restorations.

Chromosome and sister chromatid exchange studies in Behcet's patients

Behcet's disease is a chronic multisystemic disease of unknown pathogenesis characterized by four major symptoms: oral aphthous ulcers, skin lesions, ocular symptoms and genital ulcerations. The disease is spread throughout the world, but it is most frequent in Turkey, Japan, Korea and China. Although HLA-Bw51 has been found to predominate in Behcet's cases, the genetic etiology has not yet been clarified. In this study, we investigated the chromosomal abnormalities and sister chromatid exchange rates in patients with Behcet's diseases. Thirty-eight patients with Behcet's disease (diagnosed for the first time) and 30 healthy subjects (as controls) were included in this study. Although numerical and structural chromosomal abnormalities were not detected in our patients, we found an increased rate of sister chromatid exchange in patients over the control groups (P < 0.01). On the basis of these results, we discuss the genetic etiology of Behcet's disease.

Toxicological evaluation of propane expanded tobacco

A tiered testing strategy has been developed to evaluate the potential for tobacco processes, ingredients, and other technological developments to increase or decrease the biological activity resulting from burning tobacco. The strategy is based on comparative chemical and biological testing. Propane expanded tobacco is an example of a processed tobacco used in the modern manufacture of cigarettes. Test cigarettes containing propane expanded tobacco were compared to control cigarettes containing tobacco expanded with a traditional expansion agent (Freon-11). The toxicological evaluation included chemistry studies using mainstream cigarette smoke (determination of selected constituent yields), in vitro studies using cigarette smoke condensate (Ames study in Salmonella typhimurium and sister chromatid exchange study in Chinese hamster ovary cells) and in vivo studies (13-week inhalation study of mainstream cigarette smoke in Sprague–Dawley rats and 30-week dermal tumor promotion study of cigarette smoke condensate in SENCAR mice). Although statistically significant differences in several smoke constituents were observed, most constituents from cigarettes containing 100% propane expanded tobacco were within market survey ranges. Furthermore, biological tests indicated that the cigarettes containing propane or Freon-11 expanded tobacco were not significantly different.

Studies on Sister Chromatid Exchanges in Peripheral Lymphocytes of Spray Painters

In a comparative study of sister chromatid exchanges (SCEs) in cultured lymphocytes, we evaluated the genotoxic risk in 104 male spray painters employed in repair workshops in Chennai City, India, and 50 matched healthy, unexposed controls. We found a higher frequency of SCEs among painters (3.74 +/- 0.11, mean +/- SE) than among controls (2.15 +/- 0.08), and among smoking painters (4.03 +/- 0.21) than among nonsmoking painters (3.55 +/- 0.13), with no significant difference in controls (smokers: 2.1 +/- 0.2; nonsmokers: 2.2 +/- 0.1). Alcoholism did not contribute to an increased SCE frequency. Stepwise multiple linear regression analysis on painters showed that duration of service, smoking, and alcoholism significantly affected SCE scores and explained the 14% variation observed.

Overview of the acute, subchronic, reproductive, developmental and genetic toxicology of β-chloroprene

β-Chloroprene (CD), the 2-chloro derivative of 1,3-butadiene, is used for the manufacture of the synthetic rubber, polychloroprene. Acute inhalation studies show that CD is lethal to Crl:CD® rats at >2300 p.p.m. (4 h); the primary target organ effects were pulmonary hemorrhage and edema, and hepatic necrosis. In 2- and 4-week inhalation studies in Fischer 344 (F344) and Wistar rats, early deaths occurred at 500 and ≥161 p.p.m., respectively. Organ system injury was found in the nose (degeneration/metaplasia of olfactory epithelium), liver (centrilobular necrosis), and blood (decreased red blood cell count in F344 rats only). In a 90-day inhalation study with F344 rats, degeneration/metaplasia of the olfactory epithelium and reduced nonprotein sulfhydryl content of lungs and liver were found in animals exposed to 80 p.p.m., and anemia, hepatocellular necrosis, and forestomach inflammation were observed at 200 p.p.m. In a 90-day study with B6C3F1 mice, CD caused deaths at 200 p.p.m., the highest concentration tested, and epithelial hyperplasia of the forestomach at 80 p.p.m. Other than a slight (<10%) reduction in sperm motility in male rats at 200 p.p.m., all other reproductive parameters (sperm count or morphology in males, and estrous cyclicity or cycle length in females) were unaffected in these 90-day rat/mouse studies. There were no significant indications of neurological toxicity. The study No-Observable Adverse Effect Level was 32 p.p.m. based on nasal injury in rats. Despite some early reports of reproductive system abnormalities at levels <1 p.p.m., recent studies show no embryotoxic or developmental toxicity in female Wistar or Crl:CD® rats, or in New Zealand White rabbits at CD exposure concentrations up to 25 or 175 p.p.m., respectively. In a one-generation reproduction study with Wistar rats, CD produced growth retardation in the F 0 generation exposed to 100 p.p.m., and in the F 1 offspring at 33 and 100 p.p.m.; no effects on reproductive parameters or histopathology were found. CD is nonmutagenic in standard plate incorporation bacterial reverse mutation assays (Ames assays) but positive using direct gas-phase incubation methods. Bacterial mutagenicity (primarily base pair substitution) was either negative or weakly positive when freshly prepared CD was tested. Mutagenicity increased markedly with time, presumably from CD dimer formation, and also by addition of liver S9 metabolic activation system. In vivo micronucleus, chromosome aberration and sister chromatid exchange studies in mice showed no structural chromosomal damage. Overall, the pathological effects in the liver and nose dominate the subchronic toxicity of CD. The genotoxicity of CD is inconsistent and requires further study.

Chromosome Aberrations and Sister Chromatid Exchange Studies in Patients with Prostate Cancer: Possible Evidence of Chromosome Instability

Cytogenetic studies have been carried out using the G-banding technique in peripheral blood lymphocytes of 24 patients with prostate cancer. Of these, eight belong to stage B, six to stage C/e, three to C/sv, two to Do, and the remaining five to DI stage of carcinoma. Simultaneously, sister chromatid exchanges (SCEs) were also analyzed in the peripheral blood lymphocytes of these patients, along with those of 40 age-matched control subjects. The frequency of aberrant metaphases is significantly higher in patients with prostate cancer (7.32%) than in age-matched controls (2.92%). A large number of chromosome aberrations in lymphocytes of these patients, which are generally constitutional in nature, have also been detected. In stage-B patients, the frequency of cytogenetically abnormal cells is comparatively low with regard to the number of cells scanned, and these abnormalities are generally confined only to single chromosome (except in one metaphase in patient 1, who was diagnosed with bladder carcinoma in addition to cancer of the prostate). Sister chromatid exchanges (SCEs) were also analyzed in the patients and age-matched control subjects. The mean SCE frequencies were 9.24 ± 0.62 (n = 1356) per metaphase and 0.203 per chromosome in patients, whereas in control subjects the frequencies were 5.94 ± 0.25 (n = 4000) per metaphase and 0.129 per chromosome. The SCE frequency in cancer patients was statistically significant (p < 0.001). Our results indicate that the patients with prostate cancer show a degree of chromosomal instability that might be related to a predisposition to neoplasia.

Chromosome survey of seals in the Baltic Sea in 1988-1992.

The populations of grey seals (Halichoerus grypus) and ringed seals (Phoca hispida botnica) in the Baltic Sea have decreased very much, especially during the last decades. Environmental pollution has been seen as an important cause. As top predators, the seals accumulate pollutants from their environment. High concentrations of chlorinated hydrocarbons and heavy metals have been found in seals from the Baltic Sea. In the present study the possible mutagenic effects of environmental pollutants on the seals have been studied by screening cultured lymphocytes for chromosome aberrations. Blood samples were taken from grey seal pups before weaning in March-April, and from adult ringed seals at the end of April during 1988-1992. Blood cells were cultured for 48 h for screening for chromosome aberrations, and for 61 h with bromodeoxyuridine for the study of sister chromatid exchange (SCE). The types of aberrations found were chromosome and chromatid breaks, gaps, and fragmentations. More complicated rearrangements were rare. Blood samples from a total of 47 grey seal pups and from ten adult ringed seals were analysed. The mean frequency of cells with chromosome aberrations from the grey seals was 5.7% (SD +/-5.3). The median was 4, because the distribution was skewed with some animals having a considerably higher frequency of aberrations than the average. Some cells with several aberrations and fragmentation of the chromosomes were observed among the lymphocytes from these animals. The frequencies of SCEs were not markedly higher than those normally found in humans. The frequencies of aberrations found in the adult ringed seals were lower than those found in the grey seal pups. The chromosome aberrations are probably caused by chemical pollutants.

Sister chromatid exchange studies for monitoring DNA damage in lymphocytes of malignant lymphoma patients under cytostatic therapy

Sister chromatid exchange (SCE) frequencies were studied in lymphocytes from 45 patients with malignant lymphoma. Fifteen patients were untreated when studied. The mean SCE frequency for these patients was 8.70 +/- 0.99 per mitosis. The mean score for 35 controls was 4.37 +/- 1.19. SCE mean scores were significantly higher in the untreated patients than in the controls (p < 0.001). Nine patients were treated with radiotherapy alone. The mean SCE frequency (6.80 +/- 0.87) they demonstrated was significantly lower (p < 0.01) than that found in untreated patients. Twelve patients received cyclophosphamide 1 month before the study was started. They demonstrated a mean SCE frequency (12.00 +/- 1.31) significantly higher (p < 0.05) than that found in patients who had received regimens that did not contain cyclophosphamide (9.72 +/- 1.32). From these findings we suggest that untreated patients with malignant lymphoma have elevated SCE frequencies, which may be further increased by chemotherapeutic agents.

A Study of Sister Chromatid Exchange and Somatic Cell Mutation in Hospital Workers Exposed to Ethylene Oxide

A Study of Sister Chromatid Exchange and Somatic Cell Mutation in Hospital Workers Exposed to Ethylene Oxide

A study of sister chromatid exchange and somatic cell mutation in hospital workers exposed to ethylene oxide.

To investigate the risks of exposure to ethylene oxide (EO) at current permissible levels and at past higher levels, an inception cohort of sterilizer operators and supervisors from the Central Processing Department (CPD), respiratory therapists, and engineers exposed to EO were identified at the McMaster University Medical Centre. A comparison group from Nutrition Services (NUTR) were matched with the CPD workers on the basis of sex, age, and smoking habit. The present report is based on genetic test results for the 94 CPD and matched NUTR workers only. Statistical analysis based on the mean SCE frequency in the top 5, top 10, and all cells (50 cells scored per individual) and high frequency cells (HFC) based on the 95th percentile for nonsmoking control subjects showed a direct association with current smoking but not with EO exposure. Similarly, statistical analysis of the somatic cell mutation (SCMT) variant frequencies did not demonstrate an association with EO exposure, nor with smoking. Regression analysis indicated that sex was the only other covariate that significantly affected SCE. Age was weakly associated with SCMT. A statistically significant interaction between occupational exposure and smoking habits was observed only for the mean SCE frequency of the top 5 and top 10 cells when the 11 current CPD/NUTR pairs were not included. Thus, this interaction should be interpreted with caution.

Chromosomal alterations and sister chromatid exchanges induced by zirconium oxychloride in human lymphocytes in vitro with relation to age of donors

Aqueous solutions of zirconium oxychloride were added to human peripheral blood lymphocyte culture. Cultures were set up from healthy donors of both sexes belonging to age groups of 0–10, 11–20, 21–30, 31–40, 41–50 and 51–60 years. Airdried Giemsa schedule was followed for preparation of chromosomal aberrations and micronuclei count. Fluorescence plus Giemsa staining techniques were applied for the study of sister chromatid exchange. The endpoints screened were chromosome and chromatid breaks, dicentrics and rearrangements. The frequencies of chromosomal aberrations and sister chromatid exchanges induced were compared between the samples of different age groups. The frequency of CA could not be related to age of the donor. However, the frequency of SCE increased with increase in age of female donor.

Sister chromatid exchange frequency in directly prepared cytotrophoblasts: Demonstration of in vivo deoxyribonucleic acid damage in pregnant women who smoke cigarettes

Assessing frequency of sister chromatid exchange is a sensitive method of monitoring exposure to clastogens, mutagens, and other substances that induce deoxyribonucleic acid damage. Aware that cigarette smoke is associated with increased sister chromatid exchange in many cell types, we sought to determine whether an in vivo effect of cigarette smoke could be demonstrated by study of sister chromatid exchange in chorionic villus cells. Directly prepared cytotrophoblasts and cultured mesenchymal core cells were analyzed. Mean sister chromatid exchange frequency in cytotrophoblasts from smoking subjects (8.87 sister chromatid exchanges per cell) was significantly greater than in nonsmoking subjects (5.81 sister chromatid exchanges per cell; p < 0.001); however, no significant difference in cultured mesenchymal core cells was found. Our results demonstrate that maternal exposure to cigarette smoke results in direct placental deoxyribonucleic damage, which in turn could explain deleterious effects of smoking on pregnancy. Increased sister chromatid exchange frequency was observed only in directly prepared cytotrophoblasts, showing the necessity of using this cell type to evaluate the effects of clastogens on placentas. (AM J OBSTET GYNECOL 1991;165:1877-80.)

The Djungarian hamster,Phodopus sungorus, for the analysis ofin vivosister chromatid exchange

SUMMARYThe Djungarian hamster, Phodopus sungorus, is an organism used extensively in biomedical research. In this investigation, it was examined for its suitability for the in vivo study of sister chromatid exchange (SCE). Bromodeoxyuri- dine (BrdU) incorporation was performed by subcutaneous implantation of a commercially prepared 50 mg slow-release pellet, and sister chromatid differential staining was performed using incandescent light exposure of bone marrow metaphase cells. SCE frequency was markedly increased in animals injected with cyclophosphamide (CP). Cells of P. sungorus treated with this method showed clear and distinct sister chromatid differential staining, indicating that this organism is suitable for the in vivo study of SCE.

In vivo study of sister chromatid exchange and cellular kinetics in bone marrow cells of Rana catesbeiana.

A discontinuous 5-bromodeoxyuridine administration method which allowed in vivo sister chromatid exchanges assay in bullfrog bone marrows was developed. As a prototype of an in vivo mutagenesis test, this procedure was utilized to detect the genotoxic and cytoxic effects of cyclophosphamide. A dose-dependent increase in the frequeny of SCEs was observed. Cyclophosphamide caused a slight cell-cycle delay and a dose-dependent decrease in replicative index. The present study demonstrates that in vivo SCE method in bullfrogs can be used as a monitoring system for the assessment of environmental genotoxic chemicals.

Sister-chromatid exchange studies on direct- and indirect-acting clastogens in mouse primary cell cultures

An in vitro sister-chromatid exchange (SCE) assay using mouse primary bone marrow and spleen cells was conducted with both direct- and indirect-acting genotoxic agents. 2,4,7-Trinitrofluorenone, a direct-acting genotoxic agent, induced a significant dose-related increase in SCEs. In both bone marrow and spleen cells, 2.0 μg/ml caused an approx. 3-fold increase in SCE level over control values. Cyclophosphamide, an indirect-acting genotoxicant which requires metabolic activation for its clastogenicity, induced a significant increase in SCEs in the presence of S9 from liver of rats pretreated with Aroclor-1254. A dose of 2 μg/ml resulted in a 2-fold increase in bone marrow and a greater than 5-fold increase in spleen cells. Benzo[ a]pyrene, another indirect-acting genotoxicant, also induced significant dose-related SCE responses in both cell types. It seems that primary bone marrow and spleen cell culture systems can detect both direct- and indirect-acting genotoxicants and may be useful for routine and/or comparative cytogenetic studies.

Genotoxic evaluation of chronic fluoride exposure: sister-chromatid exchange study

As part of a continuing investigation, this study was conducted to examine the genotoxic effects of chronic exposure to sodium fluoride (NaF) in drinking water on the frequency of sister-chromatid exchange (SCE) in the bone-marrow cells of male Chinese hamsters. Animals at about 3 weeks of age were randomly assigned to 6 groups, each with at least 3 hamsters, and were maintained on a low fluoride diet (< 0.2 ppm F) throughout the experiment. At 4 weeks of age, the animals in groups I–V began to receive drinking water containing fluoride at concentrations of 0, 1, 10, 50 and 75 ppm, respectively. Group VI was treated with cyclophosphamide and served as the positive control. The animals were sacrificed at 24 weeks of age by cervical dislocation. The humeri and plasma were analyzed for fluoride content, which was found to increase with the increase in fluoride concentration in drinking water. Slides of chromosomes from bone-marrow cells were prepared and blindly examined for the frequency of SCE. The mean scores of SCE for the hamsters receiving drinking water containing F concentrations up to 75 ppm for 21 weeks ranged from 4.28 to 6.28 per cell, and were not significantly different from those of the negative controls (4.60–5.44/cell). The results indicated that chronic fluoride exposure had no effect on the frequency of SCE in Chinese hamster bone-marrow cells under the conditions of the present investigation.

Effect of tetrandrine on micronucleus formation and sister-chromatid exchange in both in vitro and in vivo assays

The genotoxicity of tetrandrine, a drug potentially useful for the treatment of silicosis, was studied using the micronucleus and the sister-chromatid exchange (SCE) assay systems. Cultured Chinese hamster lung (V79) cells were used for the in vitro micronucleus and sister-chromatid exchange studies. Mouse bone marrow was used for the in vivo micronucleus assay and mouse spleen cells for the in vivo/in vitro sister-chromatid exchange analysis. The results show that SCE levels in V79 and in spleen cells were significantly elevated by treatment with tetrandrine at doses above 0.08 mg/ml and 100 mg/kg bw, respectively. Increased tetrandrine-induced SCE in vitro was metabolic activation dependent. Tetrandrine failed to induce micronuclei at any of the doses tested. A decrease of replicative index with an increase in the concentration of tetrandrine was found both in vitro and in vivo. These results indicate that tetrandrine is a weak indirect-acting genotoxicant.

Comparative study of sister-chromatid exchanges and chromosomal aberrations induced by airborne particulates from an urban and a highly industrialized location in human lymphocyte cultures

Cytogenetic effects induced by extracts of airborne particulates in human lymphocyte cultures were studied with regard to local and seasonal variations. Samples of airborne particulates were collected from an urban and a highly industrialized area in March and October, respectively. All extracts of particulates induced a significant increase of sister-chromatid exchanges (SCE) in a dose-dependent manner. Referring to the induction of sister-chromatid exchanges, local and seasonal differences were observed. Samples from the industrialized area revealed the highest activities. In addition, SCE rates found for the March samples were always higher than those for October for both locations. Furthermore, a remarkable, significant induction of chromosomal aberrations occurred with all samples from both locations and sampling periods. Aspects of health risk evaluation for exposed human populations are discussed with respect to the observed cytogenetic effects of airborne particulates in human lymphocyte cultures.

Statistical Aspects of Using Biologic Markers

This expository paper surveys a variety of statistical issues pertinent to the design and analysis of studies involving biologic markers of human genotoxic exposure. Examples with cytogenetic and mutagenic end points are presented. One principal theme is the valuable interplay of ideas among statistical analyses for in vitro, in vivo and human assays for genetic toxicity; e.g., statistical analysis of sister chromatid exchanges in vitro is suggestive of an analytical approach to the study of sister chromatid exchanges in humans. Other topics discussed include (i) combining information from a series of studies of a common suspect genotoxic exposure and (ii) the utility of historical control information.

Sister Chromatid Exchange in Chromosomes of River Buffalo (Bubalus BubalisL.)

SUMMARYA detailed study of sister chromatid exchange (SCE) in chromosomes of river buffalo (Bubalus bubalis L.) reared in Southern Italy is reported. In 34 subjects from two different farms and provinces, the total mean value of SCE/cell was found to be 8.8 ± 3.4. Of 33600 chromosomes examined, 5358 (15.9%) showed SCEs, most of which with one SCE (14.3%). An analysis of SCE-distribution on marker chromosomes (five biarmed pairs and X-chromosome) from 25 subjects, revealed non-random distribution of SCEs and possible positive relation between SCEs and heterochromatin-rich chromosome arms.