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

Effects of X-rays and cigarette smoking on leukocyte, lymphocyte and mitotic index values and SCE rates: the relationship between mitotic index and lymphocyte count

Many previous studies revealed that smoking increases leukocyte and lymphocyte counts while exposure to X-rays decreases these counts. However the relationships between lymphocyte life span and smoking as well as X-rays were not well documented. The primary aim of this study was to determine relationships between smoking X-rays (in combination and individually) and life span of lymphocytes. Blood samples from 200 healthy individuals, half of which were X-ray exposed individuals, were collected. Half of X-ray exposed and of non-X-ray exposed individuals were smokers. There were equal numbers of male and female participants. Two lymphocyte cultures, one for the sister chromatid exchange (SCE) analysis and the other for the determination of mitotic index values were prepared using one part of the blood samples collected from the individuals. From the other part of the blood sample leukocyte and lymphocyte counts were determined with a haemogram device. Evaluation of the findings suggested that leukocyte count, lymphocyte count, mitotic index were relatively lower for the X-ray exposed individuals. In addition these values were higher for smokers than nonsmokers in general. The highest SCE rates were recorded for smoking radiology technicians. The most important finding is that lymphocyte life span is relatively low in smokers and in X-ray exposed males.

Analysis of oxidative DNA damage and HPRT mutant frequencies in cancer patients before and after radiotherapy

Various markers of radiation-induced DNA damage including DNA oxidation were investigated in peripheral lymphocytes of 23 cancer patients prior to and one week after receiving radiotherapy with a cumulative dose of 54-70 Gy. Exposure to ionizing radiation nonsignificantly increased the ratio 2'deoxy-7-dihydro-8-oxoguanosine/2'deoxyguanosine (8-oxodG/dG) from 1.73 x 10(-5) to 3.33 x 10(-5). Frequencies of micronuclei significantly (p = 0.0003) increased from 6.4 to 38.9 per 1000 cells. The frequency of hypoxanthine-guanine-phosphoribosyltransferase (HPRT) mutant lymphocytes measured as 6-thioguanine resistant variant cells by 5-bromodeoxyuridine labeling, was elevated eight-fold, from 4.7 x 10(-6) to 36.2 x 10(-6) (p = 0.008) after termination of the radiotherapy, thus showing a clear response to the radiation treatment. No correlation between levels of oxidative DNA damage and frequencies of HPRT mutant lymphocytes or micronuclei could be established.

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.

Ten years after Chernobyl

This review focuses on current findings on the health consequences of the accident at the Chernobyl nuclear power plant in 1986. Acute radiation damage caused by exposure to high doses of ionizing radiation involved a few hundred people, apparently with fewer than 100 deaths within the first few months. Epidemiologically detectable increases in congenital abnormalities have not been reported thus far, with the possible exception of Down's syndrome. Owing to the long latency period of radiation-induced cancer, discernible increases in cancer incidence and mortality are not yet expected for most tumour types, especially among adults. However, dramatic increases in the number of childhood thyroid cancers have already been observed in Belarus and Ukraine and the Bryansk regions of Russia. The increase has been over 100-fold in some areas with heavy contamination. From the viewpoint of overall public health, the outlook of direct health effects of the Chernobyl accident are likely to be severe only among some limited subgroups, such as young children exposed to high levels of fallout nuclides. In absolute terms, the global number of Chernobyl-associated cancer cases can be estimated to be tens of thousands, but only a small fraction of these is likely to be discernible epidemiologically.

Chromosome aberrations and rogue cells in lymphocytes of Chernobyl clean-up workers

A cytogenetic analysis was performed on peripheral blood lymphocytes from 183 Chernobyl clean-up workers and 27 control individuals. Increased frequencies of chromosome aberrations were associated with exposure to radiation at Chernobyl, alcohol abuse and a history of recent influenza infection. However, only approximately 20% of Chernobyl clean-up workers had an increased frequency of dicentric and ring chromosomes. At the same time, an increased frequency of acentric fragments in lymphocytes of clean-up workers was characteristic. The use of multivitamins as dietary supplement significantly decreased the frequency of chromosome aberrations, especially of chromatid breaks. Rogue cells were found in lymphocytes of 28 clean-up workers and 3 control individuals. The appearance of rogue cells was associated with a recent history of acute respiratory disease (presumably caused by adenoviral infection) and, probably, alcohol abuse. Dicentric chromosomes in rogue cells were distributed according to a negative binomial distribution. Occurrence of rogue cells due to a perturbation of cell cycle control and abnormal apoptosis is suggested.