Long-lived, sensitive, and specific biomarkers of particular mutagenic agents are much sought after and potentially have broad applications in the fields of cancer biology, epidemiology, and prevention. Many clastogens induce a spectrum of chromosome aberrations, and some of them can be exploited as biomarkers of exposure. Densely ionizing radiation, for example, alpha particle radiation (from radon or plutonium) and neutron radiation, preferentially induces complex chromosome aberrations, which can be detected by the 24-color multifluor fluorescence in situ hybridization (mFISH) technique. We report the detection and quantification of stable complex chromosome aberrations in lymphocytes of healthy former nuclear-weapons workers, who were exposed many years ago to plutonium, gamma rays, or both, at the Mayak weapons complex in Russia. We analyzed peripheral-blood lymphocytes from these individuals for the presence of persistent complex chromosome aberrations. A significantly elevated frequency of complex chromosome translocations was detected in the highly exposed plutonium workers but not in the group exposed only to high doses of gamma radiation. No such differences were found for simple chromosomal aberrations. The results suggest that stable complex chromosomal translocations represent a long-lived, quantitative, low-background biomarker of densely ionizing radiation for human populations exposed many years ago.
A cytochemical lymphocytogram by PAS--reaction and nonspecific esterase test was made using blood smears from 820 children living in different regions of the Bryansk area exposed to radioactive contamination and from 46 matched controls from noncontaminated territories. Most of the children were born before the Chernobyl accident. The cytochemical lymphocytogram was informative enough to evaluate lymphocytic pool and its renewal. The lymphocytogram parameters served criteria for selection of children's groups at relative risk. The groups comprised 25-60% of the examinees depending on the contamination degree and were registered for subsequent follow-up and rehabilitation.
The authors provide data on the health status of children living in radiation polluted regions, obtained 9-11 months after the Chernobyl accident. Study of the demographic characteristics, distribution into health groups and of the hematological parameters did not reveal any significant differences with the exception of a higher anemia incidence (in children under 1 year).
The authors provide the data on the assessment of the population composition of peripheral blood lymphocytes. The assessment was performed with the aid of antilymphocytic monoclonal antibodies in children populating radioactive cesium polluted territories and exposed to ionizing radiation in small doses. 56 children were examined. They were distributed into 2 groups depending on radiation exposure: 1 year after the breakdown and 3 years after it. For comparison purposes use was made of the data obtained as a result of examination of 39 children from the unpolluted regions. Measurements were made of the T and B lymphocyte counts as well as of the main subpopulations of T cells. The irradiated children manifested no appreciable alterations in cellular immunity pointing to the status of immune deficiency regardless of the duration of radiation exposure. A moderate reduction of the T-lymphocyte count at the expense of T helpers/inducers may be of nonspecific character.
Speculation has long surrounded the question of whether past exposure to ionizing radiation leaves a unique permanent signature in the genome. Intrachromosomal rearrangements or deletions are produced much more efficiently by densely ionizing radiation than by chemical mutagens, x-rays, or endogenous aging processes. Until recently, such stable intrachromosomal aberrations have been very hard to detect, but a new chromosome band painting technique has made their detection practical. We report the detection and quantification of stable intrachromosomal aberrations in lymphocytes of healthy former nuclear-weapons workers who were exposed to plutonium many years ago. Even many years after occupational exposure, more than half the blood cells of the healthy plutonium workers contain large (>6 Mb) intrachromosomal rearrangements. The yield of these aberrations was highly correlated with plutonium dose to the bone marrow. The control groups contained very few such intrachromosomal aberrations. Quantification of this large-scale chromosomal damage in human populations exposed many years earlier will lead to new insights into the mechanisms and risks of cytogenetic damage.
A multicolor banding (mBAND) fluorescence in situ hybridization technique was used to investigate the presence inhuman populations of a stable biomarker-intrachromosomal chromosome aberrations-of past exposure to high-LET radiation. Peripheral blood lymphocytes were taken from healthy Russian nuclear workers occupationally exposed from 1949 onward to either plutonium, gamma rays or both. Metaphase spreads were produced and chromosomes 1 and 2 were hybridized with mBAND FISH probes and scored for intra-chromosomal aberrations. A large yield of intrachromosomal aberrations was observed in both chromosomes of the individuals exposed to high doses of plutonium, whereas there was no significant increase over the (low) background control rate in the population who were exposed to high doses of gamma rays. Interchromosome aberration yields were similar in both the high plutonium and the high gamma-ray groups. These results for chromosome 1 and 2 confirm and extend data published previously for chromosome 5. Intrachromosomal aberrations thus represent a potential biomarker for past exposure to high-LET radiations such as alpha particles and neutrons and could possibly be used as a biodosimeter to estimate both the dose and type of radiation exposure in previously exposed populations.