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At least 613 records · Page 34Linked to original sources
PubMed1998

Transgenic plants are sensitive bioindicators of nuclear pollution caused by the Chernobyl accident.

To evaluate the genetic consequences of radioactive contamination originating from the nuclear reactor accident of Chernobyl on indigenous populations of plants and animals, it is essential to determine the rates of accumulating genetic changes in chronically irradiated populations. An increase in germline mutation rates in humans living close to the Chernobyl Nuclear Power Plant site, and a two- to tenfold increase in germline mutations in barn swallows breeding in Chernobyl have been reported. Little is known, however, about the effects of chronic irradiation on plant genomes. Ionizing radiation causes double-strand breaks in DNA, which are repaired via illegitimate or homologous recombination. We make use of Arabidopsis thaliana plants carrying a beta-glucuronidase marker gene as a recombination substrate to monitor genetic alterations in plant populations, which are caused by nuclear pollution of the environment around Chernobyl. A significant (p<0.05) increase in somatic intrachromosomal recombination frequencies was observed at nuclear pollution levels from 0.1-900 Ci/km2, consistent with an increase in chromosomal aberrations. This bioindicator may serve as a convenient and ethically acceptable alternative to animal systems.

Animals↗
PubMed1996

Human minisatellite mutation rate after the Chernobyl accident.

Germline mutation at human minisatellite loci has been studied among children born in heavily polluted areas of the Mogilev district of Belarus after the Chernobyl accident and in a control population. The frequency of mutation was found to be twice as high in the exposed families as in the control group. Mutation rate in the Mogilev families was correlated with the level of caesium-137 surface contamination, consistent with radiation induction of germline mutation.

Adult↗
PubMed1998

Absence of RAS and p53 mutations in thyroid carcinomas of children after Chernobyl in contrast to adult thyroid tumours.

Thyroid carcinomas of an additional series of 34 children exposed to radioactive fall-out after the Chernobyl reactor accident were analysed for mutations in the H-, K- and N-RAS and the p53 gene. Allele-specific oligonucleotide hybridization, single-strand conformation polymorphism (SSCP) and direct sequencing did not disclose mutations in codons 12, 13 and 61 of RAS genes nor mutations in exons 5, 7 and 8 of p53. Considering the recently reported high prevalence of RET rearrangements of the PTC3 type in childhood tumours after Chernobyl (Klugbauer et al, 1995, Oncogene 11: 2459-2467), it follows that RET rearrangements are the most relevant molecular aberration in these radiation-induced tumours. RAS or p53 mutations do not play a role in childhood thyroid carcinogenesis after Chernobyl.

Adult↗
PubMed1997

High prevalence of activating ret proto-oncogene rearrangements, in thyroid tumors from patients who had received external radiation.

A high frequency (about 60%) of ret rearrangements in papillary thyroid carcinomas of children exposed to radioactive fallout in Belarus after the Chernobyl accident, has been reported by three recent studies (Fugazzola et al., 1995; Ito et al., 1994; Klugbauer et al., 1995). These studies suggested that the radiation exposure may be a direct inducer of activating rearrangements in the ret gene. In order to confirm the postulated link between irradiation and the role of the ret proto-oncogene in thyroid tumorigenesis, we analysed for the presence of ret activating rearrangements using RT-PCR, XL-PCR, Southern blot and direct sequencing techniques, 39 human thyroid tumors (19 papillary carcinomas and 20 follicular adenomas), from patients who had received external radiation for benign or malignant conditions. As controls, we studied 39 'spontaneous' tumors (20 papillary carcinomas and 19 follicular adenomas). Our data concerning the radiation-associated tumors, showed that: (1) the overall frequency of ret rearrangements was 84% in papillary carcinomas (16/19) and 45% (9/20) in follicular adenomas; (2) in contrast with the results obtained in the Chernobyl tumors, the most frequently observed chimeric gene was RET/PTC1 instead of the RET/PTC3 and (3) all the tumors were negative for RET/PTC2. In the 'spontaneous' tumors, only the papillary carcinomas presented a ret rearrangement (15%:3/20): 1 RET/PTC1, 1 RET/ PTC3 and 1 uncharacterized. In conclusion, our results confirm the crucial role played by the ret proto-oncogene activating rearrangements in the development of radiation-associated thyroid tumors appearing after therapeutic or accidental ionizing irradiation, and show, for the first time, the presence of RET/PTC genes in follicular adenomas appeared after external irradiation.

Adenoma↗
PubMed1997

Probability for detecting hot particles in environmental samples by sample splitting.

The presence of radioactive hot particles in environmental samples (e.g., soil, vegetation, sediments) is frequently detected by observing significant differences in the activities of sub-samples, which are otherwise alike. The probabilities for detecting hot particles in this way were calculated by using Monte Carlo methods as a function of the number of hot particles in the original sample, the number of sub-samples used, the frequency distribution of the activities of the hot particles, and the precision with which the activities of the sub-samples are determined. Assuming, for example, (i) a log-normal distribution of the activities of the hot particles with a relative standard deviation eta > or = 1, and (ii) that a difference of > 30% between the activities of the sub-sample with the largest and that with the smallest activity can be detected, splitting the original sample into three sub-samples will be sufficient to detect the presence of up to five hot particles with a probability of > 95%. If four sub-samples are used, the presence of up to 20 hot particles can be detected with this probability. In general, it will not be effective to increase the precision of the activity measurements of the sub-samples at the expense of the number of sub-samples investigated.

Environmental Pollution↗
PubMedDate not supplied

Children exposed to chronic contamination after the Chernobyl accident: cytogenetic and radiotoxicological analyses.

In this study, we describe cytogenetic studies of lymphocytes obtained from children who were exposed after the Chernobyl accident to low doses of ionizing radiation. We sought to determine possible chromosomal damage relative to internal contamination, as measured by whole-body counter and urine radiotoxicological analyses. The study was performed during a 1-mo period on the peripheral blood of children hosted in Italy, but who resided in contaminated regions of the Russian Federation and Belarus. We used conventional cytogenetics to detect chromosomal aberrations. In some cases, we also used "chromosome painting" to look for stable aberrations. There were more acentric fragments in subjects than in controls; a few chromosome and chromatid breaks werefound in the subjects, but this finding did not differ significantly between subjects and controls.

Body Burden↗
PubMed1981

Solitary thyroid nodule. 1. Clinical characteristics.

The approach to management of an isolated thyroid nodule requires some understanding of the natural history of thyroid cancer and other forms of nodular thyroid disease. The histologic classification of thyroid cancer is an important determinant of survival, as are the size of the primary tumor, presence of thyroid capsule invasion, and presence of distant metastases. Therapeutic radiation and radioactive fallout increase the risk that a thyroid nodule is malignant. Autonomously functioning thyroid nodules are usually benign follicular adenomas and may cause thyrotoxicosis.

Adenoma↗