[Show abstract][Hide abstract] ABSTRACT: The paper presents the results of the cohortal biodosimetry carried out in 435 Chernobyl clean-up workers, who were surveyed with the conventional cytogenetic technique in terms from several days to 10 years after the end of their duties in the Chernobyl accident exclusive zone. An empirical model of the aberrant cell dynamics was utilized for the calculation of mean initial yields of dicentrics and centric rings in groups with different terms and duration of staying in the Chernobyl zone. Corresponding protracted irradiation doses estimated from aberration levels ranged from 79 to 670 mGy. The probabilistic distribution of the radiation doses was constructed by the applying the Bayesian analysis to initial individual chromosome exchange yields extrapolated to the exposure termination moment. This distribution was characterized by the mean dose about 460 mGy and maximum of probability density in the interval of 50-300 mGy. For the late somatic risk assessment in clean-up workers the probabilistic distribution of equivalentally-acute radiation doses was proposed; that had the mean value about 270 mGy, modal classes of 250-350 mGy and 99.8% of the probability density concentrated within the dose range from 0 to 1000 mGy.
Full-text · Article · Jan 2005 · Radiatsionnaia biologiia, radioecologiia / Rossiĭskaia akademiia nauk
[Show abstract][Hide abstract] ABSTRACT: The post-irradiation changes of dicentric and centric ring levels were studied in Chernobyl liquidators using the data of 507 individual chromosomal surveys of persons sampled at different time after their activities at Chernobyl NPP accident zone. The time-effect relationship within 0-10.5 years after exposure was displayed as exponential decline of the mean chromosome exchange frequency with average decay half-time 2.2 y. During 10.5-13 years after exposure the increasing and stabilization of chromosome exchange yield on the level 2-3-times higher than control was observed. In the first few months after irradiation the dicentric and centric ring frequency in liquidators had the clear reverse correlation with the duration of person's duties at the Chernobyl zone. The parameters of unstable chromosome exchange elimination were independent on the initially induced aberration yield, that resulted in earlier reaching the subcontrol level in persons who had more protracted duration of duties at the Chernobyl accident zone.
No preview · Article · Jul 2004 · T͡Sitologii͡a i genetika
[Show abstract][Hide abstract] ABSTRACT: The purpose of this paper is to investigate how well various assays on blood can detect radiation dose to people exposed many years previously and, if possible, to estimate that dose. The assays were applied to persons resident close to Chernobyl in 1986. Blood samples were taken 13-15 years after the reactor accident. The assays used were the frequencies of lymphocyte chromosomal translocations, micronuclei, HPRT mutations and apoptotic cells. Translocation yields in the exposed groups were marginally higher than in their respective controls, leading to dose estimates of about 0.2 Gy but with large uncertainties. All other assays showed inconsistency from person to person or other variations apparently not related to dose. The measurement of translocations, it is concluded, is the biological method of choice for retrospective dosimetry.
No preview · Article · Feb 2004 · Radiation Protection Dosimetry
[Show abstract][Hide abstract] ABSTRACT: Aim: the cytogenetic survey has been carried out in uterine cancer patients undergoing radiation therapy to evaluate whether the pre-irradiation tumor cryodestruction could modify the radiation-induced effects in normal tissues. Methods: the conventional cytogenetic analysis of peripheral blood lymphocytes was undertaken in cryosurgically treated and non-treated patients groups in terms before, at the middle and at the end of standard external gamma-irradiation course given in classic fractionation regimen (2 Gy per fraction). Results: the similar intensity of the radiation-specific chromosome rearrangement yield increase was observed in both cryosurgically treated and non-treated patients during radiation therapy course, proving that the cryoprocedure didn't impact the biologically equivalent radiation load accumulation or enhance the patients' chromosome radiosensitivity in normal tissue cells. The aberration distribution displayed a lower proportion of heavily damaged cells in patients with tumor cryodestruction comparing with positive control group, especially at the end of radiation treatment. Less steep rising of dicentrics and centric rings per aberrant cell yield run concurrently with the reduction of polyploids and endoreplications frequency in cryosurgically treated persons during the second half of radiotherapy course, that contrasted to a significant accumulation of cells with numerically abnormal genome in patients without cryodestruction. Conclusion: the explanation of both phenomena involves the possible ability of pre-irradiation cryoprocedure to cause the enhancing of lymphocyte circulation rate between irradiated and non-exposed body zones. Taking into account the functional role of lymphocytes, that could be one of the possible mechanisms of reducing the local radiation reactions in normal tissues in persons with pre-irradiation tumor cryodestruction.
[Show abstract][Hide abstract] ABSTRACT: Data are presented for a subset of lymphocytes characterized by FISH as missing painted chromosomal material. These lymphocytes occur in both control and irradiated subjects. These cells have a much greater frequency of one-way translocations than cells in which all of the painted chromosomal material is present. Their presence contributes to interindividual variability in control translocation yields. These cells do not appear to be more prevalent in persons exposed to high radiation doses. It is suggested that their exclusion when selecting cells for analysis may improve the sensitivity of FISH as a biological dosimeter at low doses. Mechanisms for the production of these one-way translocations in vivo are also discussed, with a proposal that their variable frequency in individuals may be consistent with exposure to chemical clastogens.
No preview · Article · May 2002 · Radiation Research
[Show abstract][Hide abstract] ABSTRACT: Lymphocytes from some evacuees from Prypiat and clean-up workers (liquidators) have been studied for chromosomal aberrations. When dicentric yields from subjects are pooled in various ways, by date of evacuation, date of working at Chernobyl or delay in blood sampling, the resultant mean dose estimates are higher than have been generally assumed from dose reconstructions for Prypiat citizens or personal dosemeters worn by liquidators. Some of this difference may be due to the selection of subjects for study. However, dicentrics in one cohort of randomly selected evacuees, sampled very promptly, indicated a mean dose of ~300 mGy which is significantly in excess of mean dose reconstructions of ~10-20 mSv.
No preview · Article · Oct 1997 · Radiation Protection Dosimetry
[Show abstract][Hide abstract] ABSTRACT: Eighteen Ukrainian evacuees from the Chernobyl exclusive zone, twenty one inhabitants of radioactively contaminated areas of Belarus and twelve control donors age-matched to the exposed persons were investigated 14-15 years after the Chernobyl accident for chromosomal aberration yields detected in blood lymphocytes by fluorescence in situ hybridisation technique. Unstable aberration yields measured in both Chernobyl cohorts were close to the background frequencies. Positive age-dependence trends in control donors were determined for the all type stable aberration levels. In evacuees the tendency for diminishing the difference between them and controls for stable aberration levels with persons' age increasing was found. The total stable chromosome exchange yields in evacuees 46-55 years old and inhabitants of areas with low contamination level didn't exceed the control values, but for younger evacuees and inhabitants of sufficiently contaminated regions the statistical increase above the age relevant background meanings was detected for this end-point. The advantages of using the FISH-detectable stable aberrations and particularly the total level of stable chromosome exchanges as the end-points for retrospective biological indication of past radiation exposure in Chernobyl cohorts were discussed.
No preview · Article · · Radiatsionnaia biologiia, radioecologiia / Rossiĭskaia akademiia nauk
[Show abstract][Hide abstract] ABSTRACT: The cytogenetic screening was carried out in 100 Chernobyl clean-up workers (liquidators) with registered doses during 1 year after exposure. The bayesian analysis has been applied for constructing the individual distribution of probability density for biological doses estimated from dicentric and centric ring yields in liquidators. The coincidence of the biological and registered dose has been found in 25% of cases; among the rest persons the documented doses exceeded the biological estimations in 25% of cases and the cytogenetic doses were higher than registered ones in 50% of cases. The total distribution of biological doses was constructed by pooling the individual data in 50 mGy dose intervals. The distribution obtained had the maximum at 300-350 mGy and contained 68% of probability density in the dose range 0-1000 mGy. The probabilistic approach in cohort biodosimetry showed the necessity of corrections in radiogenic risk assessment for Chernobyl liquidators. The advantages of bayesian technique for biodosimetrical treatment of cytogenetic data in conditions of small number of cells scored and low aberration yields induced by low dose irradiation were discussed.
No preview · Article · · Radiatsionnaia biologiia, radioecologiia / Rossiĭskaia akademiia nauk
[Show abstract][Hide abstract] ABSTRACT: Dynamics of cytogenetic anomalies in liquidators of the Chernobyl accident has been studied. Dicentric and ring frequencies appeared to be the most informative criteria of radio-induced chromosome aberrations. The rate of cell elimination with dicentrics and rings was higher in liquidators exposed to more than 25 cGy of radiation that in those exposed to less than 25 cGy of radiation. The rate of elimination of chromatid-type aberrations and genomic mutations was very low in the group of liquidators exposed to higher dose of radiation.
[Show abstract][Hide abstract] ABSTRACT: The joint EU/CIS project ECP-6, was set up to examine whether cytogenetic dosimetry is possible for persons irradiated years previously at Chernobyl. The paper describes the possibility of achieving this by the examination of blood lymphocytes for unstable and stable chromosome aberrations; dicentrics and translocations. Emphasis was placed on the relatively new fluorescence in situ hybridization (FISH) method for rapid screening for stable translocations. In a collaborative experiment in vitro dose response calibration curves for dicentrics and FISH were produced with gamma radiation over the range 0-1.0 Gy. A pilot study of about 60 liquidators with registered doses ranging from 0-300 mSv was undertaken to determine whether the chromosomal methods may verify the recorded doses. It was concluded that the dicentric is no longer valid as a measured endpoint. Translocations may be used to verify early dosimetry carried out on highly irradiated persons. For the vast majority of lesser exposed subjects FISH is impractical as an individual dosemeter; it may have some value for comparing groups of subjects.