ABSTRACT
Rate of damaged cells elimination in mammals after prolonged irradiation modifies frequency of chromosomal aberrations (CAF) significantly. Hence, CAF is unlikely to be identical in a bio-object exposed to equal doses with varying dose rate for the reason of different periods of ionizing irradiation. This should be taken into account by designers of bio-dosimeters. Main time characteristics of chromosomal aberrations in mammals can be calculated from the experimentally evidenced CAF growth in the course of irradiation and decline afterwards. This assumption was tested using the data about disaster fighters at the Chernobyl nuclear power station and of experiments with chronic and fractionated exposure of rhesus macaques to 2.5 Gy (Cs137). The experimental doses ranged from 25 cGy to 250 cGy; dose rate made up 1.4 and 20 cGy/hr. Therapeutic doses were within the interval of 1.2 to 9.8 Gy. Rate of aberrant cells elimination was determined for two objects, i.e. humans and rhesus macaques. The follow-up period was approx. 6 years (61 to 2174 days). Elimination rate in the experiment was estimated using a proposed mathematical description of CAF dynamics in peripheral blood lymphocytes of monkeys. Elimination rates of aberrant peripheral lymphocytes in two bio-species were compared. The parameter is equal to (2 +/- 0.5).10(-3) d(-1) and (16 +/- 3) x 10(-3) d(-1) for the human and rhesus macaque, respectively.
Subject(s)
Chromosome Aberrations/radiation effects , Gamma Rays/adverse effects , Lymphocytes/radiation effects , Models, Statistical , Animals , Chernobyl Nuclear Accident , Dose-Response Relationship, Radiation , Follow-Up Studies , Half-Life , Humans , Karyotyping , Lymphocyte Count , Macaca mulatta , Radiation Dosage , Radiometry , Species Specificity , Time FactorsABSTRACT
Biodosimetrical estimation of radiation body burden is based on the counting of chromosomal aberration frequency in lymphocytes of the peripheral blood. This counting was made during a period of time after radiation. However, this frequency differs from counterpart, measured immediately after irradiation. This change caused by elimination of aberrant cells. In order to avoid consistent error in evaluation of dosage it is necessary to know the process generality of elimination temporally. The article contains the results of investigation of aberration frequency dynamics in lymphocytes of 41 patients' peripheral blood. The patients were observed in hospital after Chernobyl accident. The dosage of patients' irradiation varied in the range from 1.2 Gr to 9.8 Gr. Observations had been made during six years or so (from 61 to 2174 days). The results of these observations were used for the research of aberrant cells elimination rate. At the end of the analysis regularities of chromosomal aberration (dicentric and centrical rings) frequency change were obtained. The regularities comply with the exponential law of decreasing with the rate index of elimination (parameter b), which is equal (2.0 +/- 0.5) x 10(3) day(-1) in the range to 10(3) days after radiation. In some cases beyond this interval there was the change of the elimination rate. This fact should be researched additionally. The article contains a model for chromosomal aberration frequency dynamics expression. In analyzed range the b parameter can be constant, but for the extrapolation it in the area of less dosage it is essential to carry on additional investigations.
