Browsing by Author "Varfolomeyeva, Tatyana A"

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    Early hematopoiesis inhibition under chronic radiation exposure in humans.
    (Radiat Environ Biophys, 2010-05) Akleyev, Alexander V; Akushevich, Igor V; Dimov, Georgy P; Veremeyeva, Galina A; Varfolomeyeva, Tatyana A; Ukraintseva, Svetlana V; Yashin, Anatoly I
    The major goal of this study was to identify and quantitatively describe the association between the characteristics of chronic (low-dose rate) exposure to (low LET) ionizing radiation and cellularity of peripheral blood cell lines. About 3,200 hemograms (i.e., spectra of blood counts) obtained over the years of maximal exposure to ionizing radiation (1950-1956) for inhabitants of the Techa River were used in analyses. The mean cumulative red bone marrow dose (with standard errors), calculated using Techa River Dosimetry System-2000, was 333.6 +/- 4.6 mGy (SD = 259.9 mGy, max = 1151 mGy) to the year 1956. The statistical approach included both empirical methods for estimating frequencies of cytopenic states of the investigated blood cell lines (e.g. neutrophile, platelets, erythrocyte, etc.), and regression methods, including generalized linear models and logistic regressions which allowed taking into account confounding factors (e.g., attained age, age at maximal exposure, presence of concomitant diseases, and demographic characteristics). The results of the analyses demonstrated hematopoiesis inhibition manifested by a decrease in peripheral blood cellularity and an increase in the frequency of cytopenia in all blood cell lines (leukocytes, including lymphocytes, monocytes, neutrophiles, as well as platelets and erythrocytes). The intensity of hematopoiesis inhibition in the period of maximal exposures is determined by the combined influence of the dose rate and cumulative dose. The contribution of specific confounding factors was quantified and shown to be much less important than dose characteristics. The best predictor among dose characteristics was identified for each blood cell line. A 2-fold increase in dose rate is assumed to be a characteristic of radiosensitivity and a quantitative characteristic of the effect.
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    Early hematopoietic effects of chronic radiation exposure in humans.
    (Health Phys, 2010-09) Akleyev, Alexander V; Akushevich, Igor V; Dimov, Georgy P; Veremeyeva, Galina A; Varfolomeyeva, Tatyana A; Ukraintseva, Svetlana V; Yashin, Anatoly I
    The major goal of this study is to investigate and quantitatively describe the nature of the relationship between the characteristics of chronic exposure to ionizing radiation and specific patterns of hematopoiesis reduction. The study is based on about 3,200 hemograms taken for inhabitants of the Techa riverside villages over the years 1951-1956, i.e., the period characterized by a gradual decrease in dose rates. The mean cumulative red bone marrow dose was 333.6 + or - 4.6 mGy. The approach to statistical analyses involved both empirical methods and modeling (generalized linear models and logistic regressions). The results of the analyses highlighted a gradual increase in the frequency of cytopenias with dose rate. The impact of exposure on hematopoiesis reduction patterns was found to be more substantial than that of age and health status. Dose rates resulting in a two-fold increase in the frequency of cytopenias have been estimated.