CYTOGENETIC INDICATORS OF ACUTE RADIATION SICKNESS (THE CHORNOBYL EXPERIENCE). / TsYTOGENETYChNI POKAZNYKY GOSTROÏ PROMENEVOÏ KhVOROBY (ChORNOBYL'S'KYI DOSVID).

The objective of the study was to improve the biological dosimetry approach among patients with acute radiationsickness of various degrees based on the analysis of radiation-induced chromosome aberrations in peripheral bloodlymphocytes of the victims. MATERIALS AND METHODS: The study was based on primary cytogenetic data obtained in May 1986 within examina-tion of the 30 clean-up workers («liquidators¼) having got stage I-III acute radiation sickness. Dose verificationwas performed using the cytogenetic dosimetry based on a culture of peripheral blood lymphocytes with metaphaseanalysis of chromosome aberrations. RESULTS: A new method of evaluating the results of patients' cytogenetic examination at the beginning of specifictherapy has been developed. Procedure was performed using a model of multiple linear regression (complex of cyto-genetic parameters) and provided a satisfactory diagnostic level (featuring a compliance with initially definedclinical and laboratory diagnoses). Overall frequency of the aberrant cells and radiation markers increased in high-er disease stages. There was a trend of the frequency growth of chromatid-type aberrations with increasing of radi-ation burden. Adequacy of the proposed method based on the regression analysis of cytogenetic results was con-firmed through the preservation of group differences in estimates of disease stage in subjects with verified diagnosis. CONCLUSION: Cytogenetic dosimetry in the scope of examination of persons exposed to ionizing radiation is an oblig-atory component of radiation sickness stage verification. The recommended method of cytogenetic data evaluationbefore and at the beginning of detoxification therapy provides a satisfactory level of diagnostics.

THE DEPENDENCE OF DOSE-EFFECTS IN HUMAN RADIATION CYTOGENETICS. / ZALEZhNIST' DOZA-EFEKT V RADIATsIY̆NIY̆ TsYTOGENETYTsI LIuDYNY.

OBJECTIVE: To study the frequency and spectrum of chromosome aberrations in human peripheral blood lymphocytes depending on the radiation dose, the stage of the mitotic cycle and the periods of fixation of the cell culture. MATERIALS AND METHODS: The test system of blood lymphocytes of donors, the metaphase analysis of chromosome aberrations (a uniform staining of the drugs). The gamma-irradiation was performed on the device with the source 60Co at the dose rate of 0.5 Gy/min, the dose range was 0.25-4.0 Gy. The lymphocyte culture was irradiated after 0, 24, 40 and 48 hours from the beginning of the incubation, which corresponds to G0-, G1-, S-, G2-stages of the mitot- ic cycle. The cells were fixed after 52 hours and 62 hours from the beginning of the incubation. RESULTS: The author's experimental data on the regularities of chromosome aberrations formation during irradiation at the different periods of the mitotic cycle of human lymphocyte culture are presented. The character of the dose dependences of structural damages of chromosomes during the mitotic cycle with an application of the linear, lin- ear-square and parabolic models is analyzed. The greatest yield of exchange-type aberrations is registered at the irradiation in G0- and G1-stages of the mitotic cycle, which submits to the linear-square dependence on an irradia- tion dose. When irradiating cells in the S- and G2-stages, the main contribution to the spectrum of radiation-induced chromosome aberrations is made by deletions, the level of which increases linearly with the dose. This is evidenced by the negative values of the quadratic term in the regression equations for these stages. The analysis of the curves using the parabolic model Y = k · Dn has shown that, at the irradiation of lymphocytes in G0- and G1-stages, the dose dependences approach the quadratic ones, which confirms the reasonableness of the interpretation of the obtained cytogenetic data from the point of view of the «classical¼ theory of the radiation-induced chromosome aberrations formation. However, the model of the spline regression is more accurate at the approximation of the dependences of the cytogenetic effects in the region of low doses of irradiation. CONCLUSIONS: The results obtained by the irradiation of human lymphocyte culture at different stages of the mitot- ic cycle indicate that the same radiation dose induces different qualitative and quantitative cytogenetic effects depending on the physiological state of the cell at the time of irradiation. The combination of such factors as a radi- ation dose rate, a mitotic cycle stage, the post-irradiation conditions, and an individual radiosensitivity are reflect- ed in quantitative and qualitative variations of the cellular radiosensitivity.

[Changes of the cytogenetic effectiveness of the therapeutic ray of fast neutrons in water phantoms]. / Veränderungen der zytogenetischen Effektivität des therapeutischen Strahles von schnellen Neutronen im Wasserphantom.

Changes of cytogenetic effectiveness of the therapeutic ray of fast neutrons were studied in water phantom in the Medical-Biological Complex of CyclotronU-120 at the Institute for Nuclear Research of the Academy of Sciences of the Ukrainian SSR. Investigations were done in a culture of lymphocytes of the peripheral human blood by means of metaphase method to find out chromosomal aberrations. The neutrons were generated by firing a thick beryllium target with a 13.6 MeV-deuteron ray in the nuclear reaction 9Be (d,n) 10B. The investigated dose range was 25-220 cGy. The results of the studies demonstrate that the cytogenetic effectiveness of radiation is reduced with increasing depth of the water phantom. The maximum reduction of the effect was seen in a depth up to 6 cm, which is attached to absorption of low-energetic neutron fraction. The obtained results confirm necessity of to filter the therapeutically applicable beam of neutron radiation.