[Biological effectiveness of pulsed and continuous neutron radiation for Saccharomyces yeast cells]. / Biologicheskaia éffektivnost' impul'snogo i nepreryvnogo neitronnogo izlucheniia dlia kletok drozhzhei Saccharomyces.

The article presents the data on biological effectiveness of neutrons generated by the pulsed reactor BARS-6 (dose-rate up to 6 x 10(6) Gy/s) in comparison with fast neutrons of the reactor BR-10 (dose-rate 6.3 x 10(-2) Gy/s). It was shown for yeast cells of a wild type that the RBE values of pulsed neutrons varied insignificantly with a dose (2.0-1.7) white for continuous neutron irradiation clear RBE dependence on the dose was observed. It was also found that the yeast cells had identical capability of postirradiation recovery in non-nutrient medium (LHR) following both gamma-irradiation and neutron exposure irrespective of neutron dose-rate.

[Comparative study of chromosome aberration formation in lymphocytes culture under pulsed and continuous neutron irradiation]. / Sravnitel'noe izuchenie zakonomernostei obrazovaniia aberratsii khromosom v kul'ture limfotsitov cheloveka pri impul'snom i prolongirovannom neitronnom obluchenii.

Frequencies of chromosome aberration induced by prolong (continuous) neutron radiation (dose-rate 0.17 Gy/min) and pulsed neutron radiation with ultra-high dose-rate (1-4) x 10(5) Gy/s have been studied in human blood lymphocytes at G0-stage. It was demonstrated that cytogenetic efficiency of pulsed neutrons (after the substraction of approximately 50% gamma-component from the total dose) was 2 times higher than that of continuous neutron radiation.

[Technological problems in use of fast reactors for radiotherapy of patients with malignant tumors]. / Tekhnologicheskie problemy ispol'zovaniia issledovatel'skikh reaktorov na bystrykh neítronakh dlia luchevoí terapii bol'nykh zlokachestvennymi opukholiami.

The authors discuss the technological problems associated with the use of fast neutrons in radiotherapy of cancer patients and outline the approaches to the solution of these problems. The state of the art is assessed. Physical and radiobiological prerequisites for the use of fast reactors for radiotherapy of patients with malignant tumors are analyzed. Results of clinical use of BR-10 reactor at the Medical Radiology Research Center, Russian Academy of Medical Sciences, are presented. Experimental and clinical findings indicate that the results of radiotherapy may be appreciably improved if a novel perspective source of fast neutrons, a nuclear reactor, is used.

[Current problems of neutron radiobiology]. / Aktual'nye problemy radiobiologii neitronov.

A brief review of up-date problems of neutron radiobiology, related to neutron therapy development and setting up of radiation safety standards for neutrons, is present. The main attention is paid to the effects of combined gamma-neutron irradiation, peculiarities of reactor neutrons biological action and new approaches in neutron capture therapy. On the basis of own and literature data the results of cellular and whole-body studies as well as the applicability of biophysical modelling for description and interpretation of experimental data are discussed.

[Biophysical models of the formation of radiation-induced chromosome aberrations]. / Biofizicheskie modeli formirovaniia radiatsionno-indutsirovannykh khromosomnykh aberratsii.

The brief analysis of the development of biophysical models describing the formation of chromosome aberrations is given. It is shown that, though the target theory is obsolete and does not correspond to modern radiobiological knowledge, however hit and target principles are still the basic radiobiological concepts. Three main directions of the development of biophysical models are submitted; their shortcomings and possible ways of perfection of the models are specified.

[Role of DNA double strand breaks in the radiation structural mutagenesis in eukaryotic cells]. / Rol dvunitevykh razryvov DNK v protsessakh radiatsionnogo strukturnogo mutageneza v éukarioticheskikh kletkakh.

The latest experimental findings in the field of radiation-induced structural mutagenesis especially concerned with the role of the DNA double strand breaks (DSBs) in the formation of chromosome aberrations were analyzed. It was shown slow-repairable and non-repairable DSBs appeared to be the DNA critical damages leading to aberrations.

[The comparative radiosensitivity of the lymphocytes of men and women under gamma irradiation at the G0 stage of the mitotic cycle]. / Izuchenie sravnitel'noi radiochuvstvitel'nosti limfotsitov muzhchin i zhenshchin pri gamma-obluchenii v G0-stadii mitoticheskogo tsikla.

Radiosensitivity of male and female lymphocytes exposed to gamma radiation (60Co) in phase G0 of the mitotic cycle has been comparatively studied. The radiosensitivity was shown to be identical, within the limits of error, although with the recombination repair (the nonhomologous nature of X and Y chromosomes being taken into account) the number of chromosome aberrations in male cells must be 1.4 times larger than in female cells. This indicates an absence or (within the limits of error) an insignificant role of the recombination repair of double-strand DNA breaks.

Model of mammalian cell reproductive death. I. Basic assumptions and general equations.

A systemic model describing the major radiobiological effects of various types of radiation is proposed. The model base lines were substantiated, and general mathematical equations for cell survival developed. The model takes into consideration such physical and biological factors as linear energy transfer, ion track structure, and structural and functional organization of interphase chromatin. This paper presents the basic assumptions made and general equations for the cell killing.

Model of mammalian cell reproductive death. II. Comparison with experimental data and discussion.

A general equation for mammalian cell survival has been derived in the previous paper. This paper presents the results of comparison of theoretical evaluations with survival data available from the literature, including different cell lines, variations in linear energy transfer, dose rate and dose fractionation effects and the effects of ultrasoft X-rays and superheavy ions. Merits and demerits of the model are considered in comparison with other models of radiation-induced killing of mammalian cells published in the literature.

[The shape of the absorbed dosage in neutron irradiation of a water phantom]. / Formirovanie pogloshchennoi dozy pri obluchenii vodnogo fantoma neitronami.

The paper is concerned with the results of experimental and estimated investigations into the spatial distribution of an absorbed dose and the spectrum of neutrons during irradiation of a water phantom by a P-3 beam of a BP-10 reactor. The ratio of densely ionizing and rarely ionizing components of an absorbed dose as well as the ratios between neutrons of different energetic groups were shown to undergo considerable changes with the penetration of reactor neutrons into the depth of a tissue-equivalent medium. The obtained results serve as basic data in various biomedical investigations using reactor neutron beams, including the planning of their use in cancer therapy.

[A systemic model of the reproductive death of mammalian cells. The effect of radiation dose rate and fractionation]. / Sistemnaia model' reproduktivnoi gibeli kletok mlekopitaiushchikh. Vliianie moshchnosti dozy i fraktsionnirovaniia oblucheniia.

On the basis of the previously developed systemic model a study was made of the effect of dose rate on the survival of mammalian cells, RBE of small doses of heavy ions, and fractionation of radiation. There was a good agreement between theoretical and experimental results. The calculations showed that D10 (10% survival dose) is a function of dose rate P even for such ions as helium and boron which, however, exhibited an insignificant dependence of D10 on P (within the range from (10(-1) to 1 cGy/min). The influence of repair and the rate of cell division on RBE of radiation was determined.

[A systemic model of reproductive death of mammalian cells. Postulates of the model and mathematical equations of survival]. / Sistemnaia model' reproduktivnoi gibeli kletok mlekopitaiushchikh. Postulaty modeli i matematicheskie uravneniia vyzhivaemosti.

A systemic model is proposed to be applied for various types of radiation. The bases for the model are substantiated and mathematical survival equations developed.

[Systems approach to modeling radiobiological effects]. / Sistemnyi podkhod k modelirovaniiu radiobiologicheskikh éffektov.

Basic principles of the systemic approach to modelling of the radiobiological effects at different levels of cell organization have been formulated. The methodology is proposed for theoretical modelling of the effects at these levels.

[The results of research on the biological effects of neutrons]. / Itogi issledovaniia biologicheskogo deistviia neitronov.

A study was made of the peculiarities of the biological effect of neutrons as compared to gamma-radiation. A number of biological models were proposed for interpretation of the phenomenon: a biophysical model of mutations and cell inactivation, a model for interpretation of the formation of a radioresistant and radiosensitive fraction.

[Cytogenetic effect of low-level 60Co gamma-irradiation of cultured human lymphocytes in the G1 phase of the mitotic cycle]. / Tsitogeneticheskii éffekt gamma-izlucheniia 60Co pri obluchenii kul'tury limfotsitov cheloveka v G1-stadii mitoticheskogo tsikla v nizkikh dozakh.

The dose-dependence of the chromosome aberration frequency in human lymphocytes in vitro exposed to 60Co-gamma-radiation at the G1 stage of the mitotic cycle has proved to be unlike that obtained upon exposure of cells at the G0 stage of the cycle. The data obtained are accounted for by partial activation of the repair system at the G1 stage which is attributed mainly to chromatin decondensation.

[Chromosome aberrations and reproductive death of mammalian cells. Quantitative relations between these effects]. / Khromosomnye aberratsii i reproduktivnaia gibel' kletok mlekopitaiushchikh. Kolichestvennye sootnosheniia mezhdu étimi éffektami.

The data reported in the literature concerning the relationship between the yield of chromosome aberrations and the number of cells without aberrations, on the one hand, and the survival rate of mammalian cells, on the other, with a reference to different types of radiation are reviewed in this article. It is shown that the number of chromosome aberrations per one lethal damage, as to the results obtained by different authors, ranges from 0.5 to 1.5, this discrepancy is mainly due to different methods applied by different authors, and at least one chromosome aberration corresponds to a lethal damage caused by irradiation in the G1 phase.

[Formation of chromosome aberrations at different stages of the mitotic cycle in a culture of human lymphocytes irradiated with neutrons of average energy 0.35 and 0.85 MeV]. / Zakonomernosti obrazovaniia aberratsii khromosom v razlichnykh stadiiakh mitoticheskogo tsikla kul'tury limfotsitov cheloveka pri obluchenii neitronami so srednei énergiei 0.35 i 0.85 MéV.

Incidence of chromosome aberrations at different mitotic cycle stages of a human lymphocyte culture has been studied after exposure to 60Co-gamma-quanta (2 Gy) and neutrons of 0.85 Mev (1 Gy) and 0.35 MeV (0.5 Gy). The yield of chromosome aberrations with both gamma- and neutron-radiation depends on a stage of the mitotic cycle. The S stage is the most radioresistant one with both types of ionizing radiation.