No abstract available

[en] For reproductive death of mammalian cells, accumulation of damage induced by two or more particles is frequently predominant at doses of X-rays or γ-rays in excess of 500 rad. For doses of less than 100 rad of X-rays, damage due to single particles generally provides the largest contribution to cell lethality, but the relative effectiveness depends strongly on the type of cell investigated and on the conditions of exposure and environment. In addition, a marked dependence on LET is observed. For LET values at which the relative contribution of accumulation of damage has become negligible, a significant influence of dose-modifying factors such as the presence of oxygen may still be evident. This implies that 'single particle damage' is not necessarily independent of modifying factors. A similar conclusion can be derived from data on some types of micro-organisms. For the induction of chromosome aberrations, published data show that the relative contributions of the two types of mechanisms mentioned, may depend on the type of aberration studied. For tumor induction the relative contributions of the two mechanisms cannot in general be derived from incidence versus dose relations because of the influence of promoting, permitting and inhibiting conditions and the influence of cell reproductive death

No abstract available

[en] The contents of the ICRP publications 9 (1965) and 26 (1977) are outlined and the research conducted during these years considered. Expressions are derived for the frequency for induction of cancer from the most common irradiations - X rays, gamma rays and electrons. The dose limits advised by the ICRP are discussed and the first two fundamental principles are presented - that no one should be subjected to radiation without useful cause and that in those cases where irradiation is thought necessary, the medical, scientific, social and economic advantages need to be carefully considered with respect to the possible disadvantages. (C.F.)

[en] Published data on the effectiveness of different radiations for induction of cell reproductive death and chromosome aberrations, measured for a variety of mammalian cells, have been analysed with respect to components of damage increasing as a linear and a quadratic function of the dose, respectively. This analysis has shown that a large variation in the several characteristic parameters is obtained for the various types of cells studied. Furthermore, significant differences are deduced between values of some of the corresponding parameters for cell inactivation and chromosome aberrations, respectively. These differences are shown to be important with respect to the interpretation of yield versus dose curves for tumour induction

[en] Physical aspects of high LET radiation tumour therapy are shortly presented. The differences in cell survival curves dependent on the changes of LET value are presented. The survival curves of tumour cells irradiated in vitro by neutrons, X rays and photons are given. The relative biological effectiveness of neutrons is dicussed. (S.B.)

[en] A comparison of RBE - LET relations are made for reproductive death and chromosome aberrations in mammalian cells, as a means of providing insight into the type of mechanisms involved. An analysis of the survival curves for X-rays and gamma rays is discussed and a schematic representation is presented of differences in the dependence of the effectiveness per unit dose on LET, for which data were derived from experiments with X-rays, gamma rays, fast neutrons and heavy ions. (Auth./C.F.)

[en] The different reactions of different tumours on fractionated irradiation are discussed. The factors which influence tumour response to irradiation are reviewed. Some of them are related directly to cell survival curves and some to cell kinetics during and after fractionated treatment. (S.B.)

[en] Cell survival curves and dose-effect curves for transformation of C3H10T1/2 cells have been obtained after irradiation with 0.5 MeV, 4 MeV and 15 MeV neutrons and with 300 kV X rays. The experimental data have been fitted by formulas containing linear and quadratic terms only, both for survival curves and for cell transformation. From these fitted curves, parameters have been derived and the results are presented in a table. The cell survival curves obtained with neutrons were not significantly different from exponential. (Auth.)

[en] Experiments have been performed to determine the relation between shapes of survival curves for crypt cells and the effect of fractionation for X-rays and 15 MeV neutrons. (Auth./C.F.)