Chromosome Aberrations Induced in Human Lymphocytes by Neutron Irradiation

Abstract

In vitro dose--response curves of unstable chromosome aberrations in human lymphocytes have been obtained for neutron spectra of mean energies 0-7, 0-9, 7-6 and 14-7 MeV. The aberration yields have been fitted to the quadratic function Y = alphaD + betaD2, which is consistent with the single-track and two-track model of aberration formation. However with high-LET radiation, the linear component of yield, corresponding to damage caused by single tracks, predominants, and this term becomes more dominant with increasing LET, so that for fission spectrum neutrons the relationship is linear, Y = alphaD. At low doses, such as those recieved by radiation workers, limiting r.b.e. values between 13 and 47 are obtained relative to 60Co gamma-radiation. At higher doses, as used in radiotherapy, the values are much lower; ranging from 2-7 to 8 at 200 rad of equivalent gamma-radiation. Both sets of r.b.e. values correlate well with track-averaged LET but not with dose-averaged LET. When the numbers of cells without aberrations are plotted against radiation dose, curves are obtained which are similar in shape to those for conventional cell-survival experiments with comparable neutron spectra. The Do values obtained in the present study are close to those from other cell system.

Analysis of radiation-induced acentric fragments in human G0 lymphocytes

“…For low LET radiations, a nonlinear dose-yield relationship is observed, whose linear and quadratic components reflect the induction of the pair of "primary lesions" by a single or by two independent ionizing particles [2,6,7].…”

Numerical relationship between cells with radiation-induced chromosome aberrations and cells lethally injured by radiation

“…In a critical investigation of this hypothesis, extended over a large LET interval, Barendsen [1,2] compared the frequency of cells containing no chromosome aberrations with the frequency of surviving cells. Chromosome aberration data of human peripheral blood lymphocytes were taken from Lloyd et al [11,12], and lethality data of human bone marrow granulocytes were obtained from Boyum et al [6]. Barendsen found no agreement between the a values of the dose-effect relationships for chromosome aberrations and cell death in the low LET region (the aberration data being too low) and therefore postulated a different cause of reproductive cell death besides gross chromosome damage.…”

“…[6]. The open symbols represent data from the following publications: (O) neutrons [3,12], (•) a-particles (a = 0.27 Gy -1 for 242Cm, a = 0.37 Gy -1 for 239pu) [10], (ZX) 150 kV, 30 kV, and 10 kV X-rays and 13 MeV-electrons [20,21], (V) 6°Co y-rays and 250 kV X-rays [tl, 12], (~) 250 kV X-rays [13], (@) 6°Co F-rays [19], and (@) 3 MeV electrons [15]. The dashed curve represents an eye-fit which serves to indicate the general trend of the data In Figure 2 the linear-term coefficients a are plotted as a function of the track average LET, chosen here as the parameter characterizing radiation quality.…”

“…The values of Lr for photon and electron radiations were calculated from LET~ values of the corresponding electron spectra. Lr values for neutrons were taken from Lloyd et al [12] and Bauchinger et al [3]. Er values for a particles were calculated according to the data given in [10].…”

Biological Dosimetry of Ionizing Radiation

“…With high LET radiation exposure, there is a high probability of one track inducing one dicentric. In this case, the dose-effect relationship is linear (Figure 4) and the dose-effect curve fits the following equation:   YD c where Y is the dicentric yield, is the linear coefficient and D is the dose (Lloyd, 1976). …”