Dicentric chromosomes in monolayers of human lymphocytes produced by monochromatized synchrotron radiation with photon energies from 1.83 keV to 17.4 keV.

A systematic approach was used to examine the induction of dicentric chromosomes in human lymphocytes irradiated in vitro with monochromatized synchrotron radiation produced with photon energies in the range from 1.83 keV to 17.4 keV. To avoid potential confounding factors that could influence the outcome of the experiments, only blood from one individual was used. Since for the irradiation experiments with these low photon energies the local dose variations would become unacceptable, monolayers of lymphocytes attached within 3 h PHA stimulation have been used. The culture conditions ensured that the chromosome analysis could be performed exclusively in metaphases of the first cell cycle in vitro. There is a strong indication for a systematic change of the alpha coefficient of the linear quadratic dose-response relationship from 1.83 keV (alpha=1.26+/-0.28) with increasing energy up to 6.9 keV (alpha=8.24+/-0.41) and a decrease with further increase of energy up to 17.4 keV (alpha=3.83+/-1.72). A tendency for a systematic change of the beta coefficient seems to be present at energies of 6.9 keV (beta=8.04+/-0.40) and 4.8 keV (beta=9.48+/-1.57) as well as at energies of 3.10 keV (beta=2.99+/-0.51) and 1.83 keV (beta=0.40+/-0.25). These results agree in essence with the previously published large data set from Sasaki's laboratory.