Mouse testis weight loss and survival of differentiated spermatogonia following irradiation with 250 kV X-rays and 5.5 MeV fast neutrons.

Twenty eight after whole body irradiation of male BALB/c mice with 0.1-4.0 Gy of 250 kV X-rays or with 0.05-1.0 Gy of 5.5 MeV fast neutrons a decrease in testis weight and number of spermatozoa were observed. After plotting the testis weight loss against the radiation dose a mono-component curve characterized by D0 equal to 6.2 Gy and 1.31 Gy for X-rays and neutrons, respectively, was obtained. Relative biological effectiveness (RBE) was 4.25. Similar relation between the number of spermatozoa and the dose had a form of a two component curves. The sensitive components of the testis were characterized by the A-type curves with D0 equal to 0.49 Gy and 0.10 Gy for X-rays and neutrons, respectively. The resistant components were characterized by the B-type curves with D0 equal to 5.07 and 0.97 Gy for X-rays and neutrons, respectively. The RBE was 4.57. The obtained RBE values allowed to modify the total neutron dose and its fractionation in the therapy of malignant tumors at the Institute of Oncology, Krakow.