The cytogenetic effects of in vitro irradiation on Y Å 0.07385({0.00838) / 0.23329({0.03124)D / human spermatozoa have been studied by the in-0.02317({0.00955)D 2 , respectively. terspecific in vitro fertilization system between hu-When analyzing separately unrejoined and reman sperm and hamster oocytes. Semen samples joined structural abnormalities, we found that the from three healthy men were irradiated at doses incidence of unrejoined lesions was four times of 0.00, 0.10, 0.25, 0.50, 1.00, 2.00, and 4.00 higher than the incidence of rejoined anomalies. Gy. A total of 340 chromosome complements de-The induction of unrejoined abnormalities showed rived from non-irradiated human spermatozoa a linear, dose-dependent increase, whereas the inciand 987 complements from irradiated spermato-dence of rejoined abnormalities showed a quazoa were analyzed after sequential uniform stain-dratic, dose-dependent increase. G banding.
The distribution of radiation-induced breakpoints was Both the frequency of spermatozoa with structural also analyzed. Breakpoints were found to be randomly chromosome abnormalities, and the incidence of distributed among chromosomes, but a clustering of such abnormalities per cell, showed strong dose-breakpoints in G-negative bands was found: 71.5% of effect relationships that were best expressed by lin-breakpoints were located in G-negative bands, and ear-quadratic equations: Y Å 0.06413({0.00475) / 28.5% in G-positive bands. Environ. Mol. Mutagen. 0.1982({0.00833)D 0 0.00763({0.00204)D 2 and 29: 357-366, 1997 ᭧ 1997 Wiley-Liss, Inc.