Effects of neutrons on human sperm chromosomes

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Effects of ^<60>Co gamma-rays and ^<252>Cf neutrons on human sperm chromosomes were studies using our interspecific in vitro fertilization system with golden hamster oocytes to estimate relative biological effectiveness (RBE) of neutrons. The RBEs were estimated to be 1.7 and 2.0 with two indices, i.e., the frequency of chromosomally abnormal spermatozoa and the number of structural chromosome aberrations per spermatozoon. These values were considerably lower than those obtained by previous investigators in human lymphocytes (10-80), mouse spermatogonia (20-25) and early embryos (4.7-7.4).An attempt was made to apply cryopreserved golden hamster oocytes to cytogenetic study of irradiated human spermatozo. There was no significant difference in the frequency of radiation-induced sperm chromosome aberrations between the two assay systems using frozen-thawed oocytes and fresh oocytes, indicating that freezing of the oocytes does not affect the aberration frequency. Cryopreserved hamster o … More ocytes are useful to carry out spermchromosome study more conveniently and efficiently.We also tried to use cryopreserved human spermatozoa in this study. The irradiated semen samples were frozen with a simplified method, thawed at different intervals after cryopreservation, and processed for chromosome analysis. No increase of chromosome aberrations was found at any intervals, indicating that cryopreservation has no effects on radiation-induced DNA damage in spermatozoa. This method is useful for repeated use of subdivided frozen samples and transportation of sample for later cytogenetical use.To obtain background data for genetic risk assessment of radiation, spontaneous incidence of chromosome aberrations in human spermatozoa was estimated with semen samples from 51 healthy Japanese men. The frequency of chromosmally abnormal spermatozoa was 15.5(]SY.+-。[)4.2% on an average. There was no correlation between aberration frequency and age of donors. The habit of cigarette smoking was also unrelated. Less