Improvement of male pronuclear formation during cross-fertilization between Chinese hamster spermatozoa and Syrian hamster oocytes by nocodazole, and chromosome analysis of hybrid zygotes.

摘要

The cytogenetics of hybrid embryos resulting from cross-fertilization between Chinese hamster spermatozoa and Syrian hamster oocytes was investigated. Immediately after insemination, oocytes were exposed to 0.1μg/ml nocodazole for 1 h (1-h group) or 2 h (2-h group) and then cultured. The rates of sperm penetration in the 1-h (48.0%) and 2-h (75.8%) groups were significantly lower than in the control group (incubated for 2 h without nocodazole; 89.8%). However, the ratios of male pronucleus formation were higher in 1- and 2-h groups (79.4% and 74.2%, respectively) than in the control (10.6%). These results were due to sperm head decondensation induced during the meiotic arrest of oocytes at metaphase II by nocodazole. Chromosomes of hybrid zygotesobtained after nocodazole exposure were analysed at the first cleavage metaphase. The incidence of structural chromosome aberrations in the Chinese hamster genome of hybrid zygotes was high in the control (42.1%) and 1-h (48.8%) groups, but was low in the 2-h group (14.4%). It is suggested that untimely sperm head decondensation causes structural chromosome aberrations in the male genomes of hybrid zygotes.