Behavior of nuclei of testicular, caput and cauda epididymal spermatozoa injected into hamster eggs

Abstract

Isolated nuclei of testicular, caput and cauda epididymal spermatozoa of the hamster were injected into mature unfertilized eggs by micromanipulation. The nuclei decondensed within the egg cytoplasm regardless of the type of spermatozoa used and whether the eggs were activated or not. Decondensed nuclei of testicular and cauda epididymal spermatozoa could transform into pronuclei in activated eggs, whereas those of the vast majority of caput epididymal spermatozoa failed to do so at least within the time period studied (up to 9 h). The failure of nuclei of caput epididymal spermatozoa to develop into pronuclei could be due to the presence of a factor in the nuclei which prevents transformation of decondensed sperm nuclei into pronuclei. This factor might be absent or inactive in the nuclei of testicular spermatozoa and removed or inactivated again by another factor while the spermatozoa reside within the cauda epididymis.