No abstract

The time required for nuclear transformation of human spermatozoa in the cytoplasm of zona-free hamster ova was determined using semen samples from four individuals. Zona-free ova were incubated with capacitated spermatozoa for either 3 h or for 4-8 h. After the first hour of insemination, up to 85 ova were fixed at 1-h intervals. Assessments of sperm transformation were carried out on Giemsa-stained preparations of ova. Considerable variation between individuals was found in the maximal time of sperm decondensation, ranging from 2 to 7 h. Decondensing sperm heads developed into pronuclei within 3-5 h. At and subsequent to pronuclear formation, the incidence of decondensing sperm heads was considerably reduced in both insemination times. This variability in sperm transformation is relevant in clinical evaluations of the functional capacity of spermatozoa.