Ultrastructural changes in the acrosome of human sperm during freezing and thawing: a pilot trial.

As a pilot trial, a semen sample was diluted with a glucose-citrate-egg yolk diluent and frozen in 0.5 ml PVC paillettes in liquid nitrogen vapor. Motility and acrosome integrity of the sample were evaluated before and after freezing, and longevity was monitored up to 6 h postthaw. Acrosome integrity was assessed by comparing Spermac-stained thin smears with TEM. Acrosome damage was found to be progressive, and four main types of acrosome state were identified and illustrated.