Fine structure and elemental composition of fresh and frozen dog spermatozoa

Dog spermatozoa from fresh ejaculates and after freezing-thawing were air-dried on to grids and subjected to X-ray microanalysis or examined by scanning and transmission electron microscopy. The spermatozoa subjected to freezing-thawing presented major changes in their morphology, which included the loss of acrosomal contents, seen both by the swelling and rarefaction of the acrosome and the loss of electron-dense acrosomal material. In many cells the acrosomal damage, including the equatorial region, was conspicuous, with vesiculization of the acrosomal membranes. The plasmalemma remained, in most cases, apparently intact. X-ray microanalysis of the sperm aliquots showed a significant decrease in the amount of most selected elements after freezing-thawing. The extent to which concentrations of phosphorus and sulfur decreased in the sperm head region suggested that major changes in the chromatin occurred during the freeze-thaw process.