Surface structure of spermatozoa frozen for artificial insemination.

Samples of human semen frozen in liquid nitrogen ( - 196 degrees C) with no glycerol, 5 and 10% glycerol were compared with samples that were untreated, with 10% glycerol but not frozen, and spermatozoa frozen at -20 degrees C. SEM and TEM of the samples indicates that 10% glycerol caused fewer surface changes of the spermatozoa than other treatments. Motility counts after the various freezing treatments were also highest when 10% glycerol was used as the cryoprotectant. Nonetheless, cryopreservation is detrimental to spermatozoa and often causes considerable damage to the acrosome with a leakage of the acrosomal contents.