Relationship of fine structure of sperm head to fertility of frozen human semen.
Damage to the plasma membrane and acrosome of human spermatozoa was quantitated following dilution, freezing, and thawing. Semen was obtained from 23 donors of known fertility attending an artificial insemination program. Dilution of semen with the cryoprotective medium containing glycerol significantly altered all the fine-structural and semen parameters studied. Membranes of the sperm head were severely altered after freezing and thawing. The percentage of spermatozoa with intact plasma membrane, with intact acrosomes, or with intact or swollen acrosomes was significantly reduced in frozen/thawed semen, compared with fresh semen samples. The percentage of spermatozoa with an intact plasma membrane and acrosome was significantly and positively correlated with the fertility of frozen donor's semen used for insemination (r = 0.6, P less than 0.001). The deleterious effects observed in the sperm head membranes following dilution and freezing and thawing may explain why generally the fertility of frozen/thawed semen is lower than that of fresh semen and may also explain individual variation in fertility of donors after insemination of frozen semen.
D005298:Fertility; D005615:Freezing; D006801:Humans; D008297:Male; D008854:Microscopy, Electron; D012662:Semen Preservation; D013077:Sperm Head / Q000648:ultrastructure*; D013094:Spermatozoa / Q000648:ultrastructure*