Aim: The study was designed to examine the effects of cryoprotective media, and glycerolating and thawing procedures on human sperm motility and gel penetrating ability. Methods: Fifteen unselected donors provided semen varying in quality that was distributed in a factorial design across three cryoprotectants (glycerol, egg yolk-citrate-glucose-glycerol and egg yolk-tris-glucose-glycerol). Also, glycerol was added at room temperature versus at 4. Two thaw temperatures were tested (laboratory air temperature for 10 min versus a 65 waterbath for 4 seconds). The proportion of total and progressively motile sperm was estimated immediately after thawing and following incubation at 35 for 2 h. Migration of sperm for 30 min at 37 through polyacrylamide gel was tested. Results: Donors differed greatly, with post-thaw total motility of sperm ranging from 9 to 44 % (P<0.05). Egg yolk-citrate-glucose-glycerol and egg yolk-tris-glucose-glycerol were superior to glycerol alone (post-thaw values of 35, 37 and 21 %, respectively, P<0.05). This was due primarily to poor sperm survival when semen was cooled to 4 without glycerol or egg yolk. The two thaw temperatures gave similar results. Sperm migration tests paralleled the motility results, but were more sensitive in detecting differences. Conclusion: Egg yolk, particularly in a tris-based medium that is widely used in domestic animals, improved the cryopreservation of both good and poor quality human semen.
    
    

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