Continuous-step density gradient centrifugation for the selective concentration of progressively motile sperm for insemination with husband's semen.

To increase the fertilizability of sperm for use in artificial insemination with husband's semen, it is effective to concentrate progressively motile sperm from whole ejaculated semen. The simple procedure, a continuous-step density gradient technique, was developed to selectively concentrate progressively motile sperm. The ejaculated semen was placed on 6.0 ml of 80% Percoll solution, and the density gradient was formed by mixing the semen and Percoll with an L-shaped rod for two or three strokes. After centrifugation at 400 x g for 30 min, progressively motile sperm were concentrated in the sediment, whereas the immotile sperm and other types of cells remained in the upper part of the density gradient. In most specimens sperm motility was improved by more than 80% regardless of the original motility. Thus, the fertility index (sperm concentration/ml x percentage of motility x 10(-8)). was increased to 7.7 +/- 3.7 times (n = 15).