Recovery of motile sperm using the osmolality-gradient technique

A simple, effective method for collecting motile sperm from ejaculates is developed. One hundred semen samples were obtained from both fertile and infertile men. Following initial semen dilution (1: 1) to 4 mL in a hypoosmotic medium (210 mOsm/kg), the mixture was layered into the specially designed tube filled with 1 mL recovery medium in the bottom and 1 mL isolation medium in the second layer to form three discrete layers. During the next hour the highly motile sperm out-distanced the other seminal contents to reach the bottom of the tube. Compared with the parent ejaculates, the recovered specimens exhibited an increased percentage of motile sperm with significantly enhanced sperm velocity and linearity (p less than .001). This method isolated motile sperm with higher velocity than those obtained using the swim-up technique.