抄録
The most effective quantitative separation of ejaculates of semen into subsets of sperm differing in quality by density gradients requires information on the specific effects of processing conditions on sperm density. Reported density of bull sperm varies greatly. This research was undertaken to study the effects of gradient osmolality on sperm density and on separation using gradients with low viscosity and low toxicity to sperm. Semen was available from bulls used for artificial insemination. Cell volume studies revealed that live sperm volume was altered by more than 25% by exposure to solutions differing in osmolality, resulting in predictable differences in density measurable by density gradients. Control studies indicated that discontinuous Nycodenz® gradients differing by less than 1% in density could be prepared. Following centrifugation at 100,000 × g for 1 h fractions containing 96-99% unstained (live) and 91% motile sperm versus a fraction with 100% nonmotile sperm were obtained. The densities (g/ml) of live sperm separated on low osmolality gradients (220-237 mOsm), and on high osmolality gradients (342-345 mOsm) were 1.125 versus 1.145, respectively. Killed sperm on both gradients had a density of 1.233 g/ml. These gradients permit quantitative separation of sperm varying in membrane integrity and ability to function under different conditions, but do not permit sexing.
