Biology of Reproduction

In the procedure described, demembranated ram sperm models were treated to decondense their nuclei, and the movement of their sperm tails was then reactivated. The duration of movement was sustained for more than 30 min, with a tail-wave frequency of up to 14 Hz. Decondensed sperm models adhered to each other and to the slide; but adherence was prevented by addition of an anti-agglutination factor derived from dialyzed, freeze-dried ram seminal plasma, which allowed models to swim freely. Electron microscopy showed that most areas of the sperm model nuclei were decondensed and contained fine interconnected filaments with structures resembling nucleosomes at anastomosing regions. Some central, lateral, and basal regions of the nuclei were not fully decondensed. The axoneme, outer dense fibers, and fibrous sheath were not affected ultrastructurally by the extraction procedure; the mitochondria of the middle piece appeared to be extracted, while the acrosome but not the perforatorium was removed. Use of decondensed, reactivated sperm models provides a means to monitor the decondensation of sperm in vitro while maintaining minimal disruption to sperm tail components. This will allow access to the nucleus for experimental manipulation in sperm models.