Simpson, AM & White, IG 1986, 'Effect of cold shock and cooling rate on calcium uptake of ram spermatozoa', Animal Reproduction Science, vol. 12, no. 2, pp. 131-143.
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Rapid cooling (cold shock) of washed ejaculated ram sperm irreversibly reduced motility and respiration and greatly increased uptake of 4sCa2+. The effect was greater as the temperature of cooling was reduced from 15°C to 0°C, and a substantial increase in sperm calcium levels was even observed after slow cooling to temperatures below 10°C. The rise in calcium uptake on freezing sperm to -79°C was not as great as that on cold shocking sperm to 0°C. Inactivation of sperm by mild heat (50°C) had no significant effect on calcium uptake but subsequent cold shock increased the sperm calcium. Reverse immobilization of sperm by low concentrations of formaldehyde significantly reduced calcium uptake on cold shock. Addition of detergents to sperm immediately reduced motility, respiration and calcium uptake of control and cold-shocked sperm to zero.
Simpson, AM, Swan, MA & White, IG 1986, 'Action of phosphatidylcholine in protecting ram sperm from cold shock', Gamete Research, vol. 15, no. 1, pp. 43-56.
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AbstractRapid cooling (cold shocking) of washed ejaculated ram sperm to 0°C irreversibly reduced motility, tail beat frequency, and respiration and increased the uptake of 45Ca2+. The plasma membranes were removed from the sperm head, and the acrosomes were detached from the nuclei. The plasma membranes of the middle piece were removed, and the mitochondria contained pale and expanded cristae, similar in appearance to ATP‐deprived mitochondria in the “condensed” configuration. The presence of 2.0 mg/ml phosphatidylcholine (lecithin) in the medium prevented ultrastructural damage on cold shock, and the motility, tail beat frequency, respiratory rate, and calcium uptake were maintained at levels similar to washed sperm. As the “protective” effect of phosphatidylcholine against cold shock was maintained to a certain extent after rewashing and centrifuging the sperm prior to cold shock, the interaction of phosphatidylcholine with ram sperm membranes may be fairly “tight” and not easily disrupted.
