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R. F. Parrish and K. L. Polakoski

Summary. The in-vitro proteolytic activity of boar sperm acrosin was stimulated by a series of monovalent and divalent metal ions. Equivalent concentrations of monovalent cations resulted in nearly identical increases in proteolytic activity, probably related to the increased ionic strength of the incubation medium. However, at concentrations of monovalent cations that resulted in a 2- to 3-fold stimulation of proteolysis of Azocoll, divalent metal ions caused a 24-(magnesium) to 46-(calcium) fold increase in proteolytic activity. We suggest that the divalent metal ion binds to acrosin and thus increases the proteolytic activity of acrosin to an extent greater than that due to the increased ionic strength of the incubation medium.

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R. F. Parrish, J. C. Goodpasture, L. J. D. Zaneveld and K. L. Polakoski

Summary. The conversion of human proacrosin to acrosin was inhibited by polyamines. The order of effectiveness was spermine > spermidine > cadaverine > putrescine > 1,3-diaminopropane. These results are similar to those obtained for the conversion of boar proacrosin to acrosin. Unlike the effects on boar acrosin, however, polyamines did not affect the esterolytic activity of human acrosin but had a slight stimulatory effect on the proteolytic activity of human acrosin.

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L A Rispoli, J L Lawrence, R R Payton, A M Saxton, G E Schrock, F N Schrick, B W Middlebrooks, J R Dunlap, J J Parrish and J L Edwards

Consequences of heat stress exposure during the first 12 h of meiotic maturation differed depending on how and when bovine oocytes were activated. If heat-stressed oocytes underwent IVF at ∼24 h, blastocyst development was less than for respective controls and similar to that obtained for nonheat-stressed oocytes undergoing IVF at 30 h (i.e. slightly aged). In contrast, if heat-stressed oocytes underwent chemical activation with ionomycin/6-dimethylaminopurine at 24 h, blastocyst development was not only higher than respective controls, but also equivalent to development obtained after activation of nonheat-stressed oocytes at 30 h. Developmental differences in chemically activated vs IVF-derived embryos were not related to fertilization failure or gross alterations in cytoskeletal components. Rather, ionomycin-induced calcium release and MAP kinase activity were less in heat-stressed oocytes. While underlying mechanisms are multifactorial, ability to obtain equivalent or higher development after parthenogenetic activation demonstrates that oocytes experiencing heat stress during the first 12 h of meiotic maturation have the necessary components to develop to the blastocyst stage, but fail to do so after fertilization.