E.S. Critser

Bio: E.S. Critser is an academic researcher from University of Wisconsin-Madison. The author has contributed to research in topics: Sperm & In vitro fertilisation. The author has an hindex of 1, co-authored 1 publications receiving 1142 citations.

Capacitation of bovine sperm by heparin.

Abstract: Capacitation of bovine sperm was evaluated by determining the ability of sperm to fertilize bovine oocytes in vitro and to undergo an acrosome reaction upon exposure to lysophosphatidylcholine (LC). Incubation of sperm with heparin (10 micrograms/ml) increased the percentage of oocytes fertilized, but this required exposing sperm to heparin for at least 4 h before adding them to oocytes. There was no effect on the percentage of motile or acrosome-reacted sperm after exposure of noncapacitated sperm to 100 micrograms/ml LC for 15 min. When sperm were incubated for 4 h with heparin, exposure to 100 micrograms/ml LC for 15 min had no effect on the percentage of sperm that were motile, but the percentage of acrosome-reacted sperm increased from less than 10% to over 70%. The acrosome reactions (ARs) induced by LC were synchronous, reached maximal levels within 15 min, and differed (p less than 0.001) between sperm incubated under capacitating (with heparin) and noncapacitating conditions (without heparin). The time course required for heparin to capacitate sperm as judged by in vitro fertilization and to render sperm sensitive to LC induction of the AR were found to be similar. The percentage of ARs induced by LC and percentage of oocytes fertilized by sperm were found to be heparin-dose-dependent, with the maximum responses occurring at 5-10 micrograms/ml heparin. The correlation between the mean fertilization and LC-induced AR percentages was 0.997 (p less than 0.01). These studies demonstrate capacitation of bovine sperm by heparin requires at least a 4-h exposure of sperm to heparin and suggest that plasma membrane changes prior to an AR can be detected by exposure of bovine sperm to LC.

Oocyte and follicular morphology as determining characteristics for developmental competence in bovine oocytes

Abstract: Follicular size, follicular atresia, and oocyte morphology were investigated for the possible relation of these characteristics to the developmental competence of bovine oocytes. Ovaries from a local slaughterhouse were dissected to obtain a heterogeneous population of follicles. Half of each follicle was fixed for histological analysis, and the oocytes were detached carefully and cultured individually. Before in vitro maturation, the oocytes were grouped into six different classes based on the morphology of the cumulus and the ooplasm: classes 1 and 2 represent oocytes with a homogeneous ooplasm plus a compact and complete cumulus, and classes 3-6 represent oocytes with a granulated ooplasm and an incomplete and/or expanded cumulus. Oocytes from class 3 (beginning of expansion in outer cumulus layers and slight granulations in the ooplasm) developed past the 16-cell stage significantly (P < 0.05) more than oocytes with a compact and complete cumulus (classes 1 and 2) and oocytes from classes 4-6 (incomplete and/or expanded cumulus) after 5 days of in vitro culture. Oocytes from follicles measuring 3 mm or less did not develop past the 16-cell stage, whereas follicles of 3-5 mm and 5 mm or larger developed at similar rates (17% and 21% morulae, respectively). The state of the follicle did not affect whether an embryo reached at least the 16-cell stage, as comparable rates were obtained in all three groups of follicles: nonatretic (20%), intermediate (14%), and slightly atretic (16%).(ABSTRACT TRUNCATED AT 250 WORDS)