title: Relationship between calcium binding sites and membrane fusion during the acrosome reaction induced by ionophore in ram spermatozoa.
abstract: Ram spermatozoa treated with the ionophore A23187, to induce the acrosome reaction, were fixed in pyroantimonate-osmium in order to demonstrate calcium at an ultrastructural level. Prior to vesiculation, granules of precipitate occurred at points of contact between plasma and outer acrosomal membranes, suggesting a discrete role for calcium during membrane fusion. The earliest stages of vesiculation always occurred in the region just anterior to the equatorial segment and it was this same site where a marked concentration of precipitate, indicating calcium binding sites, could be demonstrated.
mesh_terms: D000177:Acrosome / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D008297:Male; D012756:Sheep; D013094:Spermatozoa / Q000187:drug effects / Q000502:physiology*
chemical_list: D000001:Calcimycin; D002118:Calcium