The cortical granule reaction in living eggs of the toad, Xenopus laevis

Abstract

The formation of a fertilization envelope in eggs of Xenopus laevis involves the addition of cortical granule F-material to the preexisting vitelline envelope. The deposition of F-material on the outer surface of the vitelline envelope can be visualized at low resolution in artificially activated, dejellied eggs (Grey et al., 1974). Conditions affecting the appearance of cortical granule F-material in such eggs were further defined in the present investigation. An absolute requirement for a noncortical granule factor in the aggregation or polymerization of extruded cortical granule material was demonstrated. An assay was developed for this noncortical granule component, polymerization-initiating activity (PI). PI activity was localized in the innermost jelly layer of the egg, that layer which is contiguous with the vitelline envelope. A method was developed for the routine recovery of extruded cortical granule contents from artificially activated, dejellied eggs possessing an intact vitelline envelope. A rapid, quantitative spectrofluorometric assay for cortical granule extrusion was described providing a basis for a biochemical investigation of this secretory process.