Immunoelectron Microscopic Demonstration of the Pre-fertilization Layer in Xenopus eggs: (Xenopus/immunoelectron...

The formation of the fertilization (F) layer in Xenopus laevis was studied by immunoelectron microscopic protein A-gold technique, employing an antiserum specific to the secretory granules in the bottom cells at the posterior portion of the pars recta of the oviduct (pars recta 2). In unfertilized eggs, the gold particles revealing the antigenic sites were specifically present over the pre-fertilization (PF) layer located between the vitelline coat and the jelly layer. Upon transformation of the PF layer into the F layer, the labeling became confined to the region on the outer surface of the F layer, suggesting the loss of antigenic site in the inner part of newly-formed F layer. These results provide an ultrastructural basis for the view that the PF layer is supplied by specific cells in the oviducal pars recta 2.