title: Egg jelly layers of Xenopus laevis are unique in ultrastructure and sugar distribution.
abstract: Jelly coats surrounding the eggs of the South African clawed toad, Xenopus laevis, consist of three transparent, gelatinous layers: the innermost layer (J1), the middle layer (J2), and the outer layer (J3). The distribution of N-acetylglucosamine within these jelly coats, as probed with FITC-conjugated wheat germ agglutinin (WGA-FITC), and the matrix ultrastructure of each layer, as visualized in platinum replicas produced by the quickfreeze, deep-etch, and rotary-shadowing technique, suggests that each layer has a unique fiber and glycoprotein composition. J1 extends nearly 200 microns from the egg surface and exhibits no WGA-FITC staining. Stereo images of platinum replicas indicates that J1 consists of a tightly knit network of 5-10 nm fibers decorated with 10-20 nm particulate components. In contrast, J2 is a relatively thin layer, extending only 25-40 microns from the outer aspect of J1. When visualized by confocal microscopy, J2 displays a multilayered WGA-FITC staining pattern. The ultrastructure of J2 consists of sheets of fine fibers that run parallel to one another and that can be identified by their ability to bind WGA-colloidal gold. The fibers of each sheet run at an oblique angle to fibers in neighboring layers. J3 extends 100 microns or more from J2. The WGA-FITC staining pattern shows high intensity in its outer region and less intensity in regions closer to J2. Like J1, the J3 ultrastructure consists of a network of 5-10 nm fibers, decorated with 10-20 nm particulate components. The results of these studies add to a growing body of information that suggests the jelly coats surrounding the eggs of many animals consist of a fibrous glycoprotein superstructure that acts as a scaffold to which globular glycoproteins are bound.
authors.affiliation: Department of Zoology, Arizona State University, Tempe 85287-1501, USA.
authors.forename: B S
authors.initials: BS
authors.lastname: Bonnell
authors.forename: D E
authors.initials: DE
authors.lastname: Chandler
mesh_terms: D000818:Animals; D050260:Carbohydrate Metabolism; D005260:Female; D010063:Ovum / Q000648:ultrastructure*; D014982:Xenopus laevis