. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 350 CHENG ET Figure 2. SEM of Strongylocentrotuspurpwatus egg surfaces. A. VL ofegg(unactivatedl in normal Na*- SW. B-D. FEs of normal Na+-SW eggs at 1,3, and 60 min postactivation. E. VL of egg (unactivated) in ChCl-substituted-SW. F-H. FEs of ChCl-suhstituted-SW eggs at 1,3, and 30 min. The microvillar projections of the ChCl-suhstituted-SW eggs did not undergo the I-T transformation. Scale bar = 1 ^m. FE permeability, but that the ovoperoxidase was not in- corporated efficiently into the structure of the FE. Th
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 350 CHENG ET Figure 2. SEM of Strongylocentrotuspurpwatus egg surfaces. A. VL ofegg(unactivatedl in normal Na*- SW. B-D. FEs of normal Na+-SW eggs at 1,3, and 60 min postactivation. E. VL of egg (unactivated) in ChCl-substituted-SW. F-H. FEs of ChCl-suhstituted-SW eggs at 1,3, and 30 min. The microvillar projections of the ChCl-suhstituted-SW eggs did not undergo the I-T transformation. Scale bar = 1 ^m. FE permeability, but that the ovoperoxidase was not in- corporated efficiently into the structure of the FE. There- fore, DAB localization of ovoperoxidase was performed. Comparing the TEM micrographs (Fig. 7) of FEs after DAB incubation, the normal SW FE (Fig. 7C) is con- spicuously darker than that of the ChCl FE (Fig. 7D). Although both normal and ChCl FEs stained more inten- sively than the controls (Fig. 7A, B), the intensity of stain- ing was higher in the normal FEs. Presumably, there was more ovoperoxidase incorporated into the FEs in normal Na+-SW than in ChCl-substituted SW. Discussion Sea urchin eggs are excellent material for many bio- logical studies because they can be harvested in large numbers, cultured in a well-defined medium (artificial seawater), and they develop synchronously. They are well suited for the study of extracellular self-assembly (Kay and Shapiro, 1985; Somers and Shapiro, 1989; Shapiro el al., 1989). The complexity of the transition of the vi- telline layer (VL) glycoprotein to the FE tempts one to try to dissect the myriad of sequential processes involved. The VL is not merely an inert cell coat, but it serves as a template or scaffolding upon which other proteins are as- sembled and intercalated under the influence of several enzymes. A requisite for proper structuralization is the presence of several ions in the seawater, Ca2+, Mg:4 (Carroll and Endress, 1982), Cl~ (Lynn et al. 1988; Green et 1990), and Na+ (Schuel et al. 1982). In the pre
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