Studies on a Cortical Layer Response to Stimulating Agents in the Arbacia Egg

The part played by inositol trisphosphate and calcium in the propagation of the fertilization wave in sea urchin eggs.

“…1 and from five other eggs are given in Table II. In two eggs (1 and 2) light emission began close to the egg equator and filled the egg outline in 25 s. In four other eggs, light emission began more diffusely in an area [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Ixm away from the equator and filled the egg outline in 10-20 s. Since the time to mean peak light emission was similar for all eggs, we assume eggs 1 and 2 to have been examples of equatorial sperm-egg fusion and interpret the spatial distribution of aequorin light emission in the other cases to be the result of a more polar sperm-egg interaction. In the two cases of presumptive equatorial sperm fusion, the local cytoplasmic free calcium concentration was greatest at the site of sperm-egg interaction; in these two cases, mean peak light emission occurred before the free calcium concentration had reached a peak at the antipode.…”

“…W P'HEN a sea urchin egg is fertilized, the fertilization envelope rises around the egg progressively, starting from the point of sperm entry (2,20,30). The envelope is formed as a result of the exocytosis of cortical secretory granules which lie immediately beneath the plasma membrane of the unfertilized egg (22,24). These granules undergo exocytosis in vitro in response to micromolar concentrations of calcium ions (11,13,40).…”

A free calcium wave traverses the activating egg of the medaka, Oryzias latipes.

“…In sea urchin eggs, these vesicles cannot be centrifugally detached from the cortex (22,33). Nevertheless, Uehara and Sugiyama (57) have elegantly demonstrated the propagation of the fertilization wave across a ring of the urchin egg surface which had been freed of vesicles by localized treatment with an anionic detergent.…”

“…One simple, but we believe substantial argument for the simple calcium theory is that medaka eggs (63), Xenopus eggs (61), hamster eggs (58), and probably even sea urchin eggs (33) can only be prick-activated in (or after transfer to) a calcium-bearing medium. Furthermore, prick-activation of medaka eggs (25; as well as frog eggs [19]) sometimes initiates development all the way to hatching or beyond, provided the pricking is supplemented by a cleavage-initiating factor which is very probably cer~triolar (23).…”

Secretory functions of egg cortical granules in fertilization and development: A critical review

“…This process appears to be identical to secretory granule formation in typical somatic cells [Dauwalder et al, 1972;Palade, 19751 . Following ovulation, the cortical granules in mature eggs release their stored contents by exocytosis in response to stimulation by sperm at fertilization or upon parthenogenetic activation by various chemical and physical agents [E. Moser, 1939;Sachs and Anderson, 19701. The stimulus-secretion coupling mechanism in eggs [Epel, 1975, 19781, as in somatic secretory cells [Baker, 1972;Heilbrunn, 19561, appears to be triggered by changes in membrane potential and ion fluxes [Jaffe, 1976;Jaffe and Robinson, 1978;Steinhardt et al, 19711.…”