Article Abstract:
The large release of calcium and subsequent cortical granule exocytosis at fertilization may depend on structural reorganization of the endoplasmic reticulum (ER). A comparison was made between the ER of live metaphase II mouse eggs and prophase I-arrested oocytes. In the mature eggs, many dense accumulations of membrane were present in the cortex but absent deeper in the cytoplasm, with a fine reticular network of ER throughout the cell. Immature oocytes had few ER accumulations in the cortex, but larger clusters were found in the deeper cytoplasm.
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Article Abstract:
Application of proteases to eggs of the starfish Asterina miniata cause cortical granule exocytosis and fertilization envelope elevation to occur almost immediately when exposed to trypsin, chymotrypsin, or pronase. The responses were prevented by protease inhibitors. The proteases did not function by harming the eggs. Thus there is an extracellularly exposed protein that may act as a receptor to transduce a signal from the sperm to begin egg activation during fertilization. This protein induces fertilization-like responses when proteolyzed.
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Article Abstract:
A study of sea urchin eggs during fertilization indicate a number of structural changes in its endoplasmic reticulum (ER). Using the spreading of the lipophilic dye DiI as indicator, it was observed that the egg's ER is fragmented during the first few minutes after fertilization but not during the first minute after insemination. This behavior has several functions for the subsequent stages of fertilization.
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