Abstract
The extent to which fertilization failure in in vitro inseminated human oocytes obtained from hyperstimulated ovaries was associated with alterations in cellular structure and cytoplasmic organization was examined by a combination of DIC, fluorescence, time-lapse video, and transmission electron microscopy. Detailed analysis of meiotically mature preovulatory (uninseminated) oocytes, and of oocytes that failed to fertilize in vitro, indicated that between 10% and 15% of grossly normal-appearing MII-stage oocytes displayed one of the following cellular perturbations: 1) a subtle change in organelle distribution, 2) a small region(s) of intracellular cytolysis, 3) a massive aggregation of SER tubules, 4) an accumulation of vesicles presumed to be of SER origin, 5) a change in the structural organization of the cortical cytoplasm and overlying plasma membrane, 6) a sudden and rapid internalization of perivitelline fluid by means of an apparently aberrant process of endocytosis, and 7) a premature and partial exocytosis of cortical granules. The description of these disorders is discussed with respect to the developmental consequences for the oocyte.
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