Fig. 7. Cortical granules are not associated with structural microfilaments prior to translocation. Oocytes were subjected to isopycnic sucrose centrifugation to stratify organelles. (A) Immunolabeled cortical granules of a control cell (B) after high-speed stratification (5000 g). Note refractile band of cortical granules in B, corresponding to immunolabeled cortical granules in A. Same scheme for C,D, except that prior to stratification, cells were treated with cytochalasin D, resulting in a slightly bulged centrifugal end, sometimes exaggerated for many µm (data not shown). We interpret this disfiguration to reflect the loss of cortical microfilaments. (E) Immunolabel and (F) DIC image of low-speed spin (1500 g) in control (E,F), or (G,H) cytochalasin conditions. Conditions were sought that would maximize resolution of the cortical granule displacement, but no difference was seen. (I-L) Cells allowed to recover in control conditions after low-speed spin (I,K, recovered for 30 minutes) or from a high-speed spin (J,L, recovered for 2 hours). (Below) Graphical representation of cells represented above, error bars represent ±1 s.d.; scale bar: 50 µm. At least 10 cells were assessed for each condition. None of the experimental conditions produce result that are significantly different from control values at P>0.10 (confidence level determined by Student’s t-test analysis), but each of the recovery conditions from stratification is significantly different from the stratification alone (*), even in the presence of cytochalasin D.

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