Figure 3.

Internal membrane dynamics in early embryos labeled with Bodipy BFA. The sequence of 2D multiphoton images begins prior to pronuclear migration and ends after cleavage. Vesicles are fairly uniformly dispersed before (a) pronuclear migration. (b) At the time the pronuclei meet, vesicles begin to aggregate around the pronuclei. From the movies it can be seen that vesicles are moving toward the centrosome in straight lines, presumably along astral microtubules, and can be seen aggregating in (e). Note the difference in the nature of the staining around the centrosome and the cytoplasm. The pericentrosomal region excludes larger vesicles, whereas the centrosomes and nucleus exclude all membrane staining. (c) In metaphase, the entire spindle midzone excludes vesicular staining. (d) Upon anaphase onset, the spindle midzone fills in with diffuse membrane staining, probably from small vesicles. (e) Late in anaphase-telophase, large vesicles can been seen trafficking toward and past the equatorial region (Movie 5 in the Supplementary material). (f) Cleavage has completed. The scale bar is 12.5 µm.