Spatial organization of actin filaments connecting secretory granules to the plasma membrane. (A) TEM images at zero tilt of a docked secretory granule and a series of secretory granules at different stages of fusion (left) and the corresponding clipping plane of the side view of the isosurface representation of their tomogram (right). Actin cytoskeleton favoring exocytosis (asterisks) of secretory granules (SG) is clearly linked to the plasma membrane (PM) through specific associated-membrane structures (V). Bars, 200 nm. (B) Slices through a tomogram of docked and fusing secretory granules. Red broken circles define an area of 90–250 nm around the granules, wherein anchor points for cortical actin at the plasma membrane were systematically localized. Bars, 100 nm.