Figure 3.

Electron tomography of Golgi stacks. Dual axis tomography was performed to obtain good resolution of membrane delineations in all specimen planes. (A) A digital slice through the 3D volume of an electron tomographic reconstruction illustrates the appearance of the Golgi area seen before addition of proPr (left field), 3 min after addition of proPr (middle field) and 2 min after removal of proPr (right field). Each membrane-delineated structure present in this digital slice was analyzed throughout the 3D volume and color-coded. Blue, Golgi cisterna or structures continuous with a Golgi cisterna except membrane buds; red, vesicles; green, tubular structures; and yellow, membrane buds. Scale bar, 100 nm. (B) Different close-up fields vesicles and membrane buds observed after removal of proPr. Arrows indicate necks of budding profiles that appear constricted by electron-dense material. Scale bar, 40 nm.