Accumulation of secretory vesicles in sec6-4 cells at the restrictive temperature 37°C. (A) Transmission electron micrograph of a budding sec6-4 cell cultured at the permissive temperature 24°C. (B) Transmission electron micrograph of a budding sec6-4 cell cultured for 45 min at the restrictive temperature 37°C. White arrowheads indicate accumulated secretory vesicles with a diameter of ∼100 nm. (C) 3D reconstruction of a budding cell with accumulated secretory vesicles (red) in a tomogram recorded from a 200-nm thick section prepared from the same culture of cells as shown in B; the PM is reconstructed in blue, the vacuole is orange, and other organelles such as Golgi cisternae or endosomal structures are in yellow. V, vacuole. Bars, 1 µm.