Figure 7.

Examination of double-stained mitotic membrane fractions. Membrane vesicles present in the 115 S mitotic Golgi velocity gradient peak were double-stained for the Golgi marker protein giantin (A), and the ER marker protein p63 (B). The Golgi and ER images are also shown after merging (C). Identical analysis of membranes in the rapidly sedimenting mitotic Golgi fraction at the bottom of the velocity gradient is also shown (D–F). In addition, an identical analysis of membranes recovered at the bottom of the velocity gradient from cells treated with brefeldin A during progression to M-phase is shown (G–I). Note that Golgi and ER membrane-staining patterns were coincident in the rapidly sedimenting membrane fraction from brefeldin A-treated, but not nontreated, mitotic cells.