Fig. 6. EGTCs may be derived from COPII vesicle cluster/chains that coalesce by homotypic fusion processes. Transmission electron micrographs of uninfected NRK cells subjected to the rapid ethane-freezing procedure followed by osmium enhancement as in Fig. 5. (A) Electron-dense material, probably corresponding to COPII, can be found on vesicles and bud profiles associated with the ER transitional elements (arrowheads). (B,C) Vesicles with this electron-dense coat are frequently found in chains or clusters (arrowheads), and these chains and clusters may well be fusing with a nearby, existing EGTC (^*).