Fig. 5. EGTCs have distinct morphological profiles that may correspond to different chronological stages of its biogenesis. Transmission electron micrographs of uninfected NRK cells subjected to the rapid ethane freezing procedure followed by osmium tetroxide treatment to enhance the morphology of membrane structures. Two morphologically distinct EGTCs are on view here. The upper left structure (I) appears to have extensive electron-dense membrane structures within it (white arrowheads) that are not found in the lower right structure. These membrane structures may reflect COPII coats that are frequently seen to line budding profiles and vesicles (black arrowheads) associated with the ERES. Bar, 0.2 µm.

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