Figure 8

ATII cells imaged in parallel by fluorescence (upper panel) and DIC (lower panel) in the presence or absence (ctrl) of PFC. Green fluorescence (LTG) denotes intracellular LBs, and shows a clear correlation with DIC. FM 1-43 (yellow, 1 μM) heavily stains exocytosed (arrowhead) or extruded surfactant (black asterisk, signal out of focus, no correlation to vesicles), weakly the plasma membrane (arrow), and also variously sized droplets of PFC (white asterisks). Note that brief exposure with FM 1-43 does not stain intracellular structures, as compared to Figure 2. A differentiation between surfactant and PFC is here difficult, but can be made according to the differential appearance in DIC (PFC = indented hollow structures, white asterisk; compare with arrowhead), or by the difference in emission intensities (Inset: at largely reduced exposure times, surfactant appears much brighter than PFC, small arrow). Droplets of PFC may be distant from the cells (red asterisk), or in intimated contact with the plasma membrane (white asterisk). No noticeable difference with regard to plasma membrane, cell morphology, size or perinuclear location of intracellular LBs, and presence of exocytosed surfactant could be detected between these groups.