Fig. 1.

Cultured lacrimal gland (LG) acinar cells reform lumina that are in open exchange with the extracellular culture media. A: a three-dimensional reconstruction of a live, cultured LG acinus stained with FM 1-43 dye (green), which labels cell membranes, and incubated in medium in which a fluid tracer, 10-kDa Texas Red dextran (red), has been added. The membrane marker delineates cell membranes and some apical vesicular structures within the cell that have exchanged with the cell membrane during the incubation period, whereas the fluorescent fluid phase tracer is apparent in the extracellular space, which includes the lumen, but not within the acinar cells. Note that some cell debris adjacent to this acinar cluster in the image nonspecifically absorbs both fluorescent dyes. Optical sections at regular intervals through the lumen are shown beside the three-dimensional reconstruction. Bar = 5 μm. B: the topography of the cell is shown through representations of the signal intensities of both markers, depicting the membrane and extracellular space, respectively.