Fig. 2. Detection of ingested polyacrylamide beads. Macrophages were fed with stiff, opsonized polyacrylamide beads with fluorescent dextran trapped inside. Unlike beads that stuck to the side of the cell (arrowhead), internalized beads are not readily visible with phase optics (a; long arrow). However, a combination of phase and fluorescence optics easily reveals all the beads (b; arrow and arrowheads). (c) Stereo reconstruction of the same cell stained with rhodamine phalloidin, showing a closed phagocytic cup around the internalized bead (long arrow). A patch of actin is concentrated beneath the external bead (arrowhead). Bar, 4 µm.