Asymmetrical signals with cytoplasmic fluorescein. The dynamic nature of the fluorescence asymmetry of fluorescein is shown (a) in a time sequence of images and (b) as a graph of total cellular and cytosolic fluorescent signals. The complete time sequence is shown in Video 1 (available). (c) The correlation between the increased fluorescence at the leading edge and the appearance of organelle-free cytoplasm is shown in the time sequence in which the top panel shows fluorescein fluorescence and the bottom panel the corresponding phase-contrast images. Images are shown at 10-s intervals. The maximum projection of organelle-free cytoplasm is marked by an asterisk in the third image pair. (d) The typical distribution of fluorescence intensity of cytoplasmic fluorescein along the axis of a polarized human neutrophil is shown. Bars: (a) 10 µm; (c) 8 µm; (d) 5 µm.