Figure 10.

Digital high-speed microscopy of intercellular Ca²⁺ waves in Cx43–GFP HeLa cells. The left top panel shows the distribution of the endoplasmic reticulum and gap junctions reconstructed from ER-Tracker fluorescence (green) and the Cx43–GFP signal (red), respectively, in a 1-μm-thick slice through the cells. A white dotted line represents the cell boundary. The pseudocolored time series of images (right), numbered 1–6, represent the relative changes in fluo-3 fluorescence at the times indicated (bottom right) after mechanical stimulation of a single cell (∗) in the presence of extracellular apyrase (40 IU/ml). (1, 2) The Ca²⁺ wave propagates to fill the entire cell in the top left. (3) A small change in [Ca²⁺]_i is observed in the adjacent cell at the site of the Cx–GFP gap junction. (4–6) The changes in Ca²⁺ continue to spread out from the gap junction. The gap junction remains blue because the GFP fluorescence dominates any Ca²⁺-based fluorescence changes, and therefore the ratio of ΔF/F does not change. The color scale was chosen to enhance the visualization of small [Ca²⁺]_i changes, and numbers represent minimal, saturating, and maximal percentage changes.