Figure 2. Dye spread in electrically coupled cells. Gap junctions mediate the spread of Lucifer yellow (LY), indicating that junctional permeability and the system of intercellular communication are intact. Arrowheads in all panels show the location of the small injury (scrape) produced by the tip of the scalpel blade. Fluorescent images of cells incorporating both dextran rhodamine (DR) and LY show that whereas the rhodamine complex did not spread from the site of the scrape (middle panel), LY spread through the gap junctions that coupled the cells (lower panel). Scale bar (upper panel) equals 50 μm.