Fig. 2. Transmission electron micrographs of wounded MDCK cell monolayers sectioned along the apicobasal axis perpendicularly to the wound margin. (A-D) Submarginal cells 5-7 cell rows away from the wound margin at 12 hours post-wounding extend basal membrane protrusions under cells in front of them in the direction of the margin (located outside of the images to the right). The initial width of the rectangular wounds was 700 µm. Images B and D are of the same regions as in A and C, respectively, but at higher magnification. (E) Cells >100 rows away from the wound edge display a more cuboidal morphology with a small amount of wedging of cells underneath each other but no long protrusions. In all images, the apical surface is on the top – with microvilli visible – and the basal side is on the bottom. Long submarginal protrusions are indicated by arrows, whereas spreading in an unwounded portion of monolayer is indicated by an arrowhead. Notice the different close cell-cell contacts apical to the looser areas around the basal protrusions, allowing sheet continuity to be maintained simultaneously with the extension of lamellipodia. All of the MDCK cells in this and subsequent figures are nontransfected, unless otherwise noted. Bars, 1 µm.