Figure 4

Meso-1 labeling of the regenerating intestine (Days 1-5 of regeneration). Meso-1 labeling (green) and nuclei DAPI stain (red) show the process of ingression and the concomitant changes in the rudiment during regeneration. (A-E) The mass of cells at the distal tip of the rudiment is not observed at 1-dpe (A), becomes noticeable at 3-dpe (B) and increases in the subsequent days (C-E). Transverse sections of (F) Toluidene blue staining of 5-dpe intestine, shows the thickening of the mesenterial tip that forms the intestinal rudiment and differential staining of the coelomic epithelium (CE) and connective tissue (CT) compartments. (G) A similar section labeled with Meso-1 antibody highlights the ingressing cells. (H-I) Two additional examples of ingressing cells at 5-dpe, one is an invagination of the coelomic epithelium (H) while in the other, cells can be observed moving from the rudiment tip into the connective tissue (I). Figure H shows regions in the coelomic epithelia (bracket) that are thicker when compared to those in the 1-dpe mesentery (see bracket in Figure 4A). At higher magnification (J) some Meso-1 labeled ingressing cells show an elongated nuclei and cellular morphology (arrows) while other cells within the connective tissue are not labeled (arrowhead). (K) At the lateral side of the rudiment, an isolated ingressing cell (arrow) can be observed. Bar = (A) 70 μ m (B-E) 100 μ m (F-G) 65 μ m, (H-I) 30 μ m (J) 13 μ m (K) 20 μ m. All sections are from 5dpe animals except A (1dpe) and B (3-dpe).