Fig. 5. Partial rescue of somite formation in pancreatin-isolated PSMs cultured with exogenous fibronectin. (A) Pancreatin-isolated chick PSMs present immunoreactivity for cellular fibronectin after 6 hours in culture. (B-D) z-projection of confocal images of dispase-isolated PSMs cultured for 2 hours (B) show faint fibronectin immunoreactivity, whereas after 4 (C) and 6 (D) hours it is more extensive. (E) Average fluorescence labelling intensity relative to background in dispase-isolated PSMs cultured for 2 (n=7), 4 (n=4) and 6 hours (n=6). (F-I) Contralateral pancreatin-isolated PSMs, cultured in control (F,G) or fibronectin-supplemented (H,I) medium and stained for F-actin (F,H) and fibronectin (G,I). (J) Bar chart of the average number of somites formed (n=20 pairs) showing that PSMs cultured with fibronectin form significantly more somites (P=0.002). Error bars represent 95% confidence limits. cFN, cellular fibronectin; +FN, PSM cultured in fibronectin-supplemented medium. Scale bars: 100 µm in A,F-I; 50 µm in A insert, B-D.