Fig. 4

Cell proliferation and migrating morphology of cardiomyocytes during regeneration of the damaged myocardium. a1 Longitudinal section of an amputated heart at 8 daar. R regenerated area, B border area. a2 High magnification of large square with a dotted line from a1. Open arrow: epicardium site. Arrow: cardiomyocytes with dividing nuclei. Small triangle: regenerated cardiac myocytes, as indicated by light H&E staining, an irregular cross-striated structure, and migrating morphology in the regenerated site. Asterisk: endogenous mature cardiac myocytes, as indicated by intensive H&E staining and a regular cross-striated structure. a3 High magnification of the small square indicated by a dotted line in a1. Open arrow: epicardium site. Small triangle: Regenerated cardiomyocytes. b Comparison of the density of α-SA⁺/PH3⁺ cardiac myocytes in different time points after apical amputation, which were from Fig. 5. *P < 0.01 vs. other groups. **P < 0.01 vs. other groups except 4-day. ***P < 0.01 vs. other groups except 2-day. The results of all time points are from three frogs, respectively