Skin sections (x 400) stained with anti-PCNA antibodies to show the proliferation activity of the epidermal cells (the proliferating cells are stained with a red colour). Histograms show the number of proliferating cells at the second, fourth and eighth days after wounding for the different groups. Values shown are means ± SD. *shows the significance in comparison with the control group. # shows the significance in comparison with the older group.