No significant difference in positive staining of nuclear PCNA was found between i n young and aged p21(+/+) mice (P>0.05), although the numbers of positive ly stained nuclear PCNA were more in number in young mice than in aged mice.

• 高龄和低龄p21(+/+)鼠PCNA阳性染色细胞出现的几率差异无显著性(P>0.；05)；但低龄鼠细胞增殖能力要强于高龄鼠;