Figure 5. Bone marrow derived cell infiltration (CD68+ and CD163+ cells) in skeletal muscle of old rats altered by insulin. Centrally nucleated fibers (reflecting cell regeneration) (A), cell infiltration (B), CD68+ cells (C), and CD163+ cells (D) in soleus muscle from young and old rats were measured 5 days after streptozotocin injection (50 mg/kg/ml) and/or insulin injection (0.25 IU/kg twice a day). * Significant difference against C group, P < 0.05; † Significant against Young group, P < 0.05. Abbreviation: C, vehicle-injected control group; S, Streptozotocin-injected group; SI, Streptozotocin and insulin co-injected group.