Fig. 1. Identification of senescent fibroblasts by monitoring total cellular glucose and glycogen degradative enzyme activities and oxidative stress markers in confluent serial subcultures.

Enzyme activities of (A) phosphofructokinase (PFK), (B) lactate dehydrogenase (LDH), and (C) glycogen phosphorylase (GP), along with levels of (D) hydrogen peroxide (H₂O₂) and (E) superoxide anions (SA), (F) lipid peroxides (LPO), (G) protein carbonyl content (PCC), and (H) oxidized glutathione (GSSG) in P5-P35 confluent cells. *p < 0.05, **p < 0.01, ***p < 0.001, and ****p < 0.0001 indicate significant difference from control P5 values (n = 6).