Figure 5: Contour diagram of FITC-Annexin V/PI double staining by flow cytometry. The three quadrants represent different cells conditions: the upper right quadrant (R1); nonviable, late apoptotic and necrotic cells (FITC^{+}/PI^{+}), lower left quadrant (R2); viable cells (FITC^{−}/PI^{−}), and lower right quadrant (R3); early apoptotic cells (FITC^{+}/PI^{−}) (a). Percentage of cells at early apoptotic stage demonstrated by FITC^{+}/PI^{−} (b). Data are expressed as means SD, . ^{a}denotes compared to control young, ^{b}P<0.05 compared to GTT, and ^{c}P<0.05 compared to SIPS.