Figure 1.

Effects of different doses of either Ni²⁺-or Cu²⁺-induced oxidative damage in U937 cells after incubation at 37°C for 24 hours. Each bar chart ± standard error in this and other figures in this article represent mean for four different experiments for each dose level of metal tested, which was assayed in triplicates. Statistical significances denoted by dot or asterisk symbols are shown as a. comparison between each control subgroup without metal ions (i.e., Ni or Cu) and its treated subgroup for the respective metal ions (i.e., Ni²⁺ or Cu²⁺ + 5, Ni²⁺ or Cu²⁺ + 10, and Ni or Cu²⁺ + 20). • or *P < 0.05; •• or **P < 0.01; ••• or ***P < 0.001 in this and other figures. Vertical bars in this and other figures denote standard deviation. The x-axis labels for Figure 1 are defined as follows: Ni²⁺ or Cu²⁺ + 0 means control samples were not treated with Ni²⁺ or Cu²⁺ ions; Ni²⁺ or Cu²⁺ + 5, 10, and 20 means samples were treated with either Ni or Cu²⁺ ions at 5, 10, and 20 µM, respectively.