Figure 3. The appearance of DNA damage after light exposure. These experiments were conducted in normal culture medium (A, C) and medium deprived of serum (B, D). Cultures were exposed to light, 1000 lux, for 48 h (C, D) or maintained in the dark (A, B) and processed for the localization of breakdown of DNA (TUNEL). It can be seen that light enhanced the numbers of TUNEL-positive cells (arrows) and this was greatest in serum-free conditions. The scale bar represents a distance of 20 μm. Quantification of several experiments for each condition shown in A-D is shown in E (black bars represent cells incubated with serum, while empty bars indicate cells incubated without serum). Statistical analysis using the one-way ANOVA followed by a post-hoc Bonferroni test and comparing with controls incubated in the dark for the same length of time in the presence of serum (n=10), showed significance levels denoted as follows: *p <0.05, ***p <0.001.