Cell viability assays for FGF2 protection of HUVEC against gp120-mediated toxicity (A-D) Phase contrast, (F-I) TUNEL staining, and (K-O) fluorescent staining of HUVEC. Panels A, F, and K show images of untreated HUVEC control; B, G, and L show HUVEC treated for 24 h with FGF2 (20 ng/ml); panels C, H, and M show HUVEC treated for 24 h with gp120 (25 ng/ml) and panels D, I, and N show HUVEC pre-treated with FGF2 for 24 h before a 24 h exposure to gp120. Panels E, J and O show the percentage of cell death as determined by Trypan blue exclusion, percentage of DNA fragmentation by TUNEL and FA/PI staining, respectively. Results shown in panels E, J and O represent the average of three separate experiments performed in triplicate. * = P < 0.05 by One-Way ANOVA with post-hoc Dunnett's when compared to control. Bar = 20 microns.