**Figure 6. **Effect of melanosomes on
the sensitivity of individual ARPE-19 cells to H_{2}O_{2}-induced
toxicity compared to cells with a comparable content of control
particles (latex beads) in co-cultures. Live cell imaging of
dynamic changes in nuclear PI fluorescence in ARPE-19 cells
pre-loaded with latex beads or melanosomes (mel) and treated
with H_{2}O_{2} delivered as **A**: a pulse
at 1000 μM or **B**: generated enzymatically by the addition
of GOx at 30 mU/ml. Numbers of cells selected for analysis in
the same co-culture wells containing the two particle types were
as follows. **A**: beads, n=216 (triangles); mel, n=216
(black circles). **B**: beads, n=110 (triangles); mel, n=71
(black circles). Data are from representative experiments and
are the percent of the pre-selected cells in each particle group
surviving (no nuclear PI) with time. The shift to the right of
the curves for mel illustrates the magnitude of the protective
effect of mel relative to beads. The curves for the two particle
types within each treatment protocol differ significantly
(GraphPad Prism 5 survival analysis, p<0.02).