Figure 6. Immunohistochemical analysis of 15-month old mice. A, B: Increased immunoreactivity for caspase-3 is present in the inner photoreceptor segment of a low-density lipoprotein receptor–deficient apolipoprotein B-100-only mouse overexpressing insulin-like growth factor II (IGF-II/LDLR^–/–ApoB^100/100; arrows, A), while no positivity is seen in the LDLR^–/–ApoB^100/100 control (B). C, D: Reduced rhodopsin staining is observed in the retinas of IGF-II/LDLR^–/–ApoB^100/100 mice, consistent with the decreased number of photoreceptor cells (arrowheads, C), whereas intense staining was present in the nondiabetic LDLR^–/–ApoB^100/100 mice (D). Original magnification in the figure is x400, and the scale bar is 25 μm. Definitions for the abbreviations are: GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; IS, inner segment; OS, outer segment.