Fig. 5.

BrdU-positive cells in the neocortex of aged APP23 mice. A, Only few labeled cells were observed in the neocortex of 24-month-old wild-type mice 4 weeks after BrdU injections.B, In contrast, there was an approximately fourfold increase in labeled cells in age-matched APP23 mice (for quantitative results, see Fig. 6). Most of these cells appeared to be associated with amyloid plaques (arrowheads). To study the cellular phenotype of these cells BrdU immunofluorescence (red) was combined with NeuN (C) CD11b (D) and S100β (E) (all ingreen), and colocalization was assessed with confocal microscopy. None of the BrdU-labeled cells were positive for NeuN (C). In contrast, the majority of the BrdU-labeled cells revealed colocalization with the microglia marker CD11b (D). Colocalization was also found with the astrocytic marker S100 β (E). Theinsert in E represents single confocal sections of both markers. Quantitative phenotyping is summarized in Table 1. Scale bars: A, B, 75 μm;C–E, 10 μm.