Three-dimensional (3D) images of PDGFR-β-positive cells in the lesion core at day 14 after 3-NP injection. (A–D) 3D reconstruction (D) of one PDGFR-β-positive cell is prepared from a series of 27 serial ultrathin sections (90-nm-thick), one of which is shown in (A–C). A PDGFR-β-positive cell has a soma located at a distance from the vasculature and extends highly branched cytoplasmic processes, which frequently have close apposition with microglia/macrophages with amoeboid morphology, with little to no intervening space. (E–G) Another example of 3D reconstruction (G) of three PDGFR-β-positive cells, prepared from a series of 26 consecutive sections, one of which is shown in (E,F). The three cells extend highly branched cytoplasmic processes that are frequently in close apposition or even interwoven with each other, forming a network. (B,C,F) Higher magnification images of the boxed areas in (A,E), respectively. PDGFR-β-positive cells have focal cytoplasmic enlargements (arrows in B,C,E; # in D,G), from which distal branches arise. Note that their somata and processes are closely associated with collagen fibrils (asterisks in B,E). The arrowhead in (E) denotes a nucleolus. Scale bars = 2 μm for (A,E); 1 μm for (B,C,F).