Hematoxylin and eosin-stained sections from normal, MPS I, and MPS I BMT-treated cats. Tissue, magnification, and micron bars located to the left of designated rows. Panels a, b, and c (cortical neurons): affected and BMT cortical neurons are swollen with cytoplasmic vacuoles, however BMT neurons were slightly less so (insets are 2X images of neurons indicated by arrows). Panels d, e, and f (hippocampal neurons): severity of neuronal cytoplasmic vacuolation is decreased in BMT (insets are 4X images of neurons indicated by arrows). Panels g, h, and I (cerebral perivascular space): number of vacuolated mononuclear cells (arrow, panel h) is nearly absent in BMT (arrow, panel i). Panels j, k, and l (choroid plexus): infiltration of choroid plexus (asterisks) by vacuolated mononuclear cells and cytoplasmic vacuolation of epithelial cuboidal cells (arrows indicate 4X insets) present in affected cat are nearly absent in BMT-treated cat. Panels m, n, and o (leptomeninges): vacuolation of fibroblasts and mononuclear cell infiltrates in affected cat are nearly absent in BMT-treated cat (arrows).