Age-dependent changes in the human third ventricle subventricular zone (tv-SVZ). (A, B) Section of the third ventricle from a child (A) reveals a single layered tall columnar epithelium with prominent cilia at the ventricular surface (inset). In an adult the ependymal layer is flattened and contains a single layer of cuboidal cells and there is marked reduction of lining cilia (B). (C, D) Acetylated tubulin immunostaining reveals abundant cilia in a pediatric (C) and few in an adult (D) tv-SVZ. Scale bars = 20 μm. (E, F) Electron microscopy demonstrates a relative abundance of cilia in a pediatric tv-SVZ (E; arrow), and the presence of lipopigment in lining ependymal cells in an adult tv-SVZ (F; arrow). A, B: Hematoxylin and eosin.