Morphology of choroid plexus epithelium (CPE) in situ and in primary culture. A. Ultrastructure: CP from lateral ventricle of an adult Sprague-Dawley rat. Apical membrane (CSF-facing) shows numerous microvilli (Mv) and many intracellular mitochondria (M). J refers to the tight junction welding two cells at their apical poles. C: centriole. G and ER: Golgi apparatus and endoplasmic reticulum. Nucleus (Nu) is oval and has a nucleolus. Arrowheads point to basal lamina at the plasma face of the epithelial cell; the basal lamina separates the CPE above from the interstitial fluid below. Basal labyrinth (BL) is the intertwining of basolateral membranes of adjacent cells. Choroidal morphology resembles proximal tubule, consistent with both cell types rapidly turning over fluid. Scale bar = 2 μm, reproduced from  with permission. B. Phase-contrast micrographs of 8d-old sheep CPE cells cultured on laminin-coated filters shows a typical cobblestone arrangement of polygonal cells (scale bar 20 μm). C. Eight-day-old sheep CPE cells grown on laminin-coated filters were stained with primary antibodies against occludin and then with FITC conjugated secondary antibodies. A continuous circumferential distribution of fluorescence consistent with the establishment of TJs in CPEC monolayer is shown. Scale bar 20 μm. Images B and C reproduced from .