Microphotographs showing the distribution of occludin and vimentin immunoreactivities in coronal sections of the tuberal region of the hypothalamus. Images were acquired either at low (B) or high (A, C, D–G) magnifications. Occludin (green) immunoreactivity is readily visualized in capillaries of the cerebral parenchyma, which are known to display well-differentiated tight junction complexes (A). Occludin-immunoreactivity is also evident at the wall of the third ventricle (B). Notably, occludin immunostaining displays a honeycomb pattern of distribution in cuboidal ependymal cells (C). Ventral to the DMH, where tanycytes appear, the occludin-immunoreactive honeycomb pattern gradually disappears and is replaced by an unorganized staining (D). This unorganized pattern of occludin-immunoreactivity becomes obvious in tanycytes of the ARH (E). In contrast, tanycytes of the median eminence exhibit a honeycomb expression pattern for occludin (F,G). Sections are counterstained using Hoechst (blue) to visualize cell nuclei and identify the morphological limits of each hypothalamic structure. 3V, third ventricle; ARH, arcuate nucleus of the hypothalamus; DMH, dorsomedial nucleus of the hypothalamus; VMH, ventromedial nucleus of the hypothalamus. Scale bar = 100μm in B; 20μm in G.