Light and electron microscopic studies of the ventricular wall

Summary Electron microscopic data confirm the results gained with rapid Golgi preparations of adult rodent brains that tanycytes occur in clusters along the lateral wall of the third ventricle. The cytoplasmic matrix of these cells is considerably denser than that of typical ependymal cells. They have filaments and microtubules throughout their cytoplasm along with mitochondria and polysomes. At the surface is a compact group of microvilli which suggest that tanycytes might selectively absorb material from the ventricle.The tanycytes are segregated from neuropil by other tanycyte processes, by neighboring ependymal cells and by astrocytes. Yet there are gaps in this sheath. At these points tanycytes either abut upon or surround nonglial components of the neural fabric.Their cytological features and relations with the neuropil suggest that tanycytes selectively absorb material from the ventricle and release it along the basal process, primarily affecting those segments of neurons immediately adjacent to the tanycyte.Supported by: NINDS Grants 5 R01 NS 09001-02 NEUA, 5T01 NB 5309, and GM 00958, and by the Eleanor Roosevelt Cancer Foundation Research Institute.Acknowledgements: This work was initiated in the Anatomy Department of the Harvard Medical School with facilities provided by Prof. S. L. Palay (U.S. Public Health Service Grant No. NB 05591). Dr. R. B. Wuerker kindly and patiently provided the instruction and orientation to electron microscopy. The major portion of the study was completed in the Neurology Department of the University of Utah with the extremely competent, challenging assistance of Dee Lerdahl, Nina Belgarian, Keith Johnson and Lynn Kendricks.