Ontogeny of caudal fourth ventricular tanycytes in the rabbit brain: A Golgi study

Abstract

A Golgi study of the floor of the caudal fourth ventricle in the developing and adult rabbit brain stem revealed the presence of several clusters of tanycytes. These tanycytes possessed ciliated apical surfaces and basal shafts extending into the substance of the medulla and pons where they intermingled with specific neuronal fields. These shafts ended in the serotonergic nuclei raphe obscurus and pallidus, and the noradrenergic locus coeruleus and nucleus intercalatus (group A2). The tanycyte shafts extended into the medullary midline early in ontogeny (day 18 of gestation), following which the neurons of the raphe began to sprout neurites. These shafts then formed the underlying structure for a large medullary dendrite bundle. These shafts developed extensive spines during early neonatal ontogeny, which then diminished in number through adulthood. the tanycyte shafts extending into locus coeruleus and nucleus intercalatus developed later in ontogeny than the midline shafts, just before birth. These shafts also persisted into adulthood in close relationship with the monoamine neurons. We suggest that the tanycytes on the floor of the fourth ventricle may take up substances from the CSF and transport them to the region of the monoamine nuclei where the shafts terminate, in a manner similar to median eminence tanycytes. The early development of shafts from fourth ventricular tanycytes suggests a possible regulatory role for these cells over the neuritic sprouting and maturation of the monoaminergic nuclei.

A disintegrin and metalloprotease 21 (ADAM21) is associated with neurogenesis and axonal growth in developing and adult rodent CNS

“…The location of their cell body, their morphology, the connection of their single basal process to blood vessels, and our finding of ADAM21 in hypothalamic tanycytes raise the possibility that the subependymal cells are related to tanycytes (Bruni, 1998). Although tanycytes have been described and studied predominantly around the third ventricle, they have also been found around the cerebral aqueduct, the fourth ventricle, and the central canal in the spinal cord and in the medial habenular nucleus Felten et al, 1981;Cupedo and de Weerd, 1985;Rafols and Goshgarian, 1985). A few tanycytes have also been described in the adult mouse SVZ (Doetsch et al, 1997).…”

Aqueductal tanycytes in the rabbit brain: A Golgi study

“…An abundant number of tanycytes with basal shafts was found lining the aqueduct of both neonatal and adult rabbits, suggesting a permanent active role for these ependymal cells. The Golgi-Cox method used in the present study permits serial observation of the entire aqueductal ependyma in many specimens, and has given remarkably clear and reproducible impregnation of neural and ependymal elements in the adult (Felten and Cashner, 1979;Cummings and Felten, 1979) and neonatal Felten et al, 1981) rabbit. This impregnation method may therefore account for the unequivocal presence of abundant aqueductal tanycytes in every rabbit brain examined in the present study.…”

The Foetal Ependyma of Cerebral Ventricles in Sheep and Goat. The Third Cerebral Ventricle in the Light and Scanning Electron Microscope

“…In the small ruminant foetuses under study, a frequent occurrence of ependymal cell mitoses was recorded only in the co-arctation region. Moreover, Flyger and Hjelmquist (1959), Stensaas and Gilson (1972), Felten et al (1981) reported the mitotic activity of ependymal cells in various regions of the ventricular system.…”

“…In some mammals, certain differences have already been found under the light microscope, in the ependymal structure, especially close above the recessus infundibuli, which were related with sex differentiation (Kumar 1968 in macaques;Rajtová 1985 in adult sheep). Some authors have reported more types of ependymal cells on the basis of their external morphology or topography (Westergaard 1970;Mitro 1976Mitro , 1987Milhouse 1971;Staníková et al 1980), Schachenmayr (1967), Mitro and Schiebler (1972), Stensaas and Gilson (1972), Haase (1980), Felten et al (1981) described both the foetal and neonatal ependyma of cerebral ventricles using the light microscope in different species of mammals, above all in laboratory rodents, but also in man. Not only the changes in the external morphology of cerebral ventricles as a whole were studied in the laboratory but also in some domesticated mammals (Fitzgerald 1961;Böhme and Franz 1967;Haase 1980;Lignereux et al 1987Lignereux et al , 1991.…”