Scanning Electron Microscopy of the Third Ventricular Wall in the Lamprey, <i>Lampetra japonica</i>

Abstract

Summary. The third ventricular wall and its adjacent region of the arctic lamprey, Lampetra japonica, were studied by scanning electron microscopy to elucidate their surface fine structures.The specimens were caught in the mouth of the river during their anadromous migration.The ventricular wall is covered entirely with the cilia of ependymal cells, with the exception of the ventral side of the lateral wall, the floor of the recessus infundibuli and a portion of the recessus posteriosus. In the ependymal layer covering the ventral side of the lateral wall, numerous protrusions of neurons are found equipped with microvilli and cilia. These neurons seem to correspond to the liquor-contacting neurons. Ependymal cells identified as tanycytes occur in the posterior portion of the floor of the recessus infundibuli.The apex of the tanycyte is provided with numerous microvilli and a bundle of cilia, while its basal projection extends towards the outer layer of neurohypophysis to make contact with the capillary wall. A small spherule considered to be a secretory substance is observed near the root of the ciliary bundle. The recessus posteriosus consists of a layer of ependymal cells and neurons with an apical projection into the ventricular cavity. Possible intraventricular macrophage (Kolmer cell) is found in the lamprey.

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

“…Similar protrusions in different species of mammals were described by Kumar (1988), Knowles (1969), Schwanitz (1969), Hannah and Geber (1972), Schechter and Weiner (1972), Coates (1973), Booz (1975), Scott et al (1975), Shioda et al (1977). Most of the authors consider these structures as a secretory product or a symptom of an active secretory process of ependymal cells with a potential specific effect.…”

Scanning and transmission electron microscope studies of the supraependymal neurons in the third ventricular wall of the arctic lamprey,Lampetra japonica.

“…In general, these elements are divisible into two categories: the supraependymal neurons and the cerebrospinal fluid (CSF)-contacting subependymal neurons with an intraventricular process. The CSFcontacting neurons in the third ventricular wall of the lamprey brain have been studied in various ways: fluorescence microscopy (HONMA, 1969;HONMA and HONMA, 1970;BAUMGARTEN, 1972;KONSTANTINOVA, 1973;OCHI and HOSOYA, 1974), Golgi impregnation in combination with retrograde axonal transport studies (YUI and HONMA, 1979) and scanning and transmission electron microscopy (SHIODA et al, 1977;NAKAI et al, 1979). However, little is known of the structure and distribution of the supraependymal neurons in the lamprey (NAKAI et al, 1979).…”

Use of different morphological techniques to analyze the cellular composition of the adult zebrafish optic tectum

“…We believe that these cells are a specific type of “liquor contact” glial cells. Liquor contact neurons, glia as well as the ependymal cells are well known in the literature (Kawata and Sano,1979; Sathyanesan and Joy,1978; Shioda et al,1977). Here we speculate that these cells might be a special form of ependymal cells (a sub‐category of astrocytes) that could be functioning as liquor distributors for the periventricular neurons.…”