ABSTRACT
The surface specializations of the wall of the third cerebral ventricle of Rana temporaria were investigated with the scanning electron microscope. These specializations can be divided into three types: cilia, large bulbous protrusions, and microvillus-like protrusions. Most parts of the ventricular surface are densely ciliated. In contrast, other regions are either scantily ciliated or devoid of cilia. Four areas of the ventricular surface are studded with numerous large bulbous protrusions. These large protrusions can be divided into two types: One type consists of intraventricular end bulbs of dendrites of secretory neurons. The other type is represented by large cytoplasmic extensions of ependymal cells. In the third ventricle of Rana, microvillus-like surface specializations of ependymal cells are ubiquitous structures. Generally, filiform protrusions of varying length are the predominant type. The microvillus-like specializations are transient structures, the number of which varies according to different physiological states of the ependymal cells.
Subject(s)
Cerebral Ventricles/ultrastructure , Rana temporaria/anatomy & histology , Animals , Anura , Choroid Plexus/ultrastructure , Cilia/ultrastructure , Ependyma/ultrastructure , Female , Hypothalamus/ultrastructure , Male , Microscopy, Electron, Scanning , Subcommissural Organ/ultrastructure , Subfornical Organ/ultrastructureABSTRACT
From combined scanning and transmission electron microscopic studies it is concluded (1) that all surface specializations of the median eminence of Rana temporaria are protrusions of ependymal cells; (2) that the microvillus-like structures of the median eminence are transient differentiations of the ependymal cell surface, associated with the activity of the ependymal cells.
Subject(s)
Cerebral Ventricles/ultrastructure , Hypothalamo-Hypophyseal System/ultrastructure , Median Eminence/ultrastructure , Animals , Anura , Ependyma/ultrastructure , Female , Male , Microscopy, Electron, Scanning , Rana temporariaABSTRACT
Scanning electrom microscopy of the ventricular surface of the pars ventralis of the tuber cinereum of the frog Rana temporaria shows that it can be divided in (1) a dorsolateral area, characterized by the presence of very numerous large, solid, bulbous protrusions (2) a medial area, where the large bulbous structures are completely absent and which is diffusely covered with very numerous cilia, (3) a transiotional area located between the two other regions. The large bulbs, shown by scanning electron microscopy, correspond with the end-bulbs of thick ventricular dendrites of nerve cells revealed by transmission electron microscopy. At least many of these intra-ventricular bulbs are dendritic endings of peptidergic neurosecretory neurons, which have been tentatively identified as adenohypophysiotropic neuro-hormone producing neurons (Derickx et al., 1972, 1973a, 1973b). The structural features of the dendritic endings plead in favour of a possible receptive role.
