Ependyma and ependymal protrusions of the lateral ventricles of the rabbit brain.

The ependymal lining of the lateral ventricles of the rabbit brain was studied by means of scanning (SEM) and transmission electron microscopy (TEM). There exist cells devoid of cilia in the anterior horn over the region of the caudate nucleus, in the inferior horn over the hippocampus and on the opposite side over cortical regions. On the surface of some of these ependymal cells, accumulations of cytoplasmic folds and globules can be found. They bulge at different height over the ependymal cells. Clots of these cell particles are tied off from the cell, coming to lie as globules either on or between the cilia of the ependyma. TEM reveals that these protrusions are cell debris consisting of different sized vesicles, cell organelles, tubuli and cell filaments. They originate from the ependymal layer but may reach down to subependymal cells. Multivesicular protrusions into the ventricular lumen are also observed. Possible causes of these protrusions are discussed; they are likely to be related to the age of the animals. On the ependyma of the caudate nucleus cilia, microvilli, microblebs and supraependymal neuronal cell processes are distributed unevenly over the surface. Within regions where cilia predominate there are cells which are tightly covered with microvilli. A certain direction of the course of the supraependymal neuronal fibers could not be found.