The outer morphology of the surface of the ependymal lining of the plexus choroideus was studied within the whole ventricular system of the brain in adult sheep using a scanning electron microscope. The more abundant occurrence of spherical secretory protrusions was found on the plexus choroideus (PCH) in the lateral cerebral ventricle. A frequent finding of the macrophagelike epiplexal cells was recorded on the PCH in the region of the lateral as well as the fourth ventricle. No differences were found in the structure of the PCH surface, which could be related to the sexual differentiation of the sheep. Our results are compared, above all, with those found in the adult goat and in the foetuses of both species of small ruminants.
Central nervous system, plexus choroideus, cerebral ventricles, adult sheepLess attention has been paid to the study of the plexus choroideus as one of the structures of the ventricular system of the brain in different species of mammals using the scanning electron microscope than to the structure of the surface of the ependymal lining. In the prenatal but also in postnatal period, the surface of the PCH in laboratory rodents was observed by Yamadori (1972), Hosoya and Fujita (1973), Chamberlain (1974), Peters (1974), Mestres and Breipohl (1976), Peters and Swan (1979), in the dog (Allen 1975;Persky 1980), in the cat (Clementi and Marini 1972), in the rhesus macaque (Ling 1983), and in humans (Scott et al. 1972(Scott et al. , 1974Otani and Tanaka 1988, O'Rahilly andMüller 1990). In farm mammals the PCH was studied in the goat and sheep foetuses but also in the adult goat (R ajtová 1997, 2000). There is no record of the structure of the surface of epithelial cells that cover the PCH in adult sheep.The aim of the work was to describe the epithelial surface of the PCH in the lateral, third and fourth cerebral ventricles in adult sheep with the aid of a scanning electron microscope.
Materials and MethodsTen healthy adult sheep (5 ewes and 5 rams) were used. The animals were killed in March and October by exsanguination following thiopental anaesthesia. Immediately after exsanguination, the heads of the animals were perfused through the a. carotis communis with 0.2 mol/l phosphate buffer solution and prefixed with Karnovsky solution. The specimens of the individual parts of the plexus choroideus were postfixed in 3% glutaraldehyde in 0.2 mol/l cacodylate buffer. The temperature of the solutions was 4 °C, pH 7.4. The specimens were processed by the method of Murakami et al. (1977), dehydrated, dried by the critical point method and coated with gold in vacuum. Then they were studied in the Tesla BS 340 scanning electron microscope with image analysis.
ResultsThe plexus choroideus ventriculi lateralis forms low folds. The periphery of the ependymal cells is irregularly round, almost elongated. The apical membranes of most lining ependymal cells are convex, covered with thick, short, densely arranged microvillus-like structures. Among them on numerous sites are abundant, predominantly small and...
