Scanning Electron Microscopy Volume 1985 Number 1 1985 Article 24 10-5-1984 The Ependyma of the Cat Central Canal, with Particular Reference to its Mitochondria-Containing Bulbs K. Rascher University of the Saarland K. H. Booz University of the Saarland A. C. Nacimiento University of the Saarland E. Donauer University of the Saarland Follow this and additional works at: https://digitalcommons.usu.edu/electron Part of the Biology Commons Recommended Citation Rascher, K.; Booz, K. H.; Nacimiento, A. C.; and Donauer, E. (1984) "The Ependyma of the Cat Central Canal, with Particular Reference to its Mitochondria-Containing Bulbs," Scanning Electron Microscopy: Vol. 1985 : No. 1 , Article 24. Available at: https://digitalcommons.usu.edu/electron/vol1985/iss1/24 This Article is brought to you for free and open access by the Western Dairy Center at DigitalCommons@USU. It has been accepted for inclusion in Scanning Electron Microscopy by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. SCANNING ELECTRON MICROSCOPY/ 1985 / I (Pa ge l 231-2 38) 0586- 5581/85$1 . 00+. 0S SEM I nc.., AMF O'Ha11.e (Chi c.ago), IL 6066 6 USA THE EPENDYMA OF THE CAT CENTRAL CANAL, WITH PARTICULAR REFERENCE TO ITS MITOCHONDRIA-CONTAINING BULBS K. Rascher*, K.H. Booz*, A.C. Nacimiento** and E. Donauer*** *Department of Anatomy, **Neurosurgery Research Laboratory, ***Department of Neurosurgery, University of the Saarland, 6650 Homburg, Federal Republic of Germany (Paper received March 20 1984, Completed manuscript rec e ived October 5 1984) Introduction Abstract Most scanning electron microscope The ultrastructure of the ependyma studies of the ependyma have dealt with in the central canal of adult cats was the lining of the brain ventricles (see examined in both the scanning and the extensive literature in Leonhardt 1980 transmission electron microscopes (SEM and Low 1982). The ependyma of the cen­ and TEM). tral canal, however, has only rarely The same morphological details were been subjected to intensive ultrastruc­ seen in the ependyma of the central can­ tural examination (Leonhardt 1976). One al as have so frequently been described of the reasons for this relative lackof in the ependyma of the brain ventricular information on the central canal may be system, for example bundles of cilia, that its free surfaces are considerably single cilia, microvilli and occasional more difficult to expose for observation small cytoplasmic protrusions. The in the SEM than are the surfaces of the supraependymal cells and supraependymal ventricles. Another may be that the cen­ nerve fibers found in the central canal tral canal has not very often been the also resembled those seen in the ven­ subject of experimental and/or patholo­ tricular system. gical research (Hall et al. 1975). The The most striking feature of the present study was undertaken in connec­ canal ependyma were the large, spherical tion with an ongoing investi gation of bodies containing numerous mitochondria. the alterations in the c e ntral canal They are therefore called mitochondria­ caused by experimentall y induced hydro­ containing bulbs. In sections the bulbs cephalus in adult cats. were seen to be connected by long, The ependyma of the cat centralcan­ slender stalks to neurons in subependy­ al has many features in common with that mal position. In some respects the of the ventricles of higher vertebrates mitochondria-containing bulbs resemble and is quite similar to that of the rab­ the processes of cerebrospinal fluid­ bit central canal (Leonhardt 1976) but contacting neurons. does differ in several respects fromthat of the rat canal (Nakayama and Kohno 1974) Both SEM and TEM revealed that the catpo­ ssesses spherical supraependymal struc­ tures containing numerous mitochondria. They could be identified as the processes of neurons lying in subependymalposition. These neurons are therefore cerebrospi­ nal fluid-contacting neurons. Their sim­ ilarity to the well-known cerebrospinal fluid (CSF)-contacting neurons of lower vertebrates (Vigh and Vigh-Teichmann 1971) KEY WORDS: Ependyma, Spinal Cord Central Canal, Mitochondria-containing Processes, may give a clue to their possible Cat, Scanning Electron Microscopy function. Materials and Methods *Address for correspondence: Adult cats were deeply anesthetized K. Rascher, Department of Anatomy, with nembutal (0. 35g/kg) and artificially University of the Saarland, 6650 Homburg, respirated before being transcardially Federal Republic of Germany perfused with a buffered mixture of 1% Phone No. 06841/166102 glutaraldehyde and 1% paraformaldehyde. The animals, which weighed between 2.3 231 Rascher K, Booz KH, Nacimiento AC et al. Figure 1. Semithin secti.onof the central canal and its immediate surroundings in the cervical intumescence. L = lumen of the canal; E = ependyma; arrow= mito­ chondria-containing bulb. Figure 2. Semi thin section of the central canal in the upper lumbar region. L = lumen of the canal; E = ependyma; arrow= mitochondria-containing bulb. Figure 3. Overview of the vent ral aspect and 3.0 kilograms, received 1 lit er of of the central canal split longitudinall~ warm perfusion fixative per kilogram Mid-thoracic region. C = heavily ciliated body weight. The spinal cord was removed ependyma; arrow= mitochondria-containing and postfixed in fresh cold fixative at bulbs; B = blood vesse l with well-devel­ least overnight before being dissected oped perivascular space . into tissue blocks for scanning andtrans­ Figure 4. Cl oseup of the cut edge of the mission electron microscopy. The samples ependyma illustratin g the synchronous for SEM were split to expose the ependyma beat of the kinocilia. Caudalto the left. and subsequently postfixed in a buffered solution of 1% osmium t et roxide. The y Semithin and thin sections were cut on a were then rinsed in 2.4 % NaCl and dehy­ Reichert microtome with g la ss knives; drated in an ascending series ofmethanol. the thin sections were viewed in a Zeiss The tissue was transferred to Freon 11 EM 9 at 60 kV. and critical point dried in Freon 13 (Co­ Results hen et al. 1968) in a Polaron apparatus. The specimens were coated with gold in a The central canal of the cat va ries Balzers sputt ering chamber and examined in shape depending upon the level of the in a Cambridge Stereosca n S4 at 20 kV. spinal cord examined. In the upper cer­ The tissue samples for TEM were rin­ vical and in the sacral regions it is a sed in phosphate buffer before being post­ narrow slit with the lateral walls almost fixed in 2% osmium tetroxide. The y were touching; in the thoracic segments it is then rinsed again in buffer. The samples more or less round whereas in both the were dehydrated in isopropanol, trans­ cervical and the lumbar intumescences it ferred to propylene oxide and embedded is again slit-like but with the dorsal in an epoxy resin (ERL 4206, Spurr 1969). 232 The ependy.ma of the cat central canal 7 • pr Figure 5. Detail of the surface of the less densely ciliated area along the dorsal cervical midline. Note the multi­ tude of microvilli on the tall protru­ sions of the apical poles of the cells. B = mitochondria-containing bulb; S smooth profile. and ventral surfaces closely apposed (compare Figures 1 and 2). The shape of the canal may be slightly altered by large blood vessels with a well-deveJoped perivascular space which penetrate into the subependymal tissue (Fig. 3). The SEM reveals that the ependyma of the can­ al has several ultrastructural features which are also characteristic of the ven­ tricular ependyma. It is fairly densely ciliated throughout (Fig. 3). The cilia are grouped in bundles so close together that the cell surfaces of the ependymo­ Figure 6. Thin section of area as in fig­ cytes can only rarely be seen. The cilia ure 5. P apical protrusion with micro­ are bent in such a manner that their beat villi; C = basal bodies of a bundle of is apparently from rostral to caudal cilia; N = nuclei of ependymocytes; arrow= (Fig. 4). The carpet of cilia becomes contacts between ependymocytes. sparser along the midline both dorsally Figure 7. Apical parts of ependymocytes and ventrally. These areas bearing fewer in ventro-median (cervical) position in­ cilia are quite narrow in the upper cer­ dicating the well-developed contacts and vical segments, broad in both intumes­ interdigitations between the cells. cences and almost invisible in thoracic levels. The less densely ciliated areas microvilli were taller along the dorsal show a multitude of microvilli on the cell aspect than along the ventral. Another apical poles. For the most part the lat­ feature which distinguished the ventral ter protrude markedly into the lumen of from the dorsal ependyma of the midlines the canal, extending their microvilli in were the cell contacts. Those of the dor­ all directions, thus giving the entire sal aspect were generally straight and surface a mossy appearance (Fig. 5). In consisted of only a few short desmosome­ thin sections the protrusions of the api­ like contacts and an occasionalapically cal poles were seen to contain a fine located gap junction. The lateral cell granular matrix and occasional microfila­ borders of the ventrally positioned epen­ ments but no larger organelles (Fig. 6). dymocytes, however, had highly developed The scanned specimens did not reveal junctional complexes with long series of any major ultrastructural differences be­ desmosome-like contacts. These cells in­ tween the dorsal and ventral surfaces of terdigitated with one another giving the the canal, but thin sectionsconsistently membranes a tortuous course (compare showed that the protrusions bearing Figures 6 and 7). 233 Rascher K, Booz KH, Nacimiento AC et al. - . "': ... ~ - .• . · - F ~ :'i , ,. J:.--' . ~:·,~""'t - ~- . & f t 1t· ;f .,. '.', ~ ! ; .... :~ ~ T ,. •~- r ·~ , . ..··~_:. / ~\; . ~ ·, ... '10 . £1:""ftt~::a! ~~"' ..· •. Figure 8. Several mitochondria-containing bulbs in ventral aspect of cervical can­ al.