Summary
The ependymal cells bordering the median eminence to the third ventricle are characterised by many microvillus-like projections and bulbous cell processes of the luminal plasma membrane. The latter contain many vesicles 500–1,000 Å in diameter. Cilia with 9+2 fibrillar pattern are seen occasionally. Adhesive devices in the from of zonula adhaerens and zonula occludens are found in the apical part of the intercellular junction. Unmyelinated nerve fibres with a mean diameter of 1 μ and containing many electron dense granules of 830–1,330 Å are often seen between the ependymal cells.
Two types of glial cells are found in the median eminence. One is characterised by a nucleus with dense blods of chromatin and dense cytoplasm, and it is associated chiefly with the nerve fibres in the region of the hypothalamo-hypophysial tract. The other type of glial cell is characterised by fine, uniformly distributed chromatin in the nucleus and a relatively pale cytoplasm and branched processes which terminate perivascularly in the base of the median eminence.
Myelinated nerve fibres are seen only in the region of the hypothalamo-hypophysial tract. Only a part of them contain electron dense granules 1,330–2,330 Å in diameter.
Three types of unmyelinated nerve fibres can be distinguished in the median eminence according to the size of the electron dense granules they contain: 1. Nerve fibres containing granules 1,330–2,330 Å in diameter. They are seen primarily in the hypothalamo-hypophysial tract, but also in the zona externa; 2. those containing granules with a mean diameter of 1,330 Å; and 3. those containing granules with a mean diameter of 1,000 Å. The last two types are both encountered in the hypothalamo-hypophysial tract, the zona externa and the perivascular region of the base of the median eminence. Under high magnification, the membrane of the granules show evidence of a trilaminar structure and the content of the granules with a low electron density appeares to consist of small microvesicles or globular components. Besides granules, these nerve fibres contain vesicles mostly 420 Å in diameter whose relative number increases towards the perivascular nerve endings. 53 per cent of the inclusions in the hypothalamo-hypophysial tract are granules and 47 per cent vesicles, while the corresponding percentages for the zona externa are 40 and 60 and for the perivascular nerve endings 20 and 80.
The mean width of the pericapillary space is 1 μ, but it varies greatly. It containes many collagen fibrils and fibroblasts. The capillary endothelium is frequently fenestrated and contains many vesicles of various sizes.
Two types of granules-containing cells are found in the pars tuberalis depending on the size of the electron dense granules: 1. cells containing granules with a mean diameter of 1,330 Å: and 2. cells containing granules with a mean diameter of 2,000 Å. In addition, there are occasional follicular cavities filled with amorphous material, microvilli and cilia of 9+2 fibrillar pattern.
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References
Bargmann, W.: Neurosekretion und hypothalamisch-hypophysäres System. Verh. Anat. Ges. 51. Versig Mainz 1953, S. 30–45.
—: Elektronenmikroskopische Untersuchungen an der Neurohypophyse. In: Zweites Internat. Symposium über Neurosekretion (eds. W. Bargmann, B. Hanström, B. and E. Scharrer), p. 1–11. Berlin-Göttingen-Heidelberg: Springer 1958.
—, u. A. Knoop: Elektronenmikroskopische Beobachtungen an der Neurohypophyse. Z. Zellforsch. 46, 242–251 (1957).
—: Über die morphologischen Beziehungen des neurosekretorischen Zwischenhirnsystems zum Zwischenlappen der Hypophyse (Licht- und elektronenmikroskopische Beobachtungen). Z. Zellforsch. 52, 256–277 (1960).
Barnes, B. G.: Ciliated secretory cells in the pars distalis of the mouse hypophysis. J. Ultrastruct. Res. 5, 453–467 (1961).
Barry, J., and G. Cotte: Etude preliminaire, au microscope electronique, de l'éminence mediane du cobaye. Z. Zellforsch. 57, 714–724 (1961).
Bern, H. A.: The secretory neuron as a doubly specialized cell. In: The general physiology of cell specialization (eds. D. Mazia and A. Tyler), p. 349–366. New York: McGraw-Hill Book Co. 1963.
Bodian, D.: Cytological aspects of neurosecretion in oposum neurohypophysis. Bull. Johns Hopk. Hosp. 113, 57–93 (1963).
Bondareff, W.: Submicroscopic morphology of granular vesicles in sympathetic nerves of rat pineal body. Z. Zellforsch. 67, 211–218 (1965).
Brightman, M. W., and S. L. Palay: The fine structure of ependyma in the brain of the rat. J. Cell Biol. 19, 415–139 (1963).
De Robertis, E.: Histophysiology of Synapses and Neurosecretion. Oxford-London-Edinburgh-New York-Paris-Frankfurt: Pergamon Press 1964.
—, and H. M. Gerschenfeld: Submicroscopic morphology and function of glial cells. Int. Rev. Neurobiol. 3, 1–65 (1961).
Dierickx, K.: The origin of the aldehyde-fuchsin-negative nerve fibres of the median eminence of the hypophysis: a gonadotropic centre. Z. Zellforsch. 66, 504–518 (1965).
Dufy, P. E., and M. Menefee: Electron microscopic observations of neurosecretory granules, nerve and glia fibers, and blood vessels in the median eminence of the rabbit. Amer. J. Anat. 117, 251–286 (1965).
Elfvin, L.-G.: The ultrastructure of the capillary fenestrae in the adrenal medulla of the rat. J. Ultrastruct. Res. 12, 687–704 (1965).
Farquhar, M. G.: “Corticotrophs” of the rat adenohypophysis as revealed by electron microscopy. Anat. Rec. 127, 291 (1957).
Farquhar, M. G., and J. F. Hartmann: Neuroglial structure and relationships as revealed by electron microscopy. J. Neuropath. exp. Neurol. 16, 18–39 (1957).
—, S. L. Wissing, and G. E. Palade: Glomerular permeability. I. Ferritin transfer across the normal glomerular capillary wall. J. exp. Med. 113, 47–66 (1961).
Fujita, H., and J. P. Hartmann: Electron microscopy of neurohypophysis in normal, adrenaline-treated and pilocarpine-treated rabbits. Z. Zellforsch. 54, 734–763 (1961).
Fuxe, K.: Cellular localization of monoamines in the median eminence and the infundibular stem of some mammals. Z. Zellforsch. 61, 710–724 (1964).
—, T. Hökfelt, and O. Nilsson: A fluorescence and electronmicroscopic study on certain brain regions rich in monoamine terminals. Amer. J. Anat. 117, 33–45 (1965).
Gerschenfeld, H. M., J. H. Tramezzani, and E. De Robertis: Ultrastructure and function in neurohypophysis of the toad. Endocrinology 66, 741–762 (1960).
Green, J. D.: The comparative anatomy of the hypophysis, with special reference to its blood supply and innervation. Amer. J. Anat. 88, 225–311 (1951).
Harris, G. W.: Neural control of the pituitary gland. London: Edward Arnold 1955.
—: The development of ideas regarding hypothalamic-releasing factors. Metabolism 13, 1171–1176 (1964).
Hartmann, J. P.: Electron microscopy of the neurohypophysis in normal and histaminetreated rats. Z. Zellforsch. 48, 291–308 (1958).
Herlant, M.: The cells of the adenohypophysis and their functional significance. Int. Rev. Cytol. 17, 299–381 (1964).
Herndon, R. M.: The fine structure of the rat cerebellum. II. The stellate neurons, granule cells, and glia. J. Cell Biol. 23, 277–293 (1964).
Holmes, R. L.: Comparative observations on inclusions in nerve fibres of the mammalian neurohypophysis. Z. Zellforsch. 64, 474–492 (1964).
—, and J. A. Kiernan: The fine structure of the infundibular process of the hedgehog. Z. Zellforsch. 61, 894–912 (1964).
—, and F. G. W. Knowles: “Synaptic vesicles” in the neurohypophysis. Nature (Lond.) 185, 710–711 (1960).
Ishii, S., N. Shimizu, M. Matsuoka, and R. Imaizumi: Correlation between catecholamine content and number of granulated vesicles in rabbit hypothalamus. Biochem. Pharmacol. 14, 183–184 (1965).
Klinkerfuss, G. H.: An electron microscopic study of the ependyma and subependymal glia of the lateral ventricle of the cat. Amer. J. Anat. 115, 71–100 (1964).
Knowles, Sir F.: Neuroendocrine correlations at the level of ultrastructure. Arch. Anat. micr. Morph. exp. 54, 343–358 (1965a).
—: Evidence for a dual control, by neurosecretion, of hormone synthesis and hormone release in the pituitary of the dogfish Scylliorhinus stellaris. Phil. Trans. B 249, 435–456 (1965b).
Kobayashi, H., H. A. Bern, R. S. Nishioka, and Y. Hyodo: The hypothalamo-hypophyseal neurosecretory system of the parakeet, Melopsittacus undulatus. Gen. comp. Endocr. 1, 545–564 (1961).
Kobayashi, T., T. Kobayashi, K. Yamamoto, and M. Imatomi: Electron microscopic observations on the hypothalamo-hypophyseal system in the rat. I. The ultrafine structure of the ontact region between the external layer of the infundibulum and pars tuberalis of the anterior pituitary. Endocr. jap. 10, 69–80 (1963).
Koelle, G. B.: A proposed dual neurohumoral role of acetylcholine: Its function at the pre- and post-synaptic sites. Nature (Lond.) 190, 208–211 (1961).
Kurosumi, K., T. Matsuzawa, and S. Shibasaki: Electron microscope studies on the fine structure of the pars nervosa and pars intermedia, and their morphological interrelation in the normal rat hypophysis. Gen. comp. Endocr. 1, 433–452 (1961).
Lederis, K.: Fine structure and hormone content of the hypothalamo-neurohypophysial system of the rainbow trout (Salmo irideus) exposed to sea water. Gen. comp. Endocr. 4, 638–661 (1964).
—: An electron microscopical study of the human neurohypophysis. Z. Zellforsch. 65, 847–868 (1965).
Luft, J. H.: Improvements in epoxy resin embedding methods. J. biophys. biochem. Cytol. 9, 409–414 (1961).
Matsuoka, M., S. Ishii, N. Shimizu, and R. Imaizumi: Effect of win 18501-2 on the content of catecholamines and the number of catecholamine-containing granules in the rabbit hypothalamus. Experientia (Basel) 21, 121–123 (1965).
Mazzuca, M.: Structure fine de l'éminence médiane du cobaye. J. Microscopie 4, 225–238 (1965).
McShan, W. H.: Ultrastructure and function of the anterior pituitary gland. In Proceedings of the second internat, congr. of endocrinology, p. 382–391. Internat, congr. series No 83. Amsterdam-New York-London-Milan-Tokyo-Buenos-Aires: Excerpta Medica Foundation 1965.
Nishioka, R. S., H. A. Bern, and L. R. Mewaldt: Ultrastructural aspects of the neurohypophysis of the white-crowned sparrow, zonotrichia leucophrys gambelii, with special reference to the relation of neurosecretory axons to ependyma in the pars nervosa. Gen. comp. Endocr. 4, 304–313 (1964).
Normann, T. C.: The neurosecretory system of the adult Calliphora erythrocephala. I. The fine structure of the corpus cardiacum with some observations on adjacent organs. Z. Zellforsch. 67, 461–501 (1965).
Novikoff, A. B.: Lysosomes and related particles. In: The cell (eds. J. Brachet and A. E. Mirsky), vol.2, p. 423–488. New York: Academic Press 1961.
Nowakowski, H.: Infundibulum und Tuber cinereum der Katze. Dtsch. Z. Nervenheilk. 165, 261–339 (1951).
Oota, Y.: Fine structure of the median eminence and the pars nervosa of the mouse. J. Fac. Sci. Univ. Tokyo, Sect. IV, 10, 155–168 (1963a).
—: Fine structure of the median eminence and the pars nervosa of the turtle, Clemmys japonica. J. Fac. Sci. Univ. Tokyo, Sect. IV, 10, 169–179 (1963b).
—, and H. Kobayashi: Fine structure of the median eminence and pars nervosa of the pigeon. Annot. Zool. Japon. 35, 128–138 (1962).
—: Fine structure of the median eminence and the pars nervosa of the bullfrog, Rana catesbeiana. Z. Zellforsch. 60, 667–687 (1963).
Palay, S. L.: The fine structure of the neurohypophysis. In: Progress in neurobiology. II. Ultrastructure and cellular chemistry of neural tissue (eds. S. Korey and J. I. Nürnberger), p. 31–49. New York: Hoeber 1957.
Pappenheimer, J. R.: Passage of molecules through capillary wall. Physiol. Rev. 33, 387–423 (1953).
Pellegrino De Iealdi, A., D. H. Farini, and E. De Robertis: Adrenergic synaptic vesicles in the anterior hypothalamus of the rat. Anat. Rec. 145, 521–531 (1963).
Rennels, E. G.: Electron microscopic alterations in the rat hypophysis after scalding. Amer. J. Anat. 114, 71–91 (1964).
Reynolds, E. S.: The use of lead citrate at high pH as an electronopaque stain in electron microscopy. J. Cell Biol. 17, 208–212 (1963).
Richardson, K. G.: The fine structure of autonomic nerve endings in smooth muscle of the rat vas deferens. J. Anat. (Lond.) 96, 427–442 (1962).
—: The fine structure of the albino rabbit iris with special reference to the identification of adrenergic and cholinergic nerves and nerve endings in its intrinsic muscles. Amer. J. Anat. 114, 173–205 (1964).
Rinne, U. K.: Neurosecretory material around the hypophysial portal vessels in the median eminence of the rat. Studies on its histological and histochemical properties and functional significance. Acta endocrin. (Kbh.) 35, Suppl. 57, 1–108 (1960).
- Hypothalamic neurosecretion in mammals with special reference to the cytological features. In: Meth. Achievm. exp. Path. (eds. E. Bajusz and G. Jasmin). Basel and New York: Karger 1, 169–205 (1966).
-, and A. U. Arstila: Ultrastructure of the neurovascular link between the hypothalamus and anterior pituitary gland in the median eminence of the rat. Neuroendocrinology (1965a), (in press).
- - Electron microscopic evidence of the significance of the granular and vesicular inclusions of the neurosecretory nerve endings in the median eminence of the rat. I. Ultrastructural alterations after reserpine injection. Med. exp. (1965b) (in press).
Rioch, D. M., G. B. Wislocki, and J. L. O'Leary: A précis of preoptic, hypothalamic and hypophysial terminology with atlas. Res. Publ. Ass. nerv. ment. Dis. 20, 3–30 (1940).
Röhlich, P. B., B. Aros u. B. Vigh: Elektronenmikroskopische Untersuchung der Neurosekretion im Cerebralganglion des Regenwurmes (Lumbricus terrestris). Z. Zellforsch. 58, 524–545 (1962).
Sabatini, D. D., K. G. Bensch, and R. J. Barrnett: New means of fixation for electronmicroscopy and histochemistry. Anat. Rec. 142, 274 (1962).
Seitz, H. M.: Zur Elektronenmikroskopischen Morphologie des Neurosekrets im Hypophysenstiel des Schweins. Z. Zellforsch. 67, 351–366 (1965).
Stutinsky, F., A. Porte et M. E. Stoeckel: Sur les modifications ultrastructurales de la pars tuberalis du Rat après hypophysectomie. C. R. Acad. Sci. (Paris) 259, 1765–1767 (1964).
Szentágothai, J.: The parvicellular neurosecretory system. In: W. Bargmann and J. P. Schadé (editors), Progress in brain research, vol. 5, Lectures on the diencephalon, p. 135–146. Amsterdam-London-New York: Elsevier 1964.
Tennyson, V. M., and G. D. Pappas: An electron microscope study of ependymal cells of the fetal, early postnatal and adult rabbit. Z. Zellforsch. 56, 595–618 (1962).
Watson, M. D.: Staining of tissue sections for electron microscopy with heavy metals. J. biophys. biochem. Cytol. 4, 223–228 (1958).
Wolfe, D. E., L. T. Potter, K. G. Richardson, and J. Axelrod: Localizing tritiated norepinephrine in sympathetic axons by electron microscopic autoradiography. Science 138, 440–442 (1962).
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Rinne, U.K. Ultrastructure of the median eminence of the rat. Zeitschrift für Zellforschung 74, 98–122 (1966). https://doi.org/10.1007/BF00342942
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DOI: https://doi.org/10.1007/BF00342942