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Different populations of granules and their distribution in the hypothalamo-neurohypophysial tract of the rat under various experimental conditions

II. The median eminence

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Summary

In connection with previous studies (Krisch, 1974), a morphologic analysis of the median eminence of male, female, pregnant, and thirsting rats has been made, in order to evaluate: 1. whether the median eminence is an additional area where oxytocin and vasopressin may be released from neurosecretory axons in the zona interna; 2. whether it is possible to distinguish different populations of axons according to the mean diameters of their granules in the external zone of the median eminence.

In the zona interna of the male and the female control animals, the oxytocin-and vasopressin-containing granules have already reached their final diameters, i.e. their size remains constant until they reach and are stored in the neurohypophysis. However, the relative proportions of these populations in the fibre layer of the median eminence indicate certain differences between male and female animals, concerning the turnover of oxytocin and vasopressin. In pregnant, as well as in thirsting animals, there is an apparent decrease of the mean granule diameters in oxytocin and vasopressin-containing axons. In particular in the latter group, ballooned axons in the fibre layer of the median eminence, containing disintegrating granules, tubular structures filled with electron dense material, and fine-flocculent material in the axoplasm, together with the morphometric results, support our concept that in case of highly increased peripheral demand the contents of the mature, large granules are released into the axoplasm of the fibre layer in the median eminence. In addition, axons containing granules smaller than 115 nm may be classified into four populations with mean diameters of 84 nm, 96 nm, 103 nm, and 110 nm.

The same populations are found in the palisade zone of the median eminence as well as in the pericapillary zone, but in contrast to the zona interna there is a fifth population of axons containing very small granules with a mean diameter of about 70–75 nm. The relative proportions of these five populations differ between the zona palisadica and the pericapillary zone on the one hand and between the experimental groups on the other hand. Some morphological findings concerning the tanycytes are discussed with respect to previously published data.

Zusammenfassung

In Fortsetzung einer früheren Arbeit wurde die Eminentia mediana von männlichen und weiblichen Ratten, sowie die trächtiger und durstender Tiere auf die Fragestellung hin untersucht, ob 1. die Eminentia mediana der erste Ort ist, wo die beiden Neurohormone Oxytocin und Vasopressin freigesetzt werden, und 2. ob sich die Axone in der externen Schicht der Eminentia mediana aufgrund der mittleren Durchmesser ihrer Granula in verschiedene Populationen differenzieren lassen.

Bei männlichen und weiblichen Kontrolltieren haben die Oxytocin-bzw. Vasopressin-granula in der Eminentia mediana bereits ihre endgültige Größe erreicht; ihr mittlerer Durchmesser ändert sich nicht mehr wesentlich bis zum Hypophysenhinterlappen. Allerdings gibt der unterschiedliche prozentuale Anteil beider Populationen in der Eminentia mediana, in Zusammenhang mit den früher bestimmten Werten für die jeweiligen Kerne und die Neurohypophyse, Hinweise auf gewisse Unterschiede im turnover beider Hormone bei männlichen und weiblichen Tieren.

Bei graviden und durstenden Ratten findet sich eine scheinbare Abnahme der Granula Durchmesser in den oxytocin-bzw. vasopressinführenden Axonen. In Verbindung mit sehr charakteristischen morphologischen Befunden, besonders bei langdurstenden Tieren, sprechen die morphometrischen Ergebnisse dafür, daß in der Eminentia mediana bereits Neurohormon freigesetzt wird, wenn eine schnelle Deckung des peripheren Bedarfes notwendig ist.

Die Axone mit Granula, die kleiner sind als 115 nm, lassen sich in der internen Schicht der Eminentia mediana aufgrund der mittleren Durchmesser ihrer Granula in vier Populationen aufteilen. Ihre mittleren Granula-Durchmesser liegen bei etwa 84 nm, 96 nm, 103 nm und 110 nm.

Dieselben vier Populationen finden sich sowohl in der Zona palisadica als auch in der perikapillären Schicht der Eminentia mediana. Im Unterschied zur Zona interna findet sich aber in diesen beiden Schichten noch eine fünfte Population von Axonen mit einem mittleren Granula-Durchmesser von etwa 70–75 nm. Der mengenmäßige Anteil dieser fünf Populationen aber ist unterschiedlich in der Zona palisadica und in der perikapillären Schicht einerseits und in den verschiedenen Tiergruppen andererseits. Einige morphologische Befunde an den Tanycyten werden im Zusammenhang mit der neueren Literatur diskutiert.

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Abbreviations

S.O.N.:

Nucleus supraopticus

P.V.N.:

Nucleus paraventricularis

DI:

Diabetes insipidus

References

  1. Akmayev, I. G., Fidelina, O. V.: Morphological aspects of the hypothalamic-hypophyseal system. V. The tanycytes: Their relations to the hypophyseal adrenocorticotrophic function. An enzyme-histochemical study. Cell. Tiss. Res. 152, 403–410 (1974)

  2. Baumgarten, H. G., Lachenmayer, L.: Indoleamine-containing nerve terminals in the rat median eminence. Z. Zellforsch. 147, 285–292 (1974)

  3. Björklund, A., Moore, R. Y., Nobin, A., Stenevi, U.: The organization of tubero-hypophyseal and reticulo-infundibular catecholamine neuron systems in the rat brain. Brain Res. 51, 171–191 (1973)

  4. Calas, A., Hartwig, H.-G., Collin, J. P.: Noradrenergic innervation of the median eminence. Microspectrofluorimetric and pharmacological study in the duck, Anas platyrhynchos. Z. Zellforsch. 147, 491–504 (1974)

  5. Castejón, O. I., Villegas, G. M.: Fine structure of the synaptic contacts in the stellate ganglion of the squid. J. Ultrastruct. Res. 10, 585–598 (1964)

  6. Clattenburg, R. E., Montemurro, D. G., Bruni, J. E., Singh, R. P.: Postcoital depletion of dense-core vesicles from the external layer of the rabbit median eminence. Z. Zellforsch. 142, 27–36 (1973)

  7. Cuello, A. C., Shoemaker, W. J., Ganong, W. F.: Effect of 6-hydroxydopamine on hypothalamic norephedrine and dopamine content, ultrastructure of the median eminence, and plasmacorticosterone. Brain Res. 78, 57–69 (1974)

  8. Doerr-Schott, J.: Cytologie et cytophysiologie de l'adénohypophyse des amphibiens. Thesis, Univ. of Strasbourg, 1966

  9. Doerr-Schott, J.: Cytologie et cytophysiologie de l'adénohypophyse des amphibiens. Ann. Biol. 7, 189–225 (1968a)

  10. Doerr-Schott, J.: Development de l'hypophyse de Rana temporaria. Etude au microscope électronique. Z. Zellforsch. 90, 616–645 (1968b)

  11. Grainger, F., Sloper, J. C.: Correlation between microtubular number and transport activity of hypothalamo-neurohypophyseal neurons. Cell. Tiss. Res. 153, 101–113 (1974)

  12. Guardabassi, A., Blanchi, D.: La cytologie hypophysaire chez Xenopus laevis Daudin. Z. Zellforsch. 56, 540–551 (1962)

  13. Güldner, F. H., Wolff, J. R.: Neurono-glial synaptoid contacts in the median eminence of the rat: Ultrastructure, staining properties, and distribution on tanycytes. Brain Res. 61, 217–234 (1973)

  14. Hökfelt, T., Fuxe, K.: On the morphology and the neuroendocrine role of the hypothalamic catecholamine neurons. In: Brain endocrine interaction. Median eminence: Structure and function. Int. Symp. Munich 1971, p. 181–223, eds.: K. M. Knigge, D. E. Scott, A. Weindel Basel: S. Karger 1972

  15. Ishii, S.: Classification and identification of neurosecretory granules in the median eminence. In: Brain endocrine interaction. Median eminence: Structure and function. Int. Symp. Munich 1971, p. 119–141, eds.: K. M. Knigge, D. E. Scott, A. Weindel. Basel: S. Karger 1972

  16. Kalimo, H., Rinne, U. K.: Ultrastructural studies on the hypothalamic neurosecretory neurons of the rat. II. The hypothalamic neurohypophysial system in rats with hereditary hypothalamic diabetes insipidus. Z. Zellforsch. 134, 205–225 (1973)

  17. Kerr, T.: Histology of the distal lobe of the pituitary of Xenopus laevis Daudin. Gen. comp. Endocr. 5, 232–240 (1965)

  18. Kobayashi, H., Matsui, T., Ishii, S.: Functional electron microscopy of the hypothalamic median eminence. Int. Rev. Cytol. 29, 281–381 (1970)

  19. Krisch, B.: Different populations of granules and their distribution in the hypothalamoneurohypophysial tract of the rat under various experimental conditions. I. Neurohypophysis, nucleus supraopticus and nucleus paraventricularis. Cell. Tiss. Res. 151, 117–140 (1974)

  20. Leonhardt H., Über ependymale Tanycyten des III. Ventrikels beim Kaninchen in elektronenmikroskopischer Betrachtung. Z. Zellforsch. 74, 1–11 (1966)

  21. McCann, S. M., Krulich, L., Cooper, K. J., Kalra, P. S., Libertun, C., Negro-Vilar, A., Ronnekleiv, O., Fawcett, C. P.: Hypothalamic control of gonadotropin and prolactin secretion, implications for fertility control. J. Reprod. Fertil., Suppl. 20, 43–59 (1973)

  22. Monroe, B. G.: A comparative study of the ultrastructure of the median eminence, infundibular stem and neural lobe of the hypophysis of the rat. Z. Zellforsch. 76, 405–432 (1967)

  23. Monroe, B. G., Newmann, B. L., Schapiro, S.: Ultrastructure of the median eminence of neonatal and adult rats. In: Brain endocrine interaction. Median eminence: Structure and function. Int. Symp. Munich 1971, p. 7–26, eds.: K. M. Knigge, D. E. Scott, A. Weindel. Basel: S. Karger 1972

  24. Norström, A.: Release in vitro of neurohypophysial proteins from neural lobe tissue slices and from isolated neurosecretory granules of the rat. Z. Zellforsch. 129, 114–139 (1972)

  25. Norström, A.: Subcellular distribution of neurophysin in rats subjected to haemorrhage, salt loading and lactation and in rats with hereditary diabetes insipidus (Brattleboro Strain). Z. Zellforsch. 140, 413–424 (1973)

  26. Norström, A., Sjöstrand, J.: Effect of suckling and parturition on axonal transport and turnover of neurohypophysial proteins. J. Endocr. 52, 107–117 (1972)

  27. Oksche, A., Farner, D. S.: Neurohistological studies of the hypothalamo-hypophysial system of Zonotrichia leucophrys gambelii (aves, passeriformes), with special attention to its role in the control of reproduction. Advances in Anatomy 48, Fasc. 4 (1974)

  28. Rempe, U.: Lassen sich bei Säugetieren Introgressionen mit multivarianten Verfahren nachweisen? Z. Zool. Syst. Evolut.-Forsch. 3, 388–412 (1965)

  29. Rinne, U. K.: Ultrastructure of the median eminence of the rat. Z. Zellforsch. 74, 98–122 (1966)

  30. Rinne, U. K.: Effect of adrenalectomy on the ultrastructure and catecholamine fluorescence of the nerve endings in the median eminence of the rat. In: Brain endocrine interaction. Median eminence: Structure and function. Int. Symp. Munich 1971, p. 165–170, eds.: K. M. Knigge, D. E. Scott, A. Weindel Basel: S. Karger 1972

  31. Robinson, A. G., Zimmermann, E. A.: Cerebrospinal fluid and ependymal neurophysin. J. clin. Invest. 52, 1260–1267 (1973)

  32. Scott, D. E., Krobisch-Dudley, G., Knigge, K. M.: The ventricular system in neuroendocrine mechanisms. II. In vivo monoamine transport by ependyma of the median eminence. Cell. Tiss. Res. 154, 1–16 (1974)

  33. Scott, D. E., Krobisch-Dudley, G., Knigge, K. M., Kozlowski, G. P.: In vitro analysis of the cellular localization of luteinizing hormone releasing factor (LRF) in the basal hypothalamus of the rat. Cell. Tiss. Res. 149, 371–378 (1974)

  34. Stoeckart, R., Jansen, H. G., Kreike, A. J.: Quantitative data on the fine structural organization of the palisade zone of the median eminence. Z. Zellforsch. 136, 111–120 (1973a)

  35. Stoeckart, R., Kreike, A. J., Jansen, H. G.: Size of granular vesicles in the rat median eminence, with special reference to the zona granulosa. Z. Zellforsch. 146, 501–515 (1973b)

  36. Unsicker, K.: On the innervation of mammalian endocrine glands (anterior pituitary and parathyroids) Z. Zellforsch. 121, 283–291 (1971)

  37. Vandesande, F., De Mey, J., Dierickx, K.: Identification of neurophysin producing cells. I. The origin of neurophysin-like substance-containing nerve fibres of the external region of the median eminence of the rat. Cell Tiss. Res. 151, 187–200 (1974)

  38. Vandesande, F., Dierickx, K., De Mey, J.: Identification of the vasopressin-neurophysin producing neurons of the rat suprachiasmatic nuclei. Cell Tiss. Res. 156, 377–380 (1975)

  39. Wagner, H.-J., Pilgrim, Ch.: Extracellular and transcellular transport of horseradish peroxidase (HRP) through the hypothalamic tanycyte ependyma. Cell. Tiss. Res. 152, 477–491 (1974)

  40. Wittkowski, W.: Elektronenmikroskopische Untersuchungen zur funktionellen Morphologie des tubero-hypophysären Systems der Ratte. Z. Zellforsch. 139, 101–148 (1973)

  41. Wittkowski, W., Scheuer, A.: Functional changes of the neuronal and glial elements at the surface of the external layer of the median eminence. Z. Anat. Entwiokl.-Gesch. 143, 255–262 (1974)

  42. Zambrano, D., De Robertis, E.: The effect of castration upon ultrastructure of the rat hypothalamus. II. Arcuate nucleus and outer zone of median eminence. Z. Zellforsch. 87, 409–421 (1968)

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Author information

Correspondence to Dr. Brigitte Krisch.

Additional information

This work was supported by the Stiftung Volkswagenwerk and Deutsche Forschungsgemeinschaft.

The author wishes to express her appreciation to Mrs. Helga Prien for her skilfull technical assistance and, in particular, to Dr. Udo Rempe (Institut f. Haustierkunde, University Kiel) who performed the mathematical operations at the PDP 10 computer.

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Krisch, B. Different populations of granules and their distribution in the hypothalamo-neurohypophysial tract of the rat under various experimental conditions. Cell Tissue Res. 160, 231–261 (1975). https://doi.org/10.1007/BF00220580

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Key words

  • Median eminence
  • Rat
  • Populations of axonal granules
  • Electron microscopy, morphometry