The fine structure of the hypothalamic secretory neurons of the White-crowned Sparrow,Zonotrichia leucophrys gambelii (Passeriformes: Fringillidae)

Summary The fine structures of the neurons and neuropils of the magnocellular supraoptic nucleus and the parvocellular nuclei of the rostral hypothalamus, including the suprachiasmatic and medial, lateral and periventricular preoptic nuclei, and the neuronal apparatus of the organum vasculosum laminae terminalis, have been examined in the male White-crowned Sparrow, Zonotrichia leucophrys gambelii, by correlated light and electron microscopy.The magnocellular supraoptic nucleus is characterized by large neurosecretory perikarya which contain a well developed Golgi complex and densecored granules 1,500–2,200 Å in diameter. The neuropil displays axons, dendrites and glial fibers. Some axonal profiles contain dense-cored vesicles 800–1,000 Å in diameter and clear vesicles 500 Å in diameter. Axo-somatic and axo-dendritic synapses are conspicuous in this nuclear region.The suprachiasmatic nucleus is characterized by an accumulation of small neurons with moderately developed cellular organelles and some dense-cored granules, approximately 1,000 Å in diameter. The profiles of axons within the neuropil contain dense-cored granules 800–1,000 Å in diameter and clear vesicles 500 Å in diameter.The neurons of the medial preoptic nucleus are relatively large and exhibit well developed cellular organelles and dense-cored granules 1,300 to 1,500 Å in diameter. Granular materials are formed within the Golgi complex. The medial preoptic nucleus is rich in secretory perikarya.Occasionally, neurons with granules 1,500–2,200 Å in diameter are encountered in the lateral preoptic and periventricular preoptic nuclei. They may be considered as scattered elements of the magnocellular (supraoptic and paraventricular) system.The organum vasculosum laminae terminalis consists of three layers, i.e., ependymal, internal and external zones, and exhibits a vascular arrangement similar to that of the median eminence. The perikarya of the parvocellular neurons and their axons in the internal zone contain numerous secretory granules ranging from 1,300 to 1,500 Å in diameter.This investigation was supported by Grant No. 5R040 Japan-U.S. Cooperative Science Program of the Japan Society for the Promotion of Science to Professor H. Kobayashi and Professor S.-I. Mikami, by a Scientific Research Grant No. 56019 from the Ministry of Education of Japan to S.-I. Mikami, by support from the Deutsche Forschungsgemeinschaft (Schwerpunktprogramm Biologie der Zeitmessung) to Prof. A. Oksche and by Grant No. GF 33334, U.S.-Japan Cooperative Science Program of the National Science Foundation to Prof. D.S. Farner.Herrn Professor Dr. Dres h.c. Wolfgang Bargmann zu seinem 70. Geburtstag am 27. Januar 1976 gewidmet.     

On different types of nerve endings in the frog median eminence after fixation with permanganate and glutaraldehyde-osmium

Summary In the frog median eminence, fixed with glutaraldehyde and osmium tetroxide, four types of nerve endings can be generally distinguished. These endings are in contact with the pericapillary spaces of primary portal vessels and can be identified by the internal structure and the size of their granules and vesicles. Type 1 contains large granules (1500–2400 Å in diameter) and small clear vesicles (300–500 Å in diameter), type 2 intermediate granules (about 1100–1700 Å in diameter) and small clear vesicles, type 3 small granules (about 600–1000 Å in diameter) and small clear vesicles, type 4 only numerous small clear vesicles. The mixed types containing the large, intermediate and small dense granules in the same ending are infrequently found.After KMnO₄ or LiMnO₄ fixation the granules and vesicles mentioned above are observed as follows. The large granules in the type 1 nerve ending appear mostly pale or less-dense. The intermediate granules in the type 2 also appear mostly pale or less-dense, but some frequently show granules of high density. The small granules in the type 3 consistently contain the dense substance and these endings can be subdivided into two different types according to the populations of different sizes of dense granules [type 3a (900–1000 Å) and type 3b (500–800 Å)]. Dense-cored and cleared-synaptic vesicles are frequently present with together in the type 3 endings. The small vesicles (300–400 Å), in the type 4, appear generally pale (type 4a), but some nerve endings contain small dense cored-vesicles (type 4b).The author wishes to thank Prof. H. Fujita for his advice and criticism.     

Weitere Untersuchungen zur Feinstruktur und Innervation des Pinealorgans von Passer domesticus L.

Zusammenfassung Im Parenchym der Epiphysis cerebri von Passer domesticus kommen Nervenzellen vor. Ihre Neuriten ziehen im langgestreckten Epiphysenstiel zur Commissura habenularum. Im proximalen Endabschnitt des Epiphysenstiels wird ein Teil dieser Fasern myelinisiert. Zwischen die Nervenfasern schieben sich zahlreiche Pinealocytenausläufer; synaptische Bänder helfen die letzteren eindeutig zu identifizieren. Im Bereich der synaptischen Bänder liegen: 1. 300 Å Vesikel, 2. 300 Å Vesikel und 800–1200 Å Granula, 3. nur 800–1200 Å große granulierte Vesikel. Die Tatsache, daß in Pinealocytenausläufern nebeneinander synaptische Bänder und Granula vorkommen, und daß apikal in zilientragenden Zellen ebenfalls Granula nachweisbar sind, spricht dafür, daß bei Passer domesticus ein Pinealzelltyp sensorische und sekretorische Strukturmerkmale besitzen kann. Außerdem werden Kontaktsynapsen beobachtet; ihre praesynaptischen Fasern enthalten die gleichen Strukturelemente wie die Fasern mit synaptischen Bändern. Die Zahl der Mikrofibrillen und Mikrotubuli variiert in den Pinealocytenausläufern, in den postsynaptischen Dendriten und in den Neuriten so stark, daß es mitunter schwierig ist, diese Fortsatztypen einwandfrei zu unterscheiden und die Zahl der zum Gehirn ziehenden Neuriten exakt zu ermitteln.Efferente sympathische Nervenfasern dringen in die Bindegewebssepten der Epiphyse ein. Sie enthalten Granula mit einem Durchmesser von 300–500 Å und 800–1200 Å. Nach Injektion von Nialamid zeigen beide Granulatypen einen elektronendichten Kern. Mikrospektrographisch ist Serotonin und Noradrenalin in diesen Nervenfasern nachweisbar. Das Material dieser Studie enthält keinen fluoreszenzmikroskopischen oder elektronenmikroskopischen Hinweis darauf, daß die sympathischen Nervenfasern durch die Basalmembran in den Zellverband des Epiphysenparenchyms eintreten. Im elektronenmikroskopischen Bild haben manche Pinealocytenausläufer eine Ähnlichkeit mit autonomen Nervenfasern.Die funktionelle Bedeutung der Vogelepiphyse als photo-neuro-endokrines Organ wird diskutiert.

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Further investigations on the structure and innervation of the pineal organ of Passer domesticus L.

Summary The pineal organ of Passer domesticus contains nerve cells within its parenchyma. Axons of the nerve cells run within the elongated stalk of the pineal organ to the habenular commissure. At the proximal end of the stalk, some axons become myelinated. In the stalk, the axons intermingle with pinealocyte processes containing synaptic ribbons. The synaptic ribbons are in contact with (1) vesicles with a diameter of 300 Å; (2) 300 Å diameter vesicles and 800–1,200 Å diameter dense-core granules; or (3) the dense-core granules only. Dense-core granules are also present in pinealocytes with 9+0 type cilia. These results suggest that sensory and secretory structures are present in the same pineal cell type. Furthermore, conventional synapses are present between receptor and nerve cells: The presynaptic fibers have the same structure as the fibers containing synaptic ribbons. The numbers of microfibrils and microtubules vary among postsynaptic fibers (dendrites), the pinealocyte processes, and the neurites. Thus it is difficult to obtain an exact count of the number of axons running to the brain.Efferent sympathetic nerve fibers enter the pineal organ associated with the connective tissue surrounding blood vessels. The fibers show granules of 300–500 Å diameter or 800–1,200 Å diameter. After nialamide injection, both types of granules contain a dense core. Microspectrographically serotonin and noradrenaline are demonstrated in the sympathetic nerve fibers. There is no evidence found in the material of this study to suggest that sympathetic nerve fibers perforate the basement membrane and enter the parenchymal cell complexes of the pineal organ. Pinealocyte processes and sympathetic nerve fibers often show a very similar ultrastructural pattern.The role of the avian pineal organ in photo-neuro-endocrine regulation is discussed.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Fine structure of the autonomic nerves of the rabbit myometrium

Summary The fine structure of the preterminal nerve fibers of the rabbit myometrial smooth muscle was studied using potassium permanganate fixation or glutaraldehyde fixation with postosmification. The preterminal fibers were mostly formed by 2–10 axons enveloped by Schwann cells. Two kinds of axons and axon terminals were found. (1) Adrenergic axons, which contained many small, granular vesicles (diameter 300–600 Å) and large granular vesicles (diameter 700–1200 Å) which represented ca. 2% of the total count of the vesicles. (2) Nonadrenergic axons, which contained small agranular vesicles (diameter 300–600 Å) and large granular vesicles (diameter 700–1200 Å). Both types of axons formed preterminal varicosities along their course. The real terminal varicosities, representing the anatomical end of the axons, were usually larger than the preterminal ones and showed close contact to the plasma membranes of the smooth muscle cells. Both adrenergic and nonadrenergic terminals were found close to the smooth muscle cells, but a gap of at least 2000 Å was always present between the two cell membranes. The axons and preterminal varicosities of both types of nerves were in intimate contact with each other within the preterminal nerve fiber. Axo-axonal interactions between the two types of axons are possible in the rabbit myometrium. The relative proportion of the nonadrenergic axons from the total was about one fourth.     

Vesicle and granule content of sympathetic ganglion cells during limb regeneration of the newt Triturus

Summary Fine structural observations were made on the vesicle and granule content of ganglion cells in the posterior subclavian ganglion and peripheral nerve fibers of the upper forelimb of the newt Triturus. The populations of vesicles and granules in normal ganglion cells and nerve fibers were compared with those observed after limb transection. In normal neurons, clear vesicles range in size from 250 to 1000 Å in diameter, but are most frequently 400–500 Å. Vesicles with dense contents (granules) also vary greatly in size, but most are 450–550 Å in diameter and correspond to dense-core vesicles. Large granules that contain acid phosphatase activity are thought to be lysosomes. During limb regeneration, in both the ganglion cells and peripheral nerves, the ratio of dense vesicles to clear vesicles increases. There is a large increase in number of dense granules with a diameter over 800 Å, particularly in the peripheral regenerating fibers. This study shows that regenerating neurons differ from normal in their content of vesicular structures, especially large, membrane-bounded granules.This work was supported by grants from the National Science Foundation (GB 7912) and from the National Cancer Institute (TICA-5055), National Institutes of Health, United States Public Health Service.     

Electron microscopic observations on synapse-like contacts between pituicytes and different types of nerve fibers in the anuran pars nervosa

Summary Pituicytes of Rana pipiens could be classified into two types, pale and dense, according to their relative densities of cytoplasm and the populations of free ribosomes and cell organelles. An intermediate type of pituicyte was also recognized.Lipid droplet such as are typical in the cytoplasm of mammalian pituicytes, are not in the cytoplasm of either types of frog pituicyte. Both types have long cytoplasmic processes which run among the nerve fibers, and some of them end at the pericapillary space.Nerve endings making synapse-like contacts with the cell bodies or the processes of the pituicyte are frequent. According to the structures and sizes of granules and vesicles in the nerve endings, these endings are classified into one of three types: 1) A, which appears to be a peptidergic neuronal ending containing dense granules 1,200–2,000 Å in diameter and small clear vesicles 300–400 Å in diameter; 2) B, which appear to be monoaminergic endings containing cored vesicles 600–1,000 Å in diameter and small clear vesicles 300–500 Å in diameter; 3) C, which appear to be cholinergic endings containing only small clear vesicles. Type C endings are relatively rare. In the synaptic area the axonal membranes appose those of the pituicytes across a gap of about 200 Å and numerous presynaptic vesicles are clustered or accumulated near the presynaptic membranes.The author wish to express his hearty thanks Professor Dr. A. Gorbman, Zoology Department, University of Washington, Seattle, U.S.A. and Professor Dr. H. Fujita for their helpful advices and criticisms. The frog tissues were obtained and fixed in Professor A. Gorbman's laboratory supported by U.S.P.H.S. grant NS 04887.     

Chromosome fibers studied by a spreading technique

Chromosomes and interphase nuclei can be spread on the surface of water in a simplified Langmuir trough. Interphase nuclei of Triturus erythrocytes display fibers with a diameter of about 250–300 Å. Very similar fibers are seen in metaphase chromosomes of cultured human cells. Fibers from grasshopper spermatocyte chromosomes (prophase) are more variable in diameter, and many fibers thinner than 200 Å extend laterally from the chromosome. In the grasshopper spermatocyte, fibers align in parallel to form plates. It is suggested that the 250–300 Å fibers may represent an inactive state of the chromosome material, and that only the thinner fibers are involved in RNA synthesis. The 250–300 Å fibers may result from the folding or coiling of a thinner fiber having the approximate dimensions of the nucleohistone molecule.     

Nerve-purkinje fiber relationship in the moderator band of bovine and caprine heart

Summary The moderator band in the heart of the ox and goat contains bundles of Purkinje fibers and nerve fibers separated by connective tissue. The axons are mostly unmyelinated and embedded in the cytoplasm of Schwann cells.Small bundles of axons run close to the Purkinje fibers. The axons dilate into varicosities 0.5 to 1.6 in diameter (mean 0.95 ), containing three types of vesicles: 1) agranular vesicles with a diameter of 400–500 Å, 2) large dense-cored vesicles with a diameter of 800–1200 Å, 3) small dense-cored vesicles with a diameter of 500 Å. Most varicosities contain agranular vesicles together with a few large dense-cored vesicles.The gap between the varicosities and the nearest Purkinje fiber is unusually wide and normally varies between 0.3 and 0.8 . No intimate nerve-Purkinje fiber contacts, with a cleft of 200 Å, were observed.     

Innervation des cellules du pancréas endocrine du Poisson Téléostéen Xiphophorus helleri H.

Summary The pancreatic islet tissue of the bony fish Xiphophorus helleri H. is innervated by amyelinic fibers. Neuroglandular junctions on the islet cells show a structure similar to that of the synapses of the central nervous system. Presynaptic projections, intrasynaptic lines, and postsynaptic bands are to be observed. In the nerve endings two kinds of vesicles occur: large granular vesicles (diameter:850–1150 Å) and small clear vesicles (diameter: 500–650 Å). Synaptic vesicles are gathered around the presynaptic dense projections. This precise organization suggests the existence of a direct nervous control involved in the metabolism of the pancreatic hormones.

Avec la collaboration technique de M. D. Streicher.     

Liquorkontaktneurone im Nucleus infundibularis

Zusammenfassung Der Nucleus infundibularis verschiedener Reptilien wurde licht- und elektronenmikroskopisch untersucht. Zellen dieses Kernes entsenden Fortsätze durch ein mehrreihiges Ependym in den 3. Ventrikel und bilden dort freie, intraventrikuläre Nervenendigungen (Liquorkontakt-Nervenendigungen, Lkne). Lichtmikroskopisch konnten in der Kerngruppe a) kleine, AChE-negative, toluidinblaue und b) große, AChE-positive, mit Toluidinblau hell erscheinende Nervenzellen unterschieden werden.Die knöpfchenförmigen LKNE weisen Elemente des endoplasmatischen Retikulums, freie Ribosomen, eine wechselnde Anzahl Mitochondrien, einzelne Lysosomen, asymmetrische Zilien (Typ 9+0) mit akzessorischem Basalkörper und Zilienwurzeln auf. Zwei LKNE-Typen sind unterscheidbar: a) LKNE mit granulierten Vesikeln mit einem Durchmesser von 800–1100 Å und b) LKNE mit großen, elektronendichten Granula (Durchmesser 1200–1600 Å).Im Lumen des 3. Ventrikels treten kleinkalibrige Axone auf, die kleine, granulierte Bläschen (Durchmesser 700–900 Å) enthalten und mit den LKNE des Nucleus infundibularis intraventrikuläre Synapsen bilden.Die Perikaryen des Nucleus infundibularis weisen ein reichliches endoplasmatisches Retikulum, zahlreiche Polyribosomen, Neurotubuli und Mitochondrien auf. Ähnlich wie bei den LKNE sind zwei Perikaryenarten zu unterscheiden: a) Perikaryen mit granulierten Vesikeln (Durchmesser 800–1100 Å) und b) solche mit elektronendichten Granula (1200–1700 Å). Außerdem kommen verschiedene Arten axosomatischer und axodendritischer Synapsen vor.Die Funktion der intraventrikulären Nervenendigungen und verschiedenen Synapsenarten in der Kerngruppe wird im Hinblick auf einen Informationsaustausch zwischen dem Liquor cerebrospinalis und dem Nucleus infundibularis diskutiert.

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Liquor contacting neurons in the infundibular nucleus

Summary The infundibular nucleus of various reptiles was studied light and electron microscopically. Cells of this nucleus send processes through a stratified ependyma into the 3rd ventricle where they form free, intraventricular nerve terminals (liquor contacting nerve endings, LCNE). In the nucleus, two kinds of neurons could be distinguished light microscopically: a) small, AChE-negative, toluidine blue neurons, and b) large, AChE-positive cells staining light with toluidine blue.The club shaped LCNE contain elements of the endoplasmic reticulum, free ribosomes, a various amount of mitochondria, and single lysosomes. The terminals bear asymmetrical cilia (type 9+0) supplied with accessory basal bodies and rootlet fibres. Two kinds of LCNE are demonstrable: a) LCNE containing dense-core vesicles with a diameter of about 800–1100 Å, and b) LCNE with large, electron-dense granules (diameter about 1,200–1,600 Å). In the lumen of the 3rd ventricle, there occur small axons that contain small granulated vesicles (diameter about 700–900 Å), and that form intraventricular synapses with the LCNE of the infundibular nucleus.The perikarya of the infundibular nucleus contain an abundant endoplasmic reticulum, numerous polyribosomes, neurotubules and mitochondria. Similarly to the LCNE, two kinds of perikarya can be distinguished: a) perikarya containing granulated vesicles (diameter about 800–1100 Å), and b) perikarya with electron-dense granules (diameter about 1200–1700 Å). Furthermore, different types of axosomatic and axodendritic synapses occur.The function of the intraventricular nerve terminals and the different types of synapses in the nucleus is discussed with regard to an exchange of informations between the cerebrospinal fluid and the infundibular nucleus.

     

Fluoreszenz- und elektronenmikroskopische Untersuchungen am Zwischenhirn-Hypophysensystem von Passer domesticus

Zusammenfassung Fluoreszierende aminerge Nervenfasern bzw. Endigungen und elektronendichte Granula mit einem Durchmesser von 500–1000 Å wurden bei Passer domesticus in den Perikaryen und im Neuropil des Nucleus infundibularis, im Neuropil des Nucleus supraopticus, im rostralen Abschnitt der neurosekretorischen Bahn (Region der Sehnervenkreuzung) und in der retikulären und Palisadenschicht der Eminentia mediana beobachtet. 2000–2500 Å große kontrastreiche Granula finden sich in den Perikaryen des Nucleus supraopticus, im Tractus supraoptico-paraventriculo-hypophyseus und im Hypophysenhinterlappen. Nach Reserpinbehandlung schwanden sowohl die gelbgrüne Fluoreszenz als auch das elektronendichte Material der 1000 Å und z. T. auch der 500–800 Å großen Bläschen. Dieses Ergebnis spricht dafür, daß beide Granulatypen Monoamine enthalten. Der Nucleus infundibularis ist nach unseren Befunden die wichtigste Quelle der etwa 1000 Å großen Granula in der Palisadenschicht der Eminentia mediana.

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Fluorescence- and electronmicroscopic studies on the hypothalamo-hypophysial system of Passer domesticus

Summary In Passer domesticus, fluorescent aminergic fibers and axon terminals and dense-core vesicles of 500 to 1000 Å diameter were found in the perikarya and the neuropile of the infundibular nucleus, in the neuropile of the supraoptic nucleus, in the rostral common neurosecretory pathway (region of the optic chiasma), in the tubero-infundibular tract, and in the reticular and palisade zones of the median eminence. 2000–2500 Å electron-dense vesicles were found in the perikarya of the supraoptic nucleus, in the proximal division of the common neurosecretory pathway and in pars nervosa of the hypophysis. After reserpine treatment, the yellow-green fluorescence as well as the dense material contained in the 1000 Å vesicles and partly also in the 500–800 Å vesicles disappeared. This suggested that the 1000 Å and the 500 Å dense-core vesicles in the hypothalamo-hypophysial system of Passer domesticus contain monoamines and that the infundibular nucleus is an important source of the 1000 Å dense-core vesicles in the palisade layer of the median eminence.

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Herrn Prof. Dr. Dr. E. Horstmann gewidmet.

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Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.

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Stipendiat der Alexander von Humboldt-Stiftung. (On leave from the Department of Veterinary Anatomy, University of Minnesota, St. Paul, Minnesota, U.S.A.).     

The neurohypophysis of the crested newt

Summary In the crested newt, the ultrastructural organization of the pars nervosa is analogous to that already known in non-mammal tetrapods. An orderly array of ependymal cells makes up the inner limiting layer while less abundant pituicytes are irregularly distributed within this organ. Light and dark pituicytes can be distinguished on the basis of the relative density of the cytoplasmic matrix and the distribution of the cell organelles.Both the ependymal cells and pituicytes are rich in dense bodies and possess extensive processes which ramify among the nerve fibers, often reaching the pericapillary space which they can line for long distances.The main components of the pars nervosa are nerve fibers and nerve terminals (type A), containing electron dense granules 1200–2000 Å in diameter together with clear vesicles averaging 250–400 Å. These fibers are likely to correspond to the aldehyde fuchsin positive neurosecretory fibers revealed by light microscopy. Differences in the granule size within the fibers and terminals lead to further recognition of two subgroups (A₁ and A₂).Other fibers and terminals (type B) containing clear vesicles and granular vesicles 600 to 1000 Å in diameter, possibly of aminergic type, are also encountered. These fibers are rare and can be seen only in the portion of the pars nervosa near the pars intermedia of the adenohypophysis.Lastly, fibers and terminals containing only clear vesicles ranging from 250 to 400 Å (type C) are occasionally found.Nerve endings are often formed by type A fibers on the perivascular space and on the perivascular processes of the ependymal cells and pituicytes. In agreement with recent findings available in the literature, the occurrence of synaptoid contacts between these terminals and both pituicytes and ependymal cells may confirm the active role of these cells in transport and release of neurosecretion.Work supported by a grant from the Consiglio Nazionale delle Ricerche.We are gratefully indebted to Dr. G. Gendusa and P. Balbi for technical assistance, dr. G. E. Andreoletti for statistical analysis.     

Electron microscopic studies on the pars intermedia in normal and in mice with hereditary nephrogenic diabetes insipidus

Summary The ultrastructure of the pars intermedia (PI) of the normal VII +/+ and hereditary nephrogenic diabetes inspidus DI Os/+ mice has been studied with particular reference to the morphology of the glandular cells and their innervation. Four types of cells were observed in both the genotypes of mice, 1) the light glandular cell, 2) the dark cell, 3) a type of cell similar to ependymal cells and 4) a small percentage of typical ACTH cells, observed mostly on the PI border of the cleft and rarely in the centre of PI. The predominant light glandular cells contain mainly two types of membrane bound granules: 1) electron dense core granules, which measure 1500–2500 Å and 2) electron lucent vesicles, which measure 3000–4000 Å in diameter. Granules of intermediate size with various density are also present in both types of mice. The electron dense core granules are predominant in DI Os/+ mice, whereas, electron lucent vesicles are predominant in the normal VII +/+ mice. Similar uniform size membrane bound electron dense granules have been observed in ACTH cells of PI and pars distalis. From earlier experimental evidences and the present observations, it is concluded that the dense core granules in PI may be synthesizing ACTH or ACTH-like substance. It is also discussed that these dense core granules may further mature and give rise to MSH in the form of electron lucent vesicles. If it is so, PI light glandular cells may have dual functions, of producing MSH and ACTH. One of the functions of ependymal-like cells, may be the transport of PI secretion.Three types of nerve endings are observed throughout the PI, making synaptic contact with the predominant cell type. The innervation is more in DI Os/+ mice than in normal mice. The classification of these nerves is according to Bargmann and co-workers 1) peptidergic neurosecretory fibers, contain mainly membrane bound dense core granules, measuring 1200 to 1800 Å, and are the classic neurosecretory granules; 2) adrenergic fibers, measuring 700–900 Å; 3) cholinergic fibers, measuring 300–400 Å. Adrenergic and cholinergic fibers are more towards the hypophysial cleft. The increased innervation, the synaptic contact, the extremely hypertrophied PI and the greater activity of its light glandular cells in the DI Os/+ mice show the PI is under the influence of the nervous system.This study was supported by MRC of Canada Grant No. MA-3759.     

Ultrastruktur der spinalen Liquorkontaktneurone beim Krallenfrosch (Xenopus laevis)

Zusammenfassung Zwischen und unter den Ependymzellen des Zentralkanals des Rückenmarkes von Xenopus laevis kommen Nervenzellen vor. Die intraependymalen Neurone sind rundlich und stehen mit dem Liquor cerebrospinalis durch eine breite Oberfläche in Berührung, von der sich längere und kürzere Fortsätze und ein Cilium (Typ 9+2) in das Lumen erheben. Die hypendymalen Neurone sind bipolar; ihr Dendrit verzweigt sich im Liquor ebenfalls in fingerförmige Fortsätze. Die Liquorkontaktfortsätze beider Zelltypen sind von feinen Filamenten ausgefüllt. Der Reissnersche Faden lagert sich manchen Fortsätzen an.In den intra- und hypendymalen Perikaryen findet man neben endoplasmatischem Retikulum, Golgi-Arealen und Mitochondrien kleine dense-core Vesikel (Durchmesser 600–900 Å). Der distale Fortsatz beider Neurontypen hat Neuritennatur. Axone, die synaptische und granulierte (Durchmesser 800–1200 Å) Vesikel enthalten, bilden relativ wenige Synapsen mit den Liquorkontaktneuronen. Im hypendymalen Neuropil findet man multipolare Nervenzellen, die 1000–1200 Å große granulierte Vesikel enthalten. Aufgrund des morphologischen Bildes wird die mögliche Rolle der Liquorkontaktfortsätze und des Ciliums bei der Funktion der Liquorkontaktneurone diskutiert.

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Ultrastructure of the spinal liquor contacting neurons in the clawed toad (Xenopus laevis)

Summary Nerve cells are situated between and below the ependymal cells of the central canal of the spinal cord of Xenopus laevis. The intraependymal neurons are round-shaped; they contact the cerebrospinal fluid by a large surface from which longer and shorter processes and a cilium (type 9+2) arise into the lumen. The hypendymal neurons are bipolar; their dendrite ramifies also into finger-like processes in the cerebrospinal fluid. The liquor contacting processes of both cell types contain fine filaments. The Reissner's fibre contacts some of the processes.In the intra- and hypendymal perikarya, small dense-core vesicles (diameter 600–900 Å) are found besides of endoplasmic reticulum, Golgi-areas and mitochondria. The distal process of both neuron types has neurite character. Axons containing synaptic and granulated (diameter 800–1200 Å) vesicles, form relatively few synapses with the liquor contacting neurons. In the hypendymal neuropile, multipolar nerve cells occur that contain granulated vesicles with a diameter of about 1000–1200 Å. On the basis of the morphological picture, the possible role of the liquor contacting processes and of the cilium in the function of the liquor contacting neurons are discussed.

     

Weitere elektronenmikroskopische Untersuchungen am Pinealorgan vonPhoxinus laevis (Teleostei,Cyprinidae)

Zusammenfassung Auch im Pinealorgan adulter Elritzen (Phoxinus laevis) sind die Außenglieder der Sinneszellen nicht degeneriert. Der Vergleich wurde zwischen adulten Exemplaren (8,6 cm) und 19,5 Monate jüngeren Tieren (3 cm) durchgeführt. Im Verhältnis zu den Jungtieren sind die Neuropilformationen und die synaptischen Strukturen adulter Elritzen stärker ausgeprägt. Bei den letzteren enthalten die Endfüße der pinealen Rezeptoren zahlreiche synaptische Bänder und 300–400 Å große Bläschen. Die Neuropilzonen sind außerdem reich an verdichteten Membranstellen (tight junctions). Im Pinealorgan des adulten Phoxinus finden sich eigenartige Einschlußkörper, die aus konzentrischen Lamellen bestehen; ähnliche Membran wirbel hat Takahashi (1969) bei zweijährigen Goldfischen beschrieben. Häufig lassen sich in den Epiphysen adulter Elritzen Axone beobachten, die mit 500–1000 Å großen granulierten Vesikeln gefüllt sind und im Verband bahnartig zusammengefaßter markloser Nervenfasern verlaufen. Die Herkunft und Bedeutung dieser granulierten Fasern werden diskutiert, ebenso wie die funktionelle Rolle des pinealen Sinnesorgans.

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Further electron microscopic studies of the pineal organ inPhoxinus laevis (Teleostei, Cyprinidae)

Summary The outer segments of pineal receptor cells of adult (8.6 cm) European minnows (Phoxinus laevis), like the lamellated outer segments of 19.5 months younger (3 cm) specimens, did not show signs of degeneration (see also Oksche and Kirschstein, 1967). Neuropile formations and synaptic structures were more prominent in adult than in youngPhoxinus. In the adult group, the end-feet of pineal receptors contained numerous synaptic ribbons and vesicles (300–400 Å in diameter). The neuropile zones were rich in tight junctions. A peculiar structure of the pineal organ of agingPhoxinus was the inclusion body formed by concentric arrangement of lamellae. Membrane whorls similar to these inclusion bodies were described in the pineal organ of two years old goldfish (Takahashi, 1969). In the pineal organ of adultPhoxinus considerable numbers of axons containing dense-core vesicles (500–1,000 Å in diameter) were observed within tract-like bundles of unmyelinated nerve fibers. The origin and significance of these granulated fibers and the functional role of the pineal sense organ have been discussed.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Ultrastructure of the peptidergic and monoaminergic neurons in the hypothalamic neurosecretory system of Anuran Batracians

Summary In the toad Bufo arenarum Hensel the following regions of the hypothalamic — neurohypophyseal system were studied under the electronmicroscope: preoptic and paraventricular nuclei, median eminence and infundibular process of the neurohypophysis.Neuronal perikarya of the preoptic nucleus are loaded with typical neurosecretory granules of peptidergic nature having a mean diameter of 1660 Å. While most neurons of the winter toad are in a storage stage a few show signs of a more active synthetic activity. A distinctive feature of preoptic neurons is the presence of large lipid droplets. The paraventricular nucleus contains small neurons containing granulated vesicles with a mean diameter of 800-1000 Å. In the region extending between these two nuclei and the median eminence axons containing either neurosecretory elementary granules or granulated vesicles are observed.The inner zone of the median eminence is occupied by axons of the preoptic neurohypophyseal tract; two types of axons, according to the size and density of the neurosecretory granules, may be recognized. The outer zone of the median eminence contains mainly axons and nerve terminals containing granulated vesicles of probable monoaminergic nature and only a few with granules of peptidergic type.The neurohypophysis contains two kinds of axons: one with more dense granules of 1800 Å and the other with granules of lesser electron density and 2100 Å. At the ending proper small clear vesicles of synaptic type are found.A progressive increase in volume of the peptidergic granules along the axon is demonstrated. This is of the order of 218% from the preoptic perikarya down to the infundibular process. The physiological significance of the two neurosecretory systems — i.e. the monoaminergic and the peptidergic — and the probable nature of the two types of peptidergic axons is discussed.Supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas and by the Air Force Office of Scientific Research (AF-AFOSR 963-67).The authors want to express their gratitude to Mrs. Defilippi-Novoa and Mr. Alberto Sáenz for their skillful assistance.     

Innervation of the testicular interstitial tissue in reptiles

Summary In the tortoise Testudo graeca, the lizards Lacerta dugesi and Lacerta pityusensis, and the snake Natrix natrix, the innervation of the testicular interstitial tissue was studied by light and electron microscopy, the acetylcholinesterase (ache) technique, the Falck-Hillarp method for the detection of catecholamines, and the application of 6-hydroxydopamine. The intertubular spaces of the reptilian testes studied contain adrenergic nerve fibers the amount and distribution of which varies considerably both in various species and in various stages of the reproduction cycle. Nerve fibers do not enter the seminiferous epithelium. Fluorescence microscopy of the lizard testis reveals catecholaminergic varicosities which are mainly arranged around blood vessels, but do not show obvious connexions to Leydig cells. Ache-positive fibers are equally distributed in lizard testes surrounding each seminiferous tubule. In Natrix natrix ache-positive fibers are irregularly spread among groups of tubules, without showing a definite relation to Leydig cells either. By electron microscopy bundles of unmyelinated axons and axon terminals can be more easily detected in the testes of immature animals than in adult. Terminals of nerve fibers containing small (400–500 Å in diameter) and large (800–1400 Å) dense-cored vesicles and sometimes small clear vesicles establish contacts with Leydig cells. Three types of contact are described. 1. Contacts par distance at a distance of about 2000 Å and basal lamina interposed; 2. membranous contacts having a 200 Å gap only between axolemma and Leydig cell plasmalemma; 3. invaginations of terminals into Leydig cell perikarya. The latter may exhibit surface specialisations, which strongly resemble postsynaptic membrane thickenings. Experiments using 6-hydroxydopamine underline the adrenergic character of testicular nerve fibers, which can be regarded as another example of non-cholinergic, ache-positive neurons. In the testis of the immature tortoise profiles of axons occur which probably represent purinergic, ache-positive neurons.Supported by a grant from the Deutsche Forschungsgemeinschaft (Un 34/1).I am much indebted to Mrs. R. Sprang for her skillfull technical assistance.     

Licht- und elektronenmikroskopische Untersuchungen des Saccus vasculosus und des Nervus und Tractus sacci vasculosi

Zusammenfassung Der Saccus vasculosus von Anguilla anguilla, Cyprinus carpio und Amiurus nebulosus wurde lichtmikroskopisch mit der AChE-Reaktion und dem fluoreszenzhistochemischen Monoaminnachweis, sowie elektronenmikroskopisch untersucht.Lichtmikroskopisch weisen die Liquorkontaktneurone und ihre Fortsätze eine starke AChE-Aktivität auf, während die Krönchenzellen inaktiv sind. Die AChE-positiven Fortsätze der Nervenzellen bilden Bündel, die in den Nervus sacci vasculosi eintreten und im Tractus sacci vasculosi weiterziehen. Diese AChE-positive Bahn kann nach Kreuzung zur Gegenseite bis in das Neuropil des Thalamus ventralis verfolgt werden. Die Liquorkontaktneurone des Saccus vasculosus, der Nervus und Tractus sacci vasculosi, sowie der Nucleus sacci vasculosi weisen keine Monoaminfluoreszenz auf.Auf den Perikaryen der Krönchenzellen kommen Synapsen vor, deren praesynaptisches Cytoplasma außer synaptischen Bläschen und Mitochondrien 800–1000 Å große granulierte Vesikel aufweist. Die Perikaryen der Liquorkontaktneurone enthalten neben den üblichen Cytoplasmabestandteilen dense core Vesikel, deren Durchmesser 700–900 Å beträgt. Axone, in denen granulierte Vesikel (Durchmesser 800 oder 1300 Å) vorkommen, bilden mit diesen Perikaryen Synapsen. Im basalen Teil des Saccusepithels findet man granulierte Bläschen (Durchmesser 800 oder 1400 Å) enthaltende Nervenfasern unterschiedlichen Durchmessers, ferner Synapsen. Der Nervus sacci vasculosi enthält klein- und großkalibrige, marklose Nervenfasern und vereinzelte Synapsen, während der Tractus sacci vasculosi aus vorwiegend kleinkalibrigen, marklosen Fasern besteht.

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Light and electron microscopic studies of the vascular sac and of the nervus and tractus sacci vasculosi

Summary The vascular sac of Anguilla anguilla, Cyprinus carpio and Amiurus nebulosus has been studied by light microscopy using AChE reaction and the fluorescence histochemical method for the demonstration of monoamines, and by electron microscopy.As demonstrated light microscopically, the cerebrospinal fluid (CSF) contacting neurons and their processes exert a strong AChE activity, while the coronet cells are inactive. The AChE-positive processes of the neurons form bundles that enter the nervus sacci vasculosi and pass on in the tractus sacci vasculosi. After crossing to the opposite side, this AChE-positive bundle can be traced into the neuropil of the ventral thalamus. Neither the CSF contacting neurons of the vascular sac, nor the nervus, tractus and nucleus sacci vasculosi show any monoamine fluorescence.As demonstrated electron microscopically, there are synapses on the perikarya of the coronet cells, their presynaptic cytoplasm being characterized by mitochondria, synaptic and granulated vesicles (diameter about 800 to 1000 Å). The perikarya of the CSF contacting neurons contain dense-core vesicles (diameter about 700 to 900 Å) besides of the usual cytoplasmic components. Axons displaying granulated vesicles with a diameter of 800 Å or 1300 Å, form synapses on these perikarya. In the basal part of the saccus epithelium, there are nerve fibres of different calibres containing dense-core vesicles (diameter about 800 Å or 1400 Å) and forming synapses. The nervus sacci vasculosi is characterized by thin and thick, unmyelinated nerve fibres, and rare synapses, while the tractus sacci vasculosi is composed of mainly small, unmyelinated fibres.

     

Ultrastructure of the subfornical organ of the chicken (Gallus domesticus)

Summary The SFO of the chicken is divided in half by a large central blood sinus; ventrally it is covered by a thin layer of ependyma (including tanycytes, dendrites, and axons) which connects the two lateral halves and protrudes as a midsagittal crest into the lumen of the third ventricle. The ependyma consists predominantly of tanycytes with long basal processes which terminate upon perivascular spaces. These cells have an extensive Golgi apparatus and abundant lysosomes; their cellular apices containing polyribosomes and a few vesicles frequently protrude into the ventricle. In addition to astrocytes, oligodendrocytes, and microglial cells, there is another glial cell population that is distinguished by the presence of parallel stacks or spherical to ovoid conglomerates of rough ER and their unique location, i.e., limited to areas ventral and ventral-lateral to the large blood sinus. Two types of neurons are present: neurons in which there is a paucity of granulated vesicles and occasional vacuoles in both the cytoplasm and nuclei, the second type of neuron elaborates many granulated vesicles. Numerous puncta adhaerentia are observed between adjacent neuronal perikarya and between glial processes and neuronal perikarya.Diverse axon types are found within the chicken SFO. Axo-dendritic and axo-somatic axon terminals and presynaptic axon dilations contain assorted combinations of electron-lucent and granulated vesicles of different maximal diameters. Based on the morphology of these axons, cholinergic, peptidergic, and serotoninergic fibers are described. There are two additional groups of axons whose classification awaits further investigation.The chicken SFO differs from the mammalian SFO in several respects: it possesses an ependyma with secretory and/or absorptive tanycytes predominating; it is divided midsagittally by a central blood sinus; its lateral and dorsal limits are nebulous; a previously undescribed peculiar type of glial cell is found in a limited portion of the organ; supraependymal neurons are lacking.Dedicated to Prof. H. Grau at the occasion of his 80th birthdayWe gratefully acknowledge the technical help of Susan Woroch and secretarial assistance of Diana Hapes and Debbie Harrison     

Etude au microscope électronique de la neurohypophyse de Rana esculenta L.

Résumé L'éminence médiane et la pars nervosa de Rana esculenta diffèrent du point de vue de leur structure.L'éminence médiane se compose de 2 zones différentes: la zone externe placée près du lobe distal et la zone interne située sous l'épendyme. Dans la zone externe, on distingue, d'après la taille et la forme des grains de sécrétion, 5 types de terminaisons.1. des terminaisons avec de fins granules sphériques denses de 800 à 1000 Å de diamètre; 2. des terminaisons avec des granules de 1000 à 1200 Å de diamètre; 3. des terminaisons avec des grains de forme irrégulière de diamètre supérieur aux précédents (1200 à 1600 Å); 4. des terminaisons avec de volumineux grains denses sphériques d'environ 1200 à 1800 Å de diamètre; 5. un petit nombre de terminaisons ne contenant que des vésicules. Les terminaisons des catégories 3 et 4 sont probablement du type neurosécrétoire.La zone interne contient de nombreuses fibres neurosécrétrices. Elles sont de 2 types, l'une avec de gros granules (1600–2400 Å), l'autre avec des granules moins volumineux (1300–2000 Å). Des fibres non neurosécrétrices ont également été observées.Dans la pars nervosa, on rencontre deux types principaux de fibres neurosécrétrices, l'une avec des grains denses de 1600 à 2400 Å de diamètre, l'autre avec des grains moins denses d'environ 1300 à 2000 Å de diamètre. Dans la zone externe bordant la pars intermedia des fibres aminergiques avec de fines granulations ont été observées.

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Electron microscopic study of the neurohypophysis of Rana esculenta L.

Summary The median eminence and the pars nervosa of Rana esculenta have a different structure.The median eminence has 2 different zones: the outer zone situated near the pars distalis and the inner zone under the ependyme. In the outer zone there are, according to the size and the shape of the granules, 5 types of nerve terminals.1. Endings containing spherical fine dense granules of 800 to 1000 Å in diameter; 2. Endings with spherical granules from 1000 to 1200 Å in diameter; 3. Endings with granules of irregular shape which are bigger than the former (1200 to 1600 Å); 4. Endings with spherical dense granules of about 1200 to 1800 Å in diameter; 5. A few endings containing only clear vesicles. Type 3 and type 4 endings are probably neurosecretory.The inner zone contains numerous neurosecretory fibres. They are of two types: one with big granules (1600–2400 Å), the second with smaller granules (1300–2000 Å). Non-neurosecretory fibres have also been observed.The pars nervosa contains two principal types of neurosecretory fibres: one with dense granules of 1600 to 2400 Å in diameter, the other with lighter granules of about 1300 to 2000 Å. In the external zone lining the pars intermedia, aminergic fibres with fine granules have been observed.

Je tiens à exprimer mes vifs remerciements, à Monsieur le Professeur E. Follenius pour l'intérêt constant qu'il prend à ce travail. Je remercie également Madame R. O. Clauss, collaboratrice technique et Madame Schwoerer, photographe, pour leur aide précieuse.