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  • 1
    Electronic Resource
    Electronic Resource
    The metencephalic floor plate of chick embryos expresses two secretory glycoproteins homologous with the two glycoproteins secreted by the subcommissural organ (2000)
    Springer
    Histochemistry and cell biology 113 (2000), S. 415-426 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The nature and the function of the compounds secreted by the floor plate (FP) of the metencephalon are little known. The FP cells of the hindbrain react with antibodies (AFRU) against the glycoproteins secreted by the subcommissural organ (SCO). One of the these proteins, RF-Gly I, is a 540-kDa core glycosylated protein. The aims of the present investigation were to identify by immunoblot the AFRU-immunoreactive compound secreted by the FP of chick embryos, to establish temporal and regional patterns of this secretory activity, and to obtain information about the fate of these compounds. It was established that the SCO and FP of chick embryos secrete two AFRU-immunoreactive compounds of 540 and 230 kDa. The two compounds secreted by the FP have been designated as FP-Gly I and FP-Gly II. The expression of these proteins was circumscribed to the metencephalic FP, and occurred from HH 29 to HH 36. Within the FP cells, FP-Gly I and FP-Gly II were confined to the supranuclear and apical regions, which under the electron microscope displayed numerous cisternae of the rough endoplasmic reticulum and granules. Aggregates of AFRU-immunoreactive material appeared on the free surface of the FP. The possibility that FP-Gly I and FP-Gly II are released into the ventricle to reach distant targets is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004180000136
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  • 2
    Electronic Resource
    Electronic Resource
    The reticular substance of the medulla oblongata of the albino rat (1967)
    Springer
    Cell & tissue research 79 (1967), S. 537-549 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The region of the reticular giganto-cellular nucleus, perfused with formalin and postfixed in osmium tetroxide, was studied with histochemical and electron microscopic techniques. The perikarya of the neurons have two zones. The peripheral cytoplasm contains Nissl bodies, mitochondria, and free RNP particles. The juxtanuclear cytoplasm contains the Golgi complex, mitochondria, RNP particles and dense bodies. The nucleus is indented and has a prominent nucleolus and a paranucleolar body. Dense bodies are found along the axon and dendrites as well. Three different types of synapses are described and two types of synaptic vesicles (spherical and ellipsoidal) are shown. The capillary endothelium shows microvilli and marginal flaps. The endothelial cytoplasm contains vacuoles, micropinocytotic vesicles, and a few dense bodies. Processes of pericapillary cells, surrounded by a basement membrane, also contain dense bodies. The dense bodies found in the neurons and endothelial cells show acid phosphatase activity. On the basis of their morphology and their enzymatic activity these bodies are identified as lysosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336311
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  • 3
    Electronic Resource
    Electronic Resource
    Differences between median eminence and neural lobe in amphibians (1966)
    Springer
    Cell & tissue research 74 (1966), S. 308-316 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The neurohypophysis of the toad Bufo arenarum Hensel can be subdivided into two well defined zones: the median eminence and the neural lobe. In its turn, the median eminence consists of two zones: a neural subependymal one, containing the axons of the hypothalamic-neurohypophysial tract; and a glandular one, made up of the capillaries of the primary plexus of the portal hypophysial system and of neurosecretory axons. Different staining techniques and certain experimental procedures (inanition, dehydration and adenohypophysectomy) showed that there are differences between the neurosecretory material of the neural lobe, which is a place of hormone liberation into the systematic circulation, and the neurosecretory material of the median eminence, which is the site of release of adenohypophysis-stimulating substances into the portal vessels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00401259
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  • 4
    Electronic Resource
    Electronic Resource
    Vascularization of the hypophysial region of the normal and adenohypophysectomized toad (1967)
    Springer
    Cell & tissue research 83 (1967), S. 207-218 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The study of standarized sections of the hypophysial regions, and in vivo observations showed the presence of communicating vessels between the capillary network of the median eminence and the large capillaries of the neurointermediate junction. Moreover, direct branches from the hypophysial artery are described which give off branches, at the level of the neural stalk, to the median eminence and to the large capillaries of the neurointermediate junction. A second portal system similar to the one described by Cruz has been observed. Its primary plexus originates in several encephalic regions, and its secondary plexus is distributed through the neural lobe and thence to the pars intermedia. The course of flow in this system is a descending one. The arterial contribution to this system appears to arise from branches from the basilar and retroinfundibular arteries. — There are small venous-type vessels between the large capillaries of the neurointermediate junction and the posterodorsal region of the pars distalis. — After adenohypophysectomy, the blood which normally goes towards the pars distalis, flows towards the pars intermedia, following the path of the communicating vessels between the median eminence and the pars intermedia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00362402
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  • 5
    Electronic Resource
    Electronic Resource
    Lectin histochemistry of the human fetal subcommissural organ (1990)
    Springer
    Cell & tissue research 262 (1990), S. 105-113 
    Details
    ISSN: 1432-0878
    Keywords: Subcommissural organ ; Lectin histochemistry ; Immunocytochemistry ; Glycoproteins ; Human fetuses ; Bovine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The subcommissural organ (SCO) of 7 human fetuses, 3 to 6.5 months old, was investigated by means of: (i) immunocytochemistry employing three different antisera against secretory products extracted from the bovine SCO and Reissner's fiber; (ii) lectin binding using concanavalin A (Con A; affinity: mannose, glucose), wheat-germ agglutinin (WGA; affinity: N-acetyl-glucosamine, sialic acid), and Limax flavus agglutinin (LFA; affinity: sialic acid). Sections of bovine SCO were processed simultaneously and examined for comparative purposes. The human fetal SCO displayed lectin-binding properties identical to those in the SCO of other mammals. Thus, Con-A-binding sites were restricted to abundant supranuclear structures that most likely corresponded to the rough endoplasmic reticulum, but were missing from granules located in the apical cytoplasm. The latter secretory material was strongly WGA- and LFA-positive and formed a distinct zone in the most apical portion of the ependymal cells. In contrast, this type of reactivity was missing in the adjacent cells of ependyma proper. In the bovine SCO, LFA-positive granules were also aggregated in an apical layer. The secretory material in the bovine SCO, especially its apical granular component, was strongly immunoreactive with the three antisera used; the human fetal SCO, however, lacked this immunoreactivity. It is postulated that the SCO of human fetuses secretes glycoproteins with a carbohydrate chain similar to-and a protein backbone different from-the secretions elaborated by the SCO of other vertebrate species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327751
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  • 6
    Electronic Resource
    Electronic Resource
    Light and electron microscopy of granules in the toad choroid plexus (1967)
    Springer
    Cell & tissue research 82 (1967), S. 362-375 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Two types of granules can be distinguished in the toad choroid plexus under the light microscope: pigment granules, mainly localized in the cells that line the free ends of the choroidal villi, and Gomori-positive granules, present in most epithelial cells. The ultrastructural analysis of the choroid plexus reveals three types of granules: multivesicular bodies (MVB), multigranulous bodies (MGB) and dense bodies (DB), and intermediate stages between the last two bodies. The pigment granules seen under the light microscope probably correspond to the DB of the electron micrographs, and the Gomori-positive granules to the MGB. The probable role of these bodies is discussed and so is the significance of the glycogen present in the choroidal cells, their processes and endothelium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323860
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  • 7
    Electronic Resource
    Electronic Resource
    Ependymal specializations (1970)
    Springer
    Cell & tissue research 111 (1970), S. 15-31 
    Details
    ISSN: 1432-0878
    Keywords: Subcommissural organ ; Toads ; Apical secretion ; Fine structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ependymal cells of the toad subcommissural organ produce pale and dense secretory granules. Both types of granules are mainly concentrated in the apical cytoplasm and in the perinuclear region. Pale and dense granules are synthesized by and packed in the rough endoplasmic reticulum, bypassing the step of the Golgi apparatus. The apical cytoplasm of some subcommissural ependymal cells protrudes into the ventricle. All the cells project a few cilia and numerous slender, long microvilli into the ventricular lumen. Contacting the cilia and the microvilli there is a filamentous material identical to that observed in the fibre of Reissner at the aqueduct of Sylvius. In addition to filaments, the fibre of Reissner contains vacuolar formations. The fibre is surrounded by numerous ependymal cilia, some of which are embedded in the filamentous material of the fibre. The presence of numerous microvilli projected into the ventricle and the large number of vesicles scattered in the supranuclear cytoplasm seem to indicate that the subcommissural organ may have absorption functions. The fact that the intercellular space of the ependymal layer of the subcommissural organ is not separated from the ventricular lumen by tight junctions but by zonulae adhaerentes could indicate that the cerebrospinal fluid penetrates these intercellular spaces bathing all sides of the ependymal cells. The presence in the ependymal cells of vesicles opening into the intercellular space would be in agreement with the latter possibility. There are some ultrastructural differences between the ependymal cells of the cephalic end of the subcommissural organ and those of the caudal end. A critical analysis of Reissner's fibre formation is made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00342098
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  • 8
    Electronic Resource
    Electronic Resource
    Ependymal specializations (1970)
    Springer
    Cell & tissue research 111 (1970), S. 32-50 
    Details
    ISSN: 1432-0878
    Keywords: Subcommissural organ ; Toads ; Basal secretion ; Fine structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The basal processes of the subcommissural ependymal cells contain filaments, microtubules, mitochondria and numerous pale and dense secretory granules. Both types of secretory granules are more numerous in the dilated portions of the ependymal processes. It is postulated that the periodical dilatations filled with secretory granules are responsible for the “rosary” appearance of the ependymal processes when stained with aldehyde fuchsin or chrome alum-hematoxylin. The ependymal processes of some ependymal subcommissural cells end on the external limiting membrane which covers the brain surface. The ependymal endings contain, among other structures, secretory granules and cisternae of the rough endoplasmic reticulum; this suggests that the secretory material may be locally synthetized. The presence in the subarachnoid space, close to the ependymal endings, of a particular type of blood capillaries supports the possibility of a vascular release of the secretory material present in the ependymal endings. The processes of other subcommissural ependymal cells end on blood capillaries localized in the subependymal neuropile. These capillaries have a distinctive perivascular space, where the external perivascular basement membrane is covered by a continuous “cuff” formed by ependymal endings containing secretory granules. Here again, the vascular release of the ependymal secretion seems very likely. Lastly, a third group of ependymal processes end on cavities lined by a basement membrane. It is thought that these cavities are “prolongations” of the perivascular space of the subependymal capillaries; this would contribute to establish numerous ependymo-vascular connections despite the scarce number of blood vessels. Some evidence supporting the possibility that the ependymal cells of the subcommissural organ are innervated is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00342099
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  • 9
    Electronic Resource
    Electronic Resource
    The effects of adenohypophysectomy on the hypothalamic-hypophysial neurosecretory system and the adrenal gland of the toad Bufo arenarum Hensel (1967)
    Springer
    Cell & tissue research 80 (1967), S. 93-107 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effects of adenohypophysectomy were studied on the hypothalamichypophysial neurosecretory system and the adrenal glands of Bufo arenarum Hensel. An increase in vascularization of the pars intermedia was found and the neurosecretory material (NSM) in the glandular region of the median eminence disappeared. Its reappearance later was accompanied by hypertrophy of the pars intermedia; differentiated chromophil cells appeared in the pars intermedia around the vessels and, at the same time, the adrenal reverted to normal. These findings are interpreted as hypertrophy and differentiation of the pars intermedia with replacement, at least partly, of the functions of the pars distalis. The probable mechanism of differentiation and the functions of chromophil cells of the pars intermedia are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331479
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  • 10
    Electronic Resource
    Electronic Resource
    Ultrastructure and immunocytochemistry of neurons in the supraoptic and paraventricular nuclei of the lizard Liolaemus cyanogaster (1980)
    Springer
    Cell & tissue research 207 (1980), S. 463-477 
    Details
    ISSN: 1432-0878
    Keywords: Hypothalamus ; Neurosecretion ; Ultrastructure ; Neurophysin ; Lizard
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The supraoptic (SON) and paraventricular (PVN) nuclei of the lizard Liolaemus cyanogaster c. were studied by use of histochemical, immunocyto-chemical and electron microscopic methods. The immunofluorescence staining for neurophysin was applied to methacrylate-embedded material before and after treatment of the sections with urea and trypsin. Pseudoisocyanine was applied to sections previously used for immunocytochemistry. The ultrastructural study showed that the SON and PVN neurons possess neurosecretory granules (nsg), distributed throughout the perikaryon, and large (2 to 12 μm) electron-dense droplets located within dilatations of the cisternae of the rough endoplasmic reticulum. Whereas the perikaryon (nsg) and the secretory droplets are stainable with pseudoisocyanine, only the former displays immunoreactivity for neurophysin. However, after treating the sections with urea and trypsin, the same secretory droplets become immunoreactive. It is suggested that the secretory droplets are sites of storage for the precursor of neurophysin, and that the tryptic digestion either triggers its conversion into neurophysin or exposes its immunoreactive sites. Based on the ultrastructure and the histochemical behavior of the secretory droplets, it is also postulated that they contain, in addition to peptides, a glycoprotein component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224620
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