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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: In hypothalamic cells cultured in serum-free medium, the quantity of tyrosine hydroxylase mRNA increases after treatment with an activator of the protein kinase A pathway (8-bromoadenosine cyclic AMP, 3-isobutyl-1-methylxanthine, or forskolin) or an activator of protein kinase C (12-O-tetradecanoylphorbol 13-acetate or sn-1,2-diacylglycerol). The tyrosine hydroxylase mRNA level decreases in the cells after inhibition of protein kinase C with calphostin C or after depletion of protein kinase C by extended phorbol ester treatment. These data suggest that both protein kinase pathways regulate tyrosine hydroxylase gene expression in hypothalamic cells. As simultaneous activation of both pathways has less than an additive effect on the tyrosine hydroxylase mRNA level, they appear to be interrelated. Compared with the rapid and dramatic increase of the tyrosine hydroxylase mRNA level in pheochromocytoma cells, activation of the protein kinase A or protein kinase C pathway in the cultured hypothalamic cells induces slow changes of a small magnitude in the amount of tyrosine hydroxylase mRNA. The slow regulation of tyrosine hydroxylase gene expression in hypothalamic dopaminergic neurons corresponds to the relatively high stability of tyrosine hydroxylase mRNA (half-life = 14 ± 1 h) in these cells.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The third ventricular walls and floor of male and female mink (Mustela vison) were analyzed with comparative light microscopy, transmission and scanning electron microscopy. Distinct regional fine structural variations were noted in the appearance of the dorsal, middle third and lower portions of the ventricular wall and floor. These variations were characterized by an abrupt decrease in the density of ciliated ependymal surfaces in the middle one-third of the ventricular wall. The ventral walls and floor of the lateral and infundibular recesses displayed smoother contours with numerous bleb-like protrusions and blunt villiform processes. Occasionally multipolar neuron-like cells were observed to lie upon the floor of the infundibular recess. Speculation is raised relative to the differing functional capacities of these various ventricular areas.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 136 (1973), S. 169-176 
    ISSN: 1432-0878
    Keywords: Cerebral ventricles ; Ependyma ; Sheep ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Scanning electron microscopy of the third ventricle of sheep demonstrates areas of ciliated ependymal cells at the dorsal and middle third. The cilia of the dorsal portion of the ventricle have biconcave discs that are attached to each cilium by a slender stalk. The lower third and floor of the ventricular wall, as well as the pineal recess, are largely covered by ependymal cells that possess numerous microvilli with only a few isolated cilia scattered along cell surfaces. The infundibular recess is papillated with apical blebs of the ependymal cells that project into the lumen of the recess. Measurements of these surface elements indicate an average diameter of 0.28 μ for cilia, 0.10 μ for microvilli and 0.50 μ for the apical blebs of the infundibular recess. The functional significance of the regional differences in surface structures is discussed in relation to cerebrospinal fluid movement, ependymoabsorption and ependymosecretion.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0878
    Keywords: Fourth ventricle ; Human ; Ependyma ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Scanning electron microscopy was used to assess the ultrastructural differences exhibited by the varigated ependymal lining of the near-term human fetal 4th ventricle. The central portion of the fourth ventricular floor, including the median sulcus is punctuated by numerous clumps of cilia. The density of cilia here is not as great as that described for other regions of the human cerebral ventricular system; accordingly, underlying substructure can be noted. There are distinct differences between ependymas that line the floor of the fourth ventricle with those of the adjacent area postrema. The latter region possesses not cilia, but instead exhibits a dense knap of microvilli. The ultra-architecture of the choroid plexus is relatively similar to that of other circumventricular organs with the exception that it possesses small isolated groups of cilia as well as microvilli. These findings are discussed with respect to the dynamics of local CSF movement and flow, ependymoabsorption and ependymosecretion
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 242 (1985), S. 301-311 
    ISSN: 1432-0878
    Keywords: Luteinizing hormone-releasing hormone (LHRH) ; Tanycytes ; Glial cells ; Ependyma ; Median eminence ; Rats, mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Light-and electron-microscopic immunocytochemistry (LM-ICC and EM-ICC) were used to visualize luteinizing hormone-releasing hormone (LHRH) in fibres associated with ventricular ependyma and tanycytes of the median eminence. LM-ICC suggests that LHRH fibers appear to enter the third ventricle. However, with EM-ICC, LHRH fibers are in fact found within ependymal canaliculi formed by adjacent ependymal cells. The canaliculi contain other myelinated and unmyelinated axons in addition to immunoreactive LHRH fibers. Thin slips of ependymal and tanycyte processes project into the canaliculi and enclose axons to varying degrees. At the median eminence many LHRH fibers bend sharply downwards from their ventricular course and travel with tanycytic processes towards their common destination — the perivascular space of the hypophysial-portal vascular system. Here, EM-ICC reveals that LHRH fibers closely contact basal processes of tanycytes. Lateral processes from tanycytes form glioplasmic sheaths which surround some individual LHRH fibers. A few LHRH terminals contact the perivascular space directly but more often are separated from the perivascular space by intervening glia. It is hypothesized that: (1) glia of this region responds to the physiological state of the animal and may determine the degree of LHRH secretion by varying the extent of glial investment of LHRH terminals; and (2) may play a role during development by providing direction and support for LHRH fibers similar to that described for radial and other glial cells.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 175 (1976), S. 265-277 
    ISSN: 1432-0878
    Keywords: Median eminence ; Macaca mulatto ; High-voltage electron microscopy ; Neurosecretion ; Ependymal cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of the normal median eminence of the male rhesus monkey (Macaca mulatta) is described using high-voltage electron microscopy. Surface specializations of ependymal cells lining the infundibular recess included cilia, apical extrusions, and microvilli. Supraependymal cells were predominantly macrophage-like, but examples of lymphocytic types were also seen. Tanycytes had long, branching, basal processes filled with numerous microtubules, some lipid droplets, and granules. The zona interna was composed of large unmyelinated neurosecretory fibers. A few myelinated fibers were also seen, but their character as neurosecretory fibers could not be established. The zona externa was composed of densely-packed profiles of neurosecretory fibers of small diameter, was well-vascularized and contained the terminations of tanycytes. Perivascular glial cells, vesiculated elements, pituicytes, and cellular elements common to connective tissue were observed. The intricate relationships between both the cellular and fibrous elements of the median eminence can be appreciated with the capability of high-voltage electron microscopy to discern ultrastructure in sections 10 times thicker than those used for low-voltage electron microscopy. The median eminence of this primate species has an ultrastructural organization similar to that described for most other species.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0878
    Keywords: LRF ; Hypothalamic localization ; Rat ; Ependyma ; Glia ; Light and electron microscopic Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Light and electron microscopic autoradiographic analysis of the medial basal hypothalamus of rat brains incubated for 30 and 60 minutes in tritiated luteinizing releasing factor (3H-LRF) revealed selective uptake in the form of silver grains over specialized ependyma (tanycytes) and perivascular glial cells in the palisade-contact zone of the median eminence. The functional capacity of tanycytes and glia are discussed in light of these data.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 150 (1974), S. 389-397 
    ISSN: 1432-0878
    Keywords: Choroid plexus ; Human fetus ; Modifications during development ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructural organization of the human fetal choroid plexus was assessed with scanning electron microscopy. The membranous modifications of choroidal ependymal cells differ remarkably between 11 and 20 weeks of intrauterine development and suggest a variable functional capacity at different times of ontogenesis. Based upon existing data coupled with the ultra-architectural organization of cilia, clavate and linear microvilli are seen with scanning electron microscopy, a multiple functional role is hypothesized for choroidal ependymal cells.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 178 (1977), S. 111-127 
    ISSN: 1432-0878
    Keywords: Rat magnocellular neurosecretion ; Neurophysin ; Vasopressin ; Choroid plexus ; Cerebrospinal fluid ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Neurosecretory pathways were examined in normal male rats by the use of the immunoperoxidase technique for the localization of neurophysin in Bouin-fixed, deparaffinized sections. Using this technique two projections of extrahypothalamic neurosecretory fibers can be traced to the sites of origin of the choroid plexuses of both horns of the lateral ventricles. Neurophysin-containing axons originating primarily from the paraventricular field course dorsolaterad to enter the choroid fissure of the dorsal horn. A caudally directed group of fibers course ventrolaterad to enter the ventral horn choroid fissures. The supraoptic nuclear field is the primary contributor to the latter group. Scattered neurosecretory neurons are found in association with both pathways, usually in contact with blood vessels supplying the choroid plexuses, or in the telencephalic subependymal stroma. Neurosecretory fibers and terminals occur within the choroid fissures and juxtaventricular neuropil. The neurosecretory terminals in the choroid fissures appear as Herring-body type neurohemal organs; in the neuropil they appear as punctate peri-neuronal densities suggestive of synaptic contacts. These morphologic findings are discussed in relation to reports indicating the presence of antidiuretic, vasopressin-like activity in cerebrospinal fluid and choroid plexus extracts together with ultrastructural evidence supportive of vasopressin-mediated transchoroidal cerebrospinal fluid absorption. These results and those of others indicate the possible involvement of the neurosecretory system in the regulation of brain interstitial-ventricular cerebrospinal fluid dynamics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 178 (1977), S. 129-141 
    ISSN: 1432-0878
    Keywords: Choroid plexus ; Vasopressin ; Neurosecretion ; Rat ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Light and electron microscopic examination of choroid plexuses from lateral ventricles of water-deprived and subcutaneously or intravenously vasopressin administered rats reveal morphologic changes typical for vasopressin responsive fluid transporting epithelia during hormonal stimulation. Ultrastructural changes noted in both dehydrated and vasopressin treated animals included: the frequent occurrence of choroidal “dark” cells, dilatation of the lateral and basal intercellular spaces, increased vacuolization of the apical cytoplasm, and a change in microvillar conformation from the normal clavate type to those with a filiform shape. On the basis of the ultrastructural changes observed it is proposed that the choroid plexus be regarded as a target tissue for vasopressin. These findings indicated that a vasopressinmediated transchoroidal cerebrospinal fluid absorption capability exists.
    Type of Medium: Electronic Resource
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