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  • Ultrastructure  (7)
  • Springer  (7)
  • American Geophysical Union
  • American Society of Hematology
  • BioMed Central
  • Blackwell Publishing Ltd
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Publisher
  • Springer  (7)
  • American Geophysical Union
  • American Society of Hematology
  • BioMed Central
  • Blackwell Publishing Ltd
  • 1
    ISSN: 1432-0878
    Keywords: Ovary ; Steroid-secreting cells ; Ultrastructure ; Chorionic gonadotropin ; Chicken
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructural characteristics of the ovarian medulla of the newly hatched white leghorn chick were studied in control animals and compared with chicks that were treated with human chorionic gonadotropin during embryonic development. The ovarian medulla was mainly occupied by epithelial cells which formed cords or islets surrounded by a basal lamina. Within this epithelial compartment, steroidogenic cells, poorly differentiated cells and a lacunary system could be recognized. When chicks were treated with human chorionic gonadotropin, steroidogenic cells became discernible; there was an increment in the amount of cytoplasm and the area of mitochondria. Poorly differentiated cells exhibited signs of stimulation, and transitional images suggested the transformation of these cells into steroidogenic cells. The epithelial cells of the lacunar system also displayed stimulated cytoplasmic organelles. Evidence was supplied suggesting that relatively undifferentiated cells persist in the ovarian medulla until hatching and can develop into steroidogenic cells under gonadotropic stimulation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 31 (1980), S. 93-108 
    ISSN: 1432-0827
    Keywords: Calculus ; Ultrastructure ; Apatite ; Transmission ; Scanning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Using transmission and scanning electron microscopy, we have studied the ultrastructure of a number of urinary calculi, mainly composed of calcium phosphate. Three fundamental kinds of calcium phosphates were detected: nonstoichiometric carbonate apatite, nonhexagonal octacalcium phosphate, and calcium-magnesium whitlockite. The influence that the organic matter, substitutions in the phosphate lattice of CO3 and Mg, and apatitic stoichiometry have on the ultrastructure of the calcium phosphate calculi has been detailed. An originating apatitic unity named U2 is assumed to be the responsible for all the different structures of calcium apatites appearing in renal calculi. On the basis of our observations, a mechanism whereby apatites grow is postulated; magnesium functions as an inhibitor for the growing mechanism.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 199 (1979), S. 519-528 
    ISSN: 1432-0878
    Keywords: Filum terminale ; Spinal cord ; Glial cells ; Ultrastructure ; Frog (Rana pipiens)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The filum terminale, or terminal portion of the spinal cord, was studied in normal adult frogs (Rana pipiens) by means of light and electron microscopy. Astroglial cells are the predominant elements in this region. The rostral portion of the filum terminale consists mainly of (1) a peripheral dense ring of myelinated and some unmyelinated nerve fibers, and processes of astrocytes terminating at the subpial space; (2) an intermediate zone, in which astrocytes are the main cellular elements in addition to a few degenerated neurons; and (3) a central region where the central canal is lined by dark and light ependymal cells. In the caudal portion of the filum terminale, the amount of neuropil is greatly reduced. This region is formed mainly by astrocytic glial cells and very few neuronal elements. The central canal in the caudal portion is located ventrally and contains a lining consisting almost exclusively of dark ependymal cells.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 282 (1995), S. 363-366 
    ISSN: 1432-0878
    Keywords: Pineal organ ; Pinealocytes ; Secretory rudimentary photoreceptors ; Ultrastructure ; Didelphis albiventris (Marsupialia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We report the presence of atypical pinealocytes as components of epiphyseal follicles in the adult South American opossum Didelphis albiventris. Their main characteristic is a bulbous-shaped apical cytoplasmic extension which protrudes towards the follicular lumen among the microvilli and cilia of neighbouring ependymal cells. They resemble the photoreceptor-like pinealocytes of sauropsids and developing photoreceptors in the retina of newborn mammals. Morphological characteristics enable us to classify them as cells of the receptor line.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 282 (1995), S. 363-366 
    ISSN: 1432-0878
    Keywords: Key words: Pineal organ ; Pinealocytes ; Secretory rudimentary photoreceptors ; Ultrastructure ; Didelphis albiventris (Marsupialia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. We report the presence of atypical pinealo-cytes as components of epiphyseal follicles in the adult South American opossum Didelphis albiventris. Their main characteristic is a bulbous-shaped apical cytoplasmic extension which protrudes towards the follicular lumen among the microvilli and cilia of neighbouring ependymal cells. They resemble the photoreceptor-like pinealocytes of sauropsids and developing photoreceptors in the retina of newborn mammals. Morphological characteristics enable us to classify them as cells of the receptor line.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1615-6102
    Keywords: Root meristems ; Cell plate ; Ultrastructure ; 2,6-dichlorobenzonitrile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of 2,6-dichlorobenzonitrile on cytokinesis of meristematic cells of onion root during both treatment and recovery has been studied by electron microscopic techniques. 2,6-dichlorobenzonitrile interferes with cell plate formation in such a way that Golgi apparatus vesicles of treated cells appear to be different than controls and seem to coalesce as anomalous partial cell plates. During recovery, an apparently normal progression of cytokinesis is observed and abnormal portions of the cell plate are retained. Nuclear constrictions are observed frequently during recovery as a result of temporal alterations in cytokinesis. Our results show that 2,6-dichlorobenzo-nitrile induces anomalous and/or incomplete cell plates, which might be caused by an altered function of Golgi apparatus.
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  • 7
    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
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