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  • 1
    Electronic Resource
    Electronic Resource
    On the presence of reciprocal synapses in the paratympanic organ of the chicken (1989)
    Springer
    Anatomy and embryology 180 (1989), S. 175-178 
    Details
    ISSN: 1432-0568
    Keywords: Paratympanic organ ; Reciprocal synapses ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The innervation pattern of the paratympanic organ was studied by TEM. The paratympanic organ is a small tapering vesicle, typical of birds, situated in the medial wall of the tympanic cavity; it contains hair cells which are similar to type II receptors of the acoustic-lateral system; these cells are characterised by synapses which are not only afferent and efferent, as previously described, but also reciprocal with efferent fibers. Our observation revealed some efferent nerve fibers which form a relationship with hair cells containing synaptic bodies situated next to the plasma membrane and near the fibers themselves. Since synaptic bodies are commonly considered to be the site where the transmission of the impulse from the receptor to the nerve fiber takes place, our pictures suggest that the efferent fibers and hair cells may be either presynaptic or postsynaptic with respect to each other in the paratympanic organ. The hypothesis is formulated that reciprocal synapses allow interaction between hair cells, thus determining an increase in the contrast of information sent by the paratympanic organ to the CNS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00309769
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The ultrastructure of the sensory hairs of the paratympanic organ receptor cells in chicken (1996)
    Springer
    Anatomy and embryology 193 (1996), S. 569-575 
    Details
    ISSN: 1432-0568
    Keywords: Hair bundle ; Stereocilia ; Fine structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The hair bundle of the receptor cells in the paratympanic organ of the chicken was studied by TEM, after fixation in aldehydes/osmium tetroxide or in aldehydes/osmium tetroxide/tannic acid. The bundles are formed by a kinocilium and by 40–70 stereocilia. The stereocilia are linked to each other by an extensive network of filaments. Three types of these connectors are present: basal, shaft and apical; the latter consist of side-to-side and tip-to-side connectors. We observed that the shaft connectors are well-highlighted only when tannic acid was used, while the other connectors are to be found in the conventionally fixed specimens also. The tip-to-side connector consists of a filament which joins the tip of a stereocilium with the side of an adjacent taller stereocilium; we suggest that the distortion of this filament would give rise to the mechanosensory transduction. The other connectors probably serve to maintain the regular spatial arrangement of the hair bundle and the mechanical coupling of the stereocilia. Our study shows that the general conformation of the hair bundle and the stereociliary links of the hair cells in the paratympanic organ of chicken are similar to those previously described in the hair cells of the acoustico lateralis system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00187928
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Reappraisal of histogenesis in the bursal lymphoid follicle of the chicken (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 187 (1990), S. 287-302 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The development of the bursal follicle and the appearance of the follicle-associated epithelial (FAE) cell and the reticuloepithelial (REp) cell were studied. The stadied. The stages of development of the bursal follicle were observed by light and electron microscopy; an anticytokeratin monoclonal antibody was also used. At the beginning of folicle development, a mesenchymal cell cluster is observed in the tunica propria; the cluster becomes wedged in a niche of the surface epithelium, and gradually it is completely surounded by the epithelium itself, which closes under the clump of mesenchymal cells. The epithelial cells lying upon the mesenchymal clump become necrotic, and anumber of mesenchymal cells bulge out, forming the FAE cells. The epithelial cells that hav closed under the mesenchymal nodule become stratified and form the REp cells; they become star-shaped because the mdedullarylymphoid cells grow between them. Finally, the cortex in formed, possibly as a result of the migration of medullary cells before they peripheralize. it is concluded that FAE cells are not specialized It is concluded that FAE cells are not specialized epithelial cells, as they do not react to an anticytokeratin monoclonal antibody; on the contrary, they are formed by mesenchymal stemcells that bulge into the lumen and change their character after moving into the epithelium. The REp cells appear in the follicular primordium shortly after the bursal follicle begins to develop; the pronounced reactivity of the REp cells to an anticytokeratin monoclonal antibody supports the hypothesis of their epithelial origin.
    Additional Material: 47 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001870308
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    Paper (German National Licenses)
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