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  • Spinal cord  (2)
  • Springer  (2)
  • American Geophysical Union (AGU)
  • 1975-1979  (2)
  • 1975  (2)
  • 1
    Electronic Resource
    Electronic Resource
    An investigation of the foetal rat spinal cord (1975)
    Springer
    Cell & tissue research 158 (1975), S. 251-268 
    Details
    ISSN: 1432-0878
    Keywords: Synapse development ; Spinal cord ; Foetal rat-Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Electrophysiological and ultrastructural studies were carried out on foetal rat spinal cord. The electrophysiological observations allowed certain identification of the site of second order sensory neurones, regions of the most functionally mature ventral horn cells and the adequacy of reflex conduction at 18 days. In the ultrastructural studies we made use of these identifications. No definitive synapses were found at 13–14.5 days in dorsal and ventral horn neuropil though some possible precursors were seen. Immature axodendritic synapses are found first in both dorsal and ventral marginal zones at 14.5 days and in both dorsal and ventral neuropil regions at 15–16 days. At 17 days there is an abrupt increase in frequency and maturity of synaptic profiles in all regions; synapses containing pleomorphic populations of vesicles are first seen in the ventral horn neuropil at this age as rare axo-somatic synapses. At 18 days the synapses population increases and multiple contacts involving axons or dendrites commonly occur. Furthermore, axo-somatic synapses are seen for the first time in the dorsal horn. From 20 days onwards mature synapses were commonplace and all earlier stages can be found. In addition axo-dendritic synapses with pleomorphic populations of vesicles were first seen in the dorsal horn. Axo-somatic synapses in the dorsal horn remained immature in appearance at this time. These findings are discussed particularly in relationship to previous studies by others on the development of motility in the rat. It appears that in the rat lumbar cord, onset of formation of different synapse types in specific locations precedes the onset of possible related function by 1–2 days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219964
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  • 2
    Electronic Resource
    Electronic Resource
    An investigation of the foetal rat spinal cord (1975)
    Springer
    Cell & tissue research 158 (1975), S. 241-249 
    Details
    ISSN: 1432-0878
    Keywords: Synapse development ; Spinal cord ; Foetal rat ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural studies on the foetal rat spinal cord show that during synaptogenesis there is difficulty in recognizing true synaptic precursors. Asymmetric densities are found at unusual sites forming, for example, somato-dendritic and somato-somatic junctions. They are also found between neurons and possible glial processes. Symmetric densities occur between nerve cells but may be confused with desmosomes. Profiles exhibiting membrane density, cleft material and 50 nm vesicles, which are the most reliable indicators of presumptive synapses, are found between neurones, but also at junctions between neurones and what may be glial processes. The picture is further confused by the presence of degenerating axodendritic synapses at early foetal stages. Caution must be exercised in defining an apparent synapse or precursor in foetal cord as that of a presumptive functional synapse because of the observed degenerating profiles and because to our knowledge, somato-somatic, somatodendritic, and neurono-glial synapses have not been observed in adult cord. It is not known whether these structures are an unwanted consequence of development or play a role in guiding development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219963
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    Paper (German National Licenses)
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