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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 152 (1974), S. 477-491 
    ISSN: 1432-0878
    Keywords: Median eminence ; Tanycytes ; Extra- and transcellular transport ; Horseradish peroxidase ; Light- and Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Penetration of the median eminence and ventrolateral walls of the III ventricle by intraventricularly injected horseradish peroxidase was studied in rats. Experimental times varied between 10 to 70 min (short-term experiments) and 12 hrs to 30 days (long-term experiments). In short-term experiments, the median eminence was found to be completely stained whereas the lateral walls of the III ventricle were penetrated only up to 1 mm in depth. Spreading of the tracer takes place predominantly through the extracellular space and cellular uptake and transport do not seem to play a role during the first 70 min following the injection. In long-term experiments, the tanycytes exhibit a variety of intracellular inclusions marked by HRP precipitate. Tanycytic perikarya contain dense bodies and lipofuscin-like aggregates. Lipoprotein granules are thought to arise from these and are interpreted as lysosomal residual bodies. In tanycytic processes and perivascular endfeet, accumulations of HRP-containing tubules and polymorphous granules are encountered suggesting a transport towards the blood vessels of the portal plexus or of the arcuate and ventromedial areas, respectively. Sporadic tanycytes which are completely and evenly stained from the ventricular surface to the end of their processes were observed in the arcuate and ventromedial area. Whether this appearance can be taken as a sign of normal cell function seems doubtful. Some possible routes of transport through the median eminence—extracellular and transcellular—are summarized in a schematic drawing, taking into account the present findings and those published elsewhere in the literature.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Retina ; Amacrine cells, sustained, transient ; Horseradish peroxidase ; Inner plexiform layer ; Rutilus rutilus (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Forty amacrine cells in retinae of a cyprinid fish, the roach, were intracellularly labelled with horseradish peroxidase following electrophysiological identification as sustained depolarizing, sustained hyperpolarizing or transient units. Labelled cells were analysed by light microscopy and compared with a catalogue of amacrine cells established in a previous Golgi study on the same species. About 30% of the cell types characterized by the Golgi method were encountered in the present study. When intracellularly labelled cells were differentiated on the basis of their dendritic organization in the plane of the retina, a given electrophysiological response pattern was found to be generated by different morphological types, and vice versa. However, examination of the ramification patterns of the dendrites within the inner plexiform layer (i.e. in the radial dimension of the retina), showed that this morphological parameter of a given amacrine cell could be correlated with its light-evoked response. Several amacrine cell types were found to possess special distal dendrites which arose from the main dendritic branches and extended well over a mm in the retina. Distal dendrites were oriented tangentially with respect to the optic nerve papilla, but did not appear to be involved in any synaptic connectivity. It is concluded that the Golgi-based classification is a valuable tool for identifying intracellularly labelled amacrine cells. However, although the correlation between layering of dendrites in the inner plexiform layer and electrophysiology was generally good, additional physiological parameters would be required to determine whether more extensive parallels exist between structural and functional characteristics of amacrine cells. Alternatively, the considerable morphological diversity of amacrine cells may be of limited physiological significance.
    Type of Medium: Electronic Resource
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