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  • 1
    Electronic Resource
    Electronic Resource
    Light- and electron-microscopic study on the maturation of the primary portal plexus during the perinatal period in rats (1983)
    Springer
    Cell & tissue research 234 (1983), S. 179-191 
    Details
    ISSN: 1432-0878
    Keywords: Hypothalamo-hypophysial system ; Capillaries ; Ontogenesis ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The maturation of the capillaries of the primary portal plexus in rats during the perinatal period has been studied lightand electronmicroscopically. The number of capillaries covering the median eminence and of those invading the nervous tissue (capillary loops) increases significantly with age. Capillary loops were observed as early as the 18th fetal day. The mitotic divisions of the endothelial cells within the preexisting capillaries seem to be the main reason for the vascular growth. Immature capillaries with a characteristic narrow lumen are surrounded by a fuzzy basal lamina; their wall is formed by a generally expanded endothelium with rather sparse organelles and inclusions, and by minute flattened areas. The maturation of the capillary results in a progressive spread of flattened endothelium followed by an enlargment of the capillary lumen. Moreover, a rising concentration of organelles and inclusions, relatively numerous luminal microvilli, and a dense and uniform basal lamina become noticeable as capillary differentiation proceeds. These data are thought to reflect the progressive increase in the metabolic activity of the endothelium as well as the establishment of capillary patency during the perinatal period of rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217411
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Permeability of the blood-brain barrier in the median eminence during the perinatal period in rats (1983)
    Springer
    Cell & tissue research 230 (1983), S. 649-660 
    Details
    ISSN: 1432-0878
    Keywords: Hypothalamo-hypophysial system ; Capillaries ; Permeability ; Ontogenesis ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An electron microscopic study has been carried out in order to examine the permeability of the blood-brain barrier in the median eminence of perinatal rats. After several minutes, intravascularly injected electron-dense tracers (lanthanum nitrate; horseradish peroxidase, 40000 MW MW: molecular weight , ferritin, 500000 MW) pass the capillary wall, the perivascular space, and become incorporated into neurosecretory axons and basal processes of tanycytes both in fetuses and young rats. In the case of immature capillaries, the materials diffuse freely through the endothelial cells, and to a lesser extent are transferred via occasional plasmalemmal vesicles and fenestrae. As the maturation of capillaries proceeds, their permeability via plasmalemmal vesicles and fenestrae increases considerably due to a gradual rise of the number of these structures. The plasmalemmata of the differentiated endothelial cells become impermeable to all of the tracers. Only ionic lanthanum appears to penetrate through transendothelial channels and intercellular junctions between adjacent endothelial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216208
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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