ISSN:
1432-0878
Keywords:
Ontogenesis
;
Capillary
;
Basement membrane
;
Cerebral cortex (Rat.)
;
Light- and Electromicroscopy
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The vascularization of the parietal-temporal region of the cerebral hemispheres has been studied in a total of 50 rats from day 11 of gestation up to adults. The first extracerebral vessels constituting the primary perineural vascular network and the first intracerebral vessels on day 12–14 of gestation show sinusoid characteristics, i.e. irregular thickness of the endothelial wall perforated by fenestrations or small holes and showing, if at all, the beginning accumulation of basement membrane (BM) material. No paired vessels have been observed which would be expected if internal vascularization of cortical anlage starts by penetrating loops. Immature capillaries developing by sprouting (and) from the preexistent vessels begin to appear at about day 15 of gestation. The further differentiation of the terminal vascular bed and the establishing of the definitive architecture is accompanied by the maturation of cortical tissue, i.e. diminution of extracellular spaces, differentiation of perivascular, astroglial and neuronal elements including the development of synapses. The continuous process of BM-formation from the first appearance until the postnatal thickening is described by four successive stages: Stage 1. Local accumulations of fine filamentous material between endothelium and opposite perivascular surfaces of sinusoids and sprouts. Stage 2. Delicate networks of filaments attached on endothelial, pericytal and adjacent glial plasma membranes (PM) of immature capillaries, plaques of lamina densa in narrow perivascular clefts. Stage 3. A thin continuous lamina densa adapted to the PM; its filaments are arranged parallel to the cell surface. In this plane they run randomly. In the lamina rara only few filaments run to the PM mainly perpendicular: stage of immature cortical capillaries. Stage 4. Thickened lamina densa, condensed filamentous pattern; narrow zone of lamina rara: stage of mature cortical capillaries. Coincidental with the rapid thickening of BM in the 3rd–4th postnatal week the characteristics of capillary growth change: The intensive sprouting is finished and the capillary length increases nearly proportionally to tissue volume later on. It is suggested that the BM plays a role in regulating differentiation and mitotic division of the adjacent cells.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00307145
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