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  • 1
    ISSN: 1432-0533
    Keywords: Cerebral ischemia ; Blood-brain-barrier ; Cerebral blood flow ; Reactive hyperemia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The behavior of the blood-brain barrier (BBB) was studied in cats following release after 1-h middle cerebral artery (MCA) occlusion. The regional cerebral blood flow (rCBF) was determined by hydrogen clearance method in the caudate nucleus and the cerebral cortex. The BBB was assayed with Evans blue (EB) tracer and by immunohistochemical peroxidaseantiperoxidase (PAP) method. Following release of MCA occlusion, there were two openings of the BBB, separated by a refractory period. The first opening, occurred shortly after recirculation; this was associated with rCBF below 15 ml/100 g/min during the ischemic period and a pronounced reactive hyperemia promptly following release of MCA occlusion. A refractory period of the BBB was indicated by the absence of EB leakage in cats injected with the tracer 30 min before killing at 3 h after recirculation, although the rCBF values in these animals were even lower (6±1 ml/100 g/min) during occlusion, and all of them showed a pronounced hyperemia after recirculation. The occurrence of the previous BBB opening in these animals was confirmed by the PAP staining. The second opening of the BBB was observed at 5 and 72 h after recirculation in cats which were injected with EB 30 min before killing, and which showed rCBF below 15 ml/100 g/min during occlusion, followed by a pronounced reactive hyperemia. No EB extravasations were observed at any time in cats in which the rCBF during occlusion was above 15 ml/100 g/min and which failed to show a marked reactive hyperemia.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0533
    Keywords: Cerebral ischemia ; Brain edema ; Cerebral microcirculation ; Hypoperfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three transient episodes of 5 min ischemia spaced at 1-h intervals were produced in Mongolian gerbils by bilateral carotid artery occlusion with an implanted vascular occlusion device. The interval of 1 h was chosen to allow for the development of postischemic hypoperfusion between the ischemic episodes. Three minutes and 1 h after each ischemic episode, and 6 and 24 h after the third occlusion, Evan's blue (EB) was injected intravenously to trace circulating blood, and the number of perfused capillaries was determined in various brain regions by fluorescence microscopy. Brain edema was evaluated by measuring specific gravity in tissue samples taken from adjacent areas. Repetitive ischemia caused progressively increasing brain edema and a progressive reduction of the number of perfused capillaries. Immediately after each ischemic episode, transient recruitment of capillaries occurred, thus excluding noreflow as a main pathogenetic factor of microcirculatory disturbances. The pattern of microcirculation 6 and 24 h after the last occlusion revealed a redistribution of circulating blood, characterized by a reduction in the number of EB-filled capillaries associated with a noticeable dilatation of the larger vascular channels. Our studies suggest a close interrelationship between post-ischemic microcirculatory hypoperfusion and the development of brain edema, the degree and extent of which progresses with the repetition of ischemic episodes when they are carried out during the periods of hypoperfusion.
    Type of Medium: Electronic Resource
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