Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism
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J. Cereb. Blood Flow Metab. · Mar 2012
Experimental subarachnoid hemorrhage causes early and long-lasting microarterial constriction and microthrombosis: an in-vivo microscopy study.
Early brain injury (EBI) after subarachnoid hemorrhage (SAH) is characterized by a severe, cerebral perfusion pressure (CPP)-independent reduction in cerebral blood flow suggesting alterations on the level of cerebral microvessels. Therefore, we aimed to use in-vivo imaging to investigate the cerebral microcirculation after experimental SAH. Subarachnoid hemorrhage was induced in C57/BL6 mice by endovascular perforation. ⋯ Approximately 30% of constricted arterioles were occluded by microthrombi and the frequency of arteriolar microthrombosis correlated with the degree of constriction (r(2)=0.93, P<0.03). The current study demonstrates that SAH induces microarterial constrictions and microthrombosis in vivo. These findings may explain the early CPP-independent decrease in cerebral blood flow after SAH and may therefore serve as novel targets for the treatment of early perfusion deficits after SAH.
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J. Cereb. Blood Flow Metab. · Mar 2012
ReviewCerebral microinfarcts: a systematic review of neuropathological studies.
Vascular cognitive impairment is an umbrella term for cognitive dysfunction associated with and presumed to be caused by vascular brain damage. Autopsy studies have identified microinfarcts as an important neuropathological correlate of vascular cognitive impairment that escapes detection by conventional magnetic resonance imaging (MRI). As a frame of reference for future high-resolution MRI studies, we systematically reviewed the literature on neuropathological studies on cerebral microinfarcts in the context of vascular disease, vascular risk factors, cognitive decline and dementia. ⋯ They are found in all brain regions, possibly more so in the cerebral cortex, particularly in watershed areas. Reported sizes vary from 50 μm to a few mm, which is within the detection limit of current high-resolution MRI. Detection of these lesions in vivo would have a high potential for future pathophysiological studies in vascular cognitive impairment.
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J. Cereb. Blood Flow Metab. · Mar 2012
Near-infrared spectroscopy assessment of cerebral oxygen metabolism in the developing premature brain.
Little is known about cerebral blood flow, cerebral blood volume (CBV), oxygenation, and oxygen consumption in the premature newborn brain. We combined quantitative frequency-domain near-infrared spectroscopy measures of cerebral hemoglobin oxygenation (SO(2)) and CBV with diffusion correlation spectroscopy measures of cerebral blood flow index (BF(ix)) to determine the relationship between these measures, gestational age at birth (GA), and chronological age. We followed 56 neonates of various GA once a week during their hospital stay. ⋯ SO(2) correlates with chronological age (r=-0.54, P value ≤0.001) but not with PMA (r=-0.07), whereas BF(ix) and rCMRO(2) correlate better with PMA (r=0.37 and 0.43, respectively, P value ≤0.001). Relative CMRO2 during the first month of life is lower when GA is lower. Blood flow index and rCMRO(2) are more accurate biomarkers of the brain development than SO(2) in the premature newborns.
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J. Cereb. Blood Flow Metab. · Mar 2012
Sequential activation of hypoxia-inducible factor 1 and specificity protein 1 is required for hypoxia-induced transcriptional stimulation of Abcc8.
Cerebral ischemia causes increased transcription of sulfonylurea receptor 1 (SUR1), which forms SUR1-regulated NC(Ca-ATP) channels linked to cerebral edema. We tested the hypothesis that hypoxia is an initial signal that stimulates transcription of Abcc8, the gene encoding SUR1, via activation of hypoxia-inducible factor 1 (HIF1). In the brain microvascular endothelial cells, hypoxia increased SUR1 abundance and expression of functional SUR1-regulated NC(Ca-ATP) channels. ⋯ Luciferase reporter assays studying Sp1 promoters of three species, and chromatin immunoprecipitation analysis in rats after cerebral ischemia, indicated that HIF binds to HIF-binding sites on the Sp1 promoter to stimulate transcription of the Sp1 gene. We conclude that sequential activation of two transcription factors, HIF and Sp1, is required to stimulate transcription of Abcc8 following cerebral ischemia. Sequential gene activation in cerebral ischemia provides a plausible molecular explanation for the prolonged treatment window observed for inhibition of the end-target gene product, SUR1, by glibenclamide.
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J. Cereb. Blood Flow Metab. · Feb 2012
CommentCortical spreading ischemia in the absence of proximal vasospasm after aneurysmal subarachnoid hemorrhage: evidence for a dual mechanism of delayed cerebral ischemia.
There are longstanding inconsistencies in the evidence thought to link vasospasm in the major branches of the Circle of Willis with delayed cerebral ischemia and poor outcome from aneurysmal subarachnoid hemorrhage (aSAH). The demonstrations, first in the laboratory, and more recently in patients with aSAH, of cortical spreading ischemia based on an abnormal response of the cerebral microcirculation to spreading depolarization offer an additional possible mechanism for delayed ischemia. That such events can occur in the substantial absence of proximal vasospasm is compatible with this concept, but the preliminary evidence needs support from more extensive studies.