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. · Jun 2007
Stroke induces ependymal cell transformation into radial glia in the subventricular zone of the adult rodent brain.
Adult ependymal cells are postmitotic and highly differentiated. Radial glial cells are neurogenic precursors. Here, we show that stroke acutely stimulated adult ependymal cell proliferation, and dividing ependymal cells of the lateral ventricle had genotype, phenotype, and morphology of radial glial cells in the rat. ⋯ Increases of radial glial cells parallel expansion of neural progenitors in the subventricular zone (SVZ). Furthermore, after stroke radial glial cells derived from the SVZ supported neuron migration. These results indicate that adult ependymal cells divide and transform into radial glial cells after stroke, which could function as neural progenitor cells to generate new neurons and act as scaffolds to support neuroblast migration towards the ischemic boundary region.
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J. Cereb. Blood Flow Metab. · May 2007
Magnetic resonance imaging evidence of cytotoxic cerebral edema in acute mountain sickness.
The present study applied T2- and diffusion-weighted magnetic resonance imaging to examine if mild cerebral edema and subsequent brain swelling are implicated in the pathophysiology of acute mountain sickness (AMS). Twenty-two subjects were examined in normoxia (21% O2), after 16 hours passive exposure to normobaric hypoxia (12% O2) corresponding to a simulated altitude of 4,500 m and after 6 hours recovery in normoxia. Clinical AMS was diagnosed in 50% of subjects during hypoxia and corresponding headache scores were markedly elevated (P<0.05 versus non-AMS). ⋯ Acute mountain sickness was also characterized by an increased brain to intracranial volume ratio (P<0.05 versus non-AMS). These findings indicate that mild extracellular vasogenic edema contributes to the generalized brain swelling observed at high altitude, independent of AMS. In contrast, intracellular cytotoxic edema combined with an anatomic predisposition to a 'tight-fit' brain may prove of pathophysiologic significance, although the increase in brain volume in hypoxia was only about 0.5% of total brain volume.
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J. Cereb. Blood Flow Metab. · May 2007
Sustained neuronal activation raises oxidative metabolism to a new steady-state level: evidence from 1H NMR spectroscopy in the human visual cortex.
To date, functional 1H NMR spectroscopy has been utilized to report the time courses of few metabolites, primarily lactate. Benefiting from the sensitivity offered by ultra-high magnetic field (7 T), the concentrations of 17 metabolites were measured in the human visual cortex during two paradigms of visual stimulation lasting 5.3 and 10.6 mins. ⋯ The lactate concentration reached the new steady-state level within the first minute of activation and came back to baseline only after the stimulus ended. The changes of the concentration of metabolites implied a rise in oxidative metabolism to a new steady-state level during activation and indicated that amino-acid homeostasis is affected by physiological stimulation, likely because of an increased flux through the malate-aspartate shuttle.
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J. Cereb. Blood Flow Metab. · May 2007
Heme oxygenase-1 stabilizes the blood-spinal cord barrier and limits oxidative stress and white matter damage in the acutely injured murine spinal cord.
We hypothesized that heme oxygenase (HO)-1, the inducible form of HO, represents an important defense against early oxidative injury in the traumatized spinal cord by stabilizing the blood-spinal cord barrier and limiting the infiltration of leukocytes. To test this hypothesis, we first examined the immunoexpression of HO-1 and compared barrier permeability and leukocyte infiltration in spinal cord-injured HO-1-deficient (+/-) and wild-type (WT, +/+) mice. Heme oxygenase was expressed in both endothelial cells and glia of the injured cord. ⋯ There was significantly greater degradation of MBP in the HO-1+/- compared with WT mice (P=0.049). Together, these findings show that HO-1 modulates oxidative stress and white matter injury in the acutely injured spinal cord. This modulation may be partially attributed to the ability of HO-1 to stabilize the blood-spinal cord barrier and limit neutrophil infiltration.
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J. Cereb. Blood Flow Metab. · May 2007
Capillary-oxygenation-level-dependent near-infrared spectrometry in frontal lobe of humans.
Brain function requires oxygen and maintenance of brain capillary oxygenation is important. We evaluated how faithfully frontal lobe near-infrared spectroscopy (NIRS) follows haemoglobin saturation (SCap) and how calculated mitochondrial oxygen tension (PMitoO2) influences motor performance. Twelve healthy subjects (20 to 29 years), supine and seated, inhaled O2 air-mixtures (10% to 100%) with and without added 5% carbon dioxide and during hyperventilation. ⋯ When SCap fell below approximately 70% with reduced flow and inspired oxygen tension, PMitoO2 decreased (P<0.001) and brain lactate release increased concomitantly (P<0.001). Handgrip strength correlated with the measured (NIRS) and calculated capillary oxygenation values as well as with PMitoO2 (r>0.74; P<0.05). These results show that NIRS is an adequate cerebral capillary-oxygenation-level-dependent (COLD) measure during manipulation of cerebral blood flow or inspired oxygen tension, or both, and suggest that motor performance correlates with the frontal lobe COLD signal.