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. · Nov 2005
Cardiac arrest/cardiopulmonary resuscitation augments cell-mediated immune function and transiently suppresses humoral immune function.
Immune system activation has implications for cerebrovascular health, but little is known about the function of the immune system after a major cerebrovascular event, such as cardiac arrest and cardiopulmonary resuscitation (CA/CPR). Cardiac arrest and cardiopulmonary resuscitation damages the hippocampus, an important component of the hypothalamic-pituitary-adrenal (HPA) axis, and alterations in HPA axis activity can affect immune function. We tested the hypothesis that CA/CPR (approximately 8 mins) would cause HPA axis dysregulation and alter the delayed type hypersensitivity (DTH) response to antigenic challenge. ⋯ Cardiac arrest and cardiopulmonary resuscitation-induced neuronal damage resulted in a persistent elevation of blood corticosterone concentration and a concomitant augmentation of the DTH response to antigenic challenge. Furthermore, immune activation before CA/CPR decreased survival after global ischemia. These data highlight the potential impact of neuronal damage on cell-mediated immune function and the role of humoral immune activation in outcome after global ischemia.
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J. Cereb. Blood Flow Metab. · Nov 2005
Interaction between astrocytes and neurons studied using a mathematical model of compartmentalized energy metabolism.
Understanding cerebral energy metabolism in neurons and astrocytes is necessary for the interpretation of functional brain imaging data. It has been suggested that astrocytes can provide lactate as an energy fuel to neurons, a process referred to as astrocyte-neuron lactate shuttle (ANLS). Some authors challenged this hypothesis, defending the classical view that glucose is the major energy substrate of neurons, at rest as well as in response to a stimulation. ⋯ Simulation results can be divided between two groups, depending on the relative neuron versus astrocyte stimulation. If this ratio is low, ANLS is observed during all the stimulus and poststimulus periods (continuous ANLS), but a high ratio induces ANLS only at the beginning of the stimulus and during the poststimulus period (triphasic behavior). Finally, our results show that current experimental data on lactate kinetics are compatible with the ANLS hypothesis, and that it is essential to assess the neuronal and astrocytic NADH/NAD+ ratio changes to test the ANLS hypothesis.
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J. Cereb. Blood Flow Metab. · Nov 2005
Influence of therapeutic hypothermia on matrix metalloproteinase activity after traumatic brain injury in rats.
Recent evidence suggests that matrix metalloproteinases (MMPs) contribute to acute edema and lesion formation following ischemic and traumatic brain injuries (TBI). Experimental and clinical studies have also reported the beneficial effects of posttraumatic hypothermia on histopathological and behavioral outcome. The purpose of this study was to determine whether therapeutic hypothermia would affect the activity of MMPs after TBI. ⋯ Hypothermic treatment, however, did not affect the delayed activation of MMP-2. Clarifying the mechanisms underlying the beneficial effects of posttraumatic hypothermia is an active area of research. Posttraumatic hypothermia may attenuate the deleterious consequences of brain trauma by reducing MMP activation acutely.
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J. Cereb. Blood Flow Metab. · Oct 2005
Comparative StudyMR perfusion and diffusion in acute ischemic stroke: human gray and white matter have different thresholds for infarction.
It is thought that gray and white matter (GM and WM) have different perfusion and diffusion thresholds for cerebral infarction in humans. We sought to determine these thresholds with voxel-by-voxel, tissue-specific analysis of co-registered acute and follow-up magnetic resonance (MR) perfusion- and diffusion-weighted imaging. Quantitative cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and apparent diffusion coefficient (ADC) maps were analyzed from nine acute stroke patients (imaging acquired within 6 h of onset). ⋯ The MTT threshold for infarction in GM is lower (P=0.014) than for WM (6.8 secs in GM and 7.1 secs in WM). A single common threshold applied to both tissues overestimates tissue at risk in WM and underestimates tissue at risk in GM. This study suggests that tissue-specific analysis of perfusion and diffusion imaging is required to accurately predict tissue at risk of infarction in acute ischemic stroke.
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J. Cereb. Blood Flow Metab. · Sep 2005
Clinical TrialA novel method to derive separate gray and white matter cerebral blood flow measures from MR imaging of acute ischemic stroke patients.
Perfusion-weighted imaging (PWI) measures can predict tissue outcome in acute ischemic stroke. Accuracy might be improved if differential tissue susceptibility to ischemia is considered. We present a novel voxel-by-voxel analysis to characterize cerebral blood flow (CBF) separately in gray (GM) and white matter (WM). ⋯ The difference in the reversed region approached statistical significance. In core, GM and WM CBF did not differ. The results suggest separate ischemic thresholds for GM and WM in stroke penumbra.