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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purpose of this study was to explore the therapeutic time window and mechanism of tetramethylpyrazine on transient focal cerebral ischemia/reperfusion injury. Middle cerebral artery occlusion was conducted in male Sprague-Dawley rats and 20mg/kg tetramethylpyrazine was injected intraperitoneally at different time points. Neurological deficit scores and brain infarction volumes were measured 72 h after reperfusion started. The expression of thioredoxin and thioredoxin reductase were examined at 6h and at 24h after reperfusion. Our results included the findings of a significant reduction in neurological deficit scores and infarction volume in the treatment group as compared to the control group. Ischemia/reperfusion injury resulted in a decrease in the expression of thioredoxin, while tetramethylpyrazine administration greatly elevated the expression of thioredoxin-1/thioredoxin-2 mRNA and thioredoxin reductase-1/thioredoxin reductase-2 mRNA. These findings suggest that administration of tetramethylpyrazine, within a 4h time period post-transient focal stroke, may reduce cerebral ischemic reperfusion damage. Moreover, the neuroprotective effect of tetramethylpyrazine may be mediated, in part, by an increase in genetic transcription of thioredoxin.
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PMID:Therapeutic time window and mechanism of tetramethylpyrazine on transient focal cerebral ischemia/reperfusion injury in rats. 1879 5

Stroke induces a strong inflammatory reaction in the brain and depresses the immune system. We sought to assess longitudinal changes in T-cell numbers in the lymphoid organs of living mice after brain ischemia. Middle cerebral artery occlusion was carried out in transgenic mice expressing green fluorescent protein (GFP+) in the T-cell population under the control of the hCD2 locus control region. Imaging was performed by three-dimensional fluorescence molecular tomography (FMT) before and at several time points after ischemia or sham operation and in controls. At day 7, GFP+ cell content in lymphoid organs was measured postmortem by flow cytometry. GFP+ cell numbers and in vivo FMT signal intensity were reduced at day 7 after ischemia and, to a lesser extent, after sham operation. Linear regression analysis demonstrated that postmortem GFP+ cell numbers and corresponding in vivo FMT data were significantly correlated in the thymus (r2 = .65, p < .0001) and lymph nodes (r2 = .67, p < .0001). These relationships allowed inferring the number of GFP+ T cells from in vivo FMT data. The results show the time course reduction of T-cell content in the lymphoid organs of living mice, providing in vivo evidence of lymphoid organ atrophy after stroke and, to a lesser extent, after head surgery with craniectomy and dura mater opening in sham-operated mice.
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PMID:Imaging changes in lymphoid organs in vivo after brain ischemia with three-dimensional fluorescence molecular tomography in transgenic mice expressing green fluorescent protein in T lymphocytes. 1912 86

We examined the effect of type 2 diabetes on stroke-induced Alzheimer's disease-like pathological and behavioral changes in rats. Rats were treated for 2 months with high fat diet (HFD) followed by streptozotocin (STZ) injection to induce type 2 diabetes (HFD-STZ model). Middle cerebral artery occlusion (MCAO) was used to induce cerebral focal ischemia. Animals were divided into four groups: Sham-NPD, Sham-HFD-STZ, MCAO-NPD and MCAO-HFD-STZ. The results showed that HFD-STZ treatment induced obesity, hypertriglyceridemia, hypercholesterolemia, hyperinsulinemia, hyperglycemia and insulin resistance, characteristics of type 2 diabetes. The performance of rats in the Morris water maze test was impaired in MCAO-NPD and Sham-HFD-STZ rats, indicating cognitive deficits. Hippocampal caspase-3+ and beta amyloid (Abeta+) cell numbers, as well as beta-site amyloid precursor protein-cleaving enzyme (BACE1) levels and activity, increased in both groups. Moreover, HFD-STZ treatment exacerbated stroke-induced cognitive deficits, additively increased MCAO-induced activation of caspase-3, and increased levels of BACE1, C99 and Abeta. However, the level of insulin decreased in MCAO-HFD-STZ rats. These results suggested that type 2 diabetes deteriorated stroke-induced brain damage and cognitive impairment, which might be associated with increased Abeta generation and cytotoxicity. We concluded that type 2 diabetes exacerbated poststroke dementia possibly due to brain injury and synergistic generation of Abeta via activation of BACE1.
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PMID:Exacerbation of poststroke dementia by type 2 diabetes is associated with synergistic increases of beta-secretase activation and beta-amyloid generation in rat brains. 1937 2

In the present study, memantine (MN) an uncompetitive N-methyl-D-aspartate (NMDA) open channel blocker has been investigated for its suitable therapeutic time-window on the basis of its influence on behavioural and biochemical changes in rats subjected to transient focal ischemia. MN (20 mg/kg, ip) was administered at pre, during and post ischemic state and the extent of neuroprotection was compared to ascertain its therapeutic time-window in stroke treatment. Neuroprotective effect was assessed by measuring glutamate, glutamine synthetase, glutathione, Na+K+ATPase, adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide (NAD), lactate and pyruvate levels. Middle cerebral artery occlusion produced neurological deficits, anxiogenic behaviour, histological changes, increased glutamate levels along with depletion of Na+K+ATPase, energy stores such as ATP, NAD, lactate, and antioxidant glutathione. MN significantly restored glutamate, glutamine synthetase, Na+K+ATPase and lactate levels on preischemic administration. In addition, MN reversed the altered neurological and behavioural paradigms significantly and prevented the neurodegeneration on preischemic treatment. However, it failed to exert any effect on energy metabolite (ATP and NAD) levels irrespective of the treatment phase. Based on the present data, it is summarized that the suitable therapeutic time window of MN is preischemic phase in stroke and it possesses only a subjective role in reversing ischemic brain biochemical alterations preferentially in favor of neuronal homeostasis.
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PMID:Pre-ischemic treatment with memantine reversed the neurochemical and behavioural parameters but not energy metabolites in middle cerebral artery occluded rats. 1946 56

The hypoxia tracer fluorine-18 fluoromisonidazole ([18F]FMISO) and its tritiated counterpart ([(3)H]FMISO) have been used as markers of potentially salvageable brain (ischemic penumbra) after stroke. In experimental models, the dynamics and half-life of [3H]FMISO allow concurrent histology after 24 h. Our aim was to further validate these techniques, by determining the optimum tracer exposure interval to delineate ischemic penumbra, and the effects of prolonged exposure on tracer retention in permanent ischemia. Middle cerebral artery occlusion (MCAO) of varying durations was created in rats using the thread occlusion model. Autoradiography using objective thresholding to define tracer-retention volume was performed to determine the time course of tracer retention in hypoxic tissues and the duration of ongoing retention after bolus administration. An ischemic duration of < or =90 min resulted in a tracer-retention volume underestimating 'tissue at risk' (histological infarction 24 h after permanent occlusion) by >1/2. Two hour ischemia resulted in a volume equal to 'tissue at risk'. Twenty-four hour permanent ischemia resulted in tracer-retaining tissue volumes greater than final infarction. However, the use of more stringent thresholding of autoradiographic signal produced a volume of FMISO retention closely approximating infarct volume. The findings indicate that the timing of imaging is crucial, with an optimal imaging time of 2 h using the current threshold. Earlier imaging is limited by tracer dynamics with this particular agent, however autoradiography with a longer ischemic interval (permanent occlusion) is feasible with modified thresholds. These findings support a role for hypoxia tracers in providing new insight into the ischemic penumbra.
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PMID:Characterisation of the timing of binding of the hypoxia tracer FMISO after stroke. 1959 80

1. Studies have documented the proliferative effects of epidermal growth factor (EGF) on neural progenitor cells in the normal or injured brain. The effect of EGF on post-stroke cerebral expression of nestin, a marker of neural progenitor cells, has not been examined in hypertensive rats. 2. In the present study, adult renovascular hypertensive Sprague-Dawley rats underwent either real or sham middle cerebral artery occlusion (MCAO). Intracerebroventricular injections of either 1 microg EGF or vehicle (0.01 mol/L phosphate-buffered saline containing 0.1 mg/mL rat serum albumin) were made 24 and 48 h after MCAO. Then, 1, 2, 3 and 4 weeks after MCAO, the postural reflex was evaluated in a blinded fashion before rat brains were processed to determine the infarct volume plus immunoreactivity for nestin and/or glial fibrillary acidic protein (GFAP). Another group of rats was used to quantify nestin expression using western blot analysis. 3. Middle cerebral artery occlusion resulted in a focal infarct that was largest at 1 week and diminished gradually over the time. The impaired postural reflex followed a similar time-course. In addition, MCAO induced a marked increase in nestin expression in both hemispheres, with a higher expression in the right hemisphere; this change was maximal at 1 week and largely subsided at 3 or 4 weeks. Within the right hemisphere, nestin expression was most pronounced in the subventricular and peri-infarct zones. Most nestin-immunoreactive cells were also positive for GFAP. 4. Thus, EGF treatment significantly increases nestin expression, reduces infarct volume and ameliorates postural reflex impairment in adult hypertensive rats.
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PMID:Intracerebroventricular injection of epidermal growth factor reduces neurological deficit and infarct volume and enhances nestin expression following focal cerebral infarction in adult hypertensive rats. 1967 37

Middle cerebral artery occlusion (MCAO) is a popular model in experimental stroke research and causes prominent ischemic damage in the forebrain. To characterize metabolic changes induced by MCAO, we have induced permanent MCAO in mice that were implanted with a microdialysis probe in either striatum or hippocampus. Immediately after the onset of ischemia, glucose levels dropped to <10% of basal values in the striatum while they dropped to 50%, and recovered thereafter, in hippocampus. Extracellular levels of glutamate rose 80-fold in the striatum but only 10-fold, and in a transient fashion, in hippocampus. In striatum, release of acetylcholine briefly increased, then dropped to very low values. Both glycerol and choline levels increased strongly during ischemia in the striatum reflecting membrane breakdown. In hippocampus, glycerol increased transiently while the increase of choline levels was moderate. Taken together, these observations delineate metabolic changes in ischemic mouse brain with the striatum representing the core area of ischemia. In comparison, the dorsal hippocampus was identified as a brain area suitable for monitoring metabolic responses in the penumbra region.
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PMID:Metabolic and transmitter changes in core and penumbra after middle cerebral artery occlusion in mice. 1996 39

Transient ischemic attacks (TIAs) are brief neurological deficits ofcerebrovascular origin that are followed by complete clinical recovery. Although a plethora of animal models exist for ischemic stroke, a verified TIA model is lacking. We aimed to optimize such a model in mice, investigating the impact of varying durations (from 2.5 to 20 minutes) of intraluminal middle cerebral artery occlusion (MCAo). Three conditions were required to mimic clinical TIA reliably: 1) an objective demonstration of occlusion and reperfusion (assessed by laser Doppler flowmetry); 2) no permanent neurological deficit (assessed by sensorimotor neurological evaluation); and 3) no lesion at 24 hours after reperfusion (assessed by magnetic resonance imaging [MRI]). We observed high incidences of MRI lesions with MCAo durations of 15 minutes or longer. In contrast, no permanent neurological deficits or MRI lesions were observed in animals with MCAo below or equal to 10 minutes. Middle cerebral artery occlusion of 12.5 minutes rarely induced MRI lesions, but histopathologic evaluation using routine and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling staining revealed minute ischemic changes even after 2.5-minute MCAo. Abundance of necrotic and apoptotic changes gradually increased with the duration of ischemia. These results indicate that 10 minutes or shorter focal cerebral ischemia proves a suitable mouse TIA model; in addition, they indicate that MRI-negative microscopic ischemic damage may occur with even a few minutes of arterial occlusion.
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PMID:An optimized mouse model for transient ischemic attack. 2008 15

Middle cerebral artery occlusion (MCAO), which leads to focal cerebral ischemia, serves as an experimental model for brain stroke. There is a large variation in protocols and techniques using the MCAO model, which may affect the outcomes seen in different studies. The current work presents and compares the diverse responses in mitochondrial NADH and cerebral blood flow (CBF) following focal ischemia induced by the MCAO technique. Ninety-six Wistar rats underwent focal cerebral ischemia by MCAO, and monitored in the core and the penumbra using a unique Multi-Site-Multi-Parametric (MSMP) system, which measures mitochondrial NADH using the fluorometric technique, and CBF using laser Doppler flowmetry (LDF). Following MCAO, 58% of the experiments yielded expected responses, namely a decrease in CBF and an increase in NADH. However, 42% of the experiments showed six other profiles of responses, in which CBF, NADH and tissue reflectance (Ref) responded differently. These profiles included: ischemia without reperfusion, death following reperfusion, minor responses in parameters during ischemia, CBF elevation in the penumbra following MCAO, spontaneous early reperfusion and late reperfusion. These results demonstrate that MCAO is a complex model, which may lead to different responses other than the common expected outcomes, i.e. mitochondrial damage and reduced blood flow in both core and penumbra. The MSMP monitoring system may serve as an important tool in early diagnosis of successful focal cerebral ischemia, reducing the percentage of unsuccessful experiments.
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PMID:Mitochondrial function and cerebral blood flow variable responses to middle cerebral artery occlusion. 2010 93

Vascular endothelial growth factor (VEGF) is known to be an important stroke-related pathogenic factor for the formation of brain edema. We examined the therapeutic effect of human serum albumin on VEGF expression in acute ischemic stroke. Adult male Sprague-Dawley (SD) rats were subjected to Middle Cerebral Artery Occlusion (MCAO), the suture was withdrawn 2 h later, and 25% albumin (1.25 g/kg) or saline (5 ml/kg) was administered intravenously after reperfusion. The model was evaluated by 2,3,5-triphenyl-tetrazolium chloride (TTC) staining, neurological deficits and brain water content. Serum albumin level was determined. VEGF expression was studied by enzyme linked immunosorbent assay (ELISA), quantitative real-time PCR and immunohistochemistry. We demonstrated that albumin administration maintained the serum albumin at a higher level than the sham group at 6 h, 1 d, 2 d and 3 d after MCAO, and significantly improved the neurological deficits and decreased the brain water content. In addition, the strong up-regulation of VEGF expression at 6 h and 1d after MCAO can be attenuated by albumin administration. However, albumin administration had no significant depressing effect on VEGF expression at 2 d, 3 d and 5 d after MCAO in the cortex and hippocampus. Strong up-regulation of VEGF immunoreactivity was noted in the saline group in the blood-brain barrier (BBB), and in neurons surrounding the peri-infarct area and periventricular area at 24 h after MCAO. The expression of VEGF in the albumin group was much weaker. Furthermore, there were high correlations between the brain water content with the serum albumin level, with serum VEGF protein level, and with brain VEGF mRNA expression at 24 h after MCAO. In conclusion, maintaining the serum albumin at a higher level, and attenuating endogenous VEGF expression at 6 h and 1d, but not 2 d, 3 d, or 5 d after MCAO, may partially contribute to the protective effects of albumin on reduction of brain edema in the early stage of ischemia.
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PMID:Protective effect of albumin on VEGF and brain edema in acute ischemia in rats. 2013 68


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