Temporal evolution and spatial distribution of the diffusion constant of water in rat brain after transient middle cerebral artery occlusion

The regional distribution and temporal evolution of the diffusion coefficient (D_w) of water in rat brain was measured during and after transient middle cerebral artery (MCA) occlusion. Male Wistar rats (n = 14) were subjected to 2 h of middle cerebral artery occlusion, induced by intracarotid insertion of a filament. Diffusion (n = 14) and perfusion (n = 7) weighted magnetic resonance imaging were performed before, and at various time points after MCA occlusion, ranging from 30 min up to 7 days. Our data demonstrate that the temporal profiles of D_w differ between the severely and the least damaged regions of tissue. In the core of the lesion, where the tissue evolved to necrosis, D_w declined significantly (P < 0.001) within 0.5 h after onset of ischemia, and remained depressed until 24 h after withdrawal of the suture. However, no statistically significant decline in D_w was found in the perifocal regions containing morphologically intact cells. Perfusion MRI qualitatively exhibited a hypoperfusion and reperfusion during, and after 2 h MCA occlusion, respectively. A significant (r ≥ 0.71, P < 0.01) correlation was found between ΔD_w (the difference in D_w between the ipsilateral ischemic and homologous contralateral control regions) obtained immediately before withdrawal of the suture (2 h of ischemia) and at specific early time points after withdrawal of the suture, and the degree of ischemic cell damage. No significant (P > 0.01) correlation was detected at an early time points of ischemia or at other time points after withdrawal of the suture. Our data suggest that values for ΔD_w obtained at 2 h, during the period of MCA occlusion and at specific early time points after withdrawal of the suture, are highly correlated to the histological outcome of the tissue, and both ΔD_w and the temporal profile of D_w may reflect underlying biophysical changes in the tissue evoked by the ischemic insult.     

Enhanced ornithine decarboxylase activity is associated with attenuated rate of damage evolution and reduction of infarct volume in transient middle cerebral artery occlusion in the rat

Ornithine decarboxylase (ODC) transgenic and alpha-difluoromethyl ornithine (DFMO)-treated rats were exposed to transient middle cerebral occlusion (MCAO) to examine the role of intraischaemic ODC-activity on the evolution of ischaemia-reperfusion damage. Magnetic resonance imaging (MRI) data show that the damage develops slower in ODC transgenic than in DFMO-treated rats, which is not caused by a difference in perfusion. Furthermore, infarct volumes are smaller in the former animals one day later. These data support the idea of endogenous neuroprotective action of ODC.     

The effects of dizocilpine (MK-801), phencyclidine, and nimodipine on infarct size 48 h after middle cerebral artery occlusion in the rat

The effects of the calcium channel blocker nimodipine and the non-competitive NMDA-antagonists MK-801 and phencyclidine (PCP) on infarct size 48 h after occlusion of the middle cerebral artery (MCA-O) were evaluated in the rat. Nimodipine was given at a dose of 0.3 mg/kg s.c. 30 min prior and 8, 16, and 24 h after MCA-O. MK-801 (1 mg/kg i.p. or 10 mg/kg i.p.) or PCP (0.3, 1.0, 3.0, 10, or 30 mg/kg i.p.) were administered 30 min prior to ischemia. In additional experiments 30 mg/kg PCP was given 1, 3, or 5 h post ischemia. Nimodipine and 1 mg/kg MK-801 reduced cortical infarct volumes significantly by 50% and 55%, respectively, while cortical infarct size fell by 32% and total infarct volume was not altered significantly after administration of 10 mg/kg MK-801. Pretreatment with 10 or 30 mg/kg PCP reduced cortical infarction by 47-53% and total infarct volumes by 39-42%. Posttreatment with PCP was effective if started at 1 or 3 h post ischemia.     

Identification of cerebral ischemic lesions in rat using eigenimage filtered magnetic resonance imaging

An accurate noninvasive time-independent identification of an ischemic cerebral lesion is an important objective of magnetic resonance imaging (MRI). This study describes a novel application of a multiparameter MRI analysis algorithm, the Eigenimage (EI) filter, to experimental stroke. The EI is a linear filter that maximizes the projection of a desired tissue (ischemic tissue) while it minimizes the projection of undesired tissues (nonischemic tissue) onto a composite image called an eigenimage. Rats (n=26) were subjected to permanent middle cerebral artery occlusion. T2- and T1-weighted coronal MRI were acquired on separate groups of animals. The animals were immediately sacrificed after each imaging session for histopathological analysis of tissue at 4-8 h, 16-24 h, and 48-168 h after stroke onset. Lesion areas from MRI were defined using EI. The EI defined lesion areas were coregistered and warped to the corresponding histopathological sections. The ischemic lesion as defined by EI exhibited ischemic cell damage ranging from scattered acute cell damage to pan necrosis. Ischemic cellular damage was not detected in homologous contralateral hemisphere regions. EI lesion areas overlaid on histopathological sections were significantly correlated (r=0.92, p<0.05) acutely, (r=0.98, p<0.05) subacutely, and (r=0.99, p<0.05) chronically. These data indicate that EI methodology can accurately segment ischemic damage after MCA occlusion from 4-168 h after stroke.     

Neuroprotection of a cocktail therapy involving anti-intercellular adhesion molecule 1 antibody and insulin-like growth factor 1 in treatment of cerebral ischemia/reperfusion injury in cats--Nuclear magnetic resonance examination and pathological validation

BACKGROUND： The pathophysiological mechanisms of ischemia are extremely complicated. It is difficult to confirm and maintain the therapeutic effects if only one neuroprotective agent is used. It is hypothesized that a cocktail therapy involving a combined application of neuroprotective agents is feasible and offers excellent therapeutic potential. OBJECTIVE： To evaluate the neuroprotective effects of a cocktail therapy of insulin-like growth factor 1 （IGF1） combined with anti-intercellular adhesion molecule 1 （ICAM1） antibody in the treatment of cerebral ischemia/reperfusion injury using medical imaging, pathology, and functional neurological deficit scoring techniques. DESIGN, TIME AND SETTING： This randomized, controlled, neuroimaging analysis of function and pathological observation was performed at the Laboratory of Molecular Imaging, Second Hospital, Hebei Medical University between September 2006 and December 2007. MATERIALS： Transient middle cerebral artery occlusion （MCAO） was induced in 24 healthy adult cats. Anti-ICAM1 antibody and IGF1 were sourced from the Shanghai Kangcheng Biological Product Co., Ltd., China. Stereotaxic apparatus was purchased from the Center for Medical Apparatus and Instruments, Shandong Liaocheng People＇s Hospital, China. The in situ apoptosis kit was provided by the Beijing Zhongshan Biotechnique Co., Ltd., China. METHODS： Twenty-four cat models of MCAO were randomly divided into four groups （n = 6）： control, IGF1, anti-ICAM 1 antibody and cocktail therapy. Following a 2-hour ischemia and subsequent lateral cerebral ventricular puncture, 100 μg IGFl（cerebral ventricular）, 100 μg anti-ICAM1 antibody （i.v.）, 50 μg IGFl（lateral cerebral ventricular） ＋ 50 μg anti-ICAM1 antibody （i.v.）, and 100 μg physiological saline （i.v.） were administered to the IGF1, anti-ICAM1 antibody, cocktail therapy and control groups, respectively. On the following day, the same administration was performed again. MAIN OUTCOME MEASURES： Pathologic     

Neuroprotection of a cocktail therapy involving anti-intercellular adhesion molecule 1 antibody and insulin-like growth factor 1 in treatment of cerebral ischemia/reperfusion injury in cats Nuclear magnetic resonance examination and pathological validatio

BACKGROUND: The pathophysiological mechanisms of ischemia are extremely complicated. It is difficult to confirm and maintain the therapeutic effects if only one neuroprotective agent is used. It is hypothesized that a cocktail therapy involving a combined application of neuroprotective agents is feasible and offers excellent therapeutic potential. OBJECTIVE: To evaluate the neuroprotective effects of a cocktail therapy of insulin-like growth factor 1 (IGF1) combined with anti-intercellular adhesion molecule...     

The effect of dopamine depletion on the H2O2 production in the rat striatum following transient middle cerebral artery occlusion

The changes in the extracellular concentrations of rat striatal H₂O₂, dopamine (DA) and its metabolites during middle cerebral artery (MCA) occlusion and reperfusion were simultaneously examined by microdialysis, and the relationship between the ischemia-induced release of DA and the generation of H₂O₂ was estimated by assessing the effect of the lesion of the substantia nigra (SN). In the rats without SN lesions, a significant increase in the striatal H₂O₂ level was observed during the ischemia and reperfusion phases. In the rats with SN lesions, the ischemia-induced H₂O₂ production was not attenuated. These results suggest that DA is not an important source of H₂O₂ in cerebral ischemia and reperfusion.     

临床-弥散加权成像不匹配在急性大脑中动脉闭塞患者动脉溶栓中的应用

目的 研究临床-弥散加权不匹配(clinical-diffusion mismatch,CDM)机制在急性大脑中动脉闭塞(middle cerebral artery occlusion,MCAO)患者动脉溶栓治疗中的作用,分析CDM机制预测缺血半暗带的可行性.方法 选择发病在6h内经磁共振血管成像(magnetic resonance angiography,MRA)检查证实为MCAO的急性脑梗死患者106例,其中动脉溶栓组36例,常规治疗组70例,依据CDM定义:美国国立卫生研究院卒中量表评分(NIHSS)≥8分,弥散加权成像(DWI)病灶体积≤25 ml,再将两组各分为CDM亚组和非CDM亚组,对各亚组发病14 d后T2加权成像(T2weighted imaging,T2WI)梗死体积、30 d及3个月NIHSS评分进行对比观察.结果 动脉溶栓组中,CDM亚组(n=15) NIHSS评分在病程30 d、3个月均低于非CDM亚组(n=21,3.20±2.40与6.76±4.00,t=-3.330,P=0.002;2.20±1.70与6.05±4.06,t=3.895,P=0.001);非动脉溶栓组中,CDM亚组(n=23) NIHSS评分在病程30 d、3个月与非CDM亚组(n=47)比较差异均无统计学意义(5.22±2.95与5.66±3.21,t=- 1.756,P =0.084;4.34±2.53与5.34±3.42,t=1.234,P=0.353);虽然存在CDM,接受溶栓者与不接受溶栓者的NIHSS评分在30 d、3个月差异均有统计学意义(3.20±2.40与5.22±2.95,t=-2.210,P=0.034;2.20±1.70与4.34 ±2.53,t=-3.128,P=0.003),反之,不符合CDM的患者接受与不接受溶栓治疗,NIHSS评分在30 d与3个月时差异均无统计学意义.入院14d后CDM患者中溶栓组T2WI显示的梗死体积明显小于非溶栓组[(6.29±4.41) ml与(60.25±49.23) ml,Z=-4.848,P=0.001].结论 CDM机制对于确定急性MCAO脑梗死缺血半暗带的存在有一定意义,对指导急性MCAO脑梗死的动脉溶栓治疗可能有一定价值.     

弥散加权成像在超急性期脑梗死诊断中的应用

目的 将磁共振弥散加权成像（DWI）与常规MR技术作对比。评价DWI对超急性期脑梗死诊断的准确性和敏感性。方法 对52例超急性期，急性期，亚急性期，慢性期的患者行DWI，快速自旋回波T2WI，FLAIR及3DTOF法磁共振血管成像检查。对所有病例的病变部位均按神经解剖进行准确定位并与患者的症状，体征相联系。结果 超急性期和急性期脑梗死在DWI图像上表现为高信号，在表观弥散系数（ADC）图上表现为低信号，ADC值低于对侧相应的区域。在超急性期和急性期，病灶的ADC值显著下降,rADC值也明显下降。平均下降约59.12%。而在慢性期ADC值明显升高，甚至较正常组织还高，平均升高达20.3%。结论 DWI对6h症状起病的急性卒中的诊断明显高于传统MRI，DWI可以在超急期发现缺血病灶，早于常规T2WI及FLAR序列图像。DWI对脑梗死的早期诊断及评价起重要的作用。     

Effect of the kappa-1 opioid agonist CI-977 on ischemic brain damage and cerebral blood flow after middle cerebral artery occlusion in the rat

The effects of the kappa-1 opioid agonist CI-977 upon the volume of ischemic brain damage (defined using quantitative neuropathology) and local cerebral blood flow (CBF) (defined using quantitative [¹⁴C]iodoantipyrine autoradiography) have been examined at 4 h and 30 min, respectively, after permanent middle cerebral artery (MCA) occlusion in halothane-anesthetised rats. Treatment with CI-977 (0.3 mg/kg, s.c.) 30 min before and 30 min after occlusion of the MCA reduced the volume of infarction in the cerebral hemisphere (reduced by 27% when compared to vehicle;P<0.05) and cerebral cortex (reduced by 32%;P<0.05), despite a marked and sustained hypotension, with only minimal effect on damage in the caudate nucleus. In the hemisphere contralateral to the occluded MCA, treatment with CI-977 (0.3 mg/kg, s.c.) 30 min prior to the induction of ischemia failed to demonstrate any significant effect on either the level of local CBF in any of the 25 regions examined or on the volume of low CBF determined by frequency distribution analysis. In the hemisphere ipsilateral to MCA occlusion, CI-977 failed to produce statistically significant alterations in either the level of local CBF in 23 of the 25 regions or on the volume of low CBF, but areas of hyperemia were observed in both the medial caudate nucleus and lateral thalamus (local CBF increased by 65% and 86%, respectively, when compared to vehicle). The results of the present study indicate that the kappa-1 opioid agonist CI-977 is neuroprotective in a rat model of focal cerebral ischemia where key physiological variables have been assessed throughout the entire post-ischemic period, and fail to demonstrate that the neuroprotective effects of CI-977 in this model are due to improved blood flow to ischemic tissue.     

Neuroprotection of a cocktail therapy involving anti-intercellular adhesion molecule 1 antibody and nsulin-like growth factor 1 in treatment of cerebral ischemialreperfusion injury in cats: Nuclear magnetic resonance examination and pathological validation

BACKGROUND: The pathophysiological mechanisms of iscbemia are extremely complicated. It is difficult to confirm and maintain the therapeutic effects if only one neuroprotective agent is used. It is hypothesized that a cocktail therapy involving a combined application of neuroprotecfive agents is feasible and offers excellent therapeutic potential.OBJECTIVE: To evaluate the neuroprotective effects of a cocktail therapy of insulin-like growth factor 1 (IGF1) combined with anti-intercellular adhesion molecule 1 (ICAMI) antibody in the treatment of cerebral ischemia/reperfusion injury using medical imaging, pathology, and functional neurological deficit scoring techniques.DESIGN, TIME AND SETTING: This randomized, controlled, neuroimaging analysis of function and pathological observation was performed at the Laboratory of Molecular Imaging, Second Hospital, Hebei Medical University between September 2006 and December 2007.MATERIALS: Transient middle cerebral artery occlusion (MCAO) was induced in 24 healthy adult cats.Anti-ICAM1 antibody and IGFI were sourced from the Shanghai Kangcheng Biological Product Co., Ltd.,China. Stereotaxic apparatus was purchased from the Center for Medical Apparatus and Instruments,Shandong Liaocheng People's Hospital, China. The in situ apoptosis kit was provided by the Beijing Zhongshan Biotechnique Co., Ltd., China.METHODS: Twenty-four cat models of MCAO were randomly divided into four groups (n = 6): control,IGF1, anti-ICAM1 antibody and cocktail therapy. Following a 2-hour ischemia and subsequent lateral cerebral ventricular puncture, 100 μg IGF1(cerebral ventricular), 100 μg anti-ICAM1 antibody (i.v.), 50 μg IGF1(lateral cerebral ventricular) + 50 μg anti-ICAM1 antibody (i.v.), and 100 μg physiological saline (i.v.)were administered to the IGF1, anti-ICAM1 antibody, cocktail therapy and control groups, respectively. On the following day, the same administration was performed again.MAIN OUTCOME MEASURES: Pathological observation of the cerebral dura mater tissue surrounding the MCAO target site was performed by electron microscopy. At days 3 and 7 following MCAO induction, the volume of the cerebral infarction was measured by Philips functional neurological deficit scoring and nuclear magnetic resonance imaging.RESULTS: Pathological observation revealed that the control group exhibited a great number of swollen neurons, glial cells and vascular endothelial cells, and showed severely injured mitochondria with an absence of the double membrane structure. The same phenomena were partially alleviated in the IGF1 and anti-ICAM1 antibody groups, and the most obvious alleviation of injuries was in the cocktail therapy group. At day 6 following MCAO establishment, the cocktail therapy group exhibited the smallest cerebral infarction volumes among the four groups (F = 71.322, P < 0.01). At days 3 and 7 following MCAO induction, the F value of Philips functional neurological deficit scoring was 10.398 and 14.430, respectively (P < 0.01); however, the best neurological functional recovery was in the cocktail therapy group.CONCLUSION: A cocktail therapy of IGF1 combined with anti-ICAM1 antibody produces better neuroprotective effects than 1GFI or anti-lCAMl alone, as judged by injury to mitochondria and swelling in and around neurons and glial cells.     

Sensorimotor impairments in rats with cerebral infarction, induced by unilateral occlusion of the left middle cerebral artery: strain differences and effects of the occlusion site

Enormous differences exist between rat strains with respect to the infarct volume induced by unilateral middle cerebral artery (MCA) occlusion. We performed three experiments to address the following questions. Firstly, whether the pattern of MCA-occlusion (MCA-O) induced sensorimotor impairments in rats are strain dependent; secondly, whether proximal (i.e., close to its origin) and distal occlusions (above the lenticulostriate branch) of the MCA affect infarct volume and the behavioral impairments to a different extent; and thirdly, whether there is a relationship between the infarct volume and behavioral deficits. We found that the pattern of sensorimotor malfunctions induced by proximal unilateral MCA-O were highly strain dependent. Of the eight strains tested, Winkelmann-Wistar rats, Spontaneously Hypertensive Stroke-Prone rats, and Wistar-Kyoto rats were most severely affected. By contrast, Brown-Norway rats showed only mild behavioral deficits after the MCA-O. The second experiment confirmed that proximal occlusions induced slightly more behavioral malfunctions than distal occlusions did. Histological evaluation of the brain damage caused by proximal and distal MCA-O, confirmed that distal MCA-O damaged nearly exclusively cortical areas, and spared the caudate/putamen. An exploratory analysis of the relationship between infarct volume and behavioral deficits did not indicate that the severity of sensorimotor malfunctions can be predicted from the size of the infarct.     

Prediction of infarct volume and neurologic outcome by using automated multiparametric perfusion-weighted magnetic resonance imaging in a primate model of permanent middle cerebral artery occlusion

By optimizing thresholds, we identified the perfusion-weighted magnetic resonance imaging (PWI) parameters that accurately predict final infarct volume and neurologic outcome in a primate model of permanent middle cerebral artery (MCA) occlusion. Ten cynomolgus monkeys underwent PWI and diffusion-weighted imaging (DWI) at 3 and 47 hours, respectively, after right MCA occlusion using platinum coils, and were killed at 48 hours. Volumes of the hypoperfused areas on PWI were automatically measured using different thresholds and 11 parametric maps to determine the optimum threshold (at which least difference was found between the average volumes on PWI and those determined using specimens or DWI). In the case of arrival time (AT), cerebral blood volume (CBV), time to peak (TTP), time to maximum (T_max), and cerebral blood flow (CBF) determined using deconvolution techniques, the volume of the hypoperfused area significantly correlated with the infarct volumes and the neurologic deficit scores with small variations, whereas in the case of mean transit time and nondeconvolution CBF, relatively poor correlations with large variations were seen. At optimum threshold, AT, CBV, TTP, T_max, and deconvolution CBF can accurately predict the final infarct volume and neurologic outcome in monkeys with permanent MCA occlusion.     

Evaluation of myelination by means of the T2 value on magnetic resonance imaging

The progress of myelination in the cerebrum was evaluated by visual inspection, and magnetic resonance (MR) imaging and the transverse relaxation time (T₂) was calculated from double echo images. Twenty-three pediatric cases, who did not show intracranial organic changes on MR examination, were included. The T₂ values in the corpus callosum (CC), frontal deep white matter (FWM), occipital deep white matter (OWM) and centrum semiovale (CS) were calculated, and the changes in these values with age were followed. During the first year of life, a rapid decrease in the T₂ value was seen, followed by a more gradual decrease. The T₂ value seemed to reach the adult level between 2 and 3 years of life in all areas examined. The T₂ values between 2 and 16 years in CC, FWM, OWM and CS were 59.7±3.6, 64.5±5.2, 69.8±4.8 and 66.3±3.3ms (mean±S.D.), respectively. The T₂ values in patients with clinically diagnosed Pelizaeus-Merzbacher disease (PMD) and late onset Krabbe disease were also calculated. In PMD, non-progressive prolongation of the T₂ value was observed in all areas. In late onset Krabbe disease, on the other hand, progressive prolongation of the T₂ values was mainly demonstrated in OWM and the posterior part of CS. These results suggest that the T₂ value in the cerebral white matter allows more objective judgement than visual inspection, and makes it possible to clarify the mechanism underlying abnormal myelination, i.e. progressive or not.     

T2-weighted magnetic resonance imaging of cerebrovascular reactivity in rat reversible focal cerebral ischemia

Cerebrovascular carbon dioxide (CO₂) reactivity is an important hemodynamic index in cerebrovascular disease. In the present study T2^*-weighted magnetic resonance image (T2^*WI) was evaluated as a non-invasive method to investigate changes in CO₂ reactivity. Fourteen rats were subjected to permanent or, 30 and 90 min of temporary middle cerebral artery occlusion. A series of T2^*WIs and diffusion-weighted magnetic resonance images (DWI) was performed hourly under normo- and hypercapnic conditions. Triphenyltetrazolium chloride (TTC) staining of brain sections was obtained at the end of experiment to evaluate ischemic damage. During ischemia, a 4–6% signal increase upon hypercapnia was observed on T2^*WI in the non-ischemic hemisphere, while no such reactivity was seen in the putamen and cortex ipsilateral to the MCA occlusion. After reperfusion, CO₂ reactivity recovered in the putamen and cortex in the 30 min ischemia group and in the cortex alone of the 90 min ischemia groups. The areas with irreversible CO₂ reactivity dysfunction coincidentally revealed no recovery on DWI and lack of TTC staining. The results indicate that T2^*WI can be used to monitor changes in CO₂ reactivity after various ischemic insults that may indicate tissue viability.     

血浆Lp-PLA2与高分辨率磁共振评估的大脑中动脉斑块特征的相关性研究

目的 应用高分辨率磁共振(HRMRI)初步研究血浆脂蛋白相关磷脂酶A2(Lp-PLA2)与大脑中动脉(MCA)斑块特征的关系.方法 收集大脑中动脉M1段狭窄的缺血性脑血管病患者99例.对MCA狭窄段进行HRMRI检查,评估斑块特征,分为不稳定斑块组(47例)和稳定斑块组(52例).检测所有患者血浆Lp-PLA2水平.结...     

Biphasic expression of TGF-β1 mRNA in the rat brain following permanent occlusion of the middle cerebral artery

Two patterns of transforming growth factor-β1 (TGF-β1) expression were identified in brains of normotensive rats following permanent occlusion of the middle cerebral artery (MCAO). First, a relative increase of TGF-β1 mRNA by 37% was found at 12 h after MCAO in the ipsilateral cingulate cortex as compared to the homotopic contralateral region. The cingulate cortex is located distant from the ischemic territory. Treatment with the glutamate receptor antagonists MK-801 and NBQX did not reduce this expression (34% and 26% increase, respectively). Therefore, peri-infarct depolarization waves were probably not responsible for induction. Secondly, an increase of TGF-β1 mRNA by 116% was found at 7 days after MCAO within infarcted tissue. This expression was not reduced by the glutamate receptor antagonists MK-801 (increase 140%) and NBQX (increase 137%), either. TGF-β1 mRNA expression in the cingulate cortex at 12 h after MCAO is possibly mediated by neurons and astroglia and may support cell survival. Expression in the infarcted tissue at 7 days after MCAO is most likely related to the invasion of monocytes and may be involved in the downregulation of inflammatory events, in neoangiogenesis, and in formation of a glial scar around the infarct.     

Inducible nitric oxide synthase appears and is co-expressed with the neuronal isoform in interneurons of the rat hippocampus after transient ischemia induced by middle cerebral artery occlusion

The hippocampus (dentate gyrus DG plus Cornu Ammonis, CA) is vulnerable to neuropathological events such as ischemia. The DG is a region where neurogenesis takes place and it has been demonstrated that ischemia stimulates neurogenesis. Nitric oxide (NO) plays a major role in ischemic damage evolution and increases in rat hippocampus after ischemia. No information is available on the presence of nNOS-immunoreactive(IR) neurons in the hippocampus of ischemic animals; whereas, the presence of the iNOS protein has been reported in the DG after focal ischemia.We evaluated, immunohistochemically, the cell types expressing nNOS and iNOS in the rat hippocampus by 24 up to 144 h after transient middle cerebral artery occlusion to ascertain whether ischemia induces changes in nNOS or iNOS expression and whether a relationship exists between these changes and the animal survival.nNOS-IR interneurons were detected in control and ischemic rats; in the latter, their number was significantly decreased at all time points. iNOS-IR interneurons appeared in the hippocampus of ischemic rats at 24 h; their number was significantly higher in the animals with longer survival and did not change at later time points. More than 50% of the nNOS-IR interneurons co-expressed iNOS-IR. All these changes were seen both in the ipsilateral and contralateral hippocampus.In conclusion, the focal ischemia affects the hippocampus which responds bilaterally to the injury. We hypothesize that the decrease in the nNOS-IR neurons is likely due to either a neuronal loss or a switching towards the iNOS production which, by inducing neurogenesis, might compensate the neuronal loss.     

SB 234551 selective ET(A) receptor antagonism: perfusion/diffusion MRI used to define treatable stroke model, time to treatment and mechanism of protection

Mismatches between tissue perfusion-weighted imaging (PWI; an index of blood flow deficit) and cellular diffusion-weighted imaging (DWI; an index of tissue injury) provide information on potentially salvageable penumbra tissue in focal stroke and can identify “treatable” stroke patients. The present pre-clinical studies were conducted to: a.) Determine PWI (using perfusion delay) and DWI measurements in two experimental stroke models, b.) Utilize these measurements to characterize selective ET_A receptor antagonism (i.e., determine efficacy, time-to-treatment and susceptibility to treatment in the different stroke models), and c.) Determine if increasing the reduced blood flow following a stroke is a mechanism of protection. Permanent middle cerebral artery occlusion (MCAO) or sham surgeries were produced in Sprague Dawley rats (SD; proximal MCAO; hypothesized to be a model of slowly evolving brain injury with a significant penumbra) and in spontaneously hypertensive rats (SHR; distal MCAO; hypothesized to be a model of rapidly evolving brain injury with little penumbra). Infusions of vehicle or SB 234551 (3, 10, or 30 µg/kg/min) were initiated at 0, 75, and/or 180 min post-surgery and maintained for the remainder of 24 h post-surgery. Hyper-intense areas of perfusion delay (PWI) in the forebrain were measured using Gadolinium (Gd) bolus contrast. DWI hyper-intense areas were also measured, and the degree of forebrain DWI-PWI mismatch was determined. Region specific analyses (ROI) were also conducted in the core ischemic and low perfusion/penumbra areas to provide indices of perfusion and changes in the degree of tissue perfusion due to SB 234551 treatment. At 24 h post-surgery, final infarct volume was measured by DWI and by staining forebrain slices. Following SD proximal MCAO, there was a significant mismatch in the ischemic forebrain PWI compared to DWI (PWI > DWI) at 60 min which was maintained up to 150 min (all p < 0.05). By 24 h post-stroke, infarct volume was identical to the area of early perfusion deficit/PWI, suggesting a slow progression of infarct development that expanded into the significant, earlier cortical penumbra (i.e., model with salvageable tissue with potential for intervention). When SB 234551 was administered within the period of peak mismatch (i.e., at 75 min post-stroke), SB 234551 provided significant dose-related reductions in cortical (penumbral) progression to infarction (p < 0.05). Cortical protection was related to an increased/normalization of the stroke-induced decrease in tissue perfusion in cortical penumbra areas (p < 0.05). No SB 234551-induced changes in reduced tissue perfusion were observed in the striatum core ischemic area. Also, when SB-234551 was administered beyond the time of mismatch, no effect on cortical penumbra progression to infarct was observed. In comparison and strikingly different, following SHR distal MCAO there was no mismatch between PWI and DWI (PWI = DWI) as early as 60 min post-stroke, with this early change in SHR DWI being identical to the final infarct volume at 24 h, suggesting a rapidly occurring brain injury with little cortical penumbra (i.e., model with little salvageable tissue or potential for intervention). In distal MCAO, SB 234551 administered immediately at the time of stroke did not have any effect on infarct volume in SHR. These data demonstrate that selective blockade of ET_A receptors is protective following proximal MCAO in SD (i.e. a model similar to “treatable” clinical patients). The protective mechanism appears to be due to enhanced collateral blood flow and salvage of penumbra. Therefore, the use of PWI-DWI mismatch signatures can identify treatable stroke models characterized by a salvageable penumbra and can define appropriate time to treatment protocols. In addition, tissue perfusion information obtained under these conditions might clarify mechanism of protection in the evaluation of protective compounds for focal stroke.     

Advanced MR imaging techniques and characterization of residual anatomy

Advances in technology in recent decades have contributed to rapid developments in non-invasive methods for imaging human anatomy, and advanced imaging methods are now one of the primary tools for clinical diagnosis after neurological trauma or disease. Here we review the current and upcoming capabilities of one of the most rapidly developing methods, magnetic resonance imaging (MRI). The underlying theory is introduced so that the reasons for the strengths, weaknesses, and future expectations of this method, can be explained. Current techniques for imaging anatomical changes, inflammation, and changes in white matter, axonal integrity, blood flow and function, are reviewed. Applications for specific purposes of assessing traumatic injury in the brain or spinal cord, and for multiple-sclerosis are also presented, and are used as examples of how the advanced techniques are being used in practice.