Purine catabolites and pial arteriolar diameter in transient cerebral ischemia]

In transient cerebral ischemia, extracellular purine catabolites and pial arteriolar diameter were measured continuously. Ischemia during one hour was induced by unilateral occlusion of left middle cerebral artery in feline. Extracellular purine catabolites were sampled by in vivo brain microdialysis technique from the gray matter at ectosylvian gyrus. These catabolites were analyzed by HPLC system. Simultaneously, reactivity of pial arteriole was observed and its diameter was measured through the cranial window using intravital microscope and width analyzer. Extracellular concentrations of adenosine, inosine, hypoxanthine and xanthine were found to be 0.80 +/- 0.16 microM, 2.01 +/- 0.95 microM, 4.01 +/- 2.73 microM and 3.93 +/- 2.39 microM, respectively. During ischemia, the concentration of adenosine increased 8.7-fold and arteriolar diameter was 170% of the resting state. These findings in extracellular adenosine concentration and pial arteriolar diameter during ischemia support a role of adenosine in regulation of cerebral blood flow. After reperfusion, arteriolar diameter had returned to 120% of the resting state. But 50 min after reperfusion, pial arteriole began to dilate again coincident with the peak of xanthine concentration. These results suggest that free radicals were produced and could affect pial arterioles 50 min after reperfusion.     

Biphasic striatal dopamine release during transient ischemia and reperfusion in gerbils

To clarify the nature of ischemic striatal dopamine release during the earliest periods of neuronal injury, we used chronoamperometry to measure dopamine levels every 60 seconds during various durations of ischemia in 32 gerbils. Catecholamine-selective electrodes were implanted into the brains of anesthetized gerbils subjected to 2, 5, or 10 minutes of transient forebrain ischemia or permanent forebrain ischemia. Four control animals showed a stable chronoamperometric baseline. In the six gerbils subjected to permanent ischemia, dopamine release was rapid during early ischemia and slowed with time. The four animals subjected to 2 minutes of ischemia showed minimal dopamine release. The six gerbils subjected to 5 minutes of ischemia demonstrated a noticeable dopamine release during ischemia, and three of the six developed a massive secondary dopamine release during reperfusion. All six animals subjected to 10 minutes of ischemia demonstrated a similar biphasic dopamine release twice the size of that observed in the 5-minute group. Pretreatment with pargyline in six additional gerbils subjected to 10 minutes of ischemia failed to modify significantly this biphasic pattern of dopamine release. We conclude that dopamine release occurs very early during ischemia and that its magnitude correlates with the duration of an ischemia insult. Reperfusion is associated with an even larger striatal dopamine release. This previously unreported biphasic dopamine release phenomenon may have important clinical implications in the management of cerebral ischemia.     

Effects of cholecystokinin octapeptide on pial arteriolar diameter

The effects of the perivascular microapplication of sulphated cholecystokinin octapeptide (CCK-8) on pial arteriolar calibre have been examined in anaesthetised cats using a video-display image-splitting technique. The microinjection of CCK-8 (10(-7) M) in the injectate did not modify the constriction or dilatation of pial arterioles provoked by the perivascular microinjection of alkalotic (pH 7.45) or acidic (pH 6.8) artificial CSFs, respectively. Thus, although CCK-8-immunoreactive neuronal processes are known to be associated with cortical blood vessels, CCK-8 appears to have minimal vasomotor effects on pial vessels.     

Capillary flow and diameter changes during reperfusion after global cerebral ischemia studied by intravital video microscopy.

The reaction of cerebral capillaries to ischemia is unclear. Based on Hossmann's observation of postischemic "delayed hypoperfusion," we hypothesized that capillary flow is decreased during reperfusion because of increased precapillary flow resistance. To test this hypothesis, we measured cerebral capillary erythrocyte velocity and diameter changes by intravital microscopy in gerbils. A cranial window was prepared over the frontoparietal cortex in 26 gerbils anesthetized with halothane. The animals underwent either a sham operation or fifteen minutes of bilateral carotid artery occlusion causing global cerebral ischemia. Capillary flow velocities were measured by frame-to-frame tracking of fluorescein isothiocyanate labeled erythrocytes in 1800 capillaries after 1-hour reperfusion. Capillary flow velocities were decreased compared to control (0.25 +/- 0.27 mm/s vs. 0.76 +/- 0.45 mm/s; P<0.001). Precapillary arteriole diameters in reperfused animals were reduced to 76.3 +/- 6.9% compared to baseline (P<0.05). Capillary diameters in reperfused animals (2.87 +/- 0.97 microm) were reduced (P<0.001) compared to control (4.08 +/- 1.19 microm). Similar reductions of precapillary (24%) and capillary vessel diameters (30%) and absolute capillary flow heterogeneity indicate that delayed (capillary) hypoperfusion occurs as a consequence of increased precapillary arteriole tone during reperfusion.     

脑缺血再灌流时脑温的动态改变

目的了解脑缺血再灌流后脑温的变化,为脑缺血动物的实验研究、以及亚低温脑保护作用机制提供理论依据。方法将SD大鼠分为四动脉阻断、双颈总动脉阻断、单侧颈总动脉阻断以及四动脉阻断10min、20min、30min后再灌流组。用点式测温仪同时测量不同部位脑组织的温度。结果脑组织内存在温度梯度;脑缺血后同一时间点纹状体、海马和颞肌的温度不一致;不同程度脑缺血后脑温的变化不一致,双侧颈总动脉阻断的脑缺血中脑温的改变呈波浪状,单侧颈总动脉阻断的脑缺血中缺血侧脑温低于对照侧;四动脉阻断的全脑缺血中,缺血后不同时间开始再灌流脑温都有回升现象;脑缺血的严重程度和持续时间可影响动物的清醒和脑温的变化。结论本实验的结果说明了在脑缺血实验研究时采用连续监测、并将脑温控制在特定的范围内,避免脑缺血和再灌流期间脑温的波动影响实验结果的准确性。     

Leukocyte-endothelium interactions in pial venules during the early and late reperfusion period after global cerebral ischemia in gerbils.

The contribution of leukocytes to secondary brain damage after cerebral ischemia is still under discussion. The purpose of the present study was to examine the pial microcirculation after global cerebral ischemia while focusing on leukocyte-endothelium interactions during the early and late reperfusion period of up to 4 days. A closed cranial window technique that leaves the dura mater intact was used. Global cerebral ischemia of 15 minutes' duration was induced in male Mongolian gerbils (n = 91). Pial microcirculation was observed by intravital fluorescence microscopy. Leukocyte-endothelium interactions (LEIs) in pial venules, vessel diameters, capillary density, and regional microvascular blood flow measured by laser Doppler flowmetry were quantified during 3 hours of reperfusion and in intervals up to 4 days after ischemia. Within 3 hours of reperfusion, the number of leukocytes (cells/100 microm x minute) rolling along or adhering to the venular endothelium increased from 0.1 +/- 0.2 to 28.4 +/- 17.4 (P < 0.01 vs. control) and from 0.2 +/- 0.2 to 4.0 +/- 3.8 (P < 0.05), respectively. There was no capillary plugging by leukocytes; capillary density remained unchanged. In the late reperfusion period, at 7 hours after ischemia, LEIs had returned to baseline values. Furthermore, from 12 hours to 4 days after ischemia, no LEIs were observed. Changes in regional microvascular blood flow did not correlate with LEIs. Global cerebral ischemia of 15 minutes' duration induces transient LEIs that reach a maximum within 3 hours of reperfusion and return to baseline at 7 hours after ischemia. LEIs are not related to changes in microvascular perfusion, which suggests mainly that the expression of adhesion receptors is necessary to induce LEIs rather than rheologic factors. It seems unlikely that this short-lasting activation of leukocytes can play a role in the development of secondary brain damage.     

Effects of dopamine on pial arteriolar diameter and CSF prostanoid levels in piglets

We examined effects of topically applied dopamine on pial arteriolar diameter and CSF prostanoid levels in newborn pigs. Vascular responses were determined using the closed cranial window technique and intravital microscopy, and prostanoids were determined by radioimmunoassay. Topical application of dopamine did not change arteriolar diameter at 10(-7)-10(-5) M, but constricted arterioles at 10(-4) (16%) and 10(-3) M (30%). Intravenous administration of indomethacin (5 mg/kg) did not alter this constriction. In addition, CSF prostanoid levels did not increase in response to application of dopamine except for a modest increase of prostaglandin E2 at 10(-3) M. We conclude that dopamine is a constrictor at high doses of piglet pial arterioles and that this response is not modified by endogenous prostanoids.     

短暂脑缺血再灌注后大鼠大脑皮质ATP含量的动态变化

目的　探讨短暂脑缺血再灌注后大鼠大脑皮质ATP含量的动态变化及其与神经功能恢复之间的关系。方法　采用线栓法建立大鼠大脑中动脉闭塞 (MCAO)模型 ,缺血 10min后于再灌注后 0h、1h、3h、6h、12h、2 4h和 72h应用毛细血管电泳法分别测定额顶叶皮质的ATP含量 ,观察其变化规律。结果　缺血 10min后额顶叶皮质ATP的含量急剧下降至对照组的 2 0 %。再灌注后ATP的含量逐渐恢复 ,于再灌注后 1h、3h、6h和 12h恢复至对照组的 70 .5 %、6 5 .7%、84 .8%和 86 .9%。再灌注后 2 4hATP含量再次下降 ,再灌注后2 4h和 72hATP含量仅为对照组的 5 0 % ,与对照组相比差异均有显著性 (P <0 0 1,P <0 0 5 )。缺血 10min再灌注后大鼠肢体功能可逐渐恢复 ,但再灌注后 2 4h起出现不愿活动和进食等表现。结论　短暂脑缺血再灌注后大鼠额顶叶皮质存在细胞能量系统功能恢复滞后的现象。同时 ,随着再灌注的进行还出现了继发性细胞能量系统功能衰竭的现象 ,这可能与脑缺血再灌注后的神经功能延迟恢复有关     

大鼠短暂局灶性脑缺血再灌注后核转录因子-kB的表达

目的　研究核转录因子 - k B(NF- k B)在局灶性脑缺血再灌注中的动态表达规律及其作用。方法　采用线栓法建立大鼠局灶性脑缺血再灌注模型。应用细胞免疫组织化学法分析 NF- k B的移位 ,采用 Western- blot法检测脑组织中核 NF- k B的表达量。结果　局灶性脑缺血再灌注后 NF- k B明显从细胞浆移位于细胞核 ,核 NF- k B的表达量显著增加 (P<0 .0 1)。结论　局灶性脑缺血再灌注能够引起 NF- k B的表达增加 ,进一步产生炎症和免疫反应 ,从而参与了脑缺血再灌注损伤的发病机制     

高血压大鼠脑缺血再灌注损伤时的病理学变化

目的研究高血压大鼠在脑缺血损伤时的病理改变。方法用线拴法将肾性高血压大鼠制作成脑缺血再灌注模型,在光镜和透射电镜下观察脑组织的病理和超微结构改变。结果高血压组大鼠与正常大鼠相比,在局灶性缺血再灌注损伤时有明显的组织学改变。结论高血压可经过多种机制加剧脑缺血性损伤。     

高血压大鼠脑缺血再灌注损伤时的病理学变化

目的 研究高血压大鼠在脑缺血损伤时的病理改变.方法 用线拴法将肾性高血压大鼠制作成脑缺血再灌注模型,在光镜和透射电镜下观察脑组织的病理和超微结构改变.结果 高血压组大鼠与正常大鼠相比,在局灶性缺血再灌注损伤时有明显的组织学改变.结论 高血压可经过多种机制加剧脑缺血性损伤.     

姜黄素降低短暂性脑缺血再灌注损伤的炎症反应

Inflammatory reactions are important pathophysiological mechanisms of ischemic brain injury.The present study analyzed the anti-inflammatory characteristics of curcumin via myeloperoxidase activity and nitric oxide content after 2-hour ischemia/24-hour reperfusion in Sprague Dawley rats.In addition,expressions of nuclear factor kappa B,tumor necrosis factor-α and interleukin-1β protein were measured.Curcumin significantly reduced myeloperoxidase and nitric oxide synthase activities and suppressed expressions of nuclear factor kappa B,tumor necrosis factor-α,and interleukin-1β in ischemia/reperfusion brain tissue.Results suggested that the neuroprotective effect of curcumin following cerebral ischemia/reperfusion injury could be associated with inhibition of inflammatory reactions.     

Changes in endogenous antioxidant enzymes during cerebral ischemia and reperfusion

OBJECTIVE: The purpose of this study was to investigate the role of catalase (Cat), glutathione S transferase (GST), glutathione reductase (GR) and glutathione peroxidase (GPx) in cerebral ischemia induced by occluding the carotid arteries of male Wistar rats. METHODS: The activities of the antioxidant enzymes Cat, GR, GPx and GST were measured in the cerebral cortex, cerebellum and hippocampus regions after varying periods of ischemia and reperfusion. RESULTS: In all ischemia/reperfusion groups (0, 1 and 24 hours of reperfusion), the enzyme activities were found to be altered when compared to the sham-operated controls. The alterations were significant (p< or =0.05) in all reperfusion groups, particularly after 1 hour of reperfusion in all brain regions; however, maximum alterations were detected in the more vulnerable hippocampus. DISCUSSION: Our findings indicate that the endogenous antioxidant enzymes are activated as soon as 1 hour after ischemia. In spite of significant up-regulation of these enzymes, a large number of neurons in selectively vulnerable regions of hippocampus undergo neurodegeneration. These biochemical changes suggest that vulnerability to oxidative stress in brain is region-specific. However, these changes which are adaptive or compromise the capacity of the brain to deal with the oxidative stress that could lead to neurodegeneration remains to be understood.     

大鼠急性局灶性脑缺血再灌注脑组织NO含量和NOS活性的变化

目的探讨一氧化氮（ＮＯ）和神经元型ＮＯ合酶（ｎＮＯＳ）是否参与急性局灶性脑缺血再灌注的发病机理。方法采用栓红法建立大鼠大脑中动脉阻塞（ＭＣＡＯ）模型,观察脑组织ＮＯ含量和一氧化氮合酶（ＮＯＳ）活性的变化及ｎＮＯＳ抑制剂７－硝基吲唑（７－ＮＩ）对再灌注期两者的影响。结果缺血３０分种ＮＯ含量和ＮＯＳ活性显著升高,缺血３小进两者下降;再灌注３０分种ＮＯＴ和ＮＯＳ再次升高,而再灌注３小时两者又下降。７－Ｎ     

Decrease in perfusion of cerebral capillaries during incomplete ischemia and reperfusion

The effect of unilateral, incomplete cerebral ischemia on CBF, unidirectional flux of alpha-aminoisobutyric acid (AIB) and sodium, and number of perfused capillaries during ischemia and reperfusion was measured in the cortex of gerbils with symptomatic ischemia. Three hours of unilateral carotid occlusion reduced the CBF to the ipsilateral cortex by 81%, with a smaller 30% decrease in the contralateral cortex. Following 11 min of reperfusion, CBF in the ipsilateral cortex returned to the preischemic value, while the contralateral blood flow decreased to 50% of control. The transfer constants for AIB and sodium in the ipsilateral cortex were reduced by 67 and 53%, respectively, after 3 h of ischemia, with no change in the contralateral cortex. The transfer constant for AIB remained decreased by 48% during the first 20 min of reperfusion, while that for sodium returned to its control value. The number of perfused capillaries was reduced 54% by 3 h of ischemia and remained decreased by 20% after 11 min of reperfusion. These data indicate that 3 h of unilateral carotid occlusion reduces the number of perfused capillaries in the ipsilateral cortex during the ischemic period. Further, the early reperfusion phase is characterized by a mismatch between capillary perfusion and CBF. Finally, early in the postischemic phase, sodium transport undergoes a selective stimulation, probably as a result of stimulation of ion transport.     

亚低温在急性脑缺血中对氨基酸和自由基含量的影响

目的研究亚低温状态下,急性脑缺血时皮质内四种氨基酸和自由基含量的改变,探讨亚低温对缺血脑组织的保护机制。方法将63只Wistar大鼠随机分为9组,假手术组7只,缺血组(手术后将其颞厂讥温度控制在36．5+-0．5℃)-缺血3h组,缺血3h分别再灌注1h、2h、3h组各7只;亚低温组(手术后将其颞肌温度控制在32．5±0．5℃)-缺血3h,缺血3h分别再灌注1h、2h、3h组各7只。动物模型参照Zealonga的大脑中动脉线栓模型并加以改进。结果比较缺血组和低温组,可见低温组缺血皮质内的谷氨酸(Glu)、天门冬安酸(Asp)、丙醛(MDA)的产生明显减少,而超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-PX)的生成和释放明显增加,γ-氨基丁酸(GABA)的含量亦增加。结论亚低温状态下4种氨基酸含量及自由基系统的改变是其保护缺血神经元的重要机制。     

A new model for inducing transient cerebral ischemia and subsequent reperfusion in rabbits without craniectomy

An artificial ball removable by an attached fiber was injected into the middle cerebral artery (MCA) of 16 rabbits, allowing the study of transient (5, 10, 15, or 30 minutes) cerebral ischemia without craniectomy. Measurements of available oxygen (aO2) in the ischemic core (the ventral part of the temporal area) followed by histologic examination verified the embolization. Electroencephalographic power spectra and steady (direct current) potentials were recorded bilaterally on the convexity remote from the actual lesion but still supplied by the MCA. Local cerebral blood flow and aO2 in the border zone between the anterior cerebral artery and the occluded MCA were measured. Embolization caused typical ischemic changes ipsilaterally and alterations characteristic of diaschisis contralaterally. Extreme border zone hyperemia developed without significant aO2 changes in the same region. Restoration of circulation via the circle of Willis induced gradual normalization. Our model for controlled embolization and recirculation proved suitable for detailed studies of the complex changes in brain function caused by transient ischemia.