COMPLETE AND INCOMPLETE CEREBRAL ISCHEMIA

脑缺血时细胞内酸中毒的发生及 再灌注过程中自由基的产生是两种机制 近年来越来越受到关注的脑损伤 年 本提案的总体目标是调查 细胞内pH值和氧自由基对细胞内 恢复脑高能磷酸盐，血流和 缺血后的电功能。 我们将在体内使用31P 核磁共振光谱法来追踪 脑ATP、磷酸肌酸（PCr）和细胞内pH（pHi）。 我们将同时测量脑血流量（CBF）， 摄取，体感诱发电位（SEP），和 脑电图（EEG）。 我们将学习完整的， 颅内压增高引起的不完全性全脑缺血 在狗身上肯定会升高。 滴定电回收率 功能（从正常到恢复不良），三个缺血 将产生持续时间，以便干预措施的效果可以 以损伤剂量依赖的方式研究。 我们将首先 确定ATP和PCr的初始恢复率， 线粒体功能的标志物，与电 ATP和PCr的恢复水平高于 完全和不完全缺血的不同持续时间。 我们将 然后检查在缺血期间达到的pHi的影响， 再灌注期间正常化率对恢复率 ATP、PCr、SEP和EEG，以操纵pHi、血糖水平 会发生变化，从而改变乳酸的产量。 完成 将缺血与不完全缺血进行比较，其中范围 由于持续的葡萄糖， 在缺血期间递送。 过度换气的影响， 临床常用的干预措施，对pHi、ATP的恢复。 还将研究PCr、EEG和SEP。 我们将调查 氧自由基的作用，首先通过测量时间 皮层超氧阴离子的出现和消失过程 在再灌注期间，第二，通过证明自由基 清除剂和抑制剂抑制超氧化物的出现， 再灌注 然后我们将评估清道夫的功效 给药后CBF、SEP、EEG、ATP、PCr恢复。 最后，我们将确定酸中毒是否会增强自由基 如果食腐动物能有效地逆转这种情况， 酸中毒的有害影响。 这些研究将提高我们的 了解脑缺血再灌注损伤机制。

Development of intracellular acidosis during cerebral ischemia and generation of free radicals during reperfusion are two mechanisms of brain injury that have received increasing attention in recent years. The overall goal of this proposal is to investigate the role of intracellular pH and oxygen-derived free radicals on the recovery of cerebral high energy phosphates, blood flow and electrical function following ischemia. We will use in vivo 31P nuclear magnetic resonance spectroscopy to track the recovery of cerebral ATP, phosphocreatine (PCr) and intracellular pH (pHi). We will simultaneously measure cerebral blood flow (CBF), 02 uptake, somatosensory evoked potentials (SEP), and electroencephalogram (EEG). We will study both complete and incomplete global cerebral ischemia produced by intracranial pres- sure elevations in dogs. To titrate recovery of electrical function (from normal to poor restoration), three ischemic durations will be produced so that effects of interventions can be studied in an injury-dose dependent manner. We will first determine whether the initial rate of recovery of ATP and PCr, as marker of mitochondrial function, correlate better with electrical recovery than steady state recovery level of ATP and PCr following various durations of complete and incomplete ischemia. We will then examine the influence of pHi achieved during ischemia and its rate of normalization during reperfusion on the rate of recovery of ATP, PCr, SEP, and EEG, To manipulate pHi, blood glucose levels will be varied, thereby altering lactic acid production. Complete ischemia will be compared to incomplete ischemia, where the range of pHi alterations should be greater because of sustained glucose delivery during ischemia. The influence of hyperventilation, a clinical intervention frequently used, on recovery of pHi, ATP. PCr, EEG and SEP will also be studied. We will investigate the role of oxygen-derived free radicals first by measuring the time course of cortical appearance and disappearance of superoxide anion during reperfusion, and second by demonstrating that free radical scavengers and inhibitors suppress superoxide appearance during reperfusion. We will then evaluate the efficacy of scavenger administration on the restoration of CBF, SEP, EEG, ATP and PCr. Finally, we will determine if acidosis potentiates free radical appearance and if scavengers can effectively reverse this detrimental effect of acidosis. These studies should enhance our understanding of ischemic-reperfusion injury mechanisms in brain.