新生儿缺氧缺血性脑病血清IL-6水平与脑血流变化的研究

目的探讨缺氧缺血脑病（HIE）新生儿血清IL-6水平和脑血流变化与缺氧缺血性脑损伤程度关系。方法采用ELXLA法对41例HIE患儿和14例对照组新生儿血清IL-6水平进行检测,同时采用经颅多谱勒超声（TCD）技术观察双侧大脑中动脉（MCA）收缩峰流速（Vs）、舒张末期流速（Vd）变化、阻力指数（RI）等的变化。结果轻、中、重度HIE患儿急性期血清IL-6水平均明显高于对照组水平（P〈0.01）,重度组增高尤其明显。中、重度组Vd,Vs低于对照组,RI指数重度组高于对照组（P〈0.01）。血清IL-6水平与脑血流速度呈显著负相关（r=0.872,P〈0.01）。结论检测血清IL-6和脑血流变化对于评价新生儿缺氧缺血性脑病脑损伤的程度具有重要临床意义。     

Long-fragment DNA of blood plasma as one of the criteria of individual sensitivity to emotional stress and to cerebral ischemia

Intravenous injection ofpolyethylenoxide WSR-301 reducing hydrodynamic blood resistance (Toms effect) improves gas exchange in the lungs and halved lethality of the animals with cerebral ischemia. The aim of the study was to establish whether free plasma DNA influences blood gases and lethality of the animals with brain ischemia. Common carotid arteries were ligated for 15 min in intact stressed and tested in the open field Wistar male rats, then some of the rats received intravenous solution of homologous long-fragment DNA (20x10(-6) g/ml of blood). Cerebral circulation, acid-base equilibrium, paO2, paCO2, asymptotic blood viscosity, plasmic concentration and length of DNA fragments in plasma, lethality and neurological status of the survivors were studied. It was found that long fragments of rat DNA show hydrodynamic Toms effect. In normal passive rats sensitive to cerebral ischemia part of plasm DNA is fragmented, gas composition and blood viscosity of blood is worse (p < 0.05) than in active animals. There is a direct correlation between the level of long-fragment DNA in plasm and paO2 (r = 0.55) and inverse--with paCO2 (r = -0.84). Intravenous injection of long-fragment DNA improved the course and reduced lethality of brain ischemia 2-3-fold. Thus, qualitative and quantitative characteristics of plasma circulating DNA are responsible for differences in blood gases in rats differently tolerable to cerebral ischemia and can serve as one of the criteria of individual sensitivity to it being essential in pathogenesis of ischemic stroke.     

Functional Cluster Analysis of CT Perfusion Maps: A New Tool for Diagnosis of Acute Stroke?

CT perfusion imaging constitutes an important contribution to the early diagnosis of acute stroke. Cerebral blood flow (CBF), cerebral blood volume (CBV) and time-to-peak (TTP) maps are used to estimate the severity of cerebral damage after acute ischemia. We introduce functional cluster analysis as a new tool to evaluate CT perfusion in order to identify normal brain, ischemic tissue and large vessels. CBF, CBV and TTP maps represent the basis for cluster analysis applying a partitioning (k-means) and density-based (density-based spatial clustering of applications with noise, DBSCAN) paradigm. In patients with transient ischemic attack and stroke, cluster analysis identified brain areas with distinct hemodynamic properties (gray and white matter) and segmented territorial ischemia. CBF, CBV and TTP values of each detected cluster were displayed. Our preliminary results indicate that functional cluster analysis of CT perfusion maps may become a helpful tool for the interpretation of perfusion maps and provide a rapid means for the segmentation of ischemic tissue.     

Progress on Complications of Direct Bypass for Moyamoya Disease

Moyamoya disease (MMD) involves progressive occlusion of the intracranial internal carotid artery resulting in formation of moyamoya-like vessels at the base of the brain. It can be characterized by hemorrhage or ischemia. Direct vascular bypass is the main and most effective treatment of MMD. However, patients with MMD differ from those with normal cerebral vessels. MMD patients have unstable intracranial artery hemodynamics and a poor blood flow reserve; therefore, during the direct bypass of superficial temporal artery (STA)-middle cerebral artery (MCA) anastomosis, perioperative risk factors and anesthesia can affect the hemodynamics of these patients. When brain tissue cannot tolerate a high blood flow rate, it becomes prone to hyperperfusion syndrome, which leads to neurological function defects and can even cause intracranial hemorrhage in severe cases. The brain tissue is prone to infarction when hemodynamic equilibrium is affected. In addition, bypass vessels become susceptible to occlusion or atrophy when blood resistance increases. Even compression of the temporalis affects bypass vessels. Because the STA is used in MMD surgery, the scalp becomes ischemic and is likely to develop necrosis and infection. These complications of MMD surgery are difficult to manage and are not well understood. To date, no systematic studies of the complications that occur after direct bypass in MMD have been performed, and reported complications are hidden among various case studies; therefore, this paper presents a review and summary of the literature in PubMed on the complications of direct bypass in MMD.     

Cerebral hemodynamic reactions to low-intensity physical exercise

Cerebral hemodynamic reactions to light physical exercise increasing stepwise on a bicycle ergometer were studied in healthy young male subjects. Hemodynamic parameters were measured by transcranial Doppler ultrasonography from the middle cerebral artery (MCA) before the start of the study and during the last few seconds of each exercise step. Cerebral hemodynamic reactions to physical exercise were characterized by a significant increase in systolic blood flow rate in the middle cerebral artery only at exercise levels of about 0.25 W/kg body weight (90 rpm at 0 W/kg) with no further increase in the blood flow rate with increases in loading to 0.5 W/kg body weight. The mechanism stabilizing blood flow rate in the cerebral arteries as physical exercise increased and, thus, the mechanism of cerebral circulatory autoregulation consisted of a arterial pressure-dependent increase in regional cerebral vascular resistance. The threshold at which the cerebral blood flow rate autoregulatory mechanism was triggered in normal subjects corresponded to a loading of about 0.25 W/kg and a systolic arterial pressure of about 140–145 mmHg. Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 94, No. 7, pp. 790–798, July, 2008.     

家兔急性不完全性脑缺血及重灌流的实验研究

采用低压低灌流方法造成家兔急性不完全性脑缺血60分钟,缺血后进行重灌流。检测了脑电图(EEG)、心输出量、平均动脉血压及脑静脉血乳酸脱氢酶(LDH)、磷酸肌酸激酶(CPK)活性以及大脑皮质水、钠、钾及环核苷酸含量,观察组织形态学改变。实验结果表明通过低压低灌流成功地复制了兔急性不完全性脑缺血模型。其特点为EEG严重抑制、大脑皮质水、钠含量升高、LDH及CPK活性显著升高。并见脑组织出现脑水肿改变。重灌流期间EEG先有所恢复后严重抑制,LDH及CPK活性仍显著升高。大脑皮质cAMP含量进一步升高,水肿程度加重。组织形态学呈现明显的缺血性损伤尤以亚微结构更为严重,表明重灌流后组织损伤加重。作者分析了上述改变发生的可能机制。     

阿托品减轻大鼠脑缺血后再灌流损害机制的初步探讨

为探讨乙酰胆碱（ａｃｅｔｙｌｃｈｏｌｉｎｅ，Ａｃｈ）在神经元缺血性损害中的作用和机制，本实验观察了Ａｃｈ能Ｍ受体拮抗剂阿托品对大鼠脑缺血再灌注损害的影响，发现阿托品（２５ｍｇ／ｋｇ，ｂｗ，ｉｐ）可明显减轻大鼠前脑缺血后再灌流所致海马ＣＡ１区神经元迟发性损害，减小大鼠大脑中动脉阻塞后再灌流损害范围，而对局部皮质血流变化无影响，表明阿托品对缺血脑组织的保护作用不是由于改善了局部脑血流，提示Ａｃｈ参与神     

Lack of neuroprotection by heat shock protein 70 overexpression in a mouse model of global cerebral ischemia

Heat shock protein 70 (Hsp70) is induced in cells by a variety of stress conditions, is known to be cytoprotective, and has been proposed to be neuroprotective during brain ischemia. A recently developed mouse model of 12-min global cerebral ischemia by bilateral common carotid artery occlusion with artificial ventilation and bilateral monitoring of regional cerebral blood flow by laser Doppler was applied. We examined the expression and possible neuroprotective role of the inducible form of Hsp70 in the mouse brain following global cerebral ischemia. Ischemia induced a marked expression of Hsp70 in the ischemia vulnerable CA1-CA3 region of the hippocampus. Intraischemic hypothermia (33°C) prevented cell damage without noticeable expression of Hsp70. A transgenic mouse overexpressing Hsp70 was subjected to 12 min of global cerebral ischemia, and the brain damage was evaluated after 4 days. No neuroprotection of ischemia-induced brain damage in hippocampus, striatum, cortex or thalamus was found in Hsp70 transgenic animals compared with wild-type littermate mice. We suggest that overexpression of Hsp70 following cerebral ischemia is an indicator of cell stress. Also, constitutively overexpression of Hsp70 is insufficient to effectively influence cell death after global cerebral ischemia in the mouse.     

Cerebroprotective effects of diquertin and ascorbic acid

Electron microscopy and electrophysiological studies revealed pronounced structural and functional changes in the brain cortex in rats with experimental cerebral ischemia. Repeated administration of diquertin and ascorbic acid significantly attenuates ischemic damage induced by circulatory disturbances.     

The effect of hyperbaric oxygen therapy on blood vessel function in diabetes mellitus

Prolonged untreated diabetes mellitus leads to microangiopathy, tissue hypoxia and ischemic lesions; it increases the risk for stroke and exacerbates brain tissue damage following ischemia. Patients exhibit advanced atherosclerosis in coronary and cerebral arteries as well as enhanced vascular responsiveness to vasoconstrictors, an attenuated response to vasodilators and impaired autoregulation of cerebral blood flow. Altered endothelial function of arterioles and an impaired vasomotor function of resistance vessels could contribute to altered regulation of regional blood flow and insufficient tissue perfusion in diabetes mellitus. Hyperbaric oxygen therapy is shown to contribute to the healing of ischemic ulcerations in diabetic patients and to improvement of several other pathologic conditions. However, information about the mechanism of how this therapy works is still very limited. We postulate that hyperbaric oxygen therapy has an effect on vascular function by modulating mechanisms of vascular responses to various dilator and constrictor agonists in cerebral resistance vessels, leading to restored vascular reactivity. In accordance to this, the therapy affects production of vasodilators and vasoconstrictors, as well as the vessel-sensitivity to these factors. Furthermore, we hypothesize that hyperbaric oxygen therapy would restore cerebral blood flow regulation that is impaired in diabetics, whereas in contrast to that, chronic intermittent hypoxia would lead to impaired cerebral blood flow. These proposed mechanisms would, if confirmed, represent a valuable advancement in the understanding of this subject.     

The development of a novel mouse model of transient global cerebral ischemia

A reproducible model of global cerebral ischemia in mice is essential for elucidating the molecular mechanism(s) of neuronal damage induced by cerebral ischemia/reperfusion injury. In the present study, we developed a mouse model of transient global ischemia induced by occlusion of the bilateral common carotid arteries and the left subclavian artery together with right subclavian artery (RSA) stenosis (CSOSS) under controlled ventilation in C57BL/10ScSn mice. The mean arterial blood pressure was maintained in the physiological range. The cortical cerebral blood flow was reduced to less than 10% of the pre-ischemic value. Twelve minutes of global ischemia induced brain damage in several brain structures. The neuropathological score in the hippocampus CA1 region was 1.7, 3.5 and 3.7 following reperfusion for 24, 48 and 72 h, respectively. Less extensive damage was seen in the dentate gyrus and cortical regions, compared with the CA1 region. Damage was observed in these regions 24h after ischemia and was not different between 48 and 72 h post-ischemia. Results indicated that this global ischemia model possessed several advantages, including reproducible cerebral ischemic insult, sufficient reperfusion and low mortality rate (10%), and could be used for studies on cerebral ischemia/reperfusion injury in mice.     

Post-ischemic coma in rat: effect of different pre-ischemic blood glucose levels on cerebral metabolic recovery after ischemia

Hyper-, normo-, and hypoglycemic rats were exposed to 10 min of complete cerebral ischemia. Regional cerebral blood flow (CBF), blood-brain glucose transfer, and cerebral consumption of oxygen and glucose were measured before, as well as three and 60 minutes after ischemia. Three min after ischemia, no differences were observed between the 3 groups of rats. One h after ischemia, the hyperglycemic rats in comparison to those of the other groups had similar whole-brain CBF and glucose consumption but appreciately lower oxygen consumption, indicating continued non-oxidative use of glucose in the hyperglycemic group. In general, regional CBF values exceeded the control value by 100–200% 3 min after ischemia and were reduced to 50% of control at 1 h after ischemia, at which time the rats were still comatose. In the brain stem of hyperglycemic rats, blood flow, however, remained elevated after ischemia. Thus, the significantly increased mortality observed in rats hyperglycemic before, during and after ischemia (Siemkowicz & Hansen 1978) was the result, not of impaired postischemic CBF, but of ischemic or postischemic damage to brain cells. We suggest that the damaging factor in the hyperglycemic group is increased lactacidosis associated with prolonged anaerobic glycolysis.     

Nucleoprotamine diet derived from salmon soft roe protects mouse hippocampal neurons from delayed cell death after transient forebrain ischemia

The nutritional benefits of nucleoprotamine (NP), the main component of fish soft roe, have been rarely addressed. In the present study, the preventive effect of oral supplements of nucleoprotamine and its derivatives, DNA and protamine (PT), extracted from salmon soft roe, on survival rate and hippocampal cell death induced by transient brain ischemia, was evaluated in mice. Artificially formulated nucleoprotamine-free (NF) diet with/without nucleoprotamine, DNA or protamine was fed orally. One week after commencement of respective diets, animals were subjected to transient brain ischemia, which was performed by common carotid artery (CCA) occlusion for 25 (severe) or 15 min (mild). After severe ischemia, the survival rate of the NF group was lower than that in the group fed standard diet or NP. Morphological changes in the hippocampal CA1 region were estimated 48 h after mild ischemia. The NP and PT groups significantly decreased the neuronal damage compared with the NF group. The number of cell death in the DNA group, however, was affected similar to that of the NF group. Our data suggests that the nucleoprotamine content in salmon soft roe could be a useful nutritional resource for the prevention of cell damage caused by ischemia such as those occurring with cerebral and/or heart infarction.     

Effects of dopamine infusion on cerebral blood flow, brain cell membrane function and energy metabolism in experimental Escherichia coli meningitis in the newborn piglet

In the present study, we tested whether maintenance of adequate cerebral perfusion pressure (CPP) by pharmacologically preventing systemic hypotension with dopamine infusion would prevent cerebral ischemia and attenuate energy depletion and neuronal injury even though intracranial pressure remains elevated in a newborn piglet meningitis model. Cerebral blood flow, measured at the end of the experiment using fluorescent microspheres, was significantly increased by dopamine infusion. The decreased cerebral cortical cell membrane Na+, K+ -ATPase activity and increased lipid peroxidation products, indicative of meningitis-induced brain damage, were significantly attenuated by dopamine infusion. Dopamine also significantly attenuated the meningitis-induced reduction in both brain ATP and phosphocreatine levels and the increase in brain lactate level. In summary, maintenance of adequate CPP with dopamine prevented cerebral ischemia, reduced cerebral energy depletion, and attenuated brain injury in neonatal bacterial meningitis.     

Individual Resistance to Cerebral Ischemia and Negative Effect of Emotional Stress on the Course of This Disorder

The ratio of low-activity and high-activity rats differed in autumn, winter, and spring litters. Initially more intensive cerebral blood flow in low-active rats and its more pronounced decrease after common carotid artery occlusion determined their higher sensitivity to cerebral ischemia (compared to high-activity animals). After 18-h immobilization stress cerebral blood flow decreased by 10-15%, which abolished the difference in the individual resistance to cerebral ischemia. Independently on emotional resistance, cerebral ischemia was not accompanied by the development of collateral blood flow in the acute period and caused death of 90% rats.     

Hypernatraemia in cerebral disorders

Six patients are described in whom cerebral damage was associated with raised plasma sodium and chloride concentrations and with extremely low urinary outputs of sodium and chloride. The patients were not clinically dehydrated and direct determinations showed that the blood and plasma volumes, the endogenous creatinine clearance, and the urinary output of antidiuretic hormone were normal. For these and other reasons it is concluded that the metabolic picture results not from diminished circulatory volume, water deficiency, sodium deficiency, undetected diabetes insipidus or osmotic diuresis, but from the cerebral damage itself.     

Effect of Cerebral Blood Flow and Cerebrovascular Autoregulation on the Distribution, Type and Extent of Cerebral Injury

Global cerebral blood flow (GCBF) is low in the human neonate compared to the adult. It is even lower in mechanically ventilated, preterm infants: 10-12 ml/100 g/minute, a level associated with brain infarction in adults. The reactivity, however, of global CBF to changes in cerebral metabolism, PaCO2, and arterial blood pressure is normal, except following severe birth asphyxia, or in mechanically ventilated preterm infants, who subsequently develop major germinal layer hemorrhage. The low level of cerebral blood flow (CBF) matches a low cerebral metabolism of glucose and a relatively small number of cortical synapses in the perinatal period. It has not been possible to define a threshold for GCBF below which electrical dysfunction or brain damage occurs (such as white matter and thalamic-basal ganglia necrosis). Three explanations for the lack of clear relation between GCBF and electrical brain activity of the preterm infant must be examined more closely: 1) low levels of CBF are adequate; 2) GCBF does not adequately reflect critically low perfusion of the white matter, and 3) acute white matter ischemia does not result in electrical silence. Two clinical patterns of brain damage following asphyxia may be explained by changes in the blood flow distribution induced by asphyxia: brainstem sparing and parasagittal cerebral injury. Hours to days after severe asphyxia, a state of marked global hyperperfusion may prevail. It is associated with poor neurological outcome and may be an entry point for trials of interventions aiming sat blocking the translation of asphyctic injury to cellular death and tissue damage.     

动脉粥样硬化性脑梗死患者血浆抗凝血酶Ⅲ的变化及其机制

 目的：探讨抗凝血酶Ⅲ（AT-Ⅲ）在动脉粥样硬化性脑梗死患者中的变化及其机制。方法：采用发色底物法检测55例动脉粥样硬化性脑梗死患者血浆中AT-Ⅲ活性,并与神经系统损伤程度、一般生化项目进行相关性分析;应用酶联免疫吸附法（ELISA）测定血浆肿瘤坏死因子（TNF-α）和白细胞介素6（IL-6）水平;酶免疫法（EIA）测定患者血浆中免疫复合物的含量;流式细胞术检测外周血单核细胞数量及表型,并与正常组55例体检者进行对照。采用ELISA法分析免疫复合物刺激外周血单核细胞后TNF-α和IL-6分泌的变化;Western blotting法观察TNF-α和IL-6对人脑血管内皮细胞AT-Ⅲ表达的影响。结果：动脉粥样硬化性脑梗死患者血浆中AT-Ⅲ活性明显降低（P<005）,且与神经系统功能损伤程度呈负相关（P<005）,与收缩压、舒张压、空腹血糖、胆固醇、甘油三酯、低密度脂蛋白、同型半胱氨酸呈负相关,与高密度脂蛋白呈正相关（P<005）;同时,患者血浆中TNF-α和IL-6水平明显升高（P<001）,伴随免疫复合物含量增多（P<001）;流式细胞术分析发现,患者外周血CD14+CD16+和CD14+CD32+单核细胞数量无明显变化（P>005）,而CD14+CD64+单核细胞数量显著增多（P<005）。经免疫复合物刺激后,外周血单核细胞TNF-α和IL-6分泌明显升高（P<001）,而TNF-α或IL-6与人脑血管内皮细胞共孵育后,均可下调其AT-Ⅲ蛋白表达水平（P<005或P<001）。结论：AT-Ⅲ在动脉粥样硬化性脑梗死患者血浆中明显降低,是脑梗死发病的危险因素之一,且与病情严重程度相关,其可能的机制是免疫复合物通过CD14+CD64+单核细胞介导促炎细胞因子的产生。升高AT-Ⅲ活性对缺血脑组织具有保护作用。     

Multilocal magnetic resonance perfusion mapping comparing the cerebral hemodynamic effects of decompressive craniectomy versus reperfusion in experimental acute hemispheric stroke in rats

This study examined the hemodynamic effects of craniectomy compared to reperfusion on the temporal evolution of cerebral perfusion in different brain regions in a rat model of focal cerebral ischemia. Three groups were investigated: no treatment, reperfusion or craniectomy at 1 h. Perfusion-weighted magnetic resonance imaging (PWI) was performed serially from 0.5 to 6 h. Relative regional cerebral blood flow was calculated for different regions and infarct volume was assessed by histology at 24 h. As conclusion, both, craniectomy and reperfusion increased cerebral perfusion in the acute phase of cerebral ischemia. While reperfusion resulted in a homogeneous improvement of perfusion in the cortex and basal ganglia, craniectomy improved only cortical perfusion in areas directly under the craniectomy site. PWI is well suited to non-invasively monitor perfusion alterations after aggressive therapeutical approaches in stroke.     

脑缺血再灌注后血栓形成与血浆纤维蛋白原水平的变化

目的 :在动物活体模型上 ,连续观察脑缺血 /再灌注时脑软膜微血管内血栓形成的过程并测量缺血 /再灌注不同时期血浆纤维蛋白原的变化。方法 :用夹闭沙土鼠双侧颈总动脉的方法复制脑缺血再灌注模型。颈动脉注入 0 .0 67%异硫氢酸荧光黄 (FITC) 0 .2ml后 ,在荧光显微镜下观察脑软膜微血管内血栓形成的过程 ,并在缺血 15min、30min、再灌注 30min、1h、6h时采血 ,用凝血酶凝固法测量血浆纤维蛋白原。结果 :单纯缺血期血流速度明显减慢 ,细动脉、细静脉管径缩小 ,有部分毛细血管内血流停滞。再灌注后 ,血流速度加快 ,随再灌时间的延长 ,白细胞粘附、贴壁明显增多 ,血管内皮增厚 ,纤维蛋白丝网络血细胞及血小板 ,呈絮状团块附着在血管内壁上 ,逐渐形成壁栓 ,阻碍血细胞的流过。缺血期和再灌注后血浆纤维蛋白原水平均高于正常对照组 ,以缺血 30min和再灌 1h时增高最为明显 (P <0 .0 1)。再灌 6h时又明显降低 ,与单纯缺血 30min组比较有显著性差异 (P <0 .0 1)。结论 :再灌注后快速恢复的血流加重了内皮细胞的损伤 ,白细胞、血小板粘附 ,导致血栓形成 ,并认为血浆纤维蛋白的形成在此病理过程中起着重要的作用