脑缺血再灌注损伤的研究进展

脑缺血再灌注损伤是一个复杂的病理生理过程,这一级联反应涉及许多环节,包括酸中毒、自由基、线粒体功能障碍等方面。随着研究的进展,近年来出现了一些新的动物模型,如动脉内导管模型、转基因小鼠模型等,为我们的研究提供了新的载体;而预灌注疗法、脊髓电刺激疗法、蛋白激酶抑制剂、神经干细胞移植等方法的出现,则为我们的治疗提供了新的思路。     

硫化氢保护脑缺血再灌注损伤的研究进展

正缺血性脑卒中致残率、病死率高,发生机制十分复杂,包括细胞能量代谢障碍、兴奋毒性、氧化应激反应、炎症反应、神经细胞凋亡以及血脑屏障受损等。当前,治疗缺血性脑卒中最有效的方法是人类重组纤溶蛋白酶激活剂,但是这种方式的治疗时间窗太窄(3~4.5 h),超出此范围之后仍旧会导致缺血再灌注损伤(ischemia/reperfusion injury,I/RI)~([1])。研究表明,硫化氢(H_2S)具有抗氧化应激、抗炎症反     

脑缺血再灌注的利与弊

在缺血性脑血管病的基础研究中，人们谈论和研究最多的是缺血再灌注损伤，尤其在动物实验方面，大多数的基础研究者报道的论文均肯定缺血再灌注对脑组织的危害性，使人们感觉到脑缺血再灌注的可怕性。可是，在临床方面，临床医师倒是想方设法去改善缺血性脑组织的血液循环，即再灌注，以     

缺血后处理对大鼠脑缺血再灌注损伤神经保护作用的研究

目的探讨大鼠脑缺血后处理对缺血再灌注损伤后神经元的保护作用。方法健康雄性SD大鼠30只,随机分为假手术组(SO组)、缺血再灌注对照组(MCAO组)、缺血后处理组(IPOC组)3组。采用线栓法制备大鼠MCAO模型及IPOC模型,分别用TTC染色法计算脑梗死体积、流式细胞术和ELISA法观察,对于大鼠缺血半暗带神经细胞凋亡率及血清神经元特异性烯醇化酶(NSE)含量的影响。结果 (1)大鼠脑缺血再灌注后24h,IPOC组较MCAO组梗死体积明显减小(P<0.05);(2)MCAO组大鼠脑缺血再灌注24h细胞凋亡发生率及血清中NSE的含量较SO组显著增加(P<0.01);(3)IPOC组神经元凋亡发生率及血清NSE较MCAO组显著降低(P<0.05或0.01)。结论大鼠脑缺血后处理对缺血再灌注神经元损伤有保护作用。     

脑缺血再灌注神经干细胞原位激活的研究

目的 探讨大鼠局灶性脑缺血再灌注后不同时间、不同脑部位神经干细胞(NSC)原位激活的变化规律。方法 建立一侧大脑中动脉闭塞缺血再灌注模型,用5-溴脱氧尿苷(BrdU)标记脑内增殖细胞,免疫组化(SP法)技术检测大鼠缺血再灌注不同时间段缺血周边皮质、双侧侧脑室下区(SVZ)、海马齿状回下区(SGZ)具有增殖能力细胞BrdU表达变化。结果 对照组脑组织双侧SVZ、SGZ可见少量BrdU阳性标记细胞;单纯脑缺血2 h组脑组织BrdU阳性细胞数未见明显增加;再灌注3天组,缺血侧皮质、双侧SVZ和SGZBrdU阳性细胞明显增多(P<0.05),7天时达到高峰(P<0.001),11天时下降,且缺血侧与对侧相比,双侧SVZ呈对称分布,而SGZ以缺血侧增加为主(P<0.05)。结论 一侧大脑中动脉闭塞缺血再灌注可致成年大鼠脑内NSC原位激活,且NSC增殖于缺血后1周达到高峰,激活部位以双侧SVZ、缺血侧海马和周边皮质为主。     

大鼠局灶性脑缺血再灌注后神经细胞的凋亡

本实验用线栓法制作局灶性脑缺血再灌注大鼠模型64只,分脑缺血90min再灌注0.5、6h、1、3、14d组,放线菌酮处理组及对照组。观察脑缺血后再灌注不同时间凋亡细胞的发生情况及其与梗塞体积、神经功能缺损积分间的关系,以及蛋白质合成抑制刺的干预作用;细胞凋亡通过Tunel染色及电镜检测。结果发现脑缺血90min再灌注0.5h开始出现凋亡细胞,24h达高峰,持续2周;梗塞灶的形成较凋亡细胞出现晚,但24h同时达到高峰,随着时间延长,凋亡细胞数减少,梗塞体积无明显变化;蛋白质合成抑制剂放线菌酮可以减少缺血后梗塞体积及凋亡细胞。     

神经生长因子对大鼠局灶性脑缺血再灌注后细胞凋亡的影响

目的　探讨大鼠局灶性脑缺血再灌注后神经生长因子 (NGF)对细胞凋亡的影响。方法　应用原位缺口末端标记 (TUNEL)法检测大鼠大脑中动脉线栓法阻断 2h ,再灌注 2 2h ,细胞凋亡情况及静脉注射NGF对细胞凋亡的影响。结果　缺血 2h ,再灌注 2 2h ,梗死区可见大量凋亡细胞 (2 4 8.4 2± 2 4 .37) ,静脉注射NGF后梗死区凋亡细胞明显减少 (190 .2 5± 2 5 .4 7) (P <0 0 1)。结论　局灶性脑缺血再灌注后细胞凋亡增加 ,静脉给予NGF可减少脑细胞凋亡     

大鼠脑缺血再灌注损伤后不同部位神经细胞Nestin的表达

目的研究大鼠脑缺血再灌注损伤后神经细胞巢蛋白（Nestin）的表达,为神经干细胞治疗脑损伤提供理论依据。方法成年健康雄性SD大鼠30只,随机分为实验组和对照组。线栓法建立大脑中动脉闭塞再灌注模型,应用免疫组化SABC法观察2组再灌注后各观察部位不同时间Nestin的表达情况。结果缺血再灌注6h Nestin阳性细胞少量表达;1d时数量增多;3d时明显增多,7d时变化最为显著;各实验组与对照组比较差别均极显著。结论Nestin阳性细胞在正常成年脑组织中广泛表达,损伤后各部位Nestin阳性细胞的表达呈一致性增强,各部位阳性细胞数的增加量在不同时间又有所不同。     

脑缺血预处理对缺血再灌注损伤的保护作用

目的　观察缺血预处理对脑缺血再灌注损伤的保护作用。方法　采用四血管阻断法对实验鼠分组进行全脑缺血预处理及缺血后再灌注, 半定量法观察海马区神经元受损情况。结果　实验组四血管阻断３ 分钟（ 预处理） 后海马区神经元受损与对照组无显著差异;３ 天间隔６ 分钟全脑缺血再灌注组神经元受损较其他组明显减轻。结论　缺血预处理对脑缺血再灌注损伤保护作用与全脑缺血预处理时间, 后续全脑缺血再灌注损伤时间及两者间的时间间隔有关。     

胰岛素对脑缺血再灌注损伤的保护作用

文章阐述了胰岛素在中枢神经系统的来源,胰岛素在全脑缺血和局灶性脑缺血中的应用度其保护机制,指出胰岛素的应用有望成为缺血性脑血管病的一种治疗方法。     

亚低温对大鼠脑缺血再灌注后出血转化及超微结构的影响

目的 观察亚低温对不同时间窗缺血再灌注大鼠出血转化的影响及脑组织超微结构的改变,探讨亚低温对局灶性脑缺血大鼠的神经元和血管的保护作用。方法 利用线栓法制作SD大鼠大脑中动脉缺血再灌注（middle cerebral artery occlusion-reperfusion,MCAOR）模型,闭塞时间分别为3 h、6 h和9 h,再分别随机分为常温组、3 h和5 h亚低温组,并设立假手术组。其中亚低温组再灌注后,用10％水合氯醛再次麻醉大鼠,将大鼠置于冰毯上降温,在15分钟内将大鼠肛温降至亚低温状态（32℃～35℃）,保持大鼠亚低温状态3 h或5 h。再灌注24 h后处死大鼠并取脑。每组取6只大鼠测量各组脑出血量;每组取2只大鼠,透射电镜下观察大鼠视交叉后皮层缺血边缘带神经元和内皮细胞的形态学变化。结果 各MCAOR组大鼠随缺血时间延长出血转化量增加,应用亚低温干预后,各组出血转化量均减少。各MCAOR组大鼠视交叉后皮层缺血边缘带超微结构显示不同程度受损,随着缺血时间延长逐渐加重。亚低温可减轻其损伤程度,以缺血3 h亚低温3 h组效果最好。结论 亚低温对大鼠缺血再灌注后脑组织具有保护作用,改善脑组织超微结构,为脑功能重建提供超微结构基础。     

嗅鞘细胞的可塑性研究

2004年诺贝尔医学和生理学奖得主Richard Axel和Linda Buck证实：原来认为不具备分化能力的小鼠嗅感觉神经元能够再次进入细胞周期发生分裂．这一发现是嗅觉神经系统可塑性的典型体现。嗅鞘细胞（olfactory ensheathing cells，OECs）作为嗅觉系统内一种特殊类型的胶质细胞．大量研究证实其可促进中枢神经系统（central nervous system．CNS）损伤的修复。但目前对OECs生物学特性的认识仍存在不同观点．其可塑性的研究近年来逐渐受到关注。可塑性指在变化的内外环境刺激下细胞改变自身特性．在形态、抗原表达和功能上呈现很大程度的可变性。目前被证实OECS表达的抗原有S100β、神经生长因子低亲和力受体（p751、胶质纤维酸性蛋白（glial fibrill aryacidicprotein，GFAP）、神经肽Y（neuropeptide Y．NPY）、O4和神经细胞黏附分子（neural cell adhesion molecule，NCAM）等。     

Impact of Energy Intake and Expenditure on Neuronal Plasticity

The Roman poet Horace was among the first to recognize that when “clogged with yesterday’s excess, the body drags the mind down with it.” Although considerable attention has been paid in neuroscience to the enhancement of neuronal function by wheel running and caloric restriction, far less is known about the other side of this issue. What are the consequences of unhealthy habits to central nervous system function? Prolonged exposure to excessive caloric intake impairs neuronal function and also contributes to obesity and other risk factors for diabetes. Diabetes, a disease characterized by reduced sensitivity to glucose and insulin, is also associated with deficits in brain structure and function. In contrast, enhancement of somatic metabolism by wheel running or caloric restriction improves central neuroplasticity. Generalizing across studies reveals a relationship between global metabolic efficiency and neuroplasticity in the hippocampus, a brain region that is essential for learning and memory. The specific principles upheld by these findings are suggestive of a continuum, with global metabolic alterations fluctuating in concert with neuroplasticity in the hippocampus.     

磁共振波谱分析在脑梗死中的研究进展

脑梗死占脑卒中的80％～85％,其死亡率、致残率及复发率都很高,而且随着我国老龄化人口的增多,其发病率亦逐年增加。在脑梗死的早期,及时诊治对抢救患者的生命、减轻神经功能缺损、改善预后至关重要。近年来,随着磁共振波谱（magnetic resonance spectroscopy,MRS）技术的发展,磁共振成像已由大体形态学向功能、代谢及分子诊断水平迈进,对了解各种疾病的生化、病理生理变化、临床诊断、判断疾病预后和治疗效果均有非常重要的意义。本文对近年来MRS在脑梗死方面的研究进行了综述。     

Analysis of Spatial and Temporal Protein Expression in the Cerebral Cortex after Ischemia-Reperfusion Injury

Background and Purpose

Hypoxia, or ischemia, is a common cause of neurological deficits in the elderly. This study elucidated the mechanisms underlying ischemia-induced brain injury that results in neurological sequelae.

Methods

Cerebral ischemia was induced in male Sprague-Dawley rats by transient ligation of the left carotid artery followed by 60 min of hypoxia. A two-dimensional differential proteome analysis was performed using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry to compare changes in protein expression on the lesioned side of the cortex relative to that on the contralateral side at 0, 6, and 24 h after ischemia.

Results

The expressions of the following five proteins were up-regulated in the ipsilateral cortex at 24 h after ischemia-reperfusion injury compared to the contralateral (i.e., control) side: aconitase 2, neurotensin-related peptide, hypothetical protein XP-212759, 60-kDa heat-shock protein, and aldolase A. The expression of one protein, dynamin-1, was up-regulated only at the 6-h time point. The level of 78-kDa glucose-regulated protein precursor on the lesioned side of the cerebral cortex was found to be high initially, but then down-regulated by 24 h after the induction of ischemia-reperfusion injury. The expressions of several metabolic enzymes and translational factors were also perturbed soon after brain ischemia.

Conclusions

These findings provide insights into the mechanisms underlying the neurodegenerative events that occur following cerebral ischemia.     

Plasticity of urinary bladder reflexes evoked by stimulation of pudendal afferent nerves after chronic spinal cord injury in cats

Bladder reflexes evoked by stimulation of pudendal afferent nerves (PudA-to-Bladder reflex) were studied in normal and chronic spinal cord injured (SCI) adult cats to examine the reflex plasticity. Physiological activation of pudendal afferent nerves by tactile stimulation of the perigenital skin elicits an inhibitory PudA-to-Bladder reflex in normal cats, but activates an excitatory reflex in chronic SCI cats. However, in both normal and chronic SCI cats electrical stimulation applied to the perigenital skin or directly to the pudendal nerve induces either inhibitory or excitatory PudA-to-Bladder reflexes depending on stimulation frequency. An inhibitory response occurs at 3–10 Hz stimulation, but becomes excitatory at 20–30 Hz. The inhibitory reflex activated by electrical stimulation significantly (P < 0.05) increases the bladder capacity to about 180% of control capacity in normal and chronic SCI cats. The excitatory reflex significantly (P < 0.05) reduces bladder capacity to about 40% of control capacity in chronic SCI cats, but does not change bladder capacity in normal cats. Electrical stimulation of pudendal afferent nerves during slow bladder filling elicits a large amplitude bladder contraction comparable to the contraction induced by distension alone. A bladder volume about 60% of bladder capacity was required to elicit this excitatory reflex in normal cats; however, in chronic SCI cats a volume less than 20% of bladder capacity was sufficient to unmask an excitatory response. This study revealed the co-existence of both inhibitory and excitatory PudA-to-Bladder reflex pathways in cats before and after chronic SCI. However our data combined with published electrophysiological data strongly indicates that the spinal circuitry for both the excitatory and inhibitory PudA-to-Bladder reflexes undergoes a marked reorganization after SCI.     

Hormonally Induced Neuronal Plasticity in the Adult Motoneurons

Sex steroids are known to play a crucial role in reproductive neuroendocrine functions in adulthood. A number of neurons in the neuroendocrine brain contain sex steroid receptors, and are thought to be a key element of functional neural circuits that are regulated by sex steroids. Motoneurons in the spinal nucleus of the bulbocavernosus in adult male rodents are one of the androgen-sensitive neural substrates. In the spinal nucleus of the bulbocavernosus, castration of adult male rats results in a significant decrease in the somatic size and dendritic length of the motoneurons, and in the number and size of chemical and electrical (gap junction) synapses onto these motoneurons. Androgen treatment of castrates reverses these changes. Furthermore, androgen has been reported to be involved in regulation of androgen receptor expression and gene expression of structural proteins such as β-actin, β-tubulin and gap junction channels in these motoneurons. The findings suggest that androgen induces morphological and molecular changes in the motoneurons that reflect their neural functions, and may provide evidence for the mechanisms of hormonally induced neuronal plasticity in the motoneurons in adulthood.     

还原型谷胱甘肽对鼠脑缺血再灌注损伤的影响

目的 观察还原型谷胱甘肽对大鼠脑缺血再灌注损伤的保护作用.方法 纯种老年雄性大鼠54只随机分组,分为大鼠致死性缺血冉灌注组(IR组)、还原型谷胱甘肽预处理组(GI组)和假手术组(SG组),并依处死动物时间各组又分为3个亚组(SG 1d,SG 3d,SG 5d;IR ld,IR 3d,IR 5d;GI ld,GI 3d,GI 5d),各6只.苏木精-伊红(HE)染色观察海马区病理变化,免疫组化(SP法)检测海马区p53蛋白的表达.观察预处理对缺血2h再灌注损伤1d、3d、5d的影响.结果 GI 3d、5d组、AI 3d、5d组海马区神经元损伤程度明显较IR对应组轻,且GI3d、5d组、AI 3d、5d组海马区存活锥体细胞数明显多于相对应的IR组(P＜0.01).p53免疫组化IR组于再灌注后1d p53蛋白表达增高,3d后显著增高,再灌注后5d有所下降,但仍高于SG组(P＜0.01);GI、AI组p53蛋白的表达显著低于相应的IR组(P＜0.01).结论 谷胱甘肽及环磷腺苷预处理能减少脑缺血再灌注损伤后锥体细胞的死亡;下调促凋亡基因p53蛋白可能是谷胱甘肽及环磷腺苷产生脑保护作用的机制之一.     

Plasticity of GFAP-immunoreactive astrocyte size and number in visual cortex of rats reared in complex environments

Previous studies have indicated effects of postweaning rearing environment complexity on astrocyte nuclei. This study examined the effects of rearing for 10, 30 or 67 days in a complex (EC), social (SC) or individual cage (IC) environment upon glial fibrillary acidic protein (GFAP) immunoreactive astrocytes of the occipital cortex. EC rats exposed to their environment for 30 days or longer had a greater surface density of astrocytic processes (Sv) than SC or IC rats. The greater surface density of EC cortical astrocytes appeared to be due to an increase in the mean size of astrocytes after 30 days of differential environmental exposure. After 67 days of environmental exposure, however, the greater Sv appeared to be due to an increase in the number of astrocytes. Astrocytic plasticity appears to develop rather slowly during exposure to a complex environment and appears to involve two stages. The first stage is a hypertrophy of existing astrocytes and the second stage involves proliferation or retarded death of astrocytes. These changes may be related to brain information processing since astrocytes are known modulators of synaptic activity and may possibly serve as regulators of synaptic density.