Early T1- and T2-weighted MRI signatures of transient and permanent middle cerebral artery occlusion in a murine stroke model studied at 9.4T

Early reperfusion following stroke results in reduced tissue injury. Paradoxically, restoration of blood flow under certain conditions may also cause delayed neuronal damage (reperfusion injury). The interrelationship of changes in T1, T2 and diffusion weighted images of tissue water were studied in mouse models of permanent and transient focal cerebral ischemia. A sham surgery or either permanent or transient (30 min) middle cerebral artery occlusion (MCAO) were induced in 14 mice. Magnetic resonance (MR) images of the brain were acquired including: T2 maps, T1 maps and diffusion weighted spin-echo images to produce apparent diffusion coefficient of water apparent diffusion coefficient (ADC) maps. Images were collected on average 90 min after MCAO in both the transient and permanent ischemia groups. Scans were repeated at 24h post-occlusion in mice with transient ischemia. Permanent MCAO resulted in decreases in ADC and no significant change in T2 acutely following MCAO. There were increases in T1 compared to sham controls within the ischemic region in mice following either transient or permanent MCAO (P<0.001). In contrast to permanent MCAO, there were increases in T2 (P<0.001) in the infarct area present in the reperfusion phase within 90 min of transient MCAO. There was considerable infarct growth at 24h (P<0.001). This study demonstrates that following either type of occlusion there are early increases in T1 suggesting an elevated water content in the stroke lesion, while only following transient MCAO are there early increases in T2, indicative of early vasogenic oedema with breakdown of the blood-brain barrier.     

A comparison of the early development of ischemic brain damage in normoglycemic and hyperglycemic rats using magnetic resonance imaging

The early evolution of ischemic brain injury under normoglycemic and streptozotocin-induced hyperglycemic plasma conditions was studied using magnetic resonance imaging (MRI). Male Sprague-Dawley rats were subjected to either permanent middle cerebral artery occlusion (MCAO), or 1-h MCAO followed by reperfusion using the intraluminal suture insertion method. The animals were divided into four groups each with eight rats: normoglycemia with permanent MCAO, normoglycemia with 1-h MCAO, hyperglycemia with permanent MCAO, and hyperglycemia with 1-h MCAO. Diffusion-weighted images (DWIs) and T2-weighted images (T2WIs) were aquired every l h from 20 min until 6 h after MCAO, at which time cerebral plasma volume images (PVIs) were acquired. Tissue infarction was determined by triphenyltetrazolium chloride staining at 7 h after MCAO. The ischemic damage, measured as the area of DWI and T2WI hyperintensity and tissue infarction, increased significantly in hyperglycemic rats in both permanent and transient MCAO models. In the permanent MCAO model, the maximal apparent water diffusion coefficient (ADC) decline under either normoor hyperglycemia was about 40%, but the speed of ADC drop was faster in hyperlgycemic rats than in normoglycemic rats. Reperfusion after l h of MCAO in normoglycemic rats partly reversed the decline in ADC, whereas the low ADC area continued to expand after reperfusion in the hyperlgycemic group. Between the two hyperglycemic groups with either permanent MCAO or reperfusion, no significant difference was found in the infarct volume measured at 7 h after MCAO. However, reperfusion dramatically increased the extent and accelerated the development rate of vasogenic edema. ADC in the hyperglycemic reperfusion group also dropped to a lower level. A large no-reflow zone was found in the ischemic hemisphere in the hyperglycemic reperfusion group. This study provides strong evidence to support that preischemic hyperglycemia exacerbates ischemic damage in both transient and permanent MCAO models and demonstrates, using MRI, that reperfusion under preischemic hyperglycemia accelerates the evolution of early ischemic injury.     

Imipramine enhances cell proliferation and decreases neurodegeneration in the hippocampus after transient global cerebral ischemia in rats

This study was aimed to determine whether imipramine chronic treatment promotes neurogenesis in the dentate gyrus (DG) and interferes with neuronal death in the CA1 subfield of the hippocampus after transient global cerebral ischemia (TGCI) in rats. After TGCI, animals were treated with imipramine (20 mg/kg, i.p.) or saline during 14 days. 5-Bromo-2′-deoxyuridine-5′-monophosphate (BrdU) was injected 24 h after the last imipramine or saline injection to label proliferating cells. In order to confirm the effect of TGCI on neuronal death and cell proliferation, a group of animals was sacrificed 7 days after TGCI. Neurogenesis and neurodegeneration were evaluated by doublecortin (DCX)-immunohistochemistry and Fluoro-Jade C (FJC)-staining, respectively. The rate of cell proliferation increases 7 days but returns to basal levels 14 days after TGCI. There was a significant increase in the number of FJC-positive neurons in the CA1 of animals 7 and 14 days after TGCI. Chronic imipramine treatment increased cell proliferation in the SGZ of DG and reduced the neurodegeneration in the CA1 of the hippocampus 14 days after TGCI. Immunohistochemistry for DCX detected an increased number of newly generated neurons in the hippocampal DG 14 days after TGCI, which was not affected by imipramine treatment. Further studies are needed to evaluate whether imipramine treatment for longer time would be able to promote survival of newly generated neurons as well as to improve functional recovery after TGCI.     

Neurodegeneration and cellular stress in the retina and optic nerve in rat cerebral ischemia and hypoperfusion models

Experimental cerebral ischemia induces a stress response in neuronal and non-neuronal cells. In the present study we aimed to evaluate detailed cellular stress responses and neurodegenerative changes in the retinas in rat focal cerebral ischemia and hypoperfusion models involving invasive vascular manipulations. Independent groups of adult male Wistar rats were subjected to i) transient middle cerebral artery occlusion (tMCAO), ii) permanent middle cerebral artery occlusion (pMCAO), iii) cortical photothrombosis of the sensorimotor cortex using Rose Bengal dye or iv) bilateral common carotid artery occlusion (BCCAO). Rats were killed, and their eyes with the optic nerves enucleated and processed for histology, immunohistochemistry for neuronal nuclei (NeuN), glial fibrillary acidic protein (GFAP), hypoxia-inducible factor 1alpha (HIF-1alpha), c-fos, alphaB-crystallin, heat shock protein (HSP) 27, HSP60 and HSP70, and detection of DNA defragmentation. The total number of the retinal ganglion cell layer (RGCL) neurons and GFAP-immunoreactive astrocytes located in the nerve fiber layer were estimated using unbiased stereological counting. Our findings indicate that although permanent and transient MCAO does not cause detectable morphological alterations in the retina or optic nerve, it evokes ischemic stress as revealed by HIF-1alpha and HSPs expression in the RGCL neurons and reactive gliosis in the Müller cells. Severe neurodegenerative changes in the retina and optic nerve of the BCCAO rats are accompanied by a significant increase in immunoreactivities for the c-fos, HSP27 and HSP70 as compared with the sham-operated animals. The retinas from the ipsilateral side of the Rose Bengal model showed a significant decrease in the total number of NeuN-positive neurons in the RGCL as compared with the contralateral ones. However, these eyes did not differ between each other in the HSPs and HIF-1alpha expression or in the GFAP-immunoreactivity of the Müller cells. In conclusion, our data suggest differential expression of various HSPs in the retina and possibly their distinct roles in the cerebral ischemia-mediated stress response and neurodegeneration.     

局灶性脑缺血大鼠海马CA_3区突触体素动态表达

目的　研究局灶性脑缺血后海马CA3 区突触体素的动态表达以及神经修复的可塑性。方法　选取健康成年SD大鼠 4 0只 ,随机分为脑缺血组和对照组 ,每组又分为术后 7、14、2 1、30天 4个时间点 (n =5 )。采用线栓法建立大脑中动脉脑缺血大鼠模型 ,应用免疫组化技术观察海马CA3 区突触体素的表达。结果　脑缺血后各时间段突触体素阳性反应物表达的光密度较对照组明显降低 (P <0 .0 1) ;缺血后 7天至 2 1天突触体素表达逐渐回升 (P <0 .0 1) ,缺血后 30天又下降 ,但仍低于对照组。结论　突触体素可作为海马CA3 区神经元功能和损伤修复的标示物。     

Spatial learning is affected by transient occlusion of common carotid arteries (2VO): comparison of behavioural and histopathological changes after '2VO' and 'four-vessel-occlusion' in rats

Place learning in the Morris water maze following transient (24 min) occlusion of the common carotid arteries (2VO), and following permanent occlusion of both vertebral arteries plus transient (20 min) clamping of the carotids (4VO) was investigated in rats 6-9 days after occlusion. Both 2VO and 4VO treatment increased the latency to find the hidden platform during escape trials; spatial bias, tested in a probe trial, was decreased. Histological analysis revealed neural necrosis in the CA1 sector of the hippocampus in 4VO rats but not in 2VO animals. The data suggest that an experimentally induced reduction in cerebral blood flow of 50% (after 2VO) or 95% (after 4VO) produces persistent functional changes even in absence of actual neural damage.     

Characterization and quantification of cerebral edema induced by synchrotron x-ray microbeam radiation therapy

Cerebral edema is one of the main acute complications arising after irradiation of brain tumors. Microbeam radiation therapy (MRT), an innovative experimental radiotherapy technique using spatially fractionated synchrotron x-rays, has been shown to spare radiosensitive tissues such as mammal brains. The aim of this study was to determine if cerebral edema occurs after MRT using diffusion-weighted MRI and microgravimetry. Prone Swiss nude mice's heads were positioned horizontally in the synchrotron x-ray beam and the upper part of the left hemisphere was irradiated in the antero-posterior direction by an array of 18 planar microbeams (25 mm wide, on-center spacing 211 mm, height 4 mm, entrance dose 312 Gy or 1000 Gy). An apparent diffusion coefficient (ADC) was measured at 7 T 1, 7, 14, 21 and 28 days after irradiation. Eventually, the cerebral water content (CWC) was determined by microgravimetry. The ADC and CWC in the irradiated (312 Gy or 1000 Gy) and in the contralateral non-irradiated hemispheres were not significantly different at all measurement times, with two exceptions: (1) a 9% ADC decrease (p < 0.05) was observed in the irradiated cortex 1 day after exposure to 312 Gy, (2) a 0.7% increase (p < 0.05) in the CWC was measured in the irradiated hemispheres 1 day after exposure to 1000 Gy. The results demonstrate the presence of a minor and transient cellular edema (ADC decrease) at 1 day after a 312 Gy exposure, without a significant CWC increase. One day after a 1000 Gy exposure, the CWC increased, while the ADC remained unchanged and may reflect the simultaneous presence of cellular and vasogenic edema. Both types of edema disappear within a week after microbeam exposure which may confirm the normal tissue sparing effect of MRT.     

Chronic infusion of nerve growth factor does not rescue pyramidal cells after transient forebrain ischemia in the rat.

Male Wistar rats received chronic intracerebroventricular infusions of nerve growth factor (NGF) starting immediately before induction of a transient forebrain ischemia and continuing until 7 days after the infarct. Ischemia was induced by carotid occlusion and simultaneous hypotension. Seven days after the infarct the brains were examined histologically and the number of necrotic cells in the hippocampus were counted. The results did not reveal any difference in treated vs. untreated animals. The data suggest that application of exogenous NGF does not prevent ischemic cell death in the hippocampus.     

BMSCs移植后通过分泌神经营养因子对大鼠脑缺血神经功能改善的实验研究

目的研究骨髓间充质干细胞(BMSCs)移植改善大鼠脑缺血后神经功能及探讨其可能机制。方法采用线栓法构建大鼠永久性脑缺血动物模型,实验动物分缺血对照组和移植治疗组(n=24/组),缺血24h后移植治疗组经尾静脉移植体外培养的同种异体骨髓间充质干细胞(2×106cells/mLPBS)。移植后14d用Nissl染色观察移植前后缺血脑组织神经元缺损变化。于移植后1、7和14d用mNSS评分检测大鼠神经功能综合评价,于移植后1、3、7和14d用ELISA方法检测缺血中心区脑组织和缺血半暗带中的海马和皮质中VEGF的表达。移植后14d用免疫荧光观察移植后缺血侧海马新生神经元的迁移。结果BMSCs移植14d后大鼠脑缺血损伤的神经功能明显改善。Nissl染色发现BMSCs移植组缺血脑组织中尼1氏体的缺损比对照组少。BMSCs移植组缺血半暗带区的海马在1和3d[(63.324±0.625)pg/mL,(60.125±1.127)pg/mL]与对照组[(31.097±0.677)pg/mL,(35.05±0.681)pg/mL]相比VEGF表达显著增加,差异具有统计学意义(P0.05),缺血半暗带区的皮质中VEGF的表达在BMSCs移植后7和14d[(36.945±0.625)pg/mL,(32.177±1.127)pg/mL],与对照组比[(31.219±0.677)pg/mL,(25.636±0.681)pg/mL]明显增加,差异具有统计学意义(P0.05)。与对照组相比,第14天,BMSCs移植组能观察到缺血侧海马新生神经元的迁移。结论BMSCs移植后可使大鼠脑缺血损伤的神经功能显著改善,其作用机制可能为移植的BMSCs通过分泌VEGF等营养因子,促进内源性神经干细胞向脑缺血损伤区迁移,参与损伤修复从而改善脑缺血神经功能。     

浅低温脑灌注在体外循环下小儿室间隔缺损修补术中的应用

目的探讨浅低温脑灌注在体外循环下小儿室间隔缺损修补术中的应用效果。方法回顾性分析2017年2月至2018年7月我院收治的81例行体外循环下小儿室间隔缺损修补术患儿的临床资料,将术中采用浅低温脑灌注治疗的43例患儿设为浅低温组,术中采用中低温下脑灌注治疗的38例患儿设为中低温组。对比2组患儿术中最低鼻咽温度,术中最低直肠温度,术中体外循环时间,术中主动脉阻断时间,术后呼吸支持时间,术后心包和纵隔引流量,麻醉前(T0)、麻醉后10 min(T1)、手术开始后20 min(T2)、手术结束时(T3)血压(BP)及心率(HR)水平变化,术中室颤,术后低血压,术后心律失常及术后短暂性神经功能障碍发生率。结果浅低温组术中最低鼻咽温度、术中最低直肠温度均高于中低温组,差异有统计学意义(P<0.05),2组术中体外循环时间、术中主动脉阻断时间、术后呼吸支持时间、术后心包和纵隔引流量比较差异无统计学意义(P>0.05);各时刻2组间收缩压(SBP)、舒张压(DBP)、HR组间比较差异无统计学意义(P>0.05),且2组SBP、DBP和HR水平均先下降后升高,其中T1、T2、T3时刻BP和HR水平均明显低于T0时刻(P<0.05),T2时刻BP和HR水平均明显低于T1时刻(P<0.05),T3时刻BP和HR水平均明显高于T2时刻,差异均有统计学意义(P<0.05);浅低温组术后心律失常发生率与中低温组均相近,差异无统计学意义(P>0.05),浅低温组术中室颤、术后低血压、术后短暂性神经功能障碍发生率均显著低于中低温组,差异有统计学意义(P<0.05)。结论在体外循环下小儿室间隔缺损修补术中,应用浅低温脑灌注治疗可减少术中室颤、术后低血压及术后短暂性神经功能障碍。     

Diffusion- and perfusion-weighted MR imaging of transient focal cerebral ischaemia in mice

Temporary focal ischaemia was induced in wild-type C57Black/6 mice by thread occlusion of the middle cerebral artery (MCA). Recirculation was started after 60 min and maintained for 24 h, after which the mouse brain was frozen in situ. Development of the cerebral infarct was monitored by diffusion-, perfusion- and T(2)-weighted magnetic resonance imaging (MRI) during ischaemia, during the early reperfusion period of 90 min, and at 24 h after reperfusion. Ischaemia caused a marked reduction of the perfusion signal intensity and of the apparent diffusion coefficient (ADC) of tissue water in the ipsilateral MCA territory. In sham-operated control animals ADC remained unchanged. Hemispheric lesion volume after 1 h MCA occlusion was 53 +/- 6% (n = 6), as defined by an ADC decrease of more than 20%. Recirculation reduced hemispheric lesion volume to only 27 +/- 13%, while there was a trend towards secondary lesion growth at 24 h. Post-ischaemic recovery of perfusion was slow, heterogeneous and incomplete. A region-of-interest analysis showed only partial and transient recovery of the ADC, particularly in the dorsolateral cortex and lateral caudate putamen, which may be explained by inadequate reperfusion in these regions. Detailed MRI studies of cerebral ischaemia and reperfusion may now also be performed in the transgenic mice.     

穹隆海马伞切割后大鼠海马内RUNX1T1 mRNA和蛋白的表达变化

目的 观察穹隆海马伞切割后不同时间点海马内RUNX1T1 mRNA和蛋白的表达变化及定位。方法 行穹隆海马伞切割术,制备模型大鼠。实验分为正常组、切割3d组、切割7d组、切割14d组、切割21d组、切割28d组。1.提取海马组织总mRNA,用Real-time PCR 检测大鼠海马组织中RUNX1T1mRNA 的表达;2.提取海马组织总蛋白,用Western blotting 检测海马内RUNX1T1蛋白的表达;3.行脑冷冻切片,行RUNX1T1免疫荧光检测和Hoechst标记,观察海马齿状回中RUNX1T1/Hoechst双标阳性细胞。 结果 Real-time PCR检测显示,切割3d组海马组织中RUNX1T1 mRNA的表达明显上调,其余各组差异不明显;Western blotting检测结果显示,正常组海马中有微量RUNX1T1蛋白表达,而切割3d组海马组织中RUNX1T1蛋白表达量明显上升,并达到高峰,7d时仍有较多的表达,此后,14d、21d、28d组中RUNX1T1蛋白表达很快又恢复到正常水平;免疫荧光检测结果表明,正常组海马齿状回中有少量的RUNX1T1/Hoechst阳性细胞,切割3d组海马齿状回中RUNX1T1/Hoechst阳性细胞数量最多,切割7d组逐渐减少,切割14d组、21d组和28d组与正常组差别不明显。结论 穹隆海马伞切割后海马内RUNX1T1 mRNA和蛋白表达在早期呈短暂性上调,并定位于海马齿状回颗粒下层,推测可能与海马神经再生过程中神经干细胞向神经元分化有关。     

Early diffusion-weighted MRI predicts regional neuronal damage in generalized status epilepticus in rats treated with diazepam

We applied diffusion-weighted MRI (DWI) in the pilocarpine-induced status epilepticus (SE) model to investigate the evolution of acute phase changes in brain diffusion with and without early anticonvulsive therapy correlated to long-term SE-induced neuronal cell loss. Hereby, DWI was performed before (baseline) and serially between 3 and 120 min after onset of SE in untreated and treated animals (n=15 in each group). Anticonvulsive-treated animals received 20 mg/kg diazepam at 15 min after onset of SE. Apparent diffusion coefficients (ADC) were calculated for the parietal, temporal and piriform cortex, thalamus, hippocampus and amygdala and compared to baseline. Neuronal cell loss was quantified at 2 weeks after onset of SE utilizing cresyle-violet-staining. The results of ADC-mapping demonstrated a significant transient increase in ADC (to 116+/-4% of baseline) in the very acute phase starting 3 min after SE onset, lasting for 10 min in both groups. In untreated animals, there was a significant gradual decline in ADC to 75+/-12% of baseline while this decline in diazepam-treated animals was significantly less pronounced (P<0.05) and ADC recovered to 93+/-6% of baseline. There was good correlation between neuronal cell loss in specific brain regions at 2 weeks after SE and maximal decrease in ADC (r>0.79). In conclusion, serial DWI is a sensitive noninvasive technique for early detection, monitoring and prediction of SE-induced neuronal alterations. Using ADC-mapping, verification of early anticonvulsive therapy in SE seems to be possible as there is good correlation between the maximal decrease in ACD in the acute phase of SE and late neuronal cell loss.     

短暂脑缺血后老年模型大鼠大脑少突胶质前体细胞的变化*☆

背景：目前老年脑内少突胶质前体细胞在短暂脑缺血后和修复过程中的变化尚不清楚。 目的：观察短暂脑缺血后老年模型大鼠大脑少突胶质前体细胞的变化。 方法：以线栓法制作大鼠短暂脑缺血模型,24只12月龄老年雄性SD大鼠随机数字表法分4组,对照组仅暴露血管,然后缝合,不进行栓塞;缺血再灌注1,7,14 d组：造模后分别再灌注1,7,14 d。 结果与结论：①短暂脑缺血后各时间点梗死中心区硫酸软骨素蛋白聚糖、未成熟少突胶质细胞的标记物(O4)和环核苷酸磷酸二酯酶阳性细胞数明显减少。②梗死周边区硫酸软骨素蛋白聚糖和O4阳性细胞数随着时间延长而逐渐增加,短暂脑缺血后7,14 d时显著增加;而环核苷酸磷酸二酯酶阳性细胞数在短暂脑缺血后1,7 d时稍有减少,脑缺血后14 d时明显增加。③脑梗死对侧区3种抗原阳性细胞数无明显变化。提示老年SD大鼠短暂脑缺血后梗死周边区少突胶质前体细胞增多,并可能分化为成熟少突胶质细胞,参与脑缺血损伤的修复过程。      

MR imaging of postischemic neuronal death in the substantia nigra and thalamus following middle cerebral artery occlusion in rats

The goal of this study was to investigate apparent diffusion coefficient (ADC) and T(2) relaxation time (T(2)) in the substantia nigra and thalamus after middle cerebral artery occlusion in rats. In the substantia nigra ipsilateral to infarct, ADC was significantly lower and T(2) was significantly higher on the third and fourth days, but they did not change significantly on the first, second, eighth and 15th days. In the ipsilateral thalamus, ADC and T(2) did not change significantly between the first and fourth days, but were significantly lower on the eighth and 15th days. This combination of MR findings suggested that secondary degeneration in the thalamus was different from that in the substantia nigra.     

Effect of bis(7)-tacrine on cognition in rats with chronic cerebral ischemia

Bis(7)-tacrine (B7T), a novel dimeric acetyl cholinesterase (AChE) inhibitor, has multiple neuroprotective activities against neuronal damage. However, its therapeutic effects in chronic cerebral ischemia remain unknown. In the present study, adult male Sprague-Dawley rats were subjected with permanent ligation of the bilateral common carotid arteries to investigate the roles of B7T on cognitive function, neuronal apoptosis and neurogenesis in the hippocampus. Results from spatial navigation test showed that chronic cerebral ischemia impaired spatial learning, B7T treatment shorten escape latency of ischemia rats as compared with saline-treated rats. Probe trial test indicated that spatial memory deficit of chronic cerebral ischemic animals was reversed by B7T treatment. Immunohistochemical results showed that B7T reduced neuronal apoptosis in the hippocampal CA1 region as compared with ischemia rats, and B7T treatment increased neurogenesis in the hippocampus. These findings suggest that B7T may exert its neuroprotective effects by inhibiting apoptosis and promoting neurogenesis in 2VO rats.     

GABA(B) receptor expression and cellular localization in gerbil hippocampus after transient global ischemia

Using in situ hybridization, the expression of the GABA receptor subtype B subunit 1 (GABA(B) R1) and subunit 2 (GABA(B) R2) following transient global ischemia in the gerbil hippocampus was investigated. In sham-operated animals, mRNAs of both subunits were mainly detected in hippocampal pyramidal cells and interneurons with lower expression levels of the GABA(B) R2 in the CA1 field. Four days after transient cerebral ischemia, neuronal message decreased in conjunction with neuronal death and both receptor subunits disappeared from the pyramidal cell layer. However, GABA(B) R1 and GABA(B) R2 were still expressed in a few cells. In situ hybridization of the GABA synthesizing enzyme glutamic acid decarboxylase 67 (GAD67) remained unchanged after the ischemic insult. Double-labeling experiments revealed that in the postischemic hippocampus GABA(B) R1 and GABA(B) R2 were not present in GFAP-reactive astrocytes, but that the surviving parvalbumin-containing interneurons possessed GABA(B) R1 and GABA(B) R2 mRNA.     

Postischemic brain infiltration of leukocyte subpopulations differs among murine permanent and transient focal cerebral ischemia models

Cellular and humoral inflammations play important roles in ischemic brain injury. The effectiveness of immunomodulatory therapies may critically depend on the chosen experimental model. Our purpose was to compare the post‐ischemic neuroinflammation among murine permanent and transient middle cerebral artery occlusion (MCAO) models. Permanent MCAO was induced by transtemporal electrocoagulation and 30 minutes or 90 minutes transient MCAO was induced by intraluminal filament in C57BL/6 mice. Infiltration of leukocyte subpopulations was quantified by immunohistochemistry and fluorescence‐activated cell sorting. Cerebral cytokine and adhesion molecule expression was measured by real‐time polymerase chain reaction (RT‐PCR). Neutrophil infiltration was noted at 24 h after transient MCAO, but did not further increase until 5 days in the permanent MCAO model. Few T cells were observed in both MCAO models at 24 h, but permanent MCAO demonstrated much more infiltrating T cells at 5 days. Pronounced microglial activation was evident at 24 h and 5 days after permanent but not after transient MCAO. The number of invading NK cells and expression of MHCII on CD11b+ cells did not differ among the three groups. Five days after MCAO, the expression of IL‐1, TNF‐α and IFN‐γ and of the adhesion molecules ICAM‐1 and VCAM‐1 was significantly higher in the permanent than in the transient MCAO groups. Cellular and humoral inflammation differs substantially among commonly used MCAO models. Neuroinflammation is more pronounced after permanent electrocoagulatory MCAO compared with 30 minutes and 90 minutes filament‐MCAO.     

晚期糖基化终产物受体和低密度脂蛋白受体相关蛋白在慢性脑血流低灌注大鼠皮层和海马的改变

目的 研究慢性脑血流低灌注对脑内受体介导的β-淀粉样肽(Aβ)转运蛋白晚期糖基化终产物受体(RAGE)和低密度脂蛋白受体相关蛋白1(LRP-1))含量及分布的影响. 方法采用双侧颈总动脉永久性结扎大鼠模型,应用免疫组织化学和免疫印迹方法对脑内RAGE和LRP-1进行定位和定量检测. 结果 免疫组织化学结果显示,与对照组相比,RAGE在皮层及海马组织中血管内皮细胞上的表达从低灌注10d起增多,而神经元上表达从低灌注30d起减少,且这种变化一直持续到低灌注180d;LRP-1的分布变化则与之相反.免疫印迹结果显示,皮层和海马中RAGE含量在低灌注术后10d即开始明显增加,且在缺血的不同时间点与相应的对照组比较都明显增多(P<0.05);LRP-1变化较晚,在缺血180d时明显增多(P<0.05). 结论 慢性脑血流低灌注可使RAGE、LRP-1在脑组织中的表达增高,同时在神经元、血管中的分布发生改变,这种变化可导致Aβ在脑内的聚集,可能在阿尔茨海默病(AD)早期发病过程中起重要作用.     

An age-related change in susceptibility of rat brain to encephalomyocarditis virus infection

Rats were inoculated intraperitoneally (i.p.) or intracerebrally (i.c.) with 1 × 10⁴ plaque forming units (PFU)/animal of the D variant of encephalomyocarditis virus (EMC-D) at 2, 4, 7, 14, 28 or 56 days of age for virological and histopathological examination. In the i.p.-inoculation study, neither viral replication nor lesions were detected in the animals inoculated at 28 and 56 days of age. In the animals inoculated when younger than 14 days of age, lesions were restricted to the brain although viral replication was detected in the brain, heart and pancreas. The brain lesions were characterized by acute meningoencephalitis with neuronal necrosis in the cerebral cortex, hippocampus and thalamus, and viral RNA was detected in degenerated and/or intact neurons. In the i.c.-inoculation study, similar age-related changes in susceptibility of rat brain to EMC-D infection were observed, but a minor difference was that viral replication and lesions were still detected in the hippocampus of some animals inoculated at 28 days of age. These results suggest that an age-related decrease in the susceptibility of rat brain to EMC virus infection may reflect an age-related change in the susceptibility of neurons themselves as well as in maturation of the immune system.