Relationship between AQP4 expression and DWI of the cerebral ischemic edema in rats

Objective: To study the correlation between aquaporin-4 (AQP4) expression and diffusion-weighted ima-ging (DWI) in the process of ischemic brain edema for the molecular biologic mechanism of DWI. Methods: A total of34 Wistar rats were divided into 8 groups randomly: Non-operated group (n=4), sham-operated group (n=6), andoperated group, receiving right midddle cerebral artery occlusion (MCAO) for 15 and 30 min, and 1, 3, 6 and 24 h re-spectively (6 subgroups, n=4). All groups were imaged with DWI and T_2WI. The apparent diffusion coefficient(ADC), relevant density (rd) and relevant area (rs) of hyperintensity of the lesions on DWI and T_2WI were meas-ured. Relevant ADC (rADC), relevant area of immunohistochemical staining for AQP4 (rS), optical density of AQP4hybridization (α) were calculated. After that the animals were sacrificed and perfused at different time intervals, cor-relations between DWI, ADC, and AQP4 expression (rS,α) in ischemic tissue was made. Results: There was a sig-nificant correlat     

Reperfusion of the rat brain tissues following acute ischemia: the correlation among diffusion-weighted imaging, histopathology, and aquaporin-4 expression

Background  Although some studies have reported that aquaporin-4 (AQP4) plays a role in the post-ischemic edema formation and diffusion-weighted imaging (DWI), little is known about the AQP4 expression in stage of the reperfusion following acute cerebral ischemia, as well as the correlation between histopathology and DWI. The aim of the study was to investigate the correlation among DWI, histopathology and the AQP4 expression in the reperfused rat brain tissues following acute ischemia.

Methods  Seventy Wistar rats were randomly divided into a control group (group A), and several occluded and reperfusion groups. They had their middle cerebral artery unilaterally occluded (MCAO) for 30 minutes (group B) followed by 30 minutes (group D) or 60 minutes (group E) of reperfusion, or 60 minutes of MCAO (group C) followed by 30 minutes (group F), or 60 minutes (group G) of reperfusion (n=10 for each group). All rats underwent DWI scanning. The relative apparent diffusion coefficient (rADC) value of each rat was calculated. All the rats were sacrificed and the cerebral ischemic tissues were examined for histopathology. Real-time fluro-quantitative polymerase chain reaction (RT-PCR) and Western-blotting were performed. The amount of AQP4 mRNA (Ex^－ΔΔCt) and AQP4 protein (Q) was statistically analyzed. The correlation between rADC values and AQP4 mRNA expression was analyzed with the Pearson correlation test.

Results  In all the reperfusion groups, the areas of hyper-intensity signal in DWI were decreased, and the rADC value increased and the AQP4 expression decreased significantly compared with the occluded group (t=26.89, t=18.26, P <0.01). There was a negative correlation between AQP4 mRNA expression and rADC values (r=-0.72, P <0.01). A mixed edema, composed of cerebral intracelluar edema and vasogenic brain edema, was observed in all the reperfusion groups. It was more prevalent in groups D and F than in the groups E and G. With the reperfusion time postponed, the cerebral intracelluar edema of the rat was significantly mitigated, but the vasogenic brain edema was not significantly changed.

Conclusions  There is a close correlation between AQP4 expression and the cerebral intracellular edema. The change of ADC values may indirectly reflect the level of the AQP4 expression. DWI may become a promising, noninvasive imaging modality to predict early stroke and reperfusion injury.

     

Relationship between AQP4 expression and structural damage to the blood-brain barrier at early stages of traumatic brain injury in rats

Background Although some studies have reported that aquaporin-4 （AQP4） plays an important role in the brain edema after traumatic brain injury （TBI）, little is known about the AQP4 expression in the early stage of TBI, or about the correlation between the structural damage to the blood-brain barrier （BBB） and angioedema. The aim of this project was to investigate the relationship between AQP4 expression and damage to the BBB at early stages of TBI. Methods One hundred and twenty healthy adult Wistar rats were randomly divided into two groups： sham operation group （SO） and TBI group. The TBI group was divided into five sub-groups according to the different time intervals： 1, 3, 6, 12, and 24 hours. The brains of the animals were taken out at different time points after TBI to measure brain water content. The cerebral edema and BBB changes in structure were examined with an optical microscopy （OM） and transmission electron microscopy （TEM）, and the IgG content and AQP4 protein expression in traumatic brain tissue were determined by means of immunohistochemistry and Western blotting. The data were analyzed with SPSS 13.0 statistical software. Results In the SO group, tissue was negative for IgG, and there were no abnormalities in brain water content or AQP4 expression. In the TBI group, brain water content significantly increased at 6 hours and peaked at 24 hours following injury. IgG expression significantly increased from 1 to 6 hours following injury, and remained at a high level at 24 hours. Pathological observation revealed BBB damage at 1 hour following injury. Angioedema appeared at 1 hour, was gradually aggravated, and became obvious at 6 hours. Intracellular edema occurred at 3 hours, with the presence of large glial cell bodies and mitochondrial swelling. These phenomena were aggravated with time and became obvious at 12 hours. In addition, microglial proliferation was visible at 24 hours. AQP4 protein expression were reduced at 1 hour, lowest at 6 hours, and began to increase at 12 hours, showing a V-shaped curve. Conclusions The angioedema characterized by BBB damage was the primary type of early traumatic brain edema. It was followed by mixed cerebral edema that consisted of angioedema and cellular edema and was aggravated with time. AQP4 expression was down-regulated during the angioedema attack, but AQP4 expression was upregulated during intracellular edema.     

Therapeutic effect of bFGF on retina ischemia-reperfusion injury

Background Basic fibroblast growth factor (bFGF) plays important roles in retina degeneration, light injury, mechanical injury, especially in retina ischemia-reperfusion injury (RIRI). This study was to investigate the therapeutical effect of bFGF on RIRI and its mechanisms.Methods Experimental RIRI was induced by increasing intraocular pressure (IOP) in the eyes of 48 rats. These rats were divided into normal control, ischemia-reperfusion and bFGF-treated groups.Histological and ultrastructural changes of in the retina of different groups were observed, and the number of retinal ganglion cells (RGCs) was quantitatively analyzed under microscopy. Apoptotic cells were detected using the TdT-dUTP terminal nick-end labeling (TUNEL) method. The expression of caspase-3 was determined by streptavidin peroxidase (SP) immunohistochemistry. Atomic absorption spectrum method was used to evaluate the intracellular calcium changes.Results At the early stage of retinal ischemia-reperfusion injury, retina edema in the treated group was significantly eliminated compared with the untreated ischemic animals. RGCs in the bFGF-treated group was more than those in the untreated ischemic group during the post-reperfusion stages. In ischemic group, apoptotic cells could be found at 6th hours after reperfusion and reached the peak at 24th hours. At 72th hours no apoptotic cells could be found. The changes in caspase-3 expression had a similar manner. The intracellular calcium of rat retina began to increase at lth hour, reached the peak at 24 hours, and began to decease at 72th hours. The change of the three markers in the treatment group showed a similar pattern, but they were all relatively less obvious.Conclusion Apoptosis may play a vital role in RIRI. bFGF may has therapeutical effects on RIRI by inhibiting the increase of intracellular calciums and caspase-3 expression.     

Effects of dexamthasone with different doses on aquaporin-4 in brain of intracerebral hemorrhage rats

Objective:To determine the relationship between the expression of aquaporin-4(AQP4) after intracerebral hemorrhage and dexamethasone treated. Methods:Collagenase Ⅶ was injected in caudate nucleus in a stereotaxis frame to establish the intracerebral hemorrhage(ICH) animal models. The intracerebral hemorrhage(ICH) rats were randomly divided into four groups: the sham group (group A), the ICH group(group B), low dose-treated group(group C), moderate dose group(group D) and high dose group(group E). The groups were respectively received an intraperitoneal dexamethasone injection with 1 mg/kg, 15 mg/kg, 30 mg/kg, twice a day for three days. The brain water content(BWC), the permeability of blood-brain barrier(BBB) and the expression of AQP4 were observed. Results:Both the BBB disruption and AQP4 expression decreased in treated groups, and the AQP4 expression had a dose-dependent manner in the dexamethasone treatment. And it seemed that low dose dexamethasone was in favor of brain swelling elimination, but the higher dosage had not similar effect. Conclusion:Dexamethesone may play a critical role on expression of AQP4 in the physiopathology of hemorrhagic edema.     

Effects of dexamethasone with different doses on aquaporin-4 in brain of intracerebral hemorrhage rats

Objective：To determine the relationship between the expression of aquaporin-4（AQP4） after intracerebral hemorrhage and dexamethasone treated. Methods：Collagenase Ⅶ was injected in caudate nucleus in a stereotaxis frame to establish the intracerebral hemorrhage（ICH） animal models. The intracerebral hemorrhage（ICH） rats were randomly divided into four groups： the sham group （group A）, the ICH group（group B）, low dose-treated group（group C）, moderate dose group（group D） and high dose group（group E）. The groups were respectively received an intraperitoneal dexamethasone injection with 1 mg/kg, 15 mg/kg, 30 mg/kg, twice a day for three days. The brain water content（BWC）, the permeability of blood-brain barrier（BBB） and the expression of AQP4 were observed. Results：Both the BBB disruption and AQP4 expression decreased in treated groups, and the AQP4 expression had a dose-dependent manner in the dexamethasone treatment. And it seemed that low dose dexamethasone was in favor of brain swelling elimination, but the higher dosage had not similar effect. Conclusion：Dexamethesone may play a critical role on expression of AQP4 in the physiopathology of hemorrhagic edema.     

生长抑素对成人活体肝移植围术期肝功能的影响及其可能机制的研究

Background The aim of this study was to investigate the possible effect of somatostatin on the liver function of recipients undergoing living donor liver transplantation.Methods Forty recipients were randomized into group A （n=20） and group B （n=20）. Recipients in group A received no somatostatin whereas somatostatin was administrated for recipients in group B perioperatively. Liver function, the plasma concentration of endothelin-1 and nitric oxide, the intragraft expressions of endothelin-1 and inducible nitric oxide syntheses at 2 hours after declamping of the portal vein were compared between the two groups.Results Compared to group A, alanine transaminase values in group B were significantly reduced at 2 hours after portal vein declamping, at the end of the operation and postoperation day 1 （P 〈0.05）, whereas aspartate aminotransferase values in group B decreased at 30 minutes after portal vein clamping, at 2 hours after portal vein declamping and at the end of the operation （P 〈0.05）. Total bilirubin values in group B were reduced significantly at 2 hours after portal vein declamping and at the end of the operation when compared to group A （P 〈0.05）. Intragraft expression of endothelin-1 was significantly downregulated at 2 hours after declamping of the portal vein accompanied with a reduction of plasma concentration of endothelin-1 in the peripheral blood （P 〈0.05）.Conclusions Somatostatin had a protective effect on liver function during the early phase after declamping of portal vein for recipients undergoing living donor liver transplantation, and the possible mechanism might be partially attributed to the downregulation of endothelin-1.     

电针影响大鼠脑缺血再灌注后水通道蛋白4 (AQP4)的表达及其在血管周边的分布

 目的 研究电针干预大鼠脑缺血再灌注损伤时脑内水通道蛋白4 (aquaporin 4,AQP4)的表达与分布改变。 方法 选用SD雄性大鼠406只,分为正常对照组(n=40),脑缺血组(n=138),脑缺血+电针组(电针处理组,n=138)和脑缺血+假电针组(n=90)。利用线栓法制作大鼠大脑中动脉阻塞(middle cerebral artery occlusion,MCAO)模型,缺血1 h后实施脑血流再灌注。电针处理组在脑缺血开始后立即给予电针刺激,穴位选择“水沟”(GV 26)与“百会”(GV 20)。利用Western blot检测AQP4的蛋白表达水平,胶体金免疫电镜观察AQP4免疫阳性颗粒在血管周边的分布,常规焦油紫染色计算脑缺血后的脑梗死体积以及脑肿胀程度。神经行为学评估通过Garcia量表进行评分。结果 (1)再灌注24 h内,电针可下调因脑缺血而诱导的AQP4表达升高,再灌注后6 h和12 h分别是缺血组的0.63倍和0.72倍(P < 0.05);(2)与正常对照组相比,血管周边AQP4的免疫阳性颗粒在再灌注后6 h增多,在再灌注后24 h减少,电针干预组中血管周边AQP4的免疫阳性颗粒密度发生改变,其变化与缺血组相反,差异有统计学意义(P < 0.05);(3)电针减轻脑缺血后的脑梗死及脑肿胀,促进神经行为功能的恢复。结论 电针下调因缺血而导致的AQP4蛋白的表达升高,并动态改变其在血管周边的分布。电针对AQP4的调控作用可能与电针的神经保护作用机制相关。     

短暂地氟醚预处理对大鼠局灶性脑缺血损伤的保护作用

目的:探讨短暂地氟醚预处理诱导脑缺血耐受的可行性。方法:30只雄性SD大鼠,随机分为三组:对照组动物不接受任何处理;吸氧组动物接受1 h吸氧预处理( 94%氧) ;地氟醚组动物吸入1 h5 .7%的地氟醚预处理。所有动物均采用右侧颈动脉尼龙线栓塞大脑中动脉致局灶性脑缺血1 2 0 min,观察再灌注后2 4 h神经行为学改变及脑梗死容积。结果:直肠温度、p H、PO2 、PCO2 、血压及血糖在预处理期间各组无明显差异。再灌后2 4 h神经行为学评分地氟醚组明显小于吸氧组和对照组( P<0 .0 5 ) ;地氟醚组脑梗死容积明显低于吸氧组和对照组,后两组梗死容积无显著性差异( P>0 .0 5 )。结论:短暂地氟醚预处理可通过诱导短暂局灶性脑缺血耐受而产生脑保护作用     

磁共振DWI高b值及ADC值在超急性脑缺血中的应用价值

目的 探讨磁共振扩散加权成像(DWI)高b值及表观弥散系数(ADC)值在超急性脑缺血诊断中的价值.方法 选成年SD大鼠,采用随机数字表法分为缺血组和对照组,依据缺血时间长短将缺血组再分为0.25、0.50、1.00、2.00、4.00 h及6.00 h组,每组各6只,共42只.缺血组行右侧大脑中动脉栓塞(MCAO),分别进行头部 T2WI、DWI(b值分别为0、400、800、2000、3000 s/mm2)扫描,记录对比噪声比(CNR)、信噪比(SNR)值,测量 T2WI、DWI高信号最大层面相对面积(rs-T2WI、rs-DWI)及相对表观扩散系数(rADC)值,观察缺血区域的影像学改变,检验灵敏度及特异度.结果 b值为2000、3000 s/mm2时DWI对超急性期脑缺血的诊断率明显高于b值为400、800 s/mm2(P<0.05),b值为400、800、2000、3000 s/mm2在诊断超急性脑缺血的敏感性分别为16.7%、50.0%、100.0%、100.0%,特异度为16.7%、50.0%、100.0%、100.0%.不同b值下ADC值差异有统计学意义(P<0.05).结论 高b值DWI在诊断超急性脑缺血明显优于低b值,尤其在脑缺血0.25 h及0.50 h显示病灶方面更具优势.     

减压后脑肿大早期磁共振弥散加权像和病理的实验研究

目的：探讨减压后脑肿大早期病理基础。方法：利用磁共振弥散加权成像（DWI）对脑水肿检测的敏感性和特异性，于减压后2h、4和6h三个时点，对18只猫作减压后脑肿大动脉DWI检查，每相应时点处死6只猫形成一组，制取脑标本作Evan‘s Blue染色、光镜和电镜检查。结果：减压后2hDWI即显示脑肿大部位为低强度信号区，其范围在减压后4和6h明显扩大，中线向对侧移位加剧；1只猫减压后6h肿大部位原低强度信号区转变为高强度信号区。减压后2h即见脑肿大部位Evan‘s Blue染色，减压后4和6h染色范围明显扩大。减压后2h光镜和电镜检查发现全脑微小血管内淤血，但以脑肿大部位为重并伴有微小血管周围间隙明显扩大；减压后6h肿大脑组织内变性坏死脑细胞增多。结论：减压后脑肿大早期（＜2h)由充血性脑肿胀和血管源性脑水肿共同构成，6h则可能有细胞毒性脑水肿发生。     

高血压脑病CT和MRI特征

目的探讨头部电子计算机断层扫描(CT)和磁共振成像(MRI)对高血压脑病的诊断价值。方法分析10例经临床确诊为高血压脑病患者的头部CT和MRI表现特征,分析其头颅CT表现及MRI中FLAIR、DWI、ADC值变化。结果3例患者头颅CT发现异常,10例患者头颅MRI发现异常,病变主要呈T1稍低、T2稍高信号、FLAIR较高信号,DWI病变呈等及稍高信号,ADC值升高,病变主要以双侧顶枕叶、小脑半球及脑干多见。结论本病的头部影像学改变为血管性水肿所致,常累及双侧顶枕叶、小脑半球等后循环系统皮质下白质,特别是MRI中FLAIR、DWI、ADC等有助于高血压脑病的诊断和鉴别诊断,预后及疗效观察等方面有重要意义。     

磁共振扩散加权在急性缺血性脑梗死的临床应用

目的探讨磁共振弥散加权成像（nirfuSion—weighted imaging DWI）在急性缺血性脑梗死中的临床应用。方法对8O例发病3—24小时,疑似急性缺血性脑梗死患者进行DwI及常规MRI扫描,并对结果进行分析。结栗发病时间〈6小时,超急性期脑梗死7倒,常规T2WI及FLAIR上无明显异常信号改变,DWI呈高信号,ADc图上呈低信号。发病时间6—24小时,急性期脑梗死73例,DWI信号改变较T2WI、FLAIR序列明显,显示部位、范围更加准确。结论磁共振弥散加权成像对急性缺血性脑梗死较常规MRl序列敏感,检查时间短,能为临床提供早期治疗的证据,应作为常规序列开展。     

子痫性脑病的CT和MRI特征

目的 探讨头部电子计算机断层扫描(CT)和磁共振成像(MRI)对子痫性脑病的诊断价值.方法 分析8例经临床确诊为子痫性脑病患者的头部CT和MRI表现特征,分析其头颅CT表现及MRI中FLAIR、DWI、ADC值变化.结果 5例患者头颅CT发现异常,以顶枕叶皮质或皮质下白质内基本对称性斑片状低密度影为主;8例患者头颅MRI发现异常,病变主要呈T1稍低、T2稍高信号、FLAIR较高信号,DWI病变呈等及稍高信号,ADC值升高,病变主要以双侧顶枕叶、小脑半球及脑干多见,且为可逆性改变.结论 本病头部可逆性的影像学改变为血管性水肿所致,常累及双侧顶枕叶、小脑半球等后循环系统皮质下白质,特别是CT显示后循环对称性低密度灶,MRI中FLAIR、DWI、ADC等有助于子痫性脑病的早期诊断和鉴别诊断,预后及疗效观察等方面有重要意义.     

7.O T磁共振灌注和弥散加权成像的缺血半暗带实验研究

目的 探讨高场强磁共振(7.0T)灌注和弥散加权成像在大鼠急性脑梗死缺血半暗带研究中的价值.方法 利用线栓法建立大鼠急性脑梗死模型.60只SD大鼠随机分成6组,即假手术对照组,栓塞0.5、1.5、3、6和24 h组,每组10只.各组大鼠于相应时间点行头颅MRI扫描:PWI、DWI、T1WI、T2WI及MRA.后处理获得脑血容量(CBV)、脑血流量(CBF)、平均通过时间(MTT)形态图,并分别计算rCBV、rCBF、rMTT相对值.测量DWI异常信号区相对体积(rVD)及PWI异常灌注区相对体积(rVP).将结果与四氮唑红(TTC)染色和病理对比.结果 假手术组各序列扫描、TTC染色及病理均未见异常.各栓塞组栓塞侧大脑中动脉供血区rCBV、rCBF明显降低,rMTT明显延长,梗死核心严重,梗死边缘较轻.各栓塞组栓塞侧大脑中动脉供血区于DWI和PWI均可见异常信号区;DWI异常信号区体积随栓塞时间延长而增大,PWI异常信号区体积随时间延长变化不明显,栓塞6 h前PWI异常信号区大于DWI异常信号区(P<0.05),6 h以后PWI、DWI梗死体积大小差异无统计学意义(P>0.05).3 h以后DWI梗死体积与24 hTTC梗死体积差异无统计学意义(P>0.05).结论 高场强磁共振灌注和弥散加权成像动态显示急性脑梗塞缺血半暗带的时间、空间变化,为进一步研究提供基础.