大鼠局灶性脑缺血再灌注后Caspase-9蛋白的表达

目的 研究Caspase-9蛋白在大鼠脑缺血再灌注损伤过程中表达水平的动态变化.方法 建立大鼠局灶性脑缺血再灌注模型,应用HE染色和免疫组织化学方法观察神经细胞死亡情况,再灌注6 h、12 h、24 h后缺血皮层Caspase-9蛋白表达.结果 与假手术组比较Caspase-9蛋白表达在各手术组明显升高,并随着缺血再灌注时间的延长Caspase-9表达逐渐升高,于再灌注24 h到达最高(P<0.01).结论 Caspase-9蛋白参与了脑缺血再灌注损伤过程.     

环氧合酶2基因在大鼠脑缺血再灌注损伤中的表达及意义

目的探讨局灶性脑缺血再灌注损伤过程中环氧合酶2基因的表达及其意义。方法采用栓线法制备大鼠大脑中动脉缺血再灌注损伤模型。随机分为8组:假手术组,缺血2h组,缺血再灌注3h、6h、12h、24h、48h、72h组,每组10只。评定神经功能损伤,HE染色观察脑组织形态学改变。Northern blot、Western blot和免疫组织化学染色方法检测脑组织环氧合酶2 mRNA和蛋白产物表达。结果神经功能缺损表现随缺血再灌注时间的延长而逐渐加重。缺血2h组环氧合酶2 mRNA和蛋白产物表达比假手术组明显增加(P<0.01),再灌注后表达逐渐增强,再灌注12h环氧合酶2的mRNA表达达高峰(0.92±0.30),再灌注24h环氧合酶2的蛋白产物表达达高峰(0.72±0.18),与其它组比较差异有显著性(P<0.01)。结论环氧合酶2基因在局灶性脑缺血再灌注损伤中的表达呈动态变化过程,环氧合酶2可能与缺血再灌注后迟发性神经细胞死亡有关。     

丹星通络汤对脑缺血再灌注大鼠神经生长因子表达的影响

目的 观察丹星通络汤( DXTLD)治疗脑缺血再灌注大鼠后脑组织神经生长因子(NGF)的变化,探讨其对脑缺血再灌注损伤的保护机制. 方法 SD大鼠40只随机分为5组(n=8):假手术组、缺血再灌注组(模型组)、尼莫地平组、DXTLD预处理小剂量组、DXTLD预处理大剂量组.线栓法建立大鼠大脑中动脉缺血再灌注模型.应用免疫组织化学染色、灰度分析等方法检测缺血2h再灌注24 h后脑组织海马区NGF的表达. 结果 各治疗组缺血侧海马区的NGF表达显著增加,与模型组比较差异有统计学意义(P＜0.05或P＜0.01).结论 DXTLD通过上调脑缺血再灌注损伤后脑组织内NGF的表达,起到保护脑的作用.     

胸腺素β4对大鼠局灶性脑缺血再灌注损伤后血脑屏障的影响

目的：观察胸腺素β4对大鼠局灶性脑缺血再灌注损伤后血脑屏障的影响,并探讨其作用机制。方法将72只SD大鼠随机分为假手术组、对照组、胸腺素β4组各24只。采用线栓法制作大鼠大脑中动脉闭塞局灶性脑缺血再灌注模型,再灌注24 h后,采用干湿重法测定缺血脑组织含水量,通过检测伊文蓝渗透到缺血侧脑组织的含量观察血脑屏障的通透性,应用RT-PCR法检测缺血脑组织紧密连接蛋白5（ Claudin-5）和基质金属蛋白酶-9（MMP-9） mRNA表达。结果脑缺血再灌注损伤24 h后,与假手术组比较,对照组缺血侧脑含水量、伊文蓝含量、MMP-9 mRNA表达明显增加,Claudin-5 mRNA表达显著减少（ P均＜0．01）;与对照组比较,胸腺素β4组缺血侧脑组织含水量、缺血侧伊文蓝含量、MMP-9 mRNA明显降低,Claudin-5 mRNA表达明显升高（P均＜0．01）。结论胸腺素β4对大鼠脑缺血再灌注损伤后的血脑屏障具有保护作用,其作用机制可能是通过促进Claudin-5 mRNA表达和抑制MMP-9 mRNA表达实现的。     

普萘洛尔和美托洛尔处理对大鼠大脑局灶性缺血再灌注损伤后Bcl-2、Bax和NGF表达的影响

目的 观察普萘洛尔、美托洛尔处理对大鼠大脑局灶性脑缺血再灌注损伤后Bcl -2、Bax和神经生长因子(NGF)表达规律的影响,探讨其脑保护作用的机制.方法 72只成年雄性Wistar大鼠(230 g±10 g)随机分为4组,假手术组、模型组、普秦洛尔给药组、美托洛尔给药组.每组又分为12 h、24 h、48 h三个亚组.采用线栓法制备大鼠大脑中动脉局灶缺血再灌注模型,采用DNA原住末端缺口标记法(TUNEL)检测神经元凋亡;HE染色观察脑组织形态病理学变化;免疫组化法测定大鼠脑缺血再灌注不同时间Bax、Bcl -2与NGF的平均灰度值.结果 与假手术组比较,模型组Bcl-2,Bax和NGF在缺血再灌注组12 h升高,24 h达高峰(P＜0.05).普萘洛尔给药组和美托洛尔给药组的Bcl -2阳性细胞均较模型组明显增加(P＜0.05),而Bax阳性细胞均较模型组则明显减少(P＜0.05),但均多于假手术组(P＜0.05).美托洛尔给药组的NGF阳性细胞与模型组无统计学意义,而普萘洛尔给药组的NGF阳性细胞较模型组显著减少(P＜0.05).结论 普萘洛尔、美托洛尔均可通过抑制Bax和促进Bcl -2表达来对大脑局灶缺血再灌注损伤后的神经元起保护作用.     

黄芪多糖预处理对大鼠局灶性脑缺血再灌注损伤的脑保护作用

线栓法建立大鼠局灶性脑缺血2小时后再灌注损伤模型;SD大鼠60只,随机分为假手术组（F组）,缺血再灌注组（IR组）,黄芪多糖预处理组（AP组）,每组20只;通过HE染色在光镜下观察神经细胞损伤变化,免疫组化法检测Bax的阳性表达。结果：光镜和电镜下,HE染色F各组无脑缺血再灌注损伤的病理改变,黄芪多糖预处理组（AP组）和缺血再灌注组（m组）均有不同程度的缺血再灌注损伤,黄芪多糖预处理组较缺血再灌注组损伤轻;假手术组Bax蛋白表达极弱,缺血再灌注组和黄芪多糖预处理组在脑缺血再灌注后2h出现在接近缺血核心区,6h后表达增多,24h达到高峰,72h开始减少。与假手术组相比,黄芪多糖预处理组和缺血再灌注组Bax蛋白阳性细胞数显著增多（P〈0．05）;与缺血再灌注组相比,黄芪多糖预处理组Bax蛋白阳性细胞数显著减少（P〈0．05）。结论：黄芪多糖对大鼠局灶性脑缺血再灌注损伤有保护作用,黄芪多糖可通过下调Bax蛋白的表达发挥脑保护作用。     

脑缺血再灌注后bcl-2、caspase-3 mRNA水平表达与大脑皮质及纹状体区炎性细胞浸润

目的探讨大鼠脑缺血再灌注后bcl-2蛋白、caspase-3 mRNA的表达及炎性细胞浸润与神经细胞凋亡的关系。方法将54只Wistar大鼠随机分为二组：假手术组，缺血再灌注组。采用原位末端标记(TUNEL)、免疫组化和原位杂交技术分别观察脑缺血再灌注后不同时间点神经细胞凋亡及损伤的变化与bcl-2、caspase-3 mRNA表达。结果bcl-2表达于缺血再灌注12～24h达高峰，再灌注2—4d呈下降趋势，至16d略高于假手术组；caspase-3 mRNA于缺血再灌注12—24h达高峰，2—4d呈降低趋势，至16d略高于假手术组。结论脑缺血再灌注后细胞凋亡介导神经细胞损伤、坏死是一个渐进的动态演变过程。bcl-2蛋白、caspase-3 mRNA表达在抑制细胞凋亡和介导神经细胞损伤等方面起非常重要的作用。     

环磷酸腺苷-蛋白酶A信号系统参与神经生长因子促进脑缺血再灌注大鼠轴突再生

目的观察脑室注射神经生长因子(NGF)对脑缺血再灌注大鼠神经再生的影响及其与环磷酸腺苷-蛋白激酶A(cAMP-PKA)信号途径的关系。方法采用线栓法制作大鼠脑缺血再灌注模型,将60只大鼠分为假手术组(对照组),单纯脑缺血再灌注组(缺血组),NGF1组,NGF2组(脑缺血再灌注并脑室注射NGF,分别注入0.5及2.5μg/100 g体重)。用放免法检测缺血周边区脑组织cAMP的含量,逆转录聚合酶链反应的方法检测生长相关蛋白43(GAP-43)及蛋白激酶A(PKA)mRNA的表达。结果缺血组6、24 h cAMP的含量下降,GAP-43及PKA mRNA表达减少,NGF治疗组脑组织GAP-43 mRNA表达较缺血组增加,且这种变化与cAMP的含量及PKA mRNA表达增加相一致,并呈剂量依赖性。结论NGF能够促进脑缺血再灌注后的轴突再生,cAMP-PKA信号途径在这个过程中起重要作用。     

精氨酰-tRNA合成酶在局灶性脑缺血再灌注大鼠中的表达及机制研究

背景目前,临床上针对哺乳动物氨基酰-tRNA合成酶的研究主要集中在精氨酰-tRNA合成酶、亮氨酰-tRNA合成酶、甲硫氨酰-tRNA合成酶、丙氨酰-tRNA合成酶的结构和功能方面,对哺乳动物尤其是大鼠脑缺血与氨基酰-tRNA合成酶关系的研究报道极少。目的探讨精氨酰-tRNA合成酶在局灶性脑缺血再灌注大鼠中的表达及机制。方法选取清洁级健康雄性SD大鼠60只,其中4只大鼠进行预实验,采用线栓法栓塞大脑中动脉建立局灶性脑缺血再灌注模型。然后将剩余的56只大鼠随机分为正常组8只、假手术组8只、脑缺血再灌注组40只。正常组不做任何外科处理;假手术组大鼠外科操作步骤与脑缺血再灌注组相同,只是线栓不进入颈内动脉、不造成脑缺血;脑缺血再灌注组大鼠建立局灶性脑缺血再灌注模型。采用反转录-聚合酶链反应(RT-PCR)测定正常组、假手术组、脑缺血再灌注组大鼠再灌注后不同时间点精氨酰-tRNA合成酶mRNA相对表达量,采用Western Blotting法测定正常组、假手术组、脑缺血再灌注组大鼠再灌注后不同时间点精氨酰-tRNA合成酶蛋白相对表达量。结果假手术组与脑缺血再灌注组大鼠再灌注2 h、脑缺血再灌注组再灌注48 h精氨酰-tRNA合成酶mRNA相对表达量及蛋白相对表达量比较,差异无统计学意义(P0.05);假手术组大鼠精氨酰-tRNA合成酶mRNA相对表达量及蛋白相对表达量均低于脑缺血再灌注组再灌注6 h、12 h及24 h(P0.05);脑缺血再灌注组大鼠再灌注6 h精氨酰-tRNA合成酶mRNA相对表达量及蛋白相对表达量均高于再灌注2 h和12 h(P0.05);脑缺血再灌注组大鼠再灌注24 h精氨酰-tRNA合成酶mRNA相对表达量及蛋白相对表达量均高于再灌注12 h和48 h(P0.05)。结论大鼠局灶性脑缺血再灌注后6 h及24 h精氨酰-tRNA合成酶表达明显升高,可能与缺血和再灌注两次损伤有关。     

大鼠局灶性脑缺血再灌注后TNF-a、SOCS-3动态表达的实验研究

目的探讨肿瘤坏死因子-a（TNF—a）、细胞因子信号转导抑制因子-3（SOCS-3）在大鼠脑缺血再灌注后的动态表达及特点,阐明TNF-a、SOCS-3在脑缺血再灌注中的作用。方法将雄性sD大鼠48只随机分为假手术组和缺血3h再灌注3h、6h、12h、24h、48h、72h、7d组,6只／组。运用改良线栓法制作大鼠局灶性脑缺血再灌注模型。用放射免疫法测定TNF-a含量及用RT—PCR法测定SOCS-3的含量。结果TNF-a含量变化：与假手术组比较,缺血再灌注纽脑组织TNF—a含量在6h明显增加,12h达到高峰,随后各时间点表达开始下降。在缺血半暗带区,TNF—a含量变化与中心区相同,但含量较低。SOCS-3mRNA含量变化：缺血再灌注组缺血中心区SOCS-3表达在6h开始有明显升高与假手术组相比有显著性差异,再灌注24h时达到高峰,随后备时间点表达相对稳定,至再灌注7d时仍过分表达。在缺血半暗带区,SOCS～3mRNA变化与中心区相同,但含量较低。结论TNF—α在大鼠局灶性脑缺血再灌注损伤中具有重要作用,可诱导SOCS-3基因的产生和表达。而SOCS-3基因是一个脑缺血后上调基因,它参与了脑缺血再灌注损伤的全过程,可能起到了内源性神经保护剂的作用。     

Pharmacokinetics of factor VIII and factor IX

Summary.  A survey of principal pharmacokinetic (PK) studies on factor VIII (FVIII) and factor IX (FIX) plasma- and rDNA-derived concentrates, analysed by means of the PKRD program, has been performed. Notwithstanding the accurate definition of the study design, released in 1991 by the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis (SSC-ISTH), a large variability of PK parameters has been pointed out. In the majority of the PK studies, the size of the population is small. In this situation, a careful individualization of haemophilia therapy is strongly recommended. The tailored prediction of loading and maintenance dosages and the need for strict control of trough FVIII/IX levels are mandatory not only to decrease the risk of bleeds but also to spare financial resources. Recently, the old problem of FVIII assay standardization has again become a concern among physicians, especially after the introduction of B-domain deleted rFVIII concentrate. The discrepancies between the widely used one-stage clotting assay and the chromogenic substrate assay seem to be solved by the introduction of a product-specific laboratory standard.     

Activation of bovine factor X (Stuart factor): conversion of factor Xaalpha to factor Xabeta.

Bovine factor X (molecular weight 55,100) is a blood coagulation factor present in plasma in a precursor or zymogen form. It is a glycoprotein which has been isolated as a two-chain structure held together by one or more disulfide bonds. During the coagulation process, factor X is converted to a serine protease by the hydrolysis of a specific peptide bond in the amino-terminal region of the heavy chain. This cleavage occurs between Arg-51 and Ile-52, giving rise to factor Xaalpha (molecular weight 45,300) and an activation peptide (molecular weight 9500). Factor Xaalpha is then converted to factor Xabeta (molecular weight 42,600) by hydrolysis of a second specific peptide bond in the carboxyl-terminal region of the heavy chain. This cleavage occurs between Arg-290 and Gly-291, giving rise to a second glycopeptide (molecular weight 2700). Factor Xaalpha and factor Xabeta have equivalent coagulant activity, indicating that the cleavage of the second peptide bond is unrelated to the activation process.     

Activation of factor VIII by factor IXa

Thrombin causes an increase in factor VIII coagulant (VIII:C) activity, which is followed by a decay of VIII:C activity to below baseline levels. It has been suggested that a similar interaction of trace amounts of thrombin and factor VIII is a necessary prerequisite before factor VIII can participate in the coagulation cascade. In the current study, factor IXa, a serine protease with structural similarities to thrombin, is shown to cause an increase and subsequent fall in VIII:C in a manner qualitatively similar to the reaction with thrombin. The reaction is inhibited by a human inhibitor to factor IX and the interaction appears to involve only VIII:C, since factor-VIII-related protein (VIII:RP) is not changed on polyacrylamide gel electrophoresis (PAGE) or radioimmunoassay during the reaction. Phospholipid increases the activation of factor VIII by factor IXa, and high concentrations of diisopropylfluorophosphate and hirudin inhibit the reaction. The physiologic significance of the interaction of factor IXa with factor VIII is not entirely clear since the concentration of factor IXa needed for activation is much greater than the concentration of thrombin required for similar activation of factor VIII. Factor IXa is most likely to play a role in the intrinsic cascade acting as an initial activator of factor VIII, since factor IXa precedes thrombin in this clotting sequence. In addition, factor IXa may be important wherever relatively high local concentrations of factor IXa and factor VIII occur, particularly in the presence of phospholipid, which may serve to localize the coagulation factors.     

Activation of factor IX by factor XIa

Blood coagulation factor IX is activated during hemostasis by two distinct mechanisms. Activation through factor VIIa/tissue factor occurs early in the course of fibrin clot formation. Activation by factor XIa appears to be important for maintaining the integrity of the clot over time. In general, coagulation proteases are activated on a phospholipid surface in the presence of a protein cofactor. Until recently, activation of factor IX by factor XIa was thought to be the exception to this rule, as phospholipid has no effect on the reaction and no cofactor had been identified. These curious observations suggest that factor IX is activated by factor XIa in the fluid phase. A large amount of new evidence now indicates that factor IX activation by factor XIa occurs on the surface of activated platelets. The data suggest, however, that this reaction differs significantly from other protease-substrate interactions on the platelet surface. This is likely to be due, in part, to the unusual structure of the factor XI molecule.     

Kinetics of factor VIII-von Willebrand factor association

The binding of factor VIII to von Willebrand factor (vWF) is essential for the protection of factor VIII against proteolytic degradation in plasma. We have characterized the binding kinetics of human factor VIII with vWF using a centrifugation binding assay. Purified or plasma vWF was immobilized with a monoclonal antibody (MoAb RU1) covalently linked to Sepharose (Pharmacia LKB Biotechnology, Uppsala, Sweden). Factor VIII was incubated with vWF-RU1-Sepharose and unbound factor VIII was separated from bound factor VIII by centrifugation. The amount of bound factor VIII was determined from the decrease of factor VIII activity in the supernatant. Factor VIII binding to vWF-RU1-Sepharose conformed to the Langmuir model for independent binding sites with a Kd of 0.46 +/- 0.12 nmol/L, and a stoichiometry of 1.3 factor VIII molecules per vWF monomer at saturation, suggesting that each vWF subunit contains a binding site for factor VIII. Competition experiments were performed with a recombinant vWF (deltaA2-rvWF), lacking residues 730 to 910 which contain the epitope for MoAB RU1. DeltaA2-rvWF effectively displaced previously bound factor VIII, confirming that factor VIII binding to vWF-RU1-Sepharose was reversible. To determine the association rate constant (k(on)) and the dissociation rate constant (k(off)), factor VIII was incubated with vWF-RU1-Sepharose for various time intervals. The observed association kinetics conformed to a simple bimolecular association reaction with k(on) = 5.9 +/- 1.9 x 10(6) M(-1) s(-1) and k(off) = 1.6 +/- 1.2 x 10(-3) s(-1) (mean +/- SD). Similar values were obtained from the dissociation kinetics measured after dilution of preformed factor VIII-vWF-RU1-Sepharose complexes. Identical rate constants were obtained for factor VIII binding to vWF from normal pooled plasma and to vWF from plasma of patients with hemophilia A. The kinetic parameters in this report allow estimation of the time needed for complex formation in vivo in healthy individuals and in patients with hemophilia A, in which monoclonally purified or recombinant factor VIII associates with endogenous vWF. Using the plasma concentration of vWF (50 nmol/L in monomers) and the obtained values for K(on) and K(off), the time needed to bind 50% of factor VIII is approximately 2 seconds.     

Proteolytic interactions of factor IXa with human factor VIII and factor VIIIa.

Factor IXa was shown to inactivate both factor VIII and factor VIIIa in a phospholipid-dependent reaction that could be blocked by an antifactor IX antibody. Factor IXa-catalyzed inactivation correlated with proteolytic cleavages within the A1 subunit of factor VIIIa and within the heavy chain (contiguous A1-A2-B domains) of factor VIII. Furthermore, a relatively slow conversion of factor VIII light chain to a 68-Kd fragment was observed after prolonged incubation. Sites of cleavage were identified within the A1 domain at Arg336-Met337 and within the factor VIII light chain at Arg1719-Asn1720. Factor IXa failed to cleave isolated factor VIII heavy chains, yet cleaved isolated factor VIII light chain. In addition, the purified A1/A3-C1-C2 dimer derived from factor VIIIa was a substrate for factor IXa; however, cleavage of the A1 subunit occurred at less than 30% the rate of cleavage of A1 in trimeric factor VIIIa. These data suggest that factor VIII light chain contributes to the binding site for factor IXa and also support a role for a heavy chain determinant located within the A2 subunit in the association of factor VIIIa with factor IXa. Furthermore, the capacity of factor IXa to proteolytically inactivate its cofactor, factor VIIIa, suggests a mode of regulation within the intrinsic tenase complex.     

Mechanism of antithrombin III inhibition of factor VIIa/tissue factor activity on cell surfaces. Comparison with tissue factor pathway inhibitor/factor Xa-induced inhibition of factor VIIa/tissue factor activity

Recent studies have shown that antithrombin III (AT III)/heparin is capable of inhibiting the catalytic activity of factor VIIa bound either to relipidated tissue factor (TF) in suspension or to TF expressed on cell surfaces. We report studies of the mechanism of which by AT III inhibits factor VIIa bound to cell surface TF and compare this inhibitory mechanism with that of tissue factor pathway inhibitor (TFPI)-induced inhibition of factor VIIa/TF. AT III alone and AT III/heparin to a greater extent reduced factor VIIa bound to cell surface TF. Our data show that the decrease in the amount of factor VIIa associated with cell surface TF in the presence of AT III was the result of (1) accelerated dissociation of factor VIIa from cell surface TF after the binding of AT III to factor VIIa/TF complexes and (2) the inability of the resultant free factor VIIa-AT III complexes to bind effectively to a new cell surface TF site. Binding of TFPI/factor Xa to cell surface factor VIIa/TF complexes markedly decreased the dissociation of factor VIIa from the resultant quaternary complex of factor VIIa/TF/TFPI/factor Xa. Addition of high concentrations of factor VIIa could reverse the AT III-induced inhibition of cell surface factor VIIa/TF activity but not TFPI/factor Xa-induced inhibition of factor VIIa/TF activity.     

Influence of von Willebrand factor on the reactivity of human factor VIII inhibitors with factor VIII

In order to determine the difference in reactivity of factor (F) VIII inhibitors against the FVIII/von Willebrand factor (vWF) complex and against vWF-deficient FVIII, we investigated a panel of 10 antibodies to FVIII from multitransfused individuals with severe haemophilia A and other pathologies. Immunoblotting of purified FVIII and purified thrombin-cleaved FVIII revealed that in all cases inhibitor epitopes could be localized in the heavy chain (A2 subunit) while in four cases they were also present in the light chain. One of the FVIII inhibitors remained unclassified. The effect on FVIII:C of purified IgG from inhibitor plasmas was tested against a high purity FVIII/vWF concentrate and a monoclonally purified FVIII concentrate with only trace contents of vWF, by two different functional assays. Our results suggest that for those inhibitors showing A2 plus light chain (LC) reactivity, the IgG concentration required to inhibit 50% of FVIII activity in vitro is higher for the FVIII/vWF complex than for the vWF-deficient FVIII. We conclude that there might be a protective role of vWF (at least in vitro) against FVIII inhibitors with A2 and LC subunit specificity.     

Antihemophilic factor (factor VIII).

Antihemophilic factor (Factor VIII) is an agent in normal plasma that corrects the coagulative defect of classic hemophillia. The plasma of hemophiliacs contains normal amounts of a variant of antihemophilic factor deficient in clot-promoting properties. In contrast, von Willebrand's disease is usually associated with a true deficiency of this protein. In this disorder, the platelets are poorly aggregated by ristocetin, a defect ascribed to deficiency of antihemophilic factor. Structural studies of antihemophilic factor suggest that it is composed of two dissociable subcomponents, one of high molecular weight that contains the bulk of protein and sustains ristocetin-induced platelet aggregation, and another of lower molecular weight with procoagulant activity. Both subcomponents have been identified in hemophilic plasma, as if the smaller subcomponent were qualitatively abnormal. Carriers of hemophilia can often be detected because their plasmas contain a disproportionately high concentration of antihemophilic factor, measured immunologically, compared with the titer of procoagulant antihemophilic factor.