玉米芯木聚糖硫酸酯抗凝血活性及其机制的研究

采用活化部分凝血活酶时间(APTT)、凝血酶时间(TT)和凝血酶原时间(PT)检测了玉米芯木聚糖硫酸酯(wisX-SB)的抗凝活性,结果表明wisX-SB能明显延长APTT和TT,而不影响PT,提示wisX-SB是通过内源性和/或共同途径发挥抗凝血作用的。采用发色底物法及纤维蛋白原转化实验分别考察了wisX-SB对凝血酶及纤维蛋白原的作用,结果提示wisX-SB的抗凝机制包括:直接抑制纤维蛋白原的转化;通过增强抗凝血酶III(AT-III)的活性,抑制凝血酶活性,从而达到抗凝目的。较低浓度时以前者为主,较高浓度下两者皆起作用。     

水蛭素融合蛋白的表达及其与靶向适配子的偶联

目的:优化表达并纯化水蛭素融合蛋白SA-H-RGD,检测其生物学活性,获得能够与生物素标记的纤维蛋白适配子G81-2结合的偶联物。方法:将序列正确的质粒p ET-44b-SA-H-RGD进行原核表达,采用不同浓度的IPTG及时间优化融合蛋白表达条件,镍亲和凝胶层析柱纯化融合蛋白,Western-blot鉴定蛋白。通过凝血酶原时间(PT)和抗血小板聚集实验检测融合蛋白活性;之后按照生物素-G81-2:SA-H-RGD摩尔比为4:1的比例制备纤维蛋白特异性的偶联物,用凝胶迁移阻滞实验(EMSA)验证二者的偶联。结果:融合蛋白SA-H-RGD在IPTG 0.9 mmol/L、5 h时在大肠杆菌中获得可溶性高效表达,纯化的融合蛋白具有延长PT的作用和抑制血小板聚集的活性,EMSA表明SA-H-RGD具有结合生物素标记的G81-2适配子的功能。结论:本研究成功地优化表达了具有抗凝血和抗血小板聚集功能的融合蛋白SA-H-RGD,获得了水蛭素融合蛋白与生物素-G81-2适配子组成的靶向偶联物。     

尖吻蝮蛇毒无出血活性纤维蛋白溶解酶对动物凝血功能的影响

为探讨尖吻蝮蛇毒无出血活性纤维蛋白溶解酶 (NHFLE)对动物凝血功能的影响 ,作者应用家兔、大鼠作动物体内外实验观察 NHFLE对血小板聚集的影响及对凝血功能的影响 ,分别测定了纤维蛋白含量、全血凝固时间(CT)、活化的部分凝血酶原时间 (APTT)、凝血酶时间 (PT)和优球蛋白溶解时间 (ELT)、凝血酶时间 (TT)以及血小板聚集率等。结果无论是体外法还是体内法 ,尖吻蝮蛇毒 NHFLE都能明显延长 CT、 APTT、 PT、 TT,缩短 ELT的溶解时间 ,明显降低纤维蛋白原的含量 ,给药后 30 min纤维蛋白原降低最明显 ,但对血小板聚集均无抑制作…     

犀角地黄汤化裁方对蛇伤患者血浆TT、PT、APTT的影响

目的观察犀角地黄汤化裁方对血循毒或混合毒蛇咬伤出现血分证的患者血浆TT、PT、APTT的影响。方法选择血循毒或混合毒蛇咬伤2h内的患者130例,随机分为2组,均给予常规治疗,治疗组加服犀角地黄汤化裁方。于就诊时、咬伤后72h测定其血浆TT、PT、APTT,并进行比较。结果2组患者在初诊时(伤后2h内)血浆TT、PT、APTT无明显差异,均在正常范围内;伤后72h三项指标均升高,对照组显著高于治疗组(P<0.05)。结论犀角地黄汤化裁方能抑制血循毒或混合毒蛇咬伤患者血浆TT、PT、APTT的延长,对蛇伤引起的凝血障碍有防治作用。     

弥漫性血管内凝血产妇围术期凝血与纤溶系统指标的检测及临床意义

目的:探讨弥漫性血管内凝血(DIC)产妇围术期凝血与纤溶系统指标检测的临床意义。方法:选择2017年1到2017年12月在我院接受治疗的DIC孕妇57例(DIC组)为研究对象,采取分层抽样的方法选择同期在我院进行产检的正常孕妇57例(健康孕妇组)及在我院体检的健康非孕妇57例(非孕妇组)作为对照,比较各组凝血酶原时间(PT)、凝血酶时间(TT)、活化部分凝血活酶时间(APTT)、纤维蛋白原(FIB)、D-二聚体(D-D)及血小板计数(PLT)变化,根据DIC组的治疗结果分为有效组和无效组,并比较两亚组治疗前PT、TT、APTT、FIB、D-D、PLT,采用Pearson相关分析法分析DIC组治疗前各检测指标间的相关性。结果:与健康孕妇组、非孕妇组比较,DIC组PT、TT、APTT延长(P0.05),D-D水平升高(P0.05),FIB、PLT水平降低(P0.05);与非孕妇组比较,健康孕妇组PT、TT、APTT缩短(P0.05),D-D水平降低(P0.05),FIB、PLT水平升高(P0.05)。DIC组患者治疗后有效组治疗前的PT、TT、APTT短于无效组(P0.05),D-D水平低于无效组(P0.05);FIB、PLT水平高于无效组(P0.05)。Pearson相关分析结果显示,除PT与APTT之间无明显相关性(P0.05)外,其他凝血、纤溶系统指标之间均存在一定的相关性(P0.05)。结论:DIC孕妇围术期凝血与纤溶系统指标异常改变,检测凝血与纤溶系统指标对DIC孕妇的诊疗具有重要意义。     

不同化疗方案对非小细胞肺癌患者凝血纤溶功能及血小板参数的影响及其临床意义

目的:探讨不同化疗方案对非小细胞肺癌患者凝血纤溶功能及血小板参数的影响及临床意义。方法:回顾性分析2013年2月至2016年2月于我院进行治疗的96非小细胞肺癌患者的临床资料,按照化疗方案的不同分为TP组(50例)及GP组(46例),TP组患者给予多西他赛联合卡铂方案(TP方案)进行化疗,GP组患者给予吉西他滨联合卡铂方案(GP方案)进行化疗,另选择45例健康体检者作为对照组。比较三组治疗前者血浆凝血酶原时间(PT)、活化部分凝血活酶时间(APTT)、血浆凝血酶时间(TT)、血浆纤维蛋白原含量(FIB)以及D-二聚体(D-dimer)、血小板数(PLT)、血小板比积(PCT)、血小板平均体积(MPV)、血小板体积分布宽度(PDW)以及大体积血小板比率(P-LCR)及TP组和GP组治疗后以上指标的差异。结果:TP组和GP组患者化疗前PT、APTT、TT、FIB、D-dimer、PLT、PCT、MPV、PDW以及P-LCR水平均明显高于对照组(P0.05),而TP组与GP组以上指标比较无显著差异(P0.05)。治疗后,TP组和GP组患者PT、APTT、TT、FIB、D-dimer、PLT、PCT、MPV、PDW以及P-LCR水平均较治疗前有所下降,且GP组TT明显长于TP组(P0.05),PLT、PCT明显低于TP组(P0.05)。结论:凝血纤溶功能及血小板参数对于评价不同化疗方案治疗非小细胞肺癌患者预后具有积极的临床价值,不同化疗方案选择对于患者凝血系统均具有一定的影响。     

硇洲马尾藻(S.naozhouense)褐藻多酚的抗凝血活性研究

本文采用溶剂萃取法提取硇洲马尾藻(S.naozhouense)褐藻多酚,并通过超滤进行分子量分级得NW1和NW2两部分,检测其总多酚的含量.通过体内和体外实验检测NW1和NW2体内对凝血时间(CT)、出血时间(BT)、凝血酶原时间(PT)和血浆凝血酶时间(TT)的影响.结果表明,硇洲马尾藻多酚NW1在10～40 mg/kg.d剂量范围能显著延长CT和BT,在5～15 mg/mL浓度范围显著增加PT和TT,表现出良好的全面抗凝血活性;NW2能显著延长CT和BT,对TT有一定的延长作用,但对PT无效果,且在高浓度(15 mg/mL)时表现出显著的缩短PT作用.     

慢性乙型肝炎患者血清白介素17A和胆碱酯酶的表达及临床意义

目的:检测慢性乙型肝炎(CHB)患者血清白介素17A(IL-17A)、胆碱酯酶(CHE)水平,并分析其临床意义。方法:选取2018年1月到2019年3月期间在重庆三峡中心医院接受治疗的CHB患者84例,根据病情严重程度将所有患者分为轻度组30例、中度组28例、重度组26例,另选取同期在重庆三峡中心医院进行体检的健康志愿者50例作为对照组。比较各组的凝血四项指标[纤维蛋白原(FIB)、凝血酶原时间(PT)、凝血活酶时间(APTT)、凝血酶时间(TT)]、肝功能指标[谷丙转氨酶(ALT)、谷草转氨酶(AST)]、IL-17A、CHE水平,采用Pearson相关分析CHB患者血清IL-17A、CHE与凝血四项、ALT、AST的相关性。结果:重度组、中度组、轻度组、对照组的FIB、CHE水平逐渐升高,PT、APTT、TT、ALT、AST、IL-17A水平逐渐降低,两两比较均有统计学差异(P0.05),IL-17A与FIB、CHE呈负相关,与PT、APTT、TT、ALT、AST呈正相关(P0.05);CHE与FIB呈正相关,与PT、APTT、TT、ALT、AST呈负相关(P0.05)。结论:CHB患者血清中IL-17A、CHE水平与患者的肝功能和凝血功能密切相关,联合检测IL-17A和CHE有助于患者的病情评估以及预后判断。     

β-乳香酸对血瘀证大鼠血液流变学和血管内皮功能的影响

目的:研究β-乳香酸(β-BA)对血瘀证大鼠血液流变学和血管内皮功能的影响。方法:24只SD大鼠随机分为4组:空白对照组、模型组、低剂量β-BA(100 mg/kg)组、高剂量β-BA(200 mg/kg)组,每组6只,每12小时给药1次、连续给药7次,第5次给药后,除空白组大鼠外,给予皮下注射盐酸肾上腺素(0.8 mg/kg)2次,间隔4小时,中间给予冰水(0-2℃)刺激5分钟造成大鼠急性血瘀证模型。最后一次给药30分钟内腹主动脉取血检测不同切变率下的全血粘度(WBV)、凝血指标、血浆内皮素-1(ET-1)、一氧化氮(NO)浓度,并取颈动脉观察病理变化。结果:与空白对照组相比,模型组全血粘度明显升高(P0.01),凝血酶时间(TT)、凝血酶原时间(PT)、活化部分凝血活酶时间(APTT)显著缩短(P0.01),纤维蛋白原(FIB)含量增加(P0.01),血浆ET-1水平升高,血浆NO含量降低(P0.01)。与模型组相比,β-BA组全血粘度明显降低,TT、APTT、PT显著延长(P0.01),纤维蛋白原含量减少(P0.01),血浆ET-1水平降低,血浆NO水平升高(P0.01)。结论:β-乳香酸能显著改善血瘀证大鼠血液流变学异常,并保护其血管内皮功能。     

不同全自动凝血仪检测结果的分析研究

目的:探讨不同全自动凝血分析仪检测结果是否具有可比性,同时对其检测结果临床可接受性进行评估,使不同全自动凝血分析仪检测结果标准化.方法:连续30天用SYSMEX CA- 1500及CA-7000全自动凝血分析仪同时检测并比对仪器配套定值质控物的PT、INR、APTT、FIB、TT值;同时连续30天利用两台仪器检测并对比新鲜血标本的PT、INR、APTT、FIB、TT值.结果:SYSMEX CA- 1500及CA-7000日间质控物各检测项目:PT、INR、APTT、FIB、TT变异系数均小于5％.CA- 1500及CA-7000全自动凝血分析仪检测新鲜血标本:PT、INR、APTT、FIB、TT统计分析结果,t检验其P值均＞0.05;相关系数r在0.993-0.999之间;两台仪器的偏差均符合1/2美国CLIA’88能力验证分析质量要求.结论:两台仪器PT、INR、APTT、FIB、TT的检测结果具有很好的相关性,经统计分析两台仪器检测结果无统计学意义.对不同凝血分析仪进行比对分析,不仅能够及时发现仪器存在的系统误差.而且使其检测结果具有很好的一致性,给临床可提供一个准确、可靠一致的实验室检测结果,使临床对疾病的诊断、疗效观察有一个统一的评判标准.     

Neutrophil cathepsin G promotes prothrombinase and fibrin formation under flow conditions by activating fibrinogen-adherent platelets

Human neutrophil proteases cathepsin G and elastase can directly alter platelet function and/or participate in coagulation cascade reactions on the platelet or neutrophil surface to enhance fibrin formation. The clotting of recalcified platelet-free plasma (PFP) or platelet-rich plasma (PRP) supplemented with corn trypsin inhibitor (to shut down contact activation) was studied in well-plates or flow assays. Inhibitors of cathepsin G or elastase significantly delayed the burst time (t(50)) of thrombin generation in neutrophil-supplemented PRP from 49 min to 59 and 77 min, respectively, in well-plate assays as well as reduced neutrophil-promoted fibrin deposition on fibrinogen-adherent platelets under flow conditions. In flow assays, purified cathepsin G was a far more potent activator of platelet-dependent coagulation than elastase. Anti-tissue factor had no effect on neutrophil protease-enhanced thrombin formation in PRP. The addition of cathepsin G (425 nm) or convulxin (10 nm) to PRP dramatically reduced the t(50) of thrombin generation from 53 min to 17 or 23 min, respectively. In contrast, the addition of elastase to PRP left the t(50) unaltered. Whereas perfusion of PFP (gamma(w) = 62.5 s(-1)) over fibrinogen-adherent platelets did not result in fibrin formation until 50 min, massive fibrin could be observed on cathepsin G-treated platelets even at 35 min. Cathepsin G addition to corn trypsin inhibitor-treated PFP produced little thrombin unless anionic phospholipid was present. However, further activation inhibition studies indicated that cathepsin G enhances fibrin deposition under flow conditions by elevating the activation state of fibrinogen-adherent platelets rather than by cleaving coagulation factors.     

血栓弹力图指导食管癌患者临床输血的价值及其与常规凝血实验检测指标的相关性分析

目的:探讨血栓弹力图(TEG)指导食管癌患者临床输血的价值及其与常规凝血实验检测指标的相关性。方法:选取2017年1月-2019年3月在我院收治的食管癌手术治疗需输血的99例患者作为研究对象,将99例患者随机分为常规凝血功能检测组和TEG组,常规凝血功能检测组采用常规凝血实验检查结果指导输血,TEG组采用TEG检查结果指导输血,对比两组输血前后的常规凝血实验检测指标以及临床用血量,对比TEG组输血前后的TEG指标,分析TEG指标与常规凝血实验检测指标的相关性。结果:两组患者输血前凝血四项和血小板计数(PLT)差异无统计学意义(P>0.05),输血后两组活化凝血酶时间(APTT)、凝血酶原时间(PT)、凝血酶时间(TT)、纤维蛋白原(FIB)均有不同程度的改善(P<0.05),TEG组PT、TT较常规凝血功能检测组低(P<0.05);输血后,TEG组患者凝血反应时间(R值)、血凝块形成时间(K值)较输血前降低,最大血凝块强度(MA值)、凝血综合指数(CI值)升高,凝血形成速率(Angle角)增大,差异有统计学意义(P<0.05);Pearson相关性分析结果显示,R值与APTT呈正相关(P<0.05),K值与PLT呈负相关,与FIB呈正相关(P<0.05),Angle角、MA值、CI值与FIB、PLT呈正相关(P<0.05);TEG组新鲜冰冻血浆、冷沉淀输注量少于常规凝血功能检测组,差异有统计学意义(P<0.05)。结论:TEG能更好地指导食管癌手术患者各种血液成分的合理输注,有效改善凝血异常情况,减少输血用量,TEG指标与常规凝血实验检测指标存在一定的相关性。     

大剂量氨甲环酸对全膝关节置换患者术后纤溶活性与炎症因子的影响

目的:探讨大剂量氨甲环酸对全膝关节置换患者术后纤溶活性与炎症因子的影响。方法:回顾性分析在我院行初次全膝关节置换术的180例患者,按照给药方式分为对照组、常规组、大剂量组,每组各60例。对照组患者直接给予生理盐水,常规组给予10 mg/kg氨甲环酸,大剂量组给予15 mg/kg氨甲环酸。比较三组术后总失血量、隐形失血量、术前与术后3天三组凝血功能(纤维蛋白原、凝血酶原时间、活化部分凝血活酶时间)、纤溶活性[纤维蛋白(原)降解产物(FDP)、D-二聚体]以及炎性因子[C-反应蛋白(CRP)、白介素-6(IL-6)]水平变化及术后2周血栓事件的发生情况。结果:大剂量组与常规组的总失血量与隐形失血量均明显低于对照组,大剂量组总失血量与隐形失血量均低于常规组(P0.05);三组患者纤维蛋白原、凝血酶原时间以及活化部分凝血活酶时间相比差异均无统计学意义(P0.05);术后3天,大剂量组和常规组FDP与D-二聚体、CRP、IL-6水平均显著低于对照组,且与常规组相比,大剂量组水平较低(P0.05);术后2周,三组肌间静脉血栓发生率比较均无显著差异(P0.05)。结论:在全膝关节置换术后使用氨甲环酸可进一步减少术后隐形失血量,且不会增加血栓事件的风险,且随着药物剂量的增加,其止血效果越强,同时具有更为显著的抗纤溶作用与抗炎效果。     

Highly selective resonance scattering detection of trace thrombin using aptamer-modified AuRe nanoprobe

The gold-rhenium (AuRe) composite nanoparticle was prepared by NaBH₄ reduction procedure, and was modified by the aptamer to obtain an AuRe nanoprobe (AuRessDNA) for thrombin. In pH 7.0 Tris–HCl buffer solution and in the presence of salt, the nanoprobe specifically combined with thrombin to form AuRe-aptamer-thrombin cluster that resulted in the resonance scattering intensity (I _560 nm) increasing at 560 nm. The increased intensity ΔI _{560 nm} was linear to the thrombin concentration in the range of 0.115–6.93 nmol/L, with a regression equation of ΔI _{560 nm} = 53.0 C + 2.5, a correlation coefficient of 0.9989, and a detection limit of 13 pmol/L. This method was applied to detect thrombin in human plasma samples, with satisfactory results.     

Cystamine Preparations Exhibit Anticoagulant Activity

Transglutaminases are a superfamily of isoenzymes found in cells and plasma. These enzymes catalyze the formation of ε-N-(γ-glutamyl)-lysyl crosslinks between proteins. Cystamine blocks transglutaminase activity and is used in vitro in human samples and in vivo in mice and rats in studies of coagulation, immune dysfunction, and inflammatory disease. These studies have suggested cystamine blocks fibrin crosslinking and has anti-inflammatory effects, implicating transglutaminase activity in the pathogenesis of several diseases. We measured the effects of cystamine on fibrin crosslinking, tissue factor-triggered plasma clot formation and thrombin generation, and coagulation factor enzymatic activity. At concentrations that blocked fibrin crosslinking, cystamine also inhibited plasma clot formation and reduced thrombin generation. Cystamine inhibited the amidolytic activity of coagulation factor XI and thrombin towards chromogenic substrates. These findings demonstrate that cystamine exhibits anticoagulant activity during coagulation. Given the close relationship between coagulation and inflammation, these findings suggest prior studies that used cystamine to implicate transglutaminase activity in disease pathogenesis warrant re-examination.     

Spatial Distribution of Factor Xa,Thrombin, and Fibrin(ogen) on Thrombi at Venous Shear

Background

The generation of thrombin is a critical process in the formation of venous thrombi. In isolated plasma under static conditions, phosphatidylserine (PS)-exposing platelets support coagulation factor activation and thrombin generation; however, their role in supporting coagulation factor binding under shear conditions remains unclear. We sought to determine where activated factor X (FXa), (pro)thrombin, and fibrin(ogen) are localized in thrombi formed under venous shear.

Methodology/Principal Findings

Fluorescence microscopy was used to study the accumulation of platelets, FXa, (pro)thrombin, and fibrin(ogen) in thrombi formed in vitro and in vivo. Co-perfusion of human blood with tissue factor resulted in formation of visible fibrin at low, but not at high shear rate. At low shear, platelets demonstrated increased Ca²⁺ signaling and PS exposure, and supported binding of FXa and prothrombin. However, once cleaved, (pro)thrombin was observed on fibrin fibers, covering the whole thrombus. In vivo, wild-type mice were injected with fluorescently labeled coagulation factors and venous thrombus formation was monitored in mesenteric veins treated with FeCl₃. Thrombi formed in vivo consisted of platelet aggregates, focal spots of platelets binding FXa, and large areas binding (pro)thrombin and fibrin(ogen).

Conclusions/Significance

FXa bound in a punctate manner to thrombi under shear, while thrombin and fibrin(ogen) distributed ubiquitously over platelet-fibrin thrombi. During thrombus formation under venous shear, thrombin may relocate from focal sites of formation (on FXa-binding platelets) to dispersed sites of action (on fibrin fibers).     

自体输血与异体输血对创伤性颅脑损伤开颅手术患者凝血功能、细胞免疫功能和神经损伤标志物的影响

摘要 目的：探讨自体输血与异体输血对创伤性颅脑损伤（TBI）开颅手术患者凝血功能、细胞免疫功能和神经损伤标志物的影响。方法：回顾性分析2019年4月~2022年5月期间在本院行开颅手术的120例TBI患者的临床资料。根据输血方式的不同将患者分为异体输血组（n=58,异体输血）和自体输血组（n=62,自体输血）,观察两组临床指标、细胞免疫功能、凝血功能、神经损伤标志物和不良反应发生率情况。结果：两组患者手术出血量、输血量、输注含凝血成分血制品比例对比,差异无统计学意义（P>0.05）。自体输血组出院时CD3⁺、CD4⁺、CD4⁺/CD8⁺高于异体输血组,CD8⁺低于异体输血组（P<0.05）。两组出院时凝血酶原时间（PT）、凝血酶时间（TT）、纤维蛋白原（FIB）、活化部分凝血活酶时间（APTT）组间对比无统计学差异（P>0.05）。自体输血组出院时S100钙结合蛋白B（S100B）、神经胶质原纤维酸性蛋白（GFAP）、神经元特异性烯醇化酶（NSE）低于异体输血组（P<0.05）。两组不良反应发生率组间比较无差异（P>0.05）。结论：自体输血用于TBI开颅手术患者,对患者的凝血功能影响较小,同时还可改善机体细胞免疫功能,降低神经损伤标志物水平。     

Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay

In response to injury, blood coagulation is activated and results in generation of the clotting protease, thrombin. Thrombin cleaves fibrinogen to fibrin which forms an insoluble clot that stops hemorrhage. Factor V (FV) in its activated form, FVa, is a critical cofactor for the protease FXa and accelerator of thrombin generation during fibrin clot formation as part of prothrombinase ^{1, 2}. Manual FV assays have been described ^{3, 4}, but they are time consuming and subjective. Automated FV assays have been reported ^5-7, but the analyzer and reagents are expensive and generally provide only the clot time, not the rate and extent of fibrin formation. The microplate platform is preferred for measuring enzyme-catalyzed events because of convenience, time, cost, small volume, continuous monitoring, and high-throughput ^{8, 9}. Microplate assays have been reported for clot lysis ¹⁰, platelet aggregation ¹¹, and coagulation Factors ¹², but not for FV activity in human plasma. The goal of the method was to develop a microplate assay that measures FV activity during fibrin formation in human plasma.This novel microplate method outlines a simple, inexpensive, and rapid assay of FV activity in human plasma. The assay utilizes a kinetic microplate reader to monitor the absorbance change at 405nm during fibrin formation in human plasma (Figure 1) ¹³. The assay accurately measures the time, initial rate, and extent of fibrin clot formation. It requires only μl quantities of plasma, is complete in 6 min, has high-throughput, is sensitive to 24-80pM FV, and measures the amount of unintentionally activated (1-stage activity) and thrombin-activated FV (2-stage activity) to obtain a complete assessment of its total functional activity (2-stage activity - 1-stage activity).Disseminated intravascular coagulation (DIC) is an acquired coagulopathy that most often develops from pre-existing infections ¹⁴. DIC is associated with a poor prognosis and increases mortality above the pre-existing pathology ¹⁵. The assay was used to show that in 9 patients with DIC, the FV 1-stage, 2-stage, and total activities were decreased, on average, by 54%, 44%, and 42%, respectively, compared with normal pooled human reference plasma (NHP).The FV microplate assay is easily adaptable to measure the activity of any coagulation factor. This assay will increase our understanding of FV biochemistry through a more accurate and complete measurement of its activity in research and clinical settings. This information will positively impact healthcare environments through earlier diagnosis and development of more effective treatments for coagulation disorders, such as DIC.     

Quadruplex formation as a molecular switch to turn on intrinsically fluorescent nucleotide analogs

Quadruplexes are involved in the regulation of gene expression and are part of telomeres at the ends of chromosomes. In addition, they are useful in therapeutic and biotechnological applications, including nucleic acid diagnostics. In the presence of K⁺ ions, two 15-mer sequences d(GGTTGGTGTGGTTGG) (thrombin binding aptamer) and d(GGGTGGGTGGGTGGG) (G3T) fold into antiparallel and parallel quadruplexes, respectively. In the present study, we measured the fluorescence intensity of one or more 2-aminopurine or 6-methylisoxanthopterin base analogs incorporated at loop-positions of quadruplex forming sequences to develop a detection method for DNA sequences in solution. Before quadruplex formation, the fluorescence is efficiently quenched in all cases. Remarkably, G3T quadruplex formation results in emission of fluorescence equal to that of a free base in all three positions. In the case of thrombin binding aptamer, the emission intensity depends on the location of the fluorescent nucleotides. Circular dichroism studies demonstrate that the modifications do not change the overall secondary structure, whereas thermal unfolding experiments revealed that fluorescent analogs significantly destabilize the quadruplexes. Overall, these studies suggest that quadruplexes containing fluorescent nucleotide analogs are useful tools in the development of novel DNA detection methodologies.     

Evaluation of Antithrombotic Activity of Thrombin DNA Aptamers by a Murine Thrombosis Model

Aptamers are nucleic acid based molecular recognition elements with a high potential for the theranostics. Some of the aptamers are under development for therapeutic applications as promising antithrombotic agents; and G-quadruplex DNA aptamers, which directly inhibit the thrombin activity, are among them. RA-36, the 31-meric DNA aptamer, consists of two thrombin binding pharmacophores joined with the thymine linker. It has been shown earlier that RA-36 directly inhibits thrombin in the reaction of fibrinogen hydrolysis, and also it inhibits plasma and blood coagulation. Studies of both inhibitory and anticoagulation effects had indicated rather high species specificity of the aptamer. Further R&D of RA-36 requires exploring its efficiency in vivo. Therefore the development of a robust and adequate animal model for effective physiological studies of aptamers is in high current demand. This work is devoted to in vivo study of the antithrombotic effect of RA-36 aptamer. A murine model of thrombosis has been applied to reveal a lag and even prevention of thrombus formation when RA-36 was intravenous bolus injected in high doses of 1.4–7.1 µmol/kg (14–70 mg/kg). A comparative study of RA-36 aptamer and bivalirudin reveals that both direct thrombin inhibitors have similar antithrombotic effects for the murine model of thrombosis; though in vitro bivalirudin has anticoagulation activity several times higher compared to RA-36. The results indicate that both RA-36 aptamer and bivalirudin are direct thrombin inhibitors of different potency, but possible interactions of the thrombin-inhibitor complex with other components of blood coagulation cascade level the physiological effects for both inhibitors.