Structural and functional characterization of an acidic platelet aggregation inhibitor and hypotensive phospholipase A(2) from Bothrops jararacussu snake venom

An acidic (pI approximately 4.5) phospholipase A(2) (BthA-I-PLA(2)) was isolated from Bothrops jararacussu snake venom by ion-exchange chromatography on a CM-Sepharose column followed by reverse phase chromatography on an RP-HPLC C-18 column. It is an approximately 13.7kDa single chain Asp49 PLA(2) with approximately 122 amino acid residues, 7 disulfide bridges, and the following N-terminal sequence: 1SLWQFGKMINYVM-GESGVLQYLSYGCYCGLGGQGQPTDATDRCCFVHDCC(51). Crystals of this acidic protein diffracted beyond 2.0A resolution. These crystals are monoclinic and have unit cell dimensions of a=33.9, b=63.8, c=49.1A, and beta=104.0 degrees. Although not myotoxic, cytotoxic, or lethal, the protein was catalytically 3-4 times more active than BthTX-II, a basic D49 myotoxic PLA(2) from the same venom and other Bothrops venoms. Although it showed no toxic activity, it was able to induce time-independent edema, this activity being inhibited by EDTA. In addition, BthA-I-PLA(2) caused a hypotensive response in the rat and inhibited platelet aggregation. Catalytic, antiplatelet and other activities were abolished by chemical modification with 4-bromophenacyl bromide, which is known to covalently bind to His48 of the catalytic site. Antibodies raised against crude B. jararacussu venom recognized this acidic PLA(2), while anti-Asp49-BthTX-II recognized it weakly and anti-Lys49-BthTX-I showed the least cross-reaction. These data confirm that myotoxicity does not necessarily correlate with catalytic activity in native PLA(2) homologues and that either of these two activities may exist alone. BthA-I-PLA(2), in addition to representing a relevant molecular model of catalytic activity, is also a promising hypotensive agent and platelet aggregation inhibitor for further studies.     

A reliable plasma marker of platelet activation: Does it exist?

Despite the clear importance of the platelet in various conditions and diseases, there are few opportunities to assess the physiological and pathological functions of this cell. Those without access to a flow cytometer or platelet aggregometer rely on secreted or release products of the platelet. Principle among these molecules are alpha granule components beta thromboglobulin and platelet factor four, and membrane constituents such as P selectin, gpV and glycocalicin. However, notwithstanding the ease of measurement of these markers (i.e., by ELISA) each one has its own particular disadvantage, mostly of methodology and specificity. Nevertheless, if our goal is to improve our ability to recognize and treat subjects with thrombotic disorders, then additional studies on these molecules may prove to be a sound investment.     

Relationship of serum interleukin-7 concentration and the coagulation state in children with nephrotic syndrome

BACKGROUND: Enhanced platelet reactivity may play a significant role in the hypercoagulable state of nephrotic syndrome (NS). Thrombocytosis with platelet aggregation cause the release of some cytokines, among them interleukin-7 (IL-7). The aim of the study was to evaluate serum IL-7 levels in children with the symptoms of NS and to determine a correlation between its concentration and platelet count, other hemostatic factors, and NS intensity. METHODS: The study was performed in two groups. I--the examined group of 26 children with NS (12 boys, 14 girls) aged 6.8 +/- 2.1 years, subjected to two examinations: A--before treatment, B--during treatment with prednisone (60 mg/kg 24 h after albuminuria regression); and II--the control group (C) of 20 healthy children. Serum IL-7 level was assayed by enzyme-linked immunosorbent assay method using a R & D Quantikine set. RESULTS: In group I, IL-7 level in examination A (33.33 +/- 33.24 pg/mL) was higher than in the control subjects (P < 0.01). In examination B, IL-7 concentration was reduced to the level of 10.86 +/- 5.22 pg/mL and did not differ from the controls (P > 0.05). A positive correlation was observed between IL-7 and platelet count and serum fibrinogen level. A negative correlation was noted with antithrombin III concentration. No correlation was found with serum levels of albumin and cholesterol or urine protein. CONCLUSION: In children with NS, serum IL-7 level increases proportionally to the elevated platelet count and other hemostatic components, but shows no correlation with serum albumin or urine protein.     

窒息新生儿外周血白细胞计数与血小板参数的动态变化分析

目的 :探讨窒息新生儿外周血白细胞计数与血小板参数的动态变化及其临床意义。方法 :将 5 8例窒息新生儿分为轻度窒息组 ( 2 0例 )和重度窒息组 ( 38例 ) ;另外选择 2 0例正常新生儿作为对照组 ,检测各组外周血白细胞计数、血小板参数 ,比较各组间白细胞数及血小板参数新生儿窒息程度的关系。结果 :外周血白细胞数及血小板计数 ( PC)、血小板平均体积 ( MPV)、血小板分布宽度 ( PDW) ,在窒息组和对照组及重度窒息组和轻度窒息组比较 ,外周血 WBC、MPV、PDW均显著升高 ( P<0 .0 1 ) ,血小板数显著减少 ( P<0 .0 5 )。窒息组治疗后与正常组比较 ,外周血白细胞数、血小板参数无显著性差异 ( P均 >0 .0 5 )。结论 :外周血白细胞数、血小板参数变化与新生儿窒息程度密切相关 ,在临床上可作为窒息后多脏器损伤的一个预警参数。     

氯吡格雷对异种移植心脏急性血管性排斥反应的影响

目的观察氯吡格雷对豚鼠-大鼠非协调性异种移植心脏急性血管性排斥反应的影响。方法采用颈部异位心脏移植模型,分2组:对照组(n=10)以眼镜蛇毒因子预处理;实验组(n=8)以眼镜蛇毒因子加氯吡格雷联合预处理。观察比较移植物存活时间、病理变化及细胞凋亡情况。结果移植物病理表现均为急性血管性排斥反应改变。实验组经氯吡格雷预处理的移植物P选择素表达积分减少[(1.66±0.32)vs(2.52±0.22),P<0.05),凋亡指数降低[(11.5±2.8)vs(15.6±3.9),P<0.05),移植物平均存活时间明显长于对照组[(50±4)hvs(41±2)h,P<0.05)。结论氯吡格雷可延长非协调性异种移植物存活时间,减轻异种移植免疫损害。     

血小板CD62p在突发性聋治疗中的意义

目的　根据血小板细胞黏附分子CD6 2p的变化 ,为突发性聋患者的治疗提供有用的指标。方法　 15 6例突发性聋患者血小板CD6 2p采用流式细胞仪测定 ,将血小板CD6 2p≥ 2 %患者分别施以基础治疗 (低分子右旋糖甙 +ATP +CoA +地塞米松 )和基础治疗 +溶栓 (巴曲酶 ) ,观察 2种方案的疗效 ,同样血小板CD6 2p <2 %患者亦施以两种治疗方案观察其疗效。结果　在血小板CD6 2p≥ 2 %组中 ,基础治疗有效率为 6 0 5 % ,基础治疗 +溶栓治疗的有效率为 84 6 % ,两者之间差异有显著性。而在血小板CD6 2p <2 %组中 ,基础治疗和基础治疗 +溶栓的有效率分别为 6 5 0 %、71 8% ,差异无显著性。结论　检测突发性聋患者CD6 2p在临床上确定治疗方案的选择有指导意义     

In vitro stimulation of monocyte tissue factor activity by autologous platelets

Washed human platelets were found to enhance phytohemagglutinin (PHA)-stimulated tissue factor (TF) synthesis when incubated with autologous mononuclear cell cultures. Furthermore, platelets increased TF synthesis even when no other stimulator was present during the incubation. Experiments utilizing similar cultures derived from blood of patients with Glanzmann's disease, von Willebrand's disease, and platelet storage pool disease indicated that platelets with each of these genetic defects possessed the capacity to enhance the synthesis of this initiator of coagulation by unstimulated cells as did normal platelets. The degree of platelet enhancement varied between individuals, but for any given donor, the extent of the effect depended on the concentration of platelets used. The effect was demonstrable at platelet/monocyte ratios ranging from a low of approximately 15 to the highest ratio used, about 300. For comparison the ratio of these two cellular elements in normal human blood is estimated to be approximately 1,000. These findings may reflect a relationship between these two cell types that can occur in vivo.