Platelet function in septic multiple organ dysfunction syndrome

Objective: Altered platelet function plays a role in the pathophysiology of multiple organ failure in sepsis. The purpose of the present study was to evaluate various aspects of platelet adhesive function in septic patients and its putative relevance for prognosis. Design: Prospective clinical study. Setting: Intensive Care Unit of the University Hospital. Patients and methods: A total of 41 patients admitted to the medical Intensive Care Unit were studied. On the day of admission, patients were evaluated by intensive care scoring systems (Elebute, APACHE II) to assess the severity of sepsis and multiple organ dysfunction syndrome (MODS), and platelet function tests were performed. All patients were observed for 28 days to assess their clinical outcomes. Eleven patients revealed septicemia without MODS (Elebute ≥12, APACHE II <20) and 20 septic patients suffered from MODS (Elebute ≥12, APACHE II ≥20). Ten non-septic patients without MODS served as a control group (Elebute <12, APACHE II <20). Flow cytometric determination of the activated fibrinogen (fg) receptor GPIIb-IIIa and as well as thrombospondin (TSP) on platelets and platelet-neutrophil adhesion (CD41 immunofluorescence) ex vivo was performed using monoclonal antibodies. The effect of plasma obtained from patients on normal platelet aggregation in vitro, and adhesion to cultured endothelial cells was evaluated. Results: The surface expression of TSP on platelets was increased in septic patients with MODS compared to controls (p<0.03). Platelet-neutrophil adhesion was not significantly altered in septicemia (p<0.09) but decreased significantly in the presence of MODS (p<0.05) when compared to controls. Logistic regression analysis showed that platelet-neutrophil adhesion was an independent predictor for poor clinical outcome (p<0.01). Plasma from septic patients sensitized normal platelets to hyperaggregate and to adhere to cultured endothelium (p<0.01). Conclusion: In septic patients platelets become activated and are hyperadhesive to other vascular cells including neutrophils and endothelium. This may induce sequestration of platelets and microcirculatory arrest, thus the development of MODS. Received: 6 June 1996 Accepted: 4 October 1996     

粘性放线菌Ⅱ型菌毛粘附与凝集活性的研究

目的:研究粘放菌Ⅱ型菌毛在细菌粘附与凝集过程中的作用。方法:制备粘放菌Ⅱ型菌毛多克隆抗体抗血清,检其对粘放菌变异株5519、5951、T14V的粘附抑制率,同时肉眼观察它对粘放菌与血链菌34间凝集反应的影响。结果:抗Ⅱ型毛多克隆抗体能减少5519、5951、T14V对玻壁的粘附量,并抑制5951、T14V与血链菌34间的凝集反应。结论:粘放菌Ⅱ型菌具有粘附与凝集的活性。     

Perinatal outcomes of women with a prior history of unexplained recurrent miscarriage

Objective: We sought to determine subsequent pregnancy outcomes in a cohort of women with a history of unexplained recurrent miscarriage (RM) who were not receiving medical treatment.

Study design: This was a prospective cohort study, of women with a history of three unexplained consecutive first trimester losses, who were recruited and followed in their subsequent pregnancy. Control patients were healthy pregnant patients with no previous adverse perinatal outcome.

Results: A total of 42 patients with a history of unexplained RM were recruited to the study. About nine (21.4%) experienced a further first trimester miscarriage, one case of ectopic and one case of partial molar pregnancy. About 74% (23/31) of the RM cohort had a vaginal delivery. There was one case of severe pre-eclampsia. The RM group delivered at a mean gestational age of 38?+?2 weeks and with a mean birthweight of 3.23?kg. None of the neonates were under the 10th centile for gestational age. Overall, there was no significant difference in pregnancy outcomes between the two cohorts.

Conclusion: Our study confirms the reassuring prognosis for achieving a live birth in the unexplained RM population with a very low incidence of adverse events with the majority delivering appropriately grown fetuses at term.     

Effect of ultrafiltration and plasma osmolarity upon the flow properties of blood: A possible mechanism for control of blood flow in the renal medullary vasa recta

Summary The normal flow properties of human blood are severely altered when its chemical composition is altered by ultrafiltration or by making plasma hypertonic with NaCl or Mannitol. As a result of ultrafiltration, the viscosity of plasma is increased and so is the concentration of high molecular weight plasma proteins (e.g. fibrinogen), causing red cell aggregation. The crenation of erythrocytes reduces their physiological fluidity and thereby greatly increases apparent blood viscosity. The combined effects of NaCl induced hypertonicity (600 mOsmol/l) and ultrafiltration (FF 0.4) increased apparent blood viscosity between 110 and 4 times (depending on hematocrit value). These effects are especially pronounced in models of the microcirculation (Millipore^® filters, 514 m mean pore diameter) and are operating at low hematocrit values. Since the renal medullary vasa recta are the only part of the circulatory bed where such chemical changes of the blood occur, the hypothesis is presented that the hypertonicity of the vasa plasma via its effect on red cells rheology controls the relatively low rate of vasa recta blood flow in antidiuresis.Presented in parts before the Spring Meeting of the Federation of American Societies of Experimental Biology (Atlantic City 1969) and the 36^th Meeting of the German Physiological Society (Mainz, 1969).Supported by grants from the Max Kade Foundation (New York, N.Y.), the John A. Hartford Foundation, Public Health Service Grant 5 P01-H.E. 11306, and from the Deutsche Forschungsgemeinschaft (Schm 84/1).     

炒紫苏子醇提物对血小板聚集活性的影响

目的:探讨炒紫苏子醇提取物对腺苷二磷酸(ADP)、花生四烯酸(AA)和血小板活化因子(PAF)诱导血小板聚集功能的影响。方法:用诱导剂ADP(终浓度3μmol/L)、PAF(终浓度7.2 nmol/L)、AA(终浓度0.35 mmol/L)分别激发血小板聚集,观察炒紫苏子醇提取物对血小板聚集的抑制作用。结果:炒紫苏子醇提取物体外能抑制由ADP、PAF和AA激发的兔血小板聚集,并表现明显的剂量依赖关系。其中,对PAF诱发的血小板聚集作用有更强的抑制作用,80mg/L就表现出明显的抑制作用(P<0.05);而对于ADP和AA激发的兔血小板聚集,640 mg/L炒紫苏子醇提取物表现出明显的抑制作用。结论:炒紫苏子醇提取物具有明显的抗血小板聚集作用。     

The effect of endothelium-derived nitric oxide on ex vivo whole blood platelet aggregation in man

Summary The effects of changes in endogenous endothelium-derived nitric oxide (NO) on forearm blood flow and ex vivo platelet aggregation have been studied in 7 healthy volunteers.Measurements were made of forearm blood flow and ex vivo collagen-stimulated platelet aggregation during unilateral brachial artery infusions of saline, acetylcholine (ACh), N^G monomethyl-L-arginine (L-NMMA), and prostacyclin (PGI₂). The uninfused arm acted as a control.Forearm blood flow was increased by ACh, an agent which stimulates NO release, and decreased by L-NMMA, an agent which stereospecifically inhibits NO synthesis.Collagen-stimulated platelet aggregation measured ex vivo in whole blood draining the infused arm was unaltered by either ACh or L-NMMA. Conversely, PGI₂, an agent which acts independently of NO, caused an increase in forearm blood flow which was accompanied by significant inhibition of platelet aggregation.The results suggest that release of endothelium-derived NO in quantities sufficient to cause substantial changes in blood vessel tone does not lead to changes in platelet aggregation in the blood flowing through the vessels. It is, however, still possible that endothelium-derived NO modulates platelet activity at the level of the endothelium. Present address: Department of Medicine and Therapeutics, University of Aberdeen Polwarth Building, Forrester Hill, Aberdeen, UK     

钙离子跨膜转运与血小板聚集阈值

钙离子作为第二信使物质,调节着众多的生理反映。本文从钙离子的跨膜转运对血小板聚集的影响出发,提出一种数学模型方法,力图以胞浆内游离钙浓度作为指标去研究和标志血小板的聚集特性,它从一个侧面去反映血小板的老化程度或病态程度。     

RGDS的抗血小板聚集及舒血管效应

血小板聚集是正常止血的要素,并依赖于膜糖蛋白Ⅱ_b/Ⅲ_a(GPⅡ_a/Ⅲ_a)复合物与血浆粘附糖蛋白(包括纤维蛋白原 von Willebrand 因子和 fibronectin)的相互作用。研究 GPⅡ_b/Ⅲ_a 受体与纤维蛋白结合确定了在介导其自身与 GP Ⅱ_b/Ⅲ_a 接触的纤维蛋白分子中存在两种不同的氨基酸序列。其中一种序列是 Arg-Gly-Asp(RGD),该序列不仅出现在纤维蛋白 Aα链中,也出现在 fibronectin 和 von Willebrand 因子中。为了阐明其生物学效应本文合成了RGDS,并进行了与抗栓有关的生物学评价。本研究提供的数据证实 RGDS 明显抑制 PAF或 ADP 诱发的血栓形成(对 PAF 诱导的血小板聚集抑制率为67%,RGDS 浓度为9.6×10~(-7)mol/L;对 ADP 诱导的血小板聚集抑制率为87%,RGDS 浓度为9.6×10~(-7)mol/L)。该观察与 RGDS 延缓血栓形成的发现相符。虽然 RGDS 对 ADP 比对 PAF 更敏感但它对 PAF 的抑制仍十分明显这些结果均属首次报道。本研究进一步揭示了 RGDS 有舒血管作用,而且它对大鼠主动脉肌条的舒张作用不可忽视(与对照相比1×10~(-5)mol/L 的 RGDS 在 NE 处理的鼠动脉肌条上的舒张幅度为8.08±5.0%,P<0.05)。对组织内 cGMP 的累积水平(与对照相比1±10~(-5)mol/L 的RGDS 引起 cGMP 水平增高4.68±1.9pmol/mg,P<0.05)研究结果表明,提高体内 cGMP 的水平可能是 RGDS 发挥生物学作用的机制之一。RGDS 的舒血管和抗血小板聚集两种作用均可作为设计与合成新型抗栓剂的实验依据。     

Enhanced physical stability of human calcitonin after methionine oxidation

Calcitonin is a blood-calcium-lowering peptide, present in different species, which inhibits the resorption of bone by osteoclasts. Human calcitonin (hCT) is one of the few calcitonin peptides, which contains a methionine residue; this residue is in position 8. Methionines are known to be readily oxidized to sulfoxides both in vivo and in vitro. The current work describes the effect of methionine oxidation on the physical stability of hCT. Aggregation kinetics of human calcitonin were studied at different pH values by intrinsic fluorescence spectroscopy, turbidity at 350 nm, microscopy analyses, Nile Red, and 1,8-ANS fluorescence emission. In all the experiments, methionine oxidation reduced the aggregation rate of human calcitonin. The effect of methionine oxidation was independent of pH. Fluorescence lifetime data also showed that the conformation of hCT in the aggregated state can be influenced by methionine oxidation. A hypothesis for the enhanced physical stability of oxidized hCT is presented and discussed.     

Effects of thromboxane synthetase inhibitors on aggregation of rabbit platelets

Thromboxane (TX) synthetase activity was selectively inhibited by (E)-3-[4-(1-imidazolylmethyl)phenyl]-2-propenoic acid hydrochloride monohydrate (OKY-046) and sodium (E)-3-[4-(3-pyridylmethyl)phenyl]-2-methyl-propenoate (OKY-1581) (OKYs). Their IC₅₀ for the rabbit platelet enzyme were found to be 11nM and 3nM respectively. Arachidonic acid (AA) or collagen induced platelet aggregation, and generated TXA₂ and prostaglandins (PGs) in rabbit platelets. OKYs inhibited platelet aggregation and TXA₂ generation without affecting PGs generation, while aspirin inhibited platelet aggregation, and TXA₂ and PGs generation. There was a parallel relation between the degree of inhibition of platelet aggregation and TXA₂ generation by OKYs, but the inhibitory effects of aspirin on platelet aggregation was related to that on both TXA₂ and PGs generation. However, OKYs and aspirin did not inhibit ADP-induced platelet aggregation which did not involve the generation of TXA₂ and PGs. These results suggested that TXA₂ generation is related to platelet aggregation induced by AA or collagen, and that the inhibitory effect of OKYs on platelet aggregation is due to the inhibition of TX synthetase.