Effect of Streptococcus sanguinis/Porphyromonas gingivalis single and combined biofilms upon platelet aggregation

Oral Diseases (2012) 18, 586–594 Objective: To assess the effect of two oral bacteria Streptococcus sanguinis and Porphyromonas gingivalis upon platelet aggregation. Materials and Methods: Streptococcus sanguinis, P. gingivalis, S. sanguniis + P. gingivalis were added to platelet‐rich plasma and platelet aggregation measured using a platelet aggregometer. Platelets were passed through a flow chamber with S. sanguinis, P. gingivalis or a biofilm of S. sanguinis and P. gingivalis coated with saliva. Platelet adhesion to the chamber was observed under a fluorescence microscope for 15 min. The positive control was platelets treated with adrenaline; the negative control was platelets treated with phosphate‐buffered saline. Results: The mean (± s.e.) aggregation magnitude of S. sanguinis and P. gingivalis was 77.7 ± 7.4% and 79.3 ± 9.9%, respectively. The aggregation magnitude of S. sanguinis + P. gingivalis was 51.3 ± 12.9%, which was significantly lower than that for S. sanguinis/P. gingivalis (P < 0.05). In the flow chamber system, platelets adhered to S. sanguinis/P.gingivalis respectively within 3 min, and reached a plateau at 5–15 min. Under the condition of the S. sanguinis‐ and P. gingivalis‐saliva biofilm, platelet adhesion to the biofilm was significantly reduced at 5–15 min (P < 0.05). Conclusions: In the static or dynamic flow system, platelets adhered to S. sanguinis or P. gingivalis. However, if S. sanguinis was mixed with P. gingivalis, the aggregation magnitude (%) was significantly reduced.     

Evaluation of platelet function and lack of response to epinephrine in pregnant women

Previous studies in healthy subjects have demonstrated a lack of response of platelets to epinephrine at a rate of 16-40% on an aggregometer. An association between the increased procoagulant factors during pregnancy and venous thromboembolism is known, and it has also been shown that prolactin levels increase platelet aggregation. We evaluated whether platelet functions in pregnant women and also assessed the lack of response to epinephrine during this period. We compared 27 healthy and volunteering pregnant women with 26 similar control subjects. Platelet functions were assessed with an aggregometer and a Platelet Function Analyzer (PFA-100). Less than 40% response to epinephrine on the aggregometer was defined as an impaired epinephrine response. The aggregation response of epinephrine was normal in 25 of the 27 pregnant women, while two of them showed a late-rising response. Eight of the 26 subject control group (30.8%) showed an impaired response to epinephrine. When we compared the 25 pregnant and 18 control subjects with normal aggregation responses, the maximum aggregation responses to ADP and epinephrine, and the Col/Epi and Col/ADP cartridge closure time values were significantly lower in pregnant women. There were no difference between second and third trimesters as regards platelet function parameters. The fact that no impaired response to epinephrine was detected in pregnant women while a 30% rate was observed in non-pregnant women indicates that the platelet malfunction caused by a disorder in the Gi protein and intracellular mechanisms is bypassed during pregnancy thanks to some physiological changes.     

The platelet aggregometer and beyond: Gustav Born at the Royal College of Surgeons

In 1960, Gustav Born was appointed to head the Department of Pharmacology at the Royal College of Surgeons in London. The next 13 years would prove to be the most productive in his scientific career and the most important in the development of the Department into an internationally respected research center. The advances in platelet biology were made possible by the evolution of the platelet aggregometer, brilliantly conceived and developed by Born and his team, into a robust and reliable scientific instrument, with which they, quite literally, revolutionized the study of platelet function. For the first time, the actions of agonists and antagonists could be quantified pharmacologically, and the biochemistry of aggregation analyzed, identifying two systems, cyclic nucleotides and phospholipid metabolism, as crucial to the understanding of the pathophysiology of human platelets. Recognizing the critical importance of the interplay between platelets, leucocytes and the vascular endothelium, in the formation and in the rupture of atheromatous plaques, his group also investigated aggregation in the microvasculature in vivo. Born’s never-ending flow of ideas and enthusiasm for their exploration created an atmosphere of discovery in his group that matched that of his colleague, John Vane. It was a collaboration between these two teams that elucidated the mechanism of action of the non-steroidal anti-inflammatory drugs (NSAIDs) and established the prophylactic use of aspirin as an anti-thrombotic therapy – indeed, two of the most significant pharmacological discoveries of the twentieth century.     

Does Bipolar Pacemaker Current Activate Blood Platelets?

Objective: The aim of this study was to investigate whether bipolar pacemaker current lead can activate blood platelets. The null hypothesis was that 1 minute of electrical stimulation of platelets would not influence their subsequent reactivity to adenosine diphosphate (ADP).
Background: Both platelets and muscle cells contain actin and myosin filaments, and both cells are activated following calcium influx. Muscle cells open their calcium channels and contract when exposed to an electric current. Current through a bipolar pacemaker lead will expose a small volume of blood, including platelets, to the depolarizing current. Platelet activation may ensue, resulting in aggregation, release reaction, and contraction. In contrast, a unipolar pacemaker system will not depolarize blood, but transmit current directly into the myocardium, and the current afterward passes through other tissues before returning to the pacemaker can.
Methods: Platelet-rich plasma was prepared from two healthy subjects. Platelet reactivity to the agonist ADP was tested in paired samples in an aggregometer in a case/control setup.
Results: Eighteen of 46 tested pairs of platelet-rich plasma showed increased reactivity in the paced sample; 26 were unchanged while two showed decreased reactivity in the paced sample. Using a two-sided sign test, the null hypothesis was rejected (P = 0.0004).
Conclusions: The study demonstrates increased reactivity to ADP in platelets exposed in vitro to stimulation by pacemaker current. The clinical relevance of these findings remains to be investigated.     

血小板低渗休克反应检测方法的建立及应用

目的通过建立合适的低渗休克反应(HSR)检测方法,监测单采血小板在保存期内的HSR变化,以监控和评估单采血小板在保存期内的功能和质量状况。方法利用血液凝集仪,分别检测血小板与等渗磷酸盐缓冲液混合后的透光率变化值和血小板与去离子水混合后的透光率变化值,从而计算出HSR值。检测20份新鲜采集的单采血小板及10份在保存期的第1,3,5和7 d的血小板HSR变化。结果新鲜采集的单采血小板HSR正常参考值范围为58%~93%(80.35%±10.39%,n=20);单采血小板在保存期的第1,3,5和7 d的HSR分别为:75.85%±11.10%,74.00%±9.04%,71.39%±6.16%和68.85%±7.89%;各天之间比较均无显著性差异(P>0.1)。结论利用血液凝集仪检测HSR是一种合适的方法,具有简便、准确和重复性好的特点;单采血小板保存至7 d仍具有较好的抗低渗休克的能力。     

电阻法测定血小板减少患者全血中血小板聚集功能

采用我校研制的全血血小板聚集仪,以电阻法检测正常人和血小板减少患者全血中血小板聚集功能。全血中血小板的数量与聚集电阻值的关系用指数曲线拟合。用曲线回归方程式推算不同血小板数值的正常电阻值,可正确、简便地判断血小板计数不一或血小板减少受检者的全血中血小板聚集功能,有临床实用价值。