Ex vivo microvesicle formation after prolonged ischemia in renal transplantation

INTRODUCTION: Patients with chronic renal failure suffer from dysfunction in coagulation. Kidney transplantation induces inflammatory reactions and thus activation of platelets. Activated platelets, in turn, form microvesicles by shedding. These microvesicles have been shown to have coagulant activities. Activated platelets in prolonged cold ischemia were associated with delayed graft function and inferior survival. We investigated ex vivo formation of microvesicles in kidney transplantation and the influence of cold graft storage on microvesicles. METHODS: 20 patients (47.4+/-10.6 years (mean+/-SD)) undergoing transplantation were included in the study after written informed consent. Dependent on cold preservation time of transplanted kidneys, recipients were allocated into two groups with 10.4+/-6.1 h (group 1) and 23.7+/-3.8 h (group 2) preservation time, respectively. Blood samples were drawn before anesthesia, 12 h, 2, 7 and 14 days after transplantation. To evaluate microvesicle release, samples were activated with thrombin-receptor-activating-peptide-6 (TRAP) or adenosine-di-phosphate. Microvesicles were counted as percentage of platelets smaller than a predetermined size in flow cytometry. RESULTS: Platelet derived ex vivo microvesicle formation was significantly higher up to 48 h after transplantation when stimulated with TRAP in group 1. Platelet count was significantly higher compared to baseline values in the short-term ischemia group but not with long-term ischemia. Creatinine was significantly lower at study end compared to baseline with no differences between both groups. CONCLUSIONS: Lower platelet microvesicle formation after ex vivo stimulation with TRAP was associated with longer graft ischemia time. This may be a sign of former activation of platelets which could influence graft function and survival.     

Factors associated with incomplete colonoscopy: a population-based study

BACKGROUND & AIMS: The U.S. Multi-Society Task Force on Colorectal Cancer sets a target of cecal intubation in at least 90% of colonoscopies. We conducted a population-based study to determine the colonoscopy completion rate and to identify factors associated with incomplete procedures. METHODS: Men and women 50 to 74 years of age who underwent a colonoscopy in Ontario between January 1, 1999, and December 31, 2003, were identified. The first (index) colonoscopy was classified as complete or incomplete. A generalized estimating equations model was used to evaluate the association between patient, endoscopist (specialty, colonoscopy volume), and setting (academic hospital, community hospital, private office) factors and incomplete colonoscopy. RESULTS: A total of 331,608 individuals had an index colonoscopy, of which 43,483 (13.1%) were incomplete. Patients with an incomplete colonoscopy were older (odds ratio [OR] 1.20 per 10-year increment; 95% confidence interval [CI]=1.18-1.22), more likely to be female (OR 1.35; 95% CI: 1.30-1.39), have a history of prior abdominal surgery (OR 1.07; 95% CI: 1.05-1.09) or prior pelvic surgery (OR 1.04; 95% CI: 1.01-1.06). For colonoscopies done in a private office, the odds of an incomplete procedure were more than 3-fold greater than for procedures done in an academic hospital (OR 3.57; 95% CI: 2.55-4.98). CONCLUSIONS: In usual clinical practice in Ontario, 13.1% of colonoscopies are incomplete. The factors most strongly associated with incomplete colonoscopy were increased patient age, female sex, and having the procedure in a private office. Quality improvement programs are needed to improve colonoscopy completion rates.     

Variability in individual responsiveness to clopidogrel: clinical implications, management, and future perspectives

Antiplatelet therapy is the cornerstone of treatment for patients with acute coronary syndromes and/or undergoing percutaneous coronary interventions. Clopidogrel, in combination with aspirin, is currently the antiplatelet treatment of choice for prevention of stent thrombosis, and clinical trials have shown that, in high-risk patients, prolonged dual antiplatelet treatment is more effective than aspirin alone in preventing major cardiovascular events. However, despite the use of clopidogrel, a considerable number of patients continue to have cardiovascular events. Numerous in vitro studies have shown that individual responsiveness to clopidogrel is not uniform in all patients and is subject to inter- and intraindividual variability. Notably, there is a growing degree of evidence that recurrence of ischemic complications may be attributed to poor response to clopidogrel. The mechanisms leading to poor clopidogrel effects are not fully elucidated and are likely multifactorial. Although the gold standard definition to assess antiplatelet drug response has not been fully established, there is sufficient evidence to support that persistence of enhanced platelet reactivity despite the use of clopidogrel is a clinically relevant entity. This paper reviews the impact of individual response variability to clopidogrel on clinical outcomes and current and future directions for its management.     

血小板特异性抗体及HLA抗体引起血小板输注无效的研究

目的分析血小板输注无效（PTR）患者血小板同种抗体,并对其HPA及HLA-Ⅰ类抗原进行基因分型,探讨血小板输注无效与血小板同种抗原／HLA—Ⅰ类抗原相关性。方法应用ELISA方法对17例血小板输注无效患者血清中的血小板抗体进行检测;运用PCR—SSP方法,采用HPA分型试剂盒检测血小板同种抗原7个抗原系统HPA-1、2、3、4、5、6、15,以及HLA分型试剂盒对HLA—A／B抗原进行基因分型。结果6名患者单独表达HLA抗体,4名患者表达血小板特异性糖蛋白抗体,3例HLA抗体和血小板特异性糖蛋白抗体共同表达．其中以GPⅡb／Ⅲa为主。对17例患者HPA系统和HLA-Ⅰ类抗原基因分型,发现HPA-3系统中a的基因频率高达0．676,b为0．324;HLA—A＊02、HLA—A＊24、HLA—A＊11和HLA—B＊60、HLA—B＊13、HLA—B＊46多见。结论HLA抗体和血小板特异性糖蛋白抗体表达引起血小板输注无效,了解胛R与HPA／HLA—Ⅰ类抗原的相关性对指导临床血小板配合性输注具有重要意义。     

儿童遗传性出凝血紊乱VWF FV GP1Bα基因研究

目的:了解广西地区不明原因出血及ITP疗效不好的患儿血管性血友病因子(von Willebrang factor,VWF)28外显子、五因子(Factor V,FV)10外显子、血小板膜糖蛋白Ⅰba(platelet glycoprotein Ib alpha,GP Ⅰ ba)基因变异情况.方法:对所收集的31例病人进...     

社区医生糖尿病防治“专题知识深入”教育方案的效果评价

目的通过“专题知识深入”优化教育方法研究,探讨对社区全科医生糖尿病管理知识与技能全面提高的影响。方法采用常规知识优化法和专题知识优化法教育管理形式对社区全科医生进行系统的糖尿病防治知识与技能教育。结果全科医生接受糖尿病知识教育程度越深,其掌握综合防治知识越全面,防治技术赵娴熟。知识优化教育成绩结果显示：常规优化法＋专题优化法教育组优于常规优化教育组（P〈0.05）、优于常规教育组（P〈0.05）。结论上海市糖尿病防治工作已下沉到社区卫生服务中心,对全科医生实施糖尿病综合防治教育管理方法研究是必要的,这对提高社区糖尿病防治效果具有积极作用。     

Transdermal 17-beta estradiol replacement therapy reduces megakaryocyte GPVI expression

The platelet-collagen interaction is a critical early event in arterial thrombus formation, and platelet GPVI is the major activating receptor for collagen. We have previously used a mouse model to demonstrate that the estrogen effects on platelets depend upon the agonist, estrogen formulation and route of administration. In the current study we used a model of transdermal estradiol (E2) administration to ovariectomized mice to address the potential inhibitory effects of E2 on platelet GPVI. Platelet GPVI expression was reduced after transdermal E2 replacement therapy (p ≤ 0.001) but no evidence of GPVI shedding was found when platelets were directly incubated with E2. In addition, significantly reduced GPVI-mediated fibrinogen binding and aggregation were observed in platelets from mice subjected to 9 days or longer of in vivo E2 treatment, but not in platelets from mice treated for 3 days or shorter, suggesting an indirect pathway. Studies with mouse bone marrow revealed that E2 replacement in ovariectomized mice reduces megakaryocyte GPVI expression. This data suggest that transdermal E2 is able to affect centrally on megakaryocyte GPVI to regulate platelet GPVI and function.     

Gypenoside XLIX, a naturally occurring gynosaponin, PPAR-alpha dependently inhibits LPS-induced tissue factor expression and activity in human THP-1 monocytic cells

Tissue factor (TF) is involved not only in the progression of atherosclerosis and other cardiovascular diseases, but is also associated with tumor growth, metastasis, and angiogenesis and hence may be an attractive target for directed cancer therapeutics. Gynostemma pentaphyllum (GP) is widely used in the treatment of various cardiovascular diseases including atherosclerosis, as well as cancers. Gypenoside (Gyp) XLIX, a dammarane-type glycoside, is one of the prominent components in GP. We have recently reported Gyp XLIX to be a potent peroxisome proliferator-activated receptor (PPAR)-alpha activator. Here we demonstrate that Gyp XLIX (0-300 microM) concentration dependently inhibited TF promoter activity after induction by the inflammatory stimulus lipopolysaccharide (LPS) in human monocytic THP-1 cells transfected with promoter reporter constructs pTF-LUC. Furthermore, Gyp XLIX inhibited LPS-induced TF mRNA and protein overexpression in THP-1 monocyte cells. Its inhibition of LPS-induced TF hyperactivity was further confirmed by chromogenic enzyme activity assay. The activities of Gyp XLIX reported in this study were similar to those of Wy-14643, a potent synthetic PPAR-alpha activator. Furthermore, the Gyp XLIX-induced inhibitory effect on TF luciferase activity was completely abolished in the presence of the PPAR-alpha selective antagonist MK-886. The present findings suggest that Gyp XLIX inhibits LPS-induced TF overexpression and enhancement of its activity in human THP-1 monocytic cells via PPAR-alpha-dependent pathways. The data provide new insights into the basis of the use of the traditional Chinese herbal medicine G. pentaphyllum for the treatment of cardiovascular and inflammatory diseases, as well as cancers.     

Synthesis and pharmacological evaluation of novel beta-nitrostyrene derivatives as tyrosine kinase inhibitors with potent antiplatelet activity

Protein tyrosine kinases have been known to be involved in regulation of platelet aggregation, suggesting a potential target for antiplatelet therapy. Our previous study showed that 3,4-methylenedioxy-beta-nitrostyrene (MNS) prevented platelet aggregation caused by various stimulators, and this action was accompanied by inhibition of tyrosine kinases. In the present study, in order to examine the structural determinants required for the actions of MNS and to develop more potent tyrosine kinase inhibitors and antiplatelet agents, a new series of beta-nitrostyrene derivatives were synthesized and pharmacologically characterized. The beta-nitrostyrene derivatives inhibited thrombin- or collagen-induced human platelet aggregation, ATP secretion, GPIIb/IIIa activation and protein tyrosine phosphorylation. In recombinant enzyme assay, some beta-nitrostyrene derivatives also demonstrated potent inhibition of Src and/or Syk kinase activity. Furthermore, there was a good correlation between the inhibitory potency of these compounds on tyrosine kinases and on platelet activation/aggregation. Among them, a benzoyl ester derivative (compound 10) possess up to 8-fold greater potency than MNS and over two orders of magnitude greater potency than genistein or tyrphostin A47 in inhibiting platelet responses to thrombin. Our data suggest that beta-nitrostyrenes may represent a new class of tyrosine kinase inhibitors with potent antiplatelet activity.