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Platelets
Kinds of Platelets Terms modified by Platelets Selected AbstractsAGEING, OESTROGEN, PLATELETS AND THROMBOTIC RISKCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 8 2007Virginia M Miller SUMMARY 1Adverse thrombotic cardiovascular events increase in women coincident with the onset of menopause. 2Age past menopause may be an important variable in defining the benefit/risk of hormone treatments. 3Few studies have examined hormonal status as a variable of ageing using a polygenomic approach of both humoral and cellular components of the coagulation system. 4Longitudinal studies of a global set of platelet functions that define procoagulant activity (i.e. adhesion, aggregation, secretion and thrombin production) in individuals with documented hormonal status are needed to better understand how hormonal changes associated with ageing impact thrombotic risk. [source] Increased circulating platelet,leukocyte aggregates in myeloproliferative disorders is correlated to previous thrombosis, platelet activation and platelet countEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 3 2001Morten Krogh Jensen Abstract: Platelet,leukocyte adhesion may occur as a consequence of platelet activation and possibly plays a key role in the deposition of activated platelets and fibrin in the thrombotic plug. The aim of the present study was to assess by whole blood flow cytometry the presence of circulating platelet,leukocyte aggregates (PLA) and the platelet,leukocyte response to platelet agonist stimulation (ADP and TRAP) in 50 patients with chronic myeloproliferative disorders (MPD) and 30 controls. PLA were identified as platelet,granulocyte/monocyte aggregates (PGMA), platelet,monocyte aggregates (PMA) and defined as the percentage of leukocytes coexpressing the platelet-specific marker glycoprotein Ib. Compared to controls the mean percentage of PGMA and PMA was increased in unstimulated whole blood from patients with MPD (7.98 vs. 1.76%; p<0.001 and 12.34 vs. 3.2%; p<0.001, respectively). The percentage of PGMA was correlated to the platelet count (r=0.46; p<0.001), percentage of P-selectin (r=0.69; p<0.001) and thrombospondin (r=0.58; p<0.001) positive platelets and platelet expression of GPIV (r=0.33; p=0.02). The mean percentage of PGMA and PMA was significantly increased in ADP-stimulated whole blood of patients (57.14 vs. 47.92%; p=0.009 and 54.91 vs. 45.89%; p<0.001, respectively). Compared to patients without a history of thrombosis, patients having experienced microvascular disturbances or a thrombotic event had a higher mean percentage of PGMA and PMA in non-stimulated whole blood (10.07 vs. 6.34%; p=0.025 and 14.81 vs. 10.48%; p=0.021, respectively) and a higher percentage of PGMA in ADP stimulated whole blood (64.32 vs. 51.50%; p<0.01). These data document an increased frequency of PLA in non-stimulated whole blood in MPD associated with a previous history of thrombosis or microvascular disturbances. [source] Insights into biaxial extensional tectonics: an examplefrom the Sand,kl, Graben, West Anatolia, TurkeyGEOLOGICAL JOURNAL, Issue 1 2003Mustafa Cihan Abstract West Anatolia, together with the Aegean Sea and the easternmost part of Europe, is one of the best examples of continental extensional tectonics. It is a complex area bounded by the Aegean,Cyprus Arc to the south and the North Anatolian Fault Zone (NAFZ) to the north. Within this complex and enigmatic framework, the Sand,kl, Graben (10,km wide, 30,km long) has formed at the eastern continuation of the Western Anatolian extensional province at the north-northwestward edge of the Isparta Angle. Recent studies have suggested that the horst,graben structures in West Anatolia formed in two distinct extensional phases. According to this model the first phase of extension commenced in the Early,Middle Miocene and the last, which is accepted as the onset of neotectonic regime, in Early Pliocene. However, it is controversial whether two-phase extension was separated by a short period of erosion or compression during Late Miocene,Early Pliocene. Both field observations and kinematic analysis imply that the Sand,kl, Graben has existed since the Late Pliocene, with biaxial extension on its margins which does not necessarily indicate rotation of regional stress distribution in time. Although the graben formed later in the neotectonic period, the commencement of extension in the area could be Early Pliocene (c. 5,Ma) following a severe but short time of erosion at the end of Late Miocene. The onset of the extensional regime might be due to the initiation of westward motion of Anatolian Platelet along the NAFZ that could be triggered by the higher rate of subduction at the east Aegean,Cyprus Arc in the south of the Aegean Sea. Copyright © 2003 John Wiley & Sons, Ltd. [source] Platelet concentrates transfusion in cardiac surgery and platelet function assessment by multiple electrode aggregometryACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 2 2009N. RAHE-MEYER Background: Platelet dysfunction contributes to the pathophysiology of bleeding complications during and after cardiac surgery. In most surgical institutions, no peri-operative point-of-care monitoring of platelet function is used. We evaluated the usefulness of the Multiplate® platelet function analyser based on impedance aggregometry for identifying groups of patients at a high risk of transfusion of platelet concentrates (PC). Methods: Platelet function parameters were determined in 60 patients before and after routine cardiac surgery. Impedance aggregometry measurements were performed on Multiplate® using ADP (ADPtest), collagen (COLtest) and thrombin receptor activating peptide (TRAPtest) as platelet activators. The correlations between the aggregometry results and the transfusion of PC were calculated. The results of the aggregation tests were also divided into tertiles and the differences in PC transfusion between the low and the high tertile were assessed. Results: Low aggregometry delimited groups of patients with significantly higher PC transfusion. In the receiver operating characteristic curve, low pre-operative aggregation in the ADPtest identified patients with high total transfusion of PC (area under the curve 0.74, P=0.001), while the ADPtest performed at the end of the operation identified patients with high PC transfusion on the intensive care unit (ICU) (area under the curve 0.76, P=0.002). Conclusions: Near-patient platelet aggregation may allow the identification of patients with enhanced risk of PC transfusion, both pre-operatively and upon arrival on the ICU. [source] What is vinculin needed for in platelets?JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 10 2010J. V. MITSIOS Summary.,Background: Vinculin links integrins to the cell cytoskeleton by virtue of its binding to proteins such as talin and F-actin. It has been implicated in the transmission of mechanical forces from the extracellular matrix to the cytoskeleton of migrating cells. Vinculin's function in platelets is unknown. Objective: To determine whether vinculin is required for the functions of platelets and their major integrin, ,IIb,3. Methods: The murine vinculin gene (Vcl) was deleted in the megakaryocyte/platelet lineage by breeding Vcl fl/fl mice with Pf4,Cre mice. Platelet and integrin functions were studied in vivo and ex vivo. Results: Vinculin was undetectable in platelets from Vcl fl/fl Cre+ mice, as determined by immunoblotting and fluorescence microscopy. Vinculin-deficient megakaryocytes exhibited increased membrane tethers in response to mechanical pulling on ,IIb,3 with laser tweezers, suggesting that vinculin helps to maintain membrane cytoskeleton integrity. Surprisingly, vinculin-deficient platelets displayed normal agonist-induced fibrinogen binding to ,IIb,3, aggregation, spreading, actin polymerization/organization, clot retraction and the ability to form a procoagulant surface. Furthermore, vinculin-deficient platelets adhered to immobilized fibrinogen or collagen normally, under both static and flow conditions. Tail bleeding times were prolonged in 59% of vinculin-deficient mice. However, these mice exhibited no spontaneous bleeding and they formed occlusive platelet thrombi comparable to those in wild-type littermates in response to carotid artery injury with FeCl3. Conclusion: Despite promoting membrane cytoskeleton integrity when mechanical force is applied to ,IIb,3, vinculin is not required for the traditional functions of ,IIb,3 or the platelet actin cytoskeleton. [source] Platelet phagocytosis as a cause of pseudothrombocytopenia,AMERICAN JOURNAL OF HEMATOLOGY, Issue 6 2009Victoria Campbell No abstract is available for this article. [source] Clinical characteristics of children with snakebite poisioning and management of complications in the pediatric intensive care unitPEDIATRICS INTERNATIONAL, Issue 6 2005Gonca Ozay AbstractBackground:,Venomous snakebite is an emergency condition with high morbidity and mortality in childhood. Nearly all venomous snakes in Turkey are members of the Viperidae family and show poisonous local and hematotoxic effects. Methods:,A total of 77 children (mean age 9.9 ± 2.9 years; age range 3,14 years) with venomous snakebites were investigated. General characteristics of the children, species of the snakes, localization of the bite, clinical and laboratory findings, treatment approaches, complications and prognosis were evaluated. Results:,The male to female ratio was 1.4. Ninety-one per cent of cases were from rural areas. Most of the bites were seen in May and June. Mean duration between snakebites and admissions to our department was 13 ± 6.5 h. According to a clinical grading score, 57.1% of patients presented to us as grade II. Mean leukocyte count, aspartate aminotransferase, lactate dehydrogenase, creatinine phosphokinase and protrombin time levels were above the normal ranges and mean activated partial tromboplastin time was below the normal range. Platelet counts inversely correlated with the grading score and duration of hospitalization. The most common complication that occurred during the treatment was tissue necrosis (13%). The mean hospital stay time was 6.3 ± 6 days. Three children with disseminated intravascular coagulation died. Fasciotomies were performed to seven (9.1%) children due to compartment syndrome. Of 10 children with tissue necrosis, three (3.9%) had finger amputation and seven (9.1%) had toe amputation. Higher grading score on admission, platelet count below 120 000/mm3, AST over 50 IU/L and existence of evident ecchymosis were found as significant risk factors for development of serious complications by logistic regression analysis. Conclusions:,Snakebite poisoning is an emergency medical condition that is particularly important in childhood. The envenomations are still considerable public health problems with a high morbidity and mortality in rural areas of Turkey. [source] The effect of Eucommia ulmoides leaf supplementation on the growth performance, blood and meat quality parameters in growing and finishing pigsANIMAL SCIENCE JOURNAL, Issue 1 2009Sung Dae LEE ABSTRACT The aim of the present study was to investigate the effect of Eucommia ulmoides leaf (EUL) supplementation on the growth performance, blood and meat quality parameters in growing and finishing pigs. Ninety gilts (L × LW × D, 20 kg initialBW) were housed 10 per pen in a front-open building with three replicate pens per treatment. Experimental treatment was started from the beginning of the growing stage (20 ± 3 kg) by supplementing EUL at 0(C), 3(T1) and 5% (T2) to the growing and finishing diet. Pigs were slaughtered by electrical stunning at 105 ± 3 kg live weight. Average daily feed intake (ADFI, kg/day) decreased (P < 0.05) by addition of EUL in growth performance, average daily gain (ADG, kg/day) was lower (P < 0.05) in T1 and T2 than in C. In hematology, leukocytes (WBC, 103/mm3) decreased (P < 0.05) in T1 and T2 than in C. Erythrocytes (RBC, 106/mm3), hemoglobin (HGB, g/dL) and hematocrit (HCT, %) increased (P < 0.05) in T1 and T2 than in C. Platelet (PLT, 103/mm3) was lower (P < 0.05) in T2 than in C and T1. In biochemical composition of serum, total protein (g/dL), r-GTP (,/L), total cholesterol (mg/dL) and triglycerides (mg/dL) were lower (P < 0.05) in T1 and T2 than in C. On longissimus dorsi muscle, crude protein was higher (P < 0.05) in T1 than in C. Crude ash was higher (P < 0.05) in T1 and T2 than in C. Yellow to blue color scale (CIE b*) in meat color was higher (P < 0.05) in T2 than in C. CIE b* in back fat color was higher (P < 0.05) in T2 than in the other treatments. In sensory evaluation scores for fresh meat, the values of meat color, fat color, drip loss and marbling were not significantly affected by addition of EUL. In cooked meat, the values of chewiness and overall acceptability were higher (P < 0.05) in T1 and T2 than in C. The results indicate that the addition of EUL affected growth performance, blood parameters and meat quality parameters in growing and finishing pigs. [source] Activation of platelets in whole blood by recombinant factor VIIa by a thrombin-dependent mechanismBRITISH JOURNAL OF HAEMATOLOGY, Issue 4 2003Barry Wilbourn Summary. Using a diluted whole blood method of flow cytometric analysis, we have shown that platelets could be activated in vitro in the presence of high concentrations (100 nmol/l) of recombinant factor (F) VIIa (rFVIIa; NovoSeven®) and 2·5 mmol/l calcium chloride. This was demonstrated by a significant increase in the mean percentage of platelets expressing CD62P and their mean fluorescent intensity (MFI) after 30 min versus platelets incubated with calcium or rFVIIa alone or diluted blood alone. The presence of rFVIIa and calcium increased the exposure of the PAC-1 activation epitope of glycoprotein (Gp) IIb/IIIa. This effect was equally influenced by the presence of calcium alone but not by rFVIIa. The effect of rFVIIa was time and concentration dependent. Thrombin generation was also necessary, as the effect of rFVIIa was completely abrogated by the additional presence of hirudin. Furthermore, soy bean trypsin inhibitor (SBTI) but not corn trypsin inhibitor (CTI) abrogated CD62P exposure, suggesting that thrombin was derived via FX but not FXII activation. Exposure of CD62P demonstrated a significant lag phase, sometimes of the order of >,30 min, as well as large intersubject variation. Significant platelet activation was observed at a concentration as low as 25 nmol/l rFVIIa. Platelet,leucocyte aggregation was also increased in the presence of 25 nmol/l rFVIIa and calcium. No significant difference was observed between levels of CD62P in diluted whole blood and platelet-rich plasma adjusted to an identical platelet count after their exposure to rFVIIa and calcium for 30 min. [source] Effects of warm-up on exercise capacity, platelet activation and platelet,leucocyte aggregation in patients with claudication ,BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 1 2005S. Pasupathy Background: The effects of exercise and warm-up were investigated in patients with claudication. Methods: This case,control crossover study involved two treadmill exercise tests, one preceded by a warm-up. Exercise continued until maximal leg pain (patients with claudication) or exhaustion (controls). Blood was taken before, and 5 and 60 min after exercise for flow cytometric analysis of platelet activation and platelet,leucocyte aggregation. Results: Both cohorts (eight patients with claudication of median age 63 years and eight healthy controls of median age 63·5 years) demonstrated improvement in exercise capacity after warm-up (13·1 per cent, P = 0·012 and 15·6 per cent, P = 0·008 respectively). Platelet activation increased after exercise in patients with claudication (fibrinogen binding: 1·11 per cent before exercise versus 2·63 per cent after exercise, P = 0·008; P-selectin: 0·68 versus 1·11 per cent, P = 0·028). Neither agonist stimulation nor warm-up altered this trend. Platelet,leucocyte (PLA) and platelet,neutrophil (PNA) aggregation were similarly increased immediately after exercise in patients with claudication (PLA: 7·6 versus 13·0 per cent, P = 0·004; PNA: 6·8 versus 10·2 per cent, P = 0·012). These remained high 60 min after exercise only in patients with claudication, but recovered to baseline levels when preceded by warm-up. Warm-up significantly desensitized PNA after stimulation with 10 µmol/l adenosine 5,-diphosphate at all time points. Conclusion: Warm-up increased the exercise capacity of patients with claudication. Exercise induced a thromboinflammatory response, with PLA and PNA persistently increased after 60 min in patients with claudication, an effect diminished after warm-up. Copyright © 2004 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source] Comparison of three different preparations of platelet concentrates for growth factor enrichmentCLINICAL ORAL IMPLANTS RESEARCH, Issue 5 2002Thorsten R. Appel Abstract: The aim of the present study was to compare three different systems for preparing platelet concentrates: two commercially available bed-side techniques (Curasan system and PCCS) and a procedure used routinely in transfusion medicine. Platelet concentrates were prepared from venous blood of 12 healthy male volunteers using the three different systems. Platelet and leucocyte counts were performed and platelet derived growth factor and transforming growth factor beta were assayed by enzyme linked immunoassay. Handling was also considered. The three systems were able to collect 19.0 ± 16.6% (laboratory system), 41.9 ± 9.7% (Curasan system) and 49.6 ± 21.0% (PCCS) of the absolute number of platelets which were originally in the venous blood volume within the platelet concentrate. Due to the amount of plasma which is left in the platelet concentrate portion, the platelet concentration could be increased between 1.4 ± 1.3 times (laboratory system), 5.0 ± 2.3 times (PCCS) and 11.7 ± 2.4 times (Curasan system) compared to the venous blood. The amount of growth factors correlated with the number of platelets within the platelet concentrates. The two systems for intraoperative use are similar in their effects on the platelets. The absolute gain of platelets seems to be the highest with the PCCS; the highest concentration of platelets per µL is gained with the Curasan system. The laboratory system may offer an alternative if an intraoperative system is not available. [source] Growth of bismuth tri-iodide platelets by the physical vapor deposition methodCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2004A. Cuña Abstract The work reports the growth of single BI3 crystals with platelets habit. Platelets were grown by physical vapor deposition (PVD) in a high vacuum atmosphere and with argon, polymer or iodine as additives. Crystals grew in the zone of maximum temperature gradient, perpendicular to the ampoule wall. Crystals grown with argon as additive show a very shining surface, have hexagonal (0 0 l) faces, sizes up to 20 x 10 mm2 and thicknesses up to 100 ,m. They were characterized by optical microscopy and scanning electron microscopy (SEM). Dendritic-like structures were found to be their main surface defect. SEM indicates that they grow from the staking of hexagonal unities. Electrical properties of the crystals grown under different growth conditions were determined. Resistivities up to 2 x 1012 ,cm (the best reported value for monocrystals of this material) were obtained. X-ray response was measured by irradiation of the platelets with a 241Am source of 3.5 mR/h. A comparison of results according to the growth conditions was made. Properties of the crystals grown by this method are compared with the ones measured for others previously grown from the melt. Also, results for bismuth tri-iodide platelets are compared with the ones obtained for mercuric and lead iodide platelets. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Platelet hyperactivity in clinical depression and the beneficial effect of antidepressant drug treatment: how strong is the evidence?ACTA PSYCHIATRICA SCANDINAVICA, Issue 3 2004R. Von Känel Objective:, Platelet hyperactivity is thought to contribute to the increased coronary artery disease (CAD) risk in depression. This study reviewed the evidence for hyperactive platelets and for effects of antidepressant drug treatment on platelet ,stickiness' in clinical depression. Method:, By means of PubMed electronic library search, 34 studies in English were identified (1983,2003) and critically reviewed. Results:, In depression, flow cytometry studies allowing detection of subtle platelet activation states consistently found at least one platelet activation marker to be increased, while the bulk of platelet aggregation studies did not suggest increased platelet aggregability. Platelets seem to be more activated in depressed patients with CAD than in depressed individuals without CAD. The selective serotonin reuptake inhibitors normalized platelet hyperactivity in four studies. Conclusion:, Data on platelet activity in depression are inconclusive. To resolve this issue and its clinical implications, studies in larger sample sizes controlling for confounders of platelet functioning and prospectively designed are needed. [source] Electrically Conductive Thin Films Prepared from Layer-by-Layer Assembly of Graphite PlateletsADVANCED FUNCTIONAL MATERIALS, Issue 7 2009Mubarak Alazemi Abstract Layer-by-layer (LBL) assembly of carbon nanoparticles for low electrical contact resistance thin film applications is demonstrated. The nanoparticles consist of irregularly shaped graphite platelets, with acrylamide/,, -methacryl-oxyethyl-trimethyl-ammonium copolymer as the cationic binder. Nanoparticle zeta (,,) potential and thereby electrostatic interactions are varied by altering the pH of graphite suspension as well as that of the binder suspension. Film thickness as a function of zeta potential, immersion time, and the number of layers deposited is obtained using Monte Carlo simulation of the energy dispersive spectroscopy measurements. Multilayer film surface morphology is visualized via field-emission scanning electron microscopy and atomic-force microscopy. Thin film electrical properties are characterized using electrical contact resistance measurements. Graphite nanoparticles are found to self-assemble onto gold substrates through two distinct yet overlapping mechanisms. The first mechanism is characterized by logarithmic carbon uptake with respect to the number of deposition cycles and slow clustering of nanoparticles on the gold surface. The second mechanism results from more rapid LBL nanoparticle assembly and is characterized by linear weight uptake with respect to the number of deposition cycles and a constant bilayer thickness of 15 to 21,nm. Thin-film electrical contact resistance is found to be proportional to the thickness after equilibration of the bilayer structure. Measured values range from 1.6,m,,cm,2 at 173,nm to 3.5,m,,cm,2 at 276,nm. Coating volume resistivity is reduced when electrostatic interactions are enhanced during LBL assembly. [source] CXC chemokine ligand 4 (Cxcl4) is a platelet-derived mediator of experimental liver fibrosis,HEPATOLOGY, Issue 4 2010Mirko Moreno Zaldivar Liver fibrosis is a major cause of morbidity and mortality worldwide. Platelets are involved in liver damage, but the underlying molecular mechanisms remain elusive. Here, we investigate the platelet-derived chemokine (C-X-C motif) ligand 4 (CXCL4) as a molecular mediator of fibrotic liver damage. Serum concentrations and intrahepatic messenger RNA of CXCL4 were measured in patients with chronic liver diseases and mice after toxic liver injury. Platelet aggregation in early fibrosis was determined by electron microscopy in patients and by immunohistochemistry in mice. Cxcl4,/, and wild-type mice were subjected to two models of chronic liver injury (CCl4 and thioacetamide). The fibrotic phenotype was analyzed by histological, biochemical, and molecular analyses. Intrahepatic infiltration of immune cells was investigated by fluorescence-activated cell sorting, and stellate cells were stimulated with recombinant Cxcl4 in vitro. The results showed that patients with advanced hepatitis C virus,induced fibrosis or nonalcoholic steatohepatitis had increased serum levels and intrahepatic CXCL4 messenger RNA concentrations. Platelets were found directly adjacent to collagen fibrils. The CCl4 and thioacetamide treatment led to an increase of hepatic Cxcl4 levels, platelet activation, and aggregation in early fibrosis in mice. Accordingly, genetic deletion of Cxcl4 in mice significantly reduced histological and biochemical liver damage in vivo, which was accompanied by changes in the expression of fibrosis-related genes (Timp-1 [tissue inhibitor of matrix metalloproteinase 1], Mmp9 [matrix metalloproteinase 9], Tgf -, [transforming growth factor beta], IL10 [interleukin 10]). Functionally, Cxcl4,/, mice showed a strongly decreased infiltration of neutrophils (Ly6G) and CD8+ T cells into the liver. In vitro, recombinant murine Cxcl4 stimulated the proliferation, chemotaxis, and chemokine expression of hepatic stellate cells. Conclusion: The results underscore an important role of platelets in chronic liver damage and imply a new target for antifibrotic therapies. (HEPATOLOGY 2010.) [source] Behaviour of haematological parameters in athletes performing marathons and ultramarathons in altitude (,skyrunners')INTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY, Issue 6 2004G. BANFI Summary We observed athletes performing marathons and ultramarathons in altitude over several years to study the behaviour of haematological parameters in order to screen eventual paraphysiological or pathological conditions (sports anaemia). We collected samples from 124 athletes participating in seven races; 23 athletes were recruited in different races: 16 for four times, four for three times, and three for two times. The pre- and post-race values of erythrocytes, haemoglobin and packed cell volume did not show statistically significant differences in the studied athletes. The erythrocytes' indices (MCV, MCH, MCHC) and red cell distribution width (RDW) also were not significantly modified by the strenuous effort. The leukocytes were significantly increased because of immunological involvement during the endurance performance. Platelets and relative indices were not significantly modified. The stability of packed cell volume and haemoglobin in athletes performing training and races in altitude is strong evidence for the use of these parameters as an index of general health status and for illustrating possible abnormal increase because of exogenous stimulation of bone marrow. The preanalytical and analytical accuracy is crucial to assure clinical validity of the collected data: we strictly observed international recommendations in this field. [source] Comparison of different methods of bacterial detection in blood componentsISBT SCIENCE SERIES: THE INTERNATIONAL JOURNAL OF INTRACELLULAR TRANSPORT, Issue 1 2009M. Schmidt Background, Over the last two decades, the residual risk of acquiring a transfusion-transmitted viral infection has been reduced to less than 1 : 1 000 000 via improvements in different techniques (e.g. donor selection, leuco-depletion, introduction of 3rd or 4th generation enzyme-linked immunosorbent assays and mini-pool nucleic acid testing (MP-NAT). In contrast, the risk for transfusion-associated bacterial infections has remained fairly stable, and is estimated to be in a range between 1 : 2000 and 1 : 3000. Platelets are at an especially higher risk for bacterial contamination, because they are stored at room temperature, which provides good culture conditions for a broad range of bacterial strains. To improve bacterial safety of blood products, different detection systems have been developed that can be divided into culture systems like BacT/ALERT or Pall eBDS, rapid detection systems like NAT systems, immunoassays and systems based on the FACS technique. Culture systems are used for routine bacterial screening of platelets in many countries, whereas rapid detection systems so far are mainly used in experimental spiking studies. Nevertheless, pathogen-reduction systems are currently available for platelet concentrates and plasma, and are under investigation for erythrocytes. Methods, In this review, the functional principles of the different assays are described and discussed with regard to their analytical sensitivity, analytical specificity, diagnostic sensitivity, diagnostic specificity and clinical efficiency. The detection methods were clustered into three groups: (i) detection systems currently used for routine screening of blood products, (ii) experimental detection systems ready to use for routine screening of blood products, and (iii) new experimental detection systems that need to be investigated in additional spiking studies and clinical trials. Results, A recent International Society of Blood Transfusion international forum reported on bacterial detection methods in 12 countries. Eight countries have implemented BacT/ALERT into blood donor screening, whereas in three countries only quality controls were done by culture methods. In one country, shelf-life was reduced to 3 days, so no bacterial screening was implemented. Screening data with culture methods can be used to investigate the prevalence of bacterial contamination in platelets. Differing results between the countries could be explained by different test definitions and different test strategies. Nevertheless, false-negative results causing severe transfusion-related septic reactions have been reported all over the world due to a residual risk of sample errors. Rapid screening systems NAT and FACS assays have improved over the last few years and are now ready to be implemented in routine screening. Non-specific amplification in NAT can be prevented by pre-treatment with Sau3AI, filtration of NAT reagents, or reduction of the number of polymerase chain reaction cycles. FACS systems offer easy fully automated handling and a handling time of only 5 min, which could be an option for re-testing day-5 platelets. New screening approaches like immunoassays, detection of bacterial adenosine triphosphate, or detection of esterase activity need to be investigated in additional studies. Conclusion, Bacterial screening of blood products, especially platelets, can be done with a broad range of technologies. The ideal system should be able to detect one colony-forming unit per blood bag without a delay in the release process. Currently, we are far away from such an ideal screening system. Nevertheless, pathogen-inactivation systems are available, but a system for all blood components will not be expected in the next few years. Therefore, existing culture systems should be complemented by rapid systems like NAT or FACS especially for day-5 platelets. [source] HELICOBACTER INFECTION IN CHILDREN WITH APPENDICITIS AND LACTOSE INTOLERANCEJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 12 2000Eva J. Soelaeman Helicobacter pylori eradication has been debated. Most investigators do not recommended treating the infection except in severe case. We report a unique case: H. pylori infection with appendicitis and lactose intolerance. Case report: A 6 year old girl was brought to children and maternity Hospital Harapan Kita due to abdominal pain and vomiting. She had 6- month history of epigastric pain. In the past 2 days, she suffered from abdominal pain arround Mc. Burney area. On physical examination, she was in pain. Her weight was 19 Kg. Vital signs were normal. Findings in heart, lung and extremities were also normal. Abdomen: severe pain in the epigastric and Mc. burney area.Laboratory investigations showed hemoglobin 12 g/dl, leukocyte 12800/ul. Platelets 289000/ul. Bleeding and clotting time were normal. Abdominal ultrasonography revealed inflammation of appendix with 9-mm diameter. Stool examination was normal.Appendectomy was done at the same time with esofagogastroduodenoscopy (EGD). On EGD, we found moderete anthral gastritis. On histopathological examination, we found H. pylori at antral of the stomach. Breath hydrogen test was positive. After H. pylori eradication and milk avoidance, abdominal pain has never occurred. Conclusion: Abdominal: pain is not specific for H. pylori infection. The pain caused by many diseases including H. pylori infection. In our case, we can control abdominal pain by H. pylori eradication. [source] Substantial Reduction of Platelet Adhesion by Heparin-Coated StentsJOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 4 2001CHRISTOPH BICKEL M.D. Although optimized antiplatelet medication has improved the clinical outcome after coronary stenting, vessel occlusion and restenosis still remain a relevant clinical problem. Platelets play a key role in this process. Therefore, the authors compared the platelet adhesion on different stent surface modifications (electropolished without coating or coated with carbon, carbon and additional heparin, silicon carbide, or heparin alone) to investigate their role in reducing platelet adhesion. All stem and additional stainless steel plates were incubated in heparinized whole blood with radiolabeled platelets. Afrer washing the stents and plates four times, radioactivity caused by the adhesion of radiolabeled platelets was measured. The adhesion of radiolabeled platelets, compared to uncoated, electropolished stents, was reduced through silicon carbide coating to 58.6%, by carbon coating with additional heparin to 32.9%, and heparin coating alone to 7.7%. Stent coating with heparin is the most effective among the examined coatings in reducing platelet adhesion in vitro. [source] Allelic frequencies of HPA-1 to 5 human platelet antigens in patients infected with hepatitis C virusJOURNAL OF MEDICAL VIROLOGY, Issue 4 2009Camila Fernanda Verdichio-Moraes Abstract Studies have suggested that hepatitis C virus (HCV) may infect not only hepatocytes but may also be carried by platelets. Platelets express more than 20 polymorphic antigenic determinants on their surface, which are called human platelet antigens (HPA). To determine the allele frequency of the HPA-1 to -5 in patients infected with HCV, blood samples were collected from 257 blood donors for the control group and from 191 patients infected with HCV. DNA was isolated and amplified for genes HPA-1 to -4 using PCR Sequence Specific Primers (PCR-SSP) and HPA-5 using PCR-Restriction Fragment Length Polymorphism (PCR-RFLP). The allelic and genotypic frequency of HPA-5a in patients infected with HCV was found to be significantly lower (P,<,0.05) than in the controls, and HPA-5b from patients infected with HCV was significantly higher (P,<,0.05) than in controls. The increase in HPA-5b allelic frequency in HCV infection may indicate a possible association between HCV infection and HPAs. J. Med. Virol. 81:757,759, 2009 © 2009 Wiley-Liss, Inc. [source] Platelets are mitogenic for periosteum-derived cellsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2003Reinhard Gruber Abstract The early stages of bone regeneration are associated with a high mitogenic activity of periosteal cells. Here we addressed the question of whether platelets that accumulate within the developing haematoma can account for this tissue response. Addition of platelets, platelet-released supernatants, platelet membranes, and microparticles to bovine periosteum-derived cells resulted in an increase in 3H-thymidine incorporation; lipid extracts had no effect. Platelet-released supernatants retained their activity after incubation at 56°C, but not at 100°C. Gel chromatographic analysis revealed the highest mitogenic activity at approximately 35 kD. Of the factors released from activated platelets, basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) increased 3H-thymidine incorporation. The mitogenic activity of platelet-released supernatants was decreased by anti-PDGF, and anti-bFGF antibodies. Platelet-released supernatants increased the number of proliferating periosteum-derived cells as determined by the expression pattern of Ki67. Platelet-released supernatants also resulted in a stimulation of cell proliferation in periosteal explants. These results suggest that platelets have the potential to stimulate the mitogenic response of the periosteum during bone repair. © 2003 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Antiplatelet Effect of Marchantinquinone, Isolated from Reboulia hemisphaerica, in Rabbit Washed PlateletsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2000CHANG-HUI LIAO Platelet activation is involved in serious pathological situations, including atherosclerosis and restenosis. It is important to find efficient antiplatelet medicines to prevent fatal thrombous formation during the course of these diseases. Marchantinquinone, a natural compound isolated from Reboulia hemisphaerica, inhibited platelet aggregation and ATP release stimulated by thrombin (0.1 units mL,1), platelet-activating factor (PAF; 2 ng mL,1), collagen (10 ,g mL,1), arachidonic acid (100 ,m), or U46619 (1 ,m) in rabbit washed platelets. The IC50 values of marchantinquinone on the inhibition of platelet aggregation induced by these five agonists were 62.0 ± 9.0, 86.0 ± 7.8, 13.6 ± 4.7, 20.9 ± 3.1 and 13.4 ± 5.3 ,m, respectively. Marchantinquinone inhibited thromboxane B2 (TxB2) formation induced by thrombin, PAF or collagen. However, marchantinquinone did not inhibit TxB2 formation induced by arachidonic acid, indicating that marchantinquinone did not affect the activity of cyclooxygenase and thromboxane synthase. Marchantinquinone did inhibit the rising intracellular Ca2+ concentration stimulated by the five platelet-aggregation inducers. The formation of inositol monophosphate induced by thrombin was inhibited by marchantinquinone. Platelet cAMP and cGMP levels were unchanged by marchantinquinone. The results indicate that marchantinquinone exerts antiplatelet effects by inhibiting phosphoinositide turnover. [source] Hydrothermal Synthesis YbMnO3 and LuMnO3 PlateletsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2008Gangqiang Zhu Single-crystalline YbMnO3 and LuMnO3 platelets have been successfully synthesized via a simple hydrothermal process at 250°C for 24 h. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and selected area electron diffraction patterns were used to characterize the as-synthesized samples. The result reveals that both of the as-synthesized YbMnO3 and LuMnO3 are of hexagonal phase. The effect of treatment time on the phase of the final products has been studied, and a possible formation mechanism of YbMnO3 and LuMnO3 is proposed. [source] Structural Analysis on Planar Defects Formed in WC Platelets in Ti-Doped WC,CoJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2006Sabine Lay Platelet-reinforced WC,Co alloys are processed by liquid-phase sintering from very fine-grained WC powders in the presence of small amounts of TiC. Large and flat WC grains develop in the material. The microstructure of these platelets is investigated by high-resolution electron microscopy in order to obtain information on their formation mechanism. Inside the grains, an extended defect parallel to the basal plane is observed. It can be described by a pair of stacking faults with a shear vector equal to 1/3 ,0-110, occurring in two successive (0001) planes. At the level of the faults, the plane spacing is slightly reduced. The defect area is similar to a thin cubic layer about 0.5 nm thick at the interior of the platelet. The enhanced grain growth of the platelets is likely related to the presence of the defect area. [source] Differential phosphorylation of myosin light chain (Thr)18 and (Ser)19 and functional implications in plateletsJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 10 2010T. M. GETZ Summary. Background:, Myosin IIA is an essential platelet contractile protein that is regulated by phosphorylation of its regulatory light chain (MLC) on residues (Thr)18 and (Ser)19 via the myosin light chain kinase (MLCK). Objective:, The present study was carried out to elucidate the mechanisms regulating MLC (Ser)19 and (Thr)18 phosphorylation and the functional consequence of each phosphorylation event in platelets. Results:, Induction of 2MeSADP-induced shape change occurs within 5 s along with robust phosphorylation of MLC (Ser)19 with minimal phosphorylation of MLC (Thr)18. Selective activation of G12/13 produces both slow shape change and comparably slow MLC (Thr)18 and (Ser)19 phosphorylation. Stimulation with agonists that trigger ATP secretion caused rapid MLC (Ser)19 phosphorylation while MLC (Thr)18 phosphorylation was coincident with secretion. Platelets treated with p160ROCK inhibitor Y-27632 exhibited a partial inhibition in secretion and had a substantial inhibition in MLC (Thr)18 phosphorylation without effecting MLC (Ser)19 phosphorylation. These data suggest that phosphorylation of MLC (Ser)19 is downstream of Gq/Ca2+ -dependent mechanisms and sufficient for shape change, whereas MLC (Thr)18 phosphorylation is substantially downstream of G12/13 -regulated Rho kinase pathways and necessary, probably in concert with MLC (Ser)19 phosphorylation, for full contractile activity leading to dense granule secretion. Overall, we suggest that the amplitude of the platelet contractile response is differentially regulated by a least two different signaling pathways, which lead to different phosphorylation patterns of the myosin light chain, and this mechanism results in a graded response rather than a simple on/off switch. [source] Platelet hyperprocoagulant activity in Type 2 diabetes mellitus: attenuation by glycoprotein IIb/IIIa inhibitionJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2008M. RAZMARA Summary.,Background:,Platelets are hyperactive in Type 2 diabetes mellitus (T2DM), and antiplatelet treatment with glycoprotein (GP) IIb/IIIa inhibitors provides better thrombotic protection in DM than in non-diabetic subjects. Objective:,We hypothesized that diabetic platelets are hyperprocoagulant, and that this hyperactivity can be inhibited by GPIIb/IIIa blockade. Methods:,Patients with T2DM and gender/age/body mass index-matched non-diabetic controls were recruited (n = 12 for both) to study the effect of GPIIb/IIIa blockade on platelet procoagulant activity. Platelet phosphotidylserine (PS), factor (F) Va expression, and platelet-derived microparticle (PDMP) generation were measured by whole blood flow cytometry. Platelet-dependent thrombin generation and plasma clotting time were monitored in recalcified platelet-rich plasma. Results:,Compared to controls, basal platelet activation was similar, while thrombin receptor activating peptide stimulated activation was enhanced in patients with T2DM. Diabetic platelets also displayed more profound elevations of platelet PS exposure, FVa binding, and PDMP generation upon stimulation. These alterations resulted in a hyperprocoagulant state, as evidenced by a marked increase in the platelet procoagulant index, enhanced thrombin generation, and a shortened plasma clotting time. GPIIb/IIIa blockade by c7E3 or SR121566 decreased platelet PS exposure and FVa binding, and diminished platelet procoagulant activity in patients with T2DM. Conclusions:,Platelets have increased procoagulant activity in patients with T2DM. The hyperprocoagulant activity is counteracted by GPIIb/IIIa blockade. [source] Protease-activated receptor-induced Akt activation , regulation and possible functionJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2007J. C. RESÉNDIZ Summary.,Background:,Thrombin induces the activation of the platelet serine/threonine kinase Akt. Akt activation is dependent on its phosphorylation at Thr308 and Ser473. The mechanism by which thrombin induces Akt phosphorylation is controversial, as is the role of Akt in platelet function. Objectives:,To investigate how protease-activated receptors (PARs) stimulate Akt and the role that Akt plays in human platelet function. Methods:,Platelets were stimulated through PAR1 or PAR4. Specific inhibitors were used to evaluate, by Western blotting, signaling pathways regulating Akt phosphorylation, and the role of activated Akt was evaluated by aggregometry and flow cytometry. Results:,Phospholipase C (PLC) controls Akt phosphorylation elicited by PARs. Stimulation of PAR1 or PAR4 resulted in rapid Akt phosphorylation, independently of secreted ADP and phosphatidylinositol-3-kinase (PI3K) activation. Akt phosphorylation ,60 s after PAR1 stimulation became entirely dependent on the purinergic receptor P2Y12 and the activation of PI3K. In contrast, PAR4 partially sustained Akt phosphorylation independently of P2Y12 and PI3K for up to 300 s. Pharmacologic inhibition of Akt reduced P-selectin expression and fibrinogen binding in platelets stimulated through PAR1, and delayed platelet aggregation in response to submaximal PAR1 or PAR4 stimulation, although aggregation at 300 s was unaffected. Conclusions:,Platelet PAR stimulation causes rapid Akt phosphorylation downstream of PLC, whereas with continuous stimulation, ADP and PI3K are required for maintaining Akt phosphorylation. Activated Akt regulates platelet function by modulating secretion and ,IIb,3 activation. [source] Platelet activation, myocardial ischemic events and postoperative non-response to aspirin in patients undergoing major vascular surgeryJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 10 2007S. RAJAGOPALAN Summary.,Objectives:,Myocardial ischemia is the leading cause of postoperative mortality and morbidity in patients undergoing major vascular surgery. Platelets have been implicated in the pathogenesis of acute thrombotic events. We hypothesized that platelet activity is increased following major vascular surgery and that this may predispose patients to myocardial ischemia.Methods:,Platelet function in 136 patients undergoing elective surgery for subcritical limb ischemia or infrarenal abdominal aortic aneurysm repair was assessed by P-selectin expression and fibrinogen binding with and without adenosine diphosphate (ADP) stimulation, and aggregation mediated by thrombin receptor-activating peptide and arachidonic acid (AA). Cardiac troponin-I (cTnI) was performed.Results:,P-selectin expression increased from days 1 to 3 after surgery [median increase from baseline on day 3: 53% (range: ,28% to 212%, P < 0.01) for unstimulated and 12% (range: ,9% to 45%, P < 0.01) for stimulated]. Fibrinogen binding increased in the immediate postoperative period [median increase from baseline: 34% (range: ,46% to 155%, P < 0.05)] and decreased on postoperative day 3 (P < 0.05). ADP-stimulated fibrinogen binding increased on day1 (P < 0.05) and thereafter decreased. Platelet aggregation increased on days 1,5 (P < 0.05). Twenty-eight (21%) patients had a postoperative elevation (> 0.1 ng mL,1) of cTnI. They had significantly increased AA-stimulated platelet aggregation in the immediate postoperative period and on day 2 (P < 0.05), and non-response to aspirin (48% vs. 26%, P = 0.036).Conclusions:,This study has shown increased platelet activity and the existence of non-response to aspirin following major vascular surgery. Patients with elevated postoperative cTnI had significantly increased AA-mediated platelet aggregation and a higher incidence of non-response to aspirin compared with patients who did not. [source] Platelet adhesion to dimeric ,2 -glycoprotein I under conditions of flow is mediated by at least two receptors: glycoprotein Ib, and apolipoprotein E receptor 2,JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 2 2007M. T. T. PENNINGS Summary.,Background: The major antigen implicated in the antiphospholipid syndrome is beta2-glycoprotein I (,2GPI). Dimerized ,2GPI binds to apolipoprotein E receptor 2, (apoER2,) on platelets and increases platelet adhesion to collagen under conditions of flow. Aim: To investigate whether the interaction between dimerized ,2GPI and platelets is sufficiently strong to resist shear stresses. Methods: We studied the interaction of platelets with immobilized dimerized ,2GPI under conditions of flow, and further analyzed the interaction using surface plasmon resonance and solid phase immunoassays. Results: We found that dimerized ,2GPI supports platelet adhesion and aggregate formation under venous flow conditions. Adhesion of platelets to dimerized ,2GPI was completely inhibited by the addition of soluble forms of both apoER2, and GPIb,, and the addition of receptor-associated protein and the removal of GPIb, from the platelet surface. GPIb, co-precipitated with apoER2,, suggesting the presence of complexes between GPIb, and apoER2, on platelet membranes. The interaction between GPIb, and dimeric ,2GPI was of intermediate affinity (Kd = 180 nm) and Zn2+, but not Ca2+ -dependent. Deletion of domain V from dimeric ,2GPI strongly reduced its binding to both GPIb, and apoER2,. Antibodies that inhibit the binding of thrombin to GPIb, inhibited platelet adhesion to dimeric ,2GPI completely, while antibodies blocking the binding of von Willebrand factor to GPIb, had no effect. Dimeric ,2GPI showed reduced binding to low-sulfated GPIb, compared to the fully sulfated form. Conclusion: We show that platelets adhere to dimeric ,2GPI under both arterial and venous shear stresses. Platelets adhere via two receptors: GPIb, and apoER2,. These receptors are present in a complex on the platelet surface. [source] Insulin resistance is a major determinant of liver stiffness in nondiabetic patients with HCV genotype 1 chronic hepatitisALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 6 2009S. PETTA Summary Background, In patients with chronic hepatitis C (CHC), liver stiffness measurement (LSM) by transient elastography (TE), is closely related to the stage of fibrosis, but may be affected by necroinflammation. Other factors, such as insulin resistance (IR), might influence the performance of LSM. Aims, To evaluate in a cohort of nondiabetic patients with genotype 1 CHC, whether IR and other anthropometric, biochemical, metabolic and histological factors contribute to LSM and to identify the best cut-off values of LSM for predicting different stages of fibrosis. Methods, Nondiabetic patients with genotype 1 CHC (n = 156) were evaluated by liver biopsy (Metavir score), anthropometric, biochemical and metabolic features including IR. Furthermore, all subjects underwent LSM by TE. Results, Severe fibrosis (F3,F4) was associated with LSM (OR 1.291; 95%CI 1.106,1.508). LSM was also independently correlated with low platelets (P = 0.03), high ,GT (P < 0.001) and high HOMA (P = 0.004) levels. A stiffness value ,8 KPa was identified as the best cut-off for predicting severe fibrosis (AUC 0.870); yet this cut-off still failed to rule out F3,F4 fibrosis in 22.7% of patients (false-negative rate) or rule in F3,F4 in 19.6% (false-positive rate). Platelets <200 × 103/mmc and a HOMA of >2.7 were the major determinants of these diagnostic errors in predicting severe fibrosis. Conclusions, In nondiabetic patients with genotype 1 CHC, insulin resistance, ,GT and platelet levels contribute to LSM independently of liver fibrosis. The identification of these three factors contributes to a more correct interpretation of LSM. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||