Relevant bibliographies by topics / Platelet activation

Academic literature on the topic 'Platelet activation'

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Published: 4 June 2021
Last updated: 20 February 2023

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Journal articles on the topic "Platelet activation"

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Zhou, W., M. A. Javors, and M. S. Olson. "Platelet-activating factor as an intercellular signal in neutrophil-dependent platelet activation." Journal of Immunology 149, no. 5 (September 1, 1992): 1763–69. http://dx.doi.org/10.4049/jimmunol.149.5.1763.

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Abstract The role of platelet-activating factor (PAF) in heterotypic cell to cell interactions in a rabbit neutrophil-platelet mixture model was investigated. Platelets were exposed to each of three chemotactic agonists: PAF, leukotriene B4 (LTB4), or FMLP. Only PAF stimulated aggregation, [3H]serotonin secretion, and cytosolic Ca2+ mobilization in platelets alone. However, platelets were stimulated by LTB4 and FMLP in the presence of neutrophils. This neutrophil-dependent platelet activation was blocked by pretreatment of platelets with PAF receptor antagonists, and was prevented by desensitization of platelets to PAF. Furthermore, the time-course of platelet activation showed a positive correlation with PAF production by neutrophils stimulated with either LTB4 or FMLP. The PAF-mediated neutrophil-platelet interaction was dependent on direct cell to cell contact, as demonstrated by experiments in which the majority of newly formed PAF was neutrophil associated (rather than released). Platelet activation did not occur when the neutrophil-platelet mixture was not stirred, minimizing cell to cell contact, or when platelets were challenged with a cell-free supernatant prepared from neutrophils activated with LTB4 or FMLP. Finally, the neutrophil-platelet interaction was abolished by SC-49992, a peptidomimetic of the fibrinogen binding sequence Arg-Gly-Asp-Phe, indicating a Arg-Gly-Asp-specific recognition mechanism. Our results demonstrate that neutrophil-generated PAF plays a crucial role in neutrophil-dependent platelet activation in this model system. This type of intercellular signaling event may be important in certain inflammatory or thrombotic processes.
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Horsewood, P., CP Hayward, TE Warkentin, and JG Kelton. "Investigation of the mechanisms of monoclonal antibody-induced platelet activation." Blood 78, no. 4 (August 15, 1991): 1019–26. http://dx.doi.org/10.1182/blood.v78.4.1019.1019.

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Abstract Antiplatelet antibodies can activate platelets causing platelet aggregation and the release reaction. However, the pathway of activation by these antibodies is unknown and several potential mechanisms are possible. In this report, we describe studies investigating potential pathways of platelet activation by IgG antibodies. We tested 16 different IgG monoclonal antibodies (MoAbs) against a variety of platelet surface components and found that six antibodies were capable of causing platelet aggregation and release. These included MoAbs against glycoprotein (GP) IIb/IIIa, CD9, GPIV, and two other not well-characterized platelet components. There was no relationship between the number of platelet binding sites and the ability of an MoAb to activate the platelets. By adding intact and F(ab')2 preparations of the MoAb to control or Fc receptor-blocked platelets, we found that in all instances the MoAbs initiated platelet activation via interacting with the platelet Fc receptors. Clustering of the platelet protein components using a secondary antibody did not cause activation. Studies into the pathway of Fc-dependent activation demonstrated that the MoAbs were capable of activating platelets by occupying Fc receptors on adjacent platelets (interplatelet activation), as well as on the same platelet (intraplatelet activation).
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Horsewood, P., CP Hayward, TE Warkentin, and JG Kelton. "Investigation of the mechanisms of monoclonal antibody-induced platelet activation." Blood 78, no. 4 (August 15, 1991): 1019–26. http://dx.doi.org/10.1182/blood.v78.4.1019.bloodjournal7841019.

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Antiplatelet antibodies can activate platelets causing platelet aggregation and the release reaction. However, the pathway of activation by these antibodies is unknown and several potential mechanisms are possible. In this report, we describe studies investigating potential pathways of platelet activation by IgG antibodies. We tested 16 different IgG monoclonal antibodies (MoAbs) against a variety of platelet surface components and found that six antibodies were capable of causing platelet aggregation and release. These included MoAbs against glycoprotein (GP) IIb/IIIa, CD9, GPIV, and two other not well-characterized platelet components. There was no relationship between the number of platelet binding sites and the ability of an MoAb to activate the platelets. By adding intact and F(ab')2 preparations of the MoAb to control or Fc receptor-blocked platelets, we found that in all instances the MoAbs initiated platelet activation via interacting with the platelet Fc receptors. Clustering of the platelet protein components using a secondary antibody did not cause activation. Studies into the pathway of Fc-dependent activation demonstrated that the MoAbs were capable of activating platelets by occupying Fc receptors on adjacent platelets (interplatelet activation), as well as on the same platelet (intraplatelet activation).
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O'Sullivan, Brian P., Matthew D. Linden, Andrew L. Frelinger, Marc R. Barnard, Michele Spencer-Manzon, James E. Morris, Raneem O. Salem, Michael Laposata, and Alan D. Michelson. "Platelet activation in cystic fibrosis." Blood 105, no. 12 (June 15, 2005): 4635–41. http://dx.doi.org/10.1182/blood-2004-06-2098.

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Abstract Cystic fibrosis (CF) is caused by a mutation of the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). We examined platelet function in CF patients because lung inflammation is part of this disease and platelets contribute to inflammation. CF patients had increased circulating leukocyte-platelet aggregates and increased platelet responsiveness to agonists compared with healthy controls. CF plasma caused activation of normal and CF platelets; however, activation was greater in CF platelets. Furthermore, washed CF platelets also showed increased reactivity to agonists. CF platelet hyperreactivity was incompletely inhibited by prostaglandin E1 (PGE1). As demonstrated by Western blotting and reverse-transcriptase-polymerase chain reaction (RT-PCR), there was neither CFTR nor CFTR-specific mRNA in normal platelets. There were abnormalities in the fatty acid composition of membrane fractions of CF platelets. In summary, CF patients have an increase in circulating activated platelets and platelet reactivity, as determined by monocyte-platelet aggregation, neutrophil-platelet aggregation, and platelet surface P-selectin. This increased platelet activation in CF is the result of both a plasma factor(s) and an intrinsic platelet mechanism via cyclic adenosine monophosphate (cAMP)/adenylate cyclase, but not via platelet CFTR. Our findings may account, at least in part, for the beneficial effects of ibuprofen in CF. (Blood. 2005;105:4635-4641)
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Speijer, Han, José W. P. Govers-Riemslag, Robert F. A. Zwaal, and Jan Rosing. "Platelet Procoagulant Properties Studied with Snake Venom Prothrombin Activators." Thrombosis and Haemostasis 57, no. 03 (1987): 349–55. http://dx.doi.org/10.1055/s-0038-1651132.

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SummaryPurified snake venom prothrombin activators were used to probe the procoagulant properties of platelet membranes. Human platelets were able to stimulate prothrombin activation by the venom activators from Oxyuranus scutellatus and Notechis scutatus, while the prothrombin activator from Echis carinatus was not affected by the presence of platelets. The prothrombinconverting activity of platelets was further studied with the venom activator from Oxyuranus scutellatus and with the factor Xa-Va complex as prothrombin activating enzymes. Stimulation of platelets with collagen, collagen plus thrombin or with the Ca-ionophore A23187 resulted in a considerable increase of platelet prothrombin converting activity probed with the factor Xa-Va complex as well as with the prothrombin activator from Oxyuranus scutellatus. The stimulatory effect of activated platelets on the rates of prothrombin activation by Oxyuranus scutellatus was similar to that determined for factor Xa-Va-catalyzed prothrombin activation. Compared to non-stimulated platelets, platelets stimulated with thrombin plus collagen exposed 20-times more procoagulant sites for as well the factor Xa-Va complex, as for the venom activator from Oxyuranus scutellatus. The actual number of procoagulant sites per platelet determined with the factor Xa-Va complex was in close agreement with the number of sites determined with the venom activator. Also the time course of appearance of procoagulant activity during platelet stimulation by collagen plus thrombin was comparable for both activator complexes. Phospholipase A2 treatment of stimulated platelets resulted in an almost complete loss of their ability to stimulate prothrombin activation by the enzyme from Oxyuranus scutellatus or by factor Xa-Va complex. The findings presented in this paper suggest: a) that the factor Xa-Va complex and the prothrombin activator from Oxyuranus scutellatus recognize the same procoagulant sites on both stimulated and unstimulated platelets and b) that negatively-charged phospholipids are essential components of these procoagulant sites.
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Quirino-Teixeira, Anna Cecíllia, Stephane Vicente Rozini, Giselle Barbosa-Lima, Diego Rodrigues Coelho, Pedro Henrique Carneiro, Ronaldo Mohana-Borges, Patrícia T. Bozza, and Eugenio D. Hottz. "Inflammatory signaling in dengue-infected platelets requires translation and secretion of nonstructural protein 1." Blood Advances 4, no. 9 (May 11, 2020): 2018–31. http://dx.doi.org/10.1182/bloodadvances.2019001169.

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Abstract Emerging evidence identifies major contributions of platelets to inflammatory amplification in dengue, but the mechanisms of infection-driven platelet activation are not completely understood. Dengue virus nonstructural protein-1 (DENV NS1) is a viral protein secreted by infected cells with recognized roles in dengue pathogenesis, but it remains unknown whether NS1 contributes to the inflammatory phenotype of infected platelets. This study shows that recombinant DENV NS1 activated platelets toward an inflammatory phenotype that partially reproduced DENV infection. NS1 stimulation induced translocation of α-granules and release of stored factors, but not of newly synthesized interleukin-1β (IL-1β). Even though both NS1 and DENV were able to induce pro-IL-1β synthesis, only DENV infection triggered caspase-1 activation and IL-1β release by platelets. A more complete thromboinflammatory phenotype was achieved by synergistic activation of NS1 with classic platelet agonists, enhancing α-granule translocation and inducing thromboxane A2 synthesis (thrombin and platelet-activating factor), or activating caspase-1 for IL-1β processing and secretion (adenosine triphosphate). Also, platelet activation by NS1 partially depended on toll-like receptor-4 (TLR-4), but not TLR-2/6. Finally, the platelets sustained viral genome translation and replication, but did not support the release of viral progeny to the extracellular milieu, characterizing an abortive viral infection. Although DENV infection was not productive, translation of the DENV genome led to NS1 expression and release by platelets, contributing to the activation of infected platelets through an autocrine loop. These data reveal distinct, new mechanisms for platelet activation in dengue, involving DENV genome translation and NS1-induced platelet activation via platelet TLR4.
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Karhausen, Jörn, Hae Woong Choi, Krishna Rao Maddipati, Joseph P. Mathew, Qing Ma, Yacine Boulaftali, Robert Hugh Lee, Wolfgang Bergmeier, and Soman N. Abraham. "Platelets trigger perivascular mast cell degranulation to cause inflammatory responses and tissue injury." Science Advances 6, no. 12 (March 2020): eaay6314. http://dx.doi.org/10.1126/sciadv.aay6314.

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Platelet responses have been associated with end-organ injury and mortality following complex insults such as cardiac surgery, but how platelets contribute to these pathologies remains unclear. Our studies originated from the observation of microvascular platelet retention in a rat cardiac surgery model. Ensuing work supported the proximity of platelet aggregates with perivascular mast cells (MCs) and demonstrated that platelet activation triggered systemic MC activation. We then identified platelet activating factor (PAF) as the platelet-derived mediator stimulating MCs and, using chimeric animals with platelets defective in PAF generation or MCs lacking PAF receptor, defined the role of this platelet-MC interaction for vascular leakage, shock, and tissue inflammation. In application of these findings, we demonstrated that inhibition of platelet activation in modeled cardiac surgery blunted MC-dependent inflammation and tissue injury. Together, our work identifies a previously undefined mechanism of inflammatory augmentation, in which platelets trigger local and systemic responses through activation of perivascular MCs.
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Coughlin, Shaun. "Protease-Activated Receptors and Platelet Function." Thrombosis and Haemostasis 82, no. 08 (1999): 353–56. http://dx.doi.org/10.1055/s-0037-1615853.

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IntroductionPlatelet activation is critical for normal hemostasis, and platelet-dependent arterial thrombosis underlies most myocardial infarctions. Thrombin is the most potent activator of platelets.1,2 For this reason, understanding the process by which thrombin activates platelets is necessary for understanding hemostasis and thrombosis and may yield novel anti-platelet therapies. This chapter focuses on our recent studies of the receptors that mediate activation of human platelets by thrombin.3,4 Thrombin signaling is mediated, at least in part, by a family of G protein-coupled protease-activated receptors (PARs), for which PAR1 is the prototype.5,6 PAR1 is activated when thrombin binds to and cleaves its amino terminal exodomain to unmask a new receptor amino terminus.5 This new amino terminus then serves as a tethered peptide ligand, binding intramolecularly to the body of the receptor to effect transmembrane signaling.5,7,8 The synthetic peptide SFLLRN, which mimics the first six amino acids of the new amino terminus unmasked by receptor cleavage, functions as a PAR1 agonist and activates the receptor independent of thrombin and proteolysis.5,9,10 Such peptides have been used as pharmacological probes of PAR function in various cell types.Our understanding of the role of PARs in platelet activation is evolving rapidly. PAR1 mRNA and protein were detected in human platelets,5,11-13 SFLLRN-activated human platelets,5,9,10 and PAR1-blocking antibodies inhibited human platelet activation by low, but not high, concentrations of thrombin.11,12 These data suggested a role for PAR1 in activation of human platelets by thrombin but left open the possibility that other receptors contribute.Curiously, PAR1 appeared to play no role in mouse platelets.14-16 PAR1-activating peptides did not activate rodent platelets, and platelets from PAR1-deficient mice responded like wild-type platelets to thrombin.16 The latter observation prompted a search for additional thrombin receptors and led to the identification of PAR3.17 PAR3 is activated by thrombin and is expressed in mouse platelets. PAR3 blocking antibodies inhibited mouse platelet activation by low, but not high, concentrations of thrombin,18 and knockout of PAR3 abolished mouse platelet responses to low, but not high, concentrations of thrombin.3 These results established that PAR3 is necessary for normal thrombin signaling in mouse platelets but also pointed to the existence of another mouse platelet thrombin receptor. Such a receptor, PAR4, was recently identified.3,19 PAR4 appears to function in both mouse and human platelets.3 The role of PAR3 in human platelets, if any, remains to be determined, and whether still unidentified receptors contribute to thrombin activation of platelets is unknown. Nonetheless, available data suggest a testable, working model in which PAR3 and PAR4 mediate thrombin activation of mouse platelets and PAR1 and PAR4 mediate activation of human platelets.To determine the roles of PAR1, PAR3, and PAR4 in activation of human platelets by thrombin, we examined PAR mRNA and protein expression in platelets and probed PAR function using specific peptide agonists. We also examined the effect of receptor desensitization, receptor blocking antibodies, and a PAR1 antagonist, used alone and in combination, on platelet activation.4
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Bevers, Edouard, Theo Lindhout, and Johan Heemskerk. "Platelet Activation and Blood Coagulation." Thrombosis and Haemostasis 88, no. 08 (2002): 186–93. http://dx.doi.org/10.1055/s-0037-1613209.

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SummaryPlatelet activation and blood coagulation are complementary, mutually dependent processes in haemostasis and thrombosis. Platelets interact with several coagulation factors, while the coagulation product thrombin is a potent platelet-activating agonist. Activated platelets come in a procoagulant state after a prolonged elevation in cytosolic [Ca2+]i. Such platelets, e. g. when adhering to collagen via glycoprotein VI, expose phosphatidylserine (PS) at their outer surface and produce (PS-exposing) membrane blebs and microvesicles. Inhibition of aminophospholipid translocase and activation of phospholipid scramblase mediate the exposure of PS, whereas calpain-mediated protein cleavage leads to membrane blebbing and vesiculation. Surface-exposed PS strongly propagates the coagulation process by facilitating the assembly and activation of tenase and prothrombinase complexes. Factor IXa and platelet-bound factor Va support these activities. In addition, platelets can support the initiation phase of coagulation by providing binding sites for prothrombin and factor XI. They thereby take over the initiating role of tissue factor and factor VIIa in coagulation activation.
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Sadoul, Karin, Jin Wang, Boubou Diagouraga, Anne-Laure Vitte, Thierry Buchou, Thérèse Rossini, Benoît Polack, Xiaodong Xi, Patrick Matthias, and Saadi Khochbin. "HDAC6 controls the kinetics of platelet activation." Blood 120, no. 20 (November 15, 2012): 4215–18. http://dx.doi.org/10.1182/blood-2012-05-428011.

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Abstract HDAC6, a major cytoplasmic deacetylase, is shown here to fine-tune the kinetics of platelet activation, a process that must be precisely regulated to ensure hemostasis after blood vessel injury while preventing pathologic thrombus formation. The discoid shape of resting platelets in the circulation is maintained by several highly acetylated microtubules organized in a marginal band. During platelet activation, microtubules undergo major reorganizations, which contribute to the shape change of activating platelets. We show that, during these activation-induced shape changes, a dramatic HDAC6-mediated tubulin deacetylation takes place, followed by microtubule reacetylation in spread platelets. In addition, although HDAC6-controlled tubulin deacetylation is not required for platelet activation, the capacity of HDAC6 to prevent tubulin hyperacetylation influences the speed of platelet spreading. These results are particularly important in view of HDAC6 inhibitors being currently used in clinical trials and represent the first example of cell signaling by lysine acetylation in platelet biology.
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Dissertations / Theses on the topic "Platelet activation"

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Bunescu, Andreia. "Cellular markers indicating activation of the hemostatic system : studies on platelets and leukocytes in peripheral human blood /." Stockholm, 2003. http://diss.kib.ki.se/2003/91-7349-759-2/.

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Cicmil, Milenko. "Platelet endothelial cell adhesion in molecule -1 (PECAM-1/CD31) signalling in platelets." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270922.

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El, Gendi Hossam Salah. "Platelet activation during coronary intervention." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271167.

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Cahill, Mary Rose. "Platelet activation : measurement of clinical significance." Thesis, Queen Mary, University of London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261799.

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Tan, Kiat Tsong. "Platelet activation status in atherosclerotic disease." Thesis, University of Leicester, 2005. http://hdl.handle.net/2381/29505.

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In order to provide more information on platelet activation that would be of interest to all clinicians involved in the care of the patient with atherosclerosis, this thesis sets out to provide data to either support or refute the following hypotheses. (1). Platelet activation in patients with stable coronary heart disease increases with the angiographic severity of disease. (2). Patients presenting with the acute manifestations of atherosclerosis have a greater degree of platelet activation than patients with stable disease. (3). Peripheral artery intervention results in the release of the cytokine, sCD40L, by platelets. (4). Platelet microparticle levels are higher in patients with Type 2 Diabetes who develop symptomatic macrovascular disease.;Using both flow cytometric and Enzyme Linked Immunosorbent Assay (ELISA) based measurements of platelet activation, this thesis confirms that platelet activation can be related to the clinical severity of atherosclerotic disease. In addition, the development of symptomatic atherosclerotic disease is associated with increased platelet microparticle levels. Peripheral artery angioplasty has also been shown to increase sCD40L release. However, there is no association between platelet activation status and the angiographic severity of coronary heart disease.
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Dunkel, Bettina. "Platelet activation and platelet-neutrophil interactions in equine recurrent airway obstruction." Thesis, Royal Veterinary College (University of London), 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498391.

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Hu, Hu. "Platelet and leukocyte activation, and platelet-leukocyte cross-talk : mechanistic aspects with special reference to diabetes mellitus /." Stockholm, 2003. http://diss.kib.ki.se/2003/91-7349-734-7.

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Arunima, Ghosh. "Role of CD36 in Platelet Function." Cleveland State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=csu1199991110.

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Vretenbrant, Öberg Karin. "The role of platelet thrombin receptors PAR1 and PAR4 in platelet activation." Doctoral thesis, Linköpings universitet, Klinisk kemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-51935.

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Platelets play a pivotal role in coagulation and haemostasis. Their most prominent task is to seal damaged blood vessels by the formation of a platelet plug at the damaged area. Once the injury is covered, platelets retract the coagulum to close the wound and allow the blood to flow freely in the vessel. Platelets are strongly activated by the essential enzyme thrombin, formed in the coagulation cascade. Activation of the platelet thrombin receptors PAR1 and PAR4 leads to shape change, secretion of granule content, and aggregation, all of which can be accomplished by each receptor individually. However more and more findings indicate that there are differences between the receptors and that they have different physiological functions. This thesis presents studies performed to elucidate the relative role of PAR1 and PAR4 in platelet activation and coagulation. We have studied the effects on platelet activation and coagulation, and revealed a possible physiological role for PAR4 in the stabilisation of the coagulum. We also investigated the relative role of PAR1 and PAR4 in the cross-talk between thrombin and epinephrine with and without inhibition of COX-1. We demonstrated that PAR4 interacts with adrenergic receptors and causes an aggregation of platelets dependent on released ATP and its receptor P2X1, thereby circumventing the inhibition by aspirin. Not only is this an interesting specific role for PAR4, but it may also be of clinical importance considering that COX-1 inhibition is the most common treatment for patients with cardiovascular disease to prevent thrombosis. We show that the number of PAR1 receptors varied between donors and that this variation was correlated to the response on receptor activation. The number of PAR1 receptors on the platelet surface was decreased after PAR1 stimulation but increased after stimulation of other receptors. In a final attempt to elucidate the nature of PAR1 and PAR4 we used mathematics to evaluate the effect of co-stimulation of the receptors. We found a strong synergistic effect for both platelet activation and aggregation. This indicates that PAR1 and PAR4 interact in a yet unknown way to regulate or amplify the effect of each other rather than merely transmitting the incoming signal the same way.
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Patel, Akruti. "NOVEL REGULATORS OF GPVI-MEDIATED PLATELET ACTIVATION." Diss., Temple University Libraries, 2017. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/473397.

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Biomedical Sciences
Ph.D.
Platelets are anucleate cells that are crucial mediators of hemostasis and thrombosis. Under physiological conditions, platelets are maintained in a quiescent state within the vasculature. Upon vascular injury, an essential receptor that initiates platelet activation upon interaction with sub-endothelial collagen is Glycoprotein VI (GPVI). The activation of platelets leads to platelet shape change, granular secretion, thromboxane A2 (TXA2) synthesis, and integrin IIb3-mediated platelet aggregation and thrombus formation. In the past, a lot of effort has been placed in understanding GPVI and its signaling in platelets, however, much is still unknown. Therefore, the focus of this thesis is to identify novel regulators of GPVI-mediated platelet signaling. Phosphoinositide 3-kinase (PI3K) is an important signaling molecule that is activated downstream of various receptors including GPVI upon platelet activation. PI3K activation leads to the generation of phosphatidylinositol (3,4,5)-trisphosphate (PIP3) subsequently leading to the recruitment of pleckstrin homology (PH) domain-containing proteins to the plasma membrane. We performed a proteomic screen to identify proteins that interacted with PIP3 using PIP3 beads, and among these proteins, we found engulfment and cell motility-1 (ELMO1). ELMO1 is a scaffold protein with no catalytic activity that regulates the actin cytoskeleton during cell motility and cell spreading in nucleated cells. ELMO1 is expressed in platelets and interacts with active RhoG. However, the function of ELMO1 is not known. Therefore, we utilized ELMO1-/- mice to investigate the role of ELMO1 in platelets. Aggregation, granular secretion, and thromboxane generation was enhanced in ELMO1-/- platelets in response to glycoprotein VI (GPVI) agonists, collagen-related peptide (CRP) and collagen, but unaltered using protease-activated receptor 4 (PAR4) agonist (AYPGKF). This suggests that ELMO1 plays a specific role downstream of GPVI despite normal surface expression level of GPVI. Furthermore, whole blood from ELMO1-/- mice, perfused over collagen, under arterial shear conditions, exhibited enhanced thrombus formation compared to blood from WT littermate controls. In an in vivo pulmonary thromboembolism model, ELMO1-/- mice showed reduced survival compared to WT littermate control. ELMO1-/- mice also showed shorter time to occlusion using the ferric-chloride injury model and reduced tail bleeding times compared to WT littermate control. This indicates that ELMO1 plays an essential role in hemostasis and thrombosis in vivo. At the molecular level, RhoG activity was enhanced in ELMO1-/- murine platelets compared to the WT littermate control in response to CRP. Together, these data suggest that ELMO1 negatively regulates GPVI-mediated thrombus formation via RhoG. Protein kinase C delta (PKC) is a serine/threonine kinase that positively and negatively regulate dense granule secretion downstream of PAR and GPVI receptors, respectively. However, the mechanism of such differential regulation is not known. We hypothesize that this differential regulation occurs via the phosphorylation of specific tyrosine sites on PKC downstream of GPVI and PARs. We observed that many of the tyrosine residues in PKC were phosphorylated in response to both GPVI and PAR activation. Interestingly, PKCY155 phosphorylation only occurred following GPVI stimulation. Hence, we generated PKCY155F KI mice to characterize the function of PKCY155 phosphorylation in platelets. Aggregation and dense granule secretion were unaffected in PKCY155F platelets upon stimulation with a PAR agonist. However, these platelet functional responses were decreased upon stimulation of PKCY155F platelets with GPVI agonists, compared to WT littermates, despite normal surface GPVI expression. Whole blood from PKCY155F mice perfused over collagen under arterial shear conditions showed decreased thrombus formation. Similarly, we observed that PKCY155F mice survive longer than controls using a pulmonary thromboembolism model. PKCY155F mice also exhibited longer time to occlusion using the ferric-chloride injury model. At the molecular level, Syk and PLC2 phosphorylation was decreased in the PKCY155F platelets following GPVI stimulation. In conclusion, PKCY155 phosphorylation positively regulates GPVI-mediated platelet activation. Together, the studies proposed in this thesis provide insights into regulation of GPVI-mediated platelet function by ELMO1 and PKCY155. ELMO1 negatively regulates GPVI-mediated platelet activation via RhoG and may provide a suitable target for antihemorrhagic therapy. While PKCY155, being a positive regulator of GPVI-mediated platelet activation, could be a potential drug target for anti-thrombotic therapy.
Temple University--Theses
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Books on the topic "Platelet activation"

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S, Authi Kalwant, Watson Steve P, Kakkar V. V, and International Symposium on Mechanisms of Platelet Activation and Control, (1992 : London, England), eds. Mechanisms of platelet activation and control. New York: Plenum Press, 1993.

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Histophysiology of the circulating platelet. Berlin: Springer-Verlag, 1990.

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Authi, Kalwant S., Steve P. Watson, and Vijay V. Kakkar, eds. Mechanisms of Platelet Activation and Control. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4615-2994-1.

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Fondation IPSEN pour la recherche thérapeutique. Meeting. The role of platelet-activating factor in immune disorders: Proceedings of the Meeting of the "Fondation IPSEN pour la recherche thérapeutique", Paris, June 25-26, 1987 (part II). Edited by Braquet P. Basel: Karger, 1988.

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M, Winslow C., and Lee M. L, eds. New horizons in platelet activating factor research. Chichester [West Sussex]: Wiley, 1987.

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Fred, Snyder, ed. Platelet-activating factor and related lipid mediators. New York: Plenum Press, 1987.

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Snyder, Fred, ed. Platelet-Activating Factor and Related Lipid Mediators. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4684-5284-6.

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1946-, Stute W., and Seminar on Empirical Processes (1985 : Düsseldorf, Germany), eds. Seminar on Empirical Processes. Basel: Birkhäuser Verlag, 1987.

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Pharmacy), Symposium on Problems on PAF (11th 1987 Tohoku College of. Trends in pharmacological research on platelet activating factor (PAF) in Japan: Proceedings of the Symposium on Problems on PAF held at the Tohoku College of Pharmacy, Sendai, Japan, September 19th, 1987. Tokyo: Ishiyaku EuroAmerica, 1988.

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Nigam, Santosh, Gert Kunkel, and Stephen M. Prescott, eds. Platelet-Activating Factor and Related Lipid Mediators 2. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-1-4899-0179-8.

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Book chapters on the topic "Platelet activation"

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McAllister-Williams, R. Hamish, Daniel Bertrand, Hans Rollema, Raymond S. Hurst, Linda P. Spear, Tim C. Kirkham, Thomas Steckler, et al. "Platelet Activation." In Encyclopedia of Psychopharmacology, 1034–35. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-540-68706-1_808.

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Unsworth, A. J., A. P. Bye, and J. M. Gibbins. "Platelet-Derived Inhibitors of Platelet Activation." In Platelets in Thrombotic and Non-Thrombotic Disorders, 541–56. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-47462-5_37.

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Mustard, J. F., R. L. Kinlough-Rathbone, and M. A. Packham. "Platelet Activation — An Overview." In PAF, Platelets, and Asthma, 23–36. Basel: Birkhäuser Basel, 1987. http://dx.doi.org/10.1007/978-3-0348-7451-9_2.

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Peerschke, Ellinor I. B., Wei Yin, and Berhane Ghebrehiwet. "Platelet Mediated Complement Activation." In Advances in Experimental Medicine and Biology, 77–87. New York, NY: Springer US, 2008. http://dx.doi.org/10.1007/978-0-387-78952-1_7.

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Ryningen, Anita, and Holm Holmsen. "Biochemistry of Platelet Activation." In Handbook of Platelet Physiology and Pharmacology, 188–237. Boston, MA: Springer US, 1999. http://dx.doi.org/10.1007/978-1-4615-5049-5_9.

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O’Flaherty, Joseph T. "Platelet-Activating Factor: Mechanisms of Cellular Activation." In Platelet-Activating Factor and Related Lipid Mediators, 283–98. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4684-5284-6_13.

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Sternberg, David, and Joshua Sonett. "Platelet Activation After Lung Transplantation." In Inflammatory Response in Cardiovascular Surgery, 393–98. London: Springer London, 2013. http://dx.doi.org/10.1007/978-1-4471-4429-8_46.

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De Clerck, F., and D. De Chaffoy De Courcelles. "Amplification Mechanisms in Platelet Activation." In Serotonin, 77–80. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-1912-9_11.

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Patrono, Carlo, and M. Vejar. "Platelet activation in unstable angina." In Predisposing Conditions for Acute Ischemic Syndromes, 70–77. Heidelberg: Steinkopff, 1989. http://dx.doi.org/10.1007/978-3-662-09434-1_8.

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Joseph, Michel, A. Capron, A. Tsicopoulos, J. C. Ameisen, J. B. Martinot, and A. B. Tonnel. "Platelet Activation by IgE and Aspirin." In PAF, Platelets, and Asthma, 169–77. Basel: Birkhäuser Basel, 1987. http://dx.doi.org/10.1007/978-3-0348-7451-9_15.

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Conference papers on the topic "Platelet activation"

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Bryckaert, M. C., A. Wasteson, G. Tobelem, F. Rendu, and J. P. Caen. "PLATELET DERIVED GROWTH FACTOR (PDGF) BINDS TO HUMAN PLATELETS AND MODULATES PLATELET ACTIVATION." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643493.

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PDGF which is released during platelet activation like the other ∝ granule components (fibrinogen, F VIII/vWF, PF4) could bind to platelet membrane Following this hypothesis, we have studied the binding of 125I pure human PDGF to washed human platelets activated by collagen. This binding was specific and time dependent and reached a plateau with 20 μg/ml of collagen. With 200 fold excess of unlabeled PDGF, the binding of 125I-PDGF decreased progressively to 10 .whereas unlabeled Epidermal Growth Factor did not compete with 125I-PDGF. Saturation curve and scatchard analysis have shown one class of sites 3,000 sites/cell with an apparent Kd = 10-8 M. The demonstration of PDGF binding to platelets led us to investigate the effects of PDGF on platelet function. PDGF inhibited the aggregation and 14C serotonin release induced by thrombin or collagen. This inhibition was dose dependent and more effective with human PDGF. A total inhibition of collagen-induced platelet aggregation was obtained with 50 ng/ml of human PDGF and 200 ng/ml of porcine PDGF. The aggregation and 14C serotonin release induced by arachidonic acid were not inhibited by PDGF. The metabolism of phosphoinositide was also investigated on washed human platelets prelabeled with 32P orthophosphate. We found that PDGF (200 ng/ml) induced a decrease of 32P associated with phosphatidylinositol 4 biphosphate (72 %) after 3 min, with a parallel increase of 32P-phosphatidylinositol 4 Phosphate (120 %) and 32P-phosphatidylinositol (120 %).In conclusion i) PDGF binds to activated platelets, ii) PDGF inhibits platelet aggregation and secretion, iii) PDGF modifies phosphoinositide metabolism. These results are in favour of a role of PDGF in a negative feed back control of platelet activation.
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Rink, T. J. "CALCIUM IN PLATELET ACTIVATION." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644772.

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Studies with calcium ionophores, permeabilised platelets, and platelets containing fluorescent calcium indicators quin2 and fura-2 have shown that elevation [Ca2+]i is an effective trigger for shape-change, aggregation, secretion and release of TxA2; and that elevation of [Ca2+]i is an important part of a complex “activation cascade” set up by natural agonists combining with their surface receptors. We have used calcium ionophores to impose [Ca2+]i changes, monitored by indicator dyes, to construct [Ca2+]i/function relationships for shape-change, secretion, aggregation, arachidonic acid release, TxA2 production, and myosin phosphorylation in intact platelets(e.g.1,2). Some of these functions can also be studied by analagous experiments using Ca2+-buffers to set known [Ca2+]i in permeabilised platelets. Our ability to monitor and modulate [Ca2+]i with fluorescent indicators has also allowed us to see what happens when [Ca2+]i changes are greately reduced or even absent and to investigate other pathways of intracellular activation. We think that formation of diacyl glycerol and activation of protein kinase-C can explain, some, but not all, of the cell activation that some agonists can apparently evoke at or near resting [Ca2+]i, and that combined or synergistic actions of Ca2+ and other intracellular mediators is the usual basis for physiological activation(3). Most agonists seem to promote both Ca2+ entry across the plasma membrahe and discharge from intracellular organelles, presumably the dense tubular system. The available evidence fits with the prevailing idea that Ins 1,4,5 P3 formed by agonist evoked hydrolysis of PIP2, is the internal messenger for Ca2+ release. Our kinetic measurements of [Ca2+]i transients require that optimal concentrations of InsP3 are formed within 250 milliseconds(4,5). The question of whether ADP receptors in human platelets are directly coupled with PIP2 breakdown remains contentious. Probably they do, weakly, and the differences from most other receptors are quantitative rather than qualitative. We do not understand the mechanisms of agonist-evoked Ca2+-entry; there is now plenty of evidence that argues against a role for membrane depolarisation and voltage-gated Ca channels, including some recent work with ionic substitution(5). Stopped-flow fluorescence analysis of [Ca2+]i rises in fura-2-loaded human platelets reveals some intriguing new insights(4,5). With thrombin, vasopressin and PAF at optimal concentrations, there is a highly reproducible delay before the signal starts to rise, which is approximately 250msec in the absence of external calcium compared to 190msec in the presence of external calcium. This suggests that Ca entry leads internal release, and gives ample time for complex coupling mechanisms for both processes.The delay with ADP, in the presence of external calcium, is much smaller suggesting a different coupling mechanism for Ca entry.
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Shadden, Shawn C., and Sahar Hendabadi. "Potential Pathways for Platelet Activation." In ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80474.

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As platelets are transported they are continuously stretched, compressed and sheared by local gradients in the flow. Exposure to elevated gradients can cause platelets to actively react with conformational, chemical and enzymatic responses, i.e. becoming activated. Once switched to the activated state, platelets perform multifaceted roles to orchestrate clotting. Mechanically-induced platelet activation under pathological conditions has been studied since the late 1970s. This work builds on [1], which introduced a trajectory-based level of activation parameter for platelets, and [2] describing coherent structures in cardiovascular flow. We introduce a new direction-independent Lagrangian measure. This measure is introduced as an activation potential in two senses. First, it provides a measure of mechanical strain, which has been shown to have the potential to activate platelets. Second, it is plotted at the initial location of the platelets. This latter condition is subtle, but it enables us to uncover an interesting observation that locations of highest activation potential tend to occur along structures that have important implications to the transport topology.
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Wurzinger, L. J., R. Opitz, and H. Schmid-Schönbein. "ULTRASTRUCTURAL INVESTIGATIONS ON THE MECHANISM OF “SHEAR-INDUCED PLATELET ACTIVATION”." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642845.

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High shear forces are suspected to play a triggering role in the initiation of arterial thrombosis, by activating platelets and the coagulation system. In an earlier study a shear stress of 170 N/m2 acting for only 7 milliseconds (ms) on platelet rich plasma (PRP) was found to induce a significant increase in platelet factor 3 availability (Thromb. Haemost. 54: 381-386; 1985). To clarify the question whether platelets can be activated directly by mechanical forces in analogy to smooth muscle cells, electron micrographs of platelets subjected to laminar shear stress were analysed with morphometric methods. The level of activation of platelet suspensions was quantified by assessing 1) the elongation of platelet profiles giving a measure for the “flatness” of the discoid resting platelets, and 2) the centralization of granules.Exposure to a shear stress of 170 N/m2 for 113 ms leaves ca. 15 % of the platelets irreversibly damaged, featuring degenerative ballooning, with break-down of internal structure and cell membrane defects. The remaining 85 % appear typically activated with rounded shape, extension of pseudopods and centralization of granules. Addition of “ADP-scavengers” to the suspension medium totally changes the appearance of sheared platelets: still a comparable proportion of them has undergone irreversible degenerative changes, but the “surviving” population lacks ultrastructural signs of platelet activation. This is reflected in values of the morphometric parameters which are close to the level of unsheared control samples.It is therefore concluded that “shear-induced platelet activation” cannot be ascribed to a direct stimulating effect of shear forces, but rather to secondary biochemical activation by adenine nucleotides leaking from a small percentage of shear destroyed platelets. The latter process, however, requires a well stirred though undiluted environment, as it is provided in vortices and eddies.
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Alzua, Brian, Mark Smith, and Yan Chen. "A Flow Cytometry Method for Characterizing Platelet Activation." In 2020 Design of Medical Devices Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/dmd2020-9070.

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Abstract Hemocompatibility testing is critical for assessing the safety of blood-contacting medical devices. Comprehensive hemocompatibility testing requires examining a wide range of possible adverse effects cause by direct or indirect blood contact, such as hemolysis, complement activation, and thrombus formation [1]. Moreover, these domains each encompass complex intercellular processes with many potential targets for analysis. For example, the current testing paradigm of platelet function may involve exposing the device to human whole blood and performing simple blood counts and/or macroscopic evaluation to determine the extent of platelet activation and clot formation as described in ASTM F2888-19. However, this approach does not capture any observations for device-mediated initiation of any steps in the platelet activation pathway prior to aggregation. We have validated a method to evaluate platelet activation by quantifying surface p-selectin expression after exposure to various materials. This method will provide an additional level of detail about potential platelet activating properties of a medical device. Flow cytometry has been used previously to measure platelet activation for clinical and research purposes. We sought to adapt this method to test for platelet activation induced by exposure of blood to medical devices or materials. We determined that processing fresh whole blood to platelet-rich plasma (PRP) by gentle centrifugation enhanced the signal compared to fresh blood itself. In each experiment, devices were exposed to PRP according to an extraction ratio of 6 cm2/mL for 1 hour. A blank control consisting of untreated PRP, and a positive control consisting of ADP, a potent agonist, were also used. After the exposure, excess plasma was removed from the articles and combined with anti-CD61 (to stain for platelets) and anti-CD62P (to stain for activated platelets) antibodies. Flow cytometry was then performed to quantify the percentage of CD62P+ over the total CD61+ cells to measure the percentage of activated platelets. In order to optimize the method, we investigated the effect of several experimental factors, including anticoagulant usage, donor variability, and selection of reference materials to serve as controls. Our results indicate that the flow cytometry-based method is consistent and reproducible, quick and easy to perform, and is well-correlated with results from the standard platelet and leukocyte count assay. The flow cytometry-based platelet activation method is a powerful supplement to the standard regimen of medical device hemocompatibility testing.
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Wyler, B., and K. J. Clemetson. "THE ROLE OF GPIb IN PLATELET ACTIVATION." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642922.

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Platelet membrane glycoprotein lb (GPIb) is known to contain a receptor for von Willebrand factor (vWf) and for thrombin. The role of GPIb in platelet activation was investigated by comparing the effect of removal of the binding sites by specific proteolysis with that of blocking them using specific antibodies. Specific removal of the 45 kDa outer part of GPIb by treatment of platelets with human leukocyte elastase caused loss of platelet agglutination response to von Willebrand factor (vWf) but also a weaker activation by thrombin similar to that found with Bernard-Soulier syndrome platelets which lack GPIb. Removal of the major part of the external region of the GPIba chain, including the 45 kDa domain, by calcium activated protease or by chymotrypsin, produced similar effects. The 45 kDa region of GPIba was purified by tryptic cleavage of isolated glycocalicin followed by gel filtration. Antibodies to this fragment were produced in rabbits and showed high specificity and affinity for the 45 kDa polypeptide. Fab fragments of IgG prepared from this anti serum affect platelet response to vWf and thrombin in a dose-dependent way. In both protease-treated and antibody-treated platelets the reduced response to thrombin, but not to vWf could be overcome by increasing the dose of thrombin. In contrast to removal of the 45 kDa domain, antibody treatment affected not only the platelet response to vWf and thrombin but also to collagen, ADP, PAF and arachidonic acid. Only the response to the calcium ionophore A23,187 was unaltered.Though not the essential receptor GPIb is clearly involved in platelet response to thrombin. A possible mechanism could involve a conformational change in the cytoplasmic/inter-membranous part of GPIb induced by binding of thrombin to the 45 kDa domain. Binding of antibodies might affect platelet activation by other agonists via a general down regulation effect. These results support the two receptor models for thrombin activation of platelets as proposed for other cell -types. In platelets the first receptor appears to be GPIb but the second receptor has not yet been identified.
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SIMON, M. F., H. CHAP, and L. DOUSTE-BLAZY. "EFFECTS OF SIN 1 ON PLATELET ACTIVATION INDUCED BY THROMBIN IN HUMAN PLATELETS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643423.

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The mechanism of platelet activation is well known. The interaction of agonist such as thrombin, on specific membrane receptor induces phosphatidylinositol-specific phospholipase C activation, with a concomitant formation of two second messengers (from PIP2): inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 is able to induce a rapid discharge of Ca2+ from internal stores and Ca2+ influx through plasma membrane by unidentified Ca2+ channels linked to receptor activation. The increase of cytoplasmic free calcium concentration leads to the activation of the calcium calmodulin dependent myosine light chain kinase which phosphoryla-tes 20 kD proteins (myosine light chain). DAG is a potent activator of protein kinase C, which phosphorylates 40 kD proteins. These different pathways act in synergism.Sin 1 is a platelet aggregating inhibitor. This compound is an active metabolite of molsidomine, which activates platelet guany-late cyclase, inducing a rapid rise in cyclic GMP level. The precise role of cyclic GMP in platelet activation is not yet known. In order to study the mechanism of action of this drug, we tried to determine the effect of Sin 1 on the different steps described above. We measured Ca2+ fluxes and phospholipase C activation in thrombin (0,5 U/ml) stimulated platelets in the presence of different doses of Sin 1 (10™7-10™3M). Serotonin secretion was inhibited by 30 % with Sin 1 (10™4M-10™5m). A parallel inhibition of phospholipase C was detected by measurement of [32P)-PA level. Platelets loaded with Quin 2 and stimulated by thrombin showed a 70 % inhibition of external Ca2+ influx as soon as a concentration of 10™7M of Sin 1 was added. A study on platelet loaded with [45Ca2+) and Quin 2 confirmed these results. On the contrary, discharge of internal Ca2+ store seemed to be unaffected.In conclusion, the major effect of Sin 1 on platelet phospholipase C pathway is an inhibition of Ca2+ influx through plasma membrane. Some further experiments are necessary to shown whether this inhibition is correlated with cyclic GMP formation (the major effect of Sin 1) and try to establish a relation between this inhibition and that exerted on phospholipase C.Sin 1 was a generous gift of Hoechst.
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Bluestein, Danny, Jolyon Jesty, Adam E. Saltman, Irvin B. Krukenkamp, and Krishnamurthy Suresh. "Platelet Activation in Flow Past Mechanical Heart Valves." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/bed-23110.

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Abstract Numerical studies, in vitro, and in vivo measurements were conducted, aimed at quantifying free emboli formation and procoagulant properties of platelets induced by flow past mechanical heart valves (MHV). Pulsatile turbulent flow simulation was conducted past a St. Jude medical MHV in the aortic position, to study the effects of valve implantation technique on the thromboembolic potential of the valve. A misaligned valve with subannualarly sutured pledgets produced accelerating jet flow through the valve orifices and a wider wake of shed vortices. Shear stress histories of platelets along turbulent trajectories exposed the platelets to elevated shear stresses around the leaflets, leading them to entrapment within the shed vortices. In vitro platelet studies were conducted past the MHV mounted in a recirculation flow loop, by measuring the platelets ability to support the activation of acetylated human prothrombin by factor xa, which enables sequestering flow induced effects and quantification of the platelets activity state. The platelet activation state increased monotonically as a function of the recirculation time past the valve, as measured by the thrombin generation rates in the assay. Finally, platelet activity state measurements were conducted in vivo, from a sheep with an implanted MHV, showing marked increase of platelet activation after valve implantation.
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Yatomi, Y., M. Higashihara, A. Tanabe, T. V. Ohashi, T. Kariya, and S. Kume. "THE SYNERGISM BETWEEN PROTEIN KINASE C ACTIVATION AND CALCIUM MOBILIZATION IN PLATELET ACTIVATION." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644510.

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It has been shown that Ca2+ mobilization and protein kinase C (C kinase) activation act synergistically to elicit the full physiological response in several systems. That was first demonstrated for the release of serotonin from platelets. To clarify whether or not such synergism can be extended to aggregation and contrast platelet functions with cytosolic free Ca2+ levels( [Ca2+]I), we observed platelet aggregation, serotonin release and [Ca2+], simultaneously by using platelets loaded with 14C-serotonin and Ca2+-sensitive photoprotein aequorin. To induce C kinase activation and Cafmobilization independently, we used the exogenous addition of 12-0-tetradecanoylphorbol 13-acetate(TPA) for the former and a Ca+ionophore, ionomycin, for the latter. Platelet-rich plasma was obtained from healthy human blood and was preincuvated with 1μM14C-serotonin for 45min. Then aequorin was introduced into platelets by incubation with 10mM EGTA and 5mM ATP as described by Johnson et al. Finally, gel-filtered platelets(GEP) were prepared and the count was adjusted to 3×108/ml with Hepes-Tyrode’s buffer containing 1mM Ca2+. GFP were preincubated with aspirin (100μ/ml) for 5 minutes, and purified human fibrinogen(500μg/ml) was added shortly before agonists. Aggregation and aequorin signal were measured by using Chronolog P.I.C.A. The synergistic effects of TPA(50-200nM) and ionomycin(50-200nM) were evident both in aggregation and serotonin release. GFP stimulated by 50nM TPA or 50nM ionomycin alone did not aggregate and released little serotonin. But when they were added together, marked aggregation and release reaction were observed. Aggregation was partially affected by apyrase(2mg/ml). Ionomycin caused a rapid increase in [Ca2+]; in a dose-dependent manner, but TPA (below 200nM) did not in this system. When ionomycin and TPA were added together, [Ca2+]; was dependent on the concentration of the former. It is concluded that synergism between Ca2+ mobilization and C kinase activation is observed for platelet aggregation as well as release reaction.
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Coeffier, E., D. Joseph, and B. B. Vargaftio. "PLATELET-LEUKOCYTE INTERACTION: ACTIVATION OF RABBIT PLATELETS BY FMLP-STIMULATED NEUTROPHILS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643158.

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The interaction of neutrophils and platelets may be important in inflammation. We have studied the effect of the chemotactic peptide, N-formyl-methionyl-leucy1-phenylalanine (FMLP) on cells in whole rabbit blood or in mixture of purified rabbit platelets and neutrophils. In whole blood, FMLP triggered an aggregation (measured by electrical impedance) dependent upon the concentration of FMLP (9.9± 0.7 and 5.2+1.2 ohms at 1 and 0.01 uM FMLP resp.). This aggregation was accompanied by a strong decrease in platelets counts (54.6± 6.0 and 45.6± 3.8% for 1 and 0.01 uM FMLP resp.) and by a smaller decrease in neutrophils counts (25.0± 1.9 and 12.9± 1.7% at 1 and 0.01 uM FMLP resp.). When platelets were incubated in the presence of neutrophils, the addition of 0.1 uM FMLP induced a marked aggregation (50.0± 1.6 versus 19.5± 1.6% of light transmission,n=8,p< .001), ATP secretion (8.4± 1.0 versus 0.1± 0.1 nmol/ml,n=6,p< .001) and a marked decrease of platelets counts. FMLP induced aggregation of purified neutrophils and release of lysozyme but lacked direct platelet-stimulating effect. The release of lactate dehydrogenase and lysozyme were unchanged under the interaction conditions. Our results indicate that the stimulation of neutrophils by FMLP induces platelet activation both in whole blood and on isolated cells. The platelet activation was reduced by about 30% with lOOuM aspirin or indomethacin and by about 70% with lOOuM BW 755C. The two PAF-acether antagonists, BN 52021 (lOOuM) and WEB 2086 (luM) suppressed platelet activation by 70-80%. Neutrophil supernatant induced platelet activation only when neutrophils were stimulated by FMLP in the presence of bovine serum albumin (BSA,0.25%). Rabbit neutrophils stimulated in the presence of BSA by 1 uM FMLP formed 2 nM PAF-acether of which only 50% were released to the extra-cellular medium. WEB 2086 (luM) inhibited totally the formation and the release of PAF-acether. These data indicate that both arachidonic acid-metabolites and PAF-acether participate in platelet activation by FMLP-activated neutrophils.
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Reports on the topic "Platelet activation"

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Tsokos, George. Complement Activation Alters Platelet Function. Fort Belvoir, VA: Defense Technical Information Center, October 2013. http://dx.doi.org/10.21236/ada612004.

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Tsokos, George. Complement Activation Alters Platelet Function. Fort Belvoir, VA: Defense Technical Information Center, October 2014. http://dx.doi.org/10.21236/ada612005.

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Tsokos, George. Complement Activation Alters Platelet Function. Fort Belvoir, VA: Defense Technical Information Center, October 2013. http://dx.doi.org/10.21236/ada612741.

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Michelson, A. D., H. MacGregor, A. Kestin, M. R. Barnard, and M. J. Rohrer. Reversible Hypothermia-Induced Inhibition of Human Platelet Activation in Whole Blood in Vitro and in Vivo. Fort Belvoir, VA: Defense Technical Information Center, January 1992. http://dx.doi.org/10.21236/ada360296.

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Snyder, F. Regional Neonatal Associates for cooperative study of platelet-activating factor (PAF). Summary report. Office of Scientific and Technical Information (OSTI), November 1992. http://dx.doi.org/10.2172/28403.

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