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Platelet Aggregation

Platelet Aggregation is the process by which platelets clump together to form a plug at the site of a blood vessel injury, contributing to the initiation of hemostasis.
This critical biological process is essential for normal blood clotting and wound healing.
Researchers studying Platelet Aggregation utilize a variety of experimental protocols to analyze and measure this phenomenon, often comparing the accuracy and reproducibility of different methods.
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Most cited protocols related to «Platelet Aggregation»

We purified platelets from whole blood (obtained from healthy volunteers) that had undergone anticoagulation with adenine citrate dextrose solution A. None of the volunteers had been taking antiplatelet drugs or had been vaccinated in the previous 10 days. We prepared platelets using methods that have been described previously.2 (link),3 (link) In a subgroup of experiments, platelets were preincubated in buffer with ChAdOx1 nCov-19 (1:2000 dilution) and washed before use. Washed platelets (75 microliters) were incubated with either buffer, a low-molecular-weight heparin (reviparin [Abbott]), or PF4 (Chromatec) in either the presence or absence of the FcγIIa receptor–blocking antibody IV.3. In some experiments, unfractionated heparin (100 IU per milliliter) was added to inhibit PF4-dependent reactions, or ChAdOx1 nCov-19 (1:50 dilution) was added per well. Serum was coincubated with PF4 and platelets in the presence of immune globulin (Privigen IVIG [CSL Behring]) at a concentration of 10 mg per milliliter. After establishing assay conditions using serum from the initial four patients, we investigated another 24 serum samples that tested positive on immunoassay to validate our findings. We refer to this modified platelet-activation test as the PF4-enhanced platelet-activation test.
To measure direct antibody binding, we used two immunoassays, a PF4–heparin enzyme-linked immunosorbent assay (ELISA) and a PF4 ELISA, with antibody binding measured by a secondary antihuman IgG, as described previously.4 (link) In addition, antibodies from two serum samples were affinity purified by immobilized PF4–heparin and immobilized PF4, and the purified antibodies were tested in the assays. (Details about this method are provided in the Supplementary Appendix, available with the full text of this article at NEJM.org.)
We defined reactivity on ELISA according to the optical-density units as strong (≥2.00), intermediate (1.00 to 1.99), or weak (0.50 to 0.99). On the PF4-enhanced platelet-activation test, reactivity was graded according to the time that had elapsed until platelet aggregation,5 (link) with shorter reaction times indicating stronger platelet activation (strong activation, 1 to 5 minutes; intermediate activation, >5 to 15 minutes; and weak activation, >15 to 30 minutes).
Publication 2021
Adenine Antibodies Antibodies, Blocking Antiplatelet Agents Biological Assay Blood Platelets Buffers Cardiac Arrest ChAdOx1 nCoV-19 Citrates Debility Enzyme-Linked Immunosorbent Assay Glucose Healthy Volunteers Heparin Heparin, Low-Molecular-Weight Immunoassay Immunoglobulins Intravenous Immunoglobulins Patients Platelet Activation Platelet Aggregation Privigen reviparin Serum Technique, Dilution Voluntary Workers
We assessed the correlates (eg, age, sex, body mass index [BMI], lipid levels, and blood pressure) of clopidogrel response using a regression-based approach as implemented in the SOLAR version 4.07 (Southwest Foundation for Biomedical Research, San Antonio, Texas),30 (link) in which we accounted for relatedness among study participants by including a polygenic component as a random effect. Triglyceride levels were logarithm-transformed for analysis and back-transformed for presentation. Distribution analyses were generated in SAS. All statistical tests were 2-sided.
Association analyses between SNPs and ADP-stimulated platelet aggregation following clopidogrel administration were performed under a variance component model that assesses the effect of genotype as an additive effect on the quantitative trait, while simultaneously estimating the effects of age, age2 (link), sex, preclopidogrel platelet aggregation, and the aforementioned polygenic component.
The polygenic component was modeled using the relationship matrix derived from the complete Amish pedigree structure available through published genealogical records maintained by the church.31 (link) The heritability of baseline platelet aggregation and clopidogrel response corresponds to the proportion of the trait variance accounted for by the polygenic component. The genomic control λ coefficient was 1.03; thus, the P values reported are unadjusted.
A power calculation indicated 80% power to detect SNPs with allele frequencies of 0.2 to 0.4 in the initial sample (n = 429), accounting for 8% to 9% of phenotypic variation at α =10−7. To determine whether the loss-of-function CYP2C19*2 variant could account for the chromosome 10q24 association signal, we estimated the independent effects of both rs12777823— the most highly associated SNP from the genome-wide association analysis— and the CYP2C19*2 variant on platelet aggregation by including both in the model simultaneously. Pairwise linkage disequilibrium correlation statistics (|D′| and r2 (link)) were computed using Haploview (http://www.broad.mit.edu).
Publication 2009
Amish Blood Pressure Chromosomes Clopidogrel CYP2C19 protein, human Genome Genome-Wide Association Study Genotype Index, Body Mass Lipids Platelet Aggregation Triglycerides
The TEG® Platelet Mapping™ assay (Haemoscope Corporation, Niles, Illinois, US) relies on evaluation of clot strength to enable a quantitative analysis of platelet function. The maximal haemostatic activity is measured by a kaolin activated whole blood sample treated with citrate. The following measurements are performed with heparin to eliminate thrombin activity: Reptilase and Factor XIII (Activator F) generate a cross-linked fibrin clot to isolate the fibrin contribution to the clot strength [9 (link)]. The contribution of the ADP or ThromboxaneA2 (TxA2) receptors to the clot formation is provided by the addition of ADP or AA.
Blood was analyzed according to instructions (Haemoscope Corporation. TEG Guide to Platelet Mapping. Monitor anti-platelet therapy, 2004). Both analyzer (series 5000) and the reagents were from Haemoscope Corporation.
For maximal clot strength (MAThrombin) one milliliter of citrate-stabilized blood was transferred to a vial containing kaolin and mixed by inversion. Kaolin activated blood (340 μl) was added to a TEG® cup containing 20 μl of 0.2 M CaCl2. To generate a whole-blood fibrin cross-linked clot, representing only the fibrin contribution included in the clot strength measurement, heparinized blood (360 μl) was transferred to a TEG® cup containing 10 μl Activator F; MAFibrin (Fig. 1). The contribution of the P2Y12 receptor, or the COX-1 pathway, to the clot formation is assessed by the addition of ADP or AA. Therefore, AA and ADP, respectively, are added to Activator F to measure the degree of ADP receptor and thromboxane A2 induced platelet aggregation. Heparinized blood (360 μl) was added to a TEG® cup in the presence of the Activator F and agonist, 10 μl ADP (2 μM, final concentration) yielding MAADP or 10 μl AA (1 mM, final concentration) for the MAAA. The platelet inhibition in response to the agonist is calculated from platelet aggregation: [(MAADP - MAFibrin)/(MAThrombin - MAFibrin) × 100] and % inhibition = (100% - % aggregation).
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Publication 2007
Biological Assay BLOOD Blood Platelets Citrates Clotrimazole Factor XIII Fibrin Hemostatics Heparin Inversion, Chromosome Kaolin Platelet Aggregation Psychological Inhibition PTGS1 protein, human Receptors, ADP Reptilase Therapeutics Thrombin Thromboxane A2
Simulations were performed in Matlab R2008b (version 7.7.0.471) using the Systems Biology Toolbox 2 (SBTOOLBOX2) with the SBPD extension package ODE solver with an absolute tolerance of 10−30 and a relative tolerance of 10−7[59] (link).
A function of thrombin concentration was fit with a Hill function to published experimental data that quantified ‘Platelet Activation Status’ by reporting surface Phosphatidylserine exposure (measured by fold increase in Annexin V binding) in response to thrombin (IIa) [60] (link) (Figure. 2B): where . Since thrombin concentration physiologically starts decreasing after monotonically rising to a peak, it was necessary to use the maximum transient thrombin concentration, , to ensure that never decreases once it has reached its maximum magnitude. is exactly equivalent to [IIa(t)] until [IIa(t)] reaches its peak value, whereafter remains constant at that maximum value. This ensures that the platelet stays activated even when thrombin levels decline.
For a given [IIa], we define the maximum platelet activation state, : where εmax describes the fractional activation state of the platelet. defines the basal activation state of the platelet at t = 0, and is set to 0.01 in most simulations (assuming a basal 1% binding strength of coagulation factors to the resting platelet surface). For full activation of platelets at [thrombin] >∼10 nM, equals 1 and protein dissociation is minimized.
The instantaneous platelet activation state ε is governed by the differential equation with the initial condition at , this solves to, The constant k is inversely proportional to the time scale of platelet activation, and was set to 0.005. This is consistent with the fact that it takes ∼200 s for platelets to mobilize calcium from intracellular stores upon stimulation with thrombin or other platelet agonists [57] . Such a form of the platelet function (ε) ensures that the platelet achieves its maximum attainable activation state (εmax) not instantaneously, but on a physiologically relevant timescale. Transients of ε are shown for values of εmax = 0.25, 0.5, 0.75 and 1.0 are shown in Figure 2c.
To account for changes in the reaction rates with platelet activation, we modified the Hockin-Mann model rate constants as follows, where η was a parameter that was used to alter the magnitude of the rate constant used in the Hockin-Mann model. Many of the Hockin-Mann model parameters were originally fitted empirically to global experimental data. For η = 1 and full platelet activation (ε = 1), the modified value becomes the original value. For η ≠ 1, the modifications may be regarded as further fits to experimental data, consistent with published values of rate constants (footnotes to Table I).
To estimate the sensitivity of our model's output to the choice of kinetic constants, a global sensitivity analysis of the models output thrombin concentration at 0 and 10 pM TF concentration was carried out by the method of weighted averaging of local sensitivities. The results of this analysis are shown in Figure S1A and Figure S1B in Text S1, and Table S1 and Table S2 in Text S1. Local sensitivity of Ti to 10 fold variations in important parameters (determined from the global sensitivity analysis) across the entire range of titrated TF concentrations is shown in Figure S1 C in Text S1.
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Publication 2010
agonists Annexin A5 Blood Coagulation Factor Blood Platelets Calcium Hypersensitivity Immune Tolerance Kinetics Phosphatidylserines Platelet Activation Platelet Aggregation Proteins Protoplasm Seizures Thrombin Transients
The Amish Pharmacogenomics of Antiplatelet Intervention (PAPI) Study (NCT0079936) recruited 429 generally healthy white participants 20 years or older between August 2006 and October 2008 (for additional details, see eMethods at http://www.jama.org). These individuals comprised a number of relative pairs informative for estimating heritabilities, including 105 parent-offspring pairs, 175 sibling pairs, 1 grandparent-grandchild pair, 48 avuncular pairs, and 12 first-cousin pairs. Medical and family histories, anthropometry, physical examinations, and blood samples after an overnight fast were obtained. Complete blood count with platelet number and levels of serum lipids (total cholesterol, high-density lipoprotein cholesterol, and triglycerides) were assayed by Quest Diagnostics (Horsham, Pennsylvania); levels of low-density lipoprotein cholesterol were calculated using the Friedewald equation.
After baseline platelet aggregation measurements were obtained, participants were given a 300-mg oral loading dose of clopidogrel followed by 75 mg per day for 6 days. Follow-up platelet aggregation studies were repeated 1 hour following the last dose of clopidogrel. A second follow-up platelet aggregation measurement was made later the same day, 1 hour after oral ingestion of 324 mg of chewable aspirin. Platelet function was assessed by optical aggregometry with a PAP8E Aggregometer (Bio/Data Corporation, Horsham, Pennsylvania) in platelet-rich plasma, stimulated with ADP (20 μmol/L) or arachidonic acid (1.6 mmol/L) (eMethods).
Publication 2009
A 300 Amish Arachidonic Acid Aspirin BLOOD Cholesterol Cholesterol, beta-Lipoprotein Clopidogrel Complete Blood Count Diagnosis Grandparent Healthy Volunteers High Density Lipoprotein Cholesterol Lipids Parent Physical Examination Platelet-Rich Plasma Platelet Aggregation Platelet Counts, Blood Serum Triglycerides Vision

Most recents protocols related to «Platelet Aggregation»

Platelet aggregation tests in the presence of several agonists were measured with an optical platelet aggregometer (APACT 4004, ELITechGroup, Puteaux, France) according to the manufacturer's instructions. For activation tests, platelets were stimulated or not with different agonists for 15 min and then incubated with various fluorophore‐conjugated antibodies. Anti‐CD62P‐PE was purchased from Becton Biolegend. Anti‐CD41‐PC7 and anti‐CD63‐PE were purchased from Beckman Coulter. Samples were analyzed in an FACSLyric (Becton Dickinson) flow cytometer.
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Publication 2023
agonists Antibodies Blood Platelets Platelet Aggregation SELP protein, human
For platelet count, blood was collected on sodium ethylene diamine tetraacetate-anticoagulated tubes. Platelet counts were obtained using the Beckman DXH 800 hematology analyzer (Beckman Coulter), which is used routinely. For platelet function assays and electron microscopy, blood was collected on citrate tubes containing 0.109 molar sodium citrate and tubes containing acid citrate dextrose. To avoid platelet activation, samples were analyzed within 2 hours after sampling. Dry tubes for serum collection were also used.
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Publication 2023
acid citrate dextrose Biological Assay BLOOD Citrates Electron Microscopy Ethylenediamines Molar Platelet Activation Platelet Aggregation Platelet Counts, Blood Serum Sodium Sodium Citrate
Platelet aggregation was tested in citrated platelet-rich plasma (PRP) using 2.5 μM adenosine diphosphate (ADP; Calbiochem), 1 mM arachidonic acid (Nu Chek Prep), 1 μg/mL Horm equine tendon collagen (Nycomed, Pharma), 10 μM Thrombin Receptor Activating Peptide-14 (TRAP14-mer; Neosystem SA), 4 μM epinephrine (Sigma-Aldrich), and 5 μM ionophore 23187 (Calbiochem) in an APACT-4004 aggregometer (Elitech) according to standard procedures [13 ]. Native PRP concentration was adjusted if the platelet count was higher than 600G/L to reach a platelet count of 500 G/L.
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Publication 2023
Adenosine Diphosphate Arachidonic Acid Collagen Epinephrine Equus caballus Ionophores Platelet-Rich Plasma Platelet Aggregation Platelet Counts, Blood Tendons thrombin receptor peptide SFLLRNP
Platelet aggregation was measured using a four-channel platelet aggregometer (Chrono-Log Corp., USA) after the addition of 0.1 μg/mL collagen or 2 μM ADP. PRP was incubated for 5 min at 37 °C. After incubation, platelet aggregation was determined as the level of light transmission monitored for 5 min. Platelet aggregation was expressed as percentage of the platelet-poor plasma (PPP) transmission values. Bleeding time was measured by the tail transection model. After treatment, the tail tip was transected with a scalpel at a point that measured 1 mm in diameter. Bleeding was assessed every 30 s using a filter paper, and the time to clot formation defined the bleeding time. Clotting time was determined by collecting blood into three separated test tubes prewarmed at 37 °C to obtain an average result. Blood clotting was tested by tipping the tube back and forth every 30 s, and clotting time was determined when blood does not flow out from tubes when tilted horizontally. Platelet count was determined using a blood cell counter HEMAVET950 (Drew Scientific, USA). d-dimer level determination was performed in plasma by use of Rat d-Dimer ELISA Kit according to instructions by the manufacturer (Abbexa, UK).
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Publication 2023
BLOOD Blood Cells Blood Platelets Clotrimazole Collagen Type I Enzyme-Linked Immunosorbent Assay LIF protein, human Light Plasma Platelet Aggregation Platelet Counts, Blood Strains Tail Times, Bleeding Transmission, Communicable Disease
Human platelets purified from citrated blood were mixed with increasing doses of GH-ALG or rabbit ATG and aggregation was monitored for 60 minutes on a TA-8V STAGO aggregometer. To induce platelet aggregation, ristocetin (1.5 mg/ml), Thrombin Receptor Activator Peptide (TRAP,1.5 µM), arachidonic acid (0.3 mg/ml), ADP (adenosine diphosphate, 5 µM), epinephrine (5 µM) and collagen (1.25 µg/ml) were evaluated.
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Publication 2023
Adenosine Diphosphate antithymocyte immunoglobulin Arachidonic Acid BLOOD Blood Platelets Collagen Epinephrine Homo sapiens Platelet Aggregation Ristocetin Thrombin Receptor Activating Peptides TRAP1 protein, human

Top products related to «Platelet Aggregation»

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The Aggregometer is a laboratory instrument used to measure the aggregation of platelets in blood samples. It detects and quantifies the clumping of platelets in response to various agonists. The Aggregometer provides real-time monitoring of platelet function, enabling researchers to assess the effectiveness of antiplatelet drugs or investigate platelet disorders.
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The Lumi-aggregometer is a laboratory instrument used for the measurement of platelet aggregation. It measures the changes in light transmission through a platelet-rich plasma sample upon the addition of an aggregating agent.
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The PFA-100 is a lab equipment product manufactured by Siemens. It is designed to measure platelet function in blood samples. The device uses a specialized cartridge to analyze the ability of platelets to aggregate in response to specific agonists, providing information about the platelet's activity and function.
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Thrombin is a serine protease enzyme that plays a crucial role in the blood coagulation process. It is responsible for the conversion of fibrinogen to fibrin, which is the main structural component of blood clots. Thrombin also activates other factors involved in the clotting cascade, promoting the formation and stabilization of blood clots.
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