ORCID Profile
0000-0002-9126-2166
Current Organisation
University of Western Australia
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Water Resources Engineering | Civil Engineering | Microbial Ecology | Wastewater Treatment Processes | Biochemistry and Cell Biology | Signal Transduction | Environmental Technologies | Cell Development, Proliferation and Death |
Ecosystem Assessment and Management of Fresh, Ground and Surface Water Environments | Urban Water Evaluation (incl. Water Quality) | Expanding Knowledge in the Biological Sciences | Rural Water Evaluation (incl. Water Quality)
Publisher: Elsevier BV
Date: 06-2004
Publisher: Wiley
Date: 31-10-2013
DOI: 10.1002/DDR.21110
Abstract: Clinical Development Phases I‐III Regulatory, Quality, Manufacturing Platelets are subcellular fragments in blood whose activation is central to atherothrombosis and cardiovascular events. Platelet activation is complex, with multiple pathways of initiation and lification involved. Antiplatelet drugs may target any of these pathways to diminish the propensity of platelets to become activated. The most well‐established antiplatelet drugs, aspirin and thienopyridines, target the thromboxane and adenosine diphosphate auto‐ lification pathways of platelet activation, respectively. These are very effective medicines, but response varies and residual on‐treatment platelet function is associated with poorer clinical outcomes. Alternative antiplatelet therapies are available and more are in development. Therefore, tailoring antiplatelet therapy to on‐treatment platelet activation is an appealing strategy and the subject of investigation. There are many different approaches to measuring platelet activation and response to stimulation with antiplatelet therapy, but there is very little agreement between them regardless of the cutoffs used. Therefore, selection of the appropriate platelet function test is important in assessing on‐treatment platelet activation for guided therapy. Recent research has shown that tailoring antiplatelet therapy can improve these laboratory measures of platelet activation, but clinical studies that assess cardiovascular benefit against potential for increased bleeding are required.
Publisher: Informa UK Limited
Date: 03-09-2021
Publisher: Georg Thieme Verlag KG
Date: 23-11-2015
Abstract: Polycystic ovarian syndrome (PCOS) affects 12 to 19% of women and has reproductive and metabolic features (endothelial dysfunction, increased diabetes, and cardiovascular risk factors). It also appears to have altered coagulation and fibrinolysis with a prothrombotic state with epidemiological evidence of increased venous thromboembolism. We aimed to comprehensively assess hemostasis in women with PCOS versus control women. In an established case-control cohort of lean, overweight, and obese women with (n = 107) and without PCOS (n = 67), with existing measures of plasminogen activator inhibitor 1 (PAI-1), asymmetric dimethylarginine (ADMA), hormonal, and metabolic markers, we also assessed prothrombin fragments 1 and 2 (PF1 & 2), plasminogen, tissue plasminogen activator (tPA), and thrombin generation (TG). Higher levels of ADMA (0.70 vs. 0.39 µmol/L, p < 0.01), PAI-1 (4.80 vs. 3.66 U/mL, p < 0.01), and plasminogen (118.39 vs. 108.46%, p < 0.01) were seen in PCOS versus controls, and persisted after adjustment for age and body mass index (BMI). PF1 & 2 was marginally lower (180.0 vs. 236.0 pmol/L, p = 0.05), whereas tPA and TG were not different between groups, after adjustment for age and BMI. Significant relationships were observed between hormonal and metabolic factors with ADMA and PAI-1. We demonstrate impaired fibrinolysis in PCOS. In the context of abnormal endothelial function and known hormonal and metabolic abnormalities, this finding may underpin an increased risk of cardiovascular disease and venous thrombosis in PCOS.
Publisher: Informa UK Limited
Date: 24-10-2012
DOI: 10.3109/10408363.2012.731377
Abstract: People with diabetes have an increased risk of life-threatening cardiovascular disease compared to the general population. Furthermore, people with diabetes are at greatly increased risk of not responding to standard anti-platelet therapy, such as aspirin, for the prevention of atherothrombotic events. This phenomenon is often referred to as treatment failure. Those who are at increased risk of such events despite aspirin therapy can be prospectively identified by a variety of laboratory measures of residual on-treatment platelet function, known as aspirin resistance. However, there is little agreement among laboratories on the approaches to these measurements, and insufficient data to guide the clinical management of people with diabetes-associated aspirin resistance if it is prospectively identified. This review provides a critical appraisal of the different approaches to the detection and evidence of mechanisms which contribute to this phenomenon, as well evidence for the potential effectiveness of different clinical approaches to overcoming aspirin treatment failure in diabetes. Potential mechanisms of aspirin resistance in diabetes include elevated platelet turnover that results in an immature platelet fraction able to synthesise the uninhibited therapeutic target of aspirin, cyclooxygenase-1 (COX-1) residual thromboxane production by both COX-1-dependent and COX-1-independent pathways up-regulation of aspirin-insensitive pathways of platelet function, such as adenosine diphosphate signalling and increased underlying atherosclerotic disease burden that results in elevated underlying platelet hyper-reactivity. High on-aspirin platelet reactivity in diabetes may be related to glycemic control. Potential approaches to treatment include controlling modifiable risk factors to achieve effective glycemic control, guided increases in aspirin dose or frequency of administration, or the use of additional antiplatelet therapies. While evidence suggests that altering antiplatelet therapy, particularly by increasing frequency of aspirin administration, can overcome incomplete inhibition of thromboxane synthesis, no clinical studies to date have assessed the effectiveness of these in preventing breakthrough atherothrombosis. While some clinicians currently alter therapy on the basis of theoretical potential benefit of these strategies following identification of aspirin resistance in the laboratory, this is not yet supported by clinical evidence of a benefit, and clear clinical guidelines for the management of aspirin resistance are lacking.
Publisher: Wiley
Date: 30-09-2014
DOI: 10.1111/BJH.13153
Abstract: Platelets are crucial subcellular elements of haemostasis at sites of vascular injury and are also known to be immune mediators in pathological thrombosis. Despite the integral role of platelets in many disease processes, there is very little information available on platelet function and response to agonists in healthy children. We recently reported important differences in the interaction of platelets with monocytes in the circulation, including increased formation of monocyte-platelet aggregates (MPAs) without concomitant increase in P-selectin expression. Our current study investigates parameters of platelet activation (PAC-1 binding and P-selectin expression) and MPA formation in response to a range of physiologically relevant platelet agonists in healthy children compared to healthy adults. All parameters were significantly higher in children in response to sub-maximal concentrations of thrombin receptor activator peptide and adenosine diphosphate, reflecting an age-specific difference in agonist-stimulated platelet reactivity in children. The results of our study challenge the general assumption that platelet reactivity in children is similar to adults. This finding is fundamental to investigating the role of platelets in diseases of childhood and pathogenesis of adult-based diseases that have their origins in childhood. Our findings underscore the need for age-specific reference ranges for platelet function in children rather than extrapolation from adult data.
Publisher: Elsevier BV
Date: 12-2008
DOI: 10.1111/J.1538-7836.2008.03184.X
Abstract: Aspirin 'resistance' is a widely used term for hyporesponsiveness to aspirin in a platelet function test. Serum thromboxane (TX) B(2) is the most specific test of aspirin's effect on platelets. (i) To examine the role of pre-existent platelet hyperreactivity in aspirin 'resistance'. (ii) To determine the correlation between aspirin resistance defined by serum TXB(2) and other assays of platelet function. To enable pre-aspirin s les to be drawn, platelet function was measured in normal subjects (n = 165) before and after aspirin 81 mg daily for seven days. The proportion of the post-aspirin platelet function predicted by the pre-aspirin platelet function was 28.3 +/- 7.5% (mean +/- asymptotic standard error) for serum TXB(2), 39.3 +/- 6.8% for urinary 11-dehydro TXB(2), 4.4 +/- 7.7% for arachidonic acid-induced platelet aggregation, 40.4 +/- 7.1% for adenosine diphosphate-induced platelet aggregation, 26.3 +/- 9.2% for the VerifyNow Aspirin Assay, and 45.0 +/- 10.9% for the TEG PlateletMapping System with arachidonic acid. There was poor agreement between aspirin-resistant subjects identified by serum TXB(2) vs. aspirin-resistant subjects identified by the other five assays, irrespective of whether the analysis was based on categorical or continuous variables. Platelet count correlated with pre-aspirin serum TXB(2) and VerifyNow Aspirin Assay, but not with any post-aspirin platelet function test. (i) Aspirin 'resistance' (i.e. hyporesponsiveness to aspirin in a laboratory test) is in part unrelated to aspirin but is the result of underlying platelet hyperreactivity prior to the institution of aspirin therapy. (ii) Aspirin resistance defined by serum TXB(2) shows a poor correlation with aspirin resistance defined by other commonly used assays.
Publisher: Oxford University Press (OUP)
Date: 25-09-2020
DOI: 10.1002/BJS.12050
Publisher: Elsevier BV
Date: 06-2015
DOI: 10.1016/J.JPROT.2015.04.003
Abstract: Major age-related diseases such as cardiovascular disease and cancer are the primary causes of morbidity and mortality in Australia and worldwide. In our recent study characterising differences in the plasma proteome between healthy children and adults, a large number of proteins differentially expressed with age were found to be of platelet origin. This study aimed to characterise differences in the resting platelet proteome and the platelet releasate of healthy children compared to healthy adults. This study represents the setup of a procedure for the proteomic analysis of platelets from children. Differentially expressed platelet proteins were identified using Two-dimensional Differential In-Gel Electrophoresis and mass spectrometry. Significant differences in the expression of nine proteins (1.1%) in the resting platelet proteome were observed in children compared to adults. Serotransferrin, fibrinogen alpha chain, glyceraldehyde-3 phosphate dehydrogenase, serum albumin, transgelin-2, calponin-2/LIM and SH3 domain protein 1 and human chorionic gonadotropin 2039797 were up-regulated, whereas thrombospondin-1 was down-regulated in children. Eleven proteins (1.5%) were differentially expressed in the platelet releasate of children compared to adults, where transferrin was also upregulated and TSP-1 was down regulated. Identified proteins are involved in processes including tissue and organ development, cell proliferation regulation and angiogenesis. Our results provide novel insights into platelet physiology as well as growth, development and ageing in healthy in iduals. The incidence of major diseases such as cardiovascular disease (CVD) and cancer increase with increasing age and are the major causes of morbidity and mortality both in Australia and worldwide. As the aged population continues to increase dramatically, so too will the financial strains associated with the long term care of the elderly population. Compared to adults, children have a significantly lower incidence of major diseases such as thromboembolic disease. This suggests that children have a protective mechanism against the development of disease. Therefore, studies focussing on the molecular changes of proteins, the machinery of the cell, between children and adults are the key to determining the underlying mechanisms responsible for the onset of major diseases. A well-defined ex le of how protein expression can change with age is that of the plasma proteome. Significant differences in the expression of numerous plasma proteins between healthy children and adults have been recently demonstrated. Interestingly, a large number of differentially expressed proteins were found to be of platelet origin. This finding forms the basis for the current study, presenting as strong evidence for the age-specific differences of the platelet proteome.
Publisher: Frontiers Media SA
Date: 18-09-2019
Publisher: Elsevier BV
Date: 2008
Publisher: Scientific and Academic Publishing
Date: 31-08-2012
Publisher: Frontiers Media SA
Date: 09-10-2020
Publisher: American Physiological Society
Date: 06-2017
DOI: 10.1152/JAPPLPHYSIOL.01057.2016
Abstract: Evidence-based guidelines recommend exercise therapy for patients with chronic heart failure (CHF). Such patients have increased atherothrombotic risk. Exercise can transiently increase platelet activation and reactivity and decrease vascular function in healthy participants, although data in CHF are scant. Eccentric (ECC) cycling is a novel exercise modality that may be particularly suited to patients with CHF, but the acute impacts of ECC cycling on platelet and vascular function are currently unknown. Our null hypothesis was that ECC and concentric (CON) cycling, performed at matched external workloads, would not induce changes in platelet or vascular function in patients with CHF. Eleven patients with heart failure with reduced ejection fraction (HFrEF) took part in discrete bouts of ECC and CON cycling. Before and immediately after exercise, vascular function was assessed by measuring diameter and flow-mediated dilation (FMD) of the brachial artery. Platelet function was measured by the flow cytometric determination of glycoprotein IIb/IIIa activation and granule exocytosis in the presence and absence of platelet agonists. ECC cycling increased baseline artery diameter (pre: 4.0 ± 0.8 mm vs. post: 4.2 ± 0.7 mm P = 0.04) and decreased FMD%. When changes in baseline artery diameter were accounted for, the decrease in FMD post-ECC cycling was no longer significant. No changes were apparent after CON. Neither ECC nor CON cycling resulted in changes to any platelet-function measures (all P 0.05). These results suggest that both ECC and CON cycling, at a moderate intensity and short duration, can be performed by patients with HFrEF without detrimental impacts on vascular or platelet function. NEW & NOTEWORTHY This is the first evidence to indicate that eccentric (ECC) cycling can be performed relatively safely by patients with chronic heart failure (CHF), as it did not result in impaired vascular or platelet function compared with conventional cycling. This is important, as acute exercise can transiently increase atherothrombotic risk, and ECC cycling is a novel exercise modality that may be particularly suited to patients with CHF.
Publisher: Elsevier BV
Date: 11-2010
DOI: 10.1016/J.BIOCEL.2010.07.012
Abstract: Platelets are small, anucleate blood elements of critical importance in cardiovascular disease. The ability of platelets to activate and aggregate to form blood clots in response to endothelial injury, such as plaque rupture, is well established. These cells are therefore important contributors to ischaemia in atherothrombosis, and antiplatelet therapy is effective for this reason. However, growing evidence suggests that platelets are also important mediators of inflammation and play a central role in atherogenesis itself. Interactions between activated platelets, leukocytes and endothelial cells trigger autocrine and paracrine activation signals, resulting in leukocyte recruitment at and into the vascular wall. Direct physical interaction may contribute also, through platelet adhesion molecules assisting localization of monocytes to the site of atherogenesis and platelet granule release contributing to the chronic inflammatory milieu which leads to foam cell development and accelerated atherogenesis. Recent studies have shown that antiplatelet therapy in animal models of accelerated atherogenesis can lead to decreased plaque size and improve plaque stability. This review examines the complexity of platelet function and the nature of interactions between activated platelets, leukocytes and endothelial cells. We focus on the growing body of evidence that platelets play a critical role in atherogenesis and contribute to progression of atherosclerosis.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 23-01-2007
Publisher: SAGE Publications
Date: 12-03-2014
Abstract: Diabetes is associated with increased cardiovascular risk. We have recently shown that the naturally occurring flavonol quercetin (Que) or the synthetic flavonol 3′,4′-dihydroxyflavonol (DiOHF) inhibits platelet function and delays thrombus formation in healthy mice. Therefore, the aim of this study was to investigate the effect of Que or DiOHF treatment on platelet function and ferric chloride–induced carotid artery thrombosis in a mouse model of type 1 diabetes. Diabetic mice treated with Que or DiOHF maintained blood flow at a significantly higher level than untreated diabetic mice at the end of the recording period. In addition, treatment with Que or DiOHF significantly reduced diabetes-induced platelet hyper-aggregability in response to platelet agonist stimulation. Furthermore, treatment with Que or DiOHF significantly inhibited dense, but not alpha, granule exocytosis in diabetic and control mice. Our demonstration that flavonols delay thrombus formation in diabetes suggests a potential clinical role for these compounds in anti-platelet therapy.
Publisher: Springer Science and Business Media LLC
Date: 05-12-2012
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-01-2022
DOI: 10.1097/CCM.0000000000005435
Abstract: To investigate platelet pathophysiology associated with pediatric extracorporeal membrane oxygenation (ECMO). Prospective observational study of neonatal and pediatric ECMO patients from September 1, 2016, to December 31, 2019. The PICU in a large tertiary referral pediatric ECMO center. Eighty-seven neonates and children ( 18 yr) supported by ECMO. None. Arterial blood s les were collected on days 1, 2, and 5 of ECMO and were analyzed by whole blood flow cytometry. Corresponding clinical data for each patient was also recorded. A total of 87 patients were recruited (median age, 65 d interquartile range [IQR], 7 d to 4 yr). The median duration of ECMO was 5 days (IQR, 3–8 d) with a median length of stay in PICU and hospital of 18 days (IQR, 10–29 d) and 35 days (IQR, 19–75 d), respectively. Forty-two patients (48%) had at least one major bleed according to a priori determined definitions, and 12 patients (14%) had at least one thrombotic event during ECMO. Platelet fibrinogen receptor expression decreased (median fluorescence intensity [MFI], 29,256 vs 26,544 p = 0.0005), while von Willebrand Factor expression increased (MFI: 7,620 vs 8,829 p = 0.0459) from day 2 to day 5 of ECMO. Platelet response to agonist, Thrombin Receptor Activator Peptide 6, also decreased from day 2 to day 5 of ECMO, as measured by binding with anti-P-selectin, PAC-1 (binds activated GPIIb/IIIa), and anti-CD63 monoclonal antibodies (P-selectin area under the curve [AUC]: 63.46 vs 42.82, respectively, p = 0.0022 PAC-1 AUC: 93.75 vs 74.46, p = 0.0191 CD63 AUC: 55.69 vs 41.76, p = 0.0020). The loss of platelet response over time may contribute to bleeding during ECMO. These novel insights may be useful in understanding mechanisms of bleeding in pediatric ECMO and monitoring platelet markers clinically could allow for prediction or early detection of bleeding and thrombosis.
Publisher: Informa UK Limited
Date: 05-01-2022
DOI: 10.1080/09537104.2021.1981849
Abstract: Burn injuries are common and often life-threatening trauma. With this trauma comes an interruption of normal hemostasis, with distinct impacts on platelets. Our interest in the relationships between burn injury and platelet function stems from two key perspectives: platelet function is a vital component of acute responses to injury, and furthermore the incidence of cardiovascular disease (CVD) is higher in burn survivors compared to the general population. This review explores the impact of burn injury on coagulation, platelet function, and the participation of platelets in immunopathology. Potential avenues of further research are explored, and consideration is given to what therapies may be appropriate for mediating post-burn thrombopathology.
Publisher: Georg Thieme Verlag KG
Date: 2007
DOI: 10.1160/TH07-01-0010
Abstract: The novel thienopyridine prodrug prasugrel, a platelet P2Y12 ADP receptor antagonist, requires in vivo metabolism for activity. Although pharmacological data have been collected on the effects of prasugrel on platelet aggregation,there are few data on the direct effects of the prasugrel’s active metabolite, R-138727, on other aspects of platelet function. Here we examined the effects of R-138727 on thrombo-inflammatory markers of platelet activation, and the possible modulatory effects of other blood cells, calcium, and aspirin. Blood (PPACK or citrate anticoagulated) from healthy donors pre- and post-aspirin was incubated with R-138727 and the response to ADP assessed in whole blood or platelet-rich plasma (PRP) by aggregometry and flow cytometric analysis of leukocyte-platelet aggregates,platelet surface P-selectin, and GPIIb-IIIa activation. Low-micromolar concentrations of R-138727 resulted in a rapid and consistent in-hibition of these ADP-stimulated thrombo-inflammatory markers.These rapid kinetics required physiological calcium levels, but were largely unaffected by aspirin. Lower IC50 values in whole blood relative to PRP suggested that other blood cells affect ADP-induced platelet activation and hence the net inhibition by R-138727. R-138727 did not inhibit P2Y12-mediated ADP-induced shape change, even at concentrations that completely inhibited platelet aggregation, confirming the specificity of R-138727 for P2Y12. In conclusion, R-138727, the active metabolite of prasugrel, results in rapid, potent, consistent, and selective inhibition of P2Y12-mediated up-regulation of thromboinflammatory markers of platelet activation.This inhibition is enhanced in the presence other blood cells and calcium,but not aspirin.
Publisher: Elsevier BV
Date: 12-2006
DOI: 10.1111/J.1538-7836.2006.02228.X
Abstract: Previous studies have shown that ischemic preconditioning (PC) not only limits infarct size, but also improves arterial patency in models of recurrent thrombosis. We hypothesize that this enhanced patency is presumably because of a PC-induced attenuation of platelet-mediated thrombosis. However, there is, at present, no direct evidence that PC acts on the platelets per se and favorably down-regulates platelet reactivity. Our goal was to test the concept that PC ischemia attenuates molecular indices of platelet activation-aggregation. Anesthetized dogs were randomly assigned to receive 10 min of PC ischemia followed by 10 min of reperfusion or a time-matched control period. Spontaneous recurrent coronary thrombosis was then initiated in all dogs by injury + stenosis of the left anterior descending coronary artery. Coronary flow was monitored for 3 h poststenosis, and molecular indices of platelet activation-aggregation were quantified by whole blood flow cytometry. Coronary patency was, as expected, better-maintained following injury + stenosis in the PC group vs. controls (53% +/- 5%* vs. 23% +/- 5% of baseline flow, respectively *P < 0.05). Moreover, PC was accompanied by: (i) a significant down-regulation of platelet-fibrinogen binding and formation of neutrophil-platelet aggregates (112% +/- 14%* vs. 177% +/- 21% and 107% +/- 8%* vs. 155% +/- 19% of baseline values in PC vs. control groups) and (ii) a trend towards a reduction in platelet P-selectin expression (148% +/- 12% vs. 190% +/- 21% of baseline *P < 0.05 and P = 0.09 vs. control). These data provide novel, direct evidence in support of the concept that ischemic PC attenuates molecular indices of platelet activation-aggregation.
Publisher: Wiley
Date: 19-08-2020
DOI: 10.1111/BJH.16152
Publisher: Informa UK Limited
Date: 18-12-2012
DOI: 10.3109/09537104.2012.749396
Abstract: Flavonols are polyphenolic compounds with broad-spectrum kinase inhibitory, as well as potent anti-oxidant and anti-inflammatory properties. Anti-platelet potential of quercetin (Que) and several related flavonoids have been reported however, few studies have assessed the ability of flavonols to inhibit exocytosis of different platelet granules or to inhibit thrombus formation in vivo. 3',4'-Dihydroxyflavonol (DiOHF) is a flavonol which is structurally related to Que and has been shown to have greater anti-oxidant capacity and to improve the endothelial function in the context of diabetes and ischaemia/reperfusion injury. While the structural similarity to Que suggests DiOHF may have a potential to inhibit platelet function, no studies have assessed the anti-platelet potential of DiOHF. We therefore investigated platelet granule inhibition and potential to delay arterial thrombosis by Que and DiOHF. Both Que and DiOHF showed inhibition of collagen, adenosine diphosphate and arachidonic acid stimulated platelet aggregation, agonist-induced GPIIb/IIIa activation as demonstrated by PAC-1 and fibrinogen binding. While both flavonols inhibited agonist-induced granule exocytosis, greater inhibition of dense granule exocytosis occurred with DiOHF as measured by both ATP release and flow cytometry. In contrast, while Que inhibited agonist-induced P-selectin expression, as measured by both platelet surface P-selectin expression and upregulation of surface GPIIIa expression, inhibition by DiOHF was not significant for either parameter. C57BL/6 mice treated with 6 mg kg(-1) IV Que or DiOHF maintained greater blood flow following FeCl3-induced carotid artery injury when compared to the vehicle control. We provide evidence that Que and DiOHF improve blood flow following arterial injury in part by attenuating platelet granule exocytosis.
Publisher: Elsevier BV
Date: 2007
DOI: 10.1016/J.THROMRES.2007.04.004
Abstract: We have previously demonstrated platelet hyperreactivity in cystic fibrosis (CF) patients. Carriers of one CF mutation (heterozygotes) have been shown to have abnormalities related to the presence of only one-half the normal amount of CF transmembrane conductance regulator protein. Platelet hyperreactivity in CF heterozygotes would be an important cardiovascular risk factor, since approximately 1 in 25 Caucasians is a CF carrier. We used highly sensitive assays of platelet activation to assess the difference between 16 CF heterozygotes and 16 age- and sex-matched healthy controls without CF mutations. We found no difference in platelet activation between CF heterozygotes and controls. The 50% reduction in the CF transmembrane conductance regulator protein in heterozygotes is insufficient to cause platelet activation.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 22-12-2009
DOI: 10.1161/CIRCULATIONAHA.109.900589
Abstract: Background— Poor clinical outcome in aspirin-treated patients has been termed aspirin resistance and may result from inadequate inhibition of platelet cyclooxygenase-1 (COX-1) by aspirin. The objectives of this study were to determine prospectively whether COX-1-dependent and other platelet function assays correlate with clinical outcomes in aspirin-treated patients. Methods and Results— Blood was collected before percutaneous coronary intervention from 700 consecutive aspirin-treated (81 or 325 mg for ≥3 days) patients. Platelet function was tested by (1) serum thromboxane B 2 (2) arachidonic acid-stimulated platelet surface P-selectin and activated glycoprotein IIb/IIIa and leukocyte-platelet aggregates and (3) platelet function analyzer (PFA)-100 collagen-epinephrine and collagen-ADP closure time (CT). Adverse clinical outcomes of all-cause death, cardiovascular death, and major adverse cardiovascular events (cardiovascular death, myocardial infarction, hospitalization for revascularization, or acute coronary syndrome) were assessed by telephone interview and/or medical record review. Clinical outcomes information was obtained at 24.8±0.3 months after platelet function testing. By univariate analysis, COX-1-dependent assays, including serum thromboxane B 2 level, were not associated with adverse clinical outcomes, whereas the COX-1-independent assay, PFA-100 collagen-ADP CT seconds, was associated with major adverse cardiovascular events ( P =0.0149). After adjustment for covariables (including sex, aspirin dose, Thrombolysis in Myocardial Infarction risk score, clopidogrel use), both serum thromboxane B 2 .1 ng/mL and PFA-100 collagen-ADP CT seconds were associated with major adverse cardiovascular events. In contrast, indirect measures of platelet COX-1 (arachidonic acid-stimulated platelet markers, shortened PFA-100 collagen-epinephrine CT) were not significantly associated with adverse clinical outcomes even after adjustment for covariables. Conclusions— In this prospective study of 700 aspirin-treated patients presenting for angiographic evaluation of coronary artery disease, residual platelet COX-1 function measured by serum thromboxane B 2 and COX-1-independent platelet function measured by PFA-100 collagen-ADP CT, but not indirect COX-1-dependent assays (arachidonic acid-stimulated platelet markers, shortened PFA-100 collagen-epinephrine CT), correlate with subsequent major adverse cardiovascular events. This study suggests that multiple mechanisms, including but not confined to inadequate inhibition of COX-1, are responsible for poor clinical outcomes in aspirin-treated patients, and therefore the term aspirin resistance is inappropriate.
Publisher: SAGE Publications
Date: 12-2001
DOI: 10.1177/026765910101600607
Abstract: It has been suggested that aprotinin results in significantly increased risk for perioperative thrombotic complications in patients with Factor V LEIDEN (F5L) due to its ability to competitively inhibit activated protein C (APC) function in vitro. No clinical studies have been performed to assess the effect of aprotinin on APC function of F5L in vivo. We developed an ex vivo model to mimic the effects of cardiopulmonary bypass with the exclusion of the patient in order to assess APC function. Blood from normal ( n = 2) and F5L heterozygous donors ( n = 2) was treated with aprotinin or placebo (saline). The blood was heparinized, added to the prime and circulated at 2 l/min through a modified cardiopulmonary bypass circuit. After 60 min of circulation, the heparin was neutralized with protamine sulfate. Blood s les, drawn at specific time points, were analysed for APC ratio. Results showed a decrease in APC ratio for both F5L and normal bloods with the addition of aprotinin (18% and 40%, respectively). APC ratios also decreased with the commencement of extracorporeal circulation for all bloods, resulting in an APC ratio of 1.35 in normal placebo-treated blood and 0.67 in F5L placebo-treated blood. The combined effect of aprotinin and extracorporeal circulation resulted in APC ratios of 0.90 for normal blood and 0.63 for F5L blood, corresponding to a severe dysfunction of APC intraoperatively (reference range 1.9-4.0). The data from this model predict an increased risk of perioperative thrombosis due to inhibition of APC function in cardiac surgical patients heterozygous for the F5L mutation. Aprotinin further compounds the severity of APC dysfunction, though the effect is more severe in normal blood. The ex vivo model employed was an effective tool for the investigation of the haemostatic effect of aprotinin. This model may be exploited for other applications such as the investigation of novel or emerging haemostatic agents prior to clinical trial.
Publisher: Humana Press
Date: 2006
Publisher: SAGE Publications
Date: 02-09-2014
Abstract: A single bout of strenuous running exercise results in perturbations to numerous biomarkers. An understanding of these is important when analysing s les from in iduals who have recently performed such exercise. A literature search was undertaken using the search terms, exercise, marathon and delayed onset of muscle soreness. The search was then refined using the terms for key biomarkers known to be altered by exercise. The magnitude of changes to biomarkers is proportional to the severity of the running bout. Familiar, moderate intensity running exercise produces brief transient changes in common biomarkers such as lactate, whereas more severe bouts of running exercise, such as marathons and ultra-marathon events can produce changes to biomarkers that are normally associated with pathology of the muscles, liver and heart. Ex les being changes to concentrations and/or activity of myoglobin, leucocytes, creatine kinase, bilirubin, cardiac troponins, lactate dehydrogenase, alanine aminotransferase and aspartate aminotransferase. While persisting for longer, these changes are also transient and full recovery occurs within days, without any apparent long-term adverse consequences. Additionally, unfamiliar exercise involving forceful eccentric muscle contractions, such as running downhill, can cause increases in creatine kinase and delayed onset of muscle soreness that peaks 36–72 h after the exercise bout. Strenuous running exercise can produce changes to biomarkers that are normally associated with disease and injury, but these do not necessarily reflect chronic pathology.
Publisher: Humana Press
Date: 2013
DOI: 10.1007/978-1-62703-339-8_18
Abstract: Flow cytometry is a powerful and versatile tool which can be used to provide substantial phenotypic data on platelets by yielding quantitative information of their physical and antigenic properties. This includes surface expression of functional receptors, bound ligands, expression of granule components, interaction of platelets with other platelets via aggregation, or interaction with other blood components, such as leukocytes or the plasma coagulation system. Quantitative assessment of these parameters may facilitate the diagnosis of inherited or acquired platelet disorders, assist in the diagnosis of diseases associated with platelet activation, or assist in the monitoring of safety and efficacy of antiplatelet therapy.
Publisher: Frontiers Media SA
Date: 21-07-2020
Publisher: Springer Science and Business Media LLC
Date: 06-2004
Publisher: Springer Science and Business Media LLC
Date: 12-2003
Publisher: Elsevier BV
Date: 10-2014
DOI: 10.1016/J.ANIREPROSCI.2014.07.014
Abstract: We tested whether the quality of spermatozoa from mature male sheep would be affected during nutrition-induced changes in testicular mass. Merino rams were fed for 65 days with diets that increased, maintained or decreased body and testis mass (n=8 per group). In semen collected on Days 56 and 63, underfed rams had less sperms per ejaculate than well-fed rams (P<0.05) and a lower sperm velocity (computer-assisted semen analysis) than well-fed or maintenance-fed rams (P<0.05). Sperm chromatin structure assay revealed more sperm DNA damage in underfed rams than in well-fed rams (P<0.05). The amount of sperm DNA damage was inversely correlated with change in scrotal circumference (r=-0.6, P<0.05), the percentages of progressive motile sperm (r=-0.8 P<0.01) and motile sperm (r=-0.6, P<0.05), and the numbers of sperms per gram of testis (r=-0.55, P<0.05). In testicular tissue collected on Day 65, underfed rams had fewer sperm per gram of testis than rams in the other two groups (P<0.001). We conclude that, in adult rams, underfeeding reduces spermatogenic efficiency and that this response is associated with a reduction in spermatozoal quality.
Publisher: Elsevier BV
Date: 04-2007
DOI: 10.1111/J.1538-7836.2007.02462.X
Abstract: To determine whether indices of platelet activation are associated with the stability of coronary artery disease (CAD). Platelet function was examined in 677 consecutive aspirin-treated patients presenting for cardiac catheterization. Patients were grouped into recent myocardial infarction (MI), no MI but angiographically documented CAD (non-MI CAD) and no angiographically detectible CAD (no CAD), as well as additional subgroups. Compared with non-MI CAD or no CAD patients, more patients with recent MI had a shortened platelet function analyzer (PFA)-100 collagen-epinephrine closure time (CT) and increased circulating monocyte-platelet aggregates, neutrophil-platelet aggregates, activated platelet surface GPIIb-IIIa and plasma soluble CD40 ligand (sCD40L). More patients with non-MI CAD had shortened PFA-100 CTs and increased monocyte-platelet aggregates compared with patients with no CAD. Platelet surface P-selectin did not differ among the groups. Subgroup analysis revealed that decreasing PFA-100 CT correlated with the stability of CAD. Indices of platelet activation, especially the PFA-100 CT, are associated with the stability of CAD, and may reflect plaque instability, an ongoing thrombotic state and/or reduced responsiveness to aspirin.
Publisher: Wiley
Date: 05-2017
DOI: 10.14814/PHY2.13189
Publisher: Elsevier BV
Date: 09-2019
Publisher: Springer Science and Business Media LLC
Date: 16-10-2012
DOI: 10.1007/S11239-012-0827-2
Abstract: Flavonols are polyphenolic compounds with reported cardiovascular benefits and have been shown to exhibit antiplatelet properties in vitro. While some studies have shown inhibition of platelet aggregation following dietary supplementation with flavonol rich foods, few studies have assessed the ability of flavonols to inhibit platelet mediated thrombus generation in vivo. Furthermore, the duration of benefit and the influence of different dosing regimens remain unclear. In this study we investigate the ability of two structurally related flavonols quercetin (Que) and 3',4'-dihydroxyflavonol (DiOHF) to inhibit platelet aggregation, platelet granule exocytosis and vessel occlusion in a well characterized mouse model of platelet mediated arterial thrombosis. We investigated the effect of a single 6 mg/kg intravenous bolus and daily 6 mg/kg intraperitoneal doses over seven consecutive days. Carotid artery blood flow after injury was better maintained in mice treated with both Que and DiOHF when compared to the vehicle for both dosage regimens. This improved blood flow corresponded to inhibition of platelet aggregation and platelet dense granule exocytosis following chemical stimulation of PAR4. We therefore provide evidence of inhibition of platelet-mediated arterial thrombosis by flavonols in vivo, and demonstrate that this effect persists for at least 24 h after the last intraperitoneal dose. These data suggest a potential clinical role for flavonols as anti-platelet therapy.
Publisher: Georg Thieme Verlag KG
Date: 19-12-2018
Abstract: Antiplatelet agents are used for the prevention and treatment of thromboembolic disease in an increasingly complex population of pediatric patients. Despite their importance for clinical outcome, there is no consensus on the most effective monitoring strategies. This review describes the current state of knowledge focusing on antiplatelet therapy monitoring in children. The authors searched five databases (PubMed-NCBI, MEDLINE-OVID, SCOPUS-Elsevier, ScienceDirect, and Cochrane) from January 2000 to October 2017 using keywords selected a priori. Identified articles were sorted according to the antiplatelet agents administered, methods of antiplatelet monitoring, and outcome measures. Twenty studies were included, with 14 cohort studies, 3 randomized controlled trials, and 3 cross-sectional studies. Eleven different antiplatelet monitoring tools were used, with the most common being Light Transmission Aggregometry, Urinary Thromboxane, Thromboelastography with Platelet Mapping, and VerifyNow. In the majority of studies, antiplatelet therapy monitoring was used to describe adequacy or responsiveness to treatment based on laboratory cut-off values, which were not uniform and sourced from adult studies or extrapolated from test manuals. Several studies evaluated monitoring related to clinical outcome or adjusted therapy to reach predefined therapeutic targets. There was no single laboratory method found to be distinctly better for monitoring antiplatelet treatment. Associations between laboratory assays and clinical outcomes or assays and gold standard measurements were highly inconsistent. The current literature lacks consensus on clinical benefits and measurable effects of monitoring antiplatelet therapy in pediatric patients. This review highlights important areas for research required to determine the value of antiplatelet therapy monitoring in children.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 05-01-2023
DOI: 10.1097/PCC.0000000000003152
Abstract: To investigate changes in von Willebrand factor (VWF) concentration, function, and multimers during pediatric extracorporeal membrane oxygenation (ECMO) and determine whether routine monitoring of VWF during ECMO would be useful in predicting bleeding. Prospective observational study of pediatric ECMO patients from April 2017 to May 2019. The PICU in a large, tertiary referral pediatric ECMO center. Twenty-five neonates and children ( 18 yr) supported by venoarterial ECMO. None. Arterial blood s les were collected within 24 hours pre-ECMO, daily for the first 5 days of ECMO, every second day until decannulation, and 24 hours post-ECMO. The STA R Max analyzer was used to measure VWF antigen (VWF:Ag) and ristocetin cofactor (VWF:RCo) activity. VWF collagen binding (VWF:CB) was measured using an enzyme-linked immunosorbent assay. VWF multimers were measured using the semi-automated Hydragel 11 VWF Multimer assay. Corresponding clinical data for each patient was also recorded. A total of 25 venoarterial ECMO patients were recruited (median age, 73 d interquartile range [IQR], 3 d to 1 yr). The median ECMO duration was 4 days (IQR, 3–8 d) and 15 patients had at least one major bleed during ECMO. The percentage of high molecular weight multimers (HMWM) decreased and intermediate molecular weight multimers increased while patients were on ECMO, irrespective of a bleeding status. VWF:Ag increased and the VWF:RCo/VWF:Ag and VWF:CB/VWF:Ag ratios decreased while patients were on ECMO compared with the baseline pre-ECMO s les and healthy children. Neonates and children on ECMO exhibited a loss of HMWM and lower VWF:CB/VWF:Ag and VWF:RCo/VWF:Ag ratios compared with healthy children, irrespective of major bleeding occurring. Therefore, monitoring VWF during ECMO would not be useful in predicting bleeding in these patients and changes to other hemostatic factors should be investigated to further understand bleeding during ECMO.
Publisher: American Physiological Society
Date: 08-2018
DOI: 10.1152/JAPPLPHYSIOL.00079.2018
Abstract: Platelet activation, including the formation of monocyte platelet aggregates (MPAs), contributes to atherosclerosis, thrombus formation, and acute coronary syndromes. Regular participation in exercise can lower cardiovascular risk, but little is known regarding the impact of exercise training on platelet function. We investigated the effect of 6 mo of walking exercise on platelet function in sedentary older adults without significant cardiovascular disease. Twenty-seven participants were randomly allocated to 6 mo of either: no-exercise ( n = 13) or 3 × 50 min/wk of supervised center-based walking ( n = 14). Circulating and agonist-induced MPAs were assessed using flow cytometry before [ month 0 (0M)] and after [ month 6 (6M)] the intervention. Circulating MPAs increased from 0M (3.7 ± 1.0%) to 6M (4.7 ± 1.6%) in the no-exercise group ( P = 0.009), whereas a nonsignificant decrease was observed in the walking group (0M 4.3 ± 1.7 vs. 6M 3.7 ± 1.2 %, P = 0.052). The change in MPAs between groups was significant ( P = 0.001). There were no differences between groups in platelet responses to agonists across the interventions (all P 0.05). Collectively, these data suggest that the absence of regular exercise may increase MPAs, which are cellular mediators involved in atherosclerosis, while regular walking inhibits such increases. The thrombotic function of platelets appears to be relatively unaltered by exercise training. This study provides novel data related to the cardioprotective effects associated with participation in exercise. NEW & NOTEWORTHY Monocyte-platelet aggregates contribute to atherosclerosis and exercise can lower cardiovascular risk. This is the first study to discover that a lack of regular physical activity is associated with increased monocyte-platelet aggregates over a 6-mo intervention period. In contrast, walking exercise inhibits increased monocyte-platelet aggregates in the circulation. This study highlights a novel pathway by which regular participation in exercise exerts its cardioprotective effects.
Publisher: Elsevier BV
Date: 2007
DOI: 10.1111/J.1538-7836.2006.02234.X
Abstract: Clopidogrel is a widely used antithrombotic agent that inhibits the platelet P2Y(12) adenosine diphosphate (ADP) receptor. There is increasing interest in 'clopidogrel resistance'. To determine whether 'clopidogrel resistance' is accounted for by a pre-existent variability in platelet response to ADP. Platelet response to 20 microm ADP was analyzed by four independent whole blood flow cytometric assays: platelet surface activated GPIIb-IIIa, platelet surface P-selectin, monocyte-platelet aggregates and neutrophil-platelet aggregates. In 25 consecutive, non-aspirin-treated healthy subjects, we studied platelet response before and after clopidogrel administration. In addition, we studied the platelet response in 613 consecutive aspirinated patients with or without coronary artery disease (CAD, as determined by angiography) who had or had not been treated with clopidogrel. In these patients, we tested for homogeneity of variance across all durations of clopidogrel exposure and severity of CAD by estimating the 'goodness of fit' of two independent models. In the healthy subjects, pre-clopidogrel response to ADP predicted post-clopidogrel response to ADP. In the patients, clopidogrel, as expected, inhibited the platelet response to ADP. However, irrespective of the duration of clopidogrel administration, the severity of CAD, and the dose of aspirin, clopidogrel did not increase the variance in the platelet response to ADP in any of the four assays of platelet response. These studies provide evidence that 'clopidogrel resistance' is accounted for by a pre-existent variability in platelet response to ADP and this variability is not increased by clopidogrel administration.
Publisher: Informa UK Limited
Date: 15-06-2022
Publisher: Georg Thieme Verlag KG
Date: 10-2004
Abstract: Flow cytometry is a powerful and versatile tool that can be used to yield definitive information regarding the phenotypic status of platelets. The method provides a quantitative assessment of the physical and antigenic properties of platelets (e.g., surface expression of receptors, bound ligands, components of granules, or interactions of platelets with other platelets, other blood cells, or components of the plasma coagulation system), thereby facilitating the diagnosis of inherited or acquired platelet disorders (e.g., Bernard-Soulier syndrome, Glanzmann thrombasthenia, storage pool disease), the pathological activation of platelets (e.g., in the setting of acute coronary syndromes, cerebrovascular ischemia, peripheral vascular disease, cardiopulmonary bypass), and changes in the ability of platelets to activate via specific stimuli (e.g., efficacy of antiplatelet therapies). Accordingly, this review summarizes the key technical and methodologic components of flow cytometric analysis of platelets, as well as specific ex les of its application to diagnosis and patient care.
Publisher: Elsevier BV
Date: 11-2023
Publisher: Elsevier BV
Date: 05-2017
DOI: 10.1016/J.MARPOLBUL.2017.02.006
Abstract: Polycyclic aromatic hydrocarbons are very important components of oil pollution. These pollutants tend to sorb to cell surfaces, exerting toxic effects on organisms. Our study developed a flow cytometric method for the detection of PAHs sorbed to phytoplankton by exploiting their spectral characteristics. We discriminated between cells with PAHs from cells free of PAHs. Clear discrimination was observed with flow cytometer provided with 375 or 405nm lasers in addition to the standard 488nm laser necessary to identify phytoplankton. Using this method, we measured the relationship between the percentages of phytoplankton organisms with PAHs, with the decrease in the growth rate. Moreover, the development of this method could be extended to facilitate the study of PAHs impact on cell cultures from a large variety of organisms.
Publisher: Springer Science and Business Media LLC
Date: 16-10-2015
DOI: 10.1038/SREP15321
Abstract: All cells are covered by glycans, an in idually unique layer of oligo- and polysaccharides that are critical moderators of self-recognition and other cellular-level interactions (e.g. fertilization). The functional similarity between these processes suggests that gamete surface glycans may also have an important, but currently overlooked, role in sexual selection. Here we develop a user-friendly methodological approach designed to facilitate future tests of this possibility. Our proposed method is based on flow cytometric quantification of female-induced sperm acrosome reaction and sperm surface glycan modifications in the Mediterranean mussel Mytilus galloprovincialis . In this species, as with many other taxa, eggs release water-soluble factors that attract conspecific sperm (chemoattraction) and promote potentially measurable changes in sperm behavior and physiology. We demonstrate that flow cytometry is able to identify sperm from other seawater particles as well as accurately measure both acrosome reaction and structural modifications in sperm glycans. This methodological approach can increase our understanding of chemically-moderated gamete-level interactions and in idual-specific gamete recognition in Mytilus sp. and other taxa with similar, easily identifiable acrosome structure. Our approach is also likely to be applicable to several other species, since carbohydrate-mediated cellular-level interactions between gametes are universal among externally and internally fertilizing species.
Publisher: Elsevier BV
Date: 02-2005
DOI: 10.1111/J.1538-7836.2005.01124.X
Abstract: To investigate the effects of abciximab, eptifibatide and no GPIIb-IIIa antagonist (control) on soluble CD40 ligand (sCD40L) and the formation of leukocyte-platelet aggregates (LPA) in 98 ACS patients undergoing percutaneous coronary intervention (PCI). sCD40L and LPA are increased in patients with ACS. sCD40L was measured by enzyme-linked immunosorbent assay (ELISA) and LPA by whole blood flow cytometry. There were no baseline differences between the three groups in sCD40L and LPA. At the end of PCI, sCD40L was unchanged in the controls, decreased by 30% (P < 0.001) in the abciximab group and by 11% (P < 0.02) in the eptifibatide group. Eighteen to 24 h after PCI, sCD40L was unchanged in the controls, reduced 30% (P < 0.001) in the abciximab-treated group and 9% (P < 0.01) in the eptifibatide-treated group. At the end of PCI, circulating monocyte-platelet aggregates (MPA) were reduced by 12% (P = NS) in the abciximab-treated group, 13% in the eptifibatide-treated group (P = NS), but slightly increased in the controls (P = NS). Eighteen to 24 h after PCI, MPA were reduced by 41% (P < 0.001) compared to baseline in the abciximab-treated group, by 23% (P = NS) in the eptifibatide-treated group, and 15% (P = NS) in the controls. In contrast to control patients presenting while on clopidogrel, control patients presenting not on clopidogrel demonstrated a reduction in sCD40L and LPA 18-24 h post-PCI (P = NS). At low receptor occupancy, GPIIb-IIIa antagonists did not augment the release of sCD40L or the number of circulating LPA. GPIIb-IIIa antagonists reduce circulating sCD40L and LPA formation in patients with ACS undergoing PCI. At low receptor occupancy, GPIIb-IIIa antagonists do not activate platelets.
Publisher: Humana Press
Date: 2013
DOI: 10.1007/978-1-62703-339-8_2
Abstract: Platelets are cell fragments which circulate in blood. They are of pivotal importance in blood clot formation, affecting thrombosis and haemostasis. By rapidly altering the activation and expression of surface receptors, platelets are able to quickly undergo structural and phenotypic changes in response to stimulation, such as collagen exposure on injured vascular endothelium. This response to stimulation allows platelets to become adhesive, aggregate to form a thrombus, and release a variety of mediators affecting coagulation, inflammation, and chemotaxis at the site of injury. Therefore, in addition to their critical role in thrombosis and haemostasis, platelets also play a role in immunity, inflammation, wound healing, haematologic malignancies, and metabolic disorders. The role of platelets in disease, particularly in atherothrombosis, is increasingly the focus of current research and antiplatelet therapy plays a significant role in the prevention and treatment of atherothrombotic and inflammatory diseases.
Publisher: Elsevier BV
Date: 02-2008
DOI: 10.1111/J.1538-7836.2007.02838.X
Abstract: Prasugrel is a novel antiplatelet prodrug of the same thienopyridine class as clopidogrel and ticlopidine. Metabolism of prasugrel generates the active metabolite R-138727, an antagonist of the platelet P2Y(12) adenosine diphosphate (ADP) receptor, leading to inhibition of ADP-mediated platelet activation and aggregation. ADP also enhances the platelet response to collagen, and these two agonists contribute to the generation of platelet procoagulant activity. We therefore examined whether R-138727 inhibits ADP- and collagen-triggered platelet procoagulant activities. As shown by whole blood flow cytometry, R-138727 inhibited surface phosphatidylserine expression on ADP plus collagen-stimulated platelets and tissue factor (TF) expression on ADP-, collagen-, and ADP plus collagen-stimulated monocyte-platelet aggregates. R-138727 reduced monocyte-platelet aggregate formation, thereby further inhibiting TF expression. ADP, collagen, and ADP plus collagen accelerated the kinetics of thrombin generation in recalcified whole blood and R-138727 significantly inhibited this acceleration. Clot strength in a modified thromboelastograph system was also inhibited by R-138727 (IC50 0.7 +/- 0.1 microM). In addition to its previously known inhibitory effects on platelet activation and aggregation, the active metabolite of prasugrel, R-138727, inhibits platelet procoagulant activity in whole blood (as determined by phosphatidylserine expression on platelets and TF expression on monocyte-platelet aggregates), resulting in the functional consequences of delayed thrombin generation and impaired clot development.
Publisher: Wiley
Date: 06-2021
DOI: 10.1002/CPZ1.178
Abstract: Platelets are small but very abundant blood cells that play a key role in hemostasis, contributing to thrombus formation at sites of injury. The ability of platelets to perform this function, as well as functions in immunity and inflammation, is dependent on the presence of cell surface glycoproteins and changes in their quantity and conformation after platelet stimulation. In this article, we describe the characterization of platelet surface markers and platelet function using platelet‐specific fluorescent probes and flow cytometry. Unlike traditional platelet tests, immunophenotypic analysis of platelets by flow cytometry allows the analysis of platelet function in s les with very low platelet counts as often encountered in clinical situations. © 2021 Wiley Periodicals LLC. Basic Protocol 1 : Immunophenotyping of platelet surface receptors Alternate Protocol : Fix‐first method for immunophenotyping of platelet surface receptors Basic Protocol 2 : Determination of platelet activation using P‐selectin expression and/or PAC1 binding Basic Protocol 3 : Determination of procoagulant platelets using annexin V binding or antibodies specific for coagulation factor V/Va or X/Xa Support Protocol : Preparation of isolated platelets
Publisher: Wiley
Date: 16-12-2015
DOI: 10.1002/CYTO.A.22587
Abstract: Platelets are subcellular blood elements with a well-established role in haemostasis. Upon activation platelets express P-Selectin (CD62P) on the cell membrane and bind to P-Selectin glycoprotein ligand 1 expressing monocytes, influencing them toward a pro-adhesive and inflammatory phenotype. It is well established that elevated circulating monocyte-platelet aggregates (MPAs) are linked to atherothrombosis in high risk patients. However, whole blood flow cytometry (FCM) has recently shown that circulating MPAs may also occur in the absence of platelet activation, particularly in healthy children. A potential limitation of conventional FCM is the potential for coincident events to resemble monocyte platelet aggregates. Here we report a novel imaging cytometry approach to further characterize monocyte-platelet aggregate formation by P-Selectin dependent and P-Selectin independent mechanisms and distinguish circulating MPAs from coincidental events. Monocytes were identified by expression of the lipopolysachharide receptor (CD14 BV421), while platelets were identified by expression of the glycoprotein Ib (CD42b APC). Differentiation of P-Selectin dependent and P-Selectin independent binding was achieved with AF488 labeled CD62P. Overall analysis of circulating and in vitro generated MPAs by conventional and imaging cytometry methods showed very strong correlation (r(2) = >0.99, P < 0.01). The Bland-Altman bias of -1.72 was not significantly different to zero. However, when measuring only P-Selectin negative MPAs, a lack of correlation (r(2) = 0.27, P = n.s.) likely reflects better discrimination of coincidence events using imaging cytometry. Our data demonstrate that IFC is more accurate in enumerating MPAs than conventional FCM, which over-estimates the number of MPAs due to the presence of coincident events.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 02-2013
Publisher: Wiley
Date: 04-04-2014
DOI: 10.1002/CYTO.A.22462
Abstract: An important measure of male quality is sperm viability i.e., the percentage of live sperm within an ejaculate, as this provides an accurate measure of the number of sperm potentially available for egg fertilization. Sperm viability is often determined by fluorescence microscopy using dyes that differentially stain viable and nonviable sperm, but the technique has a number of limitations. Here, a flow cytometry (FCM) method was developed, which allows the rapid determination of honeybee sperm viability, facilitating high throughput analyses. Using s les with known sperm viabilities, it was found that data obtained from FCM were more accurate and less variable compared with data obtained for the same s les using fluorescence microscopy. It was also found that a previously reported additional population of honeybee sperm found in datasets using FCM is caused by freeze-thawing s les. In conclusion, the method described here allows to quantify sperm viability of honeybees quickly and with high accuracy. This will be of great value for future scientific research and could also be of value to guide future bee breeding programs, given the agricultural importance of honeybees as pollinators.
Publisher: American Society of Hematology
Date: 15-06-2005
DOI: 10.1182/BLOOD-2004-06-2098
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 :4635-4641)
Publisher: American Physiological Society
Date: 06-2016
Abstract: Advances in science education research have the potential to improve the way students learn to perform scientific interpretations and understand science concepts. We developed active, collaborative activities to teach skills in manipulating flow cytometry data using FlowJo software. Undergraduate students were given compensated clinical flow cytometry listmode output (FCS) files and asked to design a gating strategy to diagnose patients with different hematological malignancies on the basis of their immunophenotype. A separate cohort of research trainees was given uncompensated data files on which they performed their own compensation, calculated the antibody staining index, designed a sequential gating strategy, and quantified rare immune cell subsets. Student engagement, confidence, and perceptions of flow cytometry were assessed using a survey. Competency against the learning outcomes was assessed by asking students to undertake tasks that required understanding of flow cytometry dot plot data and gating sequences. The active, collaborative approach allowed students to achieve learning outcomes not previously possible with traditional teaching formats, for ex le, having students design their own gating strategy, without forgoing essential outcomes such as the interpretation of dot plots. In undergraduate students, favorable perceptions of flow cytometry as a field and as a potential career choice were correlated with student confidence but not the ability to perform flow cytometry data analysis. We demonstrate that this new pedagogical approach to teaching flow cytometry is beneficial for student understanding and interpretation of complex concepts. It should be considered as a useful new method for incorporating complex data analysis tasks such as flow cytometry into curricula.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 27-06-2006
DOI: 10.1161/CIRCULATIONAHA.105.596627
Abstract: Background— Thrombotic events still occur in aspirin-treated patients with coronary artery disease. Methods and Results— To better understand aspirin “resistance,” serum thromboxane B 2 (TXB 2 ) and flow cytometric measures of arachidonic acid–induced platelet activation (before and after the ex vivo addition of aspirin and indomethacin) were analyzed in 700 consecutive aspirin-treated patients undergoing cardiac catheterization. In 680 of 682 evaluable patients, serum TXB 2 concentrations were reduced compared with nonaspirinated healthy donors. Twelve patients had serum TXB 2 that was lower than nonaspirinated healthy donors but ng/mL. Arachidonic acid stimulated greater platelet activation in patients with high serum TXB 2 ( ng/mL) than in patients with low serum TXB 2 . Addition of ex vivo aspirin reduced arachidonic acid–induced platelet activation to similar levels regardless of serum TXB 2 concentrations, which suggests that patients with high residual serum TXB 2 concentrations were either noncompliant or underdosed with aspirin. Among the remaining 98% of patients, ex vivo administration of either aspirin or indomethacin failed to prevent platelet activation across all degrees of arachidonic acid–induced platelet activation and aspirin doses. Although the patients were not randomized with respect to clopidogrel treatment, multivariate analysis showed that arachidonic acid–induced platelet activation was less in patients receiving clopidogrel. Conclusions— There is a residual arachidonic acid–induced platelet activation in aspirin-treated patients that (1) is caused by underdosing and/or noncompliance in only & % of patients and (2) in the remaining patients, occurs via a cyclooxygenase-1 and cyclooxygenase-2 independent pathway, in direct proportion to the degree of baseline platelet activation, and is mediated in part by adenosine diphosphate–induced platelet activation.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 26-10-2020
Publisher: Oxford University Press (OUP)
Date: 11-2021
Abstract: There is little evidence around the potentially protective role of previous Bacillus Calmette-Guerin (BCG) vaccination on postoperative mortality in patients with perioperative SARS-CoV-2 vaccination. Prior BCG vaccination did not protect SARS-CoV-2 infected patients against postoperative pulmonary complications and 30-day mortality.
Publisher: Informa UK Limited
Date: 06-01-2020
DOI: 10.1080/09537104.2019.1709630
Abstract: Flow cytometry is a valuable tool in determining the phenotype and function of platelets accurately. The emergence of platelet flow cytometry in recent years provides an attractive alternative to other platelet analytical techniques, with advantages such as requiring small volumes and being highly sensitive to minimal changes in receptor function and expression. Here we present a methodical approach encompassing the stages in the development and optimization of platelet flow cytometry panels based on our extensive experience in this area.
Publisher: Georg Thieme Verlag KG
Date: 16-02-2012
Abstract: The term resistance has been applied to interin idual variability in platelet reactivity during antiplatelet therapy or to thrombosis despite appropriate therapy. In particular "aspirin resistance" and "clopidogrel resistance" have been the subject of intense investigation for their association with poor cardiovascular outcomes. Several mechanisms have been investigated including resistance arising from poor bioavailability, especially in clopidogrel therapy as resulting from a loss of function variant in hepatic metabolism required for prodrug activation. A limitation of studies linking on-treatment reactivity and clinical outcome is that they have been performed in high-risk patients with recent atherothrombotic disease. On-treatment platelet reactivity correlates with acuity of recent atherothrombosis, and variability in pretreatment platelet function predicts on-treatment platelet function for both aspirin and clopidogrel. It is therefore likely that high on-treatment platelet function at the time of testing may often result from underlying platelet hyperreactivity related to acute atherothrombosis, rather than true pharmacological resistance. The association of high on-treatment platelet reactivity with poor clinical outcomes may therefore be attributed to variability in underlying burden of disease instead of, or in addition to, pharmacological resistance to antiplatelet therapy.
Publisher: Elsevier BV
Date: 02-2010
Publisher: American Physiological Society
Date: 06-2016
Abstract: We have developed and validated a conceptual framework for understanding and teaching organismal homeostasis at the undergraduate level. The resulting homeostasis conceptual framework details critical components and constituent ideas underlying the concept of homeostasis. It has been validated by a broad range of physiology faculty members from community colleges, primarily undergraduate institutions, research universities, and medical schools. In online surveys, faculty members confirmed the relevance of each item in the framework for undergraduate physiology and rated the importance and difficulty of each. The homeostasis conceptual framework was constructed as a guide for teaching and learning of this critical core concept in physiology, and it also paves the way for the development of a concept inventory for homeostasis.
Publisher: American Society of Hematology
Date: 26-04-2012
DOI: 10.1182/BLOOD-2011-11-393900
Abstract: The effects of eltrombopag, a thrombopoietin-receptor agonist, on platelet function in immune thrombocytopenia (ITP) are not fully characterized. This study used whole blood flow cytometry to examine platelet function in 20 patients receiving eltrombopag treatment at days 0, 7, and 28. Platelet surface expression of activated GPIIb/IIIa, P-selectin, and GPIb was measured with and without low and high adenosine diphosphate (ADP) and thrombin receptor activating peptide (TRAP) concentrations. Before eltrombopag treatment with no ex vivo agonist, platelet activation was higher in ITP patients than controls. Platelet GPIb and activated GPIIb/IIIa expression without added agonist was unchanged following eltrombopag treatment, whereas a slight increase in P-selectin was observed. Expression of P-selectin and activated GPIIb/IIIa in response to high-dose ADP was lower during eltrombopag treatment than at baseline. Eltrombopag led to a slight increase in platelet reactivity to TRAP only in responders to eltrombopag but not to levels above those in controls whole blood experiments demonstrated that this increase was probably because of higher platelet counts rather than higher platelet reactivity. In conclusion, although thrombocytopenic ITP patients have higher baseline platelet activation than controls, eltrombopag did not cause platelet activation or hyper-reactivity, irrespective of whether the platelet count increased.
Publisher: Elsevier BV
Date: 2011
DOI: 10.1016/J.TCM.2012.01.001
Abstract: Polycystic ovarian syndrome (PCOS), diagnosed based on hyperandrogenism, ovulatory dysfunction, and polycystic ovaries, is one of the most common disorders of reproductive-aged females. Etiology includes both genetic and environmental/lifestyle factors contributing to both insulin resistance and hyperandrogenism. Clinically, PCOS has reproductive, psychological, and metabolic features, the latter predisposing to cardiovascular disease (CVD). Hemostatic abnormalities have an association with and a demonstrated pathophysiological role in CVD in non-PCOS populations but have not been adequately explored in PCOS. This review focuses on the hemostatic system in PCOS, exploring also relationships to the metabolic and hormonal abnormalities of the syndrome, and aims to identify whether hemostatic abnormalities are present as potential contributors to increased cardiovascular risk. Ultimately, this area may reveal preventative and therapeutic opportunities, which could improve the cardiovascular health of women with PCOS.
Publisher: Wiley
Date: 18-10-2021
DOI: 10.1111/IMCB.12505
Abstract: We hypothesize that thrombosis with thrombocytopenia syndrome recently described after administration of adenovirus‐vectored vaccines for severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) occurs as a result of the unique properties of the adenovirus vectors, which can have widespread biodistribution throughout the body. The antigen is delivered to megakaryocyte cells, which act as part of the primary immune system and distribute the antigen within progeny platelets, also a key component of the immune system. The interaction of the antigen induces preformed antiplatelet factor 4 (PF4) antibodies to bind to PF4–heparan sulfate complexes in the absence of exogenous heparin, at sites where the heparan sulfate concentration in the vascular glycocalyx is optimal for complex formation, causing thrombosis and thrombocytopenia as observed clinically. This hypothesis is testable in cell culture and animal models, and potentially in vivo , and if proven correct has significant implications for vaccine development and our understanding of the links between the coagulation and immune systems.
Publisher: Elsevier BV
Date: 2017
DOI: 10.1016/J.YMETH.2016.10.002
Abstract: Platelets are subcellular blood elements with a well-established role in haemostasis. Upon activation platelets undergo granule exocytosis, resulting in α-granule P-Selectin being expressed on the cell membrane. This allows binding of activated platelets to P-Selectin glycoprotein ligand 1 (PSGL-1) expressing leukocytes, forming leukocyte-platelet aggregates (LPAs). Whole blood flow cytometry (FCM) has demonstrated that elevated circulating LPAs (especially monocyte LPAs) are linked to atherothrombosis in high risk patients, and that activated platelet binding influences monocytes towards a pro-adhesive and pro-atherogenic phenotype. However, a limitation of conventional FCM is the potential for coincident events to resemble LPAs despite no tethering. Imaging cytometry can be used to characterize LPA formation and distinguish circulating MPAs from coincidental events. Platelets and leukocyte subsets are identified by expression of surface markers (e.g. the lipopolysachharide receptor CD14 on monocytes, glycoprotein Ib CD42b on platelets). In conventional FCM, all events with both leukocyte and platelet characteristics are designated as LPAs. However, by using an 'internal' mask based on the brightfield image and the fluorescent platelet identifier, imaging flow cytometry is able to distinguish leukocytes with tethered platelets (genuine LPAs) from leukocyte with coincidental, untethered platelets nearby. Mechanisms (e.g. adhesion molecules) or consequences (e.g. signal transduction) can then be separately analysed in platelet tethered and untethered leukocytes. Imaging flow cytometry therefore provides a more accurate approach for both enumeration and analysis of LPAs than conventional FCM.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 17-08-2010
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 04-2017
Publisher: Elsevier BV
Date: 04-1994
Publisher: Elsevier BV
Date: 10-2023
Publisher: Public Library of Science (PLoS)
Date: 24-06-2013
Publisher: Elsevier BV
Date: 02-2010
Publisher: Elsevier BV
Date: 04-2004
DOI: 10.1053/J.JVCA.2004.01.014
Abstract: To determine if preoperative heparin therapy causes an increase in the incidence of intraoperative heparin resistance by reducing the concentration of antithrombin in plasma. Prospective laboratory investigation of clinical s les. Public tertiary care hospital and public pathology service. Forty-six patients undergoing cardiac surgery involving cardiopulmonary bypass. Fourteen patients received preoperative heparin therapy (POHI group) and 32 patients were controls (CONT group). The concentration of antithrombin, activated coagulation time (ACT), and clinical parameters were measured at intervals. More POHI patients had on-bypass heparin resistance than CONT (43% and 3%, respectively, p < 0.01). The POHI group had a lower concentration of antithrombin than the CONT group before (80.9% and 92.6%, respectively, p < 0.01) and while on cardiopulmonary bypass (51.6% and 57.5%, respectively, p = 0.04). Comparison of heparin-resistant and heparin-responsive POHI patients showed that the concentration of antithrombin did not differ before bypass (82.4% and 79.8%, respectively, p = 0.53) or during bypass (51.8% and 51.4%, respectively, p = 0.91). In fact, antithrombin concentrations were slightly higher in the heparin-resistant POHI patients (not significant). POHI patients received more heparin than CONT patients (medians 787 U/kg and 600 U/kg, respectively, p = 0.01) and were transfused with more fresh frozen plasma on bypass (p = 0.03). Preoperative heparin causes an increased incidence of heparin resistance and reduced antithrombin concentrations. However, heparin resistance was not causally related to reduced antithrombin because antithrombin concentrations were not different between heparin-resistant and heparin-responsive patients in the POHI group.
Publisher: SERDI
Date: 2014
DOI: 10.14283/JFA.2014.14
Abstract: Background: Whilst resistance training has been proven to convey considerable benefits to olderpeople immediately post-exercise there may be elevated transient risks for cardiac events and falls. Objectivesand Measurements:We assessed the acute effects of eccentrically-biased (EB) and conventional (CONV)resistance exercise on: platelet number, activation and granule exocytsosis and mean velocity of centre ofpressure displacement (Vm). Design, Setting, Participants and Intervention:Ten older adults (7 males, 3females 69 ± 4 years) participated in this randomised controlled cross-over study in which they performed EBand CONV training sessions that were matched for total work and a control condition. Results:Immediately post-exercise there was a statistically significant difference in platelet count between the control condition, in which ithad declined (pre 224 ± 35 109/L post 211 ± 30 109/L: P 0.05) and CONV in which it had increased (pre 236 ±55 109/L post 242 ± 51 109/L: P 0.05). There was no change in platelet activation and granule exocytsosis orVm following EB and CONV. Conclusions:Overall, while minor differences between regimens were observed,no major adverse effect on parameters of platelet function or centre of pressure displacement were observedacutely following either regimen. Eccentrically-biased and conventional resistance exercise training regimens donot appear to present an elevated acute risk in the context of changes to platelet function contributing to a cardiacevent or postural stability increasing falls risk for apparently healthy older adults.
Publisher: Elsevier BV
Date: 11-2005
DOI: 10.1111/J.1538-7836.2005.01603.X
Abstract: Monocytes and neutrophils form heterotypic aggregates with platelets initially via engagement of platelet surface P-selectin with leukocyte surface P-selectin glycoprotein ligand-1 (PSGL-1). The resultant intracellular signaling causes the leukocyte surface expression of tissue factor and activation of leukocyte surface Mac-1 (integrin alphaMbeta2, CD11b/CD18). The activation-dependent conformational change in monocyte surface Mac-1 results in the binding of coagulation factor Xa (FXa) and/or fibrinogen to Mac-1. The aim of this study was to develop whole blood flow cytometry assays of these procoagulant activities and to investigate the effects of platelet binding to monocytes and neutrophils. Citrate or D-Phe-Pro-Arg-chloromethylketone (PPACK) anticoagulated whole blood was incubated with monoclonal antibodies against CD14 (PECy5), CD42a (PE), FITC-conjugated test antibody and an agonist, and then fixed with FACS lyse. Appropriate isotype negative controls were prepared in parallel. A BD FACSCalibur was used to analyze monocytes and neutrophils, which were identified based on CD14 fluorescence, forward and 90 degrees light scatter. These populations were further gated into CD42a-positive (platelet-bound) and CD42a-negative (platelet-free). Geometric mean fluorescence and per cent positive data were collected for each subpopulation to measure the binding of test antibodies directed at CD42a, tissue factor, coagulation FXa, bound fibrinogen, activated Mac-1, and CD11b. Compensation controls were prepared on six normal donors prior to the study and these settings were used throughout the 10 donor study. Negative controls verified the lack of cross talk, particularly in the quantified FITC and PE parameters. The physiologic agonists collagen and ADP increased monocyte-platelet and neutrophil-platelet aggregates and increased leukocyte surface Mac-1/CD11b and surface-bound tissue factor, FXa and fibrinogen. Whereas the increases in Mac-1/CD11b were mainly independent of leukocyte-platelet binding, the increases in surface-bound tissue factor, FXa and fibrinogen were mainly dependent on leukocyte-platelet binding. (i) We have developed novel whole blood flow cytometry assays to measure bound tissue factor, coagulation FXa, fibrinogen, activated Mac-1 and CD11b on the surface of monocytes and neutrophils, allowing independent analysis of monocytes and neutrophils with and without surface-adherent platelets. (ii) The monocyte and neutrophil surface binding of tissue factor, FXa and fibrinogen is mainly dependent on platelet adherence to monocytes and neutrophils, whereas the monocyte and neutrophil surface expression of CD11b and activated Mac-1 is mainly independent of platelet adherence to monocytes and neutrophils.
Publisher: Wiley
Date: 10-2016
DOI: 10.14814/PHY2.12951
Publisher: Elsevier BV
Date: 11-2011
Start Date: 2017
End Date: 06-2020
Amount: $372,500.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2015
End Date: 12-2015
Amount: $440,000.00
Funder: Australian Research Council
View Funded Activity