Systemic infections after acute stroke

After an acute stroke, systemic infection can complicate the recovery process and lead to a worse clinical outcome, including a higher risk of mortality. Post-stroke infection (PSI) is responsible for the majority of the mortality occurring between 1 week and 1 month after stroke, peaking towards the end of the second week. The effects of PSI on longer-term outcome and other aspects of recovery, such as cognition, mood and quality of life, are largely unknown. The cerebrovascular event itself may result in a systemic immunosuppressed state, hence lowering the threshold for subsequent systemic bacterial infections. Although there have been advances in the basic understanding of the pathophysiological mechanisms of PSI, clinical studies have not provided any clear guidelines on the best methods of managing or preventing PSI. This article provides a review of the current knowledge of the phenomenon of PSI and the possible future developments in the understanding and treatment of PSI

Microvesicles as biomarkers in diabetes, obesity and non-alcoholic fatty liver disease: current knowledge and future directions

NAFLD is the most common chronic liver disease, frequently associated with diabetes. Both of these insulin resistant states have increased cardiovascular risk factors associated, and a prevalent cause of mortality in these diseases. Microvesicles are heterogonously sized, phospholipid rich spheres released by cells upon activation and apoptosis. Evidence is continuing to accumulate of microvesicles being not only markers of disease severity but as also having a functional role in the pathophysiology of disease progression.<br/

Platelet microvesicles (microparticles) in cardiac surgery

SIGNIFICANT POSTOPERATIVE BLEEDING is a common risk of cardiac surgery, with approximately 3.5% of patients requiring surgical re-exploration.1 Re-exploration is associated with adverse outcomes, including infections, ischemia, and increased 30-day mortality.2 Similar adverse outcomes are related to erythrocyte transfusions associated with cardiac surgery,3 in addition to the immunologic and administrative hazards of transfusion.4 These risks are important because the majority of patients undergoing cardiac surgery receive a blood transfusion despite the lack of evidence to support liberal transfusion strategies.5 The frequency and significance of bleeding after cardiac surgery warrant investigation of the hematologic changes throughout the procedure. This review focuses on the (patho)physiology of platelet-derived microvesicles in the setting of cardiovascular surgery, a developing area in the understanding of the control of coagulation

Do we really understand the pathophysiology and clinical impact of poststroke infection?

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Long-chain n-3 fatty acid supplementation in men increases resistance to activated protein C

It has recently and controversially been demonstrated that fish oil supplementation may not be beneficial for everyone, but to date there have been no biological explanations. We suggest that resistance to the anticoagulant, activated protein C (APC), be considered as a potential mechanism, because it has been demonstrated that the type of fatty acids on phospholipids modulates function of the APC pathway. The APC ratio in plasma was decreased by 7% after fish oil supplementation in healthy men (P&lt;.005; n=35). The decrease in APC ratio equates to an increase in APC resistance. Fish oil lowered the APC ratio by (1) increasing low-density lipoprotein (LDL) cholesterol (P&lt;.01) and apolipoprotein B (P&lt;.05) and (2) increasing platelet microparticles (P&lt;.05). In vitro, purified LDL decreased the APC ratio and increased microparticle formation. These changes affecting the anticoagulant APC could contribute toward a prothrombotic state, potentially explaining the recent observation that fish oil supplementation may not always be of benefit. These findings will need to be repeated in different disease states

Leukocyte extracellular vesicle concentration is inversely associated with liver fibrosis severity in NAFLD

The enhanced liver fibrosis (LFS) score and the nonalcoholic fatty liver disease (NAFLD) fibrosis score (NFS) are algorithmic-derived scores for diagnosing severe (F3/F4) liver fibrosis. In a pilot, substudy of the Wessex Evaluation of fatty Liver and Cardiovascular markers in NAFLD with OMacor thErapy (WELCOME) trial, we tested whether measurements of plasma platelet-, endothelial-, and leukocyte-derived extracellular vesicles (EVs) counts are (a) associated with, and predict, F3/F4 fibrosis and (b) able to improve risk prediction of F3/F4 fibrosis in NAFLD, building upon LFS or NFS algorithms. Twenty-six individuals with NAFLD had liver fibrosis severity determined by Kleiner scoring after liver biopsy. Plasma samples stained with CD41a, CD42b, CD31, CD105, CD14, CD16, and CD284 antibodies were analyzed using flow cytometry to measure platelet-, endothelial-, and leukocyte-derived EVs counts. The independence of associations between EVs and F3/F4 fibrosis were tested using logistic regression. Receiver operator characteristic (ROC) curves were used to evaluate F3/F4 fibrosis prediction models. LFS was more strongly associated with F3/F4 fibrosis than NFS (χ2= 15.403, P &lt; 0.0001, and χ2= 6.300, P = 0.012, respectively). The association between LFS and F3/F4 fibrosis was further improved by addition of CD14+ EVs (χ2=20.847,P = 0.016 vs. χ2=12.803,P = 0.015, respectively) or CD16+ EVs (χ2=22.205,P = 0.009 vs. χ2=17.559,P = 0.001, respectively), and the area under the ROC for LFS (AUC = 0.915, se = 0.055, P = 0.001) was increased by the addition of CD14+ or CD16+ EVs (AUC = 0.948, se = 0.042, and P &lt; 0.001 and AUC = 0.967, se = 0.055, P &lt; 0.001, respectively) as predictor variables. In this small preliminary study, CD14+ and CD16+ EV counts show potential to predict liver fibrosis severity with either marker improving the ability of the LFS to identify F3/F4 fibrosis in this small preliminary cohort study

Single platelet variability governs population sensitivity and initiates intrinsic heterotypic responses

Investigations into the nature of platelet functional variety and consequences for homeostasis require new methods for resolving single platelet phenotypes. Here we combine droplet microfluidics with flow cytometry for high throughput single platelet function analysis. A large-scale sensitivity continuum was shown to be a general feature of human platelets from individual donors, with hypersensitive platelets coordinating significant sensitivity gains in bulk platelet populations and shown to direct aggregation in droplet-confined minimal platelet systems. Sensitivity gains scaled with agonist potency (convulxin &gt; TRAP-14&gt;ADP) and reduced the collagen and thrombin activation threshold required for platelet population polarization into pro-aggregatory and pro-coagulant states. The heterotypic platelet response results from an intrinsic behavioural program. The method and findings invite future discoveries into the nature of hypersensitive platelets and how community effects produce population level responses in health and disease.</p

Extracellular vesicle flow cytometry analysis and standardization

The term extracellular vesicles (EVs) describes membranous vesicles derived from cells, ranging in diameter from 30 to 1,000 nm with the majority thought to be in the region of 100–150 nm. Due to their small diameter and complex and variable composition, conventional techniques have struggled to accurately count and phenotype EVs. Currently, EV characterization using high-resolution flow cytometry is the most promising method when compared to other currently available techniques, due to it being a high-throughput, single particle, multi-parameter analysis technique capable of analyzing a large range of particle diameters. Whilst high resolution flow cytometry promises detection of the full EV diameter range, standardization of light scattering and fluorescence data between different flow cytometers remains an problem. In this mini review, we will discuss the advances in high-resolution flow cytometry development and future direction of EV scatter and fluorescence standardization. Standardization and therefore reproducibility between research groups and instrumentation is lacking, hindering the validation of EVs use as diagnostic biomarkers and therapeutics

Droplet microfluidics with reagent micromixing for investigating intrinsic platelet functionality

Introduction: recision mapping of the functional structure of platelet populations holds great promise for the identification of hyper-reactive subtypes that are likely to be disease drivers, having value in prognostics and as therapeutic targets. However, the ability to measure the intrinsic functional capacity of individual platelets is confounded by potent paracrine cross-talk, resulting in phenotypic remodeling of the entire platelet population, and in doing so obscuring the identity of hyper-reactive platelets.Methods: to address this we have developed a droplet microfluidics strategy for single platelet confinement to exclude paracrine signaling. Consideration of the Poisson distribution was used for high throughput single platelet encapsulation and the preparation of minimal platelet collectives serving as digital models for understanding the role of hyper-reactive platelets coordinating system-level behavior by paracrine signaling. Platelets are retrieved from the droplets for phenotyping using standard flow cytometry. In addition, we have incorporated a staggered herringbone micromixing element for accurate agonist and antibody dispensing in droplets.Results: the methodology was used for characterizing sensitivity distributions from healthy blood donors in response to convulxin (agonist of the GPVI receptor, the major platelet receptor for collagen). P-selectin exposure and αIIbβ3 integrin activation were used as analytical end-points to demonstrate the existence of hyper-reactive platelets that direct 20-fold gains in system level sensitivity.Conclusions: the analytical workflow represents an enabling tool for the accurate classification of platelet subtypes and description of their underlying biology