scholarly journals Preliminary study of the effect of hemolysis on platelet aggregation through microscopic observation under physiological shear flow

2021 ◽  
Vol 35 (2) ◽  
pp. 62-67
Author(s):  
Nobuo Watanabe ◽  
Naoki Kawada
Keyword(s):  
Platelet Aggregation ◽  
Shear Flow ◽  
Microscopic Observation ◽  
Preliminary Study

scholarly journals Distinct dietary alpha-linolenic acid-dependent shifts in the fecal microbiome composition suppresses aging-associated inflammatory responses and thrombus formation

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
S.S Saeedi Saravi ◽  
N.R Bonetti ◽  
G.G Camici ◽  
T.F Luscher ◽  
J.H Beer
Keyword(s):  
Platelet Aggregation ◽  
Shear Flow ◽  
Plasma Levels ◽  
Inflammatory Responses ◽  
Thrombus Formation ◽  
Funding Source ◽  
High Shear ◽  
Fecal Microbiome ◽  
Microbiome Composition

Abstract Background Aging is associated with alterations in the fecal microbiome composition. The microbiota-derived trimethylamine-N-oxide (TMAO) correlates with arterial thrombotic events, e.g. myocardial infarction and stroke, the leading causes of mortality worldwide. The omega-3 fatty acid (n-3 FA) α-linolenic acid (ALA) has been shown to be protective against thrombosis and associated pathologies. Therefore, we hypothesized that long-term dietary ALA supplementation protects against the aging-associated microbiome dysbiosis, and reduces inflammatory and thrombotic responses. Methods 24 week-old male C57BL/6 mice were fed either a high ALA (7.3g%) or low ALA (0.03g%) diet for 12 months. We examined the compositional changes of fecal microbiota of the animals treated with high vs. low ALA via 16S rRNA gene sequencing. The plasma levels of TMAO and its precursors choline and betaine, and LPS were measured by ELISA. Additionally, the platelet aggregation in response to thrombin, and thrombus formation on collagen under high-shear flow conditions of 3000/sec (to mimic blood flow in stenosed arteries) were investigated. Results Genomic analyses showed that the abundance of Phylum Proteobacteria and the family of desulfovibrio were reduced 71.72% and 51.73% in the aged high ALA-treated mice (p<0.01 and p<0.001, resp.) that may result in decrease in TAMO production and the subsequent inflammatory responses. However, microbial diversity of Bacteroidetes or Fermicutes and Bacteroidetes/Fermicutes ratio did not demonstrate a significant change between high vs. low ALA groups. Interestingly, the dietary intake of high ALA increased the abundance of Lachnospiraceae (p<0.01) that may exert anti-inflammatory effects. Importantly, high ALA significantly decreased the plasma levels of TMAO (p<0.01) and its precursor choline (P<0.05), but not betaine. The pro-inflammatory cytokine TNF-α showed a significant reduction (p<0.05), whereas plasma IL-1β did not change significantly following high ALA supplementation. An increased thrombus formation on collagen under high-shear flow (36.34%, p<0.01) and thrombin-induced platelet aggregation (31.31%, p<0.05) were found in the aged mice. Conclusion These studies demonstrate that an ALA-rich diet induces beneficial bacterial shifts in the aging-associated fecal microbiome that may lead to the suppression of inflammatory and thrombotic responses. Hence, long-term dietary ALA supplementation may be exploited as a nutritional antithrombotic strategy in the aging. Microbiome-Thrombosis-Aging Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Swiss National Science Foundation (SNSF)

scholarly journals Artificial surface effect on red blood cells and platelets in laminar shear flow

Blood ◽  
1990 ◽  
Vol 75 (7) ◽  
pp. 1568-1575
Author(s):  
TM Alkhamis ◽  
RL Beissinger ◽  
JR Chediak
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Shear Rate ◽  
Shear Flow ◽  
Platelet Adhesion ◽  
Surface Effect ◽  
Test Surface ◽  
Adp Release ◽  
Laminar Shear Flow ◽  
Laminar Shear

Red blood cell (RBC) effects on platelet adhesion to a nonbiologic test surface (tetrafluoroethylene propylene copolymer) and platelet aggregation during laminar shear flow for shear rates to 5,680 s-1 (corresponding to shear stress to 200 dyne/cm2) were investigated. Results on hemoglobin (Hb) and adenosine diphosphate (ADP) release from RBCs, percent decrease of single platelets in the bulk, and percent of test surface covered with platelets were obtained in a cone-and-plate (CP) viscometer for samples of whole blood, suspensions of RBC ghosts in platelet-rich plasma (PRP), and suspensions of RBCs in either PRP or platelet-poor plasma. Results obtained over the shear rate range studied for samples of normal hematocrit indicated that low-stress shearing led to ADP and Hb release from intact RBCs; shear-induced release of ADP from RBCs was about twice that of platelets, and of the total ADP released, the ADP released from RBCs contributed about six times that of the platelets to single platelet reduction in the bulk and about twice that of the platelets to platelet adhesion, ie, coverage of the test surface with platelets. Results obtained for various hematocrits showed that above a threshold hematocrit of about 25% to 35% the RBCs (suspended in PRP) had a greater contribution to ADP release, platelet adhesion, and platelet aggregation than the platelets themselves. Single platelet reduction for samples of RBC ghosts suspended in PRP correlated with shear rate level and not with shear stress.

scholarly journals Artificial surface effect on red blood cells and platelets in laminar shear flow

Blood ◽  
1990 ◽  
Vol 75 (7) ◽  
pp. 1568-1575 ◽  
Author(s):  
TM Alkhamis ◽  
RL Beissinger ◽  
JR Chediak
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Shear Rate ◽  
Shear Flow ◽  
Platelet Adhesion ◽  
Surface Effect ◽  
Test Surface ◽  
Adp Release ◽  
Laminar Shear Flow ◽  
Laminar Shear

Abstract Red blood cell (RBC) effects on platelet adhesion to a nonbiologic test surface (tetrafluoroethylene propylene copolymer) and platelet aggregation during laminar shear flow for shear rates to 5,680 s-1 (corresponding to shear stress to 200 dyne/cm2) were investigated. Results on hemoglobin (Hb) and adenosine diphosphate (ADP) release from RBCs, percent decrease of single platelets in the bulk, and percent of test surface covered with platelets were obtained in a cone-and-plate (CP) viscometer for samples of whole blood, suspensions of RBC ghosts in platelet-rich plasma (PRP), and suspensions of RBCs in either PRP or platelet-poor plasma. Results obtained over the shear rate range studied for samples of normal hematocrit indicated that low-stress shearing led to ADP and Hb release from intact RBCs; shear-induced release of ADP from RBCs was about twice that of platelets, and of the total ADP released, the ADP released from RBCs contributed about six times that of the platelets to single platelet reduction in the bulk and about twice that of the platelets to platelet adhesion, ie, coverage of the test surface with platelets. Results obtained for various hematocrits showed that above a threshold hematocrit of about 25% to 35% the RBCs (suspended in PRP) had a greater contribution to ADP release, platelet adhesion, and platelet aggregation than the platelets themselves. Single platelet reduction for samples of RBC ghosts suspended in PRP correlated with shear rate level and not with shear stress.

scholarly journals Aquaporin-1: a major modulator of aging-mediated platelet/endothelial dysfunction in atherothrombosis

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
S.S Saeedi Saravi ◽  
G.G Camici ◽  
T.F Luscher ◽  
J.H Beer
Keyword(s):  
Endothelial Cells ◽  
Platelet Aggregation ◽  
Endothelial Dysfunction ◽  
Shear Flow ◽  
Platelet Adhesion ◽  
Funding Source ◽  
Rolling Velocity ◽  
Caveolin 1 ◽  
Aquaporin 1 ◽  
Aqp1 Expression

Abstract Background Aging is associated with development of cardiovascular diseases, including atherothrombosis. Aquaporin-1 (AQP1) is a water channel that also transports hydrogen peroxide (H2O2). Regarding to the role of oxidative stress in atherothrombosis, we hypothesized that AQP1 modulates aging-associated platelet/endothelial dysfunction. Methods Human aortic endothelial cells (HAEC) from passages 5 (young) to 15 (senescent/old) were subjected to fluorescent immunocytochemistry to detect AQP1 protein expression and subcellular localization. The cells were also probed for AQP1 and the phospho/total proteins (AMPK, acetyl-coA-carboxylase (ACC), caveolin-1 and eNOS) for studying the signal transduction by immunoblotting. The endothelial cells were transfected with constructs containing H2O2 biosensor HyPer targeted to cell nucleus or cytosol followed by fluorescence imaging. The transcriptional levels of pro-inflammatory/pro-atherogenic vs. anti-inflammatory/atheroprotective genes in the cells were assessed by qRT-PCR. Human blood samples were taken and treated with or without AQP1 inhibitor (Bacopaside II, 10 μM) to examine the platelet adhesion and rolling velocity on vWF under high shear flow (100 dyn/cm2). Also, platelet aggregation in response to collagen (2 μM), ADP (1 μM) and TRAP (1 μM) were recorded. Results First, the senescence of HAEC was adjusted by a significant increase in β-galactosidase activity from passage 5 to 15. AQP1 immunofluorescence showed a remarkable increase in the young (P.5) compared to senescent (P.15) cells. Immunoblot analyses showed that aging leads to significant increases in AQP1 intensity and phosphorylation of caveolin-1 (Tyr14) and ACC (Ser79), along with decreases in phosphorylation of eNOS (Ser1177) and AMPK (Thr172) (p<0.01, n>6). Fluorescence imaging documented a robust H2O2 production in the senescent endothelial cell cytosol, but not nucleus, and activated TNF-α gene, whereas the transcription of hemoxygenase-1 gene enhanced in the young cells (p<0.01). AQP1 inhibition reduced platelet adhesion and thrombus formation, and elevated platelet rolling velocity on vWF under shear flow (p<0.01). Also, a decrease was found in platelet aggregation in response to AQP1 inhibition (p<0.05). Conclusion These studies, for the first time, demonstrate that aging induces AQP1 expression in endothelial cells and platelets, and modulates the dephosphorylation of AMPK/eNOS. These may lead to platelet/endothelial dysfunction and production of pro-coagulant/pro-inflammatory factors via ACC activation. Therefore, AQP1 inhibition could potentially be exploited as a therapeutic strategy for improving age-related atherothrombosis. Figure 1. Aging increases AQP1 expression in HAEC that leads to dephosphorylation of AMPK and eNOS. AQP inhibition also improves platelet function. *p<0.05, **p<0.01 compared to control. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Swiss National Science Foundation (SNSF)

The “Dead Digit, Palpable Pulse” Syndrome: A Preliminary Study of the Value of Antiplatelet Drugs in This Disorder

1979 ◽  
Author(s):  
W Morris-Jones ◽  
F Preston
Keyword(s):  
Platelet Aggregation ◽  
Antiplatelet Drugs ◽  
Controlled Clinical Trials ◽  
Therapeutic Value ◽  
Palpable Pulse ◽  
Platelet Aggregate ◽  
The Mean ◽  
Preliminary Study ◽  
The Dead ◽  
Spontaneous Platelet Aggregation

We report here the results of a pilot study to investigate the value of antiplatelet drugs in patients with pregangrene of one or both feet associated with palpable peripheral pulses but without clinical or laboratory evidence of a myeloproliferative disorder in diabetes mellitus. 32 patients were studied. For each patient pregangrene of one or both feet had been present for a minimum period of six weeks. All patients had failed to respond to medical therapy. Platelet aggregation, using ADP, collagen and adrenaline was assessed before therapy. PRP was also tested for spontaneous platelet aggregation (SPA). BTG assays and platelet aggregate ratios were also performed. Aspirin, 325mgs t.d.s. and persantin 100mgs t.d.s. produced significant and maintained clinical improvement in 5 of the 7 patients with SPA- 7 of 12 patients with hypersensitive platelets and 3 of 13 patients with normo-or hyposensitive platelets. Sympathectomy was performed in patients who failed to respond to drug therapy. The mean PAR was 0.94 for the non-responder group and 0.78 for the responder group. The mean BTG for non-responders was 44ng/ml (normal 50). The mean BTG for the responder group was 59.1ng/ml. The results suggest that antiplatelet drugs may be of therapeutic value in patients with the “dead-digit palpable pulse” syndrome arid that controlled clinical trials are indicated.

Preliminary Study on Shear-Flow-Creep Experiment for the Fracture of Hard-Rock

2011 ◽  
Vol 90-93 ◽  
pp. 542-546
Author(s):  
Gang Wang ◽  
Yu Jing Jiang ◽  
Ming Bin Wang
Keyword(s):  
Shear Flow ◽  
Hard Rock ◽  
Creep Tests ◽  
Nuclear Waste Storage ◽  
Experiment System ◽  
Waste Storage ◽  
Geological Conditions ◽  
Constant Normal Stiffness ◽  
Preliminary Study ◽  
In Virtue Of

The nuclear waste storage projects, hydropower and etc are often installed in the hard crystalline rocks. The creep phenomenon of the hard rocks appears in virtue of the complex geological conditions, especially when the excavation brings about damage and cracks to the rockmass, and they largely weaken the hydraulic performances of surrounding rock. Once the excavation-caused cracks are well connected with the native ones together, the engineering safety will be brought great harm to. By dint of newly developed shear-flow-creep coupled experiment system, on condition of the constant normal stiffness boundary conditions, the coupled shear-flow-creep tests are conducted. Not only the tests testify that the equipments is reasonable and effective and the creep largely influences the seepage performance of the rock crack, but also the coupling characters are primarily proved up.

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