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The Potential of Plants as Treatments for Venous Thromboembolism
Published in Namrita Lall, Medicinal Plants for Cosmetics, Health and Diseases, 2022
Lilitha L. Denga, Namrita Lall
The tenase complex proteolytically creates more FXa by activating additional FX (Autin et al. 2004). FXa then forms the prothrombinase complex with FVa. The prothrombinase complex rapidly converts prothrombin to thrombin, which further amplifies the cascade and converts soluble fibrinogen to insoluble fibrin (Smith, Travers, and Morrissey 2015).
Anatomy, physiology, and histology of the skin
Published in Michael Parker, Charlie James, Fundamentals for Cosmetic Practice, 2022
Once prothrombinase has been activated by either pathway (usually this happens due to a combination of both), it cleaves the proenzyme prothrombin into activated thrombin. Thrombin then converts fibrinogen into its active, insoluble component: fibrin. As mentioned regarding platelet plug formation, fibrin forms a meshwork which stabilises the platelet plug. As fibrin fibres stabilise the clot, they also cause it to contract and pull the edges of the damaged vessel closer together and stopping the chances of further bleeding. Red and white blood cells are too large to fit through any residual gaps; however, plasma is sometimes able to seep through. This is why you may notice straw-coloured plasma overlying a healing wound before it becomes waterproof via a combination of clotting factors and the aforementioned platelet plug.
Cellular Components of Blood
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
After platelet activation by thrombin and collagen, procoagulant activity increases. This procoagulant action requires Ca++ influx across the plasma membrane, and reorientation of phosphatidyl serine from the inner layer to the outer layer of the platelet membrane with the expression of binding sites for specific coagulation processes. Platelet factor 3, an exposed membrane phospholipid, is available for coagulation and protein complex formation. The first reaction involves factors IXa, VIII and X in the formation of factor Xa. The second (or prothrombinase) reaction results in the formation of thrombin from the interaction of factors Xa, V and II. The irreversible fusion of platelets aggregated at the site of endothelial injury is enhanced by ADP and other enzymes released during the platelet release reaction. Thrombin also promotes platelet plug formation.
TEG®6s system measures the contributions of both platelet count and platelet function to clot formation at the site-of-care
Published in Platelets, 2020
Joao D. Dias, Carlos G Lopez-Espina, Kevin Bliden, Paul Gurbel, Jan Hartmann, Hardean E Achneck
The small but statistically significant reductions in reaction time parameters (CK.R, CKH.R, and CRT.ACT) with increasing platelet counts are consistent with the cell-based model of hemostasis [1]. Accelerated clot formation at higher platelet concentrations may be due to the increased number of phospholipid membranes providing a substrate for tenase and prothrombinase complexes [1]. During the propagation phase of the hemostatic process, tenase and prothrombinase complexes are assembled on the platelet surface, and large-scale thrombin generation takes place. A lower platelet count decreases the speed of this process. Unlike platelet count, changes in platelet function did not affect reaction time parameters in our study. This may be explained by the fact that provision of surfaces for the hemostatic process by platelets is independent of their function. Alternatively, it is possible that abciximab, through steric hindrance and conformational changes, prevents binding to the αIIbβ3 receptor, blocking secondary platelet activation, but not the initial platelet activation. This would mean that platelets continue to be activated and generate thrombin, leading to a feedback loop increasing the number of available platelets. When the effects of both MA and reaction time parameters are combined, the TEG®6s analyzer can be used to accurately monitor functional platelets at any count.
Carbonic Anhydrase Inhibitors suppress platelet procoagulant responses and in vivo thrombosis
Published in Platelets, 2020
Ejaife O. Agbani, Xiaojuan Zhao, Christopher M. Williams, Riyaad Aungraheeta, Ingeborg Hers, Erik R. Swenson, Alastair W. Poole
Collagen stimulation of platelets has been shown to increase the formation of a procoagulant phenotype amongst platelets aggregating over exposed sub-endothelium [1,2]. Procoagulant platelets actively support thrombin generation and amplify coagulation by providing an extensive surface area of exposed aminophospholipids, particularly phosphatidylserine (PS), which promotes assembly of the tenase and prothrombinase complexes on the platelet surface [3,4]. This subpopulation of platelets is characterized by PS-laden balloon-like membranes and by microvesiculation, amongst other features [4–7]. Recently, we identified two phenotypes of this subpopulation as ballooned non-spread (BNS) and ballooned and procoagulant-spread platelets (BAPS) [4,6–8]. Furthermore, we showed that selective inhibition of their formation either by pharmacological inhibition or by water channel aquaporin-1 gene ablation did not impair secretion mechanisms, yet suppressed procoagulation in vitro and thrombus formation in vivo after injury [6]. Therefore, drugs specifically targeting procoagulant platelet formation may provide a new way to control platelet driven thrombosis without blocking essential platelet granular releasates.
Proteomic analysis reveals procoagulant properties of cigarette smoke-induced extracellular vesicles
Published in Journal of Extracellular Vesicles, 2019
Birke J. Benedikter, Freek G. Bouwman, Alexandra C. A. Heinzmann, Tanja Vajen, Edwin C. Mariman, Emiel F. M. Wouters, Paul H. M. Savelkoul, Rory R. Koenen, Gernot G. U. Rohde, Rene van Oerle, Henri M. Spronk, Frank R. M. Stassen
PS-dependent thrombin generation was determined using an in-house prothrombinase assay. In the presence of negatively charged phospholipids, such as PS, factor Va and factor Xa assemble to form the active prothrombinase complex, which converts prothrombin into its active form thrombin. A reaction mix of 5 mg/ml BSA, 1.0 nM bovine factor Va, 0.05 nM bovine factor Xa and 5 mM CaCl2 was prepared in HEPES-NaCl (HN) buffer (25 mM HEPES and 175 mM NaCl, pH 7.7 at room temperature). Ten microlitres of phospholipid standard (10% PS, 90% PC; ranging from 10 to 250 nM), mock-treated EVs or annexin V-treated EVs (5 × 108 particles/ml) were added to 190 μl of the reaction mix. After 10 min incubation, human prothrombin (Haematologic Technologies Incorporated) was added to a final concentration of 500 nM and incubated for 1 min. Next, 50 μl was subsampled and transferred to 150 μl cuvette buffer (50 mM Tris, 175 mM NaCl, 20 mM EDTA, 0.5 mg/ml ovalbumin, pH 7.9) and incubated for 7 min 37°C. Thereafter, 50 μl of the thrombin substrate S2238 (Chromogenix) was added and the absorption at 405 and 490 nm was measured every 30 s for 15 min.