Platelet Structure Research Articles

Structural and morphological characterization of Mg0.8Al0.2(OH)2Cl0.2 hydrotalcite produced by mechanochemistry method

Chlorine intercalated Mg–Al layered double hydroxides (Mg–Al–Cl–LDH) with a chemical formula Mg0.8Al0.2(OH)2Cl0.2 were successfully produced by the one-step mechanochemistry method and subsequent water washing followed by drying in oven for 1h at 80°C. The samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FT–IR), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), elemental mapping analysis, transmission electron microscopy (TEM), X-ray fluorescence (XRF), and the differential thermogravimetric analysis (DTGA). Results revealed that the structural characteristics of Mg–Al–Cl–LDH were affected strongly by milling time. At the beginning of milling (up to 1h), Hydrotalcite (HT) and Brucite were the dominant phases, while the progressive mechanical activation was completed as milling time increased, which resulted in the formation of nanostructured Mg–Al–Cl–LDH. Based on XRD and FTIR data, Mg0.8Al0.2(OH)2Cl0.2 with high purity was obtained at 5h milling. The interlayer spacing of LDH is also strongly influenced by milling time so that it escalated from 7.737±0.001 to 8.005±0.002 (1–15h) and then decreased to 7.937±0.001 for 20h milled sample. Electron microscopic observation displayed that the final product had hexagonal platelet structure with lateral dimension of 20–100nm. Therefore, the synthesis of Mg0.8Al0.2(OH)2Cl0.2 via mechanochemistry owing to simplicity and versatility can be a promising candidate for use in catalyst carriers, drug delivery, and gene delivery.

Effects of abacavir administration on structural and functional markers of platelet activation.

Current abacavir exposure has been reported to be associated with cardiovascular disease. Changes in platelet reactivity could plausibly explain the clinically observed pattern of association. To determine if platelet reactivity changed following abacavir exposure and whether this effect was reversible on cessation of the drug. In an open-label, interventional study abacavir, 600 mg daily, was added to a suppressive antiretroviral regimen in 20 adult HIV-positive men. Platelet function, estimated by the phosphorylated vasodilator-stimulated phosphoprotein (P-VASP) assay and through measurement of the expression and shedding of platelet-specific receptors, was assessed at baseline, following 15 days of abacavir and at completion of a 28-day washout period. The VASP-index decreased significantly from 79.1% [interquartile range (IQR) 47.8-87.6] to 32.6% (IQR -11.5-51.0) following 15 days of abacavir administration (P = 0.010), and returned to baseline levels following the washout period (day 43 =76.3%; IQR 40.7-92.3). There was no change in resting (prostaglandin E1 alone) P-VASP but a slight increase in P-VASP within stimulated platelets (prostaglandin E1 and adenosine diphosphate). Integrin β3 levels decreased significantly [208.5 ng/ml (IQR 177.0-231.1) to 177.5 ng/ml (IQR 151.7-205) P < 0.001] and there was a nonsignificant trend towards decreased soluble glycoprotein VI levels [baseline; 72.5 ng/ml (95% CI 58.3-81.5) vs. day 15; 45.0 ng/ml (95% CI 33.0-98.2) P = 0.79]. Abacavir led to reversible changes in platelet function and structure. The clinical implications of these changes are uncertain; they may represent negative feedback mechanisms in response to an abacavir-associated prothrombotic state.

Effect of ZrO2 Addition on Densification and Mechanical Properties of MgAl2O4–CaAl4O7–CaAl12O19 Composite

Although the platelet structure of calcium hexaluminate (CaAl12O19, or CA6) grains can strengthen and toughen the Al2O3–MgO–CaO system materials designed in the high‐alumina region, it also results in poor densification and subsequent accelerated slag penetration for refractory application. Considering this aspect, MgAl2O4–CaAl4O7–CaAl12O19 composite was fabricated by solid‐state reaction sintering in this work, and the effect of ZrO2 addition on densification and mechanical properties was investigated. The results showed that the CA6 grains presented a more equiaxed morphology by addition of ZrO2, contributing to form highly dense microstructures after heating at 1600°C without evident grain coarsening. The compressive strength and flexural strength were greatly enhanced mainly due to the significant decrease in porosity and pore sizes. Besides, the increased content of ZrO2 plays an active role in toughening this composite attributed to the dense microstructure and strong bonding with higher strength, as well as considerable t‐ZrO2 transformability.

Effect of TiO&lt;sub&gt;2&lt;/sub&gt; and MgO on Microstructure of α-Alumina Ceramics and its Sintering Behavior

Observation on the effect of adding titanium oxide (TiO2) and magnesium oxide (MgO) on the sintering of α-alumina (Al2O3) has been performed. In this study, technical alumina used as basic material in which the sample is formed by the pressureless sintering/cold press and sintered at 1500°C which is lower than alumina sintering temperature at 1700°C. Elemental analysis, observation of microstructure, hardness, fracture toughness and density measurements were carried out to determine the physical and mechanical properties of alumina. The results indicate a change in the microstructure where the content of the platelet structure are much more than the equilateral structure. At sintering temperature of 1500°C, neck growth occurs at ceramics grain, supported by the results of the density test which indicate perfect compaction has occurred in this process.

The study of anticoagulants selection in platelet-rich plasma preparation

To investigate the effect of the anticoagulants on PRP quality, so as to clarify the appropriate anticoagulant used in PRP production. The microstructure change of platelets collected via heparin, citrate, acid citrate dextrose (ACD) and citrate-theophylline-adenosine-dipyridamole ( CTAD) was observed by TEM following time course. The extent of spontaneous activation of platelets in four groups was detected by measuring sP-selectin in plasma. The TGF-β1 release amount of activated PRP of four groups was measured. CTAD is superior to other anticoagulants in maintaining the integrity of platelet structures for a long time and preventing platelet spontaneous activation. ACD slightly surpassed heparin and citrate in above two aspects. ACD-PRP and CTAD-PRP released significantly more TGF-β1 compared with heparin and citrate. The PRP quality and biological effects were strongly associated with the type of Anticoagulants. ACD and CTAD are optimal anticoagulants in PRP production for they can maintain platelet viability at a high level.

Crystallization of Poly(ϵ-caprolactone) composites with graphite nanoplatelets: Relations between nucleation and platelet thickness

Poly(ϵ-caprolactone) (PCL) composites containing graphite with various layered platelet structures were prepared by solution mixing for crystallization study. The results reveal that the crystallization of PCL is highly dependent on the graphite structure. All three kinds of graphite particles, including graphene nanosheets, graphite nanoplatelets and natural graphite flakes, show evident nucleating effect on the PCL crystallization. But their nucleation activity reduces with increased platelet thickness. However, the presence of graphite particles, especially graphite nanoplatelets and graphene nanosheets, also impedes the movements of PCL chain and increases the system viscosity, resulting in an evident increase of crystallization activation energy. But the nucleating effect is dominant role in the current system because all composites show higher crystallization rates than the neat PCL. The obtained results of this work can provide additional way to design or to control crystallization of PCL composites.

One-pot synthesis of graphene oxide sheets and graphene oxide quantum dots from graphite nanofibers

A one-pot synthesis of graphene oxide (GO) sheets and GO quantum dots using graphite nanofibers (GNF) as starting material is reported. Two types of GNF starting materials, namely herringbone and platelet structures, were used. HRTEM revealed that platelet GNF produces quantum dots typically less than 10 nm in size while herringbone GNF produces relatively larger GO sheets. SAED patterns indicate that the produced GO sheets have a hexagonal crystal structure. UV–Vis, PL, XPS, and Raman show salient differences between the produced GO nanostructures which correlate well with the morphological analysis. Unlike the GO sheets, the GO quantum dots are photoluminescent. The difference in PL properties was attributed to the higher oxygen content in GO quantum dots which were shown by XPS. The results offer a new insight to the importance of starting material in the synthesis of graphene nanostructures.

Dispersion and interaction of graphene oxide in amorphous and semi-crystalline nano-composites: a PALS study

The influence of dispersion and interaction of Graphene Oxide (GO) in semicrystalline Polyhydroxy butyrate (PHB) and glassy amorphous Poly(tBP-oda) is explored by Positron Annihilation Lifetime Spectroscopy (PALS). The ortho-Positronium lifetimes which represent the main free volume hole size of both polymers are mainly affected by the large differences in internal stresses built up by the shrinkage of the polymers during their preparation, restricted by the platelet structure of GO. The ortho-Positronium intensities, which represent the ortho-Positronium formation probabilities, suggest a strong dependency of on the dispersion of the nano-particles and their aspect ratio.

Bioinspired Hierarchical Alumina-Graphene Oxide-Poly(vinyl alcohol) Artificial Nacre with Optimized Strength and Toughness.

Due to hierarchical organization of micro- and nanostructures, natural nacre exhibits extraordinary strength and toughness, and thus provides a superior model for the design and fabrication of high-performance artificial composite materials. Although great progress has been made in constructing layered composites by alternately stacking hard inorganic platelets and soft polymers, the real issue is that the excellent strength of these composites was obtained at the sacrifice of toughness. In this work, inspired by the layered aragonite microplatelets/chitin nanofibers-protein structure of natural nacre, alumina microplatelets-graphene oxide nanosheets-poly(vinyl alcohol) (Al2O3/GO-PVA) artificial nacre is successfully constructed through layer-by-layer bottom-up assembly, in which Al2O3 and GO-PVA act as "bricks" and "mortar", respectively. The artificial nacre has hierarchical "brick-and-mortar" structure and exhibits excellent strength (143 ± 13 MPa) and toughness (9.2 ± 2.7 MJ/m(3)), which are superior to those of natural nacre (80-135 MPa, 1.8 MJ/m(3)). It was demonstrated that the multiscale hierarchical structure of ultrathin GO nanosheets and submicrometer-thick Al2O3 platelets can deal with the conflict between strength and toughness, thus leading to the excellent mechanical properties that cannot be obtained using only one size of platelet. We strongly believe that the work presented here provides a creative strategy for designing and developing new composites with excellent strength and toughness.

Improving of Micro Porous Layer based on Advanced Carbon Materials for High Temperature Proton Exchange Membrane Fuel Cell Electrodes

AbstractThis work reports the study of four different carbon materials for their application as carbon material in microporous layers for high temperature proton exchange membrane fuel cells electrodes. The microporous layers were prepared with carbon black (a commercial one, Vulcan XC72), two different carbon nanofibers, CNF, (Ribbon and Platelet structure) and carbon nanospheres, all of them prepared in our lab. The microporous layers were characterized by XRD. The hydrophobicity, electrical conductivity, and permeability to different gases were also evaluated. The stability is an important issue to be overcome in the field of proton exchange membrane fuel cells. Thus, accelerated thermal and electrochemical degradation tests in phosphoric acid media were carried out to evaluate the stability of the different advanced materials tested under the same conditions. From all the performed essays, the carbon nanospheres were the best nano‐carbon materials because of the lower degradation degree shown by the microporous layer prepared with them and the good conductivity and permeability achieved, whereas CNF with a Platelet structure showed a low electrochemical stability due to their greater edge plane exposure which favors their corrosion.

Platelet Structure and Function

1. George A. Fritsma, MS, MLS[⇑][1] 1. The Fritsma Factor, Your Interactive Hemostasis Resource, Fritsma & Fritsma LLC, Birmingham, AL 1. Address for Correspondence: George A. Fritsma, MS, MLS, The Fritsma Factor, Your Interactive Hemostasis Resource, Fritsma & Fritsma LLC, 153 Redwood Drive, Birmingham, AL 35173, George{at}fritsmafactor.com 1. Diagram platelet structure, including glycocalyx, plasma membrane, filaments, microtubules, and granules. 2. Illustrate platelet adhesion, including the role of von Willebrand factor 3. Illustrate platelet aggregation, including the role of fibrinogen 4. List the secretions of platelet dense bodies and α-granules 5. Demonstrate the relationship of platelets and the plasma coagulation mechanism. Platelets are blood cells that are released from bone marrow megakaryocytes and circulate for approximately 10 days. They possess granular cytoplasm with no nucleus and their diameter when seen in a Wright-stained peripheral blood film averages 2.5 um with a subpopulation of larger cells, 4–5 um. Mean platelet volume (MPV), as measured in a buffered isotonic suspension flowing through the impedance-based detector cell of a clinical profiling instrument, is 8–10 fL. Circulating, resting platelets are biconvex, although in EDTA blood they tend to “round up.” On a blood film, platelets appear circular to irregular, lavender, and granular, although their diminutive size makes them hard to examine for internal structure.1 In the blood, their surface is even, and they flow smoothly through veins, arteries, and capillaries. The normal peripheral blood platelet count is 150–400,000/μL. This count represents only two thirds of available platelets because the spleen sequesters the remainder. In hypersplenism or splenomegaly, increased sequestration may cause a relative thrombocytopenia. Under conditions of hemostatic need, platelets move from the spleen to the peripheral blood and answer cellular and humoral stimuli by becoming irregular and sticky, extending pseudopods, and adhering to neighboring structures or aggregating with one another. Platelet Plasma Membrane The platelet plasma membrane is a standard bilayer composed of proteins and lipids (Figure 1). The predominant lipids are phospholipids, which form the basic structure, and cholesterol, which distributes asymmetrically throughout the phospholipids. The phospholipids form a bilayer with their polar heads oriented toward aqueous environments—toward the plasma externally… ABBRVIATIONS: ADP-adenosine diphosphate; ATP-adenosine triphosphate; CAM-cell adhesion molecule; cAMP-cyclic adenosine monophosphate; DAG-diacylglycerol; DTS-dense tubular system; ECM-extracellular matrix; EGF-endothelial growth factor; GMP-guanidine monophosphate; GP-glycoprotein; HMWK-high-molecular-weight kininogen; Ig-immunoglobulin; IP3-inositol triphosphate; IP-PGI2 receptor; MPV-mean platelet volume; P2Y1 and P2Y12-ADP receptors; PAI-1-plasminogen activator inhibitor-1; PAR-protease-activated receptor; PF4-platelet factor 4; PGG2-prostaglandin G2; PGH2-prostaglandin H2; PDCI-platelet-derived collagenase inhibitor; PDGF-platelet-derived growth factor; PECAM-1-platelet–endothelial cell adhesion molecule-1; PGI2-prostaglandin I2 (prostacyclin); RGD-arginine-glycine-aspartic acid receptor target; SCCS-surface-connected canalicular system; STR-seven-transmembrane repeat receptor; TGF-β-transforming growth factor-β; TPα and TPβ-thromboxane receptors; TXA2-thromboxane A2; VEGF/VPF-vascular endothelial growth factor/vascular permeability factor; VWF-von Willebrand factor 1. Diagram platelet structure, including glycocalyx, plasma membrane, filaments, microtubules, and granules. 2. Illustrate platelet adhesion, including the role of von Willebrand factor 3. Illustrate platelet aggregation, including the role of fibrinogen 4. List the secretions of platelet dense bodies and α-granules 5. Demonstrate the relationship of platelets and the plasma coagulation mechanism. [1]: #corresp-1

The class II PI 3-kinase, PI3KC2α, links platelet internal membrane structure to shear-dependent adhesive function.

PI3KC2α is a broadly expressed lipid kinase with critical functions during embryonic development but poorly defined roles in adult physiology. Here we utilize multiple mouse genetic models to uncover a role for PI3KC2α in regulating the internal membrane reserve structure of megakaryocytes (demarcation membrane system) and platelets (open canalicular system) that results in dysregulated platelet adhesion under haemodynamic shear stress. Structural alterations in the platelet internal membrane lead to enhanced membrane tether formation that is associated with accelerated, yet highly unstable, thrombus formation in vitro and in vivo. Notably, agonist-induced 3-phosphorylated phosphoinositide production and cellular activation are normal in PI3KC2α-deficient platelets. These findings demonstrate an important role for PI3KC2α in regulating shear-dependent platelet adhesion via regulation of membrane structure, rather than acute signalling. These studies provide a link between the open canalicular system and platelet adhesive function that has relevance to the primary haemostatic and prothrombotic function of platelets.

Viscoelasticity and Ultrastructure in Coagulation and Inflammation: Two Diverse Techniques, One Conclusion.

The process of blood clotting has been studied for centuries. A synopsis of current knowledge pertaining to haemostasis and the blood components, including platelets and fibrin networks which are closely involved in coagulation, are discussed. Special emphasis is placed on tissue factor (TF), calcium and thrombin since these components have been implicated in both the coagulation process and inflammation. Analysis of platelets and fibrin morphology indicate that calcium, tissue factor and thrombin at concentrations used during viscoelastic analysis (with thromboelastography or TEG) bring about alterations in platelet and fibrin network ultrastructure, which is similar to that seen in inflammation. Scanning electron microscopy indicated that, when investigating platelet structure in disease, addition of TF, calcium or thrombin will mask disease-induced alterations associated with platelet activation. Therefore, washed platelets without any additives is preferred for morphological analysis. Furthermore, morphological and viscoelastic analysis confirmed that thrombin activation is the preferred method of fibrin activation when investigating fibrin network ultrastructure.

Coronary intervention in diabetes: is it different

Diabetics are at an increased risk of cardiovascular morbidity and mortality as a consequence of inherent metabolic abnormalities and comorbidities. Furthermore, these patients derive less benefit from the standard therapies...

Roll, adhere, spread and contract: Structural mechanics of platelet function

Platelets are involved in life-sustaining processes such as hemostasis, wound healing, atherothrombosis and angiogenesis. Mechanical trauma to blood vessels causes platelet activation resulting in their adherence and clot formation at the damaged site, culminating in clot retraction and tissue repair. Two of the major players underlying this process are the cytoskeleton, i.e., actin and microtubules, and the membrane integrin receptors. Rare congenital bleeding disorders such as Glanzmann thrombasthenia and Bernard–Soulier syndrome are associated with genetic alterations of platelet surface receptors, also affecting the platelet cytoskeletal structure. In this review, we summarize the current knowledge about platelet structure and adhesion, and delve into the mechanical aspects of platelet function. Platelets lack a nucleus, and can thus provide a minimal model of a biological cell. New biophysical tools may help to scrutinize platelets anew and to extend the existing knowledge on cell biology.

Sol–gel synthesis of titanium oxide supported nickel catalysts for hydrogen and carbon production by methane decomposition

TiO2-supported NiO hybrids have been synthesized by the sol–gel method and further processed into catalysts for hydrogen production by methane decomposition. The structures of the metal oxides and catalysts are characterized using field emission electron microscopy, transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and N2 adsorption-desorption test. The catalytic performance of the catalysts is evaluated in terms of hydrogen yield rate, methane conversion and carbon yield. It is found that the TiO2-supported catalysts show better catalytic performance when compared with the unsupported catalyst, which is attributed to the uniform dispersion of ultrafine nickel particles as well as the appropriate metal-support interaction. The catalyst performance is dependent on the ratio of NiO and TiO2. The 1NiO–2TiO2 exhibits the highest carbon yield of 321.1 g C g−1 Ni at 500 °C. The structures of the produced carbons are characterized by transmission electron microscopy and X-ray diffraction. It is found that the resulting filamentous carbon materials exhibit uniform diameters and various morphologies including hollow tube, platelet, bow-like and herringbone structures.

Design of porous Ag platelet structures with tunable porosity and high catalytic activity

Porous Ag structures have recently attracted great interest due to their unique characteristics, relatively low cost and good biocompatibility.

Epithelial (E)-Cadherin Is a Novel Regulator of Platelet Function

Epithelial (E-) cadherin is an adhesion molecule that mediates cell-cell interactions, and is important in pluripotent stem cell reprogramming. We are investigating the role of E-cadherin in megakaryocyte differentiation and platelet function, and propose that E-cadherin mediates interactions that facilitate the essential roles of platelets. We have evidence that mature megakaryocytes and platelets express E-cadherin, and therefore generated a megakaryocyte-specific E-cadherin knockout mouse using the PF4-Cre system. E-cadherin deleted mice are viable and fertile. Despite having normal platelet counts and mean platelet volume, platelet function is abnormal. E-cadherin deletion in platelets significantly increases bleeding time in adult mice, with wild type (Ecadw/w) bleeding times of 225±52 secs, and homozygous deletion (Ecadf/f) times of 880±134 secs (p=0.005). In vivo platelet depletion using systemic administration of anti-CD42b antibody in the Ecadf/f mice causes death, likely due to hemorrhage and failure of hemostasis, which is not observed in Ecadw/w with similar levels of platelet depletion, suggesting a platelet function defect that becomes more evident under stress. We performed immunofluorescence to probe platelet structure as a potential explanation for the phenotypes, and observed disrupted b-tubulin architecture in the E-cadherin null platelets. Also, static platelet adhesion assays revealed that E-cadherin deficient platelets have impaired adhesion on fibrinogen, relative to a BSA substrate (p=0.0005). We have extended our studies to the human system, and initial studies using an E-cadherin blocking antibody in human platelets show impairment of aggregation in response to ADP, epinephrine, and thrombin. Taken together, the results demonstrate that E-cadherin contributes to the delicate balance between bleeding, hemostasis, and thrombosis. Future studies will focus on identifying how E-cadherin regulates hemostasis, with an emphasis on the interactions mediated by E-cadherin, whether between platelets, or with other cells in the blood. DisclosuresNo relevant conflicts of interest to declare.

The structure of water near a charged crystalline surface

The structure of water near a synthetic clay surface, Laponite, is probed experimentally by total neutron scattering, in both liquid and arrested states. It is shown that the crystalline structure of the Laponite platelets and their charge distribution determine polarization of the closest water layers, with a local density higher than that of bulk water. Interestingly these layers show long range order in the plane parallel to the Laponite surface, while no indication of strong hydrogen bonding between water and Laponite is found.

High dose proton implantations into silicon: a combined EBIC, SRP and TEM study

AbstractProton (H+) implantations are used in power semiconductor devices to introduce recombination centers (Hazdra et al., Microelectron. J. 32(5), 449–456 (2001)) or to form hydrogen related donor complexes (Zohta et al., Jpn. J. Appl. Phys. 10, 532–533 (1991)). Proton implantations are also used in the 'smart cut' process to generate defects that can be used to cleave thin wafers (Romani and Evans, Nucl. Instrum. Methods Phys. Res. B 44, 313–317 (1990)). However, the implantation damage resulting from H+implantations is not completely understood. In this study, protons with energies from 400 keV up to 4 MeV and doses up to 1016 H+/cm² were implanted into highly ohmic boron doped m:Cz silicon (100). Electron Beam Induced Current (EBIC) measurements were performed to locally determine the minority charge carrier diffusion length. The diffusion length decreases with increasing implantation dose and incorporated damage. Spreading Resistance Profiling (SRP) measurements were performed to analyze the charge carrier concentration profiles for different annealing procedures. The electrical activation and growth of the defect complexes varies strongly with the annealing parameters. Transmission Electron Microscopy measurements were made to investigate the microscopic structures formed by the high dose implantation processes. Due to the high local damage density resulting from low energy and high dose H+ implants, platelet structures are formed. During high‐energy high‐dose H+implantations, the implanted hydrogen generates strain in the crystal lattice resulting in changes in the distances between atomic planes. (© 2014 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)