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Shear stress

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https://www.readbyqxmd.com/read/28636424/fluid-shear-stress-regulates-hepg2-cell-migration-though-time-dependent-integrin-signaling-cascade
#1
Hongchi Yu, Yang Shen, Jingsi Jin, Yingying Zhang, Tang Feng, Xiaoheng Liu
Hepatocellular carcinoma (HCC) is a subtype of malignant liver cancer with poor prognosis and limited treatment options. It is noteworthy that mechanical forces in tumor microenvironment play a pivotal role in mediating the behaviors and functions of tumor cells. As an instrumental type of mechanical forces in vivo, fluid shear stress (FSS) has been reported having potent physiologic and pathologic effects on cancer progression. However, the time-dependent mechanochemical transduction in HCC induced by FSS remains unclear...
June 21, 2017: Cell Adhesion & Migration
https://www.readbyqxmd.com/read/28634141/one-step-preparation-of-spherical-drug-particles-by-contamination-free-dry-milling-technique-with-corn-starch-beads
#2
Toshiyuki Niwa, Maria Yoshida, Naoko Hayashi, Keita Kondo
The novel dry milling technique has been developed by using a mechanical powder processor for improving the dissolution properties of poorly water-soluble drugs. It was found that the drug crystals were well pulverized by co-processing with fine particles of corn starch (CS). The morphological observation and particle size evaluation revealed that the processed products formed the composite particles with ordered-mixed structure, having double-layered particles with a core of CS and a coating layer of phenytoin (Phe), as a model drug...
June 17, 2017: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/28633977/vascular-endothelial-cell-mechanosensing-new-insights-gained-from-biomimetic-microfluidic-models
#3
REVIEW
Kelsey M Gray, Kimberly M Stroka
In vivo, cells of the vascular system are subjected to various mechanical stimuli and have demonstrated the ability to adapt their behavior via mechanotransduction. Recent advances in microfluidic and "on-chip" techniques have provided the technology to study these alterations in cell behavior. Contrary to traditional in vitro assays such as transwell plates and parallel plate flow chambers, these microfluidic devices (MFDs) provide the opportunity to integrate multiple mechanical cues (e.g. shear stress, confinement, substrate stiffness, vessel geometry and topography) with in situ quantification capabilities...
June 17, 2017: Seminars in Cell & Developmental Biology
https://www.readbyqxmd.com/read/28630943/parasites-lacking-the-micronemal-protein-mic2-are-deficient-in-surface-attachment-and-host-cell-egress-but-remain-virulent-in-vivo
#4
Simon Gras, Allison Jackson, Stuart Woods, Gurman Pall, Jamie Whitelaw, Jacqueline M Leung, Gary E Ward, Craig W Roberts, Markus Meissner
Background: Micronemal proteins of the thrombospondin-related anonymous protein (TRAP) family are believed to play essential roles during gliding motility and host cell invasion by apicomplexan parasites, and currently represent major vaccine candidates against Plasmodium falciparum, the causative agent of malaria. However, recent evidence suggests that they play multiple and different roles than previously assumed. Here, we analyse a null mutant for MIC2, the TRAP homolog in Toxoplasma gondii. Methods: We performed a careful analysis of parasite motility in a 3D-environment, attachment under shear stress conditions, host cell invasion and in vivo virulence...
2017: Wellcome Open Research
https://www.readbyqxmd.com/read/28630907/wind-invariant-saltation-heights-imply-linear-scaling-of-aeolian-saltation-flux-with-shear-stress
#5
Raleigh L Martin, Jasper F Kok
Wind-driven sand transport generates atmospheric dust, forms dunes, and sculpts landscapes. However, it remains unclear how the flux of particles in aeolian saltation-the wind-driven transport of sand in hopping trajectories-scales with wind speed, largely because models do not agree on how particle speeds and trajectories change with wind shear velocity. We present comprehensive measurements, from three new field sites and three published studies, showing that characteristic saltation layer heights remain approximately constant with shear velocity, in agreement with recent wind tunnel studies...
June 2017: Science Advances
https://www.readbyqxmd.com/read/28630304/transitional-turbulent-spots-and-turbulent-turbulent-spots-in-boundary-layers
#6
Xiaohua Wu, Parviz Moin, James M Wallace, Jinhie Skarda, Adrián Lozano-Durán, Jean-Pierre Hickey
Two observations drawn from a thoroughly validated direct numerical simulation of the canonical spatially developing, zero-pressure gradient, smooth, flat-plate boundary layer are presented here. The first is that, for bypass transition in the narrow sense defined herein, we found that the transitional-turbulent spot inception mechanism is analogous to the secondary instability of boundary-layer natural transition, namely a spanwise vortex filament becomes a [Formula: see text] vortex and then, a hairpin packet...
June 19, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28626203/rheological-approach-for-determining-yield-stresses-in-flowable-resin-composites-prior-to-setting
#7
Masaki Asakura, Tatsuhide Hayashi, Shozo Tsuruta, Mitsunori Yamamoto, Shuichiro Kobayashi, Akimichi Mieki, Tatsushi Kawai
The purpose of this study is to develop a method for quantifying the fluidity of flowable resin composites using determinations of yield stress. Five commercially available composites (AliteFlo LV, Flow-it ALC, Venus flow, Tetric N-flow, Revolution Formula2) were investigated. Yield stress values were obtained by plotting shear stresses for a range of shear rates, followed by fitting of Casson fluid models to flow curve data and extrapolation to the stress axis. To confirm that yield stress reflected fluidity, apparent viscosity at the lower shear rate (0...
June 15, 2017: Dental Materials Journal
https://www.readbyqxmd.com/read/28624707/substrate-stiffness-and-ve-cadherin-mechano-transduction-coordinate-to-regulate-endothelial-monolayer-integrity
#8
Roberto C Andresen Eguiluz, Kerim B Kaylan, Gregory H Underhill, Deborah E Leckband
The vascular endothelium is subject to diverse mechanical cues that regulate vascular endothelial barrier function. In addition to rigidity sensing through integrin adhesions, mechanical perturbations such as changes in fluid shear stress can also activate force transduction signals at intercellular junctions. This study investigated how extracellular matrix rigidity and intercellular force transduction, activated by vascular endothelial cadherin, coordinate to regulate the integrity of endothelial monolayers...
June 9, 2017: Biomaterials
https://www.readbyqxmd.com/read/28623080/increased-constitutive-nitric-oxide-production-by-whole-body-periodic-acceleration-ameliorates-alterations-in-cardiomyocytes-associated-with-utrophin-dystrophin-deficiency
#9
Jose R Lopez, Juan Kolster, Rui Zhang, Jose Adams
Duchenne Muscular Dystrophy (DMD) cardiomyopathy is a progressive lethal disease caused by the lack of the dystrophin protein in the heart. The most widely used animal model of DMD is the dystrophin-deficient mdx mouse; however, these mice exhibit a mild dystrophic phenotype with heart failure only late in life. In contrast, mice deficient for both dystrophin and utrophin (mdx/utrn(-/-), or dKO) can be used to model severe DMD cardiomyopathy where pathophysiological indicators of heart failure are detectable by 8-10weeks of age...
June 13, 2017: Journal of Molecular and Cellular Cardiology
https://www.readbyqxmd.com/read/28622076/human-ips-derived-endothelial-cells-for-3d-microphysiological-systems
#10
Yosuke K Kurokawa, Rose T Yin, Michael R Shang, Venktesh S Shirure, Monica L Moya, Steven C George
Microphysiological systems, or "organ-on-a-chip", platforms, aim to recapitulate in vivo physiology using small-scale in vitro tissue models of human physiology. While significant efforts have been made to create vascularized tissues, most reports utilize primary endothelial cells which hinder reproducibility. Here we report the use of human induced pluripotent stem cell-derived endothelial cells (iPS-EC) in developing 3D microvascular networks. We established a CDH5-mCherry reporter iPS cell line, which expresses the vascular endothelial (VE)-cadherin fused to mCherry...
June 16, 2017: Tissue Engineering. Part C, Methods
https://www.readbyqxmd.com/read/28621129/a-multiscale-shear-lag-analysis-of-stiffness-enhancement-in-polymer-graphene-nanocomposites
#11
Asanka Weerasinghe, Chang-Tsan Lu, Dimitrios Maroudas, Ashwin Ramasubramaniam
Graphene and other 2D materials are of emerging interest as functional fillers in polymer-matrix composites. In this work, we present a multiscale atomistic-to-continuum approach for modeling interfacial stress transfer in graphene-HDPE nanocomposites. Via detailed characterization of atomic-level stress profiles in sub-micron graphene fillers, we develop a modified shear-lag model for short fillers. A key feature of our approach lies in the correct accounting of stress concentration at the ends of fillers that exhibits a power-law dependence on filler ("flaw") size, determined explicitly from atomistic simulations, without any ad hoc modeling assumptions...
June 16, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28620766/phenotype-transformation-of-aortic-valve-interstitial-cells-due-to-applied-shear-stresses-within-a-microfluidic-chip
#12
Xinmei Wang, Joohyung Lee, Mir Ali, Jungkyu Kim, Carla M R Lacerda
Despite valvular heart diseases constituting a significant medical problem, the acquisition of information describing their pathophysiology remains difficult. Due to valvular size, role and location within the body, there is a need for in vitro systems that can recapitulate disease onset and progression. This study combines the development of an in vitro model and its application in the mechanical stimulation of valvular cell transformation. Specifically, porcine aortic valvular interstitial cells (PAVIC) were cultured on polydimethylsiloxane microfluidic devices with or without exposure to shear stresses...
June 15, 2017: Annals of Biomedical Engineering
https://www.readbyqxmd.com/read/28620384/measuring-leukocyte-adhesion-to-primary-endothelial-cells-after-photon-and-charged-particle-exposure-with-a-dedicated-laminar-flow-chamber
#13
Nadine Erbeldinger, Felicitas Rapp, Svetlana Ktitareva, Philipp Wendel, Anna S Bothe, Till Dettmering, Marco Durante, Thomas Friedrich, Bianca Bertulat, Stephanie Meyer, M C Cardoso, Stephanie Hehlgans, Franz Rödel, Claudia Fournier
The vascular endothelium interacts with all types of blood cells and is a key modulator of local and systemic inflammatory processes, for example, in the adhesion of blood leukocytes to endothelial cells (EC) and the following extravasation into the injured tissue. The endothelium is constantly exposed to mechanical forces caused by blood flow, and the resulting shear stress is essential for the maintenance of endothelial function. Changes in local hemodynamics are sensed by EC, leading to acute or persistent changes...
2017: Frontiers in Immunology
https://www.readbyqxmd.com/read/28620320/abnormal-haemodynamic-flow-patterns-in-bicuspid-pulmonary-valve-disease
#14
Malenka M Bissell, Margaret Loudon, Stefan Neubauer, Saul G Myerson
Abnormal flow patterns in the aortas of those with bicuspid aortic valves (BAVs) are increasingly recognized as important in the pathogenesis of aortic dilatation but pulmonary flow patterns in bicuspid pulmonary valves have not been studied. Bicuspid pulmonary valve disease is rare and a small numbers of case reports describe concomitant pulmonary artery dilation similar to the dilation of the ascending aorta, which is often seen in BAVs disease. We examined three cases of bicuspid pulmonary valve disease, 10 healthy volunteers and 10 patients with BAV disease but a tricuspid pulmonary valve...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28619950/how-neutrophils-resist-shear-stress-at-blood-vessel-walls-molecular-mechanisms-subcellular-structures-and-cell-cell-interactions
#15
REVIEW
Daniela Begandt, Sarah Thome, Markus Sperandio, Barbara Walzog
Neutrophils are the first cells arriving at sites of tissue injury or infection to combat invading pathogens. Successful neutrophil recruitment to sites of inflammation highly depends on specific molecular mechanisms, fine-tuning the received information into signaling pathways and converting them into well-described recruitment steps. This review highlights the impact of vascular flow conditions on neutrophil recruitment and the multitude of mechanisms developed to enable this sophisticated process under wall shear stress conditions...
June 15, 2017: Journal of Leukocyte Biology
https://www.readbyqxmd.com/read/28617509/controlled-rotation-and-translation-of-spherical-particles-or-living-cells-by-surface-acoustic-waves
#16
Ianis Bernard, Alexander A Doinikov, Philippe Marmottant, David Rabaud, Cédric Poulain, Pierre Thibault
We show experimental evidence of the acoustically-assisted micromanipulation of small objects like solid particles or blood cells, combining rotation and translation, using high frequency surface acoustic waves. This was obtained from the leakage in a microfluidic channel of two standing waves arranged perpendicularly in a LiNbO3 piezoelectric substrate working at 36.3 MHz. By controlling the phase lag between the emitters, we could, in addition to translation, generate a swirling motion of the emitting surface which, in turn, led to the rapid rotation of spherical polystyrene Janus beads suspended in the channel and of human red and white blood cells up to several rounds per second...
June 15, 2017: Lab on a Chip
https://www.readbyqxmd.com/read/28617485/non-trivial-rheological-exponents-in-sheared-yield-stress-fluids
#17
Elisabeth Agoritsas, Kirsten Martens
In this work we discuss possible physical origins of non-trivial exponents in the athermal rheology of soft materials at low but finite driving rates. A key ingredient in our scenario is the presence of a self-consistent mechanical noise that stems from the spatial superposition of long-range elastic responses to localized plastically deforming regions. We study analytically a mean-field model, in which this mechanical noise is accounted for by a stress diffusion term coupled to the plastic activity. Within this description we show how a dependence of the shear modulus and/or the local relaxation time on the shear rate introduces corrections to the usual mean-field prediction, concerning the Herschel-Bulkley-type rheological response of exponent 1/2...
June 15, 2017: Soft Matter
https://www.readbyqxmd.com/read/28616345/wrapping-of-the-ascending-aorta-revisited-is-there-any-role-left-for-conservative-treatment-of-ascending-aortic-aneurysm
#18
REVIEW
José María González-Santos, María Elena Arnáiz-García
Dilatation of the ascending aorta (AA) is a common finding in patients with aortic valve disease. The clinical practice guidelines recommend replacing the AA whenever the diameter exceeds 45 mm. However, no consensus has been reached regarding the approach when the aorta is only moderately dilated. Although the risk in aorta replacement is generally low, it may be higher when associated with other complex surgical procedures or it is carried out in elderly patients or patients with significant comorbidity. This would justify the use of alternative surgical techniques, which reduce surgical risk and guarantee a durable correction of the aortic pathology...
May 2017: Journal of Thoracic Disease
https://www.readbyqxmd.com/read/28613905/unexpected-effects-of-activator-molecules-polarity-on-the-electroreological-activity-of-titanium-dioxide-nanopowders
#19
Alexander Viktorovich Agafonov, Olga I Davydova, Anton S Krayev, Olga S Ivanova, Olga L Evdokimova, Tatiana V Gerasimova, Alexander E Baranchikov, Vladimir V Kozik, Vladimir K Ivanov
Titanium dioxide nanoparticles, obtained using the sol-gel method and modified with organic solvents such as acetone, acetonitrile, benzene, diethyl ether, dimethylsulfoxide, toluene and chloroform, were used as the filler of polydimethylsiloxane-based electrorheological fluids. The effect of electric field strength on the shear stress and yield stress of electrorheological fluids was investigated, as well as the spectra of their dielectric relaxation in the frequency range from 25 to 106 Hz. Modification of titanium dioxide by polar molecules was found to enhance the electrorheological effect, as compared with unmodified TiO2, in accordance with the widely accepted concept of polar molecule dominated electrorheological effect (PM-ER)...
June 14, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28612189/the-inclusion-of-chitosan-in-poly-%C3%AE%C2%B5-caprolactone-nanoparticles-impact-on-the-delivery-system-characteristics-and-on-the-adsorbed-ovalbumin-secondary-structure
#20
Sandra Jesus, Elizangela H Fragal, Adley F Rubira, Edvani C Muniz, Artur J M Valente, Olga Borges
This report extensively explores the benefits of including chitosan into poly-ε-caprolactone (PCL) nanoparticles (NPs) to obtain an improved protein/antigen delivery system. Blend NPs (PCL/chitosan NPs) showed improved protein adsorption efficacy (84%) in low shear stress and aqueous environment, suggesting that a synergistic effect between PCL hydrophobic nature and the positive charges of chitosan present at the particle surface was responsible for protein interaction. Additionally, thermal analysis suggested the blend NPs were more stable than the isolated polymers and cytotoxicity assays in a primary cell culture revealed chitosan inclusion in PCL NPs reduced the toxicity of the delivery system...
June 13, 2017: AAPS PharmSciTech
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