scholarly journals Shear relaxation governs fusion dynamics of biomolecular condensates

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Archishman Ghosh ◽  
Divya Kota ◽  
Huan-Xiang Zhou
Keyword(s):  
Shear Stress ◽  
Elastic Moduli ◽  
Environmental Cues ◽  
Cellular Functions ◽  
Finite Rate ◽  
Ample Evidence ◽  
Viscous Liquids ◽  
Interfacial Tensions ◽  
Shear Relaxation ◽  
Optically Trapped

AbstractPhase-separated biomolecular condensates must respond agilely to biochemical and environmental cues in performing their wide-ranging cellular functions, but our understanding of condensate dynamics is lagging. Ample evidence now indicates biomolecular condensates as viscoelastic fluids, where shear stress relaxes at a finite rate, not instantaneously as in viscous liquids. Yet the fusion dynamics of condensate droplets has only been modeled based on viscous liquids, with fusion time given by the viscocapillary ratio (viscosity over interfacial tension). Here we used optically trapped polystyrene beads to measure the viscous and elastic moduli and the interfacial tensions of four types of droplets. Our results challenge the viscocapillary model, and reveal that the relaxation of shear stress governs fusion dynamics. These findings likely have implications for other dynamic processes such as multiphase organization, assembly and disassembly, and aging.

scholarly journals Shear Relaxation Governs Dynamic Processes of Biomolecular Condensates

2021 ◽  
Author(s):  
Archishman Ghosh ◽  
Divya Kota ◽  
Huan-Xiang Zhou
Keyword(s):  
Shear Stress ◽  
Elastic Moduli ◽  
Dynamic Processes ◽  
Environmental Cues ◽  
Cellular Functions ◽  
Ample Evidence ◽  
Viscous Liquids ◽  
Interfacial Tensions ◽  
Shear Relaxation ◽  
Optically Trapped

Phase-separated biomolecular condensates must respond agilely to biochemical and environmental cues in performing their wide-ranging cellular functions, but our understanding of condensate dynamics is lagging. Ample evidence now indicates biomolecular condensates as viscoelastic fluids, where shear stress relaxes at a finite rate, not instantaneously as in viscous liquids. Yet the fusion dynamics of condensate droplets has only been modeled based on viscous liquids, with fusion time given by the viscocapillary ratio (viscosity over interfacial tension). Here we used optically trapped polystyrene beads to measure the viscous and elastic moduli and the interfacial tensions of four types of droplets. Our results challenge the viscocapillary model, and reveal that the relaxation of shear stress governs fusion and other dynamic processes of condensates.

Atherosclerosis at arterial bifurcations: evidence for the role of haemodynamics and geometry

2016 ◽  
Vol 115 (03) ◽  
pp. 484-492 ◽  
Author(s):  
Umberto Morbiducci ◽  
Annette M. Kok ◽  
Brenda R. Kwak ◽  
Peter H. Stone ◽  
David A. Steinman ◽  
...  
Keyword(s):  
Risk Factors ◽  
Shear Stress ◽  
Systemic Risk ◽  
Biological Response ◽  
Arterial System ◽  
Ample Evidence ◽  
Fluid Forces ◽  
Flow Features ◽  
Systemic Risk Factors

SummaryAtherosclerotic plaques are found at distinct locations in the arterial system, despite the exposure to systemic risk factors of the entire vascular tree. From the study of arterial bifurcation regions, emerges ample evidence that haemodynamics are involved in the local onset and progression of the atherosclerotic disease. This observed co-localisation of disturbed flow regions and lesion prevalence at geometrically predisposed districts such as arterial bifurcations has led to the formulation of a ‘haemodynamic hypothesis’, that in this review is grounded to the most current research concerning localising factors of vascular disease. In particular, this review focuses on carotid and coronary bifurcations because of their primary relevance to stroke and heart attack. We highlight reported relationships between atherosclerotic plaque location, progression and composition, and fluid forces at vessel’s wall, in particular shear stress and its ‘easier-tomeasure’ surrogates, i.e. vascular geometric attributes (because geometry shapes the flow) and intravascular flow features (because they mediate disturbed shear stress), in order to give more insight in plaque initiation and destabilisation. Analogous to Virchow’s triad for thrombosis, atherosclerosis must be thought of as subject to a triad of, and especially interactions among, haemodynamic forces, systemic risk factors, and the biological response of the wall.

scholarly journals ON THE MECHANICAL RESPONSE OF A PRESSURIZED FUNCTIONALLY-GRADED CYLINDER

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Vlado Lubarda
Keyword(s):  
Shear Stress ◽  
Power Law ◽  
Functionally Graded Material ◽  
Elastic Moduli ◽  
Mechanical Response ◽  
Maximum Shear Stress ◽  
Radial Distance ◽  
Functionally Graded ◽  
Graded Material ◽  
Radial Inhomogeneity

A pressurized functionally-graded cylinder is considered made of the material whose elastic moduli vary with the radial distance according to the power-law relation. Some peculiar features of the mechanical response are noted for an incompressible functionally-graded material with the power of radial inhomogeneity equal to two. In particular, it is shown that the maximum shear stress is constant throughout the cylinder, while the displacement changes proportional to 1/r along the radial distance. No displacement takes place at all under equal pressures applied at both boundaries.

Pure Material Instability and the Concept of Yield Stress

1999 ◽  
Vol 9 (2) ◽  
pp. 58-63 ◽  
Author(s):  
Corneliu Balan
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Network Structure ◽  
Flow Curve ◽  
Constitutive Relations ◽  
Structural Instability ◽  
Pure Material ◽  
Viscous Liquids ◽  
Internal Network ◽  
Constant Shear Stress

Abstract The paper is concerned with the rheological study of gels, complex materials which are characterised by an internal network structure developed in viscous liquids. This category of materials exhibits in viscometric motion a yield state at a critical value of the applied shear stress. The yield shear stress defines the plateau behaviour in the steady flow curve. The creeping experiments and the dynamics of the Oldroyd’s 3 constants model put in evidence the connection between the loss of stability of the network structure and the coexisting strain rates at a constant shear stress. The correlation between theory, numerical simulations and experiments are established. All the results are qualitatively consistent with the statement that the concept of yield stress is ’natural defined‘ in the context of the pure material (structural) instability (i.e. instability at zero Reynolds number) of constitutive relations with non-monotone flow curve.

scholarly journals The influence of elastic moduli of core materials on shear stress distributions at the adhesive interface in resin built-up teeth

2017 ◽  
Vol 36 (1) ◽  
pp. 95-102 ◽  
Author(s):  
Ayaka CHIBA ◽  
Takashi HATAYAMA ◽  
Kimisuke KAINOSE ◽  
Masatoshi NAKAJIMA ◽  
David H. PASHLEY ◽  
...  
Keyword(s):  
Shear Stress ◽  
Elastic Moduli ◽  
Stress Distributions ◽  
Adhesive Interface ◽  
Core Materials

scholarly journals Cell spinpods are a simple inexpensive suspension culture device to deliver fluid shear stress to renal proximal tubular cells

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Timothy G. Hammond ◽  
Corey Nislow ◽  
Ivan C. Christov ◽  
Vecihi Batuman ◽  
Pranay P. Nagrani ◽  
...  
Keyword(s):  
Shear Stress ◽  
Suspension Culture ◽  
Fluid Shear Stress ◽  
Industrial Applications ◽  
Specific Pattern ◽  
Fluid Shear ◽  
Cellular Functions ◽  
Renal Proximal Tubular Cells

AbstractRotating forms of suspension culture allow cells to aggregate into spheroids, prevent the de-differentiating influence of 2D culture, and, perhaps most importantly of all, provide physiologically relevant, in vivo levels of shear stress. Rotating suspension culture technology has not been widely implemented, in large part because the vessels are prohibitively expensive, labor-intensive to use, and are difficult to scale for industrial applications. Our solution addresses each of these challenges in a new vessel called a cell spinpod. These small 3.5 mL capacity vessels are constructed from injection-molded thermoplastic polymer components. They contain self-sealing axial silicone rubber ports, and fluoropolymer, breathable membranes. Here we report the two-fluid modeling of the flow and stresses in cell spinpods. Cell spinpods were used to demonstrate the effect of fluid shear stress on renal cell gene expression and cellular functions, particularly membrane and xenobiotic transporters, mitochondrial function, and myeloma light chain, cisplatin and doxorubicin, toxicity. During exposure to myeloma immunoglobulin light chains, rotation increased release of clinically validated nephrotoxicity cytokine markers in a toxin-specific pattern. Addition of cisplatin or doxorubicin nephrotoxins reversed the enhanced glucose and albumin uptake induced by fluid shear stress in rotating cell spinpod cultures. Cell spinpods are a simple, inexpensive, easily automated culture device that enhances cellular functions for in vitro studies of nephrotoxicity.

scholarly journals The Mechanosensory Role of Primary Cilia in Vascular Hypertension

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Surya M. Nauli ◽  
Xingjian Jin ◽  
Beerend P. Hierck
Keyword(s):  
Shear Stress ◽  
Primary Cilia ◽  
Fluid Shear Stress ◽  
Vascular System ◽  
Vascular Endothelial Cells ◽  
Vascular Endothelial ◽  
Fluid Shear ◽  
Cellular Functions ◽  
Continuous Problem

Local regulation of vascular tone plays an important role in cardiovascular control of blood pressure. Aside from chemical or hormonal regulations, this local homeostasis is highly regulated by fluid-shear stress. It was previously unclear how vascular endothelial cells were able to sense fluid-shear stress. The cellular functions of mechanosensory cilia within vascular system have emerged recently. In particular, hypertension is insidious and remains a continuous problem that evolves during the course of polycystic kidney disease (PKD). The basic and clinical perspectives on primary cilia are discussed with regard to the pathogenesis of hypertension in PKD.

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