Experimental evaluation of stiffness predictions of multiaxial flax fibre composites by classical laminate theory.

Despite the good mechanical properties of natural fibre composites, their use in load-bearing components is still limited, which may be due to lack of knowledge and confidence in calculating the performance of the composites by mechanical models. The present study is providing an experimental evaluation of stiffness predictions of multiaxial flax fibre composite by classical laminate theory (CLT). The experimental base is (i) multiaxial flax fibre composites fabricated with two types of biaxial non-crimp fabrics, having a nominal yarn orientation of ±45°, and (ii) uniaxial flax fibre composites fabricated with the same flax yarn as used in the fabrics.

Fluid shear stress suppresses ICAM-1-mediated transendothelial migration of leukocytes in coculture model.

The adhesion and migration of leukocytes to arterial endothelial cells (ECs), one of the indicators of early atherogenesis, is believed to be correlated with the blood flow conditions and interactions between vascular cells including vascular smooth muscle cells (SMCs). In this study, we investigated the effect of fluid shear stress on the transendothelial migration of leukocytes in a coculture model (CM) composed of human umbilical ECs and SMCs, a layer of collagen type I, and a porous membrane. Following exposure to a fluid shear stress of 1.

Haemodynamically dependent valvulogenesis of zebrafish heart is mediated by flow-dependent expression of miR-21.

Heartbeat is required for normal development of the heart, and perturbation of intracardiac flow leads to morphological defects resembling congenital heart diseases. These observations implicate intracardiac haemodynamics in cardiogenesis, but the signalling cascades connecting physical forces, gene expression and morphogenesis are largely unknown. Here we use a zebrafish model to show that the microRNA, miR-21, is crucial for regulation of heart valve formation.

A novel method for measuring tension generated in stress fibers by applying external forces.

The distribution of contractile forces generated in cytoskeletal stress fibers (SFs) contributes to cellular dynamic functions such as migration and mechanotransduction. Here we describe a novel (to our knowledge) method for measuring local tensions in SFs based on the following procedure: 1), known forces of different magnitudes are applied to an SF in the direction perpendicular to its longitudinal axis; 2), force balance equations are used to calculate the resulting tensions in the SF from changes in the SF angle; and 3), the relationship between tension and applied force thus established is extrapolated to an applied force of zero to determine the preexisting tension in the SF. In this study, we measured tensions in SFs by attaching magnetic particles to them and applying known forces with an electromagnetic needle.

Heartbeat regulates cardiogenesis by suppressing retinoic acid signaling via expression of miR-143.

Cardiogenesis proceeds with concomitant changes in hemodynamics to accommodate the circulatory demands of developing organs and tissues. In adults, circulatory adaptation is critical for the homeostatic regulation of blood circulation. In these hemodynamics-dependent processes of morphogenesis and adaptation, a mechanotransduction pathway, which converts mechanical stimuli into biological outputs, plays an essential role, although its molecular nature is largely unknown.

Measurements of strain on single stress fibers in living endothelial cells induced by fluid shear stress.

Fluid shear stress (FSS) acting on the apical surface of endothelial cells (ECs) can be sensed by mechano-sensors in adhesive protein complexes found in focal adhesions and intercellular junctions. This sensing occurs via force transmission through cytoskeletal networks. This study quantitatively evaluated the force transmitted through cytoskeletons to the mechano-sensors by measuring the FSS-induced strain on SFs using live-cell imaging for actin stress fibers (SFs).

Direct measurement of shear strain in adherent vascular endothelial cells exposed to fluid shear stress.

Functional and morphological responses of endothelial cells (ECs) to fluid shear stress are thought to be mediated by several mechanosensitive molecules. However, how the force due to fluid shear stress applied to the apical surface of ECs is transmitted to the mechanosensors is poorly understood. In the present paper, we performed an analysis of an intracellular mechanical field by observation of the deformation behaviors of living ECs exposed to shear stress with a novel experimental method.

Microelastic mapping of living endothelial cells exposed to shear stress in relation to three-dimensional distribution of actin filaments.

The surface topography and local elastic moduli of endothelial cells exposed to shear stress were measured using atomic force microscopy. Bovine aortic endothelial cells were exposed to shear stress of 2Pa for 6, 12 or 24h. In addition, a confocal laser-scanning microscope used in conjunction with the atomic force microscope was used to observe the actin filament structure of these endothelial cells to elucidate the relationship between mechanical properties and cytoskeletal structure.