Shear stress on blood cells and platelets transported in a turbulent flow dictates the fate and biological activity of these cells. We present a theoretical link between energy dissipation in turbulent flows to the shear stress that cells experience and show that for the case of physiological turbulent blood flow: (a) the Newtonian assumption is valid, (b) turbulent eddies are universal for the...

RATIONALE Endothelial microRNA-126 (miR-126) modulates vascular development and angiogenesis. However, its role in the regulation of smooth muscle cell (SMC) function is unknown. OBJECTIVE To elucidate the role of miR-126 secreted by endothelial cells (ECs) in regulating SMC turnover in vitro and in vivo, as well as the effects of shear stress on the regulation. METHODS AND RESULTS Cocultur...

BACKGROUND Endothelial cells (ECs) are continuously exposed to hemodynamic forces imparted by blood flow. While it is known that endothelial behavior can be influenced by cytokine activation or fluid shear, the combined effects of these two independent agonists have yet to be fully elucidated. METHODOLOGY We investigated EC response to long-term inflammatory cues under physiologically relevan...

RATIONALE Lymphatic vessels function to drain interstitial fluid from a variety of tissues. Although shear stress generated by fluid flow is known to trigger lymphatic expansion and remodeling, the molecular basis underlying flow-induced lymphatic growth is unknown. OBJECTIVE We aimed to gain a better understanding of the mechanism by which laminar shear stress activates lymphatic proliferati...

We characterize the edge of chaos, the boundary which separates initial conditions which lead to chaotic behavior from those which directly decay to the laminar state, for a nine-dimensional shear flow model. This boundary is the eight-dimensional stable manifold of an unstable periodic orbit, whose properties are characterized. Furthermore, we compute the probability that perturbations of a gi...

Atherosclerosis preferentially occurs in areas of turbulent blood flow and low fluid shear stress, whereas laminar blood flow and high shear stress are atheroprotective. Inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), stimulate expression of endothelial cell (EC) genes that may promote atherosclerosis. Recent findings suggest a steady laminar blood flow decreases EC apo...

According to our observation of turbulence generation, all small length scales are generated by shear layer instability. The size of small vortices should be determined by the smallest stable shear layer, e.g. smallest shear layer like laminar sub-layer in the wall bounded flow. This paper provides a new estimation of the smallest length scale by using the shear layer stability analysis, which ...

An essential cofactor for the endothelial NO synthase is tetrahydrobiopterin (H4B). In the present study, we show that in human endothelial cells, laminar shear stress dramatically increases H4B levels and enzymatic activity of GTP cyclohydrolase (GTPCH)-1, the first step of H4B biosynthesis. In contrast, protein levels of GTPCH-1 were not affected by shear. Shear did not change protein express...

We investigated the effect of hemodynamic shear forces on the expression of adhesive molecules, E-selectin, and intercellular adhesion molecule-l (ICAM-1) on human umbilical vein endothelial cells (HUVEC) exposed t o laminar (8 dynes/ cmz) or turbulent shear stress 18.6 dyneslcrn' average), or to a static condition. Laminar flow induced a significant timedependent increase in the surface expres...

Endothelial cell alignment along the direction of laminar fluid flow is widely understood to be a defining morphological feature of vascular homeostasis. While the role of associated signaling and structural events have been well studied, associated intercellular stresses under laminar fluid shear have remained ill-defined and the role of these stresses in the alignment process has remained obs...