Shear stress experienced by echinoderm eggs in the oviduct during spawning: potential role in the evolution of egg properties

Shear stresses experienced by eggs in the oviduct of the echinoid Arbacia punctulata during spawning were calculated using engineering equations that describe laminar flow through pipes. Shear stresses in the oviduct ranged from 0 to 58.7 Pa. Two properties of eggs were identified that have the potential either to minimize the shear stress in the oviduct or to reduce the damage experienced by eggs exposed to high shear stress. These properties are the viscosity of the eggs and the presence of extracellular layers on eggs of A. punctulata. The viscosity of eggs decreases with increasing shear rates, which reduces the magnitude of shear stress experienced in the oviduct, while the extracellular layers mitigate the effect of shear stress on the eggs. Eggs with intact extracellular layers were damaged less frequently than were those with the extracellular layers removed. The results of this research indicate that physical stresses may be important selective factors in the evolution of gamete properties.

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Strain distribution over plaques in human coronary arteries relates to shear stress

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01081.2007 ◽

2008 ◽

Vol 295 (4) ◽

pp. H1608-H1614 ◽

Cited By ~ 125

Author(s):

Frank J. H. Gijsen ◽

Jolanda J. Wentzel ◽

Attila Thury ◽

Frits Mastik ◽

Johannes A. Schaar ◽

...

Keyword(s):

Shear Stress ◽

Coronary Arteries ◽

Plaque Rupture ◽

Stress And Strain ◽

Shear Stresses ◽

High Shear ◽

High Shear Stress ◽

Plaque Composition ◽

Downstream Region ◽

Shear Stress And Strain

Once plaques intrude into the lumen, the shear stress they are exposed to alters with hitherto unknown consequences for plaque composition. We investigated the relationship between shear stress and strain, a marker for plaque composition, in human coronary arteries. We imaged 31 plaques in coronary arteries with angiography and intravascular ultrasound. Computational fluid dynamics was used to obtain shear stress. Palpography was applied to measure strain. Each plaque was divided into four regions: upstream, throat, shoulder, and downstream. Average shear stress and strain were determined in each region. Shear stress in the upstream, shoulder, throat, and downstream region was 2.55 ± 0.89, 2.07 ± 0.98, 2.32 ± 1.11, and 0.67 ± 0.35 Pa, respectively. Shear stress in the downstream region was significantly lower. Strain in the downstream region was also significantly lower than the values in the other regions (0.23 ± 0.08% vs. 0.48 ± 0.15%, 0.43 ± 0.17%, and 0.47 ± 0.12%, for the upstream, shoulder, and throat regions, respectively). Pooling all regions, dividing shear stress per plaque into tertiles, and computing average strain showed a positive correlation; for low, medium, and high shear stress, strain was 0.23 ± 0.10%, 0.40 ± 0.15%, and 0.60 ± 0.18%, respectively. Low strain colocalizes with low shear stress downstream of plaques. Higher strain can be found in all other plaque regions, with the highest strain found in regions exposed to the highest shear stresses. This indicates that high shear stress might destabilize plaques, which could lead to plaque rupture.

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Calin from Hirudo medicinalis, an inhibitor of von Willebrand factor binding to collagen under static and flow conditions

Blood ◽

10.1182/blood.v85.3.705.bloodjournal853705 ◽

1995 ◽

Vol 85 (3) ◽

pp. 705-711 ◽

Cited By ~ 37

Author(s):

J Harsfalvi ◽

JM Stassen ◽

MF Hoylaerts ◽

E Van Houtte ◽

RT Sawyer ◽

...

Keyword(s):

Shear Stress ◽

Platelet Adhesion ◽

Thrombus Formation ◽

High Shear ◽

High Shear Stress ◽

Flow Conditions ◽

Shear Rates ◽

Von Willebrand ◽

Willebrand Factor ◽

Low Shear

Calin from the saliva of the medicinal leech, Hirudo medicinalis, is a potent inhibitor of collagen mediated platelet adhesion and activation. In addition to inhibition of the direct platelet-collagen interaction, we presently demonstrate that binding of von Willebrand to coated collagen can be prevented by Calin, both under static and flow conditions in agreement with the occurrence of binding of Calin to collagen, confirmed by Biospecific Interaction Analysis. To define whether Calin acted by inhibiting the platelet-collagen or the platelet- von Willebrand factor (vWF)-collagen-mediated thrombus formation, platelet adhesion to different types of collagens was studied in a parallel-plate flow chamber perfused with whole blood at different shear rates. Calin dose-dependently prevented platelet adhesion to the different collagens tested both at high- and low-shear stress. The concentration of Calin needed to cause 50% inhibition of platelet adhesion at high-shear stress was some fivefold lower than that needed for inhibition of vWF-binding under similar conditions, implying that at high-shear stress, the effect of Calin on the direct platelet- collagen interactions, suffices to prevent thrombus formation. Platelet adhesion to extracellular matrix (ECM) of cultured human umbilical vein endothelial cells was only partially prevented by Calin, and even less so at a high-shear rather than a low-shear rate, whereas the platelet binding to coated vWF and fibrinogen were minimally affected at both shear rates. Thus, Calin interferes with both the direct platelet- collagen interaction and the vWF-collagen binding. Both effects may contribute to the inhibition of platelet adhesion in flowing conditions, although the former seems to predominate.

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The Initiation and Propagation of Fatigue Cracks in Mild Steel Pieces of Square Section

Aeronautical Quarterly ◽

10.1017/s0001925900000755 ◽

1954 ◽

Vol 4 (1) ◽

pp. 1-18 ◽

Cited By ~ 8

Author(s):

H. L. Cox ◽

J. E. Field

Keyword(s):

Shear Stress ◽

Tensile Stress ◽

Mild Steel ◽

Fatigue Cracks ◽

Maximum Shear Stress ◽

Shear Stresses ◽

High Shear ◽

Stress Range ◽

High Shear Stress ◽

General Direction

SummaryAn investigation has been made to determine the positions and directions of initiation and the directions of propagation of fatigue cracks and to examine the correlation between these positions and directions and the planes on which maximum tensile and maximum shear stresses are generated.To afford as wide a range as possible of the ratio of maximum shear stress to maximum tensile stress, tests have been made under combinations of alternating bending and torsion; and in order to separate partially the regions of high shear stress from those of high direct stress, the tests have been made on pieces of square section with the plane of bending parallel to one diagonal of the section. Two series of tests have been made; one a preliminary series on pieces having no parallel portion and the other on pieces having a parallel portion about three times the length of the side of the square section. The positions and directions of initiation and the directions of propagation of fatigue cracks have been observed and compared with the positions and directions of the maximum tensile and shear stresses.Fatigue cracks may be initiated as a result of either high shear stress or high tensile stress and in the present series of tests on mild steel, cracking in tension has occurred in preference to cracking in shear when the ratio of the tensile stress range to the shear stress range has exceeded about 1.6; for values of this ratio less than 1.6, the cracks started in shear (and vice versa); propagation along the plane of maximum shear appears to be preferred up to a slightly greater value of the tensile/shear ratio (about 1.7 possibly). The general direction of a crack formed as a result of high tension usually follows the plane of maximum tension and that of a crack formed as a result of shear usually follows the plane of maximum shear. In detail both types of crack—in this mild steel—deviate quite widely from their general directions but this deviation bears no obvious relation to the microstructure of the material. Cracks propagating along one plane of maximum shear occasionally show a marked tendency to branch along the associated plane of maximum shear; but this tendency is not always observed and in other cases no tendency to branch has been noted.

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The High Shear Stress Rheology of Liquid Lubricants at Pressures of 2 to 200 MPa

Journal of Tribology ◽

10.1115/1.2920248 ◽

1990 ◽

Vol 112 (2) ◽

pp. 246-252 ◽

Cited By ~ 75

Author(s):

S. Bair ◽

W. O. Winer

Keyword(s):

Shear Stress ◽

Glass Transition ◽

Shear Flow ◽

Flow Characteristics ◽

Steady Shear ◽

Shear Stresses ◽

High Shear ◽

High Shear Stress ◽

Limiting Shear Stress ◽

Steady Shear Flow

The steady shear flow characteristics of two liquid lubricants were measured in a new rheometer at shear stresses to 10 MPa. All measurements were performed well below the glass transition pressure. Both Newtonian and rate-independent (limiting shear stress) behaivor was observed.

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Formation of Procoagulant Platelet Derived Microparticles through Platelet GPIb-Interaction with Von Willebrand Factor under High Shear Stress.

Blood ◽

10.1182/blood.v106.11.414.414 ◽

2005 ◽

Vol 106 (11) ◽

pp. 414-414

Author(s):

Armin J. Reininger ◽

Harry F.G. Heijnen ◽

Hannah Schumann ◽

Wolfgang Schramm ◽

Zaverio M. Ruggeri

Keyword(s):

Shear Stress ◽

Von Willebrand Factor ◽

High Shear ◽

High Shear Stress ◽

Shear Rates ◽

Tissue Factors ◽

Membrane Tethers ◽

Microparticle Formation ◽

Von Willebrand ◽

Willebrand Factor

Abstract We describe here novel findings of the mechanism of initial platelet contact with immobilized von Willebrand factor (VWF) under high shear stress and how this leads to the formation of procoagulant platelet derived microparticles. In a parallel plate perfusion chamber whole blood was perfused over multimeric VWF or dimeric VWF A1 domain at shear rates between 2,000 s−1 and 40,000 s−1. Platelet attachment to VWF always occurred through glycoprotein Ibα receptors located in discrete adhesion points (DAPs), i.e. few limited membrane areas of 0.05 to 0.1 μm2 that arrested the platelets on the surface. The ongoing flow translocated such anchored platelets downstream, thus pulling membrane tethers from the intact and unstimulated platelet. Tethers could remain connected with the platelet body or be eventually severed, which occurred preferentially at shear rates above 6,000 s−1. Depending on the length of the severed membrane fragment they represented either isolated tethers or microparticles (arrowheads; see Figure below), the latter defined by a diameter of 50 to 100 nanometers. The shear rate threshold for microparticle formation was between 6,000 s−1 and 10,000 s−1. Immuno-fluorescence and immuno-electron microscopy showed glycoprotein Ibα clustered in DAPs of microparticles and tethers, i.e. the contact sites with the surface immobilized VWF. The microparticles also exhibited tissue factors on their surface and showed significant procoagulant activity measured by thrombin generation. We propose that after GPIbα anchoring to VWF in flowing blood passive mechanical pulling of membrane from platelets may generate platelet derived microparticles that can potentially support thrombogenesis. Figure Figure

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