Interactions among erythrocytes under shear.

Brooks, Donald E.; Goodwin, James W.; Seaman, G. V. F.

doi:10.1152/jappl.1970.28.2.172

Cited by 195 publications

(145 citation statements)

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“…This relationship was used to calculate blood viscosity: ϭ [Ϫ0.20 ϩ (0.11 ϫ hematocrit)]/ 100. under control conditions was 3.90 Ϯ 0.14 ϫ 10 Ϫ2 poises (range 3.14 to 4.44 ϫ 10 Ϫ2 poises). Viscosity has been demonstrated to remain stable in vessels with a radius Ͼ300 m (14) and at shear rates exceeding 100 s Ϫ1 (6), which is the case in the present study. Data were read directly from the strip charts under baseline conditions while the dogs were standing quietly on the treadmill and near the end of each step of the graded treadmill exercise protocol, when a steady state was reached.…”

Section: Methodssupporting

confidence: 71%

β-Adrenergic receptor blockade impairs NO-dependent dilation of large coronary arteries during exercise

Okajima

Takamura

Véquaud

et al. 2003

American Journal of Physiology-Heart and Circulatory Physiology

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Okajima, Masaki, Masayuki Takamura, Philippe Vé -quaud, Robert Parent, and Michel Lavallé e. ␤-Adrenergic receptor blockade impairs NO-dependent dilation of large coronary arteries during exercise. Am J Physiol Heart Circ Physiol 284: H501-H510, 2003. First published October 3, 2002 10.1152/ajpheart.00419.2002-Shear stress-dependent nitric oxide (NO) formation prevents immoderate vascular constriction. We examined whether shear stress-dependent NO formation limits exercise-induced coronary artery constriction after ␤-adrenergic receptor blockade in dogs. Control exercise led to increases (P Ͻ 0.01) in coronary blood flow (CBF) by 38 Ϯ 5 ml/min from 41 Ϯ 5 ml/min and in the external diameter of epicardial coronary arteries (CD) by 0.24 Ϯ 0.03 mm from 3.33 Ϯ 0.20 mm. CD and shear stress were linearly related. After propranolol, CD fell (P Ͻ 0.01) during exercise (0.08 Ϯ 0.03 from 3.23 Ϯ 0.19 mm), and the slope of the relationship between CD and shear stress was reduced (P Ͻ 0.01). This slope was not further altered by the additional blockade of NO formation. In propranolol-treated resting dogs, flow-dependent effects of intracoronary adenosine to mimic exercise-induced increases in shear stress (after propranolol) led to increases (P Ͻ 0.01) in CD (0.09 Ϯ 0.02 from 3.68 Ϯ 0.27 mm). Thus both shear stress-dependent NO formation and ␤-adrenergic receptor activation are required to cause CD dilation during exercise. Suppression of ␤-adrenergic receptor activation leads to impaired shear stress-dependent NO formation and allows ␣-adrenergic constriction to become dominant. nitric oxide; adrenergic receptors; endothelium; shear stress; coronary vessels NITRIC OXIDE (NO) and ␤-adrenergic receptor activation are the major determinants of large epicardial coronary artery dilation during exercise. In those vessels, endothelium-derived NO formation during exercise is a flow-dependent process, secondary to increases in shear stress (20). Preventing the rise in coronary blood flow (CBF) (20), endothelial denudation (3), or blockade of NO formation (27) blunts large epicardial coronary dilation. Therefore, NO-dependent dilation of conductance coronary arteries during exercise may be considered as a secondary phenomenon triggered by the dilation of resistance coronary vessels. In addition to NO, ␤-adrenergic receptors directly contribute to conductance vessel dilation during exercise, because their blockade leads to a paradoxical constriction sensitive to ␣-adrenergic receptor blockade (2). In resistance vessels, ␤-adrenergic receptor activation causes dilator responses during exercise and serves as a feedforward mechanism (10, 11). In contrast, NO is not essential for increasing CBF and ensuring a close match between myocardial oxygen supply and demand during exercise (1,4,24,25).One intriguing observation is the complete failure of the large epicardial coronary artery to dilate during exercise performed after ␤-adrenergic receptor blockade (2). Despite the elevated shear stress caused by the decrease in large epicardial coro...

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Section: Methodssupporting

confidence: 71%

β-Adrenergic receptor blockade impairs NO-dependent dilation of large coronary arteries during exercise

Okajima

Takamura

Véquaud

et al. 2003

American Journal of Physiology-Heart and Circulatory Physiology

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“…The assumption of Newtonian rheology ignores the well known "shear-thinning" property of blood. 31 However, according to Brooks et al 32 shear thinning is only significant at shear rates below 100 s −1 , and in this study, shear rates (specifically volume-averaged square roots of the second invariant of the shear-rate tensor) were ∼ 300 s −1 and above across all configurations.…”

Section: Blood Flowsupporting

confidence: 44%

Computational modelling of the interaction of shock waves with multiple gas-filled bubbles in a liquid

Betney

Tully²,

Hawker³

et al. 2015

Physics of Fluids

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This study presents a computational investigation of the interactions of a single shock wave with multiple gas-filled bubbles in a liquid medium. This work illustrates how multiple bubbles may be used in shock-bubble interactions to intensify the process on a local level. A high resolution front-tracking approach is used, which enables explicit tracking of the gas-liquid interface. The collapse of two identical bubbles, one placed behind the other is investigated in detail, demonstrating that peak pressures in a two bubble arrangement can exceed those seen in single bubble collapse. Additionally, a parametric investigation into the effect of bubble separation is presented. It is found that the separation distance has a significant effect on both the shape and velocity of the main transverse jet of the second bubble. Extending this analysis to effects of relative bubble size, we show that if the first bubble is sufficiently small relative to the second, it may become entirely entrained in the second bubble main transverse jet. In contrast, if the first bubble is substantially larger than the second, it may offer it significant protection from the incident shock. This protection is utilised in the study of a triangular array of three bubbles, with the central bubble being significantly smaller than the outer bubbles. It is demonstrated that, through shielding of bubbles until later in the collapse process, pressures over five times higher than the maximum pressure observed in the single bubble case may be achieved. This corresponds to a peak pressure that is approximately 40 times more intense than the incident shock wave. This work has applications in a number of different fields, including cavitation erosion, explosives, targeted drug delivery/intensification, and shock wave lithotripsy.

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“…In the next step, the viscosity law as given in Equation 3 was modified by adding a diameter-dependent term to the original parametric description of the in vitro data: (8) ?7mod= [1 +('10. 45 1) (1-HD)C-1 (_D \4A] (_D 4(1 -A) (1-0.45)C-1 VD-W J D-W where 'qmod is modified viscosity, W has the dimension of a length, and A is a constant.…”

Section: Modified Viscosity Lawmentioning

confidence: 99%

Resistance to blood flow in microvessels in vivo.

Pries

Secomb

Gessner

et al. 1994

Circulation Research

535

579

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Resistance to blood flow through peripheral vascular beds strongly influences cardiovascular function and transport to tissue. For a given vascular architecture, flow resistance is determined by the rheological behavior of blood flowing through microvessels. A new approach for calculating the contribution of blood rheology to microvascular flow resistance is presented. Morphology (diameter and length), flow velocity, hematocrit, and topological position were determined for all vessel segments (up to 913) of terminal microcirculatory networks in the rat mesentery by intravital microscopy. Flow velocity and hematocrit were also predicted from mathematical flow simulations, in which the assumed dependence of flow resistance on diameter, hematocrit, and shear rate was optimized to minimize the deviation between measured and predicted values. For microvessels with diameters below %z40 ,um, the resulting flow resistances are markedly higher and show a stronger dependence on hematocrit than previously estimated from measurements of blood flow in narrow glass tubes. For example, flow resistance in 10-am microvessels at normal hematocrit is found to exceed that of a corresponding glass tube by a factor of =4. In separate experiments, flow resistance of microvascular networks was estimated from direct measurements of total pressure drop and volume flow, at systemic hematocrits intentionally varied from 0.08 to 0.68. The results agree closely with predictions based on the above-optimized resistance but not with predictions based on glass-tube data. The unexpectedly high flow resistance in small microvessels may be related to interactions between blood components and the inner vessel surface that do not occur in smooth-walled tubes. (Circ Res. 1994;75: 904-915.) Key Words * blood viscosity * peripheral resistancemicrovascular networks * pressure drop * hematocrit E arly in the 19th century direct measurements of arterial and venous blood pressure by Jean Leonard Marie Poiseuille12 revealed that the pressure drop in the circulation occurs mainly in the peripheral vascular bed (the microcirculation), which consists of large numbers of tiny vessels. The microcirculation is therefore the site of most of the resistance to flow, which depends on the architecture of the microvascular network and on the rheological behavior of blood flowing through it. Information about bulk rheological properties of blood has been obtained using rotational viscometers. The findings of such studies, including the nonlinear increase of viscosity with increasing hematocrit and with decreasing shear rate,3-5 have strongly influenced the interpretation of physiological and pathophysiological behavior of the peripheral circulation.However, knowledge of the bulk material properties of blood does not provide a sufficient basis for understanding blood flow through narrow cylindrical tubes. In tubes with diameters >1 mm, the measured apparent viscosities correspond to bulk values from rotational viscometry, but a marked reduction of viscosity is...

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Interactions among erythrocytes under shear.

Cited by 195 publications

References 0 publications

β-Adrenergic receptor blockade impairs NO-dependent dilation of large coronary arteries during exercise

β-Adrenergic receptor blockade impairs NO-dependent dilation of large coronary arteries during exercise

Computational modelling of the interaction of shock waves with multiple gas-filled bubbles in a liquid

Resistance to blood flow in microvessels in vivo.

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