Rheology of blood and flow in the microcirculation

Merrill, Edward W.; Gilliland, E. R.; Cokelet, Giles C.; Shin, Hye‐Won; Britten, Anthony; Wells, Roe E.

doi:10.1152/jappl.1963.18.2.255

Cited by 65 publications

(20 citation statements)

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“…Curve A shows a group of canine blood samples with an DISCUSSION As first shown by Brundage (7), the apparent viscosity of blood depends on the shear rate of the flow. This shear rate dependence has lately been confirmed by many authors (5,(8)(9)(10)(11) cause this phenomenon was observed in all blood samples without exception we conclude that red cell aggregation is a normal feature of normal red cells suspended in plasma of normal protein composition. "Aggregation" is seen as a reversible grouping of red cells suspended in plasma, the formation or breakup of the aggregates depending on the flow conditions.…”

Section: Resultssupporting

confidence: 83%

On the shear rate dependence of red cell aggregation in vitro

Schmid‐Schönbein

Gaehtgens²,

Hirsch³

1968

J. Clin. Invest.

147

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A B S T R A C T Non-Newtonian viscosity of blood, i.e., the rise in apparent viscosity at low flow, was believed to be a result of reversible aggregation of red cells at low velocity gradients (shear rate). By making a cone-plate viscometer transparent, direct observation was made possible of the blood flowing under defined shear rates. Red cell aggregates, occurring ii' all cases at low flow, were reversibly dispersed by increasing the shear rate. This behavior was independent of the addition of anticoagulants, but it could be altered by changing the plasma protein composition. Red cells in serum did not form aggregates; such nonaggregating samples did show an increase in viscosity at low shear rates. Since the sedimentation rate can be influenced by many parameters, it is not reliable in describing red cell aggregation. Aggregation of red cells is linked with a marked separation of plasma and cells. Such a separation is of considerable influence on cone-plate viscometry.

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Section: Resultssupporting

confidence: 83%

On the shear rate dependence of red cell aggregation in vitro

Schmid‐Schönbein

Gaehtgens²,

Hirsch³

1968

J. Clin. Invest.

147

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“…Although the cascade of complex interactions from platelet activation, aggregation, and thrombus formation is qualitatively well studied; 35,38,40,41 a systematic screening of the specific interaction of immobilized and circulating VWF and thrombocytes (VWF initiated platelet arrest) and the impact of VWF glycosylation has so far not been provided. This also calls for reducing the system to its main players.…”

Section: Resultsmentioning

confidence: 99%

Circulating but not immobilized N-deglycosylated von Willebrand factor increases platelet adhesion under flow conditions

et al. 2013

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The role of von Willebrand factor (VWF) as a shear stress activated platelet adhesive has been related to a coiled-elongated shape conformation. The forces dominating this transition have been suggested to be controlled by the proteins polymeric architecture. However, the fact that 20% of VWF molecular weight originates from glycan moieties has so far been neglected in these calculations. In this study, we present a systematic experimental investigation on the role of N-glycosylation for VWF mediated platelet adhesion under flow. A microfluidic flow chamber with a stenotic compartment that allows one to mimic various physiological flow conditions was designed for the efficient analysis of the adhesion spectrum. Surprisingly, we found an increase in platelet adhesion with elevated shear rate, both qualitatively and quantitatively fully conserved when N-deglycosylated VWF (N-deg-VWF) instead of VWF was immobilized in the microfluidic channel. This has been demonstrated consistently over four orders of magnitude in shear rate. In contrast, when N-deg-VWF was added to the supernatant, an increase in adhesion rate by a factor of two was detected compared to the addition of wild-type VWF. It appears that once immobilized, the role of glycans is at least modified if not-as found here for the case of adhesionnegated. These findings strengthen the physical impact of the circulating polymer on shear dependent platelet adhesion events. At present, there is no theoretical explanation for an increase in platelet adhesion to VWF in the absence of its N-glycans. However, our data indicate that the effective solubility of the protein and hence its shape or conformation may be altered by the degree of glycosylation and is therefore a good candidate for modifying the forces required to uncoil this biopolymer. V C 2013 AIP Publishing LLC. [http://dx

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“…The principle of this viscometer, which consists of coaxial cylinders separated by a small anulus in which the sample is located has been described (26,27). Utilizing a water bath connected to a channel inside the rotor and a thermistor connected to a thermo regulator at the exit from the channel, sample temperature could be maintained at +0.1°0C.…”

Section: Introductionmentioning

confidence: 99%