A rheological in vitro system has been developed to study and quantify cellular adhesion under precisely defined external shear forces. The system is similar to a cone-and-plate viscosimeter. A rotating transparent cone produces both steady and pulsatile flow profiles on cultured cells. Direct visualization of cells by phase-contrast or fluorescence optics and connection of the optical system to a computer-controlled x/y-linear stage allows automatic recording of any point of the cell cultures. With the use of up to 12 individual rheological units, this setup allows the quantitative analysis of cell substrate adhesion by determination of cell detachment kinetics. Two examples of application of this rheological system have been studied. First, we show that the extracellular matrix protein laminin strongly increases endothelial cell adhesion under fluid shear stress. In a second approach, we obtained further support for the concept that shear stress-induced formation of actin filament stress fibers is important for endothelial cells to resist the fluid shear stress; inhibition of stress fiber formation by doxorubicin resulted in significant detachment of endothelial cells exposed to medium levels of fluid shear stress (5 dyn/cm2). No detachment was seen under resting conditions.
Zusammenfassung: Der Cauchy-Green-Tensor einer beliebig vorgegebenen Grundstr6mung wird ffir kleine St6rungen linearisiert und das Ergebnis in geschlossener Form angegeben. AnschlieBend werden das Stabilit~itsverhalten einer viskoelastischen Fltissigkeit hinsichtlich spezieller St6rungen untersucht und verschiedene Grenzfalle (kurze und lange Wellen) diskutiert. Zum SchluB wird ein durch die elastischen Eigenschaften der Fltissigkeit bestimmter Instabilit~itsmechanismus ftir Maxwell-und Doi-Edwards-Fluide aufgezeigt.Abstract: The Cauchy-Green tensor of a given basic flow is linearized for small perturbations and the result is given in explicit form. The stability behaviour of an elastic fluid is then investigated for a special type of perturbation, and several limiting cases (short and long waves) are discussed. Finally, an instability mechanism of Maxwell and Doi-Edwards fluids caused by the elastic properties of these fluids is demonstrated.
Zusammenfassung: Die Stabilit~it der ebenen Couette-Str6mung zweier nichtnewtonscher Fluidmodelle mit Relaxation wird ffir kleine St6rungen in der viskosimetrischen Ebene untersucht. Um die Darstellung der Ergebnisse zu vereinfachen, wird sie auf einFluidmodell mit konstanten Stoffdaten beschrgnkt.
Abstract:The stability of plane Couette flow for two models of non-Newtonian liquid having relaxation properties was investigated for small perturbations in the viscometric plane. To simplify the presentation of the results only models with constant material properties are considered.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.