Summary.A viscometer chamber (combination of cone plate and Couette-type) adaptable to the standard Wells-Brookfield-Mieroviscometer is described. The instrument allows measurements at shear rates between 0.23 and 160 see-l; it incorporates a guard ring against surface artefacts. Measurements with normal human blood, standardized for hematocrit value, give excellent agreement with data obtained previously on the GDM-viscometers.Key words: Blood rheology --Non newton viscosity of blood --Rotational viscometers.Zusammen]assung. Einc Zusatzkammer fiir das herk5mmliche Wells-BrookfieldMikroviskometer wird beschrieben, die aus einer Kombination der Platte-Kegel und der Couette-Anordnung besteht. Das Instrument gcstattet Messungen bei Sehergraden zwisehen 0,23 und 160 see-l; es enth~lt einen Schutzring gegen Oberfl~chen-Artefakte. Messungen mit normalem menschlichem Blur ergeben bei standardisiertem tI~imatokrit-Wert ausgezeichnete t:%ereinstimmnng mit friiher gemessenen Daten mit dem GDM-Viskometer.S¢hliisselw6rter: Blutrheologie --Nicht-Newtonsche Viscosit/£t des Blutes --Rotationsviskosimeter.Hemorheology as a new scientific discipline has become a field of increasing interest in experimental, theoretical, and clinical medicine. This interest was prompted primarily by evidence suggesting that the physiology and pathophysiology of the paracapillary bed is not only controlled by the properties of the micro-vessels, but to the same extent by the complex rheological properties of blood and blood elements flowing in the exchange vessels.Systematic investigations into the factors responsible for the so-called "anomalous viscosity of blood" in vitro (for review see Merrill
The formation of primary (rouleaux) and secondary (rouleaux networks) RCA was studied by microcinematography (12 frames/sec) and photometry in a counterrotating "rheoscope" chamber. The blood was first subjected to rapid viscometric flow (460 sec-1, all RBC dispersed and aligned in flow) and then brought abruptly to full stop. In normal human blood, primary and secondary RCA occurred simultaneously, and were completed within 8 to 10 sec after stop. Blood from pregnant women at term, known for its pronounced red cell aggregation, shows a dissociation between the formation of short primary rouleaux (initiated even before full stop and completed 1-2 see thereafter) and secondary RCA completed 3-5 see after stop. RCA increases the light transmission of blood (measured by an increase in photovoltage V), the process and its first derivative (dV/dt equals I) can be recorded. After flow stop, there is an exponential decay of I(I equals t-I-o with e-lambda-t). The half time of this decay is recorded and correlated to the kinetics of red cell aggregate formation In human blood the half time of this process varies between 1.0 and 6.0 sec. In suspensions of human RBC in artificial plasmas, t-1/2 decreases with increasing concentration of fibrinogen and/or Dextran 250000, the second component appearing at concentrations above 500 mg-%. The method lend sitself for the quantification of RCA in small blood samples (20 mul).
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