PubMed · 3577320
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P G Reitnauer. 1987. [Measuring erythrocyte aggregation using a simple laboratory set-up].. https://pubmed.ncbi.nlm.nih.gov/3577320/
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In low flow rates, red blood cells (RBCs) fasten together along their axis of symmetry and form a so-called rouleaux. The scattering of He-Ne laser light by a rouleau consisting of n (2 < or = n < or = 8) average-sized RBCs is investigated. The interaction problem is treated numerically by means of an advanced axisymmetric boundary element--fast Fourier transform methodology. The scattering problem of one RBC was solved first, and the results showed that the influence of the RBC's membrane on the scattering patterns is negligible. Thus the rouleau is modeled as an axisymmetric, homogeneous, low-contrast dielectric cylinder, on the surface of which appears, owing to aggregated RBCs, a periodic roughness along the direction of symmetry. The direction of the incident laser light is considered to be perpendicular to the scatterer's axis of symmetry. The differential scattering cross sections in both perpendicular and parallel scattering planes and for all the scattering angles are calculated and presented in detail.
Erythrocyte aggregation and elongation index (EI) (deformability) are measured at temperatures ranging from 5 degrees C to 37 degrees C by aggregometer MA1, and diffractometer Rheodyne SSD and the LORCA, respectively. The test samples are prepared from blood obtained from healthy subjects in test tubes containing EDTA as an anticoagulant and prior to measurement are placed in a water bath for 30 min, maintained at respective temperatures. The aggregation process is given in terms of primary aggregation time and indices of aggregation. These show significant to highly significant changes with the increase of temperature compared to that at 5 degrees C. The EI increases with the increase of shear stress but shows significant decrease with the decrease of temperature.
To study the shear-thinning rheological behavior of blood, an acoustical measurement of the erythrocyte aggregation level can be obtained by analyzing the frequency dependence of ultrasonic backscattering from blood. However, the relation that exists among the variables describing the aggregation level and the backscattering coefficient needs to be better clarified. To achieve this purpose, a three-dimensional random model, the Neyman-Scott point process, is proposed to simulate red cell clustering in aggregative conditions at a low hematocrit (H<5%). The frequency dependence of the backscattering coefficient of blood, in non-Rayleigh conditions, is analytically derived from the model, as a function of the size distribution of the aggregates and of their mass fractal dimension. Quantitative predictions of the backscatter increase due to red cell aggregation are given. The parametric model of backscatter enables two descriptive indices of red cell aggregation to be extracted from experimental data, the packing factor W and the size factor delta. Previously published backscatter measurements from porcine whole blood at 4.5% hematocrit, in the frequency range of 3.5 MHz-12.5 MHz, are used to study the shear-rate dependence of these two indices.