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Biomedical subjects

S Chien

Publications and source records attributed to S Chien.

At least 325 records · Page 18Linked to original sources
PubMed1975

Observations on blood viscosity changes after acute myocardial infarction.

Serial blood rheologic measurements were made in 25 patients with acute myocardial infarction; measurements included blood and plasma viscosities, hematological data and plasma protein concentrations. The blood viscosity was elevated on admission and for more than 21 days after acute myocardial infarction. However, the cause of the elevated viscosity was changed as a function of time after acute myocardial infarction. During the first three days after admission, the high blood viscosity was mainly attributable to high hematocrit values. Thereafter, the hematocrit fell, but blood viscosity remained high. High blood viscosity after the first three days of acute myocardial infarction can be correlated with increases in plasma viscosity and red cell aggregation, which in turn are explained by elevations of alpha 2 globulin and fibrinogen concentrations. Patients with higher blood viscosity on admission had a significantly higher incidence of complications, i.e., shock, thromboembolism and left ventricular failure.

Alpha-Globulins↗
PubMed1975

Deformability of sickle cells as studied by microsieving.

The effect of deoxygenation on deformability of sickle cells (Hb SS RBC) was studied quantitatively by a microsieving technique with the use of polycarbonate filters having micropores of 5 mum in diameter. The rate of pressure rise and the relative resistance during filtration through polycarbonate sieves increased progressively when the P02 of Hb SS RBC suspensions was reduced below 80 mm. Hg. Control studies on Hb AA RBC did not show any significant change in either parameter when deoxygenated. The present study on the filterability of Hb SS RBC and our previous data on the viscometric behavior of Hb SS RBC serve to establish the quantitative relation between P02 and the deformability of Hb SS RBC.

Anemia, Sickle Cell↗
PubMed1975

Effects of major abdominal operations on human blood rheology.

Serial blood rheological measurements were systematically carried out in 14 patients undergoing major elective abdominal operations for a period up to 10 days after operation. The measurements included blood viscosity over a wide range of shear rates (0.01 to 208 sec.-minus 1), hematological data, and plasma protein concentrations. Significantly elevated plasma viscosity preoperatively accounted for a normal blood viscosity in the presence of anemia. After an initial drop due to hemodilution lasting for 1 to 3 days after operation, blood viscosity returned to normal by the tenth postoperative day. This was the result of an increased plasma viscosity, primarily due to rise in plasma fibrinogen and alpha2- and beta2-globulin concentrations. The red cell deformability of these patients was normal except for one patient who received seven units of transfused blood. The results of this investigation suggest that abnormal rheological properties of blood and plasma should be considered in therapeutic attempts to improve microcirculatory flow and oxygen delivery to tissues.

Abdomen↗
PubMed1973

Strain energy function of red blood cell membranes.

The several widely different values of the elastic modulus of the human red blood cell membrane which have been reported in the literature are incorporated into a single strain energy function consisting of two terms. One term gives the small stresses and low elastic modulus which is observed when the red cell membrane is deformed at constant area. The second term contributes a large isotropic stress dependent on the change of area. The strain energy function is applied to the process of sphering of red blood cells in a hypotonic solution. It is shown that a nearly perfect sphere can result even though the red blood cell membrane is homogeneous in all areas of the cell. Results pertinent to sieving and micropipette experiments are also explored.

Biomechanical Phenomena↗
PubMed1973

Role of surface electric charge in red blood cell interactions.

The role of the surface charge of human red blood cells (RBC's) in affecting RBC aggregation by macromolecules was studied by comparing the behavior of normal RBC's with that of RBC's treated with neuraminidase, which removes the sialic acids from the cell membrane and reduces the zeta potential. RBC aggregation in dextrans with different molecular weights (Dx 20, Dx 40, and Dx 80) was quantified by microscopic observation, measurement of erythrocyte sedimentation rate, and determination of low-shear viscosity. Dx 20 did not cause aggregation of normal RBC's, but caused considerable aggregation of neuraminidase-treated RBC's. Neuraminidase-treated RBC's also showed stronger aggregation than normal RBC's in Dx 40 and 80. Together with the electron microscopic findings that the intercellular distance in the RBC rouleaux varies with the molecular size of dextrans used, the present study indicates that the surface charge of RBC's inhibits their aggregation by dextrans and that the electrostatic repulsive force between cell surfaces may operate over a distance of 20 nm.

Blood Sedimentation↗
PubMed1973

Influence of the ionic composition of fluid medium on red cell aggregation.

The effects of ionic strength and cationic valency of the fluid medium on the surface potential and dextran-induced aggregation of red blood cells (RBC's) were investigated. The zeta potential was calculated from cell mobility in a microelectrophoresis apparatus; the degree of aggregation of normal and neuraminidase-treated RBC's in dextrans (Dx 40 and Dx 80) was quantified by microscopic observation, measurement of erythrocyte sedimentation rate, and determination of low-shear viscosity. A decrease in ionic strength caused a reduction in aggregation of normal RBC's in dextrans, but had no effect on the aggregation of neuraminidase-treated RBC's. These findings reflect an increase in electrostatic repulsive force between normal RBC's by the reduction in ionic strength due to (a) a decrease in the screening of surface charge by counter-ions and (b) an increase in the thickness of the electric double layer. Divalent cations (Ca(++), Mg(++), and Ba(++)) increased aggregation of normal RBC's in dextrans, but had no effect on the aggregation of neuraminidase-treated RBC's. These effects of the divalent cations are attributable to a decrease in surface potential of normal RBC's and a shrinkage of the electric double layer. It is concluded that the surface charge of RBC's plays a significant role in cell-to-cell interactions.

Barium↗