The effect of factor XIII and fibronectin on the viscoelasticity of fibrinogen surface layers.
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Elasticity↗
Biomedical subjects
S Chien
Publications and source records attributed to S Chien.
Red cell vacuoles: their size and distribution under normal conditions and after splenectomy.
The frequency of occurrence of vacuoles in red blood cells was studied by transmission electron microscopy. Small vacuoles were found in about 13% of the cell sections, and they had a mean diameter of 130 +/- 72 nm (mean +/- SD). It can be estimated that there were about 20 small vacuoles per erythrocyte. The frequency of vacuoles was similar in density-separated cell fractions. In splenectomized patients, the small vacuoles were 4 times more frequent; there was again no difference in vacuole density between top and bottom fractions of density-separated red blood cells. The bottom fraction of red blood cells from splenectomized patients, however, had a high incidence of large vacuoles (greater than 300 nm in diameter) and clustering of small vacuoles. These large vacuoles were probably the result of aggregation and fusion of small vacuoles, and their size allowed detection by light microscopy. Hence, the well-known "pocked" or "pitted" red blood cells of splenectomized individuals were more frequent in the bottom fraction. We conclude that small vacuoles occur normally in erythrocytes, that they tend to cluster and fuse during cell aging, and that the spleen is capable of removing these structures when they reach a certain size.
Erythrocytes↗
Impaired echinocytic transformation of ankyrin- and spectrin-deficient erythrocytes in mice.
The membrane skeleton of the red blood cell plays an important role in the determination of cell deformability and cell shape. Under various in vitro conditions, red blood cells undergo an echinocytic or stomatocytic shape transformation. The mechanism of this fundamental process is not well understood. We have studied the red cell shape transformation in normoblastic anemia mice (nb/nb) and spherocytic anemia mice (sph/sph), which are deficient in ankyrin and spectrin, respectively. We found that both ankyrin-deficient cells (nb/nb) and spectrin-deficient cells (sph/sph) have a reduced capacity to undergo echinocytic transformation with various echinocytogenic treatments, that is, incubation with sodium salicylate (40 and 120 mM), calcium loading (50 microM A23187 + 2.2 mM Ca2+), or metabolic depletion (24 hr at 37 degrees C). These results suggest that the functional integrity of the membrane skeleton is essential for the maintenance and transformation of the red cell shape.
Anemia↗
Morphometric studies on human leukocyte granules.
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Adult↗
The role of arterial endothelial cell mitosis in macromolecular permeability.
The present experiments were performed on twelve male Wistar rats to study the quantitative, topographic correlation between transendothelial permeability of Evans Blue-albumin (EBA) conjugate and endothelial cell replication at the single-cell level. En face preparations of the thoracic aorta were examined by fluorescence microscopy. We found a high degree of correlation between endothelial cell mitosis and EBA leaky spots. Although endothelial cell mitosis is very rare in occurrence, nearly all junctions around the dividing cells were leaky (99%), in contrast to only 0.03% of the non-mitotic cells. In addition, electron microscopic observations showed that the junction around a dividing endothelial cell is leaky, whereas that around a dying cell is not. With the aid of our theoretical model, we were able to analyze the dynamics of macromolecular passage through leaky endothelial junctions. The duration of endothelial cell mitosis was estimated to be 67 min, which constituted 0.01% of the duration of the total cell cycle. The time-dependent change in junctional geometry during endothelial cell turnover leads to an inverse relationship between macromolecular size and duration of junctional leakage. For albumin the duration of leakiness across aortic endothelial cell is approximately 3.7 hr. The present findings lend support to our hypothesis that transiently open junctions surrounding the dividing endothelial cells provide the major pathway through which macromolecules enter the subendothelial space to result in lipid accumulation.
Animals↗
Enhanced macromolecular permeability of aortic endothelial cells in association with mitosis.
Experiments were performed on thoracic aortae of 12 male Sprague-Dawley [corrected] rats to determine the statistical frequency of isolated leaks to Evans blue-albumin (EBA) conjugate at the level of individual cells and to assess the relationship of such leaks to the cell turnover process. Fluorescence microscopy was used to detect leakage of EBA around individual cells, and hematoxylin staining was used to identify cells in mitosis on the same specimens. Although endothelial cell mitosis is very rare in occurrence, 99% of the cells in the M phase were associated with EBA leakage. Since these dividing cells accounted for only one third of all cellular leakage sites, we concluded that significant leakage also occurred in other phases of the cell cycle, probably prior to and after the M phase, or during non-denuding desquamation.
Albumins↗
Leukocyte relaxation properties.
Study of the mechanical properties of leukocytes is useful to understand their passage through narrow capillaries and interaction with other cells. Leukocytes are known to be viscoelastic and their properties have been established by micropipette aspiration techniques. Here, the recovery of leukocytes to their normal spherical form is studied after prolonged deformation in a pipette which is large enough to permit complete entry of the leukocyte. The recovery history is characterized by the time history of the major diameter (d1) and minor diameter (d2). When the cell is removed from the pipette, it shows initially a small rapid recoil followed by a slower asymptotic recovery to the spherical shape. In the presence of cell activation and formation of pseudopods, the time history for recovery is prolonged compared with passive cell recovery. If a protopod pre-existed during the holding period, the recovery only begins when the protopod starts to retract.
Cell Movement↗
Effects of total hip replacement and bed rest on blood rheology and red cell metabolism.
In order to better understand the pathophysiologic changes in the immediate postoperative period after total hip replacement surgery and to distinguish alterations due to the surgical operation from those due to bed rest, we examined rheologic parameters and red cell metabolism of patients before, 1 day after, and 5 to 6 days after total hip replacement and compared the results to those obtained from normal volunteers placed at bed rest for 5 days. Bed rest in the control group led to increases in hematocrit, mean corpuscular hemoglobin concentration, red cell DPG and ATP levels, and plasma concentrations of total proteins, globulins, and fibrinogen, with attendant increases in whole blood viscosity, plasma viscosity, blood viscosity, relative blood viscosity with hematocrit adjusted to 45%, and viscometric aggregation index, and the viscosity of red cell suspensions in Ringer's solution at 45% hematocrit decreased at low shear rate. The patient group, despite the postoperative lowering of their hematocrit, mean corpuscular hemoglobin concentration, and total plasma proteins and a consequent decrease of whole blood viscosity, revealed disproportionate increases in blood viscosity, relative blood viscosity, and viscometric aggregation index. These rheologic changes, which reflect an enhanced red cell aggregability, may contribute to complications of thrombophlebitis. Enforced inactivity, when superimposed on the effects of trauma, blood loss, transfusion with bank blood, and the low-flow state, would exaggerate these rheologic problems. The results suggest that management of total hip replacement patients should include hemorrheologic considerations (e.g., preoperative intentional hemodilution) and early postoperative activity.
2,3-Diphosphoglycerate↗
Passive deformation analysis of human leukocytes.
The following analysis presents an experimental and theoretical study of the passive viscoelastic behavior of human leukocytes. Individual neutrophils in EDTA were observed both during their partial aspiration into a small micropipette and after expulsion from a large micropipette where the cell had been totally aspirated and deformed into a sausage shape. To analyze the data, a passive model of leukocyte rheology has been developed consisting of a cortical shell containing a Maxwell fluid which describes the average properties of the cell cytoplasm. The cortical shell represents a crosslinked actin layer near the surface of the cell and is assumed to be under pre-stressed tension. This model can reproduce the results of experiments using micropipette for both short-time small deformation and slow recovery data after large deformation. In addition, a finite element scheme has been established for the same model which shows close agreement with the analytical solution.
Blood Viscosity↗
Continuous monitoring of erythrocyte sedimentation process: a new possible mechanism of erythrocyte sedimentation.
An automated system is constructed to record the complete course of erythrocyte sedimentation process. In this system a light source and a paired photodetector are employed to monitor the change of light transmittance at the junction of plasma and the sedimenting red blood cell column, thus providing a continuous record of erythrocyte sedimentation as a function of time. Differentiation of this sedimentation--time curve yields a velocity--time curve of erythrocyte sedimentation. Frequently recorded "spikes" on top of the velocity--time curve imply the episodes of very rapid fall of erythrocytes in the sedimentation tube that cannot be explained by the currently accepted theory of erythrocyte sedimentation based mainly on Stokes' law, and a new mechanism of rouleau coalescing and fracturing is proposed to account for them.
Blood Sedimentation↗
Studies on sequestration of neuraminidase-treated red blood cells.
The effects of reduction in the surface charge of red blood cells (RBCs) on regional blood flow and RBC distribution were studied in rats anesthetized with pentobarbital sodium. RBCs were treated with neuraminidase to reduce their electrophoretic mobility by 56%. Normal and neuraminidase-treated RBCs labeled with 51Cr or 111In were injected into a femoral vein while an equal volume of blood was simultaneously withdrawn from a femoral artery. More than 70% of the neuraminidase-treated RBCs injected disappeared from the circulating blood in 30 min compared with less than 2% of normal RBCs. The relative distributions of neuraminidase-treated RBCs to normal RBCs, as determined from radioactivity counting, were significantly greater than 1 in the spleen (5.65 +/- 0.97, mean +/- SD), the liver (2.84 +/- 0.21), the lung (1.48 +/- 0.31), and the kidney (1.49 +/- 0.27), indicating a preferential trapping of neuraminidase-treated RBCs in these regions. This ratio was approximately 1 in all other organs. Regional blood flows in tissues were determined with 15-micron microspheres in the control period and after the infusion of neuraminidase-treated RBCs (experimental). Experimental-to-control blood flow ratios were 0.40 +/- 0.05 in the spleen, 0.66 +/- 0.06 in the liver, 0.78 +/- 0.03 in the lung, and 0.78 +/- 0.09 in the kidneys; this ratio was approximately 1 in all other organs. An experimental-to-control blood flow ratio less than 1 indicates a reduction in blood flow; this occurred in the same organs as those with trapping of neuraminidase-treated RBCs.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Dynamic changes in viscoelastic properties in cytotoxic T-lymphocyte-mediated killing.
The biophysical properties of cytotoxic T lymphocytes during the killing of their target cells was investigated by using a human cytotoxic T lymphocyte clone, F1, and the target cell, JY, for which it is specific. In single cytotoxic cell/target cell pairs after their conjugation there are changes in the viscoelastic properties of the target cell in association with the lethal hit delivery and post-binding cytolytic steps. On the basis of these changes in the target cell, the complex cytolytic event can be divided into stages: the viscoelastic coefficients exhibited an initial increase followed by a return to resting values; thereafter these coefficients decreased below control and then rose again prior to lysis. The eventual killing of the target cell involves bubbling and swelling of the nucleus, clustering of granules, damage to the cytoplasmic membrane, cell swelling, and lysis. The viscoelastic changes involved in target cell death suggest the loss of integrity of its cytoskeletal apparatus.
Cell Line, Transformed↗
Dependence of technetium-99m red blood cell labeling efficiency on red cell surface charge.
The mechanisms by which [99mTc]pertechnetate becomes attached to stannous-primed red blood cells are not known in detail. To study the problem further, the effect of red cell surface charge on labeling efficiency was evaluated. Red cell surface charge was reduced by using the enzyme neuraminidase to remove the terminal charge-bearing sialic acid moiety of the membrane glycoprotein. Forty-five blood samples from six volunteers were treated with neuraminidase for varying lengths of time, resulting in the removal of from 11% to 99% of the normal negative surface charge, as determined from electrophoretic mobility measurements. There was excellent linear correlation between labeling efficiency and the remaining red cell surface charge for values down to 20% of normal (r = 0.89). When surface charge was less than 20% of normal, labeling efficiency was constant at 30%. Eleven blood samples from three donors were divided into two groups that were treated with neuraminidase either before or after they were labeled. The labeling efficiency was independent of the order in which the steps were performed. No evidence for shifting of the radiolabel from the cell membrane to hemoglobin was found. The results suggest that clinical conditions associated with a reduction of sialic acid on the erythrocyte membrane may be one cause of decreased red blood cell labeling efficiency, and that increased membrane permeability for reduced technetium species may be responsible for the decrease.
Adult↗
New autoperfusion preparation for long-term organ preservation.
The problems in long-term organ preservation are ischemia and toxicity from metabolic waste. A simple self-perfusing self-cleaning system has been developed that kept the heart, lungs, and kidney functioning for a mean time of 24 hours. Nine adult dogs were anesthetized and artifically ventilated. The heart and lungs were removed en bloc while being perfused by the heart. One kidney was connected to the descending aorta and inferior vena cava. No anticoagulant was used. Another group of six dogs without functioning kidneys was used as the control group. In the experimental group, urine output ranged from 26 to 48 ml/hr, aortic systolic pressures were 80-107 mm Hg, heart rate was 85-100 beats/min, serum potassium content was 3.25-4.40 mmol/l, and serum sodium content was 155-163 mmol/l. In the experimental group, blood creatinine levels decreased from 0.95 to 0.47 mg/dl during preservation; in the control group, blood creatinine levels decreased from 0.96 to 0.79 mg/dl. Lung biopsies in the preparation with the longest survival showed good preservation for as long as 24 hours, and no thrombi were present. This preparation has the advantage of no ischemic time, no foreign material in the circulation, and the ability to automatically maintain acid-base balance and blood electrolytes. The simplicity of this autoperfusion preparation may allow greater transport distance in organ procurement for subsequent transplantation.
Animals↗
A simple technique for multiorgan preservation.
A simple technique for multiorgan preservation with no ischemic time was developed. In five mongrel dogs, the heart and lungs were separated and removed with the liver, pancreas, kidneys, and a small portion of intestine en bloc while they were being self-perfused. A respirator was used for oxygenation. Arterial and venous blood pressures were measured by indwelling catheters. Fresh blood, glucose, electrolytes, mannitol, prednisolone, and a fat emulsion (Soyacal) were infused through the portal vein. The organs were experimentally perfused for 12 hours. Aortic systolic pressure ranged from 75 to 125 mm Hg, central venous pressure from 0 to 5 mm Hg, portal venous pressure from 0 to 3 mm Hg, bile output from 5 to 20 ml/hr, urine output from 10 to 70 ml/hr, and hematocrit value from 35% to 55%. The heart and lungs were normal and physiologically functional during the preservation time. The pancreas and small intestine appeared normal. Three of the livers showed some congestion. The kidney in one organ block appeared to have some edematous swelling after 16 hours. The technique for multiorgan preservation presented here is simple and effective. The preliminary data are encouraging and suggest further evaluation.
Animals↗
Time-dependent effects of endotoxin on the ultrastructure of aortic endothelium.
The aortic endothelium from control and Escherichia coli (E. coli) endotoxin-treated rats and rabbits was examined by transmission and scanning electron microscopy. Following the intravenous injection of endotoxin, the animals were sacrificed at intervals ranging from 1 min to 4 hr. As early as 1 min after endotoxin, there was a widening of the subendothelial space (SES) and an increase in tortuosity of the internal elastic lamina (IEL). At 5 min, the tortuosity of the IEL increased to a peak value, and the SES showed an increase in the amount of smooth muscle cells (SMC). Initial endothelial damage occurred 5 min after endotoxin: SEM showed some spindle-shaped endothelial cells starting to peel from the underlying SES, and TEM showed some endothelial cells protruding or arching into the lumen. The new findings in this study are that endotoxin injection a) has a very rapid (less than 15 min) effect on rat and rabbit aortic endothelium, including localized endothelial injuries in the intima, and b) induces ultrastructural alterations also in the SES, IEL and portions of the tunica media. These effects were largely reversed within 1 hr after endotoxin administration, thus indicating that the endothelium and other components of the arterial wall can recover with great speeds.
Animals↗
Echinocyte-stomatocyte transformation and shape control of human red blood cells: morphological aspects.
Red cell morphology was studied after the induction of echinocytic transformation by metabolic depletion, Ca2+ loading, and salicylate and stomatocytic transformation with chlorpromazine. The results indicate that the red cell has an energy-dependent shape control mechanism that allows it to counteract shape-changing stimuli such as metabolic depletion. Albumin was found to induce stomatocytic transformation, whereas gamma-globulins induced echinocytic transformation. Loading of the red cell with calcium resulted in polymorphous membrane damages such as submembranous, "blister-like" lesions, and membrane disintegration; the red cell age had no influence on this process. Conversely, the stomatocyte-echinocyte transformation induced by chlorpromazine and salicylate was shifted towards echinocytes in density-separated old red cells. Sphero-stomatocytes were capable of echinocytic transformation with spicule formation within the red cell vacuoles, whereas sphero-echinocytes were unable to undergo stomatocytic transformation without hemolysis. These observations may help to unravel the complexity of echinocyte-stomatocyte transformation of red blood cells.
Calcium↗
The time course of filtration test as a model for microvascular plugging by white cells and hardened red cells.
The propensity of white blood cells and rigidified red blood cells to plug narrow channels was studied in an in vitro model. Blood cell suspensions (20 ml) with a hematocrit level of 10% were pumped through Nuclepore filters with a nominal pore diameter of 5 micron at constant flow rates (0.82-6.1 ml/min), and the pressure-time curves were recorded. An initial fast rise (K1) and a later slow rise (K2) of the pressure-time curve were observed; according to earlier studies (Skalak, R., Impelluso, T., Schmalzer, E.A., and Chien, S. (1983), Biorheology 20, 41), K1 reflects the dynamic plugging-unplugging process and K2 the permanent plugging of pores by rigid cells. Changes of the flow rate had no influence on K1 (greater than or equal to 1.6 ml/min) or K2. The addition of small concentrations of mononuclear leukocytes to the red cell suspensions resulted in a dose-dependent increase in K1, but did not affect K2. Admixture of partially hardened red cells (0.03% glutaraldehyde for 30 min) with normal red cells at a constant total hematocrit caused increases of both K1 and K2. From these results we conclude that both white cells and hardened red cells tend to plug narrow channels. White cells, however, may cause less permanent plugging than rigidfied red cells. These results may help to understand microcirculatory disorders seen in sickle cell crisis or leukocytosis and leukemia.
Blood Flow Velocity↗