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Biomedical subjects

P L La Celle

Publications and source records attributed to P L La Celle.

18 recordsLinked to original sources
PubMed1989

Perturbation of red blood cell flow in small tubes by white blood cells.

The flow of blood in the microcirculation is facilitated by the dynamic reduction in viscosity (Fahraeus-Lindquist effect) resulting from the axial flow of deforming erythrocytes (RBCs) and from the decrease in the ratio of cell to vessel diameter. RBC velocity exceeds that of average fluid velocity; however the slower moving white blood cells (WBC) perturb flow velocity and the ratio of cell to vessel diameter by obstructing red cell flow through formation of "trains" of red cells collecting behind the white cell. This effect of white cells was studied quantitatively in a model in vitro tubes less than 10 microns in diameter with the demonstration that flow resistance increases linearly with white cell numbers up to 1,000 WBC/mm3 at tube hematocrit of 17.7%. The increase in resistance exceeds the flow resistance of WBC and appears to relate directly to train formation. A mechanical model of train formation developed to predict WBC influence in flow resistance over the range of WBC studied reasonably fits observed WBC effects.

Biophysical Phenomena↗
PubMed1987

Erythrocyte-endothelial cell adherence in senescence and in hemolytic disorders.

Adherence of normal human erythrocytes to cultured endothelial cells when exposed to in vitro fluid shear forces typical of venules, capillaries and arterioles is very low, less than 0.03 percent, in the presence of an albumin-buffer but increases five fold by the effects of autologous plasma. Senescent erythrocytes obtained by density separation had an adherence frequency in the normal cell range, suggesting that predisposition to endothelial adherence is not a key factor in regulation of life span by the sequestration, identification and phagocytosis modulated by immune recognition. Sickle cells' frequency of adherence exceeds that of normal cells particularly at low shear forces calculated to resemble those of veins and sinuses, and increases five to ten fold when autologous plasma obtained during sickle crisis is present; these findings add support to the hypothesis that excessive tendency for sickle cell adherence may contribute to the vascular obstructive phenomena of the disorder. The behavior of hereditary spherocytes and thalassemic erythrocytes resembles normal cells, suggesting that hemolytic mechanisms are not significantly dependent on erythrocyte-endothelial cell interaction. Erythrocytes from patients having diabetes exhibit the characteristics of control cells, suggesting that their membrane adhesion to endothelium may not be critical to initiation of vessel wall pathophysiological processes; however, the behavior in relation to damaged endothelial cells may differ importantly.

Anemia, Sickle Cell↗
PubMed1986

Alterations by leukocytes of erythrocyte flow in microchannels.

The effects of leukocytes on blood rheology in the microcirculation may be predicted to result from the rheological characteristics of the individual white blood cell types and their behavior at entrances of small vessels; their influence on flow resistance of blood due to their disturbance of erythrocyte flow; and the obstruction caused by their adherence to endothelial cells or geometrical hindrance of their flow at irregular or narrow regions. Deformation of leukocytes in micropipettes indicates the relative rigidity of lymphocytes and blast cells from leukemias in contrast to granulocyte viscoelastic properties, and entry times for lymphocytes in 2.6-4.6-microns channels were 11-151 s but milliseconds in 9.1-micron tubes. Lymphocytes and erythrocytes rarely (less than 1%) adhered to cultured endothelium; however, granulocytes adhered avidly at shear stresses of 10-100 dyn/cm2, typical of microcirculation. In the 9.1-microns flow tube at Hct = 17.7 +/- 2.6%, increasing [WBC] caused a linear increase in flow resistance, but above [WBC] = 1000/mm3 resistance tended to plateau. These data support the interpretation that granulocyte adherence to endothelial cells with the potential for obstruction of flow may be a more significant rheological consequence of leukocytes in blood than their resistance to flow because of their relative rigidity or their influence on flow resistance by perturbation of the erythrocyte flow.

Capillary Action↗
PubMed1986

Erythrocyte-endothelial cell adherence in sickle cell disorders.

Detachment of individual sickle erythrocytes from cultured endothelial cell monolayers has been evaluated by a fluid-shearing technique in an effort to quantitate adherence at shear forces that would be anticipated in the in vivo circulation. Nonirreversibly sickled cells (non-ISC) were more adherent at normal oxygen tensions than control cells. More than 1% non-ISC remained attached to the monolayer at forces greater than physiologic shear stresses in capillary and venous circulations, and many of the most avidly attached cells, once separated, immediately reattached to adjacent endothelial cells. These data suggest that hemoglobin S-containing erythrocytes may have a higher frequency of adherence in vivo in regions of low shear stress where prolonged erythrocyte-endothelial cell contact could occur. Some of these cells detached by shear force would subsequently reattach in in vivo conditions. Plasma-enhanced attachment frequency and plasma from blood in a case of sickle crisis caused further increase. These observations further support the concept that sickle erythrocyte-endothelial cell interaction may be a significant factor in initiation of vascular occlusive events in sickle cell disease.

Anemia, Sickle Cell↗
PubMed1981

Electroviscous flow and electrophoretic motion during erythrocyte entry in a glass capillary in the presence of applied electric potential gradients.

One means of measuring an effect of erythrocyte deformability on red cell flow is to determine how long it takes erythrocytes to enter or flow through an aperture whose diameter is smaller than 8 micrometers. It is convenient to impose an electric potential difference across the aperture so that the passage of an erythrocyte can be monitored by electronic means. We report here that such electric potential gradients may have a large influence on red cell entry times, primarily through the mechanism of erythrocyte electrophoretic mobility.

Electrophoresis↗
PubMed1981

Effects of the calcium-mediated enzymatic cross-linking of membrane proteins on cellular deformability.

Excess calcium binding affects the shape and dynamics of cellular deformation of human erythrocytes. It may be hypothesized that incorporation of calcium may modify cellular deformability by processes which include specific cross-linking of membrane proteins with resultant changes in cell shape and deformability. Since previous studies indicate that accumulation of calcium ions causes development of gamma-glutamyl-epsilon-lysine bridges in membrane proteins, under control of a membrane transamidating enzyme which specifically requires calcium ions for activation, experiments were devised to examine the relationship between cross-linking and deformability and to determine the effects of specific inhibitor of membrane protein cross-linking on the calcium-dependent modification of erythrocyte to the echinocytic shape. The elastic shear modulus of the membrane was not significantly affected by calcium-induced cross-linking, indicating that induced shape change, not altered elasticity, causes the observed reduction in cellular deformability. These findings support the interpretation that Ca++-induced and transamidase-catalyzed cross-linking of membrane proteins contributes to fixation of altered cellular shape and decreased cellular deformability.

Adult↗
PubMed1981

Biochemical factors influencing erythrocyte deformability and capillary entrance phenomena.

Evaluation of the effects of biochemical modification of erythrocytes by low pressure filtration through Nuclepore filters of 2.8 and 3.0 micrometer pore diameter and glass micropipettes of 2.7 and 3.0 micrometer internal diameter and channel length greater than 100 micrometer indicates the relative sensitivity of the micropipette in detection of reduction of cellular deformability. In dynamic studies of erythrocyte entrance behaviour on micropipettes, the significance of induced relative sphericity on cellular deformability was evident. Reduction of intracellular ATP, cellular pH, sphere induction by bifunctional membrane protein cross-linking reagents and lead caused diminution in cellular deformability, attributable to the more spherical shape. Similarly echinocyte formation by effects of aged plasma, oleate and senscence, and stomatocyte induction by chlorpromazine caused marked decrease in capillary entry of cells having flow velocities of approximately 100 micrometer/s in contrast inhibitors of the glucose carrier, of calmodulin and manipulated decrease in membrane lipid of bilayer fluidity did not cause detectable change in cellular deformability. These data emphasize the relative importance of erythrocytic shape as a determinant of cellular deformability and suggest that necessity for adequate control of shape change is necessary when examining effects of biochemical manipulations on membrane elasticity and cellular deformability. The preliminary date from capillary entrance experiment indicate the importance of dynamic experiments in in vitro studies of microcirculation.

Adenosine Triphosphate↗
PubMed1979

Parallel decrease of erythrocyte membrane deformability and spectrin solubility at low pH.

Reduction of pH over the range 6.0-4.5 results in a decrease of erythrocyte deformability in parallel with the induced progressive sphericity of cells. At low deformation rates employed, increase of hemoglobin viscosity was not significant. A decrease of membrane elasticity was detected in cells when sphering, the major determinant of cellular deformability, was prevented at pH 5.0 by hyperosmotic medium. The pronounced change of deformability and the reduced elasticity occurred at calculated intracellular pH values at which solubility in vitro of extracted erythrocyte spectrin is also markedly reduced. The parallel decrease of deformability and spectrin solubility supports the hypothesis that spectrin aggregation may contribute to regulation of erythrocyte deformability through effects on shape and membrane elastic characteristics.

Erythrocyte Membrane↗
PubMed1975

Calcium and magnesium ATPases of the spectrin fraction of human erythrocytes.

Using a rapid method of preparation, spectrin has been isolated from human erythrocytes and its ATPase activity investigated. The ATPase activity with calcium has two distinct components, one with optimal activity when calcium and ATP are of equal concentration (low-Ca-ATPase) and another which is activated above 1 mM CaCl2 and is maximal at 100 mM CaCl2. There is also a Mg-ATPase with maximal activity at 10 mM MgCl2. The high-Ca-ATPase of spectrin, but not the low-Ca-ATPase, is inhibited by magnesium, while the Mg-ATPase is inhibited by Ca in excess of ATP. None of these activities exhibits the calcium-stimulated magnesium-dependent activity characteristic of the red cell calcium pump.

Adenosine Triphosphatases↗
PubMed1975

Absence of one component of spectrin adenosine triphosphatase in hereditary spherocytosis.

The stimulation by calcium and magnesium of ATPase activity of isolated ghosts, of water-soluble protein (spectrin), and of residual vesicles, derived from normal erythrocytes and from hereditary spherocytes (H.S.), has been measured. The ATPase activity found in normal water-soluble protein (WSP) at low levels of calcium (0.1-2.0 mM) is essentially absent in H.S. water-soluble protein, but the ATPase activity with magnesium and with high levels of calcium (60-100 mM) is the same in H.S. and normal WSP. Compared to normal, H.S. ghosts have increased Mg2+-stimulated activity. This increased activity is retained by the sedimentable vesicles ("residue") after extraction of the ghosts with 0.025 mM EDTA. The Ca2+, Mg2+-ATPase associated with the calcium pump is not significantly different in H.S.

Adenosine Triphosphatases↗
PubMed1975

Intrinsic material properties of the erythrocyte membrane indicated by mechanical analysis of deformation.

Deformation of the erythrocyte membrane by the micropipette technique permits analysis of intrinsic material characteristics of the membrane and provides a means to differentiate purely membrane factors from such extrinsic factors as surface area-to-volume ratio. Using small micropipettes (less than 0.5 microns radius) to deform cells, it is evident that the red cell membrane behaves like a solid for periods of time up to 5-10 min of sustained deformation; for long periods of strain, permanent deformations occur, indicative of the semi-solid structural character. In the time range in which the membrane behaves like a solid, the material is linearly elastic up to strains of 400%, implying a loose network structure in the membrane plane, and evaluation of the elastic parameter mu (mu for normal discocytes equals 7 x 10(-3) dynes/cm) suggests that the elements comprising the network may have a molecular weight of approximately that of the water-soluble membrane protein spectrin. Whether the network system is cross-linked or simply a polymer solution remains unanswered. Experimental data indicate that plastic flow of the membrane under conditions of protracted strain may lead to permanent deformation of the membrane, whereas uniform dilation of the membrane, requiring over 1000 times more energy than for plastic flow, results in membrane failure and lysis. Analyses of the data from larger micropipettes of limiting mean cylindrical diameter show their utility in evaluating extrinsic factors, e.g., surface area-to-volume relationships, which are related to the capability of the whole cell to form a new configuration with implicit resistance to total surface area change, as the cell enters narrow channels of the microcirculation. Thus, micropipettes with diameters in the 2.7-3.0-microns range can provide sensitive comparisons of cellular deformability of erythrocytes.

Animals↗