Biomedical subjects

C Acquaye

Publications and source records attributed to C Acquaye.

5 recordsLinked to original sources

PubMed1994

Bepridil as an antisickling agent: membrane internalization and cell rigidity.

The calcium channel antagonist, bepridil, beta-(2-methylpropoxy)methyl-N-phenyl-N-(phenylmethyl)-1-pyrrol idineethanamine monochloride monohydrate, inhibits the sickling of deoxygenated sickle (SS) erythrocytes, as determined by light microscopy. The anti-sickling effect was seen only in dilute suspensions of red cells. In concentrated erythrocyte suspensions, sickling was not inhibited and measurements of hematocrit and cell density were unchanged by bepridil. The determination of cell volume in dilute suspensions was complicated by bepridil's tendency to aggregate, but rapid measurements by electronic sizing also indicated no increase in cell volume, up to a bepridil concentration of 200 microM. Ektacytometry of dilute sickle cell suspensions suggested an explanation for the anti-sickling action of bepridil. Osmotic scan ektacytometry disclosed that bepridil initially increased the surface area of the red cell, as shown by a shift in the low osmolality minimum. This change was complete in 10 sec, the shortest time that could be measured. Subsequently, at concentrations that were observed to inhibit the sickling of deoxygenated sickle cells (100 microM or greater), red cells underwent a loss in surface area that was complete in 1 min. There was a concomitant loss of cell deformability. Light and scanning electron microscopy has previously shown that bepridil is a stomatocytic agent. Using transmission electron microscopy, we verified that the loss of surface area was a consequence of endocytosis, presumably as the end stage of the stomatocytic transformation induced by bepridil. Bepridil did not inhibit intracellular hemoglobin S polymerization even at 200 microM, as shown by oxygen scan ektacytometry. Bepridil thus appears to inhibit the sickling of deoxygenated SS cells by inducing endocytosis and lowering cell deformability. This mechanism may explain the anti-sickling effect of other basic amphiphiles, such as chlorpromazine.

Anemia, Sickle Cell↗

PubMed1993

Modified celluloses for erythrocyte deformability fractionation.

Cellulose columns have been used to separate erythrocytes into deformability classes, but recoveries have been variable and incomplete. Columns of modified cellulose (propylaminocarbonylmethyl cellulose [PAC] and butylisourea cellulose [BIC]) were effective in increasing the recovery of both normal and sickle cells applied to the columns, with reasonable yields of rigid cells in the late fractions. In particular, sickle cells were recovered in 95% yield, and late eluting cells had a sharply reduced deformability index.

Anemia, Sickle Cell↗

PubMed1990

Isolation and quantitation of human erythrocyte deformability classes.

A new technique is described that fractionates erythrocytes according to their deformability. The method is a modification of the method of Beutler et al. (J Lab Clin Med 1976;88:328-33), in which small cellulose columns are used to remove white cells from blood samples. We find that when the length-to-width ratio of the columns is increased, the mixed cellulose bed also fractionates the red cells. Measurement of mean cell volume, mean corpuscular hemoglobin concentration, hemoglobin level, deformability index, and cell density showed that deformability is the physical property of the erythrocyte that forms the basis for the fractionation. This is a separation modality that complements the numerous density gradient techniques for red cells. The following experimental results can be obtained by using the technique: (1) The number of cells with a defined degree of rigidity can be quantitated in an erythrocyte population. (2) Large numbers of cells that differ with respect to their deformability can be isolated. (3) Application of the method to sickle cells has quantitated the remarkable heterogeneity of these cells with regard to their deformability.

Anemia, Sickle Cell↗

PubMed1988

Electron microscopic studies of the intracellular polymerization of sickle hemoglobin.

Transmission electron microscopy has been used to study intracellular sickle hemoglobin polymer in unfractionated cells from the arterial and venous blood of patients and after external deoxygenation. We detect polymerized hemoglobin in up to 10% of the cells in the venous circulation, especially in cells that are "cigar-shaped" and appear to be irreversibly sickled. We could not see well-defined polymer in mixed arterial samples; nevertheless, we found electron opaque spots, which could be ferritin granules, hemosiderin, or small aggregates of hemoglobin S. However, upon sequential chemical deoxygenation using 1.0% sodium metabisulphite, polymer formation was seen at oxygen saturation values of 75%-85%. Cells that were physically deoxygenated using gas mixtures containing nitrogen-carbon dioxide-oxygen mixtures were found to contain distinct polymers of deoxyhemoglobin S at oxyhemoglobin saturation values of 50%-75%. As deoxygenation increases, we detect short, randomly arranged polymer in a loose network, with occasional long polymers. Upon further deoxygenation, the length and number of polymer forms increased. Between 0% and 50% saturation, most erythrocytes were full of long, parallel, closely packed polymers that tend to align and run parallel to the cell membrane. In both chemical and physically deoxygenated blood samples, cells were seen at 50%-75% oxyhemoglobin saturation that retained their normal biconcave disc shape, although they contained significant amounts of polymer. The structural changes in sickle erythrocytes seen in vitro due to physical or chemical deoxygenation of cells, may reflect in vivo intracellular changes in the sickle cell patient.

Anemia, Sickle Cell↗

PubMed1987

The development of a filtration system for evaluating flow characteristics of erythrocytes.

A complete description of the pathophysiology of sickle cell disease requires a physiologically meaningful measurement of red cell deformability. We have designed and built a system which allows one to determine filtration characteristics of erythrocytes. A dilute red cell suspension is forced through a 3.0-micron polycarbonate Nuclepore membrane with a constant positive pressure of 20 mm Hg. Under these conditions blockage of the pores in the polycarbonate membrane is insignificant and flow is linear. We use the relative number of cells filtered through the membrane as a means of approximating the means deformability of cells in the suspension. Using this system we have compared erythrocytes from various mammals and shown that our technique is sensitive in detecting not only differences in cell deformabilities between mammalian species but also changes in cell deformability of human red cells due to exchange transfusion and application of drugs. There was a positive correlation between cell filtrability and percentage cell recovery (coefficient of correlation, 0.65) and a negative correlation between cell size and filtrability (coefficient of correlation, -0.61). The filtrabilities of normal volunteers and sickle cell disease patients were found to be 71.8 +/- 6.6 and 53.6 +/- 5.0%, respectively. This system is sensitive and reliable, and should be useful in evaluating both the contribution of filtrability to the viability of red cells in vivo and potential therapeutic agents for sickle cell disease.

Anemia, Sickle Cell↗