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Biomedical subjects

J S Wiley

Publications and source records attributed to J S Wiley.

At least 109 records · Page 6Linked to original sources
PubMed1977

Selective loss of calcium permeability on maturation of reticulocytes.

Calcium and sodium permeability of human reticulocytes have been studied and compared to mature erythrocytes. Mature erythrocytes had extremely low Ca2+ permeability which was less than 0.1% of values published for squid axon or HeLa cells. Calcium entry was markedly increased in reticulocyte-rich suspensions and the uptake was linearly related to the percentage of reticulocytes present. The data suggest that reticulocytes are 43-fold more permeable to Ca2+ than mature cells although their Ca2+ concentration is not increased. Sodium influx into reticulocyte-rich suspensions was also increased in direct proportion to the percent of reticulocytes present. Reticulocytes are sixfold more permeable to Na+ than mature cells so the ratio of Ca2+:Na+ permeability falls by sevenfold as the reticulocyte changes to an erythrocyte. [3H]Ouabain binding was increased in reticulocyte-rich cell suspensions and the correlation suggested a value of about 4,000 sites per reticulocyte compared with 362+/-69 per mature cell. Maturation of the human reticulocyte produces disproportionate changes in cation permeability and in particular a selective loss of Ca2+ permeability.

Anemia↗
PubMed1976

Red cell calcium leak in congenital hemolytic anemia with extreme microcytosis.

A child with congenital hemolytic anemia, extreme microcytosis and bizarre red cell morphology has been studied. Splenectomy at the age of 21 mo greatly improved the hemolytic anemia, although red cell morphology was unchanged. Aniso- and poikilocytosis were marked on a stained smear, and there were many small hyperchromatic cells of irregular shape. The MCV of 25 cu mu was very low and the MCHC was normal. Osmotic fragility of fresh blood was increased, and postsplenectomy blood showed a fraction of extremely fragile cells. Concentration and fluxes of Na+ and K+ were normal, except K+ efflux, which was stimulated by external Ca2+. Inward Ca2+ movement into the patient's red cells was elevated three- to fourfold above red cells of the same mean age. Red cell Ca2+ concentration was raised 2.5 times normal and most of the Ca2+ was localized in the stroma. Red cell lipid, sialic acid, and ouabain-binding sites, all per milliliter of cells, were increased by 16%-23%, and, since these substances estimate the amount of membrane, it was likely that Ca2+ content per unit of membrane area was at least twice normal. Deformability of the cells, as judged by their filterability was markedly impaired. It was concluded that the red cell membrane was defective, and an increased membrane Ca2+ content was associated with reduced deformability, hemolysis, and distorted red cell morphology in this syndrome.

Anemia, Hemolytic, Congenital↗
PubMed1976

Potassium uptake and release by human blood platelets.

Thrombin is known to reduce the K+ content of human platelets, but the subcellular origin of the lost K+ is not known. The effect of aggregating agents on K+ release was studied in platelets labeled in plasma by preincubation with 42KCI. Platelets were separated from plasma by gel filtration through Sepharose 2B equilibrated with K+ -free Tyrode's buffer. Platelet K+ was 116nEq/10(8) platelets, of which 23% was found to be extracellular immediately after gel filtration. K+ influx was 65 nEq/10(8) platelets/hr at pH 7.5 and was more rapid at pH 7.9. About 70% of cell K+ exchanged with plasma in 4 hr with first-order kinetics, while a minor fraction of about 30% exchanged with a slower time course. This slowly exchanging fraction of platelet K+ was thought to arise from heterogeneity in the platelet population. Epinephrine and ADP aggregated gel-filtered platelets and released serotonin, but with loss of only 5%-10% of cell K+ and no beta-glucuronidase. In contrast, thrombin released up to 30% of platelet K+, whether aggregation occurred or was prevented by not stirring the cells. The specific activity of K+ released by all aggregating agents was identical to the specific activity of total platelet K+. Thrombin (0.01-0.2 NIH U/ml) released serotonin and also beta-glucuronidase (an enzyme of the alpha-granule), and there was a linear relation between release of K+ and this enzyme (r = 0.88). No lysis of platelets occurred, since lactic dehydrogenase was not detected. Pretreatment of platelets with aspirin in vitro inhibited thrombin-induced release of serotonin but had no effect on the loss of K+ or beta-glucuronidase. In contrast, the ingestion of aspirin by mouth inhibited the release of serotonin, beta-glucuronidase, and K+ by thrombin. The data suggested that the K+ loss induced by thrombin was primarily derived from release of alpha-granules and that these organelles contained about 20% of the total platelet K+ in a freely exchangeable and nonsequestered state.

Aspirin↗
PubMed1975

Inhibition of cation cotransport by cholesterol enrichment of human red cell membranes.

1. Human red cells were enriched with cholesterol by incubation with lipid dispersions having a high cholesterol: phospholipid mol ratio and the kinetics of the furosemide-sensitive cotransport for Na+ and K+ were measured. 2. Influxes of both K+ and Na+ through this system were inhibited by 70 and 76% in cholesterol-rich cells (cholesterol: phospholipid mol ratio 1.80) and the Km of the furosemide-sensitive flux components for both K+ and Na+ decreased. 3. Effluxes of both K+ and Na+ are inhibited by furosemide and the magnitudes of these furosemide-sensitive components are markedly decreased in cholesterol-rich cells. 4. The inhibitory effect of cholesterol enrichment on this carrier-mediated transport of cations suggests that cholesterol may either alter the position of the carrier or retard its movement within a more viscous membrane micro-environment.

Biological Transport, Active↗
PubMed1975

Modification of red cell membrane structure by cholesterol-rich lipid dispersions. A model for the primary spur cell defect.

Cholesterol-rich membranes are the hallmark of "spur" red cells. Spur cells accumulate cholesterol from cholesterol-rich serum lipoproteins. Previous studies suggested that this added cholesterol is responsible for both the altered morphology and the destruction of spur cells. To examine this process in the absence of other serum factors, cholesterol-lecithin dispersions with varying amounts of unesterified cholesterol (C) relative to phospholipid (P) were prepared, and their influence on normal human red cells was studied. Cholesterol-rich lipid dispersions (C/P mole ration greater 1.0) transferred cholesterol to both red cell membranes and serum lipoproteins, and cholesterol-poor dispersions (C/P mole ration less 1.0) depleted red cells of cholesterol. Changes in membrane cholesterol paralleled changes in membrane surface area, as calculated from osmotic fragility, with a 0.22 percent variation in surface area per 1.0 percent variation in cholesterol content. Cold-induced compression of membrane surface area was increased in cholesterol-poor red cells (C/P equals 0.4), whereas the surface area of cholesterol-rich membranes (C/P equals 1.80) underwent no compression. Although the Na and K permeability of red cells severely depleted of cholesterol was increased, lesser degrees of depletion had no effect, and the permeability of cholesterol-rich cells was normal. However, increasing membrane cholesterol caused a progressive decrease in red cell deformability, as measured by filtration. Cholesterol-poor red cells were spherocytic in appearance and cholesterol-rich cells were broad and flat, indicative of their surface areas. In addition, cholesterol-rich cells had an irregular contour due to folding of the periphery of the cell. This shape abnormality was identical to that of both spur cells after splenectomy and normal red cells incubated in spur serum. Normalization of the C/P of spur serum by added phospholipid prevented the increase in membrane cholesterol and surface area and the transformation of cell shape. These studies establish that the cholesterol content of red cells is dependent on the C/P of their milieu, either lipoproteins or cholesterol-lecithin dispersions. Moreover, the surface area, deformability, and contour of cholesterol-rich red cells are a direct function of their increased membrane C/P. Although cholesterol-rich spur cells are further modified in the circulation of patients with spleens, this abnormality of the membrane lipid bilayer, induced by cholesterol-rich cholesterol-lecithin dispersions, represents the primary spur cell defect.

Anemia, Hemolytic↗
PubMed1975

Characteristics of the membrane defect in the hereditary stomatocytosis syndrome.

Cation permeability and lipid composition have been studied in the red cells of five patients with various features of the hereditary stomatocytosis syndrome. Hemolysis was compensated in four patients, and only one patient was anemic. Cell NA+ was increased an average of 3 mueq per ml cells and cell K+ decreased 14 mueq per ml cells. Both active and passive fluxes of Na+ and K+ were increased by two to six times normal. Tritiated ouabain binding was increased an average of 2.5-fold, suggesting a proportionally greater number of cation pumps per cell. The coupling ratio of active Na+:K+ fluxes was normal (3:2). Calcium permeability was increased compatible with the degree of reticulocytosis, and cell Ca2+ content was normal. The lowered sum of Na+ plus K+ was associated with a high MCHC and low cell water. When examined in wet preparations, red cells assumed either a bowl-shaped or an irregular contour, and they appeared as target cells on dry smears. Only when cell water was increased in hypotonic media were stomatocytes seen on smear. The total lipid content of red cells was increased in four patients, although it was normal in one. The mole ratio of cholesterol to phospholipid was always normal; however, phospholipid analysis showed an increased proportion of phosphatidyl choline. The abnormal cells were osmotically resistant due to both an increased membrane surface area and a low total cation content. These patients show two hallmarks of hereditary stomatocytosis: bowlshaped red cells observed on wet preparations and a marked increase in Na+ and K+ permeability. The heterogeneity of this syndrome in our patients and in others reported with hereditary stomatocytosis appears to result from (1) variability in the increase in surface area which results from an excess of membrane lipid content, particularly phosphatidylcholine, and (2) a variability in cell water content which may be either decreased or increased as a result of changes in the sum of Na+ plus K+ ions.

Anemia, Hemolytic↗
PubMed1974

A furosemide-sensitive cotransport of sodium plus potassium in the human red cell.

The influxes of Na(+) and K(+) into the human red cell appear to be interrelated. This relationship was investigated under conditions in which either Na(+) or K(+) concentration outside the cell was varied or one cation was replaced by Mg(2+), choline(+), or Li(+). The effects of furosemide on Na(+) and K(+) movements were studied in the presence of ouabain. When ouabain was present, Na(+) influx was higher with K(+) ions externally than with other cations externally. Furosemide inhibited this K(+)-stimulated Na(+) influx, but it had little effect when K(+) was absent. Ouabain-insensitive K(+) influx was stimulated two-fold by external Na(+) compared with other cations. Furosemide also inhibited this stimulation, but it had little effect when Mg(2+) or choline(+) replaced external Na(+). Thus it was confirmed that synergism exists between the ouabain-insensitive influxes of Na(+) and K(+) and it was demostrated that furosemide inhibits this cooperative effect. The ouabain-insensitive influx of both K(+) and Na(+) showed a hyperbolic "saturating" dependence on the external concentration of the transported cation. Furosemide therefore eliminates a saturable component of influx of each cation. The net uptake of Na(+) in the presence of ouabain was stimulated by K(+) ions. A similar effect was observed with red cells, in which Li(+) replaced nearly all the internal Na(+) plus K(+) ions. In these cells, net Na(+) uptake was stimulated by external K(+), and net K(+) uptake was stimulated by external Na(+). Furosemide inhibited this mutual stimulation of net cation entries. The inhibitory action of furosemide was not limited to inward flux and net movement of Na(+) and K(+). Furosemide also inhibited the efflux of Na(+) into Na(+)-free media and the efflux of K(+) into K(+)-free media. It appeared, therefore, that the action of furosemide was not explained by inhibition of exchange diffusion. These data are consistent with an ouabain-insensitive transport process that facilitates the inward cotransport of Na(+) plus K(+)-ions, and that can produce a net movement of both ions. Although this process under some conditions mediates an equal bidirectional flux of both Na(+) and K(+), it cannot be defined as exchange diffusion. The contransport process is inhibited by furosemide.

Biological Transport, Active↗
PubMed1970

Red cell survival studies in hereditary spherocytosis.

The in vivo survival of hereditary spherocytes has been investigated with the (51)Cr red cell survival technique. Spherocytes invariably showed a shorter survival in a normal recipient than in the donor's own circulation. Moreover transfusion of spherocytes from a mother to her son, both with hereditary spherocytosis, showed that "foreign" spherocytes have a shorter survival than the "self" spherocytes of the recipient. These findings are attributed to splenic reticuloendothelial blockade, specific towards hereditary spherocytes in the patient's own circulation. There was no correlation between the Na(+) influx and the hemolytic tendency of hereditary spherocytes when the latter was measured by the survival t(1/2) in compatible normal recipients. However osmotic fragility influenced cell survival since cells with high fragility were rapidly sequestered in the normal spleen. It is suggested that both cell shape and a selective reticuloendothelial blockade in the spleen are important factors in determining the severity of hemolysis in the individual patient.

Blood Transfusion↗
PubMed1968

Some aspects of adenosine triphosphate synthesis from adenine and adenosine in human red blood cells.

1. The synthesis of ATP has been studied in human erythrocytes. Fresh cells showed no net synthesis of ATP when incubated with adenine or adenosine, although labelled adenine was incorporated into ATP in small amounts.2. Cold-stored cells (3-6 weeks old) became progressively depleted of adenine nucleotides but incubation with adenosine or adenine plus inosine restored the ATP concentration to normal within 4 hr. Incorporation of labelled adenine or adenosine into the ATP of incubated stored cells corresponded to net ATP synthesis by these cells.3. Synthesis of ATP from adenosine plus adenine together was 75% derived from adenine and only 25% from adenosine, indicating that nucleotide synthesis from adenine inhibits the simultaneous synthesis of nucleotide from adenosine.

Adenine↗
PubMed1967

Potassium transport and nucleoside metabolism in human red cells.

1. A study has been made of active cation transport in relation to the metabolism of nucleosides and deoxynucleosides in human red blood cells.2. Lactate production from inosine depended on the cellular inorganic phosphate available for phosphorolysis and was raised to some 4 times the normal rate from glucose. Inosine inhibited glucose metabolism according to the amount of glucose-6-phosphate produced. Guanosine behaved similarly, but glucose-6-phosphate was not formed from adenosine, deoxyinosine and deoxyguanosine.3. Glucose metabolism was related to the ATP content of the cells, which was raised by incubation with adenosine, or with inosine plus adenine.4. Adenosine and deoxyadenosine raised the potassium influx above the values found with inosine and deoxyinosine under conditions when the lactate production was constant. Active potassium influx was correlated with the ATP concentration in the cells, but independent of the lactate production when the latter was raised above normal.

Adenosine Triphosphate↗