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Biomedical subjects

J C Ellory

Publications and source records attributed to J C Ellory.

At least 199 records · Page 11Linked to original sources
PubMed1975

Evidence against the participation of the gamma-glutamyltransferase-gamma-glutamylcylclotransferase pathway in amino acid transport by rabbit erythrocytes.

The GSH concentration of rabbit erythrocytes was monitored under conditions of large net transport of alanine, phenylalane and lysine in the absence of glucose. In no case was there an appreciable alteration in GSH concentration during amino acid uptake. It is suggested that the gamma-glutamyltransferase-gamma-glutamylcyclotransferase pathway does not participate in amino acid transport by these cells.

Alanine↗
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

The molecular form of acetylcholinesterase as determined by irradiation inactivation.

The molecular size of acetylcholinesterase (EC 3.1.1.7) from the electric organ of Electrophorus electricus and erythrocyte ;ghosts' was estimated in both membrane-bound and purified preparations by irradiation inactivation. Results suggest that the form of the enzyme in the membrane is a monomer of molecular weight approx. 75000 and that multiple forms of the enzyme observed in solubilized preparations are aggregates of this monomer.

Acetylcholinesterase↗
PubMed1974

Antibody-induced alterations in the kinetic characteristics of the Na:K pump in goat red blood cells.

The kinetic characteristics of the Na:K pump in high potassium (HK) and low potassium (LK) goat red cells were investigated after altering the intracellular cation concentrations. At low concentrations of intracellular K (K(c)), increasing K(c) at first stimulates the active K influx in HK cells, but at higher K(c) the pump is inhibited. These results suggest that in HK cells K(c) acts both at a stimulatory site at the inner aspect of the pump and by competition with intracellular Na (Na(c)) at the Na translocation sites. In LK cells, K(c) inhibits the active K influx and the sensitivity of LK cells to inhibition is much greater than the sensitivity of HK cells. Exposure of LK cells to an antibody (anti-L), raised in an HK sheep by injection of LK sheep cells, increased the active K influx at any given K(c). The effect of the antibody was greater at higher intracellular K concentrations, and in cells with very low concentrations of K the antibody had little effect on the pump rate. The failure of anti-L to stimulate the pump in low K(c) LK cells was not due to failure of the antibody to bind to the cells. Anti-L combining at the outer surface of the cell reduces the affinity of the pump at the inner surface for K at the inhibitory sites. The maximal pump rate in LK cells at optimal Na and K concentrations is less than the maximal pump rate of HK cells under the same circumstances.

Animals↗
PubMed1974

Interaction of HK and LK goat red blood cells with ouabain.

The characteristics of the interaction of Na-K pumps of high potassium (HK) and low potassium (LK) goat red blood cells with ouabain have been determined. The rate of inhibition by ouabain of the pump of HK cells is greater than the rate of inhibition of the pumps of LK cells. Treatment of LK cells with an antibody (anti-L) raised in HK sheep by injecting LK sheep red cells increases the rate of inhibition of the LK pumps by ouabain to that characteristic of HK pumps; reduction of intracellular K (K(c)) in LK cells increases the rate at which ouabain inhibits their pumps and exposure of these low K(c) cells to anti-L does not affect the rate of inhibition. There is considerable heterogeneity in the pumps of both HK and LK cells in the rate at which they interact with ouabain or the rate at which they pump or both. LK pumps which are sensitive to stimulation by anti-L bind ouabain less rapidly than the remainder of the LK pumps and exposure to antibody increases the rate at which ouabain binds to the sensitive pumps; the difference between the two types of pumps disappears if intracellular K is very low. The calculated number of ouabain molecules bound at 100% inhibition of the pump is about the same for HK and LK cells. Although exposure to anti-L increases the apparent number of ouabain binding sites in LK cells at normal K(c), it does not alter the apparent number of sites in LK cells when K(c) has been reduced.

Animals↗
PubMed1974

Calcium movements in single crustacean muscle fibres.

1. Internal microinjection of the Ca-sensitive photoprotein aequorin or the isotope (45)Ca have been used to assess Ca movements in single muscle fibres from the barnacle Balanus nubilus and the crab Maia squinado.2. Progressive isosomotic replacement of external Na by Li, choline, sucrose or Tris was associated with a rapid increase in the level of light emission from internally injected aequorin. This response was dependent upon the presence of external Ca. The light output was maximal for Na concentrations < 50 mM in the replaced salines, while Na concentrations > 350 mM produced no apparent increase in the resting light emission.3. If the Ca concentration in the external saline was altered, no effect was observed in Na replaced salines when the Ca concentration was < 1 mM, but maximal effects were observed at concentrations of Ca of ca. 100 mM.4. The increased light emission from aequorin in Na-replaced salines was substantially inhibited by 1 mM-La(3+) applied externally, but not by N-ethyl maleimide (NEM), propanolol or D-600.5. Following microinjection of (45)Ca and 2 hr equilibration, the residual efflux of Ca was shown to be sensitive to the removal of external Ca and Na, the extent of each component being variable.6. The Na-sensitive Ca efflux was partially inhibited by external La(3+) (1 mM), but not by high concentrations of Mg(2+), Ca(2+), Mn(2+) or Co(2+). It was stimulated by NEM and ethacrynic acid, which was considered to be due to an indirect effect upon the sarcoplasmic reticulum.7. It is concluded that Ca movements in these single crustacean muscle fibres involve Na gradients and a Ca: Ca exchange and from the relative insensitivity of Ca movements to various inhibitors, in contrast to the Mg system, it seems that there may be two independent modes for divalent cation transport in this preparation.

Animals↗
PubMed1974

Thallium and the sodium pump in human red cells.

1. Thallium (Tl) inhibits the ouabain-sensitive K influx in human red cells in high-Na medium. At 1 mM external K concentration [K(o)], the ouabain-sensitive K influx decreases steadily with increasing Tl concentration, up to 0.9 mM outside; at 0.17 mM-K(o), however, Tl stimulates the ouabain-sensitive K influx below 0.1 mM-Tl(o) and inhibits it at higher concentrations.2. In a K-free medium in which all except 5 mM-Na is replaced by choline, and into which red cells show zero control ouabain-sensitive Na efflux, Tl is able to support ouabain-sensitive Na efflux up to 2.1 m-mole/l. cells.hr following a sigmoid activation curve which is half-maximal between 0.03 and 0.05 mM-Tl(o) and that follows two-site kinetics up to 0.1 mM-Tl(o). Beyond 0.15 mM-Tl(o), the Tl-activated ouabain-sensitive Na efflux attained is inhibited slightly.3. When the ouabain-sensitive Na efflux is measured at 5 mM-Na(o) and 5 mM-K(o), increasing concentrations of Tl have little effect on it, 0.9 mM-Tl(o) inhibiting by some 14%; in similar conditions, the ouabain-sensitive K influx is inhibited by about 40%.4. The dependence of ouabain-sensitive K influx on external K concentration at 5 mM-Na(o), which follows a slightly sigmoid curve in the absence of Tl, changes to hyperbolic at 0.06 mM-Tl(o) at the same time that ouabain-sensitive K influx is inhibited. The fitted V(max) values for ouabain-sensitive K influx are the same in the presence and in the absence of 0.06 mM-Tl(o).5. In high-Na cells, loaded by nystatin treatment, the ouabain-sensitive K influx measured at 0.2 mM-Na(o) follows a hyperbolic curve between 0.05 and 0.4 mM-K(o), and is inhibited by Tl in a strictly competitive fashion.6. The effects of Tl on ouabain-sensitive Na efflux and ouabain-sensitive K influx are interpreted in terms of a high-affinity substitution for K at the external K sites of the Na pump and suggest that in human red cells Tl can be actively transported inwards in exchange for internal Na.7. Thallium can inhibit about 25% of the ouabain-insensitive Na efflux into 5 mM-Na(o) and part of this inhibition occurs with a high Tl-affinity; the ouabain-insensitive K influx is inhibited by Tl both in high-Na and in 5 mM-Na medium, but with a different concentration dependence than the ouabain-insensitive Na efflux.

Binding Sites↗