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J C Ellory

Publications and source records attributed to J C Ellory.

At least 163 records · Page 9Linked to original sources
PubMed1980

Increased human red cell cation passive permeability below 12 degrees C.

The rate of most biological reactions declines as the temperature is reduced; indeed, cooling is often used to limit or terminate reactions. We report here a paradoxical temperature response of red cell K and Na permeability below 12 degrees C. This may be interpreted thermodynamically in terms of a membrane-ordering phenomenon, an observation supported by a variety of other physical measurements on red cell membranes reported in the literature.

Anions↗
PubMed1980

L-Tryptophan transport in human red blood cells.

1. The initial rate of L-tryptophan uptake into human red cells as a function of the concentration in the medium was studied at 25 and 37 degrees C. 2. Uptake was resolved into saturable and linear components. Kinetic constants at 37 degrees C were, apparent Km 1.55 mM, V 0.145 mmol/l cell water per min and apparent KD 0.0103 min-1. 3. Inhibitor studies showed that L-tryptophan transport via the saturable component represents uptake by a previously unidentified transport system, designated the T-system. The linear component represents L-tryptophan transport via the L-system. 4. The substrate specificity of the T-system is apparently limited to the aromatic amino acids, L- and D-tryptophan, L-tyrosine and L-phenylalanine. The main route of L-phenylalanine transport is, however, via the L system. L-Tyrosine is partly transported via the T-system, partly via the L-system.

Amino Acids↗
PubMed1980

Chloride-activated passive potassium transport in human erythrocytes.

Passive K+ transport in human erythrocytes (defined as ouabain-insensitive transport) was inhibited 70% by replacement of Cl- by several permeant monovalent anions. The Vmax of Cl--dependent K+ influx was 1.14 mmol . liter-1, hr-1; its apparent Km for K+ was 4.7 mM. There was a much smaller component of Na+ influx dependent on Cl- (Vmax, 0.23 mmol . liter-1 . hr-1). Furosemide and other inhibitors of Cl- transport inhibited passive K+ transport to the same extent as replacement of Cl-, but 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid, a specific inhibitor of anion exchange in erythrocytes, was ineffective. The Cl--dependent K+ transport, which may be K+/Cl- cotransport, could reflect a mechanism for regulating cell volume.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1980

Stimulation of the sodium-potassium pump by trypsin in low potassium type erythrocytes of goats.

1. Treatment of low K goat red cells with trypsin stimulated the Na-K pump more than twofold. Dose dependence and time course experiments indicated a half-maximal stimulation at 1.6 mg trypsin/ml. (37 degrees C, 3 hr), and a maximum effect after 5 hr (10 mg/ml). 2. Trypsin had only a small and variable effect on the ouabain-insensitive component of K influx. 3. The Na-K pump activity of high K goat red cells was not affected by trypsinization. 4. When intracellular K was varied by the PCMBS technique, it was found that the trypsin stimulation was greatest (2-5-fold) in cells with the highest K (40 m-mole/1. cells) and lowest (1.1-fold) in cells with low K (<1 m-mole/1. cells). 5. The trypsin effect was reversed by nystatin treatment or hypotonic lysis. 6. Trypsin did not increase the number of ouabain-binding sites. 7. It is concluded that trypsinization modifies the L antigen in low K goat red cells to decrease the apparent internal affinity for K of the Na-K pump in these cells.

Animals↗
PubMed1979

Properties of a goat anti-L antibody: further evidence for heterogeneity of the L antigen.

The preparation and properties of an antibody (anti-L) against low potassium type (LK) goat red cells raised in a high potassium type (HK) goat are described. This reagent stimulated active potassium transport, but showed only weak serological activity against low potassium type (LK) sheep and goat red cells. The results are discussed in relation to the hypothesis that anti-L antibody has two specificities--a sodium pump-stimulating activity (anti-Lp) and a serological activity (anti-L1y).

Animals↗
PubMed1979

Transport of tryptophan and other amino acids by mammalian erythrocytes.

Mammalian erythrocytes are known to have 4 distinct amino acid transport systems. The C system is found in sheep erythrocytes and is specific for neutral amino acids of intermediate size. Human cells lack the C system and have two alternative neutral amino acid transport mechanisms: the L system which is selective for large hydrophobic amino acids and a Na-dependent alanine-cysteine system. The L system is absent from ruminant and cat erythrocytes. Human rabbit and cat cells, but not sheep erythrocytes, have a specific dibasic amino acid transport mechanism (Ly system). L-Tryptophan uptake by human erythrocytes is mediated by two routes: a saturable high-affinity transport mechanism selective for L-tryptophan and a low affinity uptake mediated by the L system. The saturable component of L-tryptophan transport occurs by a previously unidentified uptake system, and is the major route for L-tryptophan uptake at physiological substrate concentrations. This system is absent from sheep and cat erythrocytes.

Animals↗
PubMed1978

Amino acid transport properties of erythrocytes from normal newborn lambs and lambs with an inherited defect in amino acid transport.

An amino acid transport defect which occurs in the erythrocytes of adult sheep is also present in foetal erythrocytes from newborn lambs which have inherited the lesion. The transport defect in erythrocytes from adult sheep is associated with high intracellular levels of ornithine and lysine and a markedly diminished GSH concentration. Although the lesion in foetal cells also results in the accumulation of ornithine and lysine, the intracellular GSH concentration is only moderately diminished.

Alanine↗
PubMed1978

A calcium-activated potassium channel present in foetal red cells of the sheep but absent from reticulocytes and mature red cells.

Red cells of adult sheep, like those of other ruminants, lack the calcium-activated potassium channel which is present in the membrane of human red cells. Since the activities of other transport systems in the sheep red cell are known to decrease during maturation of the cell or during development of the animal it was investigated whether the K+ channel is present in red cells from younger animals or in reticulocytes. Using the divalent cation ionophore A23187 to increase the intracellular Ca of intact cells, it was found that the K+-selective channel is present in foetal red cells from the foetus or newborn animal but not in reticulocytes. The presence of the channel showed no dependence on the K+ genotype of the sheep and was not associated with either "high K+"- or "low K+"-type Na+ pump. No Ca2+-dependent change in K+ permeability was found in red cells from either newborn or adult donkeys suggesting that its presence in the red cells of the foetus may not be general. The role of the K+ channel in the mammalian red cell and the relationship between the K+ channel and the Na+ pump are discussed.

Animals↗
PubMed1978

Na-K pump and Na-K-ATPase: disparity of their temperature sensitivity.

As previously observed in red blood cells, ouabain-sensitive K influx of kidney cells grown in culture for 3 days was much less inhibited by cooling that Na-K-ATPase of the same cells. (At 5 degrees C K influx was 9.7% of that at 38 degrees C, Na-K-ATPase, 1--2%.) Resealed ghosts of erythrocytes of ground squirrels were made containing 24Na and ATP, and the Na efflux and ATP hydrolysis were measured simultaneously. Under these conditions there was no difference in the reduction of activity with cooling, and the amount of reduction was close to that of active K transport in intact cells. The high sensitivity to temperature, characteristic of broken membranes, could not be induced in intact cells or resealed ghosts by eliminating either the Na/K gradient or the ATP gradient nor by chelation of cellular and extracellular Ca. It could not be eliminated in broken membranes by protection with ATP or Mg. Structural reorganization of membrane during lysis may cause the increase in temperature sensitivity of Na-K-ATPase.

Adenosine Triphosphate↗