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Biomedical subjects

J C Ellory

Publications and source records attributed to J C Ellory.

At least 181 records · Page 10Linked to original sources
PubMed1977

A change in the internal affinity of LK goat red-cell sodium pumps induced by high pH.

The K inhibition of ouabain-sensitive ATPase activity of LK goat red cell membranes is greatly reduced at high pH. This effect is reversible, and specific, since the apparent affinities for ATP, ouabain or external K do not alter. Anti-L-treated membranes show a similar alkali-induced affinity change, but have a lower pH optimum.

Adenosine Triphosphatases↗
PubMed1977

Substrate specificity of amino acid transport in sheep erythrocytes.

The specificity of amino acid transport in normal (high-glutathione) sheep erythrocytes was investigated by studying the interaction of various neutral and dibasic amino acids in both competition and exchange experiments. Apparent Ki values were obtained for amino acids as inhibitors of L-alanine influx. Amino acids previously found to be transported by high-glutathione cells at fast rates (L-cysteine, L-alpha-amino-n-butyrate) were the most effective inhibitors. D-Alanine and D-alpha-amino-n-butyrate were without effect. Of the remaining amino acids studied, only L-norvaline, L-valine, L-norleucine, L-serine and L-2,4-diamino-n-butyrate significantly inhibited L-alanine uptake. L-Alanine efflux from pre-loaded cells was markedly stimulated by extracellular L-alanine. Those amino acids that inhibited L-alanine influx also stimulated L-alanine efflux. In addition, D-alanine, D-alpha-amino-n-biutyrate, L-threonine, L-asparagine, L-alpha, beta-diaminoproprionate, L-ornithine, L-lysine and S-2-aminoethyl-L-cysteine also significantly stimulated L-alanine efflux. L-Lysine uptake was inhibited by L-alanine but not by D-alanine, and the inhibitory potency of L-alanine was not influenced by the replacement of Na+ in the incubation medium with choline. L-Lysine efflux from pre-loaded cells was stimulated by L-alanine but not by D-alanine. It is concluded that these cells possess a highly selective stero-specific amino acid-transport system. Although the optimum substrates are small neutral amino acids, this system also has a significant affinity for dibasic amino acids.

Alanine↗
PubMed1977

Caffeine and the contractility of single muscle fibres from the barnacle Balanus nubilus.

1. In single striated muscle fibres from the barnacle Balanus nubilus tension development following axial injection of caffeine (50 mM in 150 mM-KCl, pH 7.1) was used as an index of releasable Ca. It was shown that fibres incubated in 0 Ca (Na replaced) salines for up to 400 min gave ca. 15% of the control tension response. Inclusion of 1 mM-La in the 0 Ca (Na) saline significantly reversed this decline.2. Estimates of the total fibre calcium assayed under the same experimental conditions indicated a 67% loss of fibre Ca in 0 Ca, and only a 37% loss in La-0 Ca media. No correction was made for the loss of calcium from the extracellular space.3. Experiments with (45)Ca indicated that the efflux of calcium from this preparation was inhibited by 1 mM-La externally and that this effect was still significant even in the presence of 0 Ca (Na) salines. The caffeine-stimulated efflux of Ca was also reduced by ca. 70% in the presence of 1 mM La saline externally.4. The influx and efflux of (14)C caffeine were shown to be rapid, and apparently passive. The diffusion coefficient for caffeine following intracellular injection was 2.4 +/- 0.2 x 10(-6) cm(2) sec(-1) at 18-22 degrees C.5. There was no significant loss of (140)La over a period of 2 hr following axial micro-injection into the fibres.6. In (140)La uptake experiments there was a progressive increase in the La space over 10.5 hr, in contrast to the results with [(3)H]inulin, whose uptake saturated in ca. 1.5 hr. The probability of surface binding and the precipitation of La salts in the extensive extracellular space was suggested as an explanation.7. It is concluded that internal Ca within the sarcoplasmic reticulum, and not cleft or extracellular Ca is the most significant source for these caffeine-induced contractions. Fluxes across the surface membrane can however alter the internal Ca stores over longer periods of time.

Adenosine Triphosphate↗
PubMed1977

The interaction of monovalent cations with the sodium pump of low-potassium goat erythrocytes.

1. The activation by Na ions and the effect of the anti-L antibody on the sodium pump of low-potassium type (LK) erythrocytes, have been studied by measuring ouabain-sensitive ATPase activity of red cell membranes of LK goats. The experimental data were first corrected for incomplete occupation of the external K sites of the pump, using a saturation function obtained from influx experiments.2. Double-reciprocal plots of the corrected rates against Na concentration at various fixed K concentrations, yield a pattern of competitive K inhibition when it is assumed that three equivalent sodium sites take part in the internal activation of LK-(Na+K)-ATPase. The dissociation constant of Na at each site (K(m)) lies between 10 and 20 mM and that of K as competitive inhibitor (K(i)), between 1.5 and 4.5 mM.3. The maximal rate of hydrolysis of LK goat (Na + K)-ATPase is not different from those usually obtained with the high-potassium type (HK) red cell enzyme. Then, the low pumping rate of LK erythrocytes in physiological conditions is only reflecting the poor Na affinity, both absolute and relative, at the internal Na sites of their sodium pumps.4. The stimulation of the ouabain-sensitive ATPase activity by sensitization of the membranes with anti-L serum, is mediated by a threefold reduction of the K(m)/K(i) ratio at each site. K(m) decreases by a factor of 10, but there is also a smaller diminution of K(i). The maximal rate of hydrolysis, however, is unchanged by the anti-L treatment. The least-squares fitting of the pooled data by the rate equation, converges better with less than three and more than two equivalent sodium sites.5. The affinity sequence at two external K sites of the LK goat erythrocyte sodium pump, determined in the presence of 100 mM external Na, is Rb > K > Cs. It is obtained from the concentration dependence in influx experiments, and is the same as reported for human red cells.6. Cubic-root Dixon plots of the corrected ouabain-sensitive ATPase activity against the concentration of K and its congeners, show the sequence Tl > K > Rb > Na > Cs for the affinities at the internal cation sites of the LK sodium pump. Anti-L treatment decreases the relative magnitude of Na and Cs selectivities, it being not certain whether a Rb-Na transition then occurs.7. The results are discussed in terms of possible mechanisms whereby the sodium pump of LK and HK red cells may adjust the properties of their cation sites upon translocation of monovalent cations.

Adenosine Triphosphatases↗
PubMed1976

Effects of ATP and magnesium ions on the fluorescence of harmala alkaloids. Restrictions for the use of harmala alkaloids as fluorescent probes for (Na+ + K+)-ATPase.

1. Harmine and harmaline were investigated as potentially useful fluorescent inhibitors of (Na+ + K+) activated ATPase. 29 From spectroscopic measurements both compounds were shown to form 1 : 1 complexes with ATP, the dissociation constants being 0.65 mM and 1.83 mM for harmine and harmaline respectively. Addition of Mg2+ and enzyme further affected these equilibria. 3. Although it was possible to demonstrate a competitive effect of harmine at the sodium-loading site of the enzyme, other inhibitory effects, including inhibitions of ouabain binding and the ouabain-insensitive ATPase were found. 4. It was concluded that the harmala alkaloids can inhibit (Na+ + K+)-activated ATPase in a complex way involving both Na- and ATP-binding sites. This severely limits their usefulness as spectroscopic probes.

Adenosine Triphosphatases↗
PubMed1976

Amino acid transport in normal and glutathione-deficient sheep erythrocytes.

1. Uptake rates for 23 amino acids were measured for both normal (high-GSH) and GSH-deficient (low-GSH) erythrocytes from Finnish Landrace sheep. 2. Compared with high-GSH cells, low-GSH cells had a markedly diminished permeability to D-alanine, L-alanine, alpha-amino-n-butyrate, valine, cysteine, serine, threonine, asparagine, lysine and ornithine. Smaller differences were observed for glycine and proline, whereas uptake of the other amino acids was not significantly different in the two cell types.

Alanine↗
PubMed1975

Asymmetric membrane expansion and modification of active and passive cation permeability of human red cells by the fluorescent probe 1-anilino-8-napththalene sulfonate.

1. The membrane perturbations induced by the interaction of the fluorescent probe 1-anilino-8-naphthalene sulfonate (ANS) with human red blood cells were studied. 2. ANS below 0.5 mM inhibits partially (20% maximum) the ouabain-insensitive Na+ and K+ influx and efflux. Above 0.5 mM ANS increases both Na+ and K+ leak fluxes. The increased cation leaks are larger for Na+ than K+. 3. The (Na+ +K+)-ATPase and ouabain-sensitive Na+ and K+ fluxes are inhibited by ANS. Ouabain-insensitive, Mg2+-dependent ATPase activity of ghosts is stimulated by [ANS] less than 0.3 mM and inhibited by [ANS] greater than 0.3 mM. 4. ANS also inhibits the Na+-dependent, ouabain-insensitive K+ influx that is inhibited by ethacrynic acid and furosemide. 5. Red cells become crenated with [ANS] less than 1 mM and sphere at [ANS] greater than 1 mM. In the former conditions hypotonic hemolysis is decreased whereas the latter increase osmotic fragility. 6. It is suggested that ANS expands the membrane asymmetrically by binding preferentially to the external membrane surface. 7. It is concluded that ANS is a general inhibitor of ion transport, particularly of those processes thought to involve facilitated-diffusion mechanisms. The increased cation leaks observed at high ANS concentrations may be related to prehemolytic membrane disruption. 8. The membrane perturbations caused by ANS are compared to those caused by other reversible inhibitors of anion exchange in red blood cells. Their possible modes of action are discussed.

Adenosine Triphosphatases↗
PubMed1975

Sodium and chloride transport by the intestine of the European flounder Platichthys flesus adapted to fresh or sea water.

1. Everted intestinal sacs prepared from Platichthys flesus adapted to sea water (SW) have higher rates of salt and water transport than did sacs prepared from fresh water adapted (FW) fish. 2. Intestines mounted in Ussing chambers gave stable open-circuit voltages and short-circuit currents after pre-incubation for 20--30 min of --1.91 +/- 0.14 (14) mV and --45.0 +/- 5.1 (14) muA/cm2, SW fish, and --1.24 +/- 0.14 (11) mV and --18.2 +/- 3.6 (11) muA/cm2, FW fish. 3. Isotope flux measurements indicated a net Na transport of 21.5 +/- 4.1 (11) neq/cm2-min in SW fish intestines, but no significant Na transport in FW fish (7.6 +/- 7.6 (9) new/cm2-min). Both preparations showed an active Cl transport, 26.6 +/- 6.1 (12) neq/cm2-min for SW and 18.5 +/- 9.7 (17) neq/cm2-min for FW fish. 4. No significant difference in the uptake of Na or Cl across the mucosa was observed between FW and SW fish. The uptake of both ions showed some saturation at high concentrations. 5. Interactions between Na and Cl uptake were small, although Cl uptake was significantly higher in Na-free solutions. 6. It is concluded that electrogenic Cl transport may be the dominant mechanism for water and salt transport in flounder intestine, and that adaptation to a saline environment involves regulation of pumping rather than Na or Cl entry across the mucosal membrane.

Animals↗