scholarly journals Amino acid transport by resealed ghosts from pigeon erythrocytes

1982 ◽  
Vol 202 (3) ◽  
pp. 613-621
Author(s):  
K P Wheeler
Keyword(s):  
Amino Acids ◽  
Concentration Gradient ◽  
Acid Transport ◽  
Ph Values ◽  
Intracellular Amino Acids ◽  
Net Flux ◽  
High Concentrations ◽  
Dependent Transport ◽  
Resealed Ghosts ◽  
Net Fluxes

Resealed ghosts from pigeon erythrocytes were shown to haemolyse during incubation in isotonic media with pH values greater than about 7 and high concentrations of Na+ inside the ghosts seemed to enhance this effect. At lower pH values the ghosts were stable but still highly permeable to Na+ and K+, and moderately permeable to sucrose. Under the latter conditions the ghosts transported amino acids in a way qualitatively but not quantitatively similar to intact erythrocytes. The Na+-dependent transport of serine and alanine by the ghosts consisted essentially of an exchange of extracellular for intracellular amino acids, with no significant net flux. In contrast, net fluxes of glycine in the direction of the Na+-concentration gradient across the ghost membrane were demonstrated. However, under one condition a small net influx of glycine occurred against the prevailing Na+-concentration gradient. Unlike Na+-dependent glycine uptake, the uptake of six other amino acids by intact pigeon erythrocytes was not influenced by the nature of the anion present. The significance of these findings in relation to previous work on the Na+-gradient hypothesis of membrane transport is discussed.

scholarly journals Digestion and nutrient net fluxes across the rumen, and the mesenteric- and portal-drained viscera in sheep fed with fresh forage twice daily: net balance and dynamic aspects

2003 ◽  
Vol 89 (5) ◽  
pp. 649-666 ◽  
Author(s):  
Didier Rémond ◽  
Laurence Bernard ◽  
Béatrice Chauveau ◽  
Pierre Nozière ◽  
Claude Poncet
Keyword(s):  
Amino Acids ◽  
Small Intestine ◽  
Amino Acid ◽  
Protein Amino Acid ◽  
Orchard Grass ◽  
Net Uptake ◽  
Flux Measurements ◽  
Net Flux ◽  
Net Fluxes ◽  
Net Release

Digestion and portal net flux of nutrients were studied in sheep fed twice daily with fresh orchard-grass. Digestive flows were measured in six fistulated sheep using the double-marker technique. Three sheep were fitted with catheters and blood-flow probes, allowing nutrient net flux measurements across the portal-drained viscera (PDV), the mesenteric-drained viscera (MDV) and the rumen. Total tract apparent digestion of N was similar to portal net appearance of N, calculated as the sum of free amino acids (FAA), peptide amino acids (PAA), NH3, and urea net fluxes. PAA accounted for 25 % of non-protein amino acid net release across the PDV. With the exception of glycine and glutamate, the small intestine was the main contributor to this PAA net release. The essential amino acid (EAA) apparent disappearance between the duodenum and the ileum was lower than the net appearance of EAA (FAA + PAA) across the MDV. The value of PDV:MDV flux of free EAA was, on average, 78 %. The rumen accounted for 30 % of the net uptake of EAA by the PDV tissues not drained by the mesenteric vein. Rumen net release of acetate, propionate, butyrate, 3-hydroxybutyrate, and lactate accounted for 70, 55, 46, 77 and 52 %, respectively, of their portal net releases. Conversely, the small intestine was a net consumer of arterial acetate and 3-hydroxybutyrate. Dynamic study of nutrient net fluxes across the PDV showed that throughout a feeding cycle, the liver faced a constant flux of amino acids (AA), whereas volatile fatty acid and NH3net fluxes varied in response to the meal. The present study specified, in forage-fed sheep, the partitioning of nutrient net fluxes across the PDV and the role of peptides in portal net release of AA.

Echinococcus granulosus: specificity of amino acid transport systems in protoscoleces

Parasitology ◽  
1987 ◽  
Vol 95 (1) ◽  
pp. 71-78 ◽  
Author(s):  
S. A. Jeffs ◽  
C. Arme
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Glutamic Acid ◽  
Echinococcus Granulosus ◽  
Concentration Gradient ◽  
Amino Acid Transport ◽  
Transport Systems ◽  
Acid Transport ◽  
Transport And Diffusion ◽  
And Diffusion

SUMMARYProtoscoleces ofEchinococcus granulosusabsorb the l-amino acids proline, methionine, leucine, alanine, serine, phenylalanine, lysine and glutamic acid by a combination of mediated transport and diffusion. All eight amino acids were accumulated against a concentration gradient. Comparison ofKtandVmaxvalues suggests that a low affinity for a particular compound is compensated for by a relatively larger number of transport sites for that compound. Four systems serve for the transport of the eight substrates studied: 2 for neutral (EgNl, EgN2) and 1 each for acidic (EgA) and basic (EgB) amino acids. All eight amino acids are incorporated into protein to varying degrees and substantial portions of absorbed l-alanine and l-methionine are metabolized into other compounds.

Modulation of Amino Acid Transport in Rat Liver Slices by Tissue Preincubation

1980 ◽  
Vol 35 (11-12) ◽  
pp. 1019-1023 ◽  
Author(s):  
Volker Ehrhardt
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Rat Liver ◽  
Amino Acid Transport ◽  
Specific Substrate ◽  
Acid Transport ◽  
Liver Slices ◽  
High Concentrations ◽  
Preincubation Medium ◽  
Stimulation Of

In rat liver slices, a prolonged preincubation resulted in a stimulation of AIB and alanine uptake. The increase of transport of both amino acids can be ascribed to a reduction of Kt without an alteration of Vt. The enhancement of transport seems to be restricted to the A mediation as indicated by the findings that only the Na+-dependent, MeAIB-inhibitable portion of AIB transport was increased by the prolonged preincubation, and, furthermore, that the uptake of cysteine, a specific substrate for system ASC in liver cells, was not affected. The effect of an extended preincubation on AIB transport was abolished by the addition of high concentrations of AIB and alanine to the preincubation medium. Several other amino acids tested did not affect the increase of AIB transport. The observed stimulation of transport seems not to be due to the derepression of the synthesis of transport proteins, as cycloheximide and 5-azacytidine did not block the increase of AIB uptake. The enhancement of amino acid transport does not appear to be a result of a release from transinhibition since the uptake of alanine was markedly enhanced after 3 h of preincubation while the alanine concentrations in the incubated liver slices did not change significantly.

scholarly journals Oil Phase Solubility Rather Than Diffusivity Determines the Release of Entrapped Amino Acids and Di-Peptides from Water-in-Oil-in-Water Emulsions

Molecules ◽  
2022 ◽  
Vol 27 (2) ◽  
pp. 394
Author(s):  
Esra Kocaman ◽  
Davide Rabiti ◽  
Juan Sebastian Murillo Moreno ◽  
Asli Can Karaca ◽  
Paul Van der Meeren
Keyword(s):  
Amino Acids ◽  
Release Kinetics ◽  
Phase Solubility ◽  
Acidic Ph ◽  
Acid Transport ◽  
Double Emulsions ◽  
Ph Values ◽  
Neutral Ph ◽  
Oil In Water ◽  
Kinetics Of

The permeation of amino acids and di-peptides with different hydrophobicities across the oil phase in W/O/W double emulsions was investigated at different concentrations, considering the pH of the aqueous phase. Moreover, the particle size, yield of entrapped water and release kinetics of the double emulsions was evaluated as a function of time. Regarding the release of the entrapped amino acids and di-peptides, their hydrophobicity and the pH had a significant effect, whereas the concentration of the dissolved compound did not lead to different release kinetics. The release of the amino acids and di-peptides was faster at neutral pH as compared to acidic pH values due to the increased solute solubility in the oil phase for more hydrophobic molecules at neutral pH. Regarding the effect of the type of oil, much faster amino acid transport was observed through MCT oil as compared to LCT oil, which might be due to its higher solubility and/or higher diffusivity. As di-peptides released faster than amino acids, it follows that the increased solubility overruled the effect from the decreased diffusion coefficient of the dissolved compound in the oil phase.

PAPER CHROMATOGRAPHY OF COMPLEX BIOLOGICAL MATERIALS BY SOLVENT REDEVELOPMENT WITHOUT PRIOR REMOVAL OF SALTS OR PROTEINS

1960 ◽  
Vol 38 (10) ◽  
pp. 1137-1147 ◽  
Author(s):  
Arthur E. Pasieka
Keyword(s):  
Amino Acids ◽  
Paper Chromatography ◽  
Filter Paper ◽  
Complex Mixtures ◽  
Two Dimensional ◽  
One Dimensional ◽  
Equivalent Time ◽  
Biological Compounds ◽  
High Concentrations ◽  
Subsequent Staining

A solvent redeveloping technique has been devised by which amino acids, peptides, and sugars can be separated from complex mixtures in the presence of high concentrations of salts and proteins. The separations are effected by two to four successive 18-hour solvent developments with drying between each 18-hour period before subsequent staining of the chromatograms. Better separations and resolutions are obtained by such successive 18-hour solvent developments than by one continuous solvent development for an equivalent time. The effect of these redevelopments on the separations and resolutions of biological compounds is illustrated at various stages by photographs of one- and two-dimensional chromatograms. The redevelopment technique requires filter paper sheets up to 4 ft in length for one-dimensional analytical and preparative types of chromatograms.

Quantitative Changes in Plasma Amino Acids Induced by Oral Contraceptives

1971 ◽  
Vol 41 (4) ◽  
pp. 301-307 ◽  
Author(s):  
I. L. Craft ◽  
T. J. Peters
Keyword(s):  
Amino Acids ◽  
Oral Contraceptives ◽  
Plasma Concentrations ◽  
Plasma Amino Acids ◽  
Total Plasma ◽  
Hormone Production ◽  
Contraceptive Pills ◽  
High Concentrations ◽  
Normal Women ◽  
Quantitative Changes

1. Plasma amino acids have been determined in healthy untreated women and in those receiving synthetic steroids to suppress ovulation. Both groups were studied early in the cycle when endogenous sex hormone production is low, and again later in the same cycle, when endogenous or exogenous hormones are at high concentrations respectively. 2. In normal women there is a significant decrease in plasma concentrations of serine, glutamate and ornithine, and of total amino acids in the second half of the cycle. 3. At this time those taking oral contraceptives have significant decreases in plasma concentrations of proline, glycine, alanine, valine, leucine and tyrosine, and of total plasma amino acids. In addition plasma glutamate, glycine, isoleucine and tyrosine concentrations are significantly lower than in normal women. 4. In the interval between completing one course of contraceptive pills and commencing the next, total plasma amino acid concentration reverts to normal, but a significant decrease in plasma glycine concentration persists. 5. It is suggested that these changes are due to the influence of endogenous and exogenous sex hormones respectively.

scholarly journals Amino acid transport in normal and glutathione-deficient sheep erythrocytes

1976 ◽  
Vol 154 (1) ◽  
pp. 43-48 ◽  
Author(s):  
J D Young ◽  
J C Ellory ◽  
E M Tucker
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Cell Types ◽  
The Other ◽  
Acid Transport ◽  
Sheep Erythrocytes ◽  
Uptake Rates

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, α-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.

Amino Acid Transport in a Water-mould: The Possible Regulatory Roles of Calcium and N6-(Δ2-isopentenyl)adenine

1975 ◽  
Vol 53 (9) ◽  
pp. 975-988 ◽  
Author(s):  
Danny P. Singh ◽  
Hérb. B. LéJohn
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Osmotic Shock ◽  
Inhibitory Effect ◽  
Transport Systems ◽  
Acid Transport ◽  
Isopentenyl Adenine ◽  
Energy Dependent ◽  
Water Mould

Transport of amino acids in the water-mould Achlya is an energy-dependent process. Based on competition kinetics and studies involving the influence of pH and temperature on the initial transport rates, it was concluded that the 20 amino acids (L-isomers) commonly found in proteins were transported by more than one, possibly nine, uptake systems. This is similar to the pattern elucidated for some bacteria but unlike those uncovered for all fungi studied to date. The nine different transport systems elucidated are: (i) methionine, (ii) cysteine, (iii) proline, (iv) serine–threonine, (v) aspartic and glutamic acids, (vi) glutamine and asparagine, (vii) glycine and alanine, (viii) histidine, lysine, and arginine, and (ix) phenylalanine–tyrosine–tryptophan and leucine–isoleucine–valine as two overlapping groups. Transport of all of these amino acids was inhibited by azide, cyanide, and its derivatives and 2,4-dinitrophenol. These agents normally interfere with metabolism at the level of the electron transport chain and oxidative phosphorylation. Osmotic shock treatment of the cells released, into the shock fluid, a glycopeptide that binds calcium as well as tryptophan but no other amino acid. The shocked cells are incapable of concentrating amino acids, but remain viable and reacquire this capacity when the glycopeptide is resynthesized.Calcium played more than a secondary role in the transport of the amino acids. When bound to the membrane-localized glycopeptide, it permits concentrative transport to take place. However, excess calcium can inhibit transport which can be overcome by chelating with citrate. Calculations show that the concentration of free citrate is most important. At low citrate concentrations (less than 1 mM) in the absence of exogenously supplied calcium, enhancement of amino acid transport occurs. At high concentrations (greater than 5 mM), citrate inhibits but this effect can be reversed by titrating with calcium. Evidently, the glycopeptide acts as a calcium sink to regulate the concentration of calcium made available to the cell for its membrane activities.N6-(Δ2-isopentenyl) adenine (a plant growth 'hormone') and analogues mimic the inhibitory effect of citrate and bind to the glycopeptide as well. Replot data for citrate and N6-(Δ2-isopentyl) adenine inhibition indicate that both agents have no more than one binding constant. These results implicate calcium, glycopeptide, and energy-dependent transport of solutes in some, as yet undefinable, way.

Acid-Base and Ionic Exchanges at Gills and Kidney After Exhaustive Exercise in the Rainbow Trout

1988 ◽  
Vol 136 (1) ◽  
pp. 461-481 ◽  
Author(s):  
CHRIS M. WOOD
Keyword(s):  
Rainbow Trout ◽  
Exhaustive Exercise ◽  
Strong Ion Difference ◽  
Dynamic Modulation ◽  
Extracellular Acidosis ◽  
Titratable Acid ◽  
Na Efflux ◽  
Net Flux ◽  
Ionic Exchanges ◽  
Net Fluxes

Unidirectional Na+ and Cl− fluxes, net fluxes of Na+, Cl−, other ions, titratable acid (TA), ammonia and acidic equivalents (net H+) across the gills, together with the comparable renal fluxes, were monitored throughout a 24-h period after exhaustive exercise (simple chasing) in the rainbow trout. The gills were the major site of flux. The renal excretion of [TA-HCO3−], ammonia, lactate and most electrolytes increased after exercise, coincident with diuresis. Relative to the gills, the kidney accounted for only 8% of net H+ flux, 0–15% of net electrolyte losses and 50% of lactate loss, though the latter was negligibly small. Approximately 1000 μequiv kg−1 of net H+ were transported across the gills to the water during the first 4h, and then fully recovered over the subsequent 8h, coincident with periods of extracellular acidosis and alkalosis recorded in previous studies. Ammonia efflux increased during the first 4h; changes in titratable acid flux and extracellular PNHNH3 and NH4+ levels suggest that this elevation occurred partially as NH3 diffusion in the first hour, and thereafter mainly as NH4+ exchange. Small net Na+ losses (≊300 μequivkg−1), moderate net K+ losses (≊600 μequiv kg−1) and large net Cl− losses (≊1200 μequiv kg−1) correlated well with previously reported plasma changes; only the Na+ deficit was fully corrected by 24 h. Na+ influx was stimulated and Cl− influx inhibited during the 0–4 h period of net H+ excretion, whereas Na+ influx returned to control levels and Cl− influx increased during the 4–12 h period of net H+ uptake. These data indicate dynamic modulation of Na+/NH4+,H+ and C1−/HCO3−,OH− exchanges; however, an excess of Cl− over Na+ efflux also contributed to net H+ excretion. Acidic equivalent flux correlated well with [Na+-Cl−] net flux, in accord with strong ion difference theory.

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