Transport of amino acids by isolated gills of the mussel Mytilus californianus Conrad

1975 ◽  
Vol 62 (2) ◽  
pp. 313-325
Author(s):  
S. H. Wright ◽  
T. L. Johnson ◽  
J. H. Crowe
Keyword(s):  
Amino Acids ◽  
Significant Role ◽  
Transport Mechanism ◽  
Surrounding Medium ◽  
Gill Tissue ◽  
Mytilus Californianus ◽  
Animal Nutrition ◽  
Neutral Amino Acids ◽  
Kinetics Of

The unidirectional influx of cycloleucine into in vitro preparations of gill tissue of the mussel, Mytilus californianus, was determined. Influx was found to be linear for at least an hour, and the kinetics of cycloleucine influx conformed to Michaelis-Menten type kinetics. The transport mechanism(s) for cycloleucine is relatively specific for the L-enantiomorph of neutral amino acids, and is capable of accumulating cycloleucine to intracellular concentrations much higher than those of the surrounding medium. Evedence is presented that the transport of amino acids by gill tissue plays a significant role in whole animal nutrition.

Kinetics of Influx of Peptides and Amino Acids into Hamster Jejunum in Vitro: Physiological and Theoretical Implications

1990 ◽  
Vol 79 (3) ◽  
pp. 267-272 ◽  
Author(s):  
D. Burston ◽  
D. M. Matthews
Keyword(s):  
Amino Acids ◽  
Free Amino Acids ◽  
Free Amino ◽  
Transport Rate ◽  
Side Chain ◽  
Neutral Amino Acids ◽  
Acidic Amino Acids ◽  
Wide Range ◽  
Kinetics Of

1. This paper reports a comparison of the kinetics of influx into hamster jejunum of a series of dipeptides of neutral, basic and acidic amino acids, and a tripeptide of neutral amino acids, with those of corresponding free amino acids. 2. Kt, the substrate concentration at which the transport rate is half the maximal transport rate, and Vmax, the maximal transport rate, were more similar from one peptide to another than among amino acids, with the result that, over a wide range of concentrations, rates of influx of individual peptides varied much less than those of amino acids. 3. It is suggested that this may account for the rates of absorption of amino acids being closely related to the amino acid composition of the protein fed, instead of being widely dissimilar as with corresponding mixtures of free amino acids. 4. With neutral amino acids, both Kt and Vmax. fell with increasing length of the side-chain, as observed on many previous occasions. This did not occur with the corresponding homologous dipeptides, which shows that the hypothesis that the apparent affinity for transport is related to the lipophilic properties of the side-chain cannot be applied to peptides.

scholarly journals Identification in skeletal muscle of a distinct extracellular pool of amino acids, and its role in protein synthesis

1971 ◽  
Vol 121 (5) ◽  
pp. 817-827 ◽  
Author(s):  
R. C. Hider ◽  
E. B. Fern ◽  
D. R. London
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Incubation Medium ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Longus Muscle ◽  
Kinetics Of

1. The kinetics of radioactive labelling of extra- and intra-cellular amino acid pools and protein of the extensor digitorum longus muscle were studied after incubations with radioactive amino acids in vitro. 2. The results indicated that an extracellular pool could be defined, the contents of which were different from those of the incubation medium. 3. It was concluded that amino acids from the extracellular pool, as defined in this study, were incorporated directly into protein.

Transcerebral exchange kinetics of large neutral amino acids during acute inspiratory hypoxia in humans

2019 ◽  
Vol 79 (8) ◽  
pp. 595-600
Author(s):  
Rasmus H. Dahl ◽  
Ronan M. G. Berg ◽  
Sarah Taudorf ◽  
Damian M. Bailey ◽  
Carsten Lundby ◽  
...  
Keyword(s):  
Amino Acids ◽  
Large Neutral Amino Acids ◽  
Neutral Amino Acids ◽  
Exchange Kinetics ◽  
Kinetics Of

Trans-tegumental absorption of L-alanine and L-leucine by a monogenean, Diclidophora merlangi

Parasitology ◽  
1978 ◽  
Vol 76 (1) ◽  
pp. 29-37 ◽  
Author(s):  
D. W. Halton
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Amino Acid ◽  
Sea Water ◽  
Low Molecular Weight ◽  
Acid Uptake ◽  
Neutral Amino Acids ◽  
Freeze Dried ◽  
Significant Difference

SummaryAn in vitro investigation has been made of the relative roles of the gut and tegument in the absorption of the neutral amino acids L-alanine and L-leucine by a marine fish-gill parasite, Diclidophora merlangi. The use of ligatures to preclude oral ingestion of trace-labelled medium has proved inadequate, invariably damaging the tegument, as revealed by stereoscan electron microscopy, and resulting in artifactual levels of absorption. Three alternative procedures have given consistently reliable data on the route of entry of low molecular weight substrates. (1) Ultrastructural examination of worms previously incubated in electron-dense cationic tracers has shown that, in vitro, there is no oral intake of sea water. (2) The suspending of worms in trace-labelled medium with the mouth out of the medium and comparing amino acid uptake with that of worms totally immersed in medium has revealed no statistically significant difference in the absorption levels. (3) Application of section (freeze-dried) auto-radiography to detect diffusible isotope has demonstrated directly transtegumental absorption of a neutral amino acid. It is concluded from these experiments that Diclidophora has a tegumental transport system for absorbing certain neutral amino acids, and whilst, clearly, the worm is sanguinivorous and digests blood in a well-developed gut, it may also be capable of supplementing this diet with low molecular weight organic nutrient absorbed directly from sea water via the tegument.

scholarly journals Cloning and Expression of the Major SecretedCathepsin B-Like Protein from Juvenile Fasciola hepatica andAnalysis of Immunogenicity following Liver FlukeInfection

2003 ◽  
Vol 71 (12) ◽  
pp. 6921-6932 ◽  
Author(s):  
Ruby H. P. Law ◽  
Peter M. Smooker ◽  
James A. Irving ◽  
David Piedrafita ◽  
Rebecca Ponting ◽  
...  
Keyword(s):  
Amino Acids ◽  
Cathepsin B ◽  
Fasciola Hepatica ◽  
Cathepsin L ◽  
Cloning And Expression ◽  
Significant Similarity ◽  
Peptide Substrates ◽  
Liver Flukes ◽  
Kinetics Of

ABSTRACT The functions of the cathepsin B-like proteases in liver flukes are unknown and analysis has been hindered by a lack of protein for study, since the protein is produced in small amounts by juvenile flukes. To circumvent this, we isolated and characterized a cDNA encoding the major secreted cathepsin B from Fasciola hepatica. The predicted preproprotein is 339 amino acids in length, with the mature protease predicted to be 254 amino acids long, and shows significant similarity to parasite and mammalian cathepsin B. Only one of the two conserved histidine residues required for cathepsin B exopeptidase activity is predicted to be present. Recombinant preproprotein was produced in yeast, and it was shown that the recombinant proprotein can undergo a degree of self-processing in vitro to the mature form, which is active against gelatin and synthetic peptide substrates. The recombinant protein is antigenic in vaccinated rats, and antibodies to the protein are detected early after infection of rats and sheep with F. hepatica. The kinetics of the response to cathepsin B and cathepsin L after infection of sheep and rats confirm the temporal expression of these proteins during the life cycle of the parasite.

Plasma and brain kinetics of large neutral amino acids and of striatum monoamines in rats given aspartame

1990 ◽  
Vol 28 (5) ◽  
pp. 317-321 ◽  
Author(s):  
M. Romano ◽  
L. Diomede ◽  
G. Guiso ◽  
S. Caccia ◽  
C. Perego ◽  
...  
Keyword(s):  
Amino Acids ◽  
Large Neutral Amino Acids ◽  
Neutral Amino Acids ◽  
Kinetics Of

scholarly journals Apical Membrane Permeability of Mytilus Gill: Influence of Ultrastructure, Salinity and Competitive Inhibitors on Amino Acid Fluxes

1987 ◽  
Vol 129 (1) ◽  
pp. 205-230
Author(s):  
STEPHEN H. WRIGHT ◽  
TIMOTHY W. SECOMB ◽  
TIMOTHY J. BRADLEY
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Apical Membrane ◽  
Sea Water ◽  
Gill Tissue ◽  
Permeability Barrier ◽  
Acid Uptake ◽  
Passive Permeability ◽  
Membrane Area ◽  
Kinetics Of

The apical membrane of gill integumental cells from the mussels Mytilus edulis and M. californianus serves as a permeability barrier separating sea water from a cytoplasm rich in amino acids and other small organic molecules. Morphometric analysis of transmission electronmicrographs indicates that the membrane area of these cells is increased between 10- and 18-fold by the presence of a microvillous brush border. The microvilli do not appear to influence the kinetics of solute transport across the cell apex, as determined using a mathematical model of the relationship between membrane structure and the kinetics of transport. Rates of amino acid loss from the integument were low, and estimates of the upper limit of the passive permeability of the apical membrane to amino acids ranged from 0.5 to 10×10−10cm s−1. Abrupt exposure of intact mussels or isolated gill tissue to 60% sea water (19% salinity) resulted in a transient, 40- to 80-fold increase in the rate of loss of all amino acids from integumental tissues. Upon exposure to full-strength sea water, efflux rates returned to near control values. Exposure to 60% sea water also inhibited the carrier-mediated accumulation of amino acid: uptake of 0.5 μmol1−1 [14C]alanine and [14C]taurine was reduced by 80% compared to control uptake in 100% sea water. This inhibition was not adequate to account for the increase in net efflux of taurine from gill tissue into 60% artificial sea water (ASW), though the inhibition of alanine uptake may have contributed significantly to the increased loss of this amino acid. Efflux of discrete structural classes of amino acid occurred when integumental tissues were exposed to 50 μmoll−1 concentrations of structurally related analogues. It is concluded that the apical membrane of gill cells has a very low passive permeability to amino acids, and that the overall permeability of the gill can be increased in a reversible fashion by exposure to reduced salinity or to high external concentrations of amino acid.

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