The effects of exposure to ammonia on ammonia and taurine pools of the symbiotic clam

1997 ◽  
Vol 200 (21) ◽  
pp. 2797-2805 ◽  
Author(s):  
R Lee ◽  
J Childress ◽  
N Desaulniers
Keyword(s):  
Amino Acid ◽  
Sea Water ◽  
Gill Tissue ◽  
Ammonia Concentration ◽  
Major Product ◽  
Single Amino Acid ◽  
Ammonia Assimilation ◽  
Visceral Mass ◽  
Taurine Level ◽  
Chemoautotrophic Bacteria

The nutrition of the gutless clam Solemyareidi is supported by the activity of intracellular chemoautotrophic bacteria housed in its gill filaments. Ammonia (the sum of NH3 and NH4+) is utilized as a nitrogen source by the association and is abundant in the clam's environment. In the present study, clams were exposed to 0.01­1.3mmoll-1 ammonia for 22­23h in the presence of thiosulfate as a sulfur substrate. Ammonia exposure increased the ammonia concentration in the tissue pools of the gill, foot and visceral mass from 0.5 to 2µmolg-1wetmass, without added ammonia, to as much as 12µmolg-1wetmass in the presence of 0.7 and 1.3mmoll-1 external ammonia. Gill tissue ammonia concentrations were consistently higher than those in the foot and visceral mass. The elevation of tissue ammonia concentration compared with the medium may be due in part to an ammonia trapping mechanism resulting from a lower intracellular pH compared with sea water and greater permeability to NH3 compared with NH4+. Rates of ammonia incorporation into organic matter (assimilation) were determined using 15N as a tracer. 15N-labeled ammonia assimilation was higher in gill than in foot and increased as a function of 15N-labeled ammonia concentration in the medium. The size of the free amino acid (FAA) pool in the gill also increased as a function of ammonia concentration in the medium. This entire increase was accounted for by a single amino acid, taurine, which was the predominant FAA in both gill and foot tissue. Aspartate, glutamate, arginine and alanine were also abundant but their levels were not influenced by external ammonia concentration. Ammonia assimilation appeared to occur at rates sufficient to account for the observed increase in taurine level. These findings suggest that taurine is a major product of ammonia assimilation.

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.

scholarly journals Intracellular Na+ and the control of amino acid fluxes in the integumental epithelium of a marine bivalve

1989 ◽  
Vol 142 (1) ◽  
pp. 293-310
Author(s):  
S. H. Wright ◽  
D. A. Moon ◽  
A. L. Silva
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Sea Water ◽  
Gill Tissue ◽  
Transport Systems ◽  
Amino Acid Transporters ◽  
Marine Bivalve ◽  
Chemical Gradients ◽  
Influx Pathways ◽  
Taurine Efflux

The accumulation of amino acids from sea water into the integumental epithelium of the bivalve gill can occur against chemical gradients in excess of 10(6) to 1. The energy to drive this transport has been proposed to come from the inwardly directed Na+ electrochemical gradient. The present study examined the influence of intracellular and extracellular [Na+] on influx and efflux of amino acids in gill tissue from the mussel, Mytilus californianus. Influx of alanine was inhibited by more than 90% when external [Na+] was reduced from 425 to 2 mmol l-1, and by 85% when intracellular [Na+] was increased from approximately 11 to approximately 100 mmol l-1 (by means of a 30-min exposure to the ionophore, nigericin). Efflux of taurine and alanine from gill tissue into normal-Na+ sea water was very low (less than 5% of the Jmax of the carrier-mediated influx pathways). Reducing the external Na+ from 425 to 2 mmol l-1 increased taurine efflux by only 20%. Raising cell [Na+] to approximately 100 mmol l-1 increased taurine efflux 2.7-fold; further increases in cell [Na+] increased taurine efflux another 7.5-fold. These data, in conjunction with results from earlier studies, suggest that activation of integumental amino acid transporters requires an interaction of multiple sodium ions with binding sites of low affinity for this ion. This set of characteristics results in transport systems that are well-adapted for the net accumulation of amino acids from sea water.

Ionic and osmotic influence on prostaglandin release from the gill tissue of a marine bivalve, Modiolus demissus

1980 ◽  
Vol 84 (1) ◽  
pp. 169-185
Author(s):  
W. Freas ◽  
S. Grollman
Keyword(s):  
Arachidonic Acid ◽  
Sea Water ◽  
Gill Tissue ◽  
Adductor Muscle ◽  
Prostaglandin Synthesis ◽  
Marine Bivalve ◽  
Visceral Mass ◽  
Prostaglandin Release ◽  
Hyposmotic Stress ◽  
Wet Weight

1. Prostaglandin E2 (PGE2) was identified in Modiolus demissus gill tissue on the basis of solvent extraction, thin layer and column chromatography, bioassay, and radioimmunoassay. The presence of PGE2 was detected in both tissue and sea water incubate surrounding the tissue. 2. Both hyposmotic stress and magnesium-free sea water significantly increased release of prostaglandins into sea water. Hyposmotic stress also significantly increased prostaglandin synthesis. 3. Examination of tissues revealed that homogenates of the mantle and lower visceral mass contained significantly fewer nanograms immunoreactive prostaglandins per gram wet weight than homogenates of the gill, posterior adductor muscle, upper visceral mass, or siphon tissue. 4. Prostaglandin release could be increased by addition of arachidonic acid, and inhibited by addition of acetylsalicylic acid or indomethacin.

Single Amino Acid Based Self-Assemblies of Cysteine and Methionine

2018 ◽  
Author(s):  
Nidhi Gour ◽  
Bharti Koshti ◽  
Chandra Kanth P. ◽  
Dhruvi Shah ◽  
Vivek Shinh Kshatriya ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Self Assembly ◽  
Aromatic Amino Acids ◽  
Neutral Condition ◽  
Single Amino Acid ◽  
Binding Assays ◽  
Human Neuroblastoma ◽  
Cytotoxicity Assays ◽  
First Time

We report for the very first time self-assembly of Cysteine and Methionine to discrenible strucutres under neutral condition. To get insights into the structure formation, thioflavin T and Congo red binding assays were done which revealed that aggregates may not have amyloid like characteristics. The nature of interactions which lead to such self-assemblies was purported by coincubating assemblies in urea and mercaptoethanol. Further interaction of aggregates with short amyloidogenic dipeptide diphenylalanine (FF) was assessed. While cysteine aggregates completely disrupted FF fibres, methionine albeit triggered fibrillation. The cytotoxicity assays of cysteine and methionine structures were performed on Human Neuroblastoma IMR-32 cells which suggested that aggregates are not cytotoxic in nature and thus, may not have amyloid like etiology. The results presented in the manuscript are striking, since to the best of our knowledge,this is the first report which demonstrates that even non-aromatic amino acids (cysteine and methionine) can undergo spontaneous self-assembly to form ordered aggregates.

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