... was insensitive to amiloride (0.1 mmol l −1 ) or to a 10-fold elevation in seawater K + concentration (to 100 mmol l −1 ), suggesting that the mechanism does not directly involve Na + or K + transporters, but was inhibited by blockade of glutamine synthetase, the enzyme that traps ammonia-N to fuel the ornithine...

... exposed to HEA in a time-series analysis [500 μmol l −1 (NH 4 ) 2 SO 4 ; 15, 30, 45 and 60 min], as well as in a methionine sulfoxamine (MSOX) pre-injection experiment [to inhibit glutamine synthetase (GSase)]. These correlations consistently suggest that brain [T Amm ] is involved in the hyperventilatory...

... decrease branchial ammonia excretion and become ureotelic. The objective of this study was to determine the influences of cortisol and ammonia on ammonia excretion relative to expression of Rhesus (Rh) glycoproteins and the ammonia-fixing enzyme, glutamine synthetase (GS). In vivo infusions...

... the movement of NH 3 across cell membranes. This study examines the effects of crowding and feeding on ammonia excretion in gulf toadfish ( Opsanus beta ) within the context of Rh glycoproteins and the ammonia-fixing enzyme, glutamine synthetase (GS). Four Rh isoforms (Rhag, Rhbg, Rhcg1 and Rhcg2) were...

...Y. K. Ip; A. M. Loong; B. Ching; G. H. Y. Tham; W. P. Wong; S. F. Chew SUMMARY This study aimed to examine whether the stenohaline freshwater stingray, Potamotrygon motoro , which lacks a functional ornithine—urea cycle, would up-regulate glutamine synthetase (GS) activity and protein abundance...

... cycle (O–UC) enzyme activity and mRNA expression,we subjected toadfish to two-day and seven-day crowding regimes. Plasma cortisol levels were measured and liver tissue was assayed for ammonia and urea concentrations. Liver glutamine synthetase (GS), carbamoyl phosphate synthetase III (CPS), ornithine...

..., respectively, of fish exposed to 25‰ water. There were significant increases in glutamine synthetase(GS) activity in muscle and liver of these fish. In addition, exposure to 25‰ water for 4 days led to significant increases in GS protein abundance in both muscle and liver, indicating that increases...

... and/or glutamine in their brains, and if acute ammonia intoxication could be prevented by the administration of methionine sulfoximine [MSO; an inhibitor of glutamine synthetase (GS)] or MK801 [an antagonist of n -methyl d -aspartate type glutamate (NMDA) receptors]. For P. schlosseri and B. boddaerti exposed...

..., after exposure to air for 17 days, there were significant increases in ammonia content in all these tissues in P. expansa , accompanied by significant increases in glutamine content (2.9-, 2.5-, 4.5- and 3.4-fold,respectively). Simultaneously, there were significant increases in glutamine synthetase...

... Mus musculus or as in other African lungfish reported elsewhere. However,similar to other African lungfish and tetrapods, hepatic arginase of P. dolloi is present mainly in the cytosol. Glutamine synthetase activity is present in both the mitochondrial and cytosolic fractions of the liver of P. dolloi...

... exposure. Instead, ammonia produced through amino acid catabolism was detoxified to glutamine, leading to the accumulation of glutamine in the body during the first 72 h of aerial exposure. Complimenting the increased glutamine formation was a significant increase in glutamine synthetase activity...

...Patrick J. Walsh; Gregory D. Mayer; Mónica Medina; Matthew L. Bernstein; John F. Barimo; Thomas P. Mommsen SUMMARY We characterized the expression of the nitrogen metabolism enzyme glutamine synthetase [GSase; L-glutamate: ammonia ligase (ADP-forming), E.C. 6.3.1.2] in tissues of the gulf toadfish...

... glutamine,primarily in the muscle, accompanied by an increase in glutamine synthetase(GSase) activity in liver. The aim of the present study was to assess the effect on GSase expression in various tissues of exposure of B. sinensis to exogenous ammonia. Exogenous ammonia increases internal ammonia...

.... and Ratha, B. K. ( 1997 ). Carbamyl phosphate synthetases in an air-breathing teleost, Heteropneustes fossilis . Comp. Biochem. Physiol . 116B , 57 –63. Shankar, R. A. and Anderson, P. M. ( 1985 ). Purification and properties of glutamine synthetase from liver of Squalus acanthias . Arch...

... N-enrichment of the amide-N in glutamine in the tissues of fish exposed to 15 N-labelled ammonia was virtually the same as that of ammonia-N: i.e. approximately twice that of urea-N in the excreta and the tissues. Glutamine contents and glutamine synthetase activities in the liver and muscle...

... Atlantic cod ( Gadus morhua ) embryos, CPSase III, ornithine transcarbamoylase (OTCase), glutamine synthetase (GSase) and arginase activities were all expressed prior to hatching. Urea excretion was detected shortly after fertilization and rates were high relative to those of ammonia excretion (50–100...

... glutamine content, which peaked at 48 h. The increase in glutamine content could account for the decreases in the amounts of ammonia and urea excretion during air exposure. The specific activities of hepatic glutamate dehydrogenase (amination) and glutamine synthetase in these experimental fish increased...

... and S. velum . This is evidence for nitrate utilization, either assimilation or respiration, by some vent species and is consistent with the high levels of nitrate availability at vents. The ammonia assimilation enzymes glutamine synthetase (GS) and glutamate dehydrogenase (GDH) were detected in all...

... in the sea anemone Aiptasia pulchella , caused by darkness or depletion of the alga Symbiodinium , was partially or completely reversed by supplementing the medium with organic carbon compounds (e.g. α-ketoglutarate). Second, the activity of the ammonium-assimilating enzyme glutamine synthetase...

...Todd E. Hopkins; Chris M. Wood; Patrick J. Walsh ABSTRACT We examined the relationship between plasma cortisol levels, hepatic glutamine synthetase (GNS) activity and the form of nitrogen excreted (e.g. urea, ammonia) in undisturbed versus confined/crowded (acutely stressed) gulf toadfish...