Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.3.4.6 (urease)
 7,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Portacaval shunting in rats results in several metabolic alterations similar to those seen in patients with hepatic encephalopathy. The characteristic changes include: (a) diminution of cerebral function; (b) raised plasma ammonia and brain glutamine levels; (c) increased neutral amino acid transport across the blood-brain barrier; (d) altered brain and plasma amino acid levels; and (e) changes in brain neurotransmitter content. The aetiology of these abnormalities remains unknown. 2. To study the degree to which ammonia could be responsible, rats were made hyperammonaemic by administering 40 units of urease/kg body weight every 12 h and killing the rats 48 h after the first injection. 3. The changes observed in the urease-treated rats were: (a) whole-brain glucose use was significantly depressed, whereas the levels of high-energy phosphates remained unchanged; (b) the permeability of the blood-brain to barrier to two large neutral amino acids, tryptophan and leucine, was increased; (c) blood-brain barrier integrity was maintained, as indicated by the unchanged permeability-to-surface-area product for acetate; (d) plasma and brain amino acid concentrations were altered; and (e) dopamine, 5-hydroxytryptamine (serotonin) and noradrenaline levels in brain were unchanged, but 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of 5-hydroxytryptamine, was elevated. 4. The depressed brain glucose use, increased tryptophan permeability-to-surface-area product, elevated brain tryptophan content and rise in the level of cerebral 5-HIAA were closely correlated with the observed rise in brain glutamine content. 5. These results suggest that many of the metabolic alterations seen in rats with portacaval shunts could be due to elevated ammonia levels. Furthermore, the synthesis or accumulation of glutamine may be closely linked to cerebral dysfunction in hyperammonaemia.
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PMID:Hyperammonaemia causes many of the changes found after portacaval shunting. 170 23

In this paper, near-infrared (NIR) light emitting L-noradrenaline functionalized CdSeTe QDs (NA-CdSeTe) were synthesized and applied to the biosensing of urea. When the pH value of NA-CdSeTe solution was adjusted from neutral to alkalinity, the noradrenaline on the surface of QDs would turn to quinone, which triggered the fluorescence quenching of NA-CdSeTe probe due to the charge transfer interactions between QDs and the proximal quinone. Based on the fact that the hydrolysis of urea in the presence of urease would release OH- and slightly change the pH value of the solution, the fluorescence intensity of NA-CdSeTe QDs could be linked to the enzymatic degradation of urea. The novel urea-biosensing system could effectively determinate urea in the dynamic concentration range from 0.057 to 13mmol/L. Furthermore, NA-CdSeTe probe could serve as an "optical window" for the bioimaging of urea with high selectivity in the serum samples and HepG2 cells. The urea-bioimaging system could effectively probe urea in the dynamic concentration range from 0.2 to 5mmol/L. This NIR probe was excellent candidate not only for its sensitive with urea but also its real-time bioimaging. We expected that this NIR probe based strategy could pave the way for developing simple, no enzyme immobilization required and good sensitive method related detections for further medical applications.
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PMID:L-noradrenaline functionalized near-infrared fluorescence CdSeTe probe for the determination of urea and bioimaging of HepG2 Cells. 2855 Nov 23