Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1832588 (PSS)
 2,979 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The main object of the present study was to determine whether ascorbate, an antioxidant which has been shown to protect nitric oxide (NO) from attack by scavenger molecules, might be released from nitrergically-innervated smooth muscle; ascorbate release from the rat anococcygeus was measured by use of h.p.l.c. with electrochemical detection. 2. Incubation of rat anococcygeus muscles in normal physiological salt solution (PSS; 30 min) resulted in release of ascorbate into the bathing medium (7.7 +/- 0.9 nmol g-1 tissue). This release was increased by 96% when muscles were incubated in high K+ (70 mM) PSS. The resting release of ascorbate was unaffected by tetrodotoxin (TTX; 1 microM), omega-conotoxin GVIA (10 nM) or omission of calcium ions from the PSS (with addition of 0.2 mM EGTA), but all three procedures attenuated the increased release observed under depolarizing conditions. Resting release of ascorbate was unaffected by glutamate (100 microM), aspartate (100 microM), gamma-aminobutyric acid (100 microM) or carbachol (50 microM). 3. A second h.p.l.c. peak, which always preceded the ascorbate peak, was identified as urate. Urate release from the anococcygeus, following 30 min incubation in normal PSS, was 64.6 +/- 12.7 nmol g-1 tissue but, unlike ascorbate, urate release was unchanged in high K+ PSS. In functional experiments, urate (100-400 microM) partially protected NO (15 microM)-induced relaxations of the rat anococcygeus from inhibition by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO; 50 microM), but not from inhibition by hydroquinone or duroquinone (both 100 microM). 4. Muscles chemically sympathectomized with 6-hydroxydopamine (6-OHDA, 500 microM; 2 h) still exhibited release of ascorbate (2.5 +/- 0.4 nmol g-1 tissue) and urate (22.2 +/- 2.9 nmol g-1 tissue); in both cases the release was similar to that observed in time-matched control tissues not exposed to 6-OHDA. High K+ PSS produced a TTX-sensitive increase in release of ascorbate, but not urate, from 6-OHDA-treated muscles. 5. The results demonstrate that significant amounts of ascorbate and urate are released from the rat anococcygeus muscle. Ascorbate, but not urate, release appears to be enhanced by activation of nerves which are resistant to 6-OHDA pretreatment. Since both antioxidants can protect NO from attack by scavenger molecules, their release in nitrergically-innervated tissues may be important for the provision of the correct redox environment to allow NO to fulfill its proposed neurotransmitter role.
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PMID:Release of the antioxidants ascorbate and urate from a nitrergically-innervated smooth muscle. 942 23

A bilayer of the polyelectrolytes poly(dimethyldiallylammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) (PSS) was formed on a 3-mercapto-1-propanesulfonic-acid-modified Au electrode. Subsequently, multiwall carbon nanotubes (MWCNTs) wrapped by positively charged PDDA were assembled layer-by-layer with negatively charged glucose oxidase (GOx) onto the PSS-terminated bilayer. Electrochemical impedance spectroscopy and atomic force microscopy were adopted to monitor the regular growth of the PDDA-MWCNTs/GOx bilayers. Using GOx as a model enzyme, the assembled multilayer membranes showed some striking features such as the adsorbed form of GOx on individual MWCNT, uniformity, good stability, and electrocatalytic activity toward oxygen reduction. Based on the consumption of dissolved oxygen during the oxidation process of glucose catalyzed by the immobilized GOx, a sensitive amperometric biosensor was developed for the detection of glucose up to 5.0 mM with a detection limit of 58 microM. The sensitivity increased with increasing sensing layers up to five bilayers. Ascorbic acid and uric acid did not cause any interference due to the use of a low operating potential. The present method showed high reproducibility for the fabrication of carbon-nanotubes-based amperometric biosensors.
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PMID:Multilayer membranes for glucose biosensing via layer-by-layer assembly of multiwall carbon nanotubes and glucose oxidase. 1643 Aug 53

Ascorbate has previously been shown to enhance both alpha(1)- and beta(2)-adrenergic activity. This activity is mediated by ascorbate binding to the extracellular domain of the adrenergic receptor, which also decreases the oxidation rate of ascorbate. H1 histamine receptors have extracellular agonist or ascorbate binding sites with strong similarities to alpha(1-) and beta(2)-adrenergic receptors. Physiological concentrations of ascorbate (50 microM) significantly enhanced histamine contractions of rabbit aorta on the lower half of the histamine dose-response curve, increasing contractions of 0.1, 0.2, and 0.3 microM histamine by two- to threefold. Increases in ascorbate concentration significantly enhanced 0.2 microM histamine (5-500 microM ascorbate) and 0.3 microM histamine (15-500 microM ascorbate) in a dose-dependent manner. Histamine does not measurably oxidize over 20 h in oxygenated PSS at 37 degrees C. Thus the ascorbate enhancement is independent of ascorbate's antioxidant effects. Ascorbate in solution oxidizes rapidly. Transfected histamine receptor membrane suspension with protein concentration at >3.1 microg/ml (56 nM maximum histamine receptor) decreases the oxidation rate of 392 microM ascorbate, and virtually no ascorbate oxidation occurs at >0.0004 mol histamine receptor/mol ascorbate. Histamine receptor membrane had an initial ascorbate oxidation inhibition rate of 0.094 min.microg protein(-1).ml(-1), compared with rates for transfected ANG II membrane (0.055 min.microg protein(-1).ml(-1)), untransfected membrane (0.052 min.microg protein(-1).ml(-1)), creatine kinase (0.0082 min.microg protein(-1).ml(-1)), keyhole limpet hemocyanin (0.00092 min.microg protein(-1).ml(-1)), and osmotically lysed aortic rings (0.00057 min.microg wet weight(-1).ml(-1)). Ascorbate enhancement of seven-transmembrane-spanning membrane receptor activity occurs in both adrenergic and histaminergic receptors. These receptors may play a significant role in maintaining extracellular ascorbate in a reduced state.
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PMID:Ascorbate enhancement of H1 histamine receptor sensitivity coincides with ascorbate oxidation inhibition by histamine receptors. 1676 Feb 60