Ascorbate concentration in fish ontogeny

1992 ◽  
Vol 40 (2) ◽  
pp. 273-279 ◽  
Author(s):  
K. Dabrowski
Keyword(s):  
Ascorbate Concentration ◽  
Fish Ontogeny

Homeostatic control of ascorbate concentration in CNS extracellular fluid

1982 ◽  
Vol 253 (1-2) ◽  
pp. 353-356 ◽  
Author(s):  
James O. Schenk ◽  
Ellen Miller ◽  
Ronald Gaddis ◽  
Ralph N. Adams
Keyword(s):  
Extracellular Fluid ◽  
Homeostatic Control ◽  
Ascorbate Concentration

scholarly journals Effectiveness of Dichrostachys glomerata Spice Phenolics in Reduction of Oxidative Stress Associated with Obesity and Type 2 Diabetes; a Randomized, Double-Blind Placebo-Controlled Clinical Trial

2013 ◽  
Vol 2 (2) ◽  
pp. 1 ◽  
Author(s):  
Dieudonne Kuate ◽  
Anne Pascale Nouemsi Kengne ◽  
William Dakam ◽  
Blanche Cunegonde Omgba Etoundi ◽  
Ghislain Djiokeng Paka ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Phenolic Content ◽  
Antioxidant Activities ◽  
Controlled Clinical Trial ◽  
Double Blind ◽  
Double Blind Placebo ◽  
Ascorbate Concentration ◽  
Concomitant Reduction ◽  
Random Groups

This work evaluated the effect of <em>Dichrostachys glomerata </em>on the improvement of antioxidant biomarkers in obesity and type 2 diabetes participants, in an eight-week randomized, double-blind, placebo-controlled design study. The active (400 mg) or placebo formulation were administered twice daily throughout the study period to two normoglycemic and two diabetic obese random groups. Plasma levels of a total of 8 biochemical parameters were taken at the baseline and after 4 and 8 weeks of treatment. No differences in urate variation were observed while the plasma phenolic content as well as the reduced glutathione level, ascorbate concentration, FRAP value and enzymatic antioxidant activities significantly increased with a concomitant reduction of MDA after 8 weeks compared to placebo (P &lt; 0.01). On the contrary to urate and ascorbate, plasma polyphenol content correlated well with FRAP level in both treated groups indicating that phenolics from the spice greatly contributed to the antioxidant activity.

Ascorbate prevents microvascular dysfunction in the skeletal muscle of the septic rat

2001 ◽  
Vol 90 (3) ◽  
pp. 795-803 ◽  
Author(s):  
John Armour ◽  
Karel Tyml ◽  
Darcy Lidington ◽  
John X. Wilson
Keyword(s):  
Blood Pressure ◽  
Skeletal Muscle ◽  
Cecal Ligation ◽  
Microvascular Dysfunction ◽  
Sprague Dawley ◽  
Arterial Blood ◽  
Sprague Dawley Rats ◽  
Plasma Ascorbate ◽  
Ascorbate Concentration

Septic patients have low plasma ascorbate concentrations and compromised microvascular perfusion. The purpose of the present experiments was to determine whether ascorbate improves capillary function in volume-resuscitated sepsis. Cecal ligation and perforation (CLP) was performed on male Sprague-Dawley rats. The concentration of ascorbate in plasma and urine, mean arterial blood pressure, and density of continuously perfused capillaries in the extensor digitorum longus muscle were measured 24 h after surgery. CLP caused a 50% decrease (from 56 ± 4 to 29 ± 2 μM) in plasma ascorbate concentration, 1,000% increase (from 46 ± 13 to 450 ± 93 μM) in urine ascorbate concentration, 20% decrease (from 115 ± 2 to 91 ± 2 mmHg) in mean arterial pressure, and 30% decrease (from 24 ± 1 to 17 ± 1 capillaries/mm) in the density of perfused capillaries, compared with time-matched controls. A bolus of intravenous ascorbate (7.6 mg/100 g body wt) administered immediately after the CLP procedure increased plasma ascorbate concentration and restored both blood pressure and density of perfused capillaries to control levels. In vitro experiments showed that ascorbate (100 μM) inhibited replication of bacteria and prevented hydrogen peroxide injury to cultured microvascular endothelial cells. These results indicate that ascorbate is lost in the urine during sepsis and that a bolus of ascorbate can prevent microvascular dysfunction in the skeletal muscle of septic animals. Our study supports the view that ascorbate may be beneficial for patients with septic syndrome.

Ascorbate enhancement of H1 histamine receptor sensitivity coincides with ascorbate oxidation inhibition by histamine receptors

2006 ◽  
Vol 291 (5) ◽  
pp. C977-C984 ◽  
Author(s):  
Patrick F. Dillon ◽  
Robert S. Root-Bernstein ◽  
Charles M. Lieder
Keyword(s):  
Oxidation Rate ◽  
Rabbit Aorta ◽  
Keyhole Limpet Hemocyanin ◽  
Histamine Receptor ◽  
Histamine Receptors ◽  
Dependent Manner ◽  
Receptor Membrane ◽  
Ascorbate Concentration ◽  
Wet Weight ◽  
Dose Dependent

Ascorbate has previously been shown to enhance both α1- and β2-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 α1- and β2-adrenergic receptors. Physiological concentrations of ascorbate (50 μM) 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 μM histamine by two- to threefold. Increases in ascorbate concentration significantly enhanced 0.2 μM histamine (5–500 μM ascorbate) and 0.3 μM histamine (15–500 μM ascorbate) in a dose-dependent manner. Histamine does not measurably oxidize over 20 h in oxygenated PSS at 37°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 μg/ml (56 nM maximum histamine receptor) decreases the oxidation rate of 392 μM 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·μg protein−1·ml−1, compared with rates for transfected ANG II membrane (0.055 min·μg protein−1·ml−1), untransfected membrane (0.052 min·μg protein−1·ml−1), creatine kinase (0.0082 min·μg protein−1·ml−1), keyhole limpet hemocyanin (0.00092 min·μg protein−1·ml−1), and osmotically lysed aortic rings (0.00057 min·μg 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.

Regulation of violaxanthin de-epoxidase activity by pH and ascorbate concentration

1995 ◽  
Vol 45 (2) ◽  
pp. 169-175 ◽  
Author(s):  
Charlotte Eva Bratt ◽  
Per-Ola Arvidsson ◽  
Marie Carlsson ◽  
Hans-Erik �kerlund
Keyword(s):  
Ascorbate Concentration

Effect of ageing on extracellular ascorbate concentration in rat brain

1993 ◽  
Vol 609 (1-2) ◽  
pp. 36-40 ◽  
Author(s):  
Lennart Svensson ◽  
Chiping Wu ◽  
Peter Hulthe ◽  
Kenn Johannessen ◽  
Jo¨rgen A. Engel
Keyword(s):  
Rat Brain ◽  
Ascorbate Concentration

scholarly journals Spectrophotometric determination of ascorbic acid by horseradish peroxidase

2020 ◽  
Vol 10 (2) ◽  
pp. 17-22
Author(s):  
Vladan Đurić ◽  
Nebojša Deletić
Keyword(s):  
Hydrogen Peroxide ◽  
Ascorbic Acid ◽  
Pharmaceutical Products ◽  
Reaction Conditions ◽  
Hydrogen Peroxide Decomposition ◽  
Peroxide Decomposition ◽  
Daily Dose ◽  
Ascorbate Concentration ◽  
Absorbance Changes

L-ascorbic acid is one of the essential nutrients and most common food supplements, fortificants, and preservatives. It is commercially available as solutions, drops, tablets, capsules, crystal powder, beverage mixtures, multivitamin formulations, and multi antioxidant formulations. The usual daily dose is from 25 mg to 1.5 g. Ascorbic acid is a distinctly reducing agent with low redox potential (0.18 and 0.08 V at pH 4.5 and 6.4, respectively). Based on ascorbate property, numerous methods for its quantitative determination are developed, from titrimetric, electrochemical, and chromatographic methods, to fluorometric and kinetic ones. Enzyme peroxidase is interfered with by ascorbic acid, which decreases the oxidation speed of its co-substrates during hydrogen peroxide decomposition by peroxidase. Absorbance changes at the wavelength of corresponding reagents are in correlation with ascorbate concentration. During this study, benzidine and o-tolidine have been used as chromogenic reagents. Reaction conditions were optimized for various buffer systems, calibration curves were constructed, and limits of detection (0.04 mmol/L) and quantification (0.12 mmol/L) were calculated. Using calibration charts, it was possible to detect ascorbic acid within limits from 0.4 to 10 mmol/L. The optimized method was applied for the determination of ascorbic acid in pharmaceutical products. The method was characterized by exceptional sensitivity and accuracy, but only for preparations not containing substances that affect enzyme peroxidase.

Stability of ascorbate in urine: relevance to analyses for ascorbate and oxalate.

1985 ◽  
Vol 31 (10) ◽  
pp. 1703-1705 ◽  
Author(s):  
A H Chalmers ◽  
D M Cowley ◽  
B C McWhinney
Keyword(s):  
Room Temperature ◽  
Final Concentration ◽  
Disodium Edta ◽  
Ph Values ◽  
Ascorbate Concentration ◽  
The Mean ◽  
Urine Specimens

Abstract Ascorbate is unstable in urine at room temperature at pH values ranging from 1 to 12. At pH 7 and above, oxalate is generated in amounts directly proportional to the ascorbate concentration. In 12 different urines, adjusted to pH 12 and incubated for 20 h at room temperature, there was a significant correlation between the amount of oxalate formed and the initial ascorbate concentration (r = 0.97, p less than 0.01). The mean (+/- SD) concentration of oxalate (1.32 +/- 0.70 mmol/L) formed during this period approximated the initial ascorbate concentration (1.57 +/- 1.09 mmol/L). Disodium EDTA, 10 mmol/L final concentration, stabilizes ascorbate in urine and inhibits its conversion to oxalate at pH values of 4.4 to 7.0 during a 24-h period. We therefore propose that urine specimens for ascorbate and oxalate analyses be collected with disodium EDTA present such as to give about this final concentration.

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