Ascorbic Acid Concentration (ascorbic + acid_concentration)

Distribution by Scientific Domains


Selected Abstracts


Ascorbic acid concentration is reduced in the secondary aqueous humour of glaucomatous patients

CLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 4 2009
Mauro T Leite MD
Abstract Background:, We aimed to evaluate the ascorbic acid concentration in secondary aqueous humour (AH) from glaucomatous patients and to compare it with primary AH from primary open-angle glaucoma patients and non-glaucomatous patients. Methods:, Primary AH samples were prospectively obtained from clinically uncontrolled primary open-angle glaucoma patients and senile cataract patients (controls) prior to trabeculectomy and cataract surgery. Secondary AH samples were obtained from eyes with previous intraocular surgery, prior to trabeculectomy or cataract surgery. AH (0.1 mL) was aspirated by inserting a 26-gauge needle into the anterior chamber just before surgery and then immediately stored at ,80°C. The ascorbic acid concentration was determined in a masked fashion by high-pressure liquid chromatography. Results:, A total of 18 patients with senile cataract, 16 glaucomatous patients with primary AH (no previous intraocular surgery) and 11 glaucomatous patients with secondary AH (previous intraocular surgery) were included. There was no difference in mean age between groups (P = 0.15). The mean ± standard deviation concentration of ascorbic acid in the secondary AH from glaucomatous patients (504 ± 213 µmol/L [95% confidence interval {CI}, 383,624]) was significantly lower than the concentration of ascorbic acid found in the primary aqueous of primary open-angle glaucoma (919 ± 427 µmol/L [95% CI, 709,1128]) and control patients (1049 ± 433 µmol/L [95% CI, 848,1249]; P < 0.01, Kruskal-Wallis test). Conclusions:, The ascorbic acid concentration in secondary AH of glaucomatous patients was approximately twofold lower in comparison with primary AH of glaucomatous and cataract patients. The implications of a reduced concentration of ascorbic acid in the secondary AH deserve further investigation. [source]


New Methylene Blue (NMB) Encapsulated in Mesoporous AlMCM-41 Material and Its Application for Amperometric Determination of Ascorbic Acid in Real Samples

ELECTROANALYSIS, Issue 15 2007
Shabnam Sohrabnezhad
Abstract New methylene blue (NMB) dye incorporated into AlMCM-41 surfactant-free and hybrid surfactant-AlMCM-41 mesophase. UV-vis evidence shows that new methylene blue dye protonated in both cases of zeolites. New methylene blue is electroactive in zeolites and their electrochemical activity has been studied by cyclic voltammetry and compared to that of NMB in aqueous solutions. New methylene blue molecules are not released to the solution during CV measurements and are accessible to H3O+ ions. The presence of surfactant affects the kinetics of the redox process through proton ions diffusion. The midpoint potentials (Em) values show that new methylene blue dye incorporated into AlMCM-41 can be reduced easily with respect to solution new methylene blue. New methylene blue interacting with surfactant polar heads and residual Br, ions as a results, it shows a couple of peaks in high potential with respect to new methylene blue solution. The electrode made with methylene blue-AlMCM-41 without surfactant was used for the mediated oxidation of ascorbic acid. The anodic peak current observed in cyclic voltammetry was linearly dependent on the ascorbic acid concentration. The calibration plot was linear over the ascorbic acid concentration range 1.0×10,5 to 5.0×10,4 M. The detection limit of the method is 1.0×10,5 M, low enough for trace ascorbic acid determination in various real samples. [source]


Modification of guar gum through grafting of 4-vinyl pyridine using potassium peroxymonosulphate/ascorbic acid redox pair

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007
Abhishek Srivastava
Abstract In the present article, the graft copolymerization of 4-vinyl pyridine onto guar gum initiated by potassium peroxymonosulphate/ascorbic acid redox pair in an aqueous medium was studied gravimetrically under a nitrogen atmosphere. Grafting ratio, grafting efficiency, and add on increased on increasing the concentration of potassium peroxymonosulphate from 5.0 × 10,4 to 10 × 10,4 mol/L and ascorbic acid concentration from 0.4 × 10,3 to 2.0 × 10,3 mol/L. On increasing the hydrogen ion concentration from 2.5 × 10,3 to 10.0 × 10,3 mol/L, grafting ratio, efficiency, add on and conversion were increased. Maximum grafting was obtained when guar gum and monomer concentration were 1.0 g/L and 20.0 × 10,2 mol/L, respectively. An increase in temperature from 30 to 35°C increased the grafting ratio, but conversion and homopolymer decreased. The graft copolymers were characterized by IR spectroscopy and thermogravimetric analysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]


THE EFFECT OF PRETREATMENT OF SHREDDED CELERIAC USING SOLUTIONS OF ENZYMATIC BROWNING INHIBITORS ON THE QUALITY OF MINIMALLY PROCESSED PRODUCT

JOURNAL OF FOOD QUALITY, Issue 5 2007
BIETA, RADZIEJEWSKA-KUBZDELA EL
ABSTRACT The study investigated the effect of soaking celeriac flakes in solutions containing various concentrations of enzymatic browning inhibitors on the quality of stored minimally processed product. Ascorbic acid (0.2,0.5%), 4-hexylresorcinol (0.003,0.01%), sodium chloride (0.1,0.5%) and sodium lactate (2,3%) were used as browning inhibitors. On the basis of the conducted tests, it was found that among the applied browning inhibitors, only ascorbic acid had an advantageous effect on the quality of stored celeriac flakes. Along with an increase in its concentration in the solution (0.2,0.5%) used for the pretreatment of the flakes, the value of color parameter a* decreased, while the value of parameter b* increased. At the concentration of ascorbic acid in the solution exceeding 0.25%, flake color in the sensory examination was evaluated as desirable. An increase of ascorbic acid concentration in the solution in the range from 0.2 to 0.4% resulted in a decrease in the total mesophilic and psychrophilic bacteria counts, respectively, by 3 and 1 log cfu/g of the stored product. PRACTICAL APPLICATIONS Minimal processing of celeriac provides convenience for consumers and many economic benefits for producers. Minimal processing of celeriac can induce disadvantageous changes in tissue, which may lead to darkening of the flakes and deterioration of product sensory attributes. Moreover, shredded raw material constitutes an excellent medium for the development of microorganisms. This article contains information about the effectiveness of enzymatic browning inhibitors for extending the shelf life of celeriac flakes. We show a range of concentrations of inhibitors, which improve the preservation of color, intrinsic taste and microbial quality of minimally processed celeriac. [source]


Physicochemical, Nutritional, and Functional Characterization of Fruits Xoconostle (Opuntia matudae) Pears from Central-México Region

JOURNAL OF FOOD SCIENCE, Issue 6 2010
Salvador H. Guzmán-Maldonado
Abstract:, Xoconostle cv. Cuaresmeño (Opuntia matudae) has attracted domestic and international industry attention; however, variations of composition from xoconostle structures have not been evaluated. Industries discard the pulp (endocarp) and peel (pericarp) as wastes and utilize the skin (mesocarp), which is the edible portion. The physicochemical, nutritional, and functional characterization of structures from xoconostle pear from 3 major sites of production in Mexico were assessed. Skin yield ranged from 58% to 64% and was higher to that of peel (22% to 24%) and pulp (12% to 18%) yields. pH, °Brix, and acidity were similar among xoconostle structures. Total fiber showed by peel (18.23% to 20.37%) was 2-fold higher than that of skin. Protein and ether extract were higher in xoconostle pulp compared to that showed by peel and skin. Iron content of xoconostle peel (6 to 9.6 mg/100 g, DWB) was higher to that of skin and pulp and prickly pear pulp. Soluble phenols of peel (840 to 863 mg GAE/100 g, DWB) were almost similar to that of skin (919 to 986 mg GAE/100 g, dry weigh basis); meanwhile, ascorbic acid concentration of skin was 2-fold higher compared to that of peel. The phenolic fraction of xoconostle structures consisted of gallic, vanillic, and 4-hydroxybenzoic acids; catechin, epicatechin, and vanillin were also identified by high-performance liquid chromatography,didoe array detection (HPLC-DAD). Xoconostle peel showed higher antioxidant activity (TEAC) compared to that of skin (2-fold) and pulp (6-fold) of commonly consumed fruits and vegetables. The potential of xoconostle peel and pulp for the production of feed or food is promissory. Practical Application:, Outstanding nutritional and functional properties of xoconostle cv. Cuaresmeño fruits are demonstrated. Increased consumption could contribute positively to improve the diet of rural and urban consumers. The high fiber, mineral, and antioxidant components of xoconostle peel and pulp suggest that these fruit structures, which are currently discarded as waste, have promissory use as feed or food by industry. [source]


Influence of rootstock and scion on antioxidant capacity of juice from new pomelo and mandarin varieties

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2009
Eran Raveh
Abstract BACKGROUND: New pomelo and mandarin scion varieties growing under subtropical arid conditions were investigated for total antioxidants in the juice. Four different rootstocks,sour orange (Citrus aurantium (L.); SO), Volkamer lemon (C. volkameriana (Ten & Pasq.)), SB812 (C. sunki (Hort. ex Tan.) × Poncirus trifoliate (L.)) and C. macrophylla (Wester),were tested. RESULTS: Fruit juice was tested for total antioxidants, ascorbic acid and total polyphenol contents. Cyclic voltammetry (CV) analysis revealed three different antioxidant groups for pomelo and four groups for mandarin. CV analysis for the pomelo scion/rootstock combinations showed that ascorbic acid concentration was highest for scions grafted onto SO. Total polyphenol levels were similar among the pomelo varieties. Mandarin analysis revealed that ,Merav' scion/SO had the highest ascorbic acid concentration (1.91 ± 0.01 mmol L,1). Total polyphenol analysis discovered that ,Merav' 4/119-/SB812 gave the highest levels, while ,Ora Shani' scion grafted on to any tested rootstock contained the lowest CONCLUSION: We suggest that the SO rootstock is superior to Volka, 812 and macrophylla in terms of juice antioxidant capacity. For the pomelo, both ,Flamingo' scions were found to have high antioxidant production capacity, with ,Flamingo' 3/73 being slightly superior regardless of the rootstock. The best mandarins were ,Merav' hybrids in combination with SO rootstock. Copyright © 2009 Society of Chemical Industry [source]


A response surface methodology approach to optimise pretreatments to prevent enzymatic browning in potato (Solanum tuberosum L) cubes

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 1 2002
C Reyes-Moreno
Abstract The objective of this work was to find the best combinations of ascorbic acid concentration/soaking time (Pretreatment 1), 4-hexylresorcinol concentration/soaking time (Pretreatment 2) and ascorbic acid concentration,4-hexylresorcinol concentration/soaking time (Pretreatment 3) to prevent the development of enzymatic browning in raw potato cubes (10,mm,×,10,mm,×,10,mm). Potato variety Alpha was used as study model because of its low susceptibility to enzymatic browning. Response surface methodology was applied in all pretreatments on two response variables (Hunter L value and total colour difference) to find the best conditions for carrying out the pretreatments. The various pretreatments had variation levels for ascorbic acid (AA) concentration (1 and 3) and 4-hexylresorcinol (4HR) concentration (2 and 3) of 1,4 and 0.04,0.20,g,l,1 respectively; in all pretreatments the variation level for soaking time was 3,6,h. A central composite experimental design with two factors at five levels was used. Predictive models for Hunter L value and total colour difference were developed as a function of process or independent variables. The optimisation technique was applied to obtain maximum Hunter L values and minimum values of total colour difference. Surface superposition of these variables allowed identification of the best combinations of process variables for each pretreatment as (1) 2.9,g,l,1 AA/4.8,h, (2) 0.04,g,l,1 4HR/2.6,h and (3) 2.42,g,l,1 AA,0.15,g,l,1 4HR/5.41,h. © 2001 Society of Chemical Industry [source]


Estimation of plasmalemma conductivity to ascorbic acid in intact leaves exposed to ozone

PHYSIOLOGIA PLANTARUM, Issue 4 2000
Irina Bichele
To establish the capacity of the leaf mesophyll plasmalemma of Phaseolus vulgaris L. to supply ascorbate (ASC) into the cell wall by simple diffusion, a method for calculating plasmalemma diffusional conductivity to ascorbic acid (AA) in intact leaves was evaluated. The core of the approach is that in the presence of a sink for ascorbate in the cell wall, cell wall total ascorbic acid concentration [TAA]cw (=[ASC]cw+[AA]cw) reaches zero at some positive whole-leaf total ascorbic acid concentration [TAA]l. It is shown that [TAA]l at [TAA]cw=0 is proportional to the sink for ASC in the cell wall and the reciprocal of plasmalemma conductivity. The predicted proportional relationship between [TAA]cw and [TAA]l was confirmed by decreasing TAA levels in leaves through predarkening. Furthermore, increasing the sink intensity for ASC in the cell wall by the acute exposure of leaves to 450 nmol ozone mol,1 during re-illumination, [TAA]cw reached zero at 2.7-fold higher [TAA]l than without ozone, and the slope of the relationship increased twofold. Plasmalemma diffusional conductivities to AA of 2.9×10,6 and 1.8×10,6 m s,1, needed to maintain [TAA]cw at the observed level, were calculated from the increase in [TAA]l at [TAA]cw=0 and from the two different estimates of the sink for ASC. A value of 1.3×10,6 m s,1 was calculated on the basis of the oil-water distribution coefficient for TAA. It is concluded that the demand for ASC in the mesophyll cell wall of the investigated leaves could be met by simple diffusion of AA through the plasmalemma. From the measured increase in the slope of the relationship [TAA]cw versus [TAA]l, an increase in the cell wall pH of 0.3 units was estimated under the influence of ozone. [source]


Effect of high environmental temperatures on ascorbic acid, sulfhydryl residue and oxidized lipid concentrations in plasma of dairy cows

ANIMAL SCIENCE JOURNAL, Issue 3 2007
Masahito TANAKA
ABSTRACT Information on oxidative stress under hot conditions from the levels of cells to organs and the whole body has accumulated in the last decades. Although a hot climate decreased dairy performance, changes of oxidative stress markers under hot conditions have remained obscure. Therefore, the effect of high environmental temperature on ascorbic acid, sulfhydryl (SH) residue and oxidized lipids concentrations in plasma from a total of 128 dairy cows was investigated. The monthly average maximum day temperature varied from 9.2°C in January to 32°C in August of 2004 in this institute. High ambient temperatures increased the rectal temperature of dairy cows up to 39.3°C in August. One of the reducing equivalents in plasma, SH residue concentration, decreased in July compared with December (P < 0.05). Another antiradical molecule, ascorbic acid concentration in plasma, also decreased in July (P < 0.01). The oxidative stress index, thiobarbituric acid reactive substance (TBARS), which was produced from the oxidation of polyunsaturated fatty acids under oxidative conditions, increased in summer (P < 0.05). A significant positive relationship of SH residue and ascorbic acid concentrations in the hot season was observed (P < 0.01). A negative correlation between rectal temperatures and ascorbic acid concentrations in the hot season was obtained (P < 0.01). However, TBARS concentration varied independently of the SH residue and ascorbic acid concentration. These results suggest that the response of oxidative stress markers of SH residue, ascorbic acid and TBARS concentration to oxidative stress under hot conditions were not shown to be the same, and that oxidative stress in dairy cows in the hot season increased. [source]


Ascorbic acid concentration is reduced in the secondary aqueous humour of glaucomatous patients

CLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 4 2009
Mauro T Leite MD
Abstract Background:, We aimed to evaluate the ascorbic acid concentration in secondary aqueous humour (AH) from glaucomatous patients and to compare it with primary AH from primary open-angle glaucoma patients and non-glaucomatous patients. Methods:, Primary AH samples were prospectively obtained from clinically uncontrolled primary open-angle glaucoma patients and senile cataract patients (controls) prior to trabeculectomy and cataract surgery. Secondary AH samples were obtained from eyes with previous intraocular surgery, prior to trabeculectomy or cataract surgery. AH (0.1 mL) was aspirated by inserting a 26-gauge needle into the anterior chamber just before surgery and then immediately stored at ,80°C. The ascorbic acid concentration was determined in a masked fashion by high-pressure liquid chromatography. Results:, A total of 18 patients with senile cataract, 16 glaucomatous patients with primary AH (no previous intraocular surgery) and 11 glaucomatous patients with secondary AH (previous intraocular surgery) were included. There was no difference in mean age between groups (P = 0.15). The mean ± standard deviation concentration of ascorbic acid in the secondary AH from glaucomatous patients (504 ± 213 µmol/L [95% confidence interval {CI}, 383,624]) was significantly lower than the concentration of ascorbic acid found in the primary aqueous of primary open-angle glaucoma (919 ± 427 µmol/L [95% CI, 709,1128]) and control patients (1049 ± 433 µmol/L [95% CI, 848,1249]; P < 0.01, Kruskal-Wallis test). Conclusions:, The ascorbic acid concentration in secondary AH of glaucomatous patients was approximately twofold lower in comparison with primary AH of glaucomatous and cataract patients. The implications of a reduced concentration of ascorbic acid in the secondary AH deserve further investigation. [source]


Antioxidant and inflammatory responses of healthy horses and horses affected by recurrent airway obstruction to inhaled ozone

EQUINE VETERINARY JOURNAL, Issue 3 2005
C. M. DEATON
Summary Reasons for performing study: Inhaled ozone can induce oxidative injury and airway inflammation. Horses affected by recurrent airway obstruction (RAO) have a decreased pulmonary antioxidant capacity, which may render them more susceptible to oxidative challenge. It is currently unknown whether RAO-affected horses are more susceptible to oxidative stress than those unaffected by RAO. Objectives: To determine whether ozone exposure induces greater oxidative stress and airway inflammation in RAO-affected horses in remission than in healthy horses. Methods: Seven healthy control horses and 7 RAO-affected horses were exposed to 0.8 ppm ozone for 2 h at rest. Results: At baseline, bronchoalveolar lavage fluid (BALF) ascorbic acid concentrations were lower in RAO-affected horses than healthy controls. Ozone appeared to preferentially oxidise glutathione rather than ascorbic acid 6 h after exposure. Individual healthy and RAO-affected horses demonstrated oxidation of BALF glutathione after ozone exposure. Overall, RAO-affected horses did not demonstrate increased oxidative stress following ozone exposure, compared with healthy horses. Ozone did not induce significant airway inflammation in either group. Conclusions: RAO-affected horses in remission are not more sensitive to ozone despite a decreased pulmonary antioxidant capacity. Sensitivity to ozone appears to be independent of initial pulmonary antioxidant status. Potential relevance: Horses with high susceptibility to oxidative stress may benefit from antioxidant supplementation. [source]


Evaluation of a sunscreen photoprotective effect by ascorbic acid assessment in human dermis using microdialysis and gas chromatography mass spectrometry

EXPERIMENTAL DERMATOLOGY, Issue 3 2005
Nathalie Lévêque
Abstract:, Ultraviolet irradiation causes adverse effects like sunburn, photosensitivity reactions or immunologic suppression. The aim of this study was to evaluate the photo-protective outcome of a sunscreen cream (SPF8) by the determination of erythema indexes and the assessment of ascorbic acid and its metabolites in human dermis. These substances were used as markers of oxidative effect. Eight healthy female subjects were enrolled in this study. Two abdominal areas were exposed to solar simulated irradiation with three minimal erythema dose, one with SPF8 application and the other site without SPF8 application. Two other areas were used as control, one without SPF8 application and the other site after SPF8 application. Ascorbic acid and its metabolites (dehydroascorbic acid, threonic acid, oxalic acid and xylose) were collected from human dermis by microdialysis and assessed by gas chromatography mass spectrometry. Irradiated site without sunscreen application had significantly demonstrated lower dermis ascorbic acid concentrations and a higher erythema index than the three other sites (P < 0.05). Threonic acid, oxalic acid and xylose dermis concentrations were significantly higher in site III than in the control site I (P < 0.05). The protected-irradiated site did not show erythema formation and there was stability of ascorbic acid dermis concentrations with non-variation in its metabolites. The assessment of ascorbic acid and its metabolites in human dermis could be an efficient tool to demonstrate the oxidative process and consequently to control the efficiency of sunscreen creams against undesirable UV effects. [source]


Serum ascorbic acid concentrations in previously unsupplemented greyhounds after administration of a single dose of ascorbic acid intravenously or per os

JOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 7-8 2002
K. C. Scott
Summary Plasma vitamin C concentrations (mean + SD) were measured after a large (1 g) dose of vitamin C was administered orally or intravenously to each of four trained greyhounds in a randomized cross-over design. Concentrations increased (p<0.05) for 2 h but returned to baseline by 6 h after supplementation. Peak concentrations were greater (p<0.01) after intravenous than oral administration (6.1±1.2 vs. 0.54±0.23 mg/dl). This suggests that vitamin C must be administered many times daily to maintain plasma concentrations above normal. [source]


Effects of smoking and gingival inflammation on salivary antioxidant capacity

JOURNAL OF CLINICAL PERIODONTOLOGY, Issue 3 2006
Nurcan Buduneli
Abstract Aim: This study evaluated possible effects of smoking and gingival inflammation on salivary antioxidants in gingivitis patients. Methods: Twenty otherwise healthy gingivitis patients (10 self-reported smokers) and 20 periodontally and systemically healthy volunteer subjects were enrolled in the study. Whole saliva samples and full-mouth clinical periodontal recordings were obtained at baseline and one month following initial phase of treatment in gingivitis patients. Salivary cotinine, glutathione and ascorbic acid concentrations, and total antioxidant capacity were determined, and the data generated were tested by non-parametric tests. Results: Salivary cotinine measurements resulted in re-classification of three self-reported non-smokers as smokers. Smoker patients revealed significantly higher probing depths but lower bleeding values than non-smoker patients (p=0.044 and 0.001, respectively). Significant reductions in clinical recordings were obtained in non-smoker (all p<0.05) and smoker (all p<0.01) patients following periodontal treatment. Salivary total glutathione concentrations were reduced following therapy in gingivitis patients who smoke (p<0.01). Otherwise, no statistically significant differences were found between the groups in biochemical parameters at baseline or following treatment (p>0.05). Conclusions: Within the limits of this study, neither smoking nor gingival inflammation compromised the antioxidant capacity of saliva in systemically healthy gingivitis patients. [source]


Vitamin C Requirements of the Angelfish Pterophylum scalare

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2000
Jozef H. Blom
Ascorbic acid requirements of fishes of the cichlid family appear to vary widely. Juvenile angelfish, a widely produced ornamental cichlid, were maintained on diets containing graded levels of ascorbyl monophosphate. Liver ascorbic acid concentrations after 96 d of feeding were significantly reduced in groups receiving 120 mg or less ascorbic acid equivalents/kg diet. However, no differences in growth or mortality between groups were found, and no external signs of ascorbic acid deficiency were observed, indicating a high resistance of this species against prolonged ascorbic acid deficiency. Based on the long possible life span of angelfish in the aquarium, we proposed a conservative dietary ascorbic acid requirement of 360 mg/ kg diet, necessary to maintain maximum tissue storage of this vitamin. [source]


Effect of high environmental temperatures on ascorbic acid, sulfhydryl residue and oxidized lipid concentrations in plasma of dairy cows

ANIMAL SCIENCE JOURNAL, Issue 3 2007
Masahito TANAKA
ABSTRACT Information on oxidative stress under hot conditions from the levels of cells to organs and the whole body has accumulated in the last decades. Although a hot climate decreased dairy performance, changes of oxidative stress markers under hot conditions have remained obscure. Therefore, the effect of high environmental temperature on ascorbic acid, sulfhydryl (SH) residue and oxidized lipids concentrations in plasma from a total of 128 dairy cows was investigated. The monthly average maximum day temperature varied from 9.2°C in January to 32°C in August of 2004 in this institute. High ambient temperatures increased the rectal temperature of dairy cows up to 39.3°C in August. One of the reducing equivalents in plasma, SH residue concentration, decreased in July compared with December (P < 0.05). Another antiradical molecule, ascorbic acid concentration in plasma, also decreased in July (P < 0.01). The oxidative stress index, thiobarbituric acid reactive substance (TBARS), which was produced from the oxidation of polyunsaturated fatty acids under oxidative conditions, increased in summer (P < 0.05). A significant positive relationship of SH residue and ascorbic acid concentrations in the hot season was observed (P < 0.01). A negative correlation between rectal temperatures and ascorbic acid concentrations in the hot season was obtained (P < 0.01). However, TBARS concentration varied independently of the SH residue and ascorbic acid concentration. These results suggest that the response of oxidative stress markers of SH residue, ascorbic acid and TBARS concentration to oxidative stress under hot conditions were not shown to be the same, and that oxidative stress in dairy cows in the hot season increased. [source]


Ascorbic acid and reproduction in fish: endocrine regulation and gamete quality

AQUACULTURE RESEARCH, Issue 8 2001
K Dabrowski
Abstract High ascorbic acid concentrations have been associated with gonad and brain tissues in teleost fishes. Although a direct dietary effect on gamete quality has been given some attention recently, the mechanism of action of ascorbate along the cascade of reproductive events in the hypothalamus, pituitary and gonads has not been defined. Data relating to gamete production and quality, as well as a possible protective role for ascorbate against cumulative genetic defects during gametogenesis and congenital malformation during gestation (embryonic development) is reviewed. It is suggested that the gonad growth in response to gonadotropin stimulation involves direct interaction between catecholamines and steroid hormones and their receptor sites. This interaction acts as a regulatory mechanism of ascorbate absorption, transfer and metabolism (degradation and/or renewal) in the reproductive system. We conclude that ascorbic acid is a leading nutrient in reproductive tissue functions and further research is needed on: (1) its antioxidant effect on gametes' (sperm and ova) capacity to prevent DNA damage occurring prior to (endogenous) and after spawning (environmental insults); (2) its dietary requirement to optimize survival and physiological recovery in multiple spawners; (3) the integration mechanism of ascorbic acid action as part of the overall endocrine regulation of neurohormonal,hormonal pathway in fish reproduction; and (4) the possible role for ascorbate in regulating fish maturation and/or infertility in the presence of enhanced UV-radiation or conditions of intensive aquaculture (hypoxia, oxygen supersaturation, dietary pro,, and antioxidants). [source]


Manganese increases L-DOPA auto-oxidation in the striatum of the freely moving rat: potential implications to L-DOPA long-term therapy of Parkinson's disease

BRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2000
Pier Andrea Serra
We have previously shown that manganese enhances L-dihydroxyphenylanine (L-DOPA) toxicity to PC12 cells in vitro. The supposed mechanism of manganese enhancing effect [an increase in L-DOPA and dopamine (DA) auto-oxidation] was studied using microdialysis in the striatum of freely moving rats. Systemic L-DOPA [25 mg kg,1 intraperitoneally (i.p.) twice in a 12 h interval] significantly increased baseline dialysate concentrations of L-DOPA, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and uric acid, compared to controls. Conversely, DA and ascorbic acid concentrations were significantly decreased. A L-DOPA oxidation product, presumptively identified as L-DOPA semiquinone, was detected in the dialysate. The L-DOPA semiquinone was detected also following intrastriatal infusion of L-DOPA. In rats given L-DOPA i.p., intrastriatal infusion of N-acetylcysteine (NAC) significantly increased DA and L-DOPA dialysate concentrations and lowered those of L-DOPA semiquinone; in addition, NAC decreased DOPAC+HVA and uric acid dialysate concentrations. In rats given L-DOPA either systemically or intrastriatally, intrastriatal infusion of manganese decreased L-DOPA dialysate concentrations and greatly increased those of L-DOPA semiquinone. These changes were inhibited by NAC infusion. These findings demonstrate that auto-oxidation of exogenous L-DOPA occurs in vivo in the rat striatum. The consequent reactive oxygen species generation may account for the decrease in dialysate DA and ascorbic acid concentrations and increase in enzymatic oxidation of xanthine and DA. L-DOPA auto-oxidation is inhibited by NAC and enhanced by manganese. These results may be of relevance to the L-DOPA long-term therapy of Parkinson's disease. British Journal of Pharmacology (2000) 130, 937,945; doi:10.1038/sj.bjp.0703379 [source]