Showing papers on "Ascorbic acid published in 1979"
TL;DR: This chapter discusses selected methods for the determination of ascorbic acid in animal cells, tissues, and fluids and suggests that prompt stabilization is especially important in the case of plasma or serum.
Abstract: Publisher Summary This chapter discusses selected methods for the determination of ascorbic acid in animal cells, tissues, and fluids. Methods for determining ascorbic acid are numerous. In general, chemical analyses for the vitamin are divided into two groups; the determination of the reduced form and the determination of the oxidized form. The former group of analyses is usually based upon the oxidation–reduction properties of ascorbic acid. These are widely used as the fundamental reactions in the measurement of vitamin C. The latter group of analyses is usually based upon the oxidation of the ascorbic acid and the subsequent formation of a hydrazone or a fluorophore. Best results are obtained if samples, especially plasma, are quickly stabilized with either trichloroacetic acid or metaphosphoric acid and immediately analyzed. Prompt stabilization is especially important in the case of plasma or serum. The greater stability of ascorbic acid in acid solution is because of the decreased tendency for the hydrolysis of the lactone ring with decreasing pH.
1,843 citations
TL;DR: Direct observation of the interaction between vitamin E and vitamin C and the resulting vitamin E radical then reacting with vitamin C to regenerate vitamin E is reported, which is felt to be an important feature in the maintenance of vitamin E levels in tissues.
Abstract: VITAMIN E (α-tocopherol) and vitamin C (ascorbic acid) react rapidly with organic free radicals, and it is widely accepted that the antioxidant properties of these compounds are responsible in part for their biological activity1–5. Tissue vitamin C levels are often considerably greater than those of vitamin E, for example in liver the values are approximately 2 mM and 0.02 mM, respectively. Nevertheless, vitamin E is considerably more lipophilic than vitamin C, and in biomembranes has been found to be the more potent antioxidant, particularly with respect to lipid peroxidation; penetration to a precise site in the membrane may be an important feature of the protection against highly reactive radicals6. Tappel has suggested that the two vitamins act synergistically, vitamin E acting as the primary antioxidant and the resulting vitamin E radical then reacting with vitamin C to regenerate vitamin E7. We now report direct observation of this interaction, which we feel may be an important feature in the maintenance of vitamin E levels in tissues.
1,391 citations
TL;DR: It is reported that transplants of embryonic substantia nigra, implanted into the parietal cortex m adult rats, are able to establish a new dopamlnerglc input to the previously denervated neostrlatum, and that the newly-formed 'nigrostHatal' DA pathway may compensate for at least some aspects of the lesion-induced motor disturbances.
776 citations
TL;DR: The iron chelator desferrioxamine inhibits peroxidation at all concentrations tested, and it also inhibits the iron-catalysed formation of hydroxyl radicals from superoxide (O2-.).
Abstract: The peroxidation of membrane phospholipids induced in vitro by ascorbic acid or by dialuric acid (hydroxybarbituric acid) does not occur in the absence of traces of metal ions. Peroxidation induced by adding iron salts to phospholipids can either be promoted or inhibited by the chelators EDTA, diethylenetriaminepenta-acetic acid and bathophenanthrolinesulphonate, depending on the ratio [chelator]/[iron salt]. The iron chelator desferrioxamine inhibits peroxidation at all concentrations tested, and it also inhibits the iron-catalysed formation of hydroxyl radicals (OH.) from superoxide (O2-.). Since desferrioxamine is approved for clinical use, it might prove a valuable tool in the treatment of inflammation, poisoning by autoxidizable molecules and radiation damage.
620 citations
01 Jan 1979
TL;DR: The method described in this paper has the greatest sensitivity, being able to demonstrate the presence of 0.10 μg of phosphorus per ml. It is based on the reduction of phosphomolybdate complex with ascorbic acid, and is essentially identical to the method published by Chen, Toribara and Warner (1956).
Abstract: Several different procedures are recommended for the determination of total phosphorus in biologic samples. The method described here has the greatest sensitivity, being able to demonstrate the presence of 0.10 μg phosphorus per ml. It is based on the reduction of phosphomolybdate complex with ascorbic acid. The procedure described here is essentially identical to the method published by Chen, Toribara and Warner (1956).
538 citations
TL;DR: The two groups showed no appreciable difference in changes in symptoms, performance status, appetite or weight, and were unable to show a therapeutic benefit of high-dose vitamin C treatment.
Abstract: One hundred and fifty patients with advanced cancer participated in a controlled double-blind study to evaluate the effects of high-dose vitamin C on symptoms and survival. Patients were divided randomly into a group that received vitamin C (10 g per day) and one that received a comparably flavored lactose placebo. Sixty evaluable patients received vitamin C and 63 received a placebo. Both groups were similar in age, sex, site of primary tumor, performance score, tumor grade and previous chemotherapy. The two groups showed no appreciable difference in changes in symptoms, performance status, appetite or weight. The median survival for all patients was about seven weeks, and the survival curves essentially overlapped. In this selected group of patients, we were unable to show a therapeutic benefit of high-dose vitamin C treatment.
530 citations
TL;DR: Findings demonstrate and association between nutrition status and hospital course and a worsening trend during hospitalization.
448 citations
Journal Article•
TL;DR: It is shown that many factors involved in host resistance to neoplasia are significantly dependent upon the availability of ascorbate and the relationship between these factors and asCorbic acid metabolism is presented in detail.
Abstract: Host resistance to neoplastic growth and invasiveness is recognized to be an important factor in determining the occurrence, the progress, and the eventual outcome of every cancer illness. The factors involved in host resistance are briefly reviewed, and the relationship between these factors and ascorbic acid metabolism is presented in detail. It is shown that many factors involved in host resistance to neoplasia are significantly dependent upon the availability of ascorbate.
412 citations
TL;DR: The evidence suggests that an increase in the consumption of some local foods whose supply is plentiful, could lead to significant improvement in blood iron status and the benefit cost ratio in terms of latex production alone could be 260:1.
362 citations
TL;DR: C cultured skin fibroblasts from patients with scleroderma are suggested to demonstrate a metabolic abnormality expressed as increased synthesis of type I and type III procollagens in a normal ratio, which may play a role in the excessive accumulation of collagen in the skin and other organs affected in sclerodma.
Abstract: To assess potential abnormalities in collagen metabolism in systemic scleroderma, skin fibroblast lines from patients with this disease were established and compared to control cell lines derived from healthy subjects. For studies on the biosynthesis of procollagen, the cells were incubated with [(14)C]proline in a medium supplemented with ascorbic acid and beta-aminopropionitrile, and the synthesis of nondialyzable [(14)C]hydroxyproline, in relation to DNA or cell protein, was taken as an index of procollagen formation. Five of eight scleroderma fibroblast cell lines demonstrated procollagen biosynthesis rates significantly higher than the controls, and the mean rate of procollagen synthesis by scleroderma fibroblasts was about twice that of the control cells. Control experiments demonstrated that the specific activity of the intracellular free proline was not different in scleroderma and control fibroblasts, and the mean population doubling times of the scleroderma and the control fibroblast cell lines were the same. The relative synthesis of the genetically distinct procollagens was examined by isolating type I and type III procollagens from the cell culture medium using DEAE-cellulose chromatography. The ratios of type I/III procollagens in scleroderma cell lines did not differ from the controls. The helical stability of the collagenous portion of type I and type III procollagens, estimated by the resistance of (14)C-collagen to limited proteolytic digestion with pepsin under nondenaturing conditions, was the same in both scleroderma and control cultures. The capacity of the cells to synthesize enzymatically active and immunologically reacting collagenase was also studied; no marked differences in these parameters could be observed. The results suggest that cultured skin fibroblasts from patients with scleroderma demonstrate a metabolic abnormality expressed as increased synthesis of type I and type III procollagens in a normal ratio. This abnormality may play a role in the excessive accumulation of collagen in the skin and other organs affected in scleroderma.
236 citations
TL;DR: Experimental evidence is presented indicating that ascorbate is a ‘02 scavenger, and it is suggested that the inhibition of methylene blue-catalyzed photoinactivation of Escherichia coli ribosomes was mediated via the scavenging of ‘ 02 by asCorbate.
TL;DR: A new role for the high ascorbate level present in the anterior chamber fluid and the lens has been suggested, which might have this novel physiological function of protecting against damage due to superoxide and its derivatives produced during normal cellular oxidation.
Abstract: The cation pump activity of the ocular lens was damaged by exposure to light in the presence of riboflavin phosphate. The intensity of light was similar to that used for reading purposes. The observed light-induced damage was due to superoxide or its derivatives, the superoxide being produced photochemically. Such damage was attenuated by vitamin C in amounts comparable to that in the aqueous humor. Thus, a new role for the high ascorbate level present in the anterior chamber fluid and the lens has been suggested. Ascorbate in other tissues also might have this novel physiological function of protecting against damage due to superoxide and its derivatives produced during normal cellular oxidation.
TL;DR: The approach of researchers at Brookhaven National Laboratory to the homogeneous generation of hydrogen is to convert the luminescent excited state of tris(2,2'-bipyridine)-ruthenium(II) (*Ru(bpy)/sub 3/O/sup 2 +/) to the more strongly reducing (and longer lived) ion Ru (bpy/sub 3//sup +/) as mentioned in this paper.
Abstract: The approach of researchers at Brookhaven National Laboratory to the homogeneous generation of hydrogen is to convert the luminescent excited state of tris(2,2'-bipyridine)-ruthenium(II) (*Ru(bpy)/sub 3//sup 2 +/) to the more strongly reducing (and longer lived) ion Ru(bpy)/sub 3//sup +/. The Ru(bpy)/sub 3//sup +/ reduces a metal complex which reacts with H/sub 3/O/sup +/ or H/sub 2/O to form an unstable hydride. The hydride in turn decomposes to yield hydrogen. The blue cobalt(I) bipyridine complexes produced by Na(Hg) or electrochemical reduction of cobalt(II) bipyridine complexes are very powerful reducing agents and are not likely to form stable hydrides in solution. Cobalt(I) bipyridine complexes are thus excellent candidates for mediating the homogeneous formation of hydrogen. This expectation has been confirmed: visible-light irradiation of solutions containing Ru(bpy)/sub 3//sup 2 +/, ascorbate, Co/sup 2 +/, and bpy or phen derivatives produces hydrogen with a quantum yield of up to 0.13 mol einstein/sup -1/. Low yields of H/sub 2/ are also produced in the absence of Co/sup 2 +/.
TL;DR: It was found that the half-life of ascorbic acid was inversely related to the dosage and that the pool could be increased to about 20 mg/kg bodyweight by increasing the dosage.
TL;DR: In this paper, a double proportional injector is described, and an improvement of the continuous flow-injection method is discussed, where sample and reagent are both injected into an inert carrier stream; the reagent is consumed only in the presence of the sample, and can otherwise be recovered continuously.
TL;DR: Factors responsible for the differences in color quality between preserves commercially manufactured from Hood and Tioga strawberry varieties were determined and reactive phenolics play a major role in the color deterioration of strawberry preserves.
Abstract: Factors responsible for the differences in color quality between preserves commercially manufactured from Hood and Tioga strawberry varieties were determined. Color analyses on Hood and Tioga preserves during a 26-wk storage period revealed that color deterioration occurred at a much faster rate in Tioga preserves than in Hood preserves, and that this deterioration was due to a faster rate of browning. Compositional analyses of fruit showed that the Tioga variety contained higher levels of leucoanthocyanins, flavanols and total phenolics while the Hood variety contained higher levels of anthocyanin pigment, ascorbic acid, and free amino acids. It is proposed that reactive phenolics (leucoanthocyanins, flavanols) play a major role in the color deterioration of strawberry preserves.
Journal Article•
TL;DR: Tobacco-specific nonvolatile N -nitrosamines in tobacco and in fresh mainstream and sidestream smoke of cigarettes and cigars were quantitatively determined with a thermal energy analyzer using N ′-nitrosonornicotine as internal standard for the quantitative analysis.
Abstract: Tobacco-specific nonvolatile N -nitrosamines in tobacco and in fresh mainstream and sidestream smoke of cigarettes and cigars were quantitatively determined with a thermal energy analyzer The smoke was trapped in ascorbic acid solution buffered at pH 45 and extracted with dichloromethane, and the organic phase was chromatographed and analyzed by high-performance liquid chromatography-thermal energy analyzer methodology (sensitivity, 250 pg/injection) The nonvolatile nitrosamines were further enriched by repeated chromatography and positively identified by gas-liquid chromatography-mass spectrometry [2′-14C] N ′-nitrosonornicotine served as internal standard for the quantitative analysis
The tobacco of five different cigarettes contained between 022 and 70 ppm of the carcinogenic N ′-nitrosonornicotine, 013 and 074 ppm of the carcinogenic 4-( N -methyl- N -nitrosamino)-1-(3-pyridyl)-1-butanone, and 044 to 32 ppm of the newly identified N ′-nitrosoanatabine In unaged mainstream and sidestream smoke of the same cigarettes, values ranged between 024 and 37 and 015 and 61 µg/cigarette for N ′-nitrosonornicotine, between 011 and 042 and 019 and 066 µg/cigarette for 4-( N -methyl- N -nitrosamino)-1-(3-pyridyl)-1-butanone, and between 033 and 46 and 015 and 15 µg/cigarette for N ′-nitrosoanatabine, respectively The relatively high concentrations of these carcinogenic N -nitrosamines in sidestream smoke are discussed as possible tobacco-specific indicators for indoor pollution
TL;DR: Work described in this paper suggests that the transmembrane reduction is effected by ascorbic acid, a compound in its oxidized form (dehydroascorbate) rapidly enters the cell and accomplishes the non-enzymatic reduction of ferricyanide.
Abstract: Actively metabolizing human erythrocytes catalyze the extracellular reduction of ferricyanide to ferrocyanide. Because neither of these anions can enter the cell, reducing equivalents generated in the course of glycolysis must in some manner be transferred across the cell membrane, thereby resulting in ferricyanide reduction. Work described in this paper suggests that the transmembrane reduction is effected by ascorbic acid. This compound in its oxidized form (dehydroascorbate) rapidly enters the cell. Here it obtains reducing equivalents which appear to come from NADH made available at the level of glyceraldehyde 3-phosphate dehydrogenase. Once reduced, it leaves the cell as ascorbic acid and accomplishes the non-enzymatic reduction of ferricyanide.
TL;DR: In six infants, from two families, the umbilical cords were still attached at 3 weeks of age, five of these developed severe local and disseminated infections from which four died, and two were tested, and both had defective neutrophil mobility.
TL;DR: This study examined alterations in episodic LH release in response to prolonged, slow infusions of dopamine, norepinephrine, or epinephrine into the thire ventricle in adult, ovariectomized (OVX) rats, and the influence of priming with ovarian steroids on the LH response to the catecholamines.
Abstract: This study examined alterations in episodic LH release in response to prolonged, slow infusions of dopamine (DA), norepinephrine (NE), or epinephrine (EPIN) into the third ventricle in adult, ovariectomized (OVX) rats, and the influence of priming with ovarian steroids on the LH response to the catecholamines. Unanesthetized rats with right atrial cannulae were bled continuously at slow rates for 1–1½ h prior to infusion, 1–1½ h during infusion, and up to 1 h afterwards. The amines were protected from oxidation by ascorbic acid, and infused in an artificial cerebrospinal fluid (CSF) vehicle (pH 7.29-7.33) into the third ventricle at a rate of 25–27 μl/h. Blood samples were analyzed for LH by radioimmunoassay. In unprimed, OVX rats, infusions of artificial CSF, as well as low doses of DA (2–4 μg/h) or NE (0.3–0.6 μg/h), had no effect on episodic LH release or mean blood LH levels. However, administration of 8.5 and l7μg DA/h, and 5.5 and 11 μg NE/h, resulted in a decrease in blood LH levels and, in most animals, prolonged intervals between peak blood LH levels during infusion or inhibitions which began rapidly and lasted for nearly the entire infusion period or longer. In contrast, infusion of 5.7 and 11.5 μg EPIN/h had no effect on blood LH levels in unprimed rats. In OVX rats primed 3 days prior to infusion with 50 μg estradiol benzoate and 25 mg progesterone (OEP), administration of CSF or the same doses of DA that previously inhibited episodic LH release had no effect on LH secretion. However, these steroids completely reversed the LH response to 11 μg NE/h, with increases in LH release occurring during infusion. EPIN, in doses ineffective in unprimed rats (5.7 and 11.5 μg/h), also caused elevations in blood LH levels in OEP rats. Finally, in rats primed with 5 μg estradiol benzoate/100 g b.w./day for the 2 days prior to infusion, none of the three neurotransmitters had any effect on LH release. These experiments indicate that in the absence of ovarian steroids intraventricular administration of DA can decrease mean blood LH levels and episodic LH release, and that this amine has no excitatory effect on LH release in steroid-primed rats. In contrast, NE and EPIN increased LH release in OEP rats, suggesting possible excitatory roles for both amines in the regulation of LH secretion. These data also indicate the critical importance of ovarian steroids in determining not only if a neurotransmitter (EPIN) can increase LH release, but also the direction in the LH response to a given neurotransmitter (NE). Finally, in addition to confirming the concept of an excitatory noradrenergic link in the regulation of LH release, studies in nonsteroid primed rats suggest the possible existence of noradrenergic receptors whose activation is subsequently inhibitory to episodic LH secretion.
TL;DR: Sodium L-ascorbate at nonlethal concentrations potentiated the effect of 5-fluorouracil (FUra), x-irradiation, bleomycin, RO20-1724, prostaglandin E1, and sodium butyrate on NB cells but did not produce such an effect on glioma cells.
Abstract: Mouse neuroblastoma (NB) cells in culture were more sensitive to sodium L-ascorbate than were rat glioma cells by the criterion of growth inhibition (due to cell death and reduction in cell division). Sodium L-ascorbate at nonlethal concentrations potentiated the effect of 5-fluorouracil (FUra), x-irradiation, bleomycin, RO20-1724, prostaglandin E1, and sodium butyrate on NB cells but did not produce such an effect on glioma cells. Sodium L-ascorbate did not enhance the effect of vincristine, 6-thioguanine, or 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) except at higher drug doses and it reduced the cytotoxic effect of methotrexate and 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC) on NB cells. Sodium D-ascorbate produced effects similar to those produced by sodium L-ascorbate on NB cells. L-Ascorbic acid-2-sulfate (barium salt) affected neither the growth rate nor the effect of 5-FUra on NB cells. Glutathione, a reducing agent, was more toxic to NB cells in comparison to D- OR L-ascorbate; however, at a similar concentration it failed to potentiate the effect of 5-FUra on NB cells.
TL;DR: The rate constants for electron transfer from a series of substituted isomeric dihydroxy- and diaminobenzenes to different substituted phenoxyl radicals were measured by observing the decay or buildup of one of the radicals invoved.
Abstract: The rate constants for electron transfer from a series of substituted isomeric dihydroxy- and diaminobenzenes to different substituted phenoxyl radicals were measured by observing the decay or buildup of one of the radicals invoved. In many cases the electron transfer reactions were reversible and the equilibrium constants could be calculated from the individual rate constants for attainment of equilibrium and from the concentrations of the species involved at equilibrium. From the equilibrium constants the one-electron redox potentials for 15 individual Q/sup -/./Q/sup 2 -/ pairs were determined, using the value for hydroquinone (23 mV at pH 13.5) as a reference. The potential for catechol (43 mV) is near that of hydroquinone; resorcinol is oxidized much less readily (300 mV), while phenol is even a weaker reductant (>500mV). Methyl, methoxy, and hydroxy substituents decrease the redox potentials while acetyl and carboxyl substituents increase these values. Ascorbate has a potential (15mV) similar to that of hydroquinone, while TMPD (82mV) and p-phenylenediamine (183mV) are less easily oxidized.
Patent•
23 Feb 1979TL;DR: In this paper, a test system for the determination of a constituent in a sample, having means responsive to the presence of said constituent in said sample to produce at least one oxidizing substance, wherein said composition comprises a hydrazone and 8-amino-1-napthol-5,7-disulfonic acid (Chicago acid).
Abstract: Test means, such as a composition or device, method of making a test device and process for determination of at least one oxidizing substance, such as a peroxide, are disclosed. More particularly, the contemplated test means comprises a hydrazone and 8-amino-1-napthol-5,7-disulfonic acid (Chicago acid). Further provided is a test system for the determination of a constituent in a sample, having means responsive to the presence of said constituent in said sample to produce at least one oxidizing substance and a composition for determining said at least one oxidizing substance, wherein said composition comprises a hydrazone and 8-amino-1-napthol-5,7-disulfonic acid (Chicago acid). The test system is preferably of the type which determines peroxides formed from enzymatic conversion of constituents in biological fluids. When in the form of compositions the test means can optionally be incorporated with a carrier, such as a tablet or matrix, to provide a test device. The test system is highly sensitive to low levels of body fluid constituents to be detected, while also being highly resistant to interfering reducing substances, such as ascorbic acid, often present in body fluids.
TL;DR: Regular intake of multivitamin raised the blood levels of riboflavin and ascorbic acid to normal in all, but failed to raise the thiamin and vitamin B6 levels to the normal acceptable levels in 2.9 and 20% of the subjects, respectively.
TL;DR: The simple diet of the Tarahumara Indians, composed primarily of beans and corn, provided a high intake of complex carbohydrate and was low in fat and cholesterol, and would, by all criteria, be considered antiatherogenic.
TL;DR: Investigating the effect of administration of several pterins on serum phenylalanine concentration (Phe) and urinary pterin excretion was investigated in two patients with atypical phenylketonuria (PKU) and demonstrates that BH4, BH2, L -sepiapterin and Neh4, in admixture with ascorbic acid, can be absorbed easily upon oral administration.
TL;DR: This demonstrates the specific neurochemical, physiological, and behavioral alterations in dopaminergic systems produced by ascorbic acid and suggests possible therapeutic uses for asCorbate in conditions involving functional dopamine excess.
TL;DR: This chapter presents the analysis of ascorbic acid by liquid chromatography with amperometric detection, and ion-exchange or reverse-phase packing materials have been found to be the most compatible with the technique.
Abstract: Publisher Summary This chapter presents the analysis of ascorbic acid by liquid chromatography with amperometric detection. Liquid chromatography with electrochemical detection (LCEC) approach affords the convenience of sample preparation, sensitivity, and selectivity equal or superior to any method for ascorbic acid published to date. The sensitivity of LCEC is superior by two orders of magnitude when compared to liquid chromatography with ultraviolet detection. In addition, the selectivity associated with electrochemistry is a decided advantage. Although the use of pellicular, high-performance, and anion-exchange packing materials is adequate for most sample types, increased selectivity is obtainable when microparticulte reverse-phase packings and different ion-pairing reagents are employed. Ideal mobile phases for LCEC are aqueous buffers with or without a solvent (typ-methanol or acetonitrile). Because of this requirement, ion-exchange or reverse-phase packing materials have been found to be the most compatible with the technique.
TL;DR: Epidermal growth factor at nanomolar concentrations stimulated DNA synthesis in confluent, serum‐starved cultures of calf aorta and human uterine smooth muscle cells and rabbit lens epithelial cells to demonstrate binding and dissociation of 125I‐labelled EGF.
Abstract: Epidermal growth factor (EGF) at nanomolar concentrations stimulated DNA synthesis in confluent, serum-starved cultures of calf aorta and human uterine smooth muscle cells. Stimulation of DNA synthesis in lens epithelial cells was studied for comparison. L and D-ascorbic acid potentiated the effect of serum and EGF on DNA synthesis in calf aorta cells. In contrast L-ascorbic acid had minimal potentiating effect with serum and no effect with EGF present along with serum on DNA synthesis in human uterine smooth muscle and rabbit lens epithelial cells. EGF and ascorbic acid increased cell number when added to stationary phase cultures. Specific binding of 125I-labelled EGF to smooth muscle cells was demonstrated. Receptor concentration in calf-aorta smooth muscle cells was higher in dense cultures compared to sparse cultures. The time course of binding and dissociation of 125I-labelled EGF was similar in "dense" and "sparse" cultures. Human uterine smooth muscle cells in culture exhibited a finite lifespan. There was no stimulation of DNA synthesis in response to serum and EGF in cells of high population doubling level (PDL); although 125I-labeled EGF binding was higher in old cells (high PDL) compared to young cells (low PDL). This increase in binding was shown to be due to changes in the concentration of receptors without changes in their affinity for EGF.
TL;DR: In this article, ten leafy green vegetables commonly eaten by farmers in Nigeria have been analyzed for their vitamin and mineral contents, including riboflavin, pyridoxine and ascorbic acid.