Showing papers on "Ascorbic acid published in 1974"
TL;DR: The results point to a reaction between H2O2 and O2- (Haber-Weiss reaction) as a major source of the ·OH radicals and to a combined action of blocking ·OH formation as well as accelerating its removal.
896 citations
TL;DR: A rapid simple micromethod for the determination of l -ascorbic acid in plasma and other biological tissues using orthophosphoric acid and ferric iron is presented and can be used to accurately determine 0.1 μg of the vitamin in samples of plasma andOther biological tissues.
363 citations
TL;DR: The findings suggest that this simple and safe form of medication is of definite value in the palliation of terminal cancer and should be employed as a standard supportive measure to reinforce established methods of treatment in the general management of earlier and more favorable cases.
301 citations
01 Jan 1974
TL;DR: The enzyme is very specific for G-6-P, although other phosphate esters can be hydrolyzed, and it is therefore necessary to assay the suspensions immediately after thawing.
Abstract: Publisher Summary This chapter focuses on glucose-6-phosphatase (G6Pase), which was first described by Fantl et al. Numerous attempts have been made to determine G6Pase activity in blood and so relate its activity to liver damage. G6Pase is applied in biochemistry and clinical chemistry. The inorganic phosphate liberated is determined with ammonium molybdate; ascorbic acid is used as the reducing agent. The amount of phosphate liberated per unit time, determined as the blue phosphomolybdous complex at 700 or 840 nm, is a measure of the G6Pase activity. The optimum pH for the enzyme reaction lies between 6.2 and 6.51. Only doubly distilled water should be used. The sucrose, G-6-P solution and the cacodylate buffer should be stored at 0–4°C. Freshly obtained tissue should be homogenized first in a precooled blender and then in glass-Teflon homogenizer with ice-cold sucrose solution. The enzyme is stable for several months at −35°C in the absence of EDTA. The instability of the enzyme causes serious errors, it is therefore necessary to assay the suspensions immediately after thawing. The enzyme is very specific for G-6-P, although other phosphate esters can be hydrolyzed.
297 citations
Journal Article•
TL;DR: In this article, it was shown that ethanol can be converted to acetaldehyde only by coupled autoxidation of certain phenolic substances occurring in the wine, such as di-and tri-hydroxyphenols, ascorbic acid, melanoidins, reductones, enediols, etc.
Abstract: Evidence is presented showing that oxidation of ethanol to acetaldehyde by direct chemical reaction with air occurs at an appreciable rate in wine only by a coupled autoxidation of certain phenolic substances occurring in the wine. The oxidation of vicinal di- and tri-hydroxyphenols like caffeic acid, catechin, or myricetin in 12% ethanol model wine produced acetaldehyde. Similar reaction in aqueous 1-propanol produced propanal showing that the source of the volatile aldehyde is the wine9s alcohol. A mechanism is postulated which appears to be general for autoxidation of phenols, ascorbic acid, melanoidins, reductones, enediols, and related compounds whereby the oxidation of the phenol to a quinone (or ascorbic to dehydroascorbic, etc.) coproduces a strong oxidant, probably hydrogen peroxide, which then can oxidize other substances in the wine such as ethanol. Relevance of these findings to wine storage and aging reactions is discussed.
275 citations
TL;DR: The tocopherols have their greatest effect in protection of animal fats, carotenoids, and vitamin A, and in combinations with other known antioxidants improves the shelf-life of all vegetable oils, as well as potato chips.
Abstract: In the quest to use antioxidant compounds occurring in nature or related compounds, extensive studies have been made on vegetable oils, animal fats, apocarotenal, and vitamin A as substrates with ascorbyl palmitate, tocopherols, and ascorbic acid as antioxidants. Antioxidant efficiency varies with the substrate. Ascorbyl palmitate at a level of 0.01% provides a useful increase in the shelf-life of vegetable oils. Alone it is better than butylated hydroxytoluene and butylated hydroxyanisole and in combinations with other known antioxidants improves the shelf-life of all vegetable oils, as well as potato chips. Solubility problems with ascorbyl palmitate and other esters of ascorbic acid are discussed. The tocopherols have their greatest effect in protection of animal fats, carotenoids, and vitamin A. Experiments utilizing tocopherols and tocopherol combinations are presented. The activity of ascorbic acid, an excellent scavenger of oxygen, is reviewed. Quenchers of singlet oxygen do not inhibit the direct oxidation of fats and oils under the conditions used.
199 citations
TL;DR: Dopamine was localized to the intraganglionic ‘small intensely fluorescent’ cells, and also to the characteristically beaded fibres forming a network in close contact with virtually all ganglion cell bodies.
Abstract: 1. Dopamine was identified by formaldehyde histochemistry and cytospectrofluorometry in the rabbit's superior cervical ganglion. Dopamine was localized to the intraganglionic ;small intensely fluorescent' cells, and also to the characteristically beaded fibres forming a network in close contact with virtually all ganglion cell bodies. The extensive beaded fibres are therefore presumed to be processes of the small intensely fluorescent cells.2. Changes in the dopamine content of these interneurones were studied by recording alterations in their relative fluorescence intensity in conjunction with changes in the slow inhibitory post-synaptic potential (s.-i.p.s.p.) response of the ganglion to orthodromic nerve input.3. Dopamine content was lower after several hours in vitro even without special stimulation; this was in accord with a regularly observed spontaneous reduction of the s.-i.p.s.p. response.4. After a period of conditioning stimulation of the preganglionic nerve, in the presence of an anticholinesterase agent (eserine) and an inhibitor of catecholamine synthesis (alpha-methyl-p-tyrosine), the s.-i.p.s.p. was selectively and markedly reduced. The dopamine fluorescence in the small intensely fluorescent cell interneurones was also significantly reduced, to a mean value of about 55 or 60% of the fluorescence in the dopamine interneurones of the paired but unstimulated control ganglion. A significant reduction in dopamine fluorescence was always accompanied by a marked loss of s.-i.p.s.p. response; the reverse was not always true.5. Treatment with the muscarinic agent bethanechol for 30 min, with no alpha-methyl-p-tyrosine or eserine present, similarly resulted in reductions in the s.-i.p.s.p. response of the ganglia and in the formaldehyde-induced fluorescence of the dopamine interneurones.6. A functional uptake of extrinsic dopamine by the dopamine interneurones was also demonstrated: temporary exposure to dopamine restored a large fraction of both the s.-i.p.s.p. response and the dopamine fluorescence of the small intensely fluorescent cells, in ganglia already subjected either to the conditioning stimulation of the preganglionic nerve or to the action of bethanechol.7. It is concluded that (a) preganglionic impulses, by a cholinergic muscarinic synaptic action, can induce a release of dopamine from dopamine interneurones (small intensely fluorescent cells) in the superior cervical ganglion, (b) the ability of the ganglion to respond with a s.-i.p.s.p. to orthodromic input may be viewed as being dependent on the supply of functionally releasable dopamine in these interneurones, (c) the functionally releasable transmitter in vitro appears to comprise roughly 50% of the total dopamine content of the interneurones, and (d) the results fulfil some of the requirements of the hypothesis that a dopamine interneurone is activated muscarinically by preganglionic nerve impulses and mediates the production of s.-i.p.s.p. in sympathetic ganglion cells.
179 citations
TL;DR: Ferritin-Fe(III) was rapidly and quantitatively reduced and liberated as Fe(II) by FMNH(2), FADH(2) and reduced riboflavin and gave complex second-order kinetics with overlapping fast and slow reactions.
Abstract: Ferritin-Fe(III) was rapidly and quantitatively reduced and liberated as Fe(II) by FMNH(2), FADH(2) and reduced riboflavin Dithionite also released Fe(II) from ferritin but at less than 1% of the rate with FMNH(2) Cysteine, glutathione and ascorbate gave a similar slower rate and yielded less than 20% of the total iron from ferritin within a few hours The reduction of ferritin-Fe(III) by the three riboflavin compounds gave complex second-order kinetics with overlapping fast and slow reactions The fast reaction appeared to be non-specific and may be due to a reduction of Fe(III) of a lower degree of polymerization, equilibrated with ferritin iron The amount of this Fe(3+) ion initially reduced was small, less than 03% of the total iron Addition of FMN to the ferritin-dithionite system enhanced the reduction; this is due to the reduction of FMN by dithionite to form FMNH(2) which then reduces ferritin-Fe(III) A comparison of the thermodynamic parameters of FMNH(2)-ferritin and dithionite-ferritin complex formation showed that FMNH(2) required a lower activation energy and a negative entropy change, whereas dithionite required 50% more activation energy and showed a positive entropy change in ferritin reduction The effectiveness of FMNH(2) in ferritin-Fe(III) reduction may be due to a specific binding of the riboflavin moiety to the protein portion of the ferritin molecule
165 citations
TL;DR: The enhancement in vitro of leukocyte mobility by ascorbate at concentrations found in some normal tissues appears to be dependent upon stimulation of the leukocytes hexose monophosphate shunt.
Abstract: Incubation of human leukocytes with ascorbic acid at neutral pH and at concentrations 10-50 times that of normal blood levels augmented both the in vitro random migration and chemotaxis of the cells by 100-300% without influencing their phagocytic capacity. Enhancement of mobility by ascorbate was evident for isolated neutrophils, eosinophils, and mono-nuclear leukocytes and was independent of the specific chemotactic stimulus. Stimulation by ascorbate of the hexose monophosphate shunt of adherent neutrophils and augmentation by ascorbate of neutrophil mobility had comparable dose-response relationships, could be reversed by washing the cells, and were both suppressed by preincubation of the neutrophils with 6-aminonicotinamide, but not with the neutrophil-immobilizing factor. Glutathione, the proposed intermediate for ascorbate action, similarly stimulated hexose monophosphate shunt activity and enhanced migration. The enhancement in vitro of leukocyte mobility by ascorbate at concentrations found in some normal tissues, therefore, appears to be dependent upon stimulation of the leukocyte hexose monophosphate shunt.
163 citations
TL;DR: It is suggested that ascorbic acid may accelerate the healing of pressure-sores and be used as a first line treatment for deep vein thrombosis.
163 citations
TL;DR: Marked increases in the amylase concentration of saliva occurred in response to sympathetic stimulation in the four subjects studied, accompanied by increases in heart rate and blood pressure and small, variable changes in salivary flow rates.
TL;DR: Inhibition of the autoxidation of ascorbic acid and of pyrogallol by superoxide dismutase demonstrates the role of superoxide radicals in these autoxidations.
TL;DR: It is suggested that a daily low dose of trimethoprim–sulfamethoxazole was the most effective in preventing colonization of the periurethral area with enterobacteriaceae.
Abstract: Twenty-seven adult women and thirteen girls with recurrent urinary infections were treated to eradicate their infection and then observed for recurrences while sequentially receiving three prophylactic drug regimens and a period with no drug therapy. The prophylactic regimens consisted of sulfamethoxazole, 500 mg daily, methenamine mandelate, 2 g daily, together with ascorbic acid 2 g daily, or trimethoprim, 40 mg, in combination with sulfamethoxazole, 200 mg daily. Children received half the adult doses. Thirty-three infections (3.6 per patient-year) occurred in patients on no drug therapy, 22 (2.5 per patient-year) in those taking sulfamethoxazole, 13 (1.6 per patient-year) in those taking methenamine mandelate and ascorbic acid, and 1 (0.1 per patient-year) in those taking trimethoprim–sulfamethoxazole. Trimethoprim–sulfamethoxazole was also the most effective in preventing colonization of the periurethral area with enterobacteriaceae. These results suggest that a daily low dose of trimethopri...
TL;DR: Clinical observations are presented under the three headings of the expectations, the findings, and improvements in the chelation scheme in the light of these findings.
Abstract: At University College Hospital and the Whittington Hospital in London we have 31 children with thalassemia major, most of them under 16 years of age. They are mostly the offspring of parents who have emigrated from Cyprus in the last 20 years. The 24 who require transfusion are maintained on a moderateley high scheme; i.e., the hemoglobin is raised from 9 up to 14 g % by six or eight weekly transfusions. Since there can no longer be any doubt that thalassemic patients with transfusional siderosis develop symptoms attributable to iron overload, usually starting around puberty, we have felt that the only hope of a reasonable long-term prognosis lies in the use of iron-chelating agents. Thalassemic patients on maintenance transfusion do not usually excrete significant quantities of iron in the urine in response to desferrioxamine until they are about three years old, because they must have an abnormal iron load to respond to the drug at all. This in itself is the central problem of chelation therapy. Once they have passed their third birthday, all our patients receive desferrioxamine, 500 mg intramuscularly six days a week, and 2 g/pint in the blood at transfusion. We have had twelve patients on long-term chelation, ten for three years and two for five years; the remaining patients are either too young or have only recently come into our care. The injections have been well tolerated, and there have been no complications of any kind from the use of desferrioxamine. We have measured the amount of iron excreted in the urine, and clinical observations have included liver biopsy and endocrinological studies in some patients. Measurements of liver-iron concentration have been done by Dr. Michael Barry. It is still too early to assess the clinical value of the chelation scheme we are using, but nevertheless some useful observations can be made at this stage. These clinical observations will be presented under the three headings of our expectations, our findings, and improvements in our chelation scheme in the light of these findings. Our expectations are outlined in FIGURE 1, which shows the factors affecting iron balance in a thalassemic patient on chelation therapy. First on the input side is excessive gastrointestinal iron absorption, which can reach 10 mg/day in an anemic patient. We know little about this except that it is reduced by transfusion,l and that it can be a substantial item in our patients. The major factor on the input side is iron received as blood, which averages 5-15 mg/day in our patients, according to age and transfusion status. On the output side, there are spontaneous losses of iron in the urine and stool. Our patients over four years old, when not chelated, lose on average 1.5 mg/24 hr (range 0.1-2.2
TL;DR: The most effective reductant was a system composed of ferredoxin, grana lamellae, ascorbic acid, dichlorophenolindophenol, and light, and no NADPH requirement was observed when this reducing system was employed.
TL;DR: A double-blind study to evaluate vitamin C supplements for respiratory-Infection prophylaxis was conducted among 641 children at a Navajo boarding school over a 14-week period.
Abstract: A double-blind study to evaluate vitamin C supplements for respiratory-Infection prophylaxis was conducted among 641 children at a Navajo boarding school over a 14-week period. Supplements of 1 and 2 g, or placebo, were given daily. A sample of each group had serial blood ascorbic acid determinations, which showed significant rises among groups treated with vitamin C, but no difference in mean levels between those receiving 1 and those given 2 g. Although there was no difference between treatment groups in number of respiratory episodes, those given vitamin C had fewer days of morbidity than those receiving placebo, both in older (34 per cent) and in younger (28 per cent) age groups. In active surveillance, there were 26 per cent fewer symptomatic days observed in younger vitamin C groups, and 33 per cent fewer in older girls on vitamin C. No such difference was seen in older boys. Nasal discharge and cough were the two symptoms apparently benefited. Significantly more children on vitamin C had n...
TL;DR: This reactivity with d-glucuronolactone suggests a normal role of daunorubicin reductase in ascorbic acid synthesis or in the glucuronic acid cycle, or both.
TL;DR: The experience with ascorbic acid enhancement of desferrioxamineinduced urinary iron excretion in thirteen patients with thalassemia major is reported and correlates the results with age and iron saturation percentage.
Abstract: Repeated blood transfusions and increased gastrointestinal iron-absorption convey a massive iron burden to the patient with thalassemia major that ultimately produces visceral hemosiderosis, a major cause of severe morbidity and mortality in that disease. Efforts to remove iron by chelation have been hampered by the limited efficiency of the agents available and by a tendency for decreasing effectiveness with chronic administration. Better chelating agents or methods of increasing the efficiency of the currently available agents would be welcome. In 1969, a group of South African investigators reported the successful use of ascorbic acid in increasing the effectiveness of chelation therapy in conditions associated with iron overload, including thalassemia. This paper reports our experience with ascorbic acid enhancement of desferrioxamineinduced urinary iron excretion in thirteen patients with thalassemia major and correlates the results with age and iron saturation percentage.
Journal Article•
TL;DR: It is suggested that the optimum daily dose of vitamin C is less than 250 mg, except possibly at the time of acute illness, when a larger daily intake may be beneficial.
Abstract: Between December 1972 and February 1973, 2349 volunteers participated in a double-blind trial to assess the effect of large doses of vitamin C on the incidence and severity of winter illness. In addition, records were kept but no tablets taken during March. Subjects were randomly allocated to eight treatment regimens: three prophylactic-only (daily dose 0.25, 1 or 2 g), two therapeutic-only (4 or 8 g on the first day of illness), one combination (1 g daily and 4 g on the first day of illness), and two all-placebo. None of the groups receiving vitamin C showed a difference in sickness experience that was statistically significant from that of the placebo groups, but the results obtained were compatible with an effect of small magnitude from both the prophylactic and therapeutic regimens, and an effect of somewhat greater magnitude from the combination regimen. The combination regimen was associated more with a reduction in severity than frequency of illness, although the extra dosage was limited to the first day of illness. In spite of the eightfold range in daily dose, the three prophylactic-only regimens showed no evidence of a dose-related effect, but the 8 g therapeutic dose was associated with less illness than the 4 g therapeutic dose. There was no evidence of side effects from the 1 and 2 g prophylactic doses of vitamin C, and no evidence of a rebound increase in illness during the month following withdrawal of the daily vitamin supplements. On the basis of this and other studies it is suggested that the optimum daily dose of vitamin C is less than 250 mg, except possibly at the time of acute illness, when a larger daily intake may be beneficial.
TL;DR: The potential value of ascorbic acid in the supportive treatment of cancer is a matter for urgent study at many levels and offers the promise of general improvement in the results of cancer management.
TL;DR: In some cases, liquid chromatography with electrochemical detection provides better sensitivity, selectivity, and speed than traditional methods, while minimizing the need for analytical reagents.
Abstract: High-performance liquid chromatography can be combined with hydrodynamic thin-layer electrochemistry for determination of trace amounts of organic constituents in complex samples. With small and inexpensive analyzers based on these two techniques, as little as 1 pg of an electrochemically active component can be detected in a few minutes. Because many of the important low-molecular-weight organic constituents of body fluids— both endogenous metabolites and drugs—undergo electrochemical reactions, it seems reasonable to presume that useful assays might be developed by using the above methodology. Beginning to explore this presumption, we illustrate how uric acid, ascorbic acid, catecholamines, and related tyrosine metabolites might be measured in urine and serum. In some cases, liquid chromatography with electrochemical detection provides better sensitivity, selectivity, and speed than traditional methods, while minimizing the need for analytical reagents. We describe the basic approach and progress to date and suggest future applications.
TL;DR: High doses of vitamin C, popularly used as a home remedy against the common cold, destroy substantial amounts of vitamin B when ingested with food, and daily ingestion of 0.5 gm or more of ascorbic acid without regular evaluation ofitamin B 12 status is probably unwise.
Abstract: High doses of vitamin C, popularly used as a home remedy against the common cold, destroy substantial amounts of vitamin B when ingested with food. Because this undesirable effect is unequivocal when measured in vitro, while the value of ascorbic acid in preventing the common cold is highly equivocal, daily ingestion of 0.5 gm or more of ascorbic acid without regular evaluation of vitamin B 12 status is probably unwise. ( JAMA 230:241-242, 1974)
TL;DR: It is supposed that a reoxidizable heavy metal bound to the membrane structures is responsible for the inhibitory effect of the soluble fraction and of l -ascorbic acid.
01 Jan 1974
TL;DR: In this paper, the effects of feeding 75 mg cadmium/kg of diet from hatching to 4 or 6 weeks of age were studied in Japanese quail (Coturnix cotturnix japonica).
Abstract: Histological sequelae of feeding 75 mg cadmium/kg of diet from hatching to 4 or 6 weeks of age were studied in Japanese quail (Coturnix coturnix japonica). The effects of cadmium were compared with those of zinc and iron deficiencies at 4 weeks, and the protective effects of ascorbic acid against cadmium were investigated at 4 and 6 weeks. Testicular hypoplasia and growth retardation occurred in 4-week-old quail fed either cadmium-containing or zinc-deficient diets. Severe anemia and bone marrow hyperplasia were present in birds fed either cadmium-containing or iron-deficient diets. The morphological appearance of circulating erythrocytes was not the same with both treatments. Both heart ventricles were hypertrophied in response to cadmium at 6 weeks, whereas hypertrophy was not apparent microscopically at 4 weeks, even though the weight was significantly increased in relation to body weight. Left ventricular hypertrophy occurred in iron-deficient quail by 4 weeks. Enteropathy of the small intestine was more severe after 6 weeks of cadmium feeding than after 4 weeks. Cadmium caused decreased granules in the adrenal medullary cells at both 4 and 6 weeks of age. Conditions that were less severe at 6 than at 4 weeks of cadmium ingestion were: testicular development, anemia, and periodicmore » acid-Schiff reactivity of esophageal mucus glands. Ascorbic acid added to the cadmium containing diet significantly alleviated or prevented almost all aspects of cadmium toxicity in quail at 4 and/or 6 weeks of age. It protected against some changes that were not observed in either zinc- or iron-deficient birds. 40 references, 22 figures, 4 tables.« less
TL;DR: The results suggest that the charges on lysine e-amino groups in the oLHα play a role in the recombination with oLhβ, but that the charge on the oHHβ amino groups is not crucial for subunit-subunit interaction.
TL;DR: It is suggested that theredox potential for cytochrome a (contributing 70% at 605–630 nm and 50% at 445–455 nm) is a function of the redox state of cy tochrome a 3 .
TL;DR: L -Ascorbic acid absorption in man appears to be similar to that observed in the guinea pig, and equimolar concentrations of glucose enhanced absorption, presumably by acting as an energy metabolite.