Showing papers on "Ascorbic acid published in 1969"
TL;DR: It is considered that lipid peroxide formation occurs as a result of the operation of the microsomal electron-transport chain switching from hydroxylation to oxidize unsaturated lipids of the endoplasmic reticulum.
Abstract: 1. Liver microsomes form lipid peroxide when incubated with ascorbate or NADPH, but not with NADH. Increasing the concentration of ascorbate beyond the optimum (0.5mm) decreases the rate of lipid peroxide formation, but this effect does not occur with NADPH. Other reducing agents such as p-phenylenediamine or ferricyanide were not able to replace ascorbate and induce lipid peroxide formation. 2. The rate of ascorbate-induced peroxidation is optimum at pH6.0 whereas the rate of the NADPH system is optimum at pH7.0. Both systems require phosphate for maximum activity. 3. Lipid peroxide formation occurs at the maximum specific rate in very dilute microsome suspensions (0.15mg. of protein/ml.). 4. Treatment of microsomes with deoxycholate and other detergents causes membrane disintegration and inhibits lipid peroxide formation. 5. Lipid peroxide formation is accompanied by a rapid uptake of oxygen and there is a large excess of oxygen utilized for each molecule of malonaldehyde measured in the peroxide method. 6. Boiled microsomes form lipid peroxide in the presence of ascorbate, but not if NADPH is added. 7. Lipid peroxide formation induced by NADPH is strongly inhibited by p-chloromercuribenzoate, weakly inhibited by N-ethylmaleimide and unaffected by iodoacetamide. Ascorbate-induced peroxidation in untreated microsomes is unaffected by p-chloromercuribenzoate, but inhibited if boiled microsomes are used. These experiments may be interpreted on the basis that a ferredoxin-type protein forms part of the system in which NADPH induces lipid peroxide formation. 8. Most heavy-metal ions, with the exception of inorganic iron (Fe(2+) or Fe(3+)), which activates, inhibit both ascorbate-induced and NADPH-induced peroxidation. Mg(2+) increases the rate of peroxidation whereas Ca(2+) inhibits it. 9. Lipid peroxide formation is inhibited strongly by GSH and weakly by cysteine. Ascorbate-induced peroxidation is much more sensitive than NADPH-induced peroxidation. 10. Peroxidation is strongly inhibited by addition of low concentrations (0.01-0.1mm) of cytochrome c or of haemoglobin. 11. It is considered that lipid peroxide formation occurs as a result of the operation of the microsomal electron-transport chain switching from hydroxylation to oxidize unsaturated lipids of the endoplasmic reticulum.
510 citations
TL;DR: A lower range of phosphate concentrations (2, 4, 6, and 8 mM) was studied for maintenance of 2,3-DPG and ATP during storage under blood banking conditions and the lowest concentration, 2 mM, which corresponds to CPD was found to be the best concentration for maintaining 2, 3- DPG and thus hemoglobin function.
Abstract: Serial oxygen dissociation curves were performed on blood units preserved in acid-citrate-dextrose (ACD), ACD-adenine, and ACD-adenine-inosine. Dividing blood from a single donor into two or more bags allowed direct comparison between preservatives. During the 1st wk of storage in ACD, a progressive increase in oxygen affinity was observed. Thereafter, little further change was noted. Oxygen affinity increased even more rapidly during initial storage in ACD-adenine. However, with the inclusion of inosine as a preservative, oxygen affinity remained unaltered during the first 2 wk. Increases in oxygen affinity correlated well with falling levels of red cell 2,3-diphosphoglycerate (2,3-DPG) during storage. No significant changes in glutathione, reduced form (GSH), or A3 (A(I)) hemoglobin levels were noted during the first 3 wk of storage. No significant accumulation of ferrihemoglobin was detected. When blood stored 20 days in ACD or ACD-adenine was incubated with inosine for 60 min at 37 degrees C, 2,3-DPG and adenosine triphosphate (ATP) were resynthesized, and oxygen affinity was decreased. The distribution of 2,3-DPG in fresh and stored red cells appeared to influence experimental values for Hill's n, a measure of heme-heme interaction.
203 citations
TL;DR: Information relating to body pool size, rate of depletion, minimal requirements for vitamin C, rates of repletion and metabolic end-products of L-ascorbic acid are presented.
191 citations
TL;DR: Wound repair was delayed or inhibited in fish on low C diets and results generally supported diet and tissue levels needed for rapid growth and absence of histopathology.
Abstract: Duplicate groups of small coho salmon and rainbow trout were fed a water-soluble vitamin test diet containing 0, 5, 10, 20, 40 or 100 mg of ascorbic acid per 100 g of dry diet Both salmon and trout fed deficient diets developed acute lordosis or scoliosis with resultant high mortality Rainbow trout appeared to exhaust ascorbic acid reserves more rapidly than coho salmon Blood levels of ascorbate reflected diet content of vitamin C at lower levels of intake and anterior kidney tissue content increased directly with C level in diet Wound repair was delayed or inhibited in fish on low C diets and results generally supported diet and tissue levels needed for rapid growth and absence of histopathology A dietary need for vitamin C for both species was evident
183 citations
TL;DR: A mixture of hydrogen peroxide and ascorbic acid has been found to generate an antibacterial mechanism which is active against gram-negative bacteria and it is suggested that the effector mechanism involves the generation of short-lived free radicals which disturb the integrity of the cell wall.
Abstract: A mixture of hydrogen peroxide and ascorbic acid has been found to generate an antibacterial mechanism which is active against gram-negative bacteria. It results in bacterial death and renders the organism sensitive to lysis by lysozyme. Under the conditions used, horseradish peroxidase did not augment the antibacterial effect. It is suggested that the effector mechanism involves the generation of short-lived free radicals which disturb the integrity of the cell wall. This effect alone might kill bacteria by interfering with selective permeability, but in the presence of lysozyme a further bactericidal activity is accomplished by complete disruption of the cell. It is proposed that a transient antibacterial system such as that described could exist within phagocytic cells. Free radicals would be formed through the interaction of certain oxidizable substances and hydrogen peroxide, which is produced during the enhanced metabolic activity that accompanies ingestion of bacteria. Such a system would help to explain why macrophages, which are apparently devoid of preformed bactericidins, are nonetheless very efficient in killing most phagocytosed bacteria.
132 citations
TL;DR: Interrenal ascorbic acid and serum cortisol were measured in non-specificity stressed yearling coho salmon and rainbow trout and showed markedly decreased during stress but increased to normal if adaptation occurred.
131 citations
TL;DR: Measurements have been made of the absorption spectra of the lenses of human, baboon, rhesus monkey, Squirrel monkey, squirrel monkey, bush baby and Galago crassicaudatus.
Abstract: 1. Measurements have been made of the absorption spectra of the lenses of human, baboon (Papio), rhesus monkey (Macaca), squirrel monkey (Saimiri sciureus) and bush baby (Galago crassicaudatus).
2. In all these species an absorption maximum was found between 365 and 368 nm.
3. The pigment responsible for this absorption was water-soluble and aqueous extracts were examined. Protein-free aqueous extracts showed an additional maximum at 260 nm which could be only partially accounted for by the presence of ascorbic acid.
4. Chromatography of the protein-free solution from human lenses yielded a fast-moving yellow component with a blue fluorescence. Its absorption spectrum was very similar to that of the original protein-free solution. A fast-moving yellow component from the baboon lens had a yellow fluorescence.
5. The human lenses appeared to contain more of the yellow, water-soluble pigment at birth than in adult life. The concentration remains constant during adult life.
6. There is evidence for the appearance of another pigment in the human lens in later adult life. It is not water-soluble and has an absorption maximum at about 330 nm.
127 citations
106 citations
TL;DR: The proposed mechanism of mammalian catabolism of phytanic acid involves initial α oxidation leading through α-hydroxyphytanic acid to pristanic acid, and subsequent β oxidations, and the addition of Fe+++ ions greatly stimulates this reaction.
104 citations
TL;DR: The ability of several species of birds to synthesize L-ascorbic acid is correlated with their phylogeny, and the pattern of evolution of the ascorbic acid pathway among birds is similar to that among mammals.
Abstract: The ability of several species of birds to synthesize L-ascorbic acid is correlated with their phylogeny. In the more primitive species, synthesis of L-ascorbic acid occurs in the kidney. Among the highly evolved passeriform species, kidney and liver can synthesize L-ascorbic acid in some, whereas in others synthesis occurs in the liver. In still others, the capacity for the synthesis of L-ascorbic acid is apparently lost. The pattern of evolution of the ascorbic acid pathway among birds is thus similar to that among mammals.
100 citations
TL;DR: In this paper, the ozone-injured pine needles increased 16% and that of the one-year-old needles decreased slightly after 30 days exposure to 0.30 ppm ozone for 33 days.
Abstract: Photochemical oxidant injury to ponderosa pine (Pinus ponderosa Laws) is a severe problem in the southern California mountains. Three-year-old ponderosa pines fumigated in controlled environment chambers with ozone at 0.15, 0.30, or 0.45 ppm had apparent photosynthesis rates reduced by 10, 70, and 85%, respectively, after 30 days exposure. A fumigation with 0.30 ppm ozone for 33 days depressed the cold perchloric acid extracted polysaccharides of both current and one-year-old needles by 40%. The 80% ethanol soluble sugar concentration of current year, ozone-injured needles increased 16% and that of the one-year-old needles decreased slightly. Both carbohydrate fractions of control trees in carbon-filtered air increased moderately. Higher, endogenous concentrations of ascorbic acid in needles did not protect the tissue from ozone injury. Apparent photosynthesis rate was a sensitive index for ozone dosage response. Needle carbohydrate depletion probably induces premature abscission.
TL;DR: An enzyme from the leaves of spinach beet that catalyses the hydroxylation of p-coumaric acid to caffeic acid in the presence of ascorbate has been purified about 1000-fold on a protein basis.
Abstract: 1. An enzyme from the leaves of spinach beet (Beta vulgaris L.) that catalyses the hydroxylation of p-coumaric acid to caffeic acid in the presence of ascorbate has been purified about 1000-fold on a protein basis. 2. It is activated by high concentrations of ammonium sulphate and sodium chloride. 3. The preparation shows both hydroxylase and catechol oxidase activities, in a constant ratio throughout the purification procedure; they are similarly activated by salts. 4. Ascorbate acts as a reductant in quantities equivalent to the caffeic acid produced by hydroxylation. 5. Ascorbate can be replaced by tetrahydrofolic acid, NADH, NADPH or 2-amino-4-hydroxy-6,7-dimethyl-5,6,7,8-tetrahydropteridine, but not by caffeic acid. Among these, the pteridine is the most effective, but the reaction is not inhibited by aminopterin. In experiments with saturating concentrations of NADH and the pteridine, these reductants compete in the reaction and are equivalent on a molar basis. 6. No cofactor has been separated from the enzyme by prolonged dialysis. 7. The relation of the enzyme to other hydroxylases and phenolases is discussed.
TL;DR: The activity of rat liver phenylalanine hydroxylase has been measured in systems which, in addition to the components necessary forhydroxylation, contained ascorbic acid and catalase and certain non-reducing inhibitors can also stabilize the enzyme.
Abstract: The activity of rat liver phenylalanine hydroxylase has been measured in systems which, in addition to the components necessary for hydroxylation, contained ascorbic acid and catalase. 6-Methyl-tetrahydropterine or the corresponding 6,7-dimethyl compound was used as tetrahydropterine cofactor. Simple kinetic experiments lead to the determination of rate constants for the following reactions: the aerobic oxidation of the tetrahydropterine cofactor, the reduction of the dihydropterine cofactor by ascorbic acid and other reductants and the conversion of the dihydropterine cofactor from an active to an inactive form. These rate constants are used for the calculation of the actual concentration of tetrahydropterine cofactor in the hydroxylase system and for correction of the measured rates of hydroxylation for the inactivation of the dihydropterine cofactor.
Ascorbic acid, as well as other reductants that may be present, increase the instability of phenylalanine hydroxylase, but this effect is negligible at sufficiently high catalase concentrations. Certain non-reducing inhibitors can also stabilize the enzyme.
The initial rate of reaction at 30° is linear during the first 5 or 6 min. In contrast at temperatures of 25° and below there is a lag period, whose duration may be reduced by preincubation of the enzyme with tetrahydropterine cofactor. A similar preincubation of the enzyme with l-phenylalanine seems to activate the hydroxylase briefly.
TL;DR: A new catalyst system for polyacrylamide gels at low pH has been developed that is more effective and not inhibited by molecular oxygen.
TL;DR: A study of the metabolism of ascorbic-l-c-C acid in experimental human scurvy was conducted with the following results: I) Labeling the body ascbic acid pool during the depletion phase resulted in no detectable urinary excretion of l-labeled reduced ascorbinic acid or & hydroascorbic acid.
TL;DR: In this article, the authors compared the vitamin content of UHT processed milk with that of the original raw milk, and found that up to 50% of the vitamins were lost during 90 days' storage.
Abstract: The vitamin content of ultra-high-temperature (UHT) processed milk was compared with that of the original raw milk. Three processes were used. In the first, which caused no change in oxygen content, the milk was heated and cooled in a plate-type heat exchanger. In the second, the milk was again heated indirectly and then evaporatively cooled, leaving in the milk about one-third of the initial oxygen content. In the third process the milk was heated by direct steam injection and cooled by evaporation and contained little or no residual oxygen.On processing and during subsequent storage for 90 days there was no loss of vitamin A, carotene, vitamin E, thiamine, riboflavine, pantothenic acid, biotin or nicotinic acid. There was little or no loss of vitamin B6 or vitamin B12 on processing, but up to 50% of each of these vitamins was lost during 90 days' storage. All the dehydroascorbic acid (DHA) and about 20% of the ascorbic acid (AA) was lost on processing. There was no further loss of AA during 90 days’ storage when no residual oxygen was present, but in milks containing more than about 1 ppm oxygen all the AA was lost within 14 days. About 20% of the folic acid was lost on processing; thereafter, as with ascorbic acid, the extent of the loss on storage depended on the residual oxygen content of the milk: in the absence of oxygen the folic acid was stable.
TL;DR: The results suggest that the intestinal mucosal uptake of cobalt is slightly greater than that of iron, and cobalt, unlike iron, is not sequestered in the mucosa and subsequently lost with desquamation of the intestinal epithelium.
TL;DR: The effect of hippocampal stimulation on the release of gonadotropin was studied in rats and the blockade of ovulation was overcome by injection of picrotoxin or by transection of the medial corticohypothalamic tract.
Abstract: The effect of hippocampal stimulation on the release of gonadotropin was studied in rats. The hippocampus was unilaterally stimulated by electrolytic deposition of iron from stainless steel unipolar electrodes. Stimulation of the ventral hippocampus (area CA3 or subiculum) prevented spontaneous o violation in proestrous rats and prevented ovulation induced by amygdaloid or preoptic stimulation in rats made to be persistently in estrus by continuous illumination. Stimulation of the dorsal hippocampus also prevented spontaneous ovulation. No effect on ovulation was observed after stimulation of other areas of the brain. The blockade of ovulation was overcome by injection of picrotoxin or by transection of the medial corticohypothalamic tract. Plasma levels of LH (as measured by the ovarian ascorbic acid depletion) were found significantly lower 3 hr after hippocampal stimulation in proestrous rats injected with progesterone. Also, the elevated plasma LH of ovariectomized rats was depressed after stimulation...
TL;DR: It is suggested on the basis of these results that the most likely candidates for the two additional high potential electron-accepting sites in laccase are the two diamagnetic copper atoms in the molecule and that these copper atoms would have to be present as a Cu2+-Cu2+ pair in the native molecule.
TL;DR: It is suggested that tissue ascorbic acid concentrations should be restored to normal before desferrioxamine is used for either the diagnosis or the treatment of iron overload.
Abstract: Summary. The levels of tissue ascorbic acid tend to be low in subjects with iron overload. The present study was undertaken to find out whether this ascorbic acid deficiency affected the quantities of iron excreted in the urine after the administration of the iron chelate, desferrioxamine. Basal tests were done and were then repeated after 7 days of ascorbic acid therapy. Desferrioxamine-induced urinary iron excretion increased by 88 per cent in 13 individuals with transfusional siderosis, 60 per cent in five with idiopathic haemochromatosis and 350 per cent in 12 Bantu subjects with dietary siderosis. Over the same period the mean leucocyte ascorbic acid concentrations rose by 164 per cent, 157 per cent and 551 per cent respectively. In contrast, no change was noted in either urinary iron excretion or in ascorbic acid concentrations in six normal white and six normal Bantu control subjects. These results suggest that tissue ascorbic acid concentrations should be restored to normal before desferrioxamine is used for either the diagnosis or the treatment of iron overload.
TL;DR: Findings suggest the presence of a transhydrogenase activity in intact erythrocytes and it appears that NAD + content may be influenced by factors other than those affecting glycolysis directly.
TL;DR: In this article, the photochemical reactions of chlorophyll intermediates in vitro have been studied by the flash photolysis method, where the flash excitation of pigment solutions has been shown to involve the population of a triplet state where the oxidation-reduction processes occur.
Abstract: — The photochemical reactions of chlorophyll intermediates in vitro have been studied by the flash photolysis method. The flash excitation of pigment solutions has been shown to involve the population of a chlorophyll triplet state where the oxidation-reduction processes occur. The mechanism and kinetics of pigment triplet decay have been investigated from 20°to — 50°C and the ability of chlorophyll molecules to carry out triplet-triplet energy transfer has been established. The latter phenomenon has been used to show up the role of chlorophyll triplets in the reversible photooxidation reaction with P-quinone. There have been studied initial products of pigment photoreduction with ascorbic acid and phenylhydrazine. Experimental data of the mechanism of the initial oxidation and reduction in chlorophyll photosensitized reactions have been analysed. There have been also obtained the differential spectra of chlorophyll triplets and radicals. A calculation has been made of rate constants for a few elementary reactions.
TL;DR: It has been suggested that quinone adducts of the type described here may be important in biological systems.
TL;DR: Ascorbic acid functioned as a true catalyst, i.e., it accelerated the reaction but it was not oxidized simultaneously with the linoleate, and it is proposed that the dehydroascorbic acid radical initiates the linolesate oxidation reaction.
TL;DR: Applicability and feasibility of this method have been demonstrated in over 2000 hr of repeated blood glucose recordings in 12 diabetic and 6 normal subjects.
Abstract: A glucose oxidase-peroxidase method for continuous automated monitoring of blood glucose has been developed. The response is linear over the range 0-800 mg/100 ml. Sensitivity can be maintained for 24 hr or longer and can be restored by rinsing the analytic system with sulfuric acid to permit studies of longer than 48 hr in duration. A precision of ± 1% can be maintained between rinses for samples containing 100-600 mg of glucose per 100 ml. This method is satisfactorily specific for glucose: The response with other sugars is less than 1% of the response obtained with the same concentration of glucose. Ascorbic acid causes no significant inhibition of the response to glucose. The inhibition by uric acid has been reduced fifty-fold compared to that in other methods. Transit through the sampling catheter and analytic system requires 15 min. Timed from the first detectable response to a change in concentration, 25% of total response is achieved in 30 sec and 90% in 80 sec. Fifty percent of an oscillation with a half-period of 45 sec can be detected; no oscillations this short were observed in records of human blood glucose. Applicability and feasibility of this method have been demonstrated in over 2000 hr of repeated blood glucose recordings in 12 diabetic and 6 normal subjects.
TL;DR: Both steroid treatments (TP and E + P) decreased plasma LH levels without altering pituitary LH concentrations detectably, and both treatments apparently reduced the rate of LH release.
Abstract: The effects of short-term steroid treatment on the blood and pituitary LH and FSH levels of previously castrated adult male and female rats were examined, using ovarian ascorbic acid depletion (OAAD) and HCG-augmentation bioassays for LH and FSH activities. Pituitary and plasma FSH activities, 3 days after an injection of 1) testosterone propionate (TP) or 2) estradiol benzoate plus progesterone (E + P), were compared in 5 experiments. Concomitant changes in plasma and pituitary LH levels were studied in 3 of these experiments and 2 others. In 2 further studies in spayed rats, both stored and circulating LH and FSH were examined after 7 days of TP treatment. In addition, pituitary FSH and plasma LH were studied 24 hr after single injections of TP. Both steroid treatments (TP and E + P) decreased plasma LH levels without altering pituitary LH concentrations detectably. The TP effect on plasma LH was evident after only 24 hr. Thus, both treatments apparently reduced the rate of LH release. Because of the re...
TL;DR: The absorption spectrum of the lens of the grey squirrel has been measured, revealing an absorption maximum at 370 nm, and peak densities in the intact lens ranged from 12 to 20.
Abstract: 1. The absorption spectrum of the lens of the grey squirrel (Sciurus carolinensis leucotis) has been measured, revealing an absorption maximum at 370 nm. Peak densities in the intact lens ranged from 12 to 20.
2. This peak is not present in the lenses of horse, cow, pig, dog, cat, ferret (Mustelo furo), or guinea-pig (Cavia porcellus).
3. The pigment responsible for this absorption is water-soluble and aqueous extracts have been examined. Protein-free aqueous extracts show an additional maximum at 265 nm, which can only partially be accounted for by the presence of ascorbic acid.
4. The absorption spectrum of extracts of lens material from the ground squirrel (Citellus mexicanus) also had maxima at 265 and 370 nm.
5. Chromatography of the protein-free solution separated two yellow components, both of which had a yellow fluorescence. The faster component had a very similar absorption spectrum to the original protein-free solution.
6. Possible functions of the yellow pigment are discussed.