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Showing papers on "Ascorbic acid published in 1972"


Journal ArticleDOI
07 Jul 1972-Science
TL;DR: The formation of carcinogenic N-nitroso compounds by the chemical reaction between nitrous acid and oxytetracycline, morpholine, piperazine, N-methylaniline, methylurea, and (in some experiments) dimethylamine was blocked by ascorbic acid.
Abstract: The formation of carcinogenic N-nitroso compounds by the chemical reaction between nitrous acid and oxytetracycline, morpholine, piperazine, N-methylaniline, methylurea, and (in some experiments) dimethylamine was blocked by ascorbic acid. The extent of blocking depended on the compound nitrosated and on the experimental conditions. Urea and ammonium sulfamate were less effective as blocking agents. The possibility of in vivo formation of carcinogenic N-nitroso compounds from drugs could be lessened by the combination of such drugs with the ascorbic acid.

500 citations


Journal ArticleDOI
TL;DR: The rate of collagen synthesis relative to the rate of synthesis of noncollagen proteins expressed as radioactivity incorporated per milligram of cellular protein was determined in several lines of cultured fibroblasts using an assay which measures [14C]proline incorporation into the polypeptide chains of collagen.

366 citations


Journal ArticleDOI
TL;DR: The extrinsic tag provided a valid measure of absorption despite marked differences in the iron status of the subject, and with wide changes in absorption imposed by adding desferrioxamine or ascorbic acid to the test meal.
Abstract: The paper describes the use of an extrinsic tag of inorganic radioiron to determine the total absorption of nonheme iron from a complete meal. The method was developed by measuring the iron absorbed from vegetable foods containing biosynthetically incorporated (55)Fe (intrinsic tag) and from (59)Fe added as a small dose of inorganic iron to the same meal (extrinsic tag). In studies with maize, black bean, and wheat, a consistent extrinsic: intrinsic radioiron absorption ratio averaging 1.10 was observed. Similar results were obtained with either ferrous or ferric iron as the extrinsic tag, and with doses of the latter ranging from 0.001 to 0.5 mg iron added to a test meal containing 2-4 mg of food iron. Adding the radioiron at different stages in preparation of the test meal also had little effect. Separate administration of the extrinsic tag was less satisfactory when small portions of a single food were employed, but with a complete meal, the separate dose was preferable. The extrinsic tag provided a valid measure of absorption despite marked differences in the iron status of the subject, and with wide changes in absorption imposed by adding desferrioxamine or ascorbic acid to the test meal. These findings indicate that there is a common pool of nonheme iron, the absorption of which is influenced by various blocking or enhancing substances present in the meal.

284 citations



Journal ArticleDOI
TL;DR: It is concluded that 9-aminoacridine is the preferred fluorescent probe for use in the range of ΔpH = 2–4 pH units and that Liposomes offer a model membrane system in which controlled pH gradients may be established.

258 citations



Journal ArticleDOI
TL;DR: The uronic acid sequence of several alginate samples has been determined by splitting the alginates into alternating and homopolymeric fractions by partial acid hydrolysis, and determining the relative proportions of mannuronic acid blocks and guluronic Acid blocks in the homopolymer fraction by p.r.m. spectroscopy.

222 citations


Journal Article

179 citations


Journal ArticleDOI
TL;DR: Test meals of 750 ml.
Abstract: 1. Test meals of 750 ml. water containing a range of concentrations of hydrochloric, nitric, sulphuric, cyclamic (cyclohexylsulphamic), tartaric, L-ascorbic and citric acids were instilled into the stomachs of sixteen healthy subjects.2. The greater the concentration of an acid in the instilled meal, the greater was the volume of meal recovered after a fixed interval.3. For the weak acids, tartaric, ascorbic and citric, the concentrations which gave a recovery of 450 ml., out of the 750 ml. instilled, increased with increase in the molecular weight of the acid.4. For the strong acids, hydrochloric, nitric, sulphuric and cyclamic, the concentrations which gave a recovery of 450 ml., out of the 750 ml. instilled, were approximately equal. These concentrations were less than those for weak acids.5. The strong acids with high molecular weights were slightly more effective in slowing gastric emptying than were those with low molecular weights.6. The approximate equality of effectiveness of nitric, sulphuric and cyclamic acids to hydrochloric acid is attributed to the presence of chloride ion in the duodenal contents. Thus all the strong acids instilled produce an environment of hydrochloric acid around the receptor.7. A model for a duodenal receptor responding to acids is proposed.

154 citations


Journal Article
TL;DR: Findings are consistent with an important role for H2O2 in the 6-hydroxydopamine-induced degeneration of nerve terminals and may explain why 5-Hydroxyopamine does not produce degenerative changes.
Abstract: We studied the inhibitory action of various compounds, including hydrogen peroxide, on the uptake of [3H]dopamine by rat brain slices. Dialuric acid, 6-hydroxydopamine, and 5-hydroxydopamine consumed oxygen and generated hydrogen peroxide in solution as a result of aerobic oxidation, as measured with an oxygen electrode. The regeneration by catalase of half the oxygen consumed by 6-hydroxydopamine confirmed that oxygen consumption was equal to H202 production. The rate of oxygen uptake (H202 production by dialuric acid or 6-hydroxydopamine was augmented by the addition of ascorbic acid. In addition, alloxan, which is the oxidized form of dialuric acid, consumed oxygen when ascorbate was added. The mechanism for this can be envisaged as reduction of the oxidized compounds by ascorbate, followed by reoxidation to form more H202, with continuous recycling. Concomitant with increased production of H202, there was increased inhibition of [3H]dopamine uptake. Ascorbate by itself did not inhibit the uptake of [3H]dopamine and did not produce measurable quantities of H202. 6-Hydroxydopamine, a compound that causes nerve terminal degeneration in vivo, was compared with 5-hydroxydopamine, which does not. As both compounds are structural analogues of dopamine, they can inhibit the uptake of [3H]dopamine into brain slices by competing for the uptake mechanisms. Additionally, both may inhibit uptake irreversibly by generating H2O2, which causes oxidative damage. 6-Hydroxydopamine produced H202 at about 12 times the rate yielded by 5-hydroxydopamine. Ascorbate potentiated H2O2 production by 6-hydroxydopamine but suppressed that from 5-hydroxydopamine. These findings are consistent with an important role for H2O2 in the 6-hydroxydopamine-induced degeneration of nerve terminals and may explain why 5-hydroxydopamine does not produce degenerative changes.

153 citations


Journal Article
TL;DR: It was found that in terms of the average number of colds and days of sickness per subject the vitamin group experienced less illness than the placebo group, but the differences were smaller than have been claimed and were statistically not significant.
Abstract: A large scale double-blind trial was conducted to test the claim that the intake of one gram of vitamin C per day substantially reduces the frequency and duration of "colds". It was found that in terms of the average number of colds and days of sickness per subject the vitamin group experienced less illness than the placebo group, but the differences were smaller than have been claimed and were statistically not significant. However, there was a statistically significant difference (P <0.05) between the two groups in the number of subjects who remained free of illness throughout the study period. Furthermore the subjects receiving the vitamin experienced approximately 30% fewer total days of disability (confined to the house or off work) than those receiving the placebo, and this difference was statistically highly significant (P <0.001). The reduction in disability appeared to be due to a lower incidence of constitutional symptoms such as chills and severe malaise, and was seen in all types of acute illness, including those which did not involve the upper respiratory tract.

Book ChapterDOI
TL;DR: The reduction in hydroxylation is regarded as direct evidence for the participation of ascorbic acid in the hydroxyation of protocollagen proline in vivo.
Abstract: Publisher Summary This chapter discusses the biological hydroxylations and ascorbic acid with regard to collagen metabolism. Collagen hydroxyproline and hydroxylysine are formed by the enzymatic hydroxylation of specific proline and lysine residues incorporated into peptide linkage. When, in isolated collagen-forming systems, hydroxylation is prevented by the exclusion of oxygen or by means of the chelating agent, α,α ′ -dipyridyl, an unhydroxylated polypeptide termed protocollagen is produced. Separate enzymes, known as protocollagen proline and lysine hydroxylase, are involved in the formation of collagen hydroxyproline and hydroxylysine. They belong to a class of hydroxylases, members of which all require for activity, molecular oxygen, ferrous ion, a 2-ketoacid, and a reductant, the most effective being ascorbic acid. The α-ketoacid is the cosubstrate in the mixed function oxidation, and undergoes a stoichiometric decarboxylation during the course of the hydroxylation. The reduction in hydroxylation is regarded as direct evidence for the participation of ascorbic acid in the hydroxylation of protocollagen proline in vivo . The occurrence in ascorbic acid deficiency of a normal or even increased hydroxyproline excretion is not immediately reconcilable with inhibited hydroxylation.


Journal ArticleDOI
TL;DR: Phenobarbital induction studies indicated that the microsomal protein-synthesizing system responds to such treatment in vitamin C deficient guinea pigs, and the increase in drug enzyme activities and the level and activity of electron transport components are equal to, if not greater than, those observed in normal animals.

Journal ArticleDOI
TL;DR: Chondrocytes grown in monolayer culture from the joints of young rabbits synthesized collagen provided that ascorbic acid was present in the nutrient medium and apparently produced a collagen resembling that of skin and cultured cutaneous fibrocyte having a chain composition [α1(I)] 2 α2.

Journal ArticleDOI
TL;DR: No adverse effect of high tyrosine levels on the intellectual performance of smaller premature infants, who on the whole have a greater risk for other complications of prematurity.
Abstract: Blood tyrosine concentrations were followed from birth to nursery discharge in 71 premature infants fed a high protein formula supplemented by 60 mg/day of ascorbic acid. In 89% of infants blood tyrosine concentrations were abnormal, and in 38% of infants the maximum level observed was 15.0 mg/100 ml or higher. Maximum blood tyrosine levels correlated significantly with gestational age (p = In a follow-up study performed at 15 months of age, infants with high tyrosine levels had no increase in the incidence of neurological abnormalities. Between 7 and 8 years of age a second follow-up study was performed on 62 children. This included a WISC, a Wide-Range Achievement Test (WRAT), and tests for psychomotor and language maturity. Two children had died in the interval, and five of the 62 were retarded for full testing. The full scale WISC I.Q. of all children correlated with birth weight at the 10% confidence level (p = High tyrosine infants had a significantly lower performance I.Q. than low tyrosine infants (82.4 and 97.8 respectively; p = We observed no adverse effect of high tyrosine levels on the intellectual performance of smaller premature infants, who on the whole have a greater risk for other complications of prematurity.

Journal ArticleDOI
TL;DR: The results are interpreted in terms of a scheme in which one mole of cyanide binds more tightly and more rapidly to a 2+ a 3 3+ than to a 3+ a3 3+ .

Journal ArticleDOI
TL;DR: Embryonic chick chondrocytes growing in suspension culture excrete into the medium chondromucoprotein which appears to be identical to chondomucop protein isolated from epiphyseal cartilage.

Journal ArticleDOI
01 Aug 1972-Nature
TL;DR: Investigation of levels of ascorbic acid in blood cells from healthy women, some of whom were taking oral contraceptives, and pregnant women and others receiving an injected contraceptive found none was receiving supplementary vitamins.
Abstract: ANIMAL experiments1–4 indicate that oestrogens increase the rate of ascorbic acid breakdown and lower tissue levels. Vitamin C is poorly stored by humans and widespread sub-clinical deficiencies occur. We have investigated levels of ascorbic acid in blood cells from healthy women, some of whom were taking oral contraceptives. We have also studied pregnant women and others receiving an injected contraceptive. None was receiving supplementary vitamins.

Journal ArticleDOI
TL;DR: The accuracy and specificity of the RTHRLA was determined by measurement of hLH activity in a variety of human pituitary fractions having widely divergent contents of LH, FSH and TSH, and comparison of these results with those obtained using the ovarian ascorbic acid depletion and ventral prostate growth bioassays.
Abstract: A rat testis homogenate radioligand receptor assay (RTH-RLA) has been characterized with respect to its usefulness for measurement of LH activity in fractions derived from human pituitary glands. The precision of the RTH-RLA appears adequate as judged by standard statistical analysis of inter- and intra-assay variations in response. The accuracy and specificity of the RTHRLA was determined by measurement of hLH activity in a variety of human pituitary fractions having widely divergent contents of LH, FSH and TSH, and comparison of these results with those obtained using the ovarian ascorbic acid depletion (OAAD) and ventral prostate growth (VPW) bioassays. LER-907 was the reference preparation for all assays used in these comparisons. However LER-907, the 2nd IRP-HMG and the 2nd IS-hCG all gave parallel inhibition curves in the RTHRLA. The mean index of discrimination (ID) RLA/OAAD for measurement of LH content in 20 human pituitary glycoprotein hormone preparations was 1.29. The mean ID RLA/VPW for 8 sim...

Journal ArticleDOI
TL;DR: Since ascorbic acid oxidation is readily catalyzed by metal ions, the oxidation was also followed in the presence of disodium ethylenediamine‐tetraacetate, and the results duplicated those obtained by following the aerobic oxidations of ascorBic acid in the absence of a chelating agent.

Journal ArticleDOI
TL;DR: Methods for the chromatography of the very labile 2-hydroxyestradiol-17β on paper, thin layers and columns without oxidative decomposition are described, showing that amounts as small a 2 μg are easily and quantitatively recovered when using these new reducing chromatographic systems.


Journal ArticleDOI
TL;DR: It is suggested that the reduced secretion of collagen, which is probably caused by a deficiency of hydroxylation of proline and lysine in the absence of ascorbate, may eventually produce the defect in collagen synthesis which is observed in scorbutic animals.


Journal ArticleDOI
TL;DR: The recent work of several investigators confirms the existence of a non-passive, saturable process for ascorbic acid absorption in man and values of Vmax and Km are calculated using the equations of saturable absorption kinetics.

Journal ArticleDOI
TL;DR: Clinical aspects of this deficiency disease are dramatic attesting to the essential function of this diet ingredient in normal processes.
Abstract: Salmon, trout, char, carp, aquarium fish and probably many more kinds of fishes develop specific avitaminosis C symptoms when denied dietary sources of ascorbic acid. Clinical aspects of this deficiency disease are dramatic attesting to the essential function of this diet ingredient in normal processes. Subclinical manifestations of the disease may play even more important roles in resistance to bacterial or viral infection, and certainly adequate ascorbate circulating and tissue storage levels would be critical deter-minants for repair of those tissues damaged by parasitic invasion or physical contusions.

Journal ArticleDOI
TL;DR: In this article, it is shown that ascorbic acid is oxidized at platinum electrodes in a two-electron process and there are two reaction paths of the oxidation, one corresponding to an irreversible electrode reaction of the substance without appreciable adsorption with α n a ≈ 0.4, the other being the oxidation of the adsorbed substance in the potential range of Pt surface oxide formation.

Journal ArticleDOI
01 Mar 1972-Heart
TL;DR: It was found that there was a significant fall in the leucocyte ascorbic acid to scorbutic levels within I2 hours of the infarction in each case, and this occurred when the white blood cell count was at its maximum.
Abstract: Leucocyte ascorbic acid was measured in 3I patients who had sustained an acute myocardial infarction. Nine of the patients were seen within 6 hours of the infarction and 22 patients within 12 hours. It was found that there was a significant fall in the leucocyte ascorbic acid to scorbutic levels within I2 hours of the infarction in each case, and this occurred when the white blood cell count was at its maximum. The fall also coincided with the peak plasma cortisol level. The level remained less than normalfor the next two weeks and the reduction in leucocyte ascorbic acid at two weeks was related to the size of the myocardial infarction as reflected by the serum aspartate aminotransferase level. It is suggested that thefall in leucocyte ascorbic acid is due to the migration of ascorbic acid laden leucocytes to the site of the infarction and the dilution of the white cellpool by cells which have not yet taken up their ascorbic acidfrom the plasma. This is in keeping with the finding of higher heart muscle concentrations of ascorbic acid in patients dying a coronary death as compared with patients dying a non-coronary death. These changes appear to be under the influence of the adrenal glands and are a response to traumatic stress.

Journal ArticleDOI
TL;DR: Overall nutrient concentration was critical, but the larvae tolerated a wide range of levels of glucose and of the amino acid mixture and excessive amounts of lipids were harmful.