Showing papers on "Ascorbic acid published in 1989"
TL;DR: The data demonstrate that ascorbate is the most effective aqueous-phase antioxidant in human blood plasma and suggest that in humans ascorBate is a physiological antioxidant of major importance for protection against diseases and degenerative processes caused by oxidant stress.
Abstract: We have shown recently that the temporal order of antioxidant consumption in human blood plasma exposed to a constant flux of aqueous peroxyl radicals is ascorbate = protein thiols greater than bilirubin greater than urate greater than alpha-tocopherol and that detectable lipid peroxidation starts only after ascorbate has been consumed completely. In this paper, we show that it is indeed ascorbate that completely protects plasma lipids against detectable peroxidative damage induced by aqueous peroxyl radicals and that ascorbate is the only plasma antioxidant that can do so. Plasma devoid of ascorbate, but no other endogenous antioxidant, is extremely vulnerable to oxidant stress and susceptible to peroxidative damage to lipids. The plasma proteins' thiols, although they become oxidized immediately upon exposure to aqueous peroxyl radicals, are inefficient radical scavengers and appear to be consumed mainly by autoxidation. Our data demonstrate that ascorbate is the most effective aqueous-phase antioxidant in human blood plasma and suggest that in humans ascorbate is a physiological antioxidant of major importance for protection against diseases and degenerative processes caused by oxidant stress.
1,802 citations
TL;DR: Reduced glutathione and the shift of the iron (II)/iron (III) ratio in favor of iron ( III) suggest that these changes might contribute to pathophysiological processes underlying PD.
Abstract: The regional distributions of iron, copper, zinc, magnesium, and calcium in parkinsonian brains were compared with those of matched controls. In mild Parkinson's disease (PD), there were no significant differences in the content of total iron between the two groups, whereas there was a significant increase in total iron and iron (III) in substantia nigra of severely affected patients. Although marked regional distributions of iron, magnesium, and calcium were present, there were no changes in magnesium, calcium, and copper in various brain areas of PD. The most notable finding was a shift in the iron (II)/iron (III) ratio in favor of iron (III) in substantia nigra and a significant increase in the iron (III)-binding, protein, ferritin. A significantly lower glutathione content was present in pooled samples of putamen, globus pallidus, substantia nigra, nucleus basalis of Meynert, amygdaloid nucleus, and frontal cortex of PD brains with severe damage to substantia nigra, whereas no significant changes were observed in clinicopathologically mild forms of PD. In all these regions, except the amygdaloid nucleus, ascorbic acid was not decreased. Reduced glutathione and the shift of the iron (II)/iron (III) ratio in favor of iron (III) suggest that these changes might contribute to pathophysiological processes underlying PD.
1,392 citations
TL;DR: The results may indicate that an increased level of lipid peroxidation continues to occur in the parkinsonian nigra up to the time of death, perhaps because of continued exposure to excess free radicals derived from some endogenous or exogenous neurotoxic species.
Abstract: Polyunsaturated fatty acid (PUFA) levels (an index of the amount of substrate available for lipid peroxidation) were measured in several brain regions from patients who died with Parkinson's disease and age-matched control human postmortem brains. PUFA levels were reduced in parkinsonian substantia nigra compared to other brain regions and to control tissue. However, basal malondialdehyde (MDA; an intermediate in the lipid peroxidation process) levels were increased in parkinsonian nigra compared with other parkinsonian brain regions and control tissue. Expressing basal MDA levels in terms of PUFA content, the difference between parkinsonian and control substantia nigra was even more pronounced. Stimulating MDA production by incubating tissue with FeSO4 plus ascorbic acid, FeSO4 plus H2O2, or air alone produced lower MDA levels in the parkinsonian substantia nigra, probably reflecting the lower PUFA content. These results may indicate that an increased level of lipid peroxidation continues to occur in the parkinsonian nigra up to the time of death, perhaps because of continued exposure to excess free radicals derived from some endogenous or exogenous neurotoxic species.
1,373 citations
TL;DR: It was concluded that rutin and quercetin are able to suppress free radical processes at three stages: the formation of superoxide ion, the generation of hydroxyl (or cryptohydroxyl) radicals in the Fenton reaction and theformation of lipid peroxy radicals.
945 citations
TL;DR: The marked inhibition of Fe absorption by phytates and the significant counteracting effect of ascorbic acid have wide nutritional implications.
602 citations
TL;DR: Analysis adjusted for patient compliance showed a stronger benefit from the high-fiber supplement during the middle 2 years of the trial, providing evidence for inhibition of benign large bowel neoplasia by grain fiber supplements in excess of 11 g/day in this study population.
Abstract: Over a 4-year period in a chemoprevention trial on large bowel neoplasia, 58 patients with familial adenomatous polyposis were treated with 4 g of ascorbic acid (vitamin C)/day plus 400 mg of alpha-tocopherol (vitamin E)/day alone or with a grain fiber supplement (22.5 g/day). In this randomized, double-blind, placebo-controlled study, we determined the effects of these supplements on rectal polyps in these patients. Analysis by intent to treat suggested that the high-fiber supplement had a limited effect. Analysis adjusted for patient compliance showed a stronger benefit from the high-fiber supplement during the middle 2 years of the trial. The results provide evidence for inhibition of benign large bowel neoplasia by grain fiber supplements in excess of 11 g/day in this study population. The findings are consistent with the hypothesis that dietary grain fiber and total dietary fat act as competing variables in the genesis of large bowel neoplasia.
321 citations
TL;DR: Ascorbic acid induces lipid peroxidation and reactive aldehydes and this step may be necessary for the stimulation of collagen gene expression by ascorBic acid in cultured human fibroblasts.
314 citations
TL;DR: An increased risk of cataract with lower educational achievement, decreased cloud cover at place of residence, use of aspirin less than once a month, diets low in selected nutrients, and lower levels of an antioxidant index are found.
Abstract: • In a hospital-based case-control study of 1441 patients with age-related cataracts and 549 controls, we studied associations between types of cataract—nuclear, cortical, posterior subcapsular, and mixed—and a number of physiologic, behavioral, environmental, and biochemical variables. Using polychotomous logistic regression analysis, we found an increased risk of cataract with lower educational achievement (all types of cataract), decreased cloud cover at place of residence (all types), use of aspirin less than once a month (posterior subcapsular and mixed), diets low in selected nutrients (posterior subcapsular, nuclear, and mixed), higher blood pressure (nuclear and mixed), lower body mass index (nuclear and mixed), use of cheaper cooking fuels (cortical, nuclear, and mixed), and lower levels of an antioxidant index based on red blood cell levels of glutathione peroxidase and glucose-6-phosphate dehydrogenase and plasma levels of ascorbic acid and vitamin E (posterior subcapsular and mixed). All risks cited were significantly different from those for the other cataract types, a finding that emphasizes the need to investigate the epidemiology of specific types of cataract.
299 citations
TL;DR: The alteration of this effect by four different antioxidants, as well as an inhibitor of superoxidase dismutase, indicated that oxygen-free radicals may have a role in the methamphetamine-induced neurotoxicity.
282 citations
TL;DR: In this article, the electrochemical and vibrational spectroscopic properties of highly ordered pyrolytic graphite (HOPG) were determined before and after modification by anodization or pulsed laser irradiation, which greatly accelerated the heterogeneous electron-transfer-rate constants for the Fe(CN)6(3/4-) and dopamine redox systems on HOPG by approximately six orders of magnitude.
Abstract: The electrochemical and vibrational spectroscopic properties of highly ordered pyrolytic graphite (HOPG) were determined before and after modification by anodization or pulsed laser irradiation. Both treatments greatly accelerated the heterogeneous electron-transfer-rate constants for the Fe(CN)6(3-/4-) and dopamine redox systems on HOPG by approximately six orders of magnitude. At intermediate electrochemical pretreatment (ECP) potentials, a spatially heterogeneous surface resulted, with surface regions exhibiting the 1360/cm band being separated by tens of microns. The results clearly indicate that graphitic edge plane is necessary for fast electron transfer, and that the pretreatment procedures accelerate k0 by generating edge-plane defects in the HOPG lattice. The mechanisms of defect generation for the two procedures appear very different, with ECP appearing to follow a nucleation process leading to a spatially heterogeneous surface, while the laser pulse appears to shatter the HOPG lattice, leading to a more uniform distribution of active sites. The results provide important conclusions about the relationship between carbon electrode microstructure and heterogeneous electron transfer activity. Of particular interest is the heterogeneous electron transfer rate between carbon electrodes and various well-known redox systems such as ascorbic acid, ferri/ferrocyanide, and the catecholamines. Not only are these systems of significant analytical interest, but they serve asmore » benchmarks for comparisons of electrode performance.« less
279 citations
TL;DR: Limiting dilution analysis in microtiter wells suggests that approximately 0.30% of the cells in isolated rat calvaria populations are osteoprogenitor cells, that one osteopogenitor cell gives rise to one bone nodule, that cooperativity between different cells in vitro is not necessary for bone formation, and that dexamethasone stimulates the expression of osteoprogensitor cells.
TL;DR: Analysis of diet and lung cancer among the multiethnic population of Hawaii in 1983-1985 suggests that other constituents of vegetables, such as lutein, lycopene, and indoles, and others, may also protect against lung cancer in humans.
Abstract: We conducted a population-based study of diet and lung cancer among the multiethnic population of Hawaii in 1983-1985. We completed interviews for 230 men and 102 women with lung cancer and 597 men and 268 women controls, frequency-matched to the patients by age and sex. A quantitative dietary history assessed the usual intake of foods rich in vitamins A and C and carotenoids. A clear dose-dependent negative association was demonstrated between dietary beta-carotene and lung cancer risk in both sexes. After adjusting for smoking and other covariates, the men in the lowest quartile of beta-carotene intake had an odds ratio of 1.9 (95% confidence interval, 1.1-3.2) compared to those in the highest quartile of intake. The corresponding odds ratio for women was 2.7 (95% confidence interval, 1.2-6.1). No clear association was found for retinol, vitamin C, folic acid, iron, dietary fiber, or fruits. All vegetables, dark green vegetables, cruciferous vegetables, and tomatoes showed stronger inverse associations with risk than beta-carotene. This observation suggests that other constituents of vegetables, such as lutein, lycopene, and indoles, and others, may also protect against lung cancer in humans.
TL;DR: The results suggest that vitamin C may play an important role in endochondral bone formation by modulating gene expression in hypertrophic chondrocytes.
TL;DR: It appears that the prooxidant effect of ascorbate is related to the ability of asCorbate to promote the formation of a proposed Fe(II):Fe(III) complex and not due to oxygen radical production.
TL;DR: The results showed a statistically significant decrease in the levels of GSH-Px, vitamins E, C and A, zinc, transferrin and albumin in the SDAT group, suggesting an alteration of free radical scavengers in the malnourished subgroup of theSDAT population could combine the radical and nutritional hypothesis advanced by some authors.
Abstract: Lipid peroxidation products and defenses against free radical damage were determined in serum of 55 patients with senile dementia of the Alzheimer type (SDAT) and compared with values in 24 age-matched healthy control subjects. The following parameters were evaluated: lipid-conjugated dienes and trienes, malondialdehyde, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity in erythrocytes, vitamins E, C and A, zinc, selenium and copper, ceruloplasmin, transferrin and albumin. The results showed a statistically significant decrease in the levels of GSH-Px, vitamins E, C and A, zinc, transferrin and albumin in the SDAT group. On the other hand, most of the deficiencies concern the malnourished subgroup of the SDAT population (SOD, GSH-Px, vitamins E and C, selenium, zinc, transferrin and albumin). Such an alteration of free radical scavengers in the malnourished subgroup of the SDAT population could combine the radical and nutritional hypothesis advanced by some authors.
TL;DR: Several types of experiments demonstrate that SC myelin formation can be controlled by regulating the ability of the SC to assemble basal lamina, illustrating that acquisition of basalLamina is a crucial prefatory step for further SC differentiation.
Abstract: Several recent observations suggest that Schwann cell (SC) differentiation, including myelin formation, is dependent upon the development of basal lamina which characteristically surrounds each axon-SC unit in peripheral nerve. This dependence can be tested in a neuron-SC culture system developed in our laboratory in which SC differentiation, including basal lamina formation and myelination, is faithfully reproduced. The use of serum-free, defined medium (DM) with this culture system allows axon-driven SC proliferation but not basal lamina formation or myelination. We previously demonstrated that ascorbic acid, in the presence of a nondialyzable serum factor(s), stimulates basal lamina assembly and myelin formation with similar dose-response relationships (Eldridge et al., 1987). We hypothesized that ascorbic acid acts to promote SC myelination indirectly, by enabling the assembly of basal lamina. We now provide support for this hypothesis by demonstrating the following. (1) Pepsin-resistant triple-helical collagen molecules were produced only by SCs grown in the presence of ascorbic acid, suggesting that triple-helical type IV collagen may mediate the effect of ascorbic acid on basal lamina formation. (2) The formation of myelin by oligodendrocytes, which myelinate axons in the CNS without the concomitant deposition of basal lamina, was little affected by ascorbic acid, suggesting that the biosynthesis and assembly of myelin per se does not require ascorbic acid. (3) The provision of exogenous basal lamina matrix to SCs grown with neurons in DM without ascorbic acid promoted control levels of myelination (and basal lamina formation); the provision of exogenous fibrillar collagen matrix did not. (4) Purified laminin promoted control levels of myelination in the absence of ascorbic acid, but purified type IV collagen and heparan sulfate proteoglycan (HSPG) did not. Laminin caused SCs to assemble basal lamina-like structures that contained not only laminin but also HSPG and non-triple-helical type IV collagen. Thus, several types of experiments demonstrate that SC myelin formation can be controlled by regulating the ability of the SC to assemble basal lamina, illustrating that acquisition of basal lamina is a crucial prefatory step for further SC differentiation.
TL;DR: Sliced strawberries (cvs.‘Pajaro’ and 'G-3′) and partially ripe pears (cv. ‘Bartlett’) were dipped in various solutions (citric acid, ascorbic acid, and/or calcium chloride) and stored in air or in controlled atmospheres (CA) for 7 days at 2.5°C followed by one day at 20°C as discussed by the authors.
Abstract: Sliced strawberries (cvs.‘Pajaro’ and 'G-3′) and partially ripe pears (cv.‘Bartlett’) were dipped in various solutions (citric acid, ascorbic acid, and/or calcium chloride) and stored in air or in controlled atmospheres (CA) for 7 days at 2.5°C followed by one day at 20°C. Fruit slices respired at a higher rate than whole fruits at both temperatures. CA storage suppressed respiration and ethylene production rates of sliced fruits. Firmness of strawberry and pear slices was maintained by storage in air + 12% CO2 and in a 0.5% O2 atmosphere, respectively, or by dipping in 1% calcium chloride. These treatments also resulted in lighter colored pear slices than the air control treatment.
TL;DR: It is indicated that immediately after exposure to a large fluence of ultraviolet radiation the enzymic and nonenzymic antioxidant capacity of skin decreases significantly.
TL;DR: Application of different types of free radical scavengers, such as ascorbic acid, reduced glutathione, α-tocopherol-acetate and bovine serum albumin, delayed the development of the HR and are consistent with the hypothesis that membrane deterioration during bacterially induced HR is caused by various forms of activated oxygen.
Book•
18 Oct 1989
TL;DR: The structure and distribution of molecular components in the Vitreous, and the role of vitreous in Neovascularization and Effects of Hemorrhage on the VitREous, are explained.
Abstract: I Introduction.- A. General Background.- B. Historical Perspective.- 1. Vitreous Structure.- 2. Vitreous Biochemistry.- References.- II Embryology of the Vitreous.- A. Structural Development.- 1. Primary Vitreous.- 2. Secondary Vitreous.- 3. Zonular System.- B. Cellular Development.- 1. Hyalocytes.- 2. Fibroblasts.- C. Molecular Development.- 1. Collagen.- 2. Hyaluronic Acid.- 3. Other Molecular Components.- References.- III Biochemistry.- A. Collagen.- B. Hyaluronic Acid (HA).- C. Collagen-HA Interaction.- D. Noncollagenous Proteins.- E. Glycoproteins.- F. Low-Molecular-Weight Substances.- 1. Sodium.- 2. Potassium.- 3. Chloride.- 4 Calcium.- 5. Phosphates.- 6. Bicarbonate.- G. Miscellaneous Compounds.- 1. Ascorbic Acid.- 2. Lactic Acid.- 3. Amino Acids.- 4. Lipids.- H. Species Variations.- 1. Glycosaminoglycans.- 2. Collagen.- 3. Protein.- 4. Glycoproteins.- 5. Lipids.- 6. Miscellaneous.- References.- IV Structure of the Vitreous.- A. Organization and Distribution of Molecular Components.- B. Vitreous Body.- C. Vitreous Base.- D. Vitreous Cortex.- 1. Hyalocytes.- 2. Fibroblasts.- E. Basal Laminae and Vitreoretinal Interface.- F. Zonules.- References.- V Functions of the Vitreous.- A. Developmental.- B. Optical.- 1. Media Transparency.- 2. Accommodation.- C. Mechanical.- D. Physiology and Metabolism.- References.- VI Development and Aging of the Vitreous.- A. Development to the Adult.- 1. Structural Development.- 2. Molecular Development.- 3. Morphologic Changes During Development.- B. Aging.- 1. Rheology.- 2. Biochemistry.- 3. Morphology.- C. Posterior Vitreous Detachment.- 1. Definition.- 2. Epidemiology.- 3. Pathogenesis.- 4. Sequelae.- References.- VII Pathobiology of the Vitreous.- A. Developmental and Inherited Disorders.- 1. Hyaloid Vascular System.- 2. Dominant Exudative Vitreoretinopathy.- 3. Retinopathy of Prematurity.- 4. Wagner's Disease.- 5. Vitreoretinal Dystrophy of Goldmann-Favre.- B. Connective-Tissue Disorders.- 1. Marian's Syndrome.- 2. Ehlers-Danlos Syndrome.- 3. Stickler Syndrome.- C. Diabetes Mellitus.- 1. Biochemical Effects.- 2. Vitreous Effects.- D. Cell Invasion.- 1. Cell Proliferation at the Vitreoretinal Interface.- 2. Trauma.- 3. Inflammation.- 4. Neoplasia.- E. Vascular Invasion and Effects of Vitreous Hemorrhage.- 1. Role of Vitreous in Neovascularization.- 2. Effects of Hemorrhage on the Vitreous.- F. Vitreoretinal Traction.- 1. Peripheral Traction.- 2. Traction on Retinal Blood Vessels.- 3. Posterior Pole Traction.- G. Miscellaneous Conditions of the Vitreous.- 1. Myopia.- 2. Aphakia.- 3. Retinitis Pigmentosa.- 4. Vitreous Opacities.- H. Effects of Surgical Intervention.- 1. Vitrectomy.- 2. Photocoagulation.- 3. Cryopexy.- 4. Intravitreal Injections.- References.- Color Plates.
TL;DR: The presence of the concentration gradient suggests that a mechanism for the secretion of vitamin C into the stomach exists, and those patients who by the Correa model are at greatest risk for gastric cancer have the lowest gastric levels of ascorbic acid.
TL;DR: The results argue against the participation of an Fe2-Fe3+-O2 complex, or a critical 1:1 ratio of Fe2+ to Fe3+, in the initiation of lipid peroxidation in liposomes and rat-liver microsomes.
Abstract: When Fe2+ ions are added to rat-liver microsomes, lipid peroxidation begins after a short lag period. Fe2+-dependent peroxidation in the first few minutes of the incubation can be increased by adding Fe3+, ascorbic acid or Pb2+ ions; these stimulations are not additive. By contrast, Pb2+ ions inhibit peroxidation of microsomes in the presence of Fe3+/ascorbate or Fe3+-ADP/NADPH. In liposomes made from ox-brain phospholipids, Fe2+-dependent peroxidation is stimulated slightly by Fe3+, but much more so by ascorbic acid, Al3+ or Pb2+; these stimulations are not additive. Liposomal peroxidation in the presence of Fe3+/ascorbate is inhibited by Pb2+ or Al3+. These results argue against the participation of an Fe2+-Fe3+-O2 complex, or a critical 1:1 ratio of Fe2+ to Fe3+, in the initiation of lipid peroxidation in liposomes and rat-liver microsomes.
TL;DR: The characterization of a unique stromal cell line derived from mouse bone marrow (MBA‐15), which expresses osteoblastic phenotype in vitro and forms bone in vivo, is reported, indicating that the MBA‐15 cell line possesses osteoclastic features in vivo and osteogenic capacity in vivo.
Abstract: Marrow stroma has been shown to have osteogenic potential. Here we report the characterization of a unique stromal cell line derived from mouse bone marrow (MBA-15), which expresses osteoblastic phenotype in vitro and forms bone in vivo. More than 70% of cells in culture were histochemically positive for alkaline phosphatase. The enzyme levels were enhanced threefold when cultures were treated with dexamethasone. Gel electrophoresis of [3H]-proline-labeled cultures showed that MBA-15 cells produced only type I collagen. These cells were responsive to PTH, as indicated by a 50-fold increase in intracellular cAMP. Prostaglandin E2, but not calcitonin, stimulated cAMP up to 70-fold. When cultures were grown to confluence and fed daily with ascorbic acid and beta-glycerophosphate, the cells formed a Von Kossa positive, thick extracellular matrix, shown to contain hydroxyapatite crystals. MBA-15 cells produced mineralized bone when implanted in diffusion chambers. These results indicate that the MBA-15 cell line possesses osteoblastic features in vitro and osteogenic capacity in vivo.
TL;DR: The data suggest that ethanol feeding causes a marked alteration of vitamin E metabolism in the liver and that the combination of ethanol with a low‐vitamin E intake results in a decrease of hepatic α‐tocopherol content which renders the liver more susceptible to free radical attack.
TL;DR: Chitosan was progressively reabsorbed by the host, with very satisfactory clinical recoveries of the 52 defects treated, for which tooth mobility and pocket depths were significantly reduced.
TL;DR: The combination of DT diaphorase and SOD is an efficient system for maintaining cDAoQ in its fully reduced state, a prerequisite for detoxication of the quinone by conjugation with sulfate or glucuronic acid.
TL;DR: In this paper, a controlled anodic growth of polyaniline, polyphenol and polypyrrole films is exploited for changing their permeability to solute species, and fine molecular weight cutoffs are obtained by varying the electropolymerization time or monomer concentration.
TL;DR: Rainbow trout may survive bacterial challenge and improve humoral antibody production when fed 5 or 10 times growth requirement levels of vitamin C, directly related to vitamin C intake.
TL;DR: Investigation in isolated human neutrophils utilizing a new ascorbic acid assay, which combined the techniques of high performance liquid chromatography and coulometric electrochemical detection found accumulation was mediated by a high affinity and a low affinity transporter, both of which were saturable and temperature dependent.