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Query: UMLS:C0086543 (cataract)
 29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tocopherols and tocotrienols (vitamin E) and ascorbic acid (vitamin C) as well as the carotenoids react with free radicals, notably peroxyl radicals, and with singlet molecular oxygen (1O2), this being the basis of their function as antioxidants. RRR-alpha-tocopherol is the major peroxyl radical scavenger in biological lipid phases such as membranes or low-density lipoproteins (LDL). L-Ascorbate is present in aqueous compartments (e.g. cytosol, plasma, and other body fluids) and can reduce the tocopheroxyl radical; it also has a number of metabolically important cofactor functions in enzyme reactions, notably hydroxylations. Upon oxidation, these micronutrients need to be regenerated in the biological setting, hence the need for further coupling to nonradical reducing systems such as glutathione/glutathione disulfide, dihydrolipoate/lipoate, or NADPH/NADP+ and NADH/NAD+. Carotenoids, notably beta-carotene and lycopene as well as oxycarotenoids (e.g. zeaxanthin and lutein), exert antioxidant functions in lipid phases by free-radical or 1O2 quenching. There are pronounced differences in tissue carotenoid patterns, extending also to the distribution between the all-trans and various cis isomers of the respective carotenoids. Antioxidant functions are associated with lowering DNA damage, malignant transformation, and other parameters of cell damage in vitro as well as epidemiologically with lowered incidence of certain types of cancer and degenerative diseases, such as ischemic heart disease and cataract. They are of importance in the process of aging. Reactive oxygen species occur in tissues and cells and can damage DNA, proteins, carbohydrates, and lipids. These potentially deleterious reactions are controlled in part by antioxidants that eliminate prooxidants and scavenge free radicals. Their ability as antioxidants to quench radicals and 1O2 may explain some anticancer properties of the carotenoids independent of their provitamin A activity, but other functions may play a role as well. Tocopherols are the most abundant and efficient scavengers of peroxyl radicals in biological membranes. The water-soluble antioxidant vitamin C can reduce tocopheroxyl radicals directly or indirectly and thus support the antioxidant activity of vitamin E; such functions can be performed also by other appropriate reducing compounds such as glutathione (GSH) or dihydrolipoate. The biological efficacy of the antioxidants is also determined by their biokinetics.
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PMID:Antioxidant functions of vitamins. Vitamins E and C, beta-carotene, and other carotenoids. 144 60

Data from several national surveys consistently show that American children have lower than recommended intakes of vitamin E, which is reflected in lower than average serum levels. Reduction in dietary fat can further exacerbate the low vitamin E status of children. The consequences of low vitamin E intake may include impaired immune responses, as seen in a study of over 500 Canadian children. Low vitamin E status has been correlated with increased risk of atherosclerosis and cardiovascular disease, cancer, cataract and impaired immune responses in adult populations. Since early signs of chronic degenerative diseases of aging have been seen in autopsies of children, efforts should be made to ensure that prolonged low intakes of vitamin E are avoided in children as well as adults.
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PMID:Vitamin E status of US children. 150 6

Cataract is one of the major causes of age-dependent visual impairment and blindness. The geographic distribution of cataract is known to be associated with the intensity and duration of sunlight--especially of the ultraviolet frequency--at particular places. Exposure of animals and humans to oxygen has also been known to result in cataract formation. Studies described in this communication indicate that the ocular lens is physiologically damaged when exposed to an environment of active species of oxygen, commonly referred to as oxyradicals. Several photochemical and nonphotochemical models have been described. The results suggest that an intraocular generation of active oxygen may constitute a significant risk factor in the overall pathogenesis of senile cataracts. The cataractogenic effect of oxyradicals, however, can be thwarted by nutritional and metabolic antioxidants such as ascorbate, vitamin E, and pyruvate. These agents, therefore, may be useful for prophylaxis or therapy against cataracts.
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PMID:Scientific basis for medical therapy of cataracts by antioxidants. 198 7

The relationship between antioxidant nutrient status and senile cataract was examined in 77 subjects with cataracts and 35 control subjects with clear lenses. Subjects with low (below the 20th percentile) and moderate (20th-80th percentiles) plasma nutrient and nutrient intake levels of vitamin C, vitamin E, and carotenoids were compared with subjects with high levels (above the 80th percentile). The odds ratio (OR) of cortical (CX) cataract among subjects with low plasma carotenoid levels was 7.2 (P less than 0.05) and the OR of posterior subcapsular (PSC) cataract for persons with low plasma vitamin C was 11.3 (P less than 0.10). Low vitamin C intake was associated with an increased risk of CX (OR = 3.7, P less than 0.10) and PSC (OR = 11.0, P less than 0.05) cataract. Subjects who consumed fewer than 3.5 servings of fruit or vegetables per day had an increased risk of both CX (OR = 5.0, P less than 0.05) and PSC cataract (OR = 12.9, P less than 0.01).
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PMID:Epidemiologic evidence of a role for the antioxidant vitamins and carotenoids in cataract prevention. 198 9

Vitamin E is well accepted as nature's most effective lipid-soluble, chain-breaking antioxidant, protecting cell membranes from peroxidative damage. Free-radical-mediated pathology has been implicated in the development over time of degenerative diseases and conditions. This paper reviews the current research on the protective role and requirements for vitamin E and the other antioxidants in preventing or minimizing free-radical damage associated with specific diseases and lifestyle patterns and processes, including cancer, aging, circulatory conditions, arthritis, cataract, pollution, and strenuous exercise. While awaiting results of further human studies, research evidence suggests that an adequate intake of vitamin E and the other antioxidants can provide protection from the increasingly high free-radical concentrations caused by air pollutants and current lifestyle patterns.
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PMID:Protective role of vitamin E in biological systems. 201 17

Although cataract of the eye lens is a known late effect of ionizing radiation exposure, most of the experimental work to date has concentrated on single, acute high doses or multiple, fractionated, chronic exposures. Many papers have dealt with biochemical alterations in metabolism and cellular components, with microscopic and electron microscopic lesions to the epithelial and cortical layers, and with clinical cataract formation. However, the minimum cataractogenic dose for rats has for many years been considered to be about 2 Gy for a single, acute dose of low LET radiation. Our purpose in designing this pilot study was three fold: firstly, to determine whether any physical damage could be detected after low, acute exposure to neutron radiation (10 and 100 cGy); secondly, to compare the relative effectiveness of fast (14 MeV) neutrons with gamma-rays; and thirdly, to investigate the possibility that vitamin E could protect the lenses from radiation damage. The results revealed that morphological damage was already discernible within minutes after exposure to neutrons or gamma-rays, that it became greater after 24 hours, that neutrons were more damaging than gamma-rays, and that vitamin E could effectively reduce the cataractogenic damage induced by ionizing radiation. Control, non-irradiated lenses with or without vitamin E, either in vivo or in vitro, showed no damage. Also, it appeared that in vitro irradiation was more damaging to lenses than in vivo irradiation, so this culture technique may prove to be a sensitive tool for assessing early damage caused by ionizing radiation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Radiation cataractogenesis induced by neutron or gamma irradiation in the rat lens is reduced by vitamin E. 208 Apr 28

Age-related cataract is a condition characterized by multiple mechanisms and multiple risk factors. The mechanisms that bring about a loss in transparency include oxidation, osmotic stress, and chemical adduct formation. Risk factors for cataract include diabetes, radiation (ultraviolet B, x-ray), certain pharmaceutical substances, certain nutritional states, and possibly acute episodes of dehydration. Interaction occurs between and among mechanistic factors and risk factors. Thus nutrition must be considered as one part of a tapestry of intertwined events and responses. Certain experimental models for nutritional cataract have been useful for study of the cataractogenic process but are probably not important factors in the human disease. Little current evidence supports significant roles in human senile cataract for imbalances of tryptophan or other amino acids, deficiencies of calcium or selenium, or excessive intake of selenium. Overconsumption of galactose is likely to be hazardous only in subjects with genetic inability to metabolize this sugar. Vitamins with antioxidant potential (riboflavin, vitamin E, vitamin C, carotenoids) deserve further research scrutiny to ascertain their significance in cataract etiology. Excessive caloric intake needs to receive added emphasis as a factor contributing to cataract. Diabetes increases the likelihood of cataract three- to four-fold. Obesity, defined as more than 20% overweight, is considered a major risk factor for non-insulin-dependent, or type II, diabetes (69, 73). Weight control can be recommended as a prudent, safe, economic, and effective means of lowering risk probability for diabetes and the associated complication of cataract.
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PMID:Nutritional factors in cataract. 220 Apr 64

Sibling cases of familial vitamin E deficiency accompanied by ataxia, polyneuropathy and mental retardation were reported. Case 1 was a 37-year-old male who developed progressive gait disturbance, deformity of the feet and head tremor from childhood, after normal delivery and development of early childhood. On physical examination, he had cataract, high arched palate and pes cavus. Neurological examination revealed mental retardation (WAIS 68), scanning speech, muscular atrophy of the face and extremities with predominance in the lower limbs, absent Achilles tendon reflex, disturbance of superficial and deep sensation predominant in distal limbs, and marked gait ataxia. Ataxia was both cerebellar and sensory in nature. Laboratory data of the blood showed no significant abnormalities including blood glucose and vitamin B12 except a markedly low level of serum vitamin E. The brain CT scan revealed severe cerebellar atrophy and marked dilatation of the cisterna magna and the subarachnoid space around the cerebellum. Motor nerve conduction velocity in the leg was decreased. Biopsy specimen from the quadriceps muscle showed neurogenic atrophy. Sural nerve biopsy revealed decrease in large myelinated fibers with axonal degeneration and regeneration. Oral administration of alpha-tocopherol acetate, 600 mg per day, diminished ataxia significantly. Based on lysosomal enzyme activity in leukocytes, clinical and laboratory examination, lipidosis or spinocerebellar degeneration was excluded. Chronic lipid malabsorption or beta lipoprotein deficiency which can cause decrease in vitamin E absorption, was not recognized. On oral loading with 2 g of alpha-tocopherol acetate, the decrease rate of serum vitamin E was normal. Consequently the low vitamin E was considered to have resulted from selective impairment of vitamin E absorption.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Familial idiopathic vitamin E deficiency associated with cerebellar atrophy]. 226 7

In this study we have investigated the oxidative metabolism of red cells (RBC), plasma, serum and aqueous humour of healthy subjects and of age-matched cataractous patients with and without chronic renal failure (CRF). Reduced glutathione (GSH) levels in RBC were lower in CRF patients than in the other groups. Oxidized glutathione (GSSG) plasma levels in CRF patients were higher than those of controls and cataractous subjects. The activity of the enzyme glucose-6-phosphate dehydrogenase in RBC was significantly reduced in CRF patients with respect to the other two groups. The levels of malondialdehyde (MDA) in RBC and in lens were about twice in CRF patients compared with the other two groups. The plasma levels of vitamin E were diminished in CRF patients; on the contrary, the biological liquid oxidant activity (BLOA) of serum in CRF patients was significantly higher than in controls and in cataractous patients without CRF. Cataractous patients with and without CRF showed similar levels of GSH in aqueous humour; on the contrary, the content of GSSG was significantly higher in CRF patients. Our findings seem to demonstrate that CRF patients are exposed to oxidative stresses that could probably act synergistically with uraemia and carbamylation of lens proteins. This synergism could explain why CRF represents a relatively high risk factor for cataract.
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PMID:Systemic human diseases as oxidative risk factors in cataractogenesis. II. Chronic renal failure. 226 73

Clinicopathological studies were performed on 156 lenses of human senile cataract obtained by cataract operations between 1970 and 1988. It became clear that the aging influences the functional destruction of the equatorial region, the pathological changes of the bow area, and changes of the extralens environment. After operation for the atrophic type of the posterior subcapsular cataract, aftercataract easily develops on the intraocular lens and this requires treatment. Long-term observations were carried out in 180 Wistar male rats under the same laboratory condition and histological studies were performed. The similarities between the senile Wistar rat cataract and the human senile cataract indicate that the Wistar rat cataract is useful as a model for studying the human senile cataract. These rats were initially classified into six groups (control, vitamin E diet, EPC eye drops, catalin eye drops and reduced catalin eye drops). To study the effects of the agents (vitamin E, ARI, EPC, catalin, reduced catalin) on the cataract in senile Wistar rats the mean cell density of lens epithelia were measured at 2 or 3-month intervals. There were no statistically significant differences in treated groups and the control group. The results suggest that these agents affect another factor of lens apart from the proliferative activity of lens epithelial cell. Effects of anti-cataract agents were investigated using cultured lens epithelial cells. When cultured rat lens epithelial cells were incubated in medium containing selenite, super-oxide dismutase (SOD) activity and GSH in the cells markedly decreased, and GSSG was markedly increased. When cultured rabbit lens epithelial cells were incubated in medium contained selenite and glutathione, SOD activity was maintained normal level. When cultured lens epithelial cells were incubated in medium contained selenite and pirenoxin, SOD activity also maintained a normal level. These results suggest that both glutathione and pirenoxin are effective as anti-cataract agents. Cataracts in spontaneously hypertensive rats (SHR) was investigated on male of Wistar-Kyoto rats (WKY), stroke resistant SHR (SHRSR) and stroke-prone SHR (SHRSP) rats aged 3 to 9 months. Cataracts in these rats were classified as follows: Type 0: no opaciiy, Type 1: nuclear opacity, Type 2: posterior subcapsular opacity, Type 3: nuclear opacity associated posterior subcapsular opacity and Type 4: complete opacity in both lenses. Incidence of cataract in WKY was 2.6%, SHRSR, 76.8% ant SHRSP, 88.2%. Incidence of nuclear opacity was remarkably higher in SHRSP (48.5%). In SHR aged from 3 to 5 months, nuclear opacity was ahead of the appearance of posterior subcapsular opacity which was increased during aging.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[Cataract--clinic and pathology]. 227 35


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