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

Vitreous replacement with air, pure octafluorocyclobutane (C4F8), and mixtures of 40% C4F8 and 60% air was done in owl monkeys to determine ocular toxicity and duration of gas within the vitreous compartment. Large volumes of gas mixture and pure C4F8 caused posterior subcapsular cataract formation. Pure C4F8 expands in the vitreous within 24 to 48 hours. A 1.0-ml mixture of 40% C4F8 and 60% air lasted 12.7 days and did not cause ocular changes. However, anterior chamber aqueous replacement with pure C4F8 or gas mixture resulted in cataract production. Twenty-four and fourty-eight hours after injection of 0.1-ml pure C4F8 in the vitreous of experimental rabbits, presence of oxygen, nitrogen, and carbon dioxide was shown by gas chromatographic analysis. This finding supports the hypothesis of volume expansion secondary to diffusion of above-mentioned gases inside the C4F8 gas bubble.
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PMID:Octafluorocyclobutane in vitreous and aqueous humor replacement. 80 78

After listing the bibliography, the author sugests cases in which neuroleptanalgesia is specially advisable in ophthalmic surgery, mainly in delicate and not too long operations (cataract, glaucoma a.s.o.). In cases of ocular hypertension "Diamox" is previously injected. In the premedication "Valium", and in some patients "Fentanest" and "Droperidol". During surgery the patient breathes spontaneously; oxygen is provided by means of a nasopharyngeal sound. In cataract operations akinesia is recommended. Neuroleptanalgesia has been employed in 140 eyes, mainly in cataracts (80 cases) and chronic simple glaucoma (40 cases).
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PMID:[Neuroleptanalgesia in ophthalamic surgery (author's transl)]. 89 89

Warburg experiments showed the oxygen consumption by lens epithelium and iris tissue without and after addition of 4 mg methylprednisolone to 100 cc medium. In the last case the O2-uptake of the epithelium seemed diminished, that of the iris tissue showed significantly reduced to 50%. The determination of the consumption of glucose was done by measuring its level in the medium before and after a 5 day's incubation, without and after addition of 4 mg-% of methylprednisolone, by means of the "Merckotest". The consumption of the epithelia lowered to 1/6; contrarily rose that of the iris tissue significantly to the double amount. The metabolism of the iris tissue showed a good adaptation in compensating a lower respiratory activity by a augmented glycolysis, which is impossible to the lens epithelium. This may be one of the factors inducing a cortisonic cataract.
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PMID:[The influence of cortisone upon the metabolism of surviving lens epithelia and iris tissue (author's transl)]. 108 50

The growth of lens epithelium and iris tissue was studied by biomicroscopy and electronmicroscopy, its velocity measured. With the Warburg-method it was possible to show the oxygen-uptake of both tissues without and after addition of different substances. Pilocarpine lowered the O2-uptake of the epithelia to less than 1/3 of its normal value, whilst it raised that of the iris to the double amount. Napthochinone inhibited the O2-uptake of both tissues to little more than half of the normal level. The least differences as compared to the controls showed methyl-prednisolone: it lowered scarcely the O2-uptake of the epithelium, and the O2-uptake of the iris to almost half the normal rate. The author concludes that cataract developes, if oxygen-uptake of lens epithelium and iris tissue are reduced in the same way without any possibility of compensation. Under certain conditions this cell-biological method may be employed to detect cataractogenous substances.
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PMID:[Studies on tissue cultures from calf eyes]. 123 35

This study was undertaken to investigate the endocrine stress response during cataract surgery in local anaesthesia (LA) with or without additional sedation with midazolam (Dormicum). 20 patients for cataract surgery in LA were randomly allocated to the midazolam-group (before injection of LA, sedation with single doses of 1 mg midazolam until the patient was sleeping, but awakeable), and to the control-group without sedation. Premedication and LA were standardized. The investigation was performed at 7 measuring points starting at the arrival in the preparation room up to 30 min after surgery. Adrenaline in plasma was significantly lower in the midazolam-group. Intraoperatively, adrenaline increased in the control-group and decreased in the midazolam-group. In time course, noradrenaline in plasma decreased in the midazolam-group, in contrast to the control-group. With respect to ADH, ACTH and cortisol, no significant differences were found in group levels or time course, and concentrations remained within normal range. In contrast to the control-group, mean arterial pressure decreased in the midazolam-group during the course of time. There were no differences in heart rate or arterial oxygen saturation between the two groups. Local anaesthesia and premedication were sufficient to prevent psychic and surgical stressors. The slight sympathoadrenergic response in the control-group was significantly reduced by small doses of midazolam. Thus, a careful supplementation of local anaesthesia with midazolam appears advantageous for patients with cardiovascular disorders.
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PMID:[Endocrine stress response in cataract operations with local anesthesia]. 131 23

Cultured rabbit lenses were irradiated with UV (311 nm peak; 295-340 nm) for 30 to 60 min. The entire spectrum lies in the near-UV, the major component is UVB, with a minor portion (25%) of UVA, and is henceforth referred to as near-UV(B). Posterior irradiation caused no cataract and no significant ionic imbalances compared to anterior irradiation, which caused opacification and marked changes in sodium and calcium concentrations. Anterior irradiation also resulted in reduced Na/K-ATPase activity in the epithelium. ATPase activity was not immediately inhibited; rather, only after culture was enzyme activity reduced. The concentration of reduced glutathione (GSH) decreased rapidly in the epithelium and more slowly in the underlying lens fibers. Loss of GSH was more rapid and extensive when irradiation occurred in the presence of oxygen. Irradiation under anaerobic conditions resulted in opacification but was considerably less extensive than when irradiation of lenses occurred in the presence of 7% oxygen. Near-UV(B) damage following anaerobic irradiation and 20 hrs of culture resulted in an increase in sodium levels and loss of GSH; calcium levels were not significantly elevated. Since irradiation of tryptophan solutions produced small amounts of hydrogen peroxide, the possibility of hydrogen peroxide-mediated damage was investigated but no role could be substantiated. Peroxide detoxification by the epithelium of near-UV(B) cataracts was observed, as measured by its ability to eliminate hydrogen peroxide added as a bolus.
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PMID:Mechanisms involved in cataract development following near-ultraviolet radiation of cultured lenses. 132 94

The relationship between free oxygen radicals and cataract formation has been discussed. The behavior in lenses of the enzyme superoxide dismutase (SOD), which eliminates active oxygen, and glutathione (GSH), which has a defensive action against cataract, were investigated. SOD activity in human cataractous lenses and in porcine lenses was measured by electron spin resonance spectrometry. GSH was measured by high performance liquid chromatography. SOD and GSH significantly decreased in human lenses with senile cataracts as the cataracts advanced. The SOD and GSH values showed a positive correlation. The SOD activity in human lenses was localized dominantly in the lens epithelium and was also found in the shallow layer of the cortex. SOD activity appears to act as a barrier against photooxidation.
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PMID:Superoxide dismutase activity in cataractous lenses. 133 22

Since many years experimental evidences have suggested an association between nutrition and lens opacities. A dietary deficiency of antioxidants and reactive oxygen scavengers may be involved in the pathogenesis of the "idiopathic" human senile cataract, as it has been demonstrated in some experimental cataracts. We tested the levels of ascorbic acid (vit. C), alpha-tocopherol (vit. E), reduced glutathione (GSH) and malondialdehyde (MDA) in the plasma or in the red blood cells (RBC) of 42 patients who were affected by surgically significant cataract and of 40 age-matched controls. Plasma vit. C mean level was 4.46 gamma/ml in cataracts and 4.62 gamma/ml in controls, while vit. E level was 7.70 and 7.09 gamma/ml respectively. RBC GSH was found to be 342 gamma/ml in cataracts and 346 in controls, while the MDA content was 4.06 picoMol/ml and 4.08 picoMol/ml respectively. The level of each tested nutrient or metabolite was not found to be statistically different between cataractous patients and controls, nor any significant trend was found to be present when the nutrients and metabolites were correlated to each other. Our results do not support the hypothesis of a nutritional deficiency in human senile cataracts. However, a defect in the antioxidative metabolism pathways could be present either systemically or at lens level.
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PMID:Cataract risk factors: blood level of antioxidative vitamins, reduced glutathione and malondialdehyde in cataractous patients. 136 41

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

The function of the eye lens is to collect and focus light on the retina. To do so, it must remain clear during the decades of life. Upon aging, lens constituents are damaged and precipitate in opacities called senile cataracts. Laboratory and epidemiologic data indicate that the damage is due in part to light and active forms of oxygen. Antioxidant nutrients - ascorbate, carotenoids, and tocopherol - appear to offer protection against cataract. Fifty million persons worldwide are blind due to cataract, and, in the U.S., there are 1.2 million cataract surgeries performed at an annual cost (including physician visits) of over $3.2 billion. It has been estimated that a 10-year delay in the development of cataract would eliminate the need for half the surgeries. Since it will not be possible to replace most of the damaged lenses, it is essential to determine the efficacy of supplying adequate levels of antioxidant nutrients early in life to preserve lens function.
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PMID:Effect of photooxidation on the eye lens and role of nutrients in delaying cataract. 145 May 91


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