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

Research on the sugar metabolism of the crystalline lens, past and preent, is reviewed. The chief energy source in the lens is the Embden-Meyerhof pathway; respiration and oxidative phosphorylation become more important as the lens ages. The function of the alpha-glycerophosphate cycle is not fully understood. The mechanisms involved in cataract formation, including those of hypoglycemic cataract and osmotic cataracts, are discussed. Sugar cataracts can be delayed or prevented with such aldose reductase inhibitors as flavonoids. By inhibiting aldose reductase, the formation and accumulation of sugar alcohols is stopped. This approach may be useful as a medical therapy for human diabetic senile cataracts.
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PMID:Sugar metabolism in the crystalline lens. 10 Aug 92

In order to determine the advertising practices of ophthalmologists in the United States, and to understand their feelings toward advertising, a multiple-choice survey of 5,000 ophthalmologists (all Fellows of the American Academy of Ophthalmology) was mailed on July 5, 1988. The questionnaire was mailed to an nth-name sample taken from a Zip-sequence mailing list obtained from the Academy. Six weeks after the mailing over 2,000 replies had been obtained. The replies were analyzed using DBase III software. Survey data were crosstabulated so that advertising practices and attitudes could be analyzed with respect to the age of the ophthalmologist, volume of cataract surgeries per month, and geographic location. There seemed to be a direct correlation between cataract surgery volume and tendency to advertise. There was a greater tendency for younger ophthalmologists to advertise. There did not seem to be great geographic variation with respect to advertising practices.
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PMID:Attitudes toward advertising among Fellows of the American Academy of Ophthalmology: 1988. 234 76

The ocular lens, which is continually exposed to light and ambient oxygen, is at high risk of photooxidative damage resulting in cataract. Oxygen free radicals appear to impair not only lens crystallins which will aggregate and precipitate forming opacities but also proteolytic enzymes whose function it would be to eliminate the damaged proteins. Apart from an enzymatic defense system consisting of superoxide dismutase, catalase and glutathione peroxidase against excited oxygen species the lens contains the antioxidant vitamins C, E and presumably beta-carotene as another line of defense. In vitro and in vivo studies in different animal species have demonstrated a significant protective effect of vitamins C and E against light-induced cataract. Sugar and steroid cataracts were prevented as well. Epidemiological evidence in humans suggests that persons with comparatively higher intakes or blood concentrations of antioxidant vitamins are at a reduced risk of cataract development. These positive findings established by several research groups justify extensive intervention trials with antioxidant vitamins in humans using presenile cataract development as a model.
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PMID:Antioxidant vitamins in cataract prevention. 265 16

Sugar cataract formation has been demonstrated to result from lenticular sorbitol accumulation. In the lens, the activity of aldose reductase has been observed to increase with the onset of diabetes, while the activity of sorbitol dehydrogenase decreases. This shift in activities of these two Sorbitol Pathway enzymes favors the increased accumulation of sorbitol. Immunohistochemical studies with antibodies prepared against purified rat lens aldose reductase reveal a striking increase in immunoreactive positive staining for aldose reductase in lenses from diabetic rats. Two weeks after the onset of diabetes, increased immunohistochemical staining for aldose reductase appears beneath the epithelial region where water cleft formation occurs, and the intensity of this staining increases with the formation of vacuoles. By 6-8 weeks, the presence of large vacuoles and areas of liquifaction containing dense immunoreactive stain can be observed. Examination of human cataractous lenses with antibodies prepared against purified human placenta aldose reductase suggest similar increases in immunoreactive staining in the human diabetic lens. Cataractous lenses from diabetic patients revealed increased immunoreactive staining for aldose reductase, which was associated with the presence of vacuoles in both the anterior or posterior superficial cortical layers. Examination of similar vacuole containing regions from non-diabetic cataractous lenses revealed no increase in immunoreactive staining for aldose reductase. These results suggest that the enhanced activity of aldose reductase observed in diabetes is due to an increased amount of enzyme, rather than enzyme activation.
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PMID:Immunohistochemical localization for aldose reductase in diabetic lenses. 310 Apr 73

Morphologic alterations in cortical fiber cell membranes of the developing Emory mouse cataract were studied with scanning, transmission and freeze-fracture electron microscopy. Scanning electron microscopy revealed the extensive formation of prominent ridges on the surfaces of normal-appearing fibers, greatly enlarged degenerating fibers and globular structures in the relatively superficial cortical regions of the cataractous lenses where such a surface pattern was not found in the normal controls. Transmission electron microscopy showed undulating 13 nm pentalamellar structures, which were thinner than 17 nm heptalamellar (or pentalamellar) structures of gap junctions, were distributed within the cell membranes having ridge patterns. Some globular structures were encircled by repeated undulating 13 nm pentalamellar structures and multilamallar membranes. Freeze-fracture studies demonstrated that 13 nm pentalamellar structures consisted of square crystalline arrays of 6 nm intramembrane particles whereas 17 nm heptalamellar profiles showed randomly-packed 9 nm intramembrane particles of typical lens fiber gap junctions. It is suggested that the extensive formation of ridges in the relatively superficial cortical regions of the Emory mouse lenses may be associated with a degenerative process of lens fiber cell membranes during cataractogenesis.
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PMID:Alterations in fiber cell membranes of Emory mouse cataract: a morphologic study. 358 65

The trabeculectomy developed independently by Sugar, Vasco-Posada, Koryllos and Cairns is equivalent to a sinusotomy with an additional cyclodialysis effect if the modified technique suggested by Watson is used. About 309 cases are reported, some of which were followed up for up to 12 years. No late failures or complications were observed. Failures are due to absence of the cyclodialysis effect. Regression of a bleb often occurs without any deterioration in intraocular pressure. The development of aqueous veins and scleral vessels around the incision is not uncommon. The causal relationship between postoperative hypotension and the development or spread of cataract is discussed.
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PMID:[Extended sinusectomy (trabeculectomy with cyclodialysis effect). Late results and analysis of failures]. 372 68

Heretofore, the intracellular accumulation of sorbitol has been associated exclusively with deleterious (cataractogenic) changes in the lens. This study demonstrates a beneficial role for the sorbitol pathway in the rabbit lens, namely that of counteracting extracellular, glucose-derived, osmotic stress with the intracellular production of osmotically active sorbitol. Large and sudden increases in the extracellular glucose concentration lead to dehydration of the lens, a response that can be diminished by intracellular sorbitol and fructose production. These results are discussed in light of the impact (beneficial/detrimental) of aldose reductase inhibitors on the lens. Sugar cataract formation appears to result from continuous, rather than cyclical, activity of a pathway which normally may have a protective function in the lens.
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PMID:Sorbitol production in the lens: a means of counteracting glucose-derived osmotic stress. 380 97

Medical treatment of cataract depends on understanding the mechanism of cataract formation. This is established in sugar cataract, in which sugar is metabolised to sugar alcohol. Sugar alcohol accumulates and the resultant osmotic stress is considered to cause lens fibre damage. The conversion of sugar to alcohol is effected by the enzyme aldose reductase and interest now centres around the use of aldose reductase inhibitors. A controlled clinical trial into the effect of the spirohydantoin Sorbinil in adult diabetic cataract has started at Oxford. Aldose reductase inhibitors may also act on non-diabetic cataract, which is supported by some clinical evidence. The biochemical basis of this and other possible treatments for cataract are outlined.
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PMID:Medical therapy in the prevention of cataract. 393 85

Freeze-fracture electron microscopy of calf lens nuclear cytoplasm undergoing a cold cataract opacification shows the formation of domains within the bulk cytoplasm. The size distribution of these domains (from a few tens of nanometers to a few micrometers) is compatible with previous size evaluations obtained from light scattering experiments for the 'large scattering elements' responsible for cold cataract opacification. In addition, these domains appear to be devoid of crystallins of higher molecular weight and enriched in low-molecular-weight species.
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PMID:Spatial reorganization of low-molecular-weight proteins during cold cataract opacification. 674 82

Sugar cataracts rapidly develop in dogs fed a diet containing 30% galactose. While studies on the formation and progression of these sugar cataracts suggest that they are osmotic in nature and are linked to aldose reductase, sugar cataract formation in the dog to date has not been completely prevented by the administration of aldose reductase inhibitors sorbinil and M79175. To demonstrate that the formation and progression of sugar cataracts in galactose-fed dogs can be dose-dependently inhibited by the administration of aldose reductase inhibitors, 9-month old male beagles were placed on diet containing 30% galactose with/without 10 or 16 mg kg-1 day-1 of M79175 for up to 39 months. Cataract progression in all dogs was followed by periodic slit lamp examination and documented by retroillumination photography. Although large variations in cataract formation and progression were observed, all dogs fed a 30% galactose diet for 39 months developed cataracts. Lens changes were significantly less in galactose-fed dogs treated with either 10 or 16 mg kg-1 M79175 and no cataract formation was observed in 3 of 6 galactose-fed dogs treated with 16 mg kg-1 M79175. These observations confirm that aldose reductase plays a key role in initiating cataract formation in galactose-fed dogs and that cataract formation can be prevented by adequate inhibition of aldose reductase.
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PMID:Dose-dependent prevention of sugar cataracts in galactose-fed dogs by the aldose reductase inhibitor M79175. 953 47


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