Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0086543 (cataract)
 29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Cataract formation in streptozotocin-induced diabetes in rats was reduced by approximately 85% when a diet rich in maize oil (300 g/kg diet) (fat diet) was given, thus confirming results of earlier studies. However, the concentration of sorbitol in the lens of diabetic animals remained high, the values for diabetic rats given the standard diet and the fat died being 65 and 40 mumol/g protein respectively. 2. With the standard diet, the fatty acid profile of the triglycerides of the epididymal fat pads was characterized by a greater relative proportion of saturated fatty acids for the diabetic animals compared to that for the normal animals. The fat diet moderated the tendency towards saturation in the diabetic animals. 3. The fat diet had other effects on the diabetic animals; these included a reduced mortality rate, increased body-weight, a decrease in the daily water intake, and in the daily urinary excretion of glucose and urea. 4. In the diabetic animals the fat diet had no effect on the specific activities in the liver of hexokinase (EC 2.7.1.1), glucokinase (EC 2.7.1.2), phosphofructokinase (EC 2.7.1.11) and pyruvate kinase (EC 2.7.1.40). However, the specific activity of glucose-6-phosphatase (EC 3.1.3.9) was reduced, while that of malate dehydrogenase (decarboxylating) (NADP) (EC 1.1.1.40) was increased. The NAD+:NADH ratio, as calculated from liver pyruvate and lactate concentrations, tended to increase. 5. The results suggested that the fat diet moderated the long-term metabolic effects of diabetes.
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PMID:The effect of an unsaturated-fat diet on cataract formation in streptozotocin-induced diabetic rats. 13 11

Senile nuclear cataractous lenses were divided into three groups of increasing nuclear color. These groups were considered as successive stages in the development of senile nuclear cataract. The cortex and the nucleus of normal and cataractous lenses were separated into water-soluble, urea-soluble and urea-insoluble fractions. Fractionation on a Sephadex G-200 column of the water-soluble components revealed five protein fractions for both cortex and nucleus. Only minor quantitative differences in polypeptide chain composition were found by isoelectric focusing between corresponding protein fractions isolated from normal and cataractous lenses. The weight percentages of the water-soluble, urea-soluble, and urea-insoluble fractions of cortex and nucleus from the normal and cataractous lenses were determined. A decrease of the amounts of the water-soluble and urea-soluble fractions and a concomitant increase of the urea-insoluble fraction were observed in the nucleus as a function of cataract development. Lens wet weight and protein content did not change significantly. The carbohydrate content of the urea-soluble fractions increased, that of the urea-insoluble fraction decreased. A striking decrease of the phospholipid content in the urea-insoluble fraction was found.
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PMID:Protein changes in the human lens during development of senile nuclear cataract. 93 70

Short-term incubation of bovine alpha-crystallin with ascorbate alters the protein conformational stability. The denaturation curves with urea and guanidinium-chloride show different patterns, suggesting a deviation from a two-state mechanism owing to the presence of one or more intermediates in the unfolding of ascorbate-modified alpha-crystallin. Furthermore, the latter protein profiles are shifted to lower denaturant concentrations indicating a destabilizing action of ascorbate, which is capable of facilitating protein dissociation into subunits as demonstrated by gel filtration with 1.5 M-urea. The decrease in conformational stability cannot be ascribed to any major structural alteration, but rather to localized changes in the protein molecule. In fact, no difference between native and ascorbate-treated alpha-crystallin can be detected by amino acid analysis but perturbation of the tryptophan and tyrosine environment is indicated by alterations in intrinsic fluorescence. Furthermore, turbidity and light-scattering measurements suggest an involvement of the lysine side chains, since aggregability patterns with acetylsalicylic acid are significantly altered. The ascorbate-destabilizing effect on the conformational stability of alpha-crystallin, probably exerted through oxidative modification of amino acid residues and/or the formation of covalent adducts, provokes unfavourable steric interactions between residues along the polypeptide chains, thus favouring aggregation and insolubilization of crystallins which can lead to cataract formation, as also demonstrated by proteolytic digestion patterns which show a lower rate of degradation of the ascorbate-modified alpha-crystallin.
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PMID:Conformational stability of bovine alpha-crystallin. Evidence for a destabilizing effect of ascorbate. 141 62

Plasma membrane with its associated extrinsic proteins was isolated from normal and cataractous rat lenses by centrifugation of the total water insoluble fraction from homogenized lenses on a discontinuous sucrose gradient. Membrane, which we call "native" membrane, was recovered mainly from the 25/45% sucrose interface. Development of the experimental U18666A cataract resulted in plasma membrane shifting to higher density (the 50/55% sucrose fraction) and great increases in the urea soluble protein content of the lens. At early stages of cataract development, most of the increased urea soluble protein was membrane associated, presumably as extrinsic protein. With advancing cataract, most of the urea soluble protein appeared in an essentially membrane-free pellet fraction. The urea soluble protein associated with the cataract membrane was shown by combined IEF, SDS-PAGE, Western blotting, amino acid compositional analysis and protein sequence determinations to be mainly composed of modified alpha- and beta-crystallins. Alpha A-crystallin truncated by not more than 27 residues from the carboxyl terminus plus beta b1 crystallin truncated by 49 residues from the amino terminus were conclusively identified. In addition to beta b1, a population of six alpha-crystallin derived polypeptides were specifically enriched in the cataract membrane fraction. Four of these six alpha-crystallins appear to be truncated from their carboxyl terminus, a modification which should have increased their hydrophobicity. The pellet fraction, which accumulated in the lens nucleus as the cataract advanced, was enriched in urea soluble gamma-crystallin derived polypeptides. We suggest that protein insolubilization in this experimental cataract involves the selective and tight association of principally modified alpha-crystallins to the fiber cell plasma membrane.
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PMID:Selective association of crystallins with lens 'native' membrane during dynamic cataractogenesis. 142 24

Urea-soluble and intrinsic membrane proteins from normal and galactose cataractous rat lenses were analyzed by SDS-PAGE. During cataract formation, MP22 increased whereas MP26 decreased almost to nil and MP24 emerged. However, the relative amount of MP18 remained essentially unchanged. These results suggested a conversion of MP26 to MP22 during cataract formation. We also observed the changes in the relative abundance of the polypeptides of the urea-soluble fraction with cataractogenesis.
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PMID:Changes of urea-soluble and intrinsic membrane proteins in rat lenses during the formation of galactose cataract. 147 76

In an effort to elucidate the molecular changes which take place in the human lens with the onset of nuclear cataract, the urea-insoluble protein fraction, solubilized with dithiothreitol, was digested with trypsin. Tryptic peptides separated by HPLC, were examined by both mass spectrometry and Edman degradation. A pentapeptide Gly-Glu-Tyr-Pro-Arg which is contained within the beta-crystallin sequence was isolated. This finding provides direct evidence that beta-crystallin is present in the urea-insoluble protein fraction which is known to be characteristic of human nuclear cataract lenses.
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PMID:Direct approach to identification, at the molecular level, of modified proteins in human nuclear cataractous lenses: beta-crystallin is a component of the urea-insoluble protein fraction. 147 78

Studies were carried out comparing the ability of urea extraction and sonication to solubilize the water-insoluble (WI) protein fraction from human lens tissue. Sonication and urea extraction were able to solubilize greater than 80% of the insoluble protein whether whole lenses or lens nuclei were used. This was true for normal lens and +1 cataracts; however, only 60% solubilization was obtained with the WI fraction from more advanced cataracts. Equal aliquots of a WI fraction from both pooled normal and pooled cataract lens nuclei were solubilized with and without reducing agents. The addition of dithiothreitol (DTT) had no significant effect on solubilization of the normal lens WI fraction. DTT did increase the protein solubilized from the cataract WI fraction by 30% with urea extraction; however, no increase was seen with sonication. When sodium borohydride was used as the reducing agent, essentially the same results were obtained. The solubilized protein populations were identical by SDS-PAGE and amino acid analysis. The addition of reducing agents had no effect on the amino acid content of the solubilized proteins with the single exception of lysine. This amino acid was markedly decreased in the proteins extracted in the presence of 40 mM sodium borohydride, but not with DTT. These data suggest that the borohydride not only increased the amount of protein solubilized, but likely also stabilized glycated lysine residues during the acid hydrolysis. Therefore, sonication readily provides a soluble preparation of the WI proteins from normal and cataract lens nuclei without the need for denaturing agents, however, disulfide-linked and lysine modified crystallins were best solubilized with urea.
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PMID:Studies on the solubilization of the water-insoluble fraction from human lens and cataract. 148 36

L-buthionine-S,R-sulfoximine (BSO), a specific inhibitor of GSH biosynthesis, was administered four times daily to mouse pups on post-natal days 7 and 8, inducing initiation of opacification on day 9. The initial progression of the cataract (less than 24 hr) was divided into four stages: (1) developing floriform; (2) mature floriform; (3) degenerate floriform; and (4) amorphous translucent cataract. Following this, dense corticonuclear opacities developed within several days. Two-dimensional gel electrophoresis of water-soluble whole lens extracts indicated that the most rapid early cataractous changes, occurring mainly during stage 2, were loss of the two major components of the heavy beta-crystallin fraction, a 31-kDa basic polypeptide and an acidic component at 27 kDa, concomitant with the appearance of new species at 30 and 25 kDa. This was followed by more extensive modification of both alpha and beta-crystallins during stages 3 and 4 and the appearance of abnormal species at 26, 19 and 18 kDa, which were slightly more acidic than the major normal alpha A-crystallin polypeptide. The gamma-crystallin components, relatively unaffected at stage 4, were then lost rapidly as dense opacities ensued. By contrast with the water-soluble fraction, the normal day 9 urea-soluble fraction was deficient in gamma-crystallin polypeptides and enriched in anodic components whose relative electrophoretic mobilities were similar to those reported previously for phosphorylated bovine alpha A-crystallin and several cytoskeletal polypeptides. At stage 4 of the cataract, the modifications of normal alpha and beta-crystallin components in the urea-soluble fraction paralleled those in the water-soluble fraction, but the products seen were more numerous. In addition, the cytoskeletal proteins were no longer detectable. Substantial increases in lens Ca2+ that precede all of the above changes in lens polypeptide composition suggest that Ca(2+)-activated proteolysis may play a major role in development of BSO cataracts.
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PMID:Progressive modifications of mouse lens crystallins in cataracts induced by buthionine sulfoximine. 162 46

The lens nucleus has various colors, sizes and hardness. It is of significance to investigate the components of the nucleus and the factors participating in the mechanism of development of cataract. Recently, the author demonstrated that free lipid in cataract does not undergo quantitative change, compared with that in the normal lens but that the cholesterol and phospholipid in the nucleus and cortex increase in the urea-soluble protein fraction. An assay of lipid-protein complex (lipoprotein) was made and also quantitative changes were studied using nucleus with different colors in senile cataract. The study was made by the technique developed by the author because no other experimental procedure has been established for lipoprotein in the tissue. Chylomicron, VLDL, LDL and HDL were identified in lipoprotein. The amount of lipoprotein decreased as the color of the nucleus became dense, but only HDL among these increased. The catabolism of lipoprotein advanced when the color of nucleus changed from light yellow to brown, suggesting that disorder in mass transfer is caused.
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PMID:[The biochemical study in the nucleus opacification of the senile cataractous lens]. 189 58

The polypeptides in portions of human lens epithelium from individuals of various ages were resolved by two-dimensional (2D) gel electrophoresis. The epithelium was divided into a central area of 12.5 mm2, a surrounding area of 50.2 mm2, and an area which was outside of this region. The proteins were solubilized in urea and run on gels to determine if differences existed in the major polypeptides of the lens epithelium with regard to position in the lens as well as if differences might occur with age. The patterns obtained were remarkably similar in regions of the epithelium examined. The results also demonstrated that the composition of the major polypeptides were not substantially altered in the adult epithelium with age. Two-dimensional gels of proteins from a 3-month-old specimen prepared in a manner similar to that used during extracapsular cataract extraction were also similar to the other samples; however, this sample contained slightly increased staining of proteins greater than 30 kD.
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PMID:Two-dimensional gel electrophoresis of human lens epithelium: a study of spatial protein patterns and aging. 206 30


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