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

The composition and origin of the urea soluble polypeptides which accumulate in the U18666A rat-cataract were studied. Chromatography on Sephacryl S-200 in 7.2 M urea separated the USP into 19-20 and 22-26 kDa enriched fractions. The polypeptide composition of these fractions was probed by immunoblotting of IEF and 2-D electrophoresis gels. The cataract USP largely focused at pHs comparable to alpha- and beta-crystallins. Immunoblotting of 2-D gels showed the USP to be composed predominantly of alpha- and beta-derived crystallins; little gamma-polypeptide was detected in the gels. Some of the insoluble alpha-crystallin appeared to be degraded. Changes in the lens WSP which accompanied the increase in USP were also measured. WSP decreased more than USP increased. Decreases in soluble high molecular weight proteins (alpha- plus beta-crystallins) and medium molecular weight proteins (beta-crystallins) were calculated which together could entirely account for the increased USP. An unexpected decrease in the lens soluble low molecular weight proteins (gamma-crystallins) appeared largely due to the selective leakage of gammas from the lens. The protein content of the ocular humors from eyes with cataracts increased 4 fold and contained polypeptides that focused on IEF like gamma-light crystallin and reacted with the gamma-crystallin antiserum. The cause of the protein insolubilization in the U18666A cataract is unknown but could be partially due to increased aggregation of alpha-crystallins secondary to loss of gamma-crystallins from the lens.
 ...
PMID:On the composition and origin of the urea-soluble polypeptides of the U18666A cataract. 224 43

One mm thick layers were reproducibly sliced from the punched-out inner cylinder of bovine lenses. The layers were obtained by a special designed freeze-sectioning device. Biochemical analysis of these layers revealed a detailed picture of the lenticular distribution of the amount of water-insoluble and urea-insoluble fractions. Furthermore, the distribution of the content of glucose, fructose and sorbitol was established. The results clearly show the usefulness of a microsectioning device to obtain layers for subsequent biochemical analysis which may lead to a comprehensive understanding of age- and/or cataract-related alterations within one lens.
 ...
PMID:Biochemical analysis of bovine lens sections obtained by a new sectioning device. 248 16

A single subcutaneous injection of sodium selenite at the dose of 20 mumol/kg body weight induced bilateral nuclear cataracts in suckling rats. This selenite-induced cataract incidence can be increased by pretreating animals with a glutathione synthesis inhibitor. Sodium dodecyl sulfate polyacrylamide electrophoresis of urea-soluble proteins from selenite-induced cataractous lenses showed the appearance of high molecular weight aggregates and decomposed products of lens proteins. These products were found in association with the emergence of a 45 K band. Incubation of water-soluble lens proteins with selenite in vitro produced changes similar to those demonstrated in selenite-induced cataractous lenses. Furthermore, selenite induced the gradual development of opalescence and the oxidation of sulfhydryl in the lens protein solution. Therefore, we presume that the oxidation of lens protein sulfhydryl by selenite is associated with both aggregate formation and the decomposition of lens proteins, and that these changes may provide a partial explanation for the mechanism of selenite cataract.
 ...
PMID:The decomposition and aggregation of rat lens protein induced by selenite in vitro and in vivo. 255 35

The use of diuretic drugs, which previously has been found to be associated with the incidence of cataract, is further investigated to elucidate the nature of the association. Diuretic drugs with different modes of action are considered separately. The degree of association of each correlates with the mean plasma urea level which itself is associated with cataract. However, the association is with cataract in general rather than with any specific type of lens opacity.
 ...
PMID:Diuretic drugs as risk factors in cataractogenesis. 290 8

Nuclear cataract resulting from an overdose of selenite was characterized by a five-fold increase in nuclear urea-soluble protein. The origin of this urea-soluble protein was examined by two-dimensional electrophoresis, immunoblotting with monospecific antisera against rat lens crystallins, and tryptic mapping. Cataractous urea-soluble protein was primarily composed of insolubilized beta- and gamma-crystallin polypeptides. Polypeptides from cataractous urea-soluble protein, and normal beta L-crystallin aggregates were compared by tryptic mapping. Approximately 19% of the urea-soluble protein from opaque nuclei was composed of 24.7 and 24.0 K polypeptides derived by limited proteolysis of 26.5 K beta L-crystallin polypeptide. Incubation of 26.5 K beta-crystallin polypeptide with purified rat lens calpain II in vitro caused production of fragments with similar molecular weights to polypeptides found in cataractous lenses. These results support the hypothesis that proteolysis may contribute to formation of urea-soluble protein in selenite cataract.
 ...
PMID:Origin of urea-soluble protein in the selenite cataract. Role of beta-crystallin proteolysis and calpain II. 303 41

The denaturation behavior of bovine lens gamma-crystallin fractions II, III, and IV and their susceptibility to proteolysis in vitro was compared to determine whether differences in their stability could play a role in cataract formation. Tertiary and secondary structure changes induced by increasing concentrations of urea, guanidine hydrochloride, and sodium dodecyl sulfate and by increasingly alkaline pH were followed by near-UV and far-UV circular dichroism, Trp fluorescence emission, and exposure of sulfhydryl groups. Major differences were found in the denaturation and proteolysis behavior of the three gamma-crystallin fractions. In general, the unfolding of gamma-II and gamma-III crystallins is rather gradual, suggesting the presence of intermediate unfolding states; in contrast, the order-disorder transition of gamma-IV crystallin is abrupt. The gamma-IV crystallin fraction is the most stable in urea and guanidine hydrochloride, but is most susceptible to nonspecific proteolysis and alkaline pH denaturation. Differences in denaturation and proteolysis behavior are attributed to the inherent differences in the tertiary structures of these crystallins.
 ...
PMID:Structure and stability of gamma-crystallins. Denaturation and proteolysis behavior. 329 26

During 1981 - 1986 3 women with similar complaints were seen. Their symptoms were tetany and congestive cardiac failure (CCF) without a previous history of cardiac disease or alcohol abuse. One patient did have a history of cataract removal and epilepsy and all 3 had ECGs showing prolonged Q-T intervals and echocardiograms consistent with the diagnosis of cardiomyopathy. Biochemical profiles were similar: hypocalcaemia, hyperphosphataemia and normal serum urea levels. Parathyroid hormone levels were inappropriately low in all 3 cases. The tetany and CCF responded to calcium +/- magnesium infusions together with diuretics and in 2 cases, digoxin therapy. All 3 patients are well at present, and are controlled on 1-alpha-hydroxyvitamin D3 and calcium supplements.
 ...
PMID:Cardiac dysfunction in primary hypoparathyroidism. A report of 3 cases. 334 Sep 68

Individual crystallins, urea-soluble and urea-insoluble proteins were isolated from the nucleus and cortex of types I-IV cataractous lenses and normal lenses. The levels of protein sulphydryls (P-SH), disulphides (S-S), as well as surface (F-SH) and buried (S-SH) in these proteins were determined by reaction with 5, 5'-dithiotris- (2-nitrobenzoic acid) or performic acid oxidation followed by amino acid analysis. During nuclear colour development there is a progressive decrease in the sulphydryl content of the crystallins. In the nuclei of advanced cataractous lenses, the P-SH decreases to 10% of the levels found in the normal nucleus. Similar but smaller changes take place in the cortex. No specific changes were found between the crystallins, with the exception of beta S crystallin. The cysteine remains constant in all lens types suggesting no higher oxidation products are formed. There is a significant shift in the distribution of cysteine in the nucleus of type III and IV lenses. Urea-insoluble proteins are the predominant species, accounting for about 70% of the total cysteine pool. This is consistent with the accumulation of modified insoluble polypeptides during senile nuclear cataract formation.
 ...
PMID:The state of sulphydryl groups in proteins isolated from normal and cataractous human lenses. 366 65

Lens fiber proteins with apparent molecular weights 57,000, 70,000, 82,000, and 100,000 were components in urea insoluble, membrane-rich fractions. Monoclonal antibodies against these proteins labeled membranes by immunofluorescence microscopy of sheep lens cryosections and are thus referred to as membrane proteins MP57, MP70, MP82, and MP100. MP70 has previously been localized in fiber junctional membranes (Kistler et al 1985, J Cell Biol 101:28-35). Using radioimmunoassays, the authors found a different membrane protein composition for the cortical and nuclear sheep lens regions. In addition, the membrane protein composition altered with the overall lens age. All the above membrane antigens were eventually cleaved by proteolysis in older fibers, and their degradation patterns could be grouped into distinct classes. The results are of basic importance for cataract research.
 ...
PMID:Aging of lens fibers. Mapping membrane proteins with monoclonal antibodies. 370 26

Intumescent cataractous lenses were investigated as to their water content and protein composition. Nuclei were separated from cortices. Water-soluble, water-insoluble, urea-soluble and urea-insoluble portions were quantified and the subunit composition of the water-soluble crystallin fraction was looked at on SDS-gel electrophoresis. Compared to normal lenses it is observed that the water content in intumescent cataract is increased, water-soluble and urea-soluble fractions are diminished, whereas the urea-insoluble portions are augmented. No major changes are noted in the subunit composition of the soluble protein fractions. Particularly, the relative amount of gamma-crystallins is diminished in intumescent cataractous lenses.
 ...
PMID:Lens proteins in intumescent cataract. 373 13


<< Previous 1 2 3 4 5 6 7 8 Next >>