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)

Purified lens fiber membrane fractions from Emory mouse lenses and cataract-resistant control lenses were compared by SDS-PAGE. The differences in polypeptide patterns were determined for three ages. There was a striking alteration in MP24/MP26 ratio during aging and cataractogenesis which appears to be due to a normal age-dependent conversion of MP26 to MP24, and which is accelerated during cataractogenesis.
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PMID:Alterations of urea-insoluble membrane fraction, MP26, of Emory mouse lenses in aging and cataractogenesis. 234 82

Antisera have been made to synthetic peptides corresponding to the expected tryptic fragments from the C-terminal region of human alpha A2 crystallin (T19 corresponds to residues 158-163; T20 corresponds to residues 164-173). These antisera were used on conjunction with a sensitive radioimmunoassay, to identify the elution times of peptides resolved on a C18 column from a tryptic digest of water soluble and water insoluble proteins from the human lens. Isolation and purification of the peptides reactive with the anti-peptide sera, followed by the use of tandem mass spectrometry to determine the amino acid sequences in the peptides, demonstrated that the antisera reacted specifically with the T19 and T20 sequences. Using the antisera specific for the T19 sequence, analysis of the peptides resolved from tryptic digests of individual lenses demonstrated no major differences between the elution profiles of five normal vs. ten cataractous lenses, while analysis of the same digests with the antiserum to the T20 sequence demonstrated major changes in reactivity and/or elution time of tryptic peptides from eight of the cataractous lenses analyzed. Together, these studies strongly suggest that during human cataract formation, covalent changes occur in the C-terminal region of the alpha A2 molecule. In addition, these studies provide the general methodology, whereby antisera specific for known sequences of a polypeptide chain, can be used to locate the sequences involved in covalent modification during the process of senile cataractogenesis of the human lens.
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PMID:Analysis of tryptic peptides from the C-terminal region of alpha-crystallin from cataractous and normal human lenses. 237 63

Comparative physico-chemical and spectroscopic analyses were carried out in human lens proteins obtained from extracts of normal, senile and PUVA cataracts. Mass recovery analysis reveals a large protein concentration loss in the PUVA cataract relative to the normal lens and senile cataract. This protein loss parallels an increase in the degraded polypeptide chains. However, the tryptophan content (2.1 mol/mol of 20 kDa protein subunit) and the apparent fluorescence quantum yield (phi f = 0.056) of the tryptophan residues which are believed to be involved in the development of UV-induced cataracts are unchanged after age-related alterations and/or in vivo photochemistry associated with psoralen (8MOP) photosensitized reactions.
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PMID:Degradation of crystallins from a psoriatic patient undergoing PUVA therapy. 238 75

Epidermal growth factor (EGF) is a polypeptide that stimulates the growth of various tissues, including the cornea. The presence of EGF in tears from normal volunteers and in aqueous humor from cataract patients was investigated via human EGF (hEGF)-specific radioimmunoassay. Immunoreactive hEGF was found to be present at similar concentrations in both reflex (ranging from 0.7 to 8.1 ng/ml) and non-reflex tears (ranging from 1.9 to 9.7 ng/ml), but was undetectable in aqueous humor. Immunoreactive EGF in human tears was indistinguishable immunologically, biologically and biochemically from urine EGF and standard hEGF.
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PMID:Presence of epidermal growth factor in human tears. 278 49

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.
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PMID:Origin of urea-soluble protein in the selenite cataract. Role of beta-crystallin proteolysis and calpain II. 303 41

Antisera against synthetic peptides corresponding to various regions of the Main Intrinsic Polypeptide (MIP26K) of fiber lens membranes have been used to probe Western blots of Emory mouse lens proteins resolved by SDS-polyacrylamide gel electrophresis. When compared with clear lenses from control animals of approximately the same age, the MIP26K component from Emory mouse lenses demonstrated no quantitative changes in the binding of anti-MIP26K256-263 and anti-MIP26Kwhole sera. In contrast, the MIP26K component from Emory mouse lenses bound significantly better to two other antisera directly against other parts of the molecule (antiMIP26K229-237 and anti-MIP26K252-259). Furthermore, this increase in binding was approximately proportional to the degree of lens opacification. Together, these results demonstrate that during the opacification process of the Emory mouse lens, there occur covalent changes in the MIP26K molecule that, in part, may mimic those occurring in the human senile cataract.
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PMID:Changes in the major intrinsic polypeptide (MIP26K) during opacification of the Emory mouse lens. 304 12

The beta-crystallin basic principal polypeptide (beta Bp) appears to be altered in the lens of the Philly mouse and may be the main defect in this hereditary cataract. Northern blot analysis showed that an mRNA encoding for beta Bp is present in the Philly mouse lens, but normal beta Bp could not be detected. Instead, a different protein related to beta Bp has been observed. Western blot analysis with antibodies against specific beta Bp peptide sequences showed that the Philly protein shares the same amino-terminal residue as beta Bp but lacks a part of the carboxyl-terminal half of normal beta Bp. The altered protein is slightly smaller than beta Bp and has a more acidic isoelectric point by two-dimensional gel electrophoresis. It also lacks the property of heat stability characteristic of normal beta Bp. The mapping of the alteration in beta Bp may give insight into the nature of the heat stability of this protein as well as some indication of the structural components that are necessary to maintain optical clarity in the lens.
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PMID:Alteration of a developmentally regulated, heat-stable polypeptide in the lens of the Philly mouse. Implications for cataract formation. 319 22

Experimental nuclear cataract produced by an overdose of sodium selenite exhibited limited proteolysis, including breakdown of main intrinsic polypeptide (MIP26) to 24 and 22 kD fragments. Micro-sequencing and site specific immunologic probes were used in the present study to determine regions of cleavage in MIP26 during selenite cataractogenesis. Data suggested that proteolysis occurred in the C-terminus of MIP26. This may have lead to exposure of normally hidden amino acid residues on the C-terminal extension of MIP26. Loss of antigenicity of the N-terminus occurred. These significant changes to the MIP26 molecule might adversely affect communication between lens fiber cells and contribute to selenite cataract.
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PMID:Proteolytic changes in main intrinsic polypeptide (MIP26) from membranes in selenite cataract. 328 27

The formation of membrane protein disulfide was investigated at various stages of development of X-ray-induced cataract in the rabbit. Intermolecular disulfide bonding of lens membrane proteins was detected not only in the mature cataract (occurring 8-9 weeks after the X-ray dose) but also at 1 week prior to maturation, in which no significant increase in lens hydration occurs and where opacification is confined mainly to the posterior subcapsular region. Two-dimensional diagonal electrophoresis revealed that polypeptides with apparent molecular weights of 21, 23, 25, 31, 35, 46 and 53 kilodaltons were involved in cross-linking. The MP26 membrane polypeptide was not significantly involved in the disulfide bonding. The oxidation of membrane proteins in stages other than mature was evident only in the lens nucleus (which remained clear) and not in the cortex. The results of this study indicate that an intermolecular disulfide linkage of cytosolic proteins to membranes occurs prior to formation of mature cataract, and may be a precursor to protein aggregation and insolubilization in the mature nuclear cataract.
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PMID:Disulfide-linked membrane proteins in X-ray-induced cataract. 365 24

A comparison of mammalian gamma-crystallins has been made by computer-graphics model building of several gamma-crystallin sequences based on the atomic co-ordinates of the X-ray determined structure of calf gamma-II crystallin. The complete family of rat gamma-crystallins is compared together with the orthologous protein, gamma 1-2 crystallin, from rat, human and calf lens, and the orthologous protein, gamma 2-1 crystallin, from rat and human lens. In human gamma-crystallins, a major structural difference, the replacement of an arginine by a cysteine, occurs in one of the four-fold repeated folded hairpins, which may affect stability. Sequence variations involving buried residues were observed, leading to small differences in core packing of the different sequences which may be related to their regional location in the lens. Model-building studies also indicate that the surfaces of the different gamma-crystallins vary in number of exposed hydrophobic residues and ion pairs. These differences would affect protein-water interactions and therefore contribute to refractive index. A major variable region of the gamma-crystallin structures involves polar residues surrounding the inter-domain contact and the length of the polypeptide connecting the two domains. An attempt is made to correlate bovine gamma-crystallins which are known to be responsible for cold cataract with the corresponding sequences from rat lens.
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PMID:Structural variation in mammalian gamma-crystallins based on computer graphics analyses of human, rat and calf sequences. 1. Core packing and surface properties. 373 18


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