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)

Circular dichroism and fluorescence measurements showed a reduced conformational order in proteins of a normal human lens when they were incubated in vitro with melittin, a bee venom peptide. Since melittin is also known to react with lipids to induce a breakdown of vesicular structure, the observed denaturation of water-soluble proteins of a human lens that developed a cataract due to multiple bee stings may be accounted for by the effects of melittin to some extent. The melittin-induced decrease of conformational order, as observed in our in-vitro studies could thus be of physiological significance.
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PMID:Melittin-induced conformational changes in human lens protein. 178 5

By using a highly specific and sensitive homologous radioimmunoassay, we found that the content of epidermal growth factor (EGF) in the lateral one-third of whole cataractous human lenses (age range 45-85 yr) extracted at elective intracapsular lens surgery, varied from undetectable to 106.25 pg mg-1 water soluble protein (WSP) (mean +/- S.D. = 39.70 +/- 38.90). When the lenses were grouped according to the stage of the cataract, i.e. immature (n = 3), mature (n = 4), and hypermature (n = 3), the means +/- S.D. were 92.56 +/- 26.23, 23.89 +/- 7.71, and 7.92 +/- 2.00 pg mg-1 WSP, respectively. In ten age-matched whole 'normal' lenses that we removed within 2-12 hr after death, the values in EGF of the lateral one-third of the lenses ranged from 2.91 to 36.40 pg mg-1 WSP (19.39 +/- 13.65). No correlation between the age of the lenses and the content of EGF could be demonstrated at the 95% confidence interval for the cataractous and 'normal' lenses. The quantity of endogenous EGF correlated significantly (P less than 0.01) with the clinical stage of the cataract and is probably related to the mitotic activity of the equatorial proliferative zone. We discuss the importance of EGF in normal and cataractous lenses and postulate that EGF in the lens is endogenous in origin.
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PMID:Radioimmunoassay of epidermal growth factor in human lenses at various stages of development of cataract. 178 13

Cataract development was studied in two groups of Emory mice by periodical biomicroscopic examinations (beginning at 5 weeks of age) and by a final evaluation of water-soluble SH groups in the lenses. The experimental group was given 256 micrograms iodide/kg body weight with the drinking water throughout the study. The untreated control group received tap water. Iodide treatment induced a delay of cataract formation, resulting in a significant reduction of the time to progress from cataract degree 1 to degree 2 (iodide-treated group 12.8 +/- 1.7 weeks, untreated group 9.9 +/- 1.0 weeks; p less than 0.025). A still significant difference in the degree of cataract was also found between the two groups at week 47 of age. No difference was found in the content of water-soluble SH groups. The results are discussed in relation to the known antioxidant and .OH-scavenging effect of iodide and to the oxidative changes in the lens occurring during progression of cataract development.
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PMID:Influence of iodide on cataractogenesis in Emory mice. 180 12

Collagen undergoes progressive browning with age and diabetes characterized by yellowing, fluorescence, and cross-linking. The present research was undertaken in order to investigate the nature of the collagen-linked fluorescence. Human collagen was exhaustively cleaved into peptides by enzymatic digestion. Upon purification, a highly fluorescent chromophore was identified and purified from old human collagen. Structure elucidation revealed the presence of an imidazo [4,5-b] pyridinium-type structure acting as a cross-link between arginine, lysine, and a pentose. This advanced glycosylation end-product and protein cross-link results from the reaction of pentoses with proteins and was named pentosidine. Further work indicated that long-term glycosylation of proteins with hexoses also leads to pentosidine formation through sugar fragmentation. The proposed mechanism of pentosidine formation involves the dehydration of the pentose-derived Amadori compound to form an intermediate which is attacked under base catalysis by the guanido group of arginine. The strict requirement for the Amadori rearrangement is uncertain. However, oxidation is definitely involved since pentosidine is not formed in the absence of oxygen. Five-carbon sugars contributing to pentosidine formation could be formed from larger sugars by oxidative fragmentation or from trioses, tetroses, and ketoses by condensation and/or reverse aldol reactions. Pentosidine increases exponentially in human skin at autopsy. Mean age-adjusted skin levels were significantly increased in subjects with uremia and especially in type 1 diabetics with uremia vs. controls. In skin biopsy, levels were significantly elevated in all diabetic (type 1) vs. control subjects. The highest degree of association was with the cumulative grade of diabetic complication (retinopathy, nephropathy, arterial stiffness, and joint stiffness). Pentosidine also forms in various proteins other than collagen, although to a much lesser extent. In blood, pentosidine is mainly associated with plasma proteins and is highly elevated during uremia. In the lens, it is associated with both water-soluble and -insoluble protein fractions and is especially elevated during brunescent cataract formation. The origin of pentosidine in vivo is uncertain. Evidence suggests that the pentoses are the most reactive sugars in pentosidine formation in vitro; however, the origin and importance of free pentoses in vivo, especially during the diabetic state, are not certain. Possible origins include hemolysis and/or a defect in the primary pentose metabolism.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Pentosidine: a molecular marker for the cumulative damage to proteins in diabetes, aging, and uremia. 181 79

Normal and cataractal decapsulated lenses of man were studied by NMR method-spin echo to obtain information concerning efficient coefficients of self diffusion, times of spin-spin relaxation of water protons (T2) and water content in the lens (c) at 25 degrees C in the course of cataractogenesis. It has been found that the values T2 and c at 25 degrees C are much higher in the nuclei of completely turbid lenses than in the transparent ones; the self-diffusion coefficients in the turbid lenses were also higher. At -9 degrees C a significant decrease of the content of undestroyed by frost (bound) water was observed at the stage of mature cataract as compared to transparent lenses. It is suggested that the most specific differences between the nuclei of transparent and completely turbid lenses are related to increased diffusion mobility of water molecules, apparently, at the expense of damaged plasmic membranes of the lens fibres noted during cataract development.
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PMID:[Diffusion properties of water in the human crystalline lens during cataract development]. 189 8

The accessibility of tryptophanyl fluorophores in crystalline proteins to water molecules was estimated by measuring the enhancement of the fluorescence of lens homogenates in 70% D2O as compared to 100% H2O. Assuming that two sorts of fluorophores exist in the proteins, one entirely accessible to H2O and D2O and the other--absolutely not, we have calculated the portion of either group in the protein fluorescence (alpha and 1-alpha, correspondingly). Measurement of murine lens homogenates fluorescence at different stages of radiation-induced cataract, initiated with total gamma irradiation in a dose 5 Gy have shown an increased accessibility of tryptophanyl for water with cataract development. At earlier stages of cataract (appearance of scattered dot opacities) the portion of water-accessible tryptophanyl increased from 0.14 to 0.18, i.e. by a factor of 1.3. The data obtained suggest that protein globules unfold in the coarse of cataract development.
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PMID:[Increase of accessibility of murine lens protein fluorophores to water in the development of radiation-induced cataract]. 189 34

The water-soluble proteins from mice lenses (normal and cataract lenses) were investigated by methods of absorption spectrophotometry and kinetics of UV-induced radical decay. General characteristic of internal structure of extraction proteins was investigated by recombination kinetic method. It was shown that concentration of water-soluble proteins lowered ten times in lenses of mature cataract, i. e. 90% protein molecules were connected in lenses of mature cataract.
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PMID:[Study of soluble proteins of mouse crystalline lenses (normal and in cataract)]. 189 84

Our laboratory has demonstrated the potential of non-invasive biophysical methods in studying cataractogenesis. Initially these studies involved in vitro spectroscopic assays (UV, fluorescence and phosphorescence) on excised lenses or lens matter. In addition, we performed NMR pulse relaxation studies on extracted lenses which demonstrated an age-related increase in the T1 and T2 values of the normal lens. The in vitro fluorescence and NMR data suggested potential parameters for monitoring human and animal lenses in vivo. We then developed in vivo lens fluorescence densitography utilizing the Scheimpflug camera and have recently employed our Magnetic Resonance Imaging (MRI) method (using specially constructed small coils) to measure the moderately bound lens water compartment (T2) in vivo. Both of these in vivo methods correlate with our in vitro data and they demonstrate age-related changes in the normal lens; - i.e. - a progressive increase in fluorescence intensity and longer T2 values. Indices have been developed which permit us to detect abnormal lens fluorescence and changes in the moderately bound lens water (T2) compared with normal values for each specific age group by decade. These 2 non-invasive biophysical techniques can detect pre-cataractous changes in the living clear lens, months to years before any type of opacity becomes manifest with the conventional slit lamp method. The MRI technique can be performed in less than 20 minutes and the lens fluorescence method requires 4-6 minutes; thus they provide a rapid and objective in vivo measure of the status of the living lens as well as a method for evaluating anti-cataract drug efficacy.
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PMID:NMR & fluorescence studies on human and animal lenses. 191 33

This preliminary report has two parts. The first is based upon data obtained from a group of cataract patients in southern Florida (USA) with the object of relating the types of cataracts removed to their personal background and their protein biochemistry. Intra-capsular cataract surgery patients at the Venice Eye Clinic (Florida) were interviewed, and their extracted lenses were classified. The parameters were: age, place of residency, occupation, medical and family history and indoor/outdoor activity. Subcapsular cataracts were found mainly in the youngest patients and in those who were in Florida the least. Mixed cataracts predominated in the oldest patients, while non-nuclear cataracts were associated most with outdoor activity. Water-insoluble protein was elevated in nuclei of lenses with nuclear opacities. Soluble proteins in the nuclei of nuclear cataracts had increased levels of voided (heavy) protein, beta-crystallins, and less than 20 Kd peptides. The above changes were enhanced in brunescent cataracts. In lenses with cortical opacities, only increased size heterogeneity in the beta-crystallin region was observed. The second part of this report is based upon direct measurements of the optical properties of freshly extracted intra-capsular cataracts obtained in Rochester, New York (USA). The purpose was to attempt to learn the relative contributions that absorption, scattering, and fluorescence make toward obscuring vision. A general conclusion is that the shorter wavelengths of radiant energy in environmental lighting influence the above-stated optical properties the most, and thus appear to be the major contributors to obscured vision.
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PMID:Relationships between human cataracts and environmental radiant energy. Cataract formation, light scattering and fluorescence. 191 41

A tendency to reduce the use of benzophenone absorbers is currently evident in the manufacture of the UV-absorbing IOLs, mainly because the cutoff wavelengths are inferior to those provided by benzotriazoles. In principle, by incorporating large amounts of benzophenones it may be possible to achieve high cutoff wavelengths. A covalently bondable benzophenone UV absorber, Cyasorb UV-2098, was incorporated in poly(2-hydroxyethyl methacrylate) (PHEMA) in increasing concentrations, and certain associated phenomena were investigated. At 4% w/w absorber content, the nonhydrated polymers turned partially opaque. In water-swollen hydrogels, opacification occurred at a lower absorber content (2% w/w). By using extraction techniques and gas chromatography, we also found that up to 8% w/w of the absorber remained unpolymerized and could leach out from any material containing less than 5% w/w absorber. In samples with higher initial content of absorber, the amount of unreacted, leachable absorber was significantly higher (25% to 30%). Based on this study model (hydrogel/Cyasorb UV-2098), we concluded that benzophenone absorbers cannot provide cutoff wavelengths higher than those provided by benzotriazoles.
J Cataract Refract Surg 1991 Sep
PMID:Further studies on ultraviolet-absorbing hydrogels for intraocular lenses: relationship between concentration of a polymerizable benzophenone, absorption, and extractability. 194 93


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