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)

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.
 ...
PMID:Degradation of crystallins from a psoriatic patient undergoing PUVA therapy. 238 75

Proteins, including lens proteins, were incubated in the presence of 3-hydroxyanthranilic acid (30 HA) under oxidizing conditions. Samples were monitored for alterations in color, fluorescence, sulfhydryl content, lysine availability, methionine content, tryptophan content and protein size. Incubation of proteins with 30 HA produced rapid brown coloration and a correspondingly rapid decrease in sulfhydryl content. Alpha-, beta- and gamma-crystallins were all found to react with 30 HA. An increase in protein fluorescence (excitation 340/emission 425 nm) accompanied the color development. No significant decrease in the content of tryptophan or any other amino acid was detected by amino acid analysis. The levels of available lysine were not affected significantly by treatment with 30 HA. Oxidation of methionine to methionine sulfoxide and the covalent cross-linking of polypeptides was obtained by subsequent treatment of the tanned proteins with H2O2. The modifications observed are very similar to those found in the senile nuclear cataract lens.
 ...
PMID:The reaction of proteins with 3-hydroxyanthranilic acid as a possible model for senile nuclear cataract in man. 251 71

Fluorescence of intact lenses of F1 (CBA x C57BL6) mice at different stages of X-ray cataract induced by gamma irradiation (5.00 Gr) has been studied by synchronous scanning of fluorescence, the shift between emission and excitation wave lengths being 20 nm. The ratio between peek intensities of the nontryptophan and tryptophan fluorescence within the synchronous scanning spectra (K) has increased 3.5 times as much at the stage of singular dot-like opacities. K-parameter correlated with GSH level in the lenses (r = -0.9). According to the results achieved, K could be regarded as an informative indicator of the development of X-ray cataract at the stage previous to turbidity.
 ...
PMID:[The fluorescence of mouse crystalline lenses at different stages of radiation cataract studied by synchronous scanning]. 265 53

Blindness due to opacification of the lens, or cataract, afflicts 50 million persons worldwide. In the United States over 541,000 cataract extractions are done annually at a cost of over $3.8 billion. Conservative estimates indicate that the prevalences of cataracts in Americans aged 65-75 and 75-85 years are 18% and 46%, respectively. Cataracts are even more prevalent in some other populations. It is estimated that the need for cataract extractions would be diminished by half if onset of cataract could be delayed by only ten years. Hypotheses regarding the etiology of cataract include oxidative perturbations of protein metabolism, diverse pathologic conditions, and perhaps glycation of lens proteins. Epidemiologic data indicate that elevated plasma levels of specific nutrients (i.e., carotenoids, ascorbate, tocopherol, and taurine) are associated with diminished incidence of certain types of cataract. Biochemical evidence suggests that each of these compounds can delay photooxidative damage to lens proteins. Roles in lens metabolism for selenium and tryptophan have been suggested. Elucidation of mechanisms by which caloric restriction delays cataract development is a promising area of current research.
 ...
PMID:Associations between nutrition and cataract. 268 67

Intracapsular cataracts obtained within 3 h after surgical extraction were photographed with the CCRG technique and immediately subjected to fluorescence spectroscopy followed by 31P- and 13C-nuclear magnetic resonance (NMR) spectroscopy. Fluorescence spectroscopy demonstrates an excellent correlation between nontryptophan fluorescence intensities and lens color. An interesting correlation was also observed between the degree of light scatter as determined by the 290-nm excitation peak for intrinsic lens tryptophan fluorescence and the CCRG (photographic) appearance of these cataractous lenses. Based on 100 cataracts analyzed, there is a strong correlation between this kind of light scattering measurement and the type and degree of lens opacification. A similar correlation is evident with the 31P-NMR organophosphate profiles in the lenses in which the sugar phosphate levels are elevated only in diabetic patients with cataracts ('diabetic cataracts'). Aside from fluorescence and 31P-NMR spectroscopy, selected lenses were also incubated with 5.5 nM 13C-glucose as soon as they were obtained, and the foregoing spectroscopy was performed, followed by 13C-NMR analyses to detect and monitor for sorbitol accumulation in young versus old normal lenses and in diabetic cataracts. These studies clearly demonstrate a direct correlation between nontryptophan-fluorescent chromophore levels, light scattering (determined by tryptophan excitation peaks), lens age and cataract type. In addition, the organophosphate profiles clearly delineate the diabetic cataracts, and the 13C-NMR spectra correlate well with the age-related decrease in aldose reductase activity.
 ...
PMID:Photographic and spectroscopic correlations of human cataracts. 271 Apr 94

beta-Crystallins (beta 1-, beta 2- and beta 3-crystallin) comprise nearly half the protein of the human lens. The effect of near-UV radiation, which is one of the possible risk factors in cataract formation, on the beta-crystallins is investigated in this study. Protein intersubunit crosslinking, change in charge of the protein subunits to more acidic species and changes in protein tertiary structure (conformation) by 300 nm irradiation are reported. The fluorescence yield of protein tryptophan residues decreases by 300 nm irradiation. There is an increase in nontryptophan fluorescence (lambda cx 340 nm, lambda cm 400-600 nm), and in protein absorption at 340 nm, due to the formation of tryptophan photooxidation products. Both tryptophan and its oxidation products can be photoexcited by 300 nm irradiation and the latter are known to be good photosensitizers. The results provide evidence for the generation of H2O2 in the irradiated human beta-crystallin solutions by the Type I photosensitizing action of the chromophores absorbing at 300 nm. The H2O2 is generated via the intermediate production of O2 anion; the latter spontaneously dismutates to H2O2, presumably via O2- protein interactions. The amount of H2O2 generated per absorbed photon is compared for various solutions of beta 1-, beta 2- and beta 3-crystallins from human lenses of different age.
 ...
PMID:The effects of near-UV radiation on human lens beta-crystallins: protein structural changes and the production of O2- and H2O2. 276 85

This paper focuses on damage to soluble lens proteins during ultraviolet (UV) light exposure and its prevention by ascorbate (Vitamin C). Using 2.3 X 10(-3) W/cm2 UV A and 0.4 X 10(-4) W/cm2 UV B, aminopeptidase inactivation in lens supernatants is significant after 60 min. Protein aggregation and decreases in tryptophan levels, phenomena associated with UV-induced and cataract-related damage, are observed only after longer (6 h) UV exposure. Thus, it would appear that measurements of aminopeptidase activity can be used to anticipate damage to lens structural proteins. Ascorbate (15 mM) added to soluble lens proteins prior to photoirradiation can prevent some of these changes. The data presented suggest plausible relationships between impaired proteolysis and cataract formation.
 ...
PMID:Measures of leucine aminopeptidase can be used to anticipate UV-induced age-related damage to lens proteins: ascorbate can delay this damage. 343 Nov 68

The soluble proteins of a newborn human lens exhibit almost no non-tryptophan fluorescence. On aging, an increase in the fluorescence of all native crystallins is found except for gamma 2-crystallin. With formation of nuclear cataract, a further increase is seen for gamma 1-crystallin. The fluorophore, excitation 355 nm/emission 420 nm, is mainly associated with one species of the gamma 1-crystallin population. It is also present as such in the soluble fraction and increases significantly with nuclear cataract formation. At least one of the gamma 1-crystallins seems to play an important role in the cataractogenic process.
 ...
PMID:Non-tryptophan fluorescence of crystallins from normal and cataractous human lenses. 359 93

The concentration of the free aromatic amino acids tryptophan and tyrosine, the antioxidant uric acid and some unidentified compounds have been determined in the water-soluble extracts of parts from clear and nuclear-cataractous human lenses. With age (29-90 years) and cataract formation, associated with increasing nuclear pigmentation, no significant changes were observed in content of tryptophan, tyrosine and uric acid. Furthermore, these compounds did not show variation in distribution within the lens. An unidentified fluorophore, excitation and emission maxima of 345 and 425 nm, respectively, increases significantly in content with nuclear cataract formation, especially in the nucleus. Another unidentified, presumably aromatic compound shows a striking age-related decrease.
 ...
PMID:Distribution of aromatic and fluorescent compounds within single human lenses. 365 75

Conformational changes in the three crystallins alpha-, beta-, and gamma- in a singlet-oxygen generating system were investigated by fluorescence studies of tryptophan and covalently-bound sulfhydryl probe 4-[(N-iodoacetoxy)N-methyl]amino-7-nitrobenz-2-oxa-1,3-diazole (IANBD). Upon excitation at 295 nm, the tryptophan emission maxima of the crystallins were red-shifted by irradiation with visible light in the presence of the photosensitizer methylene blue. beta- crystallin showed the largest shift (4 nm) of the emission spectrum. Time course of the fluorescence changes by irradiation showed that the decrease in the tryptophan fluorescence yield occurs most rapidly for beta-crystallins, as compared to alpha- or gamma-crystallins. Fluorescence changes of IANBD-labeled crystallins show a 40% decrease in the fluorescence intensity of the sulfhydryl probe for beta-crystallin after one hour of irradiation. For alpha- and gamma-crystallin smaller decreases (7% and 15% respectively) were observed. Since all the sulfhydryl groups of beta-crystallin are known to be exposed on the surface of the protein (Andley et al, 1982, Biochemistry 21, 1853), these results suggest that the pronounced changes in conformation of beta-crystallin by singlet oxygen may be due to a rapid loss of the protein tertiary structure by oxidation of the sulfhydryl groups. These results have potential significance in understanding the age and cataract-related changes in the ocular lens in view of the fact that several key lens enzymes are associated with beta-crystallins in vivo.
 ...
PMID:Fluorescence studies on tryptophan and sulfhydryl group changes of bovine lens crystallins in a photodynamic system. 404 65


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>