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Query: UMLS:C0086543 (cataract)
 29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The authors report two unusual pedigrees of flake-like cataracts inherited as an isolated mendelian trait, presumably autosomal dominant. The most striking biomicroscopic feature is an accumulation of large white irregular flakes ('type B opacities') scattered throughout the equatorial cortex, with apparently less involvement of the nucleus. Some of these opacities are globular, but most are flattened and have feathery edges. These type B opacities are clinically and microscopically identical in the two families. Type B lesions are characterized histologically by irregular pale-staining areas. Ultrastructurally, these areas show large collections of microglobular degeneration immediately adjacent to normal-appearing lens fibers. Electron probe studies demonstrate normal calcium levels. 'Type A' opacities are biomicroscopically smaller, punctate, and clinically non-specific. Ultrastructurally, type A opacities include clusters of medium sized lenticular globules, each of which is larger than the individual microglobular abnormalities of type B lesions, although the aggregated type B lesion is considerably larger than an individual type A lesion. The microscopic appearance of this inherited cataract appears to be unique.
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PMID:Inherited snowflake cataracts. 654 90

The chemical nature of spheroliths in human cataract lenses was explored by means of laser microprobe mass analysis. The results suggest that the crystallites mainly consist of calcium carbonate.
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PMID:Laser microprobe analysis (LAMMA) of spheroliths in human cataract lenses. 665 2

Cytoplasmic aldehyde dehydrogenase from bovine lens was purified to apparent homogeneity by using ion-exchange and affinity chromatography. Sedimentation-equilibrium ultracentrifugation, gel-filtration chromatography and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis show that the enzyme is a dimer of Mr 114000, with subunits of Mr 57000. The enzyme does not dissociate into monomers in the presence of Ca2+ or Mg2+. The enzyme has a pI of 5.0, an activation energy of 35.1kJ/mmol and a pK value of 8.6 with acetaldehyde as substrate. The enzyme is a prolate ellipsoid with a Stokes radius of 4nm. Progesterone, deoxycorticosterone and chlorpropamide inhibited enzyme activity, and this inhibition may play a role in cataract formation in patients maintained on systemic corticosteroids and in tablet-dependent diabetics.
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PMID:Bovine lens aldehyde dehydrogenase. Purification and preliminary characterization. 665 65

Changes similar to posttranslational modifications that are observed with osmotic cataract formation in vivo can be seen with homogenates of lenses. These modifications are the loss of a 31,000 molecular weight (MW) beta crystallin polypeptide, an increase in a 25,000 MW membrane polypeptide. These modifications are potentiated by calcium and occur more rapidly at 37 degrees C than at 4 degrees C. Inhibitors of pepsin or of serine proteases do not influence these modifications, although proteolysis may be responsible for the changes observed.
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PMID:In vitro alterations similar to posttranslational modification of lens proteins. 669 42

Subcutaneous injection of sodium selenite into young rats produces a nuclear cataract within 72 hours. A three-fold elevation in lens calcium and a two-fold increase in lens inorganic phosphate have been found to precede opacification. Scanning electron micrographs suggested weakened cell-to-cell adhesion in the cataractous nuclear zone.
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PMID:Lens calcium and selenite-induced cataract. 670 55

The spheroliths , mostly to be found in the brown nucleus of Morgagni's hypermature cataract, are up to 0.25 mm in diameter and consist of radially arranged crystals of calcium carbonate of oxalate. From the spheroliths extend, in varying degrees, marginally radial structures of a very fine filamentous, streaky character, that do not enter the altered protein of the lenticular nucleus. This, most probably, is a newly formed protein structure (a structure of mucopolysaccharides according to Zimmerman and Johnson 1958) in which secondary deposits of calcium carbonate or oxalate crystals accumulate. The spheroliths are usually round or kidney-shaped and rarely consist of more than one or two individual bodies.
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PMID:[Spheroliths of the lens]. 672 26

Previous studies have shown that cell uncoupling is paralleled by an increase in tightness and crystallinity of gap junction particle arrays. Gap junction crystallinity is believed to be part of the uncoupling mechanism because it can be produced in gap junctions isolated from lens fibers on direct exposure to uncoupling agents such as divalent cations or hydrogen ions. Some doubts, however, have been raised on the capacity of lens fiber junctions to crystallize and uncouple in situ. The present study shows that the gap junctions of rat lens fibers indeed crystallize after a treatment that increases drastically the membrane permeability to ions. The treatment consists of a brief immersion of the lenses in liquid nitrogen, followed by incubation for several hours in Tyrode's solution at 37 degrees C. Immediately after liquid nitrogen treatment, the lenses start gaining sodium and calcium while losing potassium, and eventually become opaque. Addition of 10 mM EDTA to calcium and magnesium-free Tyrode's solutions inhibits particle crystallization and lens cataract, whereas low concentrations of EDTA (1 mM) are not effective. These findings, together with preliminary data on the capacity of lens fibers to heal over, indicate that the gap junctions of lens fibers are capable of crystallizing and uncoupling in situ.
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PMID:Gap junction crystallization in lens fibers after an increase in cell calcium. 678 27

The Emory mouse develops a late-appearing hereditary cataract having many characteristics which suggest its usefulness as an animal model for human senile cataract. This paper presents some results of analyses designed to determine biochemical changes associated with initiation and development of the cataract. The measurements carried out include water-soluble and water-insoluble protein, glutathione, protein sulfhydryl, non-protein disulfide, sodium, potassium, calcium and free phosphate. The most useful and consistent index of cataract progression seems to be the conversion of soluble to insoluble protein, a change which in the normal aging mouse lens is accompanied by some conversion of total sulfhydryl to disulfide. Cataract development also produces a significant reduction in the glutathione concentration.
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PMID:The Emory mouse cataract: loss of soluble protein, glutathione, protein sulfhydryl and other changes. 683 31

Cooperative Cataract Research Group (CCRG) photographic procedures developed by Chylack have made it possible to localize and analyze specific lens opacities for their ultrastructural and chemical characteristics. One group of human lens opacities has been shown to have a high phosphorus/sulfur ratio (as compared to normal lens fiber cells) and an accumulation of unit membranes. The present paper describes another variety of human lens opacity with the following characteristics: (1) high calcium, low sulfur, undetectable phosphorus, as determined by Energy Dispersive X-ray Analysis (EDXA) of bulk specimens in the scanning electron microscope (SEM), or "thick" sections with the transmission mode of the SEM; (2) spheroidal shape; (3) up to approximately 300 microns in size; and (4) birefringence. Microchemical analysis of these opacities shows that the calcium is in the form of calcium oxalate. These calcium-containing opacities, which have been detected in 14 out of 406 human cataractous lenses, have a characteristic morphology, as seen in the CCRG stereo photographs. Therefore, the presence of these calcium opacities, if not obscured by other kinds of opacities, can be detected with a high degree of accuracy in the fresh lens from the CCRG photographs alone.
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PMID:Calcium-containing opacities in the human lens. 688 7

A 19-year-old male with advanced renal failure developed bilateral cataracts indistinguishable from those considered characteristic of calcium deficiency. The biochemical findings during the dialysis treatment showed severe hypocalcemic episodes. A hypothetical mechanism to explain this kind of cataract is mentioned.
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PMID:Hypocalcemic cataract. 699 51


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