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

Age-related cataract is a condition characterized by multiple mechanisms and multiple risk factors. The mechanisms that bring about a loss in transparency include oxidation, osmotic stress, and chemical adduct formation. Risk factors for cataract include diabetes, radiation (ultraviolet B, x-ray), certain pharmaceutical substances, certain nutritional states, and possibly acute episodes of dehydration. Interaction occurs between and among mechanistic factors and risk factors. Thus nutrition must be considered as one part of a tapestry of intertwined events and responses. Certain experimental models for nutritional cataract have been useful for study of the cataractogenic process but are probably not important factors in the human disease. Little current evidence supports significant roles in human senile cataract for imbalances of tryptophan or other amino acids, deficiencies of calcium or selenium, or excessive intake of selenium. Overconsumption of galactose is likely to be hazardous only in subjects with genetic inability to metabolize this sugar. Vitamins with antioxidant potential (riboflavin, vitamin E, vitamin C, carotenoids) deserve further research scrutiny to ascertain their significance in cataract etiology. Excessive caloric intake needs to receive added emphasis as a factor contributing to cataract. Diabetes increases the likelihood of cataract three- to four-fold. Obesity, defined as more than 20% overweight, is considered a major risk factor for non-insulin-dependent, or type II, diabetes (69, 73). Weight control can be recommended as a prudent, safe, economic, and effective means of lowering risk probability for diabetes and the associated complication of cataract.
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PMID:Nutritional factors in cataract. 220 Apr 64

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.
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PMID:Associations between nutrition and cataract. 268 67

Selenium toxicity was investigated in cultured rabbit lenses to provide further information about the role of Ca++ in Se cataract. At a dose of 0.1 mM for 20 hr, Se induces a 10% change in Na levels within 6 hr, a 30% increase after 20 hr, and a three-fold increase within 48 hr of subsequent culture after removal of Se. In contrast, Ca++ levels remained normal throughout the first 24 hr. Only a small, 25% decline in GSH was noted. Not until lenses begin to swell and become noticeably opaque and turbid were Ca++ levels found to be elevated. Thus, at 72 hr, 48 hr following the removal of selenium, Ca++ had increased to a concentration of 0.7 mM. Ca++ accumulation appears to be a consequence of osmotic stress rather than pump inhibition while Na accumulation is a direct consequence of Se-inhibited Na pump.
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PMID:Effects of selenium on ion homeostasis and transparency in cultured lenses. 291 10

The epidemiological and historical aspects of some important and representative wildlife diseases from Scandinavia are discussed. In noninfectious diseases, examples include cataract in moose (Alces alces), atherosclerosis in hybrid hares (Lepus timidus X L. europaeus), and ethmoid tumors in moose. The epizootiological and historical aspects of the recent epizootics of myxomatosis in European rabbits (Oryctolagus cuniculus) and rabies and sarcoptic mange in red foxes (Vulpes vulpes) are reviewed. The decline and subsequent increase in population abundances of tetraonids including the capercaillie (Tetrao urogallus), black grouse (Lyrurus tetrix), and hazel hen (Tetrastes bonasia) are discussed, and an hypothesis on predation by foxes is presented as a possible explanation for these population fluctuations. The potential impact of environmental pollution on wildlife populations is emphasized with reference to mercury in wildlife from Sweden and the possible effects of cadmium and selenium resulting from acidification. A bibliography of important references is presented pertaining to these and other diseases of wildlife from Scandinavia.
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PMID:A review of wildlife diseases from Scandinavia. 331 19

As part of an exploratory study of nutrition and senile cataract relationships between biochemical markers of nutritional status and senile cataract were examined in 112 subjects aged 40-70 y. Seventy-seven subjects had a cataract in at least one lens. Blood levels were determined for total carotenoids, vitamin A, vitamin D, vitamin E, vitamin C, riboflavin, thiamin, vitamin B-6, zinc, copper, selenium, and magnesium. Subjects were grouped into quintiles for each nutrient. Logistic regression was used to estimate the odds ratios (ORs) for cataract among subjects in the highest quintile and the middle three quintiles relative to subjects in the lowest quintile. ORs were adjusted for age, sex, race, and presence of diabetes. Results suggest that risk of cortical cataract was reduced for subjects in the highest quintile of vitamin D and total carotenoids and that persons with cataract may have lower levels of vitamin C and higher levels of vitamin B-6 and Se.
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PMID:Nutritional status in persons with and without senile cataract: blood vitamin and mineral levels. 338 22

Massive cortical cataract was produced 15-30 days after a single injection of an overdose of sodium selenite into 14-day-old rats. Most of the cortical cataract appeared to be due to extensive liquefaction of cortical fibers. Water influx, following initial damage to the epithelium by selenium, and action of lens proteases were probable mechanisms for the extensive liquefaction. Remarkably, selenite cortical cataract spontaneously cleared after several months, restoring essentially normal cells to the epithelium and outer and mid-cortex. Major mechanisms for clearing probably involved: (1) removal of damaged proteins from the lens by extensive proteolysis; and (2) replacement of fibers by resumption of normal fibergenesis. The data emphasized the remarkable reparative potential of the lens, and indicated the usefulness of the selenite cortical cataract as a model to study such processes.
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PMID:Histologic changes in selenite cortical cataract. 341 27

This report describes a direct chemical method for rapidly estimating DNA synthesis and net rates of epithelial cell differentiation in the ocular lens in vivo. DNA synthesis in the lens of control and selenium-treated rats (12- or 13 days of age) was estimated by chemically isolating and measuring trichloroacetic acid (TCA)-insoluble 3H from the lens following injection of [3H]thymidine. Labeled substrate for DNA synthesis peaked in the lens at 1 hr after injection, decreased markedly by the third hour and was essentially gone by hour 12. Synthesis of labeled DNA in the lens was largely complete by about 3 hr. The [3H]DNA content of the whole lens, measured as TCA-insoluble 3H, remained constant for at least 4 months. The distribution of labeled epithelial cells between the epithelial-cell layer and fiber-cell mass was followed for up to 1 month after injection by measuring the ratio of [3H]DNA in the capsule (epithelial-cell layer) to lens body. Between days 2-3 and day 14 after injection, the ratio of [3H]DNA in the epithelial-cell layer to lens fiber cells decreased linearly in a semilogarithmic plot of the ratio vs. time; i.e. the rate of change of the ratio followed first-order kinetics. Thus, the rate constant (k) for the rate of change in the ratio of [3H]DNA in the capsule layer to lens body can provide an estimate of the percentage of the labeled epithelial cells which leave the capsule per day through differentiation into fiber cells. An apparent rate constant of 0.27 day-1 was estimated from the mean of five experiments; i.e. 27% of labeled epithelial cells were differentiating into cortical fiber cells per day. Therefore, about 70% of the germinative epithelial cells would be replaced every 4 days in these rats. This value is in good agreement with results of studies using autoradiographic technics. The selenium cataract is reported to involve rapid damage to lens epithelial cells. Incorporation of [3H]thymidine into DNA was decreased by at least 60% in the lens of selenium-treated rats. Selenium did not decrease the availability of substrate in the lens for DNA synthesis. The cause of the decreased incorporation of [3H]thymidine into the selenium-exposed lenses remains to be determined.
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PMID:Direct chemical measurement of DNA synthesis and net rates of differentiation of rat lens epithelial cells in vivo: applied to the selenium cataract. 362 47

The purposes of these experiments were 1) to measure microscopic changes in the epithelium associated with selenite cataract, and 2) to describe the formation and subsequent clearing of selenite cortical cataract. Fourteen-day old suckling rat pups received a single subcutaneous injection of an overdose of sodium selenite at 2.25 mg Se/kg b.w. Development of cortical cataract was observed by biomicroscopy, and changes in epithelium were studied by light microscopy of flat-mounted lens epithelia. Selenite administration caused cortical cataract 15-30 days after injection in addition to previously characterized nuclear cataract. The cortical cataract progressed through equatorial vacuolization, opacity, and finally clearing of the cataract. Mitosis was suppressed and karyorrhexis was observed in the germinative zone of the epithelium 5 hours after selenite injection. Pathological disorganization of the epithelium followed. Changes included vacuolization, loss of meridional rows, and defective fiber formation. Restoration of epithelial morphology was associated with clearing of cortical opacity. Epithelial damage at 5 hours was the earliest change yet recorded for selenite cataract, and these data are consistent with our working hypothesis that the initial site of attack of selenium in both cortical and nuclear cataract is the lens epithelium.
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PMID:Selenite-induced epithelial damage and cortical cataract. 395 36

Selenium-induced cataracts in young rats were used to compare light scattering and dry mass concentration along the lens axis. Selenium-treated rats and control rats were examined 1, 2, 4 and 6 days after subcutaneous injection of selenium or 0.9% NaCl. The development of nuclear cataract was followed with a Scheimpflug slit-lamp camera. Light-scattering was determined by densitometry of the negatives taken by the Scheimpflug camera. Dry mass concentration was determined by quantitative microradiography of the extracted lenses. Increasing light scatter was seen from day 2 to day 6. The dry mass concentration, however, was not changed until day 6. Two distinct zones were found surrounding the center of the nucleus, one with increased and one with decreased dry mass. The rapid changes in dry mass concentration were probably caused by shifts in water distribution within the lens. Similar zones of hydration have also been found in human senile nuclear cataract. Selenium-induced cataract in the rat is discussed in relation to human nuclear cataract.
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PMID:Selenium-induced cataract--a correlation of dry mass content and light scattering. 395 3

The protective effect of premature weaning on the incidence of selenite-induced cataracts in young rats can be abolished by the timely administration of the main components of nourishment, including water. The results suggest that water which is a common factor of all supplemented nutrients could play an important role in the development of selenium cataract.
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PMID:Nutritional dependence of the incidence of selenite-induced cataracts in rats. 624 24


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