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

The precise factors responsible for the cataract formation are not known. The role of Na+-K+-ATPase in maintaining ionic concentration of lens and lens membrane permeability and its involvement in the formation of cataracts has been of recent interest. Thus the present study was undertaken to study the effect of pre-treatment with Ouabain, a known Na-K-ATPase inhibitor, on the intra-lenticular ionic concentration and the rule of lens membrane permeability in cataractogenesis. Fresh goat lenses were used for the experimental work. Isolated lens culture technique was used. The electrolytes were estimated before and 24 hours after Ouabain pre-treatment. The electrolyte pattern showed significant changes after pre-treatment with Ouabain. Lens sodium ion concentration increased significantly with a concommitant decrease in potassium ion concentration. Intra-lenticular chloride concentration also showed a significant increase as compared to control. Calcium and magnesium ion concentrations also showed slight increase after the inhibition of Na+-K+-ATPase system by Ouabain.
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PMID:Effect of inhibition of lens membrane Na+-K+ ATPase by ouabain pre-treatment--an in vitro study. 285 21

Selenite-cataracts incorporated many morphological characteristics observed in human senile catracts. Progressive elevation of sodium, marked loss of potassium, several fold increment of calcium; considerable loss of magnesium levels, a dose-response reduction of total-ATPase activity and significant hydration are the important features observed in the lens during the progressive treatment of selenite. The sodium-potassium imbalance is found to be a secondary effect during the development of cataract and is suggested to bring about by an abnormal accumulation of calcium ions and inactivation of transport enzyme. The calcium activated proteases could be the promoting factor for the proteolysis and insolubilization of lens proteins in the inducement of selenite cataract. The impact of selenite on the SH containing ATPase anzymes could be the cause of impairment in energy metabolism, derangement of electrolytes and osmotic imbalance which, in turn, accelerate the cortical involvement of lens opacities.
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PMID:State of electrolytes, osmotic balance and the activity of ATPase in the lenses of selenite--induced cataracts. 297 78

Membrane response to the various temperatures as one of the external factors was investigated in the lenses of the poikilothermal animal and the homothermal animal. The rainbow trout lens was used as the poikilothermal material and the rat lens as the homothermal material. The rainbow trout lens maintained in vitro its transparency without the changes of cation balance at 0 degrees C - 25 degrees C, while cold cataract developed in the rat lens under the same conditions. Na, K-ATPase activity was detected at 0 degrees C in rainbow trout lens but it was not detected in the rat lens. Lactic acid in the rainbow trout lens was produced for 30 successive days at 0 degrees C, while that in the rat lens was not produced. The cataract developed at 37 degrees C in rainbow trout lens, which we called "warm cataract." Warm cataract developed not only when the lens was incubated in vitro but also when rainbow trout was kept in fresh water at 37 degrees C. Significant differences were detected in components of membrane lipids in the rainbow trout lenses compared to bovine lenses as the mammalian lens. The cholesterol/phospholipid ratio in the trout lens membrane was lower than that in bovine lens. This suggests that a poikilothermal animal lens can maintain the membrane fluidity at low temperatures. These results might suggest that the membrane characteristics in the rainbow trout lens play a role to maintain its transparency at low temperatures.
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PMID:Effect of temperature on the rainbow trout lens. 299 Aug 20

This study focused on whether changes in lens levels of glutathione and calcium, early events associated with cataract formation, were related or that one might cause the other. The first part of the investigation was concerned with the extent to which an increase in levels of intracellular calcium might alter GSH levels in lens fiber and epithelial cells. The results demonstrate that calcium accumulation, either at 19 degrees C or 37 degrees C, did not diminish the concentration of GSH. More importantly, GSH levels did not decline in opaque regions of a calcium-loaded lens. The reciprocal part of the problem focused on whether a decline in lens thiol might lead to an increase in levels of calcium and subsequent opacification. In particular, it was shown that treatment of lenses with parachloromercuribenzene sulphonic acid (PCMBS), a nonpenetrating sulphydryl probe, resulted in a 10-30% loss of membrane SH groups in the epithelium. Diminished numbers of SH groups was accompanied by chloride fluxes and an increase in membrane permeability to sodium and calcium with an influx of sodium and calcium leading to opacities. It is important to note that these changes occurred in the absence of any change in cellular levels of soluble protein-SH or GSH. Additional experiments suggest that calcium transport was not impaired, as evidenced by lack of inhibition of Ca-ATPase activity in lenses treated with PCMBS. The results suggest that one explanation for opacification is that oxidative insults, which diminish GSH levels, leads to a loss of important membrane SH groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The importance of membrane sulfhydryl groups to calcium homeostasis in the lens. 299 53

The response of the poikilothermal lens to various incubation temperatures in vitro was compared with that of the homothermal lens. The rainbow trout lens was used as the poikilothermal lens and the rat lens as the homothermal lens. In contrast to rat lenses, cataract developed at 37 degrees C in rainbow trout lenses, which was called 'warm cataract'. Warm cataract developed not only when lenses were incubated in vitro but also when rainbow trout were kept in water at 37 degrees C. Water, Na+, Ca2+ and insoluble protein increased and K+ and Mg2+ decreased in warm cataract lenses, but GSH and soluble protein sulfhydryl levels did not change. This cataract was irreversible after only 5 min incubation at 37 degrees C. On the other hand, rainbow trout lenses remained transparent without the change of cation balance at 0-25 degrees C while cold cataract developed in rat lenses. Na,K-ATPase activity was detected at 0 degrees C in rainbow trout lens homogenates, but not in rat lens homogenates. Na+-K+ ratio (Na+/K+) increased when the rainbow trout lens was treated with ouabain at 0 degrees C. In the rainbow trout lens, lactic acid was produced continuously for 30 days at 0 degrees C while it was not in the rat lens between 1 hr and 10 days after. These results strongly suggest that Na,K-ATPase acts as a cation pump at 0 degrees C and that ATP is supplied by glycolysis in the rainbow trout lens in order to maintain the transparency. The above results also suggest that enzymes and membrane structures in rainbow trout lens are adapted to a cold-temperature habitat and that Na,K-ATPase and anaerobic glycolysis are important for the maintenance of lens transparency at low temperatures.
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PMID:Studies on the eye lens in poikilothermal animals. I. Comparative studies on cation maintenance systems in rainbow trout and rat lenses. 299 50

Previous morphological and biochemical studies indicate that a late appearing hereditary Emory mouse cataract may be a good model for certain human senile cataracts. The development of lenticular opacity in the Emory mouse is a slow process which provides an opportunity to conduct analysis of the progression of alterations that lead to cataract development. Biochemical investigations have not yet demonstrated any specific correlation between alterations in the lens and the extent of opacity. We have conducted studies to determine the role of Na+K+-ATPase in the development of cataract in the Emory mouse. In this report we present results obtained on the site and level of activity of Na+K+-ATPase in six- and twelve-month-old Emory mouse lenses in which visible cataractous changes are beginning to appear. CFW mice (the parent strain) were used for controls in this study. Ultrastructural cytochemistry for the localization of Na+-K+-ATPase exhibited the enzyme reaction product for this enzyme to be present mainly between the lateral epithelial cell membranes and between the apical epithelial cell membranes and superficial cortical fiber membranes. In cortical fibers the reaction product was localized between fiber membranes. Although there was very little or no significant differences in the extent of reaction product in epithelial cells, the reaction product in the cortical fibers of six-month-old Emory mouse was less extensively distributed as compared to lenses from control CFW mice of the same age.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Sodium-potassium-dependent-ATPase activity in Emory mouse lens. 301 58

The steady-state kinetics of hydrolysis of Mg2+ ATP by the epithelial Na,K-ATPase of individual human lenses were determined. Among the cataract lens population, four distinct kinetic types were observed: negative kinetic co-operativity. Michaelis-Menten kinetics, positive kinetic co-operativity, and substrate inhibition kinetics. Negative kinetic co-operativity and Michaelis-Menten kinetics were also observed in a group of presumably clear lenses from non-diabetic individuals ages 16-42 years. Substrate inhibition kinetics were found to be prevalent in individuals with mature onset diabetes. Substrate inhibition kinetics were also observed for Na,K-ATPase isolated from lenses which had been incubated in high glucose. It would appear that this modification leads to an inhibition of Na,K-ATPase-dependent K+ influx into these cultured lenses.
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PMID:ATP hydrolysis kinetics of Na,K-ATPase in cataract. 301 82

When rat lens is incubated in 30 mM galactose overnight, the extent of accumulation of rubidium ions (Rb) and myoinositol (MI) are affected, as well as the Na-K ATPase activity. Rb accumulation and Na-K ATPase activity are only slightly affected compared to the dramatic drop in MI accumulation. These changes are completely abolished by sorbinil, which blocks polyol formation, or by rendering the galactose medium hypertonic to offset the osmotic effect of polyol formation. On the other hand, the addition of excess MI to the galactose medium had no effect on correcting these changes. The results obtained are consistent with the polyol-osmotic theory of sugar cataract formation.
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PMID:The accumulation of myoinositol and rubidium ions in galactose-exposed rat lens. 301 19

Prolactin has been known to affect the water and electrolyte balance. Because increased lens hydration has been shown to be a common phenomenon in most, if not all types of cataracts, we have been interested in investigating a possible role of prolactin in sugar cataract induction and progression. For this study, we have used morphological and biochemical approaches. The prolactin delivery method involved intraperitoneal implantation of one or more pellets in Sprague-Dawley female rats. Following implantation of the desired number of prolactin or control (nonprolactin) pellets, animals were either fed galactose and lab chow, or lab chow diet. Gross morphological observations of whole lenses, slit-lamp examination of lenses and light microscopic analysis of lens sections showed that in the galactose-fed prolactin group, galactose associated alteration progressed faster and total opacification (mature cataract development) was achieved earlier than in the nonprolactin group. The levels of galactose and dulcitol were higher in the lenses of galactose-fed prolactin treated rats as compared to lenses from nonprolactin (control) rats. No significant difference in lens Na+-K+ ATPase activity between the prolactin and nonprolactin group was observed. Our results indicate that prolactin accelerates galactose-induced cataractogenesis in rats.
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PMID:Effect of prolactin on galactose cataractogenesis. 303 35

The role of reduced glutathione (GSH) in lens membrane function was studied by depleting GSH with 1-chloro-2,4-dinitrobenzene (CDNB), a reaction catalyzed by GSH-S-transferase. Depletion of GSH in the lens epithelium by 70-90% led to a decrease in uptake and increase in efflux of 86Rb. ATP levels and Na+/K+-ATPase activity were normal while there was a slight decrease in lactate production. The results provide the first direct evidence that depletion of endogenous GSH per se does not lead to inactivation of Na+/K+-ATPase. However, lenses deficient in GSH when challenged with a normally tolerated level of H2O2 showed significant inactivation of membrane ATPase without a further increase in membrane permeability. Pretreatment with CDNB resulted in a 3-fold stimulation of the hexose monophosphate shunt activity which is attributed to the unexpected finding of a significant increase in the level of oxidized glutathione in the lens. It is concluded that deficiency of GSH causes a marked increase in membrane permeability and such lenses are susceptible to oxidative damage resulting in inactivation of the Na+/K+ pump, thus leading to ionic changes and cataract development.
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PMID:Effect of glutathione depletion on cation transport and metabolism in the rabbit lens. 318 92


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