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)

Na,K-ATPase, an enzyme intrinsic to the membrane of most cells, is inhibited in cataract. Na,K-ATPase, activity in clear non-cataractous lenses is found predominantly in the lens epithelium. The lens fiber cells would appear to be unique, among mammalian cells in that Na,K-ATPase activity is low if not absent. The study presented here indicates that Na,K-ATPase is present, often in high concentration, but progressively more functionally compromised as the fiber cells mature. The membrane lipid environment as causative agent in the loss of normal function of Na,K-ATPase, is considered in this study. The data indicate a correlation between increasing cholesterol/phospholipid ratio, increasing phospholipase A2 activity and decreasing Na,K-ATPase activity in normal clear lenses. The phospholipase A2 activity is higher in cortex and nucleus than in the epithelium of normal bovine and human lenses. The phospholipase A2 is Ca2+ dependent and may be membrane associated.
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PMID:Na,K-ATPase and phospholipid degradation in bovine and human lenses. 131 22

Rabbit eye aqueous humor contains lysolecithin (LPC); the LPC concentration markedly increases, if the integrity of the hemato-aqueous barrier is impaired. It is assumed that LPC plays a causal role in the development of cataract because of its detergent action. We have studied the mechanism of LPC cumulation in the aqueous after a mechanical, endotoxic or immunological damage to the hemato-aqueous barrier. We measured in aqueous samples the activity of lecithin cholesterol acyltransferase (LCAT, EC 2.3.1.43), an enzyme which produces LPC and cholesteryl esters in the plasma. The transfer of phospholipids from the plasma into the aqueous was examined in vivo in 32p-prelabeled rabbits. Whereas LCAT was absent in the aqueous humor of intact eyes, an increased transesterification activity could be detected in all cases of impaired hemato-aqueous barrier. The proportion of LPC in aqueous phospholipids was similar to that found in high density lipoproteins, whereas whole plasma and low density lipoproteins contained a much lower proportion of LPC. An increased plasma level of LPC induced by the treatment of rabbits with phospholipase A2 in vivo, did not by itself lead to a preferential passage of plasma LPC through the blood-aqueous barrier. The experimental results rather imply that an impaired blood-aqueous barrier permitted an enhanced transfer from the plasma of intact HDL carrying also LPC and LCAT, and that the enzyme subsequently produced increased amounts of LPC in situ.
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PMID:Lecithin cholesterol acyltransferase and possible origin of lysolecithin in rabbit aqueous after a damage of blood-aqueous barrier. 273 51

The objectives of this study were to investigate the cause of the great difference in the concentration of phospholipids between the cortex and nucleus of the ocular lens and to further investigate the mechanism of cataract induction by the sterol synthesis-inhibitor U18666A. The nucleus of the young rat lens was found to contain less than one-third the concentration (micrograms/mg lens region, dry wt) of total phospholipid present in the cortex. The sterol to phospholipid molar ratio in the nucleus was more than double that in the cortex. Phosphatidylcholine plus phosphatidylethanolamine were the principal phospholipids in both the lens cortex and nucleus. The activity of phospholipase A2 (PLA2), an enzyme important for turnover of cellular phospholipids, was measured in the total water-insoluble fraction from whole lenses and from isolated lens regions by the release of 1-14C-linoleic acid from the number two position of a synthetic phosphatidylcholine. The cortex was found to possess about 75% of the total PLA2 activity in the lens. Most of the remaining activity was in the nucleus. The low concentration of phospholipid in the lens nucleus could be due to breakdown of phosphoglycerides by PLA2 in the cortex as equatorial fiber cells shift toward the nucleus with aging. The cataract induced in rats by the sterol synthesis inhibitor U18666A was found to involve a major loss of total sterol from the lens cortex and almost total substitution of desmosterol for the cholesterol remaining in this region. By comparison, nuclear sterols were little affected by drug treatment and cataract development.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regional distribution of lipids and phospholipase A2 activity in normal and cataractous rat lens. 398 44

In order to determine the content of group II phospholipase A2 in the aqueous humour we studied 41 cataract patients including 8 men and 33 women with age ranging between 65 and 92 (mean +/- SD being 77.0 +/- 6.7) years. In all patients preoperative biomicroscopy showed neither aqueous flare nor cells. Eleven patients (26.8%) had pseudoexfoliation syndrome. Aqueous humour tap was done at the beginning of cataract surgery before perforating the corneoscleral wound. We used time-resolved fluoroimmunoassay for the detection of group II phospholipase A2 in the aqueous humour. The group II phospholipase A2 content in the aqueous humor varied between less than measurable (in 23 patients) and 3.3 ng/ml, with an interquartile range from less than measurable to 1.4 ng/ml. There was no significant difference in the group II phospholipase A2 content of the aqueous humour whether or not the patient had pseudoexfoliation syndrome. The results show that the aqueous humour of cataract patients contains only minute amounts of group II phospholipase A2.
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PMID:Phospholipase A2 content of aqueous humour in cataract patients. 765 42