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)

Endocrine abnormalities in myotonic dystrophy (MyD) reflect some of the multi-systemic involvement resulting from this disorder. One of these, abnormal insulin secretion, is considered to be caused by receptor dysfunction. Bone abnormalities, cataract and calcium transport defect suggest the abnormal calcium metabolism in MyD. The calcium metabolism is chiefly regulated by parathyroid hormone (PTH). An interest in the similarity between MyD and pseudohypoparathyroidism, which is a disorder of PTH receptor dysfunction, encouraged the authors to evaluate renal PTH receptor function from the responses of urinary adenosine 3',5'-monophosphate (cAMP) and phosphate excretion after administration of human PTH(1-34). The responses of cAMP were high in 3 cases, low in one case, but normal in the 4 other cases. The phosphaturic responses were elevated in 3 cases, reduced in 3 cases, and normal in 2 other cases. Since these abnormal responses closely mimic those in hypoparathyroidism, there may also be renal PTH receptor dysfunction in some cases of MyD. The results of the present study suggest another peptide hormone receptor defect, similar to insulin, which supports the hypothesis of generalised receptor dysfunction in MyD.
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PMID:Evaluation of renal parathyroid hormone receptor function in myotonic dystrophy. 299 4

The age-related changes of calpain II (high-Ca2+-requiring form of Ca2+-dependent cysteine proteinase; EC 3.4.22.17) and alpha-crystallin in the lens of hereditary cataract (Nakano; cac/cac) mouse were studied. Before the onset of the cataract formation, i.e., at the end of the 2nd week after birth, the calpain activity in Nakano mice was as high as that in the control ICR mice, but it decreased rapidly as the cataract progressed to completion during the 4th and the 12th week. Marked degradation of lens proteins ensued between the 2nd and the 4th weeks, and one of these proteins was identified, using monospecific antibodies, as B chain of alpha-crystallin. A chain of alpha-crystallin was not degraded in vivo, in contrast to its known susceptibility to calpain in vitro. The present data suggest that in Nakano mice, calpain may be involved in the onset or early stage of the cataract formation.
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PMID:Age-related changes of calpain II and alpha-crystallin in the lens of hereditary cataract (Nakano) mouse. 299 2

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

Calpain II (EC 3.4.22.17), a calcium-dependent neutral protease, was purified approximately 7000-fold from the soluble of rat lens. The estimated molecular weight of rat lens calpain II was 120,000, and the enzyme was composed of 80,000 and 28,000 MW subunits. Calpain II required 400 microM calcium, a reducing agent, and pH = 7.5 for maximal activity. The enzyme could not be activated by magnesium, and was inhibited by leupeptin and iodoacetate, but not by phenylmethylsulfonyl fluoride. Purified calpain II degraded rat alpha, beta H-, and beta L-crystallins, insoluble proteins, and intrinsic membrane proteins, gamma-Crystallin was not degraded. The proteolysis caused by purified calpain II was similar to proteolysis occurring during the formation of several experimental cataracts in rodents; this suggested that the enzyme may play a role in cataract formation.
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PMID:Purification of calpain II from rat lens and determination of endogenous substrates. 301 81

Lens repair and calcification have been studied in an experimental rabbit model of anterior segment necrosis. Findings were compared with those in a human senile cataractous lens with subcapsular calcification. Rabbit lenses subjected to anterior segment ischemia underwent a repair process similar to that observed in perforating lens injuries. Cellular response included the formation of fibroblast-like cells that covered epithelial defects of the anterior pole. These observations suggest that the lens epithelium can transform into fibroblast-like cells. The calcification process was a non-cell-induced, and the observed mineral was probably nucleating on organic molecules. Elemental analysis demonstrated that crystals contained calcium and phosphorus with a ratio of 2:1. The mineral was probably hydroxyapatite. Since morphological findings in rabbit lenses closely resemble those of the studied cataractous human lens, the rabbit model appears to simulate one type of lens calcification in senile cataract.
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PMID:Human and experimental lens repair and calcification. 302 47

Selenite cataract is a fairly recently described, experimental animal model for cataract (1). Selenite cataract has been extensively characterized histologically (2) and biochemically (3,4). The model has been particularly useful for studies on the roles of calcium accumulation and lens proteolysis in cataract formation (4). This review describes current knowledge of the biochemical mechanism for selenite cataract and indicates how the model may be used for further understanding of cataractogenesis in general.
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PMID:Selenite cataract: a review. 303 16

Fifteen dogs with primary hypoparathyroidism diagnosed at the University of California Veterinary Medical Teaching Hospital were compared with 13 previously reported cases. Age, sex, breed, and historical and physical findings were similar in both groups of dogs. Middle-aged females were affected primarily. A history of neurologic or neuromuscular disease was present in all 28 dogs, with 18 dogs having seizures. Posterior lenticular cataract formation secondary to hypocalcemia was suspected in six dogs. The most characteristic biochemical finding in all dogs was profound hypocalcemia (less than 6.5 mg/dl) and mild hyperphosphatemia. Serum magnesium concentrations were decreased in two dogs. Serum parathyroid hormone concentrations were consistent with the diagnosis of primary hypoparathyroidism in eight of nine dogs. Lymphocytic parathyroiditis was diagnosed in the 12 dogs from which tissue was submitted for histopathology. Successful management of the patient depended on frequent monitoring of the serum calcium concentration during initial and maintenance therapy.
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PMID:Primary hypoparathyroidism in the dog. Report of 15 cases and review of 13 previously reported cases. 306 94

A long-term system of organ culture for bovine lenses was used to investigate the effect of osmotic stress on lens opacification and crystallin loss. Lenses were pre-incubated in control medium containing L-[U-14C]tyrosine so that labelled crystallins were produced. The fate of these crystallins was studied in relation to two forms of osmotic stress. The addition of either ouabain or EGTA to the medium induced severe osmotic swelling and disturbance of the lens monovalent cation balance, but only the former treatment was followed by an increase in lens calcium. The changes due to osmotic stress were accompanied by loss of transparency and protein only in the lenses with increased calcium. Both opacification and increased calcium were found largely to be confined to the outer cortical fibres. Protein loss increased with time as lens calcium continued to increase. The protein recovered from the incubation medium was characterized by gel filtration and immunological techniques. The first protein detected was beta L-crystallin, and this formed the major part of the lost protein throughout, although alpha- and gamma-crystallins were detected at a later stage. Increased calcium also resulted in a change in the susceptibility of the crystallins to aggregation, since there was an increase in [14C]tyrosine incorporated into the lens high-molecular-weight (HM) fraction after exposure to ouabain, but not after exposure to EGTA. The relevance of these findings to human cataract is discussed.
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PMID:Calcium-induced opacification and loss of protein in the organ-cultured bovine lens. 308 64

The Emory mouse develops a late-onset hereditary cataract bearing some resemblances to human senile cataract. It was used as a model system for testing the effects of several drugs expected to have anticataractogenic potential. A low level of added dietary alpha-tocopherol had only a marginal effect. Penicillamine increased lens soluble protein, a good index of lens viability. Triethylenetetramine was too toxic to permit satisfactory treatment. Mercaptopropionylglycine produced several positive effects including a retardation of cataract at 6 months of age; parameters which increased under drug treatment were lens weight, soluble protein content and protein sulfhydryl, but not glutathione. There was no effect on the total calcium concentration.
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PMID:The Emory mouse cataract: the effects on cataractogenesis of alpha-tocopherol, penicillamine, triethylenetetramine, and mercaptopropionylglycine. 319 85

During 1981 - 1986 3 women with similar complaints were seen. Their symptoms were tetany and congestive cardiac failure (CCF) without a previous history of cardiac disease or alcohol abuse. One patient did have a history of cataract removal and epilepsy and all 3 had ECGs showing prolonged Q-T intervals and echocardiograms consistent with the diagnosis of cardiomyopathy. Biochemical profiles were similar: hypocalcaemia, hyperphosphataemia and normal serum urea levels. Parathyroid hormone levels were inappropriately low in all 3 cases. The tetany and CCF responded to calcium +/- magnesium infusions together with diuretics and in 2 cases, digoxin therapy. All 3 patients are well at present, and are controlled on 1-alpha-hydroxyvitamin D3 and calcium supplements.
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PMID:Cardiac dysfunction in primary hypoparathyroidism. A report of 3 cases. 334 Sep 68


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