Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0086543 (cataract)
 29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Parathyroid hormone (PTH), calcitonin (CT)and calciferol (Vit. D3) operate synchronously to maintain a balance between calcium and phosphate levels in serum. An aberration of specific steps in the homeostatic process results in hypo/hyper phosphatemia. These aberrations may eventually lead to several diseased states. PTH and Vit. D3 induced hypercalcemia can, however, be significantly inhibited by calcitonin (CT). These findings have been correlated with the levels of calcium and phosphate obtained from human senile cataractous lenses of cortical and nuclear types. The comparison of the results indicate that amongst these three hormones PTH is most vulnerable in leading towards conditions for possible cataract formation in rat lens.
 ...
PMID:Endocrine regulation of calcium and phosphate in rat eye lens and its significance in cataract formation. 216 90

The Nakano mouse is a hereditary cataract model whose most characteristic change is a deficiency in lens Na+,K(+)-ATPase. Consequently, there is a change in lenticular sodium and potassium ion levels just before cataract formation. The amounts of calcium ion also change suddenly in the lens, with accumulated levels higher than any other type of cataract. Other biochemical changes coincide with the development of lens opacity, including decreases in the levels of reduced glutathione, ATP, biosynthetic activity of proteoglycans in epithelial cells, and the permeability of gap junction channels in fiber cells. The decrease in the activity of Na+,K(+)-ATPase results in changes in a number of key metabolic parameters, resulting in the eventual opacification of the Nakano mouse lens at approximately 30 days of age.
 ...
PMID:Hereditary cataract of the Nakano mouse. 219 7

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.
 ...
PMID:Nutritional factors in cataract. 220 Apr 64

Cataracts were produced in rat lenses by either feeding a diet containing 50% galactose or by inducing diabetic condition by intravenous injection of streptozotocin. Proteolysis of crystallins, protease activity of calpain II enzyme (EC 3.4.22.17), and presence of calpain molecule (antigen) were determined at four cataract stages--I, cortical vacuoles, II, vacuoles plus hazy cortex, III, nuclear cataract, and IV, mature cataracts. Calpain activity was normal or moderately elevated at early stages of galactose and diabetic cataracts. Later stages III and IV showed proteolysis of lens crystallins, increased proportion of insoluble proteins, loss of calpain enzyme activity and calpain molecule from the soluble fraction, and reduced amounts of calpain associated with insoluble pellet. In galactose cataract, the largest increase in lens calcium were found when proteolysis was present. These results provide evidence for calpain-induced proteolysis of lens crystallins in two in vivo models of sugar cataracts in rodents.
 ...
PMID:Calpain II in two in vivo models of sugar cataract. 220 51

The mechanism of lens protein aggregation with age and/or cataract formation was investigated using the peptides resolubilized from the insoluble protein fraction of normal and cataractous human lenses. The insoluble fraction was treated with reductants for cleaving disulfide bonds, or with chelating agents for removing calcium ions from the aggregates. This study demonstrates that the insoluble protein aggregates consist of an approximately 400 Kd complex, which is formed by the peptides with lower molecular weight. Protein aggregation in the cataractous lens might be caused by disulfide bonds whereas, in aging, the aggregate might be preferentially formed by calcium ion bridges rather than by disulfide bonds. It was observed that the aggregate from the cataractous lenses involved a peptide with a molecular mass lower by 1 Kd or 2 Kd than the peptides found in the normal lens. The composition of crystallins in aggregating proteins and their secondary structures were also different in the normal and the cataractous lenses. Such changes of molecular weight, conformation, and/or crystallin species in the lens may lead to the disintegration of the orderly arrangement of crystallins, resulting in the diffused reflection and lens opacities which are seen in senile cataract.
 ...
PMID:Characterization of water-insoluble proteins in normal and cataractous human lens. 221 64

Total calcium and total protein contents have been determined in Emory mouse cataracts from 6 to 19 months of age and also in age-matched Cataract-resistant control lenses. The normal lens calcium is about 0.006 micrograms/mg fresh lens weight; in cataracts the value increases from about 0.02 in beginning cataracts to 0.4 in severe cataracts. Calcium does not increase with age in control lenses. Elevation of calcium levels never precedes initial cataractous changes and is most probably a secondary change. This mouse cataract, unlike human senile cataracts, invariably accumulates calcium and the magnitude is roughly proportional to the severity of cataract. It appears to be a simpler and more homogenous type than human cataract and is therefore more suitable for biochemical studies.
 ...
PMID:The Emory mouse cataract: increased accumulation of calcium during cataractogenesis. 248 87

Vitamin D3 in the presence of calcium lactate induced significant hypercalcemia and hyperphosphatemia while calcitonin in the presence of a chelating agent (EGTA) induced hypocalcemia and hypophosphatemia in the rat lens. The physiologic significance of these changes in relation to cataract formation was understood by correlating the ratio of calcium and phosphate in the rat lens with the similar ratio obtained from human cataractous lenses of cortical and nuclear types.
 ...
PMID:Vitamin D3 and calcitonin-induced regulation of calcium and phosphate in rat lens--its significance in cataract formation. 254 57

Among 38 cases of hypoparathyroidism, 32 patients were found to have hypocalcemic cataract. The morphology and mechanism of cataract formation were studied by clinical observation and biochemical calcium determinations, which indicated that the development of hypocalcemic cataract was related to the calcium level in blood but not to the duration of disease. The results suggest that early diagnosis and treatment of hypocalcemia may be useful in controlling the development of cataract. Calcium determinations showed that the blood calcium level was related to that in the aqueous humor. It is probable that the blood calcium content may reflect the calcium level in the aqueous humor, thus evaluating the tendency for cataract development.
 ...
PMID:[Clinical observations and calcium determinations in hypocalcemic cataract]. 263 1

A 3 years old boy was admitted due to recurrent attacks of tetany and carpopedal spasm since one and a half years of age. The tetany lasting for 1-2 minutes in each episode was often preceded by an upper respiratory tract infection and occurred 2-3 times a month. Both birth and family history were unremarkable. Physical findings showed mild psychomotor retardation with positive Chvostek sign. Laboratory examination revealed hypocalcemia, hyperphosphatemia, and low serum parathyroid hormone level. EEG showed abnormal tracing with increased slow waves. Head CT Scan demonstrated symmetrical calcification in the basal ganglia region. The clinical features and laboratory findings were consistent with hypoparathyroidism. The mechanism of calcium deposit in the basal ganglia still remains unclear. Tetany, muscle cramping and seizures secondary to hypocalcemia are the most common neurologic signs which respond quickly to calcium replacement. Subsequent supplemental therapy resolved movement disorders and mental retardation. If early treatment prior to the tetanic episodes is instituted in a patient with hypoparathyroidism, it may prevent the development of complications such as intracranial calcifications, cataract and permanent retardation.
 ...
PMID:[Primary hypoparathyroidism with basal ganglia calcification: report of a case]. 263 91

Incubation of intact rat lenses under conditions that stimulated a net influx of calcium resulted in a pronounced loss of transparency and a major decrease in the levels of spectrin. The progressive loss of this cytoskeletal component coincided with the appearance of polypeptides of approximately 150 kDa which showed immunoreactivity with an antibody raised to spectrin. These bands disappeared on further incubation. It is, therefore, suggested that a calcium-activated protease is present in the lens which is capable of degrading spectrin by the initial removal of approximately 90 kDa fragments. This process calcium-induced proteolysis may be the basis for the cytoskeletal reorganisation observed during the differentiation of lens fibre cells and may be involved in cataract development.
 ...
PMID:Calcium-induced cleavage and breakdown of spectrin in the rat lens. 266 53


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>