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

The controversy as to the relationship between the degree of control of diabetes and the progression of the complications of the disease has not been solved. However, in this review, various studies suggesting a relationship between the metabolic abnormality and the diabetic complications are examined. The disadvantages of the uncontrolled diabetes mellitus can be divided into two major categories-short-term and long-term. The short-term disadvantages of controlled diabetes mellitus include the following: (1) ketoacidosis and hyperosmolar coma; (2) intracellular dehydration; (3) electrolyte imbalance; (4) decreased phagocytosis; (5) immunologic and lymphocyte activity; (6) impairment of wound healing; and (7) abnormality of lipids. The long-term disadvantages of uncontrolled diabetes melitus include the following: (1) nephropathy; (2) neuropathy; (3) retinopathy; (4) cataract formation; (5) effect on perinatal mortality; (6) complications of vascular disease; and (7) the evaluation of various clinical studies suggesting the relationship of elevated blood glucose levels and complications of diabetes mellitus. It is suggested that until the question of control can absolutely be resolved, the recommendation is that the blood glucose levels should be controlled as close to the normal as possible.
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PMID:Why control blood glucose levels? 81 31

In Part I1 of this study, the thermolability of lens hexokinase was implicated in the development of an experimental "hypoglycemic" cataract. After eight hours of glucose deprivation, there is a precipitous loss of lens hexokinase. This occurs approximately nine hours prior to the disorganization of the other enzymatic steps in glycolysis. Epithelial hexokinase, as an immediate response to glucose deficiency, shifts from the soluble to the insoluble phase. There is no such shift in the cortex-nucleus where only soluble hexokinase is found. After eight hours of glucose deprivation, both soluble and insoluble hexokinases throughout the lens undergo rapid deactivations. During the first eight hours of glucose deprivation the loss of lenticular ATP and K+ and the gain in wet weight can be reversed by restoring normal glucose levels; beyond eight hours the changes are irreversible. During the period of reversibility, hexokinase activity levels are normal; during the period of irreversibility hexokinase activity is 10 to 20 per cent of normal. Of the substances tested (mannose, galactose, fructose, glutamine, adenosine) only mannose could sustain the lens in the absnece of glucose. Neither endogenous free glucose nor glycogen could sustain the lens in the face of glucose deprivation. There appear to be no alternative exogenous or endogenous energy yielding substrates. The younger the animal, the more susceptible is its lens to glucose deprivation. This most certainly is a reflection of the increased susceptibility of younger lenses to osmotic stress, since lenses in each age group manifested similar changes in hexokinase activity, ATP, Na+, and K+ level.
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PMID:Mechanism of "hypoglycemic" cataract formation in the rat lens. II. Further studies on the role of hexokinase instability. 93 98

Warburg experiments showed the oxygen consumption by lens epithelium and iris tissue without and after addition of 4 mg methylprednisolone to 100 cc medium. In the last case the O2-uptake of the epithelium seemed diminished, that of the iris tissue showed significantly reduced to 50%. The determination of the consumption of glucose was done by measuring its level in the medium before and after a 5 day's incubation, without and after addition of 4 mg-% of methylprednisolone, by means of the "Merckotest". The consumption of the epithelia lowered to 1/6; contrarily rose that of the iris tissue significantly to the double amount. The metabolism of the iris tissue showed a good adaptation in compensating a lower respiratory activity by a augmented glycolysis, which is impossible to the lens epithelium. This may be one of the factors inducing a cortisonic cataract.
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PMID:[The influence of cortisone upon the metabolism of surviving lens epithelia and iris tissue (author's transl)]. 108 50

Leucinaminopeptidase (LAP), lactatedehydrogenase (LDH) and glucose-6-phosphatdehydrogenase (GPDH) were analysed in the lenses of two different breeds of mice. Compared to the lenses of a control stock (Agnes Blum, Jena), in the healthy seeming, heterozygous mice the same activities of LAP, LDH, and GPDH were found. But in the breed with evident microphthalmos and cataract LDH was increased. Possible connections are discused.
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PMID:[Enzymatic studies in lenses of different breeds of mice (author's transl)]. 108 53

Glucose, pyruvate, l-lactate, and citrate concentrations of the aqueous humour were examined in 51 patients aged 54-87 years with senile cataracts, and in one patient with a clear lens. Furthermore, the ratios of glucose in aqueous/glucose in plasma and citrate in aqueous/citrate in plasma were investigated. Among the parameters recorded, age dependence could only be demonstrated for glucose concentrations in the aqueous humour, as this parameter decreases with increasing age. However, a chance significance because of multipleignificance tests cannot be left out of account in this material. The parameters in question are unfit for an evaluation of possible changes in the energy metabolism of the lens in relation to cataract development because no significant differences were found between concentrations and ratios in different clinical types of cataract. Also, considerable ranges of variation were recorded.
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PMID:Concentrations of some metabolites in the aqueous humour of human senile cataractous eyes. 117 99

Lenses from 100 gram albino rats remain clear and possess normal levels of Na+, K+, ATP, and hexokinase activity for 20 hours incubated in medium containing 12 mM glucose. Below 2.0 mM glucose, a cataract forms and there is an abrupt rise in lens Na+ and wet weight, a fall in lens K+, ATP, and hexokinase activity. The cataract is a thin lamellar opacity involving the anterior and posterior surfaces of the lens. If the lens is deprived of glucose for 48 hours, a nuclear cataract forms; the cortex between the superficial lamellar opacity and the nucleus being clear. This experimental cataract bears a striking resemblance to the hypoglycemic cataract seen in children. The thermal deactivation of hexokinase follows rapidly upon the depletion of its substrates (ATP and glucose) and is a primary factor leading to cataract formation. This was established by incubating the lens with 2-deoxyglucose, a competitive inhibitor of lens hexokinase. This compound blocks the entry of glucose into the glycolytic sequence. The cataract formed in its presence is identical morphologically and biochemically to that observed in a glucose-free medium. The effects of 2-deoxyglucose are prevented by increasing the glucose level; this rules out a direct toxic influence of 2-deoxyglucose and further supports the primary role of hexokinase thermolability in the etiology of this experimental cataract. This in vitro system appears to be an excellent experimental model for the study of the human hypoglycemic cataract.
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PMID:Mechanism of "hypoglycemic" cataract formation in the rat lens. I. The role of hexokinase instability. 118 8

It was established earlier that the maintenance of rats on a galactose-rich diet induced in rat liver a sequental induction of enzymes, converting galactose to glucose (galactokinase, galactoso-1-phosphaturidytransferase and uridyndiphosphogalactose-4-epimerase); this was followed by the repression of these enzymes. Against the background of the enzyme repression, the continuation of galactose treatment leads to the development of galactosemia symptoms; cataracts, liver lesions growth retardation. Animals with the increased susceptibility to galactose were found in population of Wistar rats; in these animals rapidly developing enzyme induction is followed by sharp repression of enzymes of the galactose metabolism and in them cataracts appear 17-19 days after the start of feeding a galactose-rich diet. A part of the population is resistant to the galactosemic effect of galactose and in these animals cataracts develope only 40-44 days after the beginning of the galactose feeding. By inbreeding of individuals extremely susceptible to galactose and those resistant to it, new substrains of rats were obtained. It is found that in the rats of the galactose-susceptible substrain a number of galactosemic features develope spontaneously and that these features are inheritable. Thus, 85% of the animals of the age of 2.5-6 months have cataract, lens opacities and other lens impairments. In the galactose-resistant substrain no cataracts or lens opacities develope and only slight changes of the lens are observed in 15% of the animals. In the susceptible substrain other features characteristic of galactosemia occur: an increase in the size of thymus, spleen and liver. It is established that in 3.5-5 month old rats of the galactose-susceptible substrain the galactoso-1 phosphaturidyltransferase activity in blood hemolysates is 15 times lower than in rats of galactose-resistant substrain, and in liver the activity of this enzyme is 1.4 times lower. The activity of liver galactokinase and uridyldiphosphogalactose-4-epimerase is slightly higher in rats of galactose-susceptible substrain than in galactose-resistant 1.
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PMID:[Development of a rat subline with symptoms of hereditary galactosemia and study of its biochemical characteristics]. 124 Aug 12

Senile cataract is the major cause of curable blindness in Tunisia (51%). Other factors than advanced age seem to play a role in senile cataract. The simultaneous of senile cataract with the trachoma makes the surgical operation problematic. In order to evaluate the frequency of such risk factors, we have realized a prospective study in two groups of patients recruited in 4 hospitals centers in Tunisia. The two groups of patients were homogenous regarding to age (more than 45 old year) sex and geographic origins. Cataract was present in the first group (287), but not in the second group (169) risk factors which were evidenced are: diabetes or abnormal glucose test tolerance, high systemic blood pressure, especially diastolic, low education and non professional occupation, family history of cataract. Evolutive trachoma was found in 5.1% of cases compared to only 0.6% in controls (p = 0.02). Trachoma sequela were found in the two groups. The importance of an evaluation of such risk factors in senile cataract is raised.
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PMID:[Senile cataract and trachoma in Tunisia]. 134 67

Chromium (Cr) is of known biological importance, necessary for the maintenance of normal glucose metabolism. There is a lower level of blood Cr concentrations in cases of diabetes. Diabetes carries a risk of cataract development, so the potential effects of Cr on the eye may need to be studied in more depth. The presence of this trace element in both normal and cataractous human lenses has to our knowledge not been investigated so far. The concentration of total Cr in 61 human lenses and 38 blood samples was determined by electrothermal atomic absorption spectrometry with Zeeman effect (EAASZ). Analysis of the levels of Cr in human lenses shows a significant difference between normal and diabetic populations, and an absence of difference between senile and diabetic populations.
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PMID:A study of chromium in human cataractous lenses and whole blood of diabetics, senile, and normal population. 137 49

To learn whether glycation plays a role in insolubilization or in senile cataractogenesis, the reactivity of lens protein from normal and senile cataractous lenses and individual crystallin prepared from human lens with various sugars [glucose, glucose-1-phosphate (G-1-P), glucose-6-phosphate (G-6-P) and fructose], and the insolubility of those proteins were determined. The reactivity of human lens protein to glucose was increased in a dose-dependent manner, and it was demonstrated that 17.9, 18.5 and 24 kDa proteins were susceptible to glycation with sugars. The study also showed that alpha-, beta-crystallins and high molecular weight (HMW) aggregate obtained from cataractous lens have some weak reactivity against sugars. It was demonstrated that the proteins obtained from normal lens of older age and from cataractous lenses have higher insolubilities to glucose than do normal younger ones. Measurement of glycosylated protein by affinity column chromatography revealed that cataractous lenses contained a larger amount of glycosylated protein than normal ones. These results suggest that there is an age-related increase of glycation in normal human lens protein, and that such glycation increases the amount of insolubilized protein with the effect of aging. The author also speculates that an abnormal acceleration of glycation in the human lens may induce senile cataract formation.
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PMID:Glycation and insolubility of human lens protein. 146 10


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