More than 5 million cataract surgery is carried out in many third world countries including India. The enzymes associated with the synthesis, catabolism and utilization of glutathione, ascorbic acid and proteins in the lens have been reported with the progression of cataract. It shows increase percentages of urea DTT soluble (UDTTS) and urea DTT insoluble (UDTTIS) fraction in all types of cataractous lenses. The average values of UDTTS and UDTTIS proteins in normal human lenses are 9.21 ± 0.08 and 1.22 ± 0.04 ug/mg (mean ± s.e.) respectively. Similarly the average values of the same protein fractions in cataractous lenses are 90.23 ± 10.3 and 81.46 ± 7.6 ug/mg (mean ± s.e.) respectively. The lowest and highest values for UDTTS fraction were obtained in PSC- CS and Brown cataract and are 40.2 and 242.9 ug/mg respectively. The results presented in the current study show both cataract formation and normal ageing are accompanied by a decrease in the solubility of the lens proteins. Most of the color of the lens is associated with urea-insoluble protein fractions. Amongst urea-insoluble fraction, the brown protein fraction was more predominant over yellow protein fraction.
Key words : UDTTS, UDTTIS, Human, Lens, Protein fractions
A socio-economic cause of visual defect during aging is not only an important health problem but also one, especially in the tropical countries. Inhibiting or cure in the progression would present a major achievement for human welfare and is therefore one of the priorities of medical research in our country. 41 million people are blind globally of which, 17 million (42%) people are experiencing profound or total loss of vision due to cataract.
Recent research has clearly shown that oxidative stress is a very important risk factor for cataract development (Truscott et al., 2005).
The lens protein crystalline account for 80-90% of the soluble proteins of the lens which provide consistency and transparency of the lens (De Jong, 1981). It is suggested by the observation that, at physiological concentration, ascorbic acid inhibits (about 25%) insolubilization and darkening of the lens from exposure to near UV light. Since dehydro ascorbic acid can be reduced by glutathione (Miratashi, 2001) . It seems possible that ascorbic acid could from part of a protective system as ascorbic acid is antioxidant and in human it is not synthesis in the body but needed through diet (Pandya et al., 2012).
The color of lens is due to glycation and aggregation of lens proteins. Due to aggregation of small molecular weight lens proteins heavy molecular weight aggregates come into existence. The cataractous protein appears to be stabilized by disulphide bonds whereas the protein from normal lenses is not (Dilley, 1975). To find out the changes leading to the production of modified protein fractions from the cataractous and normal human lens and the relationship between them, this study was conducted.
Materials and methods
The urea-soluble, urea-insoluble, Urea- DTT soluble and Urea-DTT insoluble lens proteins fractionation was done by the standard method of Coghland and Augusteyn (1977). Determination of protein was done by the method of Lowry et al., (1951).
The weighed lenses were homogenized in cold distilled water and centrifuged at 4,000 g for 30 mins. and the supernatant was used for other experiment and the residues were dissolved in 8 M urea and centrifuged again. The supernatant obtained was used for other experiment and residues were again dissolved in 8 M urea containing 0.1 nm DTT and centrifuged again. The supernatant obtained was used for the estimation of yellow fraction of lens proteins. The residue were dissolved in 0.3 N NaOH and estimated as brown fractions of lens proteins. The procedure is summarized in figure -1.
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Figure - 1
The lenses of the patients who underwent extracapsular cataract surgery at Nagari Eye Hospital, Ahmedabad, by medical Dr. involved in surgery, were collected. Several eyes with clear lens were obtained from C. H. Samaria eye bank, Red Cross society, Ahmedabad, India.
Statistical analysis: All results were expressed in mean s.e.. One way analysis of variance (ANOVA) was used to test the significance of difference and Bonferroni test to test the significance of difference between control and different cataract types. The p value less than 0.05 is considered as significant. The results are expressed graphically by considering values of control lens as control as 100%.
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- Institution / Hochschule
- C. U. Shah Science College