Possible role of polyamines in gyrate atrophy.

PURPOSE: Gyrate atrophy (GA) is marked by hyperornithinemia and lowered ornithine amino transferase (OAT). However there are patients of GA without hyperornithinemia and those with hyperornithinemia without GA. Some cases of GA have been reported to have low lysine. The purpose of the study was to determine if polyamines, the metabolites of ornithine, and lysine have any diagnostic role in GA. METHODS: Ornithine in plasma was estimated by two-dimensional paper chromatography, with elution of the coloured spot, and the absorbance measured using a spectrophotometer at 560 nm. OAT assay in lymphocytes was done spectrophotometrically using ornithine as substrate. Blood and urinary polyamines were extracted with n-butanol, benzoylated and analysed with HPLC; putrescine, spermine, spermidine, and cadaverine were assayed individually at 254 nm with the UV detector using ODS, G18 column with 63% methanol as solvent. RESULTS: Of the 7 patients investigated, 6 had features typical of GA. One was diagnosed to have atypical retinitis pigmentosa (case 3). The first five cases had elevated ornithine and diminished OAT, but cases 6 and 7 had near-normal ornithine and case 7 had near-normal OAT. However, all 7 patients had increased levels of total polyamines in urine compared to normals. Five had increased putrescine and three had increased spermine. All the 7 had decreased cadaverine in urine. Thus, though there were inconsistencies with ornithine and OAT, all the 7 patients had elevated polyamines from ornithine and decreased cadaverine. CONCLUSION: In addition to estimating ornithine and OAT in GA, it is suggested that urinary polyamines may be analysed as the latter appears to correlate better with the clinical condition and help in the diagnosis to a greater extent. Moreover, while ornithine is an innocuous amino acid, polyamines are known to damage DNA and proteins.

Two new functions of inositol in the eye lens: antioxidation and antiglycation and possible mechanisms.

The extent of glycation of human eye lens proteins with glucose in presence of added inositol was examined in vitro using [U14C] glucose. Lens homogenate was reacted with varying concentrations of glucose and glucose + inositol. At the end of the reaction, the proteins were precipitated with TCA, centrifuged, dissolved in NaOH and the radioactivity was measured. Inositol decreased the glycation by 57-67%. Pure inositol and glucose suitably labelled with 3H or 14C when reacted and followed by paper chromatography and HPLC showed that glucosyl inositol was present along with unreacted free glucose. Preliminary studies made of the UV spectra of pure inositol (i) when reacted with H2O2 showed that inositol removed H2O2 from the reaction mixture (ii) when reacted with arachidonic acid showed that they formed a conjugate. The observations indicate that the antioxidant property of inositol could be the result of its' quenching action on reactive oxygen, intermediates and conjugate-formation with compounds like arachidonic acid and the antiglycating property due to scavenging of glucose. The antioxidant and the antiglycating properties of inositol may be beneficial in delaying or averting cataract.

Transthyretin (prealbumin) in eye structures and variation of vitreous-transthyretin in diseases.

PURPOSE: To evaluate the presence of transthyretin (TTR, prealbumin) a protein which binds retinol to retinol-binding protein in various ocular tissues and to study its quantitative changes in the vitreous humor in various diseases. METHOD: Estimation of TTR was done by electrophoresis of 10 mg protein in each sample of tears, aqueous humor, vitreous, retina, and lens by an Imaging Densitometer using prealbumin as the standard. RESULTS: TTR was present in all the eye structures except the lens and tear. The retina and the vitreous had relatively higher amounts of TTR compared with aqueous. The identity of TTR was confirmed by immuno-electrophoresis using anti-human TTR. Two bands in SDS electrophoresis revealed that this protein is a heterodimer. There was a significant decrease in vitreous TTR in diabetes with hypertension and increase in one case each of diabetes with hypertension associated with leukaemia or carcinoma with hepato-splenomegaly. CONCLUSION: Vitreous TTR is probably from retina and retinal pigment epithelium. The level of vitreous TTR is likely to have diagnostic significance in some retinal diseases.

Pregnancy-exaggerated galactosemia and congenital cataracts.

One child in a family and two children in another family had galactosemia and congenital cataract. Two of them had total soft cataracts while in one, cataract was less soft. In addition, they had mild lactosuria. The mothers of the affected children had significant lactosuria and mild galactosuria without cataracts. Fathers did not have galactosuria or lactosuria. Clinically unaffected siblings in one family had mild galactosuria and lactosuria. Pregnancy-exaggerated galactosemia was suspected in these two mothers who gave birth to children with congenital cataract. As an extension of this work, 5001 pregnant women were screened for galactose in urine just before the delivery of babies. Mild galactosuria was present in 54 (1.08%). Three children had congenital cataract and one had changes in posterior pole and cornea. Restriction of lactose by reducing intake of milk and milk products during pregnancy by mothers with galactosuria is recommended to avoid the birth of children with congenital cataract.

Free lysine, glycine, alanine, glutamic acid and aspartic acid reduce the glycation of human lens proteins by galactose.

The amino acids lysine, glycine, alanine, glutamate and aspartate formed adducts with galactose at physiological pH and temperature as shown by incorporation of U[14C] galactose. The percentage of galactose reacting with lysine, glycine, alanine, glutamate and aspartate was 4.5 to 7.8, 7.9 to 10.8, 3.2 to 4.6, 2.8 to 4.8 and 3 to 5.2, respectively. Studies with lysine showed that the extent of glycation of the free amino acid increased with time. Incubation of lens homogenate with galactose, effected glycation of proteins. Addition of lysine in concentrations of 5 and 10 mM to equimolar concentrations of galactose decreased the glycation of lens proteins by 64% to 71%; glycine, alanine, glutamate and aspartate decreased glycation by 23 to 68%, 32 to 61%, 35 to 56% and 26 to 61% respectively. Under similar conditions, glycine reacts to a greater extent than lysine, alanine, glutamic and aspartic acids. However, lysine was more effective than glycine, alanine, aspartic and glutamic acids in decreasing glycation of lens proteins by galactose. The decrease of glycation with added lysine increased with time. In general increase of amino acid concentration rather than that of sugar augmented the decrease of glycation of lens proteins.