Visual functions of workers exposed to organic solvents in petrochemical industries.

AIM: The purpose of this study was to evaluate the visual functions of workers exposed to organic solvents in petrochemical industries. MATERIALS AND METHODS: Thirty workers from the petroleum refinery and 30 age-matched controls (mean age) were recruited. Visual functions and occupational exposure levels were assessed among both the groups. Visual acuity, contrast sensitivity, color vision, and visual fields were evaluated at the workplace. The biological samples, namely blood and urine, were collected at the workplace and transported to the laboratory for analysis. The urinary excretion of hippuric and methylhippuric acid as well as creatinine was measured by high performance liquid chromatography. RESULTS: The mean age of the workers and controls were 39.7 ± 7.6 years and 38.6 ± 8.1, years respectively. The mean years of experience of the workers were 15.6 ± 6.8 years. Visual acuity was >0.01 LogMAR among both the control and case groups. The contrast sensitivity was reduced at 12cpd among workers. Comparison between groups was done using independent sample t-test. The mean difference in color confusion index was 0.11 ± 0.05 (P = 0.037*). The mean difference in visual fields was -0.31 ± 0.36 dB (P = 0.933). The mean difference in urinary hippuric acid level (urinary metabolite of toluene) between the groups was 0.19 ± 0.96 g/g creatinine (P = 0.049FNx01). The mean difference in the excretion of methylhippuric acid (urinary metabolite of xylene) was 0.06 ± 0.04g/g creatinine (P = 0.154). We also found that exposure was a significant risk factor for color vision defect with an odds ratio of 4.43 (95% CI: 1.36-14.4); P = 0.013. CONCLUSION: The study results showed that contrast sensitivity and color vision were affected among workers in petrochemical industry.

Serum PON1 arylesterase activity in relation to hyperhomocysteinaemia and oxidative stress in young adult central retinal venous occlusion patients.

AIM: To estimate the arylesterase activity of serum paraoxonase-1 (PON1-ARE), which is reported to have an antioxidant and antiatherogenic potential and to correlate with plasma homocysteine (Hcys) and plasma TBARS in young adult central retinal venous occlusion (CRVO) patients. METHODS: A case-control prospective study carried out in 10 CRVO patients (mean age 27+/-5 years; 7 males, 3 females) and 20 healthy controls (mean age 29+/-5 years; 15 males, 5 females). RESULTS: The CRVO patients showed a significantly lowered serum PON1-ARE activity (P=0.009) along with a significant increase in the levels of plasma Hcys (P=0.018) when compared to the control subjects. There was a negative correlation between serum PON1-ARE and plasma Hcys levels (P=0.058) as well as between PON1-ARE and plasma TBARS levels (P=0.001) in the CRVO patients. CONCLUSION: This is the first report of lowered serum PON1-ARE level as a risk factor for CRVO (OR= 1.108, CI=0.914, 1.314; P=0.296), which is found to correlate with oxidative stress.

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.

Beneficial effect of lysine and amino acids on cataractogenesis in experimental diabetes through possible antiglycation of lens proteins.

Rats were given a single injection of streptozotocin. They became diabetic with a blood sugar of around 300 mg dL-1. They were divided into three groups of six rats each. Group II was the diabetic control. Each one of group III diabetic rats received daily 2 ml of 2% solution of lysine supplement orally. Group IV received daily 2 ml of a 2% solution of a mixture of amino acids supplement for 120 days. In addition there were 6 rats as normal control (Group I). Periodically ophthalmic examination was done by slit lamp. Blood glucose, proteins, hemoglobin, free amino acids, glycosylated hemoglobin and glycated lens proteins were also analysed. Body weight was recorded. The diabetic controls decreased in body weight. The blood sugar levels were lowered from about 295 mg dL-1 to 99 mg dL-1 in the lysine-fed group and from 268 mg dL-1 to 126 mg dL-1 in the amino acids mixture-fed group. The levels of glycosylated hemoglobin and glycated lens proteins increased in diabetic controls while they were normal in other groups. The free amino acid levels in blood were lower in groups receiving lysine or amino acids than in diabetic controls indicating their better utilization. In diabetic control, all the animals developed cataract in 70-90 days; five out of six did not develop cataract in the lysine supplemented group. Four of six did not develop cataract in the amino acid mixture-supplemented group. None developed cataract in normal controls. Lysine and amino acids have anticataractous and antidiabetic effects.

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.

First report of congenital or infantile cataract in deranged proteoglycan metabolism with released xylose.

AIM: To investigate the chemical pathology in the blood and lens, in cases of congenital or infantile cataract in children excreting predominantly non-reducing carbohydrates in urine. METHODS: Urine samples from children with congenital or infantile cataract, and age and sex-matched controls, were analysed for (i) inherited errors of metabolism, (ii) paper chromatography of sugars, (iii) spectrophotometric assay of glycosaminoglycans (GAG), (iv) cetyl trimethyl ammonium bromide test, (v) electrophoresis using Alcian blue, (vi) ion exchange chromatography with IR 120 resin, and (vii) HPLC for xylose. Blood and lens material were also tested for GAG fragments and xylose. beta Glucuronidase was assayed in lymphocytes and urine. RESULTS: Of 220 children of both sexes below 12 years of age, with congenital or infantile cataract treated in Sankara Nethralaya, Madras, India, during a period of 2 years, 145 excreted fragments of GAG (heparan and chondroitin sulphates) in their urine. There was no such excretion among the control group of 50 children. The same was found accumulated in the blood and lenses of affected children. In addition, xylose was present in small amounts in the urine and blood and xylitol was present in the lens. There was a significant elevation in the activity of beta glucuronidase in lymphocytes and urine, when compared with normals. All the above findings suggest deranged proteoglycan metabolism. As the urine contained mostly GAG fragments and very little xylose, Benedict's reagent was not reduced. This ruled out galactosaemia. CONCLUSION: An increase of beta glucuronidase activity might have caused extensive fragmentation of GAG with resultant accumulation in the blood and lens and excretion in urine. Small amounts of xylose may have come from xylose links between GAG and core protein of proteoglycans. Owing to their polyanionic nature, GAG fragments in the lens might abstract sodium, and with it water, thereby increasing the hydration of the lens. Excessive hydration and the osmotic effect of xylitol from xylose might cause cataract. While corneal clouding has been reported in inborn acid mucopolysaccharidosis, congenital or infantile cataract with deranged metabolism of proteoglycans (acid mucopolysaccharide-xylose-protein complex) is reported in children for the first time.

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.

Free alanine, aspartic acid, or glutamic acid reduce the glycation of human lens proteins.

The amino acids lysine and glycine are reported to react with glucose at physiological pH and temperature and undergo non-enzymic glycation. Three other amino acids present in relatively larger amounts in the lens i.e. alanine, aspartic acid and glutamic acid were also found to undergo non-enzymic glycation as found by incorporation of uniformly labelled (U-[14C]) glucose into the amino acids. The glucose incorporation was 1.6 to 2.5% for alanine, 35 to 50% for aspartic acid and 2.3 to 3.3% for glutamic acid. Each amino acid of varying concentrations lowered the extent of in vitro glycation of lens proteins significantly in glucose-treated homogenates of normal lens from humans. The decrease in glycation for alanine was between 32 and 69%, that for aspartate was between 18 and 74%, and for glutamate was between 52 to 74%. Decreased glycation was greater for higher concentrations of glucose. Scavenging of intracellular glucose and decreasing the extent of glycation of lens proteins could be the mechanism of action by which the amino acids alanine, aspartic acid and glutamic acid could exercise a beneficial effect on cataract and diabetic retinopathy.