Embryopathy in experimental diabetic gestation: assessment of oxidative stress and antioxidant defence.

Maternal diabetes is associated with an increased rate of congenital fetal anomaly. In the present study, diabetes was induced by streptozotocin in female rats one week prior to conception and the embryos were examined during organogenesis. Experimental diabetes is associated with over-production of free radicals and disturbed antioxidant defence, particularly in malformed embryos. Oxidative stress is demonstrated by increased MDA accumulation and reduced glutathione levels. Despite large differences in the reduced/oxidised glutathione ratios during organogenesis in the control, diabetic non-malformed and malformed embryo groups, the half-cell redox potential was constant for each group during the experimental period. Calculated redox potentials indicated that although embryo cells from the control and diabetic mother groups were of the same chronological age, the stages of development were different. Increased oxidative stress in rat embryos was associated with increased glutathione peroxidases and glutathione-S-transferase activity. This may, in part, provide an explanation for the observed accumulation of oxidised glutathione in malformed embryos. Moreover, decreased levels of vitamin C and selenium were observed. Increased oxidative stress and perturbations in antioxidant defence contribute to the high incidence of congenital anomalies in experimental diabetic gestation.

Effect of some xenobiotics on kynurenine hydrolase and kynurenine aminotransferase of mouse liver.

The effects of some xenobiotics on the activity of the B6-dependent kynurenine hydrolase (KH) and kynurenine aminotransferase (KATE) in mouse liver, were investigated. Polychlorinated biphenyl (Aroclor 1254) (400mg/kg/day x4) markedly decreased the activity of both enzymes. Benzo(a)pyrene (BP) and 3-methylcholanthrene (3-MC) (40mg/Kg/day x1) as well as phenobarbital (PB) (75mg/kg/day x3) did not alter the activity of KH, while that of KATE was mildy reduced. The response of the two enzymes to treatment with chlorpromazine (CPZ) (5mg/Kg/day x5) were opposite with marked elevation of KH and inhibition of KATE activities. Treatment with B-naphthoflavone (B-NF) (80mg/Kg/day x2), Pyrazole (200mg/Kg/day x1) or indole (400mg/kg/day x1) produce no change in the activity of either enzyme. It, seems therefore, that Aroclor (1254) and chlorpromazine may cause disordered kynurenine metabolism through alterations in the activities of its metabolizing enzymes. This, in turn, might affect nicotinamide adenine dinucleotide biosynthesis and/or the accumulation of some tryptophan metabolites suspected of being carcinogenic or co-carcinogenic.

Urinary alpha-naphthyl acetate esterases: a preliminary screening test for bladder cancer.

The urinary activities of alpha-naphthyl acetate esterases were measured for groups of bilharzial and nonbilharzial patients with benign urologic diseases and for others with bladder cancer. All these patients showed elevation in the urinary enzyme activity over that given by healthy controls. Bilharzial and nonbilharzial bladder cancer patients exhibited significant increase in urinary enzyme activity as compared with corresponding groups with benign urologic diseases A level of 50 units of enzyme activity was taken as a limit to discriminate between bladder cancer patients and those patients with benign urologic diseases. The specificity and sensitivity of this urinary test exceeded 90% with low falsely positive and negative results. The data of the present study recommended the use of urinary alpha-naphthyl acetate esterases activity as a preliminary screening test for bilharzial and nonbilharzial bladder cancer patients.

beta-Glucuronidase in schistosomal intestinal polypi of the colon.

The results of a clinical, histopathological and biochemical study on twenty patients with schistosomal polyposis of the large bowel and ten patients with normal colon as a control are reported. The biopsy showed clearly the absence of any malignant or premalignant changes in all the twenty bilharzial patients. Results of the biochemical study showed that there is a statistically significant increase in beta-glucuronidase activity in schistosomal polypi compared to normal mucosa. This enzymatic activity is absent in schistosoma ova. The causes of the increase in the enzyme activity have been attributed to leucocytic infiltration present in schistosomal granulomata and possible to some degree of liver disfunction. The protein content of the excess mucus present in the colon could also activate the enzyme. Our results also show that the increased enzyme activity does not necessarily have carcinogenic properties. We did not come across a single case of malignancy even in a patient with very high level of enzyme activity (11615 units) or in those patients with a prolonged history of the disease.

Studies on the effectiveness of liver and bacterial beta-glucuronidase enzymes in the hydrolysis of urinary beta-glucosiduronides of some tryptophan metabolites.

The effectiveness of Escherichia coli and bovine liver beta-glucuronidases in the hydrolysis of the urinary beta-glucosiduronides of tryptophan metabolites was studied. Moreover, the effect of the prolonged contact of these conjugates to the urinary enzyme was investigated in the first and second voiding urine samples. It is found that both enzymes have no important role in releasing the free carcinogens from their glucosiduronides. The presence of free carcinogens could be attributed to the spontaneous hydrolysis of some labile conjugates. However, the prolonged contact of the freely active substances during the sleeping hours with the epithelium of the bladder may enhance the process of bladder carcinogenicity. The increased accumulation of these metabolites in the first voiding urine could be interpreted in terms of their rate of excretion rather than by the enzymatic hydrolysis of their conjugates.

Studies on the effectiveness of mammalian and bacterial beta-glucuronidase enzymes in the hydrolysis of urinary beta-glucosiduronides of some tryptophan metabolites excreted in urine.

The effectiveness of E. coli and bovine liver beta-glucuronidases in the hydrolysis of the urinary beta-glucosiduronides of tryptophan metabolites was studied. Some of these metabolites demonstrate carcinogenic activity in the mouse bladder. Moreover, the effect of the prolonged contact of these conjugates to the urinary enzyme was investigated in the first and second voiding urine samples. The former urine was that retained in the bladder during sleep (about 8 hours) and the latter was collected 3 hours after the first. It is found that both enzymes have no important role in releasing the free carcinogens from their glucosiduronides. The presence of free carcinogens could be attributed to the spontaneous hydrolysis of some labile conjugates. However, the prolonged contact of the freely active substances during the sleeping hours with the epithelium of the bladder may enhance the process of bladder carcinogenicity. The increased accumulation of these metabolites in the first voiding urine could be interpreted in terms of their rate of excretion rather than by the enzymatic hydrolysis of their conjugates.

Functional capacity of the tryptophan-niacin pathway in the premenarchial phase and in the menopausal age.

Studies on the interrelationship between female hormones associated with reproduction and the vitamin B6-dependent enzymes along the kynurenin pathway of trytophan metabolism were carried out in girls with an age less, and more than 10 years (just before the onset of the first menstrual cycle), and in postmenapausal women with and without relative (excess) production of estradioll from the adrenal cortex. It is found that most of the determined metabolites are retained by the girls with age less than 10 years after tryptophan loading without and with vitamin B6 supplementation. Estradiol from either the ovaries (in girls just before menarch), or the adrenal cortex-in postmenopausal women with relative (excess) production of this hormone-interferes with the further degradation of 3-hydroxyanthranilic acid. However, this interference could be completely restored by vitamin B6 supplementation. The extra presence of a partial impairment in the kynureninase enzyme is also suggested in these postmenopausal women. In the latter case, this enzymatic activity could be partially resored by vitamin B6 supplementation. On the contrary, the enzymes: kynureninases and adrenocortical estradio. Pyridoxine supplementation partially corrected the inhibition especially that of 3-hydroxykynurenine transaminase enzyme.