Functional deficiencies of sulfite oxidase: Differential diagnoses in neonates presenting with intractable seizures and cystic encephalomalacia.

Sulfite oxidase is a mitochondrial enzyme encoded by the SUOX gene and essential for the detoxification of sulfite which results mainly from the catabolism of sulfur-containing amino acids. Decreased activity of this enzyme can either be due to mutations in the SUOX gene or secondary to defects in the synthesis of its cofactor, the molybdenum cofactor. Defects in the synthesis of the molybdenum cofactor are caused by mutations in one of the genes MOCS1, MOCS2, MOCS3 and GEPH and result in combined deficiencies of the enzymes sulfite oxidase, xanthine dehydrogenase and aldehyde oxidase. Although present in many ethnic groups, isolated sulfite oxidase deficiency and molybdenum cofactor deficiency are rare inborn errors of metabolism, which makes awareness of key clinical and laboratory features of affected individuals crucial for early diagnosis. We report clinical, radiologic, biochemical and genetic data on a Brazilian and on a Turkish child with sulfite oxidase deficiency due to the isolated defect and impaired synthesis of the molybdenum cofactor, respectively. Both patients presented with early onset seizures and neurological deterioration. They showed no sulfite oxidase activity in fibroblasts and were homozygous for the mutations c.1136A>G in the SUOX gene and c.667insCGA in the MOCS1 gene, respectively. Widely available routine laboratory tests such as assessment of total homocysteine and uric acid are indicated in children with a clinical presentation resembling that of hypoxic ischemic encephalopathy and may help in obtaining a tentative diagnosis locally, which requires confirmation by specialized laboratories.

Polioencephalomalacia in adult sheep grazing pastures with prostrate pigweed.

Polioencephalomalacia was diagnosed in 2 animals from different farms. In apparently healthy animals from same farms, fecal thiaminase and a significant reduction in erythrocyte trans-ketolase activity was observed. The presence of thiaminase in Amaranthus blitoides could have contributed to the development of polioencephalomalacia in sheep grazing on natural pastures.

Lipoxygenase and other enzymes of arachidonic acid metabolism in the brain of chicks affected by nutritional encephalomalacia.

1. Prostaglandin endoperoxide synthetase (PES) and lipoxygenase (Lox) activities were compared in the cerebella and cerebra of vitamin E-sufficient young chicks and in chicks in which nutritional encephalomalacia (NE) was induced by a diet deficient in vitamin E. 2. Eicosanoid production patterns were qualitatively similar in the brains of both groups of chicks, but prostaglandin production was 50-60% less in cerebella of ataxic chicks, compared to control cerebella, while the opposite trend was observed in the cerebellar Lox pathway, as measured by radioimmunoassay of 15-HETE. 3. Cerebellar phospholipase A2 activity was twice that of the cerebrum but was not affected by NE. 4. Purification of Lox activity from the cerebellar homogenates produced a lower yield and enrichment when the starting material was taken from ataxic chicks, compared to the controls. 5. In addition there were qualitative differences in the purified fractions from both groups, as seen by pH optima and kinetics. 6. The results are consistent with the view that the cerebellum has less antioxidant protection than the cerebrum and that its higher phospholipase A2 activity and greater propensity to oxygenate arachidonic acid via the Lox pathway at the expense of the PES pathway may render this region of the brain particularly vulnerable to oxidative damage in NE.

Vitamin E and selenium participation in fatty acid desaturation. A proposal for an enzymatic function of these nutrients.

A critical review of the literature on the effects of vitamin E and selenium deficiences on unsaturated fatty acid metabolism reveals that some of these effects are inconsistent with the antioxidant hypothesis of these nutrients as their only biological function. On the basis of these data it is proposed that vitamin E and selenium play a role in the desaturation of n-3 and n-6 polyunsaturated fatty acids by participating in the microsomal electron transport chain and in a proposed peroxidase moiety of the desaturase complex, respectively. A re-interpretation of the experimental literature in terms of the proposed hypothesis is provided, with some suggestions to test its main tenets.

Pyruvate dehydrogenase phosphate (PDHb) phosphatase activity in fibroblasts from Leigh's disease.

The defective activation of pyruvate dehydrogenase complex (PDHC) in Leigh's disease (subacute necrotizing encephalomyelopathy) could be due to deficiency of pyruvate dehydrogenase phosphate (PDHb) phosphatase (EC 3.1.3.43). This enzyme catalyzes the dephosphorylation and activation of phospho-PDHC. In cultured skin fibroblasts, we assayed this enzyme by measuring the rate of activation of the exogenously added, purified phospho-PDHC (bovine kidney). PDHb phosphatase activity did not differ significantly among normal control cells, Leigh's lines, spinocerebellar ataxias, or other neurologic disorders. The results do not support the idea that PDHb phosphatase is deficient in Leigh's disease.

Normal activities of hepatic pyruvate dehydrogenase and pyruvate carboxylase in Leigh's syndrome.

A case of Leigh's syndrome (subacute necrotizing encephalomyelopathy, SNE), proven by autopsy, was reported. The persistent elevation of pyruvate and lactate in blood and hyperalanemia suggested an impairment of pyruvate oxidation, but the enzyme activities of pyruvate dehydrogenase (PDH) and pyruvate carboxylase (PC) in liver tissues of the patient revealed normal. It is postulated that Leigh's syndrome and both enzyme deficiencies are distinct entities.

Erythrocyte transketolase activity in suspected cases of Leigh's disease, or subacute necrotising encephalomyelopathy.

Erythrocyte transketolase activity and the effect of adding thiamine pyrophosphate (% thiamine pyrophosphate effect) were measured in 111 subjects suspected to suffer from Leigh's disease (subacute necrotising encephalomyelopathy). From clinical evidence these subjects were divided into five groups: (1) necropsy-proved cases of subacute necrotising encephalomyelopathy, (2) cases positive for urinary thiamine pyrophosphate: adenosine triphosphate phosphotransferase inhibitor, (3) clinically likely cases of subacute necrotising encephalomyelopathy (patients still alive, or on whom no necropsy was performed), (4) cases diagnosed as diseases other than subacute necrotising encephalomyelopathy (control group), (5) cases for which no diagnosis had been made. Comparison of erythrocyte transketolase activities with and without added thiamine pyrophosphate and of the % thiamine pyrophosphate effect for each group compared with the control group showed no statistically significant differences from normal values for any of these parameters. Similarly, there were no differences between the two sexes in transketolase activity, and no correlation between transketolase activity and age. These results indicate that erythrocyte transketolase activity is not altered in subacute necrotising encephalomyelopathy and is unlikely to be of value for the diagnosis of Leigh's disease.

Studies on ATP: thiamine diphosphate phosphotransferase activity in rat brain.

The experiments described in this paper serve as a contribution to the solution of the discrepancies which exist in the assay of ATP:thiamine diphosphate phosphotransferase activity (EC 2.7.4.15), presently in use as a tool for the diagnosis of Leigh's disease (SNE, subacute necrotizing encephalomyelopathy). The results obtained with this phosphotransferase assay can, in part, be explained by the presence of thiamine triphosphate (ThTP) in the preparation of thiamine diphosphate (ThDP) used as a substrate, by the inhibition by ATP of the ThTP phosphohydrolase activity, present in fractions of rat brain homogenates, and by the stimulation by ThDP of the ATPase activity. When [2(-14)C-thiazole]thiamine was used for the synthesis of [14C]ThTP in fractions of rat brain, it was found that after chromatographic separation of thiamine and its phosphates, 14C radioactivity could be demonstrated in the ThTP fractions, even in the absence of an enzyme source. Probably a complex is formed between [14C]thiamine and a phosphate ester which behaves chromatographically as ThTP. It is concluded that the assay system for the measurement of ThTP synthesis in its present form is, in our hands, not suitable for diagnostic purposes.

Congenital lactic acidosis due to pyruvate carboxylase deficiency: absence of an inhibitor of TPP-ATP phosphoryl transferase.

Two children are described who suffered from episodes of metabolic acidosis and progressive mental and motor deterioration. The patients showed periodic elevation of blood lactate, pyruvate and alanine, which was accompanied by vomiting, hypotonia or convulsions. The concentrations of lactate and pyruvate in cerebrospinal fluid were found to be increased. Liver biopsies revealed a decrease in pyruvate carboxylase activity and normal pyruvate decarboxylase activity. No inhibitor of TPP-ATP phosphoryl transferase was detected in urine from the patients. These findings suggest that congenital lactic acidosis due to pyruvate carboxylase deficiency is probably a different disease entity from Leigh's encephalomyelopathy. A possible mechanism of brain damage caused by a defect in pyruvate carboxylase is postulated.

Faecal thiaminase in clinically normal sheep associated with outbreaks of polioencephalomalacia.

Three flocks in which in with one of more sheep had succumbed to polioencephalomalacia (cerebrocortical necrosis) were used for faecal thiaminase studies. Up to one third of the clinically normal animals in these flocks to be excreting thiaminase on any one day and over half the flock could be thiaminase excretors at some time during an outbreak. The possible detrimental effects of sub-clinical thiamine antagonism in sheep are therefore worthy of consideration. Thiaminase excretion by individual animals was variable and sometimes intermittent. It was unaffected by changes in diet, pasture or enviroment. In two of the flocks multiple cases of polioencephalomalacia followed the administration of the anthelmintics, levamisole hydrochloride and thiabendazole. This aspect merits further investigation in view of the widespread use of anthelmintics of this type, especially as the profuse diarrhoea which can be associated with outbreaks of polioencephalomalacia may be wrongly attributed to gastro-intestinal parasitism.

[Catalase-like activity in cerebrospinal fluid in patients with cerebral stroke]. / Aktywnosc katalazopodobna w plynie mózgowo-rdzeniowym chorych z udarem mózgu

Catalase-like activity was determined in the cerebrospinal fluid of 16 patients with cerebral haemorrhage, 24 cases od encephalomalacia due to thrombosis, and 10 controls. It was demonstrated that catalase-like activity in the cerebrospinal fluid of patients with cerebral stroke is significantly raised in relation to the activity observed in controls. This rise is patricularly evident in the first 24 hours after the onset. The rise was statistically significant only in the group of encephalomalacia.

Leigh's disease: significance of the biochemical changes in brain.

Analysis of five brains from patients with Leigh's disease demonstrates an accumulation of thiamine pyrophosphate and a deficiency of thiamine triphosphate. The enzyme which converts thiamine pyrophosphate to thiamine triphosphate was normally active in two of these brains, suggesting that the inhibitor found in Leigh's disease is probably producing the observed neurochemical changes. Reasons for the histological similarity between Leigh's and Wernicke's diseases are suggested.