Publications by authors named "Nyhan W"

The clinical phenotype in Lesch-Nyhan disease has been analyzed in 19 patients studied in hospital. In each case the diagnosis was made on the basis of inactivity of the enzyme hypoxanthine guanine phosphoribosyltransferase in erythrocyte lysates. All had hyperuricemia, and the presence of 'orange sand' in the diaper was a prominent early complaint.

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Administration of oral Pemoline produces long lasting amphetamine-type stereotyped behavior and persistent self-biting behavior in rats. The effects of haloperidol, pimozide, diazepam, and serotonin depletion by pretreatment with p-chlorophenylalanine (PCPA) or chronic pretreatment with p-chloroamphetamine (PCA) on abnormal behavior produced by pemoline were studied. Diazepam consistently increased the duration of stereotyped behavior.

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The absence of activity of the enzyme hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.

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A Samoan patient and a Saudi-Arabian patient were found to have abnormalities in the pattern of organic acid metabolites characteristic of 3-methylcrotonylglycinuria, propionic acidaemia and lactic acidosis. Both patients died early in life. The metabolic pattern is diagnostic of multiple carboxylase deficiency and an enzymatic diagnosis was made in a subsequent affected sibling of the first patient.

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Biotin-responsive multiple carboxylase deficiency is an inherited disorder of organic acid metabolism in man in which there are deficiencies of propionyl-coenzyme A (CoA), 3-methylcrotonyl-CoA, and pyruvate carboxylases that can be corrected with large doses of biotin. It has been proposed that the basic defect in patients with the early infantile form of the disease is in holocarboxylase synthetase, the enzyme that covalently attaches biotin to the inactive apocarboxylases to form active holocarboxylases. We have developed an assay for holocarboxylase synthetase in extracts of human fibroblasts using as substrate apopropionyl-CoA carboxylase partially purified from livers of biotin-deficient rats.

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The pathogenesis of familial hyperuricemia has been investigated in two kindreds in whom hyperuricemia was present in members of successive generations. Enzymatic and metabolic studies, including the incorporation of isotopically labeled glycine into urinary uric acid and assessment of the total excretion of oxypurines in one family, excluded a metabolic etiology. No secondary cause of hyperuricemia was identified in either family.

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Dietary deficiency of biotin was documented in an 11-year-old retarded boy as a consequence of a dietary prescription containing raw eggs. Clinical manifestations were alopecia totalis and an erythematous, exfoliative dermatosis. Metabolic characteristics included increased excretion of 3-methylcrotonylglycine, 3-hydroxyisovaleric acid, 3-hydroxypropionic acid, methylcitric acid, and lactic acid, as well as a propensity for the development of ketosis.

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The activities of then glycine cleavage system in the liver and brain of patient with nonketotic hyperglycinemia was extremely low as compared with those of control human liver and brain. The activities of glycine decarboxylase (P-protein) and the aminomethyl carrier protein (H-protein), two of the four protein components of the glycine cleavage system, were considerably reduced in both the liver and brain; the extent of reduction was greater in the H-protein. The activity of the T-protein was normal.

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Proteins were separated on two-dimensional acrylamide gels obtained from brain samples of patients with Joseph disease, Huntington disease (HD) and multiple sclerosis. Similar protein separations were made from cultured skin fibroblasts of Joseph disease patients. Two major classes of proteins, one with a MW of 50,000 probably representing the glial filamentous acidic protein, or another class with a MW of 40,000 (proteins Jc, Jd, L1 and L2) were increased in the cerebellum of six Joseph disease patients.

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The in vitro effects of deoxyadenosine and an adenosine deaminase inhibitor, deoxycoformycin, on the synthesis of DNA and the metabolism of purines were investigated in human leukemic T-cells. In the presence of 10 microM deoxycoformycin, the synthesis of DNA was completely inhibited by concentrations of deoxyadenosine of 10 microM or greater. In contrast, the synthesis of DNA in normal bone marrow cells was not inhibited in the presence of up to 20 microM deoxycoformycin and up to 10 microM deoxyadenosine.

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Multiple carboxylase deficiency is characterized by deficient activities of three biotin-dependent enzymes, propionyl coenzyme A carboxylase, pyruvate carboxylase, and beta-methylcrotonyl coenzyme A carboxylase. A newborn infant was seen with metabolic ketoacidosis, hyperammonemia, organic aciduria, seizures, and coma. Multiple carboxylase deficiency was subsequently confirmed by enzyme activity determinations in his peripheral blood leukocytes and cultured skin fibroblasts.

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Two metabolites, 4-hydroxyisovaleric acid and mesaconic acid, have been identified and quantified in the urine of a patient with isovaleric acidemia. These compounds do not appear to have been reported previously as being components of human metabolism. In addition, large quantities of 3-methylbutyrolactone, the lactone of 4-hydroxyisovaleric acid, were observed in the volatile profile obtained by headspace chromatography.

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A deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase(HGPRT) is associated with a varying clinical picture which may include hyperuricaemia, neurological abnormalities and bizarre self-mutilating behaviour. Due to technical problems with the usual in vitro enzyme assays, it has not been possible to establish a correlation between the degree of the enzyme deficiency and the severity of the clinical manifestations. In this study, the HGPRT activity of 12 patients with various clinical features was measured by quantitative analysis of the incorporation of radioactive precursors into purine compounds in intact fibroblasts.

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A stable isotope dilution assay for methylcitric acid in amniotic fluid was developed to provide rapid prenatal diagnosis of the inherited disorders propionic acidemia and methylmalonic acidemia. The method utilizes two 2H3-labeled diastereoisomers of methylcitric acid as internal standards, isolation by liquid partition chromatography and quantitation of the trimethyl esters by chemical ionization selected ion monitoring gas chromatography-mass spectrometry. Methylcitric acid at a concentration of 0.

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Prenatal diagnosis of propionic acidemia can be performed by two independent methods: measuring an elevated quantity of the metabolite methylcitrate in amniotic fluid; and demonstrating deficient activity of propionyl-CoA carboxylase in amniocytes cultured from the fluid. Discordant results in a pregnancy at risk for propionic acidemia were obtained. Elevated concentration of methylcitrate indicated an affected fetus, but the activity of propionyl-CoA carboxylase was normal.

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