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W J Rhead

Publications and source records attributed to W J Rhead.

At least 55 records · Page 3Linked to original sources
PubMed1987

Clinical and biochemical variation and family studies in the multiple acyl-CoA dehydrogenation disorders.

We report clinical and biochemical studies in patients with multiple acyl-CoA dehydrogenation disorders (MAD) and their parents. A severely affected (MAD:S) patient presented with neonatal acidosis leading to death and excreted a wide range of straight- and branched-chain acyl CoA derivatives. Two patients with mild variants of the same disorder (MAD:M) presented with neurologic abnormalities, acidotic coma, and/or poor growth; they primarily excreted ethylmalonate and variable amounts of adipate. Fibroblasts from the MAD:S patient demonstrated severely defective radiolabeled substrate oxidation, while the MAD:M cells had milder oxidative defects. Fibroblasts from two other MAD:M and six other MAD:S patients demonstrated analogous defects in substrate oxidation. As a group, MAD:S cells deficient in electron transfer flavoprotein:ubiquinone oxidoreductase had significantly lower residual oxidative activities than did MAD:S cells deficient in electron transfer flavoprotein. Fibroblasts from the parents of four MAD:S patients oxidized radiolabeled substrates significantly less effectively than did normal infant controls but were indistinguishable from normal adult cells. We found relatively higher residual oxidative activities in maternal than in paternal cells. Amniocytes from a fetus at risk for MAD:S catabolized labeled substrates normally; the infant has been clinically and biochemically normal up to 30 months of age.

Acyl-CoA Dehydrogenase↗
PubMed1986

The multiple acyl-coenzyme A dehydrogenation disorders, glutaric aciduria type II and ethylmalonic-adipic aciduria. Mitochondrial fatty acid oxidation, acyl-coenzyme A dehydrogenase, and electron transfer flavoprotein activities in fibroblasts.

The multiple acyl-coenzyme A (CoA) dehydrogenation disorders (MAD) include severe (S) and mild (M) variants, glutaric aciduria type II (MAD:S) and ethylmalonic-adipic aciduria (MAD:M). Intact MAD:M mitochondria oxidized [1-14C]octanoate, [1-14C]palmityl-CoA, and [1,5-14C]glutarate at 20-46% of control levels; MAD:S mitochondria oxidized these three substrates at 0.4-18% of control levels. In MAD:M mitochondria, acyl-CoA dehydrogenase (ADH) activities were similar to control, whereas MAD:S ADH activities ranged from 38% to 73% of control. Electron transfer flavoprotein (ETF) activities in five MAD:M cell lines ranged from 29 to 51% of control (P less than 0.01); ETF deficiency was the primary enzymatic defect in two MAD:M lines. In four MAD:S patients, ETF activities ranged from 3% to 6% of control (P less than 0.001); flavin adenine dinucleotide addition increased residual ETF activity from 4% to 21% of control in a single MAD:S line (P less than 0.01). Three MAD:S patients had ETF activities ranging from 33 to 53% of control; other investigators found deficient ETF-dehydrogenase activity in these MAD:S and three of our MAD:M cell lines.

Acyl Coenzyme A↗
PubMed1986

Sudden child death and 'healthy' affected family members with medium-chain acyl-coenzyme A dehydrogenase deficiency.

A family is described in which the father and three (and probably all four) of his children had a decreased capacity for the oxidation of medium-chain fatty acids. One of the children suddenly died at the age of 16 months following an episode of a rapidly deteriorating Reye syndrome-like illness with hypoketotic hypoglycemia and dicarboxylic aciduria, but without any previous alarming symptoms. The eldest sibling had died at the age of 19 months under similar conditions. The other family members had always been healthy. On fasting, all affected family members accumulated in their plasma the medium-chain fatty acids octanoic, decanoic, and cis-4-decenoic acids. Their urinary organic acid excretion profile could be characterized as "dicarboxylic aciduria." A deficiency of medium-chain acyl-coenzyme A dehydrogenase was demonstrated in a postmortem liver sample of the index patient. Cultured fibroblasts from the father and the two healthy children had a decreased rate of [14C]octanoate oxidation. It is suggested that a deficiency of medium-chain acyl-coenzyme A dehydrogenase may lead to a life-threatening illness when other complicating factors such as diarrhea and vomiting result in an abnormal depletion of the body's glycogen stores. Careful monitoring of at-risk patients during a minor illness is necessary.

Acyl-CoA Dehydrogenase↗
PubMed1985

14C-labeled substrate catabolism by human diploid fibroblasts derived from infants and adults.

Untransformed diploid skin fibroblasts from eight normal adults, aged 24 to 74 years, catabolized several 14C-labeled substrates less effectively than cells from ten normal male infants. 14C-labeled substrate metabolism was quantitated either by measuring the evolution of 14CO2 from the 14C-labeled compounds or the incorporation of 14C into cellular protein via transamination of tricarboxylic acid cycle intermediates derived from the 14C-labeled substrates. With these methods, adult cells catabolized [1-14C]butyrate, [1-14C]octanoate, and 1-[2-14C]leucine at rates 44 to 64% of those found in infant cells. The oxidation of [1,4-14C]succinate and [U-14C]malate was identical in both infant and adult cells, while [2,3-14C]succinate catabolism was mildly decreased in adult cells (65-80% of control). These observations parallel those made in rat tissues and confirm that the same phenomenon occurs in cultured human fibroblasts.

Adult↗
PubMed1985

Catalytic defect of medium-chain acyl-coenzyme A dehydrogenase deficiency. Lack of both cofactor responsiveness and biochemical heterogeneity in eight patients.

Medium-chain acyl-coenzyme A (CoA) dehydrogenase (MCADH; EC 1.3.99.3) deficiency (MCD) is an inborn error of beta-oxidation. We measured 3H2O formed by the dehydrogenation of [2,3-3H]acyl-CoAs in a 3H-release assay. Short-chain acyl-CoA dehydrogenase (SCADH; EC 1.3.99.2), MCADH, and isovaleryl-CoA dehydrogenase (IVDH; EC 1.3.99.10) activities were assayed with 100 microM [2,3-3H]butyryl-, -octanoyl-, and -isovaleryl-CoAs, respectively, in fibroblasts cultured from normal controls and MCD patients. Without the artificial electron acceptor phenazine methosulfate (PMS), MCADH activity in fibroblast mitochondrial sonic supernatants (MS) was 54% of control in two MCD cell lines (P less than 0.05). Addition of 10 mM PMS raised control acyl-CoA dehydrogenase activities 16-fold and revealed MCADH and SCADH activities to be 5 (P less than 0.01) and 73% (P greater than 0.1) of control, respectively. Thus, the catalytic defect in MCD involves substrate binding and/or dehydrogenation by MCADH and not the subsequent reoxidation of reduced MCADH by electron acceptors. 20 microM flavin adenine dinucleotide (FAD) did not stimulate MCD MCADH activity in either the 3H-release or electron-transfer(ring) flavoprotein-linked dye-reduction assays. Mixing experiments revealed no MCADH inhibitor in MCD MS; IVDH activities were identical in both control and MCD MS. In postmortem liver MS from another MCD patient, 3H2O formation from [2,3-3H]octanoyl-CoA was 15% of control. When 3H2O formation was assayed with 200 microM [2,3-3H]acyl-CoAs, 15 mM PMS, and 20 microM FAD in fibroblast sonic supernatants from seven MCD cell lines, SCADH, MCADH, and IVDH activities were 72-112% (P greater than 0.1), 4-9% (P less than 0.01), and 86-135% (P greater than 0.1) of control, respectively, revealing no significant biochemical heterogeneity among these patients.

Acyl Coenzyme A↗
PubMed1984

Abetalipoproteinemia. Report of an unusual patient.

Abetalipoproteinemia (Bassen-Kornzweig syndrome, acanthocytosis) was diagnosed at age 13 months in a black male. At age 13 months, the electroretinogram was nonrecordable and a pigmentary retinopathy was obvious with ophthalmoscopy. Following dietary modification and vitamin supplementation, the scotopic electroretinogram improved to about 30% of normal.

Abetalipoproteinemia↗
PubMed1983

Dicarboxylic aciduria: deficient [1-14C]octanoate oxidation and medium-chain acyl-CoA dehydrogenase in fibroblasts.

Dicarboxylic aciduria, an inborn error of metabolism in man, is thought to be caused by defective beta-oxidation of six-carbon to ten-carbon fatty acids. Oxidation of [1-14C]octanoate was impaired in intact fibroblasts from three unrelated patients with dicarboxylic aciduria (19 percent of control), as was the activity of medium-chain (octanoyl-)acyl-CoA dehydrogenase in the supernatants of sonicated fibroblast mitochondria (5 percent of control). These data confirm that dicarboxylic aciduria is caused by an enzyme defect in the beta-oxidation cycle.

Acyl-CoA Dehydrogenase↗
PubMed1980

Demonstration of a specific mitochondrial isovaleryl-CoA dehydrogenase deficiency in fibroblasts from patients with isovaleric acidemia.

To study the enzymatic basis of isovaleric acidemia, we have developed assay methods for isovaleryl-CoA and butyryl-CoA dehydrogenases that measure the amount of tritium released from the respective [2,3-3H]acyl CoAs. Because assay of these enzymes in human fibroblast homogenates was subject to interference by nonspecific reactions, we have isolated mitochondria from cultured skin fibroblasts by protease treatment, homogenization, and differential centrifugation. By using this assay method with these isolated mitochondria, we have demonstrated a specific deficiency of isovaleryl-CoA dehydrogenase [isovaleryl-CoA: (acceptor) oxidoreductase, EC 1.3.99.10] activity in cultured skin fibroblasts from five patients with isovaleric acidemia. In contrast, mitochondrial butyryl-CoA dehydrogenase [butyryl-CoA: (acceptor) oxidoreductase, EC 1.3.99.2] activity in these cells was preserved at normal levels. These results have been reproduced by using the conventional dye reduction assays. These observations give further support to the hypothesis that isovaleryl CoA is dehydrogenated by a specific enzyme and that isovaleric acidemia is due to a deficiency of this enzyme.

Amino Acid Metabolism, Inborn Errors↗
PubMed1980

Isovaleryl-CoA dehydrogenase: demonstration in rat liver mitochondria by ion exchange chromatography and isoelectric focusing.

There has been ambiguity concerning the specificity of the enzymes that dehydrogenate short branched-chain acyl-CoAs. It previously had been assumed that isovaleryl-CoA is dehydrogenated by n-butyryl-CoA dehydrogenase [butyryl-CoA:(acceptor) oxidoreductase, EC 1.3.99.2]. To solve this problem, we fractionated five short-chain acyl-CoA dehydrogenases (isovaleryl-CoA, n-butyryl-CoA, isobutyryl-CoA, n-octanoyl-CoA, and glutaryl-CoA dehydrogenases) from rat liver mitochondria by isoelectric focusing and DEAE-cellulose column chromatography. The isovaleryl-CoA dehydrogenase [isovaleryl-CoA:(acceptor) oxidoreductase, EC 1.3.99.10] peak was almost completely separated from the peaks of n-butyryl CoA- and n-octanoyl-CoA dehydrogenases by isoelectric focusing, and it was well separated from glutaryl-CoA dehydrogenase [glutaryl-CoA:(acceptor) oxidoreductase (decarboxylating), EC 1.3.99.7] and n-octanoyl-CoA dehydrogenase by DEAE-cellulose column chromatography. The isovaleryl-CoA dehydrogenase peak partly overlapped that of n-butyryl-CoA and isobutyryl-CoA dehydrogenases in the latter procedure. These results unequivocally demonstrate that isovaleryl-CoA is oxidized by a specific isovaleryl-CoA dehydrogenase. The other dehydrogenase peaks also demonstrated activity toward a single substrate, except that isobutyryl-CoA dehydrogenase activity could not be clearly resolved from n-butyryl-CoA dehydrogenase activity.

Animals↗
PubMed1976

Cystine metabolism in human fibroblasts. Comparison of normal, cystinotic, and gamma-glutamylcysteine synethetase-deficient cells.

Incubation of normal human skin fibroblasts or fibroblasts derived from patients with erythrocyte deficiency of gamma-glutamylcysteine synthetase (gamma-glutamylcysteine synthetase-deficient) in culture medium containing L-[35S]cystine resulted in incorporation of radioactivity into protein, cysteine, and glutathione, gamma-Glutamylcysteine synthetase-deficient fibroblasts synthesized glutathione from [35S]cystine at 30% the rate of normal cells and contained 30% the normal amount of glutathione. Cystinotic fibroblasts incorporated [35S]cystine into the large intracellular cystine pool not found in normal or gamma-glutamylcysteine synthetase-deficient cells and also appeared to synthesize glutathione more slowly than normal cells. However, the radioactivity recovered as cystine was reduced greatly and the rate of [35S]cystine incorporation into glutathione increased if cystinotic cells were first depleted of their intracellular cystine pool before incubation in [35S]cystine. This suggests that the apparent reduced rate of glutathione synthesis observed in untreated cystinotic cells was a secondary effect caused by dilution of the [35S]cystine by the large pool of nonradioactive cystine. Cystinotic cells depleted of cystine by treatment with mercaptoethylamine reaccumulate 30 to 50% of their initial cystine in 24 hours in the absence of extracellular cystine. Both normal and cystinotic cells lose more than 90% of their intracellular glutathione in 24 hours in cystine-free medium. Both cell types can reutilize cysteine from glutathione for protein synthesis.

Amino Acid Metabolism, Inborn Errors↗
PubMed1976

Effect of selenium compounds on selenium content, growth and 35S-cystine metabolism of skin fibroblasts from normal and cystinotic individuals.

Kidney samples from children with the inborn metabolic disease cystinosis contain 4 times more selenium (Se) than do kidney samples from normal individuals (p = 0.1). However, when cultured skin fibroblasts from cystinotic patients and normal control individuals are incubated in Se-D,L-methionine, Se-D,L-cystine, Se-cystamine X HCl, Se-urea, selenite or in medium without added selenium, only the cystinotic fibroblasts grown in Se-urea or selenite (SeO3=) contain more selenium than do the corresponding normal cells (p less than 0.05). In both types of cultured fibroblasts, the order of descending toxicity per ppm selenium is: Se-urea greater than Se-cystamine greater than Se-cystine greater than or equal to SeO3= much greater than Se-methionine. High (apparently toxic) concentrations of Se-urea and Se-cystamine lower the elevated intracellular free (nonprotein) cystine content of cystinotic fibroblasts to less than 60% of control values; at lower concentrations, these compounds raise the cystine content of these cells to over 140% of control values. Appropriate concentrations of SeO3=, Se-cystine and Se-methionine also elevate the free cystine content of the cystinotic cells. During a 75 minute incubation in 35S-cystine, the incorporation of 35S into the acid precipitable (protein) fraction of both cell types is significantly inhibited by Se-cystamine (approximately 55% control; p less than 0.05). The incorporation of 35S-cystine into glutathione is inhibited by Se-cystine (approximately 40% control) in both fibroblast types (p less than 0.05). In cystinotic cells, Se-cystamine significantly reduces incorporation of 35S-cystine into the cystine pool (40% control) as does SeO3= (67% control; p less than 0.05). Protein and glutathione synthesis in cystinotic fibroblasts are more strongly inhibited by Se-cystine and SeO3=, respectively, than in normal fibroblasts (p less than 0.05). These studies demonstrate that selenium compounds exhibit a different sequence of toxicity in fibroblasts than in the intact animal and that some previously unreported metabolic effects (i.e. inhibition of glutathione synthesis) may contribute to their toxicity.

Amino Acids↗