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W J Rhead

Publications and source records attributed to W J Rhead.

At least 37 records · Page 2Linked to original sources
PubMed1992

Short-chain acyl-coenzyme A dehydrogenase activity, antigen, and biosynthesis are absent in the BALB/cByJ mouse.

BALB/cByJ (J) mice have short-chain acyl-CoA dehydrogenase (SCAD) deficiency and an organic aciduria similar to that of human SCAD deficiency. [9,10(n)-3H]- and [15,16(n)-3H]palmitate oxidations in J mouse fibroblasts were 96 and 35% of control, respectively, consistent with an isolated SCAD defect. Acyl-CoA dehydrogenase activities were assayed in muscle and fibroblast mitochondria from BALB/cBy controls (Y) and SCAD-deficient J mice. Medium-chain acyl-CoA dehydrogenase (MCAD) activities were comparable in both J and Y mice from all tissues. In the presence of MCAD antiserum, SCAD activities in J mice were undetectable in both tissues. Apparent Km and Vmax values in liver mitochondria suggested a somewhat increased affinity of MCAD for butyryl-CoA in J mice, as compared with MCAD from other species. Immunoblot studies using mitochondria revealed identical apparent SCAD molecular weight in liver, muscle, and fibroblasts from Y mice and no detectable SCAD antigen in J mice; MCAD antigen was detected in comparable amounts from both Y and J mice. Radiolabeling and immunoprecipitation studies in J mouse fibroblasts revealed no SCAD synthesis, but normal MCAD synthesis. These data argue against the existence of tissue-specific SCAD isoforms in the mouse and confirm that this mouse strain is a model for the human organic aciduria resulting from this beta-oxidation defect.

Acyl-CoA Dehydrogenase↗
PubMed1991

Species variation in organellar location and activity of L-pipecolic acid oxidation in mammals.

The oxidation of L-pipecolic acid to alpha-aminoadipic acid was studied in eight species of mammals using an assay system more sensitive than those previously employed. After percoll-gradient fractionation, activity was localized to the mitochondrial-enriched fractions in tissues from rabbit, guinea pig, pig, dog, and sheep, with guinea pig kidney cortex showing greatest specific activity. These results contrast with the peroxisomal oxidation of L-pipecolic acid observed in macaques and man (Mihalik and Rhead 1989; Mihalik et al. 1989). Rats and mice had undetectable levels of both peroxisomal and mitochondrial L-pipecolic acid oxidation. In the rat, peroxisomal oxidation activity was not induced by feeding with either clofibrate or clofibrate and L-pipecolic acid. Thus, among mammals, both the ability to oxidize L-pipecolic acid and the organellar location of this oxidation is species dependent.

Animals↗
PubMed1991

Inborn errors of fatty acid oxidation in man.

Inborn errors of fatty acid oxidation have only been recently identified. The clinical and biochemical presentations of these disorders are presented, as are analytic, biochemical and enzymatic approaches to their diagnosis. Recent clinical, biochemical and molecular information is summarized in detail. The identification and characterization of riboflavin-responsive beta-oxidation disorders is discussed. Approaches for clinical and biochemical screening are also described for these disorders.

Fatty Acids↗
PubMed1991

An atypical case of cytochrome c oxidase deficiency with biochemical heterogeneity in fibroblasts.

A patient presenting in the first year of life with feeding difficulties and failure to grow had variable but persistent lactic acidemia noted at age 20 months. Nonspecific nutritional and biochemical therapy was accompanied by improvement in general clinical status, growth, gait, and development. However, she died in a catastrophic illness at the end of the third year of life. Studies in intact fibroblast mitochondria were consistent with an isolated but partial defect in cytochrome c oxidase. On direct assay of this enzyme complex in fibroblast homogenates and mitochondria, activity was much more severely depressed (less than or equal to 8% of control). Her fibroblasts normally synthesized the three cytochrome c oxidase subunits encoded on the mitochondrial genome. These data confirm that this patient had cytochrome c oxidase deficiency and demonstrate significant biochemical heterogeneity, since the results of the intact mitochondrial studies correlate better with her clinical course than do those of the direct enzymatic assays.

Cells, Cultured↗
PubMed1991

A case of glutaric acidemia type II (severe multiple acyl-CoA dehydrogenation disorder) with subsequent prenatal exclusion in a sibling.

A case of severe multiple acyl-CoA dehydrogenation disorder is described. This is the second such case reported to have had an elevated maternal serum alpha-fetoprotein and normal amniotic alpha-fetoprotein. The child's 3-day extrauterine life was characterized by intractable acidosis, respiratory distress, and ventricular fibrillation. The characteristic biochemical, morphologic, and microscopic findings of this condition are reviewed. A subsequent pregnancy was evaluated using chorionic villus sampling and analysis of cultured trophoblasts. The trophoblasts were biochemically normal, and a normal child was subsequently delivered. Since the manifestations of this disorder developed in utero, prenatal diagnosis and therapy offer the only hope for a more prolonged survival.

Acidosis↗
PubMed1990

Identification of a common mutation in patients with medium-chain acyl-CoA dehydrogenase deficiency.

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is one of the most common recessively inherited metabolic diseases in man. We have studied fibroblast cultures obtained from three patients with MCAD deficiency by sequencing the entire coding region of MCAD mRNA. A single A to G nucleotide replacement which resulted in lysine329-to-glutamic acid329 substitution of the MCAD protein was identified in all cultures. Furthermore, this point mutation was present in 91% (31 of 34) of mutant MCAD alleles, indicating that the majority of cases with MCAD deficiency are caused by this type of mutation.

Acyl-CoA Dehydrogenase↗
PubMed1990

Juvenile multiple sclerosis-like episodes associated with a defect of mitochondrial beta oxidation.

We describe a young girl who presented with recurrent episodes of central nervous system (CNS) demyelination mimicking multiple sclerosis. Metabolic evaluations and decreased oxidation of [9,10(n)-3H] palmitate demonstrated defective mitochondrial beta oxidation, but complementation studies of the patient's cells, fused with cell lines with known defects of beta oxidation, failed to identify a known disorder. While progressive CNS demyelination has occurred in patients with defective peroxisomal very long-chain fatty acid oxidation, this is the 1st time it has occurred with defective mitochondrial beta oxidation. This patient appears to represent a novel disorder of beta oxidation producing intermittent demyelination with profound CNS symptoms. Recognition of the defect led to appropriate therapy, which caused marked clinical improvement.

Amino Acid Metabolism, Inborn Errors↗
PubMed1989

L-pipecolic acid oxidation in the rabbit and cynomolgus monkey. Evidence for differing organellar locations and cofactor requirements in each species.

L-Pipecolic acid oxidation was studied in the rabbit and cynomolgus monkey. Tissue homogenates from both species incubated with L-[2,3,4,5,6-3H]pipecolic acid produced a single radioactive product identified as alpha-aminoadipic acid. In the rabbit, L-pipecolic acid oxidation was greatest in kidney cortex with progressively lesser specific activities in liver, heart, and brain. When rabbit kidney cortex was fractionated by differential centrifugation or on Percoll gradients, activity paralleled that of the mitochondrial marker, glutamate dehydrogenase. In sonicated mitochondria, 92% of the activity was in the soluble fraction. Activity was inhibited by both rotenone and antimycin A and was maximal when FAD, phenazine ethosulfate, and glycerol were included in the assay; Km,app was 0.74 +/- 0.16 mM. Nipecotic acid, piperidine, and cis-2,4-piperidine dicarboxylic acid did not inhibit L-pipecolic acid oxidation, while L-proline had a Ki greater than or equal to 10 mM. D-Alanine and kojic acid, substrate and inhibitor of D-amino acid oxidase, respectively, were also not inhibitory. When monkey kidney cortex was fractionated on Percoll gradients, L-pipecolic acid oxidation activity paralleled that of the peroxisomal marker, catalase. After organellar subfractionation, the activity was membrane-associated and maximal at pH 8.5; Km,app was 4.22 +/- 0.30 mM. L-Pipecolic acid oxidation produced hydrogen peroxide, suggesting involvement of an oxidase in alpha-aminoadipic acid formation. Antimycin A did not inhibit the reaction. No specific cofactor requirements were identified and phenazine ethosulfate inhibited the reaction. D-Pipecolic acid, L-proline, and the other compounds cited above did not significantly inhibit the activity.

Animals↗
PubMed1989

Mitochondrial encephalomyopathy with associated aminoacidopathy in a male sibship.

We report two brothers with a previously undescribed type of mitochondrial encephalomyopathy and associated aminoacidopathy. Both have growth failure, progressive intellectual decline, deafness, neurologic dysfunction, exercise intolerance, lactic acidosis, and abnormal plasma and cerebrospinal fluid amino acid levels (elevated levels of alanine and low levels of threonine, methionine, citrulline, tryptophan, ornithine, arginine, and lysine). A muscle biopsy specimen taken from the younger, more severely affected brother showed abnormal mitochondrial morphology. Activities of the following enzymes in cultured fibroblasts from both boys were normal: pyruvate dehydrogenase, pyruvate carboxylase, phosphoenolpyruvate carboxykinase, cytochrome oxidase, reduced nicotinamide-adenine dinucleotide-cytochrome c reductase, and succinate cytochrome c reductase. Fibroblast mitochondria from the younger boy showed undetectable (less than 1% of control values) adenosine triphosphate synthesis with pyruvate and malate, whereas adenosine triphosphate synthesis with succinate was 70% of control values. These data indicate probably deficient activity of complex I of the electron transport chain. The boys' mother has progressive neurosensory hearing loss; their sister is clinically normal. Both mother and sister have many of the biochemical abnormalities found in the boys. It is possible, but not proved, that this disorder is inherited through maternal mitochondria.

Amino Acid Metabolism, Inborn Errors↗
PubMed1989

Short-chain acyl-coenzyme A dehydrogenase deficiency in mice.

A murine model for short-chain acyl-coenzyme A dehydrogenase (SCAD) deficiency has been identified and characterized in BALB/cByJ mice. These mice have undetectable SCAD activity, severe organic aciduria; excreting ethylmalonic and methylsuccinic acids and N-butyrylglycine, and develop a fatty liver upon fasting or dietary fat challenge. The mutant mice develop hypoglycemia after an 18-h fast, and have elevated urinary and muscle butyrylcarnitine concentrations. Most of these findings parallel those of human disorders associated with SCAD deficiency and other beta-oxidation defects. This mouse model presents important opportunities to investigate the biology of mammalian fatty acid metabolism and the related human diseases.

Acyl-CoA Dehydrogenase↗
PubMed1989

Peroxisomal L-pipecolic acid oxidation is deficient in liver from Zellweger syndrome patients.

L-Pipecolic acid, a cyclic imino acid produced during the degradation of lysine, accumulates in body fluids of infants with the generalized peroxisomal disorders, including Zellweger syndrome, neonatal adrenoleukodystrophy, and infantile Refsum disease. Peroxisome-enriched fractions from normal human liver oxidized L-[3H]pipecolic acid to alpha-[3H]aminoadipic acid (AAA). When human liver organelles were separated on a Percoll gradient, L-[3H]pipecolic acid oxidation activity (as measured by [3H]AAA formation) most closely segregated with the peroxisomal marker, catalase, and was not associated with the mitochondria. L-Pipecolic acid oxidation was not inhibited by antimycin A and rotenone and produced H2O2, consistent with its involving a peroxisomal oxidase. We measured L-pipecolic acid oxidation in liver specimens from patients with peroxisomal disorders. While liver homogenates from adult (n = 5) and infant (n = 10) controls formed 47.1 +/- 6.6 and 48.3 +/- 10.0 pmol AAA/mg protein/h, respectively, Zellweger syndrome livers (n = 8) formed only 1.7 +/- 0.3 pmol AAA/mg protein/h. L-pipecolic acid oxidation in normal infant livers was low at birth and increased with age, but Zellweger syndrome livers showed little activity at any age. Thus, the high circulating levels of L-pipecolic acid in Zellweger syndrome probably result from defective peroxisomal oxidation of L-pipecolic acid to AAA.

2-Aminoadipic Acid↗
PubMed1988

Long-chain acyl-coenzyme A dehydrogenase deficiency: biochemical studies in fibroblasts from three patients.

We studied fibroblasts from three patients with long-chain acyl-coenzyme A dehydrogenase (LCADH) deficiency; siblings H.C. and J.C. had milder clinical phenotypes than unrelated patient R-1. In H.C., J.C., and R-1 oxidation of [9,10(n)-3H]palmitate was 50, 48, and 28% of control, respectively, with R-1 having significantly less activity than H.C. and J.C. (p less than 0.05). Assays of mitochondrial short-chain and medium-chain acyl-coenzyme A dehydrogenases were normal in H.C. and J.C. However, mitochondrial LCADH activities in all three ranged from 17 to 21% of control. Flavin adenine dinucleotide addition increased LCADH activities in all three to 27-36% of control. In the presence of monospecific medium-chain acyl-coenzyme A dehydrogenase antiseria, LCADH activity decreased 17% in controls, and fell to less than or equal to 11% of control in J.C. and R-1. The heterogeneity observed in the [3H]palmitate oxidation studies was not explained by differences in LCADH activities under any assay condition.

Acyl-CoA Dehydrogenase, Long-Chain↗
PubMed1987

Trisomy 2q and monosomy 11q in the same individual: the importance of considering the deleted segment.

A female infant with multiple dysmorphic features and developmental delay was found to have partial duplication of the long arm of chromosome 2 and partial deletion of the long arm of chromosome 11 derived from a paternal balanced translocation, 46,XY,t(2;11)(q33:q25). Clinically, the infant had features of both 2q+ and 11q- syndromes. The importance of considering both the duplicated and deleted segment in unbalanced products resulting from familial translocations is emphasized.

Abnormalities, Multiple↗
PubMed1987

Complementation analysis of fatty acid oxidation disorders.

We assayed [9,10(n)-3H]palmitate oxidation by fibroblast monolayers from patients with fatty acid oxidation disorders. Activities in the different disorders were (percent control): short-chain acyl-coenzyme A (CoA) dehydrogenase deficiency (115%), medium chain acyl-CoA dehydrogenase deficiency (18%), long-chain acyl-CoA dehydrogenase deficiency (28%), multiple acyl-CoA dehydrogenation disorder, mild and severe variants (49% and 7%), and palmityl-carnitine transferase deficiency (4%). Multiple acyl-CoA dehydrogenation disorder, medium chain acyl-CoA dehydrogenase-deficient lines, and long-chain acyl-CoA dehydrogenase-deficient lines all complemented one another after polyethylene glycol fusion, with average activity increases of 31-83%. We detected two complementation groups in the severe multiple acyl-CoA dehydrogenation disorder lines, consistent with deficiencies of either electron transfer flavoprotein or electron transfer flavoprotein:ubiquinone oxidoreductase. The metabolic block in the latter cell lines is threefold more severe than in the former (P less than 0.001). No intragenic complementation was observed within either group. We assigned two patients with previously unreported severe multiple acyl-CoA dehydrogenation disorder to the electron transfer flavoprotein:ubiquinone oxido-reductase-deficient group.

Acyl-CoA Dehydrogenase, Long-Chain↗
PubMed1987

Short-chain acyl-coenzyme A dehydrogenase deficiency. Clinical and biochemical studies in two patients.

We describe two patients with short-chain acyl-coenzyme A (CoA) dehydrogenase (SCADH) deficiency. Neonate I excreted large amounts of ethylmalonate and methylsuccinate; ethylmalonate excretion increased after a medium-chain triglyceride load. Neonate II died postnatally and excreted ethylmalonate, butyrate, 3-hydroxybutyrate, adipate, and lactate. Both neonates' fibroblasts catabolized [1-14C]butyrate poorly (29-64% of control). Neonate I had moderately decreased [1-14C]octanoate catabolism (43-60% of control), while neonate II oxidized this substrate normally; both catabolized radiolabeled palmitate, succinate, and/or leucine normally. Cell sonicates from neonates I and II dehydrogenated [2,3-3H]butyryl-CoA poorly (41 and 53% of control) and [2,3-3H]octanoyl-CoA more effectively (59 and 95% of control). Mitochondrial acyl-CoA dehydrogenase (ADH) activities with butyryl- and octanoyl-CoAs were 37 and 56% of control in neonate I, and 47 and 81% of control in neonate II, respectively. Monospecific medium-chain ADH (MCADH) antisera inhibited MCADH activity towards both butyryl- and octanoyl-CoAs, revealing SCADH activities to be 1 and 11% of control for neonates I and II, respectively. Fibroblast SCADH and MCADH activities were normal in an adult female with muscular SCADH deficiency.

3-Hydroxybutyric Acid↗