PubMed Health⌕ Search

Biomedical subjects

R J Wanders

Publications and source records attributed to R J Wanders.

At least 451 records · Page 25Linked to original sources
PubMed1987

Thermodynamics of the control of metabolism.

A theory is presented, describing the control analysis of metabolic systems in terms of Gibbs free energies, extending earlier work of Kacser and Burns (25), and Heinrich and Rapoport (29). It is shown that relationships exist between flux control coefficients (the degree to which enzymes control steady-state fluxes) and free-energy elasticity coefficients, defined as the fractional change in the rate of a reaction induced by a standard change in one free-energy difference, while all the other free-energy differences are kept constant. Application of this extended control analysis to some biochemical reactions, including proton translocation, demonstrates that 1. Problems arising in the control analysis because of conservation (sum concentration of substrate and product constant) can be circumvented. 2. Although free-energy elasticity coefficients are maximal when the reaction is close to equilibrium, they can also be significant when the reaction is not close to equilibrium. 3. Problems in the control analysis caused by compartmentation can be resolved by defining control parameters that refer to the organelle as a whole. 4. These latter control parameters obey the above-mentioned relationships.

Animals↗
PubMed1987

Peroxisomes and peroxisomal functions in muscle. Studies with muscle cells from controls and a patient with the cerebro-hepato-renal (Zellweger) syndrome.

In the present study we investigated peroxisomal functions in cultured human muscle cells from control subjects and from a patient with the Zellweger syndrome, a genetic disease characterized by the absence of morphologically distinguishable peroxisomes in liver and kidney. In homogenates of cultured muscle cells from control subjects, catalase is contained within subcellular particles, acyl-CoA:dihydroxyacetonephosphate acyltransferase activity is present and palmitoyl-CoA can be oxidized by a peroxisomal beta-oxidative pathway; these findings are indicative of the presence of peroxisomes in the cells. In homogenates of cultured muscle cells from the patient with the Zellweger syndrome, acyl-CoA:dihydroxyacetonephosphate acyltransferase activity was deficient, peroxisomal beta-oxidation of palmitoyl-CoA was impaired and catalase was not particle-bound. These findings indicate that functional peroxisomes are absent in muscle from patients with the Zellweger syndrome. We conclude that cultured human muscle cells can be used as a model system to study peroxisomal functions in muscle and the consequences for this tissue of a generalized dysfunction of peroxisomes.

Brain Diseases↗
PubMed1987

Neonatal adrenoleukodystrophy. Impaired plasmalogen biosynthesis and peroxisomal beta-oxidation due to a deficiency of catalase-containing particles (peroxisomes) in cultured skin fibroblasts.

Neonatal adrenoleukodystrophy belongs to the newly recognized group of inherited diseases, the peroxisomal disorders. Based on the reported similarities between neonatal adrenoleukodystrophy and the cerebro-hepato-renal (Zellweger) syndrome, we have studied peroxisomal functions in cultured skin fibroblasts from 5 neonatal adrenoleukodystrophy patients. The results indicate that multiple peroxisomal enzyme activities are deficient in fibroblasts from neonatal adrenoleukodystrophy patients. Digitonin titration experiments revealed that peroxisomes are strongly deficient in these fibroblasts as found earlier in fibroblasts from Zellweger patients. These findings not only explain the generalized loss of peroxisomal functions in neonatal adrenoleukodystrophy, but also provide an explanation for the observed resemblance in clinical and biochemical abnormalities between neonatal adrenoleukodystrophy and Zellweger syndrome. The implications for the pre- and postnatal detection of this disease will be discussed.

Adrenoleukodystrophy↗
PubMed1987

Bile acids in peroxisomal disorders.

We examined serum bile acids in patients with different peroxisomal disorders. Patients with Zellweger syndrome (n = 23), infantile form of Refsum disease (n = 6) and neonatal adrenoleukodystrophy (n = 4) consistently had increased levels of bile acid precursors. Patients with X-linked adrenoleukodystrophy, (n = 5) classical Refsum disease (n = 3), hyperpipecolic acidaemia (n = 4) and rhizomelic chondrodysplasia punctata (n = 9) did not have increased bile acid precursor levels. Total serum bile acids (41 micrograms ml-1) and the percentage of bile acid precursors (80%) were highest in typical Zellweger patients who died young. Long-living Zellweger patients, neonatal adrenoleukodystrophy patients and infantile Refsum disease patients had, on average, less cholestasis and a lower percentage of bile acid precursors. We also observed that total serum bile acids and the percentage of bile acid precursors decreased with age in long-living Zellweger patients. Screening for bile acid precursors, combined with very long chain fatty acids analysis is, in our experience, an easy and reliable first-line approach to the detection of peroxisomal disorders.

Adrenoleukodystrophy↗
PubMed1987

Genetic diseases caused by peroxisomal dysfunction. New findings in clinical and biochemical studies.

Peroxisomes play an essential role in human cellular metabolism. Peroxisomal disorders, a group of genetic diseases caused by peroxisomal dysfunction, can be classified in three groups namely a group of disorders with a general peroxisomal dysfunction (Zellweger syndrome; infantile type of Refsum's disease; neonatal adrenoleukodystrophy, hyperpipecolic acidemia), a group with an impairment of some, but not all peroxisomal functions (rhizomelic chondrodysplasia punctata) and a group with impairment of only a single peroxisomal function (acatalasemia, X-linked adrenoleukodystrophy/adrenomyeloneuropathy; adult type of Refsum's disease; peroxisomal thiolase deficiency; peroxisomal acyl-CoA oxidase deficiency; hyperoxaluria type I). In this paper we report the typical findings in ophthalmological examinations of patients suspected of Zellweger syndrome contributing to the clinical diagnosis of this disorder. In biochemical studies using a rapid gaschromatographic detection method for plasmalogens we confirmed that plasmalogens are severely deficient in all tissues of Zellweger patients studied. Moreover, using a recently developed radiochemical method, de novo plasmalogen biosynthesis was found to be impaired in fibroblasts from patients with Zellweger syndrome, infantile Refsum's disease, neonatal adrenoleukodystrophy or rhizomelic chondrodysplasia punctata, this in contrast to X-linked chondrodysplasia in which a normal plasmalogen biosynthesis was found. From the literature it is known that peroxisomal beta-oxidation with both long-chain (C16:0) and very long-chain (C24:0; C26:0) fatty acids is deficient in Zellweger syndrome, infantile Refsum's disease and neonatal adrenoleukodystrophy. In contrast, in X-linked adrenoleukodystrophy only the peroxisomal beta-oxidation of the very long chain fatty acids is impaired. As a result very long-chain fatty acids accumulate in tissues, plasma, fibroblasts and amniotic fluid cells from patients with Zellweger syndrome, infantile Refsum's disease, neonatal and X-linked adrenoleukodystrophy, but not in rhizomelic chondrodysplasia punctata or X-linked chondrodysplasia. Finally we confirmed that the peroxisomal enzyme alanine glyoxylate aminotransferase is severely deficient in liver from a patient that died because of the neonatal type of hyperoxaluria type I, but not in liver from Zellweger patients.

Chromatography, Gas↗
PubMed1987

Peroxisomal fatty acid beta-oxidation in relation to the accumulation of very long chain fatty acids in cultured skin fibroblasts from patients with Zellweger syndrome and other peroxisomal disorders.

The peroxisomal oxidation of the long chain fatty acid palmitate (C16:0) and the very long chain fatty acids lignocerate (C24:0) and cerotate (C26:0) was studied in freshly prepared homogenates of cultured skin fibroblasts from control individuals and patients with peroxisomal disorders. The peroxisomal oxidation of the fatty acids is almost completely dependent on the addition of ATP, coenzyme A (CoA), Mg2+ and NAD+. However, the dependency of the oxidation of palmitate on the concentration of the cofactors differs markedly from that of the oxidation of lignocerate and cerotate. The peroxisomal oxidation of all three fatty acid substrates is markedly deficient in fibroblasts from patients with the Zellweger syndrome, the neonatal form of adrenoleukodystrophy and the infantile form of Refsum disease, in accordance with the deficiency of peroxisomes in these patients. In fibroblasts from patients with X-linked adrenoleukodystrophy the peroxisomal oxidation of lignocerate and cerotate is impaired, but not that of palmitate. Competition experiments indicate that in fibroblasts, as in rat liver, distinct enzyme systems are responsible for the oxidation of palmitate on the one hand and lignocerate and cerotate on the other hand. Fractionation studies indicate that in rat liver activation of cerotate and lignocerate to cerotoyl-CoA and lignoceroyl-CoA, respectively, occurs in two subcellular fractions, the endoplasmic reticulum and the peroxisomes but not in the mitochondria. In homogenates of fibroblasts from patients lacking peroxisomes there is a small (25%) but significant deficiency of the ability to activate very long chain fatty acids. This deficient activity of very long chain fatty acyl-CoA synthetase is also observed in fibroblast homogenates from patients with X-linked adrenoleukodystrophy. We conclude that X-linked adrenoleukodystrophy is caused by a deficiency of peroxisomal very long chain fatty acyl-CoA synthetase.

Facial Bones↗
PubMed1987

Peroxisomal dysfunction in chondrodysplasia punctata, rhizomelic type.

The rhizomelic type of chondrodysplasia punctata (RCDP) is recognizable at birth because of the typical phenotype and radiological features. Most patients die young, some survive until their teens but all are severely retarded. Recent studies showed RCDP to be a peroxisomal disorder. Peroxisomal investigations may be important in defining the prognosis for an individual patient, and are definitely of use in antenatal diagnosis.

Adolescent↗
PubMed1987

Age-related deficiency of the synthesis of platelet activating factor by leukocytes from Zellweger patients.

Ca2+-ionophore A23187-induced synthesis of the alkoxyether lipid platelet activating factor (PAF) by leukocytes from Zellweger patients was undetectable in two patients studied at 3 and 4 weeks of age, reduced in a third patient studied at 2 months of age, and in the low normal range in four patients studied between 4 months and 5 years of age. We have previously reported that plasmalogen-type phosphatidylethanolamine (PE) levels of erythrocytes are reduced in Zellweger patients up to 20 weeks of age, but normal in older patients. These levels were reduced in the three patients with abnormal PAF synthesis, and normal in the other four patients. The results suggest a close relationship between the age of the patients at sampling, and both the A23187-induced capacity of leukocytes to synthesize PAF and the plasmalogen PE levels in their erythrocytes.

Abnormalities, Multiple↗
PubMed1986

Acyl-CoA:dihydroxyacetone phosphate acyltransferase in human skin fibroblasts: study of its properties using a new assay method.

In relation to the finding that human skin fibroblasts are capable of de novo either phospholipid biosynthesis, we have studied the properties of acyl-CoA:dihydroxyacetone phosphate acyltransferase in fibroblast homogenates using a new assay method. The results indicate that the acylation of dihydroxyacetone phosphate shows an optimum at pH 5.5 with a broad shoulder of activity up to pH 6.4 and a decline in activity up to pH 8.2. At pH 5.5 the acyltransferase accepts dihydroxyacetone phosphate, but not glycerol 3-phosphate as a substrate. Furthermore, the transferase activity was found to be membrane-bound and inactivated by Triton X-100 at concentrations above 0.025% (w/v). Similar properties have been described for the enzyme as present in rat-liver and guinea-pig liver peroxisomes. These data, together with the finding that acyl-CoA:dihydroxyacetone phosphate acyltransferase is deficient in cultured skin fibroblasts from patients without peroxisomes (Zellweger syndrome), suggest that in cultured skin fibroblasts the enzyme is primarily located in peroxisomes.

Acyltransferases↗
PubMed1986

Peroxisomal beta-oxidation of palmitoyl-CoA in human liver homogenates and its deficiency in the cerebro-hepato-renal (Zellweger) syndrome.

The presence of a beta-oxidation system in peroxisomes has been well documented. Rather than a duplicate of the mitochondrial beta-oxidation system, peroxisomes seem specially equipped to initiate the oxidation of very-long-chain fatty acids. Thus, the accumulation of very-long-chain fatty acids in tissues and body fluids from patients with a limited (X-linked adrenoleukodystrophy) or generalized (cerebro-hepato-renal (Zellweger) syndrome, infantile Refsum disease, neonatal adrenoleukodystrophy) peroxisomal dysfunction probably results from an impairment in the peroxisomal beta-oxidation system. In order to study this, we have developed an original assay which allows measurement of the overall peroxisomal beta-oxidation activity in human liver homogenates. Compared to controls, a strong deficiency of this activity was detected in liver from Zellweger patients using palmitoyl-CoA as a substrate.

Acyl Coenzyme A↗
PubMed1986

Regulation of squalene synthetase activity in rat liver: elevation by cholestyramine, but no diurnal variation.

Squalene synthetase activity in liver microsomes from rats sacrificed at three different times of the diurnal cycle showed no significant differences. Addition of 4% cholestyramine to the food resulted in a marked increase in activity (280% of control), independent of the time of killing. 3-Hydroxy-3-methylglutaryl coenzyme A reductase and cholesterol 7 alpha-hydroxylase activity, determined as positive controls, were also found to be elevated by cholestyramine and additionally showed a diurnal variation. On the other hand, five control enzyme activities, not directly related to cholesterol metabolism, i.e. glutamate dehydrogenase, NADPH cytochrome-c reductase, beta-hexosaminidase, catalase and acyl coenzyme A oxidase, showed neither an influence of cholestyramine feeding nor a time of sacrifice dependent variation.

Animals↗
PubMed1986

A prenatal test for the cerebro-hepato-renal (Zellweger) syndrome by demonstration of the absence of catalase-containing particles (peroxisomes) in cultured amniotic fluid cells.

In this paper we show that whereas acyl-CoA: dihydroxyacetone phosphate acyltransferase, a membrane-bound peroxisomal enzyme, is deficient in homogenates of cultured amniotic fluid cells of fetuses with Zellweger syndrome, catalase a soluble peroxisomal matrix enzyme is present in normal amounts. Digitonin titration experiments revealed a striking difference in the percentage of particle-bound catalase in control and Zellweger amniocytes: in Zellweger amniocytes all catalase activity was found to be present in the soluble cytoplasm, (less than 5% particle-bound), whereas in control amniocytes catalase was found to be predominantly particle-bound (62% +/- 8%, n = 5). Measurement of the percentage of particle-bound catalase by means of digitonin titrations thus provides a simple prenatal test for Zellweger syndrome via the direct demonstration of the presence or absence of catalase-containing particles (peroxisomes).

Acyltransferases↗
PubMed1986

Infantile Refsum disease: deficiency of catalase-containing particles (peroxisomes), alkyldihydroxyacetone phosphate synthase and peroxisomal beta-oxidation enzyme proteins.

In recent years a number of biochemical abnormalities have been described in patients with the infantile form of Refsum disease, including the accumulation of very long chain fatty acids, trihydroxycoprostanoic acid and pipecolic acid. In this paper we show that catalase-containing particles (peroxisomes), alkyl dihydroxyacetone phosphate synthase and acyl-CoA oxidase protein are deficient in patients with infantile Refsum disease. These findings suggest that in the infantile form of Refsum disease, as in the cerebro-hepato-renal (Zellweger) syndrome the multiplicity of biochemical abnormalities is due to a deficiency of peroxisomes and hence to a generalized loss of peroxisomal functions. As a consequence the infantile form of Refsum disease can be diagnosed biochemically by methods already available for the prenatal and postnatal diagnosis of the cerebro-hepato-renal (Zellweger) syndrome.

Acatalasia↗
PubMed1986

Infantile Refsum's disease: biochemical findings suggesting multiple peroxisomal dysfunction.

Infantile Refsum's disease was diagnosed in three male patients, presenting with facial dysmorphia, retinitis pigmentosa, neurosensory hearing loss, hepatomegaly, osteopenia and delayed growth and psychomotor development. An elevated plasma phytanic acid concentration and a deficient phytanic acid oxidase activity in fibroblasts were found with an accumulation of very long chain fatty acids in plasma and fibroblasts. There were elevated pipecolic acid levels in plasma, urine and CSF, and abnormal bile acid metabolites in plasma. Deficient activity of acylCoA: dihydroxyacetone phosphate acyl transferase was found in thrombocytes and fibroblasts of these patients as well as an impaired de novo plasmalogen biosynthesis in fibroblasts. These biochemical abnormalities, previously described in the Zellweger syndrome, suggest multiple peroxisomal dysfunction in our patients.

Acyltransferases↗