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R C Sengers

Publications and source records attributed to R C Sengers.

At least 55 records · Page 3Linked to original sources
PubMed1993

Problems with the biochemical diagnosis in mitochondrial (encephalo-)myopathies.

Patients suffering from a mitochondrial (encephalo-)myopathy have a remarkable clinical heterogeneity. A reliable and extensive investigation must be performed in order to obtain a correct diagnosis, but many factors may influence the ultimate results of these investigations leading, under certain circumstances, to an incorrect diagnosis. Patients selection is of crucial importance. Metabolic examination of body fluids, particularly with respect to lactate accumulation, is used as a selection criterion for further examinations. Numerous aspects associated with this metabolic examination have been critically evaluated, including the phenomenon of other causes of lactic acidaemia apart from mitochondrial disorders. Correct performance of in vivo function tests may contribute to a reduction of the number of missed diagnoses. Selection of the controls for biochemical investigations must be accurately be performed to obtain reliable reference values. Knowledge of the age-dependency of the biochemical parameters is necessary for a correct interpretation. It goes without saying that the choice of the tissue for biochemical investigations is of utmost importance. Knowledge of the tissue-specific occurrence of some defects in the mitochondrial respiratory chain is necessary. The biochemical examinations can be performed both in biopsy and autopsy material but only under certain conditions. Diagnostic approach requires application of reliable biochemical methods which are described. One of the most intriguing aspects in the diagnosis of mitochondrial disorders is the significance of a defect in relation to the residual enzyme activity found in the patient. Moreover, attention is paid to relevant items such as the occurrence of multiple and secondary defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis, Lactic↗
PubMed1993

A retrospective study of patients with the hereditary syndrome of congenital cataract, mitochondrial myopathy of heart and skeletal muscle and lactic acidosis.

The objectives of this study were to describe the course of two forms of an hereditary syndrome characterised by congenital cataract, mitochondrial myopathy of heart and skeletal muscle and lactic acidosis. We also sought to determine clinical, physicochemical and histopathological data which might allow early distinction between the two forms. We compared the ages at which clinical and physicochemical signs appeared in 16 patients. In 5 patients, enzyme-histochemical and ultrastructural data of skeletal muscle were available and muscle fibre composition analysed morphometrically. In any particular family only one form of the syndrome occurred. Amongst the patients who did not survive (range 14-34 years) 4 patients died in the neonatal period and 7 died at a median age of 23 years. The median age of the survivors was 19 years (range 15-42 years). Outflow obstruction of the left ventricle was noted in four deceased patients at variable times prior to death. The other deceased patients were not examined, but the cause of death was invariably heart failure. In none of the surviving patients was outflow obstruction noted. Enzyme-histochemical and ultrastructural findings were not specific for the course of the disease. In one biopsy, taken at the age of 3.5 months from a patient who survived, strong lipid accumulation was noted. Morphometric analysis showed proliferation of the mitochondria in muscle fibres, which increased during the course of the disease.

Acidosis, Lactic↗
PubMed1993

Genetic mapping of the beta 1- and gamma-subunits of the human skeletal muscle L-type voltage-dependent calcium channel on chromosome 17q and exclusion as candidate genes for malignant hyperthermia susceptibility.

Malignant hyperthermia susceptibility (MHS) is an autosomal dominant disorder of skeletal muscle which manifests as a life-threatening hypermetabolic crisis triggered by commonly-used inhalation anaesthetics and depolarizing muscle relaxants. Defects in the ryanodine receptor (RYR1) protein have been proposed to underly MHS, but significant genetic heterogeneity in MHS has recently been demonstrated. In order to investigate the potential roles played by other skeletal muscle calcium channels in MHS, we isolated cosmids containing the gene encoding the beta 1-subunit of skeletal muscle L-type voltage-dependent calcium channel (CACNLB1). We identified a new, highly polymorphic dinucleotide repeat motif close to this gene, and linkage analysis placed the marker proximal to the HOX2B locus, previously localized to chromosome segment 17q21-q22. We recently identified a novel marker within the gamma-subunit locus (CACNLG) at band 17q24, and since both markers are within the 17q11.2-q24 region reported to contain the MHS2 locus, we tested them for linkage in MHS families whose disease trait has been shown not to co-segregate with markers for the RYR1 region on chromosome 19q13.1. Our results exclude CACNLB1 and CACNLG as candidate genes for MHS2, and do not support the reported chromosome 17q localization for the MHS2 locus in our families.

Base Sequence↗
PubMed1993

Measurement of totally activated pyruvate dehydrogenase complex activity in human muscle: evaluation of a useful assay.

A sensitive radiochemical method for the determination of the pyruvate dehydrogenase complex (PDHC) activity in skeletal muscle tissue, based on the decarboxylation of [1-14C]-pyruvate to 14CO2, is described. Measurements can be carried out either in muscle homogenate or in 600-g supernatant, both obtainable from a small muscle biopsy specimen (20 mg). In addition to NAD+, thiamine pyrophosphate and coenzyme A in the incubation mixture, a preparation of NADH:cytochrome c reductase (NADHCR) together with cytochrome c has a stimulating effect on the PDHC activity. NADHCR constitutes an oxidation system for NADH to prevent feedback inhibition. Addition of L-carnitine also results in stimulation of PDHC by trapping the produced acetyl-CoA as acetylcarnitine. Special care for radioactive pyruvate, with freeze drying and storage at -20 degrees C under nitrogen, and determination of the purity during every PDHC assay, is required. In the presented assay a Km value of 0.084 mmol/l was found for pyruvate. Nonsigmoidal kinetics was found with a Hill coefficient of 1.63. With the described method, a totally Mg2+,Ca(2+)-stimulated PDHC activity is measured. Addition of a purified specific pyruvate dehydrogenase phosphatase did not yield a higher PDHC activity. Finally, comparison of total PDHC activity with [1-14C]-pyruvate oxidation rates, both measured in the supernatant prepared from fresh muscle, shows an equimolar correlation, indicating that total PDHC activity is rate limiting in the assay for the pyruvate oxidation rate. Neonatal muscle exhibits five to ten times lower PDHC activities and pyruvate oxidation rates than controls (age > 3 years).

Adolescent↗
PubMed1993

Deficiency of the adenine nucleotide translocator in muscle of a patient with myopathy and lactic acidosis: a new mitochondrial defect.

In a patient with a mitochondrial myopathy, presenting with lactic acidosis, 31P-nuclear magnetic resonance spectroscopy in resting muscle showed half the creatine phosphate level of controls. The creatine phosphate resynthesis rate after aerobic exercise was only 18% of that in controls. However, the activities of complexes I to V catalyzing oxidative phosphorylation and the pyruvate and the 2-oxoglutarate dehydrogenase complexes showed a 2- to 20-fold increase. In line with this, the uncoupled mitochondrial respiration rate was significantly higher than in controls. In contrast, the respiration of the mitochondria from the patient was less stimulated by ADP than that of control mitochondria. This finding could point to a defect in complex V, the enzyme directly involved in ATP synthesis. The activity of complex V, measured as the mitochondrial ATPase activity, and its concentration, as judged from Western blots using antisera against the F1 part of complex V, were, however, also greatly increased in the patient. Alternatively, the transport system, importing ADP into and exporting ATP out of the mitochondrial matrix, the ADP/ATP or adenine nucleotide translocator, could be affected. Immunostaining of Western blots revealed a 4-fold decrease in the concentration of the adenine nucleotide translocator in the patient. Because oxidative phosphorylation was not disturbed in fibroblasts and lymphocytes, we conclude that this patient suffers from a muscle-specific deficiency of his mitochondrial adenine nucleotide translocator, a defect unknown so far.

Acidosis, Lactic↗
PubMed1992

Differentiation of human skeletal muscle cells in culture: maturation as indicated by titin and desmin striation.

This report describes a phenotyping study of differentiating human skeletal muscle cells in tissue culture. Satellite cells (adult myoblasts), isolated from biopsy material, showed a proliferative behaviour in high-nutrition medium, but fused to form myotubes when grown in low-nutrition medium. The expression and structural organization of the intermediate filament proteins desmin and vimentin as well as the sarcomeric constituents alpha-actin, alpha-actinin, nebulin, myosin and especially titin during myofibrillogenesis in vitro, were studied by means of indirect immunofluorescence assays. The proliferating myoblasts contained both desmin and vimentin, alpha-actinin and the filamentous form of actin. Shortly after the change of medium, expression of titin, sarcomeric myosin and skeletal muscle alpha-actin was found in mononuclear cells in a diffuse, filamentous (titin, myosin, alpha-actin) or punctate (titin, myosin) pattern. Four to 10 days after the medium change, mature myotubes showed desmin, titin, alpha-actinin, nebulin, sarcomeric myosin and actin cross-striations, while vimentin was no longer detected. We conclude that human skeletal muscle cell cultures are an appropriate model system to study the molecular basis of myofibrillogenesis. Especially the presence of desmin in a striated fashion points to a high degree of maturation of the muscle cell cultures.

Actinin↗
PubMed1992

Prenatal diagnosis of systemic disorders of the respiratory chain in cultured amniocytes and chorionic villus fibroblasts by studying the formation of lactate and pyruvate from glucose.

Formation of lactate and pyruvate from glucose was studied in cultured amniocytes and chorionic villus fibroblasts from controls, either untreated or treated with azide, an inhibitor of cytochrome c oxidase, or other inhibitors of the mitochondrial respiratory chain. Amniocytes with an established cytochrome c oxidase deficiency were also investigated. Control amniocytes treated with azide as well as cytochrome c oxidase deficient amniocytes displayed strongly increased lactate-to-pyruvate ratios after incubation with glucose, compared to control cells. Elevated lactate-to-pyruvate ratios were also found in chorionic villus fibroblasts in which complexes I, III or IV were inhibited by rotenone, antimycin or azide, respectively. We conclude that measurement of lactate and pyruvate production from glucose in cultured amniocytes and/or chorionic villus fibroblasts allows adequate prenatal diagnosis of systemic cytochrome c oxidase deficiency and presumably of other systemic deficiencies of mitochondrial respiratory chain enzymes.

Amnion↗
PubMed1992

Combined deficiencies of the pyruvate dehydrogenase complex and enzymes of the respiratory chain in mitochondrial myopathies.

In six patients with mitochondrial (encephalo-) myopathy investigations of skeletal muscle revealed a defect of pyruvate dehydrogenase complex (PDHC) in combination with one or more respiratory chain complex deficiencies. A combination of defects of this kind has not been reported previously. Five of the six patients presented within the 1st year of life and had a severe clinical course. Intrafamilial variability of the clinical course in dizygotic twins both suffering from a cytochrome c oxidase deficiency and one of them also from a PDHC deficiency suggests an additional effect of PDHC deficiency on the clinical symptoms. Immunoblot studies of PDHC in five of the patients revealed no abnormalities in their subunit pattern, rendering a defect of mitochondrial protein import or assembly unlikely. The finding of a combined PDHC and respiratory chain deficiency has implications for the diagnostic approach, for therapy and genetic counselling. The exact pathogenetic mechanism of this combination of defects remains to be elucidated.

Female↗
PubMed1992

Myopathology and a mitochondrial DNA deletion in the Pearson marrow and pancreas syndrome.

A patient with the Pearson marrow and pancreas syndrome is presented. She showed an anaemia with neutropenia and thrombopenia, failure to thrive, diarrhoea, disturbed glucose homeostasis and lactic acidosis. An exocrine pancreatic insufficiency was lacking. The disease followed a fatal course. Biochemical investigations of skeletal muscle revealed a disturbed mitochondrial energy metabolism, while many ultrastructural abnormal features were observed in the muscle tissue. Molecular genetic studies showed a de novo deletion in the mitochondrial DNA (mtDNA), different in size from the already published deletions and flanked by two 4 bp direct repeats, interspaced by 4-5 non-repeated nucleotides. mtDNA from 12 other tissues showed the same deletion in different percentages. No obvious relation between these percentages and tissue dysfunction was found. In spite of an open reading frame of 74 codons, only little transcription product of the genomic region resulting from the deletion was found.

B-Lymphocytes↗
PubMed1992

High-resolution physical mapping of four microsatellite repeat markers near the RYR1 locus on chromosome 19q13.1 and apparent exclusion of the MHS locus from this region in two malignant hyperthermia susceptible families.

Malignant hyperthermia susceptibility (MHS) is a potentially lethal, hereditary disorder of skeletal muscle that may be triggered by inhalation anesthetics and depolarizing muscle relaxants. Defects in the gene encoding the ryanodine receptor (RYR1) localized on human chromosome 19q13.1 have been proposed to be responsible for MHS. Using a chromosome 19-specific human/hamster somatic cell hybrid mapping panel, we were able to determine that four closely linked microsatellite repeat markers bracket RYR1 with the order 19cen-D19S75-D19S191-RYR1-(D19S47, D19S190)-19ter. Application of the four markers to genetic studies of MHS showed recombination between the markers and MHS in two families, with linkage analysis apparently excluding the MHS locus from the RYR1 region of 19q13.1. These results therefore support the recent observations of genetic heterogeneity in MHS.

Animals↗
PubMed1992

Postnatal development of pyruvate oxidation in quadriceps muscle of the rat.

In order to evaluate the age dependency of enzymes involved in the energy-generating system, skeletal muscle specimens from rats of different ages were investigated for several mitochondrial enzymes. [1-14C]pyruvate (+/- ADP) oxidation rates and pyruvate dehydrogenase complex (PDHC) activity increased significantly from low early values during the neonatal period to nearly adult values at the end of the suckling period. Other enzymes of the pyruvate oxidation route such as citrate synthase and cytochrome c oxidase showed similar patterns of development. Immunoblot studies of PDHC detected a clear increase in the intensity of the bands of the alpha subunits of E1 (pyruvate dehydrogenase) and E2 (dihydrolipoyl transacetylase) within the first 3 weeks of life. The ratio between the individual PDHC proteins indicated that E1 alpha, the regulatory subunit of the multienzyme complex, is the most rapidly increasing protein with age.

Acetyltransferases↗
PubMed1992

Enzyme activities of the mitochondrial energy generating system in skeletal muscle tissue of preterm and fullterm neonates.

Quadriceps muscle specimens from autopsy of 28 neonates (gestational age 25-42 weeks) were investigated to determine pyruvate and malate oxidation rates and several enzymes of the mitochondrial oxidative process. In general, the levels of all mitochondrial parameters measured, including carnitine levels, were lower in the neonates who died within the first week of life than those in the control group (age > 5 years). Pyruvate and malate oxidation rates (P < 0.05), activities of pyruvate dehydrogenase complex (P < 0.10) and succinate: cytochrome c oxidoreductase (P < 0.05) increased significantly with gestational age. Pyruvate oxidation rates (P < 0.05) as well as activities of citrate synthase (P < 0.05) and NADH:Q1 oxidoreductase (P < 0.05) were significantly lower in the group of very preterm infants at an age of 1-7 days compared with very preterm infants at an age between 3-8 weeks. We conclude from our study that special reference values are necessary for a correct biochemical diagnosis of mitochondrial encephalomyopathies in the neonatal period. Differences between preterm and fullterm children of the same age (1 week) indicate a maturational process in human muscle tissue during gestation. Comparison of two different age groups within the very preterm neonates point to a postnatal maturation of the mitochondrial energy metabolism, at least in preterm neonates.

Carnitine↗
PubMed1992

Changes in volume densities and distribution of mitochondria in rat skeletal muscle after chronic hypoxia.

In order to test the hypothesis that subsarcolemmal aggregation of skeletal muscle mitochondria, as noted in some patients with mitochondrial myopathies, is caused by an impaired oxygen supply to mitochondria, we exposed two groups of rats to 8% O2 during 44 or 45 days. One group performed mild exercise, as did a normoxic control group. After hypoxia we investigated fibre type composition, fibre diameter and capillarity of soleus and extensor digitorum longus (e.d.l.) muscles. Mitochondrial volume densities were determined by morphometric analysis. In both e.d.l. and soleus muscle fibre type composition was unchanged and fibre diameter was reduced after hypoxia. Capillary network was unchanged, hence capillary density was increased in both muscles after hypoxia (P less than 0.05 in untrained soleus). Total mitochondrial volume density was increased in soleus muscle, which was due to an increase in the volume density of intermyofibrillar mitochondria (P less than 0.05 in the trained group), whereas the volume density of subsarcolemmal mitochondria decreased. In e.d.l. muscle the volume density of both intermyofibrillar and subsarcolemmal mitochondria decreased. We conclude that subsarcolemmal aggregation of mitochondria did not occur after chronic hypoxia. In soleus and e.d.l. muscle, different changes in the volume densities of mitochondria occurred. This may be related to the relative amounts of type I and type II fibres within these muscles.

Animals↗
PubMed1991

Successful treatment of pure myopathy, associated with complex I deficiency, with riboflavin and carnitine.

We describe a 6-year-old boy who presented with progressive muscle weakness. Additional investigations revealed the existence of a myopathy and a pure motor neuropathy. Biochemical studies in muscle tissue showed a defect of NADH dehydrogenase (complex I). The patient dramatically improved on treatment with riboflavin and L-carnitine. Seven months after the start of the treatment, complex I activity was determined again and appeared to be normalized. Normalization of the enzymatic defect at this level has not been reported before. We provide a survey of nine patients with pure myopathy, associated with complex I deficiency and onset of symptoms in childhood.

Biopsy↗
PubMed1991

Increased volume density of peripheral mitochondria in skeletal muscle of children with exercise intolerance.

Muscle biopsies from 17 children with exercise intolerance and other miscellaneous symptoms and signs showed changes in mitochondrial content. The patients could not be classified according to known criteria. The histopathological changes were quantified by morphometric analysis and the clinical data were statistically analysed to detect intercorrelations. After a mean follow up period of 6.8 years (range 0.5-13.6), patients were re-examined and the course of the disease was determined. No clinical entity could be established. None of the patients showed aggravation of the exercise intolerance, but 71% noted no improvement. An increased volume density of peripheral mitochondria was shown in 59%. Based on clinical history, histopathological changes and course we suggest that some of these patients suffer from a yet unknown disturbance in energy metabolism. Recognition of these patients is important for appropriate counselling.

Adolescent↗