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Biomedical subjects

S DiMauro

Publications and source records attributed to S DiMauro.

At least 271 records · Page 15Linked to original sources
PubMed1989

Heteroplasmy of mitochondrial genomes in clonal cultures from patients with Kearns-Sayre syndrome.

We have analyzed heteroplasmy of mitochondrial DNA in clonal cultures from two patients with Kearns-Sayre syndrome, and have found that individual muscle or fibroblast clones contained either a mixed (i.e. heteroplasmic) population of normal and deleted mitochondrial DNAs, or only normal mitochondrial DNAs (i.e. homoplasmic at a level of detection of less than 1% deleted genomes). The heteroplasmic clones grew significantly more slowly than did "homoplasmic" clones, probably due to defects of respiratory chain enzymes containing mtDNA-encoded polypeptides.

Chromosome Deletion↗
PubMed1989

A direct repeat is a hotspot for large-scale deletion of human mitochondrial DNA.

Kearns-Sayre syndrome (KSS) and progressive external ophthalmoplegia (PEO) are related neuromuscular disorders characterized by ocular myopathy and ophthalmoplegia. Almost all patients with KSS and about half with PEO harbor large deletions in their mitochondrial genomes. The deletions differ in both size and location, except for one, 5 kilobases long, that is found in more than one-third of all patients examined. This common deletion was found to be flanked by a perfect 13-base pair direct repeat in the normal mitochondrial genome. This result suggests that homologous recombination deleting large regions of intervening mitochondrial DNA, which previously had been observed only in lower eukaryotes and plants, operates in mammalian mitochondrial genomes as well, and is at least one cause of the deletions found in these two related mitochondrial myopathies.

Base Composition↗
PubMed1989

Recurrent myoglobinuria and HIV seropositivity: incidental or pathogenic association?

There have been few cases of polymyositis in patients with AIDS, and polymyositis is rarely a cause of myoglobinuria. We studied a 20-year-old homosexual man with recurrent myoglobinuria. He was asymptomatic between episodes. Each episode was accompanied by muscle pain, limb weakness, high serum levels of creatine kinase, and pigmenturia. Muscle biopsy showed active necrosis without inflammation or abnormalities of glycolytic or other energy-generating enzymes. Antibodies to HIV were present in serum. Clinical evidence of AIDS has not developed in 2 years. Recurrent myoglobinuria may be another consequence of HIV infection.

Adult↗
PubMed1989

Detection of "deleted" mitochondrial genomes in cytochrome-c oxidase-deficient muscle fibers of a patient with Kearns-Sayre syndrome.

Using in situ hybridization and immunocytochemistry, we studied a muscle biopsy sample from a patient with Kearns-Sayre syndrome (KSS) who had a deletion of mitochondrial DNA (mtDNA) and partial deficiency of cytochrome-c oxidase (COX; EC 1.9.3.1). We sought a relationship between COX deficiency and abnormalities of mtDNA at the single-fiber level. COX deficiency clearly correlated with a decrease of normal mtDNA and, conversely, deleted mtDNA was more abundant in COX-deficient fibers, especially ragged-red fibers. The distribution of mtRNA had a similar pattern, suggesting that deleted mtDNA is transcribed. Immunocytochemistry showed that the nuclear DNA-encoded subunit IV of COX was present but that the mtDNA-encoded subunit II was markedly diminished in COX-deficient ragged-red fibers. Because the mtDNA deletion in this patient did not comprise the gene encoding COX subunit II, COX deficiency may have resulted from lack of translation of mtRNA encoding all three mtDNA-encoded subunits of COX.

Base Sequence↗
PubMed1989

Metabolic and functional adaptation of the diaphragm to training with resistive loads.

To study the metabolic and functional changes that occur during training with inspiratory flow resistive loads, a chronically instrumented unanesthetized sheep preparation was used. Sheep were exposed to resistances ranging from 50 to 100 cmH2O.l-1.s, for 2-4 h/day, 5-6 days/wk, for a total of 3 wk. Load intensity was adjusted to maintain arterial Po2 (PaO2) above 60 Torr and arterial PCO2 (PaCO2) below 45 Torr. Training produced significant (P less than 0.05) increases in citrate synthase, 3-hydroxyacyl-CoA dehydrogenase, and cytochrome oxidase in the costal and crural diaphragm of the trained sheep (n = 9) compared with control sheep (n = 7). Phosphofructokinase did not increase. In the quadriceps, citrate synthase, 3-hydroxyacyl-CoA dehydrogenase, and phosphofructokinase did not change with training but cytochrome oxidase increased significantly (P less than 0.01). Function of the diaphragm was assessed in a subset of five sheep exposed to the same severe load 1 wk before and 2 days after the final training session. After training, sheep had a lower PaCO2 (10-40%), generated a higher transdiaphragmatic pressure (20-40%), and could sustain this level of transdiaphragmatic pressure for 0.5-2 h longer. The respiratory duty cycle was 10-15% lower, whereas minute ventilation and tidal volume were 20-30% higher in the posttraining test. We conclude that 1) training with inspiratory flow resistive loads improves the performance of the respiratory neuromuscular system and 2) the shift in enzyme profile of the diaphragm is at least in part responsible for this improvement.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1989

Exercise intolerance, lactic acidosis, and abnormal cardiopulmonary regulation in exercise associated with adult skeletal muscle cytochrome c oxidase deficiency.

A 27-yr-old woman with lifelong severe exercise intolerance manifested by muscle fatigue, lactic acidosis, and prominent symptoms of dyspnea and tachycardia induced by trivial exercise was found to have a skeletal muscle respiratory chain defect characterized by low levels of reducible cytochromes a + a3 and b in muscle mitochondria and marked deficiency of cytochrome c oxidase (complex IV) as assessed biochemically and immunologically. Investigation of the pathophysiology of the exercise response in the patient revealed low maximal oxygen uptake (1/3 that of normal sedentary women) in cycle exercise and impaired muscle oxygen extraction as indicated by profoundly low maximal systemic arteriovenous oxygen difference (5.8 ml/dl; controls = 15.4 +/- 1.4, mean +/- SD). The increases in cardiac output and ventilation during exercise, normally closely coupled to muscle metabolic rate, were markedly exaggerated (more than two- to threefold normal) relative to oxygen uptake and carbon dioxide production accounting for prominent tachycardia and dyspnea at low workloads. Symptoms in our patient are similar to those reported in other human skeletal muscle respiratory chain defects involving complexes I and III, and the exaggerated circulatory response resembles that seen during experimental inhibition of the mitochondrial respiratory chain. These results suggest that impaired oxidative phosphorylation in working muscle disrupts the normal regulation of cardiac output and ventilation relative to muscle metabolic rate in exercise.

Acidosis, Lactic↗
PubMed1989

Cytochrome c oxidase deficiency in Leigh's syndrome: genetic evidence for a nuclear DNA-encoded mutation.

Although an apparently generalized defect of cytochrome c oxidase (COX) occurs in many patients with subacute necrotizing encephalomyelopathy (Leigh's syndrome), the mode of inheritance in this disorder is not known. We transformed COX-deficient fibroblasts from a child with Leigh's syndrome with simian virus 40 to obtain cells with an infinite life span. These cells were still COX-deficient, grew normally in HAT medium, and were ouabain-sensitive. We fused these cells with a HAT-sensitive, ouabain-resistant variant of HeLa cells (HeLacot) and isolated surviving hybrid clones in ouabain-containing HAT medium. Prolonged cultivation of the hybrids was accompanied by preferential loss of HeLacot mitochondrial DNA (mtDNA), as determined by mtDNA restriction patterns of parental and hybrid cell DNA with the restriction endonuclease HaeII. COX activity was normal or higher than normal in hybrids, including the progeny of cell clones that had lost almost all the HeLacot mtDNA. These data demonstrate that COX deficiency in this Leigh's syndrome patient's cells was corrected by a nuclear DNA-encoded factor from the HeLacot parent and ruled out an mtDNA mutation as the basis for COX deficiency. This system can be used to determine whether different generalized mitochondrial disorders are due to mutations of nuclear or mtDNA.

Brain Diseases, Metabolic↗
PubMed1989

[Myopathy due to succinate cytochrome C oxidoreductase deficiency: possible defect of complex II of the respiratory chain].

The case of a 24 years-old woman with weakness since the teens and progressive loss of muscle strength is reported. The muscle biopsy showed increased number of mitochondria. In two occasions the respiratory chain enzymes showed important reduction of the succinate-cytochrome-C-reductase, suggesting a possible defect in the complex II of the respiratory chain. Large doses of vitamins C and K were prescribed. There was improvement of muscle strength. A discussion about the most common syndromes marked by mitochondrial abnormalities in muscle is made, as well as about the type of work-up that should be done in suspect cases of respiratory chain defects.

Adult↗
PubMed1989

Mitochondrial diseases.

Mitochondrial diseases, and particularly mitochondrial myopathies or encephalomyopathies, have drawn increasing attention in the past decade. Initially defined by morphologic changes in muscle ("ragged red fibers" and ultrastructural abnormalities of mitochondria), mitochondrial encephalomyopathies can now be classified according to biochemical defects involving: (1) mitochondrial transport; (2) substrate oxidation; (3) Krebs cycle; (4) respiratory chain; and (5) oxidation-phosphorylation coupling. For each biochemical group of disorders, the authors describe clinical presentations and biochemical findings. These disorders are especially interesting from the genetic point of view because mitochondria have their own DNA (mtDNA), which encodes 13 polypeptides, all of them subunits of respiratory chain complexes. Other mitochondrial proteins are encoded by nuclear DNA, synthesized in the cytoplasm, and imported into the mitochondria by a complex mechanism. Because mtDNA is inherited strictly by maternal, cytoplasmic inheritance, mitochondrial diseases can be transmitted by Mendelian or by non-Mendelian, maternal inheritance, as illustrated by human pathology.

Brain Diseases, Metabolic↗
PubMed1989

Disorders of glycogen metabolism of muscle.

Glycogen is a crucial source of energy in the initial stages of muscle activity and during exercise of high intensity. There are 10 well-defined biochemical defects of glycogen metabolism expressed in muscle and affecting the following enzymes: alpha 1,4 glucosidase (glycogenesis type II), debrancher enzyme (III), brancher enzyme (IV), phosphorylase (V), phosphofructokinase (VII), phosphorylase b kinase (VIII), phosphoglycerate kinase (IX), phosphoglycerate mutase (X), lactate dehydrogenase (XI). These disorders cause two main syndromes: one characterized by exercise intolerance with cramps and myoglobinuria, the other by fixed weakness. However, there are examples of clinical and biochemical heterogeneity for each disease, and molecular genetic analysis is already showing evidence of genetic heterogeneity. Although our understanding of the biochemical errors has progressed considerably, the pathogenesis of symptoms and signs remains incomplete.

Enzymes↗
PubMed1988

Isolation of a cDNA encoding the B isozyme of human phosphoglycerate mutase (PGAM) and characterization of the PGAM gene family.

We previously reported the isolation of a full-length cDNA specifying the muscle-specific isozyme of human phosphoglycerate mutase (PGAM-M). We now report the isolation of a full-length cDNA specifying the non-muscle-specific, or brain (B), isozyme of human PGAM (PGAM-B). The PGAM-B cDNA encodes a deduced protein 254 amino acids long, 79% identical to PGAM-M, and contains a 913-nucleotide 3'-untranslated region, as compared to the unusually short 37-nucleotide 3'-untranslated region of PGAM-M. Northern analysis demonstrates the non-muscle-specific nature of PGAM-B transcription, while genomic Southern analysis implies the presence of a large PGAM family in the human genome. Most of the PGAM-hybridizing sequences in both the human and mouse genomes seem to be related to the B-isozyme gene; many members of the PGAM-B gene family in humans are apparently processed genes. These results agree with the evolutionary analysis, which indicates that the PGAM-B gene is the progenitor of the PGAM-M gene.

Amino Acid Sequence↗
PubMed1988

Subunit Va of human and bovine cytochrome c oxidase is highly conserved.

We have isolated a full-length cDNA clone specifying the nuclear-encoded subunit Va of the human mitochondrial respiratory enzyme cytochrome c oxidase (COX; EC 1.9.3.1.). The deduced sequence of the polypeptide is 95% identical to that of the corresponding subunit of bovine COX, which makes it the most conserved polypeptide among the known bovine/human pairs of COX subunits. This polypeptide contains an N-terminal presequence which is rich in basic and hydroxylated residues, but differs from the deduced presequences of all other previously isolated COX subunits in that it also contains a negatively charged residue. We find no evidence of tissue-specific isoforms of subunit Va, as Northern analysis showed a single, identically-sized transcript in RNA from human muscle, liver, and brain, while coxVa cDNAs isolated from both endothelial and fetal muscle cDNA libraries had identical nucleotide sequences.

Amino Acid Sequence↗
PubMed1988

Duchenne muscular dystrophy: deficiency of dystrophin at the muscle cell surface.

Dystrophin is the altered gene product in Duchenne muscular dystrophy (DMD). We used polyclonal antibodies against dystrophin to immunohistochemically localize the protein in human muscle. In normal individuals and in patients with myopathies other than DMD, dystrophin was localized to the sarcolemma of the fibers. The protein was absent or markedly deficient in DMD. The sarcolemmal localization of dystrophin is consistent with other evidence that there are structural and functional abnormalities of muscle surface membranes in DMD.

Cell Membrane↗
PubMed1988

Sequence of cDNAs encoding subunit Vb of human and bovine cytochrome c oxidase.

We have isolated a full-length human fetal muscle cDNA clone specifying the nuclear-encoded subunit Vb of the human mitochondrial respiratory chain enzyme, cytochrome c oxidase (COX; EC 1.9.3.1), and a partial-length brain cDNA clone specifying the analogous bovine subunit. The two cDNAs are 85% identical at the nucleotide level. Similar to other proteins imported into mitochondria, the deduced human COX Vb protein contains a presequence, 31 amino acids long, rich in basic residues. We find no evidence for tissue-specific transcripts for subunit Vb of human COX, as Northern analysis of total RNA from human muscle, liver, and brain showed a single, identically sized transcript in each cell type, while partial-length cDNA clones isolated from human muscle and endothelial cell cDNA libraries were identical in sequence to the fetal muscle cDNA.

Amino Acid Sequence↗
PubMed1988

McArdle's disease: biochemical and molecular genetic studies.

We have analyzed muscle biopsy specimens from 48 patients with biochemically proven phosphorylase deficiency (McArdle's disease) by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting, and immunotitration (enzyme-linked immunosorbent assay [ELISA]). Thirty-five of the 42 patients studied by SDS-PAGE and immunoblot, and 41 of the 48 patients studied by ELISA had no detectable enzyme protein. Six patients had markedly decreased phosphorylase protein by all three assays, and only 1 patient had a normal amount of protein. No apparent correlation existed between the presence or absence of enzyme protein and the clinical presentation or muscle glycogen concentration. Northern analysis was performed on muscle RNA in 4 patients: messenger RNA was normal in 2, abnormally short in 1, and absent in the fourth, indicating heterogeneity of the molecular lesion in McArdle's disease.

Biopsy↗
PubMed1988

Molecular defects in cytochrome oxidase in mitochondrial diseases.

Defects of cytochrome c oxidase (COX) show remarkable clinical, biochemical, and genetic heterogeneity. Clinically, there are two main groups of disorders, one dominated by muscle involvement, the other by brain dysfunction. Biochemically, the enzyme defect may be confined to one or a few tissues (reflecting the existence of tissue-specific isozymes) or affect all tissues. Immunologically reactive enzyme protein is decreased in some forms of COX deficiency but not in others. Because COX is encoded both by nuclear and by mitochondrial genes, COX deficiencies may be due to mutations of either genome and may offer useful models to study the communication between nuclei and mitochondria. We have isolated full-length cDNA clones encoding human COX subunits IV, Vb, and VIII and a partial-length clone for subunit Va. These clones are being used as probes to analyze the DNA and RNA of patients with COX deficiency.

Brain Diseases↗