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Biomedical subjects

S DiMauro

Publications and source records attributed to S DiMauro.

At least 235 records · Page 13Linked to original sources
PubMed1992

Reversible mitochondrial myopathy with cytochrome c oxidase deficiency.

Two siblings, a boy and a girl born in a nonconsanguineous marriage, presented with a similar clinical course. Sucking and breathing difficulties appeared within a few weeks of birth. Clinical examination revealed profound muscular hypotonia, hepatomegaly, increased serum creatine kinase activities, and lactic acidosis. Both infants were treated with gavage feeding, the boy also needing ventilatory support. Clinically they improved gradually. Now, the boy aged 4 years and the girl aged 28 months are free of clinical signs. Muscle biopsy specimens taken at 3 months showed, in both, ragged red fibres, abnormal mitochondria, and reduced cytochrome c oxidase (COX) staining. Biochemical analysis showed COX activity to be reduced to about 25% of the normal mean. The second biopsy specimen from the boy at 16 months was normal on morphological examination, but the girl's second specimen at 13 months still showed abnormal features. These cases are examples of the rare benign reversible COX deficiency. Early diagnosis is crucial to provide intensive treatment until spontaneous clinical improvement appears.

Biopsy↗
PubMed1992

Respiratory failure revealing mitochondrial myopathy in adults.

Two patients, a 70-yr-old black woman and a 56-yr-old black man, presented with respiratory failure unexplained by intrinsic lung disease. Both had been dependent on a respirator for several weeks. No abnormalities of the central or peripheral nervous system or long-standing muscle weakness was noted. The findings from ophthalmologic and cardiac evaluations were normal. The serum creatinine kinase concentration was mildly elevated in case 1, and needle electromyography showed myopathic potentials in case 2. In both instances, muscle biopsy established the diagnosis of mitochondrial myopathy. Biochemical studies of muscle extracts showed partial deficiency of complex 3 in patient 2 and of complex 4 in patient 1. Both patients were weaned from the ventilator after long periods of ventilatory assistance. These observations document a hitherto undescribed presentation of adult-onset mitochondrial myopathy.

Aged↗
PubMed1992

The mitochondrial tRNA(Leu(UUR)) mutation in mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (MELAS): genetic, biochemical, and morphological correlations in skeletal muscle.

Mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (MELAS) has recently been associated with an A----G transition at position 3243 within the mitochondrial tRNA(Leu(UUR)) gene. Besides altering the tRNA(Leu(UUR)) sequence, this point mutation lies within a DNA segment responsible for transcription termination of the rRNA genes. We have studied the distribution and expression of mutant mtDNAs in muscle biopsies from MELAS patients. Histochemical, immunohistochemical, and single-fiber PCR analysis showed that ragged-red fibers (RRF) are associated both with high levels of mutant mitochondrial genomes (greater than 85% mutant mtDNA) and with a partial cytochrome c oxidase deficiency. By quantitative in situ hybridization, the steady-state ratios of mRNAs:rRNAs were found to be similar to controls in six of eight patients studied. In two other patients the relative levels of heavy-strand mRNAs were slightly increased, but a patient with myoclonic epilepsy and RRF also exhibited a similar increase. These results directly correlate the A----G transition at mtDNA position 3243 with muscle mitochondrial proliferation, partial respiratory-chain impairment, decreased mitochondrially synthesized protein content, and no specific alterations in mitochondrial ratios of mRNAs:rRNAs.

Acidosis, Lactic↗
PubMed1992

A new mtDNA mutation in the tRNA(Lys) gene associated with myoclonic epilepsy and ragged-red fibers (MERRF).

Myoclonic epilepsy with ragged-red fibers (MERRF) has been associated with an A--G transition at mtDNA nt 8344, within a conserved region of the tRNA(Lys) gene. Although the 8344 mutation is highly prevalent in patients with MERRF, it is not observed in 10%-20% of the cases, suggesting genetic heterogeneity. We have sequenced the tRNA(Lys) gene of five MERRF patients lacking the common 8344 mutation. One of these showed a novel T-->C transition at nucleotide position 8356, disrupting a highly conserved base pair in the T psi C stem. The mutant mtDNA population was essentially homoplasmic in muscle but was heteroplasmic in blood (47%). Neither 20 patients with other mitochondrial diseases nor 25 controls carried this mutation. These findings suggest that tRNA(Lys) alterations may play a specific role in the pathogenesis of MERRF syndrome.

Adult↗
PubMed1991

Mitochondrial DNA deletion in a girl with manifestations of Kearns-Sayre and Lowe syndromes: an example of phenotypic mimicry?

Lowe oculocerebrorenal syndrome is an X-linked recessive disease whose locus has been assigned to Xp25. However, several reports of affected females without obvious chromosomal abnormalities suggest genetic heterogeneity of the Lowe phenotype. Although the biochemical defect in typical Lowe syndrome is not known, there is evidence suggesting that mitochondrial metabolism may be impaired. We have studied a girl who presented with an oculocerebrorenal syndrome, but later developed symptoms and signs of mitochondrial encephalomyopathy. Molecular genetic analysis of muscle mitochondrial DNA showed the presence of a population of partially deleted mtDNAs (heteroplasmy). The deletion was 7803 bp long and encompassed several genes encoding subunits of the respiratory chain enzymes. Our results suggest that mitochondrial DNA deletions may mimic several symptoms of the Lowe phenotype and reinforce the concept that a defect of mitochondrial metabolism could be involved in the pathogenesis of the X-linked disease.

Base Sequence↗
PubMed1991

Depletion of muscle mitochondrial DNA in AIDS patients with zidovudine-induced myopathy.

Long-term zidovudine therapy in patients with human immunodeficiency virus (HIV) infection can cause a destructive mitochondrial myopathy with histological features of ragged-red fibres (RRF) and proliferation of abnormal mitochondria. In 9 zidovudine-treated patients with this myopathy we found severely reduced amounts (up to 78% reduction vs normal adult controls) of mitochondrial DNA (mtDNA) in muscle biopsy specimens by means of Southern blotting. In 2 HIV-positive patients who had not received zidovudine, muscle mtDNA content did not differ from that in the 4 controls. Depletion of mtDNA seems to be reversible, since 1 patient showed a substantial reduction in RRF and a concomitant pronounced increase in muscle mtDNA content after zidovudine therapy was discontinued. Depletion of muscle mtDNA is probably due to zidovudine-induced inhibition of mtDNA replication by DNA polymerase gamma and is not a secondary effect of HIV infection.

Autoradiography↗
PubMed1991

Autosomal recessive lethal infantile cytochrome C oxidase deficiency.

Three bedouin children with mitochondrial myopathy due to cytochrome c oxidase deficiency presented with progressive muscle weakness, failure to thrive, proximal renal tubular acidosis, and lactic acidemia leading to death. Two died by age 5 months and one by age 16 months. Cytochrome c oxidase was markedly reduced in skeletal muscle extracts of all three. Three other children of the same family with most probably the same metabolic aberration are also described. We suggest an autosomal recessive inheritance for this lethal mitochondrial myopathy.

Acidosis, Renal Tubular↗
PubMed1991

Deletion of mitochondrial DNA in patients with combined features of Kearns-Sayre and MELAS syndromes.

A 9-year-old girl and an 11-year-old boy had ptosis, progressive external ophthalmoplegia, pigmentary retinopathy, and sensorineural hearing loss. The girl had diabetes mellitus and the boy had hypoparathyroidism. Both children also developed recurrent vomiting and cerebral infarcts with lactic acidosis. Muscle biopsy specimens showed ragged-red fibers and Southern analysis demonstrated a distinct heteroplasmic deletion of muscle mitochondrial DNA in each patient but no evidence of the point mutation in the transfer RNALeu(UUR) gene recently identified in mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). These 2 children had combined features of Kearns-Sayre syndrome and MELAS, suggesting that mitochondrial DNA deletions occasionally can have pleomorphic clinical expression.

Acidosis, Lactic↗
PubMed1991

Short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency in muscle: a new cause for recurrent myoglobinuria and encephalopathy.

We report on a 16-year-old girl with short-chain L-3-hydroxyacyl-coenzyme A (CoA) dehydrogenase deficiency resulting in juvenile-onset recurrent myoglobinuria, hypoketotic hypoglycemic encephalopathy, and hypertrophic/dilatative cardiomyopathy. Urinary organic acids showed traces of 3-hydroxy-dodecanedioic acids and small amounts of suberic, sebacic, and adipic acids. There was a marked decrease in L-3-hydroxyacyl-CoA dehydrogenase activity in muscle with acetoacetyl-CoA as substrate (2.48 mumol/min/gm; normal = 6.90 +/- 1.80 mumol/min/gm of tissue; n = 11), contrasting with normal L-3-hydroxyacyl-CoA dehydrogenase activity with 3-ketooctanoyl-CoA and 3-ketopalmitoyl-CoA as substrates. Short-chain L-3-hydroxyacyl-CoA dehydrogenase activity was normal in fibroblasts, suggesting a tissue-specific defect.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1991

Localization of mitochondrial DNA in normal and pathological muscle using immunological probes: a new approach to the study of mitochondrial myopathies.

We have studied the usefulness of anti-DNA antibodies to detect ragged-red fibers (RRF) in muscle biopsies from patients with mitochondrial myopathies. We have found that these antibodies are excellent probes for the localization of mitochondrial DNA (mtDNA) in RRF, and for the diagnosis of depletion of mtDNA in a newly described group of fatal myopathies of infancy.

Antibodies↗
PubMed1991

An adult-onset myopathy characterized by a double ring appearance of muscle fibers.

We report a 33-yr-old man with an unusual neuromuscular disorder characterized by progressive generalized weakness of 3 yr duration whose muscle biopsy showed a double ring appearance in most muscle fibers. This double ring appearance was due to a peripheral outer sarcoplasmic mass and an inner ring of annular myofibrils surrounding a core of normal longitudinally oriented myofibrils. Nerve conduction studies were normal. Electromyography showed fibrillations, positive waves, and increased brief duration, low amplitude, polyphasic potentials.

Adult↗
PubMed1991

Replication-competent human mitochondrial DNA lacking the heavy-strand promoter region.

We identified two patients with progressive external ophthalmoplegia, a mitochondrial disease, who harbored a population of partially deleted mitochondrial DNA (mtDNA) with unusual properties. These molecules were deleted from mtDNA positions 548 to 4,442 and encompassed not only rRNA sequences but the heavy-strand promoter region as well. A 13-bp direct repeat was found flanking the breakpoint precisely, with the repeat at positions 535 to 547 located within the binding site for mitochondrial transcription factor 1 (mtTF1). This is the second mtDNA deletion involving a 13-bp direct repeat reported but is at least 10 times less frequent in the patient population than the former one. In situ hybridization studies showed that transcripts under the control of the light-strand promoter were abundant in muscle fibers with abnormal proliferation of mitochondria, while transcripts directed by the heavy-strand promoter, whether of genes residing inside or outside the deleted region, were not. The efficient transcription from the light-strand promoter implies that the major heavy-and light-strand promoters, although physically close, are functionally independent, confirming previous in vitro studies.

Base Sequence↗
PubMed1991

Adult Reye's syndrome: a review with new evidence for a generalized defect in intramitochondrial enzyme processing.

A 42-year-old woman developed a flu-like illness and died 8 days later with Reye's syndrome (RS). There are 26 other cases of adult-onset RS reported. Biochemical, immunologic, and molecular studies of liver, brain, and skeletal muscle revealed a non-uniform decrease in several mitochondrial residual enzyme activities in liver and brain. Pyruvate carboxylase activity was negligible. Cross-reacting material was present in normal abundance in isolated liver mitochondria for several enzymes that had reduced catalytic activity including pyruvate carboxylase. Subunit II (encoded by mitochondrial DNA) and subunit IV (encoded by nuclear DNA) of cytochrome c oxidase also were present in normal abundance with normal electrophoretic mobility. These observations, combined with pertinent findings of other investigators, allow us to speculate that the intramitochondrial matrix chemical environment is disturbed by preceding pathophysiologic events resulting in a lowered ATP/ADP ratio. The lowered intramitochondrial energetic state interferes with the refolding and assembly of imported mitochondrial proteins, causing a loss of the catalytic efficiency of these enzymes. This explains the selective vulnerability of mitochondria in RS and the non-uniform, disproportionate loss of enzyme activity.

Adult↗
PubMed1991

Differential diagnosis of fatal and benign cytochrome c oxidase-deficient myopathies of infancy: an immunohistochemical approach.

To differentiate the 2 major myopathies of infancy due to cytochrome c oxidase (COX) deficiency, we studied muscle biopsies from 4 patients with fatal myopathy and 4 with benign myopathy using biochemical, histochemical, and immunohistochemical techniques. Immunohistochemistry with antibodies directed against individual subunits of COX differentiated the 2 phenotypes: the fatal infantile myopathy was characterized by absence of the nuclear DNA (nDNA)-encoded subunit VIIa,b of COX, while in the benign myopathy both VIIa,b and the mitochondrial DNA (mtDNA)-encoded subunit II were absent. Early differential diagnosis between fatal and benign COX-deficient myopathies is of critical importance for prognosis and management of these infants, because the benign form is initially life-threatening but ultimately reversible.

Biopsy↗
PubMed1991

Biochemical and molecular analysis of cytochrome c oxidase deficiency in Leigh's syndrome.

We studied three patients with Leigh's syndrome (LS) and cytochrome c oxidase (COX) deficiency. Biochemical studies in brain, muscle, heart, liver, kidney, and fibroblasts disclosed a generalized COX deficiency. Kinetic studies of COX activity in brain mitochondria showed a low Vmax and a normal Km for reduced cytochrome c. Immunologic studies showed decrease of all COX subunits studied, without a specific defect of any one of them. Southern blot analysis excluded large deletions of mitochondrial DNA (mtDNA) but revealed a generalized increase in mtDNA quantity. Although Northern blot analysis showed no alteration in the 12 COX subunit mRNAs studied, two of three patients showed a decreased steady state rate of COX transcription in brain. COX deficiency in LS thus appears to be related to a decreased amount of otherwise normal COX holoenzyme.

Biochemistry↗
PubMed1991

mtDNA depletion with variable tissue expression: a novel genetic abnormality in mitochondrial diseases.

We studied two related infants with a fatal mitochondrial disease, affecting muscle in one and liver in the other. Quantitative analysis revealed a severe depletion of mtDNA in affected tissues. This genetic abnormality was also observed in muscle of an unrelated infant with myopathy and in muscle and kidney of a fourth child with myopathy and nephropathy. Biochemistry, immunohistochemistry, and in situ hybridization showed that the depletion of mtDNA in muscle fibers was correlated with a respiratory chain defect and with lack of mitochondrially translated proteins. Although the differential tissue involvement in these infants suggests mtDNA heteroplasmy, sequence analysis of mtDNA replication origins did not reveal any abnormality that could account for the low copy number.

Blotting, Southern↗