Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.5.3 (complex I)
 8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mitochondrial disorder is an inborn error of metabolism affecting the cellular respiratory chain. Defective energy production leads to a wide variety of clinical manifestations (ataxia, epilepsy, dementia, myopathy, polyneuropathy, retinal pigment anomalies, and cardiomyopathy with conduction anomalies). Hearing loss is a regular feature and is often the first clinical symptom. Audiologic data from 26 members of a family in three generations is presented. One of these patients was examined for the biochemical error. Respiratory study of muscle biopsy revealed a mild defect in the NADH-ubiquinone oxidoreductase step of the oxidative phosphorylation (complex I). The content of cytochrome aa3 (complex IV) was also reduced. Adult onset sensorineural hearing loss starting in the high frequency region progresses with a fairly constant speed in this family. A cochlear type of hearing loss is found in the less pronounced cases. Advanced cases present features of retrocochlear affection with decreasing speech recognition, elevated acoustic reflex thresholds, and increased ABR latency with derangement of potentials. Caloric sensitivity was unaffected.
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PMID:Audiologic findings in a family with mitochondrial disorder. 180 40

Leigh's disease is one of the mitochondrial encephalomyopathies. This article presents a 7-month-old baby boy who had been well-being since birth until 6 months of age when episodic downward gaze of both eyes with limitation of horizontal eye movement were noted. This episode of cranial nerve palsies lasted about 4-5 days and subsided spontaneously. The second attack was noted one month later, to be associated with hypotonia and truncal ataxia. Episodic hyperventilation with resultant gasping and myoclonus was noted at the third attack but spontaneous respiration resumed soon with persistent ophthalmoplegia and truncal ataxia. Lumbar puncture, brain MRI, amino acid assay and cardiac echo all showed negative finding. The oral glucose lactate stimulation test revealed an elevation of lactic acid, brain stem evoked potential indicated bilateral obscure 4th and 5th waves, and muscle biopsy showed ragged red fibres with aggregation of structurally abnormal mitochondria noted under electron microscope. Coenzyme Q, thiamine and carnitine had been given before biochemical study; however, the neurological symptoms did not show any improvement. Biochemical study finally revealed normal respiratory chain enzymes including NADH-coenzyme Q reductase, succinate coenzyme Q reductase and cytochrome c oxidase while other enzymes were technically unavailable for study. Unfortunately the patient died at 18-month-old due to respiratory failure.
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PMID:Mitochondrial encephalomyopathy presenting with clinical Leigh's disease: report of a case. 184 64

A patient with chronic progressive external ophthalmoplegia (CPEO) who had abundant cytoplasmic bodies in muscle fibers and a deletion of mitochondrial DNA is reported. The patient was a 26-year-old male suffering from ophthalmoplegia from age 21. He had a marfanoid skeletal abnormality and perceptive hearing loss, but had neither retinopathy, ataxia, nor dementia. In the mitochondria isolated from the biopsied skeletal muscle, NADH-ubiquinone oxidoreductase activity was slightly decreased, succinate-cytochrome c reductase activity was slightly increased, and cytochrome c oxidase activity remained normal. Southern blot analysis of the muscle DNA identified heteroplasmy composed of a normal-sized mitochondrial DNA and a mutant mitochondrial DNA with a 4.2-kilobase deletion. The PCR plus S1 analysis showed that the deletion extended from nucleotide position 7860 +/- 60 to 12,090 +/- 70. The histological studies of the biopsied muscle revealed ragged-red fibers and cytochrome c oxidase-negative fibers in 15.7% and 18.6% of the muscle fibers, respectively. Other conspicuous histological change was abundant cytoplasmic bodies surrounded by clusters of abnormal mitochondria. The cytoplasmic bodies were found preferentially in type 1 fibers, and exclusively in cytochrome c oxidase-negative fibers and in ragged-red fibers. Focal existence of cytoplasmic bodies in muscle fibers with abnormal mitochondria suggests that segregated distribution of the abnormal mitochondria with deleted mitochondrial DNA is involved in the pathogenesis of cytoplasmic bodies.
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PMID:Cytoplasmic body and mitochondrial DNA deletion. 196 59

Identical twins developed myoclonic epilepsy in their teens. One twin remained mildly affected but the other went on to develop sensorineural deafness and ataxia with lactic acidosis and ragged red fibres leading to a diagnosis of mitochondrial encephalopathy. Multiple stroke-like episodes with hemiparesis followed, indicating progression from a MERRF to a MELAS phenotype. Biochemical studies revealed a severe deficiency of mitochondrial NADH-ubiquinone reductase and a moderate deficiency of cytochrome aa3. Western immunoblotting experiments using polyclonal antibodies raised against human placental cytochrome oxidase identified a similar profile of bands to those seen in controls, supporting the view that cytochrome aa3 deficiency in this case may be a secondary consequence of a failure of assembly related to a severe proximal respiratory chain defect.
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PMID:Progression from MERRF to MELAS phenotype in a patient with combined respiratory complex I and IV deficiencies. 285 17

A patient with intention and action myoclonus, epilepsy, ataxia, and mental deterioration in association with ragged-red fibers in striated muscle is described. This patient demonstrated a unique form of erratic myoclonus with continuous EEG spike activity during eye closure. Both the myoclonus and the EEG spiking disappeared on opening the eyes. A defect in the activity of complex I in the respiratory chain was demonstrated.
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PMID:The syndrome of myoclonic epilepsy with ragged-red fibers. Report of a case and review of the literature. 312 68

Two patients with mitochondrial encephalomyopathy (MEP) serve to emphasize the variability of this group of diseases. Cerebral insults, mitochondrial cardiopathy, relapsing ileus, cerebral angioma, ataxia, and myoclonic seizures characterized the first case of an adult man with similar diseases in his family, interpreted as transitional form between mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) and myoclonus epilepsy associated with ragged red fibers (MERRF). The second patient, a floppy infant with cardiomyopathy and myoclonism, statomotoric and mental retardation showed combined defects in mitochondrial respiratory chain at NADH-CoQ reductase and cytochrome c oxidase and a deficiency of carnitine. In both patients neuropathologically criteria of Leigh's syndrome could be demonstrated in the cerebral cortex, in case 2 also clinically. The classificatory problems of the relationships between KSS, MELAS, MERRF, Leigh's as well as Alpers' syndromes are discussed.
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PMID:Mitochondrial myopathies with necrotizing encephalopathy of the Leigh type. 322 73

The clinical features of 66 patients with histologically defined mitochondrial myopathy are described. The age of onset of symptoms ranged from birth to 68 years, but was before 20 years in 61%. Nineteen patients had similarly affected relatives. Three groups of cases could be identified clinically: a combination of progressive external ophthalmoplegia and weakness of the limbs induced or increased by exertion (55%); such limb weakness alone (18%); and those with clinical features, such as ataxia, dementia, deafness, involuntary movements and seizures, predominantly or exclusively arising from the CNS (27%). There was considerable overlap between these groups, and pigmentary retinopathy, present in 36% of patients, occurred in all three. At a mean disease duration of twenty years, 9 patients (all from Group 3) were severely disabled but 42 were still able to work. In vitro studies of mitochondrial metabolism, performed in 33 cases, most commonly showed deficiencies of the mitochondrial respiratory chain localized to complex I (18 patients) or complex III (9). No typical clinical picture emerged for any of the identifiable biochemical defects.
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PMID:The clinical features of mitochondrial myopathy. 377 73

We describe two patients with mitochondrial myopathies who presented with complex multisystem diseases predominantly affecting the central nervous system. In both cases the disease ran a fluctuating clinical course, eventually leading to profound impairment of intellectual function. In Case 1 dementia was associated with optic atrophy, absent pupillary responses, impaired eye movements and generalized dystonic rigidity without evidence of weakness or loss of muscle bulk. In Case 2 myoclonus preceded the onset of ataxia, generalized weakness and mental confusion by several years. Biochemical studies on isolated muscle mitochondria revealed defects in the mitochondrial respiratory chain which were located at NADH-CoQ reductase in Case 1, and at cytochrome b in Case 2. This study illustrates the potential value of muscle biopsy in the diagnosis of unusual and otherwise unexplained cerebral syndromes in man, even in the absence of muscle weakness.
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PMID:Mitochondrial encephalomyopathies: biochemical studies in two cases revealing defects in the respiratory chain. 710 66

We report on a new maternally-inherited syndrome characterized by a combination of sensorineural hearing loss, ataxia and myoclonus in a large kindred from Sicily. Hearing loss was the most widespread and sometimes the only symptom found in family members. Sequence analysis of the mitochondrial DNA regions encompassing the tRNA genes revealed the presence of a heteroplasmic insertion at nucleotide position 7472. The insertion adds a seventh cytosine to a six-cytosine run that is part of the mitochondrial tRNASer(UCN) gene. Conformational analysis showed that this mutation is likely to alter the structure of the T psi C loop in the tRNASer(UCN) clover leaf secondary structure. Moreover, the degree of heteroplasmy in blood and muscle was correlated with the clinical phenotype, and homoplasmic mutant hybrids showed decreased complex I activity, low oxygen consumption and high lactic acid output, indicating faulty oxidative phosphorylation. Finally, mutation was absent in 381 unrelated maternal lineages, suggesting specific segregation with the disease. We propose that the C7472 insertion-mutation is pathogenic, and etiologically related to hearing loss and other symptoms that define a novel maternally-inherited clinical entity.
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PMID:Maternally inherited hearing loss, ataxia and myoclonus associated with a novel point mutation in mitochondrial tRNASer(UCN) gene. 758 83

The point mutation at bp 8993 of human mtDNA in the ATPase 6 gene is associated with neurogenic weakness, ataxia and retinitis pigmentosa, and with subacute necrotizing encephalomyelopathy (Leigh disease) when present at high copy number. In this study we describe three new multiplex families with the ATPase 8993 mtDNA mutation and demonstrate a correlation between the percentage heteroplasmy of this mutation and the clinical phenotype. By combining this study with previous data we produce a graph of age of onset of symptoms versus percentage heteroplasmy of the mutation. Finally, we determine that ATP synthesis with NAD-linked substrates in cultured lymphoblast mitochondria from three patients with Leigh disease who had a high percentage heteroplasmy was on average 66% of the rate seen in control lymphoblast mitochondria. Similar rates are observed in lymphoblast mitochondria isolated from patients with Leigh disease due to complex I deficiency. This percentage appears to be independent of the rate of electron transport in mitochondria from patient cell lines with the mtDNA 8993 mutation.
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PMID:The 8993 mtDNA mutation: heteroplasmy and clinical presentation in three families. 804 52


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