Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0085584 (encephalopathy)
 18,178 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Migraine and the MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) syndrome have some clinical features in common. First, cerebral infarctions, most often in the posterior cerebral regions, which are a main symptom of MELAS, may complicate migraine. Second, migrainous headache with vomiting is also a characteristic feature of the MELAS syndrome. Less frequently, hemicranial headache is present in another mitochondrial disease, myoclonic epilepsy with ragged-red fibers (MERRF). Moreover, there is a mild bias toward maternal transmission in migraine. Apart from clinical resemblance, there is some experimental evidence for mitochondrial dysfunction in migraine. There may be depression of respiratory chain enzyme activity in muscle and platelets, and magnetic resonance spectroscopy has revealed a defective energy metabolism in brain and muscle of migraine patients. There has not been a systematic study of mitochondrial DNA in migraine, however. We therefore analyzed the mitochondrial DNA in lymphocytes of 23 migraine patients with aura. Southern blot and polymerase chain reaction analysis of mitochondrial DNA failed to detect any large-scale deletions or point mutations at base pair 3243 (MELAS) and base pair 8344 (MERRF). Our data show that deletions of mitochondrial DNA and the most frequent point mutations of MELAS and MERRF syndromes are not common in migraine with aura. In particular, these data do not support the hypothesis that some cases of migraine may be monosymptomatic forms of a MELAS syndrome. We cannot exclude, however, that migraine may be associated with different point mutations of mitochondrial DNA or with mutations of autosomally coded respiratory chain subunit genes.
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PMID:Mitochondrial DNA in migraine with aura. 864 80

In situ hybridization to mitochondrial ribosomal RNA (rRNA) has been used to study the distribution of mitochondria in paraffin-embedded autopsy brain tissue from two patients with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) and other organs from one of the patients. Comparison of in situ hybridization and electron microscopic findings in an antemortem biopsy specimen of pylorus from the latter patient showed a close correspondence between the distribution of hybridization signal on light microscopy and of mitochondria in ultrathin sections. Strong hybridization signal was present over smooth muscle fibres of the muscularis externa, which contained abnormal accumulations of mitochondria on electron microscopy. Hybridization to sections of skeletal muscle confirmed previous reports of 'ragged-red' fibres in this disorder and of mitochondrial accumulations in the walls of intramuscular blood vessels. To try to elucidate the role of vessel wall accumulation of mitochondria in the genesis of the stroke-like lesions, the distribution of mitochondrial rRNA was assessed in sections of brain from both of the cases of MFLAS and several cases of atherothrombotic cerebrovascular disease. Blood vessels in and adjacent to the cerebral lesions of MELAS showed strong hybridization signal with the mitochondrial probes, as was also seen in infarcts of various ages in the control brains. Only weak signal was present in the walls of blood vessels distant from the lesions, in both MELAS and control brains. These findings suggest that mitochondria accumulate in vascular endothelium and tunica media as a normal response to cerebral infarction or ischaemia. The accumulation of mitochondria in the cerebral lesions of MELAS may, at least in part, be a reaction to the destructive effects of the underlying metabolic dysfunction.
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PMID:Assessment of the distribution of mitochondrial ribosomal RNA in melas and in thrombotic cerebral infarcts by in situ hybridization. 868 87

Molecular diagnosis for mitochondrial diseases offers a powerful means to clarify that mitochondrial DNA (mtDNA) defects have different characteristics from those of nuclear DNA. Regarding the relationship between genotype and phenotype, there is a dual heterogeneity. It means that one mutation, for example, a 3243 mutation, has several clinical phenotypes, including MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes), myopathy only, diabetes and/or deafness and even CPEO (chronic progressive external ophthalmoplegia). Conversely, one phenotype, for instance, MELAS has several genetypes; 3243, 3271, and 3291 mutations. The second unique event in mitochondrial DNA mutation is heterogenous distribution of mutant mtDNA in a mitochondrion or a cell that is called heteroplasmy. The extend of heteroplasmy seems different from tissue to tissue providing clues to explain the variability of tissue impairment and heterogenous clinical symptoms. The above evidence suggests that we should take care in selecting tissues to be tested. The third problem remained is on maternal inheritance. It makes the genetic counselling on mitochondrial diseases at clinics difficult and laborious. In conclusion, mtDNA analysis must be used as a last resort to get final diagnosis.
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PMID:[Mitochondrial encephalomyopathies: 3243 mutation as a central matter]. 875 18

A number of human diseases are caused by inherited mitochondrial DNA mutations. Two of these diseases, MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) and MERRF (myoclonic epilepsy and ragged-red fibres), are commonly caused by point mutations to tRNA genes encoded by mitochondrial DNA. Here we report on how these mutations affect mitochondrial function in primary fibroblast cultures established from a MELAS patient containing an A to G mutation at nucleotide 3243 in the tRNA(Leu(UUR) gene and a MERRF patient containing an A to G mutation at nucleotide 8344 in the tRNA(Lys) gene. Both mitochondrial membrane potential and respiration rate were significantly decreased in digitonin-permeabilized MELAS and MERRF fibroblasts respiring on glutamate/malate. A similar decrease in mitochondrial membrane potential was found in intact MELAS and MERRF fibroblasts. The mitochondrial content of these cells, estimated by stereological analysis of electron micrographs and from measurement of mitochondrial marker enzymes, was similar in control, MELAS and MERRF cells. Therefore, in cultured fibroblasts, mutation of mitochondrial tRNA genes leads to assembly of bioenergetically incompetent mitochondria, not to an alteration in their amount. However, the cell volume occupied by secondary lysosomes and residual bodies in the MELAS and MERRF cells was greater than in control cells, suggesting increased mitochondrial degradation in these cells. In addition, fibroblasts containing mitochondrial DNA mutations were 3-4-fold larger than control fibroblasts. The implications of these findings for the pathology of mitochondrial diseases are discussed.
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PMID:Altered mitochondrial function in fibroblasts containing MELAS or MERRF mitochondrial DNA mutations. 880 26

The expression of several mitochondrial and nuclear genes involved in ATP production was examined in cells cultured from muscle biopsies of patients harboring mitochondrial pathologies. The transcript patterns in muscle cells from the patients affected by carnitine palmitoyl transferase II or 2-ketoglutarate dehydrogenase deficiencies were almost similar to control patterns. In the opposite, patterns were strikingly abnormal in all the other cell cultures from patients with defects in enzymatic complexes involved in oxidative phosphorylation: mitochondrial complex II and III deficiencies, two MELAS syndromes (myopathy, encephalopathy, lactic acidosis and stroke like episodes), a case of Kearns-Sayre syndrome and a case of chronic progressive external ophthalmoplegia. In cultured muscle cells from patients with mtDNA mutations, the percentage of mutated mtDNA was low as compared with those determined in the corresponding skeletal muscle biopsy. Moreover, the complex II defect resulting of a nuclear mutation was not expressed in the cell cultures. Thus, an undetermined transcriptional event, transmitted from muscle biopsies to cultured muscle cells, should be involved to account for such abnormal transcript patterns.
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PMID:Expression of oxidative phosphorylation genes in muscle cell cultures from patients with mitochondrial myopathies. 906 96

A mitochondrial tRNALeu(UUR) mutation at nucleotide 3,243 is known to be found in most patients with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes) and has also been identified in several families with maternally inherited diabetes mellitus and hearing loss. We report here audiologic features in patients with hearing loss associated with the mutation. Four patients without and five with MELAS were studied. Most of the patients had bilateral progressive sensorineural hearing loss. The most common shape of the audiogram was sloping, while cases in the advanced stages had flat audiograms. Speech discrimination scores were generally poor and did not parallel the degree of hearing loss. The present study suggests that the lesion for hearing loss could include both cochlear and retrocochlear involvement, but does not demonstrate a significant difference in the audiologic findings between patients with and without MELAS.
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PMID:Audiologic findings in patients with a point mutation at nucleotide 3,243 of mitochondrial DNA. 910 27

We report a new mutation, an A-->T transition at nt 3243 in the mitochondrial tRNA(leu)(UUR) gene, in a 9-year-old girl who presented with muscle weakness of 3 years duration complicated by rapidly progressive encephalopathy. In muscle, the activity of the mitochondrial respiratory chain complexes I, III, and IV was markedly reduced. The mutation, involving a highly conserved base pair in the dihydrouridine loop, was heteroplasmic in muscle (81.4%), skin (69.3%), and blood (13.8%) and was not present in blood of 50 healthy individuals. The mitochondrial 3243 base is a "hot spot" for mutations; an A-->G transition at this position is found in a high proportion in most MELAS patients. Since the A-->T transition creates a new recognition site for the restriction enzyme TspRI, both ApaI and TspRI should be used to exclude a mutation at nt 3243.
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PMID:Mitochondrial encephalomyopathy associated with a novel mutation in the mitochondrial tRNA(leu)(UUR) gene (A3243T). 916 4

Eight carriers of the A3243G mutation of mitochondrial DNA without stroke-like episodes were monitored for up to 7 years in clinical and metabolic studies, by magnetic resonance imaging (MRI) and positron emission tomography (PET). None developed mitochondrial encephalopathy (MELAS), but 2 developed diabetes mellitus, 1 terminal kidney failure and 2 cardiomyopathy. One patient improved markedly under ubiquinone. Electroencephalography showed progressive slowing in 2 cases, but electrophysiological tests and MRI were otherwise noncontributary. PET showed widespread cortical and basal ganglion metabolic deficits in 6 cases. We conclude that internal medical complications are more common than MELAS in adult carriers of the mutation. PET findings, firstly reported in such patients, suggest that chronic subclinical encephalopathy is very frequent, and PET may play a role in monitoring in the future.
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PMID:Follow-up in carriers of the 'MELAS' mutation without strokes. 947 18

We examined brain energy metabolism by phosphorus-31 magnetic resonance spectroscopy (31P-MRS) in the occipital cortex in a mother and a daughter with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) during photic stimulation. The peak area ratio of phosphocreatine markedly decreased during photic stimulation, and subsequently increased after the stimulation. This method, photic stimulation-31P-MRS, may be useful in assessing brain energy metabolism in neurological diseases.
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PMID:Photic stimulation-induced alteration of brain energy metabolism measured by 31P-MR spectroscopy in patients with MELAS. 956 64

We analyzed 29 patients with progressive external ophthalmoparesis (PEO) either alone or as part of a multisystem disorder. Ragged-red fibers were very abundant (10-20%) in 15 patients, and many of them were also cytochrome c oxidase-negative. Biochemical analysis of the respiratory chain showed partial defects of single or multiple complexes in 18 patients (64%). Eleven PEO patients (38%) harbored single large-scale mtDNA deletions in muscle, which averaged 5.4 kb in size and 47% in relative abundance. One PEO patient harbored the A3243G mutation (MELAS mutation) in muscle (63%). Our findings, the first reported in Portuguese patients, confirm that single large-scale mtDNA deletions are a significant cause of PEO. Although ophthalmoparesis was the main clinical feature in the majority of patients, the clinical spectrum is broad, ranging from severe encephalopathy of childhood to a milder, though disabling, muscle weakness in adults.
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PMID:Mitochondrial DNA analysis in ocular myopathy. Observations in 29 Portuguese patients. 960 91


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