Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0162671 (MELAS)
 587 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) is one of the clinically-defined mitochondrial diseases, characterized by early onset and stroke-like symptoms. A point mutation at nucleotide pair 3243 within the tRNA-Leu (UUR) gene is found in 80% of MELAS patients and another mutation at nucleotide pair 3271 in 10%. In vitro and in vivo expression studies on 3243 mutant genome show that it affects both the transfer RNA and transcription termination functionally. By virtue of further analyses on relationship between the mutations and phenotypes, a new approach to deal with the disease could be obtainable.
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PMID:[MELAS (mitochondrial myopathy, encephalopathy lactic acidosis, and stroke-like episodes): clinical features and mitochondrial DNA mutations]. 841 15

Two MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) patients with diabetes mellitus (DM), and their family members are described clinically and genetically. The probands have the following features in common; normal early development, short stature, deterioration of intellectual ability, convulsions, cardiac conduction defect, sensorineural hearing loss, cortical blindness, and hemiparesis. Biochemical tests showed high levels of lactate and pyruvate in the blood and cerebrospinal fluid. Muscle biopsy showed ragged-red fibers. Molecular genetic analysis of both patients revealed that they had an A-to-G substitution at nucleotide position 3243 of the mitochondrial DNA in a heteroplasmic fashion. From these clinical and molecular genetic data they were diagnosed as having MELAS. In addition, fasting blood glucose levels were also high and they were diagnosed as having insulin-dependent DM. Some of the maternal family members in both cases also had insulin-dependent DM and several clinical symptoms of MELAS. DM and clinical features of MELAS were transmitted exclusively in the maternal line. In these cases, DM and MELAS might be a clinical manifestation of the same metabolic defect.
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PMID:Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) and diabetes mellitus: molecular genetic analysis and family study. 844 2

We report an autopsy case of a 19 year-old man with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) a subgroup of mitochondrial encephalomyopathy presenting cardiomyopathy. He had repeatedly suffered from transient unconsciousness, hemiplegia, hemianopsia and convulsion attacks since the age of 9, and he died of severe congestive heart failure. In laboratory findings, blood lactate and pyruvate were markedly increased. Skeletal muscle biopsy demonstrated numerously scattered ragged-red fibers with modified Gomori's trichrome staining. Enzymatic activities of the mitochondrial respiratory chain showed a marked decrease of NADH cytochrome c reductase (complex I). In postmortem examination, the heart was 310g in weight and had right ventricular dilatation. Microscopically, degenerated and scattered myocardial cells (ragged-red fibers), interstitial edema and microvascular hyperplasia were demonstrated in the myocardium. Under the electron microscope, abnormal mitochondria proliferated and myofibrils were unusually sparse. Immunohistochemical studies with specific antibodies against the mitochondrial electron transfer enzyme subunits revealed a reduction of immunoreactive materials for complex I in the myocardium. These results suggested the relationship of myocardial disorders and decreased activity of complex I in electron transfer enzymes in this patient.
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PMID:[A study of myocardial disorders in an autopsy case of mitochondrial encephalomyopathy]. 846 36

Two previously healthy women are described who in their late thirties suffered transient strokelike episodes, consisting of initial headache and vomiting, with various subsequent neurological signs that were only partially reversible. Investigations revealed elevated serum creatine kinase, lactic acidosis, hypertriglyceridaemia, and ragged red fibres in the muscle biopsy specimens. In both patients in vitro studies were performed on intact muscle mitochondria and muscle homogenate. Only in one was a mitochondrial defect found, located at the level of coenzyme Q. We conclude that these patients suffered from adult-onset mitochondrial encephalopathy, lactic acidosis and strokelike episodes (MELAS syndrome). Although the syndrome is often associated with long-standing neurological multisystem disease from childhood onwards, it should also be suspected in adults with strokelike signs of otherwise unexplained origin.
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PMID:Mitochondrial encephalomyopathy, lactic acidosis and stroke in adults: two cases. 849 10

Mitochondrial DNA (mtDNA) mutation associated with sensorineural hearing loss (SNHL) has previously been described in MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) and in aminoglycoside-induced deafness. The authors of this study report three cases of SNHL associated with mtDNA mutation (3243A-->G). They examined the clinical features of this type of SNHL by audiologic studies and examined the mtDNA mutation by the polymerase chain reaction technique. In the three cases described, the SNHL had an adult onset and was bilateral and symmetrical. All patients had adult-onset diabetes mellitus. Audiologic studies revealed that the SNHL in all patients derived from the cochlea rather than from retrocochlear sites. It is presumed that mtDNA mutation results in mitochondrial dysfunction in cochlear tissues (i.e., hair cells and stria vascularis) and in neurons of the auditory pathway. Genetic analysis of mtDNA offers new insight into the diagnosis and treatment of SNHL.
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PMID:Bilateral sensorineural hearing loss associated with the point mutation in mitochondrial genome. 854 26

N-Acetylaspartate (NAA), which constitutes the major proportion of the dominant resonance in proton MR spectra of brain, is localized in mature brain exclusively in neurons and neuronal processes. A decrease in NAA has been observed in many cerebral pathologies and has usually been interpreted as an index of irreversible neuronal loss. The authors report a follow-up study of six patients with acute brain damage (four from demyelinating lesion and two from mitochondrial encephalopathy with lactic acidosis and stroke-like episodes [MELAS]). All patients underwent serial MR spectroscopy examinations. The four patients with acute demyelinating lesions initially showed decreases in NAA in the centers of the lesions that ranged between 34-72% of values from homologous brain volumes in the other hemisphere. All four patients subsequently showed substantial recovery of NAA as their clinical status improved. The two patients with MELAS syndrome had large decreases of NAA signal (50% and 20% of normal values, respectively) from their occipital lobe lesions during the acute stroke-like episodes. After the acute phase of the illness a progressive increase of NAA in the same volumes was seen in both patients (to 76% and 60% of normal values, respectively). These results demonstrate that significant recovery of NAA can occur after acute brain damage. The potential contribution of reversible neuronal dysfunction (as well as neuronal loss) must be considered in the interpretation of decreases in the NAA resonance associated with acute brain pathology.
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PMID:Reversible decreases in N-acetylaspartate after acute brain injury. 854 93

MELAS, a syndrome characterized by Myopathy, Encephalopathy, Lactic Acidosis and Stroke-like episodes, is one of a group of diseases known as mitochondrial encephalopathies. These genetically-transmitted diseases result in metabolic abnormalities associated with mitochondrial dysfunction, which contribute to neuronal destruction. Clinical manifestations include dementia, seizures, muscle weakness and stroke-like episodes. Accurate diagnosis is difficult to make and effective treatment is nonexistent at this time. The focus of care is supportive and the nurse's role centers on identification of deficits and maintenance of existing function.
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PMID:MELAS: a mitochondrial encephalomyopathy syndrome. 856 43

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


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