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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A 9-year-old female MELAS patient with myoclonus is reported, with emphasis on the results of electrophysiological studies of the myoclonus. At age 5 years she experienced a stroke-like episode, and a diagnosis of MELAS was made at age 6 years on the basis of muscle biopsy findings. At age 9 years spontaneous and segmental myoclonus, predominantly affecting the upper extremities, developed because of complications. Electrophysiological examination, including of somatosensory-evoked potentials (SEPs) and averaged EMG for long loop reflexes, revealed so-called "giant SEP" and enhanced long loop reflexes reflecting cortical hyperexicitability. Jerk-locked averaging yielded no myoclonus related spikes, but myoclonus-contingent 4-5 Hz theta bursts appeared. These findings suggest that some types of MELAS may be associated with cortical types of myoclonus.
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PMID:Cortical reflex myoclonus associated with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS): a case report. 144 10

The segregation of mutant and wild-type mtDNA was investigated in transformants constructed by transferring human mitochondria from individuals belonging to four pedigrees with the MELAS encephalomyopathy-associated mtDNA mutation (MELAS is mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) into human mtDNA-less (rho 0) cells. Five of 13 clonal cell lines containing mixtures of wild-type and mutant mtDNAs were found to undergo a rapid shift of their genotype toward the pure mutant type. The other 8 cell lines, which included 6 exhibiting nearly homoplasmic mutant mtDNA, on the contrary, maintained a stable genotype. Subcloning experiments and growth rate measurements clearly indicated that an intracellular replicative advantage of mutant mtDNA was mainly responsible for the dramatic shift toward the mutant genotype observed in the unstable cell lines.
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PMID:Marked replicative advantage of human mtDNA carrying a point mutation that causes the MELAS encephalomyopathy. 145 94

A T-to-C transition mutation at nucleotide position 3,250 in the mitochondrial tRNA(Leu)(UUR) gene was present in a family with mitochondrial myopathy. Two of three muscle biopsies examined had complex I (NADH-ubiquinone oxidoreductase) deficiency. Heteroplasmy of wild and mutant mitochondrial DNA was detected by Nae I digestion of the polymerase chain reaction products with a modified primer. This was found in blood or muscle samples or both from all seven members examined. Similar to the 3,243 mutation in most patients with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes), the new mutation site was located in the dihydrouridine loop and embedded in the binding region of mitochondrial transcription termination factor. Elucidation of the effects of this mutation may help clarify the role of mitochondrial tRNAs and transcription termination.
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PMID:A novel point mutation in the mitochondrial tRNA(Leu)(UUR) gene in a family with mitochondrial myopathy. 151 79

The pathogenetic mechanism of the mitochondrial tRNA(LeuUUR) gene mutation responsible for the MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) syndrome was investigated in transformants obtained by transfer of mitochondria from three genetically unrelated MELAS patients into human mitochondrial DNA (mtDNA)-less (rho 0) cells. Marked defects in mitochondrial protein synthesis and respiratory activity were observed in transformants containing virtually pure mutant mtDNA, as compared to the parent of the rho 0 cells (the 143B cell line) or to transformants containing exclusively wild-type mtDNA, derived from one of the patients or a maternally related asymptomatic individual. A striking protective effect against the mutation was exerted in the transformants by levels of residual wild-type mtDNA above 6%. The MELAS mutation occurs within the mtDNA binding site for a protein factor (mTERF) that promotes termination of transcription at the 16S rRNA/tRNA(LeuUUR) gene boundary. A marked decrease in affinity of purified mTERF for the mutant target sequence was observed in in vitro assays. By contrast, RNA transfer hybridization experiments failed to show any significant change in the steady-state amounts of the two rRNA species, encoded upstream of the termination site, and of the mRNAs encoded downstream, in the transformants carrying the MELAS mutation.
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PMID:MELAS mutation in mtDNA binding site for transcription termination factor causes defects in protein synthesis and in respiration but no change in levels of upstream and downstream mature transcripts. 158 55

Point mutation of mitochondrial DNA has been described in the blood from a MELAS patient. The 39-year-old patient developed progressive dementia, stroke-like episodes, heart conduction defect (Lown-Ganong-Levin syndrome) and cortical blindness. CT scan revealed brain atrophy and low density areas in the bilateral occipital lobes. Laboratory tests showed hyperglycemia and lactic acidosis. Muscle biopsy showed ragged red fibers on Gomori trichrome staining. He was clinically diagnosed as having MELAS and insulin-dependent diabetes mellitus. Onset of diabetes mellitus and MELAS was almost same. Family history showed his mother's brother and sisters had also insulin-dependent diabetes mellitus. We amplified the leucine (UUR) tRNA gene from the patient's blood with polymerase chain reaction (PCR) and analysed it by restriction enzyme analysis and sequencing. Genetic analysis showed A-to-G substitution at the nucleotide position 3243 in the leucine (UUR) tRNA gene. This substitution made a new restriction site Apa I. Mutant DNA coexisted with wild type DNA (heteroplasmy). It is shown that in some types of mitochondrial encephalomyopathies, especially patients of Kearns-Sayre syndrome (KSS), diabetes mellitus is often complicated. And in KSS patients insulin receptor in normal, but insulin secretion from beta cells of pancreas is decreased. In MELAS patients, however, has diabetes mellitus been reported to be rarely complicated and relationship between MELAS and diabetes mellitus is not done. As far as we know, two cases, including ours, with genetically diagnosed MELAS have been reported to have diabetes mellitus.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[MELAS associated with diabetes mellitus and point mutation in mitochondrial DNA]. 159 Nov 3

Defects in mitochondrial DNA (mtDNA) are associated with several different human diseases, including the mitochondrial encephalomyopathies. The mutations include deletions but also duplications and point mutations. Individuals with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) carry a common A-to-G substitution in a highly conserved portion of the gene for transfer RNA(Leu(UUR)). Although the MELAS mutation may be comparable to the defect in the tRNA(Lys) gene associated with MERRF (myoclonus epilepsy associated with ragged-red fibres), it is also embedded in the middle of a tridecamer sequence necessary for the formation of the 3' ends of 16S ribosomal RNA in vitro. We found that the MELAS mutation results in severe impairment of 16S rRNA transcription termination, which correlates with a reduced affinity of the partially purified termination protein for the MELAS template. This suggests that the molecular defect in MELAS is the inability to produce the correct type and quantity of rRNA relative to other mitochondrial gene products.
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PMID:Impairment of mitochondrial transcription termination by a point mutation associated with the MELAS subgroup of mitochondrial encephalomyopathies. 175 69

A female patient who had clinical characteristics of MELAS but with no apparent muscle symptoms was reported. She was in good health until 12 years and 5 months of age when she began to have afebrile generalized tonic-clonic convulsions. Thereafter, she had repeated stroke-like episodes, including headache, vomiting, convulsions, hemiparesis and left ehemianopsia. She had neither muscle weakness, fatigability nor atrophy. Laboratory examinations disclosed elevated lactate and pyruvate levels in the serum and cerebrospinal fluids, transient focal low density areas on brain CT and right sensorineural deafness by audiometry. No ragged-red fibers (RRF) were found in the first biopsy at 13 years and 6 months of age, and two RRF-like fibers containing red granular materials in the subsarcolemnal regions in the second at 15 years and 3 months of age. A biochemical assay on the two biopsied muscles demonstrated normal enzyme activities in the mitochondrial electron transport system. She was diagnosed as having MELAS because of remarkable mitochondrial abnormalities in smooth muscle cells in the intramuscular arterioles which were clearly demonstrated by succinic dehydrogenase (SDH) stain and on electron microscopy. It was suggested that the stroke-like episodes in this patient were induced by a preferential damage to the mitochondria in the blood vessel walls. Thus, we conclude that a simple method of identifying the strongly SDH-reactive blood vessels (SSV) in frozen sections is critical in supporting or making diagnosis of MELAS.
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PMID:[MELAS without ragged-red fibers: a case report]. 176 Feb 9

A case of mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes, in which a pituitary growth hormone (GH) secretion deficiency of hypothalamic origin was revealed through neuro-endocrinological examinations, was described. The case was a 10-year-old girl, who had been suffering from generalized tonic seizures since age 5, four episodes of alternating hemiplegia since age 6, stunted growth since age 7, and simple partial motor seizures as well as gelastic seizures since age 8. Marked elevation of lactate and pyruvate in both serum and CSF, abundant ragged red fibers in biopsied muscle, and low density areas in the left occipital lobe and bilateral globus pallidus in addition to diffuse brain atrophy on CT scan and MRI of the head were demonstrated, although the activities of muscle enzymes complex I-IV were within normal ranges. Pituitary GH secretion was deficient under the loadings with insulin, L-DOPA, sleep, and a single growth hormone releasing factor (GRF) administration, but normal GH response was registered under the repetitive stimulation with GRF. Activities of other hormonal axes were normal. It is likely that short stature commonly observed in MELAS patients is due to hypothalamic dysfunction, which might be brought out by chronic ischemia and energy deficiency of the diencephalon based upon mitochondrial abnormality of that region. It is likely that gelastic seizure in this case is due to hypothalamic dysfunction.
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PMID:[Hypothalamic GH Deficiency and gelastic seizures in a 10-year-old girl with MELAS]. 187 57

We present two unrelated MELAS patients, and compare them with 24 patients derived from the literature. In most patients the stroke-like features of the MELAS syndrome occur late in the course of the disease. The diagnosis is based on characteristic clinical symptoms, presence of lactic acidemia, mitochondriopathy in muscle, and low density lesions on cerebral CT, most frequently occurring in the posterior and parieto-temporal regions. In some cases, a metabolic defect could not be demonstrated, in other cases a partial deficiency of various respiratory chain enzymes was found.
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PMID:MELAS syndrome. Report of two patients, and comparison with data of 24 patients derived from the literature. 190 52

Neuropathological studies were carried out in two patients with mitochondrial encephalomyopathies in whom the underlying lesions in muscle mitochondrial DNA (mtDNA) and respiratory enzyme complexes have been investigated. The first, a man with Kearns-Sayre syndrome, died at the age of 49 years. Autopsy showed an old parietal lobe infarct, diffuse spongiform leukoencephalopathy of cerebral and cerebellar white matter and mild spongiform change in deep grey matter and brainstem nuclei. Heteroplasmy of skeletal muscle mitochondrial DNA with a 3.5 kb mtDNA deletion in one of two mtDNA populations was found. The second case, a woman, suffering from myoclonic epilepsy, cerebellar ataxia, bilateral sensorineural deafness, several 'stroke-like' episodes died at age 52. At autopsy, an old infarct was seen in the L internal capsule. Severe loss of neurons and gliosis were found in the dentate nuclei, moderate changes in the red nuclei and inferior olivary nuclei and mild changes in the substantial nigra and locus coeruleus. In both patients, skeletal muscle biopsy showed numbers of ragged-red fibres and intramitochondrial paracrystalline inclusions at electron microscopy. A defect in the synthesis of the ND5 subunit of the respiratory complex I was suggested in the second patient in whom a diagnosis of MELAS was made.
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PMID:Mitochondrial encephalomyopathies: a correlation between neuropathological findings and defects in mitochondrial DNA. 190 31


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