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PubMed1992

[Clinical application of molecular diagnosis for mitochondrial encephalomyopathies].

Among various mitochondrial encephalomyopathies, there are three distinct clinical entities, including chronic progressive external ophthalmoplegia (CPEO), myoclonus epilepsy associated with ragged-red fibers (MERRF), and mitochondrial myopathy, encephalopathy, lactic acidosis and strokelike episodes (MELAS). They are now clearly demonstrated to have the respective specific mitochondrial (mt) DNA mutations, which facilitate us to analyse mtDNA for practical diagnosis. With molecular analysis on 40 CPEO, 6 MERRF and 40 MELAS patients, most patients in the individual disorders had the disease-specific mutations. In CPEO, 31 of 40 patients had deleted mtDNA in a heteroplasmic distribution; the mutant mtDNA were present in a large amount in the skeletal muscle and other symptomatically affected organs as observed on Southern blotting and polymerase chain reaction (PCR). In MERRF (6 out of 6 patients) and MELAS (32 out of 40 patients), mutant mtDNA was easily detectable with PCR not only in skeletal muscle but also in blood cells from several patients examined. The results lead us to conclude that molecular analysis helps to obtain definite diagnosis of the diseases without loss of time.

Base Sequence↗
PubMed1992

[A case of chronic progressive external ophthalmoplegia associated with familial hypercholesterolemia].

A 52-year-old woman with chronic progressive external ophthalmoplegia (CPEO) with familial hypercholesterolemia (FH) was reported. Her mother died from heart disease, and her elder sister has hypercholesterolemia with swelling of Achilles tendons. She had slowly progressive external ophthalmoplegia, bilateral ptosis, swelling of Achilles tendons since twenties. At 40 years of age, she was pointed out hypercholesterolemia. Physical examination was within normal limits except for bilateral swelling of Achilles tendons. Neurological findings showed bilateral ptosis, disturbance of eye movements, mild proximal muscle weakness and dysesthesia in bilateral hands. Routine laboratory findings were within normal limits except for high serum cholesterol level (512 mg/dl). In the biopsied muscle, there was mild variation in fiber size with several ragged-red fibers and focal cytochrome c oxidase defective fibers. Biochemical analysis of the biopsied muscle revealed normal values in the mitochondrial fraction. Southern blot analysis of the mitochondrial DNA (mtDNA) of the muscle disclosed mixed population of mtDNA, consisting of the normal one and partially deleted (4.9-kilobase). Southern blot analysis of the leukocytes from the patient against the cDNA of LDL receptor was normal at least using the restriction enzyme of BglII, XbaI, EcoRI, PvuII and BamHI. This case has CPEO with deleted mtDNA associated with familial hypercholesterolemia, which is caused to nuclear DNA abnormalities, and is thought to be an important case for us to study the relationship between deleted mtDNA and abnormal nuclear DNA in CPEO.

Chromosome Deletion↗
PubMed1997

Clinical, morphological, biochemical, and neuroradiological features of mitochondrial encephalomyopathies. Presentation of 19 patients.

Nineteen patients (9 females, 10 males) with mitochondrial encephalomyopathies (ME) were studied. The diagnosis was established according to clinical and histopathological criteria. Leading clinical features were chronic progressive external ophthalmoplegia (CPEO) and muscle weakness in 95% of the patients. Pigmentary retinopathy was seen in 63%, and was always associated with CPEO. Hypacusis was present in 47% and cerebellar ataxia in 63% of patients. Clinical or electrophysiological signs of involvement of the central nervous system (CNS) were found in 21% of the patients. In muscle biopsy ragged red fibers were the predominant histopathological findings (100% of the patients), while COX-negative fibers were seen in 74%, deletions of the mitochondrial DNA in 42%, and defects of the respiratory chain in 32% of the patients. Increased blood lactate levels were found in 79% of the patients. Needle electromyography revealed myopathic features in 74%, features of denervation in 16%, and was normal in the remainder. Imaging studies showed cerebral atrophy in 58%, cerebellar atrophy in 16%, and hyperintense lesions of the white matter, pyramidal tract or extrapyramidal system in 16% of the cases. It is concluded that the clinical manifestations of ME can be very variable. Diagnosis of ME should be always considered in young patients presenting with CPEO and muscle weakness. In most cases, diagnosis can be made by a few selected investigations, while detection of genetic abnormalities may lead to the diagnosis in the remaining cases.

Adult↗
PubMed1998

[Ocular mitochondrial myopathies: a spectrum of clinical presentations].

PURPOSE: To determine the spectrum of clinical presentations of patients with chronic progressive external ophthalmoplegia (CPEO). METHODS: Retrospective study of 13 cases with CPEO. RESULTS: Eight patients presented an isolated CPEO, three patients had an associated retinopathy (Kearns-Sayre syndrome), one case suffered from retinopathy, deafness, diabetes mellitus and dysphagia, and one patient had an associated dysphagia. Mitochondrial DNA deletions were found in two cases. CONCLUSIONS: Our cases illustrate the wide spectrum of mitochondrial ocular myopathies. As patients present mostly with ptosis and ophthalmoplegia, ophthalmologists should be aware of these rare conditions.

Adult↗
PubMed1993

Ophthalmologic manifestations in MELAS syndrome.

We describe a 15-year-old boy with full-blown mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) and chronic progressive external ophthalmoplegia (CPEO). He presented with visual disturbance, hearing impairment, continuous partial epilepsy on the right aspect of the face, and right hemiparesis since the age of 13. Four months later, he experienced another strokelike episode with continuous partial epilepsy on the left hand. Serial computed tomographic scans revealed bilateral parieto-occipital hypodense lesions with gyral enhancement and an additional low-density lesion in the right frontal area 4 months later, respectively. Results of laboratory examinations disclosed lactic acidosis and mitochondrial myopathy with many ragged-red fibers. To identify the defective gene in mitochondrial DNA, a simple molecular test was performed by using restriction endonuclease Apa I. A transition from A to G was found at nucleotide position 3243 of the tRNA(Leu) gene. Interestingly, the patient also had marked external ophthalmoplegia and ptosis commonly found in patients with CPEO. Therefore, we suggest that ophthalmoplegia also occurs in the MELAS syndrome.

Adolescent↗
PubMed1996

Residual muscle cytochrome c oxidase activity accounts for submaximal exercise lactate threshold in chronic progressive external ophthalmoplegia.

The data from histological, biochemical, and mitochondrial DNA (mtDNA ) studies of muscle biopsies from 10 patients affected with chronic progressive external ophthalmoplegia (CPEO) were related to dynamic and metabolic parameters of incremental submaximal exercise. Maximum power output was reduced in all patients as compared to controls. Analysis of the venous lactate curve during exercise revealed a lactate threshold at exercise levels ranging from 40 to 50% of the predicted maximal power output. An earlier significant increase in lactate could be detected by calculating the mean delta lactate. Lactate values were inversely correlated with the cytochrome c oxidase (COX) activity of isolated muscle mitochondria. No relationship was found between lactate values and the number of ragged red fibers, or cytochrome c oxidase-negative fibers of the proportion of deleted mtDNA measured in muscle biopsy specimens. The discussion underscores the value of lactate kinetics in assessing skeletal muscle function, as well as the use of muscle COX levels to predict the effectiveness of wild-type complementation of deleted skeletal muscle mtDNA in in vivo contractile performance of CPEO subjects.

Adult↗
PubMed1993

"All-or-none" cytochrome c oxidase positivity in mitochondria in chronic progressive external ophthalmoplegia: an ultrastructural--cytochemical study.

Teased single muscle fibers from 6 patients with chronic progressive external ophthalmoplegia (CPEO) showed a segmental defect in cytochrome c oxidase (COX) activity. On ultrastructural--cytochemical examination, the majority of mitochondria in COX-positive segments were COX-positive, whereas all mitochondria in COX-negative segments were COX-negative. This "all-or-none" COX positivity in mitochondria in CPEO with deleted mitochondrial DNA can be explained by the "threshold effect," which induces the tissue-specific involvement and clinical heterogeneity.

Electron Transport Complex IV↗
PubMed1995

Multiple mitochondrial DNA deletions in a patient with mitochondrial myopathy and cardiomyopathy but no ophthalmoplegia.

Deletions of muscle mitochondrial DNA are known in mitochondrial myopathy patients who have chronic progressive external ophthalmoplegia (CPEO). A 41-year-old patient with no apparent family history of this condition suffers from hypertrophic cardiomyopathy, slight muscle atrophy, and weakness of the extremities, but not from CPEO. A muscle biopsy showed the presence of ragged-red fibers, and Southern blot analysis disclosed multiple deletions of muscle mitochondrial DNA. This combination of clinical features in our patient is atypical in mitochondrial myopathy with demonstrable deleted muscle mitochondrial DNA. Pleomorphic clinical expression is suggested.

Adult↗
PubMed1992

Enzyme activity analyses along ragged-red and normal single muscle fibres.

Mitochondrial myopathies are morphologically characterized by ragged-red fibres (RRF). Serial cross-section revealed that the ragged-red appearance was only focal. This is in agreement with a partial cytochrome c oxidase (COX) deficiency in chronic progressive external ophthalmoplegia (CPEO). Since most of these patients show deletions of the mitochondrial genome single fibre analyses were performed determining COX and succinate dehydrogenase (SDH) in serial muscle sections from two patients with CPEO. High SDH activity was demonstrated in RRF; in contrast COX activity was lower in RRF in a patient, possibly representing a focal assembly of mitochondria with deletions in their genomes. The variation of enzyme activities along the muscle fibre was especially high in RRF. This study presents the first quantitative evidence that enzyme activities vary considerably along fibres in muscle from patients with a mitochondrial myopathy.

Adult↗
PubMed1995

Genotype to phenotype correlations in mitochondrial encephalomyopathies associated with the A3243G mutation of mitochondrial DNA.

We studied 22 subjects carrying the A3243G point mutation of human mitochondrial DNA (mtDNA). In 14 cases the clinical phenotype was characterized by mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), while 8 patients had chronic progressive external ophthalmoplegia (CPEO). The proportion of A3243G heteroplasmy in muscle was determined by two methods; densitometry on a diagnostic restriction-fragment length polymorphism and solid-phase mini-sequencing. We found a highly significant inverse correlation between the percentage of A3243G mutation and the specific activity of complex I, the respiratory complex with the highest number of mtDNA-encoded subunits, suggesting a direct effect of the mutation on mtDNA translation. No correlation was observed between the percentage of mutated mtDNA and the presence or absence of specific clinical features, such as stroke, ophthalmoplegia and diabetes mellitus. However, in the MELAS group the percentage of mutated mtDNA molecules was strongly correlated with the age of onset, while no such correlation was found in the CPEO group, suggesting a different time-dependent evolution of the mutation in the two groups. Finally, in contrast with other mtDNA mutations associated with ragged-red fibres (RRF), in both MELAS3243 and CPEO3243 we observed a high proportion of RRF that were positive to the histochemical reaction to cytochrome c oxidase, a morphological feature that seems to be specific for the neuromuscular phenotypes associated with mutations affecting the tRNA(Leu(UUR)) gene.

Adolescent↗
PubMed1987

Congestive heart failure due to mitochondrial cardiomyopathy in Kearns-Sayre syndrome.

Despite extensive analysis of the ultrastructural changes in skeletal muscle fibers in chronic progressive external ophthalmoplegia (CPEO), similar changes in the heart muscle fibers of patients with cardiac involvement in CPEO, called Kearns-Sayre syndrome, have not been described in detail. We report the clinical long-term course in a patient with Kearns-Sayre syndrome in whom mitochondrial cardiomyopathy was suspected in vivo and was confirmed at autopsy as the underlying cause of severe dilative cardiomyopathy. Enlarged, abnormally structured, excessively augmented mitochondria and loss of myofibrils could be shown both in skeletal and heart muscle cells.

Adult↗
PubMed2005

Sensorineural hearing loss in patients with chronic progressive external ophthalmoplegia or Kearns-Sayre syndrome.

In the present study we assessed the prevalence and nature of hearing loss in patients with chronic progressive external ophthalmoplegia (CPEO) or Kearns-Sayre syndrome (KSS) due to single large-scale mitochondrial DNA (mtDNA) deletion or mtDNA tRNA (Leu (UUR)) A3243G point mutation (A3243G PM). 14 patients with mtDNA deletion and three patients with A3243G PM underwent audiological evaluation comprising pure-tone and speech audiometry as well as transient evoked otoacoustic emissions (OAE). Audiological evaluation revealed hearing impairment in 10/17 patients. Hearing loss was mild to moderate predominantly affecting high frequencies in five patients with subjective hearing problems (three patients with mtDNA deletions, two patients with A3243G PM). Subclinical hearing deficits restricted to high frequencies were seen in further five asymptomatic patients (four patients with mtDNA deletions, one patients with A3243G PM). Audiological findings suggested a cochlear origin of hearing loss in all subjects. Our results demonstrate that CPEO or KSS patients due to mtDNA deletion or A3243G PM are at high risk of developing sensorineural hearing deficits.

Adult↗
PubMed2001

Retrospective study of a large population of patients affected with mitochondrial disorders: clinical, morphological and molecular genetic evaluation.

Mitochondrial disorders are human genetic diseases with extremely variable clinical and genetic features. To better define them, we made a genotype-phenotype correlation in a series of 207 affected patients, and we examined most of them with six laboratory examinations (serum CK and basal lactate levels, EMG, cardiac and EEG studies, neuroradiology). We found that, depending on the genetic abnormality, hyperckemia occurs most often with either chronic progressive external ophthalmoplegia (CPEO) and ptosis or with limb weakness. Myopathic EMGs are more common than limb weakness, except in patients with A8344G mutations. Peripheral neuropathy, when present, is always axonal. About 80% of patients with A3243G and A8344G mutations have high basal lactate levels, whereas pure CPEO is never associated with increased lactate levels. Cardiac abnormalities mostly consist of conduction defects. Abnormalities on CT or MRI of the brain are relatively common in A3243G mutations independently of the clinical phenotype. Patients with multiple mtDNA deletions are somehow "protected" against the development of abnormalities with any of the tests. We conclude that, despite the phenotypic heterogeneity of mitochondrial disorders, correlation of clinical features and laboratory findings may give the clinician important clues to the genetic defect, allowing earlier diagnosis and counselling.

Adolescent↗
PubMed1994

Automatic sequencing of mitochondrial tRNA genes in patients with mitochondrial encephalomyopathy.

We have investigated nine children with infantile onset of mitochondrial myopathy and two adults with myoclonus epilepsy and ragged-red fibers (MERRF) and chronic progressive external ophthalmoplegia (CPEO), respectively. These patients lacked any of the previously known pathogenic tRNA mutations. Southern blot analysis of muscle mtDNA revealed no deletions. The tRNA genes of muscle mtDNA were sequenced. Restriction enzyme analysis of PCR fragments was performed to verify the presence of the mutations identified by automatic sequencing. Several tRNA mutations were found, but they were all homoplasmic. Furthermore, the mutations were either present in controls or did not change nucleotides conserved between species. This strongly suggests that none of the tRNA mutations identified in the 11 patients with mitochondrial encephalomyopathy was pathogenic. It can thus be concluded that mitochondrial tRNA mutations and mtDNA deletions probably are an infrequent cause of mitochondrial disorders in infants. Patients with MERRF and CPEO may lack both pathogenic point mutations of tRNA genes and deletions of mtDNA.

Adult↗
PubMed2005

A novel heteroplasmic tRNA(Leu(CUN)) mtDNA point mutation associated with chronic progressive external ophthalmoplegia.

We have sequenced all mitochondrial tRNA genes from a patient with chronic progressive external ophthalmoplegia (CPEO) and mitochondrial myopathy, who had no detectable large mtDNA deletions. Direct sequencing failed to detect previously reported mutations and showed a heteroplasmic mutation at nucleotide 12,276 in the tRNA(Leu(CUN)) gene, in the dihydrouridine stem, which is highly conserved through the species during evolution. RFLP analyses confirmed that 18% of muscle mtDNA harbored the mutation, while it was absent from DNA of fibroblasts and lymphocytes of the proband and in 110 patients with other encephalomyopathies. To date, besides large and single nucleotide deletions, several point mutations on mitochondrial tRNA genes have been reported in CPEO patients, but only three were in the gene coding for tRNA(Leu(CUN)).

Animals↗
PubMed2006

Mitochondrial DNA deletions inhibit proteasomal activity and stimulate an autophagic transcript.

Deletions within the mitochondrial DNA (mtDNA) cause Kearns Sayre syndrome (KSS) and chronic progressive external opthalmoplegia (CPEO). The clinical signs of KSS include muscle weakness, heart block, pigmentary retinopathy, ataxia, deafness, short stature, and dementia. The identical deletions occur and rise exponentially as humans age, particularly in substantia nigra. Deletions at >30% concentration cause deficits in basic bioenergetic parameters, including membrane potential and ATP synthesis, but it is poorly understood how these alterations cause the pathologies observed in patients. To better understand the consequences of mtDNA deletions, we microarrayed six cell types containing mtDNA deletions from KSS and CPEO patients. There was a prominent inhibition of transcripts encoding ubiquitin-mediated proteasome activity, and a prominent induction of transcripts involved in the AMP kinase pathway, macroautophagy, and amino acid degradation. In mutant cells, we confirmed a decrease in proteasome biochemical activity, significantly lower concentration of several amino acids, and induction of an autophagic transcript. An interpretation consistent with the data is that mtDNA deletions increase protein damage, inhibit the ubiquitin-proteasome system, decrease amino acid salvage, and activate autophagy. This provides a novel pathophysiological mechanism for these diseases, and suggests potential therapeutic strategies.

Autophagy↗
PubMed2004

Interaction of poly(ethylene oxide) with fumed silica.

Interaction of poly(ethylene oxide) (PEO, 600 kDa) with fumed silica A-300 (SBET = 316 m2/g) was investigated under different conditions using adsorption, infrared (IR), thermal analysis (TG-DTA), AFM, and quantum chemical methods. The studied dried silica/PEO samples were also carbonized in a flow reactor at 773 K. The structural characteristics of fumed silica, PEO/silica, and pyrocarbon/fumed silica were investigated using nitrogen adsorption-desorption at 77.4 K. PEO adsorption isotherm depicts a high affinity of PEO to the fumed silica surface in aqueous medium. PEO adsorbed in the amount of 50 mg per gram of silica (PEO monolayer corresponds to CPEO approximately 190 mg/g) can disturb approximately 70% of isolated surface silanols. However, at the monolayer coverage, only 20% of oxygen atoms of PEO molecules take part in the hydrogen bonding with the surface silanols. An increase in the PEO amount adsorbed on fumed silica leads to a diminution of the specific surface area and contributions of micro- (pore radius R < 1 nm) and mesopores (1 < R < 25 nm) to the pore volume but contribution of macropores (R > 25 nm) increases with CPEO. Quantum chemical calculations of a complex of a PEO fragment with a tripple bond SiOH group of a silica cluster in the gas phase and with consideration for the solvent (water) effect show a reduction of interaction energy in the aqueous medium. However, the complex remains strong enough to provide durability of the PEO adsorption complexes on fumed silica; i.e., PEO/fumed silica nanocomposites could be stable in both gaseous and liquid media.

Adsorption↗
PubMed2005

Novel biomimetic polymersomes as polymer therapeutics for drug delivery.

Novel amphiphilic diblock copolymers, cholesterol-end-capped poly(2-methacryloyloxyethyl phosphorylcholine) (CMPC), which have poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) as hydrophilic segment and cholesterol as hydrophobic segment, was specially designed as drug delivery systems. Fluorescence probe technique and transmission electron microscope (TEM) characterizations indicated that this novel amphiphilic copolymer formed micelles structure in water and the critical micelle concentration (CMC) was determined to be 1.57 x 10(-7) mol/l. A commercial obtained polymeric amphiphiles, Cholesterol end capped PEO (CPEO), which had a similar structure with CMPC, was used as a control in the cytotoxicity test. While CPEO showed obvious cytotoxicity, cytotoxicity of this novel amphiphiles was not observed as indicated by cell culture. Anti-cancer drug adriamycin (ADR) was incorporated into the micelles by oil-in-water method. The size of the drug-containing micelles was less than 200 nm, and the size distribution of the drug-containing micelles showed a narrow and monodisperse unimodal pattern. The release rate of ADR from the nanosphere was slow and the release continued over 7 days and the release rate decreased with the increase of molecular weights of the copolymer and the amount of the drug entrapped. These experimental results suggested that the nanoparticles prepared from CMPC block copolymers could be a good candidate for injectable drug delivery carrier.

3T3 Cells↗