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Mitochondrial dysfunction has been implicated as a central mechanism in the metabolic myopathy accompanying critical limb ischemia (CLI). However, whether mitochondrial dysfunction is directly related to lower extremity ischemia and the structural and molecular mechanisms underpinning mitochondrial dysfunction in CLI patients is not understood. Here, we aimed to study whether mitochondrial dysfunction is a distinctive characteristic of CLI myopathy by assessing mitochondrial respiration in gastrocnemius muscle from 14 CLI patients (65.3 ± 7.8 y) and 15 matched control patients (CON) with a similar comorbidity risk profile and medication regimen but without peripheral ischemia (67.4 ± 7.4 y). Furthermore, we studied potential structural and molecular mechanisms of mitochondrial dysfunction by measuring total, sub-population, and fiber-type-specific mitochondrial volumetric content and cristae density with transmission electron microscopy and by assessing mitophagy and fission/fusion-related protein expression. Finally, we asked whether commonly used biomarkers of mitochondrial content are valid in patients with cardiovascular disease. CLI patients exhibited inferior mitochondrial respiration compared to CON. This respiratory deficit was not related to lower whole-muscle mitochondrial content or cristae density. However, stratification for fiber types revealed ultrastructural mitochondrial alterations in CLI patients compared to CON. CLI patients exhibited an altered expression of mitophagy-related proteins but not fission/fusion-related proteins compared to CON. Citrate synthase, cytochrome c oxidase subunit IV (COXIV), and 3-hydroxyacyl-CoA dehydrogenase (β-HAD) could not predict mitochondrial content. Mitochondrial dysfunction is a distinctive characteristic of CLI myopathy and is not related to altered organelle content or cristae density. Our results link this intrinsic mitochondrial deficit to dysregulation of the mitochondrial quality control system, which has implications for the development of therapeutic strategies., Competing Interests: The authors declare no conflict of interest.

Myopathy is among the well documented and the most disturbing adverse effects of statins. The underlying mechanism is still unknown. Mitochondrial dysfunction related to coenzyme Q10 decline is one of the proposed theories. The present study aimed to investigate the mechanism of atorvastatin-induced myopathy in rats. In addition, the mechanism of the coenzyme Q10 protection was investigated with special focus of mitochondrial alterations. Sprague-Dawely rats were treated orally either with atorvastatin (100mg/kg) or atorvastatin and coenzyme Q10 (100mg/kg). Myopathy was assessed by measuring serum creatine kinase (CK) and myoglobin levels together with examination of necrosis in type IIB fiber muscles. Mitochondrial dysfunction was evaluated by measuring muscle lactate/pyruvate ratio, ATP level, pAkt as well as mitochondrial ultrastructure examination. Atorvastatin treatment resulted in a rise in both CK (2X) and myoglobin (6X) level with graded degrees of muscle necrosis. Biochemical determinations showed prominent increase in lactate/pyruvate ratio and a decline in both ATP (>80%) and pAkt (>50%) levels. Ultrastructure examination showed mitochondrial swelling with disrupted organelle membrane. Co-treatment with coenzyme Q10 induced reduction in muscle necrosis as well as in CK and myoglobin levels. In addition, coenzyme Q10 improved all mitochondrial dysfunction parameters including mitochondrial swelling and disruption. These results presented a model for atorvastatin-induced myopathy in rats and proved that mitochondrial dysfunction is the main contributor in statin-myopathy pathophysiology., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Aims: Myopathy or neuropathy has been associated with lamivudine/telbivudine therapy in hepatitis B patients. We aim to describe the pathological changes of lamivudine/telbivudine-associated neuromyopathy., Methods: We retrospectively recruited six patients who were diagnosed with nucleotide analogues-associated myopathy or neuropathy. Muscle and nerve biopsy were performed, and the specimens were prepared for the light microscopy and electron microscopy. Genomic DNA was extracted from frozen muscle specimens, and the mitochondrial DNA (mtDNA) content was quantified by real-time PCR., Results: Recovery of the myopathy can be achieved after the discontinuation or changing the drugs to entecavir. Muscle and nerve biopsy revealed similar changes under either the light or electronic microscopy in all the subjects. Quantitative real-time PCR revealed decrease of mtDNA content in the affected muscle., Conclusions: MtDNA depletion results in mitochondrial dysfunction in the lamivudine/telbivudine-associated neuromyopathy. Myopathy was characterised by mitochondrial dysfunction accompanied with neurogenic damage due to axonal neuropathy. Ultrastructure changes of mitochondria included vacuolisation, simplification of the cristae and homogenised matrix., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Over 4 million individuals in the United States, and over 140 million individuals worldwide, are exposed daily to arsenic-contaminated drinking water. Human exposures can range from below the current limit of 10 μg/L to over 1mg/L, with 100 μg/L promoting disease in a large portion of those exposed. Although increased attention has recently been paid to myopathy following arsenic exposure, the pathogenic mechanisms underlying clinical symptoms remain poorly understood. This study tested the hypothesis that arsenic induces lasting muscle mitochondrial dysfunction and impairs metabolism. Compared to nonexposed controls, mice exposed to drinking water containing 100 μg/L arsenite for 5 weeks demonstrated impaired muscle function, mitochondrial myopathy, and altered oxygen consumption that were concomitant with increased mitochondrial fusion gene transcription. There were no differences in the levels of inorganic arsenic or its monomethyl and dimethyl metabolites between controls and exposed muscles, confirming that arsenic does not accumulate in muscle. Nevertheless, muscle progenitor cells isolated from exposed mice recapitulated the aberrant myofiber phenotype and were more resistant to oxidative stress, generated more reactive oxygen species, and displayed autophagic mitochondrial morphology, compared to cells isolated from nonexposed mice. These pathological changes from a possible maladaptive oxidative stress response provide insight into declines in muscle functioning caused by exposure to this common environmental contaminant., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Mitochondrial alterations are the most common feature of human myopathies. A biopsy of quadriceps muscle from a 50-year-old woman exhibiting myopathic symptoms was examined by transmission electron microscopy. Biopsied fibers from quadriceps muscle displayed numerous subsarcolemmal mitochondria that contained crystalloids. Numbering 1-6 per organelle, these consisted of rows of punctuate densities measuring ∼0.34 nm; the parallel rows of these dots had a periodicity of ∼0.8 nm. The crystalloids were ensconced within cristae or in the outer compartment. Some mitochondria without crystalloids had circumferential cristae, leaving a membrane-free center that was filled with a farinaceous material. Other scattered fibrocyte defects included disruption of the contractile apparatus or its sporadic replacement by a finely punctuate material in some myofibers. Intramitochondrial crystalloids, although morphologically striking, do not impair organelle physiology to a significant degree, so the muscle weakness of the patient must originate elsewhere.

Introduction: The mitochondrial network within cells is mediated by fission and fusion processes., Methods: We investigated the expression of the proteins responsible for these events during conditions of altered oxidative capacity., Results: With chronic contractile activity, the mitochondrial reticulum increased in size, along with concomitant increases in the fusion proteins Opa1 and Mfn2 (by 36% and 53%; P < 0.05). When we induced muscle disuse through denervation for 7 days, fragmented mitochondria were observed, along with significant decreases in the expression of Mfn2 and Opa1 (by 84% and 70%). To assess the effects of aging on mitochondrial morphology, young (5 month) and aged (35 month) Fisher 344 Brown Norway rats were used. Aged animals also possessed smaller mitochondria and displayed increased levels of fission proteins., Conclusions: Chronic muscle use increases the ratio of fusion:fission proteins, leading to reticular mitochondria, whereas muscle disuse and aging result in a decrease in this ratio, culminating in fragmented organelles., (Copyright © 2013 Wiley Periodicals, Inc.)

Introduction: Skeletal muscle fiber composition and muscle energetics are not static and change in muscle disease. This study was performed to determine whether a mitochondrial myopathy is associated with adjustments in skeletal muscle fiber-type composition., Methods: Ten rats were treated with zidovudine, an antiretroviral nucleoside reverse transcriptase inhibitor that induces a myopathy by interfering with mitochondrial functions. Soleus muscles were examined after 21 weeks of treatment. Ten untreated rats served as controls., Results: Zidovudine induced a myopathy with mitochondrial DNA depletion, abnormalities in mitochondrial ultrastructure, and reduced cytochrome c oxidase activity. Mitochondrial DNA was disproportionally more diminished in type I compared with type II fibers, whereas atrophy predominated in type II fibers. Compared with those of controls, zidovudine-exposed soleus muscles contained an increased proportion (256%) of type II fibers, whereas neonatal myosin heavy chains remained repressed, indicating fiber-type transformation in the absence of regeneration. Microarray gene-expression analysis confirmed enhanced fast-fiber isoforms, repressed slow-fiber transcripts, and reduced neonatal fiber transcripts in the mitochondrial myopathy. Respiratory chain transcripts were diminished, whereas the enzymes of glycolysis and glycogenolysis were enhanced, indicating a metabolic adjustment from oxidative to glycolytic capacities. A coordinated regulation was found of transcription factors known to orchestrate type II fiber formation (upregulation of MyoD, Six1, Six2, Eya1, and Sox6, and downregulation of myogenin and ERRγ)., Conclusions: The type I to type II fiber transformation in mitochondrial myopathy implicates mitochondrial function as a new regulator of skeletal muscle fiber type.

The data obtained in this study suggest an integrated cascade of destructive and compensatory reactions triggered by disruption of metabolic equilibrium in skeletal muscle cells. Actual parameters of the pathologic process are determined by the intensity and dynamics of the injurious stimulus rather than by its specific nature and also depend on the adaptive potential of target muscular fibers. General analysis of experimental pathologic processes differing in dynamics of injurious impacts permitted to distinguish chronic and acute variants of the development of pathologic changes and the respective spectra of structural reactions. Acute injuries (contracture and lysis) appear to roughly fall into the two categories, confined and extended. De novo restoration of complicated cell architecture being rather "expensive", limitation of damage acquires special significance. Many of the confined destructive events may be regarded as "adaptive" in respect to a higher organizational level. In chronic pathologic processes, gradual accumulation of structural and energetic disturbances leaves time for adaptive rearrangements to develop. The most prominent adaptive reactions are at first confined to mitochondrial compartment and thereafter give place to its structural decompensation. Increasing fragmentation of mitochondrial reticulum may be "preventive" in that it contributes to isolation and removal of its irreversibly damaged parts and can therefore be considered as the first ("metabolic") phase of the damage restriction strategy. Under the threat of total demolition of a skeletal muscle fiber, its "mechanical" fragmentation associated with local destruction of the contractile apparatus becomes of primary importance along with extracellular factors participating in fast removal and reparation of the damaged fragment. Insufficiency of these reactions or extreme character of the impact promotes the spread of the lesion over the entire fiber or its large part. Extended forms of damage are associated with intense infiltration by inflammatory cells and, after elimination of cell debris, produce a structural defect compensated by newly formed regenerating fibers and connective tissue expansion.

We studied the ultrastructural characteristics in patients with myofibrillar myopathy (MFM) and differentiated between MFM-subtypes using electron microscopic (EM) findings. The ultrastructural findings in 19 patients with different genetically proven MFMs (9 desmin, 5 alphaB-crystallin, 3 ZASP, 2 myotilin) were analyzed. In one ZASPopathy, we additionally performed an immunoEM study, using antibodies against desmin, alphaB-crystallin, ZASP and myotilin. The ultrastructural findings in desminopathies and alphaB-crystallinopathies were very similar and consisted of electrondense granulofilamentous accumulations and sandwich formations. They differed in the obvious presence of early apoptotic nuclear changes in alphaB-crystallinopathies. ZASPopathies were characterized by filamentous bundles (labeled with the myotilin antibody on immunoEM), and floccular accumulations of thin filamentous material. Tubulofilamentous inclusions in sarcoplasm and myonuclei in combination with filamentous bundles were characteristic for myotilinopathies. We conclude that MFMs ultrastructural findings can direct diagnostic efforts towards the causal gene mutated, and that EM should be included in the diagnostic workup of MFMs.

This study investigated the effects of probenecid to inhibit the multi-drug resistance-associated protein-1 (MRP-1) in mediating the efflux and myotoxicity in rat skeletal muscles, with administration of rosuvastatin. Male Sprague-Dawley rats were administered daily, for 15 days, with either rosuvastatin (50, 100 or 200 mg/kg) or probenecid (100 mg/kg) alone, or with a combination of rosuvastatin (50, 100 or 200 mg/kg) and probenecid (100 mg/kg). Skeletal muscle toxicity was elevated with probenecid administered with 200 mg/kg/day of rosuvastatin, with the elevation of creatine kinase by 12-fold, alanine aminotrasferase by 10-fold and creatinine by 9-fold at day 15, with no adverse effects observed when probenecid was given alone. Mitochondria ultrastructural damage with enlargement, disruption, cristolysis and vaculation was seen in the soleus and plantaris of animals administered with probenecid and high dosages of statin. These muscles were also expressing more succinic dehydrogenase (SDH)-positive and cytochrome oxidase (CyOX)-positive fibers. Although generally well-tolerated, statins produce a variety of adverse skeletal muscle events. Hydrophilic statins, with reduced levels of non-specific passive diffusion rates into extra-hepatic tissues, are still seen to produce myopathy. This highlights the important roles of transport mechanisms in statin transport at the skeletal muscles. Excessive influx, reduced efflux or the combination of the two could result in elevated cellular levels of statins at the skeletal muscles, resulting in toxicity. This study provides preliminary evidence that the MRP-1 transporter and efflux at skeletal muscles possibly play significant roles in statin-induced myopathy.

In recent years, an increasing number of studies have demonstrated that a myopathy is present, contributes, and, to a certain extent, determines the pathogenesis of peripheral arterial occlusive disease (PAD). These works provide evidence that a state of repetitive cycles of exercise-induced ischemia followed by reperfusion at rest operates in PAD patients and mediates a large number of structural and metabolic changes in the muscle, resulting in reduced strength and function. The key players in this process appear to be defective mitochondria that, through multilevel failure in their roles as energy, oxygen radical species, and apoptosis regulators, produce and sustain a progressive decline in muscle performance. In this 2-part review, we highlight the currently available evidence that characterizes the nature and mechanisms responsible for this myopathy. In part 1, the authors review the functional and histomorphological characteristics of the myopathy and focus on the biochemistry and bioenergetics of its mitochondriopathy. In part 2, they then review accumulating evidence that oxidative stress related to ischemia reperfusion is probably the major operating mechanism of PAD myopathy. Important new findings of a possible neuropathy and a shift in muscle fiber type are also reviewed. Learning more about these mechanisms will enhance our understanding of the degree to which they are preventable and treatable.

Morphological changes induced by clofibrate in type-1 predominant soleus, type-2 predominant tensor fasciae latae, and type-1 and -2 mixed biceps femoris muscles and diaphragm in rats were investigated. Administration of the agent at 500 or 750 mg/kg/day by oral gavage for 14 or 28 days caused lesions in the soleus muscle and diaphragm, bur no changes in the tensor fasciae latae and biceps femoris muscles. In soleus muscle, vacuolation of muscle fibers was observed in all animals treated with clofibrate, and degeneration of muscle fibers and infiltration of leukocytes were noted at 750 mg/kg/day. In diaphragm, vacuolation of muscle fibers was also observed in all animals treated with clofibrate, and these lesions were located in type-1 skeletal muscles densely stained with NADH-TR. The vacuoles seen in soleus muscle and diaphragm were positive for oil red O staining. In addition, increase of lipid droplets and mitochondrial hypertrophy was seen in soleus muscle, ultrastructurally. These data suggest that sensitivity to clofibrate-induced muscle toxicity differs among muscles, with type-1 fibers being susceptible.

Here, we examine the role of "non-muscle" caveolins (Cav-1 and Cav-2) in skeletal muscle biology. Our results indicate that skeletal muscle fibers from male Cav-1(-/-) and Cav-2(-/-) mice show striking abnormalities, such as tubular aggregates, mitochondrial proliferation/aggregation, and increased numbers of M-cadherin-positive satellite cells. Notably, these skeletal muscle defects were more pronounced with increasing age. Because Cav-2-deficient mice displayed normal expression levels of Cav-1, whereas Cav-1-null mice exhibited an almost complete deficiency in Cav-2, these skeletal muscle abnormalities seem to be due to loss of Cav-2. Thus, Cav-2(-/-) mice represent a novel animal model-and the first genetically well-defined mouse model-that can be used to study the pathogenesis of tubular aggregate formation, which remains a poorly understood age-related skeletal muscle abnormality. Finally, because Cav-1 and Cav-2 were not expressed within mature skeletal myofibers, our results indicate that development of these abnormalities probably originates in stem/precursor cells, such as satellite cells or myoblasts. Consistent with this hypothesis, skeletal muscle isolated from male Cav-3(-/-) mice did not show any of these abnormalities. As such, this is the first study linking stem cells with the genesis of these intriguing muscle defects.

Fifteen horses with pituitary pars intermedia dysfunction were studied. The horses were of various breeds and between 15 and 28 years of age. Control horses matched for breed and age were studied for comparison. Evaluations included complete blood cell count and serum biochemical analysis, electromyography, and gluteus medius muscle biopsies for histochemical, morphometric, and ultrastructural analysis. No differences were found between groups of horses on routine laboratory analysis or electromyography. We demonstrated that muscle wasting in diseased horses was the result of atrophy of types 2A and 2B muscle fibers and loss of type 2B myofibers. Mild non-specific non-inflammatory myopathic alterations such as myofiber size variation, internal nuclei, perimysial, endomysial and sarcoplasmic fat accumulation were observed. At the ultrastructural level, subsarcolemmal mitochondrial accumulation and increased lipid droplets were evident. Similar to other species, this study confirmed atrophy of type 2 fibers as the cause of muscle mass loss in horses with Cushing's disease.

The presence of abnormalities in fibromyalgia muscle using current methodological approaches is well established. The more serious abnormalities are demonstrated by histologic studies particularly on electron microscopy: disorganisation of Z bands and abnormalities in the number and shape of mitochondria. Biochemical studies and P 31 magnetic resonance spectroscopy show inconstant abnormalities of ATP and phosphocreatine levels. Mitochondrial abnormalities reduced capillary circulation and thickened capillary endothelium may result in decreased availability of oxygen and impaired oxidative phosphorylation as well as ATP synthesis. These abnormalities do not seem to be the consequences of the much-discussed deconditioning of muscles although these consequences are not well known. Further studies of energy metabolism of the muscle during exercise are needed.

Clinical and biopsy study of nine patients on statin therapy suffering from various myopathic syndromes is reported. Biopsy findings showed non specific myopathic signs and mitochondrial changes, such as subsarcolemmal accumulation, morphological alterations, lipid increase and Cox-negative fibers. These findings confirm that statins may cause muscle damage and impair oxidative metabolism.

Tubular aggregates are specific subcellular structures that appear in skeletal muscle fibres under different pathological conditions. The origin of the tubular aggregates is generally ascribed to proliferating membranes of sarcoplasmic reticulum. There are, however, histochemical indications for the presence of mitochondrial enzymes in tubular aggregates suggesting contribution of mitochondria to the genesis of tubular aggregates. In this study we used an immunocytochemical detection technique to assess participation of mitochondria and of sarcoplasmic reticulum in derivation of tubular aggregates. The fast skeletal muscle fibres (m. gastrocnemius) of mice bearing the double invalidation for both the mitochondrial and the cytosolic isoforms of creatine kinase (CK), an enzyme involved in energetics of muscle cells, were employed as a model muscle with tubular aggregates (Steeghs et al., Cell 89, 93-103, 1997). Immunogold labelling of the bc1 complex, a specific integral protein of the inner mitochondrial membrane, provided strong signals in both the mitochondria and tubular aggregates but not in other ultrastructural components of muscle fibres. A similar strong immunogold signal was obtained when labelling for SERCA1, a specific enzyme of the sarcoplasmic reticulum membrane, in regions of typical occurrence of the sarcoplasmic reticulum and in tubular aggregates. In double labelling experiments, we found simultaneous labelling of tubular aggregates with both the bc1 and SERCA1 antibodies. It is concluded, that in CK-/- mouse both the inner mitochondrial membrane and the membrane of the sarcoplasmic reticulum participate in the formation of tubular aggregates.

This report deals with the pathology and genetic basis of dilated cardiomyopathy in 10 Holstein-Friesian cows aged 3-6 years, a disease similar to that reported in Simmental-Red Holstein and Holstein-Friesian cattle in several other countries. The main clinical signs were associated with systemic circulatory failure, and at necropsy the animals showed cardiomegaly, severe congestion and fibrosis of the liver, and systemic cardiac oedema. Histologically, hypertrophy and vacuolation of the cardiac muscle fibres and severe fibrosis were noted. Electron microscopically, the sarcoplasm of the hypertrophic fibres was seen to be filled with fine structures of low electron-density, together with thin filamentous material, suggesting myofibrillar lysis. The mitochondria showed increased size, an abnormal cristae pattern and vacuolation due to partial loss of cristae. Pedigree analysis of the affected cattle indicated an autosomal recessive mode of inheritance. The family line of this cardiomyopathy overlapped with that of hereditary myopathy of the diaphragmatic muscles in Holstein-Friesian cattle, the pathological aspects and inheritance mode of which were reported previously. The available evidence suggested a genetic association between these two pathologically distinct diseases., (Copyright Harcourt Publishers Ltd.)

A combination of electrophysiological, pathological, and biochemical studies were performed in myopathy induced by 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors. Simvastatin (a lipophilic inhibitor) or pravastatin (a hydrophilic inhibitor) were administered by gavage to rabbits. In Group I (simvastatin-treated group, 50 mg/kg/day for 4 weeks), four rabbits showed muscle necrosis and high serum creatine kinase (CK) levels, and all six rabbits showed electrical myotonia. In Group II (pravastatin-treated group, 100 mg/kg/day for 4 weeks), no rabbit showed either condition. In Group III (pravastatin-treated group, 200 mg/kg/day for 3 weeks plus 300 mg/kg/day for 3 weeks), one rabbit showed muscle necrosis and high serum CK level and two rabbits showed electrical myotonia. The pathological findings were muscle fiber necrosis and degeneration with increased acid phosphatase activity by light microscopy, autophagic vacuoles and mitochondrial swelling, and disruption and hypercontraction of myofibrils by electron microscopy. Ubiquinone content decreased in skeletal muscle by 22 to 36% in Group I, by 18 to 52% in Group II, and by 49 to 72% in Group III. However, mitochondrial enzyme activities of respiratory chain were normal in all groups. These results indicate that myopathy was not induced by a secondary dysfunction of mitochondrial respiration due to low ubiquinone levels., (Copyright 1998 Academic Press.)

The ultrastructural features of a case of severe hyperthyroid myopathy are presented. Along with the moderate increase in mitochondrial size and number usually observed in most patients with hyperthyroid myopathy, some of the skeletal muscle mitochondria in the present case also contained paracrystalline rectangular inclusions. This finding has not been previously reported in hyperthyroid myopathy and further supports the current view that mitochondrial abnormalities play a major role in the pathogenesis of muscle dysfunction in hyperthyroid patients.

There is controversy as to whether zidovudine (ZDV) induces a mitochondrial myopathy that is distinguishable from human immunodeficiency virus (HIV)-associated myopathy in ZDV-naive patients. Mitochondrial abnormalities were evaluated in skeletal muscle obtained from 18 HIV-positive, ZDV-exposed patients, and 9 who were drug naive. All patients had clinical myopathy, and underwent neuromuscular evaluation with information recorded on timing and dosage of ZDV. All underwent muscle biopsies and samples were examined without knowledge of clinical history or ZDV status. Biopsy samples were evaluated by light and electron microscopy. Mitochondrial abnormalities were seen in ZDV-treated and -naive groups, and did not correlate with ZDV exposure or cumulative ZDV dosage. Mitochondrial abnormalities displayed significant correlation with the presence and severity of myofiber degeneration on biopsy, regardless of ZDV status. As mitochondrial abnormalities reflect myofiber degeneration, present in both patient groups, they may not be used as evidence of primary mitochondrial dysfunction. The etiology of myofiber degeneration in patients with HIV infection, whether ZDV-exposed or -naive, remains unclear.

A 41-years-old man with ileitis terminalis was presented. He was operated on for chronic abdominal pain, and the histological investigation revealed the Crohn's disease. From among the extraintestinal complications the rare muscle involvement joined the inflammatory bowel disease. The leading symptoms were the progressive muscle pain and tenderness presented early before the verification of intestinal problems. His complaints referred mainly to the calf muscles. The electromyography (EMG) was normal, the serum creatinine-kinase (CK) activity has not increased. The most characteristic histological findings were the slight mononuclear cell infiltrations with large histiocytic cells in the perimysial connective tissue. Occasionally the infiltrations were more prominent resembling granuloma formations. The oxidative enzyme reactions and the electron micrographs showed mild mitochondrial changes. Neither non-steroid antiinflammatory nor steroid medication subsided the complaints.

We studied a 9-year-old girl with progressive weakness of her extremities for two years. Her neurologic evaluation showed weakness of proximal muscles but no ophthalmoparesis. With the exception of elevated serum lactic acid, the general blood screen, EMG, nerve conduction velocity tests, and ECG were normal. Light and electron microscopy of a muscle biopsy showed proliferation of mitochondria containing disorganized cristae. Activities of respiratory chain enzymes containing mitochondrial DNA (mtDNA)-encoded subunits were significantly impaired in muscle homogenates. A G-->A transition at position 15990 previously detected in this patient's muscle was not present in peripheral blood cells of her mother or sister. However, the patient's WBCs appeared to contain a very small percentage of mutant mtDNAs, indicating that the mutation may have originated during early embryogenesis.

A 65-year-old man developed a painless proximal myopathy 7 years after commencing cyclosporin therapy following a successful cadaveric renal transplant. Muscle histology showed ragged red fibres and biochemical studies suggested mitochondrial dysfunction. The possible pathogenesis of this mitochondrial myopathy, particularly its relationship to cyclosporin-induced hypomagnesaemia, is discussed.

Objective: To describe a syndrome of severe progressive myopathy, cardiomyopathy, and gastrointestinal dysmotility in 2 patients with asymptomatic primary biliary cirrhosis (PBC) and circulating antimitochondrial autoantibodies, and to review pertinent literature concerning this syndrome., Methods: Clinical, electrophysiologic, serologic, and pathologic studies of the 2 affected patients were conducted., Results: Skeletal muscle involvement was manifested by progressive weakness of the proximal muscles, marked diaphragmatic dysfunction with consequent hypoventilation and respiratory failure, and moderately elevated levels of muscle-associated enzymes. Serum from both patients contained antimitochondrial antibodies that reacted with components of the mitochondrial keto acid dehydrogenase enzyme complex. Results of electromyography were consistent with a myopathic process. The microscopic and ultrastructural changes in the skeletal muscles were distinct from those of typical myositis, and were notable for striking subsarcolemmal aggregation of abnormal mitochondria in the absence of significant inflammation., Conclusion: Severe skeletal muscle, cardiac, and gastrointestinal pathology with abnormalities of the muscle mitochondria develops in a subset of patients with mild PBC and antimitochondrial antibodies. The pathogenesis of this syndrome is unclear, but may be related to the presence of the antimitochondrial autoantibodies.

Lovastatin (LS) is a potent HMG-CoA inhibitor used in the treatment of hypercholesterolemia. In humans it can cause a severe, necrotizing myopathy with myoglobinuria and renal failure. To investigate the pathogenesis of LS-induced myopathy we studied the effects of LS on rat skeletal muscle. Lewis rats were gavage-fed 1 mg/g body weight/day of LS. Control rats received carboxymethylcellulose-based suspension by gavage. Gastrocnemius and soleus, fast and slow twitch muscles respectively, were studied by light and electron microscopy. By day 10 LS-treated rats became severely weak. Gastrocnemius was severely affected with degeneration of membranous organelles and microvacuole formation, but soleus was spared. Eventually, 20-50% of the gastrocnemius but none of the soleus fibers became necrotic. Non-necrotic fibers showed no increases of acid phosphatase, indicating that autophagy was not excited. We conclude that LS causes muscle injury by inducing degeneration of membranous organelles, and fast twitch muscle fibers are selectively vulnerable to LS myopathy.

The first disease due to disturbances in a cell organelle was discovered in 1959-62, and its basis was loose-coupling of oxidative phosphorylation in the skeletal muscle mitochondria accompanied by severe alterations of their structure (Luft's disease). During the 1980s, functional disturbances and structural alterations in the mitochondria were observed in more than 100 disease entities, mainly in parts of the central nervous system and skeletal muscles. A second breakthrough in this area was the discovery in 1963-64 that mitochondria had their own DNA, mtDNA. Following the observation in 1988 of mutations of mtDNA in mitochondrial diseases, such mutations--mainly deletions and point mutations--were observed in almost all mitochondrial diseases. A remarkable extension of the area is the notion that "normal" ageing is accompanied by decreased oxidative phosphorylation and the appearance of mtDNA mutations. During the last two years, such changes have been demonstrated in diseased states in tissues and organs, which are especially reliant on oxygen supply: in the central nervous system (Parkinson's disease, some types of epilepsy and seizures, Huntington's disease, possibly also in Alzheimer's disease); in heart muscle (cardiomyopathies) and in skeletal muscle. Type 2 diabetes or NIDDM engages two tissues most reliant on oxygen consumption, the pancreatic islets (insulin secretion) and skeletal muscle (insulin sensitivity). Both these functions are genetically determined, the latter to a high degree also controlled by "environmental" factors. The evident age factor in the development of NIDDM could be on a par with the "normal" ageing process.(ABSTRACT TRUNCATED AT 250 WORDS)

Myopathy may occur as a complication of human immunodeficiency virus type 1 (HIV) infection or from its treatment, zidovudine (ZDV). We reviewed our experience with HIV-infected subjects referred for neuromuscular evaluation and compared features of myopathy in ZDV-treated (+ZDV) and untreated (-ZDV) patients. Fifty patients had myopathy, 25 diagnosed by pathologic criteria and 25 by clinical and other laboratory support. Twenty patients with myopathy had weight loss sufficient for the diagnosis of HIV wasting syndrome. Thirty-one subjects were +ZDV and 19 were -ZDV. Patients in each group presented with proximal weakness, although myalgia was more common in +ZDV patients. Both groups had elevated serum CK to a similar degree (medians: +ZDV, 485; -ZDV, 471). Muscle biopsies revealed myofiber degeneration, variable inflammatory infiltrates, inclusion bodies, and mitochondrial abnormalities in both groups. We followed response to ZDV withdrawal in 15 patients. Four had increased strength, three noted less myalgia, and eight had no clinical improvement. Twelve of 13 patients improved with prednisone. Although it is difficult to distinguish the myopathies of HIV and ZDV by clinical or pathologic criteria, in the majority of our patients, myopathy is due to HIV rather than ZDV.

Respiratory parameters of skeletal muscle were determined in permeabilized muscle fibers by adapting a technique described by Veksler et al. for cardiac fibers (Biochim Biophys Acta, 892:191-196, 1987). This method consists of the permeabilization of muscle fibers by saponin by allowing respiratory substrates and inhibitors to reach the mitochondria. In this way, the mitochondria may be studied inside the fibers as if they were isolated. We have verified, using various techniques, that the mitochondria remain intact during this procedure. This method has been applied to the study of six newborn infants for whom a diagnosis of a mitochondrial defect was suspected. In all cases, the defect was to be found on the permeabilized fibers, and this was confirmed by an enzymatic study. The advantage of this new method, associated with the measurement of the enzymatic activities on a crude homogenate, is to enable a simple and rapid diagnosis on a small amount of sample without damaging the mitochondria during the isolation procedure.

A morphological and quantitative study of skeletal muscle fibres and of capillary supply was performed on needle and open biopsies of quadriceps femoris muscle from 40 patients with chronic progressive external ophthalmoplegia (CPEO) with partial deficiency of cytochrome c oxidase (COX). Muscle biopsies from 5 healthy adult subjects were used as control. The study was carried out by light and electron microscopy, using an Automatic Interactive Image Analysis System (IBAS I,II). A significant decrease in fibre diameters and preferential type I fibre atrophy was seen. Red ragged fibres and fibres with cytoarchitectural changes after enzyme-histochemical reactions for detection of oxidative activities were also observed. Seventy per cent of affected fibres showed an intense subsarcolemmal rim of oxidative activity corresponding to ultrastructural accumulation of enlarged, polymorphous mitochondria in subsarcolemmal areas. The study of the capillary distribution in muscle revealed a reduction of the number of capillaries per fibre and surrounding a fibre. The primary metabolic error of the disease with defects in the oxygen utilisation, the fibre atrophy and the muscle disuse are the possible variables influencing the capillary number in CPEO patients.

A frequent occurrence of ophthalmoplegia and muscle fatigability in mitochondrial myopathy (MAM) often makes its differential diagnosis from myasthenia rather difficult. Neuromuscular transmission was investigated in 9 patients with MAM, presenting marked fatigability. The aim of the study was to see whether there were any other causes of muscle fatigability in addition to the metabolic factors. Classical electrostimulation as well as the SFEMG, which is very sensitive in detecting neuromuscular transmission disorders, were used. The findings were far from uniform: we found normal neuromuscular transmission in 5 cases, in 3 patients we observed slight abnormalities of neuromuscular transmission, in 1 case neuromuscular transmission disturbances seemed to be of neurogenic origin. Our results allow an assumption that the causes of muscle fatigability in MAM are of a much more complex nature than it has been anticipated. They might depend not only on the metabolic disorders within the muscle fibre itself but also on the impaired function of the peripheral nerve or of the neuromuscular junction. All the mechanisms combined may also play a role, though in individual patients the contribution of particular factors responsible may vary.

The association of chronic intestinal pseudoobstruction with ophthalmoplegia has been reported previously in visceral myopathies. We report a case of this association in which muscle mitochondria had a crystalline appearance, a dense core, and decreased cytochrome c oxidase and succinate cytochrome c reductase activities. The absence of evident mitochondrial DNA deletion in the skeletal muscle of this patient does not exclude the possibility of localized deletion or mutation of mitochondrial DNA in digestive muscle.

Two patients, a 70-yr-old black woman and a 56-yr-old black man, presented with respiratory failure unexplained by intrinsic lung disease. Both had been dependent on a respirator for several weeks. No abnormalities of the central or peripheral nervous system or long-standing muscle weakness was noted. The findings from ophthalmologic and cardiac evaluations were normal. The serum creatinine kinase concentration was mildly elevated in case 1, and needle electromyography showed myopathic potentials in case 2. In both instances, muscle biopsy established the diagnosis of mitochondrial myopathy. Biochemical studies of muscle extracts showed partial deficiency of complex 3 in patient 2 and of complex 4 in patient 1. Both patients were weaned from the ventilator after long periods of ventilatory assistance. These observations document a hitherto undescribed presentation of adult-onset mitochondrial myopathy.

Four mitochondrial myopathy cases are reported. In addition to complaints, clinical and laboratory findings the changes in number, size, shape and in structure of the mitochondria in skeletal muscles are detailed. In three of their cases the disease is monosystemic, one case seems to be multisystemic in character: beside the morphologically proven muscle and liver changes it is likely that cardiac muscle and the central nervous system is also affected on the base of the clinical symptoms.

We have studied five children with mitochondrial myopathy manifesting within or soon after the first year of life. Muscle biopsies showed ragged-red fibers and decreased respiratory chain activity. All five patients had a severe decrease (2 to 34% of normal) in the amount of muscle mitochondrial DNA (mtDNA). The depletion of mtDNA correlated with absence of mtDNA-encoded translation products and with loss of cytochrome c oxidase enzyme activity in individual muscle fibers. This mitochondrial myopathy of childhood illustrates one phenotypic expression of a novel pathogenetic mechanism in mitochondrial diseases, the specific depletion of mtDNA in affected tissues.

A 3-year-old boy presenting with convulsions and carpopedal spasm had hypomagnesemia and hypermagnesuria due to congenital magnesium-losing nephropathy. Despite chronic oral and intermittent intravenous magnesium supplementation, he remained chronically hypomagnesemic. At age 4, he developed a progressive proximal myopathy and dilated hypertrophic cardiomyopathy that ultimately contributed to his death at age 14 years. Skeletal and cardiac muscle specimens showed a mitochondrial myopathy with increased numbers of enlarged, structurally abnormal mitochondria. Muscle magnesium content was markedly decreased. Chronic oral and intermittent intravenous magnesium supplementation may be inadequate to prevent the progressive cardioskeletal myopathy associated with the chronic magnesium deficiency of congenital magnesium-losing nephropathy.

This report describes a sporadic late-onset myopathy in two unrelated adults which was marked by polyglucosan inclusions surrounded by abnormally structured mitochondria, the latter finding a localized, possibly reactive phenomenon. The polyglucosan material was characterized by a battery of histochemical and enzyme histochemical techniques; revealed common antigenicity with Lafora bodies, corpora amylacea and muscle fiber inclusions in types IV and VII glycogenoses; and contained ubiquitin. Additional lectin histochemical and associated digestion preparations disclosed the presence of alpha-glycosyl residues as apparently the sole carbohydrate component in polyglucosan bodies while the above mentioned common antigenicity with Lafora bodies and other inclusions suggests an additional, so far unidentified, protein component.

A patient with mitochondrial myopathy is described. Examination of his fundus revealed bilateral vitelliform degeneration of the maculae. This lesion is a focal abnormality of the retinal pigment epithelium and may be a manifestation of the underlying mitochondrial disease.

Electron microscopic features of muscle biopsies from 13 human immunodeficiency (HIV)-positive patients who had myopathy while receiving zidovudine (AZT) were compared with biopsies from five patients with HIV-induced myopathy who were not treated with AZT. All specimens showed disorganization of the myofibrillar structures, along with a varying degree of nemaline (rod) bodies, vacuolization, inflammation, and endothelial tubuloreticular profiles. One untreated and all AZT-treated patients had cytoplasmic bodies, which in the latter were abundant, large, and irregular. Two untreated patients had a peculiar osmiophilic destruction of the muscle fibers, with numerous tubuloreticular profiles in the endothelial cells and brisk inflammation that included lymphoplasmatoid cells. The AZT-treated group had ubiquitous abnormal mitochondria that complemented the presence of ragged red fibers seen by light microscopy. There was subsarcolemmal proliferation of mitochondria, with marked variation in size and shape and proliferation or disorganization of their cristae. Paracrystalline inclusions were seen in one patient. Blind re-examination of the electron micrographs showed abnormal mitochondria that readily distinguished patients with AZT-associated myopathy from those with untreated HIV-induced myopathy. Immunocytochemistry using antibodies to single- and double-stranded DNA revealed severe reduction of mitochondrial DNA compared with the normal nuclear DNA. Although the myopathies associated with HIV and AZT share common myopathologic features, the mitochondrial abnormalities are unique to the AZT-treated patients. Since mitochondrial DNA is specifically reduced, the structural changes noted on electron microscopy are probably associated with mitochondrial dysfunction. Zidovudine, a DNA chain terminator that inhibits the mitochondrial gamma-DNA polymerase, is toxic to muscle mitochondria.

The effect of riboflavin supplementation on muscle performance and exercise metabolism was investigated in four patients with multiple acyl-coenzyme A dehydrogenase deficiency (MAD). Maximum oxygen consumption and endurance measurements were performed to assess the patients' aerobic capacity and energy metabolism during exercise. They were tested before and after treatment with pharmacological doses of riboflavin. The initially low maximum oxygen consumption and high levels of blood lactate during submaximal exercise suggest that the oxidation of both fatty acids and carbohydrates was severely impaired. All four patients experienced a dramatic improvement in aerobic performance under riboflavin supplementation.

We have studied the usefulness of anti-DNA antibodies to detect ragged-red fibers (RRF) in muscle biopsies from patients with mitochondrial myopathies. We have found that these antibodies are excellent probes for the localization of mitochondrial DNA (mtDNA) in RRF, and for the diagnosis of depletion of mtDNA in a newly described group of fatal myopathies of infancy.

The myopathy caused by zidovudine (AZT) appears to be common but is incompletely characterized, particularly regarding prognosis. Twenty patients with HIV infection developed a necrotizing myopathy while taking AZT for 9 to 30 months. Ten presented with myalgia and 17 with proximal muscle weakness. Serum CK was elevated in all (two to 11 times normal), and EMG suggested active myopathy in all but two. There were scattered granular degenerating fibers, with scant or no inflammation, in a pattern consistent with a toxic myopathy in all 18 patients biopsied. Three patients with an HIV-related inflammatory myopathy were distinguished by histologic differences. After stopping AZT (n = 15), myalgia promptly resolved (10 of 10). Strength improved more slowly with 12 of 15 regaining normal or nearly normal strength, but three have persistent weakness. CK returned to normal in 12 of 15, and follow-up EMG (n = 11) documented reduced fibrillation density in all 11 patients. These findings underscore the need for early diagnosis of this reversible myopathy.

Although it is well known that the respiratory failure is a major cause of death in most patients with chronic neuromuscular disease, predominant respiratory dysfunction without severe involvement of limb muscles is an unusual complication of mitochondrial myopathy in adult age. We experienced two cases of mitochondrial myopathy with severe involvement of respiratory function and only mild involvement of limb muscles. One is a 16 year old female and another is a 22 year old male. The diagnosis is based on morphologic characteristics of "ragged red fibers" under the light microscope and abnormal mitochondrias on the electron microscope in the muscle biopsy.

A six-month-old boy with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome developed repeated crops of purpuric macules on his soles and palms, which were histologically identified as hemorrhage into the dermis without inflammatory infiltrates. Transmission electron microscopy of the skin eruptions revealed various stages of endothelial degeneration in the dermal capillaries associated with consequent extravasation of erythrocytes. The degenerative change was characterized by swollen and vacuolated mitochondria which showed disintegration of their cristae. These morphological changes in the mitochondria of the endothelial cells resembled those seen in skeletal muscle fibers. Similar changes were also noted in other tissues of the skin, such as the axons of myelinated peripheral nerves and some of the keratinocytes in the epidermis. Although these fine structural features are difficult to differentiate from artifacts, abnormal mitochondria could result in functional disturbance particularly in the tissues that require relatively high kinetics, and thus contribute the symptoms of myopathy, encephalopathy, acidosis and stroke-like episodes.

Mitochondrial myopathy can be caused by several metabolic defects in the mitochondria. Cells with high levels of oxidative metabolism, such as skeletal muscle, myocardium and brain cells, are particularly vulnerable to these defects. We describe the structural changes in muscle biopsies from 49 patients with mitochondrial myopathy. The younger patients were often symptom-free, but the possibility of a genetic defect was suggested by the family history. "Ragged-red fibres" were found in 10% of the biopsies. Typical paracrystalline inclusions were seen in the mitochondria of the oldest patients. Electron-lucent matrix and increased thickness of the inner membranes of the mitochondria in particular were found in the younger patients. Disorganization of cristae, with cristolysis and unfolding of the cristae was also found. We suggest that structural mitochondrial changes in mitochondrial myopathy constitute a stepwise process and that the mitochondrial alterations of the cristae may represent an early stage in the morphogenesis of mitochondrial disease.

We describe eight children with complex I deficiency, four of them with an isolated, the other four with an additional deficiency of complex IV. Clinical, chemical and morphological findings were compared from patients with isolated and combined deficiency. In both groups, the age of onset of symptoms was between the 1st day and the 4th month of life. Clinical and biochemical heterogeneity were observed. We found no correlation between residual activity of complex I in muscle, blood lactate level, and severity of clinical symptoms. Newborns presenting with severe lactic acidosis and children with later onset myopathy were seen in both groups. The group with combined complex I deficiency showed a more severe clinical course. By light microscopy ragged red fibres were only found in two patients with combined deficiency. However, by electron microscopy structural alterations of the mitochondria were observed in six out of seven muscle specimens.