Integrated analysis of the involvement of nitric oxide synthesis in mitochondrial proliferation, mitochondrial deficiency and apoptosis in skeletal muscle fibres.

Nitric oxide (NO) is an important signaling messenger involved in different mitochondrial processes but only few studies explored the participation of NO in mitochondrial abnormalities found in patients with genetic mitochondrial deficiencies. In this study we verified whether NO synthase (NOS) activity was altered in different types of mitochondrial abnormalities and whether changes in mitochondrial function and NOS activity could be associated with the induction of apoptosis. We performed a quantitative and integrated analysis of NOS activity in individual muscle fibres of patients with mitochondrial diseases, considering mitochondrial function (cytochrome-c-oxidase activity), mitochondrial content, mitochondrial DNA mutation and presence of apoptotic nuclei.

Deletion of Kinin B2 Receptor Alters Muscle Metabolism and Exercise Performance.

Metabolic syndrome is a cluster of metabolic risk factors such as obesity, diabetes and cardiovascular diseases. Mitochondria is the main site of ATP production and its dysfunction leads to decreased oxidative phosphorylation, resulting in lipid accumulation and insulin resistance. Our group has demonstrated that kinins can modulate glucose and lipid metabolism as well as skeletal muscle mass.

Nitric oxide synthesis is increased in cybrid cells with m.3243A>G mutation.

Nitric oxide (NO) is a free radical and a signaling molecule in several pathways, produced by nitric oxide synthase (NOS) from the conversion of L-arginine to citrulline. Supplementation of L-arginine has been used to treat MELAS (mitochondrial encephalopathy with lactic acidosis and stroke like syndrome), a mitochondrial disease caused by the m.3243A>G mutation.

Complex I spectrophotometric assay in cultured cells: detailed analysis of key factors.

The diagnosis of mitochondrial encephalomyopathies caused by complex I (C-I) deficiency relies mainly on the spectrophotometric C-I assay. Considered difficult, this assay lacks reliability and has high nonspecific activity. We studied the key factors of this assay in cultured cells (cybrid and fibroblast): ubiquinone analogues, rotenone inhibition to determine specific activity, and mode of permeabilization of mitochondrial membranes.

The mutations m.5628T>C and m.8348A>G in single muscle fibers of a patient with chronic progressive external ophthalmoplegia.

We identified a double mutation in a patient with chronic progressive external ophthalmoplegia, located in the tRNA(Ala) (m.5628T>C) and tRNA(Lys) (m.8348A>G) genes.

Old mice present increased levels of succinate dehydrogenase activity and lower vulnerability to dyskinetic effects of 3-nitropropionic acid.

Huntington's disease (HD) is a neurodegenerative disorder, with an age-related onset and a progressive development, characterized by choreiform movements. 3-nitropropionic acid (3NP) induces the inhibition of succinate dehydrogenase (SDH), an increase in oxidative stress and anatomic changes that are related to the pathophysiology of HD. Hence, this toxin is a useful tool to study this pathology.

Effects of short-term zidovudine exposure on mitochondrial DNA content and succinate dehydrogenase activity of rat skeletal muscle cells.

Long-term use of zidovudine (AZT) may cause mitochondrial abnormalities in various tissues, including a toxic myopathy in AIDS patients associated with mitochondrial DNA (mtDNA) depletion. In the present study, we examine the short-term (48 h) effect of AZT (10, 30 and 100 microg/ml) on the mitochondrial succinate dehydrogenase (SDH) and mtDNA content of rat cultured skeletal muscle. The effect of AZT on cytochrome c oxidase (COX) enzyme was also analyzed.

Progressive myopathy with a combined respiratory chain defect including Complex II.

Biochemical defects in the respiratory chain are mostly associated with deficiencies in Complexes I, III and IV, caused by nuclear or mitochondrial DNA mutations. Combined defects including Complex II have been reported very rarely and have muscular symptoms as the main manifestation, including muscle weakness, exercise intolerance and myoglobinuria. We report a patient with a fatal progressive myopathy and muscle biopsy showing diffuse reduction in succinate dehydrogenase activity, ragged red fibers and intense lipid accumulation.

Age-related mitochondrial DNA point mutations in patients with mitochondrial myopathy.

Mutations in the control region (D-loop) of mitochondrial DNA (mtDNA) have been described in normal old individuals and it is suggested that they originated from oxidative damage. Respiratory chain defects may lead to increased free radical generation, increased susceptibility to oxidative damage and further increased accumulation of age-related mutations. The objective of this study was to verify whether patients with a mitochondrial disease are more predisposed to accumulate the A189G and T408A mutations in the D-loop and confirm their age-associated nature.

The role of nitric oxide in muscle fibers with oxidative phosphorylation defects.

NO has been pointed as an important player in the control of mitochondrial respiration, especially because of its inhibitory effect on cytochrome c oxidase (COX). However, all the events involved in this control are still not completely elucidated. We demonstrate compartmentalized abnormalities on nitric oxide synthase (NOS) activity on muscle biopsies of patients with mitochondrial diseases.

Frequency of dystrophic muscle abnormalities in chronic progressive external ophthalmoplegia: analysis of 86 patients.

Background: There are few reports describing the coexistence of dystrophic features with those typical of mitochondrial myopathies in muscle biopsy. A recent study suggested that dystrophic features are frequent in patients with chronic progressive external ophthalmoplegia (CPEO) with a high mutation load, but the actual frequency of these abnormalities in CPEO remains undetermined.

Objective: To review the occurrence of dystrophic abnormalities in a large series of patients with CPEO to assess the frequency of such abnormalities and to verify whether they are correlated with specific mitochondrial DNA (mtDNA) mutations.

Duchenne muscular dystrophy: alpha-dystroglycan immunoexpression in skeletal muscle and cognitive performance.

The Duchenne muscular dystrophy (DMD) is a muscular dystrophy with cognitive impairment present in 20-30% of the cases. In the present study, in order to study the relationship between the alpha-dystroglycan (alpha-DG) immunostaining in skeletal muscle and cognitive performance in DMD patients, 19 were assessed. Twelve patients performed the intelligence quotient (IQ) below the average.

Ectopic development of skeletal muscle induced by subcutaneous transplant of rat satellite cells.

The present study analyzes the ectopic development of the rat skeletal muscle originated from transplanted satellite cells. Satellite cells (10(6) cells) obtained from hindlimb muscles of newborn female 2BAW Wistar rats were injected subcutaneously into the dorsal area of adult male rats. After 3, 7, and 14 days, the transplanted tissues (N = 4-5) were processed for histochemical analysis of peripheral nerves, inactive X-chromosome and acetylcholinesterase.

Frequency of duplications in the D-loop in patients with mitochondrial DNA deletions.

Small duplications (miniduplications) of the D-loop of human mitochondrial DNA (mtDNA) have been described in patients with mtDNA deletions, mtDNA point mutations and in normal aged tissues. The origin of these miniduplications is still unknown but it is hypothesized that they could be formed after oxidative damage. The respiratory chain (RC) is the main source of free radicals in mitochondria and it is believed that a defect in RC increases free radical generation.

A novel myopathy-associated mitochondrial DNA mutation altering the conserved size of the tRNA(Gln) anticodon loop.

We report a novel mitochondrial DNA alteration in a 12-year-old boy with myopathy. We identified a single nucleotide insertion (an adenine) in the mitochondrial tRNA-glutamine gene. This addition of an additional adenine in a polyadenine stretch (at mitochondrial DNA positions 4366-4369), alters the length of the evolutionary conserved anticodon loop from seven to eight bases.

Centronuclear myopathy. Histopathological aspects in ten patients with childhood onset.

Centronuclear myopathy is a rare congenital myopathy. According to the period of onset of signs and symptoms and the degree of muscular involvement three clinical forms are distinguished: severe neonatal; childhood onset; and adult onset. We describe herein the muscle biopsy findings of ten patients with the childhood onset form of the disease including three cases with ultrastructural study.

Mitochondrial DNA defects in Brazilian patients with chronic progressive external ophthalmoplegia.

We report herein on eleven Brazilian patients with mitochondrial DNA (mtDNA) deletions, found among thirteen patients with chronic progressive external ophthalmoplegia (CPEO) and ragged-red fibers (RRF). The molecular data was correlated with the morphological and clinical findings. The muscle biopsies were studied by histochemistry, immunohistochemistry and DNA analysis.

Mitochondrial encephalomyopathy and hypoparathyroidism associated with a duplication and a deletion of mitochondrial deoxyribonucleic acid.

Diabetes mellitus is the most frequent endocrinopathy associated with mitochondrial disorders, particularly in patients with duplications of mitochondrial DNA (mtDNA). Although hypoparathyroidism has also been described in mitochondrial diseases, there have been few molecular studies in these cases, most of which identified the presence of single mtDNA deletions in the patients' tissues. We studied muscle DNA of a 12-yr-old patient with incomplete Kearns-Sayre syndrome and hypoparathyroidism.

Fatal reducing body myopathy. Ultrastructural and immunohistochemical observations.

Two female infants who developed normally during infancy began to have progressive muscle hypotonia and weakness from 2 years 10 months and 2 years 3 months of ages, respectively. Both patients had rapidly progressive muscle weakness with death from respiratory failure at 4 years 11 months and 3 years 9 months, respectively. In addition to mild inflammation in their muscle biopsies, the most striking finding was the presence of numerous reducing bodies (RB) in almost all degenerating fibers.

Reducing bodies in distal myopathy with rimmed vacuole formation.

A 42-year-old woman with distal myopathy with rimmed vacuoles had intracytoplasmic inclusion bodies similar to those described in reducing body myopathy. Since these inclusions were found in fibers with high acid phosphatase activity and occasional rimmed vacuoles, their formation appeared to correlate with active myofibrillar degeneration, but their origin remains unknown.

[Periodic paralysis: anatomo-pathological study of skeletal muscles in 14 patients].

Periodic paralysis is a rare disease, characterized by transient weakness associated with abnormal levels of serum potassium. Muscle biopsy may show a wide range of abnormalities, vacuoles being more specifically linked to the disease. We analysed 17 muscle biopsies from 14 patients with periodic paralysis (14 hypokalemic, 2 hyperkalemic).

Carrier detection of Duchenne and Becker muscular dystrophy using muscle dystrophin immunohistochemistry.

To ascertain whether dystrophin immunohistochemistry could improve DMD/BMD carrier detection, we analyzed 14 muscle biopsies from 13 DMD and one BMD probable and possible carriers. All women were also evaluated using conventional methods, including genetic analysis, clinical and neurological evaluation, serum CK levels, EMG, and muscle biopsy. In 6 cases, there was a mosaic of dystrophin-positive and dystrophin-deficient fibers that allowed to make the diagnosis of a carrier state.

[Mitochondrial myopathy: report of 12 cases with histochemical study of the skeletal muscle].

Twelve patients with histologically defined mitochondrial myopathy are described. There were 9 males and 3 females. The age of onset ranged from birth to 35 years with a median of 14 years.