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Biomedical subjects

S Servidei

Publications and source records attributed to S Servidei.

At least 109 records · Page 6Linked to original sources
PubMed1990

Impaired skin fibroblast carnitine uptake in primary systemic carnitine deficiency manifested by childhood carnitine-responsive cardiomyopathy.

Evidence is emerging that primary systemic carnitine deficiency, a potentially lethal but eminently treatable inborn error of fatty acid oxidation, involves a cellular defect in the uptake of carnitine. We present four unrelated children with primary carnitine-responsive cardiomyopathy, weakness (with or without hypoketotic hypoglycemic encephalopathy), low serum and/or tissue carnitine concentrations, and severe renal carnitine leak. Dicarboxylic acids were absent in the urine of three children who were tested, and all four had a rapid and dramatic improvement in cardiac function, strength, and somatic growth after carnitine therapy. We studied carnitine uptake in cultured skin fibroblasts from all four children and seven of the eight healthy nonconsanguinous parents. [3H]L-carnitine uptake was evaluated in vitro under linear time kinetics. Substrate concentrations were varied from 0.1 to 1000 microM. Physiologic uptake was determined at carnitine concentrations between 0.1 and 50 microM. Nonspecific uptake was determined at a concentration of 10 mM. The four patients had negligible uptake throughout the physiologic range, implying a marked deficiency in the specific high-affinity, low-concentration, carrier-mediated uptake mechanism. At a concentration of 5 mumol/L, the mean velocity of uptake in the four patients was 2% of control values. Their parents showed intermediate maximal rates of carnitine uptake ranging from 13 to 44% of control Vmax values, but normal Km values, suggesting that the heterozygotes had a reduced number of normal functioning carnitine transporters. The observed reduction in Vmax values for the parents supports an autosomal recessive inheritance pattern and may be a more sensitive indicator of heterozygosity than serum carnitine concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Transport, Active↗
PubMed1990

Nucleus-driven multiple large-scale deletions of the human mitochondrial genome: a new autosomal dominant disease.

We studied several affected and one nonaffected individuals belonging to three unrelated pedigrees. The pathological trait was an autosomal dominant mitochondrial myopathy due to large-scale multiple deletions of the mitochondrial genome. Clinically, symptomatic patients had progressive external ophthalmoplegia, muscle weakness and wasting, sensorineural hypoacusia, and, in some cases, vestibular areflexia and tremor. The muscle biopsies of all patients examined showed ragged-red fibers, neurogenic changes, and a partially decreased histochemical reaction to cytochrome c oxidase. Multiple mtDNA heteroplasmy was detected in the patients by both Southern blot analysis and PCR amplification, whereas the unaffected individual had the normal homoplasmic hybridization pattern. These findings confirm and add further details to the existence of a new human disease--defined clinically as a mitochondrial myopathy, genetically as a Mendelian autosomal dominant trait, and molecularly by the accumulation of multiple, large-scale deletions of the mitochondrial genome--that is due to impaired nuclear control during mtDNA replication.

Adolescent↗
PubMed1989

An autosomal dominant disorder with multiple deletions of mitochondrial DNA starting at the D-loop region.

Deletions of muscle mitochondrial DNA (mtDNA) have recently been found in patients with mitochondrial myopathy. However, as most of the described cases were sporadic, and individual deletions involved different portions of mtDNA, the mechanism(s) producing the molecular lesions, as well as their mode of transmission, remain unclear. By studying families with mtDNA heteroplasmy, valuable information can be obtained about the role of inheritable factors in the pathogenesis of these disorders. We have studied four members of a family with autosomal dominant mitochondrial myopathy. Multiple deletions, involving the same portion of muscle mtDNA, were identified in all patients. Sequence analysis of the mutant mtDNAs, performed after DNA amplification by the polymerase-chain reaction showed that all the deletions start within a 12-nucleotide stretch at the 5' end of the D-loop region, a site of active communication between the nucleus and the mtDNA. The data indicate that a mutation of a nuclear-coded protein can destroy the integrity of the mitochondrial genome in a specific, heritable way.

Base Sequence↗
PubMed1989

Mitochondrial DNA deletions in progressive external ophthalmoplegia and Kearns-Sayre syndrome.

We investigated the correlations of deletions of mitochondrial DNA in skeletal muscle with clinical manifestations of mitochondrial myopathies, a group of disorders defined either by biochemical abnormalities of mitochondria or by morphologic changes causing a ragged red appearance of the muscle fibers histochemically. We performed genomic Southern blot analysis of muscle mitochondrial DNA from 123 patients with different mitochondrial myopathies or encephalomyopathies. Deletions were found in the mitochondrial DNA of 32 patients, all of whom had progressive external ophthalmoplegia. Some patients had only ocular myopathy, whereas others had Kearns-Sayre syndrome, a multisystem disorder characterized by ophthalmoplegia, pigmentary retinopathy, heart block, and cerebellar ataxia. The deletions ranged in size from 1.3 to 7.6 kilobases and were mapped to different sites in the mitochondrial DNA, but an identical 4.9-kilobase deletion was found in the same location in 11 patients. Biochemical analysis showed decreased activities of NADH dehydrogenase, rotenone-sensitive NADH-cytochrome c reductase, succinate-cytochrome c reductase, and cytochrome c oxidase, four enzymes of the mitochondrial respiratory chain containing subunits encoded by mitochondrial DNA. We conclude that deletions of muscle mitochondrial DNA are associated with ophthalmoplegia and may result in impaired mitochondrial function. However, the precise relation between clinical and biochemical phenotypes and deletions remains to be defined.

Blotting, Southern↗
PubMed1989

Exercise intolerance, lactic acidosis, and abnormal cardiopulmonary regulation in exercise associated with adult skeletal muscle cytochrome c oxidase deficiency.

A 27-yr-old woman with lifelong severe exercise intolerance manifested by muscle fatigue, lactic acidosis, and prominent symptoms of dyspnea and tachycardia induced by trivial exercise was found to have a skeletal muscle respiratory chain defect characterized by low levels of reducible cytochromes a + a3 and b in muscle mitochondria and marked deficiency of cytochrome c oxidase (complex IV) as assessed biochemically and immunologically. Investigation of the pathophysiology of the exercise response in the patient revealed low maximal oxygen uptake (1/3 that of normal sedentary women) in cycle exercise and impaired muscle oxygen extraction as indicated by profoundly low maximal systemic arteriovenous oxygen difference (5.8 ml/dl; controls = 15.4 +/- 1.4, mean +/- SD). The increases in cardiac output and ventilation during exercise, normally closely coupled to muscle metabolic rate, were markedly exaggerated (more than two- to threefold normal) relative to oxygen uptake and carbon dioxide production accounting for prominent tachycardia and dyspnea at low workloads. Symptoms in our patient are similar to those reported in other human skeletal muscle respiratory chain defects involving complexes I and III, and the exaggerated circulatory response resembles that seen during experimental inhibition of the mitochondrial respiratory chain. These results suggest that impaired oxidative phosphorylation in working muscle disrupts the normal regulation of cardiac output and ventilation relative to muscle metabolic rate in exercise.

Acidosis, Lactic↗
PubMed1989

Disorders of glycogen metabolism of muscle.

Glycogen is a crucial source of energy in the initial stages of muscle activity and during exercise of high intensity. There are 10 well-defined biochemical defects of glycogen metabolism expressed in muscle and affecting the following enzymes: alpha 1,4 glucosidase (glycogenesis type II), debrancher enzyme (III), brancher enzyme (IV), phosphorylase (V), phosphofructokinase (VII), phosphorylase b kinase (VIII), phosphoglycerate kinase (IX), phosphoglycerate mutase (X), lactate dehydrogenase (XI). These disorders cause two main syndromes: one characterized by exercise intolerance with cramps and myoglobinuria, the other by fixed weakness. However, there are examples of clinical and biochemical heterogeneity for each disease, and molecular genetic analysis is already showing evidence of genetic heterogeneity. Although our understanding of the biochemical errors has progressed considerably, the pathogenesis of symptoms and signs remains incomplete.

Enzymes↗
PubMed1988

Late onset scleroatonic familial myopathy (Ullrich disease): a study of two sibs.

We report on sibs with scleroatonic familial myopathy (Ullrich disease). Muscular weakness was of relatively late onset in relation to other cases reported in the literature. Short stature and moderate growth hormone deficiency were noted during follow-up. Differential diagnosis with other neuromuscular disorders, particularly rigid spine syndrome, is discussed.

Abnormalities, Multiple↗
PubMed1988

McArdle's disease: biochemical and molecular genetic studies.

We have analyzed muscle biopsy specimens from 48 patients with biochemically proven phosphorylase deficiency (McArdle's disease) by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting, and immunotitration (enzyme-linked immunosorbent assay [ELISA]). Thirty-five of the 42 patients studied by SDS-PAGE and immunoblot, and 41 of the 48 patients studied by ELISA had no detectable enzyme protein. Six patients had markedly decreased phosphorylase protein by all three assays, and only 1 patient had a normal amount of protein. No apparent correlation existed between the presence or absence of enzyme protein and the clinical presentation or muscle glycogen concentration. Northern analysis was performed on muscle RNA in 4 patients: messenger RNA was normal in 2, abnormally short in 1, and absent in the fourth, indicating heterogeneity of the molecular lesion in McArdle's disease.

Biopsy↗
PubMed1988

Late-onset muscle phosphofructokinase deficiency.

A 75-year-old man had a 10-year history of slowly progressive limb weakness without cramps or myoglobinuria. Clinical, morphologic, and biochemical studies showed muscle phosphofructokinase (PFK) deficiency. Erythrocyte PFK activity in his asymptomatic daughter was 63% of normal, compatible with a carrier state. The chronic myopathic variant of muscle PFK deficiency appears to be transmitted as an autosomal recessive trait and may be due to a distinct genetic defect.

Aged↗
PubMed1987

Cytochrome c oxidase deficiency in Leigh syndrome.

We studied 6 mitochondrial enzymes in crude extracts and isolated mitochondria from 5 children with pathologically proven subacute necrotizing encephalomyelopathy (Leigh syndrome). Samples were taken from brain (5 patients), skeletal muscle (4 patients), liver (4 patients), kidney (4 patients), heart (1 patient), and cultured fibroblasts (3 patients). An isolated defect of cytochrome c oxidase (COX) activity was found in brain (decrease of activity to 15 to 39% of the normal mean), muscle (9 to 20%), kidney (1 to 67%), and in the 1 available heart (4%) from a patient with cardiopathy. COX activity was also decreased in liver of 3 patients (2 to 13% of normal) and in cultured fibroblasts of 2 patients (18 and 27%), but it was normal in both liver and fibroblasts from 1 patient. Immunotitration using polyclonal antibodies against human heart COX showed essentially normal amounts of cross-reacting enzyme protein in various tissues from different patients. Electrophoresis of COX immunoprecipitated from brain mitochondrial extracts showed normal patterns of COX subunits in 2 patients. This study confirms the theory that COX deficiency is an important cause of Leigh syndrome.

Brain↗
PubMed1987

Myo-, neuro-, gastrointestinal encephalopathy (MNGIE syndrome) due to partial deficiency of cytochrome-c-oxidase. A new mitochondrial multisystem disorder.

A 42-year-old woman had a 10-year history of external ophthalmoplegia, malabsorption resulting in chronic malnutrition, muscle atrophy and polyneuropathy. Computer tomography revealed hypodensity of her cerebral white matter. A metabolic disturbance consisted of lactic acidosis after moderate glucose loads with increased excretion of hydroxybutyric and fumaric acids. Post-mortem studies revealed gastrointestinal scleroderma as the morphological manifestation of her malabsorption syndrome, ocular and skeletal myopathy with ragged red fibers, peripheral neuropathy, vascular abnormalities of meningeal and peripheral nerve vessels. Biochemical examination of the liver and muscle tissues revealed a partial defect of cytochrome-c-oxidase (complex IV of the respiratory chain). This mitochondrial multisystem disorder may represent a separate entity to be classified between the spectrum of myoencephalopathies and oculo-gastrointestinal muscular dystrophy.

Adult↗
PubMed1987

Infectivity of influenza B virus in cultured human muscle.

Severe muscle symptoms, particularly in children, are frequently associated with influenza B virus infection. In this study we examined the effects of influenza B virus (Lee Strain) on cultured human muscle by light and electron microscopy (EM), immunofluorescence, hemadsorption and plaque assays. Muscle injury was also evaluated by the appearance of muscle-specific creatine kinase (CK) in the culture medium. By fluorescence immunocytochemistry viral antigen was demonstrated in muscle cell nuclei within 3 h postinoculation (p.i.) and in the cytoplasm at 6 h p.i. Membrane-associated viral antigen was seen at 16 h p.i., at which time budding influenza virus-like particles could be demonstrated by EM, both in myoblasts and multinucleated myotubes. At 16 h all cells were hemadsorption positive. Plaque assays showed peak virus production at 48 h (p.i.), at which time cytopathic effects (cell retraction, pycnosis and cytoplasmic vacuolization) were prominent and some cells detached from the substratum. Leakage of muscle-specific CK isozyme into the culture medium could be demonstrated as early as 6 h p.i. with peak enzyme activity around 40-48 h p.i. Cytopathic changes and virus production were observed both in myoblasts and myotubes indicating that both cell types are susceptible.

Creatine Kinase↗
PubMed1987

Mitochondrial myopathies.

The mitochondrial myopathies or encephalomyopathies with known biochemical defects can be divided into 5 groups: (1) defects of mitochondrial transport, such as CPT deficiency or carnitine deficiencies; (2) defects of substrate utilization, such as PDHC deficiency or defects of beta-oxidation; (3) defects of the Krebs cycle, such as fumarase deficiency; (4) defects of oxidation-phosphorylation coupling, such as Luft disease, and (5) defects of the respiratory chain. These disorders are reviewed, with particular emphasis on the defects of the respiratory chain. Defects of complex I, III and IV show remarkable clinical and biochemical heterogeneity. All 3 complexes contain some subunits encoded by mtDNA and others encoded by nuclear DNA. At least some of the cytoplasmically made subunits appear to be tissue specific and may be developmentally regulated, thus explaining the genetic heterogeneity of these disorders.

Adenosine Triphosphatases↗
PubMed1987

Severe cardiopathy in branching enzyme deficiency.

A 7 1/2-year-old girl had exercise intolerance and exertional dyspnea. Four months later, congestive heart failure developed, with recurrent chylous pleural effusions, and she died at age 8 1/2 years. Endomyocardial biopsy tissue showed abundant PAS-positive, diastase-resistant cytoplasmic deposits. Similar inclusions were seen in muscle, skin, and liver specimens. Postmortem studies showed that the abnormal polysaccharide was especially abundant in heart and muscle, but was also present in all other tissues, including the central nervous system. Glycogen isolated from heart, muscle, and spinal cord showed a shift of the iodine spectrum toward higher than normal wavelengths. Branching enzyme activity was lacking in the muscle biopsy specimen and in all postmortem tissues; glycogenolytic enzymes had normal activities. These studies show that cardiomyopathy can be the first symptom of generalized branching enzyme deficiency and that the degree of accumulation of the abnormal polysaccharide may vary in different tissues.

Biopsy↗
PubMed1987

Mitochondrial encephalomyopathy and partial cytochrome c oxidase deficiency.

A 52-year-old man had slowly progressive weakness and wasting of limb-muscles, sensorineural hearing loss, and complex partial seizures. CT showed cerebral atrophy, but he was not demented. Muscle biopsy showed ragged-red fibers and decreased histochemical stain for cytochrome c oxidase. Biochemical studies showed decreased cytochrome c oxidase activity in crude muscle extracts and in isolated mitochondria (44 and 30% of normal), while other mitochondrial enzymes were normal. A comparable decrease of immunologically reactive enzyme protein was shown by immunotitration with antibodies against human heart cytochrome c oxidase. Partial defects of cytochrome c oxidase may cause adult-onset, slowly progressive mitochondrial encephalomyopathies.

Atrophy↗