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PubMed2005

Preservation of in vitro muscle fiber function in dermatomyositis and inclusion body myositis: a single fiber study.

Five patients with untreated dermatomyositis, five with inclusion body myositis, and 16 healthy elderly volunteer subjects (controls) underwent open (dermatomyositis and inclusion body myositis) or percutaneous (controls) muscle biopsy. Biopsied muscles included deltoid, biceps and vastus lateralis. Chemically skinned single muscle fibers were activated with Ca(+2); the slack test was performed to determine maximal unloaded shortening velocity (Vo). Parameters measured include single fiber cross sectional area, maximal force, specific force and Vo. 429 Type I and 94 Type IIA fibers were studied. Cross sectional area and maximal force were greater in inclusion body myositis than dermatomyositis or control for Type I and IIA fibers. Specific force of Type I fibers was similar in inclusion body myositis and dermatomyositis but greater than in controls. Vo was greater in Type I, but not IIA, fibers in dermatomyositis compared with inclusion body myositis and controls. The force and velocity generating capacity of single muscle fibers is preserved in patients with dermatomyositis and inclusion body myositis suggesting that dysfunction of the contractile proteins does not contribute to clinical muscle weakness.

Adult↗

PubMed1995

Respiratory chain enzyme defects in patients with idiopathic inflammatory myopathy.

OBJECTIVE: To analyse muscle respiratory chain enzymes in idiopathic inflammatory myopathy. METHODS: Four consecutive female patients seen at our hospital with idiopathic inflammatory myopathy were studied. Muscle histochemical staining included NADH tetrazolium reductase and succinate dehydrogenase tests. Activity of rotenone sensitive NADH cytochrome c reductase (complex I and III) succinate dehydrogenase (complex II), succinate cytochrome c reductase (complex II and III), cytochrome c oxidase (complex IV), and citrate synthase (a mitochondrial matrix enzyme), was measured spectrophotometrically in muscle homogenates. Free carnitine, and short and long chain acylcarnitine esters were determined in muscle homogenates by a radiochemical procedure. RESULTS: Three patients had mitochondrial proliferation in nonregenerating muscle fibres; these patients had defects of respiratory chain enzyme complexes. Carnitine concentrations, measured in two of the four patients, revealed carnitine deficiency in one. CONCLUSION: Our results suggest that mitochondrial dysfunction may be present in patients with inflammatory myositis.

Adolescent↗

PubMed2005

Postural muscle dyscoordination in children with cerebral palsy.

The present paper gives an overview of the knowledge currently available on muscular dyscoordination underlying postural problems in children with cerebral palsy (CP). Such information is a prerequisite for developing successful therapeutic interventions in children with CP. Until now, three children with CP functioning at GMFCS (Gross Motor Function Classification System) level V have been documented. The children totally or partially lacked direction specificity in their postural adjustments and could not sit independently for more than 3 seconds. Some children functioning at GMFCS level IV have intact direction-specific adjustments, whereas others have problems in generating consistently direction-specific adjustments. Children at GMFCS levels I to III have an intact basic level of control but have difficulties in fine-tuning the degree of postural muscle contraction to the task-specific conditions, a dysfunction more prominently present in children with bilateral spastic CP than in children with spastic hemiplegia. The problems in the adaptation of the degree of muscle contraction might be the reason that children with CP, more often than typically developing children, show an excess of antagonistic coactivation during difficult balancing tasks and a preference for cranial-caudal recruitment during during reaching. This might imply that both stereotypies might be regarded as functional strategies to compensate for the dysfunctional capacity to modulate subtly postural activity.

Adaptation, Physiological↗

PubMed2005

Atypical shoulder muscle activation in multidirectional instability.

OBJECTIVE: Surface and intramuscular electromyography was used to investigate shoulder muscle activity in subjects with multidirectional instability (MDI). METHODS: Subjects (seven MDI, 11 control) performed repetitive shoulder abduction/adduction, flexion/extension and internal/external rotation movements on an isokinetic dynamometer. The activity of the deltoid, infraspinatus, supraspinatus, latissimus dorsi, and pectoralis major muscles were recorded using double-differential surface and intramuscular fine-wire electrodes. A repeated measures analysis of variance evaluated group differences in the amplitude, onset, termination and duration of the muscle activity. RESULTS: Significant activation parameter differences for the supraspinatus, infraspinatus, posterior deltoid and pectoralis major muscles were found in the subjects with MDI. The rotator cuff and posterior deltoid muscles demonstrated abbreviated periods of activity when performing internal/external rotation, despite activation amplitudes that were similar to the controls. In contrast, the activation of the pectoralis major differed from the control group in both the amplitude and time domains when performing shoulder extension. CONCLUSIONS: MDI is associated with atypical patterns of muscle activity that occur even when highly constrained movements are used to elicit the activity. SIGNIFICANCE: In addition to glenohumeral hyperlaxity, the results suggest that dysfunctional neuromuscular control of the rotator cuff is also a contributing factor to the pathoetiology of MDI.

Adult↗

PubMed2006

A method for quantifying dynamic muscle dysfunction in children and young adults with cerebral palsy.

Cerebral palsy (CP) is caused by a lesion to the brain resulting in adaptations to the structure and function of the muscles and compromised mobility. Spastic cerebral palsy is commonly assessed by the limb kinematics and kinetics measured in a gait laboratory. However, these measures do not directly quantify the patterns of muscle dysfunction that occur during movements. Recent studies have shown that electromyographic (EMG) signals from children with CP have abnormal magnitude, timing and frequency content. Here we demonstrate how wavelet decomposition of the EMG signals into time-frequency space coupled to principal component analysis of the EMG spectra can be used as a powerful tool to quantify the patterns of muscle dysfunction. Data were compared between 17 children with spastic diplegic CP and 36 asymptomatic controls for the rectus femoris, semimembranosus, medial gastrocnemius and tibialis anterior muscles. CP muscle generated higher mean EMG frequencies. Imbalances in activity between the tibialis anterior and medial gatrocnemius contributed to equinus ankle during the swing phase. Patterns of co-activations between antagonistic muscles differed between CP and asymptomatic patients and were EMG frequency dependent. Muscle dysfunction was greater in the distal compared to the proximal lower limb. Muscle dysfunction between the tibialis anterior and medial gastrocnemius was distinguished with 96% sensitivity at 95% specificity.

Adolescent↗

PubMed2006

Drug insight: Testosterone and selective androgen receptor modulators as anabolic therapies for chronic illness and aging.

Several regulatory concerns have hindered development of androgens as anabolic therapies, despite unequivocal evidence that testosterone supplementation increases muscle mass and strength in men; it induces hypertrophy of type I and II muscle fibers, and increases myonuclear and satellite cell number. Androgens promote differentiation of mesenchymal multipotent cells into the myogenic lineage and inhibit their adipogenic differentiation, by facilitating association of androgen receptors with beta-catenin and activating T-cell factor 4. Meta-analyses indicate that testosterone supplementation increases fat-free mass and muscle strength in HIV-positive men with weight loss, glucocorticoid-treated men, and older men with low or low-normal testosterone levels. The effects of testosterone on physical function and outcomes important to patients have not, however, been studied. In older men, increased hematocrit and increased risk of prostate biopsy and detection of prostate events are the most frequent, testosterone-related adverse events. Concerns about long-term risks have restrained enthusiasm for testosterone use as anabolic therapy. Selective androgen-receptor modulators that are preferentially anabolic and that spare the prostate hold promise as anabolic therapies. We need more studies to determine whether testosterone or selective androgen-receptor modulators can induce meaningful improvements in physical function and patient-important outcomes in patients with physical dysfunction associated with chronic illness or aging.

Aging↗

PubMed2002

Bladder dysfunction in acute transverse myelitis: magnetic resonance imaging and neurophysiological and urodynamic correlations.

AIMS: To evaluate micturition abnormalities in acute transverse myelitis and correlate these with evoked potentials, magnetic resonance imaging (MRI), and urodynamic findings. SETTING: Tertiary care teaching hospital. PATIENTS: 18 patients with acute transverse myelitis, aged 4-50 years; 15 had paraparesis and three quadriparesis. METHODS: Patients with acute transverse myelitis had a neurological evaluation and tibial somatosensory and motor evoked potential studies in the lower limbs. Spinal MRI was carried out using a 1.5 T scanner. Urodynamic studies were done using Dantec UD 5500 equipment. Neurological outcome was determined on the basis of Barthel index score at six months as poor, partial, or complete. In some patients, urodynamic studies were repeated at six and 12 months. RESULTS: Spinal MRI in 14 of the 18 patients revealed T2 hyperintense signal changes extending for at least three spinal segments in 13; one patient had normal MRI. In the acute stage, 17 patients had a history of urinary retention and one had urge incontinence. On follow up at six months two patients regained normal voiding, retention persisted in six, and storage symptoms developed in 10, of whom five also had emptying difficulties. Urodynamic studies showed an areflexic or hypocontractile bladder in 10, detrusor hyperreflexia with poor compliance in two, and detrusor sphincter dyssynergia in three. Early abnormal urodynamic findings commonly persisted at the six and 12 months examinations. Persistent abnormalities included detrusor hyperreflexia, dyssynergia, and areflexic bladder. The urodynamic abnormalities correlated with muscle tone and reflex changes but not with sensory or motor evoked potentials, muscle power, MRI signal changes, sensory level, or six months outcome. CONCLUSIONS: Bladder dysfunction is common in acute transverse myelitis and may be the only sequel. Urodynamic study is helpful in evaluating the bladder dysfunction and also in its management.

Adolescent↗

PubMedDate not supplied

Dynamic lateral patellar tilt in the anterior cruciate ligament-deficient knee. A magnetic resonance imaging analysis.

An open-configuration magnetic resonance imaging scanner was used to document patellar tracking abnormalities in 11 anterior cruciate ligament-injured knees. The contralateral normal knees were used as controls. Images were obtained with the quadriceps muscles at rest (knee flexion at 40 degrees, 25 degrees, and 10 degrees) and with the quadriceps muscles contracted (knee flexion at 40 degrees and 25 degrees). When the quadriceps muscles were at rest there were no differences in patellar alignment between the anterior cruciate ligament-injured knees and the contralateral normal knees. When the quadriceps muscles were maximally contracted at 40 degrees of flexion, the patellae of the anterior cruciate ligament-injured knees tilted laterally 3.6 degrees relative to the resting state. When the quadriceps muscles were contracted at 25 degrees of flexion, the patellae of the anterior cruciate ligament-injured knees tilted laterally approximately 4 degrees relative to the resting state. Quadriceps-active lateral patellar tilt at 25 degrees of flexion was greater in the anterior cruciate ligament-injured knees than in the contralateral normal knees, and it correlated with instrumented measurements of anterior tibial translation. Dynamic lateral patellar tilt during open kinetic chain exercises and during other activities that produce anterior tibial translation may contribute to extensor mechanism dysfunction in the anterior cruciate ligament-injured knee.

Adult↗

PubMed1998

Pharyngeal dysphagia caused by isolated myogen dystrophy of musculus cricopharyngeus.

Five patients suffering from idiopathic cricopharyngeal dysfunction (without Zenker's diverticulum) were treated surgically. Together with cricopharyngeomyotomy biopsies were taken at the level of the cricopharyngeus. Histological, enzyme hystochemical and electronmicroscopic examinations were performed on all patients. In two cases the histology revealed myogen dystrophy (presence of necrosis, myophagocytosis, abnormal fiber structure, basophilic fibers, fibrosis, mild cellular reaction and predominancy of fiber type I). Since the complete patient evaluation (clinical features, electromyography, serum creatinin phosphokinase level, etc.) could rule out any general, muscle disorders, the cause of the idiopathic pharyngeal dysfunction must have been in these two cases an isolated myogen dystrophy of the cricopharyngeus.

Aged↗

PubMed1994

Amylin regulation of fuel metabolism.

The 37-amino acid amylin, co-secreted from the pancreatic beta cells with insulin in response to nutrient stimuli has actions in a number of tissues of metabolic interest. In muscle it opposes glycogen synthesis and activates glycogenolysis, an action likely to underly its stimulation of lactate flux. Amylin therefore appears to have the effect of transposing carbon from peripheral stores to the liver, where it is made available for hepatic synthesis of glucose, glycogen, and lipid. While amylin induces insulin resistance in skeletal muscle, it does not oppose insulin action in fat and may therefore favor fuel deposition in this tissue. Amylin acts on the beta cell to inhibit insulin secretion. Relative impairment of insulin secretion, muscle insulin resistance, relatively preserved insulin sensitivity in fat, increased lactate turnover, and increased hepatic glucose production are features of insulin resistance and early non-insulin-dependent diabetes mellitus. Amylin is elevated in these dysfunctional metabolic states and may be involved in their pathogenesis.

Amyloid↗

PubMedDate not supplied

Genetics, an alternative way to discover, characterize and understand ion channels.

1. The conventional approach to understanding the structure and properties of ion channels has been to use physiological characterization. 2. Purification and molecular cloning of ion channel genes has enabled more detailed structure-function analyses to be undertaken. 3. An alternative approach to the identification of genes of pathophysiological importance has been the use of genetic linkage approaches and positional cloning or positional candidate analysis of ion channel genes. 4. Using genetic approaches, mutations have been described that cause inherited neurological disorders of neurons (e.g. epilepsy, migraine, deafness, ataxia and startle disease), skeletal muscle (myotonia, malignant hyperthermia, periodic paralysis and myasthenia) and cardiac muscle (long QT syndrome and ventricular fibrillation). 5. For each disease, gene structure-function analyses of the mutant alleles have provided further insights into the biology of ion channels. 6. The present brief review examines the methods used in genetic linkage studies and positional cloning of disease genes. Understanding how ion channel gene mutations give rise to dysfunctional channels will be important in defining and treating the episodic and chronic channelopathies.

Alleles↗

PubMed2001

Oscillation in the activities of MEK/ERK1/2 during cardiopulmonary bypass in pigs.

BACKGROUND: Because cardiopulmonary bypass (CPB) is associated with edema and vasoreactive dysfunction and ERK1/2 pathway is involved in vascular contractility and permeability, a time course study was performed to monitor MEK/ERK1/2/Elk-1 activities during CPB. METHODS: Pigs were subjected to normothermic CPB for 90 minutes followed by post-CPB perfusion for 180 minutes. Atrial myocardium was sampled before CPB, 5 minutes after CPB onset, 5 minutes after weaning from CPB, and at the end of post-CPB. Skeletal muscle and mesenteric vessels samples were harvested before CPB, 5 minutes after CPB institution, and every 30 minutes thereafter to the end of post-CPB. Samples were analyzed by immunoblotting and immunofluorescence microscopy with the use of specific antibodies against active (phosphorylated) forms of ERK1/2, MEK1/2, and Elk-1. RESULTS: Pigs that were subjected to CPB showed an increase in phospho-ERK1/2 after 30 minutes of CPB, followed by a decrease after 90 minutes. Another phosphorylation peak was observed 30 to 60 minutes of post-CPB, followed by a decrease to below baseline at the end of reperfusion. MEK1/2 and Elk-1 activation profiles paralleled ERK1/2 activity peaks. Control samples showed no significant increase above basal levels. CONCLUSIONS: Activation of MEK/ERK1/2/Elk-1 pathways closely follows major CPB surgical manipulations (institution and termination) and could be related to morbidity during and after CPB.

Animals↗

PubMed2006

Impaired exercise-induced blood volume in type 2 diabetes with or without peripheral arterial disease measured by continuous-wave near-infrared spectroscopy.

OBJECTIVE: Diabetes is a significant risk factor for peripheral arterial disease (PAD) and is associated with accelerated atherosclerosis and limb loss. However, the pathophysiology involved in PAD is unclear. This study was conducted to evaluate the hemodynamic response to exercise of patients with and without diabetes and PAD. RESEARCH DESIGN AND METHODS: The hemodynamic response in calf muscles of patients with diabetes, PAD, or both was determined using near-infrared spectroscopy (NIRS). Patients performed both a plantar-flexion and treadmill-walking exercise regimen. RESULTS: Skeletal muscle capillary blood volume expansion during exercise, as measured by NIRS, was significantly impaired in the lower extremities of diabetic patients with a normal ankle-brachial index. The relative deoxygenation and oxygenation recovery times measured by NIRS correlates significantly with the presence of PAD. CONCLUSIONS: Patients with diabetes have reduced capillary volume expansion even without PAD. This is likely due to impaired vasodilation secondary to endothelial dysfunction. Further studies are needed to determine whether pharmaceutical intervention improves the blood volume expansion in the diabetic state.

Aged↗

PubMed1997

[Skeletal musculature modifications and mechanisms of fatigue in chronic heart failure].

The majority of patients with chronic heart failure (CHF) have a decreased exercise tolerance. It has not been well established if muscle fatigue is related to a peripheral myopathy with specific metabolic, histologic and biochemical abnormalities. CHF patients demonstrate depressed oxidative capacity and activation of anaerobic glycolysis, leading to a reduction in the energy substrates. In addition, the skeletal muscles of the lower limbs demonstrate a shift toward type IIb fibers. Many factors, such as prolonged immobilization, reduced blood flow and neuroendocrine activation, can be cited in order to explain the origin of this myopathy. Recent studies show that immobilization is not the only reason for modifications in skeletal muscle composition, since patients with disuse atrophy show an increased percentage in myosin heavy chain I, while IIb is decreased. The opposite pattern is observed in CHF. It would appear that several factors such as deconditioning, prolonged immobilization and reduced blood flow, may produce muscular atrophy. The reasons behind specific changes in fibre composition may be found in metabolic factors such as insulin resistance, TNF levels and dysfunction of the ergo-metabolo muscle receptors.

Chronic Disease↗

PubMed1997

Post-ischaemic organ dysfunction: a review.

OBJECTIVES: The aim of this review is to consider the pathophysiology of ischaemia-reperfusion in organs that may be affected by either its local or remote consequences. Potential therapeutic strategies are also considered. DESIGN: A general discussion of the biochemical (including oxygen free radicals, complement, cytokines) and cellular events (endothelial cells, neutrophils) responsible for the mediation of reperfusion injury is presented, with special consideration of the organ-specific differences affecting the myocardium, central nervous system, gut, liver, kidney and skeletal muscle. Similarly, events which promote remote organ injury are described. CONCLUSIONS: Although it is recognised that prolonged ischaemia results in tissue and organ damage, the concept of reperfusion-induced tissue injury, defined as tissue damage occurring as a direct consequence of revascularisation, is relatively recent. Such events may increase the morbidity and mortality of patients undergoing vascular reconstruction, trauma surgery and transplantation. A clear understanding of the factors responsible for its development is therefore vital if protocols that reduce its impact are to be developed.

Animals↗

PubMed2001

Transfection of MCF-7 carcinoma cells with human integrin alpha7 cDNA promotes adhesion to laminin.

The laminin-binding alpha7beta1 integrin receptor is highly expressed by skeletal and cardiac muscles, and has been suggested to be a crucial molecule during myogenic cell migration and differentiation. Absence of integrin alpha7 subunit contributes to a form of muscular dystrophy in integrin alpha7 null mice, whereas specific mutations in the alpha7 gene are associated in humans with congenital myopathy. To examine in more detail the potential role of integrin alpha7 in human-related muscular disorders, we cloned alpha7 cDNA by RT-PCR from human skeletal muscle mRNA and then expressed the full-length human integrin alpha7 cDNA by transfection in several cell lines including MCF-7, COS-7, and NIH3T3 cells. The isolated cDNA corresponds to the human alpha7X2B alternative splice form. Expression of human alpha7 was further confirmed by transfection of chimeric human/mouse alpha7 cDNA constructs. To demonstrate the functionality of expressed human alpha7, adhesion experiments with transfected MCF-7 cells have confirmed the specific binding of human alpha7 to laminin. In addition, mouse polyclonal and monoclonal antibodies were generated against the extracellular domain of human alpha7 and used to analyze by flow cytometry MCF-7 and NIH3T3 cells transfected with the full-length of human alpha7 cDNA. These results show for the first time the exogenous expression of functional full-length human alpha7 cDNA, as well as the development of monoclonal antibodies against the human alpha7 extracellular domain. Antibodies developed will be useful for further analysis of human disorders involving alpha7 dysfunction and facilitate isolation of muscle stem cells (satellite cells) and thereby expand the opportunities for genetically modified transplantation treatment of human disease.

3T3 Cells↗

PubMed1995

Late-onset mitochondrial myopathy.

In the majority of patients with mitochondrial encephalomyopathies, signs and symptoms appear in the first three decades of life. Here we report on a group of 9 older patients (> 69 years old) with late-onset skeletal myopathy characterized by focal accumulations of deleted mitochondrial DNAs (mtDNAs) and altered muscle energy status, suggestive of a primary mitochondrial disease. The clinical phenotype was somewhat variable. However, all patients shared a common feature of insidious moderate proximal muscle weakness; some also showed fatigability and axial muscle weakness. In situ hybridization analysis demonstrated accumulations of messenger RNAs transcribed from deleted mtDNAs in a relatively large number of muscle fibers in the patient group. These fiber segments appeared as ragged red with the modified Gomori trichrome stain and hyperreactive with a modified succinate dehydrogenase stain. Most were negative for cytochrome c oxidase activity. On transverse sections their mean frequency was 0.69% (trichrome) and 1.97% (succinate dehydrogenase) significantly above control levels. Multiple mtDNA deletions were demonstrated by the polymerase chain reaction in both the patients and an age-matched control group, but not in younger control subjects. Phosphorus 13 magnetic resonance spectroscopy of resting muscle showed a decreased phosphocreatine-inorganic phosphate ratio in the patient group. The myopathy in this group of patients appears to result from mitochondrial dysfunction related to the clonal expansion of different mtDNA deletions in individual fiber segments. While the origin of the mtDNA mutations is not clear, the phenotype seems to represent an exaggerated form of what is observed in the normal aging process.

Aged↗

PubMed1998

Increased vulnerability to eccentric exercise-induced dysfunction and muscle injury after concentric training.

OBJECTIVE: To test whether concentric (CON)-only resistance training increases the vulnerability to eccentric (ECC) exercise-induced dysfunction and muscle injury. DESIGN: Before-after trial. SETTING: General community. PATIENTS OR OTHER PARTICIPANTS: Nine men (77 +/- 3 kg body weight) who were not trained in resistance exercise. INTERVENTION: Nine weeks of CON-only training of the left quadriceps femoris (QF); performance of 10 sets of 10 ECC actions with each QF using a load equivalent to 85% of the posttraining CON 1-repetition maximum (1RM). MAIN OUTCOME MEASURES: CON 1RM for the untrained and trained QF measured immediately after training, and again 1, 3, 8, and 10 days after the bout of ECC exercise; cross-sectional area and spin-spin relaxation time (T2) of each QF determined by magnetic resonance imaging (MRI) before and 3 days after the ECC exercise bout. RESULTS: As a result of the ECC bout, the CON 1RM was reduced by approximately 30% in the trained limb and 16% in the untrained limb. Strength did not return to normal in the trained limb even after 10 days of recovery; however, in the untrained limb strength was restored by day 8. As assessed by MRI, the trained limb showed a greater area of muscle injury compared with the untrained QF. The T2 of the injured area was similar in both limbs, suggesting that the intensity of injury was similar, but more widespread in the trained limb. CONCLUSION: CON-only training increases the vulnerability to ECC exercise-induced dysfunction and muscle injury, probably by increasing the CON 1RM, thus allowing the individual to be exposed to greater ECC loading potential.

Analysis of Variance↗