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At least 991 records · Page 55Linked to original sources
PubMed2000

Clinical, biochemical and molecular genetic correlations in Friedreich's ataxia.

Friedreich's ataxia (FRDA) is an autosomal recessive disorder with a frequency of 1 in 50 000 live births. In 97% of patients it is caused by the abnormal expansion of a GAA repeat in intron 1 of the FRDA gene on chromosome 9, which encodes a 210 amino acid protein called frataxin. Frataxin is widely expressed and has been localized to mitochondria although its function is unknown. We have investigated mitochondrial function, mitochondrial DNA levels, aconitase activity and iron content in tissues from FRDA patients. There were significant reductions in the activities of complex I, complex II/III and aconitase in FRDA heart. Respiratory chain and aconitase activities were decreased although not significantly in skeletal muscle, but were normal in FRDA cerebellum and dorsal root ganglia, although there was a mild decrease in aconitase activity in the latter. Mitochondrial DNA levels were reduced in FRDA heart and skeletal muscle, although in skeletal muscle this was paralleled by a decline in citrate synthase activity. Increased iron deposition was seen in FRDA heart, liver and spleen in a pattern consistent with a mitochondrial location. The iron accumulation, mitochondrial respiratory chain and aconitase dysfunction and mitochondrial DNA depletion in FRDA heart samples largely paralleled those in the yeast YFH1 knockout model, suggesting that frataxin may be involved in mitochondrial iron regulation or iron sulphur centre synthesis. However, the severe deficiency in aconitase activity also suggests that oxidant stress may induce a self-amplifying cycle of oxidative damage and mitochondrial dysfunction, which may contribute to cellular toxicity.

Aconitate Hydratase↗
PubMed1984

Polyneuropathy in critically ill patients.

Five patients developed a severe motor and sensory polyneuropathy at the peak of critical illness (sepsis and multiorgan dysfunction complicating a variety of primary illnesses). Difficulties in weaning from the ventilator as the critical illness subsided and the development of flaccid and areflexic limbs were early clinical signs. However, electrophysiological studies, especially needle electrode examination of skeletal muscle, provided the definite evidence of polyneuropathy. The cause is uncertain, but the electrophysiological and morphological features indicate a primary axonal polyneuropathy with sparing of the central nervous system. Nutritional factors may have played a role, since the polyneuropathy improved in all five patients after total parenteral nutrition had been started, including the three patients who later died of unrelated causes. The features allow diagnosis during life, and encourage continued intensive management since recovery from the polyneuropathy may occur.

Adult↗
PubMed2006

Obesity-related derangements in metabolic regulation.

An epidemic surge in the incidence of obesity has occurred worldwide over the past two decades. This alarming trend has been triggered by lifestyle habits that encourage overconsumption of energy-rich foods while also discouraging regular physical activity. These environmental influences create a chronic energy imbalance that leads to persistent weight gain in the form of body fat and a host of other abnormalities in metabolic homeostasis. As adiposity increases, so does the risk of developing comorbidities such as diabetes, hypertension, and cardiovascular disease. The intimate association between obesity and systemic metabolic dysregulation has inspired a new area of biochemistry research in which scientists are seeking to understand the molecular mechanisms that link chronic lipid oversupply to tissue dysfunction and disease development. The purpose of this chapter is to review recent findings in this area, placing emphasis on lipid-induced functional impairments in the major peripheral organs that control energy flux: adipose tissue, the liver, skeletal muscle, and the pancreas.

Adipose Tissue↗
PubMed1980

Metabolic effects of L-phenyllactate in perfused kidney, liver, and muscle.

L-Phenyllactate (L-PL) can promote growth of normal and germ-free rats eating a phenylalanine (Phe)-free diet, but the sites and pathway of its conversion to Phe have not been extensively studied. We perfused rat kidneys, livers, and hindquarters with L-PL and measured Phe release and effects on organ function. Renal release of Phe the during perfusion with L-PL was 3.0 times control (P less than 0.001) and increased 2.5-fold with addition of glutamine (P less than 0.001); with phenylpyruvate (PP), it was 3.5 times control (P less than 0.001). Sixty-four percent of L-PL disappearance could be accounted for by appearance of PP and Phe. Although renal gluconeogenesis from lactate was inhibited 28% by L-PL, neither glomerular filtration rate (0.44 ml . min-1 . g wet weight-1) nor sodium reabsorption (94.3%) were impaired. There was no net release of Phe or PP by rat livers or hindquarters perfused with L-PL and hepatic gluconeogenesis, urea synthesis, and potassium balance were unaffecte by L-PL. Thus, the kidney, but not skeletal muscle or liver, converts L-PL to Phe, presumably by the pathway L-PL leads to PP leads to Phe. In acute experiments with isolated organs, L-PL does not cause significant renal or hepatic dysfunction.

Animals↗
PubMedDate not supplied

Hyperthyroid myopathy with mitochondrial paracrystalline rectangular inclusions.

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.

Aged↗
PubMed1995

[Complete deficiency of adhalin (50 kDa DAG) in skeletal muscle of malignant limb-girdle muscular dystrophy].

Malignant limb-girdle muscular dystrophy was first described by Miyoshi and co-workers in 1966, and has clinical features similar to Duchenne muscular dystrophy but is inherited through an autosomal recessive trait. This paper describes a patient with malignant limb-girdle muscular dystrophy with complete deficiency of adhalin (50 kDa dystrophin-associated glycoprotein (DAG)) in skeletal muscle. The patient was an 11-year-old Japanese girl whose parents were cousin. She learned to walk at one year and 3 months of age. Her gait became unsteady at 3 years of age, and motor dysfunction in the lower extremities progressed thereafter. At 8 years of age, she had difficulty in standing up from a sitting position, but could walk without assistance. At 11 years, she could walk with support, but could not stand up without assistance. Her intelligence was normal. Muscle atrophy was not apparent due to obesity, but her calves appeared hypertrophic. She had generalized muscle weakness, predominantly in the pelvic girdle muscle. Muscle tone was slightly hypotonic, and deep tendon reflexes of the legs were absent or hypoactive. Her sensory system appeared normal. Serum creatine kinase level was elevated to 30 times above the upper limit of the normal range in the patient and normal in her parents. EMG showed a mild myopathic pattern. CT scan of muscle revealed marked low density in the upper legs and mild in the lower legs. Muscle histology showed muscle fiber necrosis with a small number of regenerating fibers. Opaque fibers were occasionally observed, but not as many as in Duchenne type. Fiber splitting was seen frequently.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1995

The relationship between muscle tenderness and craniomandibular disorders: a study of 35-year-olds from the general population.

Of a random sample of 345 subjects aged 35 years and drawn from the general population of Västerbotten County, Sweden, 276 (80%) participated in an epidemiologic survey on muscle tenderness of the jaw, neck, shoulder, arm, hand, and calf, and on the prevalence of signs and symptoms of craniomandibular disorders. The control group consisted of 144 subjects (52%) who had no tenderness. The remaining subjects were separated into groups: (1) 59 subjects (21%) with tenderness only in jaw muscles; (2) 26 subjects (9%) with tenderness only in neck/shoulder muscles; (3) 39 subjects (14%) with tenderness in muscles of the jaw and neck/shoulder; and (4) eight subjects (3%) with tenderness in all palpated muscles of the neck, shoulder, arm, hand, and calf. Women were found to have palpation tenderness significantly more often than men (P < .05). The main finding of this study was the presence of a significantly higher proportion of signs and symptoms of craniomandibular disorders in the group who had both jaw muscle tenderness and neck/shoulder muscle tenderness and in the group who had generalized tenderness than in the control group. The results indicate that in epidemiologic and clinical research of craniomandibular disorders, a distinction between local, regional, and general tenderness should be made since the etiology may differ.

Adult↗
PubMed2007

A new analytical method to diagnose congenital myasthenia with stimulated single-fiber electromyography.

Stimulated single-fiber electromyography (SSF-EMG) is useful to assess neuromuscular junction (NMJ) abnormalities in children. Conventionally mean consecutive difference (MCD) analysis measures the jitter for each muscle-fiber potential. We present a new algorithm that analyzes the entire SSF-EMG waveform. Cross-correlational coefficients (between 0-1.0) are calculated for consecutive pairs of 100 SSF-EMG waveforms obtained at each needle position in orbicularis oculi, and averaged. A lower normal limit (0.722, mean -3 SD) was established from 123 SSF-EMG samples in 10 adult control subjects, and applied to SSF-EMG data from 23 children referred for a suspected myasthenic syndrome. Results were compared with MCD analysis and related to the final clinical diagnosis. Our results showed that compared with conventional MCD measurement, the new algorithm had better specificity (87% vs. 53%) but similar sensitivity (88% for both). These findings indicate that the cross-correlational method is a useful predictor of NMJ dysfunction in children.

Adolescent↗
PubMed1996

A comparison of closed kinetic chain and isokinetic joint isolation exercise in patients with patellofemoral dysfunction.

Recently, there has been attention to the clinical application of closed kinetic chain and joint isolation exercise. Our purpose was to compare the effect of joint isolation and closed kinetic chain exercise on quadriceps muscle performance and perceived function in patients with patellofemoral pain. Twenty-three patients participated in an 8-week training period and were assigned to either a closed kinetic chain or a joint isolation exercise training group. An 8-inch (20.3 cm) retro step-up test was performed at baseline, 8 weeks, and 1 year. Seated knee extension testing was measured at baseline and at 8 weeks using peak concentric torque on an isokinetic dynamometer at 90 degrees/sec, 180 degrees/sec, and 360 degrees/sec. Perceived functional status was rated as excellent, good, fair, or poor based on questionnaire response. Statistical analysis showed that both groups had significant improvement in peak torque at all speeds, but only the closed kinetic chain group showed significant improvement in closed kinetic chain testing and perceived functional status. We concluded that closed kinetic chain training may be more effective than joint isolation exercise in restoring function in patients with patellofemoral dysfunction.

Exercise Therapy↗
PubMed1995

Contralateral hamstring (biceps femoris) coactivation patterns and anterior cruciate ligament dysfunction.

It has been postulated that coactivation of antagonist hamstring musculature during active knee extension aids the anterior cruciate ligament (ACL) in maintaining joint stability by exerting an opposing torque to anterior tibial displacement induced by the quadriceps. It was the purpose of this study to compare contralateral patterns of hamstring coactivation in subjects who have suffered ACL dysfunction with subjects who have normal knees. Five subjects who had suffered ACL dysfunction (INJ) and five uninjured (UNI) subjects performed maximal flexions and extensions of the knee on a modified isokinetic dynamometer at 100 degrees and 300 degrees.s-1. Simultaneous recordings of torque, angular displacement, and electromyographic (EMG) activity from the hamstring musculature were computer processed. No significant differences (P < 0.05) in torque were found between ACL/normal and right/left limbs for the INJ and UNI groups, respectively. For the INJ subjects, mean coactivation of the normal limb hamstrings during extension averaged twice that of the ACL limb. In contrast, no significant difference was found for the same comparison between right and left limbs in the UNI group. The results of this study suggest that asymmetry in hamstring coactivation during knee extension may result from ACL dysfunction.

Adult↗
PubMed2003

Respiratory muscle injury, fatigue and serum skeletal troponin I in rat.

To evaluate injury to respiratory muscles of rats breathing against an inspiratory resistive load, we measured the release into blood of a myofilament protein, skeletal troponin I (sTnI), and related this release to the time course of changes in arterial blood gases, respiratory drive (phrenic activity), and pressure generation. After approximately 1.5 h of loading, hypercapnic ventilatory failure occurred, coincident with a decrease in the ratio of transdiaphragmatic pressure to integrated phrenic activity (P(di)/ integral Phr) during sighs. This was followed at approximately 1.9 h by a decrease in the P(di)/ integral Phr ratio during normal loaded breaths (diaphragmatic fatigue). Loading was terminated at pump failure (a decline of P(di) to half of steady-state loaded values), approximately 2.4 h after load onset. During 30 s occlusions post loading, rats generated pressure profiles similar to those during occlusions before loading, with comparable blood gases, but at a higher neural drive. In a second series of rats, we tested for sTnI release using Western blot-direct serum analysis of blood samples taken before and during loading to pump failure. We detected only the fast isoform of sTnI, release beginning midway through loading. Differential detection with various monoclonal antibodies indicated the presence of modified forms of fast sTnI. The release of fast sTnI is consistent with load-induced injury of fast glycolytic fibres of inspiratory muscles, probably the diaphragm. Characterization of released fast sTnI may provide insights into the molecular basis of respiratory muscle dysfunction; fast sTnI may also prove useful as a marker of impending respiratory muscle fatigue.

Animals↗
PubMed1997

Quantitative assessments of elbow flexor muscle performance using twitch interpolation in post-polio patients: no evidence for deterioration.

A large number of patients previously affected by polio have symptoms, including increased weakness and fatigue, which are collectively known as a post-polio syndrome. Prospective measurements of strength and endurance using twitch interpolation in post-polio patients are lacking and hence the exact rate of decline in muscle function in these patients is not well defined. We therefore measured performance of the elbow flexor muscles twice, at a mean of 2.5 years apart in a group of selected post-polio subjects (Group A, n = 13) and matched control subjects (n = 11), and in a second group of unselected polio patients from a post-polio clinic (Group B, n = 40) at a mean of 1.7 years apart. All subjects performed 10 attempted maximal voluntary isometric contractions of the elbow flexor muscles, during which voluntary activation of the elbow flexor muscles was measured using a sensitive form of twitch interpolation. The first group of selected polio subjects (Group A) and matched control subjects also performed 45 min of submaximal exercise. During this time, at 5-min intervals, maximal voluntary force, voluntary activation and the amplitude of twitch responses to single and paired stimuli were measured in order to investigate central and peripheral components of muscle fatigue. There was no change in the polio patients' strength, voluntary activation or peripheral muscle endurance between testing sessions, despite an 80% probability of detecting a 2.5% change per year in these variables. The unselected group of patients from the post-polio clinic (Group B) showed no change in maximal voluntary strength or voluntary activation between the first and second test. There was an absence of decline in muscle performance in these polio patients over the test interval, despite a subjective deterioration in muscle function consistent with the 'post-polio syndrome'. This supports the view that symptoms of the post-polio syndrome are not due to a progressive neuronal dysfunction.

Adult↗
PubMed1992

Pathophysiology and therapy of heart failure, new insights and developments. Part I.

During the last decades heart failure has become a syndrome of major concern. Despite a decline in the occurrence of coronary artery disease and improved treatment of systemic hypertension, its primary aetiologic factors, the incidence of heart failure has been ever increasing. It is estimated that in the U.S.A. and most of western Europe approximately 1% of the population suffers from congestive heart failure. Its importance is directly related to its very adverse prognosis with an annual mortality rate as high as 50-60% in the advanced stages of failure. Although treatment with certain vasodilators or converting enzyme inhibitors may improve survival to some extent, the remaining mortality rate still remains high. As it is also extremely difficult to improve the clinical well-being of heart failure patients, emphasis is now on the early phase of failure and in particular on the preceding stage of asymptomatic ventricular dysfunction. Recent animal and human data indicate the significance of myocardial hypertrophy as a first step towards progressive myocardial muscle dysfunction superimposed on the initial cardiac event which leads to asymptomatic ventricular dysfunction. Moreover, there is evidence that neurohumoral activation occurs before heart failure has developed. Although available data only relate to circulating neurohormones, early alterations in local paracrine or autocrine acting systems may well be at issue. Also, whereas heart failure is generally considered a cardiac disorder, there is accumulating evidence that peripheral systems such as the skeletal musculature and the kidney are markedly involved. Changes in peripheral tissue function are not necessarily related to a reduction in cardiac pump function and tissue perfusion, but may be intrinsic of nature. Thus, significant abnormalities in skeletal muscle oxidative metabolism occur which are not secondary to regional flow disturbances. The recognition of cardiac and peripheral changes before or during the early phases of heart failure are likely to alter the current strategies in the treatment of this syndrome.

Cardiomegaly↗
PubMed2002

Clinical features and neuroradiological findings of mitochondrial pathology in six neonates.

OBJECTS: We hoped to itemize the clinical and neuroradiological features of six neonates with mitochondrial disorders. METHODS: We examined a case series of six neonates. The diagnosis of mitochondrial cytopathy was made on the basis of spectrophotometric measurements of respiratory chain enzyme activities in skeletal muscle biopsy specimens. Magnetic resonance (MR) imaging was performed in all cases. CONCLUSIONS: The antenatal onset in five cases and the lack of any symptom-free interval are suggestive of fetal expression of the disease. No specific symptoms were found: arthrogryposis congenita multiplex in one, progressive hepatocellular dysfunction in three, encephalomyelopathy and cardiomyopathy in four. Complex I deficiency was found in three patients, while one patients had a defect of complex IV and the last a combined defect of complexes I and IV. Neuroradiological findings were either cerebral atrophy or white matter abnormalities of the brain stem in all cases but one and gave additional information, because clinical symptoms are not quite specific. The combination of clinical and MRI findings in neonatal cases can rule out hypoxic ischemic encephalopathy, which suggests an additional screening method to look for mitochondrial disorder.

Brain↗
PubMed1996

Modulation of pressure pain thresholds during and following isometric contraction in patients with fibromyalgia and in healthy controls.

This study aimed at evaluating the influence of submaximal isometric contraction on pressure pain thresholds (PPTs) in 14 fibromyalgia (FM) patients and 14 healthy volunteers, before and after skin hypoesthesia. PPTs were determined with pressure algometry over m. quadriceps femoris before, during and following an isometric contraction. Maximum voluntary contraction (MVC) was assessed using a computerized dynamometer. A contraction of 22% MVC on average was held until exhaustion (max. 5 min) and PPTs were assessed every 30 sec. A local anesthetic cream and a control cream were applied following a double-blind design and PPTs were reassessed. In healthy volunteers PPTs increased during contraction (P < 0.001), then decreased after the end of contraction (P < 0.001) but remained above precontraction values during the 5 min of post-contraction assessments (P < 0.001). In FM patients PPTs decreased in the middle of the contraction period (P < 0.05) and remained below precontraction levels during the rest of the contraction period (P < 0.05) and during the 5 min of post-contraction assessment (immediately post-contraction NS; 2.5 min post-contraction P < 0.01; 5 min post-contraction P < 0.05). The normalized PPTs were significantly lower in patients than in controls during contraction (start P < 0.01; middle P < 0.001; end P < 0.001) and at all times during post-contraction assessments (P < 0.001). Anesthetic cream raised PPTs at rest in controls (P < 0.01) but not in FM patients, and did not influence contraction or post-contraction PPTs in either group. Therefore, the increased pressure pain sensibility in FM patients is more pronounced deep to the skin. The observed decrease of PPTs during isometric contraction in FM patients could be due to sensitization of mechanonociceptors caused by muscle ischemia and/or dysfunction in pain modulation during muscle contraction.

Adult↗
PubMed1996

Muscular causes of exercise intolerance in horses.

The muscular system of the horse is remarkable in its athletic scope and capacity to adapt to the demands placed on it. Muscular fatigue often causes exercise intolerance in horses as a primary muscular dysfunction or secondary to abnormalities in other integrated systems such as the cardiovascular, respiratory, or skeletal system. This article reviews basic muscular physiology leading to a discussion of the physiologic causes of muscular fatigue. In addition, a review of pathologic muscle disorders such as muscle strains and exertional myopathies that lead to poor performance is provided.

Animals↗
PubMed2006

Isolation and molecular characterization of a new Muscovy duck parvovirus from Muscovy ducks in the USA.

Between 1997 and 1999 several cases of a new disease in Muscovy ducks were reported in Pennsylvania, USA. The cases were characterized by locomotor dysfunction, weakness, recumbency, 40 to 60% morbidity and 10 to 40% mortality. The most characteristic microscopic lesions were moderate to severe degenerative rhabodomyopathy. In order to characterize the aetiological agent, virus isolation was attempted from the spleen, liver, heart, skeletal muscle and intestine by inoculation of 14-day-old Muscovy duck embryos with tissue homogenates. Deaths occurred on the second egg passage and parvoviruses were isolated by serial passage of allantoic fluid from dead embryos and then in Muscovy duck embryo fibroblast (MDEF) cultures. Parvovirus particles were observed in allantoic fluids and supernatants of MDEF cultures by transmission electron microscopy. Two genomic fragments, comprising 1108 nucleotides of the right open reading frame that codes for the structural viral proteins 1, 2 and 3, were amplified by polymerase chain reaction from one of the isolates, Muscovy duck parvovirus (MDPV)/PSU-31010. Comparison of this fragment with available sequences of other MDPV and related goose parvovirus (GPV) isolates showed that it had only 84.5% sequence identity with other MDPV isolates and 84.6% identity with the GPV isolates. This region shares over 99% identity among previously sequenced MDPV isolates and 95% identity among the related GPV isolates. This suggests that MDPV/PSU-31010 is divergent from all other sequenced MDPV and GPV isolates, and may represent a new group of avian parvoviruses.

Amino Acid Sequence↗