Needle biopsy of skeletal muscle in the diagnosis of myopathy and the clinical study of muscle function and repair

Oldies, but goldies-preserved morphology and stability of antigenic determinants in decades-old cryosections of human m. vastus lateralis

Fibre typing by immunohistochemistry on cryosections from human skeletal muscle biopsies is an essential tool in the diagnosis and research of muscular diseases, ageing, and responses to exercise training and disuse. Preserving a good quality in these frozen specimens can be challenging especially if they are stored for longer periods before histological processing, which is often the case in studies with a large number of test subjects and/or repeated sampling separated by multiple years. We demonstrate in this article that both, the morphology and reactivity of epitopes to myosin heavy chain isoforms and dystrophin are well preserved in up to 18-year-stored unfixed and unstained cryosections of human m. vastus lateralis (n = 241). Any variation in staining intensity between samples was unrelated to the age of the biopsy donor or the storage period of the unstained cryosections, and in all cases, the obtained images were appropriate for image analysis, such as the determination of the fibre type composition and the fibre cross-sectional area, and quantitative analysis of muscle capillarisation.

The molecular athlete: exercise physiology from mechanisms to medals

Human skeletal muscle demonstrates remarkable plasticity, adapting to numerous external stimuli including the habitual level of contractile loading. Accordingly, muscle function and exercise capacity encompass a broad spectrum, from inactive individuals with low levels of endurance and strength to elite athletes who produce prodigious performances underpinned by pleiotropic training-induced muscular adaptations. Our current understanding of the signal integration, interpretation, and output coordination of the cellular and molecular mechanisms that govern muscle plasticity across this continuum is incomplete. As such, training methods and their application to elite athletes largely rely on a "trial-and-error" approach, with the experience and practices of successful coaches and athletes often providing the bases for "post hoc" scientific enquiry and research. This review provides a synopsis of the morphological and functional changes along with the molecular mechanisms underlying exercise adaptation to endurance- and resistance-based training. These traits are placed in the context of innate genetic and interindividual differences in exercise capacity and performance, with special consideration given to aging athletes. Collectively, we provide a comprehensive overview of skeletal muscle plasticity in response to different modes of exercise and how such adaptations translate from "molecules to medals."

Diagnosing muscle disease in a cohort of classic dermatomyositis patients seen at a rheumatologic dermatology outpatient clinic

BACKGROUND

Existing criteria to improve the probability of capturing dermatomyositis (DM) include muscle biopsy but little is known about whether less invasive diagnostic procedures may be just as useful.

OBJECTIVE

We aimed to determine whether skin biopsy, electromyography, or magnetic resonance imaging of the involved muscle could be done in lieu of muscle biopsy.

METHODS

Two hundred and seventy-five patients were reviewed to investigate the presence of cutaneous and muscle disease, their timing in relation to diagnosis, and results of skin biopsies, muscle biopsies, magnetic resonance imaging, and electromyography.

RESULTS

Of the cases with findings consistent with DM on muscle biopsy, 65% were in agreement with diagnostic features on electromyography or magnetic resonance imaging. Results of skin and muscle biopsies supported DM in 67% of patients who underwent both procedures.

LIMITATIONS

A limited number of patients had muscle biopsies.

CONCLUSION

In the presence of DM-specific skin findings, less invasive procedures may be sufficient to diagnose DM and guide its management.

Human Vastus Lateralis Skeletal Muscle Biopsy Using the Weil-Blakesley Conchotome

Percutaneous muscle biopsy using the Weil-Blakesley conchotome is well established in both clinical and research practice. It is a safe, effective and well tolerated technique. The Weil-Blakesley conchotome has a sharp biting tip with a 4 - 6 mm wide hollow. It is inserted through a 5 - 10 mm skin incision and can be maneuvered for controlled tissue penetration. The tip is opened and closed within the tissue and then rotated through 90 -180° to cut the muscle. The amount of muscle obtained following repeated sampling can vary from 20 mg to 290 mg which can be processed for both histology and molecular studies. The wound needs to be kept dry and vigorous physical activity kept to a minimum for approximately 72 hr although normal levels of activity can restart immediately following the procedure. This procedure is safe and effective when close attention is paid to the selection of subjects, full asepsis and post procedure care.  Both right and left vastus lateralis are suitable for biopsy dependent on participant preference.

Splicing biomarkers of disease severity in myotonic dystrophy

OBJECTIVE

To develop RNA splicing biomarkers of disease severity and therapeutic response in myotonic dystrophy type 1 (DM1) and type 2 (DM2).

METHODS

In a discovery cohort, we used microarrays to perform global analysis of alternative splicing in DM1 and DM2. The newly identified splicing changes were combined with previous data to create a panel of 50 putative splicing defects. In a validation cohort of 50 DM1 subjects, we measured the strength of ankle dorsiflexion (ADF) and then obtained a needle biopsy of tibialis anterior (TA) to analyze splice events in muscle RNA. The specificity of DM-associated splicing defects was assessed in disease controls. The CTG expansion size in muscle tissue was determined by Southern blot. The reversibility of splicing defects was assessed in transgenic mice by using antisense oligonucleotides to reduce levels of toxic RNA.

RESULTS

Forty-two splicing defects were confirmed in TA muscle in the validation cohort. Among these, 20 events showed graded changes that correlated with ADF weakness. Five other splice events were strongly affected in DM1 subjects with normal ADF strength. Comparison to disease controls and mouse models indicated that splicing changes were DM-specific, mainly attributable to MBNL1 sequestration, and reversible in mice by targeted knockdown of toxic RNA. Splicing defects and weakness were not correlated with CTG expansion size in muscle tissue.

INTERPRETATION

Alternative splicing changes in skeletal muscle may serve as biomarkers of disease severity and therapeutic response in myotonic dystrophy.

The feasibility and acceptability of muscle biopsy in epidemiological studies: findings from the Hertfordshire Sarcopenia Study (HSS)

BACKGROUND

Sarcopenia, the loss of muscle mass and strength, is associated adversely with disability, morbidity and mortality. Epidemiological findings suggest influences operating across the life course may be important. Our aim was to ascertain the feasibility and acceptability of obtaining muscle tissue from healthy older people in order to ultimately identify cellular mechanisms underlying life course influences on sarcopenia.

METHODS

105 men with documented birth weight consented to detailed assessment of muscle mass and strength, and a biopsy of the vastus lateralis using the Weil-Blakesley conchotome. Acceptability was ascertained by questionnaire and a 100 mm pain Visual Analogue Scale (VAS). 100 mm indicated severe pain.

RESULTS

Muscle biopsy was successfully carried out in 102 out of 105 participants, mean yield 107 mg (range 20-290 mg). There were no serious wound complications. Ninety-three participants completed feedback questionnaires. The median pain VAS score during the procedure was 7 mm (Interquartile range [IQR] 1-34), 4 mm (IQR 0-16) one day after the procedure and 1mm (IQR 0-4) 7 days after the procedure. 60 (65%) participants were back to their normal levels of activity one day after the procedure. 85 (91%) found this procedure acceptable and would have the procedure again.

CONCLUSION

Muscle biopsy using a Weil-Blakesley conchotome is both feasible and acceptable in community dwelling older men participating in epidemiological research. The excellent yield of biopsy tissue will allow morphological and molecular studies of muscle to be integrated into an epidemiological study facilitating investigation of the mechanisms underpinning sarcopenia that could potentially be altered by life course influences.

Functional assessment of isolated mitochondria in vitro

Mitochondria play a pivotal role in cellular function, not only as a major site of ATP production, but also by regulating energy expenditure, apoptosis signaling, and production of reactive oxygen species. Altered mitochondrial function is reported to be a key underlying mechanism of many pathological states and in the aging process. Functional measurements of intact mitochondria isolated from fresh tissue provides distinct information regarding the function of these organelles that complements conventional mitochondrial assays using previously frozen tissue as well as in vivo assessment using techniques such as magnetic resonance and near-infrared spectroscopy. This chapter describes the process by which mitochondria are isolated from small amounts of human skeletal muscle obtained by needle biopsy and two approaches used to assess mitochondrial oxidative capacity and other key components of mitochondrial physiology. We first describe a bioluminescent approach for measuring the rates of mitochondrial ATP production. Firefly luciferase catalyzes a light-emitting reaction whereby the substrate luciferin is oxidized in an ATP-dependent manner. A luminometer is used to quantify the light signal, which is proportional to ATP concentration. We also review a method involving polarographic measurement of oxygen consumption. Measurements of oxygen consumption, which previously required large amounts of tissue, are now feasible with very small amounts of sample obtained by needle biopsy due to recent advances in the field of high-resolution respirometry. We illustrate how careful attention to substrate combinations and inhibitors allows an abundance of unique functional information to be obtained from isolated mitochondria, including function at various energetic states, oxidative capacity with electron flow through distinct complexes, coupling of oxygen consumption to ATP production, and membrane integrity. These measurements, together with studies of mitochondrial DNA abundance, mRNA levels, protein expression, and synthesis rates of mitochondrial proteins provide insightful mechanistic information about mitochondria in a variety of tissue types.

Human muscle function and fatigue

Fatigue is defined as a failure to maintain the required or expected force. The force of a voluntary contraction is graded according to both the tension generated in each muscle fibre and the number of fibres recruited. The same is true of fatigue. Percutaneous electrical stimulation of a muscle via its motor nerve allows the contractile function to be measured independently of volition. Studies have been made of the forces generated isometrically at different stimulation frequencies (frequency: force curve), and of fatiguability (tendency to lose force in a given time at specified stimulation frequencies), in the quadriceps and adductor pollicis muscles. Electrical stimulation recordings of the programmed stimulation myograms distinguish forms of muscle fatigue. Low frequency fatigue which implies impaired excitation-contraction coupling is long-lasting, whereas high frequency fatigue which represents impaired muscle membrane excitation recovers rapidly. Electromyographic (EMG) indicators of fatigue are well recognized but their use is limited because they cannot alone indicate whether alterations in excitation-contraction coupling underlie fatigue. Alterations in the power spectrum of the EMG precede (force) fatigue in sustained maximum voluntary contractions. Fatigue may ultimately be due to a failure of the rate of energy supply to meet demand, but the precise expression of this defect may vary, such that failure of excitation or of activation may predominate over failure of the energy supply.

Fatigue in human metabolic myopathy

The ability of muscle fibres to sustain force can be related to their economy of energy utilization and to their capacity to regenerate energy under the prevailing conditions (aerobic or anaerobic) of contraction. The pathophysiology of muscle fatigue is analysed in patients with thyroid dysfunction and with impaired glycogenolysis, and in a patient with abnormal mitochondrial function. Muscle from hypothyroid patients, like cooled muscle, is slow in relaxing and shows a reduced energy requirement (energy economy) and reduced fatiguability, whereas muscle of hyperthyroid patients may show the opposite features. In myophosphorylase deficiency the energy economy is normal in the fresh state and increases as contraction proceeds; however, fatigue is premature and associated with impaired excitation rather than an overall depletion of energy stores. With abnormal mitochondrial function the muscle tends to be effectively anaerobic and fatigue is associated with impaired excitation-contraction coupling. This appears to result from either muscle ischaemia or the dominant use of anaerobic metabolism for energy regeneration. Fatigue in these disorders of energy metabolism may ultimately be due to a reduced supply of ATP but direct evidence of this is lacking and, if it occurs, its physiological expression is probably variable.

Effect of metabolic changes on force generation in skeletal muscle during maximal exercise

During vigorous, strong contractions there is a rapid decline in the mechanical output or tension development in skeletal muscle. Several studies have indicated that this rapid decline in force development (often referred to as fatigue), is caused by metabolic changes in the muscles. During brief intense exercise there is a rapid breakdown of phosphocreatine and glycogen and a concomitant increase in the lactate and hydrogen ion concentration. The muscle lactate concentration is increased from about 1-2 mmol kg-1 wet weight at rest before exercise to approximately 25-30 mmol kg-1 wet weight immediately after intensive brief exercise to exhaustion. The muscle pH (i.e. the pH of muscle homogenates) falls from about 7.0 at rest to approximately 6.4 at exhaustion. The changes in the concentrations of ATP, ADP, and AMP are small. It is suggested that the changes in intracellular pH might affect the force generation of skeletal muscle by two different mechanisms: (1) The fall in intracellular pH reduces the activity of key enzymes in glycolysis, thus reducing the rate of ATP resynthesis, and (2) the increased hydrogen ion concentration has a direct effect on the contractile processes, thus reducing the rate of ATP utilization. It is suggested that the increased hydrogen ion concentration might be the common regulator for the maximal rate at which ATP is being utilized and the maximal rate at which it is being resynthesized.

Characterization of the human skeletal muscle proteome by one-dimensional gel electrophoresis and HPLC-ESI-MS/MS

Changes in protein abundance in skeletal muscle are central to a large number of metabolic and other disorders, including, and perhaps most commonly, insulin resistance. Proteomics analysis of human muscle is an important approach for gaining insight into the biochemical basis for normal and pathophysiological conditions. However, to date, the number of proteins identified by this approach has been limited, with 107 different proteins being the maximum reported so far. Using a combination of one-dimensional gel electrophoresis and high performance liquid chromatography electrospray ionization tandem mass spectrometry, we identified 954 different proteins in human vastus lateralis muscle obtained from three healthy, nonobese subjects. In addition to a large number of isoforms of contractile proteins, we detected all proteins involved in the major pathways of glucose and lipid metabolism in skeletal muscle. Mitochondrial proteins accounted for 22% of all proteins identified, including 55 subunits of the respiratory complexes I-V. Moreover, a number of enzymes involved in endocrine and metabolic signaling pathways as well as calcium homeostasis were identified. These results provide the most comprehensive characterization of the human skeletal muscle proteome to date. These data hold promise for future global assessment of quantitative changes in the muscle proteome of patients affected by disorders involving skeletal muscle.

Collagen vascular diseases: cutaneous manifestations in ophthalmology

PURPOSE

To describe the effects of collagen vascular diseases on the eyelids and periorbital tissues.

METHODS

Retrospective review of dermatologic pathology slides at Massachusetts General Hospital and eye pathology slides at Massachusetts Eye and Ear Infirmary, Boston, Massachusetts.

RESULTS

A spectrum of dermatologic manifestations of collagen vascular diseases was observed, affecting the eyelids and periorbital region.

CONCLUSIONS

Collagen vascular diseases may present complicated diagnostic and clinical challenges for the practicing ophthalmologist. Familiarity with the cutaneous periocular manifestations of these diseases may facilitate early recognition, diagnosis, and ophthalmologic intervention where necessary.

Hormonal and metabolic responses to maintained hyperglycemia during prolonged exercise

We studied the effects of maintained hyperglycemia (12 mmol/l) on endurance exercise to determine the hormonal and metabolic responses, the maximal rate of glucose infusion (i.e., utilization), and the effects on muscle glycogen stores. Eight men undertook two trials during which they exercised on a cycle ergometer at an intensity of approximately 70% peak O(2) uptake for 120 min. In the first trial (trial A), subjects had their blood glucose concentration clamped at 12 mmol/l 30 min before exercise and throughout exercise. The same rate and volume of infusion of saline as had occurred for trial A were used in a placebo trial (trial B). Maintained hyperglycemia resulted in significantly lowered plasma concentrations of nonesterified fatty acid, glycerol, 3-hydroxybutyrate, epinephrine, norepinephrine, and growth hormone (P < 0.001) during exercise, whereas concentrations of plasma insulin were significantly elevated (P < 0.001). Calculations of the rates of total carbohydrate oxidation showed that trial A resulted in significantly higher values when compared with trial B (P < 0.01) and that the maximal rates of glucose infusion varied between 1.33 and 2.78 g/min at 100-120 min. Muscle glycogen concentrations were significantly depleted (P < 0.01) after both trials (trial A, 170.3 micromol/g dry wt decrease; trial B, 206 micromol/g dry wt decrease), although this apparent difference may be accounted for by storage of 22.6 g glucose during the 30-min prime infusion. The results from this study confirm that maintained hyperglycemia attenuates the hormonal response and promotes carbohydrate oxidation and utilization and that muscle glycogen may not be spared.

Optimization of preparation of mitochondria from 25-100 mg skeletal muscle

A method for isolation of mitochondria from 25-100 mg skeletal muscle is described. The instrumental developments include a refined homogenization setup, special handling techniques, and equipment for biopsy storage. The preparation medium was a standard ionic medium. All fractions were assayed for marker enzymes and the data used in optimization of the yield. It was observed that the homogenization procedure exerts strong control on the integrity of the isolated mitochondria. The method was developed with pigeon breast muscle as the model tissue and used virtually unaltered for preparation from muscles of pigs, rats, and humans. The relative yield was 40-50% and the mitochondria were well coupled and showed high rates of phosphorylating respiration.

Sensory characterization of somatic parietal tissues in humans with chronic fatigue syndrome

Patients with chronic fatigue syndrome (CFS) mainly complain of symptoms in the musculoskeletal domain (myalgias, fatigue). In 21 CFS patients the deep (muscle) versus superficial (skin, subcutis) sensitivity to pain was explored by measuring pain thresholds to electrical stimulation unilaterally in the deltoid, trapezius and quadriceps and overlying skin and subcutis in comparison with normal subjects. Thresholds in patients were normal in skin and subcutis but significantly lower than normal (hyperalgesia) in muscles (P < 0.001) in all sites. The selective muscle hypersensitivity corresponded also to fiber abnormalities at muscle biopsy (quadriceps) performed in nine patients which were absent in normal subjects (four cases): morphostructural alterations of the sarchomere, fatty degeneration and fibrous regeneration, inversion of the cytochrome oxidase/succinate dehydrogenase ratio, pleio/polymorphism and monstruosity of mitochondria, reduction of some mitochondrial enzymatic activities and increments of common deletion of 4977 bp of mitochondrial DNA 150-3000 times the normal values. By showing both sensory (diffuse hyperalgesia) and anatomical (degenerative picture) changes at muscle level, the results suggest a role played by peripberal mechanisms in the genesis of CFS symptoms. They would exclude the heightened perception of physiological signals from all districts hypothesized by some authors, especially as the hyperalgesia is absent in skin/subcutis.

Use of dynamic tests of muscle function and histomorphometry of quadriceps muscle biopsies in the investigation of patients with chronic alcohol misuse and chronic fatigue syndrome

Ischaemic lactate/ammonia tests, serum carnosinase and creatine kinase assays and percutaneous needle muscle biopsies were performed on 10 patients with chronic fatigue syndrome (CFS), and 10 with chronic alcohol misuse complaining of muscular symptoms. Basal serum lactate levels were significantly elevated in the alcohol misusers compared to the CFS patients, but all were within the reference range. Lactate profiles after ischaemic forearm exercise did not differ significantly for the two patient groups. In one patient previously diagnosed as having CFS, myoadenylate deaminase deficiency was identified on the basis of a flat ammonia response to ischaemia and absent muscle adenosine monophosphate deaminase activity. In addition, two further patients in the CFS group were subsequently shown to have other disorders: one had polymyositis and one had myopathy with mild type II fibre atrophy of unknown cause. Histomorphometric examination of muscle needle biopsy in the alcohol misusers showed features of chronic alcohol-induced skeletal myopathy in six patients and polymyositis in one patient. Type II fibre atrophy factors were significantly elevated in the alcohol group but were within the reference range in CFS patients. Dynamic tests of muscle function and muscle histology are valuable tools in excluding alternative pathology in CFS, whereas muscle histomorphometry is of the greatest value in the diagnosis of chronic alcoholic myopathy.

Some aspects of modern orthotics

Orthotics is changing more rapidly than ever before, largely resulting from improved understanding of the human requirements and the current state of technological abilities. Walking is always seen as a basic requirement for normal activity and as such it is in this area that most research and development effort is expended. This paper outlines some of the current developments in this interesting topic and includes seating and posture as these are often viewed as precursors to successful standing and then, possibly, gait.

The content of free amino acids in the human duodenal mucosa

The free amino acid concentrations and the total protein content of the duodenal mucosa were determined in biopsy specimens obtained during endoscopic examinations in 10 healthy subjects. The amino acids were separated and quantified by ion exchange chromatography using fluorescence detection. The protein content was analysed according to Lowry. The amino acid pattern found in the duodenal mucosa was quite different from that in the plasma. The total amounts of all individual free amino acids were considerably higher in the mucosa than in the plasma (16.2 +/- 0.6 mmol/kg biopsy weight compared to 2.4 +/- 0.1 mmol/l). Taurine, glutamate and aspartate constituted more then 65% of the total content of all amino acids in the mucosa. Glutamine, the most abundant amino acid in plasma (21%), ranked only as sixth in the duodenal mucosa (4%); still, the absolute concentrations were quite similar in the mucosa and plasma (0.60 +/- 0.05 mmol/kg vs. 0.53 +/- 0.02 mmol/l). This study demonstrates the possibility of determining free amino acids in endoscopic biopsy specimens from the human duodenum. The technique is recommended for repeated sampling in clinical studies on the amino acid metabolism of the intestinal mucosa.

Biochemical and muscle studies in patients with acute onset post-viral fatigue syndrome

AIMS

To investigate in detail various biochemical and pathophysiological indices of muscle pathology in acute onset post-viral fatigue syndrome (PVFS).

METHODS

Twenty three patients with PVFS (of mean duration 4.6 years) were subjected to needle biopsy for histomorphometry and total RNA contents. Plasma analysis included serology and creatine kinase activities. Indices of whole body mass were also measured--namely, whole body potassium content and plasma carnosinase activities.

RESULTS

About 80% of the patients had serology indicative of persistent enteroviral infection as determined by VP1 antigen assay. Only about 10% of that same group of patients had serological indications of current enterovirus infection by IgM assay; a separate subset of 10% showed antibody changes suggestive of reactivation of Epstein-Barr virus. Quantitative morphometric analysis of skeletal muscle fibres indicated that the quadriceps muscle was normal or displayed only minor abnormalities in 22 patients. The Quetelet's Index (body mass index) and whole-body potassium values (index of lean body mass) were not affected in PVFS. The mean plasma carnosinase and creatinine kinase activities were also generally normal in these patients. The mean muscle RNA composition--mg RNA/mg DNA: was significantly reduced in acute onset PVFS by about 15%. The protein:DNA ratio was not significantly affected.

CONCLUSIONS

Patients with acute onset PVFS, therefore, lose muscle protein synthetic potential, but not muscle bulk. Histopathology is consistent with these observations. These perturbations may contribute to the apparent feature of perceived muscle weakness associated with the persistent viral infection in the muscle themselves.

Item assessment in the development of a diagnostic motor performance test for myopathy in children

The authors conducted an assessment study of newly developed motor performance items for the diagnosis of myopathy. 17 children who had had muscle biopsy for this diagnosis in the recent past were administered 14 items based on the measurement of static, dynamic and explosive muscle strength and muscle endurance. Individual items did not have perfect discriminative power, but the results were encouraging enough to warrant detailed study with combinations of the items, so that in future fewer children will have to undergo unnecessary muscle biopsies.

Fibre areas and histochemical fibre types in the quadriceps muscle of paraplegic subjects

With the advent of functional electrical stimulation (FES) there is the possibility of paraplegic patients regaining some degree of locomotor activity. It is of interest to document the changes in composition histochemistry and size of muscle fibres in such patients both before and after such therapy. We have examined biopsy specimens from quadriceps muscles obtained from 7 male patients, age range 24-47 years, who had been paraplegic for times ranging from 11 months to 9 years and we report the histochemical appearance of the muscle the fibre type composition and the mean fibre areas. In 5 of the 7 subjects there was a marked or complete predominance of fibres which stained as type 2 with the ATPase reaction at pH 9.4. At acid pH these fibres were seen to be predominantly 2B (fast fatigable). The 2 subjects who had been paralysed for the shortest periods had proportions of type 1 fibres which were relatively well preserved. The mean fibre areas of type 2 fibres were below the normal range (2500-7500 microns 2) in every case as were the type 1 fibres in the 4 patients in which these were still present. There was no relationship between the length of time the patient had been paralysed and the mean fibre areas which suggests that atrophy occurs fairly quickly following loss of voluntary control and precedes the loss of type 1 characteristics. Our findings provide an explanation for the rapid onset of fatigue in paraplegic patients taking part in FES programmes since muscles deficient in type 1 fibres will be unable to maintain force for any length of time.

Diseases and disorders of muscle

Muscle may suffer from a number of diseases or disorders, some being fatal to humans and animals. Their management or treatment depends on correct diagnosis. Although no single method may be used to identify all diseases, recognition depends on the following diagnostic procedures: (1) history and clinical examination, (2) blood biochemistry, (3) electromyography, (4) muscle biopsy, (5) nuclear magnetic resonance, (6) measurement of muscle cross-sectional area, (7) tests of muscle function, (8) provocation tests, and (9) studies on protein turnover. One or all of these procedures may prove helpful in diagnosis, but even then identification of the disorder may not be possible. Nevertheless, each of these procedures can provide useful information. Among the most common diseases in muscle are the muscular dystrophies, in which the newly identified muscle protein dystrophin is either absent or present at less than normal amounts in both Duchenne and Becker's muscular dystrophy. Although the identification of dystrophin represents a major breakthrough, treatment has not progressed to the experimental stage. Other major diseases of muscle include the inflammatory myopathies and neuropathies. Atrophy and hypertrophy of muscle and the relationship of aging, exercise, and fatigue all add to our understanding of the behavior of normal and abnormal muscle. Some other interesting related diseases and disorders of muscle include myasthenia gravis, muscular dysgenesis, and myclonus. Disorders of energy metabolism include those caused by abnormal glycolysis (Von Gierke's, Pompe's, Cori-Forbes, Andersen's, McArdle's, Hers', and Tauri's diseases) and by the acquired diseases of glycolysis (disorders of mitochondrial oxidation). Still other diseases associated with abnormal energy metabolism include lipid-related disorders (carnitine and carnitine palmitoyl-transferase deficiencies) and myotonic syndromes (myotonia congenita, paramyotonia congenita, hypokalemic and hyperkalemic periodic paralysis, and malignant hyperexia). Diseases of the connective tissues discussed include those of nutritional origin (scurvy, lathyrism, starvation, and protein deficiency), the genetic diseases (dermatosparaxis, Ehlers-Danlos syndrome, osteogenesis imperfecta, Marfan syndrome, homocystinuria, alcaptonuria, epidermolysis bullosa, rheumatoid arthritis in humans, polyarthritis in swine, Aleutian disease of mink, and the several types of systemic lupus erythematosus) and the acquired diseases of connective tissues (abnormal calcification, systemic sclerosis, interstitial lung disease, hepatic fibrosis, and carcinomas of the connective tissues). Several of the diseases of connective tissues may prove to be useful models for determining the relationship of collagen to meat tenderness and its other physical properties. Several other promising models for studying the nutrition-related disorders and the quality-related characteristics of meat are also reviewed.

Preoperative cardiopulmonary exercise testing: determining the limit to exercise and predicting outcome after thoracotomy

Over the past 15 years evaluation of the patient with exertional complaints has changed from a simple qualitative estimate of overall fitness to a detailed assessment of cardiovascular and pulmonary pathophysiology. By quantifying exercise impairment and identifying the physiological limit to exercise, CPEx can help direct and evaluate the efficacy of medical and surgical interventions. Although no clear consensus has emerged, an objective determination of the etiology of exercise intolerance may also help identify the patient at increased risk for postthoracotomy complications.

Single cell morphology of muscle in patients with chronic muscle pain

In 119 patients referred with suspected fibromyalgia, biopsies from the quadriceps muscle were analyzed for "rubber band" morphology, and isokinetic quadriceps strength was measured. Eighty-four fulfilled the criteria for fibromyalgia, 26 had chronic myofascial pain (CMP) and 9 had other diseases including 5 with concomitant fibromyalgia. Twenty-four CMP patients and 48 fibromyalgia patients were randomly selected to match with regard to sex, age, smoking and drinking habits. "Rubber band" morphology was blindly graded on a biopsy score scale from 0 to 2. A statistically significant difference in biopsy score was found between the two matched groups (P = 0.003); median biopsy score in fibromyalgia was 0.42 and 0.25 in CMP. A cut-off value at 0.33 gave a specificity of 71% and a sensitivity of 63%. Isokinetic muscle strength did not differ in the fibromyalgia and CMP groups and was not related to the biopsy score. "Rubber band" morphology is seen more often in fibromyalgia patients than in CMP patients. The exact genesis of this phenomenon is still unknown but theories connected with the possible pathogenesis of the syndrome are presented.

Mechanism of muscle wasting in myotonic dystrophy

Myotonic dystrophy is associated with progressive muscular atrophy. In order to determine the mechanism of muscle wasting in this condition, we measured fractional mixed skeletal muscle protein synthesis in the postabsorptive state in 8 patients with myotonic dystrophy, and compared the results with those of 10 normal subjects. Fractional muscle protein synthesis was determined by measuring the increment of 13C leucine in mixed skeletal muscle protein obtained by needle biopsy from the quadriceps muscle during a primed-continuous infusion of L-(1-13C) leucine. We used plasma 13C alpha-ketoisocaproate (representing intracellular leucine labeling) as the precursor pool for the calculation of fractional muscle protein synthesis and leucine kinetics. Fractional muscle protein synthesis was depressed in the patients with myotonic dystrophy (28% decrease, p less than 0.02). Leucine flux, leucine oxidation, and the nonoxidative portion of leucine flux were not different between the patients with myotonic dystrophy and the normal control subjects. Muscle atrophy in myotonic dystrophy reflects a selective decrease in muscle protein synthesis without any similar decrease in nonmuscle protein synthesis. This decrease may result from an impaired end-organ response to anabolic hormones or substrates.

Baseline measurements for stable isotope studies: an alternative to biopsy

Studies of protein metabolism with stable isotopes require determination of the 'natural' isotopic enrichment in tissues. This has previously been determined by taking a pre-test muscle biopsy or by using the isotopic enrichment of a separate control group of subjects. In this study we have measured and compared the 'natural' 13C enrichment of leucine in plasma protein and muscle protein in 14 subjects. The mean enrichment of leucine (delta 13CPDB) in muscle protein, -26.627, was not significantly different from that in plasma protein, -27.152. The data indicate that the 13C enrichment of leucine in plasma protein reflects that of muscle protein and provides an attractive alternative to an additional muscle biopsy in studies of protein metabolism with stable isotopes.

Muscle growth and exercise

This paper first reviews muscle growth and then considers the influence of exercise in growth. Knowledge about how muscle cells grow and some factors that may influence the growth pattern are discussed first since these effects must be considered before the influence of exercise becomes clear. Growth of muscle can occur in three ways: (1) by an increase in muscle cell numbers, (2) by an increase in muscle fiber diameter, and (3) by an increase in fiber length. All three of these mechanisms are involved in muscle growth. However, growth in cell numbers is limited to the prenatal and immediately postnatal period, with the animals and man being born with or soon reaching their full complement of muscle cells. Thus, growth occurs by either hypertrophy of the existing muscle fibers by adding additional myofibrils to increase the muscle mass or by adding new sarcomeres to the ends of the existing muscle fibers to increase their length. Both of these mechanisms occur during the growth process. Growth in the girth of the muscle fibers appears to take place by splitting of the myofibrils. This may be stimulated by development of stress creating an unequal pressure with splitting at the Z-band and development of additional SR and T-tubule systems. This adds to the diameter or girth of myofibers without any hyperplasia. The growth in length occurs at either end of the fibers and results in addition of new sarcomeres. In both cases, new myofibrillar protein must be synthesized and deposited in the muscle cells. It is suggested that adaptation by adding or removing sarcomeres is physiologically determined by the degree of force a muscle can generate that is in turn dependent on the degree of overlap of the thick and thin filaments. Thus, the amount of tension would control the number of in-series sarcomeres in a single muscle fiber. Nutrition is also known to play an important role in muscle and was discussed from the standpoint of the effects of nutritional adequacy and restriction. Although a nutritionally balanced and calorically adequate diet is required to achieve optimum muscle growth, it may be less efficient in terms of protein deposition than a moderately restricted diet. Muscle and bone deposition, however, can be limited on severely restricting the dietary intake. Although fat deposition is the first tissue to suffer on a severely restricted diet, muscle and bone follow next with the nervous system, brain and eyes being the last systems to be affected.(ABSTRACT TRUNCATED AT 400 WORDS)

Growth hormone treatment in adults with growth hormone deficiency: effect on muscle fibre size and proportions

The effect of a 6-month period of substitution therapy with recombinant human growth hormone (rhGH) on muscle fibre size and muscle fibre type proportions has been investigated in a group of 13 adults with growth hormone deficiency. All had a peak growth hormone (GH) response to insulin-induced hypoglycaemia of less than 7 mU/l. There was no statistically significant change in the lesser fibre diameter or fibre proportions of either type 1 or type 2 muscle fibres in the rhGH group, as compared with placebo.

Changes in skeletal muscle after discontinuation of growth hormone treatment in young adults with hypopituitarism

Skeletal muscle strength and size were measured for 1 year following discontinuation of human growth hormone (hGH) treatment in 11 patients with hypopituitarism. Quadriceps and forearm flexor maximum voluntary isometric strength and size were measured. At the end of the study, endocrine status was reassessed by an insulin tolerance test. Three of the 11 subjects were found to have normal hGH secretion and were not included in the analysis. At 12 months, quadriceps strength, size and fibre areas were 94.0 +/- 8.5%, 94.5 +/- 6.3% and 85.6 +/- 17.7% (mean +/- SD), respectively, of baseline values. Forearm flexor strength and size were 101.4 +/- 7.9% and 92 +/- 9.2% of control values. Although these changes are relatively small, they suggest a role for growth hormone in the maintenance of muscle in the adult.

Effect of beta-hydroxybutyrate on whole-body leucine kinetics and fractional mixed skeletal muscle protein synthesis in humans

Because intravenous infusion of beta-hydroxybutyrate (beta-OHB) has been reported to decrease urinary nitrogen excretion, we investigated in vivo metabolism of leucine, an essential amino acid, using L-[1-13C]leucine as a tracer during beta-OHB infusion. Leucine flux during beta-OHB infusion did not differ from leucine flux during normal saline infusion in nine normal subjects, whereas leucine oxidation decreased 18-41% (mean = 30%) from 18.1 +/- 1.1 mumol.kg-1.h-1 (P less than 0.01), and incorporation of leucine into skeletal muscle protein increased 5-17% (mean = 10%) from 0.048 + 0.003%/h (P less than 0.02). Since blood pH during beta-OHB infusion was higher than the pH during saline infusion, we performed separate experiments to study the effect of increased blood pH on leucine kinetics by infusing sodium bicarbonate intravenously. Blood pH during sodium bicarbonate infusion was similar to that observed during the beta-OHB infusion, but bicarbonate infusion had no effect on leucine flux or leucine oxidation. We conclude that beta-OHB decreases leucine oxidation and promotes protein synthesis in human beings.

31P nuclear magnetic resonance studies of high energy phosphates and pH in human muscle fatigue. Comparison of aerobic and anaerobic exercise

The goal of these experiments was to investigate the relationship of ATP, phosphocreatine (PCr), inorganic phosphate (Pi), monobasic phosphate (H2PO4-), and pH to human muscle fatigue. Phosphates and pH were measured in adductor pollicis using 31P nuclear magnetic resonance at 2.0 Tesla. The force of muscle contraction was simultaneously measured with a force transducer. The effects of aerobic and anaerobic exercise were compared using two exercise protocols: 4 min sustained maximal voluntary contraction (MVC) and 40 min of repeated intermittent contractions (75% MVC). The sustained maximal contraction produced a rapid decline of MVC and PCr, and was accompanied by a rapid rise of Pi, H+, and H2PO4-. Intermittent exercise produced steady state changes of MVC, pH, and phosphates. No significant changes of ATP were found in either protocol. During fatiguing exercise, PCr and Pi had a nonlinear relationship with MVC. H+ showed a more linear correlation, while H2PO4- showed the best correlation with MVC. Furthermore, the correlations between MVC and H2PO4- were similar in sustained (r = 0.70) and intermittent (r = 0.73) exercise. The highly significant linear relationship between increases of H+ and H2PO4- and the decline of MVC strongly suggests that both H+ and H2PO4- are important determinants of human muscle fatigue.

Leucine incorporation into mixed skeletal muscle protein in humans

Fractional mixed skeletal muscle protein synthesis (FMPS) was estimated in 10 postabsorptive healthy men by determining the increment in the abundance of [13C]-leucine in quadriceps muscle protein during an intravenous infusion of L-[1-13C]leucine. FMPS in our subjects was 0.046 +/- 0.003%/h. Whole-body muscle protein synthesis (MPS) was calculated based on the estimation of muscle mass from creatinine excretion and compared with whole-body protein synthesis (WBPS) calculated from the nonoxidative portion of leucine flux. A significant correlation (r2 = 0.73, P less than 0.05) was found between MPS (44.7 +/- 3.4 mg.kg-1.h-1) and WBPS (167.8 +/- 8.5 mg.kg-1.h-1). The contribution of MPS to WBPS was 27 +/- 1%, which is comparable to the reports in other species. Morphometric analyses of adjacent muscle samples in eight subjects demonstrated that the biopsy specimens consisted of 86.5 +/- 2% muscular as opposed to other tissues. Because fiber type composition varies between biopsies, we examined the relationship between proportions of each fiber type and FMPS. Variation in the composition of biopsies and in fiber-type proportion did not affect the estimation of muscle protein synthesis rate. We conclude that stable isotope techniques using serial needle biopsies permit the direct measurement of FMPS in humans and that this estimation is correlated with an indirect estimation of WBPS.

Effect of anaerobic and aerobic exercise promoted by computer regulated functional electrical stimulation (FES) on muscle size, strength and histology in paraplegic males

The influence of anaerobic and aerobic exercise, promoted by computer regulated functional electrical stimulation (FES) was evaluated in four paraplegic males. Quadriceps muscle bulk was monitored by serial computerised axial tomography (CT) scanning and histology by muscle biopsies from the vastus intermedius. Anaerobic exercise consisted of 60 degree straight leg raising against increasing weights (range 1.4-11.4 kg) over a period of ten weeks. Aerobic exercise consisted of pedalling a modified Monark bicycle ergometer at 50 rpm against a fixed load ranging from 0-3/8 kilopond (0-18.75 watts) over a period of eight months. In both exercise studies the same work was not achieved by each paraplegic. FES was regulated by a closed loop system which is not presently commercially available, the frequency of the sequential muscle stimulator was 40 Hz with a pulse width of 300 microseconds. Quadriceps muscle area of both legs increased 62.7% (p less than 0.01) after anaerobic exercise; similar but less pronounced effects followed aerobic exercise. Histologically two distinct patterns were noted from the outset, one had normal fibre type distribution the remainder had marked Type 1 loss. Both exercise regimens failed to change these although the number of internal nuclei per 100 fibres steadily increased (from 7.0% to 13.8% to 26.0%) as did the % of fibres with internal nuclei (5.4% to 10.5% to 25.7%) throughout the exercise periods. The significance of these observations is not immediately apparent but may signify continuing damage which may be due to the eccentric rather than the concentric nature of FES promoted muscular contraction.

Needle biopsy for muscle diagnosis and research: an Italian experience

We report our experience of needle biopsy over the past two and a half, viz. 395 cases. We find that the technique meets the needs of diagnosis and research very satisfactorily. We describe its advantages over open biopsy and recommend it in preference to the latter, provided that the necessary technical skill for processing the sample is available.

Dermatomyositis

Dermatomyositis and polymyositis are related disorders of unknown cause in which immunologic changes may be important. They sometimes overlap with other collagen vascular diseases, and not infrequently are associated with malignancy. The clinical features of the adult and juvenile forms of the disorder and the visceral manifestations of DM-PM are outlined, along with enzymatic, electromyographic, and histologic aids to diagnosis. While the cutaneous lesions often are resistant to treatment, systemic involvement may respond to corticosteroids or to immunosuppressive drugs. Treatment definitely alters the prognosis in cases not associated with malignancy.

Citrate interference with the determination of acetylcarnitine: a method for its elimination

Citrate can interfere with the determination of acetylcarnitine when measured by a radioisotopic method. In this report we present a modified procedure designed to avoid this effect. Recovery of added acetylcarnitine was approximately 95%. Acetylcarnitine in normal human plasma was found to range from 0.8 to 19.9 nmol/ml with a mean of 6.3; that of human skeletal muscle ranged from 0.1 to 1.6 nmol/mg protein with a mean of 1.08. The results confirm that exercise gives rise to increased acetylcarnitine content of plasma.

The effect of marathon running on carnitine metabolism and on some aspects of muscle mitochondrial activities and antioxidant mechanisms

Carnitine is an essential co-factor in the catabolism of fats as an energy source. The primary purpose of this study was to investigate the effect of running a marathon on the metabolism of carnitine by endurance-trained athletes, and to evaluate the effect of carnitine administration on the performance of such exercise. The effects of marathon running on mitochondrial enzymes and cellular anti-oxidants were also examined to assess whether the expression of these activities is altered by exercise. Subjects were 10 experienced male marathon runners aged between 19 and 25 years. Running a marathon caused a fall in the plasma content of unesterified carnitine (37%) and an increase in the level of acetylcarnitine present (288%). Loading of the athletes with L-carnitine for 10 days before running a marathon abolished the exercise-induced fall in plasma-free carnitine (P less than 0.05) whilst amplifying the production of acetylcarnitine (P less than 0.05). Carnitine loading of the athletes studied made no detectable improvement in performance of the marathon (P greater than 0.05). Cytochrome oxidase, succinate cytochrome C reductase and superoxide dismutase activities present in skeletal muscle were unaltered by marathon running. However, such exercise caused a large increase in the tissue content of oxidized glutathione (189%) at the expense of reduced glutathione (-18%).

Carnitine status, plasma lipid profiles, and exercise capacity of dialysis patients: effects of a submaximal exercise program

Carnitine status, blood lipid profiles, and exercise capacity were evaluated in a combined group of hemodialysis (N = 4) and continuous ambulatory peritoneal dialysis (N = 6) patients before and after an 8-week submaximal exercise program. Maximal aerobic capacity (VO2max) was only 18.5 +/- 5.9 (mean +/- SD) mL O2/kg/min, well below the expected 30 to 35 mL O2/kg/min for age-matched sedentary controls. Plasma short-chain acylated carnitine levels, which were two to three times normal values, were reduced after the exercise program, but the long-chain acylcarnitines were significantly reduced during acute exercise. Muscle biopsies of the vastus lateralis were performed at rest in five patients prior to and after the 8-week exercise program. Total carnitine in skeletal muscle was 3.09 (.076 SD) mumol/g ww, with only 11.3% acylated prior to the exercise program, which was much lower than the 4.25 +/- 1.27 mumol/g ww, with 28.5% acylated in a group of healthy athletic subjects (N = 28). Muscle free carnitine concentrations decreased significantly following the 8-week training period, with only a slight reduction in total carnitine. The percent of acylated carnitine was therefore significantly increased (P less than 0.05) from 11.3% to 25.2% after the experimental period. Pretraining carnitine palmitoyl transferase activity at rest was 0.57 +/- 0.28 nmol palmitoyl carnitine formed/5 min/mg mitochondrial protein, which was not changed by exercise training v 1.80 +/- 0.51 nmol/5 min/mg protein in 28 healthy normals (P less than 0.001). Free fatty acid concentrations were reduced significantly during acute exercise as a result of the exercise training program whereas other plasma lipids were not altered. (ABSTRACT TRUNCATED AT 250 WORDS)

Protein synthesis and degradation in biopsies of rat skeletal muscle

The use of 20- to 40-mg biopsies of rat skeletal muscle to measure protein synthesis and degradation rates in vitro was investigated and compared to that of the intact extensor digitorum longus (EDL) and soleus muscles. During incubations in oxygenated Krebs-Ringer bicarbonate buffer with glucose, insulin, 23 amino acids at 10 times rat plasma levels, and [14C]tyrosine, the specific activity of intracellular tyrosine approximated that of the incubation medium and was constant in the biopsy, the EDL, and the soleus. The rate of incorporation of tyrosine into the protein of the biopsy was constant for 3 hr and was 39 and 32% of the rates of the EDL and soleus, respectively. The rate of release of tyrosine from protein in the biopsy during incubations in buffer with glucose and cycloheximide was constant for 3 hr and was intermediate between the rates of the EDL and soleus. The effects of starvation on the in vitro protein metabolism of the biopsy were the same as on the intact muscles. The 42% decrease in synthesis and the 53% increase in degradation in the biopsy were intermediate between the changes measured in the EDL and soleus muscles. The ability of this technique to identify proportional changes in the in vitro protein synthesis and degradation rates makes this a valid technique suitable for the measurement of changes of in vitro protein metabolism using serial biopsies from larger animals, including man.

Lobulated fibers in neuromuscular diseases

Lobulated fibers have been observed in biopsies of 13 patients with various neuromuscular disorders including limb-girdle muscular dystrophy (3), distal myopathy (2), scapuloperoneal muscular dystrophy (2), congenital myopathy, Kugelberg-Welander syndrome, hypothyroidism, steroid myopathy, osteomalacia and systemic lupus erythematosus (on steroids). In all cases there were fibers characterised by small subsarcolemmal triangular aggregates or more diffuse collections extending into the interior of the muscle fiber. These were strongly reactive with oxidative enzymes, acid phosphatase, periodic acid-Schiff (PAS), Verhoeff-van Gieson (VVG) and also stained red with the Gomori trichrome technique. In 5 cases core-like fibers were also seen. Morphometric analysis of the NADH-tetrazolium reductase (NADH-TR) preparations in 11 cases showed atrophy of the lobulated fibers. Ultrastructural studies of lobulated fibers disclosed large peripheral mitochondrial aggregates and focal areas with Z-line streaming and disrupted myofibrils. We consider this structural change of the muscle fiber as a reflection of muscle cell disruption and suggest that they may progress from lobulated fibers to more atrophic core-like fibers.