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1.
Hum Mol Genet ; 21(16): 3525-34, 2012 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-22581779

RESUMEN

FIG4 is a ubiquitously expressed phosphatase that, in complex with FAB1/PIKFYVE and VAC14, regulates the biosynthesis of the signaling lipid PI(3,5)P(2). Null mutation of Fig4 in the mouse results in spongiform degeneration of brain and peripheral ganglia, defective myelination and juvenile lethality. Partial loss-of-function of human FIG4 results in a severe form of Charcot-Marie-Tooth neuropathy. Neurons from null mice contain enlarged vacuoles derived from the endosome/lysosome pathway, and astrocytes accumulate proteins involved in autophagy. Other cellular defects include astrogliosis and microgliosis. To distinguish the contributions of neurons and glia to spongiform degeneration in the Fig4 null mouse, we expressed Fig4 under the control of the neuron-specific enolase promoter and the astrocyte-specific glial fibrillary acidic protein promoter in transgenic mice. Neuronal expression of Fig4 was sufficient to rescue cellular and neurological phenotypes including spongiform degeneration, gliosis and juvenile lethality. In contrast, expression of Fig4 in astrocytes prevented accumulation of autophagy markers and microgliosis but did not prevent spongiform degeneration or lethality. To confirm the neuronal origin of spongiform degeneration, we generated a floxed allele of Fig4 and crossed it with mice expressing the Cre recombinase from the neuron-specific synapsin promoter. Mice with conditional inactivation of Fig4 in neurons developed spongiform degeneration and the full spectrum of neurological abnormalities. The data demonstrate that expression of Fig4 in neurons is necessary and sufficient to prevent spongiform degeneration. Therapy for patients with FIG4 deficiency will therefore require correction of the deficiency in neurons.


Asunto(s)
Encéfalo/patología , Flavoproteínas/genética , Neuronas/fisiología , Animales , Astrocitos/patología , Astrocitos/fisiología , Enfermedad de Charcot-Marie-Tooth/genética , Enfermedad de Charcot-Marie-Tooth/patología , Flavoproteínas/metabolismo , Expresión Génica , Ratones , Ratones Transgénicos , Microglía/metabolismo , Microglía/patología , Enfermedades Neurodegenerativas/genética , Enfermedades Neurodegenerativas/patología , Fosfoinosítido Fosfatasas , Monoéster Fosfórico Hidrolasas , Células de Schwann/metabolismo , Células de Schwann/patología
2.
Hum Mol Genet ; 19(13): 2668-81, 2010 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-20400459

RESUMEN

Myotubularins are a family of dual-specificity phosphatases that act to modify phosphoinositides and regulate membrane traffic. Mutations in several myotubularins are associated with human disease. Sequence changes in MTM1 and MTMR14 (also known as Jumpy) have been detected in patients with a severe skeletal myopathy called centronuclear myopathy. MTM1 has been characterized in vitro and in several model systems, while the function of MTMR14 and its specific role in muscle development and disease is much less well understood. We have previously reported that knockdown of zebrafish MTM1 results in significantly impaired motor function and severe histopathologic changes in skeletal muscle that are characteristic of human centronuclear myopathy. In the current study, we examine zebrafish MTMR14 using gene dosage manipulation. As with MTM1 knockdown, morpholino-mediated knockdown of MTMR14 results in morphologic abnormalities, a developmental motor phenotype characterized by diminished spontaneous contractions and abnormal escape response, and impaired excitation-contraction coupling. In contrast to MTM1 knockdown, however, muscle ultrastructure is unaffected. Double knockdown of both MTM1 and MTMR14 significantly impairs motor function and alters skeletal muscle ultrastructure. The combined effect of reducing levels of both MTMR14 and MTM1 is significantly more severe than either knockdown alone, an effect which is likely mediated, at least in part, by increased autophagy. In all, our results suggest that MTMR14 is required for motor function and, in combination with MTM1, is required for myocyte homeostasis and normal embryonic development.


Asunto(s)
Acoplamiento Excitación-Contracción , Proteínas Tirosina Fosfatasas no Receptoras/genética , Proteínas de Pez Cebra/genética , Pez Cebra/genética , Animales , Autofagia , Modelos Animales de Enfermedad , Embrión no Mamífero/embriología , Embrión no Mamífero/metabolismo , Regulación del Desarrollo de la Expresión Génica , Técnicas de Inactivación de Genes , Homeostasis , Músculo Esquelético/fisiología , Músculo Esquelético/ultraestructura , Miopatías Estructurales Congénitas/metabolismo , Miopatías Estructurales Congénitas/patología , Proteínas Tirosina Fosfatasas no Receptoras/metabolismo , Pez Cebra/embriología , Pez Cebra/metabolismo , Proteínas de Pez Cebra/metabolismo
3.
Hum Mol Genet ; 19(12): 2433-44, 2010 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-20338942

RESUMEN

Collagen VI is an integral part of the skeletal muscle extracellular matrix, providing mechanical stability and facilitating matrix-dependent cell signaling. Mutations in collagen VI result in either Ullrich congenital muscular dystrophy (UCMD) or Bethlem myopathy (BM), with UCMD being clinically more severe. Recent studies demonstrating increased apoptosis and abnormal mitochondrial function in Col6a1 knockout mice and in human myoblasts have provided the first mechanistic insights into the pathophysiology of these diseases. However, how loss of collagen VI causes mitochondrial dysfunction remains to be understood. Progress is hindered in part by the lack of an adequate animal model for UCMD, as knockout mice have a mild motor phenotype. To further the understanding of these disorders, we have generated zebrafish models of the collagen VI myopathies. Morpholinos designed to exon 9 of col6a1 produced a severe muscle disease reminiscent of UCMD, while ones to exon 13 produced a milder phenotype similar to BM. UCMD-like zebrafish have increased cell death and abnormal mitochondria, which can be attenuated by treatment with the proton pump modifier cyclosporin A (CsA). CsA improved the motor deficits in UCMD-like zebrafish, but failed to reverse the sarcolemmal membrane damage. In all, we have successfully generated the first vertebrate model matching the clinical severity of UCMD and demonstrated that CsA provides phenotypic improvement, thus corroborating data from knockout mice supporting the use of mitochondrial permeability transition pore modifiers as therapeutics in patients, and providing proof of principle for the utility of the zebrafish as a powerful preclinical model.


Asunto(s)
Colágeno Tipo VI/genética , Modelos Animales de Enfermedad , Músculo Esquelético/metabolismo , Distrofias Musculares/genética , Pez Cebra/genética , Animales , Apoptosis , Colágeno Tipo VI/metabolismo , Ciclosporina/farmacología , Embrión no Mamífero/metabolismo , Embrión no Mamífero/patología , Exones/genética , Técnicas de Silenciamiento del Gen , Humanos , Ratones , Mitocondrias Musculares/efectos de los fármacos , Mitocondrias Musculares/patología , Actividad Motora/efectos de los fármacos , Músculo Esquelético/anomalías , Músculo Esquelético/ultraestructura , Distrofias Musculares/metabolismo , Distrofias Musculares/patología , Sarcolema/efectos de los fármacos , Sarcolema/metabolismo , Sarcolema/patología , Pez Cebra/embriología
4.
Ann Neurol ; 68(5): 717-26, 2010 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-20839240

RESUMEN

OBJECTIVE: Centronuclear myopathy (CNM) is a rare congenital myopathy characterized by prominence of central nuclei on muscle biopsy. CNM has been associated with mutations in MTM1, DNM2, and BIN1 but many cases remain genetically unresolved. RYR1 encodes the principal sarcoplasmic reticulum calcium release channel and has been implicated in various congenital myopathies. We investigated whether RYR1 mutations cause CNM. METHODS: We sequenced the entire RYR1 coding sequence in 24 patients with a diagnosis of CNM from South Africa (n = 14) and Europe (n = 10) and identified mutations in 17 patients. The most common genotypes featured compound heterozygosity for RYR1 missense mutations and mutations resulting in reduced protein expression, including intronic splice site and frameshift mutations. RESULTS: The high incidence in South African patients (n = 12/14) in conjunction with recurrent RYR1 mutations associated with common haplotypes suggested the presence of founder effects. In addition to central nuclei, prominent histopathological findings included (often multiple) internalized nuclei and type 1 fiber predominance and hypotrophy with relative type 2 hypertrophy. Although cores were not typically seen on oxidative stains, electron microscopy revealed subtle abnormalities in most cases. External ophthalmoplegia, proximal weakness, and bulbar involvement were prominent clinical findings. INTERPRETATION: Our findings expand the range of RYR1-related phenotypes and suggest RYR1 mutations as a common cause of congenital myopathies with central nuclei. Corresponding to recent observations in X-linked CNM, these findings indicate disturbed assembly and/or malfunction of the excitation-contraction machinery as a key mechanism in CNM and related myopathies.


Asunto(s)
Músculo Esquelético/patología , Miopatías Estructurales Congénitas/etiología , Canal Liberador de Calcio Receptor de Rianodina/genética , Adolescente , Niño , Preescolar , Europa (Continente) , Genotipo , Heterocigoto , Humanos , Masculino , Mutación , Miopatías Estructurales Congénitas/diagnóstico , Miopatías Estructurales Congénitas/genética , Miopatías Estructurales Congénitas/patología , Fenotipo , Canal Liberador de Calcio Receptor de Rianodina/metabolismo , Sudáfrica
5.
Br J Anaesth ; 106(5): 706-12, 2011 May.
Artículo en Inglés | MEDLINE | ID: mdl-21498494

RESUMEN

BACKGROUND: Transversus abdominis plane (TAP) block is an alternative to spinal morphine for analgesia after Caesarean section but there are few data on its comparative efficacy. We compared the analgesic efficacy of the TAP block with and without spinal morphine after Caesarean section in a prospective, randomized, double-blinded placebo-controlled trial. METHODS: Eighty patients were randomized to one of four groups to receive (in addition to spinal anaesthesia) either spinal morphine 100 µg (S(M)) or saline (S(S)) and a postoperative bilateral TAP block with either bupivacaine (T(LA)) 2 mg kg(-1) or saline (T(S)). RESULTS: Pain on movement and early morphine consumption were lowest in groups receiving spinal morphine and was not improved by TAP block. The rank order of median pain scores on movement at 6 h was: S(M)T(LA) (20 mm)

Asunto(s)
Analgesia Obstétrica/métodos , Analgésicos Opioides/administración & dosificación , Cesárea , Morfina/administración & dosificación , Bloqueo Nervioso/métodos , Dolor Postoperatorio/prevención & control , Músculos Abdominales , Adulto , Analgesia Obstétrica/efectos adversos , Analgésicos Opioides/efectos adversos , Anestesia Obstétrica/métodos , Anestesia Raquidea , Antieméticos/administración & dosificación , Método Doble Ciego , Esquema de Medicación , Femenino , Humanos , Morfina/efectos adversos , Bloqueo Nervioso/efectos adversos , Dimensión del Dolor/métodos , Satisfacción del Paciente , Embarazo , Estudios Prospectivos , Prurito/inducido químicamente
6.
J Neuromuscul Dis ; 8(1): 53-61, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-32925088

RESUMEN

We report the recruitment activities and outcomes of a multi-disease neuromuscular patient registry in Canada. The Canadian Neuromuscular Disease Registry (CNDR) registers individuals across Canada with a confirmed diagnosis of a neuromuscular disease. Diagnosis and contact information are collected across all diseases and detailed prospective data is collected for 5 specific diseases: Amyotrophic Lateral Sclerosis (ALS), Duchenne Muscular Dystrophy (DMD), Myotonic Dystrophy (DM), Limb Girdle Muscular Dystrophy (LGMD), and Spinal Muscular Atrophy (SMA). Since 2010, the CNDR has registered 4306 patients (1154 pediatric and 3148 adult) with 91 different neuromuscular diagnoses and has facilitated 125 projects (73 academic, 3 not-for-profit, 3 government, and 46 commercial) using registry data. In conclusion, the CNDR is an effective and productive pan-neuromuscular registry that has successfully facilitated a substantial number of studies over the past 10 years.


Asunto(s)
Esclerosis Amiotrófica Lateral , Atrofia Muscular Espinal , Distrofia Muscular de Cinturas , Distrofia Muscular de Duchenne , Distrofia Miotónica , Sistema de Registros , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Canadá , Niño , Preescolar , Femenino , Humanos , Lactante , Masculino , Persona de Mediana Edad , Adulto Joven
7.
Neuromuscul Disord ; 28(9): 766-777, 2018 09.
Artículo en Inglés | MEDLINE | ID: mdl-30122513

RESUMEN

Centronuclear myopathies (CNM) are a group of rare inherited muscular disorders leading to a significantly reduced quality of life and lifespan. To date, CNM epidemiologic reports provide limited incidence and prevalence data. Here, an integrated model utilizing available literature is proposed to obtain a better estimate of overall CNM patient numbers by age, causative gene, severity and geographic region. This model combines published epidemiology data and extrapolates limited data over CNM subtypes, resulting in patient numbers related to age and disease subtype. Further, the model calculates a CNM incidence twofold the current estimates. The estimated incidence of 17 per million births for severe X-linked myotubular myopathy (XLMTM), the main subtype of CNM, corresponds to an estimated prevalence of 2715 in the US, 1204 in the EU, 688 in Japan and 72 in Australia. In conclusion, the model provides an estimate of the CNM incidence, prevalence and survival, and indicates that the current estimates do not fully capture the true incidence and prevalence. With rapid advances in genetic therapies, robust epidemiologic data are needed to further quantify the reliability of incidence, prevalence and survival rates for the different CNM subtypes.


Asunto(s)
Miopatías Estructurales Congénitas/epidemiología , Humanos , Incidencia , Modelos Teóricos , Miopatías Estructurales Congénitas/genética , Prevalencia
8.
Clin Biomech (Bristol, Avon) ; 22(2): 230-8, 2007 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-17141925

RESUMEN

BACKGROUND: To determine the behaviour of the human foot during in vivo loading and unloading. METHODS: Fluoroscopic imaging was used to investigate the movement of the bones and 13 skin markers during loading and unloading for the medial aspect of the left foot. A foot-pressure measuring system was compared with a force plate used to gather kinetic information, simultaneously. Four male and two female subjects performed three tasks that mimicked jumping, walking, and sprinting. Two-dimensional vector displacements were calculated between bone landmarks over time. Foot rigidity was assessed by a 5 mm length variability threshold determined as the difference between the third and first quartiles of the data set. FINDINGS: The displacement between the first metatarso-phalangeal joint and distal aspect of the calcaneous varied more than the 5 mm threshold. A new foot model was developed which included three rigid segments joined together by hinge joints located at the first metatarso-phalangeal joint and between the anterior talus and navicular. The comparison between skin mounted markers and bone landmarks yielded a range of correlation slopes close to 1.00 for both the x- and y-directions. Foot pressure and force plate comparisons were promising (%RMS(error) approximately 10%) for the vertical ground reaction forces but not so for the centres of pressure (%RMS(error) up to 50%). INTERPRETATION: A multi-segment foot model is required to better represent the behaviour of a human foot. No consistent skin marker movement was determined. Better pressure distribution devices need to be developed to determine more accurate foot kinetics. Precise foot kinematics are required in order that accurate ankle moments and reaction forces be determined for the purpose of assessing foot and ankle function.


Asunto(s)
Fenómenos Biomecánicos/métodos , Fluoroscopía/métodos , Pie/anatomía & histología , Pie/patología , Caminata , Femenino , Marcha , Humanos , Articulaciones , Masculino , Modelos Teóricos , Movimiento , Presión , Análisis de Regresión , Estrés Mecánico , Factores de Tiempo
9.
J Electromyogr Kinesiol ; 16(4): 352-64, 2006 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-16263310

RESUMEN

The purpose of this study was to use an electromyography (EMG) based muscle model to investigate the performance enhancement of stretch-shortening cycle (SSC) tasks at different elbow flexion-extension velocities. A torque motor was used to oscillate the forearms of seven healthy male subjects (23-40 years) during SSC and non-SSC contractions at four frequencies of movement (.58, 1.5, 2.4 and 3.3Hz) over a range of 105 degrees -162 degrees of elbow extension. The torque was integrated as a function of joint angle to yield the work produced by the elbow flexors. The elbow flexors were transcutaneously stimulated with a voltage equivalent to 60% maximum voluntary isometric contraction torque for 4s at 50Hz. EMG of the elbow flexors and extensors was recorded from the biceps and triceps respectively. The processed EMG was used to drive a Hill based model to predict the torque of the elbow flexors. Results indicate that muscle work increases from non-SSC to SSC trials. Work decreases for SSC and non-SSC trials with increasing velocity. The simulated constant activation muscle model predicted work well for all trials and conditions, indicating muscle model accuracy. The EMG driven model predicted well for all non-SSC trials, but significantly underestimated the work for SSC tasks, suggesting that the contractile component is directly involved in optimising muscle work during SSC tasks.


Asunto(s)
Articulación del Codo/fisiología , Contracción Isométrica/fisiología , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Reflejo de Estiramiento/fisiología , Adulto , Electromiografía , Estudios de Evaluación como Asunto , Humanos , Masculino , Modelos Biológicos , Factores de Tiempo , Torque
10.
J Electromyogr Kinesiol ; 16(1): 32-41, 2006 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-16219477

RESUMEN

The purpose of this study was to determine the mechanisms responsible for improving ballistic elbow extension. In doing so, an electromyography (EMG)-driven model was developed to predict the actual triceps torque so that the model parameters between subjects could be compared. Thirty-two subjects performed maximum isometric trials at 60 degrees , 90 degrees and 120 degrees of elbow extension to determine torque-angle relations. Dynamic elbow extension trials were then performed against relative loads of 0%, 20%, 40%, 60% and 80% and absolute loads of 1.1 and 2.2 kg. These trials were used to determine the torque-angular velocity relation for each subject. The model predicted the triceps torque during the unloaded, 1.1 and 2.2 kg trials with an average r = 0.964 and an average root mean square error of 4.34 Nm. As a result of the good predictions, a forward dynamics approach was used to substitute different neuro-muscular mechanisms of a poor performance with those from an individual that displayed a superior performance. Performance was shown to improve when these modifications were made. Therefore, the EMG-driven model was capable of modeling the actual muscle torque which allowed for the identification of areas of weakness of a poor performance. A prescription for improvement was identified, albeit artificially, on an individual basis. The next stage is to determine which specific interventions can accomplish those theoretically proposed.


Asunto(s)
Articulación del Codo/fisiología , Electromiografía , Músculo Esquelético/fisiología , Humanos , Contracción Isométrica , Masculino
11.
J Comp Neurol ; 351(4): 617-31, 1995 Jan 23.
Artículo en Inglés | MEDLINE | ID: mdl-7721987

RESUMEN

Regulation of protein function through tyrosine phosphorylation is critical in the control of many developmental processes, such as cellular proliferation and differentiation. Growing evidence suggests that tyrosine phosphorylation also regulates key events in neural development. Although a large body of data has demonstrated that protein tyrosine kinases play an important role in neural development, much less is known about their counterparts, protein tyrosine phosphatases (PTPases). Using polymerase chain reaction (PCR) with degenerate primers and a neonatal rat cortex cDNA library, we have identified seven PTPases expressed in the developing rat brain. Four of these are transmembrane PTPases: LAR, LRP, RPTP gamma, and CPTP1. Three are nonreceptor PTPases: PTP-1, P19-PTP, and SHP. Northern hybridization analysis demonstrates that only CPTP1 is preferentially expressed in neural tissues, whereas the others are found abundantly in nonneural tissues as well as in the brain. Within the embryonic and early postnatal brain, the seven PTPases have overlapping, yet unique, distributions. For example, LAR mRNA is highly expressed by both proliferating and postmitotic cells in the cerebral cortex at embryonic day 17 and in all layers of the cortex at postnatal day 4. In contrast, RPTP gamma mRNA is expressed by postmitotic neurons in the embryo and predominantly by neurons in the superficial layers of the postnatal cortex. Several of the PTPases examined here are expressed at very high levels in the embryonic cortical plate and postnatal neocortex, including the subplate and subventricular zone. The spatial and temporal regulation of PTPase gene expression suggests that these PTPases have important roles in signal transduction during early neuronal differentiation and neural development.


Asunto(s)
Encéfalo/metabolismo , Expresión Génica/genética , Proteínas Tirosina Fosfatasas/genética , Animales , Embrión de Mamíferos , Hibridación in Situ , Fosforilación , Reacción en Cadena de la Polimerasa , Ratas
12.
Neuroscience ; 60(1): 133-44, 1994 May.
Artículo en Inglés | MEDLINE | ID: mdl-8052407

RESUMEN

In rats, morphological and synaptic maturation of the striatum, a brain area involved in the control of movement and in cognitive behaviour, proceeds for several weeks postnatally. Little is known, however, about the molecular events associated with the final maturation of the striatum. In particular, there is little information on molecules playing a role in cell adhesion, a phenomenon of particular importance for neuronal development. We have examined the time course and topography of expression of the highly polysialylated form of the neural cell adhesion molecule in the rat striatum during postnatal development and in the adult, and compared it to growth-associated protein-43, a marker of axonal growth. As earlier during development [Aaron L. I. and Chesselet M.-F. (1989) Neuroscience 28, 701-710], immunolabelling for polysialylated neural cell adhesion molecule was very intense in the entire striatum at postnatal days 17-19. At postnatal days 21 and 22, loss of polysialylated neural cell adhesion molecule immunoreactivity in the caudal part of the striatum contrasted with the persistence of immunoreactivity at more rostral levels. Most of the striatum was devoid of polysialylated neural cell adhesion molecule immunoreactivity by postnatal day 25. At this age, as well as in the striatum of adult rats, immunolabelling was only observed along the ventricular edge of the striatum. In contrast to polysialylated neural cell adhesion molecule immunoreactivity, immunolabelling for growth-associated protein-43 had reached its adult pattern by postnatal day 17, indicating that polysialylated neural cell adhesion molecule persists beyond the period of major axonal growth. In the adult, an area of stronger growth associated protein-43 immunoreactivity overlapped with the region which retained immunoreactivity to polysialylated neural cell adhesion molecule. The results indicate that, in the developing rat striatum, the neural cell adhesion molecule remains highly sialylated not only during the ingrowth of cortical and nigral inputs but also during the formation of dendritic spine and synaptogenesis. Loss of polysialyated neural cell adhesion molecule occurs at the time of emerging spontaneous activity in cerebral cortex, and precedes the development of mature responses to cortical stimulation and adult membrane properties in a majority of striatal neurons.


Asunto(s)
Moléculas de Adhesión Celular Neuronal/biosíntesis , Neostriado/crecimiento & desarrollo , Neostriado/metabolismo , Ácidos Siálicos/metabolismo , Animales , Femenino , Proteína GAP-43 , Immunoblotting , Inmunohistoquímica , Masculino , Glicoproteínas de Membrana/biosíntesis , Neostriado/anatomía & histología , Proteínas del Tejido Nervioso/biosíntesis , Proteínas de Neurofilamentos/biosíntesis , Ratas , Ratas Sprague-Dawley
13.
Neurosci Lett ; 179(1-2): 25-8, 1994 Sep 26.
Artículo en Inglés | MEDLINE | ID: mdl-7845617

RESUMEN

Previous investigators have used electrical stimulation superimposed on voluntary efforts to show that humans are capable of maximum muscle activation. In the present study this notion was tested using the interpolated twitch technique enhanced by triggered averaging and doublet stimulation of the human biceps brachii. It was found that the decline in extra torque evoked by percutaneous stimulation with increasing levels of voluntary effort was nonlinear and that none of the twelve subjects was able to elicit a voluntary effort large enough to prevent extra torque of elbow flexion. The exponential nature of the declining extra torque indicated that an extrapolated maximum muscle force could be considerably larger than that to which subjects were able to elicit voluntarily.


Asunto(s)
Músculo Esquelético/fisiología , Adulto , Brazo/inervación , Brazo/fisiología , Estimulación Eléctrica , Femenino , Humanos , Contracción Isométrica/fisiología , Masculino , Músculo Esquelético/inervación
14.
Sports Med ; 24(2): 82-96, 1997 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-9291550

RESUMEN

Suitably processed electromyographic (EMG) signals can be combined with Hill-type musculoskeletal models to noninvasively achieve estimations of individual muscle forces. This method has particular advantages over other methods for the assessment of a given performance. The purpose of this review is to report on the current issues facing the human movement scientist who wishes to extend the kinetic information yielded by linked segment models to the kinetics of individual muscles. Such an extension is necessary when considering co-contraction of antagonistic muscles, the role of bi-articular muscles, co-ordination, movement efficiency or bone-on-bone forces. Currently, linked segment models have not been successfully extended to individual muscle forces for diagnostic purposes by using the EMG approach or any other approach. Most models have been designed for a specific purpose and have only been evaluated over a narrow range of movement conditions. More generalised models will require greater complexity and possibly more extensive calibration or an increased number of specific inputs or greater computational effort. This review shows the promise of the EMG approach and presents the challenges, as well as the strategies, that should enable more general, accurate and precise estimates of individual muscle forces.


Asunto(s)
Electromiografía , Músculo Esquelético/fisiología , Animales , Fenómenos Biomecánicos , Articulación del Codo/fisiología , Humanos , Modelos Biológicos , Contracción Muscular , Fatiga Muscular , Redes Neurales de la Computación
15.
Med Sci Sports Exerc ; 29(10): 1366-73, 1997 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-9346169

RESUMEN

Nine male karate athletes and 13 untrained men did maximal voluntary isometric (MVC) and ballistic elbow extension actions, the latter unloaded (L0) and against a load equal to 10% MVC (L10). The karate group achieved greater (P < 0.05) isometric (32%) and ballistic action peak torque with L0 (30%) and L10 (40%). With L10 the ratio of ballistic action to isometric action, peak torque was 13% greater in the karate group, indicating a load specific training adaptation. With L0 the corresponding ratio did not differ significantly between groups. Ballistic action peak rate of torque development (51%, 51%) and peak acceleration (15%, 9%) with L0 and L10, respectively, were greater in the karate group. In contrast, peak velocity and movement time did not differ significantly between groups. Electromyographic recordings of agonist triceps and antagonist biceps were made during the isometric and ballistic actions. Since ballistic actions (L10) were initiated from a preloaded condition, the occurrence and duration of premovement agonist depression were monitored. In ballistic actions there were no group differences in agonist activation, the ratio of ballistic to isometric action agonist activation, or antagonist coactivation. Premovement agonist depression occurred infrequently in both groups, with no group differences. It is concluded that karate athletes have enhanced elbow extension ballistic performance, but it could not be related to amplified agonist activation, altered antagonist activation, or more frequent occurrence of agonist premovement depression.


Asunto(s)
Artes Marciales/fisiología , Movimiento/fisiología , Músculo Esquelético/fisiología , Aceleración , Adulto , Análisis de Varianza , Brazo/fisiología , Fenómenos Biomecánicos , Estudios de Casos y Controles , Articulación del Codo/fisiología , Electromiografía , Diseño de Equipo , Humanos , Masculino , Torque
16.
Med Sci Sports Exerc ; 28(12): 1498-504, 1996 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-8970144

RESUMEN

UNLABELLED: A major movement related limitation for children with spastic cerebral palsy (CP) is the compromised gait pattern, which may explain their excessive energy cost of locomotion. The aims of this study were to determine differences in the O2 cost of locomotion between children with CP (7 males, 2 females; 12.7 +/- 2.8 yr) and able-bodied controls (7 male, 1 female; 13.6 +/- 2.1 yr) and to assess the contribution that cocontraction of agonist and antagonist muscles had upon the elevated O2 cost seen in children with CP versus able-bodied controls. The treadmill submaximal walking protocol consisted of 2 x 4 min intermittent stages at 3 km.h-1 and 90% of the predetermined fastest walking speed (FWS) at 0% grade. Electromyographic data were collected during the final minute of each bout from vastus lateralis and hamstrings (thigh) and tibialis anterior and soleus (lower leg). Significant (P < 0.05) differences were noted at 3 km.h-1 for mass-relative VO2. (CP: 16.6 +/- 6.5 vs control: 10.2 +/- 1.2 ml.kg-1.min-1), % VO2max (CP: 53.5 +/- 26.0 vs CONTROL: 22.5 +/- 4.93) and heart rate (CP: 143 +/- 41 vs CONTROL: 91 +/- 14 beats.min-1). Thigh and lower leg muscle cocontraction accounted for 51.4% and 42.8%, respectively, of the variability in VO2 for the subjects with CP at 3 km.h-1. These results suggest that cocontraction is a major factor responsible for the higher energy cost of walking seen in children with CP.


Asunto(s)
Parálisis Cerebral/fisiopatología , Contracción Muscular/fisiología , Consumo de Oxígeno/fisiología , Caminata/fisiología , Adolescente , Niño , Electromiografía , Femenino , Humanos , Pierna/fisiología , Masculino
17.
Med Sci Sports Exerc ; 31(12): 1703-8, 1999 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-10613418

RESUMEN

UNLABELLED: It has been established in able-bodied children that traditional biomechanical descriptors of gait such as stride length or stride frequency do not fully account for the differences seen in the energy cost of locomotion noted with age. Hence, measures of total body mechanical power output have been adopted to explain these differences. PURPOSE: The aim of this study was to estimate the ability of this mechanical power calculation to explain the variability in the metabolic energy cost of treadmill walking in children with spastic cerebral palsy (CP). METHODS: Thirteen subjects volunteered for the study. One group consisted of eight (6 male, 2 female) children with CP (age 12.2 +/- 2.7 yr). The second group consisted of five (4 male, 1 female) able-bodied controls (age 13.4 +/- 2.8 yr). The treadmill walking protocol consisted of one 4-min stage at 0% grade, 3 km x h(-1). Infrared markers were placed on 12 anatomical landmarks and data were collected using the OPTOTRAK motion analysis system over a 5-s time period during the last 30 s of the 4-min stage. On-line oxygen consumption VO2 measurements were obtained throughout using the Beckman Horizon Metabolic Cart. RESULTS: Relative VO2 (mL x kg(-1) x min(-1)) was significantly (P < 0.05) different between the two groups (CP: 16.6 +/- 6.5 vs control: 10.2 +/- 1.2). Simple linear regression analysis demonstrated that mechanical power measurements, incorporating transfers of energy between and within adjacent body segments, accounted for 87.2% of the total variability noted in VO2 for the children with CP, compared with only 2.4% in the able-bodied subjects. CONCLUSIONS: The results indicate that mechanical power differences explain the majority of the variability noted in VO2 in children with CP at a submaximal walking speed.


Asunto(s)
Parálisis Cerebral/fisiopatología , Consumo de Oxígeno/fisiología , Caminata/fisiología , Adolescente , Fenómenos Biomecánicos , Niño , Prueba de Esfuerzo , Femenino , Humanos , Masculino , Modelos Teóricos , Análisis de Regresión
18.
J Infect ; 9(2): 170-3, 1984 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-6501906

RESUMEN

Bacteraemia caused by Yersinia enterocolitica was associated in a 60-year-old diabetic man with right upper-quadrant abdominal tenderness and abnormal liver function tests. Biopsy of the liver demonstrated granulomas with acute necrosis. To the authors' knowledge, this is the first report of granuloma formation in the human liver associated with this infection. Yersinia enterocolitica should therefore be added to the list of organisms associated with granulomatous hepatitis in human beings.


Asunto(s)
Granuloma/etiología , Hepatitis/etiología , Sepsis/complicaciones , Yersiniosis/complicaciones , Biopsia , Niño , Granuloma/patología , Hepatitis/patología , Humanos , Hígado/patología , Masculino , Persona de Mediana Edad , Yersiniosis/patología , Yersinia enterocolitica
19.
Electromyogr Clin Neurophysiol ; 36(8): 487-94, 1996 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-8985677

RESUMEN

Simultaneous activity of agonist and antagonistic muscles during a task is known as cocontraction. The primary aim of the present study was to use a cocontraction index (CI) to quantify differences in EMG activity between a group of CP and control children at two different walking speeds. The secondary aim was to compare the amount of time the muscles were activated ("on" thresholds) between the groups. Seventeen subjects volunteered for the study. One group consisted of 9 (7M, 2F) children with CP (age 12.7 +/- 2.8 years, mean +/- SD). The second group consisted of 8 able-bodied controls (7M, 1F). The discontinuous submaximal treadmill walking protocol had two 4min stages at 0% gradient. Speeds selected were 3 km.h-1 and 90% of the pre-determined fastest walking speed (FWS). Two sites of CI were measured from the EMGs of tibialis anterior and soleus (leg) and vastus lateralis and hamstrings (thigh). Significantly (p < 0.05) higher CI values were noted for the CP subjects compared to the controls, irrespective of speed or cocontraction site and there was a significant (p < 0.05) increase in CI values with increased walking speed for both CP and control subjects. Phasic analyses for 5% max EMG and 10% max EMG "on" thresholds demonstrated significant (p < 0.05) main effects for group (CP subjects had a longer time period of muscle activation than controls) and speed (muscles were active longer at 90% FWS than 3 km.h-1). The precise mechanisms by which cocontraction contributes toward abnormal gait and wasted mechanical energy require further research incorporating both electromyographic and kinematic analysis.


Asunto(s)
Parálisis Cerebral/fisiopatología , Marcha , Contracción Muscular , Adolescente , Niño , Electromiografía , Prueba de Esfuerzo , Femenino , Humanos , Pierna , Masculino
20.
Hawaii Med J ; 50(12): 416-7, 420, 1991 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-1769818

RESUMEN

The late 20th century is witnessing an explosion of biomedical knowledge in the discipline of molecular genetics. In this regard many medical specialties will be transformed in terms of diagnosis and treatment. The technology and the recent clinical research in psychiatry is one of these.


Asunto(s)
Trastornos Mentales/genética , Ligamiento Genético , Humanos , Biología Molecular
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