RESUMO
Motor function recovery from injury requires the regeneration of not only muscle fibers, but also the neuromuscular junction-the synapse between motor nerve terminals and muscle fibers. However, unlike muscle regeneration which has been extensively studied, little is known about the molecular mechanisms of NMJ regeneration. Recognizing the critical role of agrin-LRP4-MuSK signaling in NMJ formation and maintenance, we investigated whether increasing MuSK activity promotes NMJ regeneration. To this end, we evaluated the effect of DOK7, a protein that stimulates MuSK, on NMJ regeneration. Reinnervation, AChR cluster density, and endplate area were improved, and fragmentation was reduced in the AAV9-DOK7-GFP-injected muscles compared with muscles injected with AAV9-GFP. These results demonstrated expedited NMJ regeneration associated with increased DOK7 expression and support the hypothesis that increasing agrin signaling benefits motor function recovery after injury. Our findings propose a potentially new therapeutic strategy for functional recovery after muscle and nerve injury, i.e., promoting NMJ regeneration by increasing agrin signaling.
Assuntos
Proteínas Musculares , Junção Neuromuscular , Agrina/metabolismo , Junção Neuromuscular/lesões , Junção Neuromuscular/fisiologia , Receptores Colinérgicos/metabolismo , Sinapses/metabolismo , Proteínas Musculares/metabolismo , Animais , Camundongos , RegeneraçãoRESUMO
Volumetric muscle loss (VML) following a severe trauma or injury is beyond the intrinsic regenerative capacity of muscle tissues, and hence interventional therapy is required. Extensive muscle loss concomitant with damage to neuromuscular components overwhelms the muscles' remarkable regenerative capacity. The loss of nervous and vascular tissue leads to further damage and atrophy, so a combined treatment for neuromuscular junction (NMJ) along with the volumetric muscle regeneration is important. There have been immense advances in the field of tissue engineering for skeletal muscle tissue and peripheral nerve regeneration, but very few address the interdependence of the tissues and the need for combined therapies to repair and regenerate fully functional muscle tissue. This review addresses the problem and presents an overview of the biomaterials that have been studied for tissue engineering of neuromuscular tissues associated with skeletal muscles.
Assuntos
Materiais Biocompatíveis , Músculo Esquelético/lesões , Músculo Esquelético/fisiologia , Regeneração Nervosa/fisiologia , Engenharia Tecidual/métodos , Animais , Humanos , Junção Neuromuscular/lesões , Junção Neuromuscular/fisiologiaRESUMO
Neonatal brachial plexus injury (NBPI) causes disabling and incurable muscle contractures that are driven by impaired growth of denervated muscles. A rare form of NBPI, which maintains afferent muscle innervation despite motor denervation, does not cause contractures. As afferent innervation regulates various aspects of skeletal muscle homeostasis through NRG/ErbB signaling, our current study investigated the role of this pathway in modulating contracture development. Through pharmacologic modification with an ErbB antagonist and NRG1 isoforms, we discovered that NRG/ErbB signaling does not modulate the development of contractures in neonatal mice. Instead, ErbB inhibition impeded growth in nondenervated skeletal muscles, whereas increased ErbB activation exacerbated denervation-induced skeletal muscle atrophy. This potential regulatory effect of NRG/ErbB signaling on neonatal muscle growth warrants deeper investigation.
Assuntos
Contratura/genética , Receptores ErbB/genética , Músculo Esquelético/metabolismo , Atrofia Muscular/genética , Neuregulina-1/genética , Animais , Animais Recém-Nascidos , Plexo Braquial/efeitos dos fármacos , Plexo Braquial/lesões , Plexo Braquial/metabolismo , Contratura/metabolismo , Contratura/fisiopatologia , Receptores ErbB/antagonistas & inibidores , Receptores ErbB/metabolismo , Regulação da Expressão Gênica , Camundongos , Morfolinas/farmacologia , Denervação Muscular/métodos , Desenvolvimento Muscular/genética , Músculo Esquelético/citologia , Músculo Esquelético/crescimento & desenvolvimento , Músculo Esquelético/inervação , Atrofia Muscular/metabolismo , Atrofia Muscular/fisiopatologia , Neuregulina-1/metabolismo , Junção Neuromuscular/efeitos dos fármacos , Junção Neuromuscular/lesões , Junção Neuromuscular/metabolismo , Transdução de SinaisRESUMO
Disruption of neuromuscular junctions and denervation of some muscle fibers occurs in ageing skeletal muscle and contribute to loss of muscle mass and function. Aging is associated with mitochondrial dysfunction and loss of redox homeostasis potentially occurs through increased mitochondrial generation of reactive oxygen species (ROS). No specific link between increased mitochondrial ROS generation and denervation has been defined in muscle ageing. To address this, we have examined the effect of experimental denervation of all fibers, or only a proportion of the fibers, in the mouse tibialis anterior (TA) muscle on muscle mitochondrial peroxide generation. Transection of the peroneal nerve of mice caused loss of pre-synaptic axons within 1-3 days with no significant morphological changes in post-synaptic structures up to 10 days post-surgery when decreased TA mass and fiber size were apparent. Mitochondria in the denervated muscle showed increased peroxide generation by 3 days post-transection. Use of electron transport chain (ETC) substrates and inhibitors of specific pathways indicated that the ETC was unlikely to contribute to increased ROS generation, but monoamine oxidase B, NADPH oxidase and phospholipase enzymes were implicated. Transection of one of the 3 branches of the peroneal nerve caused denervation of some TA muscle fibers while others retained innervation, but increased mitochondrial peroxide generation occurred in both denervated and innervated fibers. Thus the presence of recently denervated fibers leads to increased ROS generation by mitochondria in neighboring innervated fibers providing a novel explanation for the increased mitochondrial oxidative stress and damage seen with aging in skeletal muscles.
Assuntos
Envelhecimento/metabolismo , Mitocôndrias/metabolismo , Denervação Muscular/métodos , Fibras Musculares Esqueléticas/metabolismo , Nervo Fibular/lesões , Sarcopenia/metabolismo , Envelhecimento/genética , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Complexo de Proteínas da Cadeia de Transporte de Elétrons/genética , Complexo de Proteínas da Cadeia de Transporte de Elétrons/metabolismo , Regulação da Expressão Gênica , Genes Reporter , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Masculino , Camundongos , Camundongos Transgênicos , Mitocôndrias/patologia , Monoaminoxidase/genética , Monoaminoxidase/metabolismo , Inibidores da Monoaminoxidase/farmacologia , Fibras Musculares Esqueléticas/patologia , NADPH Oxidases/genética , NADPH Oxidases/metabolismo , Junção Neuromuscular/lesões , Junção Neuromuscular/metabolismo , Oxirredução , Estresse Oxidativo , Peróxidos/metabolismo , Fosfolipases/genética , Fosfolipases/metabolismo , Sarcopenia/genética , Sarcopenia/patologiaRESUMO
Recent data have shown that preservation of the neuromuscular junction (NMJ) after traumatic nerve injury helps to improve functional recovery with surgical repair via matrix metalloproteinase-3 (MMP3) blockade. As such, we sought to explore additional pathways that may augment this response. Wnt3a has been shown to inhibit acetylcholine receptor (AChR) clustering via ß-catenin-dependent signaling in the development of the NMJ. Therefore, we hypothesized that Wnt3a and ß-catenin are associated with NMJ destabilization following traumatic denervation. A critical size nerve defect was created by excising a 10-mm segment of the sciatic nerve in mice. Denervated muscles were then harvested at multiple time points for immunofluorescence staining, quantitative real-time PCR, and western blot analysis for Wnt3a and ß-catenin levels. Moreover, a novel Wnt/ß-catenin transgenic reporter mouse line was utilized to support our hypothesis of Wnt activation after traumatic nerve injury. The expression of Wnt3a mRNA was significantly increased by 2 weeks post-injury and remained upregulated for 2 months. Additionally, ß-catenin was activated at 2 months post-injury relative to controls. Correspondingly, immunohistochemical analysis of denervated transgenic mouse line TCF/Lef:H2B-GFP muscles demonstrated that the number of GFP-positive cells was increased at the motor endplate band. These collective data support that post-synaptic AChRs destabilize after denervation by a process that involves the Wnt/ß-catenin pathway. As such, this pathway serves as a potential therapeutic target to prevent the motor endplate degeneration that occurs following traumatic nerve injury.
Assuntos
Denervação Muscular , Junção Neuromuscular/lesões , Proteínas Wnt/metabolismo , Via de Sinalização Wnt , beta Catenina/metabolismo , Animais , Linhagem Celular , Masculino , Camundongos da Linhagem 129 , Camundongos Transgênicos , Denervação Muscular/métodos , Junção Neuromuscular/metabolismo , Receptores Colinérgicos/metabolismo , Via de Sinalização Wnt/fisiologiaRESUMO
Duchenne muscular dystrophy (DMD) is a devastating neuromuscular disease in which weakness, increased susceptibility to muscle injury, and inadequate repair underlie the pathology. While most attention has focused within the muscle fiber, we recently demonstrated significant alterations in the neuromuscular junction (NMJ) morphology and resulting neuromuscular transmission failure (NTF) 24 h after injury in mdx mice (murine model for DMD). Here we determine the contribution of NMJ morphology and NTF to the recovery of muscle contractile function post-injury. NMJ morphology and NTF rates were assessed day 0 (immediately after injury) and days 1, 7, 14 and 21 after quadriceps injury. Eccentric injury of the quadriceps resulted in a significant loss of maximal torque in both WT (39 ± 6 %) and mdx (76 ± 8 %) with a full recovery in WT by day 7 and in mdx by day 21. Post-injury alterations in NMJ morphology and NTF were found only in mdx, were limited to days 0 and 1, and were independent of changes in MuSK or AChR expression. Such early changes at the NMJ after injury are consistent with mechanical disruption rather than newly forming NMJs. Furthermore, we show that the dense microtubule network that underlies the NMJ is significantly reduced and disorganized in mdx compared to WT. These structural changes at the NMJ may play a role in the increased NMJ disruption and the exaggerated loss of nerve-evoked muscle force seen after injury to dystrophic muscles.
Assuntos
Distrofina/fisiologia , Distrofia Muscular de Duchenne/patologia , Junção Neuromuscular/lesões , Junção Neuromuscular/metabolismo , Regeneração/fisiologia , Animais , Western Blotting , Células Cultivadas , Imunofluorescência , Imunoprecipitação , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos mdx , Contração Muscular , Distrofia Muscular de Duchenne/genética , Distrofia Muscular de Duchenne/metabolismo , Junção Neuromuscular/fisiopatologia , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Receptores Colinérgicos/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Rotator cuff tears are a major cause of morbidity. Following rotator cuff tears, muscle atrophy and fatty infiltration begin in the tissue, limiting repair potential and leading to a higher re-tear rate and a worse functional outcome. We evaluated whether fatty degeneration resulting from a complete supraspinatus tear with retraction is associated with an injury to the suprascapular nerve. Four skeletally mature New Zealand white rabbits were randomized to receive an index procedure on either their right or left shoulder with the opposite shoulder serving as a control. At the index procedure, the supraspinatus tendon was transected at its insertion and allowed to retract. At 3 months, the rabbits were euthanized, and both supraspinatus muscles were harvested. The specimens were then examined with confocal microscopy and histology. Atrophy was grossly visible in all four test muscles, and fatty infiltration was confirmed with osmium tetroxide staining. In all four rabbits, the degree of denervation (p = 0.71) and partial denervation (p = 0.91) was not significantly different between control and experimental muscle. Rotator cuff tear does not affect the motor endplate or innervation status of the supraspinatus. Fatty infiltration occurs independent of denervation of the supraspinatus.
Assuntos
Placa Motora/lesões , Placa Motora/patologia , Traumatismos dos Nervos Periféricos/patologia , Lesões do Manguito Rotador , Manguito Rotador/patologia , Traumatismos dos Tendões/patologia , Tecido Adiposo/patologia , Animais , Modelos Animais de Doenças , Músculo Esquelético/patologia , Atrofia Muscular/patologia , Degeneração Neural/patologia , Junção Neuromuscular/lesões , Junção Neuromuscular/patologia , Coelhos , Manguito Rotador/inervaçãoRESUMO
Both the neural and glial components of the neuromuscular junction (NMJ) have been identified as potential sites for anti-ganglioside antibody (Ab) binding and complement-mediated injury in murine models for the human peripheral nerve disorder Guillain-Barré syndrome (GBS). Some patients suffering from the acute motor axonal neuropathy (AMAN) forms of GBS recover very rapidly from paralysis; it has been proposed that in these cases the injury was restricted to the distal motor axons and nerve terminals (NTs) which are able to regenerate over a very short time-frame. To test this hypothesis, the ventral neck muscles of mice (n=45) expressing cytosolic fluorescent proteins in their axons (CFP) and Schwann cells (GFP) were subjected to a single topical application of anti-ganglioside Ab followed by a source of complement. Group A (n=15) received Ab that selectively bound to the NTs, group B (n=15) received Abs that bound both to the NTs and the perisynaptic Schwann cells (pSCs) and group C (control animals; n=15) only received complement. Evolution of the injury was documented by in vivo imaging, and following euthanasia the muscles were reimaged ex vivo both quantitatively and qualitatively, either immediately, or after 1, 2, 3 or 5 days of regeneration (each n=3 per group). Within 15 minutes of complement application, a rapid loss of CFP overlying the NMJ could be seen; in group A, the GFP signal remained unchanged, whereas in group B the GFP signal was also lost. In group C no changes to either CFP or GFP were observed. At 24 h, 6% of the superficial NMJs in group A and 12% of the NMJs in group B exhibited CFP. In both groups, CFP returned within the next five days (group A: 93.5%, group B: 94%; p=0.739), with the recovery of CFP being preceded by a return of GFP-positive cells overlying the NMJ in group B. Auxiliary investigations revealed that the loss of CFP at the NMJ correlated with a loss of NT neurofilament immuno-reactivity and a return of CFP at the NMJ was accompanied by a return of neurofilament. In ultrastructural investigations, injured NTs were electron lucent and exhibited damaged mitochondria, a loss of filaments and a loss of synaptic vesicles. The examination of muscles after five days of regeneration revealed physiological NT-profiles. The results described above indicate that following a single anti-ganglioside Ab-mediated and complement-mediated attack, independent of whether there are healthy and mature perisynaptic Schwann cells overlying the NMJ, the murine NT is capable of recovering both its architectural and axolemmal integrity very rapidly. This data supports the notion that an equivalent mechanism may account for the rapid recovery seen in some clinical cases of AMAN.
Assuntos
Anticorpos Monoclonais/administração & dosagem , Autoanticorpos/administração & dosagem , Proteínas do Sistema Complemento/toxicidade , Gangliosídeos/imunologia , Neurônios Motores/patologia , Junção Neuromuscular/lesões , Terminações Pré-Sinápticas/imunologia , Regeneração/fisiologia , Animais , Anticorpos Monoclonais/toxicidade , Autoanticorpos/toxicidade , Humanos , Camundongos , Camundongos Transgênicos , Neurônios Motores/imunologia , Músculos do Pescoço/imunologia , Músculos do Pescoço/patologia , Junção Neuromuscular/imunologia , Junção Neuromuscular/patologia , Regeneração/imunologiaRESUMO
Muscle fibers degenerate and regenerate in response to contractile damage, during aging, and in various muscle diseases that weaken the fibers. It is known that degeneration and regeneration of the segment of the postsynaptic fiber produces dramatic alterations in the neuromuscular junction (NMJ) that forms on the regenerated fiber, but the mechanisms here are incompletely understood. We have used a laser microbeam to damage the postsynaptic fibers at individual NMJs in the sternomastoid muscle of living young adult mice and then followed the synapses vitally over time using fluorescent proteins expressed in motor neurons and glial cells and staining of postsynaptic acetylcholine receptors. We find, in contrast to previous reports, that the mouse nerve terminal retains contact with the synaptic basal lamina marked by cholinesterase staining even in the absence of the target, showing that this terminal does not require a continuous supply of target-derived molecules for its maintenance. Thus, remodeling of the nerve terminal during the period of target absence does not explain the subsequent changes in the new NMJ. Rather, we see that the synapse becomes altered as the new fiber segment regenerates. Mechanisms for remodeling the synapse include failure of the regenerating muscle fiber to contact the old basal lamina and nerve terminal, growth of the nerve terminal and its glia toward the regenerating fiber, and remodeling of the initial contact as the nerve terminal becomes varicose.
Assuntos
Músculo Estriado/fisiologia , Terminações Nervosas/fisiologia , Junção Neuromuscular/fisiologia , Receptores Colinérgicos/metabolismo , Regeneração/fisiologia , Sinapses/fisiologia , Animais , Feminino , Lasers de Gás/efeitos adversos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Neurônios Motores/citologia , Neurônios Motores/metabolismo , Músculo Estriado/patologia , Terminações Nervosas/metabolismo , Neuroglia/citologia , Neuroglia/metabolismo , Junção Neuromuscular/lesões , Junção Neuromuscular/metabolismo , Junção Neuromuscular/patologia , Sinapses/metabolismo , Sinapses/ultraestruturaRESUMO
Devices employed in electrical policing rely on fundamental responses of nerve and muscle to supraphysiologic current to quell disruptive behavior. Whilst widely deployed the use of neuromuscular incapacitation (NMI) remains controversial, in part, due to gaps in understanding of the underlying mechanisms related to injury. NMI device manufacturers are thus constrained by empirical evidence for safety and effectiveness for a specific device design. Here we examine published data for several NMI devices considering ex vivo signal characteristics and in vivo responses in relation to effectiveness and injury. The sensitivity of lactate production to NMI device signal frequency (Hz) and macro-dosimetry is explored as a primary device design factor in NMI modes of injury. The non-lethal approach to policing regardless of technology will result in fatalities due to compromised health and substance abuse status unknowable at the time of NMI application. Thus, research to establish a science-based understanding of NMI injury mechanisms, particularly for lactate production and limitations of deployment, are essential for social acceptance and improved NMI device design.
Assuntos
Estimulação Elétrica/instrumentação , Ácido Láctico/biossíntese , Aplicação da Lei/métodos , Junção Neuromuscular/lesões , Junção Neuromuscular/metabolismo , Engenharia Biomédica/instrumentação , Estimulação Elétrica/efeitos adversos , Desenho de Equipamento , Segurança de Equipamentos , Humanos , Gestão da SegurançaRESUMO
Previous studies have demonstrated that end-organ deprivation after peripheral nerve injury results in targeting of regenerating nerve fibers into inappropriate pathways, which leads to poor functional recovery. Here we studied the effect of electrical stimulation on the regeneration selectivity of motor nerves after peripheral nerve injury and end-organ deprivation. We found that end-organ deprivation reduced regenerating selectivity of motor nerves, total number of regenerating motoneurons, and level of neural trophic factors in the regenerating pathways after nerve injury (p < 0.05). Electrical stimulation successfully promoted motor nerve regeneration selectivity regardless of end-organ connections (p < 0.05). This increased selectivity was accompanied by an increase in the protein level of neural trophic factors in the distal nerve stumps by 3 weeks after nerve injury (p < 0.05). There was a similar increase in the protein level of these neural trophic factors in denervated muscle. However, the RNA level of these factors decreased both in the distal nerves and in the muscle. Despite the promising effect of promoting motor nerve regeneration selectivity, electrical stimulation did not prevent motoneuron loss caused by end-organ deprivation. The present study suggests that end organs contribute to the development of selective motor nerve regeneration by increasing the neurotrophic factors in the regeneration pathways. Electrical stimulation is an efficient strategy to ameliorate the deteriorated regeneration microenvironment caused by end-organ deprivation and to promote motor nerve regeneration selectivity when end-organ connections are deprived.
Assuntos
Terapia por Estimulação Elétrica/métodos , Neurônios Motores/fisiologia , Músculo Esquelético/inervação , Fatores de Crescimento Neural/metabolismo , Regeneração Nervosa/fisiologia , Traumatismos dos Nervos Periféricos , Animais , Axônios/patologia , Axônios/fisiologia , Axotomia/efeitos adversos , Denervação/efeitos adversos , Modelos Animais de Doenças , Feminino , Neurônios Motores/patologia , Músculo Esquelético/fisiopatologia , Fatores de Crescimento Neural/genética , Junção Neuromuscular/lesões , Junção Neuromuscular/patologia , Junção Neuromuscular/fisiopatologia , Plasticidade Neuronal/fisiologia , Nervos Periféricos/patologia , Nervos Periféricos/fisiopatologia , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Recuperação de Função Fisiológica/fisiologia , Regulação para Cima/fisiologiaRESUMO
OBJECTIVE: We measured levator ani neuromuscular function before and after first delivery to identify the location, timing, and mechanism of injury. STUDY DESIGN: Fifty-eight primiparous women underwent electromyographic examination of the levator ani antepartum at 6 weeks and 6 months after the delivery. Antepartum turns/amplitude data were pooled to create a normal range. We calculated each woman's percentage of outliers from this range and assessed relationships between delivery and extent of injury. RESULTS: At 6 weeks, 14 of 58 women (24.1%) had neuropathy, with 9 of those 14 women recovering by 6 months. At 6 months, 17 of 58 women (29.3%) were neuropathic, which included 12 new injuries. Women who had elective cesarean delivery had virtually no injury, but all other modes of delivery had similar injury rates. CONCLUSION: Obstetric delivery is associated frequently with electromyographic evidence of neuropathic injury to the levator ani. The entire levator complex is at risk, and cesarean delivery while in labor is not protective.
Assuntos
Parto Obstétrico/efeitos adversos , Junção Neuromuscular/lesões , Paridade , Diafragma da Pelve/inervação , Adulto , Cesárea/efeitos adversos , Parto Obstétrico/estatística & dados numéricos , Eletromiografia , Feminino , Humanos , Incidência , Trabalho de Parto , Gravidez , Recuperação de Função Fisiológica , Fatores de Tempo , Ferimentos e Lesões/diagnóstico , Ferimentos e Lesões/epidemiologia , Ferimentos e Lesões/etiologia , Ferimentos e Lesões/fisiopatologiaRESUMO
We evaluated the effects of brief, temporary denervation caused by ischiadic nerve-freezing on the processes of degeneration and regeneration of ultrastructural features in neuromuscular junction (NMJ) architecture in different types of rat skeletal muscle fibers. Nerve terminal (NT) area was decreased significantly 12 h after nerve freezing in both fast-twitch (FT) and slow-twitch (ST) fibers. One day after nerve freezing, some terminal axons were absent; decrease in NT area was remarkable in ST fibers, and there was retraction of Schwann cells and perineural epithelial cells. Fiber type-specific differences were observed in pattern of decrease in NT area between 24 h and 7 days after nerve freezing (there was significantly more decrease in FT fibers). The primary synaptic cleft became shallow, and the secondary junctional folds shorter and wider, but the basement lamina filling the subneural apparatus was unaltered. The number of secondary junctional folds decreased gradually between 6 h and 14 days after nerve freezing in both types of fiber. In control muscle fibers, synaptic vesicle density (SVD) per terminal area was significantly higher in FT fibers. The SVD densities decreased following nerve freezing-induced destruction of NMJs, and were minimal 3 days in FT fibers or 7 days ST fibers after nerve freezing. At 3 weeks, regeneration of both FT and ST fibers was well advanced, and all parameters had recovered to control values in FT fibers 28 days after nerve freezing. Severe degradation of the ultrastructural features in NMJs occurred due to temporary denervation during muscle fiber degeneration processes, and these structural changes were all reversible and fiber type-specific.
Assuntos
Fibras Musculares de Contração Rápida/ultraestrutura , Fibras Musculares de Contração Lenta/ultraestrutura , Junção Neuromuscular/ultraestrutura , Animais , Feminino , Congelamento , Denervação Muscular , Junção Neuromuscular/lesões , Ratos , Ratos Endogâmicos F344 , Fatores de TempoRESUMO
Loss of muscle tissue at the area of the neuromuscular junction after tumor resection or after trauma precludes the reconstruction with conventional nerve grafts, because the distal nerve stump is absent. For these cases, we recommend direct insertion of the nerve grafts into the muscle. We describe a standardized technique, which has been performed in 19 patients and led to a mean motor recovery of grade M4 after Highet. The key procedure of this technique is the interfascicular dissection of the nerve grafts, which allows a wide distribution of the grafts into the muscle tissue.
Assuntos
Músculo Esquelético/inervação , Transferência de Nervo/métodos , Doenças da Junção Neuromuscular/cirurgia , Junção Neuromuscular/lesões , Nervos Periféricos/transplante , Adulto , Seguimentos , Humanos , Neoplasias Musculares/cirurgia , Regeneração Nervosa/fisiologia , Junção Neuromuscular/fisiopatologia , Junção Neuromuscular/cirurgia , Doenças da Junção Neuromuscular/etiologia , Complicações Pós-Operatórias/etiologia , Complicações Pós-Operatórias/cirurgiaRESUMO
We evaluated the degeneration and regeneration of neuromuscular junctions (NMJs) on the extensor digitorum longus muscle of Fischer 344 rats between 4 h and 3 weeks after bupivacaine hydrochloride (BPVC) injection, which induces muscle fiber necrosis, using histochemical staining by acetylcholine esterase (AchE)-silver and electron microscopy. Degeneration of muscle fibers and NMJs was observed 4 h after BPVC injection. One week after BPVC injection, some terminal axons were almost completely retracted, and the level of basal lamina-associated AchE in some NMJ regions had gradually disappeared. At that time, the depression contained a few, mostly pit-like or elongated oval invaginations: the incipient junctional folds and some NMJs did not have any secondary junctional fold. By 2 weeks after the BPVC injection, secondary junctional folds began to develop: however, the number of secondary junctional folds was clearly less than that in normal NMJs. At 3 weeks when regeneration of muscle fibers was well advanced, the staining for AchE at the end-plates became stronger and better-defined. The volume density of mitochondria in the terminal area of the terminal significantly decreased upon BPVC-induced destruction of the NMJ, and the density reached the lowest value 24 h after BPVC injection. Significant changes in the ultrastructural features of the architecture of NMJs occurred in skeletal muscle fibers damaged by BPVC during both the degeneration and regeneration processes. The changes in the ultrastructural and morphological features of the NMJ architecture during the regeneration of degenerated muscle fibers resembled those that occur during the differentiation of normal muscle fibers.
Assuntos
Esterases/metabolismo , Miofibrilas/metabolismo , Junção Neuromuscular/metabolismo , Regeneração/fisiologia , Animais , Bupivacaína/toxicidade , Microscopia Eletrônica de Transmissão e Varredura , Miofibrilas/efeitos dos fármacos , Junção Neuromuscular/efeitos dos fármacos , Junção Neuromuscular/lesões , RatosRESUMO
Peripheral nerve lesions lead to nerve degeneration and flaccid paralysis. The first objective in functional rehabilitation of these diseases should be the preservation of the neuro-muscular junction by biological means and following functional electrical stimulation (FES) may restore some function of the paralyzed limb. The combination of biological cells and technical microdevices to biohybrid systems might become a new approach in neural prosthetics research to preserve skeletal muscle function. In this paper, a microdevice for a biohybrid system to interface peripheral nerves after traumatic lesions is presented. The development of the microprobe design and the fabrication technology is described and first experimental results are given and afterwards discussed. The technical microprobe is designed in a way that meets the most important technical requirements: adaptation to the distal nerve stump, suitability to combine the microstructure with a containment for cells, and integrated microelectrodes as information transducers for cell stimulation and monitoring. Micromachining technologies were applied to fabricate a polyimide-based sieve-like microprobe with 19 substrate-integrated ring electrodes and a distributed counter electrode. Monolithic integration of fixation flaps and a three-dimensional shaping technology led to a device that might be adapted to nerve stumps with neurosurgical sutures in the epineurium. First experimental results of the durability of the shaping technology and electrochemical electrode properties were investigated. The three-dimensional shape remained quite stable after sterilization in an autoclave and chronic implantation. Electrode impedance was below 200 kOmega at 1 kHz which ought to permit recording of signals from nerves sprouting through the sieve holes.
Assuntos
Terapia por Estimulação Elétrica/instrumentação , Eletrodos Implantados , Traumatismos dos Nervos Periféricos , Animais , Impedância Elétrica , Eletrônica Médica/instrumentação , Desenho de Equipamento , Degeneração Neural/prevenção & controle , Junção Neuromuscular/lesões , Ratos , Nervo Isquiático/lesõesRESUMO
We investigated the severity and the quality of pain in the end-plate and the electrically silent site during electromyography by self-assessment. In 42 muscles of 30 patients, the mean pain score was 52.0 +/- 5.3 of 100 for the end-plate region, and it was 27.7 +/- 4.8 for the silent site. The commonest type of pain was pricking both in the end-plate region and the silent site (19 and 31%, respectively). We suggest two hypotheses for the difference. The pain fibers may be more densely situated in the end-plate, or muscle fiber contraction precipitated by needle irritation may also cause irritation of pain fibers.
Assuntos
Eletrodos/efeitos adversos , Eletromiografia/efeitos adversos , Músculo Esquelético/lesões , Agulhas/efeitos adversos , Junção Neuromuscular/lesões , Medição da Dor/estatística & dados numéricos , Dor/etiologia , Animais , Músculo Esquelético/patologia , Músculo Esquelético/fisiopatologia , Junção Neuromuscular/patologia , Junção Neuromuscular/fisiopatologia , Dor/patologia , Dor/fisiopatologia , Medição da Dor/métodos , Medição da Dor/normas , Inquéritos e Questionários/normasRESUMO
In the case of typical whiplash after low-energy rear-end collision we recommend a clear and structured therapeutic regimen to overcome and prevent neuromuscular deficits. Patients with bony and discoligamentous lesions have to be excluded, as well as patients with distinct neurologic deficits. A therapeutic rationale is the basis of full neuromuscular recovery ad integrum.
Assuntos
Traumatismos em Chicotada/terapia , Cálcio/uso terapêutico , Vértebras Cervicais/lesões , Vértebras Cervicais/fisiopatologia , Humanos , Pescoço/inervação , Junção Neuromuscular/lesões , Junção Neuromuscular/fisiopatologia , Fármacos Neuromusculares não Despolarizantes/uso terapêutico , Nervos Espinhais/lesões , Traumatismos em Chicotada/fisiopatologiaRESUMO
The influence of ageing and crushing of the sciatic nerve on the morphology of the neuromuscular junction (NMJ) and on the muscle fiber composition were studied in the rat soleus muscle using histochemical techniques associated with image analysis. The influence of a 6-month treatment with Acetyl-L-Carnitine (ALCAR, 150 mg/kg/day) on the age- and crushing-dependent changes of the NMJ and on age-related modifications of the muscle fiber composition was assessed as well. In control old and injured young rats a loss of complexity of the NMJ was observed. Treatment with ALCAR resulted in an increased endplate complexity both in old rats and in young rats injured by crushing, in comparison with respective controls. The structure of the rat soleus muscle changes with increasing age. Modification mainly consists in a type II fiber atrophy, and in the alteration of the peculiar mosaic organization of the soleus muscle fibers. In ALCAR-treated old rats, the morphology of the soleus muscle fibers was similar to that observed in adult animals. These findings suggest that treatment with ALCAR has a beneficial effect on NMJ and on muscle fiber structure in ageing or after nerve crushing. The possible mechanism of action of this 'trophic' effect of ALCAR-treatment is discussed.
Assuntos
Acetilcarnitina/farmacologia , Envelhecimento/patologia , Músculo Esquelético/anatomia & histologia , Músculo Esquelético/efeitos dos fármacos , Junção Neuromuscular/anatomia & histologia , Junção Neuromuscular/efeitos dos fármacos , Acetilcarnitina/administração & dosagem , Animais , Masculino , Músculo Esquelético/lesões , Junção Neuromuscular/lesões , Ratos , Ratos Sprague-Dawley , Nervo Isquiático/anatomia & histologia , Nervo Isquiático/efeitos dos fármacos , Nervo Isquiático/lesões , Fatores de TempoRESUMO
STUDY DESIGN: Back muscle injury caused by retractor application during posterior spine surgery in rats was examined histologically and histochemically according to the postoperative time with reference to the retraction time-pressure relationship. OBJECTIVES: The results were correlated to provide the risk factors for back muscle injury during posterior spine surgery. SUMMARY OF BACKGROUND DATA: Back muscles were examined histologically and histochemically after application of quantitative pressure and retraction time. No previous study has assessed this relationship. METHODS: Five groups were studied: Group 1, 1-hour low-pressure load group; Group 2, 1-hour high-pressure load group; Group 3, 3-hour low-pressure load group; Group 4, 3-hour high-pressure load group; and sham group. In each group, the multifidus muscle was evaluated 3 hours, 48 hours, 1 week, 3 weeks, and 6 weeks after surgery. RESULTS: In all groups except the sham group, degeneration of the muscle and neuromuscular junction was found at a very early postoperative time, but regeneration began at 1 week, and recovery was attained by 6 weeks. The extent of muscle fiber necrosis and the severity of degeneration of the neuromuscular junctions showed a parallelism with the magnitude of the pressure load and retraction time. As the duration and pressure load increased, the time required for regeneration also increased. The fiber type grouping in group 3 and 4 was consistent with the severity of degeneration of neuromuscular junctions. CONCLUSIONS: The muscular degeneration and the regeneration was largely dependent on the retraction pressure-time product. These results suggest that denervation muscle injuries are likely secondary responses to muscle retraction injury in any case of posterior spine surgery.