Study Of Neuromuscular Transmission Research Articles

Long-Term High-Density Extracellular Recordings Enable Studies of Muscle Cell Physiology.

Skeletal (voluntary) muscle is the most abundant tissue in the body, thus making it an important biomedical research subject. Studies of neuromuscular transmission, including disorders of ion channels or receptors in autoimmune or genetic neuromuscular disorders, require high-spatial-resolution measurement techniques and an ability to acquire repeated recordings over time in order to track pharmacological interventions. Preclinical techniques for studying diseases of neuromuscular transmission can be enhanced by physiologic ex vivo models of tissue-tissue and cell-cell interactions. Here, we present a method, which allows tracking the development of primary skeletal muscle cells from myoblasts into mature contracting myotubes over more than 2 months. In contrast to most previous studies, the myotubes did not detach from the surface but instead formed functional networks between the myotubes, whose electrical signals were observed over the entire culturing period. Primary cultures of mouse myoblasts differentiated into contracting myotubes on a chip that contained an array of 26,400 platinum electrodes at a density of 3,265 electrodes per mm2. Our ability to track extracellular action potentials at subcellular resolution enabled study of skeletal muscle development and kinetics, modes of spiking and spatio-temporal relationships between muscles. The developed system in turn enables creation of a novel electrophysiological platform for establishing ex vivo disease models.

Loss of MUNC13-1 function causes microcephaly, cortical hyperexcitability, and fatal myasthenia.

Objective:To identify the molecular basis of a fatal syndrome of microcephaly, cortical hyperexcitability, and myasthenia.Methods:We performed clinical and in vitro microelectrode studies of neuromuscular transmission, examined neuromuscular junctions cytochemically and by electron microscopy (EM), and searched for mutations by Sanger and exome sequencing.Results:Neuromuscular transmission was severely compromised by marked depletion of the readily releasable pool of quanta, but the probability of quantal release was normal. Cytochemical and EM studies revealed normal endplate architecture. Exome sequencing identified a homozygous nonsense mutation in the N-terminal domain of MUNC13-1 (UNC13A) truncating the protein after 101 residues.Conclusions:Loss of Munc13-1 function predicts that syntaxin 1B is consigned to a nonfunctional closed state; this inhibits cholinergic transmission at the neuromuscular junction and glutamatergic transmission in the brain. Inactivation of syntaxin 1B likely accounts for the patient's cortical hyperexcitability because mutations of syntaxin 1B cause febrile seizures with or without epilepsy, haploinsufficiency of the STX1B is associated with myoclonic astatic epilepsy, and antisense knockdown of stx1b in zebrafish larvae elicits epileptiform discharges. A very recent publication also shows that syntaxin 1B has a separate obligatory role for maintenance of developing and mature neurons and illustrates impaired brain development in syntaxin 1A/1B double knockout mice. We therefore attribute our patient's microcephaly to the truncating homozygous Munc13-1 mutation that consigns syntaxin 1B to a permanently closed nonfunctional state akin to a knockout.

Enhydrina schistosa (Elapidae: Hydrophiinae) the most dangerous sea snake in Sri Lanka: Three case studies of severe envenoming

Sea snakes are highly venomous and inhabit tropical waters of the Indian and Pacific Oceans. Enhydrina schistosa is a common species of sea snake that lives in the coastal waters, lagoons, river mouths and estuaries from the Persian Gulf through Sri Lanka and to Southeast Asia. It is considered one of the most aggressive sea snakes in Sri Lanka where fishermen and people wading are at high risk. However, sea snake bites are rarely reported. In this report, we describe three cases where E. schistosa was the offending species. These three patients presented to two hospitals on the west coast of Sri Lanka within the course of 14 months from November 2011 with different degrees of severity of envenoming. The first patient was a 26-year-old fisherman who developed severe myalgia with very high creatine kinase (CK) levels lasting longer than 7 days. The second patient was a 32-year-old fisherman who developed gross myoglobinuria, high CK levels and hyperkalaemia. Both patients recovered and their electromyographic recordings showed myopathic features. The nerve conduction and neuromuscular transmission studies were normal in both patients suggesting primary myotoxic envenoming. The third patient was a 41-year-old man who trod on a sea snake in a river mouth and developed severe myalgia seven hours later. He had severe rhabdomyolysis and died three days later due to cardiovascular collapse. In conclusion, we confirm that E. schistosa is a deadly sea snake and its bite causes severe rhabdomyolysis.

Neurophysiological testing in congenital myasthenic syndromes: A systematic review of published normal data

Introduction: Congenital myasthenic syndromes are a heterogeneous group of inherited neuromuscular disorders. Neurophysiological testing has a major role in screening suspected cases and guiding genetic testing. We performed a systematic literature review to ascertain whether sufficient age-specific normative data exist for these techniques. Methods: We searched Ovid Medline (1948 to October 2012) for citations on repetitive nerve stimulation (RNS) or single fiber electromyography (SFEMG) in children. Results: We identified 5 articles containing data on 48 normal children studied with RNS and 1 article containing data on SFEMG in 20 normal children. A variety of techniques were used, including a variety of stimulation frequencies. Nevertheless, the data identify significant differences in the response to RNS in children as compared with adults, emphasizing the need for adequate age-appropriate normal values. Conclusions: We found a paucity of published normal data for pediatric neuromuscular transmission studies. Further studies using standardized techniques are needed to expand the currently limited pool of available data. Muscle Nerve 48:711–715, 2013

A single-fibre electromyography study of neuromuscular transmission in patients with cluster headache

Background and purposeMutations of CACNA1A, which encodes a neuronal P/Q Ca2+ channel, are present in patients with familial hemiplegic migraine, and possibly in other types of migraine as well. This calcium channel is also involved in neuromuscular transmission. In our previous study we confirmed that the single-fibre electromyography (SFEMG) method can demonstrate a neuromuscular transmission deficit in migraine with aura. The aim of our present study was to estimate the neurotransmitter dysfunction in cluster headache and to compare the results between patients with cluster headache and those with migraine with aura. Material and methodsWe selected 6 patients with cluster headache and 6 patients with migraine with typical aura. SFEMG of the voluntarily activated extensor digitorum communis muscle was performed. ResultsThe SFEMG results were in the normal range in the cluster headache group and in the healthy controls. Slight neuromuscular transmission disturbances were present in patients with migraine with aura. ConclusionsThe abnormal neuromuscular transmission detectable by SFEMG may reflect a genetically determined dysfunction of the P/Q Ca2+ channels in a group of migraineurs with aura. Conversely, absence of neuromuscular abnormalities in cluster headache patients could be explained by different aetiology not resulting in channelopathy. Single-fibre electromyography could be a helpful tool in clinically questionable cases in differentiating between cluster headache and migraine with aura.

Colonic endoscopic full-thickness biopsies: from the neuropathological analysis of the myenteric plexus to the functional study of neuromuscular transmission

Better understanding of the pathophysiological mechanisms involved in severe dysmotility disorders is crucial to improve patient management and identify novel therapeutic targets. Recent studies suggested that endoscopic full-thickness biopsies (eFTBs) could be developed as an alternative to surgical biopsies. However, currently it remains unknown whether eFTBs would allow myenteric plexus analysis on whole mounts and the evaluation of neuromuscular transmission. To determine with eFTB specimens the ability to analyze on whole mounts the key parameters of the myenteric plexus, ie, ganglia and neurons, and to perform functional evaluation of neuromuscular transmission. An experimental pilot study in 6 pigs was conducted in accordance with French institutional guidelines. Under general anesthesia, pigs underwent a rectosigmoidoscopy. In each pig, an eFTB was performed at 25, 30, and 35 cm from the anal margin with an EMR-based technique. Tissue specimens were immediately processed for immunohistochemical and/or functional ex vivo analysis of neuromuscular transmission. In 2 pigs, over-the-scope clips were used to seal the perforation. Feasibility of obtaining specimens containing myenteric plexus and muscularis propria, quantitative and standardized immunohistochemical evaluation of ganglia and myenteric neurons, ex vivo assessment of neuromuscular transmission and its pharmacology, and closure rate (ancillary study). Adequate tissue specimens were obtained in 100% of the procedures, on average, in 6±2 minutes. Immunohistochemical analysis of a whole mount of the myenteric plexus showed that each eFTB contained 14±5 ganglia and 1562±1066 myenteric neurons. In circular muscle strips, electrical field stimulation or exposure to a pharmacological agent induced a specific tissue response. A successful closure was achieved in 50% of cases. Nonsurvival study; safety of the procedure needs to be specifically assessed and compared with recently published data. We demonstrate, for the first time, that full-thickness biopsy specimens obtained by using an endoscopic approach allow the performance of a precise study of the ENS phenotype on whole mounts of the myenteric plexus and the performance of functional studies such as evaluation of neuromuscular transmission. However, further studies are warranted to identify the optimal and safest endoscopic procedure before application of eFTB in humans.

Colonic Endoscopic Full-Thickness Biopsies: From the Neuropathological Analysis of the Myenteric Plexus to the Functional Study of Neuromuscular Transmission

Background Better understanding of the pathophysiological mechanisms involved in severe dysmotility disorders is crucial to improve patient management and identify novel therapeutic targets. Recent studies suggested that endoscopic full-thickness biopsies (eFTBs) could be developed as an alternative to surgical biopsies. However, currently it remains unknown whether eFTBs would allow myenteric plexus analysis on whole mounts and the evaluation of neuromuscular transmission. Objective To determine with eFTB specimens the ability to analyze on whole mounts the key parameters of the myenteric plexus, ie, ganglia and neurons, and to perform functional evaluation of neuromuscular transmission. Design An experimental pilot study in 6 pigs was conducted in accordance with French institutional guidelines. Intervention Under general anesthesia, pigs underwent a rectosigmoidoscopy. In each pig, an eFTB was performed at 25, 30, and 35 cm from the anal margin with an EMR-based technique. Tissue specimens were immediately processed for immunohistochemical and/or functional ex vivo analysis of neuromuscular transmission. In 2 pigs, over-the-scope clips were used to seal the perforation. Main Outcome Measurements Feasibility of obtaining specimens containing myenteric plexus and muscularis propria, quantitative and standardized immunohistochemical evaluation of ganglia and myenteric neurons, ex vivo assessment of neuromuscular transmission and its pharmacology, and closure rate (ancillary study). Results Adequate tissue specimens were obtained in 100% of the procedures, on average, in 6 ± 2 minutes. Immunohistochemical analysis of a whole mount of the myenteric plexus showed that each eFTB contained 14 ± 5 ganglia and 1562 ± 1066 myenteric neurons. In circular muscle strips, electrical field stimulation or exposure to a pharmacological agent induced a specific tissue response. A successful closure was achieved in 50% of cases. Limitations Nonsurvival study; safety of the procedure needs to be specifically assessed and compared with recently published data. Conclusions We demonstrate, for the first time, that full-thickness biopsy specimens obtained by using an endoscopic approach allow the performance of a precise study of the ENS phenotype on whole mounts of the myenteric plexus and the performance of functional studies such as evaluation of neuromuscular transmission. However, further studies are warranted to identify the optimal and safest endoscopic procedure before application of eFTB in humans.

Progressive external ophthalmoplegia as initial manifestation of sporadic late-onset nemaline myopathy

Sporadic late-onset nemaline myopathy (SLONM) is a rare disease and typically presents in patients older than 40 years with slowly progressive weakness in a limb-girdle distribution and unremarkable family history [1, 2]. Serum creatine kinase is usually normal, and electromyography may show myopathic changes. Nemaline rods in affected muscle fibers are considered the histopathological hallmark of nemaline myopathy and are mainly found within the sarcoplasm, inside of myonuclei, or both [3]. Ocular involvement has never been described in a patient with SLONM. We report a patient with SLONM suffering from prominent involvement of external ocular muscles. A 60-year-old female patient was reexamined for a chronic progressive oculopharyngeal syndrome that was present for 6 years. Initial symptoms were double vision and ptosis, followed by weakness of eye-closure. Two years after the onset of symptoms, she presented an exclusive picture of external ophthalmoplegia. During the following years she was unable to open or close her eyes voluntarily, lost her ability to whistle or smile, developed a hoarse voice and swallowing difficulties. There was no diurnal variation of symptoms, or fatigability. Family history for neuromuscular diseases was unremarkable. On examination she had complete bilateral ptosis and palsy of extraocular muscles, while pupillar size and pupillar reactions to light and accommodation were normal. She had a myopathic face with atrophy of masseter and temporalis muscles, severe bilateral facial palsy, and severe dysphonia. Strength was MRC grade 4 for neck flexion, head rotation, and neck extension. Further neurological examination was normal, notably fundoscopy and proximal and distal limb strength. Laboratory examinations provided normal values for standard parameters, serum creatine kinase, a comprehensive panel of autoimmune antibodies, including antibodies against acetylcholine receptor or muscle-specific kinase, anti-HIV 1/2 antibodies, and p24 antigen. Serum ACE, soluble Interleukin-2 receptor levels, serum and urine calcium levels, and repeated imaging studies ruled out sarcoidosis. Protein electrophoresis and immunofixation did not show any paraprotein, findings that rule out an association with HIV, sarcoidosis, or monoclonal gammopathy, as described in some patients in the literature [4–7]. MRI revealed symmetric atrophy of ocular muscles and fatty degeneration of pterygoideus medialis and masseter muscles, no signs of edema or contrast enhancement. Thorough neuromuscular transmission studies as well as spinal cord and brain imaging were unremarkable. No other organs were involved. Muscle biopsy of the sternocleidomastoideus revealed numerous rods, which appeared to be O. Wengert A. Meisel Department of Neurology, Charite-Universitatsmedizin Berlin, Chariteplatz 1, 10117 Berlin, Germany

An In Vitro Model for Studying Neuromuscular Transmission in the Mouse Pharynx

The muscles of the pharynx are controlled by networks of neurons under the control of specific regions in the brain stem, which have been fairly well studied. However, the transmission between these neurons and the pharyngeal muscles, at the motor end plates, is less well understood. Therefore, an in vitro model for the study of neuromuscular transmission in the pharyngeal muscle of the mouse was developed. Ring preparations from the inferior constrictor and the cricopharyngeus muscles were isolated and mounted for isometric force recording at physiologic temperature. Preparations from the diaphragm and the soleus muscles were examined in parallel. The muscles were stimulated at supramaximal voltage with short tetani at 100 Hz. Following direct stimulation of the muscle fibers, using a longer pulse duration, the rate of force development of the pharyngeal muscles was similar to that of the diaphragm and faster than that of the soleus muscle. By varying the duration of the stimulation pulses, conditions where the nerve-mediated activation contributed to a major extent of the contractile responses were identified. Gallamine completely inhibited the nerve-mediated responses. In separate experiments the dose dependence of gallamine inhibition was examined, showing similar sensitivity in the inferior pharyngeal constrictor compared to the diaphragm and soleus muscles. We conclude that reproducible contractile responses with an identifiable nerve-induced component can be obtained from the mouse inferior pharyngeal constrictor. The pharyngeal muscles have contractile characteristics similar to those of the faster diaphragm. The sensitivity to the neuromuscular blocking agent gallamine of the inferior pharyngeal constrictor was in the same concentration range as that of the diaphragm and soleus muscles.

Light on limb-girdle myasthenia

In the current issue of Brain , Slater et al . (2006) describe their findings in eight patients in seven kinships suffering from limb-girdle myasthenia (LGM). All eight had progressive weakness in a proximal limb-girdle distribution that began in the first or second decade of life, a decremental EMG response on 3 Hz stimulation and a favourable response to anticholinesterase medications. The oculobulbar muscles were spared except for slight facial weakness and ptosis in some patients. None had short-term fatigability induced by exercise, and none had detectable anti-AChR antibodies. Thus, they differed from most myasthenic patients in whom oculobulbar involvement heralds the onset of the disease and who typically experience increased weakness after exercise. In addition to thoroughly describing the clinical features of their patients, Slater et al. also investigated each patient by intracellular microelectrode studies of neuromuscular transmission and by quantitative light and electron microscopy analysis of the structure of the neuromuscular junction (NMJ). Although the clinical, electrophysiological and morphological findings in the LGM patients observed by Slater et al. were similar, the authors indicate that LGM may encompass a heterogeneous group of conditions. To date, no fewer than 61 patients in 36 kinships have been reported under the rubric of LGM (McQuillen, 1966; Johns et al ., 1971, 1973; Wolters and Leeuwin, 1976; Dobkin and Verity, 1978; Oh and Kuruoglu, 1992; Azulay et al ., 1994; Vasant et al ., 1994; Furui et al ., 1997; Zephir et al ., 2001; Rodolico et al ., 2002; Shankar et al ., 2002; Slater et al ., 2006). Sparing of the oculobulbar muscles, proximal …

The importance of electrodiagnostic studies in acute organophosphate poisoning

Six patients with acute organophosphate pesticide poisoning in whom electrodiagnostic studies influenced or supported specific decisions in management are described. One patient was admitted to hospital with a diagnosis of acute alcoholic intoxication. Electrodiagnostic studies revealed single stimulus induced repetitive responses and decrement–increment responses at 30 and 50 Hz repetitive nerve stimulation, findings that are indicative of a depolarization block due to inactivation of acetylcholinesterase at the motor end-plate. The patient was subsequently treated as a case of acute organophosphate poisoning. The administration of edrophonium (0.1 mg) to another patient with normal neuromuscular transmission studies unmasked the latent electrophysiological abnormalities. Three instances are described in which electrodiagnostic studies were useful in predicting whether pralidoxime administration was likely to be useful and for how long was pralidoxime therapy to be continued. Phrenic nerve conduction study in one patient with impending respiratory failure revealed an unstimulable phrenic nerve. The potential role of phrenic nerve conduction studies and neuromuscular transmission studies in influencing decisions like intubation and mechanical ventilation is discussed.

The study of normal and abnormal neuromuscular transmission with single fibre electromyography

The use of single fibre electromyography (SFEMG) in the study of neuromuscular transmission across individual motor endplates in situ is reviewed. The neuromuscular jitter can be studied both during voluntary contraction and electrical activation of the muscle fibre. The differences, pitfalls and advantages of these methods are discussed. Findings in myasthenia gravis and other disorders of the neuromuscular transmission are examined.

Responses of the isolated sympathetic nerve‐ductus deferens preparation of the guinea‐pig

Responses of the isolated sympathetic nerve‐ductus deferens preparation of the guinea‐pig

Prolonged Muscle Weakness After Neuromuscular Blockade in the Intensive Care Unit

As noted, quadriparesis with reduced reflexes and difficulty with ventilator weaning may be seen as a result of a number of neuromuscular disorders. The clinical approach relies on exclusion of a central cause first, followed by careful examination of peripheral nerve and muscle function. Persistent neuromuscular blockade should be excluded initially because it is a readily reversible condition. Use of a train of four stimulation with a peripheral twitch monitor can quickly establish integrity of conduction across the neuromuscular junction. If necessary, further electrophysiologic studies allow differentiation among the relevant diagnostic possibilities. CIP is characterized by nerve conduction and EMG findings consistent with axonal degeneration of sensory and motor fibers. GBS is distinguished by evidence of demyelination on nerve conduction studies, in addition to elevated spinal fluid protein. Persistent neuromuscular blockade is identified by a decremental response on repetitive stimulation studies of neuromuscular transmission. The acute myopathy following neuromuscular blockage does not involve sensory responses. Needle EMG examination reflects a myopathic pattern, rather than a neurogenic one as seen in CIP or GBS. In myopathic patients who are unable to move their limbs at all (precluding a full EMG examination), a muscle biopsy identifies muscle as the site of involvement.

Use of μ-conotoxin GIIIA for the study of synaptic transmission at the frog neuromuscular junction

We have looked at the effect of synthetic μ-conotoxin GIIIA, a selective blocker of muscle NA channels, on various parameters of synaptic transmission at the frog sartorius nerve-muscle preparation. We found that 5 μM μ-conotoxin consistently blocked muscle action potentials, but had no effect on nerve action potentials. The toxin also had no effect on the amplitude or frequency of miniature endplate potentials (MEPPs), on the amplitude or time course of endplate potentials (EPPs), or on stimulation-induced changes in EPP amplitude. The lack of an effect of synthetic μ-conotoxin GIIIA on transmitter release makes this toxin an invaluable tool in the study of neuromuscular transmission under conditions of normal levels of release.

Neuromuscular transmission studies in the healthy dog: EMG and muscle force measurement after repetitive nerve stimulation.

In 10 healthy anaesthetized female dogs the ulnar and the mandibular nerve were stimulated supramaximally by repetitive electric impulses according to a fixed programme. To evaluate the neuromuscular transmission system the course of the evoked compound muscle action potential and the near-isometric force of forelimb and masticatory muscles were studied respectively. The presented results are comparable to values obtained from small hand muscles of conscious, healthy human subjects. The simultaneous measurement of both the electrical and the force response may improve the diagnostic accuracy of the examination in presumed neuromuscular transmission failure in the dog, as it does in humans.

Rats immunized with cholinergic synaptosomes: A model for Lambert‐Eaton syndrome

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder characterized by reduced acetylcholine release at the neuromuscular junction. We report a model of the disease developed by active immunization of rats with purely cholinergic nerve terminals (synaptosomes) isolated from the Torpedo electric organ. Electromyographic studies of neuromuscular transmission in these rats showed a weak initial response followed by a pronounced incremental response to paired supramaximal stimuli (8 msec apart). There was no such response in control rats. There was no evidence of a postsynaptic transmission deficit in the synaptosomes immunized rats. We conclude that immunizing rats with Torpedo cholinergic nerve terminals causes a specific presynaptic dysfunction and may serve as a model for the study of LEMS.

Neuromuscular transmission studies in human chronic Chagas' disease

An electrophysiological investigation of the state of the neuromuscular transmission (nmt) was carried out in 58 patients with the diagnosis of chronic Chagas' disease. On repetitive supramaximal nerve stimulation it was found that some patients did not show abnormalities, others had decremental muscle responses, others developed enhancement of the muscle evoked potential amplitudes, while some other patients combined both types of pathological responses. The findings suggest that some patients with chronic Chagas' disease develop impairment of nmt, though data obtained in this study do not give information about neither the type of impairment nor the localization (pre or postsynaptic, or both) of the damage.

Inactivation of end-plate acetylcholinesterase during the course of organophosphate intoxications

Blood organophosphate (OP) levels, serum butyrylcholinesterase (BChE) activity and electrophysiological neuromuscular transmission following repetitive nerve stimulation at 10 Hz and 50 Hz were studied serially in five patients with severe acute organophosphate intoxication following suicide attempts. Eight to 45 hours after oral ingestion, blood OP levels were elevated, BChE activity was markedly reduced, while repetitive nerve stimulation studies showed no or only mild abnormalities. The latter attained the maximal abnormality 32-69 h after ingestion, when BChE was inactivated further but elevated OP levels had fallen. Recovery from these abnormalities at 10 Hz nerve stimulation occurred within 100-237 h after the intoxication and it was still incomplete at 50 Hz stimulation 48-80 h later. BChE activity varied within a wide range and showed even normal values at both times. Neuromuscular transmission studies proved to be the most useful indicator for determining the severity and time course of organophosphate intoxication.

Electromyography. Neuromuscular transmission studies. By Shin J. Oh, Williams & Wilkins, Baltimore, MD, 1988, 304 pp, $49.95

Muscle & NerveVolume 12, Issue 8 p. 699-699 Book Review Electromyography. Neuromuscular transmission studies. By Shin J. Oh, Williams & Wilkins, Baltimore, MD, 1988, 304 pp, $49.95 Donald B. Sanders MD, Donald B. Sanders MD Durham, North CarolinaSearch for more papers by this author Donald B. Sanders MD, Donald B. Sanders MD Durham, North CarolinaSearch for more papers by this author First published: August 1989 https://doi.org/10.1002/mus.880120812AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume12, Issue8August 1989Pages 699-699 RelatedInformation