No abstract available.
Motor Endplate*

Single fiber electromygraphy (SFEMG) is a special EMG technique to study the microphysiology of the motor unit in humans including the functional status of individual motor end-plates in situ, and is known to be a useful test for the diagnosis of neuromuscular juction disorders. To determine the clinical applicability of SFEMFG in this country, 74 SFEMG datas of 61 patients including 54 of myasthenia gravis have been analyzed. The overall ensitivity of SFEMG in myasthenia gravis was high upto 88% and almost all patients with generalized myasthenia gravis showed significant jittering. But the specificity of SFEMG was relatively low(57%) and SFEMG could not clearly differentiate various types of myasthenia gravis. In my experience, SFEMG is a expensive and time-consuming test and I think, at present, SFEMG might have some limitations in clinical usability in this country by the aspect of costeffectiveness.
Diagnosis ; Electromyography* ; Humans ; Korea* ; Motor Endplate ; Myasthenia Gravis* ; Sensitivity and Specificity

'I'he adult form of myasthenia gravis (MG) is an autoimmune disorder characterized by the presence of anti-acetylcholine receptor immunoglobulin G antibodies (anti-ACHRIgG) which blocks the formation of acetylcholine at the motor end plate and causes anatomic deterioration of this structure. 'I'he end result is defective neuromuscular transmission manifested by progressive skeletal muscle weakness. We have experienced a full term pregnancy complicated with the myasthenia gravis. We experienced a case of myathenia gravis associated with pregnancy who underwent cesarean section. The case is presented here with a brief review of literatures concerned.
Acetylcholine ; Adult ; Antibodies ; Cesarean Section ; Female ; Humans ; Immunoglobulin G ; Motor Endplate ; Muscle, Skeletal ; Myasthenia Gravis ; Pregnancy*

Myasthenia gravis is now considered as one of autoimmune disease eintities and characterized by progressive muscle weakness upon exertion and high sensitivity to the motor end plate. Special considerations are required in the anesthetic management of the myasthenic patient undergoing surgery under general anesthesia. The myasthenic patient is generally highly sensitve to non-depolarising agents and resistant to depolarizing agents. it is advisable to avoid the non-depolarzing agents or use only small dose during anesthesia, if neccessary. Atractrium is an intermediate acting bisquatenary ammonium compound and it's effects are well dissipated by hofmann elimination and ester hydrolysis. We have had myasthenic patient undergo thymectomy. Muscle relaxation was obtained by using a small dose of atracurium during anesthesia. Patient's perianesthetic course was not remarkable except slow spontaneous recovery, but it was well reversed by anticholinesterase.
Ammonium Compounds ; Anesthesia ; Anesthesia, General ; Atracurium* ; Autoimmune Diseases ; Humans ; Hydrolysis ; Motor Endplate ; Muscle Relaxation ; Muscle Weakness ; Myasthenia Gravis ; Thymectomy

OBJECTIVETo investigate the changes of acetylcholine receptor (AChR) distribution at the neuromuscular junction (i.e. motor end-plate) following the free neurovascular muscle transfer.

METHODSAChR in the gracilis muscle of the Wistar rat following free neurovascular transfer were labeled by fluorescent alpha-bungarotoxin and radioiodinated alpha-bungarotoxin. Then confocal microscope and gamma-counting were estimated to ACHR, qualitatively and quantitatively.

RESULTSThe junctional AChR numbers decreased to a minimum at the fourth week postoperatively, whereas the extrajunctional receptor numbers increased. From the fifth week postoperatively, the number of junctional AChR's increased. Even at 30 weeks after transfer, the morphology of the neuromuscular junction failed to return to the preoperative style. The number of acetylcholine receptors at the reinnervated neuromuscular junction also remained lower than the control.

CONCLUSIONThe persistent weakness following free neurovascular muscle transfer may be attributed to these qualitative and quantitative changes at the neuromuscular junction.

Animals ; Female ; Motor Endplate ; metabolism ; Muscle, Skeletal ; transplantation ; Nerve Regeneration ; Postoperative Period ; Rats ; Rats, Wistar ; Receptors, Cholinergic ; metabolism

Recently, botulinum toxin has been widely used for the management of spasticity. However it's mechanism of action in the skeletal muscle has not been well clarified. This study was performed to investigate the histopathologic changes in the skeletal muscle after botulinum toxin injection, and to determine the clinical standards of muscle fiber conduction study as an objective indicator for the changes of muscle fiber. As a study group, 35 Sprague Dawley rats were injected intra-muscularly with the botulinum toxin type A around two heads of right gastrocnemius muscle. After the injection of botulinum toxin, histopathologic studies and muscle fiber conduction studies were performed in 5 rats of the study group at 0, 1, 3, 5, 7, 14, and 28th day respectively. Based on the morphologic studies, the mechanisms of paralysis following the botulinum toxin injection were found to be both myogenic and neurogenic, and the motor function recovered through the formation of new motor end-plate and proliferation of Schwann cells. The muscle fiber conduction study revealed that the mean latencies of study group at 1, 3, 5, 7, and 14th day after the injection of botulinum toxin were significantly prolonged than those of the control group(p<0.05). The prolongation and slow recovery of latencies in a muscle fiber conduction study after the injection of botulinum toxin significantly reflect the morphologic changes of paralized skeletal muscles.
Animals ; Botulinum Toxins* ; Botulinum Toxins, Type A ; Head ; Motor Endplate ; Muscle Spasticity ; Muscle, Skeletal ; Paralysis ; Rats* ; Rats, Sprague-Dawley ; Schwann Cells

OBJECTIVETo investigate the compensative mechanism of no further impairment of the upper limb after ipsilateral C(7) transfer for treatment of root avulsion of C(5)-C(6) of the brachial plexus.

METHODSSixty Sprague Dawley (SD) rats were randomly divided into a C7-transection group and a control group, 30 rats each. In the C(7)-transection group, the left forelimbs of the animals underwent transection of ipsilateral C(7) nerve root while C(5) and C(6) nerve roots were avulsed. In the control group, the left forelimbs only underwent C(5) and C(6) root avulsion. The representative muscles of C(7) (innervated mainly by C(7)) including latissimus dorsi, triceps, extensor carpi radialis brevis and extensor digitorum communis were evaluated with neurophysiological investigation, muscular histology and motor end plate histomorphometry 3, 6 and 12 weeks after operation. The right forelimbs of all rats were taken as the control sides.

RESULTSThree weeks after operation, the recovery rates of amplitudes of compound muscle action potential (CMAP) and CMAP latency, muscular wet weight and cross-sectional area of muscle fibers, and area of postsynaptic membranes of those four representative muscles in the C(7)-transection group were significantly lower than those of the control group (P less than 0.05 or P less than 0.01). Six weeks postoperatively, the recovery rates of CMAP amplitude and latency of the triceps showed no significant difference between the C(7)-transection group and the control group (P larger than 0.05). For the extensor carpi radialis brevis and the extensor digitorum communis, the recovery rates of the cross-sectional area of muscle fibers, the amplitude and latency of CMAP and the area of postsynaptic membranes showed no significant difference between the two groups (P larger than 0.05), while the rest parameters were still significantly different between the two group (P less than 0.05 or P less than 0.01). As far as the ultramicrostructure was concerned in the C(7)-transection group, more motor end plates of four representative muscles were observed and their ultramicrostructure also had a tendency to mature as compared with those of 3 weeks postoperatively. Twelve weeks after operation, all parameters of the C(7)-transection group were not significantly different from those of the control group (P >0.05). In the C7-transection group, the motor end plates were densely distributed and their ultramicrostructure in four representative muscles appeared to be mature as compared with those of the control group.

CONCLUSIONSAfter ipsilateral C(7) transfer for treatment of root avulsion of C(5)-C(6) of the brachial plexus, the nerve fibers of the lower trunk can compensatively innervate fibers of C(7)-representative muscles by means of motor end plate regeneration, so there is no further impairment on the injured upper limb.

Animals ; Brachial Plexus ; injuries ; surgery ; Motor Endplate ; ultrastructure ; Nerve Transfer ; methods ; Rats ; Rats, Sprague-Dawley ; Spinal Nerve Roots ; injuries ; Upper Extremity ; physiology

The vertebrate neuromuscular junction (NMJ) is considered as a “tripartite synapse” consisting of a motor axon terminal, a muscle endplate, and terminal Schwann cells that envelope the motor axon terminal. The neuregulin 1 (NRG1)-ErbB2 signaling pathway plays an important role in the development of the NMJ. We previously showed that Grb2-associated binder 1 (Gab1), a scaffolding mediator of receptor tyrosine kinase signaling, is required for NRG1-induced peripheral nerve myelination. Here, we determined the role of Gab1 in the development of the NMJ using muscle-specific conditional Gab1 knockout mice. The mutant mice showed delayed postnatal maturation of the NMJ. Furthermore, the selective loss of the gab1 gene in terminal Schwann cells produced delayed synaptic elimination with abnormal morphology of the motor endplate, suggesting that Gab1 in both muscles and terminal Schwann cells is required for proper NMJ development. Gab1 in terminal Schwann cells appeared to regulate the number and process elongation of terminal Schwann cells during synaptic elimination. However, Gab2 knockout mice did not show any defects in the development of the NMJ. Considering the role of Gab1 in postnatal peripheral nerve myelination, our findings suggest that Gab1 is a pleiotropic and important component of NRG1 signals during postnatal development of the peripheral neuromuscular system.
Animals ; Mice ; Mice, Knockout ; Motor Endplate ; Muscle, Skeletal* ; Muscles ; Myelin Sheath ; Neuregulin-1 ; Neuromuscular Junction ; Peripheral Nerves ; Presynaptic Terminals ; Protein-Tyrosine Kinases ; Schwann Cells* ; Synapses* ; Vertebrates

Since Willis described 'fatigable weakness' in 1672, most physicians consider it as a kind of hysteria due to the inconsistent fluctuation of symptoms. Erb presented three cases of 'bulbal palsy' in the 1870s, and Oppenheim and Hopper considered myasthenia gravis as a disease similar to curare poisoning and as a disease induced by attack of the motor centers by intrinsic toxins, respectively. In 1903, Elliot suggested that a 'chemical substance' mediates the nerve impulses at synapse. However, it was not until 1921 that this was demonstrated by Loewi, who provided evidence from the famous two-frog-hearts experiment. Dale later revealed the substance to be acetylcholine, and he also suggested that myasthenia gravis is due to a problem with the motor end plate. In 1934, Walker was prompted by the resemblance between myasthenia gravis and curare poisoning to apply physostigmine, a curare-poisoning antidote, to a patient, which produced a dramatic result. Since then the use of anticholinesterase inhibitors has been adopted for standard therapeutic modality. Some prominent surgeons have also applied thymectomy as a surgical modality. The most recent focus of myasthenia gravis has been immunological. In 1960, Simpson proposed the autoimmune hypothesis, and Chang et al. showed that snake venom contained a selective antagonist of the nicotinic acetylcholine receptor, alpha-bungarotoxin. The immunization of rabbits with acetylcholine receptor purified from the electrical organs of electric eels by Patrick et al. induced myasthenic symptoms and signs, and these were reversed by acetylcholinesterase inhibitors. The role of the autoimmune system has led to the introduction of an immunosuppressive modality and plasma exchange to the field of clinical neurology.
Acetylcholine ; Action Potentials ; Bungarotoxins ; Cholinesterase Inhibitors ; Curare ; Electrophorus ; History of Medicine ; Humans ; Hysteria ; Immunization ; Motor Endplate ; Myasthenia Gravis ; Physostigmine ; Plasma Exchange ; Rabbits ; Receptors, Nicotinic ; Snake Venoms ; Synapses ; Thymectomy

The surgical methods of injured peripheral nerve were limited to end-to-end neurorrhaphy, nerve graft, neurotization, etc. Recently, Several studies were executed about end-to-side neurorrhaphy in peripheral nerve injury. The purpose of this study is to investigate the axonal regeneration of end-to-side neurorrhaphy in rats, as alternative surgical method for peripheral nerve injury comparing with the state of normal, denervated, and end-to-end neurorrhaphy. Sixty female Sprague-Dawley rats were divided into four groups; group I as normal control group, group II as denervated control group, group III as end-to-end neurorrhaphy group, group IV as end-to-side neurorrhaphy group. At postoperative 4, 8, 12, 16, 20 and 24 week, nerve regeneration was assessed through electrophysiologic and histological studies. The results obtained were as follows: 1. In electrophysiologic test, the mean amplitude was higher in normal control group(group I) than either in end-to-end neurorrhaphy group(group III) or in end- to- side neurorrhaphy group(group IV)(p < 0.05). But there is no significant difference between group III and group IV. 2. The mean number of regenerating myelinated nerve fibers was higher in group I than either in group III or in group IV(p < 0.05). But there is no significant difference between group III and group IV, except at postoperative 16 week. 3. The mean number of motor end-plates at postoperative 24 week was 20.5 in group III and 18.2 in group IV, but there is no significant difference between group III and group IV. In conclusion, end-to-side neurorrhaphy through an epineural window could induce distal nerve regeneration by collateral sprouting of main peripheral nerve and positively reflected in functional improvement of the target muscle.
Animals ; Axons ; Female ; Humans ; Motor Endplate ; Nerve Fibers, Myelinated ; Nerve Regeneration* ; Nerve Transfer ; Peripheral Nerve Injuries ; Peripheral Nerves ; Rats* ; Rats, Sprague-Dawley ; Regeneration ; Transplants