GSK3β inhibitor promotes myelination and mitigates muscle atrophy after peripheral nerve injury

Delay of axon regeneration after peripheral nerve injury usually leads to progressive muscle atrophy and poor functional recovery. The Wnt/β-catenin signaling pathway is considered to be one of the main molecular mechanisms that lead to skeletal muscle atrophy in the elderly. We hold the hypothesis that the innervation of target muscle can be promoted by accelerating axon regeneration and decelerating muscle cell degeneration so as to improve functional recovery of skeletal muscle following peripheral nerve injury. This process may be associated with the Wnt/β-catenin signaling pathway. Our study designed in vitro cell models to simulate myelin regeneration and muscle atrophy. We investigated the effects of SB216763, a glycogen synthase kinase 3 beta inhibitor, on the two major murine cell lines RSC96 and C2C12 derived from Schwann cells and muscle satellite cells. The results showed that SB216763 stimulated the Schwann cell migration and myotube contraction. Quantitative polymerase chain reaction results demonstrated that myelin related genes, myelin associated glycoprotein and cyclin-D1, muscle related gene myogenin and endplate-associated gene nicotinic acetylcholine receptors levels were stimulated by SB216763. Immunocytochemical staining revealed that the expressions of β-catenin in the RSC96 and C2C12 cytosolic and nuclear compartments were increased in the SB216763-treated cells. These findings confirm that the glycogen synthase kinase 3 beta inhibitor, SB216763, promoted the myelination and myotube differentiation through the Wnt/β-catenin signaling pathway and contributed to nerve remyelination and reduced denervated muscle atrophy after peripheral nerve injury.     

Role of microtubule dynamics in Wallerian degeneration and nerve regeneration after peripheral nerve injury

Wallerian degeneration,the progressive disintegration of distal axons and myelin that occurs after peripheral nerve injury,is essential for creating a permissive microenvironment for nerve regeneration,and involves cytoskeletal reconstruction.However,it is unclear whether microtubule dynamics play a role in this process.To address this,we treated cultured sciatic nerve explants,an in vitro model of Wallerian degeneration,with the microtubule-targeting agents paclitaxel and nocodazole.We found that paclitaxel-induced microtubule stabilization promoted axon and myelin degeneration and Schwann cell dedifferentiation,whereas nocodazole-induced microtubule destabilization inhibited these processes.Evaluation of an in vivo model of peripheral nerve injury showed that treatment with paclitaxel or nocodazole accelerated or attenuated axonal regeneration,as well as functional recovery of nerve conduction and target muscle and motor behavior,respectively.These results suggest that microtubule dynamics participate in peripheral nerve regeneration after injury by affecting Wallerian degeneration.This study was approved by the Animal Care and Use Committee of Southern Medical University,China(approval No.SMUL2015081) on October 15,2015.     

Changes in a cerebellar peduncle lesion in a patient with Dandy-Walker malformation A diffusion tensor imaging study

We report a patient with severe ataxia due to Dandy-Walker malformation, who showed functional recovery over 10 months corresponding to a change in a cerebellar peduncle lesion. A 20-month-old female patient who was diagnosed with Dandy-Walker syndrome and six age- and sex-matched healthy control subjects were enrolled. The superior cerebellar peduncle, the middle cerebellar peduncle, and the inferior cerebellar peduncle were evaluated using fractional anisotropy and the apparent diffusion coefficient. The patients’ functional ambulation category was 0 at the initial visit, but improved to 2 at the follow-up evaluation, and Berg’s balance scale score also improved from 0 to 7. Initial diffusion tensor tractography revealed that the inferior cerebellar peduncle was not detected, that the fractional anisotropy of the superior cerebellar peduncle and middle cerebellar peduncle decreased by two standard deviations below, and that the apparent diffusion coefficient increased by two standard deviations over normal control values. However, on follow-up diffusion tensor tractography, both inferior cerebellar peduncles could be detected, and the fractional anisotropy of superior cerebellar peduncle increased to within two standard deviations of normal controls. The functional improvement in this patient appeared to correspond to changes in these cerebellar peduncles. We believe that evaluating cerebellar peduncles using diffusion tensor imaging is useful in cases when a cerebellar peduncle lesion is suspected.     

Effects of delayed repair of peripheral nerve injury on the spatial distribution of motor endplates in target muscle

Motor endplates(MEPs) are important sites of information exchange between motor neurons and skeletal muscle, and are distributed in an organized pattern of lamellae in the muscle. Delayed repair of peripheral nerve injury typically results in unsatisfactory functional recovery because of MEP degeneration. In this study, the mouse tibial nerve was transected and repaired with a biodegradable chitin conduit, immediately following or 1 or 3 months after the injury. Fluorescent α-bungarotoxin was injected to label MEPs. Tissue optical clearing combined with light-sheet microscopy revealed that MEPs were distributed in an organized pattern of lamellae in skeletal muscle after delayed repair for 1 and 3 months. However, the total number of MEPs, the number of MEPs per lamellar cluster, and the maturation of single MEPs in gastrocnemius muscle gradually decreased with increasing denervation time. These findings suggest that delayed repair can restore the spatial distribution of MEPs, but it has an adverse effect on the homogeneity of MEPs in the lamellar clusters and the total number of MEPs in the target muscle. The study procedures were approved by the Animal Ethics Committee of the Peking University People's Hospital(approval No. 2019 PHC015) on April 8, 2019.     

The inherent high vulnerability of dopaminergic neurons toward mitochondrial toxins may contribute to the etiology of Parkinson's disease

正Although the exact mechanism(s)of the degeneration of dopaminergic neurons in Parkinson’s disease(PD)is not well understood,mitochondrial dysfunction is proposed to play a central role.This proposal is strongly strengthened by the findings that compromised mitochondrial functions and/or exposure to mitochondrial toxins such as rotenone,paraquat,or MPTP causes degeneration of the midbrain dopaminergic     

Non-cell autonomous role of astrocytes in axonal degeneration of cortical projection neurons in hereditary spastic paraplegias

Impai red axonal deve lopment and degeneration underlie many debilitating diseases,including hereditary spastic paraplegia(HSP).HSPs are a heterogeneous group of neurogenetic disorders characterized by axonopathy of cortical motor neurons(Fink,2006;Blackstone et al.,2010).The axonal degeneration of these cortical projection neurons(PNs)in HSP patients disrupts the signals from brain to spinal motor neurons,leading to muscle weakness and spasticity.Since the discovery of the first HSP gene(SPAST)in 1999,over 80 distinct genetic loci associated with HSP have been identified.How the mutations of these divergent genes specifically result in axonal degeneration of cortical PNs remains largely unclear,which contributes to the lack of effective treatment to ameliorate,stop,or reverse axonal defects in HSPs.     

Microanatomical study of the nutrient artery of the glossopharyngeal nerve root**☆

BACKGROUND： Because the artery leading to the glossopharyngeal nerve is small and complex, insufficient blood supply can occur due to atherosclerosis, occlusion, or injury. This sometimes results in corresponding nerve degeneration, demyelination, and/or arachnoid adhesion.
OBJECTIVE： To observe the nutrient artery origin of the glossopharyngeal nerve root in the medulla oblongata region, as well as the relationship between the artery and glossopharyngeal nerve root, to verify dependence of primary glossopharyngeal neuralgia, which is related to contact and compression of the nutrient artery of the glossopharyngeal nerve root.
DESIGN, TIME AND SETTING： Repetitive measurement. The experiment was performed at Harbin Medical University and Daqing Oilfields General Hospital between November 2006 and April 2007.
MATERIALS： Ten cadaver heads （seven male and three female） were supplied by the Department of Anatomy, Harbin Medical University. A total of 15 patients （nine male and six female）, aged 38-56, that suffered from glossopharyngeal neuralgia were treated at Daqing Oilfields General Hospital and were between 38-56 years old. All cadaver heads were strictly handled according to the Guideline for Medical Ethics Committee. The patients agreed to the criteria set for the study objects.
METHODS： （1）The bilateral veins of the nutrient artery were dissected under a surgery microscope. A sliding caliper was used to measure the length of the glossopharyngeal nerve from the oblongata to the jugular foramen. The origin of the nutrient artery was noted, as well as the courser and diameter to explore the relationship between the glossopharyngeal nerve root and the vertebral artery, posterior inferior cerebellar artery, anterior inferior cerebellar artery, as well as the branching veins. （2） A total of 15 patients received glossopharyngeal neuralgia surgery. Contact or oppression of the glossopharyngeal nerve with the posterior inferior cerebellar artery, the anterior inferior cerebellar artery     

Recent developments of neuroprotective agents for degenerative retinal disorders

Retinal degeneration is a debilitating ocular complication characterized by the progressive loss of photoreceptors and other retinal neurons,which are caused by a group of retinal diseases affecting various age groups,and increasingly prevalent in the elderly.Age-related macular degeneration,diabetic retinopathy and glaucoma are among the most common complex degenerative retinal disorders,posing significant public health problems worldwide largely due to the aging society and the lack of effective therapeutics.Whilst pathoetiologies vary,if left untreated,loss of retinal neurons can result in an acquired degeneration and ultimately severe visual impairment.Irrespective of underlined etiology,loss of neurons and supporting cells including retinal pigment epithelium,microvascular endothelium,and glia,converges as the common endpoint of retinal degeneration and therefore discovery or repurposing of therapies to protect retinal neurons directly or indirectly are under intensive investigation.This review overviews recent developments of potential neuroprotectants including neuropeptides,exosomes,mitochondrial-derived peptides,complement inhibitors,senolytics,autophagy enhancers and antioxidants either still experimentally or in clinical trials.Effective treatments that possess direct or indirect neuroprotective properties would significantly lift the burden of visual handicap.     

Imbalance of matrix metalloproteinase-9 and matrix metalloproteinase tissue inhibitor-1 may contribute to hemorrhage in cerebellar arteriovenous malformations

In this study,we determined the expression levels of matrix metalloproteinase-2 and-9 and matrix metalloproteinase tissue inhibitor-1 and-2 in brain tissues and blood plasma of patients undergoing surgery for cerebellar arteriovenous malformations or primary epilepsy(control group).Immunohistochemistry and enzyme-linked immunosorbent assay revealed that the expression of matrix metalloproteinase-9 and matrix metalloproteinase tissue inhibitor-1 was significantly higher in patients with cerebellar arteriovenous malformations than in patients with primary epilepsy.The ratio of matrix metalloproteinase-9 to matrix metalloproteinase tissue inhibitor-1 was significantly higher in patients with hemorrhagic cerebellar arteriovenous malformations compared with those with non-hemorrhagic malformations.Matrix metalloproteinase-2 and matrix metalloproteinase tissue inhibitor-2 levels were not significantly changed.These findings indicate that an imbalance of matrix metalloproteinase-9 and matrix metalloproteinase tissue inhibitor-1,resulting in a relative overabundance of matrix metalloproteinase-9,might be the underlying mechanism of hemorrhage of cerebellar arteriovenous malformations.     

cAMP/PKA pathway and mitochondrial protection in oxidative stress-induced optic nerve head astrocytes

正Oxidative stress and cyclic adenosine3',5'-monophosphate (cAMP)/protein kinase A (PKA) pathway in the optic nerve head astrocytes:Glaucoma is a leading cause of blindness worldwide in individuals 60 years of age and older.Despite the widely appreciated disease relevance of structural and functional abnormalities of astrocyte in the optic nerve head(ONH) that is associated with retinal ganglion cell (RGC) axon degeneration,the molecular mechanisms underlying astrocyte dysfunction in glaucomatous ONH degeneration are poorly understood.Oxidative stress is strongly linked to glaucoma pathogenesis,and astrocytes are the responsible cell type that is mostly related to oxidative stress and glaucomatous ONH degeneration.     

Rho-associated protein extension by regulating kinase modulates neurite microtubule remodeling and vinculin distribution

Rho-associated protein kinase is an essential regulator of cytoskeletal dynamics during the process of neurite extension. However, whether Rho kinase regulates microtubule remodeling or the distri- bution of adhesive proteins to mediate neurite outgrowth remains unclear. By specifically modulat- ing Rho kinase activity with pharmacological agents, we studied the morpho-dynamics of neurite outgrowth. We found that lysophosphatidic acid, an activator of Rho kinase, inhibited neurite out- growth, which could be reversed by Y-27632, an inhibitor of Rho kinase. Meanwhile, reorganization of microtubules was noticed during these processes, as indicated by their significant changes in the soma and growth cone. In addition, exposure to lysophosphatidic acid led to a decreased mem- brane distribution of vinculin, a focal adhesion protein in neurons, whereas Y-27632 recruited vin- culin to the membrane. Taken together, our data suggest that Rho kinase regulates rat hippocampal neurite growth and microtubule formation via a mechanism associated with the redistribution of vinculin.     

Axon degeneration: make the Schwann cell great again

Axonal degeneration is a pivotal feature of many neurodegenerative conditions and substantially accounts for neurological morbidity. A widely used experimental model to study the mechanisms of axonal degeneration is Wallerian degeneration(WD), which occurs after acute axonal injury. In the peripheral nervous system(PNS), WD is characterized by swift dismantling and clearance of injured axons with their myelin sheaths. This is a prerequisite for successful axonal regeneration. In the central nervous system(CNS), WD is much slower, which significantly contributes to failed axonal regeneration. Although it is well-documented that Schwann cells(SCs) have a critical role in the regenerative potential of the PNS, to date we have only scarce knowledge as to how SCs ‘sense' axonal injury and immediately respond to it. In this regard, it remains unknown as to whether SCs play the role of a passive bystander or an active director during the execution of the highly orchestrated disintegration program of axons. Older reports, together with more recent studies, suggest that SCs mount dynamic injury responses minutes after axonal injury, long before axonal breakdown occurs. The swift SC response to axonal injury could play either a pro-degenerative role, or alternatively a supportive role, to the integrity of distressed axons that have not yet committed to degenerate. Indeed, supporting the latter concept, recent findings in a chronic PNS neurodegeneration model indicate that deactivation of a key molecule promoting SC injury responses exacerbates axonal loss. If this holds true in a broader spectrum of conditions, it may provide the grounds for the development of new glia-centric therapeutic approaches to counteract axonal loss.     

Perlecan and synaptophysin changes in denervated skeletal muscle

The present study observed sciatic nerve and gastrocnemius muscle changes in denervated rats using morphology methods,and assessed expression of perlecan,an extracellular matrix com-ponent,which is located at the skeletal muscle cell surface as acetylcholine esterase,as well as synaptophysin,a synaptic marker.Results showed degeneration and inflammation following transection of the sciatic nerve.In addition,the sciatic nerve-dominated skeletal muscle degen-erated with mild inflammation,indicating that skeletal muscle atrophy primarily contributed to denervation-induced nutritional disturbances.With prolonged injury time(1-4 weeks post-injury),perlecan expression gradually decreased and reached the lowest level at 4 weeks,but synap-tophysin expression remained unchanged after denervation.Results suggested that perlecan expression was more sensitive to denervation and reflected regional extracellular matrix changes following denervation.     

脐带间充质干细胞治疗Duchenne型肌营养不良3例报告

Due to their relative abundance,stable biological properties and excellent reproductive activity,umbilical cord mesenchymal stem cells have previously been utilized for the treatment of Duchenne muscular dystrophy,which is a muscular atrophy disease.Three patients who were clinically and pathologically diagnosed with Duchenne muscular dystrophy were transplanted with umbilical cord mesenchymal stem cells by intravenous infusion,in combination with multi-point intramuscular injection.They were followed up for 12 months after cell transplantation.Results showed that clinical symptoms significantly improved,daily living activity and muscle strength were enhanced,the sero-enzyme,electromyogram,and MRI scans showed improvement,and dystrophin was expressed in the muscle cell membrane.Hematoxylin-eosin staining of a muscle biopsy revealed that muscle fibers were well arranged,fibrous degeneration was alleviated,and fat infiltration was improved.These pieces of evidence suggest that umbilical cord mesenchymal stem cell transplantation can be considered as a new regimen for Duchenne muscular dystrophy.     

Electrical stimulation and denervated muscles after spinal cord injury

Spinal cord injury(SCI)population with injury below T10 or injury to the cauda equina region is characterized by denervated muscles,extensive muscle atrophy,infiltration of intramuscular fat and formation of fibrous tissue.These morphological changes may put individuals with SCI at higher risk for developing other diseases such as various cardiovascular diseases,diabetes,obesity and osteoporosis.Currently,there is no available rehabilitation intervention to rescue the muscles or restore muscle size in SCI individuals with lower motor neuron denervation.We,hereby,performed a review of the available evidence that supports the use of electrical stimulation in restoration of denervated muscle following SCI.Long pulse width stimulation(LPWS)technique is an upcoming method of stimulating denervated muscles.Our primary objective is to explore the best stimulation paradigms(stimulation parameters,stimulation technique and stimulation wave)to achieve restoration of the denervated muscle.Stimulation parameters,such as the pulse duration,need to be 100–1000 times longer than in innervated muscles to achieve desirable excitability and contraction.The use of electrical stimulation in animal and human models induces muscle hypertrophy.Findings in animal models indicate that electrical stimulation,with a combination of exercise and pharmacological interventions,have proven to be effective in improving various aspects like relative muscle weight,muscle cross sectional area,number of myelinated regenerated fibers,and restoring some level of muscle function.Human studies have shown similar outcomes,identifying the use of LPWS as an effective strategy in increasing muscle cross sectional area,the size of muscle fibers,and improving muscle function.Therefore,displaying promise is an effective future stimulation intervention.In summary,LPWS is a novel stimulation technique for denervated muscles in humans with SCI.Successful studies on LPWS of denervated muscles will help in translating this stimulation technique to the clinical level as a rehabilitation intervention after SCI.     

Vasopressin decreases neuronal apoptosis during cardiopulmonary resuscitation

The American Heart Association and the European Resuscitation Council recently recommend- ed that vasopressin can be used for cardiopulmonary resuscitation, instead of epinephrine. However, the guidelines do not discuss the effects of vasopressin during cerebral resuscitation. In this study, we intraperitoneally injected epinephrine and/or vasopressin during cardiopul- monary resuscitation in a rat model of asphyxial cardiac arrest. The results demonstrated that, compared with epinephrine alone, the pathological damage to nerve cells was lessened, and the levels of c-Iun N-terminal kinase and p38 expression were significantly decreased in the hippo- campus after treatment with vasopressin alone or the vasopressin and epinephrine combination. No significant difference in resuscitation effects was detected between vasopressin alone and the vasopressin and epinephrine combination. These results suggest that vasopressin alone or the vasopressin and epinephrine combination suppress the activation of mitogen-activated protein kinase and c-Iun N-terminal kinase signaling pathways and reduce neuronal apoptosis during cardiopulmonary resuscitation.     

Immediate effects of scalp acupuncture with twirling reinforcing manipulation on hemiplegia following acute ischemic stroke：a hidden association study

Data mining has the potential to provide information for improving clinical acupuncture strategies by uncovering hidden rules between acupuncture manipulation and therapeutic effects in a data set. In this study, we performed acupuncture on 30 patients with hemiplegia due to acute ischemic stroke. All participants were pre-screened to ensure that they exhibited immediate responses to acupuncture. We used a twirling reinforcing acupuncture manipulation at the speciifc lines between the bilateralBaihui(GV20) andTaiyang (EX-HN5). We collected neurologic deifcit score, simpliifed Fugl-Meyer assessment score, muscle strength of the proximal and distal hemiplegic limbs, ratio of the maximal H-relfex to the maximal M-wave (Hmax/Mmax), muscle tension at baseline and immediately after treatment, and the syndromes of traditional Chinese medicine at baseline. We then conducted data mining using an association algorithm and an artiifcial neural network backpropagation algorithm. We found that the twirling reinforcing manipulation had no obvious therapeutic difference in traditional Chinese medicine syndromes of “Deifciency and Excess”. The change in the muscle strength of the upper distal and lower proximal limbs was one of the main factors affecting the immediate change in Fugl-Meyer scores. Additionally, we found a positive correlation between the muscle tension change of the upper limb and Hmax/Mmax immediate change, and both positive and neg-ative correlations existed between the muscle tension change of the lower limb and immediate Hmax/Mmax change. Additionally, when the difference value of muscle tension for the upper and lower limbs was > 0 or < 0, the difference value of Hmax/Mmax was correspondingly positive or negative, indicating the scalp acupuncture has a bidirectional effect on muscle tension in hemiplegic limbs. Therefore, acu-puncture with twirling reinforcing manipulation has distinct effects on acute ischemic stroke patients with different symptoms or stages of disease. Improved muscle tension in the upper and lower limbs, relfected by the variation in the Hmax/Mmax ratio, is crucial for recovery of motor function from hemiplegia.     

Morphological differences in skeletal muscle atrophy of rats with motor nerve and/or sensory nerve injury

Skeletal muscle atrophy occurs after denervation. The present study dissected the rat left ventral root and dorsal root at L4-6 or the sciatic nerve to establish a model of simple motor nerve injury, sensory nerve injury or mixed nerve injury. Results showed that with prolonged denervation time, rats with simple motor nerve injury, sensory nerve injury or mixed nerve injury exhibited abnormal behavior, reduced wet weight of the left gastrocnemius muscle, decreased diameter and cross-sectional area and altered ultrastructure of muscle cells, as well as decreased cross-sectional area and increased gray scale of the gastrocnemius muscle motor end plate. Moreover, at the same time point, the pathological changes were most severe in mixed nerve injury, followed by simple motor nerve injury, and the changes in simple sensory nerve injury were the mildest. These findings indicate that normal skeletal muscle morphology is maintained by intact innervation. Motor nerve injury resulted in larger damage to skeletal muscle and more severe atrophy than sensory nerve injury. Thus, reconstruction of motor nerves should be considered first in the clinical treatment of skeletal muscle atrophy caused by denervation.     

A case of polymyositis with ophthalmoplegia☆ Laboratory examinations

OBJECTIVE： Polymyositis （PM） mainly involves proximal limb and trunk muscles. Ocular muscles are not affected, except in rare cases with both PM and myasthenia gravis （MG）. Thus, the results of laboratory examinations in such a patient deserve to be reported. METHODS： To analyze the clinical, imaging and pathology datas on a 65-year-old woman patient with PM with complex symptoms, who presented mainly ophthalmoplegia. The patient consented to all examinations and the hospital Ethics Committee approved the study. The laboratory examinations included creatine kinase （CK）, ENA, tumor marker, function of thyroid, cranial MRI, and electromyogram （EMG）. Biopsy of the left quadriceps femoris was performed, frozen specimens were stained with hematoxylin and eosin, ATPase, NADH tetrazolium reductase, periodic acid Schiff, oil red O, modified Gomory trichrome and MHC-I, to investigate the pathology of muscle fibers RESULTS： Laboratory results showed： CK, 108.32μ kat/L; antinuclear antibody： （＋）; ENA, （-）; tumor marker, （-）; normal thyroid function, MRI showed no abnormal signals in brain and extraocular muscles. Electromyography of the bilateral deltoid, biceps brachii, musculus quadriceps fexoris, anterior tibialis showed fibrillation potentials, positive potentials and short-duration, small-amplitude polyphasic potentials on voluntary movements with a full interference pattern on mild exertion. Repetitive stimulation did not result in any increment or decrement in these potentials. A muscle biopsy of the left quadriceps femoris showed many small round muscle fibers without peripheral bundle distribution and apparent myofiber degeneration, necrosis and phagocytosis. There were several focal lymphocyte infiltrations. MHC-I immunohistochemical staining was positive in most fibers revealing inflammatory infiltration of normal fibers with MHC-I expression. CONCLUSION： This patient showed increased CK, typical triad of myopathy in EMG, and apparent degeneration and necrosis in biopsy     

Early cyclosporin A treatment retards axonal degeneration in an experimental peripheral nerve injection injury model

Injury to peripheral nerves during injections of therapeutic agents such as penicillin G potassium is common in developing countries. It has been shown that cyclosporin A, a powerful immunosuppressive agent, can retard Wallerian degeneration after peripheral nerve crush injury. However, few studies are reported on the effects of cyclosporin A on peripheral nerve drug injection injury. This study aimed to assess the time-dependent efficacy of cyclosporine-A as an immunosuppressant therapy in an experimental rat nerve injection injury model established by penicillin G potassium injection. The rats were randomly divided into three groups based on the length of time after nerve injury induced by cyclosporine-A administration(30 minutes, 8 or 24 hours). The compound muscle action potentials were recorded pre-injury, early post-injury(within 1 hour) and 4 weeks after injury and compared statistically. Tissue samples were taken from each animal for histological analysis. Compared to the control group, a significant improvement of the compound muscle action potential amplitude value was observed only when cyclosporine-A was administered within 30 minutes of the injection injury(P < 0.05); at 8 or 24 hours after cyclosporine-A administration, compound muscle action potential amplitude was not changed compared with the control group. Thus, early immunosuppressant drug therapy may be a good alternative neuroprotective therapy option in experimental nerve injection injury induced by penicillin G potassium injection.