Melatonin inhibits arrhythmias induced by increased late sodium currents in ventricular myocytes / 药学学报

Melatonin (Mel) has been shown to have cardioprotective effects, but its action on ion channels is unclear. In this experiment, we investigated the inhibitory effect of Mel on late sodium currents (INa.L) in mouse ventricular myocytes and the anti-arrhythmic effect at the organ level as well as its mechanism. The whole-cell patch clamp technique was applied to record the ionic currents and action potential (AP) in mouse ventricular myocytes while the electrocardiogram (ECG) and monophasic action potential (MAP) were recorded simultaneously in mouse hearts using a multichannel acquisition and analysis system. The results demonstrated that the half maximal inhibitory concentration (IC50) values of Mel on transient sodium current (INa.T) and specific INa.L opener 2 nmol·L-1 sea anemone toxins II (ATX II) increased INa.L were 686.615 and 7.37 μmol·L-1, respectively. Mel did not affect L-type calcium current (ICa.L), transient outward current (Ito), and AP. In addition, 16 μmol·L-1 Mel shortened ATX II-prolonged action potential duration (APD), suppressed ATX II-induced early afterdepolarizations (EADs), and significantly reduced the incidence of ventricular tachycardia (VT) and ventricular fibrillation (VF) in Langendorff-perfused mouse hearts. In conclusion, Mel exerted its antiarrhythmic effects principally by blocking INa.L, thus providing a significant theoretical basis for new clinical applications of Mel. Animal welfare and experimental process are in accordance with the regulations of the Experimental Animal Ethics Committee of Wuhan University of Science and Technology (2023130).

Sural nerve conduction: Amplitude and distal latency of sensory nerve action potential

Background: The sensory nerve action potential (SNAP) is an important factor in the electro diagnostic evaluation of a patient with suspected peripheral neuropathy. Sural nerve is the most frequently studied nerve in the electrophysiology. For proper diagnosis sural sensory conduction abnormalities, a reference data are required for each electrophysiology laboratory. Aims and Objectives: The aim of the study was to find out normative reference data of amplitude and distal latency (DL) of sural SNAP for Northern Kerala population. Materials and Methods: The study was designed as cross-sectional and observational study and analysis of values was done using SPSS version 16. A total of 250 healthy subjects of age 15–50 from Northern Kerala participated in the study which included equal number of males and females. Results: Normative reference data for sensory amplitude and DL were derived in the present study. Sensory amplitude was more and DL was found to be less in female population, indicating faster nerve conduction in female. Conclusion: The reference data derived here can be utilized to detect any abnormality sural nerve sensory conduction. The gender effect on sural nerve sensory conduction parameters can be attributed to the height difference, as nerve conduction velocity is inversely proportional to height.

To evaluate peripheral neuropathy of ulnar sensory nerve through nerve conduction studies in Type 2 diabetic patients

Background: Secretory defects or defects in action of insulin precipitate a condition of chronic hyperglycemia known as diabetes mellitus, a metabolic disorder progressive in nature with long asymptomatic stage. Diabetic neuropathy is the most life threatening complication. Aims and Objectives: Early detection of peripheral neuropathy helps to take remedial measures in controlling the progression of the disease. Materials and Methods: Forty clinically detectable peripheral neuropathy Type 2 diabetic patients and 40 age-matched control subjects were selected for the study and nerve conduction test of ulnar sensory nerve was done and distal latency (DL), sensory nerve action potential (SNAP), and sensory nerve conduction velocity (SNCV) were recorded using RMS-EMG-EP-MAK II machine to predict the extent and type of neuropathy in diabetics. Results: Significant difference (P < 0.05) of DL, SNCV, and SNAP of ulnar sensory nerve was found in clinically detectable peripheral neuropathy group as compared to controls. Predominantly, axonal type (loss of amplitude) of neuropathy was present in study group. Conclusion: Electrophysiological variables of ulnar sensory nerve were affected in most of the subjects suggesting axonal loss and demyelinating changes in the nerve.

Correlation between Elbow Flexor Muscle Strength and Needle Electromyography Parameters after Musculocutaneous Nerve Injury / 法医学杂志

OBJECTIVES@#To explore the changes of elbow flexor muscle strength after musculocutaneous nerve injury and its correlation with needle electromyography (nEMG) parameters.@*METHODS@#Thirty cases of elbow flexor weakness caused by unilateral brachial plexus injury (involving musculocutaneous nerve) were collected. The elbow flexor muscle strength was evaluated by manual muscle test (MMT) based on Lovett Scale. All subjects were divided into Group A (grade 1 and grade 2, 16 cases) and Group B (grade 3 and grade 4, 14 cases) according to their elbow flexor muscle strength of injured side. The biceps brachii of the injured side and the healthy side were examined by nEMG. The latency and amplitude of the compound muscle action potential (CMAP) were recorded. The type of recruitment response, the mean number of turns and the mean amplitude of recruitment potential were recorded when the subjects performed maximal voluntary contraction. The quantitative elbow flexor muscle strength was measured by portable microFET 2 Manual Muscle Tester. The percentage of residual elbow flexor muscle strength (the ratio of quantitative muscle strength of the injured side to the healthy side) was calculated. The differences of nEMG parameters, quantitative muscle strength and residual elbow flexor muscle strength between the two groups and between the injured side and the healthy side were compared. The correlation between elbow flexor manual muscle strength classification, quantitative muscle strength and nEMG parameters was analyzed.@*RESULTS@#After musculocutaneous nerve injury, the percentage of residual elbow flexor muscle strength in Group B was 23.43% and that in Group A was 4.13%. Elbow flexor manual muscle strength classification was significantly correlated with the type of recruitment response, and the correlation coefficient was 0.886 (P<0.05). The quantitative elbow flexor muscle strength was correlated with the latency and amplitude of CMAP, the mean number of turns and the mean amplitude of recruitment potential, and the correlation coefficients were -0.528, 0.588, 0.465 and 0.426 (P<0.05), respectively.@*CONCLUSIONS@#The percentage of residual elbow flexor muscle strength can be used as the basis of muscle strength classification, and the comprehensive application of nEMG parameters can be used to infer quantitative elbow flexor muscle strength.

Molecular basis of the different effects of procainamide and N-acetylprocainamide on the maximum upstroke velocity and half-decay time of the cardiac action potential in guinea pig papillary muscle

Procainamide (PA) and its in vivo metabolite, N-acetylprocainamide (NAPA), display some pharmacological differences. Although it is agreed that PA is a class IA antiarrhythmic, it has been reported that NAPA is a pure class III antiarrhythmic that affects only the repolarizing phase of the cardiac action potential. This last concept, observed exclusively in dogs, gained wide acceptance, appearing in classic pharmacology textbooks. However, evidence in species such as mice and rats indicates that NAPA can affect cardiac Na+ channels, which is unexpected for a pure class III antiarrhythmic drug. To further clarify this issue, the effects of PA (used as a reference drug) and NAPA on the maximum upstroke velocity (Vmax) and half-decay time (HDT) of the cardiac action potential were examined in the isolated right papillaris magnus of the guinea pig heart. Both PA and NAPA affected Vmax at lower concentrations than required to affect HDT, and NAPA had weaker effects on both variables. Thus, NAPA displayed typical class IA antiarrhythmic behavior. Therefore, the concept that NAPA is a pure class III antiarrhythmic drug is more species-dependent than previously envisioned. In addition, we demonstrated that the differential pharmacology of PA and NAPA is explainable, in molecular terms, by steric hindrance of the effects of NAPA and the greater number of potent aromatic-aromatic and cation π interactions with Na+ or K+ cardiac channels for PA.

Inhibitory effects of a TRPM4 inhibitor 9-phenanthrol on electrical activity of INS-1 pancreatic β-cells / 药学学报

The Ca2+-activated monovalent cation selective transient receptor potential melastatin 4 (TRPM4) channel expressed in pancreatic β-cells is implicated in the β-cell function and insulin secretion, but how pharmacological function of TRPM4 channel affects membrane excitability of β-cells remains largely unknown. Here, we report that pharmacological inhibition of TRPM4 by specific inhibitor 9-phenanthrol attenuates electrical activities of pancreatic β-cells. In whole-cell current clamp recordings, 9-phenanthrol results in inhibition of action potential frequency induced by tolbutamide of the INS-1 pancreatic β-cells in a dose-dependent manner with an IC50 value of 14.99 ± 7.93 μmol·L-1. Similarly, 9-phenanthrol also inhibited action potential firing in INS-1 cells stimulated by current injection. Further recordings of β-cells demonstrate the significant inhibitory effects on action potential peak and action potential amplitude by 9-phenanthrol. Taken together, our results show the involvement of TRPM4 channel function in pancreatic β-cells depolarization and action potential, it provides pharmacological experimental methods and theoretical support for the study of TRPM4 channel in pancreatic β-cells.

Clinical and electrophysiological study of lower limb split signs in amyotrophic lateral sclerosis / 中华神经科杂志

Objective:To investigate the association between split foot and electrophysiology in patients with amyotrophic lateral sclerosis (ALS).Methods:The clinically definite or clinically probable ALS patients hospitalized in the Department of Neurology, the First Medical Center of Chinese People′s Liberation Army General Hospital from April 2021 to December 2022 were prospectively collected. From April 2021 to December 2022, patients who visited the Chinese People′s Liberation Army General Hospital for other reasons without abnormal electrophysiological examination were collected as the control group. The incidence of split leg [the limb whose modified Medical Research Council Muscle Strength Scale (mMRC) score of ankle dorsiflexors was lower than that of ankle plantarflexors] in ALS patients was calculated, and the incidence of split foot (the limb whose mMRC score of hallux dorsiflexors was lower than that of hallux plantarflexors) in ALS patients was calculated. The amplitude of compound muscle action potential (CMAP) of common peroneal nerve and tibial nerve was detected to observe the involvement of motor neurons innervating ankle dorsiflexors and ankle plantarflexors. The characteristics of split leg and split foot in ALS patients were analyzed from the perspective of muscle strength, and the characteristics of split foot in ALS patients were analyzed from the perspective of electrophysiology. Receiver operating characteristic (ROC) curve was used to analyze the sensitivity and specificity of peroneal nerve/tibial nerve CMAP amplitude ratio in distinguishing ALS patients from controls.Results:A total of 101 ALS patients with lower limb involvement and 110 controls with normal lower limb muscle strength were collected. Among the 101 ALS patients with lower limb involvement, strength of ankle plantarflexors was greater than that of ankle dorsiflexors in 35.64% (36/101) patients, strength of ankle dorsiflexors was greater than that of ankle plantarflexors in 5.94% (6/101) patients, and strength of ankle plantarflexors and ankle dorsiflexors was equal in 58.42% (59/101) patients. Strength of hallux dorsiflexors was lower than that of hallux plantarflexors in 53.47% (54/101) patients, strength of hallux dorsiflexors was greater than that of hallux plantarflexors in 1.98% (2/101) patients, and the strength of hallux dorsiflexors and hallux plantarflexors was equal in 44.55% (45/101) patients. The incidence of split leg was negatively correlated with age ( OR=0.25, 95% CI 0.16-0.40, P<0.05), course of disease ( OR=0.52, 95% CI 0.38-0.80 P<0.05) and ALS functional revised scores ( OR=0.29, 95% CI 0.12-0.67, P<0.05). The incidence of split foot was negatively correlated with the onset time of lower limb symptoms ( OR=0.96, 95% CI 0.93-0.99, P<0.05). Compared with the control group, the differences of the decrease of CMAP amplitude in the common peroneal nerve and tibial nerve [the common peroneal nerve (6.45±2.56) mV vs (3.63±1.83) mV, tibial nerve (12.87±4.72) mV vs (9.18±6.22) mV] were statistically significant ( t=-4.65, t=-3.44, both P<0.001) and the differences of the peroneal nerve/tibial nerve CMAP amplitude ratio (0.54±0.24 vs 0.36±0.18) decrease was statistically significant ( t=-4.31, P<0.001) in patients with split foot. ROC curve analysis showed that the area under the ROC curve of CMAP amplitude ratio of common peroneal nerve/tibial nerve in ALS patients with split foot was 0.70, indicating that the accuracy of CMAP amplitude of common peroneal nerve/tibial nerve in distinguishing ALS patients from controls was low. Conclusions:In ALS patients with lower limb involvement, strength of ankle dorsiflexors is weaker than that of ankle plantarflexors, and strength of hallux dorsiflexors is weaker than that of hallux plantarflexors. At the diagnostic level, the CMAP amplitude ratio of common peroneal nerve/tibial nerve in ALS patients with split foot has a lower accuracy in the diagnosis of ALS.

Nerve Conduction Studies in Asymptomatic HIV Positive Persons

Background: Nerve Conduction Studies were performed in asymptomatic HIV positive persons and corresponding controls to detect subclinical peripheral nervous system involvement in early stage of HIV. Aims & Objective: To perform Nerve Conduction Studies in asymptomatic HIV positive persons and corresponding controls. Material and Methods: In this study,100 participants in the age group 25-45 years were selected. In study group, 50 3 participants who were HIV positive and asymptomatic (CD4 count > 350 cells/mm ) and were not on Anti Retro Viral Treatment (ART), were included. In control group 50 healthy age matched HIV negative participants were included. We performed Nerve Conduction Studies in these participants. For motor nerves, Distal Latency (DL), Motor Nerve Conduction Velocity (MNCV), Compound Muscle Action Potential (CMAP) amplitude were measured and for sensory nerves Onset Latency (OL), Sensory Nerve Conduction Velocity (SNCV) and Sensory Nerve Action Potential (SNAP) amplitude were measured. Results: Nerve Conduction Studies in asymptomatic HIV revealed that, MNCV was significantly decreased for median motor nerve and tibial motor nerve in study group compared to control group, SNAP was significantly reduced for median sensory nerve in study group compared to control group, OL was significantly prolonged for sural nerve in study group than control group and SNCV was significantly decreased for sural nerve in study group than control group. Conclusion: Nerve Conduction Studies in asymptomatic HIV positive persons suggests subclinical peripheral nervous system involvement in early stages of HIV. Hence Nerve Conduction Studies can be important to detect subclinical peripheral nervous system involvement in the early stages of HIV.

Regulation of Axon Initial Segment Diameter by COUP-TFI Fine-tunes Action Potential Generation / 神经科学通报·英文版

The axon initial segment (AIS) is a specialized structure that controls neuronal excitability via action potential (AP) generation. Currently, AIS plasticity with regard to changes in length and location in response to neural activity has been extensively investigated, but how AIS diameter is regulated remains elusive. Here we report that COUP-TFI (chicken ovalbumin upstream promotor-transcription factor 1) is an essential regulator of AIS diameter in both developing and adult mouse neocortex. Either embryonic or adult ablation of COUP-TFI results in reduced AIS diameter and impaired AP generation. Although COUP-TFI ablations in sparse single neurons and in populations of neurons have similar impacts on AIS diameter and AP generation, they strengthen and weaken, respectively, the receiving spontaneous network in mutant neurons. In contrast, overexpression of COUP-TFI in sparse single neurons increases the AIS diameter and facilitates AP generation, but decreases the receiving spontaneous network. Our findings demonstrate that COUP-TFI is indispensable for both the expansion and maintenance of AIS diameter and that AIS diameter fine-tunes action potential generation and synaptic inputs in mammalian cortical neurons.

A Simple and Low-Cost, but Naturalistic Method for Introducing Students to Action Potentials

Abstract Current trends in science education recommend the complementary use of virtual and hands-on methods of teaching. In neurobiology, for instance, there is a plethora of virtual laboratories and simulators that can be readily combined with traditional physical labs. Unfortunately, physical laboratories are almost unaffordable for many institutions due to the high cost of equipment. In this paper, we present a simple and low-cost in vivo method for demonstrating some of the basic biophysical properties of neural action potentials. The method involves the following steps: a) dissection of the ventral nerve cord of earthworm; b) electrical stimulation; c) amplification and visualization of the medial and lateral giant fibers' action potentials; and d) recording. The system showed stability, expected amplification, high signal-to-noise ratio, and an estimated total cost of US$ 5.662. We provide guidelines for assembling the system and discus its utility as a teaching alternative for low budget institutions.

Simulation study of spinal cord stimulation evoked compound action potential / 生物医学工程学杂志

Spinal cord stimulation (SCS) for pain is usually implanted as an open loop system using unchanged parameters. To avoid the under and over stimulation caused by lead migration, evoked compound action potentials (ECAP) is used as feedback signal to change the stimulating parameters. This study established a simulation model of ECAP recording to investigate the relationship between ECAP component and dorsal column (DC) fiber recruitment. Finite element model of SCS and multi-compartment model of sensory fiber were coupled to calculate the single fiber action potential (SFAP) caused by single fiber in different spinal cord regions. The synthetized ECAP, superimposition of SFAP, could be considered as an index of DC fiber excitation degree, because the position of crests and amplitude of ECAP corresponds to different fiber diameters. When 10% or less DC fibers were excited, the crests corresponded to fibers with large diameters. When 20% or more DC fibers were excited, ECAP showed a slow conduction crest, which corresponded to fibers with small diameters. The amplitude of this slow conduction crest increased as the stimulating intensity increased while the amplitude of the fast conduction crest almost remained unchanged. Therefore, the simulated ECAP signal in this paper could be used to evaluate the degree of excitation of DC fibers. This SCS-ECAP model may provide theoretical basis for future clinical application of close loop SCS base on ECAP.

Effects of magnetic stimulation at different frequencies on neuronal excitability and voltage-gated potassium channels / 生物医学工程学杂志

As a noninvasive neuromodulation technique, transcranial magnetic stimulation (TMS) is widely used in the clinical treatment of neurological and psychiatric diseases, but the mechanism of its action is still unclear. The purpose of this paper is to investigate the effects of different frequencies of magnetic stimulation (MS) on neuronal excitability and voltage-gated potassium channels in the

Research Advances on Non-Clinical Evaluation in Vitro of Drug-Induced Arrhythmias / 中国药学杂志

Drug-induced arrhythmia is one of the main causes of failure in drug development, and it is also a major cause of drug withdrawal, therefore, accurate prediction of drug-induced arrhythmia in the non-clinical research stage is the best way to reduce cost. Literature was retrieved by formally searching PubMed, Metstr, CNKI and Baidu Scholar, 1 479 published articles were found through search method, 63 full-text articles were included. After reviewed the relevant literatures, the advantages and disadvantages of the different experimental cells and the related evaluation methods are assessed, in order to provide reference for toxicity evaluation.

Diethylmorphine effect on action potential and calcium ion current of neonatal rat cardiomyocytes in vitro / 中国组织工程研究

BACKGROUND: Opioids can regulate the changes of membrane potential and Ca2+ current in cardiomyocytes, but whether diacetylmorphine can induce the changes of cardiac rhythm, cell action potential and Ca2+ current has not been reported. OBJECTIVE: To explore the effect of diacetylmorphine on action potential and calcium current of isolated cardiomyocytes from neonatal Sprague-Dawley rats. METHODS: Five concentrations of diacetylmorphine (0, 10-2, 10-3, 10-4, 10-5 mol/L) and 20 mol/L verapamil were used to treat the cardiomyocytes of neonatal Sprague-Dawley rats cultured in vitro. The cells were divided into control group, diacetylmorphine group, diacetylmorphine+verapamil group. The latter two groups were treated with diacetylmorphine and diacetylmorphine+verapamil (20 μmol/L), respectively, while the control group was treated with the same amount of PBS. The study protocol was approved by the Animal Ethics Committee of the First Affiliated Hospital of Xinjiang Medical University on May 21, 2018 with approval No. IACUC201805-K1. RESULTS AND CONCLUSION: At 24 hours of culture with different concentrations of diacetylmorphine, the number of cardiomyocytes with abnormal morphology increased significantly in a dose-dependent manner. When the concentration of diacetylmorphine increased, the number of survived cells decreased, with a reduction in the size of cytoplasm and number of pseudopods, the cell membrane was shrunk and the nuclear structure was blurred. Compared with the control group, when diacetylmorphine was added to intervene with the cardiomyocytes, there was a significant difference in the spontaneous beating frequency and rhythm of cardiomyocytes. The negative value of resting membrane potential decreased, while the time course of action potential increased significantly, and the amplitude of action potential decreased significantly. Compared with the control group, the number of cells with changes in the membrane potential significantly increased in the diacetylmorphine group. The addition of verapamil reduced the number of cells with changes in the membrane potential. Compared with the control group, the number of cells with variation of membrane potential was increased to some extents. These findings suggest that diacetylmorphine can induce cardiomyocyte morphological abnormality, increase the spontaneous beating frequency and rhythm of cardiomyocytes, and change the membrane potential and action potential of cardiomyocytes. Verapamil acts as a calcium channel blocker that can improve the rhythm abnormality of cardiomyocytes induced by diacetylmorphine.

Repetitive transcranial magnetic stimulation significantly improves cognitive impairment and neuronal excitability during aging in mice / 生物医学工程学杂志

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive brain stimulation technique that has been paid attention to with increasing interests as a therapeutic neural rehabilitative tool. Studies confirmed that high-frequency rTMS could improve the cognitive performance in behavioral test as well as the excitability of the neuron in animals. This study aimes to investigate the effects of rTMS on the cognition and neuronal excitability of Kunming mice during the natural aging. Twelve young mice, 12 adult mice, and 12 aged mice were used, and each age group were randomly divided into rTMS group and control group. rTMS-treated groups were subjected to high-frequency rTMS treatment for 15 days, and control groups were treated with sham stimulation for 15 days. Then, novel object recognition and step-down tests were performed to examine cognition of learning and memory. Whole-cell patch clamp technique was used to record and analyze resting membrane potential, action potential (AP), and related electrical properties of AP of hippocampal dentate gyrus (DG) granule neurons. Data analysis showed that cognition of mice and neuronal excitability of DG granule neurons were degenerated significantly as the age increased. Cognitive damage and degeneration of some electrical properties were alleviated under the condition of high-frequency rTMS. It may be one of the mechanisms of rTMS to alleviate cognitive damage and improve cognitive ability by changing the electrophysiological properties of DG granule neurons and increasing neuronal excitability.

Connectivity pattern of action potentials causal network in prefrontal cortex during anxiety / 生物医学工程学杂志

Anxiety disorder is a common emotional handicap, which seriously affects the normal life of patients and endangers their physical and mental health. The prefrontal cortex is a key brain region which is responsible for anxiety. Action potential and behavioral data of rats in the elevated plus maze (EPM) during anxiety (an innate anxiety paradigm) can be obtained simultaneously by using the and in conscious animal multi-channel microelectrode array recording technique. Based on maximum likelihood estimation (MLE), the action potential causal network was established, network connectivity strength and global efficiency were calculated, and action potential causal network connectivity pattern of the medial prefrontal cortex was quantitatively characterized. We found that the entries (44.13±6.99) and residence period (439.76±50.43) s of rats in the closed arm of the elevated plus maze were obviously higher than those in the open arm [16.50±3.25, <0.001; (160.23±48.22) s, <0.001], respectively. The action potential causal network connectivity strength (0.017 3±0.003 6) and the global efficiency (0.044 2±0.012 8) in the closed arm were both higher than those in the open arm (0.010 4±0.003 2, <0.01; 0.034 8±0.011 4, <0.001), respectively. The results suggest that the changes of action potential causal network in the medial prefrontal cortex are related to anxiety state. These data could provide support for the study of the brain network mechanism in prefrontal cortex during anxiety.

Effects of hypothermia on the repolarization duration of ventricular myocytes in rats and its mechanism / 中国应用生理学杂志

To observe the effects of hypothermia on the repolarization duration and the expression of Kir2.1 protein of ventricular myocytes in isolated rat heart and explore the role of Kir2.1 protein. Eighteen healthy adult male Sprague-Dawley rats were randomly divided into three groups (n=6 per group): Control group (C group), 35℃ group (H group), 32℃ group (H group). Langendorff isolated heart models were established. After 15 min 37℃ K-H fluid banlanced perfusion, C group continued to perfuse the K-H solution at 37℃ for 30 minutes, H group continued to perfuse the K-H solution at 35℃ for 30 minutes, H group continued to perfuse the K-H solution at 32℃ for 30 minutes. At 15 min of balanced perfusion (T), and 30 min of continuous perfusion (T), the heart rate,and the MAP in the three layers of the left ventricular anterior wall were recorded, the action potential duration at 50% repolarization (MAPD), the action potential duration at 90% repolarization (MAPD) and transmural dispersion of repolarization(TDR) were calculated. At the same time, the occurrence of arrhythmia was recorded. The expression of Kir2.1 protein was measured by Western blot. The average optical density (AOD) and the distribution of Kir2.1 protein were measured by immunohistochemistry in the ventricular tissue measured by electrophysiology. Compared with T, the heart rate was decreased, MAPD and MAPD were prolonged significantly (P＜0.05), and TDR was increased significantly (P＜0.05) in H group, H group at T. Compared with C group, the HR was decreased, the MAPD was prolonged significantly (P＜0.05), TDR was increased significantly (P＜0.05),the expression and the AOD of Kir2.1 protein were decreased significantly (P＜0.05) in Hgroup, Hgroup at T. Compared with H group, the heart rate of H group was decreased significantly (P＜0.05), MAPD and MAPD were prolonged significantly (P＜0.05), and TDR was increased significantly (P＜0.05) at T. The distribution of Kir2.1 protein in group C was normal, while the distribution of Kir2.1 in H group and H group was disordered. Hypothermia prolonged the ventricular duration of repolarization and increased the dispersion of repolarization. The mechanism is related to the down-regulation the expression of Kir2.1 protein and the disorder of the distribution of Kir2.1 protein.

Potencial de ação duplo e alterações ecográficas do nervo mediano em doentes com síndrome do túnel cárpico / Double peak action potential and ultrasonography nerve evaluation in patients with carpal tunnel syndrome

Introdução: A síndrome do túnel cárpico (STC) é sustentada pela presença de lentificação do potencial de ação do nervo mediano no estudo ortodrómico de condução nervosa sensitiva em comparação com o nervo radial (EC-MR). Uma técnica modificada de registo simultâneo de ambos os nervos (EC-MRsimul) pode ser utilizada, detetando a lentificação do nervo mediano através da presença de potencial de ação sensitivo duplo (PAS-D). O objetivo deste estudo é correlacionar o PAS-D com os achados de EC-MR e com o edema perineural em doentes com diagnóstico de STC. Métodos: Indivíduos saudáveis e doentes com STC há menos de 12 meses foram submetidos a avaliação eletrofisiológica, incluindo o EC-MR e o EC-MRsimul. Foi também realizada ultrassonografia para registo da área seccional do nervo mediano (AS-NM) no punho e antebraço e, respetivo índice punho-antebraço (I-PA). Resultados: Foram recrutados 38 doentes com idade média de 54,8 ± 15,3 anos com STC e 18 indivíduos saudáveis. A diferença de latência distal entre o nervo mediano e radial foi superior nos doentes (0,80 ± 0,30ms vs. 0,15 ± 0,20ms; p=0,015). O EC­MRsimul demonstrou a presença de PAS-D nos indivíduos sintomáticos. A AS­NM no punho foi também superior nos doentes (8,9 ± 0,9mm2 vs. 6,6 ± 0,7mm2; p<0.003), tendo sido identificado um quisto sinovial e um neurinoma. O edema perineural traduzido pela AS-SM correlacionou-se positivamente com a diferença de latência interpico no EC-MR e com a presença de PAS-D. Conclusão: O PAS-D está associado à presença de lentificação da condução e ao edema perineural do nervo mediano no contexto de STC ou devido a lesões ocupantes de espaço. (AU)

Introduction: Carpal tunnel syndrome (CTS) is characterized by median nerve action potential slowing, which can be shown in comparative orthodromic sensory nerve conduction studies between median and radial nerve (NCS-MR). A modified technique with simultaneous recording of both nerves (NCS-MRsimul) can also be used to detect median nerve slowing through the presence of double peak action potential (DPp). The study aims to correlate the presence of DPp with NCS-MR findings and with perineural edema in patients diagnosed with STC. Methods: Healthy individuals and patients with CTS for less than 12 months underwent NCS-MR and MRsimul. An ultrasonography evaluation was also performed to record the medial nerve sectional area (SA-MN) on the wrist and forearm, and the wrist-to-forearm ratio (WFR) was calculated. Results: We recruited 38 patients with CTS whose mean age was 54.8 ± 15.3 years and 18 healthy individuals. Distal latency difference between the median and radial nerves was higher in patients with CTS (0.80 ± 0.30 ms vs. 0.15 ± 0.20 ms, p = 0.015). NCS-MRsimul showed DPp in symptomatic individuals. SA-MN in the wrist was also higher in patients with CTS (8.9 ± 0.9 mm2 vs. 6.6 ± 0.7 mm2 , p <0.003). Ultrasonography evaluation identified a synovial cyst and a neurinoma. Perineural edema traduced by higher SA-MN and WFR correlated positively with interpeak latency difference in NCS-MR and with the presence of DPp. Conclusions: DPp was associated with median nerve sensory action potential slowing and with perineural edema due to either CTS or to space-occupying lesions. (AU)

Application of microlectures on medical functional experiment teaching / 中华医学教育探索杂志

Taking the design and application of microlecture on action potential of neural stem as research basis, we summarized the content, structure level and learning mode of microlecture which adapted in functional experimental teaching. Application of microlecture on the course of medical function experimental teaching, including pre-class preparation, classroom teaching and after-class review can inspire students' learning enthusiasm, improve their learning efficiency and teachers' teaching quality, so as to cultivate students' innovative thinking.

Application of microlectures on medical functional experiment teaching / 中华医学教育探索杂志

Taking the design and application of microlecture on action potential of neural stem as research basis,we summarized the content,structure level and learning mode of microlecture which adapted in functional experimental teaching.Application of microlecture on the course of medical function experimental teaching,including pre-class preparation,classroom teaching and after-class review can inspire students' learning enthusiasm,improve their learning efficiency and teachers' teaching quality,so as to cultivate students' innovative thinking.