Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 89
Filter
1.
Rev. Fac. Med. (Bogotá) ; 68(2): 279-282, Apr.-June 2020.
Article in Spanish | LILACS-Express | LILACS | ID: biblio-1125637

ABSTRACT

Resumen Introducción. Los canales activados por voltaje para Na+ y para K+ presentan compuertas de activación e inactivación, las cuales se abren y se cierran dependiendo de la intensidad de la corriente eléctrica que fluye por la membrana cuando está respondiendo a un estímulo. Durante este breve momento, la membrana entra en un periodo de refractariedad que la hace insensible a otros estímulos. Objetivo. Demostrar que los periodos refractarios absoluto y relativo se presentan a medida que se va desarrollando el potencial de acción y no después de que se ha completado, mediante un análisis teórico basado en el funcionamiento eléctrico normal de los canales activados por voltaje para Na+ y K+. Cuestionamientos. En diversos textos y artículos de fisiología, las definiciones de los periodos refractarios absoluto y relativo son confusas y erróneas, puesto que no tienen en cuenta el funcionamiento normal de los canales activados por voltaje. Además, la ubicación que dan a dichos periodos con respecto al potencial de acción es desfasada y su tiempo de duración es incierto. Conclusión. Los periodos refractarios absoluto y relativo se presentan durante el desarrollo del potencial de acción y no después de que ha sido completado.


Abstract Introduction: Voltage-gated Na+ and K+ channels have activation and inactivation gates that open and close depending on the intensity of the electric current flowing through the membrane when it is responding to a stimulus. During this brief moment, the membrane enters a refractory period that makes it insensitive to other stimuli. Objective: To prove that absolute and relative refractory periods occur as the action potential develops rather than after it has been completed, by means of a theoretical analysis based on the normal electrical functioning of voltage-gated Na+ and K+ channels. Questioning: Several texts and articles on physiology provide confusing and misleading definitions of absolute and relative refractory periods, since they don't consider the normal functioning of voltage-gated channels. Furthermore, the location they give to these periods in relation to the action potential is out-of-time and their duration remains uncertain. Conclusion: Absolute and relative refractory periods occur as the action potential develops rather than after it has been completed.

2.
Article in Chinese | WPRIM | ID: wpr-824940

ABSTRACT

Objective:To obverse the therapeutic effect of superficial needling with different frequencies for intractable facial paralysis. Methods: A total of 120 patients with intractable peripheral facial paralysis were allocated into a superficial needling with high frequency group (150 times/min), a moderate frequency group (100 times/min) and a low frequency group (50 times/min) according to the random number table method. The Toronto facial grading system (TFGS) was used to evaluate facial nerve functions before treatment and after 2 weeks and 4 weeks of treatment respectively. The electromyography (EMG) test of the mandibular branch of facial nerve was used to compare the motor nerve conduction velocity (MCV), sensory nerve conduction velocity (SCV) and monophasic action potential (MAP) among different groups, and was done before treatment and after 4 weeks of treatment. The clinical efficacy was also compared. Results: After 2 weeks and 4 weeks of treatment, the changes of TFGS scores in the three groups all showed statistical significance (all P<0.05), and the TFGS score in the low frequency group was substantially higher than that in the other two groups. After treatment, the changes of the MCV and SCV in the three groups all showed statistical significance (all P<0.05), and the results in the low frequency group were higher than those in the other two groups; the change of MAP in the three groups showed no statistical significance (P>0.05). The total effective rate was 65.0%, 80.0% and 95.0% in the high frequency group, moderate frequency group and low frequency group respectively, and the between-group differences showed statistical significance (P<0.05). Conclusion: Compared with the superficial needling with high and moderate frequencies, superficial needling with low frequency can produce more significant clinical efficacy for intractable facial paralysis.

3.
Rev. Fac. Med. (Bogotá) ; 66(4): 623-627, Oct.-Dec. 2018.
Article in English | LILACS-Express | LILACS | ID: biblio-985103

ABSTRACT

Abstract Introduction: After conducting a bibliographical review on the works of various researchers at different times to explain the phenomenon of the transmission of nerve impulses, it is observed that since the eighteenth century, when modern science was born, scientific knowledge in the field of physiology had an accelerated development following the creation of new research techniques and the application of the scientific method. Thus, the philosophical theory of "animal spirits" led to the current concept of action potential, understood as a merely electrochemical phenomenon. Discussion: The establishment of the scientific method and the development of new research techniques led several researchers at different times to unravel the molecular mechanisms involved in the transmission of nerve impulses, which took two and a half centuries to reach the current concept about the origin of action potential. Conclusion: The notion "animal spirits" was valid for many centuries, while modern science took a little more than two centuries to understand the phenomenon of nerve impulse transmission.


Resumen Introducción. Después de una revisión bibliográfica sobre los trabajos de diversos investigadores en distintas épocas para explicar el fenómeno de la transmisión nerviosa, se observa que a partir del siglo XVIII, cuando surge la ciencia moderna, el conocimiento científico en el campo de la fisiología tuvo un desarrollo acelerado por la creación de nuevas técnicas de investigación y la aplicación del método científico. Así, de la teoría filosófica de los "espíritus animales" se llegó al concepto actual del potencial de acción, entendiéndose este como un fenómeno meramente electroquímico. Discusión. Con el establecimiento del método científico y el desarrollo de nuevas técnicas para la investigación, diversos investigadores en distintas épocas fueron desentrañando los mecanismos moleculares implicados en la transmisión de los impulsos nerviosos, por lo que solo bastaron dos siglos y medio para llegar al concepto actual sobre el origen del potencial de acción. Conclusión. La teoría filosófica de los espíritus animales perduró por muchos siglos, mientras que a la ciencia moderna le tomó poco más de dos siglos para entender el fenómeno de la transmisión nerviosa.

4.
Article in Chinese | WPRIM | ID: wpr-511082

ABSTRACT

Objective To evaluate efficacy of rotigaptide ZP123 on prevention of negative chronotropic effect caused by dexmedetomidine lengthening repolarization duration of the isolated rat hearts.Methods Eighteen healthy adult SD rats of either gender,weighing (300±30) g,were prepared isolated heart perfusion model by Langendorff.After 15 min perfusion and balance of K-H fluid,the isolated hearts were randomly divided into 3 groups (n=6 each): The hearts were continuously pefused for 30 min with 37℃ K-H solution in control group (group C),with dexmedetomidine 50 ng/ml in dexmedetomidine group (group D),or with rotigaptide 80 nmol/L combined with dexmedetomidine 50 ng/ml in rotigaptide combined with dexmedetomidine group (group ZD).In the whole Langendorff-perfused hearts,at the end of balanced infusion for 15 min (T0) and at 15(T1),30(T2) min of continued perfusion with K-H solution,the monophasic action potential (MAP) and heart rate (HR) were recorded from left anterior free wall,MAP duration at 50% repolarization (MAPD50) and at 90% repolarization (MAPD90),monophasic action potential amplitude (MAPA) and maximal velocity (Vmax) were calculated.Results Compared with T0,HR in group D was significantly declined at T1,T2;MAPD90 and MAPD50 in group D were significantly increased at T1,T2 (P<0.05).Compared with groups C and ZD,HR in group D was significantly declined at T1,T2;MAPD90 and MAPD50 in group D were significantly increased at T1,T2 (P<0.05).There was no significant difference in MAPA and Vmax between the three groups.Conclusion Rotigaptide antagonizes negative chronotropic effect induced by dexmedetomidine through shortening monophasic action potential duration in the myocardium of left ventricle of the isolated rat hearts.

5.
Article in Chinese | WPRIM | ID: wpr-617414

ABSTRACT

Objective: To investigate the electrophysiological mechanism of acupuncture for the visual cortex plasticity during the sensitive period. Methods: Fifty 2-week-old Wistar rats were randomly divided into a blank control group, a model group, an early-stage acupuncture group, a middle-stage acupuncture group and a late-stage acupuncture group, 10 rats in each group. Monocular deprivation amblyopia models were prepared in rats except those in the blank control group by unilateral eyelid suture. After successful modeling, no treatment was applied to the rats in the model group. Rats in each acupuncture group were treated with acupuncture at bilateral Jingming (BL 1), Cuanzhu (BL 2), Fengchi (GB 20) and Guangming (GB 37), started from the 3rd day, 12th day or 21st day after modeling separately, once a day, for a total of 9 d treatment. The neuronal discharge frequency and action potential inter-spike interval (ISI) in the rat visual cortex area 17 of each group were measured by multi-channel microelectrode array nerve signal technique. Results: The discharge number of neurons in the visual cortex of the model group was significantly lower than that in the blank control group (P0.05). The discharge number in the middle-stage acupuncture group was lower than that in the early-stage acupuncture group (P<0.05), and the discharge number of the late-stage acupuncture group was lower than that in the middle-stage acupuncture group (P<0.05). The ISI sequences of the visual cortex neurons were mainly distributed under 0.3 s in the blank control group, under 15 s in the model group, under 1 s in the early-stage acupuncture group, under 4 s in the middle-stage acupuncture group, and under 10 s in the late-stage acupuncture group, divergent in each group. Conclusion: The neuronal coding appears abnormality in the visual cortex area 17 of monocular deprivation rats, indicating that there is a plasticity change in the visual cortex neurons during the sensitive period. Acupuncture has a significant effect on the abnormal neural coding. The therapeutic efficacy is closely related to the stage to start the treatment. Early stage treatment in the sensitive period is the key to achieving the good efficacy.

6.
Chinese Journal of Anesthesiology ; (12): 1247-1249, 2017.
Article in Chinese | WPRIM | ID: wpr-666004

ABSTRACT

Objective To evaluate the effect of dexmedetomidine on action potential duration (APD)of rat ventricular myocytes and the role of α2receptors. Methods Eighteen ventricular myocytes acutely isolated from Sprague-Dawley rats by enzymatic hydrolysis were divided into 3 groups(n=6 each) using a random number table: dexmedetomidine group(D group), yohimbine group(Y group)and dexmedetomidine plus yohimbine group(DY group). Isolated ventricular myocytes were first perfused for 2 min with Tyrode′s solution alone, and APD at 90% repolarization(APD90)was recorded using whole-cell patch-clamp technique. D, Y and DY groups were subsequently perfused for 2 min with Tyrode′s solution containing dexmedetomidine 10-9mol∕L, yohimbine 10-6mol∕L, and dexmedetomidine 10-9mol∕L plus yo-himbine 10-6mol∕L, respectively, and APD90was recorded. The percentage of changes in APD90was calcu-lated. Results Compared with the isolated ventricular myocytes perfused with Tyrode′s solution alone, APD90of ventricular myocytes was significantly prolonged in group D(P<0. 01), and no significant change was found in APD90of ventricular myocytes in Y and DY groups(P>005). The percentage of changes in APD90of ventricular myocytes was significantly shortened in group DY and group Y when com-pared with group D(P<005). Conclusion Dexmedetomidine can prolong APD90of rat ventricular myo-cytes, and the mechanism is related to activating α2receptors.

7.
Article in Chinese | WPRIM | ID: wpr-502475

ABSTRACT

Objective To analyze the features of nerve conduction in patients with amyotrophic lateral sclerosis (ALS),and explore the correlation between compound muscle action potential (CMAP)amplitude and disease duration and revised amyotrophic lateral sclerosis functional rating scale (ALSFRSR).Methods Standard motor and sensory nerve conduction studies were performed in 154 patients with ALS.The following parameters were collected including CMAP amplitude,distal motor latency (DML),motor conduction velocity,sensory conduction velocity and sensory nerve action potential amplitude.Regression study was done to explore the correlation between CMAP amplitude and disease duration and ALSFRS-R.Results Motor nerve conduction abnormalities were presented in a majority of the patients with prolonged DML in the tibial nerve,median nerve and ulnar nerve as the most common form (61.06%-81.42%),followed by decreased CMAP amplitude (30.12%-53.98%),decreased MCV (12.05%-16.81%) and absence of CMAP (2.65%-9.73%).Sensory nerve conduction abnormalities were detected in a small proportion of patients and the decreased SCV,decreased SNAP amplitude and absence of SNAP in the sural nerve,median nerve and ulnar nerve were found in 1.22%-2.73%,0-1.82% and 0-1.22%patients respectively.No correlation was found between CMAP of the common peroneal nerve,tibial nerve,median nerve and ulnar nerve and the disease duration (P > 0.05),while significant positive correlation was established between CMAP amplitude of the median nerve and ulnar nerve and ALSFRS-R (r =0.273,P =0.016;r =0.357,P =0.001).Conclusions Motor nerve conduction is abnormal in a majority of ALS patients with prolonged DML as the most common form,while abnormal sensory nerve conduction is only found in a few of ALS patients.CMAP amplitude of the median nerve and ulnar nerve might be of certain clinical value in evaluating the severity of ALS.

8.
Article in Chinese | WPRIM | ID: wpr-496940

ABSTRACT

Objective To evaluate the effects of different concentrations of remifentanil on myocardial monophasic action potential (MAP) in isolated rabbit hearts.Methods Adult rabbits of both sexes,weighing 2.0-2.5 kg,were used in the study.Their hearts were excised,and retrogradely perfused with oxygenated K-H solution saturated with 95%O2-5%CO2 at 37 ℃ in a Langendorff apparatus.Twenty-four isolated hearts were randomly divided into 4 groups (n =6 each) using a random number table:control group (group C) and 3 different concentrations of remifentanil groups (group R1-3).After 15 min of stabilization,K-H solution was continuously perfused for 60 min in group C,and K-H solution containing 12,25 and 50 ng/ml remifentanil was continuously perfused for 60 min in R1,R2 and R3 groups,respectively.At 15 min of stabilization,and 15,30 and 60 min of perfusion with K-H solution,the heart rate,and the maximal velocity and amplitude of the MAP in the three layers of the left ventricular anterior wall were recorded,and the action potential duration at 90% repolarization and transmural dispersion of repolarization (TDR) were calculated.Results Compared with group C,the heart rate was significantly decreased,and the action potential duration at 90% repolarization and TDR were significantly prolonged at 15,30 and 60 min of perfusion in R1-3 groups (P<0.05).Compared with C and R1 groups,the maximal velocity and amplitude of MAP were significantly decreased at 15,30 and 60 min of perfusion in R2 and R3 groups (P<0.05).Conclusion Low-concentration remifentanil induces heart block through increasing TDR,however,high-concentration remifentanil induces heart block through inhibiting myocardial MAP depolarization and increasing TDR in the isolated rabbit hearts.

9.
Chinese Journal of Pathophysiology ; (12): 1331-1335, 2016.
Article in Chinese | WPRIM | ID: wpr-496544

ABSTRACT

[ ABSTRACT] Rebound depolarization is a special phenomenon of the neurons which generates action potential fol-lowed by a hyperpolarization stimulation.It can be recorded in many kinds of neurons and is the intrinsic membrane charac-teristic of them.Rebound depolarization plays an important role in regulating the firing pattern, rhythmic activity and sy-naptic plasticity of neurons.This review focuses on the basic characteristics, the function and mechanism of the rebound depolarization in physiological and pathological conditions, which provides reference for the clinical treatment of rebound depolarization-related diseases.

10.
Article in Chinese | WPRIM | ID: wpr-489365

ABSTRACT

Objective To investigate the role of potassium channel in remifentanil-induced prolongation of monophasic action potential duration (MAPD) in the myocardium of rabbits.Methods Eighteen adult rabbit hearts successfully perfused in a Langendorff apparatus were randomly divided into 3 groups (n =6 each) using a random number table:control group (group C),remifentanil group (group R),and K+ channel blocker tetraethylammonium group (group T).After 15 min stabilization with K-H solution,group C was continuously perfused with K-H solution for 60 min,and R and T groups were perfused with KH solution containing 12 ng/ml remifentanil and 10 ng/ml tetraethylammonium,respectively,for 60 min.At 15 min of stabilization,and 15,30 and 60 min of perfusion,heart rate,MAPD of all the three layers of the myocardium in the anterior wall of the left ventricular was recorded.MAPD at 50% and 90% repolarization (MAPD50,MAPD90) were calculated.Results Compared with group C,heart rate was significantly decreased,MAPD50 and MAPD90 were prolonged in R and T groups (P <0.05).Conclusion The mechanism by which remifentanil prolongs MAPD in the myocardium of rabbits is associated with blockade of the potassium channels.

11.
Article in Chinese | WPRIM | ID: wpr-637686

ABSTRACT

Background The visual development is completed during the critical period in human and mammals.However,the critical period is not the initial of receiving visual experience.It is known that before the onset of critical period in mammals,such as mouse,there is an earlier stage for visual development,the pre-critical period.The research of response characteristics of the visual cortical neurons and the synaptic plasticity in the pre-critical period is still in the exploratory stage.Objective The study aimed to preliminarily investigate the response properties of neurons and synaptic plasticity in mouse visual cortex during the pre-critical period.Methods Fortyeight postnatal day 13-17 C57BL/6J mice were used for in vivo whole-cell recordings and in vitro brain slice wholecell recordings.In vivo whole-cell recordings were done in anesthetized mice.Moving bars in different directions were produced and controlled by a Matlab program.Cell recordings were obtained at the depth of layer Ⅳ of visual cortex.Step current stimuli under current clamp were given to measure the membrane response properties of neurons.Optimal visual stimuli were given to measure the in vivo largest responses of membrane potentials.In vitro experiments were performed after in vivo experiments.All cells were given current step stimuli to measure the membrane response properties of neurons.Different intensities of white-matter-to-layer-Ⅳpathway stimulation were given to measure the evoked response properties.All cells from 48 mice were randomized into 4 groups according to different stimulus training modes,including low frequency stimulation (LFS),high frequency theta-burst stimulation (TBS),pre-post synaptic timing stimulation (pre-post TS) and post-pre synaptic timing stimulation (post-pre TS).Under the voltage clamp of-70 mV,excitatory postsynaptic currents (EPSCs) before and after training were recorded to measure the plastic changes of excitatory synaptic connections.pClamp 10 was used for the pre-analysis of data and Matlab 2008a was used for statistical analysis.The use and care of the animals followed the Statement for the Use of Animals in Ophthalmic and Vision Research.Results Thirty-nine cells and 48 cells were successfully recorded in the in vivo and in vitro experiments,respectively.The steady-state average number of action potentials (APs) were (1.01 ± 0.03)/sweep and (1.01 ±0.05)/sweep,the AP thresholds were (-40.2 ± 3.2) mV and (-39.6 ±2.0) mV,and the threshold step current levels were (126.7 ± 17.4) pA and (129.6 ± 17.5) pA in the in vivo and in vitro recordings,respectively,with no significant differences between them (APs:t =0.512,P =0.610;AP thresholds:t =-1.074,P =0.286;current levels:t =-0.776,P =0.440).Under the optimal visual or pathway stimulation,the average peak response of membrane potentials was (7.3 ±4.3)mV and (6.4±2.8)mV with rarely evoked APs in the in vivo and in vitro experiments,respectively,with no significant difference between them (t =1.234,P =0.221).Under the in vitro recording,the EPSCs before LFS were [(138.1 ±51.9)pA],which was significantly higher than that after LFS [(76.1 ± 34.8)pA] (t=4.437,P=0.001),but no significant differences were seen in EPSCs before and after TBS (t=-0.756,P=0.466).The EPSCs before and after pre-post TS were (122.4±62.2)pA and (78.5±46.7)pA,and those before and after post-pre TS were (131.9 ±48.0) pA and (74.3 ± 30.7) pA,showing significant differences between them (pre-post TS:t =3.558,P =0.004;post-pre TS:t =4.283,P =0.001).Conclusions The construction of fundamental neural circuits in layer Ⅳ of mouse visual cortex is completed during pre-critical period.However,the membrane responsive capability of neurons and the synaptic connections are in an immature state,and the evoked responses to visual pathway inputs are basically subthreshold.The strength of synaptic connections is depressed with low frequency stimulation or pre-post/post-pre synaptic timing stimulation,and kept unchanged with high frequency stimulation.The development of visual neural system of PSP in mouse presents different characteristics from CP.

12.
Article in English | WPRIM | ID: wpr-728544

ABSTRACT

Dihydropyridine (DHP) calcium channel blockers (CCBs) have been widely used to treat of several cardiovascular diseases. An excessive shortening of action potential duration (APD) due to the reduction of Ca2+ channel current (I(Ca)) might increase the risk of arrhythmia. In this study we investigated the electrophysiological effects of nicardipine (NIC), isradipine (ISR), and amlodipine (AML) on the cardiac APD in rabbit Purkinje fibers, voltage-gated K+ channel currents (I(Kr), I(Ks)) and voltage-gated Na+ channel current (I(Na)). The concentration-dependent inhibition of Ca2+ channel currents (I(Ca)) was examined in rat cardiomyocytes; these CCBs have similar potency on I(Ca) channel blocking with IC50 (the half-maximum inhibiting concentration) values of 0.142, 0.229, and 0.227 nM on NIC, ISR, and AML, respectively. However, ISR shortened both APD50 and APD90 already at 1 microM whereas NIC and AML shortened APD50 but not APD90 up to 30 microM. According to ion channel studies, NIC and AML concentration-dependently inhibited I(Kr) and I(Ks) while ISR had only partial inhibitory effects (<50% at 30 microM). Inhibition of I(Na) was similarly observed in the three CCBs. Since the I(Kr) and I(Ks) mainly contribute to cardiac repolarization, their inhibition by NIC and AML could compensate for the AP shortening effects due to the block of I(Ca).


Subject(s)
Action Potentials , Amlodipine , Animals , Antihypertensive Agents , Arrhythmias, Cardiac , Calcium Channel Blockers , Calcium Channels , Calcium , Cardiovascular Diseases , Inhibitory Concentration 50 , Ion Channels , Isradipine , Myocytes, Cardiac , Nicardipine , Purkinje Fibers , Rats
13.
Article in Korean | WPRIM | ID: wpr-645710

ABSTRACT

BACKGROUND AND OBJECTIVES: The aim of this study was to analyze the summating potential (SP)/action potential (AP) ratio of electrocochleography (ECoG) recorded from the position of SP peak. We compared the SP/AP ratios of negative polarity and positive polarity graphs from the same ECoG of each patient by assuming different the position of SP peak. In addition, we attempted to evaluate the utility of two different manners of recording the ECoG graph in the diagnosis of Meniere's disease. SUBJECTS AND METHOD: Retrospectively, we analyzed the results of ECoG in 67 patients with unilateral definite Meniere's disease. ECoG was analyzed in two different manners. From the AP peak, the SP peak was determined close when positioned in the negative polarity; on the other hand, SP peak was considered distant when positioned in the positive polarity. The SP/AP ratio was interpreted with reference to the base line value. The ratio of two different ECoG values from each patient of Meniere's disease was calculated. RESULTS: In the abnormal side, the negative polarity ECoG showed significantly greater value of SP/AP ratio (mean: 0.334±0.10) than the positive polarity ECoG (mean: 0.283±0.09) (p<0.001). In the normal side, the negative polarity ECoG, showed significantly greater value of SP/AP ratio (mean: 0.250±0.09) than the positive polarity ECoG (mean: 0.204±0.06), as well as in the abnormal cases (p<0.001). CONCLUSION: The standard SP/AP ratio for the diagnosis of Meniere's disease can be variable according to the manner of determining the SP peak.


Subject(s)
Action Potentials , Audiometry, Evoked Response , Diagnosis , Evoked Potentials , Hand , Humans , Meniere Disease , Methods , Retrospective Studies
14.
Article in Chinese | WPRIM | ID: wpr-479869

ABSTRACT

Objective To investigate the effects of hypothermia combined with dexmedetomidine on myocardial monophasic action potentials (MAPs) in isolated rabbit hearts.Methods Adult rabbits,weighing 2.0-2.5 kg,were heparinized and anesthetized with pentobarbital sodium 30 mg/kg.Their hearts were rapidly removed and retrogradely perfused in a Langendorff apparatus at 37 ℃.Eighteen hearts were randomly divided into 3 groups (n =6 each) using a random number table:control group (group C),hypothermia group (group H),and hypothermia+dexmedetomidine group (group HD).The hearts were continuously perfused for 60 min with 37 ℃ K-H solution in group C,with 32 ℃ K-H solution in group H,or with 32 ℃ K-H solution containing dexmedetomidine 25 ng/ml in group HD.At the end of equilibration (T0) and at 15,30 and 60 min of perfusion with K-H solution,HR and MAPs of left ventricular epicardium,mid-myocardium and endocardium were recorded.MAP duration at 50% repolarization (MAPD50) and at 90% repolarization (MAPD90),monophasic action potential amplitude (MAPA) and maximal velocity (Vmax) were calculated.Results Compared with group C,HR was significantly decreased,and MAPD50 and MAPD90 were prolonged at each time of perfusion with K-H solution in H and HD groups.There was no significant difference in HR,MAPD50 and MAPD90 between H group and HD group.There was no significant difference in MAPA and Vmax between the three groups.Conclusion Hypothermia combined with dexmedetomidine can lead to prolongation of myocardial repolarization,and dexmedetomidine exerts no effect on hypothermia-induced change in MAPs in isolated rabbit hearts.

15.
Arch. med ; 14(1): 144-149, jun. 2014. ilus
Article in Spanish | LILACS | ID: lil-724734

ABSTRACT

Objetivo: Demostrar, mediante un análisis teórico, que el concepto fisiológico principio del todo o nada que se aplica a las células excitables es una frase inadecuada y contradictoria, porque se presta a interpretaciones erróneas y desdibuja el fenómeno electrostático que subyace en los canales de Na+ activados por voltaje (Nav). Discusión: Los segmentos sensores de voltaje S4 de los canales de Na+ presentan residuos de arginina con carga positiva, que al interactuar con el medio interno se genera una repulsión eléctrica que provoca la apertura del poro del canal por donde ingresan los iones de sodio y despolarizan la membrana. Como lo anterior ocurre solamente cuando la membrana alcanza su nivel umbral, entonces la frase principio del todo o nada que figura en los textos clásicos de fisiología y en revistas indexadas es contradictoria y sin sentido. Conclusión: Puesto que es un fenómeno netamente eléctrico el que se desencadena cuando la membrana de la célula excitable alcanza una variación justa de voltaje (nivel umbral), proponemos que en lugar de seguir empleando la tradicional frase principio del todo o nada se use la frase efecto electrostático, por estar más acorde con los eventos moleculares y eléctricos que realmente acontecen en las membrana excitables…


Objective: its demostrate, through theoretical analysis, that the physiological conceptprinciple “all or none” that applies to excitable cells, is inadequate and contradictory phrase, because it lends itself to misinterpretation and electrostatic phenomenonblurs the channels underlying of voltage-gated Na+(Nav). Discussion: The segmentsvoltage sensors S4 of Na+channels present arginine residues with positive charge,which interact with the internal environment and generate electric repulsion caused bythe pore opening of the channel through which enters the sodium ions and depolarize membrane. As above occurs only when the membrane reaches a threshold level, then,the phrase “all or nothing” principle, in physiology classic texts and indexed journals is contradictory and meaningless. Conclusion: Since it is a purely electrical phenomenon which is triggered when the excitable cell membrane reaches a fair variation of voltage(threshold level), we propose that rather than continue to use the traditional phrase “allor nothing” principle, is used the phrase “electrostatic effect”, to be more consistent with the molecular and electrical events that actually occur in the excitable membrane.


Subject(s)
Action Potentials , Auditory Threshold , Ion Channels
16.
Rev. mex. ing. bioméd ; 35(2): 157-170, abr. 2014. ilus, tab
Article in English | LILACS-Express | LILACS | ID: lil-740171

ABSTRACT

In this paper we used a mathematical model to explore the effects of impaired ATP production and glucose sensitivity on the electrical response and insulin secretion of human β-cells. The model was extended by the addition of explicit empirical equations that describe recent experimental observations, namely, the increase of ATP as a function of glucose concentration and the oscillations in ATP at high glucose levels. Simulations were performed at selected glucose concentrations from an oral glucose tolerance test in normal subjects to evaluate the response of the human β-cell in normal and pathological scenarios. Our simulations reproduced experimental observations, such as the impaired insulin secretion as a consequence of β-cell dysfunction and restoration of electrical activity by the use of a sulfonylurea. Our results suggest that both reduced glucose sensitivity and impaired ATP production could be related to the pathogenesis of type 2 diabetes.


En este artículo usamos un modelo matemático para explorar los efectos de alteraciones en la producción de ATP y sensibilidad a la glucosa en la respuesta eléctrica y la secreción de insulina en células β humanas. El modelo fue extendido al añadir ecuaciones empíricas explícitas que describen recientes observaciones experimentales, como el incremento en el ATP como función de la concentración de glucosa y las oscilaciones en el ATP a altos niveles de glucosa. Se realizaron simulaciones a niveles de glucosa alcanzados durante una prueba de tolerancia a la glucosa para evaluar la respuesta de la célula β humana en escenarios normales y patológicos. Nuestras simulaciones reprodujeron varias observaciones experimentales, tales como la secreción de insulina alterada como consecuencia de la disfunción de la célula β y la restauración de la actividad eléctrica al aplicar una sulfonilurea. Nuestros resultados sugieren que tanto una reducción en la sensibilidad a la glucosa como la alteración en la producción de ATP podrían estar relacionadas a la patogénesis de la diabetes tipo 2.

17.
Chinese Journal of Anesthesiology ; (12): 1439-1441, 2014.
Article in Chinese | WPRIM | ID: wpr-471546

ABSTRACT

Objective To evaluate the effect of aminophylline on monophasic action potential (MAP) during remifentanil-induced negative chronotropic effect in the isolated rabbit hearts.Methods Eighteen healthy adult rabbits,weighing 2.0-2.5 kg,wereused in the study.Their hearts were excised and retrogradely perfused in a Langendorff apparatus.After 15 min of stabilization with K-H solution,the isolated hearts were randomly divided into 3 groups (n =6 each) using a random number table:control group (group C),remifentanil group (R group),and remifentanil + aminophylline group (RA group).Group C was perfused with 37 ℃ K-H solution for 60 min.Group R was perfused with K-H solution containing remifentanil 12 ng/ml for 60 min.Group RA was perfused with K-H solution containing remifentanil 12 ng/ml and aminophylline 30 μg/ml for 60 min.At 15 min of stabilization and 15,30 and 60 min of perfusion,HR and MAP in the myardium of left ventricle were recorded:MAP duration at 90% and 50% repolarization (MAPD90,MAPD50) was calculated.The early after depolarization,delay after depolarization and arrhythmia were recorded.Results Compared with group C,HR was significantly decreased at 15,30 and 60 min of perfusion,and MAPD50 and MAPD90 were prolonged in goup R,and HR was increased in group RA.HR was significantly higher,and MAPD50 and MAPD90 were shorter in RA group than in group R.No early after depolarization,delay after depolarization or arrhythmia developed in each group.Conclusion Aminophylline antagonizes remifentanil-induced negative chronotropic effect through shortening monophasic action potential duration in the myocardium of left ventricle of the isolated rabbit hearts.

18.
Chinese Journal of Neurology ; (12): 857-860, 2014.
Article in Chinese | WPRIM | ID: wpr-469016

ABSTRACT

Objective To validate the technique and establish the reference jitter values in voluntarily activated extensor digitorum communis using a concentric needle electrode (CNE) in healthy Chinese adults.Methods From January to August 2013,forty-two Chinese subjects from healthy examination center of our hospital were prospectively studied,including 20 males and 22 females.Routine electromyogram was tested and jitter was recorded with CNE in all subjects.The jitter values of action potentials pairs of muscle fibers were expressed as the mean consecutive difference (MCD) after 20 analyzed potential pairs.Results The mean MCD of 42 subjects was (23.0 ± 3.1) μs ranging from 17 to 32 μs.The mean jitter value of all 840 potential pairs was (22.8 ± 7.5) μs ranging from 8 to 54 μs.Upper 95% confidence limits for mean MCD and individual MCD were 29.2 μs and 37.8 μs,respectively.The mean value of MCD of 20 males and 22 females were (23.2 ± 2.8) μs and (22.8 ± 3.4) μs,respectively.There was no statistic difference between genders in MCD (t =0.44,P =0.66).There was no correlation between age and MCD (r =0.11,P =0.48).The mean value of mean interpotential interval was (802 ± 139) μs ranging from 541 to 1 160 μs.Conclusion The present study confirms the suitability of jitter analysis with CNE,which can serve as an objective and valuable method for testing the function of neuromuscular conjunctions.

19.
Salud UNINORTE ; 29(2): 288-297, mayo 2013. ilus, tab
Article in English | LILACS-Express | LILACS | ID: lil-698833

ABSTRACT

Objectives: To develop a computational tool for NEURON simulation environment, user friendly, to store the results generated during simulation and to make subsequent analysis with other tools such as Matlab and IgorPRo Materials and Methods: Data Exporter was implemented in the programming language hoc. This algorithm is divided in 13 sections or blocks. The first section is necessary to edit in a new simulation. These new configuration determine the geometry, biophysic properties the neurons to simulate and path to save data. Results: To check the efficiency of the algorithm, we simulated the propagation of action potential in TRN(thalamic reticular nucleus) neuron in different large of simulation. We determine that the time of simulation is linear respect to time of simulation. Conclusions: Data Exporter makes easier to start to neural simulation in NEURON reducing the steps of programming to geometry and biophysical properties of the neuron and to allow save data to next steps of analysis.


Objetivos: Desarrollar una herramienta computacional en ambiente lenguaje de programación hoc de NEURON y de fácil uso, que permita el rápido almacenamiento de los resultados obtenidos para su posterior análisis en otros software tales como Matlab or IgorPro. Materiales y métodos: Para el desarrollo de Data Exporter se escribió un algoritmo en lenguaje de programación hoc de NEURON. El algoritmo, escrito en un único archivo de texto, esta dividido en 13 bloques, de los cuales solo el primero debe ser modificado para adaptarlo a una geometría y biofísica neuronal particular y para determinar la ruta de almacenamiento de los datos. Resultados: Se desarrollo un software que simula la propagación de potenciales de acción a través de geometrías neuronales complejas. El uso de esta herramienta permite el almacenamiento de los resultados obtenidos, como potenciales y corrientes de membrana en diferentes puntos de toda la neurona, sin incremento significativo en el tiempo para el desarrollo de los procesos. Conclusiones: Data Exporter es un software que le da mayor flexibilidad a NEURON facilitando el acceso a nuevos neurocientíficos, los cuales pueden usarlo con solo conocer los códigos necesarios para el desarrollo de los archivos relacionados con las propiedades geométricas y biofísicas neuronales.

20.
Tianjin Medical Journal ; (12): 740-743, 2013.
Article in Chinese | WPRIM | ID: wpr-475535

ABSTRACT

Objective To investigate the relationship of T peak-T end (Tp-Te) interval and Tp-Te interval disper-sion (Tp-Ted) in different periods of myocardial ischemia in patients with acute myocardial infarction (AMI), and to assess the clinical significance of Tp-Te and Tp-Ted for prediction of the ventricular arrhythmia (VA). Methods A total of 80 pa-tients with AMI were enrolled in the study. The sizes and changes of Tp-Te and Tp-Ted were observed during the acute phase and recovery phase in patients. The differences of Tp-Te and Tp-Ted were compared between ventricular tachycardia group (A group), ventricular premature beats group (B group) and non- ventricular arrhythmia group (C group). Results The values of Tp-Te and Tp-Ted were obviously longer in acute period [(125.22±17.70) ms and (54.76±13.26) ms] than those in recovery period[ (113.84±17.37) ms and (42.06±13.95)ms] (P<0.01). The values of Tp-Te and Tp-Ted were signifi-cantly longer in A group[ (134.82±19.56) ms and (62.00±15.19) ms] than those in B [(122.94±15.09) ms and (54.09±10.56) ms ]and C group [(110.09±15.21) ms and (45.27±9.85) ms]. The values were higher in B group than those of C group. Con-clusion The Tp-Te interval and Tp-Ted prolongated in acute phase than those of recovery phase in patients with AMI. Tp-Te interval and Tp-Ted can be used as an important index to predict VA in patients with AMI.

SELECTION OF CITATIONS
SEARCH DETAIL