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The effect of short-term endurance and strength training on motor unit conduction velocity

Vila-Chã, Carolina; Falla, Deborah; Velhote, Miguel; Farina, Dario
Fonte: Aalborg University, Department of Health Science and Technology Publicador: Aalborg University, Department of Health Science and Technology
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
36.61%
AIM: The aim of this study was to investigate the effect of strength and endurance training on the conduction velocity of vastus medialis obliquus and lateralis single motor units during voluntary sustained knee extensions. METHODS: Seventeen sedentary healthy men (age, mean ± SD, 26.3 ± 3.9 yr) were randomly assigned to one of 2 groups: strength training (ST, n= 8) or endurance training (ET, n= 9). Conventional endurance and strength training was performed three days per week, over a period of 6 weeks. Motor unit conduction velocity (MUCV), maximum voluntary force (MVC) and time-to-task failure at 30% MVC of the knee extensors were measured before and immediately following training. To assess MUCV, multi-channel surface and intramuscular EMG signals were concurrently recorded from the vastus medialis obliquus (VMO) and vastus lateralis (VL) muscles during 60-s isometric knee extensions at 10% and 30% of MVC. RESULTS: After 6 weeks of training, MVC increased in the ST group (16.7 ± 7.4 %; P < 0.05) whereas time to task failure was prolonged in the ET group (33.3 ± 14.2 %; P < 0.05). Both training programs induced an increase in motor unit conduction velocity at both 10% and 30% MVC (P < 0.01). Furthermore after both training programs...

Heat Conduction Equation Solution in the Presence of a Change of State in a Bounded Axisymmetric Cylindrical Domain

OLIVEIRA, Danillo Silva de; RIBEIRO, Fernando Brenha
Fonte: ASME-AMER SOC MECHANICAL ENG Publicador: ASME-AMER SOC MECHANICAL ENG
Tipo: Artigo de Revista Científica
ENG
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The heat conduction problem, in the presence of a change of state, was solved for the case of an indefinitely long cylindrical layer cavity. As boundary conditions, it is imposed that the internal surface of the cavity is maintained below the fusion temperature of the infilling substance and the external surface is kept above it. The solution, obtained in nondimensional variables, consists in two closed form heat conduction equation solutions for the solidified and liquid regions, which formally depend of the, at first, unknown position of the phase change front. The energy balance through the phase change front furnishes the equation for time dependence of the front position, which is numerically solved. Substitution of the front position for a particular instant in the heat conduction equation solutions gives the temperature distribution inside the cavity at that moment. The solution is illustrated with numerical examples. [DOI: 10.1115/1.4003542]

Aplicação do método inverso de condução de calor na avaliação de fluidos de resfriamento para têmpera; Application of the inverse method of heat conduction in the quenchants evaluation to quenching

Cremonini, Guilherme Ernesto Serrat de Oliveira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/06/2014 PT
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A têmpera dos aços envolve a austenitização de uma peça seguida por um resfriamento rápido para promover a formação de microestrutura martensítica. É necessário avaliar os meios de têmpera para manter o processo de têmpera sob controle. Os parâmetros mais importantes no processo de resfriamento são o coeficiente de transferência de calor e/ou o fluxo de calor entre o meio de têmpera e a peça a ser resfriada. Um dos métodos de se avaliar os meios de têmpera (meios de resfriamento) e saber o que está acontecendo dentro da peça durante o resfriamento do ponto de vista térmico é o problema inverso de condução de calor. O problema inverso de condução de calor consiste na determinação de parâmetros como fluxo de calor, taxa de resfriamento e temperatura em qualquer posição através da peça, assim como o coeficiente de transferência de calor. Esses parâmetros são obtidos a partir de medições de temperatura em um ou mais pontos dentro da peça. O escopo deste trabalho foi desenvolver um software baseado no problema inverso condução de calor para avaliar meios de resfriamento para têmpera. A validação deste código foi feita usando água, óleo de soja, óleo mineral e solução aquosa de NaNO3.; Steels quenching involves part austenitization followed by a fast cooling to promote martensitic microstructure formation. It is necessary to evaluate quenchants in order to keep the quenching process under control. The most important cooling process parameters are the heat transfer coefficient and/or the heat flux between the quenchant and the part to be cooled. One of the methods to evaluate quenchants (cooling media) and to know what is happening inside the part during the cooling in the thermal point of view is the inverse heat conduction problem. The inverse heat conduction problem consists in the determination of parameters like heat flux...

Single-phase high power-factor boost ZCS pre-regulator operating in critical conduction mode

Canesin, C. A.; Goncalves, FAS; IEEE
Fonte: IEEE Publicador: IEEE
Tipo: Conferência ou Objeto de Conferência Formato: 746-751
ENG
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This paper presents a new single-phase interleaved high power factor boost pre-regulator operating in critical conduction mode, where the switches and boost diode performing zero-current commutations during its turn-off, eliminating the disadvantages related to the reverse recovery losses and electromagnetic interference problems of the boost diode, when operating in the continuous conduction mode. The interleaving technique is applied in the power cell, providing a significant input current ripple reduction in comparison to discontinuous mode of operation, due to its input current continuous conduction operation. This paper presents a complete modeling for the converter operating in critical conduction mode, resulting in an improved design procedure for interleaved techniques with high input power factor, a complete design procedure, and main simulation results from a design example with two interleaved cells rated at 1kW, 400V output voltage and 220V rms input voltage.

MOTOR NERVE CONDUCTION and REPETITIVE NERVE STIMULATION IN CAPTIVE RING-TAILED COATI (NASUA NASUA)

Mortari, Ana Carolina; Rahal, Sheila Canevese; Resende, Antonio de Lima; Teixeira, Carlos Roberto; Friciello Teixeira, Rodrigo Hidalgo; Mendes, Guilherme Maia
Fonte: Amer Assoc Zoo Veterinarians Publicador: Amer Assoc Zoo Veterinarians
Tipo: Artigo de Revista Científica Formato: 443-449
ENG
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There are few electrophysiologic studies in wild animals. The aim of this study was to determine normal data for motor nerve conduction studies and repetitive stimulation in sciatic-tibial and ulnar nerves in clinically normal captive coati. Eight adult ring-tailed coatis (Nasua nasua), two females and six males weighing 68 kg, were used. Average nerve conduction velocity was 70.81 m/sec (standard deviation [SD] = 3.98) and 56.93 m/sec (SD = 4.31) for the sciatic-tibial and ulnar nerves, respectively. Repetitive stimulation responses demonstrated minimal variations of the area of the compound muscle action potentials at low (3 Hz) and high (20 Hz) frequencies. The maximal obtained decremental area response was 8%. These normal data of conduction studies may be used in assessing abnormalities for clinical diagnosis. In addition, the obtained normal repetitive stimulation data were similar to dogs and humans and may be used for post- and presynaptic disturbances of the neuromuscular transmission in coatis.

Early Pancreas Transplant Improves Motor Nerve Conduction in Alloxan-Induced Diabetic Rats

Spadella, C. T.; Lucchesi, A. N.; Alberti, S.; Resende, L. A. L.
Fonte: Johann Ambrosius Barth Verlag Medizinverlage Heidelberg Gmbh Publicador: Johann Ambrosius Barth Verlag Medizinverlage Heidelberg Gmbh
Tipo: Artigo de Revista Científica Formato: 567-572
ENG
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The purpose of this study was to assess the temporal relationship between pancreas transplant and the development of electrophysiological changes in the sciatic and caudal nerves of alloxan-induced diabetic rats. Nerve conduction studies were performed in diabetic rats subjected to pancreas transplantation at 4, 12, and 24 weeks after diabetes onset, using nondiabetic and untreated diabetic rats as controls. Nerve conduction data were significantly altered in untreated diabetic control rats up to 48 weeks of follow-up in all time points. Rats subjected to pancreas transplantation up to 4 and 12 weeks after diabetes onset had significantly increased motor nerve conduction velocity with improvement of wave amplitude, distal latency, and temporal dispersion of compound muscle action potential in all follow-up periods (P<0.05); these parameters remained abnormal when pancreas transplantation were performed late at 24 weeks. Our results suggest that early pancreas transplant (at 4-12 weeks) may be effective in controlling diabetic neuropathy in this in vivo model.

Modeling of pre-regulator boost ZCS interleaved operating in critical conduction mode and with high power factor

Canesin, Carlos A.; Gonçalves, Flávio A. S.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 305-310
ENG
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This paper presents a new pre-regulator boost operating in the boundary area between the continuous and discontinuous conduction modes of the boost inductor current, where the switches and boost diode performing zero-current commutations during its turn-off, eliminating the disadvantages related to the reverse recovery losses and electromagnetic interference problems of the boost diode when operating in the continuous conduction mode. Additionally, the interleaving technique is applied in the power cell, providing a significant input current ripple reduction. It should be noticed that the main objective of this paper is to present a complete modeling for the converter operating in the critical conduction mode, allowing an improved design procedure for interleaved techniques with high input power factor, a complete dynamic analysis of the structure, and the possibility of implementing digital control techniques in closed loop.

Usefulness of additional nerve conduction techniques in mild carpal tunnel syndrome

Kouyoumdjian,João Aris; Morita,Maria P. A.; Molina,Amalia F. P.
Fonte: Academia Brasileira de Neurologia - ABNEURO Publicador: Academia Brasileira de Neurologia - ABNEURO
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2002 EN
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This study was done to assess the percentage of abnormality in additional nerve conduction techniques after normal median distal latency (routine) in mild carpal tunnel syndrome (CTS). Bilateral nerve conduction studies were carried out in 116 consecutive symptomatic CTS patients (153 hands). Mild cases were based on normal routine (< 3.7 ms, peak-measured, 14 cm) and at least one technique abnormal of the following: sensory median-radial difference (MR); sensory median-ulnar difference (MU4); mixed palm median-ulnar difference (MUP); median palm latency (PW); and motor median distal latency (MDL). After normal cut-off values for routine, 3.1 to 3.6 ms (< 3.7 ms), we found an abnormal MR, ranging from 86.6 to 93.4%, followed by MU4 (40 to 81.7%), MUP (20 to 71.2%), PW (0 to 41.1%), and MDL (0 to 19.6%). The most frequent abnormal association were MR plus MU4 in 90.1%, followed by MR plus MUP and MU4 plus MUP. The most frequent abnormal additional nerve conduction technique for mild CTS electrodiagnosis was MR, followed by MU4 and MUP. Percentage of MR abnormality was very high regardless of the median routine latency cut-off (< 3.1 to < 3.6 ms).

Carpal tunnel syndrome in the elderly: nerve conduction parameters

Naves,Thiago Guimarães; Kouyoumdjian,João Aris
Fonte: Academia Brasileira de Neurologia - ABNEURO Publicador: Academia Brasileira de Neurologia - ABNEURO
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2010 EN
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OBJECTIVE: To establish nerve conduction parameters for carpal tunnel syndrome (CTS) electrodiagnosis in the elderly. METHOD: Thirty healthy subjects (65-86 years), 9 male and 21 female, were studied. Routine median and ulnar sensory and motor nerve conduction studies, median mixed palmar latency, comparative latency techniques median to ulnar (sensory, mixed and motor lumbrical-interossei), median to radial (sensory), and combined sensory index (CSI) were performed in both hands. RESULTS: The upper limits of normality (97.5%) were: median sensory distal latency 3.80 ms (14 cm); median motor distal latency 4.30 ms (8 cm); median palmar latency 2.45 ms (8 cm); lumbrical-interossei latency difference 0.60 ms (8 cm); comparative median to radial 0.95 ms (10 cm); comparative median to ulnar 0.95 ms (14 cm); comparative palmar median to ulnar 0.50 ms (8 cm); and CSI 2.20 ms. Sensory and mixed latencies were measured at peak. CONCLUSION: Our results establish new nerve conduction parameters for mild CTS electrodiagnosis in the elderly and will be helpful to reduce the number of false positive cases in this age.

Conduction velocity of the rabbit facial nerve: a noninvasive functional evaluation

Vasconcelos,Belmiro Cavalcanti do Egito; Gay Escoda,Cosme; Vasconcellos,Ricardo José de Holanda; Neves,Riedel Frota Sá Nogueira
Fonte: Sociedade Brasileira de Pesquisa Odontológica e Faculdade de Odontologia da Universidade de São Paulo Publicador: Sociedade Brasileira de Pesquisa Odontológica e Faculdade de Odontologia da Universidade de São Paulo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2003 EN
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The aim of this study was to evaluate standardized conduction velocity data for uninjured facial nerve and facial nerve repaired with autologous graft nerves and synthetic materials. An evaluation was made measuring the preoperative differences in the facial nerve conduction velocities on either side, and ascertaining the existence of a positive correlation between facial nerve conduction velocity and the number of axons regenerated postoperatively. In 17 rabbits, bilateral facial nerve motor action potentials were recorded pre- and postoperatively. The stimulation surface electrodes were placed on the auricular pavilion (facial nerve trunk) and the recording surface electrodes were placed on the quadratus labii inferior muscle. The facial nerves were isolated, transected and separated 10 mm apart. The gap between the two nerve ends was repaired with autologous nerve grafts and PTFE-e (polytetrafluoroethylene) or collagen tubes. The mean of maximal conduction velocity of the facial nerve was 41.10 m/s. After 15 days no nerve conduction was evoked in the evaluated group. For the period of 2 and 4 months the mean conduction velocity was approximately 50% of the normal value in the subgroups assessed. A significant correlation was observed between the conduction velocity and the number of regenerated axons. Noninvasive functional evaluation with surface electrodes can be useful for stimulating and recording muscle action potentials and for assessing the functional state of the facial nerve.

Relationship of the total atrial conduction time to subclinical atherosclerosis, inflammation and echocardiographic parameters in patients with type 2 diabetes mellitus

Bakirci,Eftal Murat; Demirtas,Levent; Degirmenci,Husnu; Topcu,Selim; Demirelli,Selami; Hamur,Hikmet; Buyuklu,Mutlu; Akbas,Emin Murat; Ozcicek,Adalet; Ozcicek,Fatih; Ceyhun,Gokhan; Topal,Ergun
Fonte: Faculdade de Medicina / USP Publicador: Faculdade de Medicina / USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 EN
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OBJECTIVES: The aim of our study was to evaluate the total atrial conduction time and its relationship to subclinical atherosclerosis, inflammation and echocardiographic parameters in patients with type 2 diabetes mellitus. METHODS: A total of 132 patients with type 2 diabetes mellitus (mean age 54.5±9.6 years; 57.6% male) and 80 age- and gender-matched controls were evaluated. The total atrial conduction time was measured by tissue-Doppler imaging and the carotid intima-media thickness was measured by B-mode ultrasonography. RESULTS: The total atrial conduction time was significantly longer in the patients with type 2 diabetes mellitus than in the control group (131.7±23.6 vs. 113.1±21.3, p<0.001). The patients with type 2 diabetes mellitus had significantly increased carotid intima-media thicknesses, neutrophil to lymphocyte ratios and high-sensitivity C-reactive protein levels than those of the controls. The total atrial conduction time was positively correlated with the high-sensitivity C-reactive protein level, neutrophil to lymphocyte ratio, carotid intima-media thickness and left atrial volume index and negatively correlated with the early diastolic velocity (Em), Em/late diastolic velocity (Am) ratio and global peak left atrial longitudinal strain. A multiple logistic regression analysis demonstrated that the neutrophil to lymphocyte ratio...

The role of chronic atrial stretch and atrial fibrillation on posterior left atrial wall conduction

Roberts-Thomson, K.; Stevenson, I.; Kistler, P.; Haqqani, H.; Spence, S.; Goldblatt, J.; Sanders, P.; Kalman, J.
Fonte: Elsevier Inc. Publicador: Elsevier Inc.
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
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BACKGROUND: The posterior left atrium (LA) is involved in the initiation and maintenance of atrial fibrillation (AF). OBJECTIVE: The purpose of this study was to compare conduction patterns on the posterior LA in patients with mitral regurgitation (MR), with and without AF. METHODS: Epicardial mapping of the posterior LA was performed in 23 patients undergoing cardiac surgery. Patients were included in one of three groups: Group A-patients in sinus rhythm with normal left ventricular function undergoing coronary artery bypass grafting, Group B-patients in sinus rhythm with MR undergoing mitral valve surgery, or Group C-patients in persistent AF with MR undergoing mitral valve surgery. Conduction patterns, regional conduction velocity, conduction heterogeneity, conduction anisotropy, and complex fractionated atrial electrograms (CFAEs) were assessed. RESULTS: LA diameter was greater in patients in Groups C (57 +/- 4mm) and B (54 +/- 6mm) than in Group A (39 +/- 7 mm, P <0.01). Patients in Group C had a greater number of lines of conduction delay than Groups A and B (2.0 +/- 0.8 vs 1 +/- 0 and 1 +/- 0, P <0.05). The extent of conduction delay and conduction heterogeneity was greater in Group C than in Group B, which was greater than in Group A (P <0.05). The percentage of CFAEs that remained stable during AF was 61% +/- 17%. There was a significant correlation between CFAEs during AF and regions of slow conduction during pacing (R = 0.36...

Anatomically determined functional conduction delay in the posterior left atrium: Relationship to structural heart disease

Roberts-Thomson, K.; Stevenson, I.; Kistler, P.; Haqqani, H.; Goldblatt, J.; Sanders, P.; Kalman, J.
Fonte: Elsevier Science Inc Publicador: Elsevier Science Inc
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
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OBJECTIVES: This study sought to characterize the conduction properties of the posterior left atrium (PLA) in patients with different forms of structural heart disease undergoing cardiac surgery. BACKGROUND: The PLA plays an important role in the initiation and maintenance of atrial fibrillation. METHODS: This study included 34 patients having elective cardiac surgery. There were 4 groups of patients: normal left ventricular (LV) function (coronary artery bypass grafting [CABG]); severe LV dysfunction (LVF/CABG); severe mitral regurgitation (MR); severe aortic stenosis (AS). Epicardial mapping of the PLA was performed in sinus rhythm and during differential pacing. Activation patterns, regional conduction velocity (CV), conduction heterogeneity, anisotropy, and total plaque activation time (TAT) were assessed. RESULTS: Left atrial size in patients with LVF/CABG (47 +/- 7 mm) and MR (54 +/- 6 mm) was larger than patients with CABG (39 +/- 7 mm) and AS (42 +/- 6 mm; p < 0.05). During pacing, all patients developed a vertical line of conduction delay running between the pulmonary veins. The extent of this conduction delay was greater in patients with LVF/CABG and MR than patients with AS and CABG (p < 0.05). Conduction heterogeneity, anisotropy...

Preferential conduction patterns along the coronary sinus during atrial fibrillation in humans and their modification by pulmonary vein isolation

Platonov, P.; Sanders, P.; Shashidhar; Brooks, A.; Tapanainen, J.; Holmqvist, F.; Kongstad, O.; Carlson, J.
Fonte: Churchill Livingstone Inc Medical Publishers Publicador: Churchill Livingstone Inc Medical Publishers
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
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INTRODUCTION: Correlation function analysis applied to endocardial electrograms has earlier been used for analysis of agreement between signals and direction of activation during atrial fibrillation (AF). This study was aimed at evaluating whether preferential activation patterns along the coronary sinus (CS) exist in patients with AF. METHODS: Twenty-seven patients (57 ± 10 years old) admitted for electrophysiological (EP) study (10 patients) and/or AF ablation (17 patients) were studied, 8 with permanent and 19 with persistent AF. Unipolar signals were recorded during 60 seconds from a 10-pole CS catheter during AF at baseline (BL) and after isolation of left and right pulmonary veins and after additional lines in the left atrium (LA) (End). Correlation function analysis was applied to signals from each pair of adjacent electrodes, and graphs of cumulated time delay were made to enable interpretation of direction of activation. RESULTS: Correlation between paired signals was highest in the distal and middle parts of CS and lowest in the proximal CS. In 21 patients, correlation values greater than 0.8 between closely spaced electrodes suggested uniform propagation of the fibrillatory waves. In 18 of 21 patients, preferential conduction pattern along CS was seen. Of those...

Função de transferência analítica aplicada à solução de problema inverso em condução de calor; An analytic heat transfer function method to solve an inverse heat conduction problems

Fernandes, Ana Paula
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
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Esse trabalho dedica-se ao estudo da obtenção da função de transferência (ou resposta impulsiva) por meio das teorias de funções de Green e sistemas dinâmicos, para então aplicá-la à solução de problema inverso em condução de calor. Os problemas térmicos unidimensinal e tridimensional, respectivamente denominados X22 e X33Y 33Z33, são elegidos para a apresentação da fundamentação téorica do método proposto. O problema 1D trata-se de um problema clássico em condução de calor com aplicação em obtenção de propriedades termof ísicas, e, o 3D é uma aproximação teórica equivalente a um problema de condução de calor originado por um processo de usinagem. Então, conhecendo-se o per l de temperatura (seja hipotético ou experimental) e a função de transferência, mostra-se que a estimativa do uxo de calor pode ser concretizada por diferentes abordagens, ou por meio da deconvolução, ou da transformada rápida de Fourier e sua inversa, e ainda por cálculos de densidades espectrais, todas equivalentes entre si. Transpõe-se a teoria matemática usada na estimativa de uxo de calor em termos de solução computacional com o subsídio do software MATLAB. Apresentase, assim, o desempenho da técnica explorando-se vários parâmetros de con guração de um problema térmico...

The conduction system of the heart in mice chronically infected with Trypanosoma cruzi: histopathological lesions and electrocardiographic correlations

Andrade,Sonia G.; Sadigursky,Moysés
Fonte: Instituto Oswaldo Cruz, Ministério da Saúde Publicador: Instituto Oswaldo Cruz, Ministério da Saúde
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/1987 EN
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Chronic focal and diffuse myiocarditis with interstitial fibrosis developed in Swiss outbred mice and in the inbred AKR and A/J strains of mice which were chronically infected with several Trypanosoma cruzi strains belonging to three biological types (Type I, II and III). High incidence of electrocardiographic changes with predominance of intraventricular conduction disturbances, 1st. and 2nd. degree AV block, arrhythmias, comparable with those found in human Chagas' disease, were also present. Morphological study of the conduction tissue of the heart revealed inflammatory and fibrotic changes. The presence of inflammation in the inter-atrial septum almost always coincided with the inflammatory involvement of the ventricular conduction system. Focal inflammation was associated with vacuolization and focal necrosis of the specific fibers. Most of the lesions were seen affecting the His bundel (76.3% of the cases), the right bundle branch (73.3%), AV node (43.9%) and left bundle branch (37.5%). Correlation between morphological changes in the conduction tissue and electrocardiographic alteration occured in 53.0 to 62.5% of the cases, according to the experimental groups.

Sensory nerve conduction in the caudal nerves of rats with diabetes

Carvalho,Celina Cordeiro de; Maia,Juliana Netto; Lins,Otávio Gomes; Moraes,Sílvia Regina Arruda de
Fonte: Sociedade Brasileira para o Desenvolvimento da Pesquisa em Cirurgia Publicador: Sociedade Brasileira para o Desenvolvimento da Pesquisa em Cirurgia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2011 EN
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PURPOSE: To investigate sensory nerve conduction of the caudal nerve in normal and diabetic rats. METHODS: Diabetes was induced in twenty 8-weeks old Wistar male rats. Twenty normal rats served as controls. Caudal nerve conduction studies were made before diabetes induction and the end of each week for six consecutive weeks. The caudal nerve was stimulated distally and nerve potentials were recorded proximally on the animal's tail using common "alligator" clips as surface electrodes. RESULTS: After induction, nerve conduction velocities (NCV) increased slower in the diabetic than in the control group. Sensory nerve action potentials (SNAP) conduction velocities increased slower in the diabetic than in the control group (slope of regression line: 0.5 vs 1.3m/s per week; NCV in the 15th week = 39±3m/s vs 44±4m/s). Tukey's tests showed differences between groups at the 11th, 13th and 15th weeks old. From the 10th week on, SNAP amplitudes increased faster in the diabetic than in the control group (slopes of the regression line: 10 vs 8µV per week; SNAP amplitudes in the 15th week: 107±23µV vs 85±13µV). Differences at the 12th, 13th and 15th weeks were significant. CONCLUSION: In diabetic rats nerve conduction velocities were slower whereas amplitudes were larger than in normal rats.

Conduction abnormalities and ventricular arrhythmogenesis: The roles of sodium channels and gap junctions

Tse, Gary; Yeo, Jie Ming
Fonte: Elsevier Publicador: Elsevier
Tipo: Article; published version
EN
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This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.ijcha.2015.10.003; Ventricular arrhythmias arise from disruptions in the normal orderly sequence of electrical activation and recovery of the heart. They can be categorized into disorders affecting predominantly cellular depolarization or repolarization, or those involving action potential (AP) conduction. This article briefly discusses the factors causing conduction abnormalities in the form of unidirectional conduction block and reduced conduction velocity (CV). It then examines the roles that sodium channels and gap junctions play in AP conduction. Finally, it synthesizes experimental results to illustrate molecular mechanisms of how abnormalities in these proteins contribute to such conduction abnormalities and hence ventricular arrhythmogenesis, in acquired pathologies such as acute ischaemia and heart failure, as well as inherited arrhythmic syndromes.; GT received a BBSRC Doctoral CASE Studentship at the Department of Biochemistry, University of Cambridge, in conjunction with Xention Discovery, for his Ph.D. studies. This manuscript is based, in part, on the doctoral thesis of GT. GT thanks Dr. Antony Workman of University of Glasgow...

The Roles of Realistic Cardiac Structure in Conduction and Conduction Block: Studies of Novel Micropatterned Cardiac Cell Cultures

Badie, Nima
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2010
Relevância na Pesquisa
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The role of cardiac tissue structure in both normal and abnormal impulse conduction has been extensively studied by researchers in cardiac electrophysiology. However, much is left unknown on how specific micro- and macroscopic structural features affect conduction and conduction block. Progress in this field is constrained by the inability to simultaneously assess intramural cardiac structure and function, as well as the intrinsic complexity and variability of intact tissue preparations. Cultured monolayers of cardiac cells, on the other hand, present a well-controlled in vitro model system that provides the necessary structural and functional simplifications to enable well-defined studies of electrical phenomena. In this thesis, I developed a novel, reproducible cell culture system that accurately replicates the realistic microstructure of cardiac tissues. This system was then applied to systematically explore the influence of natural structure (e.g. tissue boundaries, expansions, local fiber directions) on normal and arrhythmogenic electrical conduction.

Specifically, soft lithography techniques were used to design cell cultures based on microscopic DTMRI (diffusion tensor magnetic resonance imaging) measurements of fiber directions in murine ventricles. Protein micropatterns comprised of mosaics of square pixels with angled lines that followed in-plane cardiac fiber directions were created to control the adhesion and alignment of cardiac cells on a two-dimensional substrate. The high accuracy of cell alignment in the resulting micropatterned monolayers relative to the original DTMRI-measured fiber directions was validated using immunofluorescence and image processing techniques.

Using this novel model system...

Conduction velocity of the rabbit facial nerve: a noninvasive functional evaluation; Velocidade de condução no nervo facial do coelho: uma avaliação funcional não invasiva

Vasconcelos, Belmiro Cavalcanti do Egito; Gay Escoda, Cosme; Vasconcellos, Ricardo José de Holanda; Neves, Riedel Frota Sá Nogueira
Fonte: Universidade de São Paulo. Faculdade de Odontologia Publicador: Universidade de São Paulo. Faculdade de Odontologia
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Artigo Avaliado pelos Pares Formato: application/pdf
Publicado em 01/06/2003 ENG
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The aim of this study was to evaluate standardized conduction velocity data for uninjured facial nerve and facial nerve repaired with autologous graft nerves and synthetic materials. An evaluation was made measuring the preoperative differences in the facial nerve conduction velocities on either side, and ascertaining the existence of a positive correlation between facial nerve conduction velocity and the number of axons regenerated postoperatively. In 17 rabbits, bilateral facial nerve motor action potentials were recorded pre- and postoperatively. The stimulation surface electrodes were placed on the auricular pavilion (facial nerve trunk) and the recording surface electrodes were placed on the quadratus labii inferior muscle. The facial nerves were isolated, transected and separated 10 mm apart. The gap between the two nerve ends was repaired with autologous nerve grafts and PTFE-e (polytetrafluoroethylene) or collagen tubes. The mean of maximal conduction velocity of the facial nerve was 41.10 m/s. After 15 days no nerve conduction was evoked in the evaluated group. For the period of 2 and 4 months the mean conduction velocity was approximately 50% of the normal value in the subgroups assessed. A significant correlation was observed between the conduction velocity and the number of regenerated axons. Noninvasive functional evaluation with surface electrodes can be useful for stimulating and recording muscle action potentials and for assessing the functional state of the facial nerve.; O objetivo deste estudo foi avaliar os dados padronizados de velocidade de condução para o nervo facial não lesado e o nervo facial reparado com enxerto autógeno e com materiais sintéticos. Na avaliação foram medidas as diferenças pré-operatórias de velocidade de condução do nervo facial em cada lado e verificada a existência de uma correlação positiva entre a velocidade de condução do nervo facial e o número de axônios regenerados no pós-operatório. O potencial de ação motora bilateral do nervo facial de 17 coelhos foi registrado no pré e no pós-operatório. Os eletrodos superficiais de estimulação foram colocados no pavilhão auricular (tronco do nervo facial) e os eletrodos superficiais de gravação foram colocados no músculo quadratus labii inferior. Os nervos faciais foram isolados...