Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 2 de 2
Filtrar
Filtros adicionais











Intervalo de ano
1.
Stem Cells Dev ; 24(18): 2181-92, 2015 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-26059001

RESUMO

Heart failure induced by myocardial infarct (MI) attenuates the heart rate variability (HRV) and baroreflex sensitivity, which are important risk factors for life-threatening cardiovascular events. Therapies with mesenchymal stem cells (MSCs) have shown promising results after MI. However, the effects of MSCs on hemodynamic (heart rate and arterial pressure) variability and baroreflex sensitivity in chronic heart failure (CHF) following MI have not been evaluated thus far. Male Wistar rats received MSCs or saline solution intravenously 1 week after ligation of the left coronary artery. Control (noninfarcted) rats were also evaluated. MI size was assessed using single-photon emission computed tomography (SPECT). The left ventricular ejection fraction (LVEF) was evaluated using radionuclide ventriculography. Four weeks after MSC injection, the animals were anesthetized and instrumented for chronic ECG recording and catheters were implanted in the femoral artery to record arterial pressure. Arterial pressure and HRVs were determined in time and frequency domain (spectral analysis) while HRV was also examined using nonlinear methods: DFA (detrended fluctuation analysis) and sample entropy. The initial MI size was the same among all infarcted rats but was reduced by MSCs. CHF rats exhibited increased myocardial interstitial collagen and sample entropy combined with the attenuation of the following cardiocirculatory parameters: DFA indices, LVEF, baroreflex sensitivity, and HRV. Nevertheless, MSCs hampered all these alterations, except the LVEF reduction. Therefore, 4 weeks after MSC therapy was applied to CHF rats, MI size and myocardial interstitial fibrosis decreased, while baroreflex sensitivity and HRV improved.


Assuntos
Arritmias Cardíacas/terapia , Insuficiência Cardíaca/terapia , Frequência Cardíaca/fisiologia , Transplante de Células-Tronco Mesenquimais/métodos , Volume Sistólico/fisiologia , Animais , Arritmias Cardíacas/patologia , Pressão Arterial/fisiologia , Tomografia Computadorizada por Emissão de Fóton Único de Sincronização Cardíaca , Terapia Baseada em Transplante de Células e Tecidos/métodos , Vasos Coronários/cirurgia , Insuficiência Cardíaca/patologia , Hemodinâmica , Masculino , Células-Tronco Mesenquimais/citologia , Infarto do Miocárdio/patologia , Ventriculografia com Radionuclídeos , Ratos , Ratos Wistar , Função Ventricular Esquerda/fisiologia
2.
Conf Proc IEEE Eng Med Biol Soc ; 2014: 3345-8, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25570707

RESUMO

Entropy analysis of images are usually performed using Shannon entropy, which calculates the probability of occurrency of each gray level on the image. However, not only the pixel gray level but also the spatial distribution of pixels might be important for image analysis. On the other hand, sample entropy (SampEn) is an important tool for estimation of irregularity in time series, which calculates the probability of pattern occurrence within the series. Therefore, we propose here an extension of SampEn to a two-dimensional case, namely SampEn2D, as an entropy method for extracting features from images that accounts for the spatial distribution of pixels. SampEn2D was applied to histological segments of sural nerve obtained from young (30 days) and elderly (720 days) rats. Morphometric indexes, such as the total number of myelinated fibers and the average myelinated fibers area and perimeter were also calculated. Results show that SampEn2D can extract useful information from histological nerve images, classifying elderly rat image as more regular than young rat. As SampEn2D is related to irregularity/unpredictability, we can conclude that the proposed method is complementary to morphometric indexes. Further studies are being built to validate SampEn2D.


Assuntos
Envelhecimento/fisiologia , Entropia , Processamento de Imagem Assistida por Computador/métodos , Nervo Sural/fisiologia , Animais , Bainha de Mielina/fisiologia , Probabilidade , Ratos Wistar , Nervo Sural/citologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA