Browsing by Author "Vuksanović, Vesna (8707631800)"

To investigate the role of lateral interactions, we quantified spontaneous contractions of whole and longitudinally cut ratD́s portal vein in vitro. The disruption of the wall had no effect on basic frequency determined from spectra and complexity index (CI) calculated by multiscale entropy analysis. Endothelium was disrupted and nonfunctional in all samples. Considering amplitude, frequency and CI we identified two modes of contractions. Neither mode of contractions nor the effect of aminopyridine (4-AP) depended on the integrity of the wall. We concluded that contractions in vitro originate in smooth muscle cells without involvement of the endothelium and lateral interactions. © 2013 Elsevier Ltd.

To investigate the role of lateral interactions, we quantified spontaneous contractions of whole and longitudinally cut ratD́s portal vein in vitro. The disruption of the wall had no effect on basic frequency determined from spectra and complexity index (CI) calculated by multiscale entropy analysis. Endothelium was disrupted and nonfunctional in all samples. Considering amplitude, frequency and CI we identified two modes of contractions. Neither mode of contractions nor the effect of aminopyridine (4-AP) depended on the integrity of the wall. We concluded that contractions in vitro originate in smooth muscle cells without involvement of the endothelium and lateral interactions. © 2013 Elsevier Ltd.

In this study we investigated nonlinear and linear characteristics of heart period variability with aging in supine and standing posture. Sixty healthy subjects (8-61 years) divided in three age groups participated in the study. Heart period variability was assessed by measurement of short-term scaling exponent, sample entropy, largest Lyapunov exponent and spectral low-frequency and high-frequency power. In standing, there was significant increase in short-term scaling exponent and largest Lyapunov exponent in all subjects, and significant decrease in sample entropy in children (< 15 years) and young adults (15-39 years). Increasing age is associated with reduction in sample entropy in supine posture. Mutual effect of aging and postural change was reflected on heart rate and sample entropy. Correlation between low-frequency-to-high-frequency power ratio and short-term scaling exponent was found in supine posture. In standing both low-frequency and high-frequency powers are correlated with short-term scaling exponent and sample entropy. These results show that posture, standing compared to supine, has significant effect on nonlinear properties of heart period variability in healthy subjects while the influence of healthy aging is less pronounced. The findings indicate that intrinsic properties of heart period dynamics, reflected on nonlinear measures, are altered only by robust changes of autonomic modulation of heart rate.

In this study we investigated nonlinear and linear characteristics of heart period variability with aging in supine and standing posture. Sixty healthy subjects (8-61 years) divided in three age groups participated in the study. Heart period variability was assessed by measurement of short-term scaling exponent, sample entropy, largest Lyapunov exponent and spectral low-frequency and high-frequency power. In standing, there was significant increase in short-term scaling exponent and largest Lyapunov exponent in all subjects, and significant decrease in sample entropy in children (< 15 years) and young adults (15-39 years). Increasing age is associated with reduction in sample entropy in supine posture. Mutual effect of aging and postural change was reflected on heart rate and sample entropy. Correlation between low-frequency-to-high-frequency power ratio and short-term scaling exponent was found in supine posture. In standing both low-frequency and high-frequency powers are correlated with short-term scaling exponent and sample entropy. These results show that posture, standing compared to supine, has significant effect on nonlinear properties of heart period variability in healthy subjects while the influence of healthy aging is less pronounced. The findings indicate that intrinsic properties of heart period dynamics, reflected on nonlinear measures, are altered only by robust changes of autonomic modulation of heart rate.