In this paper, we analyze how elastic and viscoelastic properties differ across seven locations along the large arteries in 11 sheep. We employ a two-parameter elastic model and a four-parameter Kelvin viscoelastic model to analyze experimental measurements of vessel diameter and blood pressure obtained in vitro at conditions mimicking in vivo dynamics. Elastic and viscoelastic wall properties were assessed via solutions to the associated inverse problem. We use sensitivity analysis to rank the model parameters from the most to the least sensitive, as well as to compute standard errors and confidence intervals. Results reveal that elastic properties in both models (including Young's modulus and the viscoelastic relaxation parameters) vary across locations (smaller arteries are stiffer than larger arteries). We also show that for all locations, the inclusion of viscoelastic behavior is important to capture pressure-area dynamics.

Recently, it has been proposed the use of speckle-tracking echography (STE) to study the left ventricle (LV) torsion dynamics, which would make LV torsion assessment more available in clinical and research cardiology. LV torsion has been described during exercise and in some sportsmen, but so far, its dynamics has not been studied in soccer players. The aims were to characterize and to compare LV apical and basal rotation, and to analyze LV torsion in professional soccer players using STE, and to determine the main differences in torsion between soccer players and age-matched non-trained individuals. The STE allowed characterizing LV rotation and torsion in both groups. LV torsion level and velocities were lesser in soccer players than in non-trained individuals. Changes in torsion in soccer players could represent physiological adaptations to training.

The influence of the renin-angiotensin system (RAS) on the aortic wall mechanical properties under angiotensin I converting enzyme inhibition (enalaprilat, 0.3 mg/kg iv) or angiotensin II receptor (AT1) blockade (E-3174, 1 mg/kg iv) was examined in eight normotensive and eight renovascular hypertensive conscious dogs. Aortic diameter (D; sonomicrometry)-pressure (P; microtransducer) hysteresis loops during steady state and during rapid distal aortic occlusion allowed (after hysteresis elimination) calculation of the aortic wall viscosity index, the purely elastic P-D relationship, and derivation into compliance-pressure curves. At the early stage ofrenovascular hypertension when activation of RAS is more pronounced, aortic wall stiffness and wall viscosity were increased as compared with normotensive states. Blood pressure remained unchanged in normotensive animals and was reduced during hypertension after antihypertensive treatments. In hypertensive animals, enalaprilat and E-3174 decreased viscosity index and shifted the compliance-pressure curve upward with respect to pretreatment conditions. In normotensive dogs, whereas E-3174 did not change the compliance-pressure curve and viscosity index, enalaprilat increased compliance and reduced viscosity index. We concluded that in normotensive dogs converting enzyme inhibition modifies arterial viscoelastic parameters by angiotensin-independent mechanisms that contribute to the modulation of the buffering function of large arteries.

PurposeIn times when digitized and blended learning paradigms are getting more profuse, the COVID-19 pandemic substantially changed the dynamics of this program, forcing all the courses to migrate to virtual modality. This study highlights the biological engineering courses at the University of the Republic (Universidad de la República) in Uruguay pertaining to the adaptations to virtual learning environments during the COVID-19 pandemic and analyzing its impact through the courses taught in the virtual setting.Design/methodology/approachGlobal education has seen a significant paradigm shift over the last few years, changing from a specialized approach to a broader transdisciplinary approach. Especially in life sciences, different fields of specializations have started to share a common space in the area of applied research and development. Based on this transdisciplinary approach, the Biological Engineering program was designed at the University of the Republic (Universidad de la República), Uruguay.FindingsThe new challenges posed by the virtual modality on the pedagogical areas like course design, teaching methodologies and evaluations and logistical aspects like laboratory-setting have sparked a considerable change in different aspects of the courses. However, despite the changes to virtual modality in this year, the student-performance showed an overall improvement compared to the last year.Originality/valueWith the changing direction of pedagogy and research in biological engineering across the world, it is quintessential to adapt university courses to the same, promoting an environment where the scientific and engineering disciplines merge and the learning methodologies lead to a dynamic and adaptive ubiquitous learning environment.

The mechanics of the arterial wall is complex, due to its material structure and load conditions, which influence the hemodynamic properties as well as the growth and remodeling process of the cardiovascular system. Arterial remodeling can be found both locally and globally. Local remodeling is typically a result of disease, while global remodeling can be found even for healthy arteries. In this study we have analyzed how elastic and viscoelastic properties differ across 7 locations along the large ovine arteries in 11 sheep. We combined the Kelvin model with experimental measurements of vessel diameter and pressure obtained in-vitro at conditions mimicking the in-vivo dynamics. Elastic and viscoelastic wallproperties were assessed by analyzing values of four model parameters across the 7 locations. To do so we solved an inverse problem, resulting in computed estimates for each of the four parameter values that minimize the residual between the data and the model. We used sensitivity analysis to compute standard errors, and confidence intervals for all model parameters. Results showed that while elastic properties including Young's modulus and the vessel wall thickness varied across locations (smaller arteries were stiffer than larger arteries) viscoelastic relaxation parameters did not differ significantly across locations. We also showed that for all locations, the inclusion of viscoelastic behavior, e.g., using the Kelvin model, is important to capture pressure-area dynamics.

Compliance is not linear within the physiological range of pressures, and linear modeling may not describe venous physiology adequately. Forearm and calf venous compliance were assessed in nine subjects. Venous compliance was modeled by using a biphasic model with high- and low-pressure linear phases separated by a breakpoint. This model was compared with a linear model and several exponential models. The biphasic, linear, and two-parameter exponential models best represented the data. The mean coefficient of determination for the biphasic model was greater than for the linear and exponential models in the calf (biphasic 0.94 +/- 0.04, exponential 0.81 +/- 0.16, P = not significant; and linear 0.54 +/- 0.05, P < 0.05) and forearm (biphasic 0.83 +/- 0.17, exponential 0.79 +/- 0.15, P = not significant; and linear 0.51 +/- 0.06, P < 0.05). The breakpoint pressure in the biphasic model was higher in the calf than the forearm, 34.4 +/- 3.9 vs. 29.1 +/- 4.5 mmHg, P < 0.05. A biphasic model can describe limb venous compliance and delineate differences in venous physiology at high and low pressures. The steep low-pressure phase of the compliance curve extends to higher pressures in the calf than in the forearm, thereby enlarging the range of pressures over which hemodynamic regulation by the calf venous circulation occurs.

The model was adequate to characterize the circadian pattern of AS. We provide the first evidence that AS in humans follows an asymmetric circadian pattern and that this differs between NG and HG. In both NG and HG, AS had a circadian profile, with the highest levels in the night. HG showed larger levels of AS, larger BP variations and rate of change and minor changes in AS during transitional periods.

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