A new method to determine arterial distensibility in small arteries

Several methods allow to measure arterial distensibilty. One of them consists in estimating the direct distensibility (D) from diameter and distending blood pressure. Herein, we propose a new method to assess the distensibility in small arteries which is based on spectral analysis of time motion mode ultrasound images of radial arteries. A Fourier transform was performed on intensity of upper and lower walls. Spectral amplitude at heart frequency from both wall spectra was estimated and summed (SumAmp). SumAmp was then compared with direct distensibility. A significant correlation was found between SumAmp and D (r = 0.7, p = 0.02)

Mesures et analyses biomécaniques des interactions macrocirculation/microcirculation sanguines

L'étude de paramètres de type distensibilité des vaisseaux constituant le système cardiovasculaire est très pertinente pour le diagnostic de certaines pathologies. Nous proposons d'estimer la corrélation entre les propriétés biomécaniques des vaisseaux sanguins de gros calibre et ceux de petit calibre. Un protocole de mesure est présenté intégrant l'acquisition de signaux d'impédance bioélectrique et de fluxmétrie laser Doppler. Une analyse de ces données est effectuée à partir de diverses techniques de traitement du signal (analyses de flux, de pressions, etc), et d'une étude statistique

A 3D modelling of the protrusion and retraction of a single cell during the motiliy and the rolling

The rolling is an important kind of cell adhesion, especially in the case of the immune mechanism, due to the leukocyte action, which is strongly influenced by molecular affinity [1]. Our purpose, in this paper, is the presentation of a 3D theorical model which describes the behaviour of the contact interface cell-wall during the rolling and the cell deformation. The first point concerns the modelling of the contact interface, which is assimilated to a circular plate, linked to the wall (e.g vein) by elastic springs. The second point concerns the modelling of the active deformation due to the change of the cytoskeleton structure during the cell motility

Influence of the mechanical damping on the rolling of a single biological cell: A stochastic approach

The rolling is an important kind of cell adhesion, especially in the case of the immune mechanism, due to the leukocyte action, which is strongly influenced by molecular affinity [1].
Our purpose, in this paper, is the presentation of a 2D model which describes the behaviour of the contact interface cell-wall during the rolling. The cell membrane and the wall are assimilated to two rectilinear elastic beams, linked by elastic springs in the case of undamped connections [2] or viscoelastic element in the case of a dissipative behavior. As a first step, the motion of the interface is analyzed, under the external actions of the dynamical fluid pressure, the Van der Waals (attractive forces) and electrostatic effects (repulsive). The second point corresponds to the combination of the vibration of the contact zone and the rupture of the existing connections under a pulling effort. The last step concerns the description of the kinetic of junction between the free ligands and receptors, which constitutes the new connections.
The numerical simulations show the rolling phenomenon, the influence of the mechanical damping on the behavior of the contact interface and the kinetics of junctions between the adhesion free molecules

Recursive Modeling of Coupling in TEM-Cell using fractional Derivative

International audienc

Modelling of radiative Coupling Between Transmission line and TEM-Cells

International audienc

Laser Doppler flowmetry in healthy rats: impact of isoflurane anesthetic on signal complexity

International audienc

Data from: Reduction of baseline corticosterone secretion correlates with climate warming and drying across wild lizard populations

1. Climate change should lead to massive loss of biodiversity in most taxa but the detailed physiological mechanisms underlying population extinction remain largely elusive so far. In vertebrates, baseline levels of hormones such as glucocorticoids (GCs) may be indicators of population state since their secretion to chronic stress can impair survival and reproduction. However, the relationship between GC secretion, climate change and population extinction risk remains unclear. 2. In this study we investigated whether levels of baseline corticosterone (the main GCs in reptiles) correlate with environmental conditions and associated extinction risk across wild populations of the common lizard Zootoca vivipara. 3. First, we performed a cross-sectional comparison of baseline corticosterone levels along an altitudinal gradient among 14 populations. Then, we used a longitudinal study in 8 populations to examine the changes in corticosterone levels following the exposure to a heat wave period. 4. Unexpectedly, baseline corticosterone decreased with increasing thermal conditions at rest in females, and was not correlated with extinction risk. In addition, baseline corticosterone levels decreased after exposure to an extreme heat wave period. This seasonal corticosterone decrease was more pronounced in populations without access to standing water. 5. We suggest that low basal secretion of corticosterone may entail down-regulating activity levels and limit exposure to adverse climatic conditions, especially to reduce water loss. These new insights suggest that rapid population decline might be preceded by a down-regulation of the corticosterone secretion