Jean-Jacques Meister

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The regulation of cytosolic-free calcium concentration of smooth-muscle and endothelial cells was mainly studied on cultured cells where the cross talk between these two coupled cell types is lost. In the present study, the cytosolic-free calcium concentration in the endothelial and the smooth-muscle cells was examined in an intact arterial wall in vitro. Strips of the main branch of rat mesenteric artery were used. Cytosolic-free calcium concentration [Ca2+]i was estimated by determining the fluorescence r

Myofibroblasts are specialized fibroblasts that contribute to wound healing by producing extracellular matrix and by contracting the granulation tissue. They appear in a phase of wound healing when the dermis strongly interacts with activated epidermal keratinocytes. Direct co-culture with keratinocytes upregulates TGFbeta activity and also induces fibroblast to differentiate into alpha-smooth muscle actin (alphaSMA)-positive myofibroblasts. TGF-beta activity alone cannot completely account for alphaSMA ind

The goal of the present study is to construct a biophysical model of the coronary artery endothelial cell response to bradykinin. This model takes into account intracellular Ca2+ dynamics, membrane potential, a non-selective cation channel, and two Ca(2+)-dependent K+ channels, as well as intra- and extracellular Ca2+ sources. The model reproduces the experimental data available, and predicts certain quantities which would be hard to obtain experimentally, like the individual K+ channel currents when the me

AIM: Non-invasive measurements of arterial diameter and wall thickness are critical in characterizing the onset and development of vascular disease. A precise dynamic method was proposed and tested for this purpose. DESIGN: A non-invasive method of measuring the variations in diameter and thickness of human arteries throughout the cardiac cycle was developed, using a high-precision ultrasonic echo-tracking system. An adaptive filtering technique was used to suppress artefacts caused by the layered tissue st

This study is concerned with the wave reflection properties of arterial stenoses. Two theoretical models have been developed for deriving the reflection coefficient: a linear model resulting from the linearization of the pressure drop-flow equation and an indirect, quasi-nonlinear model, based on the separation of pressure waves into their forward and backward running components proximal and distal to the stenosis. The linear method gave consistently lower values for the reflection coefficient when compared

The variation of wall stress distribution with age in the thoracic and abdominal aortas of normotensive rats was studied. Dimensions of the zero-stress configurations were measured at the ages of 4, 8, 12, 20, and 52 weeks. Using data from previously published inflation tests, the circumferential stress-strain relationship was obtained in each age group. The calculated stress distribution showed that the average circumferential stress remained practically constant after the age of 20 weeks. The circumferent

Actin-myosin microfilament bundles or stress-fibers are the principal tension-generating structures in the cell. Their mechanical properties are critical for cell shape, motion, and interaction with other cells and extracellular matrix, but were so far dif ...

We investigated how parameters describing the heart and the arterial system contribute to the systolic and diastolic pressures (Ps and Pd, respectively) and stroke volume (SV). We have described the heart by the varying-elastance model with six parameters and the systemic arterial tree by the three-element windkessel model, leading to a total of nine parameters. Application of dimensional analysis led to a total of six dimensionless parameters describing dimensionless Ps and Pd, i.e., pressures with respect

How cells break symmetry and organize activity at their edges to move directionally is a fundamental question in cell biology. Physical models of cell motility commonly incorporate gradients of regulatory proteins and/or feedback from the motion itself to ...

Leading edge protrusion is one of the critical events in the cell motility cycle and it is believed to be driven by the assembly of the actin network. The concept of dendritic nucleation of actin filaments provides a basis for understanding the organization and dynamics of the actin network at the molecular level. At a larger scale, the dynamic geometry of the cell edge has been described in terms of the graded radial extension model, but this level of description has not yet been linked to the molecular dy

We developed a new method to determine the location and importance of reflection sites in the arterial system. The method is based on the decomposition of the aortic pressure wave into its forward and backward components, and it provides the reflection profile of the arterial system as a wave reflection site amplitude versus distance from the heart. The reflection profile can be seen as the response of the arterial system to a pressure delta pulse where reflections upstream from the measurement location hav

Vasomotion has been studied on segments of rat mesenteric and femoral arteries perfused in vitro. We have investigated 1) the effect of perfusion flow on the characteristics of vasomotion and 2) the nature and patterns of vasomotion. We have found that perfusion flow is not a control parameter that contributes to the genesis of vasomotion but that it affects, in most cases only slightly, the frequency and amplitude of vasomotion. We have found evidence that vasomotion is low-dimensional chaotic. The correla

The goal of the present study was to analyze the intercellular calcium communication between smooth muscle cells (SMCs) and endothelial cells (ECs) by simultaneously monitoring artery diameter and intracellular calcium concentration in a rat mesenteric arterial segment in vitro under physiological pressure (50 mmHg) and flow (50 microl/min) in a specially developed system. Intracellular calcium was expressed as the fura 2 ratio. The diameter was measured using a digital image acquisition system. Stimulation

We propose a new, simple way of constructing elastic tubes which can be used to model the nonlinear elastic properties of large arteries. The tube models are constructed from a silicon elastomer (Sylgard 184, Dow Corning), which exhibits a nonlinear behavior with increased stiffness at high strains. Tests conducted on different tube models showed that, with the proper choice of geometric parameters, the elastic properties, in terms of area-pressure relation and compliance, can be similar to that of real art

AIM: We studied the effects of mental stress on the tone of the radial artery, a medium-sized muscular artery. METHODS: Using an A-mode echo-tracking device coupled to a photoplethysmograph, we took continuous measurements of the radial artery diameter, heart rate and finger arterial pressure in six healthy young volunteers. RESULTS: Under mental stress, the heart rate increased from 63 +/- 4 to 74 +/- 4 beats/min (mean +/- SEM, P < 0.01) and systolic pressure from 123 +/- 5 to 140 +/- 6 mmHg (P < 0.05). No

Intercellular Ca2+ wave propagation between vascular smooth muscle cells (SMCs) is associated with the propagation of contraction along the vessel. Here, we characterize the involvement of gap junctions (GJs) in Ca2+ wave propagation between SMCs at the ce ...

Asynchronous and synchronous calcium oscillations occur in a variety of cells. A well-established pathway for intercellular communication is provided by gap junctions which connect adjacent cells and can mediate electrical and chemical coupling. Several ex ...

Smooth muscle cell calcium dynamics and diameter were measured in intact pressurized rat mesenteric artery segments during vasoconstriction and vasomotion. Arteries showed a certain norepinephrine (NE) threshold (0.3-0.4 microM) for the onset of vasomotion, during a cumulative NE concentration-response curve. This was due to a necessary [Ca2+]i threshold (increase over basal level of 22.2 +/- 2.6%) to elicit oscillations. The calcium oscillations obtained were synchronous over the entire vessel length and p

In vitro, different techniques are used to study the smooth muscle cells' calcium dynamics and contraction/relaxation mechanisms on arteries. Most experimental studies use either an isometric or an isobaric setup. However, in vivo, a blood vessel is neithe ...

AIM: To propose a method for obtaining non-invasive highly accurate measurements of arterial diameter, thickness and pressure at a single location on a peripheral arm artery, and use this data to estimate the status of the arterial wall. METHODS: Diameter and thickness were measured with an A-mode ultrasonic echo-tracking device, with a precision of close to 1 micron. Pressure was measured with a photoplethysmograph at the finger level. A simple hemodynamic model was used to estimate, from the measured pres

Jean-Jacques Meister

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Cytosolic-free calcium in smooth-muscle and endothelial cells in an intact arterial wall from rat mesenteric artery in vitro

Dissecting the roles of endothelin, TGF-beta and GM-CSF on myofibroblast differentiation by keratinocytes

Modelling the electrophysiological endothelial cell response to bradykinin

Dynamic non-invasive measurements of arterial diameter and wall thickness

On the wave transmission and reflection properties of stenoses

Analysis of the strain and stress distribution in the wall of the developing and mature rat aorta

Ultra-soft cantilevers and 3-D micro-patterned substrates for contractile bundle tension measurement in living cells

Determinants of stroke volume and systolic and diastolic aortic pressure

Minimal model for spontaneous cell polarization and edge activity in oscillating, rotating and migrating cells

Analysis of actin dynamics at the leading edge of crawling cells: implications for the shape of keratocyte lamellipodia

Method for determining distribution of reflection sites in the arterial system

Arterial vasomotion: effect of flow and evidence of nonlinear dynamics

Simultaneous arterial calcium dynamics and diameter measurements: application to myoendothelial communication

Modeling of the wave transmission properties of large arteries using nonlinear elastic tubes

Effect of mental stress on the tone of a medium-sized muscular artery

Intercellular calcium waves in primary cultured rat mesenteric smooth muscle cells are mediated by Connexin43

Emergent properties of electrically coupled smooth muscle cells

Calcium dynamics and vasomotion in rat mesenteric arteries

Calcium dynamics and vasomotion in arteries subject to isometric, isobaric, and isotonic conditions

Non-invasive method for the assessment of non-linear elastic properties and stress of forearm arteries in vivo