Showing papers by "Juan C. del Álamo published in 2010"
TL;DR: It is proposed that the motor and actin-crosslinking functions of MyoII differentially control the temporal and spatial distribution of the traction forces, and establish mechanistic relationships between these distributions, enabling cells to move.
Abstract: Amoeboid motility results from pseudopod protrusions and retractions driven by traction forces of cells. We propose that the motor and actin-crosslinking functions of MyoII differentially control t...
94 citations
TL;DR: Analysis of the traction forces reveals that the kinematics of the pedal waves is far more complex than previously thought, showing significant spatial variation as the waves move from the tail to the head of the animal.
Abstract: Research on the adhesive locomotion of terrestrial gastropods is gaining renewed interest as it provides a source of guidance for the design of soft biomimetic robots that can perform functions currently not achievable by conventional rigid vehicles. The locomotion of terrestrial gastropods is driven by a train of periodic muscle contractions (pedal waves) and relaxations (interwaves) that propagate from their tails to their heads. These ventral waves interact with a thin layer of mucus secreted by the animal that transmits propulsive forces to the ground. The exact mechanism by which these propulsive forces are generated is still a matter of controversy. Specifically, the exact role played by the complex rheological and adhesive properties of the mucus is not clear. To provide quantitative data that could shed light on this question, we use a newly developed technique to measure, with high temporal and spatial resolution, the propulsive forces that terrestrial gastropods generate while crawling on smooth flat surfaces. The traction force measurements demonstrate the importance of the finite yield stress of the mucus in generating thrust and are consistent with the surface of the ventral foot being lifted with the passage of each pedal wave. We also show that a forward propulsive force is generated beneath each stationary interwave and that this net forward component is balanced by the resistance caused by the outer rim of the ventral foot, which slides at the speed of the center of mass of the animal. Simultaneously, the animal pulls the rim laterally inward. Analysis of the traction forces reveals that the kinematics of the pedal waves is far more complex than previously thought, showing significant spatial variation (acceleration/deceleration) as the waves move from the tail to the head of the animal.
66 citations
TL;DR: This paper summarizes the key biomechanical concepts behind these methods, reviews the current and forthcoming technologies, and evaluates the readiness of these emerging non-invasive methods for the clinical setting.
24 citations
TL;DR: An algorithm based on the Damped Least Squares (DLS) inversion method is developed and the effectiveness of this method is tested on the McKillop-Geeves model of thin filament regulation to firmly establish the observed effectiveness of DSL vs. the other parameter estimation methods.
19 citations
TL;DR: 3D force measurements revealed that migrating cells pull the substrate up in the vertical direction and inwards in the horizontal directions near the cell periphery, whereas they push the substrate down underneath the cell center.
2 citations
TL;DR: The results indicate that the spatio-temporal variation of the traction work produced by Dictyostelium cells can be described with a reduced number of modes, suggesting that the cell performs a traction work cycle composed of a repetitive sequence of steps over which random fluctuations are imposed.
1 citations
Journal Article•
1 citations
Journal Article•
TL;DR: In this article, the authors studied the motion of a microsphere in an anisotropic viscoelastic network (the cytoskeleton), permeated by a background liquid, and modeled the flow around the sphere with a generalized Stokes equation.
Abstract: The cell cytoplasm comprises an anisotropic semi-dilute filamentous network permeated by a liquid. The mechanical properties of this coupled multiphase system play a determinant role in many cell functions, ranging from cell motility to mechanotransduction.Particle Tracking Microrheology estimates the shear modulus of the cell cytoplasm from the measured motion of probing embedded microparticles. It relates the measured resistance of the probes to the viscoelasticity of the medium by assuming Stokes drag. This assumption is crucial to microrheology, but it breaks in live cells due to the structural complexity of the intracellular domain: it has marked anisotropic characteristics. This introduces severe limitations in the application of current microrheological methods to live cells due to our lack of fundamental understanding about the non-Stokesian hydrodynamics of the microrheological probes in anisotropic media.To overcome this limitation, we studied the motion of a microsphere in an anisotropic viscoelastic network (the cytoskeleton), permeated by a background liquid (the cytosol). In the limit of strong coupling between the network and the liquid, the flow around the sphere is modeled with a generalized Stokes equation using up to 5 viscoelasticity parameters. We solve this problem analytically and calculate the flow generated by the sphere and the drag force that it undergoes. Due to the incompressibility of the medium, the drag is influenced by the shear moduli in every direction. Using the calculated drag, we obtain new closed-form microrheology formulae that relate the resistance measured experimentally to the anisotropic properties of the medium. Previously used techniques render an “effective shear modulus”, which is an average of the actual shear modulii. As a result, they highly underestimate the directionality of the mechanical properties for moderately anisotropic media: they render errors in the order of 200%.