Alternative models of cell mechanics depict the living as a simple mechanical continuum, porous filament gel, tensed cortical membrane, or tensegrity network that maintains stabilizing prestress through incorporation discrete structural elements bear compression. Real-time microscopic analysis cells containing GFP-labeled microtubules and associated mitochondria revealed behave like structures composed an interconnected actin microfilaments when stresses are applied to surface integrin...

The tensegrity hypothesis holds that the cytoskeleton is a structure whose shape stabilized predominantly by tensile stresses borne filamentous structures. Accordingly, cell stiffness must increase in proportion with level of stress, which called prestress. Here we have tested prediction adherent human airway smooth muscle (HASM) cells. Traction microscopy was used to measure distribution contractile arising at interface between each and its substrate; this traction field. Because field be...

Mechanical robustness of the cell under different modes stress and deformation is essential to its survival function. Under tension, mechanical rigidity provided by cytoskeletal network; with increasing stress, this network stiffens, providing increased resistance deformation. However, a must also resist compression, which will inevitably occur whenever volume decreased during such biologically important processes as anhydrobiosis apoptosis. individual filaments can buckle, thereby reducing...

In asthma, the mechanisms relating airway obstruction, hyperresponsiveness, and inflammation remain rather mysterious. We show here that regulation of smooth muscle length corresponds to a dynamically equilibrated steady state, not static mechanical equilibrium had been previously assumed. This dynamic state requires as an essential feature continuous supply external energy (derived from tidal lung inflations) acts perturb interactions myosin with actin, drive molecular system far away...

The tensegrity model hypothesizes that cytoskeleton-based microtubules (MTs) carry compression as they balance a portion of cell contractile stress. To test this hypothesis, we used traction force microscopy to measure at the interface adhering human airway smooth muscle cells and flexible polyacrylamide gel substrate. prediction is if MTs stress, then, upon their disruption, stress balanced by would shift substrate, thereby causing an increase in traction. Measurements were done first...

Magnetic twisting cytometry probes mechanical properties of an adherent cell by applying a torque to magnetic bead that is tightly bound the surface. Here we have used three-dimensional finite element model deformation compute relationships between applied and resulting rotation lateral translation. From analysis, computed two coefficients allow elastic modulus be estimated from measurements either or translation, respectively, if degree embedding height are known. Although strains in...

Section:ChooseTop of pageAbstract <<MATERIALS AND METHODSRESULTSDISCUSSIONReferencesCITING ARTICLES

To estimate the contributions of heterogeneity in regional perfusion (Q) and alveolar ventilation (V A) to that ventilation-perfusion ratio A/Q), we have refined positron emission tomography (PET) techniques image local distributions Q V A per unit gas volume content (sQ sV A, respectively) A/Q dogs. was assessed two ways: 1) washout 13NN tracer after equilibration by rebreathing (sV A(i)), 2) an apneic a bolus intravenous infusion 13NN-saline solution collected during steady-state same...

The aim of this study is to develop unifying concepts at the microstructural level account for macroscopic connective tissue dynamics. We establish hypothesis that rate-dependent and rate-independent dissipative stresses arise in interaction among fibers matrix. A quantitative theoretical analysis specified terms geometry material properties surrounding constituents. leads notion slip diffusion boundary layers, which become understanding mechanisms underlie elasticity energy dissipation...

In fibrous connective tissue networks, mechanical loads may be transferred from one fiber to the next by friction between slipping fibers (J. Appl. Physiol. 74: 665-681, 1993). Here we tested that hypothesis; it predicts elastance of networks increases with increasing frequency, decreases strain amplitude (delta epsilon), and swelling solvent. Similarly, hysteresivity (eta) delta epsilon, swelling, and, importantly, exceeds isolated constituents matrix. Elastance eta two structurally...

The regulation of striated muscle contraction involves cooperative interactions between actin filaments, myosin-S1 (S1), tropomyosin (Tm), troponin (Tn), and calcium. These are modeled by treating overlapping tropomyosins as a continuous flexible chain (CFC), weakly confined electrostatic with actin. CFC is displaced locally in opposite directions on the surface binding either S1 or Troponin I (TnI) to apparent rate constants for myosin TnI detachment from then intrinsically coupled via...

A method to assess the three-dimensional distribution of alveolar ventilation-perfusion ratio (VA/Q) by imaging lungs with positron emission tomography (PET) during a constant-rate intravenous infusion 13NN-labeled saline solution was developed C. G. Rhodes, S. O. Valind, L. H. Brudin, P. E. Wollmer, T. Jones, D. Buckingham, and J. M. B. Hughes (J. Appl. Physiol. 66: 1896-1904 1905-1913, 1989). We have modified this methodology obtain high-resolution, low-noise PET images local VA/Q where...

To demonstrate the relationship between lingual myoarchitecture and mechanics during swallowing, we performed a finite-element (FE) simulation of deformation employing mesh aligned with vector coordinates myofiber tracts obtained by diffusion tensor imaging tractography in humans. Material properties individual elements were depicted terms Hill's three-component phenomenological model, assuming that FE was composed anisotropic muscle isotropic connective tissue. Moreover, mechanical model...

Here we investigate the origin of relaxation times governing mechanical response an integrated contractile tissue to imposed cyclic changes length. When strain-rate amplitude is held constant as frequency varied, fast events are accounted for by actomyosin cross-bridge cycling, but slow reveal processes associated with ongoing cytoskeletal length adaptation. Although both regimes innately nonlinear, these unified and their positions along axis set amplitude.

Section:ChooseTop of pageAbstract <<Materials and MethodsResultsDiscussionReferencesCITING ARTICLES

To further our understanding of the mechanisms underlying chest wall mechanics, we investigated dynamic response isolated passive rat diaphragm strip. Stress adaptation tissue was measured from 0.05 to 60 s after subjecting strips strain steps normalized amplitudes 0.005 0.04. The resistance (R), elastance (E), and hysteresivity (eta) were in same range by sinusoidally straining strip at frequencies 0.03125 10 Hz. stress (T) depended exponentially on (epsilon) relaxed recovered linearly with...