Biorheology - Volume 47, issue 5-6

Authors: Chatelin, Simon | Constantinesco, André | Willinger, Rémy

Article Type: Review Article

Abstract: Beginning in the 1960s many studies have been performed to investigate the mechanical properties of brain. In this paper we point out the difficulties linked with in vitro experimental protocols as well as the advantages of using recently developed non-invasive in vivo techniques, such as magnetic resonance elastography. Results of in vitro and in vivo work are compared, emphasizing the specificities and disparities of the in vitro as well as the in vivo results. In particular, a detailed discussion of the results obtained from dynamic shear experiments and magnetic resonance elastography is given before arriving at a tentative conclusion on …the state of knowledge of the mechanical properties of brain. Show more

Keywords: Literature review, magnetic resonance elastography, rheology

DOI: 10.3233/BIR-2010-0576

Citation: Biorheology, vol. 47, no. 5-6, pp. 255-276, 2010

Authors: Iordan, Andreea | Duperray, Alain | Gérard, Anaïs | Grichine, Alexeï | Verdier, Claude

Article Type: Research Article

Abstract: Collagen model tissues, consisting of cells embedded in a collagen matrix at different concentrations (of cells and collagen) were analyzed. Rheological properties were measured and complementary confocal microscopy analysis carried out. An important feature, corresponding to the breakdown of the collagen network (i.e., decrease in network elasticity) was observed at high collagen concentrations, due to the presence of cells. Thanks to confocal microscopy, we showed that cells elongated within the gel and could remodel it, this being a concentration-dependent feature. A careful analysis of the remodeling process showed that cells can attract collagen in their close neighborhood, this being an …irreversible process and that migrating cells create collagen-depleted regions behind them. Show more

Keywords: Tissue, collagen, rheology, confocal, reflectance, remodeling

DOI: 10.3233/BIR-2010-0575

Citation: Biorheology, vol. 47, no. 5-6, pp. 277-295, 2010

Authors: Kritharis, Eleftherios P. | Kakisis, John D. | Giagini, Athina T. | Manos, Themistoklis | Stergiopulos, Nikos | Tsangaris, Sokrates | Sokolis, Dimitrios P.

Article Type: Research Article

Abstract: While the role of hemodynamic variables on the development of intimal hyperplasia in arteriovenous fistulas for hemodialysis has been examined, less is known about the intramural biomechanical factors. In this study, arteriovenous fistulas were created by implantation of e-PTFE grafts between carotid artery and jugular vein in healthy pigs. In vivo recordings exhibited a three-fold pressure and flow elevation in grafted veins after fistula creation, remaining so until sacrifice. The chief morphological observation in grafted vessels was wall thickening at two weeks, serving to restore intramural stresses to homeostatic levels, and a less marked internal diameter enlargement, gradually normalizing intimal …shear after four weeks. The residual strains and opening angle, specifying the zero-stress configuration, increased with differences reaching significance at twelve weeks. Association with histomorphological findings on intima, media and adventitia growth disclosed a correlation between intimal hyperplasia and opening angle increase. Elastin and cellular contents diminished opposite to collagen content, most differences occurring within the first four weeks after grafting. Inflation/extension testing showed that post-fistula the vein wall became progressively thicker and stiffer, lacking restoration of compliance to baseline levels. The present data may further our understanding of the dynamics of venous biomechanical remodeling under pressure and flow-overload conditions. Show more

Keywords: e-PTFE distal vein anastomosis, histology, shear stress, intramural stress, residual stress

DOI: 10.3233/BIR-2011-0578

Citation: Biorheology, vol. 47, no. 5-6, pp. 297-319, 2010

Authors: Sánchez, Julio C. | López-Zapata, Diego F.

Article Type: Research Article

Abstract: Changes in external osmolarity arise from variations in mechanical loads on joints and may affect the homeostasis of chondrocytes, which are the only cell type responsible for matrix turnover. Accordingly, variations in membrane potential may affect cartilage production. The present study assessed the effects of variations in external osmolarity on membrane potential and the possible mechanisms responsible for this response. Membrane potential was measured by the patch clamp whole-cell technique using human articular chondrocytes freshly isolated from healthy and osteoarthritic cartilage. The membrane potential was −39±4 mV in articular human chondrocytes from healthy cartilage and −26±4 mV in those from …osteoarthritic cartilage. Increasing the osmolarity produced a reversible hyperpolarization mediated by K+ efflux through BKCa channels in both groups of chondrocytes, but the response in osteoarthritic cells was significantly reduced; no other K+ pathways were involved in this effect. Alternatively, decreasing the osmolarity elicited depolarization in healthy chondrocytes but did not produce any response in chondrocytes from osteoarthritic cartilage. The depolarization was dependent on Na+ influx through Gd3+ -sensitive stretch-activated cation channels and was independent of external Ca2+ . The differential responses observed in chondrocytes from osteoarthritic cartilage suggest that disregulation on the responses to external osmolarity may be involved in the process that leads to the alterations in the cartilage structure observed in osteoarthritis. Show more

Keywords: Chondrocytes, electrophysiology, membrane potential, osmotic challenges

DOI: 10.3233/BIR-2010-0577

Citation: Biorheology, vol. 47, no. 5-6, pp. 321-331, 2010

Authors: Hsiu, Hsin | Huang, Shih-Min | Hsu, Tse-Lin

Article Type: Correction

Abstract: Link to the original article: http://iospress.metapress.com/content/d30v614178140374/.

DOI: 10.3233/BIR-2011-0581

Citation: Biorheology, vol. 47, no. 5-6, pp. 333-333, 2010

Article Type: Other

Citation: Biorheology, vol. 47, no. 5-6, pp. 335-337, 2010