Mechanical properties of passive rat cardiac trabeculae

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dc.contributor.author Kirton, Robert S. en
dc.date.accessioned 2006-12-07T21:18:27Z en
dc.date.available 2006-12-07T21:18:27Z en
dc.date.issued 2005 en
dc.identifier.citation Thesis (PhD--Engineering Science and Biomedical Engineering)--University of Auckland, 2005. en
dc.identifier.uri http://hdl.handle.net/2292/282 en
dc.description.abstract In this thesis, the mechanical properties of quiescent, intact, viable, rat right-ventricular (RV) trabeculae were investigated. The main objective was to determine if strainsoftening, which is commonly reported during the deformation of passive cardiac tissue, is present in viable trabeculae. Strain-softening is typically manifested by a stiffer force-extension relation in the first deformation cycle relative to subsequent cycles, and is distinguished from viscoelasticity by a lack of recovery of stiffness, even after several hours of rest. The causes of this behaviour are unknown. To investigate whether strain-softening is observed during uniaxial extensions of viable cardiac tissue, stretch and release cycles of 5%, 10% and 15% muscle length were applied at a constant velocity to trabeculae mounted in a mechanical rig. The rig was custom-built for the purpose. Muscles at 26°C and 0.5 mM Ca2+ were tested in random order in the presence and absence of 50 mM 2,3-butanedione monoxime (BDM). Strain-softening was not observed in viable trabeculae undergoing physiologically relevant extensions, either in the presence or absence of BDM. However, strainsoftening was readily apparent in non-viable trabeculae undergoing the same levels of extension, whether in the presence or absence of BDM. BDM had no effect on passive compliance of viable specimens, while its presence partially inhibited, but could not prevent, stiffening of the non-viable specimens. Loss of viability was accompanied by a uniform increase of dynamic stiffness. The presence of strain-softening during length extensions of non-viable tissue, resulted in a uniform decrease of dynamic stiffness. It is therefore concluded that strain-softening is neither intrinsic to viable rat RV trabeculae nor influenced by BDM but, rather, reflects irreversible damage of tissue in partial, or full, rigor. The addition of BDM was found to alter the dynamic stiffness and phase measured in intact viable quiescent trabeculae. In the absence of BDM, these alterations were calcium- and temperature-sensitive, whereas in the presence of BDM they were not. Therefore, the BDM-induced alteration of the dynamic stiffness and phase is attributed to the inhibition of spontaneous sarcomere activity. en
dc.format Scanned from print thesis en
dc.language.iso en en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA1471695 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. en
dc.rights.uri https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm en
dc.title Mechanical properties of passive rat cardiac trabeculae en
dc.type Thesis en
thesis.degree.discipline Engineering Science and Biomedical Engineering en
thesis.degree.grantor The University of Auckland en
thesis.degree.level Doctoral en
thesis.degree.name PhD en
dc.rights.holder Copyright: The author en
pubs.local.anzsrc 0903 - Biomedical Engineering en
pubs.org-id Bioengineering Institute en


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