The incidence of restenosis has been shown to be correlated with the overstretching of the arterial wall during an angioplasty procedure. It has been proposed that slow balloon inflation results in lower intramural stresses, therefore minimizing vascular injury and restenosis rate. The analysis of the biomechanics of the arterial tissue might contribute to understand which factors trigger restenosis. However, few mechanical data are available on human arteries because of the difficulty of testing artery samples often obtained from autopsy while arteries are still considered "fresh". Various solutions mimicking the physiological environment have been used to preserve artery samples from harvesting to testing. In vitro mechanical testing is usually preferred since it is difficult to test arteries in vivo. Uniaxial and biaxial testing has been used to characterize anisotropic materials such as arteries, although methodological aspects are still debated. Several objectives were formulated and analyzed during the making of this thesis. In one study, the effect of deformation rate on the mechanical behavior of arterial tissue was investigated. The effect of several preservation methods, including cryopreservation, on the mechanical properties of porcine thoracic aortas was also analyzed. Finally, the differences in the mechanical behavior between three different types of sample geometry and boundary conditions were compared under uniaxial and equi-biaxial testing. Thoracic aortas were harvested within the day of death of pigs from a local slaughterhouse. Upon arrival, connective tissue was removed from the external wall of the artery. Then the artery was cut open along its length and cut out in rectangular samples for uniaxial testing, and square and cruciform samples for biaxial testing. Samples belonging to the freezing effect study were preserved for two months at -20°C and -80°C in isotonic saline solution, Krebs-Henseleit solution with 1.8 M dimethylsulfoxide, and dipped in liquid nitrogen. Samples belonging to the deformation rate effect study were tested uniaxially and equi-biaxially at deformation rates from 10 to 200 %/s. The uniaxial and biaxial experiments were simulated with the help of an inverse finite element software. The use of inverse modeling to fit the material properties by taking into account the non-uniform stress distribution was demonstrated. A rate-dependent isotropic hyperelastic constitutive equation, derived from the Mooney-Rivlin model, was fitted to the experimental results (i.e. deformation rate study). In the proposed model, one of the material parameters is a linear function of the deformation rate. Overall, inverse finite element simulations using the proposed constitutive relation accurately predict the mechanical properties of the arterial wall. In this thesis, it was found that easier attachment of samples (rectangular and cruciform) is accomplished using clamps rather than hooks. It was also found that the elastic behavior of arteries is nonlinear and non-isotropic when subjected to large deformations. Characterization of the arterial behavior at large deformations over a higherdeformation range was achieved using cruciform samples. The mechanical properties of arteries did not significantly change after preservation of arteries for two months. Under uniaxial and biaxial testing, loading forces were reduced up to 20% when the deformation rate was increased from 10 to 200 %/s, which is the opposite to the behaviour seen in other biological tissues. The differences observed in the mechanical behavior of fresh and thawed samples were not significant, independently of the storing medium or freezing temperature used. The lack of significant differences observed in the freezing study was likely due to the small number of samples tested per storing group. Further studies are required to clarify the impact of cryopreservation on extracellular matrix architecture to help tailor an optimized approach to preserve the mechanical properties of arteries. From the results obtained in the deformation rate study, it is concluded that the stiffness of arteries decreases with an increase in the deformation rate. In addition, the effect of deformation rate was observed to be higher than the effect of anisotropy. The inverse relationship between stiffness and deformation rate raises doubts on the hypothesized relationship between intramural stress, arterial injury, and restenosis.

Errata and corrigenda inserted at end of thesis. / Bibliography: leaves 290-337. / xxii, 337 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The objective of this thesis is to examine vasomotor reactivity in both large and small arterial vessels utilising both basic and clinical models. In 4 sections, the thesis: 1. summarises fundamental morphological and physiological principles of the coronary circulation, methods of assessing coronary vasomotor reactivity and characteristics of clinical disorders with vasomotor dysfunction ; 2. investigates regional heterogeneity of vasomotor reactivity in sheep epicardial coronary arteries ; 3. involves studies of the coronary flow phenomenon ; 4. involves a comparison of published Japanese and Caucasian coronary vasomotor reactivity studies and 5. involved an observational study of patients presenting with acute ST elevation. / Thesis (Ph.D.)--University of Adelaide, Dept. of Medicine, 2000

Thesis ((Hons) M. Sc.)--University of Adelaide, Dept of Clinical and Experimental Pharmacology, 1984. / Mounted illus. Includes bibliographical references (16 unnumbered leaves at end of vol).

Thesis (M. Phil.)--University of Hong Kong, 2007. / Also available in print.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Medicine, 2000. / Errata and corrigenda inserted at end of thesis. Bibliography: leaves 290-337.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Missouri--Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 180-204). Also available on the Internet.

Thesis (doctoral)--Lund University, 1997. / Thesis statement on t.p. verso. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri--Columbia, 2002. / "August 2002." Typescript. Vita. Includes bibliographical references (leaves 132-150).

Thesis (Ph. D.)--University of Missouri--Columbia, 1999. / "May 1999." Typescript. Vita. Includes bibliographical references (leaves 180-204). Also available on the Internet.