Morphologic and biomechanical changes of thoracic and abdominal aorta in a rat model of cigarette smoke exposure

Background: Smoking is the most relevant environmental factor that affects the development of aortic aneurysm. Smokers have elevated levels of elastase activity in the arterial wall, which leads to weakening of the aorta. The aim of this study was to verify whether cigarette smoke exposure itself is capable of altering the aortic wall. Methods: Forty-eight Wistar rats were divided into 2-, 4-, and 6-month experimental periods and into 2 groups: smokers (submitted to smoke exposure at a rate of 40 cigarettes/day) and nonsmokers. At the end of the experimental periods, the aortas were removed and cross-sectioned to obtain histologic specimens for light microscopic and morphometric analyses. The remaining longitudinal segments were stretched to rupture and mechanical parameters were determined. Results: A degenerative process (i.e., a reduction in elastic fibers, the loss of lamellar arrangement, and a reduction of smooth muscle cells) was observed, and this effect was proportional in intensity to the period of tobacco exposure. We observed a progressive reduction in the yield point of the thoracic aorta over time (P < 0.05). There was a decrease in stiffness (P < 0.05) and in failure load (P < 0.05) at 6 months in the abdominal aorta of rats in the smoking group. Conclusions: Chronic exposure to tobacco smoke can affect the mechanical properties of the aorta and can also provoke substantial structural changes of the arterial wall. © 2013 Elsevier Inc. All rights reserved.

Morphologic and biomechanical changes of thoracic and abdominal aorta in a rat model of cigarette smoke exposure

Background: Smoking is the most relevant environmental factor that affects the development of aortic aneurysm. Smokers have elevated levels of elastase activity in the arterial wall, which leads to weakening of the aorta. The aim of this study was to verify whether cigarette smoke exposure itself is capable of altering the aortic wall. Methods: Forty-eight Wistar rats were divided into 2-, 4-, and 6-month experimental periods and into 2 groups: smokers (submitted to smoke exposure at a rate of 40 cigarettes/day) and nonsmokers. At the end of the experimental periods, the aortas were removed and crosssectioned to obtain histologic specimens for light microscopic and morphometric analyses. The remaining longitudinal segments were stretched to rupture and mechanical parameters were determined. Results: A degenerative process (i.e., a reduction in elastic fibers, the loss of lamellar arrangement, and a reduction of smooth muscle cells) was observed, and this effect was proportional in intensity to the period of tobacco exposure. We observed a progressive reduction in the yield point of the thoracic aorta over time (P < 0.05). There was a decrease in stiffness (P < 0.05) and in failure load (P < 0.05) at 6 months in the abdominal aorta of rats in the smoking group. Conclusions: Chronic exposure to tobacco smoke can affect the mechanical properties of the aorta and can also provoke substantial structural changes of the arterial wall

Biomechanical model of tumor growth: application to the European ContraCancrum project

This abstract presents the biomechanical model that is used in the European ContraCancrum project, aiming at simulating tumor evolution in the brain and lung. The construction of the finite element model as well as a simulation of tumor growth are shown. The construction of the mesh is fully automatic and is therefore compatible with a clinical application. This biomechanical model will be later combined to a cellular level simulator also developed in the project.

Biomechanical model of human cornea based on stromal microstructure

The optical characteristics of the human cornea depends on the mechanical balance between the intra-ocular pressure and intrinsic tissue stiffness. A wide range of ophthalmic surgical procedures alter corneal biomechanics to induce local or global curvature changes for the correction of visual acuity. Due to the large number of surgical interventions performed every day, a deeper understanding of corneal biomechanics is needed to improve the safety of these procedures and medical devices. The aim of this study is to propose a biomechanical model of the human cornea, based on stromal microstructure. The constitutive mechanical law includes collagen fiber distribution based on X-ray scattering analysis, collagen cross-linking, and fiber uncrimping. Our results showed that the proposed model reproduced inflation and extensiometry experimental data [Elsheikh et al., Curr. Eye Res., 2007; Elsheikh et al., Exp. Eye Res., 2008] successfully. The mechanical properties obtained for different age groups demonstrated an increase in collagen cross-linking for older specimens. In future work such a model could be used to simulate non-symmetric interventions, and provide better surgical planning.

Statistical finite element model for bone shape and biomechanical properties

We present a framework for statistical finite element analysis combining shape and material properties, and allowing performing statistical statements of biomechanical performance across a given population. In this paper, we focus on the design of orthopaedic implants that fit a maximum percentage of the target population, both in terms of geometry and biomechanical stability. CT scans of the bone under consideration are registered non-rigidly to obtain correspondences in position and intensity between them. A statistical model of shape and intensity (bone density) is computed by means of principal component analysis. Afterwards, finite element analysis (FEA) is performed to analyse the biomechanical performance of the bones. Realistic forces are applied on the bones and the resulting displacement and bone stress distribution are calculated. The mechanical behaviour of different PCA bone instances is compared.

Operator, organizational, field, and depot maintenance manual : grader, road, motorized, diesel engine driven, 12-foot blade, Caterpillar model 12, serial number range 99E5309 UP, FSN 3805-197-4184.

"June 1963."

Direct support and general support maintenance repair parts and special tools lists (including depot maintenance repair parts and special tools lists) : grader, road, motorized, DED, 13,000 lb pressure at blade, 12 foot blade, 6 wheels, 4 driving, 2 steerable, leaning front wheels, w/scarifier army model 440HA, NSN 3805-00-931-7881, army model 440HAROPS, NSN 3805-01-018-2866.

Includes index.

Organizational maintenance repair parts and special tools lists : grader, road, motorized, DED, 13,000 pressure at blade, 12 foot blade, 6 wheels, 4 driving, 2 steerable, leaning front wheels, w/scarifier : Army model 440HA NSN 3805-00-931-7881 : Army model 440HAROPS NSN 3805-01-018-2866.

Includes indexes.

Organizational maintenance repair parts and special tools lists : crane, wheel mounted, 20 ton at 10 foot radius, 2 engines, diesel engine driven, 4x4 air transportable, phase III, w/blade, bulldozer, earth moving, w/block,tackle, 20 ton, w/boom, crane, 30 foot, Army model M2380, NSN 3810-00-763-7728, American Hoist and Derrick model 2380 and Army model M2385 ...

Includes index.

Operator and organizational maintenance manual : grader, road, motorized, diesel engine driven, 12 foot blade, (Caterpillar model 112F), FSN 3805-902-3083 w/Martin GS55 graderscraper, FSN 3805-900-8545.

"April 1968."

Technical manual, operator and organizational manual : grader, road, motorized, DED, type 1, 6 wheel, 4 wheel drive, front wheel steering, 12-foot blade, Caterpillar model 120, FSN 3805-466-0084.

Includes index.

Direct support, general support, and depot maintenance manual : grader, road, motorized, diesel engine driven, 12 foot blade (Caterpillar model 112F), FSN 3805-902-3808, w/Martin GS55 graderscraper, FSN 3805-900-8545.

"March 1968."

Unit maintenance repair parts and special tools lists : grader, road, motorized, DED, 13,000 lb pressure at blade, 12 foot blade, 6 wheels, 4 driving, 2 steerable, leaning front wheels with scarifier : Army model 440HA (NSN 3805-00-931-7881) : Army model 440HAROPS (NSN 3805-01-018-2866).

"May 1992."