Effect of variations in pressure and flow on the geometry of isolated canine carotid arteries

Brant, Arthur; Teodori, Michael F.; Kormos, Robert L.; Borovetz, Harvey S.

doi:10.1016/0021-9290(87)90143-6

Cited by 24 publications

(8 citation statements)

References 3 publications

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“…Due to the nonuniform nature of the urethra along its length (10), a thickness must be determined for each segment (i.e., proximal, middle, and distal segments) separately to calculate R i from the measured Ro for use in Eqs. [1][2][3][4][5]. Thus, after the biomechanical ex vivo testing was performed, specimens were fixed under zero transmural pressure in 4% paraformaldehyde overnight, followed by 30% sucrose solution.…”

Section: Animalsmentioning

confidence: 99%

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Ex vivo biomechanical properties of the female urethra in a rat model of birth trauma

Prantil

Jankowski

Kaiho³

et al. 2007

American Journal of Physiology-Renal Physiology

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Prantil RL, Jankowski RJ, Kaiho Y, de Groat WC, Chancellor MB, Yoshimura N, Vorp DA. Ex vivo biomechanical properties of the female urethra in a rat model of birth trauma. Am J Physiol Renal Physiol 292: F1229 -F1237, 2007. First published December 26, 2006; doi:10.1152/ajprenal.00292.2006.-Stress urinary incontinence (SUI) is the involuntary release of urine during sudden increases in abdominal pressures. SUI is common in women after vaginal delivery or pelvic trauma and may alter the biomechanical properties of the urethra. Thus we hypothesize that injury due to vaginal distension (VD) decreases urethral basal tone and passive stiffness. This study aimed to assess the biomechanical properties of the urethra after VD in the baseline state, where basal muscle tone and extracellular matrix (ECM) are present, and in the passive state, where inactive muscle and ECM are present. Female rat urethras were isolated in a rat model of acute SUI induced by simulated birth trauma. Our established ex vivo system was utilized, wherein we applied intraluminal static pressures ranging from 0 to 20 mmHg. Outer diameter was measured via a laser micrometer. Measurements were recorded via computer. Urethral thickness was assessed histologically. Stress-strain responses of the urethra were altered by VD. Quantification of biomechanical parameters indicated that VD decreased baseline stiffness. The passive peak incremental elastic modulus of the distal segment in VD urethras was less than for controls (1.84 Ϯ 0.67 vs. 1.19 Ϯ 0.70 ϫ 10 6 dyne/cm 2 , respectively; P ϭ 0.016). An increase was noted in passive lowpressure compliance values in proximal VD urethras compared with controls (9.44 Ϯ 2.43 vs. 4.62 Ϯ 0.60 mmHg Ϫ1 , respectively; P ϭ 0.04). Biomechanical analyses suggest that VD alters urethral basal tone, proximal urethral compliance, and distal stiffness. Lack of basal smooth muscle tone, in combination with these changes in the proximal and distal urethra, may contribute to SUI induced by VD. stress urinary incontinence; sphincter; collagen COSTS FOR URINARY INCONTINENCE exceed $16 billion annually, and stress urinary incontinence (SUI) is the most common type of urinary incontinence among middle-aged women (25,26). SUI is associated with weakened and overstretched muscles and connective tissues, which lead to reduced muscle tension in the urethral sphincter complex. This results in the inability of the urethra to close tightly during increased abdominal pressure. Particularly in younger women, neuromuscular injury during vaginal birth often causes disorders involving sphincteric mechanisms (30). The incidence of intrinsic sphincter deficiency was recently found to be greater than previously thought (18), and previous clinical studies suggested that impaired urethral closure mechanisms contribute to intrinsic sphincter deficiency in SUI.Decreased electromyographic activity of the striated urethral sphincter muscle has been detected in middle-aged women with SUI (37). Using a rat model of birth trauma, Resplande et al. (28) ...

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Section: Animalsmentioning

confidence: 99%

“…The experiments were performed with our previously described ex vivo testing apparatus (4,16), which allowed pressure-diameter data to be generated and subsequently analyzed to calculate and compare various biomechanical properties of the whole-mount urethra. Animal model and urethral isolation.…”

mentioning

confidence: 99%

Ex vivo biomechanical properties of the female urethra in a rat model of birth trauma

Prantil

Jankowski

Kaiho³

et al. 2007

American Journal of Physiology-Renal Physiology

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“…Moreover, most studies available in the literature deal with carotid arteries stemming from animals (see, e.g., Refs. 2,5,6,10,13,14,24,28,34,49). To the authors' knowledge, there are only a few in vitro tube studies of human CCA (17,25) and no in vitro tube studies on human ICA yet available in the literature.…”

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confidence: 98%

Biaxial mechanical properties of intact and layer-dissected human carotid arteries at physiological and supraphysiological loadings

Sommer

Regitnig

Költringer

et al. 2010

American Journal of Physiology-Heart and Circulatory Physiology

163

165

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Specimens of intact wall tubes of human common carotid arteries (CCA), internal carotid arteries (ICA) (n = 11, age 77.6 yr, SD 6.3), and related adventitia and media-intima tubes are mechanically examined. Cyclic, quasi-static extension-inflation tests at different axial stretches are performed on preconditioned tube specimens. Stress-free configurations show significant stress releases in the circumferential direction of the intact CCA and ICA walls and in the axial directions of the intact CCA walls and the CCA and ICA adventitias. All investigated tissues exhibit strong nonlinear, pseudoelastic mechanical behavior with small hysteresis. The "inversion" feature, where the pressure/axial stretch relationship becomes a vertical line, is found only for intact walls. Axial "inversion stretches" are 1.15 (SD 0.06) for CCA and 1.14 (SD 0.06) for ICA, and related external axial forces are 0.43 N (SD 0.15) and 0.30 N (SD 0.22), respectively. Significant negative correlations between age and axial inversion stretches for CCA (r = -0.67, P = 0.03) and ICA (r = -0.29, P = 0.04) are identified. Adventitias are very compliant at low pressures, but change into stiff tubes at high pressures. The burst pressure of the adventitia is beyond 250 kPa. A relatively low burst pressure of approximately 60 kPa is found in the media-intima tubes, in which the pressure/circumferential stretch relationships are almost independent of the axial stretches. Stress analyses indicate a high degree of material anisotropy for all investigated tissues. High circumferential and axial stresses occur in the media-intima tubes at physiological conditions. The obtained data are intended to serve for an improvement of constitutive laws, determination of constitutive parameters, and enhancing our knowledge of the mechanical functions of arteries and their associated layers in specific pathophysiological and clinical problems, such as hypertension and angioplasty with stenting.

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“…The EVPS used in this study has gone through several design iterations to improve its functionality and diversity [3,39,[244][245][246][247]. The previous generation EVPS, upon which the current design was based, is shown schematically in Several other groups have designed specialized EVPSs for studying biochemical responses of blood vessel segments to imposed biomechanical stresses.…”

Section: The Concept Of Ex Vivo Perfusion Was Originally Investigatedmentioning

confidence: 99%

“…Our laboratory's well established, validated EVPS has been used for over two decades to study the mechanopathobiological responses of intact blood vessel segments to accurately simulated physiologic biomechanical signals [3,39,[244][245][246][247][248][249]. The EVPS used in this study has gone through several iterations to improve its functionality and is described in detail below.…”

Section: History Of Ex Vivo Vascular Perfusionmentioning

confidence: 99%

In Situ Bioengineering of Arterial Vein Grafts

El-Kurdi

Morelli

Hong

et al. 2008

ASME 2008 Summer Bioengineering Conference, Parts a and B

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The autogenous saphenous vein remains the graft of choice for both coronary (500,000 annually in the US) and peripheral (80,000 annually) arterial bypass procedures. Failure of arterial vein grafts (AVGs) remains a major problem, and patients with failed grafts will die or require reoperation. Intimal hyperplasia (IH) accounts for 20% to 40% of all AVG failures. It is believed that this adverse pathological response by AVGs is largely due to their abrupt exposure to the significantly elevated circumferential wall stress (CWS) associated with the arterial system. We believe that if an AVG is given an ample opportunity to adapt and remodel to the stresses of its new environment, cellular injury may be reduced, thus limiting the initiating mechanisms of IH.The goal of this work was to develop a new mechanical conditioning paradigm, in the form of a peri-adventitially placed, biodegradable polymer wrap, to safely and functionally "arterialize" AVGs in situ. The polymer wrap was tuned so that as it degraded over a desired period of time, the mechanical support offered by it was reduced and the vein was exposed to gradually increasing levels of CWS in situ.To investigate the effects of mechanical conditioning on AVGs, we utilized both our well established, validated ex vivo vascular perfusion system (EVPS) as well as an appropriate preclinical animal model. The "engineering" component of this bioengineering study was to enhance our EVPS capabilities. Enhancements were made in the form of rigorous mathematical modeling, via subspace system identification, and automatic feedback control, via proportional iv integral and derivative control, of the arterial CWS and shear stress waveform generation capabilities of the EVPS. Pairs of freshly harvested porcine internal jugular veins (PIJVs) were perfused ex vivo under several biomechanical conditions. The acute hyperplastic response of PIJVs abruptly exposed to arterial hemodynamic conditions was compared to PIJVs perfused under normal venous conditions. In an attempt to attenuate this acute hyperplastic response, an ex vivo mechanical conditioning paradigm was imposed onto the PIJVs both via manual adjustment of EVPS parameters and via an adventitially placed tuned electrospun biodegradable polymer wrap. Early markers of IH were evaluated post-perfusion, and they included vascular smooth muscle cell apoptosis, proliferation, and phenotypic modulation. Quantification of these markers via immunohistochemical techniques provided the foundation for the final stage of this work. To assess the efficacy of the tuned electrospun biodegradable polymer wrap in attenuating the development of intimal hyperplasia in AVGs, a series of preclinical studies was performed in a pig model. PIJVs abruptly exposed to arterial levels of CWS showed a significant increase in apoptosis and in the number of synthetic smooth muscle cells, as well as a decrease in proliferation. Mechanical conditioning, via both manual adjustment of the EVPS parameters and placement of the biodegradable adventitial wra...

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Effect of variations in pressure and flow on the geometry of isolated canine carotid arteries

Cited by 24 publications

References 3 publications

Ex vivo biomechanical properties of the female urethra in a rat model of birth trauma

Ex vivo biomechanical properties of the female urethra in a rat model of birth trauma

Biaxial mechanical properties of intact and layer-dissected human carotid arteries at physiological and supraphysiological loadings

In Situ Bioengineering of Arterial Vein Grafts

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