Smooth muscle shortening: material model analysis and FE simulation

Experimental data and a suitable material model for human aortas with smooth muscle activation are not available in the literature despite the need for developing advanced grafts; the present study closes this gap. Mechanical characterization of human descending thoracic aortas was performed with and without vascular smooth muscle (VSM) activation. Specimens were taken from 13 heart-beating donors. The aortic segments were cooled in Belzer UW solution during transport and tested within a few hours after explantation. VSM activation was achieved through the use of potassium depolarization and noradrenaline as vasoactive agents. In addition to isometric activation experiments, the quasistatic passive and active stress–strain curves were obtained for circumferential and longitudinal strips of the aortic material. This characterization made it possible to create an original mechanical model of the active aortic material that accurately fits the experimental data. The dynamic mechanical characterization was executed using cyclic strain at different frequencies of physiological interest. An initial prestretch, which corresponded to the physiological conditions, was applied before cyclic loading. Dynamic tests made it possible to identify the differences in the viscoelastic behavior of the passive and active tissue. This work illustrates the importance of VSM activation for the static and dynamic mechanical response of human aortas. Most importantly, this study provides material data and a material model for the development of a future generation of active aortic grafts that mimic natural behavior and help regulate blood pressure.

Download Full-text

The Use of the Internal Perimeter to Compare Airway Size and to Calculate Smooth Muscle Shortening

American Review of Respiratory Disease ◽

10.1164/ajrccm/138.1.136 ◽

1988 ◽

Vol 138 (1) ◽

pp. 136-139 ◽

Cited By ~ 144

Author(s):

Alan L. James ◽

James C. Hogg ◽

Lindsay A. Dunn ◽

Peter D. Paré

Keyword(s):

Smooth Muscle ◽

Muscle Shortening

Download Full-text

Mechanical properties of human bronchial smooth muscle in vitro

Journal of Applied Physiology ◽

10.1152/jappl.1992.73.4.1481 ◽

1992 ◽

Vol 73 (4) ◽

pp. 1481-1485 ◽

Cited By ~ 18

Author(s):

K. Ishida ◽

P. D. Pare ◽

J. Hards ◽

R. R. Schellenberg

Keyword(s):

Mechanical Properties ◽

Smooth Muscle ◽

Electrical Field Stimulation ◽

Tracheal Smooth Muscle ◽

Cross Sectional ◽

Velocity Of Shortening ◽

Muscle Shortening ◽

Tension Generation ◽

Very High

The in vitro mechanical properties of smooth muscle strips from 10 human main stem bronchi obtained immediately after pneumonectomy were evaluated. Maximal active isometric and isotonic responses were obtained at varying lengths by use of electrical field stimulation (EFS). At the length (Lmax) producing maximal force (Pmax), resting tension was very high (60.0 +/- 8.8% Pmax). Maximal fractional muscle shortening was 25.0 +/- 9.0% at a length of 75% Lmax, whereas less shortening occurred at Lmax (12.2 +/- 2.7%). The addition of increasing elastic loads produced an exponential decrease in the shortening and velocity of shortening but increased tension generation of muscle strips stimulated by EFS. Morphometric analysis revealed that muscle accounted for 8.7 +/- 1.5% of the total cross-sectional tissue area. Evaluation of two human tracheal smooth muscle preparations revealed mechanics similar to the bronchial preparations. Passive tension at Lmax was 10-fold greater and maximal active shortening was threefold less than that previously demonstrated for porcine trachealis by us of the same apparatus. We attribute the limited shortening of human bronchial and tracheal smooth muscle to the larger load presumably provided by a connective tissue parallel elastic component within the evaluated tissues, which must be overcome for shortening to occur. We suggest that a decrease in airway wall elastance could increase smooth muscle shortening, leading to excessive responses to contractile agonists, as seen in airway hyperresponsiveness.

Download Full-text

In vivo loads on airway smooth muscle: the role of noncontractile airway structures

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y92-077 ◽

1992 ◽

Vol 70 (4) ◽

pp. 602-606 ◽

Cited By ~ 5

Author(s):

Philip Robinson ◽

Mitsushi Okazawa ◽

Tony Bai ◽

Peter Paré

Keyword(s):

Smooth Muscle ◽

Airway Smooth Muscle ◽

Muscle Activation ◽

Muscle Length ◽

Tracheal Cartilage ◽

Elastic Load ◽

Muscle Shortening ◽

Trachealis Muscle

The degree of airway smooth muscle contraction and shortening that occurs in vivo is modified by many factors, including those that influence the degree of muscle activation, the resting muscle length, and the loads against which the muscle contracts. Canine trachealis muscle will shorten up to 70% of starting length from optimal length in vitro but will only shorten by around 30% in vivo. This limitation of shortening may be a result of the muscle shortening against an elastic load such as could be applied by tracheal cartilage. Limitation of airway smooth muscle shortening in smaller airways may be the result of contraction against an elastic load, such as could be applied by lung parenchymal recoil. Measurement of the elastic loads applied by the tracheal cartilage to the trachealis muscle and by lung parenchymal recoil to smooth muscle of smaller airways were performed in canine preparations. In both experiments the calculated elastic loads applied by the cartilage and the parenchymal recoil explained in part the limitation of maximal active shortening and airway narrowing observed. We conclude that the elastic loads provided by surrounding structures are important in determining the degree of airway smooth muscle shortening and the resultant airway narrowing.Key words: elastic loads, tracheal cartilage, airway smooth muscle shortening.

Download Full-text

FE-simulation of machining processes with a new material model

Journal of Materials Processing Technology ◽

10.1016/j.jmatprotec.2013.10.014 ◽

2014 ◽

Vol 214 (3) ◽

pp. 599-611 ◽

Cited By ~ 47

Author(s):

S. Buchkremer ◽

B. Wu ◽

D. Lung ◽

S. Münstermann ◽

F. Klocke ◽

...

Keyword(s):

Fe Simulation ◽

Material Model ◽

Machining Processes ◽

New Material

Download Full-text

Tissue elastance influences airway smooth muscle shortening: comparison of mechanical properties among different species

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y02-112 ◽

2002 ◽

Vol 80 (9) ◽

pp. 865-871 ◽

Cited By ~ 10

Author(s):

Anabelle M. Opazo Saez ◽

R Robert Schellenberg ◽

Mara S Ludwig ◽

Richard A Meiss ◽

Peter D Paré

Keyword(s):

Mechanical Properties ◽

Smooth Muscle ◽

Airway Smooth Muscle ◽

Isometric Force ◽

Published Data ◽

Passive Tension ◽

Active Force ◽

Muscle Shortening ◽

Human Airways ◽

Tissue Elastance

We have observed striking differences in the mechanical properties of airway smooth muscle preparations among different species. In this study, we provide a novel analysis on the influence of tissue elastance on smooth muscle shortening using previously published data from our laboratory. We have found that isolated human airways exhibit substantial passive tension in contrast to airways from the dog and pig, which exhibit little passive tension (<5% of maximal active force versus ~60% for human bronchi). In the dog and pig, airway preparations shorten up to 70% from Lmax (the length at which maximal active force occurs), whereas human airways shorten by only ~12% from Lmax. Isolated airways from the rabbit exhibit relatively low passive tension (~22% Fmax) and shorten by 60% from Lmax. Morphologic evaluation of airway cross sections revealed that 25-35% of the airway wall is muscle in canine, porcine, and rabbit airways in contrast to ~9% in human airway preparations. We postulate that the large passive tension needed to stretch the muscle to Lmax reflects the high connective tissue content surrounding the smooth muscle, which limits shortening during smooth muscle contraction by imposing an elastic load, as well as by causing radial constraint.Key words: isometric force, isotonic shortening, elastance.

Download Full-text

Limitation of airway smooth muscle shortening by cartilage stiffness and lung elastic recoil in rabbits

Journal of Applied Physiology ◽

10.1152/jappl.1993.75.2.738 ◽

1993 ◽

Vol 75 (2) ◽

pp. 738-744 ◽

Cited By ~ 9

Author(s):

R. H. Moreno ◽

C. Lisboa ◽

J. C. Hogg ◽

P. D. Pare

Keyword(s):

Smooth Muscle ◽

Effective Dose ◽

Airway Smooth Muscle ◽

Maximal Response ◽

Positive End Expiratory Pressure ◽

Elastic Recoil ◽

Pulmonary Resistance ◽

Muscle Shortening

Airway smooth muscle can contract to 20% of its starting length when stimulated maximally and allowed to contract isotonically in vitro. In vivo airway smooth muscle contraction of this degree would result in widespread airway closure. We hypothesized that elastic loads related to cartilage stiffness and lung parenchyma-airway interdependence limit in vivo airway smooth muscle shortening. We measured pulmonary resistance in anesthetized tracheostomized New Zealand White rabbits before and after intravenous treatment with papain in a concentration that produced generalized cartilage softening. Papain treatment caused a significant increase in pulmonary resistance that was completely reversed by application of 4 cmH2O positive end-expiratory pressure and that was partially reversed by vagotomy. Papain pretreatment also resulted in a substantial alteration in the pulmonary resistance-dose relationship to intravenously administered acetylcholine. In addition, maximal resistance after the highest concentration of acetylcholine was greater in papain-treated animals than in the control animals, but the position of the dose-response relationship was not shifted (i.e., there was no change in the effective dose causing 50% maximal response). Application of 4 cmH2O positive end-expiratory pressure in untreated animals resulted in a marked decrease in the bronchoconstriction produced by an effective dose of acetylcholine causing 50% of maximal response, whereas application of 4 cmH2O negative end-expiratory pressure resulted in a marked enhancement of the bronchoconstrictor response to the same intravenous dose of acetylcholine. We conclude that cartilage elasticity and lung recoil are important determinants of the ability of airway smooth muscle to shorten and produce airway narrowing in vivo.

Download Full-text

Shortening of airway smooth muscle is modulated by prolonging the time without simulated deep inspirations in ovine tracheal strips

Journal of Applied Physiology ◽

10.1152/japplphysiol.00423.2019 ◽

2019 ◽

Vol 127 (6) ◽

pp. 1528-1538 ◽

Cited By ~ 1

Author(s):

Morgan Gazzola ◽

Fatemeh Khadangi ◽

Marine Clisson ◽

Jonathan Beaudoin ◽

Marie-Annick Clavel ◽

...

Keyword(s):

Smooth Muscle ◽

Airway Smooth Muscle ◽

In Vitro Study ◽

Time Interval ◽

Tidal Breathing ◽

Bronchodilator Effect ◽

Airway Narrowing ◽

Biochemical Processes ◽

Muscle Shortening

The shortening of airway smooth muscle (ASM) is greatly affected by time. This is because stimuli affecting ASM shortening, such as bronchoactive molecules or the strain inflicted by breathing maneuvers, not only alter quick biochemical processes regulating contraction but also slower processes that allow ASM to adapt to an ever-changing length. Little attention has been given to the effect of time on ASM shortening. The present study investigates the effect of changing the time interval between simulated deep inspirations (DIs) on ASM shortening and its responsiveness to simulated DIs. Excised tracheal strips from sheep were mounted in organ baths and either activated with methacholine or relaxed with isoproterenol. They were then subjected to simulated DIs by imposing swings in distending stress, emulating a transmural pressure from 5 to 30 cmH2O. The simulated DIs were intercalated by 2, 5, 10, or 30 min. In between simulated DIs, the distending stress was either fixed or oscillating to simulate tidal breathing. The results show that although shortening was increased by prolonging the interval between simulated DIs, the bronchodilator effect of simulated DIs (i.e., the elongation of the strip post- vs. pre-DI) was not affected, and the rate of re-shortening post-simulated DIs was decreased. As the frequency with which DIs are taken increases upon bronchoconstriction, our results may be relevant to typical alterations observed in asthma, such as an increased rate of re-narrowing post-DI. NEW & NOTEWORTHY The frequency with which patients with asthma take deep inspirations (DIs) increases during bronchoconstriction. This in vitro study investigated the effect of changing the time interval between simulated DIs on airway smooth muscle shortening. The results demonstrated that decreasing the interval between simulated DIs not only decreases shortening, which may be protective against excessive airway narrowing, but also increases the rate of re-shortening post-simulated DIs, which may contribute to the increased rate of re-narrowing post-DI observed in asthma.

Download Full-text

Determinants of airway smooth muscle shortening in excised canine lobes

Journal of Applied Physiology ◽

10.1152/jappl.1995.78.2.608 ◽

1995 ◽

Vol 78 (2) ◽

pp. 608-614 ◽

Cited By ~ 21

Author(s):

M. Okazawa ◽

S. Vedal ◽

L. Verburgt ◽

R. K. Lambert ◽

P. D. Pare

Keyword(s):

Smooth Muscle ◽

Airway Smooth Muscle ◽

Airway Wall ◽

High Concentration ◽

Airway Narrowing ◽

Wall Area ◽

Muscle Shortening ◽

Mechanical Factors ◽

Airway Dimensions ◽

Wall Geometry

There is marked heterogeneity of airway narrowing in intraparenchymal airways in response to bronchoconstricting stimuli. We hypothesized that this heterogeneity results from variations in the structure of the airway wall. Freshly excised dog lung lobes were inflated to transpulmonary pressures (PL) of between 5 and 15 cmH2O, and an aerosol containing a high concentration of carbachol was administered. The lobes were fixed and processed for light-microscopic examination and morphometric analysis of membranous airway dimensions. The relationships of smooth muscle shortening to PL and airway dimensions were analyzed using multiple linear regression. The results show that airway smooth muscle shortening was greater at lower PL and in airways with larger internal perimeter and a greater number of folds per internal perimeter and that it was less in airways with greater inner wall area. We conclude that the magnitude and variability of airway smooth muscle shortening and airway narrowing in response to maximal constricting stimuli are influenced by mechanical factors related to airway wall geometry.

Download Full-text