20 results match your criteria decrease hysteresivity

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Flexibility of microstructural adaptations in airway smooth muscle.

J Appl Physiol (1985) 2021 May 15;130(5):1555-1561. Epub 2021 Apr 15.

Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Quebec, Canada.

The airway smooth muscle undergoes an elastic transition during a sustained contraction, characterized by a gradual decrease in hysteresivity caused by a relatively greater rate of increase in elastance than resistance. We recently demonstrated that these mechanical changes are more likely to persist after a large strain when they are acquired in dynamic versus static conditions; as if the microstructural adaptations liable for the elastic transition are more flexible when they evolve in dynamic conditions. The extent of this flexibility is undefined. Read More

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Lung Functioning and Inflammation in a Mouse Model of Systemic Juvenile Idiopathic Arthritis.

Front Immunol 2021 12;12:642778. Epub 2021 Mar 12.

Laboratory of Immunobiology, Department of Microbiology and Immunology, KU Leuven, Leuven, Belgium.

Systemic juvenile idiopathic arthritis (sJIA) is an immune disorder characterized by fever, skin rash, arthritis and splenomegaly. Recently, increasing number of sJIA patients were reported having lung disease. Here, we explored lung abnormalities in a mouse model for sJIA relying on injection of IFN-γ deficient (IFN-γ KO) mice with complete Freund's adjuvant (CFA). Read More

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Airway mechanics and lung tissue viscoelasticity: effects of altered blood hematocrit in the pulmonary circulation.

J Appl Physiol (1985) 2016 07 9;121(1):261-7. Epub 2016 Jun 9.

Pathophysiological Experimental Platform, Department of Anesthesiology, Pharmacology and Intensive Care, University of Geneva, Geneva, Switzerland; and Pediatric Anesthesia Unit, Geneva Children's Hospital, Geneva, Switzerland.

The contribution of the hematocrit (Hct) of the blood in the pulmonary vasculature to the overall lung mechanics has not been characterized. We therefore set out to establish how changes of the Hct level in the pulmonary circulation affect the airway and lung tissue viscoelastic properties. The Hct level of the blood in an isolated perfused rat lung model was randomly altered. Read More

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The resistive and elastic work of breathing during exercise in patients with chronic heart failure.

Eur Respir J 2012 Jun 27;39(6):1449-57. Epub 2011 Oct 27.

Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA.

Patients with heart failure (HF) display numerous derangements in ventilatory function, which together serve to increase the work of breathing (W(b)) during exercise. However, the extent to which the resistive and elastic properties of the respiratory system contribute to the higher W(b) in these patients is unknown. We quantified the resistive and elastic W(b) in patients with stable HF (n = 9; New York Heart Association functional class I-II) and healthy control subjects (n = 9) at standardised levels of minute ventilation (V'(E)) during graded exercise. Read More

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Alpha-1 antitrypsin is markedly decreased following pulmonary F. tularensis challenge.

Front Cell Infect Microbiol 2011 26;1:20. Epub 2011 Dec 26.

Department of Biology, South Texas Center for Emerging Infectious Diseases, University of Texas at San Antonio, San Antonio, TX, USA; Department of Biology, Center of Excellence in Infection Genomnics, The University of Texas at San Antonio, San Antonio, TX, USA.

Neutrophils form the first line of defense during infection and are indispensable in this function. The neutrophil elastase is a key effector molecule of the innate immune system with potent antimicrobial activity against Gram-negative bacteria, spirochaetes, and fungi. However, the release of neutrophil elastase during bacterial infection must be checked otherwise its release in the extracellular milieu will result in damage to surrounding tissues. Read More

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The effect of fetal tracheal occlusion on lung tissue mechanics and tissue composition.

Pediatr Pulmonol 2009 Feb;44(2):112-21

Faculty of Medicine, Center for Surgical Technologies, Katholieke Universiteit Leuven, Leuven, Belgium.

Fetal tracheal occlusion (TO) is currently used to treat severe cases of congenital diaphragmatic hernia (DH). Clinical and experimental studies suggest an improved postnatal outcome, but lung tissue mechanics after TO have not been studied. We determined the effect of TO on mechanical impedance and lung tissue components in a rabbit model for DH. Read More

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February 2009

Paxillin phosphorylation, actin polymerization, noise temperature, and the sustained phase of swine carotid artery contraction.

Am J Physiol Cell Physiol 2007 Sep 27;293(3):C993-1002. Epub 2007 Jun 27.

Cardiovascular Division, Univ. of Virginia Health System, PO Box 800146, Charlottesville, VA 22908-0146, USA.

Histamine stimulation of swine carotid artery induces both contraction and actin polymerization. The importance of stimulus-induced actin polymerization is not known. Tyrosine phosphorylation of the scaffolding protein paxillin is thought to be an important regulator of actin polymerization. Read More

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September 2007

Vitamin A deficiency alters pulmonary parenchymal collagen and tissue mechanics.

Respir Physiol Neurobiol 2007 Jun 25;156(3):312-9. Epub 2006 Nov 25.

Department of Veterans Affairs Research Service, University of Iowa Carver College of Medicine, IA, USA.

The mechanical properties of the pulmonary parenchyma are strongly influenced by the collagen and elastic fibers that course through the alveolar interstitium and interconnect the bronchovascular bundles. Vitamin A deficiency (VAD) produces effacement and remodeling of the alveolar architecture, resulting in alternating areas of alveolar dilatation and collapse. To better understand the mechanical consequences and reversibility of this remodeling process, we have examined how the remodeling of collagen and elastic fibers correlates with the mechanical properties of the lung parenchyma in VAD rats. Read More

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The estimation of lung mechanics parameters in the presence of pathology: a theoretical analysis.

Ann Biomed Eng 2006 Mar 9;34(3):384-92. Epub 2006 Feb 9.

Vermont Lung Center Departments of Medicine and Molecular Physiology and Biophysics, University of Vermont Burlington, Burlington, VT 05405-0075, USA.

Mechanical lung function is frequently assessed in terms of lung resistance (R (L)), lung elastance (E (L)), and airway resistance (R (aw)). These quantities are determined by measuring input impedance at various oscillation frequencies, and allow lung tissue resistance (R (t)) to be estimated as the difference between R (L) and R (aw). These various parameters change in characteristic ways in the presence of lung pathology. Read More

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Probing the viscoelastic behavior of cultured airway smooth muscle cells with atomic force microscopy: stiffening induced by contractile agonist.

Biophys J 2005 Apr 21;88(4):2994-3007. Epub 2005 Jan 21.

Department of Physics, Nanoscience & Scanning Probe Microscopy Group, McGill University, Montreal, Quebec, Canada.

Complex rheology of airway smooth muscle cells and its dynamic response during contractile stimulation involves many molecular processes, foremost of which are actomyosin cross-bridge cycling and actin polymerization. With an atomic force microscope, we tracked the spatial and temporal variations of the viscoelastic properties of cultured airway smooth muscle cells. Elasticity mapping identified stiff structural elements of the cytoskeletal network. Read More

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Corticotropin-releasing hormone deficiency increases allergen-induced airway inflammation in a mouse model of asthma.

J Allergy Clin Immunol 2004 Oct;114(4):747-54

Physiology Program, Department of Environmental Health, Harvard School of Public Health, Boston, MA 02115-6021, USA.

Background: Corticotropin-releasing hormone (CRH) is a major regulator of adrenocorticotropic hormone and the production of glucocorticoids by the adrenal gland. Abnormal regulation of CRH and endogenous glucocorticoids has been implicated in the pathogenesis of asthma.

Objective: We postulated that CRH deficiency could increase asthma severity by disrupting hypothalamus-pituitary-adrenal axis function and the induction of glucocorticoids through inflammatory and physiologic stress. Read More

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October 2004

Variability in preterm lamb lung mechanics after intra-amniotic endotoxin is associated with changes in surfactant pool size and morphometry.

Am J Physiol Lung Cell Mol Physiol 2004 Nov 9;287(5):L992-8. Epub 2004 Jul 9.

Centre for Child Health Research, The University of Western Australia, Perth, Australia.

Antenatal exposure to intra-amniotic (i.a.) endotoxin initiates a complex series of events, including an inflammatory cascade, increased surfactant production, and alterations to lung structure. Read More

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November 2004

Tissue heterogeneity in the mouse lung: effects of elastase treatment.

J Appl Physiol (1985) 2004 Jul 12;97(1):204-12. Epub 2004 Mar 12.

Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA.

We developed a network model in an attempt to characterize heterogeneity of tissue elasticity of the lung. The model includes a parallel set of pathways, each consisting of an airway resistance, an airway inertance, and a tissue element connected in series. The airway resistance, airway inertance, and the hysteresivity of the tissue elements were the same in each pathway, whereas the tissue elastance (H) followed a hyperbolic distribution between a minimum and maximum. Read More

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Overexpression of TGF-alpha increases lung tissue hysteresivity in transgenic mice.

J Appl Physiol (1985) 2001 Dec;91(6):2730-4

TVW Telethon Institute for Child Health Research, West Perth 6872, WA, Australia.

Increased transforming growth factor (TGF)-alpha has been observed in neonatal chronic lung disease. Lungs of transgenic mice that overexpress TGF-alpha develop enlarged air spaces and pulmonary fibrosis compared with wild-type mice. We hypothesized that these pathological changes may alter the mechanical coupling of viscous and elastic forces within lung parenchyma. Read More

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December 2001

Effects of gestation and antenatal steroid on airway and tissue mechanics in newborn lambs.

Am J Respir Crit Care Med 2001 Apr;163(5):1158-63

TVW Telethon Institute for Child Health Research, Perth, Australia.

The aim of this study was to partition airway and parenchymal mechanics in newborn lambs at different gestations and following variable exposure to antenatal maternal betamethasone using the forced oscillation technique (FOT). Pulmonary impedance data were collected in 37 sedated and intubated apneic lambs with the FOT between 0.5 and 20 Hz and fitted by a model to estimate airway resistance (Raw) and inertance (Iaw) and the coefficients of tissue resistance (GL) and elastance (HL). Read More

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Effects of collagenase and elastase on the mechanical properties of lung tissue strips.

J Appl Physiol (1985) 2000 Jul;89(1):3-14

Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215, USA.

The dynamic stiffness (H), damping coefficient (G), and harmonic distortion (k(d)) characterizing tissue nonlinearity of lung parenchymal strips from guinea pigs were assessed before and after treatment with elastase or collagenase between 0.1 and 3.74 Hz. Read More

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Dynamically determined contractile states of airway smooth muscle.

Am J Respir Crit Care Med 1998 Nov;158(5 Pt 3):S176-8

Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA.

The contractile state of maximally activated bovine airway smooth muscle is altered during imposed tidal stretches that simulate the action of breathing. When the amplitude of imposed tidal stretch is very small (0.25% of muscle optimal length), the steady-state value of the muscle force, F, approximates the isometric force, the muscle stiffness, E, is large, and the muscle hysteresivity, eta, is small. Read More

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November 1998

Dissociation between hysteresivity and tension in constricted tracheal and parenchymal strips.

J Appl Physiol (1985) 1998 Jul;85(1):91-7

Meakins-Christie Laboratories, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada H2X 2P2.

The object of this study was to investigate how changes in the contractile state of smooth muscle would modify oscillatory mechanics of tracheal muscle and lung parenchyma during agonist challenge. Guinea pig tracheal and parenchymal lung strips were suspended in an organ bath. Measurements of length (L) and tension (T) were recorded during sinusoidal oscillations under baseline conditions and after challenge with 1 mM ACh. Read More

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A model of transient oscillatory pressure-flow relationships of canine airways.

Ann Biomed Eng 1995 Sep-Oct;23(5):682-90

Meakins-Christie Laboratories, McGill University, Montreal, Quebec, Canada.

In a previous paper (27) we developed a lumped parameter model of canine pulmonary airway mechanics featuring airway wall elasticity, gas inertance, and laminar and turbulent gas flow. The model accurately accounted for the steady-state pressure-flow data we obtained during sinusoidal cycling of the lung following a period of apnea. In the present paper, we extend the model to account for the transient decrease in the amplitude of the trans-airway pressure swings that we observed immediately following the apnea, which we have shown to be due to a vagally mediated bronchodilatation reflex. Read More

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January 1996

How mode of stimulus affects the relative contribution of elastance and hysteresivity to changes in lung tissue resistance.

J Appl Physiol (1985) 1995 Jan;78(1):282-7

Meakins-Christie Laboratories, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada.

Challenges with high concentrations of constrictor agonist delivered by intravenous vs. aerosol result in different modifications of the mechanical properties of lung tissues. We questioned whether low doses of a smooth muscle agonist administered via different routes (aerosol, i. Read More

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January 1995
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