Alterations In Viscoelastic Properties Research Articles

Biological Preparation and Mechanical Technique for Determining Viscoelastic Properties of Zonular Fibers.

Elasticity is essential to the function of tissues such as blood vessels, muscles, and lungs. This property is derived mostly from the extracellular matrix (ECM), the protein meshwork that binds cells and tissues together. How the elastic properties of an ECM network relate to its composition, and whether the relaxation properties of the ECM play a physiological role, are questions that have yet to be fully addressed. Part of the challenge lies in the complex architecture of most ECM systems and the difficulty in isolating ECM components without compromising their structure. One exception is the zonule, an ECM system found in the eye of vertebrates. The zonule comprises fibers hundreds to thousands of micrometers in length that span the cell-free space between the lens and the eyewall. In this report, we describe a mechanical technique that takes advantage of the highly organized structure of the zonule to quantify its viscoelastic properties and to determine the contribution of individual protein components. The method involves dissection of a fixed eye to expose the lens and the zonule and employs a pull-up technique that stretches the zonular fibers equally while their tension is monitored. The technique is relatively inexpensive yet sensitive enough to detect alterations in viscoelastic properties of zonular fibers in mice lacking specific zonular proteins or with aging. Although the method presented here is designed primarily for studying ocular development and disease, it could also serve as an experimental model for exploring broader questions regarding the viscoelastic properties of elastic ECM's and the role of external factors such as ionic concentration, temperature, and interactions with signaling molecules.

The Assessment of Upper-Limb Spasticity Based on a Multi-Layer Process Using a Portable Measurement System.

Spasticity is a common disabling complication caused by the upper motor neurons dysfunction following neurological diseases such as stroke. Currently, the assessment of the spastic hypertonia triggered by stretch reflexes is manually performed by clinicians using perception-based clinical scales, however, their reliability is still questionable due to the inter-rater and intra-rater variability. In order to objectively quantify the complex spasticity phenomenon in post-stroke patients, this study proposed a multi-layer assessment system based on a novel measurement device. The exoskeletal device was developed to synchronously record the kinematic, biomechanical and electrophysiological information in sixteen spastic patients and ten age-matched healthy subjects, while the spastic limb was stretched at low, moderate and high velocities. The mechanical impedance of the elbow joint was identified using a modified genetic algorithm to quantify the alterations in viscoelastic properties underlying pathological resistance. Simultaneously, the time-frequency features were extracted from the surface electromyography (sEMG) signals to reveal the neurophysiological mechanisms of the spastic muscles. By concatenating these single-layer decisions, a support vector regression (SVR)-based fusion model was developed to generate a more comprehensive quantification of spasticity severity. Experimental results demonstrated that the stiffness and damping components of the spastic arm significantly deviated from the nonspastic baseline, and strong correlations were observed between the proposed spasticity assessment and the severity level measured by clinical scales ( R = 0.86, P = 1.67e - 5 ), as well as the tonic stretch reflex threshold (TSRT) value ( R = - 0.89, P = 3.54e - 6 ). These promising results suggest that the proposed assessment system holds great potential to support the clinical diagnosis of motor abnormalities in spastic patients, and ultimately enables optimal adjustment of treatment protocols.

Viscoelastic properties of lower extremity muscles after elite track cycling sprint events: a case report

Sprint cycling events require a high level of anaerobic capacity and therefore may affect peripheral fatigue throughout exercise-induced muscle damage. In fact, those alterations might decrease power generation. This study was performed on a 23 years old elite track cyclist started in men’s sprint. The measurements included power output (W) and cadence (rpm), lactate concentration (La-), heart rate (bpm), Rated Perceived Exertion scale and viscoelastic properties analysis. The present study have shown a new approach to monitor the muscle properties of the lower extremity after 200m flying start and repeated sprint races. Therefore, we hypothesized that repeated sprint races might lead to alterations in viscoelastic properties of lower extremity muscles. In track cycling, especially sprint events these variations may lead to increasing muscle fatigue. Furthermore, training control and monitoring related to assessment of muscles properties can be a source of counteracting injuries and relieving fatigue.

Excessive Extracellular ATP Desensitizes P2Y2 and P2X4 ATP Receptors Provoking Surfactant Impairment Ending in Ventilation-Induced Lung Injury.

Stretching the alveolar epithelial type I (AT I) cells controls the intercellular signaling for the exocytosis of surfactant by the AT II cells through the extracellular release of adenosine triphosphate (ATP) (purinergic signaling). Extracellular ATP is cleared by extracellular ATPases, maintaining its homeostasis and enabling the lung to adapt the exocytosis of surfactant to the demand. Vigorous deformation of the AT I cells by high mechanical power ventilation causes a massive release of extracellular ATP beyond the clearance capacity of the extracellular ATPases. When extracellular ATP reaches levels >100 μM, the ATP receptors of the AT II cells become desensitized and surfactant impairment is initiated. The resulting alteration in viscoelastic properties and in alveolar opening and collapse time-constants leads to alveolar collapse and the redistribution of inspired air from the alveoli to the alveolar ducts, which become pathologically dilated. The collapsed alveoli connected to these dilated alveolar ducts are subject to a massive strain, exacerbating the ATP release. After reaching concentrations >300 μM extracellular ATP acts as a danger-associated molecular pattern, causing capillary leakage, alveolar space edema, and further deactivation of surfactant by serum proteins. Decreasing the tidal volume to 6 mL/kg or less at this stage cannot prevent further lung injury.

Viscoelastic interactions between polydeoxyribonucleotide and ophthalmic excipients

This study investigated the interaction between polydeoxyribonucleotide (PDRN) and several ionic and nonionic isotonic agents, thickeners and a preservative that were employed as excipients in ophthalmic preparations. Interaction of each individual excipient and PDRN aqueous solution was evaluated by analyzing their rheological properties. Rheological properties of PDRN solutions were evaluated by dynamic oscillatory shear tests and values of elastic modulus (G′), viscous modulus (G″) and loss tangent (tan δ) were used to assess the relative changes in viscoelastic properties. At given concentrations, sodium chloride was found to show alteration in viscoelastic properties of PDRN solution while nonionic isotonic agents like d-glucose and d-sorbitol did not alter them. Similarly, nonionic water soluble polymers like polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC) also did not interact with PDRN to alter the viscoelastic properties. However, there were changes observed when carbopol 940 was used as a thickener. Therefore, PDRN was found to interact with ionic excipients and the interactions were negligible when nonionic materials were examined, which suggests that nonionic excipients are suitable to be formulated with PDRN.

Alterations in viscoelastic properties following premature birth may lead to hypertension and cardiovascular disease development in later life.

The aim of this review was to identify the underlying relationship between preterm birth and the development of cardiovascular diseases. Preterm birth significantly affects the elastin content and viscoelastic properties of the vascular extracellular matrix in human arteries. Inadequate elastin synthesis during early development may cause a permanent increase in arterial stiffness in adulthood. Early and permanent alterations in viscoelastic properties may lead to hypertension and cardiovascular disease development in adults born prematurely.

Effects of hydrothermal aging on glass–fiber/polyetherimide (PEI) composites

The moisture absorption behavior and the influence of moisture on thermal and mechanical properties of glass–fiber/polyetherimide (PEI) laminates have been investigated. The laminates were exposed to hydrothermal aging at two different temperatures and high moisture rates. The properties of as-received and hydrothermally aged samples were compared. The hydrothermally aged laminates contained a large amount of moisture which caused decrease in the glass transition temperature and deterioration in mechanical properties (interlaminar shear strength, flexural modulus, bearing strength, etc.). Fractographic analysis revealed interfacial debonding as the dominant failure mechanism, indicating a strong influence of water degradation on fracture toughness results. Alterations in visco-elastic properties of glass/PEI composite which was exposed to hydrothermal aging were analyzed with the dynamic mechanical thermal analysis (DMTA) method. DMTA tests give evidence of plasticization of the PEI matrix.

An acoustic wave sensor incorporated with a microfluidic chip for analyzing muscle cell contraction.

We report the fabrication of a microfluidic chip or lab-on-a-chip integrated with a thickness-shear mode (TSM) acoustic wave sensor for muscle cell analysis. The sensor, essentially an AT-cut quartz crystal, serves as a detector for recording changes in acoustic wave properties occurring in an attached cardiomyocyte (single heart muscle cell) during its contraction and relaxation. Presumably, the changes resulted from alterations in viscoelastic properties (e.g. stiffness) of the cells. The effects of excitation electrode size, the presence of a microfluidic channel plate, and liquid loading on the sensor were first examined. Thereafter, muscle cell contraction analysis upon chemical stimuli were described. The potential of the chip for screening of cardiovascular drugs is discussed.

Electrothermal shrinkage reduces laxity but alters creep behavior in a lapine ligament model

Thermal denaturation of collagen in ligament tissue has the potential to enhance arthroscopic shoulder stabilization. Previous studies have shown that laser energy produces significant capsular shortening without alteration of viscoelastic properties, but little information is available on the effects of radio frequency electrothermal energy. We assessed the acute effects of radio frequency shrinkage with use of the lapine medial collateral ligament model, in which the tibial insertion was shifted proximally to produce abnormal laxity. Thermal treatment resulted in restoration of laxity from 3.33 ± 0.25 mm to 0.66 ± 0.31 mm, which was not significantly different from medial collateral ligaments replaced anatomically (0.50 ± 0.34 mm). When tested at 4.1 megapascals, cyclic and static creep strains were increased twofold to threefold in thermally-treated ligaments (P <.01), and partial failure occurred in 2 of 8 cases. We conclude that radio frequency electrothermal shrinkage is effective at reducing laxity but significantly alters viscoelastic properties, posing a risk of recurrent stretching-out at “physiological” loads. (J Shoulder Elbow Surg 2001;10:1-6.)

Interfacial Properties of Biotin Conjugate−Avidin Complexes Studied by Acoustic Wave Sensor

The adsorption of avidin, neutravidin, and biotin-labeled dextran 10,000, dextran 70,000, bovine albumin, and insulin to the gold electrodes of thickness-shear-mode acoustic wave devices was studied in a flow injection analysis configuration. Electrodes with different surface rugosity and free energy were also examined. Changes in series resonance frequency for the various molecules as a result of electrode adsorption cannot be explained in terms of the conventional mass-response effect. Perturbation of the properties of the protein and polysaccharide layers, such as their viscosity, and acoustic coupling phenomena offer a more reasonable basis to evaluate the results. In an analogous fashion, the acoustic wave sensor signals obtained for the formation of the various avidin− and neutravidin−biotin conjugate samples do not correspond to the additional mass deposited on the device surface. The responses for the binding of biotinylated insulin to avidin and to the nonglycosylated form of the parent molecule were completely different. This result is ascribed to a difference of surface free energy associated with the two protein-based interfaces. The acoustic wave sensor was also employed to investigate the formation of avidin−biotin conjugate multilayer structures on the surface of the device. Multilayer buildup is detectable for several pairs of avidin−biotin interactions, but the corresponding shifts in series resonance frequency gradually diminish in magnitude. Finally, the introduction of biotin itself appears to result in structural changes in the multilayer deposit, causing alterations in viscoelastic properties.

The effect of processing on rheological and molecular characteristics of a low density polyethylene

AbstractThe viscoelastic responses of some molten polymers, and particularly of low density polyethylene (LDPE), are known to vary with processing history. Reasons for the variations include the effects of shear history on morphological states of the polymer, or on its molecular weight parameters. A typical low density polyethylene has been used to test the shear‐history dependence concept following a variety of processing steps. The polymer was sheared in single‐screw and twin‐screw extruders, and in a high speed melter / mixer (Gelimat). Samples also were precipitated from very dilute solutions in trichlorobenzene and in p‐xylene. GPC analyses showed that, in general, these procedures did not affect the various moments of molecular weight. An exception was the Gelimat‐mixed sample, for which mild reductions in Mn and Mw were noted. In contrast, melt viscosity and elasticity readings, the former from low shear evaluations and the latter from extrudate swelling, were affected by the various procedures. A drop in melt viscosity and in elasticity was observed, being most pronounced for precipitated and twin‐screw extruded versions of the LDPE. Reductions also were observed in the specimen sheared in the Gelimat instrument. Following conditioning at the test extrusion temperature (170°C), viscous and elastic responses tended to revert to those of the unsheared control sample, the exception again being the sample sheared in the Gelimat melter / mixer. Of the various mechanisms proposed in the literature to account for transient property changes such as those reported, temporary changes in the degree of chain entanglement appear the most satisfactory explanation. Irreversible alterations in viscoelastic properties may be associated with changes in molecular weights due to processing at high shear.

Some dynamic factors in compressive deformity of the cervical spinal cord.

An investigation into the relative elastic and non-elastic components of compressive deformity of the cervical spinal cord has been made. Sixteen patients were examined by computed myelography with the neck flexed and extended, and one fresh specimen of a human spinal cord was studied under reversible transverse compression with the specimen in a stretched and shortened state. In conditions of transverse compression cord tissue undergoes an alteration in viscoelastic properties, manifesting itself as reduced expansion of the compressed segment as the cord shortens, which in some cases is independent of whether the agent is seen to actually contact the cord. The presence of degenerative changes in cord substance probably accentuates this alteration in mechanical properties.

Age-associated alterations in viscoelastic properties of canine aortic strips.

Many studies have delineated the changes in the elastic properties of arterial tissue as a function of age. Despite the fact that viscoelasticity is a prominent feature of these tissues, there is little information or characterization of age-associated changes in viscoelastic properties, over a wide range of smooth muscle activation, particularly in nonhuman tissue where atherosclerosis is not a confounding factor. In the present study, using small sinusoidal length perturbations, we determined the dynamic stiffness properties across a wide range of lengths (stretch ratios from 100 to 135%) and frequencies (from 0.25 to 35 Hz) in strips excised from ascending and descending aortas from six young (2 to 4-year-old) and 12 senescent (10- to 13-year-old) beagles. Studies were performed with the smooth muscle fully activated with calcium and norepinephrine, as well as fully inactivated with cyanide, iodoacetate, and dinitrophenol. There was a cubic nonlinear dependence of stiffness modulus on length only in senescent tissue and, surprisingly, little frequency dependence in tissue of either age. Compared to the young aortas, the three-dimensional surface representing the dependence of stiffness modulus on length and frequency from both the ascending and descending regions of aged aortas was displaced higher on the stiffness axis both with the muscle fully activated and inactivated. This age difference was accentuated at longer lengths. The phase lag between force and length was greater in the young vs. the old strips only in the activated, ascending aortic tissue. We found no age differences in the content of elastin, collagen, or in the collagen/elastin ratio, to account for these mechanical property differences.(ABSTRACT TRUNCATED AT 250 WORDS)

Passive mechanics and connective tissue composition of canine arteries.

Passive mechanics and connective tissue composition of canine arteries.

Mechanical properties of arteries

Mechanical properties of arteries

Carotid artery mechanics, connective tissue, and electrolyte changes in puppies.

ARTICLESCarotid artery mechanics, connective tissue, and electrolyte changes in puppiesRH Cox, AW Jones, and GM FischerRH Cox, AW Jones, and GM FischerPublished Online:01 Sep 1974https://doi.org/10.1152/ajplegacy.1974.227.3.563MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByAxial nonuniformity of geometric and mechanical properties of mouse aorta is increased during postnatal growthYi Huang, Xiaomei Guo, and Ghassan S. Kassab1 February 2006 | American Journal of Physiology-Heart and Circulatory Physiology, Vol. 290, No. 2Vascular AdaptationIn vivo and in vitro mechanical properties of the sheep thoracic aorta in the perinatal period and adulthoodSarah M. Wells, B. Lowell Langille, and S. Lee Adamson1 May 1998 | American Journal of Physiology-Heart and Circulatory Physiology, Vol. 274, No. 5Mechanical Properties and Active Remodeling of Blood VesselsMechanical Properties of Arteries and Arterial GraftsSelective determination of Triton-type non-ionic surfactants in different samples by on-line clean-up and FIAFresenius' Journal of Analytical Chemistry, Vol. 337, No. 4Organogenesis of the Arterial WallThe common carotid circulation in patients with essential hypertension.Stroke, Vol. 19, No. 10Age-Related Changes in Selected Animal SpeciesAortic Connective Tissue Content in White Leghorn FemalesPoultry Science, Vol. 65, No. 2Transmural organization of the arterial media. The lamellar unit revisited.Arteriosclerosis: An Official Journal of the American Heart Association, Inc., Vol. 5, No. 1Contractions in normal and atherosclerotic rabbit aortasMechanisms of Ageing and Development, Vol. 26, No. 2-3Force-Velocity Relationships of Guinea Pig UreterJournal of Urology, Vol. 131, No. 5Age-associated alterations in viscoelastic properties of canine aortic strips.Circulation Research, Vol. 53, No. 4Analysis of the passive mechanical properties of rat carotid arteriesJournal of Biomechanics, Vol. 16, No. 9Electrolyte Metabolism of the Arterial WallTHE EFFECT OF ALTERATIONS IN SCLEROPROTEIN CONTENT ON THE STATIC ELASTIC PROPERTIES OF THE ARTERIAL WALLModifications by stretches of the mechanical response of isolated cerebral and extracerebral arteries to vasoactive agentsPfl�gers Archiv European Journal of Physiology, Vol. 374, No. 1Arterial Smooth Muscle MechanicsLongitudinal force and stress of rat's esophagus: age-related changes.M P Zabinski, and P Biancani1 June 1977 | American Journal of Physiology-Endocrinology and Metabolism, Vol. 232, No. 6Interaction of Low Density Lipoproteins with Small and Large MoleculesEffects of spontaneous hypertension and age on arterial connective tissue in the ratExperimental Gerontology, Vol. 11, No. 5-6Altered arterial connective tissue in racing greyhound dogsExperientia, Vol. 31, No. 12Development of longitudina retraction of carotid arteries in neonatal dogsExperientia, Vol. 31, No. 11 More from this issue > Volume 227Issue 3September 1974Pages 563-568 Copyright & PermissionsCopyright © 1974 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1974.227.3.563PubMed4412337History Published online 1 September 1974 Published in print 1 September 1974 Metrics

Dynamic elastic properties of the aorta in radial direction.

ArticleDynamic elastic properties of the aorta in radial direction.D J Patel, W K Tucker, and J S JanickiD J Patel, W K Tucker, and J S JanickiPublished Online:01 May 1970https://doi.org/10.1152/jappl.1970.28.5.578MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByLocal pulse wave velocity estimated from small vibrations measured ultrasonically at multiple points on the arterial wall11 June 2018 | Japanese Journal of Applied Physics, Vol. 57, No. 7S1Age-associated alterations in viscoelastic properties of canine aortic strips.Circulation Research, Vol. 53, No. 4Dynamic Anisotropic Viscoelastic Properties of the Aorta in Living DogsCirculation Research, Vol. 32, No. 1Static Elastic Properties of the Left Coronary Circumflex Artery and the Common Carotid Artery in DogsCirculation Research, Vol. 27, No. 2 More from this issue > Volume 28Issue 5May 1970Pages 578-82 https://doi.org/10.1152/jappl.1970.28.5.578PubMed5442252History Published online 1 May 1970 Published in print 1 May 1970 Metrics

Hysteresis loop behavior of the aorta and other extensible tissues.

Hysteresis loop behavior of the aorta and other extensible tissues.