SEARCH · PubMed Health

Results for “ELASTICITY”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources

PubMed2004

Acquired disorders of elastic tissue: Part II. decreased elastic tissue.

Elastic fibers in the extracellular matrix are integral components of dermal connective tissue. The resilience and elasticity required for normal structure and function of the skin are attributable to the network of elastic tissue. Advances in our understanding of elastic tissue physiology provide a foundation for studying the pathogenesis of elastic tissue disorders. Many acquired disorders are nevertheless poorly understood owing to the paucity of reported cases. Several acquired disorders in which loss of dermal elastic tissue produces prominent clinical and histopathologic features have recently been described, including middermal elastolysis, papular elastorrhexis, and pseudoxanthoma-like papillary dermal elastolysis, which must be differentiated from more well-known disorders such as anetoderma, acquired cutis laxa, and acrokeratoelastoidosis. Learning objective At the conclusion of this learning activity, participants should have an understanding of the similarities and differences between acquired disorders of elastic tissue that are characterized by a loss of elastic tissue.

Adolescent↗

PubMed2006

Structure of large arteries: orientation of elastin in rabbit aortic internal elastic lamina and in the elastic lamellae of aortic media.

This study was designed to further our understanding of the elastic ultrastructure of vessels. Scanning electron microscopy and transmission electron microscopy were used to study the histomorphologic properties of the elastic fibers of rabbit aorta after purification of the elastin by means of hot alkaline treatments. The elastic fibers of whole rabbit aorta samples were also studied using confocal microscopy. Morphological assessment revealed that the elastin fibers contained in the elastic lamellae of media are perpendicular to the blood flow, and that the elastic fibers of the internal elastic lamina are parallel to the luminal flow. In conclusion, the structure of the elastin making up the elastic lamellae of the media is oriented in such a way as to sustain the circumferential mechanical stress of pulsation. By contrast, the structure of the elastin fibers that make up the internal elastic lamina provides little mechanical support for the circumferential tension, but can support longitudinal loading and act as a fenestrated membrane.

Animals↗

PubMed1987

The immunohistochemical localisation of microfibril-associated glycoprotein (MAGP) in elastic and non-elastic tissues.

We have previously identified the major antigen of elastin-associated microfibrils as a 31kD glycoprotein which we named microfibril-associated glycoprotein or MAGP. Affinity-purified antibodies to MAGP were shown to localise specifically to elastin-associated microfibrils in sections of bovine foetal nuchal ligament. In the present paper we compare the localisation of anti-MAGP antibodies and anti-tropoelastin antibodies in a range of bovine elastic and non-elastic tissues. The results show that anti-MAGP antibodies invariably localised to immuno-reactive elastic fibres, wherever they occurred. Extensive additional localisation was observed in a number of tissues. This extra distribution of anti-MAGP antibodies was found to correspond to those structures exhibiting the oxytalan histochemical staining reaction in tissues such as skin, periodontal ligament and ocular zonule. Since these oxytalan fibres have been shown to consist of 12 nm microfibrils which are morphologically similar to those of elastic fibres (and unpublished data from this laboratory confirm this conclusion), the results suggest that MAGP is a component of 12 nm microfibrils in both elastic and non-elastic tissues. Anti-tropoelastin antibodies did not localise to these oxytalan fibres, suggesting that tropoelastin is not a component of 12 nm microfibrils. MAGP was also detected in extracellular matrix regions of tissues such as skeletal muscle, Achilles tendon and spleen, suggesting that 12 nm microfibrils, containing one or more macromolecular constituents in common, make up an important structural system within the extracellular matrix in a wide range of elastic and non-elastic tissues.

Animals↗

PubMed2002

Elastic energy storage in human articular cartilage: estimation of the elastic modulus for type II collagen and changes associated with osteoarthritis.

The viscoelastic mechanical properties of normal and osteoarthritic articular were analyzed based on data reported by Kempson [in: Adult Articular Cartilage (1973)] and Silver et al. (Connect. Tissue Res., 2001b). Results of the analysis of tensile elastic stress-strain curves suggest that the elastic modulus of cartilage from the superficial zone is approximately 7.0 GPa parallel and 2.21 GPa perpendicular to the cleavage line pattern. Collagen fibril lengths in the superficial zone were found to be approximately 1265 microm parallel and 668 microm perpendicular to the cleavage line direction. The values for the elastic modulus and fibril lengths decreased with increased extent of osteoarthritis. The elastic modulus of type II collagen parallel to the cleavage line pattern in the superficial zone approaches that of type I collagen in tendon, suggesting that elastic energy storage occurs in the superficial zone due to the tensile pre-tension that exists in this region. Decreases in the elastic modulus associated with osteoarthritis reflect decreased ability of cartilage to store elastic energy, which leads to cartilage fibrillation and fissure formation. We hypothesize that under normal physiological conditions, collagen fibrils in cartilage function to store elastic energy associated with weight bearing and locomotion. Enzymatic cleavage of cartilage proteoglycans and collagen observed in osteoarthritis may lead to fibrillation and fissure formation as a result of impaired energy storage capability of cartilage.

Aged↗

PubMed2002

Estimation of the effective transversely isotropic elastic constants of a material from known values of the material's orthotropic elastic constants.

A method is illustrated for determining the effective transversely isotropic (or isotropic) elastic constants from measured orthotropic elastic constants. This method consists of constructing upper and lower bounds on the effective transversely isotropic (or isotropic) elastic constants using the known orthotropic values. This method is illustrated using three sets of elastic constants for bone. Fortunately, the upper and lower bounds are very close. Thus very good approximations for the effective transversely isotropic (or isotropic) elastic constants for cortical and cancellous bone are obtained from previously published data on the orthotropic elastic constants for those tissue types. This work is undertaken to build a greater database for the transversely isotropic elastic constants of bone with the intention of employing them in a transversely isotropic model of bone poroelasticity. An interesting aspect of the present result is that the Voigt and Reuss bounds are very tight for these anisotropic materials. This is not always the case for these bounds.

Animals↗

PubMed1997

Elastic fibre system of the female canine urethra. Histochemical identification of elastic, elaunin and oxytalan fibres.

The elastic system fibres of the female urethra were investigated in seven dogs of different breeds. The fibres were stained and differentiated with orcein, Verhoeff's iron hematoxylin, and pararosanilin-based aldehyde fuchsin, with and without previous oxidation. Orcein and aldehyde fuchsin revealed some subepithelial longitudinally orientated delicate fibres (elaunin fibres) and numerous coarse longitudinal fibres (elastic fibres) in the deeper subepithelial connective tissue containing the vascular plexus, as well as a network of fibres of different calibers in the periurethral connective tissue. Elastic system fibres were also found in association with the sinusoids of the vascular plexus and the urethral smooth musculature. Verhoeff's iron hematoxylin only reacted distinctly with coarse (elastic) fibres. When applied following oxidation, aldehyde fuchsin disclosed an extensive meshwork of additional delicate fibres (oxytalan fibres) in the subepithelial connective tissue adjacent to the basement membrane. Oxytalan fibres were also discernible in the sinusoidal adventitia of the vascular plexus, as well as between smooth and striated muscle fibres. Due to the predominantly longitudinal orientation of the elastic system fibres and the low urethral resistance to manual expression of urine from the bladder post mortally, when the elasticity of the urethra is still intact and the activity of other continence factors can be excluded, the elastic tissue is not judged to be a major contributory factor to urinary continence.

Animals↗

PubMed1997

Calcification of medial elastic fibers and aortic elasticity.

We tested the hypothesis that a simple change in wall composition (medial calcium overload of elastic fibers) can decrease aortic elasticity. Calcium overload was produced by hypervitaminosis D plus nicotine (VDN) in the young rat. Two months later, measurement of central aortic mean blood pressure in the unanesthetized, unrestrained rat showed that the VDN rat suffered from isolated systolic hypertension but that mean blood pressure was normal. Wall thickness and internal diameter determined after in situ pressurized fixation were unchanged, as was calculated wall stress. Wall stiffness was estimated from (1) elastic modulus (determined with the Moens-Korteweg equation and values for aortic pulse wave velocity in the unanesthetized, unrestrained rat and arterial dimensions) and (2) isobaric elasticity (= slope relating pulse wave velocity to mean intraluminal pressure in the phenylephrine-infused, pithed rat preparation). Both increased after VDN, and both were significantly correlated to the wall content of calcium and the elastin-specific amino acids desmosine and isodesmosine. Left ventricular hypertrophy occurred in the VDN model, and left ventricular mass was related to isobaric elasticity. In conclusion, elastocalcinosis induces destruction of elastic fibers, which leads to arterial stiffness, and the latter may be involved in the development of left ventricular hypertrophy in a normotensive model.

Analysis of Variance↗

PubMed1991

How to measure urethral elastance in a simple way. Elastance: definition, determination and implications.

The elastance of a biological tube describes the resistance of the latter to dilatation. It is defined as dP/dV, where dP is the pressure increase caused by the volume increase dV. Elastance is the reciprocal of compliance. Elastance in the female urethra can be estimated from the slope of the regression line of related values of pressure and cross-sectional area. In the present study, urethral elastance was calculated by measurement of the related pressures and cross-sectional areas during stepwise dilatation by a balloon and by determination of the pressure at which inflow through side holes in catheters with increasing diameters began. There was no difference between the elastance values obtained by the two methods. Due to the linear correlation found between pressure and cross-sectional area we conclude that urethral elastance can be estimated from measurements of urethral pressure at two or more related cross-sectional areas by a simple technique using e.g., 8F, 14F, and 20F catheters.

Adult↗

PubMed2005

Incoherent elastic and quasi-elastic neutron scattering investigation of hemoglobin dynamics.

In this work we investigate the dynamic properties of hemoglobin in glycerolD(8)/D(2)O solution using incoherent elastic (ENS) and quasi-elastic (QENS) neutron scattering. Taking advantage of complementary energy resolutions of backscattering spectrometers at ILL (Grenoble), we explore motions in a large space-time window, up to 1 ns and 14 A; moreover, in order to cover the harmonic and anharmonic protein dynamics regimes, the elastic experiments have been performed over the wide temperature interval of 20-300 K. To study the dependence of the measured dynamics upon the protein quaternary structure, both deoxyhemoglobin (in T quaternary conformation) and carbonmonoxyhemoglobin (in R quaternary conformation) have been investigated. From the ENS data the mean square displacements of the non-exchangeable hydrogen atoms of the protein and their temperature dependence are obtained. In agreement with previous results on hydrated powders, a dynamical transition at about 220 K is detected. The results show interesting differences between the two hemoglobin quaternary conformations, the T-state protein appearing more rigid and performing faster motions than the R-state one; however, these differences involve motions occurring in the nanosecond time scale and are not detected when only faster atomic motions in the time scale up to 100 ps are investigated. The QENS results put in evidence a relevant Lorentzian quasi-elastic contribution. Analysis of the dependence of the Elastic Incoherent Structure Factor (EISF) and of the Lorentzian halfwidth upon the momentum transfer suggests that the above quasi-elastic contribution arises from the diffusion inside a confined space, values of confinement radius and local diffusion coefficient being compatible with motions of hydrogen atoms of the amino acid side chains. When averaged over the whole range of momentum transfer the QENS data put in evidence differences between deoxy and carbonmonoxy hemoglobin and confirm the quaternary structure dependence of the protein dynamics in the nanosecond time scale.

Elasticity↗

PubMed1990

Brain tissue elasticity and CSF elastance.

In the analysis of the pressure-volume relationship of the intracranial system, the concept of brain elastance, sometimes called tissue elastance or CSF elastance, is often used. It is generally designated as Ecsf and is calculated as the slope of the pressure-volume curve of the system. Variations in Ecsf are related to, for example, changes in the buffering capacity of the system which, however, could be influenced by the cerebral vascular volume, compressibility of the meningeal membranes, and compressibility of the subpial brain tissue. Our interest is in isolating the effect of controlled changes in the intracranial system with changes in the subpial tissue only. Here we discuss the measurement of brain tissue elasticity and describe two experimental conditions in which simultaneous measurements showed distinct differences between the behaviour of the system CSF elastance and brain tissue elastic behaviour.

Animals↗

PubMed1994

Fibrinolysis and elastic compression: no fibrinolytic effect of elastic compression in healthy volunteers.

The local and systemic fibrinolytic response to the placing of elastic compression in healthy volunteers was studied to determine whether this method of preventing venous thromboembolism has any profibrinolytic effect, as previously demonstrated with intermittent pneumatic compression. Variations in the major parameters of fibrinolysis (euglobulin lysis time, t-PA antigen, PAI-1 antigen, PAI-1 activity) were studied in an open randomized cross-over study in 21 healthy volunteers, in which three types of treatment were tested for periods of 24 h each (without elastic compression, elastic compression of an upper limb, elastic compression of the lower limbs). Four blood samples were taken from the upper limb during each period (at 08:00 h, 10:00 h, 18:00 h, 08:00 h on the following day). The placing of elastic compression did not cause any statistically significant change in the four parameters tested between the three types of treatment. In contrast, circadian rhythm was confirmed for all the fibrinolytic factors studied with a minimal fibrinolytic activity in the morning and a maximal activity in the evening. Elastic compression does not seem to have any profibrinolytic effect in healthy volunteers but other studies are needed in patients before a definitive conclusion can be reached.

Adolescent↗

PubMed1992

Estimating the elastic modulus of non-atherosclerotic elastic arteries.

BACKGROUND: Non-invasive measurements of the diameter and wall thickness of arteries in vivo, combined with recordings of pressure, permit the assessment of some mechanical aspects of arteries in vivo. However, arteries are anisotropic cylinders with complex elastic properties which can only be determined by a detailed evaluation. Many of the parameters required to calculate the anisotropic circumferential elastic modulus cannot be obtained in patients in vivo, or can be obtained only with difficulty. AIMS: Experiments were performed to assess the true anisotropic circumferential elastic modulus, and to find simpler methods of estimation. METHODS: One hundred and twenty dog carotid arteries were mounted in vitro and were extended to four lengths, 120, 130, 160 and 180% of the retracted length. The different lengths were applied in random order. The vessels were pressurized in steps while the longitudinal force and vessel diameter were measured. When a reproducible mechanical behavior was observed, the pressure, diameter and longitudinal force were recorded. These values were used to calculate the longitudinal elastic modulus, the circumferential-longitudinal Poisson's ratio and the true anisotropic circumferential elastic modulus with respect to the dimensions of the fully unloaded vessel. A number of simpler expressions were then evaluated for their value as approximations of the true anisotropic modulus. RESULTS: Excellent estimates were obtained with a variety of expressions. CONCLUSIONS: These methods may be useful for non-invasive assessments of the elastic properties of non-atherosclerotic arteries in patients.

Animals↗

PubMed1989

[Mechanical properties and phase transformation of super-elastic Ni-Ti alloy wires. Part 1: Relation between super-elasticity and phase transformation].

The relationship between mechanical properties and thermal behavior of super-elastic Ni-Ti alloy orthodontic wires was investigated in order to use them effectively in clinics. Three types of super-elastic Ni-Ti alloy orthodontic wires, SENTALLOY-BLUE(SB), YELLOW(SY) and RED(SR), were used. Two parameters were introduced from the load-deflection curves in three point bending test to evaluate their mechanical properties. One was the super-elastic index (SEI) for super-elasticity, and the other was the E-load for the load in the super-elastic region. Their thermal behavior in the course of the transformation analyzed with DSC, and compared with the mechanical properties. The specimens heat-treated at 500 degrees C for 30 min were also examined. The differences in mechanical properties of the super-elastic Ni-Ti alloy orthodontic wires used in this study were thought to be more affected by the height of the thermic peak and the form of the DSC curves than the transformation temperature. The higher the thermic peak, the higher tended to be the SEI and the lower E-load. To the contrary, the lower thermic peak, the higher was the E-load and the lower was the SEI, and the continuous force could not be achieved. The remaining work-hardened structure was thought to influence these differences.

Dental Alloys↗

PubMed1985

[Distribution of elastic bodies (elastic globes) in healthy human skin. Studies with a dense grid].

Since the turn of the century, there have been descriptions of corpuscular structures in the human skin. These are situated at the epidermal-corial junction zone. They can be visualized well with resorcinol-fuchsin staining according to Weigert. They may attain forensic significance in the topographic assignment of isolated skin fragments to certain body regions. The research results available so far, which are in some cases contradictory, were checked and the investigations were continued. A total of 584 skin punch samples were taken from the trunk and limbs of a 39-year-old male corpse. Of these, a total of 1752 paraffin serial sections (resorcinol-fuchsin staining) were prepared and investigated for the occurrence of elastic bodies. The investigation essentially showed that in almost all serial sections, elastic bodies were found to have a frequency concentration at points on the limbs. It could not be established that there was a sharp separation of skin areas containing elastic globes and skin areas free of elastic globes. The distribution of elastic bodies is evidently subject to a pattern of its own, which does not display any interrelationships with that of the skin appendages (apocrine and eccrine sweat glands, sebaceous glands, and male body hair). Because the skin of the trunk and the limbs is relatively regularly interspersed with elastic globes, there can only be used in connection with other features (e.g. thickness of the epidermis, skin appendages) to assign isolated skin fragments to certain regions of the body.

Adult↗

PubMed1989

The elastic tissue of Bruch's membrane. Connections to choroidal elastic tissue and the ciliary epithelium of the rabbit and human eyes.

Ultrastructural observations on the elastic lamina of Bruch's membrane of the rabbit and human eyes revealed connections to the ciliary epithelium and choroidal elastic tissue. The connections to the ciliary epithelium are in the form of bundles of microfibrils that peel off the anterior extension of Bruch's membrane beyond the ora serrata and insert into the basement membrane of the pigmented epithelium of the pars plana. The connections to the choroidal elastic tissue are in the form of bundles of microfibrils (in the rabbit) or elastin and microfibrils (in the human) that cross the tissue space between the choriocapillaris and join bundles of choroidal elastic tissue. These connections suggest that the elasticity of Bruch's membrane exerts its influence distant from the membrane itself. The connections onto the pars plana of the ciliary body implicate Bruch's membrane in disaccommodation when the ciliary muscle relaxes.

Animals↗

PubMed1968

Elastic-mathematical theory of cells and mitochondria in swelling process. II. Effect of temperature upon modulus of elasticity of membranous material of egg cells of sea urchin, Strongylocentrotus purpuratus, and of oyster, Crassostrea virginica.

The elastic behavior of the cell wall as a function of the temperature has been studied with particular attention being given to the swelling of egg cells of Strongylocentrotus purpuratus and Crassostrea virginica in different sea water concentrations at different temperatures. It was found that the modulus of elasticity is a nonlinear function of temperature. At about 12-13 degrees C the modulus of elasticity (E) is constant, independent of the stress (sigma) and strain (epsilon(nu)) which exist at the cell wall; the membranous material follows Hooke's law, and E approximately 3 x 10(7) dyn/cm(2) for S. purpuratus and C. virginica. When the temperature is higher or lower than 12-13 degrees C, the modulus of elasticity increases, and the membranous material does not follow Hooke's law, but is almost directly proportional to the stresses existing at the cell wall. On increasing the stress, the function E(sigma) = E(sigma) approaches saturation. The corresponding stress-strain diagrams, sigma = sigma(epsilon(nu)), and the graphs, E(sigma) = E(sigma) and E(sigma) = E(t) are given. The cyto-elastic phenomena at the membrane are discussed.

Animals↗

PubMed2002

Cardiac titin: molecular basis of elasticity and cellular contribution to elastic and viscous stiffness components in myocardium.

Myocardium resists the inflow of blood during diastole through stretch-dependent generation of passive tension. Earlier we proposed that this tension is mainly due to collagen stiffness at degrees of stretch corresponding to sarcomere lengths (SLS) > or = 2.2 microns, but at shorter lengths, is principally determined by the giant sarcomere protein titin. Myocardial passive force consists of stretch-velocity-sensitive (viscous/viscoelastic) and velocity-insensitive (elastic) components; these force components are seen also in isolated cardiac myofibrils or skinned cells devoid of collagen. Here we examine the cellular/myofibrillar origins of passive force and describe the contribution of titin, or interactions involving titin, to individual passive-force components. We construct force-extension relationships for the four distinct elastic regions of cardiac titin, using results of in situ titin segment-extension studies and force measurements on isolated cardiac myofibrils. Then, we compare these relationships with those calculated for each region with the wormlike-chain (WLC) model of entropic polymer elasticity. Parameters used in the WLC calculations were determined experimentally by single-molecule atomic force-microscopy measurements on engineered titin domains. The WLC modelling faithfully predicts the steady-state-force vs. extension behavior of all cardiac-titin segments over much of the physiological SL range. Thus, the elastic-force component of cardiac myofibrils can be described in terms of the entropic-spring properties of titin segments. In contrast, entropic elasticity cannot account for the passive-force decay of cardiac myofibrils following quick stretch (stress relaxation). Instead, slower (viscoelastic) components of stress relaxation could be simulated by using a Monte-Carlo approach, in which unfolding of a few immunoglobulin domains per titin molecule explains the force decay. Fast components of stress relaxation (viscous drag) result mainly from interaction between actin and titin filaments; actin extraction of cardiac sarcomeres by gelsolin immediately suppressed the quickly decaying force transients. The combined results reveal the sources of velocity sensitive and insensitive force components of cardiomyofibrils stretched in diastole.

Actin Cytoskeleton↗

PubMed2004

An in vitro study simulating effects of daily diet and patient elastic band change compliance on orthodontic latex elastics.

This project investigated the effects of food exposure and patient compliance with elastic-band change on the degradation of forces in 3/16-inch, medium-wall, latex elastic bands during a simulated day of clinical wear. Six levels of daily diet/patient compliance were chosen as representative of orthodontic patients and a quasicontrol group. The groups differed with respect to how much exposure to artificial saliva and foodstuffs they experienced. After exposure in mild tension to daily diets and based on compliance with instructions about changing orthodontic elastics, the elastics were tested in tensile mode by stretching to 25 mm, where the load was recorded in newtons. The bands of three manufacturers, Rocky Mountain Orthodontics (RMO), 3M Unitek (UNO), and American Orthodontics (AMO), were examined, with 10 bands per group, per manufacturer, forming a cohort. Two-way analysis of variance and the Tukey-Kramer honestly significant difference tests were used to identify statistical significance (P > .05). With respect to bands from a single manufacturer, no differences were found between daily diet/patient compliance levels. However, differences (P < .0001) were found between manufacturers' bands. RMO > UNO > AMO in all environments. Over a 24-hour period, latex elastics maintain their applied load in the simulated oral environments.

Adolescent↗