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At least 793 records · Page 44Linked to original sources
PubMed1985

[Noninvasive assessment of the elastic properties and diameter of the major arterial vessels of the extremities in atherosclerosis].

A noninvasive method for the evaluation of the elastic properties of the major arterial vessels (the shoulder and lower third of the foot) in patients with arteriosclerosis and in healthy persons was previously worked out to study: elastic resistance of the intact and relaxed vascular wall, modulus of bulk elasticity, an internal (equivalent) vascular radius and some arterial pressure indices. A significant increment of elastic resistance of the relaxed wall of the arterial vessels was found in arteriosclerosis as compared to the control group which was unrelated directly with raised arterial pressure and could be used for diagnostic purposes. The presence of a high assymetry in a number of indices of the elastic behavior of the vascular wall on the same extremities suggested heterotopy and heterochronia of the changes observed.

Adult↗
PubMed1972

Developing elastic tissue. An electron microscopic study.

Electron microscopic identification of elastic tissue in normal and disease states has been uncertain due to the lack of a specific electron-dense stain. Recently we introduced a silver porphyrin electron microscopic stain (silver tetraphenylporphine sulfonate) for the identification of adult elastic tissue. This stain has now been employed to study the development of elastic tissue with the aim that new and old elastica can be differentiated at the electron microscopic level. Present observations showed that developing elastica consisted of two distinct morphologic components. Each portion exhibited different staining properties with the silver porphyrin and lead citrate. One component was fibrous and the other amorphous. The fibrous component stained with lead citrate while the amorphous stained with the silver porphyrin. The fibrous component was the first to appear; the amorphous portion appeared later in development and was formed within the fibrous matrix. Mature elastic tissue was devoid of the fibrous component. Based upon the morphologic appearance and staining properties, one can now differentiate between newly formed elastic tissue and the existing one in various disease states.

Animals↗
PubMed1979

Effect of elastic compression on venous hemodynamics in postphlebitic limbs.

To determine whether elastic compression alters the venous hemodynamics in the postphlebitic limb, we measured venous pressure patterns in 11 postphlebitic limbs with and without elastic compression stockings. Following cannulation of a dorsal vein of the foot, the patients underwent measurements of basal resting pressure, maximum percent decrease in venous pressure with exercise (delta VPex), peak systolic venous pressure during exercise (SVPmax), the amplitude of the pressure swing, and venous return time. Elastic compression did not alter basal resting pressure, delta VPex, or venous return time. By contrast, SVPmax decreased from 139 +/- 0.3 mm Hg to 11 +/- 8 mm Hg with elastic compression. If venous ulcers are related to the high pressure developed in the superficial veins during calf muscle systole, then elastic compression may be beneficial by decreasing systolic venous pressure and its subsequent deleterious consequences.

Bandages↗
PubMed1984

Selective staining technique for identification of human skin elastic fibers.

The staining methods proposed for the histological detection of elastic fibers are not entirely selective for the elastic fiber system and stain other tissue components also as for example nuclei and collagenous components. We worked out several staining methods which enable us to obtain a selective staining of all the elastic and pre-elastic fibers with no staining of the background by using in the staining solution polyphenols like: pyrogallol, (+) catechin, tannic acid and others. As the background is colourless, our method is suitable for the quantitation of elastic system fibers by automated computerized image analysis.

Adult↗
PubMed1983

Importance of the gerontology of elastic arteries in the development of essential hypertension.

After discussing the changes of elastic type vessels with age, several possibilities for the resetting of baroreceptors in elastic type vessels are proposed: (1) Short-term resetting. On the basis of the architecture of the wall of elastic type vessels and the physical behavior of tubes, a pressure control organ within the vessel wall is proposed, by which, due to change in contraction of the vascular smooth muscles, the stress of the baroreceptors is changed and with it their set point relative to the blood pressure. This change can occur within seconds. (2) Mid-term resetting. The wall of elastic type vessels thickens, after a prolonged forced increase of blood pressure, decreasing the ratio of radius to wall thickness. Since the wall stress is proportional to the ratio of radius to wall thickness and the baroreceptors depend on the wall stress, they will now regulate the blood pressure on an elevated level. This change will be accomplished within days or weeks. (3) Long-term resetting. With age the wall of elastic type vessels becomes stiffer. Due to the peculiar physical behavior of tubes, this means that the wall stress decreases at a given blood pressure. Therefore, to maintain the same mean blood pressure throughout life, the baroreceptors have to adjust to the continuously decreasing wall stress. If this does not occur, the blood pressure will rise. Actually, the calculated increase of proposed blood pressure due to the decreasing wall stress parallels the recorded increase in blood pressure with age of the general population.

Adolescent↗
PubMed1984

[Changes in the elastic fibers of the skin in rats after long-term motor loading and immobilization].

The histologic changes were followed up that took place in the elastic fibers of the skin of a total of 30 female rats of the Wistar line at the initial age of 45 days. The animals were kept under the conditions of enhanced or lowered locomotor activity. It was found that as functional elements in the particular layers of the skin the elastic fibers altered considerably their specific morphologic characteristic under the effect of a varying loading the body with muscular activity. The skin of those of the animals that were loaded with enhanced locomotion presented a strongly developed hyperplastic net of elastic fibers of considerable thickness and density. On the other hand, the skin of the animals that were immobilized showed atrophic and reduction processes involving the elastic tissue; in such case the characteristic structure and network arrangement were only presented by sporadic fibres and bundles. The changes seen in the structure and organization of the elastic tissue once again demonstrated the importance of the higher or lower functional loading of the body with physical work for the development of hyper- or hypotrophic processes in the various tissues and organs.

Animals↗
PubMed1982

Secretory features of chondrocytes related to morphogenesis of the elastic elements in the auricular cartilage.

The well-developed secreting vacuolar system is a characteristic feature of all chondrocytes (CH) during prenatal and early postnatal ontogenesis as well as of the CH near the perichondrium in the adult rat's auricular cartilage. Two kinds of secretion vacuoles exist, dense vacuole (DV) and electron lucent vacuoles (LV). The DV are heterogeneous in size, matrix appearance and origin. The factors (organ necessities and chemical maturation) responsible for the DV matrix heterogeneity are discussed. The presence of dilated rough endoplasmic cisternae with local parts of their cisternal surfaces without bound ribosomes suggest the existence of a direct secretory pathway which bypasses the Golgi complex. During prenatal ontogenesis the extracellular matrix of the auricular cartilage consists of bundles of elastic microfibrils and primary elastic fibres. The elastic microfibrils are tubular structures with a wall composed of 3-5 subunits. After birth the primary elastic fibres are joined to form intercellular septae. The presence of matrix vesicles is discussed with regard to the fine differentiation of the auricular elastic system by their lysosomal activity.

Animals↗
PubMed1982

Light and electron microscopic study on the oxytalan elaunin and elastic fibers in the inferior segment of the human esophagus.

A light and electron microscopic study on oxytalan, elaunin and elastic fibers was performed in the inferior segment of the human esophagus of 30 individuals aged, from 2 months to 76 years. Paraffin sections were stained by the aldehyde-fuchsin (Gomori 1950), Orcein (Unna-Tanzer 1891), resorcinol-fuchsin (Weigert 1898) and iron-hematoxylin (Verhoeff 1908), with or without a previous oxidation by peracetic acid. For the electron microscope, the fixation was performed in a 3% glutaraldehyde solution with 0.25% of tanic acid in Millonig buffer (Futaesaku et al. 1972; Cotta-Pereira et al. 1975, 1976). A subepithelial network of oxytalan fibers (fibrotubular bundles) without direct connections with the BM and indirectly related to this one through periodical reticulin like fibers, were described. More deeply the oxytalan fibers are in continuity with elaunin and these with elastic fibers, close to the LMM. The TSs and the TA are essentially formed by elastic fibers and by relatively scanty presence of elaunin ones. From the TM and probably from the LMM, among the muscle cells, oxytalan fibers gradually change to elaunin and these to elastic fibers toward the connective tissue septa situated among muscle bundles and connective layers (LPM, TSm and TA (or TSs). A fibrilar (fibrotubular) "continuum" is here admitted, extending from the TA to the subepithelial BM with a variable amount of elastin like material, according to the layer they belong. They change progressively from oxytalan to elastic fibers, passing through an intermediate phase of elaunin fibers.

Adolescent↗
PubMed1978

[Structure of the elastic framework of the walls of major human arteries].

By the method of raster electron microscopy, the structure of the elastic carcass in the human aortic arc walls and the common carotid arteries were investigated at the age of 30--40 years. Preliminary preparation of vessel samples helped to reveal elastic structures with the preserved interconnections. Peculiar features of the elastic carcass components in the sheaths of the vessel wall were demonstrated. The fenestrated membranes and elastic plexus were found to be interconnected and form a single structural complex of the elastic formations in the middle sheath of the vessels studied.

Adult↗
PubMed1981

[Matrix vesicles in various "elastic" organs].

Matrix vesicles (MV) have been found during normal development in the rabbit and rat aorta and pulmonary trunk as well as in the elastic cartilage of the rat external ear. In spite of the morphological variability of MV, two basic types can be ruled out: MV with dense osmiophilic content, and light or electron-translucent MV. MV of the first type are considered to be extracellular lysosomes. MV in the vessel wall are predominantly localized in the subendothelium, and the border-zones between media and endothelium or media and adventitia; in elastic cartilage they are localized near the perichondrium. Especially often they can be seen at the place of contact between elastic and other fibers of the intercellular space. They can even penetrate the elastic membranes and plates. The parts of the organs mentioned encounter higher functional demands and are more active during development and growth. The MV appear almost exclusively a short time before birth, and predominantly during the first 20-60 days of postnatal life. Their origin may be due to exocytosis and the detachment of parts (Mikroapokrinie) of endothelial cells, smooth muscle cells, fibrocytes and chondrocytes. The MV are considered to be a substrate for subsidiary extracellular mechanisms of adaptation during the normal ontogenesis of the elastic tissue of these organs.

Animals↗
PubMedDate not supplied

[Model of an elastic bilayer membrane].

The problem of constructing elastic models of biological and artificial membranes is discussed. Such models take into account strong anisotropy of the membrane elastic properties as well as different types of membrane deformation. It is impossible to describe elastic properties in terms of uniform anistropic models. An inhomogenous elastic layer model with microinhomogenities is proposed, it satisfies the condition E perpendicular less than E parallel less than K where E perpendicular - Young's modulus in the direction normal to the membrane plane, E parallel - Young's modulus in the plane of the membrane, K - volume elasticity modulus. It is shown that usual methods of E perpendicular calculation give the upper limit of true value.

Elasticity↗
PubMed1994

[Elasticity modulus of lyophilized cortical bone in the human femur].

The visco-elastic properties of the lyophilized cortical bone of the human femur has been studied by means of the balance rheometer. The samples of bone were harvested from healthy individuals who suddenly died or committed suicide. The donor age ranged from 35 to 45 years. The measurements were taken with the use of the balance rheometer at 20 degrees Celsius and sample deformation frequency of 12.5 Hz. It was found, that elasticity modulus of the lyophilized human cortical bone is about 30 per cent higher than the modulus of fresh cortical bone. In the elastic range the modulus depended on an amplitude of deformation. The compact lyophilized bone turned out to possess to a small degree also viscous properties; thus it should be considered as an elastic-viscous material with considerable superiority of elastic properties.

Adult↗
PubMed1994

[Mitral valve prolapse and cusp elasticity].

PURPOSE: To verify if systolic bulging of floppy mitral cusps can to elastic behavior of their myxomatous collagen tissue. METHODS: Five hearts with floppy mitral valves obtained from autopsies were distended with air (20 to 250 mmHg) through a catheter connected to the left ventricle. It was observed if some area of the atrial surface of the coapted cusps showed variable bulging according to the variation of air injection pressures. Molding of those surfaces (gypsum) allowed the same kind of analysis by other four researches. It was analyzed the cut surfaces of these radially sectioned molds. Lately, isolated tendinae chords were submitted to repeated tractions and observed if they exhibited elastic behavior. Histological study defined the presence of collagen myxomatous degeneration and quantified the amount of elastic tissue. RESULTS: In no case it was detected elastic bulding of mitral cusps. Cut surfaces of the molds confirmed that no increment of the prominent areas occurred, even in those regions with extensive, histologically confirmed, myxomatous substitution of the native collagen tissue. CONCLUSION: Increment of the degree of mitral bulging occurring during ventricular systole can not be ascertained to cusp elasticity but probably to papilar muscle traction.

Elasticity↗
PubMed1994

[Elasticity and viscoelasticity in the circulatory system. IV. Diastolic filling of the left ventricle].

This paper studying diastolic left ventricular and myocardial elastic and viscoelastic properties, some of its consequences and its quantification, constitutes the fourth part of a review on circulatory system elasticity and viscoelasticity. The ventricular elastic and viscoelastic properties depend on myocardial ones and on chamber shape and dimensions. Thus it is often necessary to quantify the ventricular and the myocardial properties separately. As an approximation, the viscoelastic effects during diastole can be neglected and the elastic properties deduced from data obtained over the entire filling; however, these properties can be quantified rigorously only when using viscoelastic models. Another method of exact quantification is based on diastatic data alone; the latter do not reflect significant viscoelastic effects because they correspond to a period in which deformation rate is very slow. This study includes several Pathophysiological applications: some alterations in ventricular elastic properties induced by the pericardium are analysed and deviations from normal ventricular and myocardial diastolic properties caused by primary angina pectoris, by effort angina pectoris and by hypertrophy due to volume and pressure overload are examined. The basic Physical and Biophysical concepts essential to the better phenomena understanding are exposed in the first part of this work which constitutes a previous paper component.

Blood Circulation↗
PubMed1994

Single beat evaluation of circumferential aortic elastin elastic modulus in conscious dogs. Potential application in non-invasive measurements.

A description of the arterial wall elastic properties comprehends both collagen and elastin, clearly shown in a biphasic stress-strain relationship. From chronically instrumented conscious dogs, aortic pressure-diameter curves can be obtained in a single beat, which is impossible to perform in human beings. In control conditions, the collagen fibers are almost not distended and the resistance to stretch is mainly supported by the elastin fibers. Therefore, the mechanical properties of the aorta are almost purely elastic in the basal beat to beat conditions. In this study we propose and test five indexes, which include as variables: systolic, diastolic and mean arterial pressure and diameter; besides, arterial compliance and pressure-strain elastic modulus as suggested to evaluate the elastic behaviour of the elastic fibers. This data can be easily obtained by non-invasive methods, such as Doppler-ultrasound techniques and auscultative esphygmomanometrical measurements, while the indexes evaluated can be retrieved from a single beat evaluation. Of three measurements performed in chronically instrumented conscious dogs on different days, one of these indexes, the ME5 = [formula: see text] x Rdias proved to be an accurate and reliable parameter to evaluate the mechanical behaviour of arteries. This kind of parameter may be useful for research and evaluation of several diseases that markedly alter the arterial wall compliance.

Algorithms↗
PubMed1994

Characterization and measurement of elastance with application to underwater breathing apparatus.

The elastic loads inherent in underwater breathing apparatus (UBA) can affect diver performance. This work quantitatively examines elastance, its measurement by static tests, and its relationship to UBA. A rigid, fixed-volume container and a vertical water column with straight and parallel sides produce elastic loads that have application to closed-circuit UBA. We derived equations to describe the pressure-volume relationships of these elements from first principles and tested the equations experimentally for system pressure produced by a swept volume in a breathing machine. Our work demonstrates that simplified equations to describe elastance may not be sufficiently accurate for all situations. In addition, static measurements of elastance of a UBA or other element will not be reproducible unless all the volumes within the testing apparatus are accounted for; we provide experimental and mathematical techniques for doing so.

Diving↗
PubMedDate not supplied

The fracture resistance of all-ceramic crowns on supporting structures with different elastic moduli.

This in vitro study evaluated the fracture resistance of all-ceramic crowns as a function of the elastic modulus of the supporting die. All-ceramic crowns were made for dies with three different elastic moduli and two different crown lengths. The occlusal surface was loaded in compression with a 12.7-mm steel ball. The fracture load increased markedly with the increase in elastic modulus. The largest increase was seen when only the occlusal surface of the crown was covered. The characteristic fracture load of the complete-crown restorations was more than double that of the occlusal-cover restorations in the dies with the lowest modulus of elasticity, while for the dies with the highest modulus of elasticity the difference in the characteristic fracture load for the two configurations was not significant.

Chemical Phenomena↗
PubMed1998

Fibrillin containing elastic microfibrils support platelet adhesion under dynamic shear conditions.

The vascular subendothelium contains macromolecular structures called microfibrils. Type VI collagen is one protein found in microfibrils that supports platelet adhesion and aggregation and we have previously evaluated the roles of platelet receptors and vWf involved in these processes under physiological shear conditions. Here we investigate the ability of fibrillin containing elastic microfibrils to support mural thrombus formation. Our results show that elastic microfibril surfaces support platelet adhesion under low shear conditions at a level similar to collagen VI tetramers. However, the degree of aggregation on the elastic microfibril surface is much higher. Both adhesion and aggregation were shown to be mediated by the GPIIb-IIIa platelet receptor. Elastic microfibrils do not support the formation of mural thrombi under high shear conditions. These results suggest roles for both collagen VI and fibrillin containing elastic microfibrils in modulating the platelet response to blood vessel injury.

Actin Cytoskeleton↗