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At least 613 records · Page 34Linked to original sources
PubMed2003

Innervation and functional characteristics of connective tissues, especially elastic fibers, in human fetal thoracic intervertebral articular capsule and its surroundings.

The articular capsules between the thoracic vertebrae, which have physiologically different functions from those of other levels of the vertebrae, have yet to be subjected to neuro-anatomical and fine structural analysis. In the present study, we analyzed serial frozen sections of decalcified thoracic vertebrae in human fetuses, and identified the articular capsule tissue with its unique distribution of elastic fibers. The fine structure of the elastic fibers was studied by transmission electron microscopy. In the early-stage fetus, the fibrous membrane forming the lateral intervertebral articular capsule contained abundant thin elastic fibers consisting of microfibrils. In the late-stage fetus, the lateral capsule of fibrous membrane was occupied by thick elastic fibers. A medial articular capsule, namely the ligamenta flava, contained numerous thick elastic fibers in both early and late-stage fetuses. The distributional differences in nerve fibers between early and late-stage fetuses were determined by immunostaining, using antibodies raised against protein gene product 9.5 (PGP 9.5; ubiquitin carboxyl-terminal hydrolase). Innervation by PGP 9.5 immunoreactive fibers was limited to the areas of the articular capsules near the blood vessels, which may indicate their functional relation with blood flow. No PGP 9.5 immunoreactive fibers were found in the ligamenta flava of the late-stage fetus. Innervation might be directly involved in the development of the intervertebral articular capsules in normal human fetuses.

Antibodies↗
PubMed2002

Elastic stabilization alone or combined with rigid fusion in spinal surgery: a biomechanical study and clinical experience based on 82 cases.

The authors report their experience with the treatment of lumbar instability by a kind of spine stabilization. The elastic stabilization, which follows a new philosophy, is obtained by an interspinous device, and should be used alone in degenerative disc disease, recurrent disc herniation and in very low grade instability, or in association with rigid fusion for the prevention of pathology of the border area. In collaboration with bioengineers, we carried out an experimental study on a lumbar spine model in order to calculate stresses and deformations of lumbar disc during simulation of motion, in physiological conditions and when elastic stabilization is combined with rigid fusion. Results suggest that elastic stabilization reduces stresses on the adjacent disc up to 28 degrees of flexion. Based on this preliminary result, we began to use elastic stabilization alone or combined with fusion in 1994. To date, we have performed 82 surgical procedures, 57 using stabilization alone and 25 combined with fusion, in patients affected by degenerative disc disease, disc herniation, recurrence of disc herniation or other pathologies. Clinical results are satisfactory, especially in the group of patients affected by recurrent disc herniation, in whom the elastic device was used alone.

Adult↗
PubMed1997

Morphometric analysis of collagen and elastic fibers in normal skin and gingiva in relation to age.

The morphometric parameters of the human gingival elastic fiber network were determined by image analysis and compared with human skin elastic fibers in relation to age. Similarly, collagen fibers were also investigated in both tissues. In this study, 47 healthy patients, 10-75 years old were studied for gingiva and another 50 patients in the same age range were included for skin biopsies. Three groups were compared: group 1 from the age of 10-24 years, group 2 from 25 to 49 years, and group 3 from 50 to 75 years. The diameters of the oxytalan fibers were invariable in both tissues, whatever the age considered. On the other hand, the diameters of elastic fibers increased regularly with age in the gingiva (P < 0.01) and in the skin (P < 0.01) between each age group. The area fraction occupied by the oxytalan fibers decreased significantly in both tissues (P < 0.01) for the skin and (P < 0.001) for the gingiva. The area fraction occupied by the gingival elastic fibers remained constant with age while the skin elastic fibers increased significantly with age between groups 2 and 1 (P < 0.01) and between groups 3 and 2 (P < 0.001). In the mid-dermis and in the mid-gingiva, the diameters of the collagen fibers increased strongly with age, between groups 2 and 1 (P < 0.01) and between groups 3 and 2 (P < 0.001). The area fraction occupied by the collagen bundles increased regularly with age in the mid-gingival (P < 0.05 between each age group), while a significant decrease was observed in the mid-dermis from the age of 50-75 years (P < 0.05). The results obtained contribute to a better understanding of some modifications which dermis and gingiva undergo with aging and provide data to perfect diagnosis and therapy in odontology and dermatology.

Adolescent↗
PubMed2003

Measurement of the elastic modulus of porcine septal cartilage specimens following Nd: YAG laser treatment.

Laser cartilage reshaping is a temperature-dependent process that results in stress relaxation with subsequent formation of a new and stable specimen geometry. The objective of this study was to quantitatively measure changes in the elastic moduli of porcine cartilage following laser heating. The elastic modulus of porcine nasal septal cartilage specimen (25 x 5 x 2 mm) was measured before and after Nd: YAG laser (lambda=1.32 Irvinem, 21.22 W/cm2) irradiation and following rehydration in saline solution. Specimens were secured in a single beam cantilever configuration and displaced using a calibrated thin beam load cell attached to a motorised micropositioner. Elastic modulus was calculated using elastic beam theory. Measurements were recorded before and immediately after laser heating, and following rehydration in saline solution (40 minutes, 25 degrees C). Specimens heated in saline (100 degrees C and then re-hydrated) were used as controls to determine the effect of total thermal denaturation. The calculated moduli before and after irradiation were 4.86 +/- .145 MPa and 1.166 +/- .055 MPa respectively. Following rehydration in saline, the modulus returned to near-baseline values (5.119 +/- .163 MPa). In contrast, elasticity remained lower in specimens boiled and re-hydrated (3.25 +/- .130 MPa). These findings suggest that cartilage matrix does not undergo complete thermal denaturation during laser reshaping, given the return in tissue properties with rehydration.

Animals↗
PubMed2005

Computation of adherent cell elasticity for critical cell-bead geometry in magnetic twisting experiments.

Quantification of the cell elastic modulus is a central issue of micromanipulation techniques used to analyze the mechanical properties of living adherent cells. In magnetic twisting cytometry (MTC), magnetic beads of radius R, linked to the cell cytoskeleton through transmembrane receptors, are twisted. The relationships between imposed external torque and measured resulting bead rotation or translation only provide values of the apparent cell stiffness. Thus, specific correcting coefficients have to be considered in order to derive the cell elastic modulus. This issue has been highlighted in previous studies, but general relationships forhandling such corrections are still lacking while they could help to understand and reduce the large dispersion of the reported values of cell elastic modulus. This work establishes generalized abacuses of the correcting coefficients from which the Young's modulus of a cell probed by MTC can be derived. Based on a 3D finite element analysis of an hyperelastic (neo-Hookean) cell, we show that the dimensionless ratio h(u)/2R, where h(u) is the cell height below the bead, is an essential parameter for quantification of the cell elasticity. This result could partly explain the still intriguing question of the large variation of measured elastic moduli with probe size.

Algorithms↗
PubMed1991

Age-related changes in aortic elasticity determined by gated radionuclide angiography in patients with systemic hypertension or healed myocardial infarcts and in normal subjects.

We estimated the aortic volume elasticity (Ve), an index of aortic stiffness, using gated radionuclide angiography, and investigated age-related changes in aortic elasticity in 22 normal control subjects, 30 hypertensive patients and 36 patients with old myocardial infarction. Ve elasticity was calculated noninvasively as a ratio of the pressure change (dP) and the percent volume change (dV/Vo) determined by radionuclide angiography [Ve = dP/(dV/Vo)]. dV/Vo was calculated from the maximal and minimal counts in the aortic arch [dV/Vo = (maximum - minimum)/minimum]. Ve increased significantly with age in normal control subjects (r = 0.62, p less than 0.001), hypertensive patients (r = 0.60, p less than 0.001) and patients with old infarcts (r = 0.59, p less than 0.001). The age-related increase in Ve was significantly greater in hypertensive patients, and that for patients with old myocardial infarcts tended to be greater than in control subjects. Thus, hypertension accelerates the decrease in aortic elasticity with aging. The greater decrease in aortic elasticity resulted in a significant age-related increase in pulse pressure in patients with hypertension and old myocardial infarction.

Adult↗
PubMed1991

Molecular mechanism of spider silk elasticity.

Spider major ampullate (drag-line) silk is an extracellular fibrous protein which has impressive characteristics of strength and elasticity. This silk has been hypothesized to predominantly consist of a single protein, containing regions of antiparallel beta-sheets which are interspersed with amorphous segments responsible for its elastic properties. A rubber-like mechanism has been suggested to account for this elasticity, but the specific molecular mechanism is unknown. Using Fourier transform infrared spectroscopy (FTIR) we found evidence of either helix formation or reorientation of preexisting helices when axial tension is applied to the spider silk fiber. CD studies of a peptide derived from the silk gene repeat sequence show that it can form beta-sheets at high temperatures while alpha-helices are induced in 2,2,2-trifluoroethanol. These results suggest a possible molecular mechanism for the elasticity of spider silk fibers. It is proposed that the elastic process involves the formation and disruption of alpha-helical Ala-rich regions which are interspersed among stable beta-sheet domains.

Amino Acid Sequence↗
PubMedDate not supplied

Measurement of oscillatory flow pressure gradient in an elastic artery model.

In vitro experiments were conducted to measure the oscillatory flow pressure gradient along an elastic tube in order to assess the recent nonlinear theory of Wang and Tarbell. According to this theory, in an elastic tube with oscillatory flow, the mean (time-averaged) pressure gradient cannot be calculated using Poiseuille's law. The effect of wall motion creates a nonlinear convective acceleration, and an induced mean pressure gradient is required to balance the convective acceleration. The induced mean pressure gradient depends on the diameter variation over a cycle, the pulsatility and unsteadiness of the flow, and the phase difference between the pressure wave form and the flow wave form. The amplitude of the pressure gradient also depends on these parameters and may deviate significantly from Womersley's rigid tube theory. A flow loop was constructed to produce oscillatory flow in an elastic tube. Flow wave forms were measured with an ultrasonic flow probe, and ultrasonic diameter crystals were used to measure wall movement. A special device for pressure drop measurement was constructed using Millar catheter tip transducers to obtain both forward and backward pressure drops that were then averaged. This averaging method eliminated the static error of the pressure transducers. The pressure-flow phase angle was varied by clamping a distal elastic section at various locations. Pressure gradients were obtained for a range of phase angles between -55 degrees and +49 degrees. The mean and amplitude of the measured pressure gradient were compared to theoretical values. Both positive and negative induced mean pressure gradients were measured over the range of phase angles. The measured pressure gradient amplitudes were always lower than predicted by Womersley's rigid tube theory. The experimental means and amplitudes are in good agreement with the elastic tube theoretical values. Thus, the experiments verify the theory of Wang and Tarbell.

Arteries↗
PubMed1983

Elastic and precursor fibres in the normal human eye.

Completely formed elastic fibres consist of a core of amorphous elastin within a mantle of microfibrils. The fibrillar component may occur as isolated bundles (oxytalan) or may be randomly intermingled with variable amounts of elastin (elaunin). The distribution of both mature elastic and incomplete oxytalan and elaunin fibres in the different parts of 53 human eyes from foetal life to old age is described, as evaluated by light microscopy of histochemical preparations. In general elastic tissue was most evident in the collagenous structures save the adult cornea in which incomplete elastic fibres occur rarely and then late in life. Precursor forms predominate in early childhood and show a limited and slow capacity for maturation. The suspensory zonular fibres of the lens appear to be composed largely of oxytalan throughout life. There is also evidence that corneal epithelium and endothelium, irideal smooth muscle and, less certainly, retinal pigment epithelium can synthesise the fibrillar component, although not elastin, of elastic tissue.

Adolescent↗
PubMed1988

A comparison of the elastic properties of human choroid and sclera.

Multiple strips of choroid (56) and sclera (64) from eight pairs of human eye-bank eyes were subjected to simple tension in a test apparatus to determine the rigidity (modulus of elasticity) of these tissues. The modulus of elasticity of the chorodial complex (choroid-Bruch's membrane-pigment epithelium) was significantly greater in posteriorly located samples than in anteriorly located ones (7.5 +/- 7.0 vs. 2.2 +/- 1.5 x 10(5) N m-2, mean +/- S.D.). The modulus of elasticity for the complex averaged across all locations was 6.0 +/- 2.8 x 10(5) N m-2 and the average stress at failure was 3.3 +/- 1.3 x 10(5) N m-2. The modulus of elasticity for scleral strips also varied with location and averaged 2.9 +/- 1.4 x 10(6) N m-2 for anterior sclera and 1.8 +/- 1.1 x 10(6) N m-2 for posterior sclera at stress levels ranging from 20- to 260 x 10(4) N m-2. There was a significant correlation of scleral stiffness with age (P less than 0.05, r = 0.80). The elastic properties of the choroidal complex may be relevant to the pathogenesis of a variety of ocular diseases, including macular degeneration, angioid streaks, choroidal folds, and choroidal ruptures.

Adolescent↗
PubMed1990

The fabric dependence of the orthotropic elastic constants of cancellous bone.

It has been proposed that the orthotropic elastic constants of cancellous bone depend upon a tensorial measure of anisotropy called fabric as well as the tissue's structural density. Cowin (1985, Mechanics Mater, 4, 137-147; 1986, J. biomech. Engng 108, 83-88) developed explicit relationships for the elastic constant, structural density and fabric relationship. In this study the orthotropic elastic moduli, structural density, and fabric components were measured for 11 cancellous bone specimens from five bovine femora and for 75 specimens from three human proximal tibiae and fitted to these relationships using a least squares analysis. The relationships explained between 72 and 94% of the variance in the elastic constants. The relationships between the elastic constants and squared or cubed power functions of structural density had better predictive value over the entire distribution of the data than did expressions with linear functions of structural density.

Aged↗
PubMed1996

Regional elastic performance of the human cornea.

The regional mechanical performance of the cornea and limbus was studied in vitro by pressure loading of 18 intact human eyes. The pressure-induced (2-100 mmHg) meridional and circumferential tangential mechanical strains of the epi-and endothelial side of the cornea were measured at the centre, the para-centre, the periphery and the limbus. Strains were computed from digital measures of distances between tiny mercury droplet markers fixed on the corneal surfaces. Corresponding in-plane membrane stresses were calculated from measurements of the regional meridional and circumferential radius of curvature and from measurements of the corneal thickness of the four regions. Young's moduli of elasticity were computed for each region in the meridional and circumferential direction assuming orthotropic elastic behaviour of the corneal stroma. A power function was used to fit the non-linear elastic stress-strain relationships. The pressure-induced meridional strains were smallest at the corneal paracentre and periphery, and largest at the limbus. The circumferential strains varied less between regions with the para-centre straining most. In the meridional direction, Young's modulus of elasticity was highest at the central and para-central corneal regions, whereas the highest circumferential elastic modulus was found at the limbus. This study supports the notation of circumferentially orientated reinforcing structures in human limbal tissue. The para-central region of the human cornea was found stiffer in the meridional direction compared with the circumferential direction, suggesting a meridionally orientated reinforcement of the para-central parts of the human cornea. These findings may have important implications for mechanical modelling of keratorefractive procedures.

Aged↗
PubMed1986

Modulus of elasticity in bending of composites and amalgams.

In this study, the modulus of elasticity in bending (a measure of rigidity) and transverse strength (a measure of edge strength) were determined for composites and amalgams. the results were as follows. The modulus of elasticity of microfilled composites is approximately one-third that of the macrofiller-containing composites. Composites containing a relatively coarse-sized macrofiller have a higher elastic modulus than those containing a finer macrofiller. The transverse strength of microfilled composites is approximately one half that of the macrofiller-containing composite, which, in turn, is close in value to the transverse strength of amalgam. High-copper amalgams are substantially more rigid than the traditional low-copper amalgams, but do not show large differences among themselves. The transverse strength among various amalgams does not appear to be related to amalgam type but does correlate to final Hg content. The modulus of elasticity of composites most likely to be used in posterior teeth is approximately one third of the modulus of elasticity of amalgam; that is, amalgams are three times more rigid.

Composite Resins↗
PubMed1991

A study of elastic tissue and actinic radiation in "aging," temporal arteritis, polymyalgia rheumatica, and atherosclerosis. The actinic storm in the modern world.

Solar radiation provokes a lifelong series of destructive changes in the supporting elastic tissues of "exposed" skin. Called actinic elastosis/lysis (or actinic "aging"), the sequence begins in early life as simple elastic hyperplasia, converts in middle life to progressive actinic elastotic degeneration, and, in late life, typically ends with a stage of resorption (elastolysis) and atrophy ("aged" skin). Superficial "exposed" arteries such as the temporal artery participate in the same sequence of degenerative elastotic changes, which, as in the skin, may provoke granulomatous responses in a few of the many subjects affected. In the case of the temporal artery, a contingent outcome may be giant cell (temporal) arteritis and its recognized systemic vascular expression, polymyalgia rheumatica. Actinic commotion at the surface of the body is often massive in degree and extent and may be expected to exert a deleterious autoimmune impact on the essential elastic tissues of the arterial system. For this reason, solar radiation should be recognized as a risk factor for other elastic-related vascular diseases, including atherosclerosis and aneurysms. Man-made radiations may be exacerbating the effects of predominant solar radiation. Of the many radiant bands that make up the actinic (electromagnetic) spectrum, little is known for certain about the identity of those that cause these prevalent disorders of elastic tissue. Until this void is filled, more care should be taken with solar and the other "safe" radiations.

Arteriosclerosis↗
PubMed1991

Regional differences in elastic recoil after percutaneous transluminal coronary angioplasty: a quantitative angiographic study.

The immediate result of percutaneous transluminal coronary angioplasty is influenced by both plastic and elastic changes of the vessel wall. To evaluate the amount of elastic recoil after coronary balloon angioplasty, the minimal luminal cross-sectional area of the largest balloon used at highest inflation pressure was compared with the minimal luminal vessel cross-sectional area directly after final balloon deflation in 607 lesions (526 patients). Elastic recoil was defined as the difference between balloon cross-sectional area and minimal luminal cross-sectional area of the dilated coronary segment immediately after balloon withdrawal. A videodensitometric analysis technique was used to avoid geometric assumptions on stenosis morphology directly after angioplasty. Mean balloon cross-sectional area was 5.3 +/- 1.6 mm2 and minimal luminal cross-sectional area after angioplasty was 2.8 +/- 1.4 mm2. Reference areas before and after angioplasty did not differ (6.0 +/- 2.6 and 6.2 +/- 2.6 mm2, respectively). Univariate analysis revealed that asymmetric lesions, lesions located in less angulated parts of the artery and lesions with a low plaque content showed more elastic recoil. Lesions located in distal parts of the coronary tree were also associated with more elastic recoil probably related to relative balloon oversizing in these distal lesions.

Aged↗
PubMedDate not supplied

Isoforms of tau protein from mammalian brain and avian erythrocytes: structure, self-assembly, and elasticity.

Previous studies on tau protein showed that the protein forms paracrystals which are unusually elastic. The paracrystals were obtained from a mixture of isoforms prepared from brain tissue, and the protein was in a mixed state of phosphorylation. Subsequently we showed that the structure and elasticity was related to the state of phosphorylation. However, this left open the possibility that the isotype composition played a role as well. We have now addressed this question by separating the individual isoforms and analyzing their structure. The paracrystals from all isoforms are similar to one another and to those of the native mixture; the same holds for the elasticity. Thus the tendency to self-associate, the apparent structure, and the elasticity are determined by those regions of tau which all isoforms have in common. In addition we compare tau paracrystals from three different sources. Apart from the porcine brain tau described earlier we have prepared paracrystals from bovine brain tau because its sequence is now known (Himmler et al., 1989). The structure and elasticity is indistinguishable from porcine tau. Second, we have prepared tau from avian erythrocytes where it is found in the membrane-associated marginal band microtubules (Murphy and Wallis, 1985). Its isoform composition differs from mammalian brain tau, but again the structural properties are similar. A notable difference is that the shift in electrophoretic mobility induced by phosphorylation with CaM kinase, typical of all brain tau isotypes, is not found in the marginal band tau. Tau shows a strong tendency of longitudinal self-association which is apparent not only in the crystallization buffer but also in standard microtubule reassembly buffer.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Immunohistochemical analysis of smooth muscle cells and volumetric density of the elastic system fibers of wild boar (Sus scrofa) penis.

The purpose of the present study was to verify the smooth muscle cell distribution and elastic system fibers volumetric density (Vv) in the corpus spongiosum and corpus cavernosum of the wild boar penis. Adult wild boars (n=13) were used. The penile mid shaft fragments were fixed with 4% phosphate buffered formalin solution and/or Bouin's liquid during 24-48 h, and processed using standard histological techniques. The sections were stained with Weigert's Resorcin-Fucsin with previous oxidation. The elastic system fibers Vv was determined in 25 random fields of each fragment using M42 test system. For immunohistochemical analysis, monoclonal anti-alpha actin smooth muscle was used. The histochemical methods detected elastic system fibers in both corpus spongiosum and corpus cavernosum of all animals. The elastic fibers Vv average was 36.6%+/-0.9 for corpus spongiosum and 11.7%+/-0.5 for corpus cavernosum. Through immunocitochemistry, a small quantity of smooth muscle cells was visualized in intimate relationship with blood vessels wall. The great amount of elastic fibers and the smooth muscle cell distribution beneath the endothelium suggest that these fibers may have an important role in penile erection process in the penis of wild boars.

Actins↗
PubMed2006

Elastic properties of the reconstructed aorta in hypoplastic left heart syndrome.

BACKGROUND: Patients with repaired coarctation of the aorta retain abnormal elastic properties of the aorta. It is not known whether patients with hypoplastic left heart syndrome also manifest abnormal elastic properties after palliative surgery. The presence of such abnormalities may have important clinical implications as reduced aortic compliance might adversely impact single right ventricular function. METHODS: We prospectively evaluated the elastic properties of the aorta in a cohort of patients with hypoplastic left heart syndrome who had undergone the Norwood procedure with aortic arch reconstruction and subsequent bidirectional Glenn or Fontan procedure. The hypoplastic left heart syndrome patients (n = 20) were compared with single-ventricle patients (n = 18) without history of arch reconstruction and patients with double-ventricular lesions (n = 22). Aortic elastic function was quantified by distensibility index and stiffness index. M-mode measurements of the transverse aortic arch were obtained with transesophageal echocardiography under general anesthesia. Patients were evaluated at a median age of 22.2 months with no age difference between patient subgroups. RESULTS: Distensibility index was significantly less (p = 0.007) and stiffness index greater (p = 0.005) in the reconstructed arch of hypoplastic left heart syndrome patients compared with single-ventricle and double-ventricle patients. CONCLUSIONS: Patients with hypoplastic left heart syndrome after Norwood palliation have increased aortic stiffness and decreased distensibility in the reconstructed transverse arch. As previous studies in adults have shown that decreased aortic compliance increases the energy cost of cardiac ejection, examination of modifications to the surgical technique that might improve elastic properties is warranted.

Aorta, Thoracic↗