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PubMed1980

Elastic fibers of pancreatic ductal systems in pancreatitis.

In an attempt to clarify the etiology of idiopathic pancreatitis, 14 cases of chronic idiopathic pancreatitis were histologically examined. A nest of small cysts consisting of cystic, distended pancreatic ductules with a complete lack of elastic fibers in the wall was observed in 3 out of 14 cases. Studies were then focused on the behavior of elastic fibers in pancreatic ductal system in 100 cases of normal pancreas, 55 cases of chronic pancreatitis and 10 cases of pancreatolithiasis. Partial hypoplasia and/or aplasia of elastic fibers in the walls of pancreatic ductules were demonstrated with a frequency of 30% in normal pancreas, 36.3% in pancreatitis and 50% in pancreatolithiasis cases. Formation of a nest of small cysts wad detected in 4 cases of normal pancreas, 3 cases of pancreatitis and 1 case of pancreatolithiasis. It was presumed that these abnormalities of elastic fibers and formation of small cysts containing inspissated secretions might act as potential etiologic or aggravating factors in pancreatitis by a mechanism of either disturbing normal pancreatic outlow or changing pressure in the duct.

Adult↗
PubMed1989

An experimental study on the effects of elastase, bleomycin and infection on the growth and tensile strength of elastic tissue in rabbit fetal membranes.

The effects of bleomycin, elastase and infection on the tensile strength of rabbit fetal membranes and the structure of the elastic tissue of rabbit amnion were studied. The experimental subjects were rabbits to which bleomycin (total dose, 20 mg) or elastase (total dose, 60 mg) was administered from 18 days of pregnancy. In addition to the fetal membranes from these treated animals, fetal membranes with amniotic infection induced by injection of Escherichia coli into the amniotic fluid (AF) of rabbits at 22 or 23 days of pregnancy were examined, and those from rabbits administered physiological saline solution were used as controls. The results obtained were as follows. Determination of tensile strength of the fetal membranes revealed that the infected membranes had minimum rupture pressure (18.67 +/- 6.30 mm Hg), followed by the elastase administration group (46.67 +/- 3.51 mm Hg). The value in the bleomycin administration group (99.67 +/- 12.89 mm Hg) was significantly higher than that in the control group (61.80 +/- 6.30 mm Hg). Histological changes in the fibroblast layer of these fetal membranes included elastic fibrosis due to excessive collagen production, which was mostly manifested as fibrosis densa, in the bleomycin administration group. In the elastase administration group, the elastic fibers were eliminated or became minute, as in the infection groups. The above results showed the adverse effects of elastase and bleomycin and the destructive effect of infection on the growth and properties of elastic tissue in the amnion, suggesting their pathophysiological importance.

Animals↗
PubMed2004

Annular elastolytic giant cell granuloma causes an irreversible disappearance of the elastic fibres.

A 67-year-old man presented with grouped red papules with a smooth surface coalescing to relatively well-demarcated plaques on his left thigh, in the axillae and on the lateral parts of the trunk. The plaques were growing slowly, and the older ones had a frilled surface. A skin biopsy showed a zone of disappearance of the elastic fibres with a rim of giant multinuclear cells with fragments of the elastic fibres in their cytoplasm. This finding is typical of annular elastolytic giant cell granuloma (AEGCG). After corticosteroid therapy, the inflammation resolved, causing the frilled surface of the lesions due to the disappearance of the elastic fibres. Remission of the skin lesions lasted for 1.5 years. A second skin biopsy taken from the site of the previous lesion showed the absence of the elastic fibres, thus their phagocytosis was irreversible.

Aged↗
PubMed2006

Arterial elasticity and erectile dysfunction in hypertensive men.

Erectile dysfunction is a common symptom among hypertensive patients that impairs quality of life and adherence to antihypertensive pharmacologic therapy. It is also associated with cardiovascular risk factors and disease. The Sexual Health Inventory in Men (SHIM) was administered to 105 ambulatory hypertensive patients, and large and small artery elasticity indices were measured. Each variable was examined in a simple linear regression model or 1-way analysis of variance model to determine each variable's relationship with the SHIM score. Variables that were significantly associated with the SHIM score in the univariate models included age, duration of hypertension, peripheral vascular disease, and small artery elasticity. Large artery elasticity was not significantly associated with the SHIM score. In the multivariate model, age, hypertension duration, and peripheral vascular disease were associated with a lower SHIM score. This study demonstrates a relationship between erectile dysfunction and reduced artery elasticity.

Blood Pressure↗
PubMed1995

Elastic recoil and intimal thickening after coronary stenting.

In this study, the long-term elastic recoil of the stents and the intimal thickening over the stents were evaluated separately. Twenty-nine patients who received a Wiktor coronary stent were angiographically followed-up at 2 weeks, 3 months, and 6 months. The elastic recoil of the stent was evaluated by the changes in minimum stent diameter. The intimal thickness was evaluated by the difference between minimum stent diameter and minimum lumen diameter. Minimum stent diameter showed no significant change up to 6 months. The significant increase (P < 0.05) of the intimal thickness was detected only between 2 weeks and 3 months. In conclusion, the Wiktor stent prevented the elastic recoil up to 6 months, and was covered by the neointima which increased its thickness mainly between 2 weeks and 3 months after stenting. It was suggested that stent restenosis was not caused by the elastic recoil, but by the intimal thickening.

Aged↗
PubMed1985

Dermal melanocytes and elastic fibers.

The relationship between dermal melanocytes and elastic fibers was studied by electron microscopy. In 3 patients with dermal melanocytosis, the long cytoplasmic processes of the melanocytes were aligned along the long axis of the elastic fiber, and encircled or embraced these fibers. The same intimacy existed between melanocytes and elastic fibers in the skin of cynomolgus macaques, who normally have dermal melanocytes. These findings suggest that dermal melanocytes, for reasons yet to be determined, interact with elastic fibers under these special conditions.

Aged↗
PubMed1987

Elastic fibers in scar tissue: scanning and transmission electron microscopic studies.

Cutaneous scar tissue (atrophic and hypertrophic) and normal dermis were examined using scanning (SEM) and transmission electron microscopy (TEM) as well as light microscopy (LM). Although LM revealed only a few Weigert stain-positive elastic fibers in scar tissue, SEM and TEM disclosed the presence of a large number of fine elastic fibers which was not present in normal dermis. Atrophic scar tissue contained more Weigert stain-positive fibers and fewer fine elastic fibers than hypertrophic scar tissue. In addition, finding suggestive of newly synthesized elastic fibers were seen in some hypertrophic scar tissue. These results indicate that there is elastogenesis in scar tissue.

Adolescent↗
PubMed1988

Elastic fibers in striae distensae.

Eight cases with striae distensae associated with obesity or prolonged corticosteroid intake were examined by light and scanning electron microscopy. Fine elastic fibers predominated in early lesions, while thick elastic fibers predominated in older lesions. In early lesions the periphery showed thick and tortuous elastic fibers, but in older lesions it was of normal appearance. It is suggested the elastic fibers in striae were newly synthesized and gradually increased and thickened with age.

Adolescent↗
PubMed1999

Arterial elastorrhexis: manifestation of a generalized elastic tissue disorder in beta-thalassaemia major.

Pseudoxanthoma elasticum-like lesions of the eye and skin are frequently observed in beta-thalassaemia, and there has been speculation about associated vascular lesions. This led to our study of histopathological material from thalassaemic patients. Histological re-examination was made of a series of 45 spleens and 45 surgical liver biopsies from 45 patients with beta-thalassaemia major, aged 6-25 yr and treated over the 20-yr period 1975-95. Correlations between clinical, laboratory and histological findings were demonstrated by statistical analysis. Arteriopathy characterized by fragmentation and multiple defects of the internal elastic lamina ('arterial elastorrhexis'), with deposits of iron and calcium salts, was found in the hilar arteries of the spleen with a frequency of 96%. Similar lesions were observed in the parenchymal arteries and the stromal elastic tissue ('stromal elastorrhexis') of the spleen, liver and lymph nodes. Arterial and elastic tissue alterations appear in the first decade of life and become generalized over the course of the disease, independent of the time of onset of transfusion and iron chelation therapy. Arterial elastorrhexis is the earliest and most frequent manifestation of a systemic elastic tissue disorder in beta-thalassaemia major. It appears to be an acquired pseudoxanthoma elasticum-like syndrome, related primarily to tissue hypoxia and disturbance of elastin metabolism.

Adolescent↗
PubMed1976

A new method of recording the elastic recovery of dental impression materials.

Assessments of the elastic recovery of elastic impression materials have so far been carried out only to a limited degree because of lack of adequate measuring instruments. A method is described which enables measurement and recording electronically of the creep properties, including the elastic recovery time and the permanent deformation, of elastic impression materials in relation to their degree of setting and to the size and time of the induced deformation. The apparatus and the experimental and mathematical methods described can easily be handled by a reasonably skillful laboratory assistant.

Dental Impression Materials↗
PubMed2006

Relationship between impaired elastic properties of aorta with left ventricle geometric patterns and left ventricle diastolic functions in patients with newly diagnosed essential hypertension.

The aim of this study was to investigate the association between elastic properties of aorta with left ventricle (LV) geometric patterns and LV diastolic functions in patients with newly diagnosed hypertension (HT). We studied 149 patients with newly diagnosed HT and 29 healthy control subjects. Echocardiographic examination was performed to all subjects. Ascending aorta (Ao) diameters (mm/m2) and Ao elastic indexes - namely, Ao strain [AS] (%), Ao distensibility [AD] (cm2 dyn(-1) x 10(-6)) were calculated. Four different geometric patterns were identified in hypertensive patients according to LV mass index (LVMI) and relative wall thickness (RWT). Tissue Doppler-derived Ea/Aa was determined from the all subjects. Patients vs. control subjects had lower mean AS and AD (p < 0.001 for both). Mean AS and AD of all geometric patterns significantly decreased compared with control group (p < 0.05 for all). Both AS and aortic AD of concentric remodelling (CR; p = 0.017 for both) and concentric hypertophic groups (p < 0.001 for both) were decreased compared with normal LV group. AS and AD of concentric hypertrophic pattern was lower than that of the CR group (p = 0.011 and 0.020 respectively) and the eccentric hypertrophic group (p < 0.001 and p = 0.002, respectively). Both AS and AD of the CR group were similar to that of the eccentric hypertrophic group (p > 0.05 for both). Both AS and AD were significantly correlated with age (beta = -0.178, p = 0.025, beta = -0.158, p = 0.029 respectively), LVMI (beta = -0.223, p = 0.022, beta = -263, p = 0.003 respectively), RWT (beta = -0.196, p = 0.019, beta = -0.189, p = 0.013 respectively) and Ea/Aa (beta = 0.174, p = 0.045, beta = 0.247, p = 0.002 respectively) in multiple linear regression analysis. Elastic properties of aorta were impaired in newly diagnosed HT. The degree of this impairment is different among various LV geometric patterns. In addition, impaired elastic properties of aorta were associated with RWT, LVMI and diastolic disfunctions, besides age, but not with LV geometry.

Adult↗
PubMed1981

The dependence of the short-range elasticity on sarcomere length in resting isolated frog muscle fibres.

The tension response of a resting muscle fibre to a sudden small stretch (ca. 1% of the fibre length) at constant velocity was analyzed according to a mechanical model in which two components are arranged in parallel: (i) The parallel elastic component (PEC) which is responsible for the resting tension of the fibre. (ii) The short-range elastic component (SREC) which has a highly non-linear tension response: Initially, the tension increases linearly with stretch, but with further stretch the increase in tension subsides and a steady tension level is attained. Both the initial short-range elastic stiffness and the steady state tension level increased with increasing sarcomere length up to 2.9-3.3 micrometer where both variables reached maximum values. The maximum value of the steady tension level was about 1% of the maximum twitch tension. With further increase of sarcomere length both the short-range elastic stiffness and the steady tension level decreased and approached zero at a sarcomere length of about 3.7 micrometer. The structural basis for the SREC is considered to be myosin heads which are cross-linking the thick and the thin filaments even in the resting state of the fibre.

Animals↗
PubMed1983

The effect of prolonged skeletal muscle stretch-shortening cycle on recoil of elastic energy and on energy expenditure.

The enhancement of performance in stretch-shortening exercises has been attributed to the recoil of elastic energy stored during the stretching phase. If the time between stretching and shortening (coupling time) is too long the stored elastic energy can be wasted. In the present study, coupling time was increased by asking ten male subjects to run on a treadmill at different speeds (2.2-5.2 m X s-1) using special soft shoes in addition to normal shoes. The results indicated that running with soft shoes required greater energy consumption than running with normal shoes except at slow speed (2.2 m X s-1). When the running speed was increased the extra energy consumed using soft shoes was parallelly enhanced (0.4 J X kg-1/step at 5.2 m X s-1). It was suggested that the effect of coupling time as limiting factor for recoil of elastic energy was relevant in fast twitch (FT) fibers, which were progressively recruited when the running speed was increased. This is consistent to the fact that cross-bridge life time in FT fibers is very short, and therefore more sensitive to coupling time. At slow running speed (2.2 m X s-1) only slow twitch (ST) fibers were recruited and the enhancement of coupling time was not long enough to provocate detachment of cross-bridges of ST fibers, which possess a long cross-bridge life time. It was concluded that the different recruitment of ST and FT fibers influenced the pattern of recoil of elastic energy which was dependent on the running speed.

Adult↗
PubMed1997

Elastic protein-based materials in tissue reconstruction.

In natural tissues, cells form multiple attachment sites to their extracellular matrix. By means of those attachments, cells deform as the tissue deforms in response to the natural mechanical stresses and strains that the tissue must sustain during function. These mechanical forces are the energy input that instruct the cells to produce the extracellular matrix sufficient to sustain those forces. Thus, an ideal artificial material should have both the attachment sites for the natural cells and a compliance that matches the natural tissue. Elastic protein-based polymers have been designed to provide both cell attachment sites and to exhibit the required elastic modulus of the tissue to be replaced. Thus, this introduces the potential to design a temporary functional scaffolding that will be remodeled, while functioning, into a natural tissue. A feasibility study applies this concept to the problem of urinary bladder reconstruction in terms of the filling and emptying of a simulated bladder comprised of an elastic protein-based matrix containing cell attachment sites with human urothelial cells growing out onto the dynamic matrix. Furthermore, the elastic protein-based materials themselves have been designed to perform the set of energy conversions that occur in living organisms and, in particular, to convert mechanical energy into chemical energy with the result of chemical signals of the sort that could provide the stimuli to turn on the genes for producing the required extracellular proteins.

Animals↗
PubMed2000

A Conewise Linear Elasticity mixture model for the analysis of tension-compression nonlinearity in articular cartilage.

A biphasic mixture model is developed that can account for the observed tension-compression nonlinearity of cartilage by employing the continuum-based Conewise Linear Elasticity (CLE) model of Curnier et al. (J. Elasticity, 37, 1-38, 1995) to describe the solid phase of the mixture. In this first investigation, the orthotropic octantwise linear elasticity model was reduced to the more specialized case of cubic symmetry, to reduce the number of elastic constants from twelve to four. Confined and unconfined compression stress-relaxation, and torsional shear testing were performed on each of nine bovine humeral head articular cartilage cylindrical plugs from 6 month old calves. Using the CLE model with cubic symmetry, the aggregate modulus in compression and axial permeability were obtained from confined compression (H-A = 0.64 +/- 0.22 MPa, k2 = 3.62 +/- 0.97 x 10(-16) m4/N.s, r2 = 0.95 +/- 0.03), the tensile modulus, compressive Poisson ratio, and radial permeability were obtained from unconfined compression (E+Y = 12.75 +/- 1.56 MPa, v- = 0.03 +/- 0.01, kr = 6.06 +/- 2.10 x 10(-16) m4/N.s, r2 = 0.99 +/- 0.00), and the shear modulus was obtained from torsional shear (mu = 0.17 +/- 0.06 MPa). The model was also employed to predict the interstitial fluid pressure successfully at the center of the cartilage plug in unconfined compression (r2 = 0.98 +/- 0.01). The results of this study demonstrate that the integration of the CLE model with the biphasic mixture theory can provide a model of cartilage that can successfully curve-fit three distinct testing configurations while producing material parameters consistent with previous reports in the literature.

Cartilage, Articular↗
PubMed2002

Linear poroelastic cancellous bone anisotropy: trabecular solid elastic and fluid transport properties.

The mechanical performance of cancellous bone is characterized using experiments which apply linear poroelasticity theory. It is hypothesized that the anisotropic organization of the solid and pore volumes of cancellous bone can be physically characterized separately (no deformable boundary interactive effects) within the same bone sample. Due to its spongy construction, the in vivo mechanical function of cancellous or trabecular bone is dependent upon fluid and solid materials which may interact in a hydraulic, convective fashion during functional loading. This project provides insight into the organization of the tissue, ie., the trabecular connectivity, by defining the separate nature of this biphasic performance. Previous fluid flow experiments [Kohles et al., 2001, Journal of Biomechanics, 34(11), pp. 1197-1202] describe the pore space via orthotropic permeability. Ultrasonic wave propagation through the trabecular network is used to describe the solid component via orthotropic elastic moduli and material stiffness coefficients. The linear poroelastic nature of the tissue is further described by relating transport (fluid flow) and elasticity (trabecular load transmission) during regression analysis. In addition, an empirical relationship between permeability and porosity is applied to the collected data. Mean parameters in the superior-inferior (SI) orientation of cubic samples (n=20) harvested from a single bovine distal femur were the largest (p<0.05) in comparison to medial-lateral (ML) and anterior-posterior (AP) orientations: Apparent elastic modulus (2,139 MPa), permeability (4.65x10(-10) m2), and material stiffness coefficient (13.6 GPa). A negative correlation between permeability as a predictor of structural elastic modulus supported a parametric relationship in the ML (R2=0.4793), AP (R2=0.3018), and SI (R2=0.6445) directions (p<0.05).

Animals↗
PubMed2003

Pressure wave propagation in fluid-filled co-axial elastic tubes. Part 1: Basic theory.

Our work is motivated by ideas about the pathogenesis of syringomyelia. This is a serious disease characterized by the appearance of longitudinal cavities within the spinal cord. Its causes are unknown, but pressure propagation is probably implicated. We have developed an inviscid theory for the propagation of pressure waves in co-axial, fluid-filled, elastic tubes. This is intended as a simple model of the intraspinal cerebrospinal-fluid system. Our approach is based on the classic theory for the propagation of longitudinal waves in single, fluid-filled, elastic tubes. We show that for small-amplitude waves the governing equations reduce to the classic wave equation. The wave speed is found to be a strong function of the ratio of the tubes' cross-sectional areas. It is found that the leading edge of a transmural pressure pulse tends to generate compressive waves with converging wave fronts. Consequently, the leading edge of the pressure pulse steepens to form a shock-like elastic jump. A weakly nonlinear theory is developed for such an elastic jump.

Animals↗
PubMed2005

Mechanics of curved plasma membrane vesicles: resting shapes, membrane curvature, and in-plane shear elasticity.

Highly curved cell membrane structures, such as plasmalemmal vesicles (caveolae) and clathrin-coated pits, facilitate many cell functions, including the clustering of membrane receptors and transport of specific extracellular macromolecules by endothelial cells. These structures are subject to large mechanical deformations when the plasma membrane is stretched and subject to a change of its curvature. To enhance our understanding of plasmalemmal vesicles we need to improve the understanding of the mechanics in regions of high membrane curvatures. We examine here, theoretically, the shapes of plasmalemmal vesicles assuming that they consist of three membrane domains: an inner domain with high curvature, an outer domain with moderate curvature, and an outermost flat domain, all in the unstressed state. We assume the membrane properties are the same in these domains with membrane bending elasticity as well as in-plane shear elasticity. Special emphasis is placed on the effects of membrane curvature and in-plane shear elasticity on the mechanics of vesicle during unfolding by application of membrane tension. The vesicle shapes were computed by minimization of bending and in-plane shear strain energy. Mechanically stable vesicles were identified with characteristic membrane necks. Upon stretch of the membrane, the vesicle necks disappeared relatively abruptly leading to membrane shapes that consist of curved indentations. While the resting shape of vesicles is predominantly affected by the membrane spontaneous curvatures, the membrane shear elasticity (for a range of values recorded in the red cell membrane) makes a significant contribution as the vesicle is subject to stretch and unfolding. The membrane tension required to unfold the vesicle is sensitive with respect to its shape, especially as the vesicle becomes fully unfolded and approaches a relative flat shape.

Computer Simulation↗