Alterations in mechanical properties of mesenteric resistance arteries in experimental portal hypertension

2009 ◽  
Vol 297 (4) ◽  
pp. G849-G857 ◽  
Author(s):  
Markus Resch ◽  
Reiner Wiest ◽  
Lukas Moleda ◽  
Sabine Fredersdorf ◽  
Benjamin Stoelcker ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Liver Cirrhosis ◽  
Portal Hypertension ◽  
Structural Changes ◽  
Cross Sectional Area ◽  
Mesenteric Arteries ◽  
Sectional Area ◽  
Resistance Arteries ◽  
Cross Sectional ◽  
Strain Stress

Splanchnic vasodilation is the pathophysiological hallmark in the development of the hyperdynamic circulatory syndrome in liver cirrhosis and portal hypertension. This has been attributed so far mainly to a marked vascular hyporeactivity to endogenous vasoconstrictors. However, myogenic tone and vessel stiffness have not been addressed in mesenteric arteries in liver cirrhosis. CCl4−-induced ascitic cirrhotic (LC) and age-matched control rats, portal vein-ligated (PVL) rats, and sham-operated rats were investigated. Third-order mesenteric resistance arteries were studied under no-flow conditions using a pressure myograph measuring media thickness and lumen diameter in response to incremental increases in intramural pressure, from which wall mechanics were calculated. Electron microscopy was used for investigation of wall ultrastructure, especially the fenestrae in internal elastic lamina (IEL). In PVL animals, no significant change in passive vessel strain, stress, media-to-lumen ratio, or cross-sectional area was noted. In contrast, in LC rats, vessel strain was markedly elevated compared with healthy control rats, indicating a marked reduction in vessel stiffness. In addition, the strain-stress curve was shifted to the right, and the elastic modulus in dependency on vessel stress decreased, demonstrating predominantly structure-dependent factors to be involved. The media-to-lumen quotient was not significantly altered, but cross-sectional area was highly increased in LC rats, indicating hypertrophic outward remodeling. These findings were paralleled by enlarged fenestrae in the IEL but no change in thickness of IEL or proportion of extracellular matrix or vascular smooth muscle in LC rats. We concluded that, in long-standing severe portal hypertension such as ascitic LC but not in short-term conditions such as PVL, mesenteric resistance arteries exhibit vascular remodeling and markedly less resistant mechanical properties, leading to decreased vessel stiffness accompanied by structural changes in the IEL. This may well contribute to the maintenance and severity of splanchnic arterial vasodilation in LC.

scholarly journals Sex Differences in the Morphological and Mechanical Properties of the Achilles Tendon

2021 ◽  
Vol 18 (17) ◽  
pp. 8974
Author(s):  
Xini Zhang ◽  
Liqin Deng ◽  
Songlin Xiao ◽  
Lu Li ◽  
Weijie Fu
Keyword(s):  
Mechanical Properties ◽  
Achilles Tendon ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Cross Sectional Area ◽  
Morphological Properties ◽  
Sectional Area ◽  
Cross Sectional ◽  
Force Peak ◽  
Strain Stress

Background: Patients with Achilles tendon (AT) injuries are often engaged in sedentary work because of decreasing tendon vascularisation. Furthermore, men are more likely to be exposed to AT tendinosis or ruptures. These conditions are related to the morphological and mechanical properties of AT, but the mechanism remains unclear. This study aimed to investigate the effects of sex on the morphological and mechanical properties of the AT in inactive individuals. Methods: In total, 30 inactive healthy participants (15 male participants and 15 female participants) were recruited. The AT morphological properties (cross-sectional area, thickness, and length) were captured by using an ultrasound device. The AT force–elongation characteristics were determined during isometric plantarflexion with the ultrasonic videos. The AT stiffness was determined at 50%–100% maximum voluntary contraction force. The AT strain, stress, and hysteresis were calculated. Results: Male participants had 15% longer AT length, 31% larger AT cross-sectional area and 21% thicker AT than female participants (p < 0.05). The plantarflexion torque, peak AT force, peak AT stress, and AT stiffness were significantly greater in male participants than in female participants (p < 0.05). However, no significant sex-specific differences were observed in peak AT strain and hysteresis (p > 0.05). Conclusions: In physically inactive adults, the morphological properties of AT were superior in men but were exposed to higher stress conditions. Moreover, no significant sex-specific differences were observed in peak AT strain and hysteresis, indicating that the AT of males did not store and return elastic energy more efficiently than that of females. Thus, the mechanical properties of the AT should be maintained and/or improved through physical exercise.

Comparison of the Cross Sectional Area, the Loss in Volume and the Mechanical Properties of LAE442 and MgCa0.8 as Resorbable Magnesium Alloy Implants after 12 Months Implantation Duration

2010 ◽  
Vol 638-642 ◽  
pp. 675-680 ◽  
Author(s):  
Martina Thomann ◽  
Nina von der Höh ◽  
Dirk Bormann ◽  
Dina Rittershaus ◽  
C. Krause ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cross Sections ◽  
Degradation Process ◽  
Cross Sectional Area ◽  
Bending Test ◽  
Sectional Area ◽  
Cross Sectional ◽  
Initial Strength ◽  
Three Point Bending ◽  
The Cross

Current research focuses on magnesium based alloys in the course of searching a resorbable osteosynthetic material which provides sufficient mechanical properties besides a good biocompatibility. Previous studies reported on a favorable biocompatibility of the alloys LAE442 and MgCa0.8. The present study compared the degradation process of cylindrical LAE442 and MgCa0.8 implants after 12 months implantation duration. Therefore, 10 extruded implants (2.5 x 25 mm, cross sectional area 4.9 mm²) of both alloys were implanted into the medullary cavity of both tibiae of rabbits for 12 months. After euthanization, the right bone-implant-compound was scanned in a µ-computed tomograph (µCT80, ScancoMedical) and nine uniformly distributed cross-sections of each implant were used to determine the residual implants´ cross sectional area (Software AxioVisionRelease 4.5, Zeiss). Left implants were taken out of the bone carefully. After weighing, a three-point bending test was carried out. LAE442 implants degraded obviously slower and more homogeneously than MgCa0.8. The mean residual cross sectional area of LAE442 implants was 4.7 ± 0.07 mm². MgCa0.8 showed an area of only 2.18 ± 1.03 mm². In contrast, the loss in volume of LAE442 pins was more obvious. They lost 64 % of their initial weight. The volume of MgCa0.8 reduced clearly to 54.4 % which corresponds to the cross sectional area results. Three point bending tests revealed that LAE442 showed a loss in strength of 71.2 % while MgCa0.8 lost 85.6 % of its initial strength. All results indicated that LAE442 implants degraded slowly, probably due to the formation of a very obvious degradation layer. Degradation of MgCa0.8 implants was far advanced.

Habitual loading results in tendon hypertrophy and increased stiffness of the human patellar tendon

2008 ◽  
Vol 105 (3) ◽  
pp. 805-810 ◽  
Author(s):  
C. Couppé ◽  
M. Kongsgaard ◽  
P. Aagaard ◽  
P. Hansen ◽  
J. Bojsen-Moller ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Patellar Tendon ◽  
Cross Sectional Area ◽  
Isometric Contractions ◽  
Sectional Area ◽  
Cross Sectional ◽  
Strength Difference ◽  
Distal Tendon

The purpose of this study was to examine patellar tendon (PT) size and mechanical properties in subjects with a side-to-side strength difference of ≥15% due to sport-induced loading. Seven elite fencers and badminton players were included. Cross-sectional area (CSA) of the PT obtained from MRI and ultrasonography-based measurement of tibial and patellar movement together with PT force during isometric contractions were used to estimate mechanical properties of the PT bilaterally. We found that distal tendon and PT, but not mid-tendon, CSA were greater on the lead extremity compared with the nonlead extremity (distal: 139 ± 11 vs. 116 ± 7 mm2; mid-tendon: 85 ± 5 vs. 77 ± 3 mm2; proximal: 106 ± 7 vs. 83 ± 4 mm2; P < 0.05). Distal tendon CSA was greater than proximal and mid-tendon CSA on both the lead and nonlead extremity ( P < 0.05). For a given common force, stress was lower on the lead extremity (52.9 ± 4.8 MPa) compared with the nonlead extremity (66.0 ± 8.0 MPa; P < 0.05). PT stiffness was also higher in the lead extremity (4,766 ± 716 N/mm) compared with the nonlead extremity (3,494 ± 446 N/mm) ( P < 0.05), whereas the modulus did not differ (lead 2.27 ± 0.27 GPa vs. nonlead 2.16 ± 0.28 GPa) at a common force. These data show that a habitual loading is associated with a significant increase in PT size and mechanical properties.

Effects of cross-sessional area and aspect ratio coupled with orientation on mechanical properties and deformation behavior of Cu nanowires

2021 ◽  
Author(s):  
Hui Cao ◽  
Wenke Chen ◽  
Zhiyuan Rui ◽  
Changfeng Yan
Keyword(s):  
Mechanical Properties ◽  
Aspect Ratio ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Cu Nanowires ◽  
The Cross

Abstract Metal nanomaterials exhibit excellent mechanical properties compared with corresponding bulk materials and have potential applications in various areas. Despite a number of studies of the size effect on Cu nanowires mechanical properties with square cross-sectional, investigations of them in rectangular cross-sectional with various sizes at constant volume are rare, and lack of multifactor coupling effect on mechanical properties and quantitative investigation. In this work, the dependence of mechanical properties and deformation mechanisms of Cu nanowires/nanoplates under tension on cross-sessional area, aspect ratio of cross-sectional coupled with orientation were investigated using molecular dynamics simulations and the semi-empirical expressions related to mechanical properties were proposed. The simulation results show that the Young’s modulus and the yield stress sharply increase with the aspect ratio except for the <110>{110}{001} Cu nanowires/nanoplates at the same cross-sectional area. And the Young’s modulus increases while the yield stress decreases with the cross-sectional area of Cu nanowires. However, both of them increase with the cross-sectional area of Cu nanoplates. Besides, the Young’s modulus increases with the cross-sectional area at all the orientations. The yield stress shows a mildly downward trend except for the <111> Cu nanowires with increased cross-sectional area. For the Cu nanowires with a small cross-sectional area, the surface force increases with the aspect ratio. In contrast, it decreases with the aspect ratio increase at a large cross-sectional area. At the cross-sectional area of 13.068 nm2, the surface force decreases with the aspect ratio of the <110> Cu nanowires while it increases at other orientations. The surface force is a linearly decreasing function of the cross-sectional area at different orientations. Quantitative studies show that Young’s modulus and yield stress to the aspect ratio of the Cu nanowires satisfy exponent relationship. In addition, the main deformation mechanism of Cu nanowires is the nucleation and propagation of partial dislocations while it is the twinning-dominated reorientation for Cu nanoplates.

scholarly journals Effects of Advanced Glycation Endproducts on the Mechanical Properties of Posterior Tibialis in Individuals with Diabetes Mellitus

2019 ◽  
Vol 4 (4) ◽  
pp. 2473011419S0045
Author(s):  
Jennifer A. Zellers ◽  
Jeremy Eekhoff ◽  
Remy Walk ◽  
Simon Y. Tang ◽  
Mary K. Hastings ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Mechanical Properties ◽  
Mechanical Testing ◽  
Advanced Glycation Endproducts ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Advanced Glycation ◽  
Cross Sectional ◽  
Glycation Endproducts ◽  
Wet Weight

Category: Diabetes Introduction/Purpose: Advanced glycation endproducts (AGEs) accumulate in tendon tissue in individuals with diabetes mellitus (DM). Although AGEs have been shown to impact tendon function by decreasing collagen sliding, this relationship has not been explored in humans with diabetes. Despite the prevalence of foot deformity in this population and implications of posterior tibialis dysfunction, the mechanical behavior of the posterior tibialis tendon has only been reported in a small (n=5), cadaveric study that did not report DM status. Therefore, the purpose of this study is to determine the effects of DM-associated AGEs accumulation on the mechanical properties of the posterior tibialis tendon. Methods: Posterior tibialis tendons were collected from individuals with and without DM undergoing lower extremity amputation. A 1-2 mm tendon transection was used for AGEs quantification. AGEs were quantified via fluorescence following papain digestion and hydrolyzation as described previously. Fluorescence was compared to a quinine standard to calculate AGEs content, which was normalized to sample wet weight. Tensile mechanical testing was completed with the remaining specimen (˜25 mm long). Tendon cross-sectional area was measured with a non-contact laser scanning device. Specimens were preloaded to 10 N and preconditioned for 10 cycles at 6% strain, subjected to stress-relaxation at 6% strain for 10 minutes, and loaded with a triangular waveform to a maximum of 10% strain at a rate of 1% strain per second. Individual values and group descriptive statistics are reported for AGEs content and mechanical testing. Relationships between AGEs content and various mechanical testing parameters were evaluated using Spearman correlation. Results: Six individuals (5 with DM, 4 male, mean(SD) age: 56(5)years) were included. AGEs content was increased in DM tendon (DM: 20.5(5.1), non-DM: 9.5 ng quinine/mg wet weight). Compared to non-DM tendon, DM tendons had larger cross-sectional area (DM: 44.3(4.9), non-DM: 11mm2). From stress relaxation, DM tendons had smaller peak (DM: 0.41(0.25), non-DM: 1.16 MPa) and equilibrium stress (DM: 0.23(0.13), non-DM: 0.83 MPa), and larger percent relaxation (DM: 46(6)%, non-DM: 29%)(Figure 1-A). DM tendons had decreased maximum stress at 10% strain (DM: 0.63(0.45), non-DM: 1.75 MPa), increased linear stiffness (DM: 35.2(27.6), non-DM: 19.2N/mm), and decreased linear modulus (DM: 8.5(7.0), non-DM: 20.1 MPa)(Figure 1-B, C) compared to non- DM tendon. Hysteresis (i.e., energy loss upon unloading) was higher in DM tendons (DM: 0.35(0.05), non-DM: 0.22), and positively correlated to AGEs (rho=0.943, p=0.005, Figure 1-D). Conclusion: Posterior tibialis tendons with DM exhibited increased AGEs content and altered mechanical properties. DM tendons were less stiff when accounting for cross-sectional area but had 2-4x the cross-sectional area of non-DM tendon, with inconsistent patterns in total tendon stiffness potentially attributable to several factors. DM tendons showed impaired energy storage and return, which was most strongly associated with AGEs. Non-DM samples were limited and the linear modulus was smaller than previously reported, however, all but one DM tendon had a modulus less than 50% of the non-DM sample. Future work will explore the mechanisms of AGEs-associated DM tendon impairments.

The significance of morphological changes in cerebral arteries after subarachnoid hemorrhage

1990 ◽  
Vol 72 (4) ◽  
pp. 626-633 ◽  
Author(s):  
Marc R. Mayberg ◽  
Tomohisa Okada ◽  
Don H. Bark
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Whole Blood ◽  
Vessel Wall ◽  
Structural Changes ◽  
Morphological Changes ◽  
Cerebral Arteries ◽  
Cross Sectional Area ◽  
Ultrastructural Changes ◽  
Sectional Area ◽  
Cross Sectional

✓ A porcine model was developed to allow quantitative assessment of morphological changes in cerebral arteries after subarachnoid hemorrhage and to determine the significance of structural changes in producing arterial narrowing. Whole blood was selectively applied to the middle cerebral artery (MCA) of seven pigs. After 10 days, vessels were perfusion-fixed and examined by light and transmission electron microscopy and immunohistochemistry. The MCA's exposed to whole blood for 10 days showed prominent luminal narrowing associated with profound ultrastructural changes affecting all layers of the vessel wall. Morphometric analysis, however, demonstrated that significant reductions in the luminal cross-sectional area (−55.8% ± 12.5%, p < 0.005) and increases in radial wall thickness (75.1% ± 10.5%, p < 0.005) were associated with only minimal increase in the cross-sectional area of the vessel wall (12.5% ± 15%,p < 0.025). By stereological analysis, the volume density of individual components of the arterial wall was unchanged in MCA's exposed to blood. Vessels exposed to blood showed a 44% reduction in smooth-muscle cell immunoreactive actin and increased collagen in the extracellular matrix of the vessel wall. These data suggest that structural changes in cerebral arteries after subarachnoid hemorrhage do not directly contribute to vessel narrowing through increases in wall mass. Nevertheless, such changes may reflect pathological mechanisms which act to augment prolonged vasoconstriction or inhibit the maintenance of normal vascular tone.

Force deficit during the onset of muscle hypertrophy

1989 ◽  
Vol 67 (6) ◽  
pp. 2600-2607 ◽  
Author(s):  
S. C. Kandarian ◽  
T. P. White
Keyword(s):  
Muscle Mass ◽  
Protein Concentration ◽  
Muscle Hypertrophy ◽  
Structural Changes ◽  
Relative Magnitude ◽  
Interstitial Space ◽  
Cross Sectional Area ◽  
Specific Force ◽  
Sectional Area ◽  
Cross Sectional

The purpose was to study selected structural changes associated with the deficit in maximum specific force (N/cm2) during the early development of skeletal muscle hypertrophy. Ablation of gastrocnemius and plantaris muscles was performed bilaterally in 35-day-old rats (n = 41), and the soleus muscle was studied from days 1 to 30 thereafter. Compared with control muscles from age-matched unoperated rats (n = 48), muscle mass and cross-sectional area increased in parallel from 28 to 52% over the 30-day postoperative period. Specific force of hypertrophied muscle was depressed 38% at days 1 and 3, and by 28% from days 5 to 30 after synergistic muscle ablation compared with age-matched control values. Interstitial space was 38% greater than the control value of 20.4 +/- 1 microliters/100 mg at day 1 only. Protein concentration was depressed 15% for 7 days after the ablation operation, and connective tissue protein concentration was unchanged. The relative magnitude of increased mean fiber cross-sectional area was less than that of muscle mass until day 7 after ablation. Mononuclear cell infiltration in interfascicular spaces occurred from days 3 to 30 without light microscopic evidence of muscle fiber injury. Initial functional deficits are explained in part by an enlarged interstitial space and decreased protein concentration; later deficits are likely accounted for by intracellular changes.

scholarly journals Mechanical Properties of Corroded-Damaged Reinforced Concrete Pile-supporting Wharves

2020 ◽  
Vol 6 (12) ◽  
pp. 2375-2396
Author(s):  
Cecielle N. Dacuan ◽  
Virgilio Abellana ◽  
Hana Astrid Canseco
Keyword(s):  
Mechanical Properties ◽  
Reinforced Concrete ◽  
Cross Sectional Area ◽  
Constant Current ◽  
Sectional Area ◽  
Reinforced Concrete Structure ◽  
Cross Sectional ◽  
Constant Current Density ◽  
Remaining Service Life ◽  
Residual Capacity

Corrosion is one of the significant deteriorations of reinforced concrete structures. It accelerated the performance loss of the structures, leading to a cross-sectional reduction of steel, which affects its mechanical properties, particularly its tensile capacity and ductility. The purpose of this study is to assess the serviceability and safety of corroded-damaged structures, particularly those exposed to aggressive marine environments. A total of 54 pcs of 150 mm-diameter and 300mm-height of cylindrical specimen were cast. Small-scaled specimens were accelerated to corrosion using impressed current techniques with a constant current density of 200 µA/cm2. Samples were immersed in a simulated environment with a 5% solution of sodium bicarbonate during corrosion acceleration. Corrosion alters the surface configuration of the steel bar. Pitting corrosions due to chloride aggression causes the residual cross-sectional area of corroded rebars to no longer round and varies considerably along its circumference and length. The reduction of the steel cross-sectional area has a significant impact on the degradation of the strength and durability of reinforcing structures. The residual capacity of the corroded reinforcement decreases with the reduction of the cross-sectional area of the steel reinforcement. The rate of corrosion affects the extent of the remaining service life of a corroded reinforced concrete structure. Doi: 10.28991/cej-2020-03091624 Full Text: PDF

Neonatal Spinal Cord Transection Decreases Hindlimb Weight-Bearing and Affects Formation of Achilles and Tail Tendons

2021 ◽  
Vol 143 (6) ◽  
Author(s):  
Sophia K. Theodossiou ◽  
Nicholas M. Pancheri ◽  
Alleyna C. Martes ◽  
Aimee L. Bozeman ◽  
Michele R. Brumley ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Spinal Cord ◽  
Locomotor Activity ◽  
Mechanical Loading ◽  
Weight Bearing ◽  
Cross Sectional Area ◽  
Spinal Cord Transection ◽  
Sectional Area ◽  
Cross Sectional ◽  
Partial Weight

Abstract Mechanical loading may be required for proper tendon formation. However, it is not well understood how tendon formation is impacted by the development of weight-bearing locomotor activity in the neonate. This study assessed tendon mechanical properties, and concomitant changes in weight-bearing locomotion, in neonatal rats subjected to a low thoracic spinal cord transection or a sham surgery at postnatal day (P)1. On P10, spontaneous locomotion was evaluated in spinal cord transected and sham controls to determine impacts on weight-bearing hindlimb movement. The mechanical properties of P10 Achilles tendons (ATs), as representative energy-storing, weight-bearing tendons, and tail tendons (TTs), as representative positional, non-weight-bearing tendons were evaluated. Non- and partial weight-bearing hindlimb activity decreased in spinal cord transected rats compared to sham controls. No spinal cord transected rats showed full weight-bearing locomotion. ATs from spinal cord transected rats had increased elastic modulus, while cross-sectional area trended lower compared to sham rats. TTs from spinal cord transected rats had higher stiffness and cross-sectional area. Collagen structure of ATs and TTs did not appear impacted by surgery condition, and no significant differences were detected in the collagen crimp pattern. Our findings suggest that mechanical loading from weight-bearing locomotor activity during development regulates neonatal AT lateral expansion and maintains tendon compliance, and that TTs may be differentially regulated. The onset and gradual increase of weight-bearing movement in the neonate may provide the mechanical loading needed to direct functional postnatal tendon formation.

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