Mechanisms of Residual Stress in Soft Tissues

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Yoram Lanir
Keyword(s):  
Residual Stress ◽  
Soft Tissues ◽  
Local Level ◽  
Mixture Theory ◽  
Meso Level ◽  
Physical Mechanisms ◽  
Organ Specific ◽  
Tissue Space ◽  
Micro Level

Although the importance of knowing the magnitude of residual stress (RS) and its functional significance are widely recognized, there is still disagreement and confusion regarding the nature of physical mechanisms giving rise to RS in tissues and organs. Here an attempt is made to examine the various mechanisms which may be involved in producing RS, and to estimate their roles and significance based on previously published experimental observations. Two concepts are introduced. The first establishes a hierarchy of different possible RS producing mechanisms from the micro (local) level of the tissue space, through the meso-level of the whole tissue, to the macro (organ) one. Whereas micro-level RS seem to be present in all soft tissues, the existence of macro- and meso-level mechanisms are tissue and organ specific. The second concept introduced highlights the significance of tissue swelling as an RS producing mechanism in the local micro-level. The implications of RS mechanism hierarchy are discussed regarding the interpretations of commonly used experimental methods aimed to study RS or to estimate its magnitude. Of the three categories of RS mechanisms, the local micro-RS is the least understood. It is analyzed here in terms of the tissue’s multiconstituent structure, in the framework of mixture theory. It is shown that the micro-RS can stem either from interactions between the solid tissue constituents or between its solids and its fluidlike matrix. The latter mode is associated with osmotic-driven tissue swelling. The feasibility of these two mechanisms is analyzed based on published observations and measured data. The analysis suggests that under conditions not too remote from the in vivo homeostatic one, osmotic-driven tissue swelling is a predominant RS producing mechanism. The analysis also suggests that a true stress-free configuration can be obtained only if all RS producing mechanisms are relieved, and outlines a manner by which this may be achieved.

Swelling of Collagen-Hyaluronic Acid Tissue-Equivalents: An Experimental Model to Evaluate Residual Stress in Soft Tissues

2013 ◽  
Author(s):  
Victor K. Lai ◽  
Spencer P. Lake ◽  
Bumjun Kim ◽  
Emily M. Weiss ◽  
Robert T. Tranquillo ◽  
...  
Keyword(s):  
Residual Stress ◽  
Hyaluronic Acid ◽  
Type I Collagen ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Tensile Load ◽  
Type I ◽  
Swelling Properties ◽  
Tissue Equivalents

Collagen gel tissue-equivalents (TEs), which are simple model tissues with tunable properties, have been used to explore many properties of soft tissues, such as how structural and compositional properties affect mechanical function [1–4]. One aspect not captured in previous TE formulations is residual stress due to interactions among components, which has an important functional role in many tissues (e.g., blood vessels [5], ligaments [6], annulus fibrosus [7]). Since the in vivo stress state of native tissues is not easily replicated in TE fabrication, a different method for “pre-stressing” collagen networks of TEs was necessary. To this end, co-gel TEs were fabricated by adding hyaluronic acid (HA) to reconstituted Type-I collagen (Col) gels. When placed in solutions of varying osmolarity, HA-Col TEs swell as the HA binds water, which in turn will stretch (and stress) the collagen network. In this way, TEs with residual stress (i.e., pre-stressed collagen fibers) can be fabricated and evaluated in order to elucidate relationships between residual stress and functional properties. Therefore, the goals of the present study were to fabricate HA-Col TEs, make initial measurements of their swelling properties, and quantify the mechanical response and changes in microstructural organization under applied tensile load.

Biological and biomedical applications of collagenous biomaterials

1990 ◽  
Vol 48 (3) ◽  
pp. 856-857
Author(s):  
Yasushi P. Kato ◽  
Michael G. Dunn ◽  
Frederick H. Silver ◽  
Arthur J. Wasserman
Keyword(s):  
Biomedical Applications ◽  
Soft Tissues ◽  
Collagen Fibers ◽  
Bone Collagen ◽  
Cover Slip ◽  
Fibroblast Migration ◽  
Cellular Expression ◽  
Defect Repair

Collagenous biomaterials have been used for growing cells in vitro as well as for augmentation and replacement of hard and soft tissues. The substratum used for culturing cells is implicated in the modulation of phenotypic cellular expression, cellular orientation and adhesion. Collagen may have a strong influence on these cellular parameters when used as a substrate in vitro. Clinically, collagen has many applications to wound healing including, skin and bone substitution, tendon, ligament, and nerve replacement. In this report we demonstrate two uses of collagen. First as a fiber to support fibroblast growth in vitro, and second as a demineralized bone/collagen sponge for radial bone defect repair in vivo.For the in vitro study, collagen fibers were prepared as described previously. Primary rat tendon fibroblasts (1° RTF) were isolated and cultured for 5 days on 1 X 15 mm sterile cover slips. Six to seven collagen fibers, were glued parallel to each other onto a circular cover slip (D=18mm) and the 1 X 15mm cover slip populated with 1° RTF was placed at the center perpendicular to the collagen fibers. Fibroblast migration from the 1 x 15mm cover slip onto and along the collagen fibers was measured daily using a phase contrast microscope (Olympus CK-2) with a calibrated eyepiece. Migratory rates for fibroblasts were determined from 36 fibers over 4 days.

A Comparative Study of the in vivo Distribution of 32P-Polyphosphates and 32P-Orthophosphate

1972 ◽  
Vol 11 (01) ◽  
pp. 70-78
Author(s):  
Esther Miller ◽  
Leopoldo Anghileri
Keyword(s):  
Radiation Dose ◽  
Comparative Study ◽  
Soft Tissues ◽  
Tumor Bearing ◽  
In Vivo Distribution ◽  
The Cross ◽  
Total Body

SummaryThe distribution of 32P-polyphosphates (lineal and cross-linked) and 32Porthophosphate in normal and tumor bearing animals has been studied. Differences between the cross-linked and the lineal form are related to a different degree of susceptibility to the hydrolysis by the phosphatases. In contrast to orthophosphate, the polyphosphates showed a lower accumulation in soft tissues which gives an advantageous reduction of the total body radiation dose.

scholarly journals Ultra-strong bio-glue from genetically engineered polypeptides

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chao Ma ◽  
Jing Sun ◽  
Bo Li ◽  
Yang Feng ◽  
Yao Sun ◽  
...  
Keyword(s):  
Soft Tissues ◽  
Covalent Bond ◽  
Genetically Engineered ◽  
Supramolecular Interactions ◽  
Molar Ratio ◽  
High Adhesion ◽  
Strong Adhesion ◽  
Order Of Magnitude

AbstractThe development of biomedical glues is an important, yet challenging task as seemingly mutually exclusive properties need to be combined in one material, i.e. strong adhesion and adaption to remodeling processes in healing tissue. Here, we report a biocompatible and biodegradable protein-based adhesive with high adhesion strengths. The maximum strength reaches 16.5 ± 2.2 MPa on hard substrates, which is comparable to that of commercial cyanoacrylate superglue and higher than other protein-based adhesives by at least one order of magnitude. Moreover, the strong adhesion on soft tissues qualifies the adhesive as biomedical glue outperforming some commercial products. Robust mechanical properties are realized without covalent bond formation during the adhesion process. A complex consisting of cationic supercharged polypeptides and anionic aromatic surfactants with lysine to surfactant molar ratio of 1:0.9 is driven by multiple supramolecular interactions enabling such strong adhesion. We demonstrate the glue’s robust performance in vitro and in vivo for cosmetic and hemostasis applications and accelerated wound healing by comparison to surgical wound closures.

scholarly journals Young Children’s Belonging in Finnish Educational Settings: an Intersectional Analysis

2021 ◽  
Author(s):  
Anna-Maija Puroila ◽  
Jaana Juutinen ◽  
Elina Viljamaa ◽  
Riikka Sirkko ◽  
Taina Kyrönlampi ◽  
...  
Keyword(s):  
Educational Policy ◽  
Educational Programs ◽  
Macro Level ◽  
Educational Settings ◽  
Policy Documents ◽  
Meso Level ◽  
Continuity And Change ◽  
Positional Power ◽  
Micro Level ◽  
Similarities And Differences

AbstractThe study draws on a relational and intersectional approach to young children’s belonging in Finnish educational settings. Belonging is conceptualized as a multilevel, dynamic, and relationally constructed phenomenon. The aim of the study is to explore how children’s belonging is shaped in the intersections between macro-, meso-, and micro-levels of young children’s education in Finland. The data consist of educational policy documents and ethnographic material generated in educational programs for children aged birth to 8 years. A situational mapping framework is used to analyze and interpret the data across and within systems levels (macro-level; meso-level; and micro-level). The findings show that the landscape in which children’s belonging is shaped and the intersections across and within the levels are characterized by the tensions between similarities and differences, majority and minorities, continuity and change, authority and agency. Language used, practices enacted, and positional power emerge as the (re)sources through which children’s (un)belonging is actively produced.

scholarly journals Organ-specific, multimodal, wireless optoelectronics for high-throughput phenotyping of peripheral neural pathways

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Woo Seok Kim ◽  
Sungcheol Hong ◽  
Milenka Gamero ◽  
Vivekanand Jeevakumar ◽  
Clay M. Smithhart ◽  
...  
Keyword(s):  
High Throughput ◽  
Low Cost ◽  
Optoelectronic Device ◽  
Antenna System ◽  
Neural Pathways ◽  
Organ Specific ◽  
Coil Antenna ◽  
Sensory Fibers

AbstractThe vagus nerve supports diverse autonomic functions and behaviors important for health and survival. To understand how specific components of the vagus contribute to behaviors and long-term physiological effects, it is critical to modulate their activity with anatomical specificity in awake, freely behaving conditions using reliable methods. Here, we introduce an organ-specific scalable, multimodal, wireless optoelectronic device for precise and chronic optogenetic manipulations in vivo. When combined with an advanced, coil-antenna system and a multiplexing strategy for powering 8 individual homecages using a single RF transmitter, the proposed wireless telemetry enables low cost, high-throughput, and precise functional mapping of peripheral neural circuits, including long-term behavioral and physiological measurements. Deployment of these technologies reveals an unexpected role for stomach, non-stretch vagal sensory fibers in suppressing appetite and demonstrates the durability of the miniature wireless device inside harsh gastric conditions.

scholarly journals The Potential of Calcium/Phosphate Containing MAO Implanted in Bone Tissue Regeneration and Biological Characteristics

2021 ◽  
Vol 22 (9) ◽  
pp. 4706
Author(s):  
Shun-Yi Jian ◽  
Salim Levent Aktug ◽  
Hsuan-Ti Huang ◽  
Cheng-Jung Ho ◽  
Sung-Yen Lin ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Calcium Phosphate ◽  
Soft Tissues ◽  
Salt Spray ◽  
Surface Characteristics ◽  
Corrosion Current ◽  
Biological Properties ◽  
Bone Tissue Regeneration ◽  
Additional Surgery

Micro arc oxidation (MAO) is a prominent surface treatment to form bioceramic coating layers with beneficial physical, chemical, and biological properties on the metal substrates for biomaterial applications. In this study, MAO treatment has been performed to modify the surface characteristics of AZ31 Mg alloy to enhance the biocompatibility and corrosion resistance for implant applications by using an electrolytic mixture of Ca3(PO4)2 and C10H16N2O8 (EDTA) in the solutions. For this purpose, the calcium phosphate (Ca-P) containing thin film was successfully fabricated on the surface of the implant material. After in-vivo implantation into the rabbit bone for four weeks, the apparent growth of soft tissues and bone healing effects have been documented. The morphology, microstructure, chemical composition, and phase structures of the coating were identified by SEM, XPS, and XRD. The corrosion resistance of the coating was analyzed by polarization and salt spray test. The coatings consist of Ca-P compounds continuously have proliferation activity and show better corrosion resistance and lower roughness in comparison to mere MAO coated AZ31. The corrosion current density decreased to approximately 2.81 × 10−7 A/cm2 and roughness was reduced to 0.622 μm. Thus, based on the results, it was anticipated that the development of degradable materials and implants would be feasible using this method. This study aims to fabricate MAO coatings for orthopedic magnesium implants that can enhance bioactivity, biocompatibility, and prevent additional surgery and implant-related infections to be used in clinical applications.

scholarly journals Using the Microwell-mesh to culture microtissues in vitro and as a carrier to implant microtissues in vivo into mice

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Melissa E. Monterosso ◽  
Kathryn Futrega ◽  
William B. Lott ◽  
Ian Vela ◽  
Elizabeth D. Williams ◽  
...  
Keyword(s):  
Hair Follicles ◽  
Live Animal ◽  
Nsg Mice ◽  
Animal Imaging ◽  
Organ Specific ◽  
Bioluminescence Signal ◽  
Serial Transplantation ◽  
Live Animal Imaging

AbstractProstate cancer (PCa) patient-derived xenografts (PDXs) are commonly propagated by serial transplantation of “pieces” of tumour in mice, but the cellular composition of pieces is not standardised. Herein, we optimised a microwell platform, the Microwell-mesh, to aggregate precise numbers of cells into arrays of microtissues, and then implanted the Microwell-mesh into NOD-scid IL2γ−/− (NSG) mice to study microtissue growth. First, mesh pore size was optimised using microtissues assembled from bone marrow-derived stromal cells, with mesh opening dimensions of 100×100 μm achieving superior microtissue vascularisation relative to mesh with 36×36 μm mesh openings. The optimised Microwell-mesh was used to assemble and implant PCa cell microtissue arrays (hereafter microtissues formed from cancer cells are referred to as microtumours) into mice. PCa cells were enriched from three different PDX lines, LuCaP35, LuCaP141, and BM18. 3D microtumours showed greater in vitro viability than 2D cultures, but neither proliferated. Microtumours were successfully established in mice 81% (57 of 70), 67% (4 of 6), 76% (19 of 25) for LuCaP35, LuCaP141, and BM18 PCa cells, respectively. Microtumour growth was tracked using live animal imaging for size or bioluminescence signal. If augmented with further imaging advances and cell bar coding, this microtumour model could enable greater resolution of PCa PDX drug response, and lead to the more efficient use of animals. The concept of microtissue assembly in the Microwell-mesh, and implantation in vivo may also have utility in implantation of islets, hair follicles or other organ-specific cells that self-assemble into 3D structures, providing an important bridge between in vitro assembly of mini-organs and in vivo implantation.

scholarly journals Challenges to the validity of topic reconstruction

2021 ◽  
Author(s):  
Matthias Held ◽  
Grit Laudel ◽  
Jochen Gläser
Keyword(s):  
Data Model ◽  
Ground Truth ◽  
Data Models ◽  
Bibliographic Coupling ◽  
Parameter Setting ◽  
Meso Level ◽  
Resolution Level ◽  
Micro Level ◽  
Research Questions ◽  
Model Algorithm

AbstractIn this paper we utilize an opportunity to construct ground truths for topics in the field of atomic, molecular and optical physics. Our research questions in this paper focus on (i) how to construct a ground truth for topics and (ii) the suitability of common algorithms applied to bibliometric networks to reconstruct these topics. We use the ground truths to test two data models (direct citation and bibliographic coupling) with two algorithms (the Leiden algorithm and the Infomap algorithm). Our results are discomforting: none of the four combinations leads to a consistent reconstruction of the ground truths. No combination of data model and algorithm simultaneously reconstructs all micro-level topics at any resolution level. Meso-level topics are not reconstructed at all. This suggests (a) that we are currently unable to predict which combination of data model, algorithm and parameter setting will adequately reconstruct which (types of) topics, and (b) that a combination of several data models, algorithms and parameter settings appears to be necessary to reconstruct all or most topics in a set of papers.

The prospects for pluralism in contract theory

Legal Studies ◽  
2021 ◽  
pp. 1-20
Author(s):  
Zhong Xing Tan
Keyword(s):  
Contract Theory ◽  
Practical Reasoning ◽  
Contemporary Literature ◽  
Contract Law ◽  
Macro Level ◽  
Meso Level ◽  
Specific Performance ◽  
Micro Level

Abstract This paper explores the promise of pluralism in the realm of contract law. I begin by identifying and rejecting conceptual strategies adopted by monistic and dualistic approaches. Turning towards pluralism, I evaluate three versions in contemporary literature: pluralism across contracting spheres and types, pluralism through consensus and convergence, and pluralism through localised values-balancing and practical reasoning. I suggest embracing some pluralism about contract pluralism, by using these models to construct a framework of ‘meta-pluralism’, where at the macro-level, we are concerned with plural spheres of contracting activity; at the meso-level, a variety of trans-substantive interpretive concepts that receive some measure of juristic consensus; and at the micro-level, practical reasoning through particularistic analysis of case-specific considerations. I illustrate the meta-pluralistic framework through a case study on the varieties of specific performance, and explain how the proposed pluralistic framework enriches our understanding of the nature of contract.

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