scholarly journals Matrix identity and tractional forces influence indirect cardiac reprogramming

2013 ◽  
Vol 3 (1) ◽  
Author(s):  
Yen P. Kong ◽  
Bita Carrion ◽  
Rahul K. Singh ◽  
Andrew J. Putnam
Keyword(s):  
Matrix Identity ◽  
Tractional Forces

Impaired wound healing in embryonic and adult mice lacking vimentin

2000 ◽  
Vol 113 (13) ◽  
pp. 2455-2462 ◽  
Author(s):  
B. Eckes ◽  
E. Colucci-Guyon ◽  
H. Smola ◽  
S. Nodder ◽  
C. Babinet ◽  
...  
Keyword(s):  
Wound Healing ◽  
Healing Process ◽  
Wild Type ◽  
Impaired Wound Healing ◽  
Wound Site ◽  
Adult Mice ◽  
Tractional Forces ◽  
Filament Network ◽  
Vimentin Intermediate Filament

It is generally assumed that the vimentin intermediate filament network present in most mesenchymally-derived cells is in part responsible for the strength and integrity of these cells, and necessary for any tissue movements that require the generation of significant tractional forces. Surprisingly, we have shown that transgenic KO mice deficient for vimentin are apparently able to undergo embryonic development absolutely normally and go onto develop into adulthood and breed without showing any obvious phenotype. However, fibroblasts derived from these mice are mechanically weak and severely disabled in their capacity to migrate and to contract a 3-D collagen network. To assess whether these functions are necessary for more challenging tissue movements such as those driving in vivo tissue repair processes, we have analysed wound healing ability in wild-type versus vimentin-deficient embryos and adult mice. Wounds in vimentin-deficient adult animals showed delayed migration of fibroblasts into the wound site and subsequently retarded contraction that correlated with a delayed appearance of myofibroblasts at the wound site. Wounds made to vimentin-deficient embryos also failed to heal during the 24 hour culture period it takes for wild-type embryos to fully heal an equivalent wound. By DiI marking the wound mesenchyme and following its fate during the healing process we showed that this impaired healing is almost entirely due to a failure of mesenchymal contraction at the embryonic wound site. These observations reveal an in vivo phenotype for the vimentin-deficient mouse, and challenge the dogma that key morphogenetic events occurring during development require generation of significant tractional forces by mesenchymal cells.

scholarly journals Macular Hole in Myopic Eyes: A Narrative Review of the Current Surgical Techniques

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Chiara De Giacinto ◽  
Marco R. Pastore ◽  
Gabriella Cirigliano ◽  
Daniele Tognetto
Keyword(s):  
Macular Hole ◽  
Surgical Management ◽  
Surgical Intervention ◽  
Current Knowledge ◽  
Surgical Techniques ◽  
Retinal Disease ◽  
Narrative Review ◽  
Vitreomacular Interface ◽  
Tractional Forces

Macular hole (MH) in myopic eyes is a disease arising from complex tractional forces exerted by vitreomacular interface, epiretinal tissue, and progressive scleral ectasia of the posterior ocular globe wall. This retinal disease requires vitreoretinal treatment for its repair, and the surgical intervention remains a challenge also for experienced surgeons. The aim of this review is to describe the current knowledge regarding the pathogenesis of MH in myopic eyes and to detail novel surgical techniques and technological advancements in its surgical management.

scholarly journals Comparative Evaluation of Biomechanical Performance of Titanium and Stainless Steel Mini Implants at Different Angulations in Maxilla: A Finite Element Analysis

2019 ◽  
Vol 53 (3) ◽  
pp. 197-205
Author(s):  
Kshitij Hemant Sabley ◽  
Usha Shenoy ◽  
Sujoy Banerjee ◽  
Pankaj Akhare ◽  
Ananya Hazarey ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Computer Aided Design ◽  
Three Dimensional ◽  
Titanium Implant ◽  
Titanium Implants ◽  
Element Analysis ◽  
Mini Implants ◽  
The Difference ◽  
Tractional Forces ◽  
Three Dimensional Models

Objective: To assess and compare the tensions and deformations (stresses and strains) generated after application of two types of forces (traction and torsion) in miniscrews of two different materials (titanium and stainless steel) placed at five different angulations. Materials and Methods: Three-dimensional models of the posterior maxillary area and the mini-implants were constructed using computer-aided design software program (CATIA P3 V5-6 R2015 B26 / 2016; Dassault Systèmes). Titanium and stainless steel materials were used for miniscrews. The area constructed was in between the maxillary second premolar and first molar. The models with mini-implants were inserted at five different angulations (30°, 45°, 60°, 75° and 90°). Torsional and tractional forces were applied on these implants, and the models were solved using ANSYS 10.0. Stress generated in implant and in the cortical and cancellous bones was evaluated and compared at all the five angulations. Results: Stress generated in stainless steel mini-implant during torsional and linear force application was less when compared with titanium mini-implant. Also, stress generated in implants of both materials increased as the angle increased from 30° to 90°. Difference in stress generated by stainless steel implant in the cortical bone for both linear and torsional forces was less when compared with titanium implant, whereas for cancellous bone, the difference was insignificant at all the angles. Conclusion: Irrespective of angles, difference in stress generated in stainless steel implants and titanium implants for both the forces was not significant, and hence, stainless steel implants can be used effectively in a clinical setting.

A Computer Program for Determining the Effect of Design Variation on Service Stresses in Railroad Wheels

1966 ◽  
Vol 88 (4) ◽  
pp. 352-357 ◽  
Author(s):  
Malcolm S. Riegel ◽  
Samuel Levy ◽  
John A. Sliter
Keyword(s):  
Experimental Stress ◽  
Test Results ◽  
Brake Shoe ◽  
Iron And Steel ◽  
Railroad Industry ◽  
Specific Effects ◽  
Computer Analyses ◽  
Design Variation ◽  
Tractional Forces ◽  
Railroad Wheels

Two computer analyses have been prepared relating service stresses in railroad wheels to wheel shape and dimensions. One program computes the temperature distribution and stresses due to heat input by brake shoe friction at the wheel tread. The other computes stresses due to lateral, vertical, and tractional forces between the wheel and rail. Both programs have been validated for certain known conditions using theoretical solutions and are in agreement with available design and experimental stress data to the degree that differences in wheel geometry and loading conditions permit a comparison with experimental stress data. The next step contemplated is better experimental confirmation by computations for specific wheels and loadings for which test results are available and use of the programs to study trends resulting from, changes in wheel geometry and dimensions. This work is directed toward optimization of wheel design, and elucidation of the nature and specific effects of excessive service loads. This research program is being sponsored at General Electric by the manufacturers of wrought steel wheels, through the American Iron and Steel Institute, as a service to the American railroad industry.

A Theoretical Model of Stretch-Induced Stress Fiber Remodeling

2008 ◽  
Author(s):  
Roland Kaunas
Keyword(s):  
Focal Adhesion ◽  
Focal Adhesions ◽  
Dynamic Structure ◽  
Cytoskeletal Proteins ◽  
Stress Fibers ◽  
Cell Contractility ◽  
Maximum Stretch ◽  
Tensional Homeostasis ◽  
Tractional Forces ◽  
Actin Stress Fibers

Cyclic stretching of endothelial cells (ECs), such as occurs in arteries during the cardiac cycle, induces ECs and their actin stress fibers to orient perpendicular to the direction of maximum stretch. This perpendicular alignment response is strengthened by increasing the magnitudes of stretch and cell contractility (1). The actin cytoskeleton is a dynamic structure that regulates cell shape changes and mechanical properties. It has been shown that actin stress fibers are ‘prestretched’ under normal, non-perturbed, conditions (2), consistent with the ideas of ‘prestress’ that have motivated tensegrity cell models (3). It has also been shown that ‘tractional forces’ generated by cells at focal adhesions tend to increase proportionately with increasing focal adhesion area, thus suggesting that cells tend to maintain constant the stress borne by a focal adhesion (4). By implication, this suggests that cells try to maintain constant the stress in actin stress fibers. Thus, it seems that cells reorganize or turnover cytoskeletal proteins and adhesion complexes so as to maintain constant a preferred mechanical state. Mizutani et al. (5) referred to this as cellular tensional homeostasis, although they did not suggest a model or theory to account for this dynamic process.

Construction of Biomimetic Environments with A Synthetic Peptide Analogue of Collagen.

1998 ◽  
Vol 530 ◽  
Author(s):  
Rajendra S. Bhatnagar ◽  
Jing Jing Qian ◽  
Anna Wedrychowska ◽  
Nancy Smith
Keyword(s):  
Cell Differentiation ◽  
Synthetic Peptide ◽  
Type I Collagen ◽  
Peptide Ligand ◽  
Type I ◽  
Surrounding Matrix ◽  
Collagen Receptors ◽  
Specific Receptors ◽  
Tractional Forces ◽  
And Migration

AbstractThe flow of chemical and mechanical signals among cells, and between cells and their environment plays a crucial role in cell differentiation and morphogenesis. In tissues, type I collagen serves as the template for cell anchorage and migration, and it mediates the flux of regulatory signals via highly specific receptors. Cells respond to mechanical cues by secreting growth factors and remodeling their surrounding matrix in an exquisitely orchestrated spatial and temporal program of matrix turnover and organization. Cellular tractional forces contribute to the organization and orientation of the newly synthesized matrix, establishing the template for subsequent morphogenesis. The junction between cells and collagen plays a key role in cell differentiation, morphogenesis and tissue remodeling. An optimal biomimetic environment would emulate this pathway for the exchange of stimuli. To achieve this goal, we have constructed templates which place cells in apposition to P-15, a synthetic peptide ligand for collagen receptors. These environments prompted 3-D colony formation, induced increased osteogenic differentiation, and the deposition of highly oriented and organized matrix by human dermal and gingival fibroblasts and by osteoblast like HOS cells. These observations support our concept for biomimetic environments for tissue engineering.

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