scholarly journals Method to study cell migration under uniaxial compression

2017 ◽  
Vol 28 (6) ◽  
pp. 809-816 ◽  
Author(s):  
Nishit Srivastava ◽  
Robert R. Kay ◽  
Alexandre J. Kabla
Keyword(s):  
Cell Migration ◽  
Uniaxial Compression ◽  
Physical And Mechanical Properties ◽  
Accurate Information ◽  
Simple Method ◽  
Novel Device ◽  
The Matrix ◽  
A Cell ◽  
Extracellular Environment ◽  
Selection Of

The chemical, physical, and mechanical properties of the extracellular environment have a strong effect on cell migration. Aspects such as pore size or stiffness of the matrix influence the selection of the mechanism used by cells to propel themselves, including by pseudopods or blebbing. How a cell perceives its environment and how such a cue triggers a change in behavior are largely unknown, but mechanics is likely to be involved. Because mechanical conditions are often controlled by modifying the composition of the environment, separating chemical and physical contributions is difficult and requires multiple controls. Here we propose a simple method to impose a mechanical compression on individual cells without altering the composition of the matrix. Live imaging during compression provides accurate information about the cell's morphology and migratory phenotype. Using Dictyostelium as a model, we observe that a compression of the order of 500 Pa flattens the cells under gel by up to 50%. This uniaxial compression directly triggers a transition in the mode of migration from primarily pseudopodial to bleb driven in <30 s. This novel device is therefore capable of influencing cell migration in real time and offers a convenient approach with which to systematically study mechanotransduction in confined environments.

scholarly journals Probing the effect of uniaxial compression on cell migration

2016 ◽  
Author(s):  
Nishit Srivastava ◽  
Robert R Kay ◽  
Alexandre J Kabla
Keyword(s):  
Cell Migration ◽  
Uniaxial Compression ◽  
Physical And Mechanical Properties ◽  
Accurate Information ◽  
Simple Method ◽  
Novel Device ◽  
Cellular Environment ◽  
The Matrix ◽  
A Cell ◽  
Selection Of

AbstractThe chemical, physical and mechanical properties of the extra-cellular environment have a strong effect on cell migration. Aspects such as pore-size or stiffness of the matrix influence the selection of the mechanism used by cells to propel themselves, including pseudopod or blebbing. How a cell perceives its environment, and how such a cue triggers a change in behaviour are largely unknown, but mechanics is likely to be involved. Because mechanical conditions are often controlled by modifying the composition of the environment, separating chemical and physical contributions is difficult and requires multiple controls. Here we propose a simple method to impose a mechanical compression on individual cells without altering the composition of the gel. Live imaging during compression provides accurate information about the cell’s morphology and migratory phenotype. Using Dictyostelium as a model, we observe that a compression of the order of 500 Pa flattens the cells under gel by up to 50%. This uniaxial compression directly triggers a transition in the mode of migration, from primarily pseudopodial to bleb driven, in less than 30 sec. This novel device is therefore capable of influencing cell migration in real time and offers a convenient approach to systematically study mechanotransduction in confined environments.

scholarly journals Mechanical Interactions between a Cell and an Extracellular Environment Facilitate Durotactic Cell Migration

2018 ◽  
Author(s):  
Abdel-Rahman Hassan ◽  
Thomas Biel ◽  
Taeyoon Kim
Keyword(s):  
Cell Migration ◽  
Computational Models ◽  
Biomechanical Model ◽  
Coarse Grained ◽  
Physiological Processes ◽  
Specific Direction ◽  
A Cell ◽  
Stiffness Profile ◽  
Contractile Forces ◽  
Extracellular Environment

ABSTRACTCell migration is a fundamental process in biological systems, playing an important role for diverse physiological processes. Cells often exhibit directed migration in a specific direction in response to various types of cues. In particular, cells are able to sense the rigidity of surrounding environments and then migrate towards stiffer regions. To understand this mechanosensitive behavior called durotaxis, several computational models have been developed. However, most of the models made phenomenological assumptions to recapitulate durotactic behaviors, significantly limiting insights provided from these studies. In this study, we developed a computational biomechanical model without any phenomenological assumption to illuminate intrinsic mechanisms of durotactic behaviors of cells migrating on a two-dimensional substrate. The model consists of a simplified cell generating contractile forces and a deformable substrate coarse-grained into an irregular triangulated mesh. Using the model, we demonstrated that durotactic behaviors emerge from purely mechanical interactions between the cell and the underlying substrate. We investigated how durotactic migration is regulated by biophysical properties of the substrate, including elasticity, viscosity, and stiffness profile.

CMC and C/C-SiC-Fabrication

2006 ◽  
Vol 50 ◽  
pp. 130-140
Author(s):  
Roland Weiss
Keyword(s):  
Physical And Mechanical Properties ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Ceramic Materials ◽  
Matrix Composites ◽  
New Family ◽  
The Matrix ◽  
Full Conversion ◽  
Selection Of ◽  
Matrix Precursor

Ceramic Matrix Composites (CMC) have a wide interest for high temperature applications. The materials can be modified by the selection of the matrix precursor as well as of the reinforcing materials. C/C-composites can be easily modified by post-treatments with silicon in order to acquire different tribological properties from good sliding behaviour up to braking systems only depending on the manufacturing technique of these materials. It will be demonstrated during the presentation that the manufacturing depends on one hand side on the material which has to be manufactured and on the other side on the structural component and the number of parts which are required. Furthermore, it will also be shown, that silicon treatments can be performed up to a full conversion of C/C materials creating a new family of monolithic ceramic materials. Within the presentation detailed information will be given on possible processing routes as well as the resulting physical and mechanical properties of the materials.

scholarly journals The Impact of Elastic Deformations of the Extracellular Matrix on Cell Migration

2020 ◽  
Vol 82 (4) ◽  
Author(s):  
A. A. Malik ◽  
B. Wennberg ◽  
P. Gerlee
Keyword(s):  
Extracellular Matrix ◽  
Cell Migration ◽  
Human Cancer ◽  
Matrix Stiffness ◽  
Human Cancer Cells ◽  
Adhesion Sites ◽  
The Matrix ◽  
A Cell ◽  
Necessary And Sufficient ◽  
The Impact

Abstract The mechanical properties of the extracellular matrix, in particular its stiffness, are known to impact cell migration. In this paper, we develop a mathematical model of a single cell migrating on an elastic matrix, which accounts for the deformation of the matrix induced by forces exerted by the cell, and investigate how the stiffness impacts the direction and speed of migration. We model a cell in 1D as a nucleus connected to a number of adhesion sites through elastic springs. The cell migrates by randomly updating the position of its adhesion sites. We start by investigating the case where the cell springs are constant, and then go on to assuming that they depend on the matrix stiffness, on matrices of both uniform stiffness as well as those with a stiffness gradient. We find that the assumption that cell springs depend on the substrate stiffness is necessary and sufficient for an efficient durotactic response. We compare simulations to recent experimental observations of human cancer cells exhibiting durotaxis, which show good qualitative agreement.

scholarly journals Immunocytochemical localization of catalase in rat liver.

1981 ◽  
Vol 29 (7) ◽  
pp. 805-812 ◽  
Author(s):  
S Yokota ◽  
H D Fahimi
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Golgi Complex ◽  
Intracellular Localization ◽  
Sodium Dodecyl ◽  
Specific Staining ◽  
Simple Method ◽  
Fab Fragments ◽  
The Matrix ◽  
A Cell

The intracellular localization of catalase has been studied using monospecific Fab fragments against rat liver catalase (RLC) and preembedding immunoelectron microscopy. Purified RLC, exhibiting a single band on sodium dodecyl sulfate gel electrophoresis, was used for the immunization of rabbits. The anti-RLC IgG was purified by affinity chromatography. Fab fragments were obtained by papain digestion and were labeled with horseradish peroxidase (HRP) using a modified two-step procedure and glutaraldehyde as coupling agents. Livers were perfused with 4% depolymerized paraformaldehyde and chopper sections were incubated with HRP-labeled Fab fragments against RLC. Because of the limited penetration of labeled Fab fragments into chopper sections a simple method for preparation of a cell suspension from aldehyde-fixed livers was devised. Adequate staining of more than 90% of cell was obtained by incubation of cell suspensions for 12--18 hr with the labeled antibody. By light microscopy specific staining was present in fine granules in the cytoplasm of hepatocytes. By electron microscopy the electron-dense reaction product was localized in the matrix of peroxisomes with no reaction in the endoplasmic reticulum and the Golgi complex. In some hepatocytes, positively reacted peroxisomes were seen side by side with unstained particles. Although focal diffusion was noted around a few peroxisomes, no evidence of cytoplasmic catalase independent of peroxisomes was found. These observations indicate that in rat liver peroxisomes are the only organelle containing substantial amounts of catalase antigen and rule out any involvement of the endoplasmic reticulum and the Golgi complex in the sequestration of this protein.

Combination of ribosome and phage display for fast selection of high affinity VHH antibody fragments

2019 ◽  
pp. 27-33
Author(s):  
YuE Kravchenko ◽  
SV Ivanov ◽  
DS Kravchenko ◽  
EI Frolova ◽  
SP Chumakov
Keyword(s):  
Phage Display ◽  
Selection Procedure ◽  
Free System ◽  
Phage Displays ◽  
High Affinity ◽  
Binding Domains ◽  
A Cell ◽  
Vhh Antibodies ◽  
Efficiency Of Selection ◽  
Selection Of

Selection of antibodies using phage display involves the preliminary cloning of the repertoire of sequences encoding antigen-binding domains into phagemid, which is considered the bottleneck of the method, limiting the resulting diversity of libraries and leading to the loss of poorly represented variants before the start of the selection procedure. Selection in cell-free conditions using a ribosomal display is devoid from this drawback, however is highly sensitive to PCR artifacts and the RNase contamination. The aim of the study was to test the efficiency of a combination of both methods, including pre-selection in a cell-free system to enrich the source library, followed by cloning and final selection using phage display. This approach may eliminate the shortcomings of each method and increase the efficiency of selection. For selection, alpaca VHH antibody sequences suitable for building an immune library were used due to the lack of VL domains. Analysis of immune libraries from the genes of the VH3, VHH3 and VH4 families showed that the VHH antibodies share in the VH3 and VH4 gene groups is insignificant, and selection from the combined library is less effective than from the VHH3 family of sequences. We found that the combination of ribosomal and phage displays leads to a higher enrichment of high-affinity fragments and avoids the loss of the original diversity during cloning. The combined method allowed us to obtain a greater number of different high-affinity sequences, and all the tested VHH fragments were able to specifically recognize the target, including the total protein extracts of cell cultures.

scholarly journals A Multiple and Multi-Level Substructure Method for the Dynamics of Complex Structures

2021 ◽  
Vol 11 (12) ◽  
pp. 5570
Author(s):  
Binbin Wang ◽  
Jingze Liu ◽  
Zhifu Cao ◽  
Dahai Zhang ◽  
Dong Jiang
Keyword(s):  
Structural Characteristics ◽  
Complex Structure ◽  
Complex Structures ◽  
System Matrix ◽  
Substructure Method ◽  
Residual Structure ◽  
The Matrix ◽  
Multi Level ◽  
Fixed Interface ◽  
Selection Of

Based on the fixed interface component mode synthesis, a multiple and multi-level substructure method for the modeling of complex structures is proposed in this paper. Firstly, the residual structure is selected according to the structural characteristics of the assembled complex structure. Secondly, according to the assembly relationship, the parts assembled with the residual structure are divided into a group of substructures, which are named the first-level substructure, the parts assembled with the first-level substructure are divided into a second-level substructure, and consequently the multi-level substructure model is established. Next, the substructures are dynamically condensed and assembled on the boundary of the residual structure. Finally, the substructure system matrix, which is replicated from the matrix of repeated physical geometry, is obtained by preserving the main modes and the constrained modes and the system matrix of the last level of the substructure is assembled to the upper level of the substructure, one level up, until it is assembled in the residual structure. In this paper, an assembly structure with three panels and a gear box is adopted to verify the method by simulation and a rotor is used to experimentally verify the method. The results show that the proposed multiple and multi-level substructure modeling method is not unique to the selection of residual structures, and different classification methods do not affect the calculation accuracy. The selection of 50% external nodes can further improve the analysis efficiency while ensuring the calculation accuracy.

scholarly journals 3D reconstruction of genomic regions from sparse interaction data

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Julen Mendieta-Esteban ◽  
Marco Di Stefano ◽  
David Castillo ◽  
Irene Farabella ◽  
Marc A Marti-Renom
Keyword(s):  
3D Models ◽  
Genomic Region ◽  
Gene Promoters ◽  
Chromosome Conformation ◽  
The Matrix ◽  
Chromatin Structural ◽  
A Cell ◽  
Similar Accuracy ◽  
Genomic Regions ◽  
Interaction Matrices

Abstract Chromosome conformation capture (3C) technologies measure the interaction frequency between pairs of chromatin regions within the nucleus in a cell or a population of cells. Some of these 3C technologies retrieve interactions involving non-contiguous sets of loci, resulting in sparse interaction matrices. One of such 3C technologies is Promoter Capture Hi-C (pcHi-C) that is tailored to probe only interactions involving gene promoters. As such, pcHi-C provides sparse interaction matrices that are suitable to characterize short- and long-range enhancer–promoter interactions. Here, we introduce a new method to reconstruct the chromatin structural (3D) organization from sparse 3C-based datasets such as pcHi-C. Our method allows for data normalization, detection of significant interactions and reconstruction of the full 3D organization of the genomic region despite of the data sparseness. Specifically, it builds, with as low as the 2–3% of the data from the matrix, reliable 3D models of similar accuracy of those based on dense interaction matrices. Furthermore, the method is sensitive enough to detect cell-type-specific 3D organizational features such as the formation of different networks of active gene communities.

scholarly journals On Exact and Approximate Approaches for Stochastic Receptor-Ligand Competition Dynamics—An Ecological Perspective

Mathematics ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 1014
Author(s):  
Polly-Anne Jeffrey ◽  
Martín López-García ◽  
Mario Castro ◽  
Grant Lythe ◽  
Carmen Molina-París
Keyword(s):  
Summary Statistics ◽  
Steady State Distribution ◽  
State Distribution ◽  
Cellular Receptors ◽  
Stochastic Description ◽  
The Matrix ◽  
Common Resource ◽  
A Cell ◽  
The Common ◽  
Cellular Medium

Cellular receptors on the cell membrane can bind ligand molecules in the extra-cellular medium to form ligand-bound monomers. These interactions ultimately determine the fate of a cell through the resulting intra-cellular signalling cascades. Often, several receptor types can bind a shared ligand leading to the formation of different monomeric complexes, and in turn to competition for the common ligand. Here, we describe competition between two receptors which bind a common ligand in terms of a bi-variate stochastic process. The stochastic description is important to account for fluctuations in the number of molecules. Our interest is in computing two summary statistics—the steady-state distribution of the number of bound monomers and the time to reach a threshold number of monomers of a given kind. The matrix-analytic approach developed in this manuscript is exact, but becomes impractical as the number of molecules in the system increases. Thus, we present novel approximations which can work under low-to-moderate competition scenarios. Our results apply to systems with a larger number of population species (i.e., receptors) competing for a common resource (i.e., ligands), and to competition systems outside the area of molecular dynamics, such as Mathematical Ecology.

Effect of pouring temperature on A356-TiB2 MMCs cast in sand and permanent moulds by in-situ method

2016 ◽  
Vol 25 (5-6) ◽  
pp. 165-169
Author(s):  
C. Rajaravi ◽  
P.R. Lakshminarayanan
Keyword(s):  
Evaluation Studies ◽  
Physical And Mechanical Properties ◽  
Xrd Analysis ◽  
Matrix Composites ◽  
Structure Property ◽  
Pouring Temperature ◽  
Matrix Metal ◽  
Property Evaluation ◽  
The Matrix

AbstractThe paper describes a different condition of pouring temperature by sand and permanent mould to produce A356-6 wt% TiB2 metal matrix composites by in-situ method salt metal reaction route. The observation of SEM micrographs shows particle distribution of the TiB2 and it appears in hexagonal shape in Al matrix. The results of X-ray diffraction (XRD) analysis confirmed the formation of those TiB2 particulates and the results showed TiB2 particles are homogeneously dispersed throughout the matrix metal. Subsequent structure-property evaluation studies indicated sub-micron size reinforcement of in-situ formed TiB2 particles with improved physical and mechanical properties as compared to sand and permanent mould of Al-TiB2 composites. From, the permanent mould Al-TiB2 composite has an advantage of increase the properties over sand mould Al-TiB2 composite.

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