Living cell motility

2007 ◽  
Vol 366 (1864) ◽  
pp. 319-328 ◽  
Author(s):  
José Coelho Neto ◽  
Oscar Nassif Mesquita
Keyword(s):  
Membrane Surface ◽  
Optical Microscope ◽  
Living Cells ◽  
Physical Models ◽  
Microscopy Technique ◽  
Bending Modulus ◽  
Membrane Fluctuations ◽  
Complex Process ◽  
Dynamical Parameters ◽  
Membrane Bending

The motility of living eukaryotic cells is a complex process driven mainly by polymerization and depolymerization of actin filaments underneath the plasmatic membrane (actin cytoskeleton). However, the exact mechanisms through which cells are able to control and employ ‘actin-generated’ mechanical forces, in order to change shape and move in a well-organized and coordinated way, are not quite established. Here, we summarize the experimental results obtained by our research group during recent years in studying the motion of living cells, such as macrophages and erythrocytes. By using our recently developed defocusing microscopy technique, which allows quantitative analysis of membrane surface dynamics of living cells using a simple bright-field optical microscope, we were able to analyse morphological and dynamical parameters of membrane ruffles and small membrane fluctuations, study the process of phagocytosis and also measure values for cell refractive index, membrane bending modulus and cell viscosity. Although many questions still remain unanswered, our data seem to corroborate some aspects of recent physical models of cell membranes and motility.

Visualization of Membrane Sorting and Fusion in Living Cells using Total Internal Reflection (TIR) and Multicolor Video Microscopy

2001 ◽  
Vol 7 (S2) ◽  
pp. 34-35
Author(s):  
Derek Toomre ◽  
Patrick Keller ◽  
Elena Diaz ◽  
Jamie White ◽  
Kai Simons
Keyword(s):  
Plasma Membrane ◽  
Total Internal Reflection ◽  
Fluorescent Protein ◽  
Time Lapse ◽  
Living Cells ◽  
Video Microscopy ◽  
Internal Reflection ◽  
Fast Time ◽  
Cellular Polarity ◽  
Microscopy Technique

Post-Golgi sorting of different classes of newly synthesized proteins and lipids is central to the generation and maintenance of cellular polarity. to directly visualize the dynamics and location of apical/basolateral sorting and trafficking we used fast time-lapse multicolor video microscopy in living cells. Specifically, green fluorescent protein color variants (cyan, CFP; yellow, YFP) of apical cargo (GPI-anchored) and basolateral cargo (vesicular stomatitis virus glycoprotein, VSVG) were generated; see FIG 1. Fast dual color fluorescence video microscopy allowed visualization with high temporal and spatial resolution. Our studies revealed that apical and basolateral cargo progressively segregated into large domains in Golgi/TGN structures, excluded resident proteins, and exited in separate transport containers. These carries remained distinct and did not merge with endocytic structures en route to the plasma membrane. Interestingly, our data suggest that the primary sorting occurs by lateral segregation in the Golgi, prior to budding (FIG 2). Further characterization of morphological differences of apical versus basolateral transport carriers was achieved using a specialized microscopy technique called total internal reflection (TIR) microscopy. with this approach only the bottom of the cell (<100 nm) was illuminated by an exponentially decaying evanescent “wave” of light. A series of images, taken at ∼1 second intervals, shows a bright “flash” of fluorescence when the vesicle fuse with the plasma membrane and the fluorophore diffuses into the plasma membrane (FIG 3).

Bilayer Membrane Bending Stiffness by Tether Formation From Mixed PC-PS Lipid Vesicles

1990 ◽  
Vol 112 (3) ◽  
pp. 235-240 ◽  
Author(s):  
J. Song ◽  
R. E. Waugh
Keyword(s):  
Present Report ◽  
Membrane Surface ◽  
Lipid Vesicles ◽  
Phosphatidyl Serine ◽  
Bilayer Membrane ◽  
Bending Stiffness ◽  
New Approach ◽  
Lipid Mixtures ◽  
Membrane Bending ◽  
Membrane Surface Charge

Recently, a new approach to measure the bending stiffness (curvature elastic modulus) of lipid bilayer membrane was developed (Biophys. J., Vol. 55; pp. 509–517, 1989). The method involves the formation of cylindrical membrane strands (tethers) from bilayer vesicles. The bending stiffness (B) can be calculated from measurements of the tether radius (Rt) as a function of the axial force (f) on the tether: B =f·Rt/2π. In the present report, we apply this method to determine the bending stiffness of bilayer membranes composed of mixtures of SOPC (1-stearoyl-2-oleoyl phosphatidyl choline) and POPS (1-palmitoyl-2-oleoyl phosphatidyl serine). Three different mixtures were tested: pure SOPC, SOPC plus 2 percent (mol/mol) POPS, and SOPC plus 16 percent POPS. The bending stiffness determined for these three different lipid mixtures were not significantly different (1.6–1.8×10-12 ergs). Because POPS carries a net negative charge, these results indicate that changes in the density of the membrane surface charge have no effect on the intrinsic rigidity of the membrane. The values we obtain are consistent with published values for the bending stiffness of other membranes determined by different methods. Measurements of the aspiration pressure, the tether radius and the tether force were used to verify a theoretical relationship among these quantities at equilibrium. The ratio of the theoretical force to the measured force was 1.12 ± 0.17.

scholarly journals Estimation of membrane bending modulus of stiffness tuned human red blood cells from micropore filtration studies

PLoS ONE ◽  
2019 ◽  
Vol 14 (12) ◽  
pp. e0226640 ◽  
Author(s):  
Rekha Selvan ◽  
Praveen Parthasarathi ◽  
Shruthi S. Iyengar ◽  
Sharath Ananthamurthy ◽  
Sarbari Bhattacharya
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Human Red Blood Cells ◽  
Bending Modulus ◽  
Membrane Bending

scholarly journals Physical Characterization of Triolein and Implications for Its Role in Lipid Droplet Biogenesis

2021 ◽  
Author(s):  
Siyoung Kim ◽  
Gregory A. Voth
Keyword(s):  
Negative Curvature ◽  
Critical Concentration ◽  
Bilayer Membrane ◽  
The Other ◽  
Coarse Grained ◽  
Membrane Properties ◽  
Bending Modulus ◽  
Cytosolic Side ◽  
Membrane Bending ◽  
Free Energy Sampling

Lipid droplets (LDs) are neutral lipid storing organelles surrounded by a phospholipid (PL) monolayer. At present, how LDs are formed in the endoplasmic reticulum (ER) bilayer is poorly understood. In this study, we present a revised triolein (TG) model, the main constituent of the LD core, and characterize its properties in a bilayer membrane to demonstrate the implications of its behavior in LD biogenesis. In all-atom (AA) bilayer simulations, TG resides at the surface, adopting PL-like conformations (denoted in this work as SURF-TG). Free energy sampling simulation results estimate the barrier for TG relocating from the bilayer surface to the bilayer center to be ~2 kcal/mol in the absence of an oil lens. Conical SURF-TG is able to modulate membrane properties by increasing PL ordering, decreasing bending modulus, and creating local negative curvature. The other conical lipid, dioleoyl-glycerol (DAG), also reduces the membrane bending modulus and populates the negative curvature regions. A phenomenological coarse-grained (CG) model is also developed to observe larger scale SURF-TG-mediated membrane deformation. The CG simulations confirm that TG nucleates between the bilayer leaflets at a critical concentration when SURF-TG is evenly distributed. However, when one monolayer contains more SURF-TG, the membrane bends toward the other leaflet. The central conclusion of this study is that SURF-TG is a negative curvature inducer, as well as a membrane modulator. To this end, a model has proposed in which the accumulation of SURF-TG in the luminal leaflet bends the ER bilayer toward the cytosolic side, followed by TG nucleation.

Numerical Analysis on Characteristic of Hydrogen Mixing and Stratification in a Containment Model

2018 ◽  
Author(s):  
Cheng Peng ◽  
Lili Tong ◽  
Xuewu Cao
Keyword(s):  
Nuclear Power ◽  
Numerical Models ◽  
Physical Models ◽  
Main Stream ◽  
Hydrogen Distribution ◽  
Containment Model ◽  
Complex Process ◽  
Safety Design ◽  
Cfd Method ◽  
Injection Location

Hydrogen explosion is one of the severe threats to the integrity of containment for nuclear power plant which has drawn many experts attention to make great efforts on hydrogen related issues, espeically after the Fukushima Dai-ichi nuclear power station accident took place. However, the issue of hydrogen distribution hasn’t been closed as a result of related complex process of hydrogen transport and the particular design of each kind of facility. In the present study, CFD method has been applied to the pre-analysis on the characteristic of hydrogen mixing and stratification in a computational containment model for the sake of probable phenomena identification and instrumentaion design of experimental study in the next phase. Firstly, physical models have been verified by the experimental data from THAI HM2. Based on the determined numerical models, five typical groups of cases have been simulated, considering the effect of initial momentum, injection location, and injection direction. During the cases, only helium has been released in the vessel isothermally, on behalf of hydrogen. The results show that the backflow from the wall to the main stream in the dome and the buoyancy force may strongly dominate the helium flow, thus affacting the mixing and stratification. The eccentric injection and horizontal injection may also influence the helium distribution, in which the wall effects and rapid shifting may play important roles. However, the inference will be examined in the experiments later. All the work will be helpful for safety design and analysis of newly-built containment in China.

scholarly journals Development of Artificial Cell Models Using Microfluidic Technology and Synthetic Biology

Micromachines ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 559 ◽  
Author(s):  
Koki Kamiya
Keyword(s):  
Synthetic Biology ◽  
Cell Membrane ◽  
Lipid Bilayer ◽  
Lipid Membranes ◽  
Lipid Vesicles ◽  
Optical Microscope ◽  
Living Cells ◽  
Biochemical Properties ◽  
Cell Models ◽  
Artificial Cell

Giant lipid vesicles or liposomes are primarily composed of phospholipids and form a lipid bilayer structurally similar to that of the cell membrane. These vesicles, like living cells, are 5–100 μm in diameter and can be easily observed using an optical microscope. As their biophysical and biochemical properties are similar to those of the cell membrane, they serve as model cell membranes for the investigation of the biophysical or biochemical properties of the lipid bilayer, as well as its dynamics and structure. Investigation of membrane protein functions and enzyme reactions has revealed the presence of soluble or membrane proteins integrated in the giant lipid vesicles. Recent developments in microfluidic technologies and synthetic biology have enabled the development of well-defined artificial cell models with complex reactions based on the giant lipid vesicles. In this review, using microfluidics, the formations of giant lipid vesicles with asymmetric lipid membranes or complex structures have been described. Subsequently, the roles of these biomaterials in the creation of artificial cell models including nanopores, ion channels, and other membrane and soluble proteins have been discussed. Finally, the complex biological functions of giant lipid vesicles reconstituted with various types of biomolecules has been communicated. These complex artificial cell models contribute to the production of minimal cells or protocells for generating valuable or rare biomolecules and communicating between living cells and artificial cell models.

scholarly journals Correction: Estimation of membrane bending modulus of stiffness tuned human red blood cells from micropore filtration studies

PLoS ONE ◽  
2020 ◽  
Vol 15 (1) ◽  
pp. e0228125
Author(s):  
Rekha Selvan ◽  
Praveen Parthasarathi ◽  
Shruthi S. Iyengar ◽  
Sharath Ananthamurthy ◽  
Sarbari Bhattacharya
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Human Red Blood Cells ◽  
Bending Modulus ◽  
Membrane Bending

scholarly journals High Resolution Light Microscopy of Live Cells

2005 ◽  
Vol 13 (3) ◽  
pp. 26-29 ◽  
Author(s):  
Vitaly Vodyanoy
Keyword(s):  
Electron Microscope ◽  
Single Cells ◽  
High Vacuum ◽  
Life Forms ◽  
Optical Microscope ◽  
Living Cells ◽  
Live Cells ◽  
Cell Organelles ◽  
Cell Structures ◽  
Independent Life

All living creatures, including humans, are made of cells. The majority of life forms exist as single cells that perform all functions to continue independent life. Some cell structures, cell organelles and particularly bacteria and viruses are commonly too small to be fully observed with an optical microscope. Therefore, an electron microscope is required. Since samples examined with an electron microscope are exposed to very high vacuum, it is impossible to view living cells. The sample preparation for electron microscopy requires that living cells be killed, frozen, dehydrated, and impregnated with heavy metals.

scholarly journals Recent Advances in Scanning Electrochemical Microscopy for Biological Applications

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1389 ◽  
Author(s):  
Luyao Huang ◽  
Ziyu Li ◽  
Yuntian Lou ◽  
Fahe Cao ◽  
Dawei Zhang ◽  
...  
Keyword(s):  
Physiological Activity ◽  
Chemical Species ◽  
Scanning Electrochemical Microscopy ◽  
Living Cells ◽  
Basic Principles ◽  
Specific Chemical ◽  
Microscopy Technique ◽  
Biological Studies ◽  
Computer Controlled ◽  
Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) is a chemical microscopy technique with high spatial resolution for imaging sample topography and mapping specific chemical species in liquid environments. With the development of smaller, more sensitive ultramicroelectrodes (UMEs) and more precise computer-controlled measurements, SECM has been widely used to study biological systems over the past three decades. Recent methodological breakthroughs have popularized SECM as a tool for investigating molecular-level chemical reactions. The most common applications include monitoring and analyzing the biological processes associated with enzymatic activity and DNA, and the physiological activity of living cells and other microorganisms. The present article first introduces the basic principles of SECM, followed by an updated review of the applications of SECM in biological studies on enzymes, DNA, proteins, and living cells. Particularly, the potential of SECM for investigating bacterial and biofilm activities is discussed.

Lattice Boltzmann Simulation of Frost Formation Process

2013 ◽  
Author(s):  
Jinjuan Sun ◽  
Jianying Gong ◽  
Guojun Li ◽  
Tieyu Gao
Keyword(s):  
Lattice Boltzmann ◽  
Formation Process ◽  
Moving Boundary ◽  
Influential Factors ◽  
Physical Models ◽  
Frost Formation ◽  
Flat Surfaces ◽  
Lattice Boltzmann Simulation ◽  
Complex Process ◽  
Moving Boundary Condition

Compared with the conventional mathematical and physical models, the lattice Boltzmann (LB) method is an effective method to simulate the heat and mass transfer in porous media. Frost crystallization aggregation is a very complex process involving inconsistency of frost structures, crystal size distributions, the complex transient shapes, and other numerous influential factors. Assuming the frost is a special porous medium consists of ice crystals and humid air, a mesoscopic model is established to predict the behavior of frost formation based on the lattice Boltzmann equation. The moving boundary condition is adopted in the two-dimensional nine-speed (D2Q9) lattices. The influences of the cold flat surfaces temperature on frost formation process are investigated. The variation laws of frost density and frost layer height are obtained and discussed. Simulation results by the LB model are in agreement with the experiment data from the references.

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