Spatiotemporal dynamics of actin concentration during cytokinesis and locomotion in Dictyostelium

1998 ◽  
Vol 111 (15) ◽  
pp. 2097-2108 ◽  
Author(s):  
S. Yumura ◽  
Y. Fukui
Keyword(s):  
Relative Concentration ◽  
Leading Edge ◽  
Live Cells ◽  
Cell Behavior ◽  
Cleavage Furrow ◽  
Two Dimensional ◽  
Dynamic Changes ◽  
Temporal Regulation ◽  
Ph Dependent ◽  
Actin Concentration

To study the spatial and temporal regulation of the actin cytoskeleton, we have analyzed the actin concentration dynamics in live Dictyostelium. The relative actin concentration was analyzed with respect to cell behavior by fluorescence morphometry. We electroporated rhodamine-actin into Dictyostelium cells and acquired images with 200–300 millisecond temporal and approximately 250 nm spatial resolutions. To convert fluorescence intensity into actin concentration, the observation was made on nearly two-dimensional cells, and the actin signal was ratioed over a volume marker (FITC-BSA or GFP). Since the emission of FITC and GFP is pH-dependent, we first measured the cytoplasmic pH in live cells and determined that the pHi in pseudopods is same as that of general cytoplasm. During cytokinesis, the relative concentration of actin in the cleavage furrow was significantly higher than in the general cytoplasm. In migrating cells, actin was recruited surprisingly rapidly, particularly in the pseudopod. We found that the region of high actin concentration moves relative to the leading edge when a pseudopod projects or retracts. When the pseudopod retracts, the actin density dissipates within 5 seconds. We have also found that actin accumulates in developing pseudopods in an oscillatory manner, and this timing coordinates with advancement of the centroid. This is the first study to reveal the dynamic changes in relative concentration of actin in live cells and to quantitatively correlate these changes with the locomotive behavior of the amoeba.

Enhanced Analytic Approach for Describing pH Triggered Fast Drug Release Systems

2021 ◽  
Vol 18 ◽  
Author(s):  
Aykut Elmas ◽  
Guliz Akyuz ◽  
Ayhan Bergal ◽  
Muberra Andac ◽  
Omer Andac
Keyword(s):  
Drug Release ◽  
Ph Dependence ◽  
Slope Angle ◽  
Ph Sensitive ◽  
Analytic Model ◽  
Two Dimensional ◽  
Analytic Equation ◽  
One Dimensional ◽  
Ph Dependent ◽  
Fast Release

Background: pH sensitive dendrimers attached to nanocarriers, as one of the drug release systems, has become quite popular due to their ease of manufacture in experimental conditions and ability to generate fast drug release in the targeted area. This kind of fast release behavior cannot be represented properly most of the existing kinetic mathematical models. Besides, these models have either no pH dependence or pH dependence added separately. So, they have remained one dimensional. Objective: The aim of this study was to establish the proper analytic equation to describe the fast release of drugs from pH sensitive nanocarrier systems. Then, to combine it with the pH dependent equation for establishing a two-dimensional model for whole system. Methods: We used four common kinetic models for comparison and we fitted them to the release data. Finding that, only Higuchi and Korsmeyer-Peppas models show acceptable fit results. None of these models have pH dependence. To get a better description for pH triggered fast release, we observed the behavior of the slope angle of the release curve. Then we puroposed a new analytic equation by using relation between the slope angle and time. Result: To add a pH dependent equation, we assumed the drug release is “on” or “off” above/below specific pH value and we modified a step function to get a desired behavior. Conclusion: Our new analytic model shows good fitting, not only one-dimensional time dependent release, but also two-dimensional pH dependent release, that provides a useful analytic model to represent release profiles of pH sensitive fast drug release systems.

The Impact of Geometric Variation on Compressor Two-Dimensional Incidence Range

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Martin N. Goodhand ◽  
Robert J. Miller ◽  
Hang W. Lung
Keyword(s):  
Design Process ◽  
Design Space ◽  
Leading Edge ◽  
Critical Value ◽  
Two Dimensional ◽  
Suction Surface ◽  
Design Intent ◽  
Manufacture Process ◽  
The Impact ◽  
Geometric Variation

An important question for a designer is how, in the design process, to deal with the small geometric variations which result from either the manufacture process or in-service deterioration. For some blade designs geometric variations will have little or no effect on the performance of a row of blades, while in others their effects can be significant. This paper shows that blade designs which are most sensitive are those which are susceptible to a distinct switch in the fluid mechanisms responsible for limiting blade performance. To demonstrate this principle, the sensitivity of compressor 2D incidence range to manufacture variations is considered. Only one switch in mechanisms was observed, the onset of flow separation at the leading edge. This switch is only sensitive to geometric variations around the leading edge, 0–3% of the suction surface. The consequence for these manufacture variations was a 10% reduction in the blade's positive incidence range. For this switch, the boundary in the design space is best defined in terms of the blade pressure distribution. Blade designs where the acceleration exceeds a critical value just downstream of the leading edge are shown to be robust to geometric variation. Two historic designs, supercritical blades and blades with sharp leading edges, though superior in design intent, are shown to sit outside this robust region and thus, in practice, perform worse. The improved understanding of the robust, region of the design space is then used to design a blade capable of a robust, 5% increase in operating incidence range.

scholarly journals Comparación de la citocompatibilidad in vitro entre los biomateriales, fibroína y polipropileno

2017 ◽  
Vol 26 (45) ◽  
Author(s):  
Alejandro Arboleda-Carvajal ◽  
Julián González ◽  
Manuel Hernando Franco-Arias ◽  
Liliana Valladares-Torres
Keyword(s):  
Cell Proliferation ◽  
Statistical Difference ◽  
Indirect Evidence ◽  
Live Cells ◽  
Cell Behavior ◽  
In Vitro Methods ◽  
Polypropylene Material ◽  
Metabolic Reduction ◽  
Number Of Cells

This study evaluates the cell behavior of HeLa cells in vitro on fibroin and polypropylene. In order to determine cell proliferation in culture much fibroin material such as polypropylene, as the number of cells / sample was performed by the metabolic reduction of  3-(4,5- dimetiltiazol-2-ilo)-2,5-difeniltetrazol Bromide, MTT assay, using direct and indirect evidence of cytotoxicity. For direct and indirect testing of cytotoxicity in fibroin and polypropylene material, a statistical difference was found in the average number of live cells for fibroin sample regardless of the type of test (p<0.005). By the use of in vitro methods, it is shown that fibroin material has better cell behavior in terms of viability, compared with polypropylene.

pH-dependent syntheses, luminescence and magnetic properties of two-dimensional framework lanthanide 1,3-diarylphosphonate complexes

2014 ◽  
Vol 38 (3) ◽  
pp. 1328 ◽  
Author(s):  
Yi-Fu Liu ◽  
Guang-Feng Hou ◽  
Ying-Hui Yu ◽  
Peng-Fei Yan ◽  
Guang-Ming Li ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Two Dimensional ◽  
Ph Dependent

The Effects of Energy Dissipation on the Transition to Planing of a Boat

1989 ◽  
Vol 33 (01) ◽  
pp. 35-46
Author(s):  
P. M. Naghdi ◽  
M. B. Rubin
Keyword(s):  
Steady State ◽  
Energy Dissipation ◽  
Detailed Analysis ◽  
Leading Edge ◽  
Steady State Solution ◽  
State Solution ◽  
Inviscid Fluid ◽  
Two Dimensional ◽  
Spray Formation ◽  
Propulsion Force

The problem of the transition to planing of a boat, in the presence of the effect of spray formation at the boat's leading edge, is investigated using a nonlinear steady-state solution of the equations of the theory of a directed fluid sheet for two-dimensional motion of an incompressible inviscid fluid. The motion of the fluid is coupled with the motion of the free-floating boat and detailed analysis is undertaken pertaining to such features as trim angle, sinkage, and propulsion force. The effects of the rate of energy dissipation arising from spray formation at the boat's leading edge, and changes in equilibrium depth, propulsion angle, and the boat's weight, are studied and shown to significantly influence the boat's planing characteristics.

Tracking the Formation and Degradation of Fatty-Acid-Accumulated Mitochondria Using Label-Free Chemical Imaging

2020 ◽  
Author(s):  
Chi Zhang ◽  
Stephen Boppart
Keyword(s):  
Fatty Acid ◽  
Structural Features ◽  
Chemical Imaging ◽  
Live Cells ◽  
Label Free ◽  
Dynamic Changes ◽  
Regulatory Processes ◽  
Transport Chain ◽  
Anti Stokes ◽  
First Time

Abstract The mitochondrion is one of the key organelles for maintaining cellular homeostasis. External environmental stimuli and internal regulatory processes alter the metabolism and functions of mitochondria. To understand these activities of mitochondria, it is critical to probe the key metabolic molecules inside these organelles. In this study, we used label-free chemical imaging modalities including coherent anti-Stokes Raman scattering and multiphoton-excited autofluorescence to study the mitochondrial activities in living cancer cells. We found that hypothermia exposure tends to induce fatty-acid (FA) accumulation in some mitochondria of MIAPaCa-2 cells. Autofluorescence images show that the FA-accumulated mitochondria also have abnormal NADH and FAD metabolism, likely induced by the dysfunction of the electron transport chain. We also found that when the cells were re-warmed to physiological temperature after a period of hypothermia, the FA-accumulated mitochondria changed their structural features, likely caused by the mitophagy process. To the best of our knowledge, this is the first time that FA accumulation in mitochondria was observed in live cells. Our research also demonstrates that multimodal label-free chemical imaging is an attractive tool to discover abnormal functions of mitochondria at the single-organelle level and can be used to quantify the dynamic changes of this organelle under perturbative conditions.

Generalisation of the Condition for Waviness in the Pressure Distribution on a Cambered Plate

1963 ◽  
Vol 67 (632) ◽  
pp. 529-530 ◽  
Author(s):  
E. Angus Boyd
Keyword(s):  
Pressure Distribution ◽  
Surface Pressure ◽  
Leading Edge ◽  
Metal Plate ◽  
Two Dimensional ◽  
Striking Result ◽  
Surface Pressure Distribution

Recently some data from tests done on a cambered plate have been published. The shape of metal plate aerofoil tested matched that taken up by a flexible two-dimensional sail. The most striking result in the rneasurements was the waviness present near the leading edge in the upper surface pressure distribution. To find the theoretical conditions under which such a waviness would occur a parabolic skeleton aerofoil was investigated, as this shape differed little from the actual aerofoil tested.

Buoyant convection from horizontal surfaces at const ant pressure

1975 ◽  
Vol 68 (3) ◽  
pp. 609-624 ◽  
Author(s):  
S. C. Traugott
Keyword(s):  
Pressure Gradient ◽  
Boundary Layers ◽  
Line Source ◽  
Leading Edge ◽  
Wall Jet ◽  
Two Dimensional ◽  
Buoyant Plume ◽  
Grashof Number ◽  
Buoyancy Driven Flows ◽  
Streamwise Pressure Gradient

A two-dimensional horizontal flow is discussed, which is induced by other, buoyancy-driven flows elsewhere. It is an adaptation of the incompressible wall jet, which is driven by conditions a t the leading edge and has no streamwise pressure gradient. The relation of this flow to the classical buoyancy-driven boundary layers on inclined and horizontal surfaces is investigated, as well as its possible connexion with a two-dimensional buoyant plume driven by a line source of heat. Composite flows are constructed by patching various such solutions together. The composite flows exhibit$Gr^{\frac{1}{4}}$scaling (Grbeing the Grashof number).

scholarly journals Two- and three-dimensional numerical simulations of the transition to oscillatory convection in low-Prandtl-number fluids

1998 ◽  
Vol 374 ◽  
pp. 145-171 ◽  
Author(s):  
DANIEL HENRY ◽  
MARC BUFFAT
Keyword(s):  
Prandtl Number ◽  
Relative Concentration ◽  
Three Dimensional ◽  
Power Spectra ◽  
Hadley Circulation ◽  
Time Dependent ◽  
Two Dimensional ◽  
General Behaviour ◽  
Shallow Cavities ◽  
Dependent Flow

The convective flows which arise in shallow cavities filled with low-Prandtl-number fluids when subjected to a horizontal temperature gradient are studied numerically with a finite element method. Attention is focused on a rigid cavity with dimensions 4×2×1, for which experimental data are available. The three-dimensional results indicate that, after a relative concentration of the initial Hadley circulation, a transition to time-dependent flows occurs in the form of a roll oscillation with a purely dynamical origin. This transition corresponds to a Hopf bifurcation with a breaking of symmetry that gives some specific properties to the time evolution of the flow: these properties are shown to be the result of the general behaviour of the dynamical systems. Calculations performed in the case of mercury compare well with the experiments with similar power spectra of the temperature, and this validates the analysis of the nature of the global flow performed in the limiting case Pr=0. All these results are discussed with respect to the linear and nonlinear analyses and to other computational experiments. Numerical results obtained in the corresponding two-dimensional situation give a different transition to the time-dependent flow: it is shown that in the three-dimensional cavity this type of two-dimensional transition is less probable than the observed transition with breaking of symmetry.

A New Approach to Thin Aerofoil Theory

1951 ◽  
Vol 3 (3) ◽  
pp. 193-210 ◽  
Author(s):  
M.J. Lighthill
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Approximate Solutions ◽  
Radius Of Curvature ◽  
Two Dimensional ◽  
General Technique ◽  
New Approach ◽  
Flow Problems ◽  
Physical Problems ◽  
First Approximation

SummaryThe general technique for rendering approximate solutions to physical problems uniformly valid is here applied to the simplest form of the problem of correcting the theory of thin wings near a rounded leading edge. The flow investigated is two-dimensional, irrotational and incompressible, and therefore the results do not materially add to our already extensive knowledge of this subject, but the method, which is here satisfactorily checked against this knowledge, shows promise of extension to three-dimensional, and compressible, flow problems.The conclusion, in the problem studied here, is that the velocity field obtained by a straightforward expansion in powers of the disturbances, up to and including either the first or the second power, with coefficients functions of co-ordinates such that the leading edge is at the origin and the aerofoil chord is one of the axes, may be rendered a valid first approximation near the leading edge, as well as a valid first or second approximation away from it, if the whole field is shifted downstream parallel to the chord for a distance of half the leading edge radius of curvature ρL. It follows that the fluid speed on the aerofoil surface, as given on such a straightforward second approximation as a function of distance x along the chord, similarly is rendered uniformly valid (see equation (52)) if the part singular like x-1 is subtracted and the remainder is multiplied by .

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