scholarly journals Reconstruction of the three-dimensional beat pattern underlying swimming behaviors of sperm

2021 ◽  
Vol 44 (7) ◽  
Author(s):  
A. Gong ◽  
S. Rode ◽  
G. Gompper ◽  
U. B. Kaupp ◽  
J. Elgeti ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Intrinsic Property ◽  
Human Sperm ◽  
Bending Waves ◽  
Flagellar Beat ◽  
Beat Pattern ◽  
Glass Interface ◽  
Two Space Dimensions ◽  
Swimming Trajectories ◽  
Physical And Chemical

Abstract  The eukaryotic flagellum propels sperm cells and simultaneously detects physical and chemical cues that modulate the waveform of the flagellar beat. Most previous studies have characterized the flagellar beat and swimming trajectories in two space dimensions (2D) at a water/glass interface. Here, using refined holographic imaging methods, we report high-quality recordings of three-dimensional (3D) flagellar bending waves. As predicted by theory, we observed that an asymmetric and planar flagellar beat results in a circular swimming path, whereas a symmetric and non-planar flagellar beat results in a twisted-ribbon swimming path. During swimming in 3D, human sperm flagella exhibit torsion waves characterized by maxima at the low curvature regions of the flagellar wave. We suggest that these torsion waves are common in nature and that they are an intrinsic property of beating axonemes. We discuss how 3D beat patterns result in twisted-ribbon swimming paths. This study provides new insight into the axoneme dynamics, the 3D flagellar beat, and the resulting swimming behavior. Graphic abstract

scholarly journals Control of helical navigation by three-dimensional flagellar beating

2020 ◽  
Author(s):  
Dario Cortese ◽  
Kirsty Y. Wan
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Rotation ◽  
Live Cells ◽  
High Speed Imaging ◽  
Flagellar Beat ◽  
Motile Cells ◽  
Beat Pattern ◽  
Swimming Trajectories ◽  
Realistic Geometries

Helical swimming is a ubiquitous strategy for motile cells to generate self-gradients for environmental sensing. The model biflagellate Chlamydomonas reinhardtii rotates at a constant 1 – 2 Hz as it swims, but the mechanism is unclear. Here, we show unequivocally that the rolling motion derives from a persistent, non-planar flagellar beat pattern. This is revealed by high-speed imaging and micromanipulation of live cells. We construct a fully-3D model to relate flagellar beating directly to the free-swimming trajectories. For realistic geometries, the model reproduces both the sense and magnitude of the axial rotation of live cells. We show that helical swimming requires further symmetry-breaking between the two flagella. These functional differences underlie all tactic responses, particularly phototaxis. We propose a control strategy by which cells steer towards or away from light by modulating the sign of biflagellar dominance.

Analysis of the Flagellar Beat Pattern of Male Ectocarpus Siliculosus Gametes (Phaeophyta) in Relation to Chemotactic Stimulation by Female Cells

1981 ◽  
Vol 92 (1) ◽  
pp. 53-66
Author(s):  
ANNETTE GELLER ◽  
DIETER G. MÜLLER
Keyword(s):  
Linear Correlation ◽  
Mode Of Action ◽  
High Speed ◽  
Sex Attractant ◽  
Cell Axis ◽  
Ectocarpus Siliculosus ◽  
Bending Waves ◽  
Flagellar Beat ◽  
Beat Pattern ◽  
Negative Linear Correlation

Heterocontic male Ectocarpus siliculosus gametes respond to the sex-attractant ectocarpen by changing their locomotive behaviour. However, the mode of action of the flagella is not changed by the presence of ectocarpen. High-speed cinemicrography shows that gametes moving close to a coverglass perform planar bending waves with their front flagellum. Straight or slightly curved swimming paths are generated by enhanced upward bends of the front flagellum to compensate for the asymmetrical insertion of both flagella. Narrower curves are connected with increasing downward bends of the front flagellum. There is a negative linear correlation between the average deflexion of the front flagellum (μm) from the cell axis and the radius of track (correlation coefficient 0.94). Additionally, freely swimming gametes exhibit elliptical and rotary wave motions, suggesting a relationship between thigmotaxis and mode of action of the front flagellum. The rigid hind flagellum performs one rapid sideward beat when the gametes swim in narrow curves. This appears to provide a steering function.

scholarly journals Human sperm accumulation near surfaces: a simulation study

2009 ◽  
Vol 621 ◽  
pp. 289-320 ◽  
Author(s):  
D. J. SMITH ◽  
E. A. GAFFNEY ◽  
J. R. BLAKE ◽  
J. C. KIRKMAN-BROWN
Keyword(s):  
Three Dimensional ◽  
Human Sperm ◽  
Boundary Integral ◽  
Slender Body ◽  
Plane Boundary ◽  
Slender Body Theory ◽  
Flagellar Beat ◽  
A Cell ◽  
Finite Distance ◽  
Head Morphology

A hybrid boundary integral/slender body algorithm for modelling flagellar cell motility is presented. The algorithm uses the boundary element method to represent the ‘wedge-shaped’ head of the human sperm cell and a slender body theory representation of the flagellum. The head morphology is specified carefully due to its significant effect on the force and torque balance and hence movement of the free-swimming cell. The technique is used to investigate the mechanisms for the accumulation of human spermatozoa near surfaces. Sperm swimming in an infinite fluid, and near a plane boundary, with prescribed planar and three-dimensional flagellar waveforms are simulated. Both planar and ‘elliptical helicoid’ beating cells are predicted to accumulate at distances of approximately 8.5–22 μm from surfaces, for flagellar beating with angular wavenumber of 3π to 4π. Planar beating cells with wavenumber of approximately 2.4π or greater are predicted to accumulate at a finite distance, while cells with wavenumber of approximately 2π or less are predicted to escape from the surface, likely due to the breakdown of the stable swimming configuration. In the stable swimming trajectory the cell has a small angle of inclination away from the surface, no greater than approximately 0.5°. The trapping effect need not depend on specialized non-planar components of the flagellar beat but rather is a consequence of force and torque balance and the physical effect of the image systems in a no-slip plane boundary. The effect is relatively weak, so that a cell initially one body length from the surface and inclined at an angle of 4°–6° towards the surface will not be trapped but will rather be deflected from the surface. Cells performing rolling motility, where the flagellum sweeps out a ‘conical envelope’, are predicted to align with the surface provided that they approach with sufficiently steep angle. However simulation of cells swimming against a surface in such a configuration is not possible in the present framework. Simulated human sperm cells performing a planar beat with inclination between the beat plane and the plane-of-flattening of the head were not predicted to glide along surfaces, as has been observed in mouse sperm. Instead, cells initially with the head approximately 1.5–3 μm from the surface were predicted to turn away and escape. The simulation model was also used to examine rolling motility due to elliptical helicoid flagellar beating. The head was found to rotate by approximately 240° over one beat cycle and due to the time-varying torques associated with the flagellar beat was found to exhibit ‘looping’ as has been observed in cells swimming against coverslips.

Validation of a Belt Model for Prediction of Hub Forces from a Rolling Tire4

2009 ◽  
Vol 37 (2) ◽  
pp. 62-102 ◽  
Author(s):  
C. Lecomte ◽  
W. R. Graham ◽  
D. J. O’Boy
Keyword(s):  
Internal Pressure ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Prediction Method ◽  
Analytical Models ◽  
Beam Model ◽  
Impedance Boundary ◽  
Bending Waves ◽  
Tire Rotation ◽  
Three Dimensional Models

Abstract An integrated model is under development which will be able to predict the interior noise due to the vibrations of a rolling tire structurally transmitted to the hub of a vehicle. Here, the tire belt model used as part of this prediction method is first briefly presented and discussed, and it is then compared to other models available in the literature. This component will be linked to the tread blocks through normal and tangential forces and to the sidewalls through impedance boundary conditions. The tire belt is modeled as an orthotropic cylindrical ring of negligible thickness with rotational effects, internal pressure, and prestresses included. The associated equations of motion are derived by a variational approach and are investigated for both unforced and forced motions. The model supports extensional and bending waves, which are believed to be the important features to correctly predict the hub forces in the midfrequency (50–500 Hz) range of interest. The predicted waves and forced responses of a benchmark structure are compared to the predictions of several alternative analytical models: two three dimensional models that can support multiple isotropic layers, one of these models include curvature and the other one is flat; a one-dimensional beam model which does not consider axial variations; and several shell models. Finally, the effects of internal pressure, prestress, curvature, and tire rotation on free waves are discussed.

Incorporation of spatial variability in modeling non-point source groundwater nitrate pollution

1996 ◽  
Vol 33 (4-5) ◽  
pp. 233-240 ◽  
Author(s):  
F. S. Goderya ◽  
M. F. Dahab ◽  
W. E. Woldt ◽  
I. Bogardi
Keyword(s):  
Spatial Variability ◽  
Point Source ◽  
Three Dimensional ◽  
Nitrate Contamination ◽  
Geostatistical Simulation ◽  
Chemical Measurements ◽  
Spatially Distributed ◽  
Potential Benefits ◽  
Zone Modeling ◽  
Physical And Chemical

A methodology for incorporation of spatial variability in modeling non-point source groundwater nitrate contamination is presented. The methodology combines geostatistical simulation and unsaturated zone modeling for estimating the amount of nitrate loading to groundwater. Three dimensional soil nitrogen variability and 2-dimensional crop yield variability are used in quantifying potential benefits of spatially distributed nitrogen input. This technique, in combination with physical and chemical measurements, is utilized as a means of illustrating how the spatial statistical properties of nitrate leaching can be obtained for different scenarios of fixed and variable rate nitrogen applications.

scholarly journals Size-controlled human adipose-derived stem cell spheroids hybridized with single-segmented nanofibers and their effect on viability and stem cell differentiation

2021 ◽  
Vol 25 (1) ◽  
Author(s):  
Jinkyu Lee ◽  
Sangmin Lee ◽  
Sung Min Kim ◽  
Heungsoo Shin
Keyword(s):  
Stem Cell ◽  
Cell Function ◽  
Average Length ◽  
Three Dimensional ◽  
Stem Cell Differentiation ◽  
Cell Spheroids ◽  
Significant Difference ◽  
Vitro Analysis ◽  
Physical And Chemical

Abstract Background Fabrication of three-dimensional stem cell spheroids have been studied to improve stem cell function, but the hypoxic core and limited penetration of nutrients and signaling cues to the interior of the spheroid were challenges. The incorporation of polymers such as silica and gelatin in spheroids resulted in relatively relaxed assembly of composite spheroids, and enhancing transport of nutrient and biological gas. However, because of the low surface area between cells and since the polymers were heterogeneously distributed throughout the spheroid, these polymers cannot increase the cell to extracellular matrix interactions needed to support differentiation. Methods We developed the stem cell spheroids that incorporate poly(ι-lactic acid) single-segmented fibers synthesized by electrospinning and physical and chemical fragmentation. The proper mixing ratio was 2000 cells/μg fibers (average length of the fibers was 50 μm - 100 μm). The SFs were coated with polydopamine to increase cell binding affinity and to synthesize various-sized spheroids. The function of spheroids was investigated by in vitro analysis depending on their sizes. For statistical analysis, Graphpad Prism 5 software (San Diego, CA, USA) was used to perform one-way analysis of variance ANOVA with Tukey’s honest significant difference test and a Student’s t-test (for two variables) (P < 0.05). Results Spheroids of different sizes were created by modulating the amount of cells and fibers (0.063 mm2–0.322 mm2). The fibers in the spheroid were homogenously distributed and increased cell viability, while cell-only spheroids showed a loss of DNA contents, internal degradation, and many apoptotic signals. Furthermore, we investigated stemness and various functions of various-sized fiber-incorporated spheroids. In conclusion, the spheroid with the largest size showed the greatest release of angiogenic factors (released VEGF: 0.111 ± 0.004 pg/ng DNA), while the smallest size showed greater effects of osteogenic differentiation (mineralized calcium: 18.099 ± 0.271 ng/ng DNA). Conclusion The spheroids incorporating polydopamine coated single-segmented fibers showed enhanced viability regardless of sizes and increased their functionality by regulating the size of spheroids which may be used for various tissue reconstruction and therapeutic applications.

Investigation of atmospheric hydrogen cyanide: a modelling perspective

2021 ◽  
Author(s):  
Antonio G. Bruno ◽  
Jeremy J. Harrison ◽  
David P. Moore ◽  
Martyn P. Chipperfield ◽  
Richard J. Pope
Keyword(s):  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Hydrogen Cyanide ◽  
Three Dimensional ◽  
Oxidation Reactions ◽  
Loss Mechanism ◽  
Mixing Ratios ◽  
The Individual ◽  
Atmospheric Loss ◽  
Physical And Chemical

&lt;p&gt;Hydrogen cyanide (HCN) is one of the most abundant cyanides present in the global atmosphere, and is a tracer of biomass burning, especially for peatland fires. The HCN lifetime is 2&amp;#8211;5 months in the troposphere but several years in the stratosphere. Understanding the physical and chemical mechanisms of HCN variability is important due to its non-negligible role in the nitrogen cycle. The main source of tropospheric HCN is biomass burning with minor contributions from industry and transport. The main loss mechanism of atmospheric HCN is the reaction with the hydroxyl radical (OH). Ocean uptake is also important, while in the stratosphere oxidation by reaction with O(&lt;sup&gt;1&lt;/sup&gt;D) needs to be considered.&lt;/p&gt;&lt;p&gt;HCN variability can be investigated using chemical model simulations, such as three-dimensional (3-D) chemical transport models (CTMs). Here we use an adapted version of the TOMCAT 3-D CTM at a 1.2&amp;#176;x1.2&amp;#176; spatial resolution from the surface to ~60 km for 12 idealised HCN tracers which quantify the main loss mechanisms of HCN, including ocean uptake, atmospheric oxidation reactions and their combinations. The TOMCAT output of the HCN distribution in the period 2004-2020 has been compared with HCN profiles measured by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) over an altitude grid from 6 to 42 km. HCN model data have also been compared with ground-based measurements of HCN columns from NDACC FTIR stations and with in-situ volume mixing ratios (VMRs) from NOAA ground-based measurement sites.&lt;/p&gt;&lt;p&gt;The model outputs for the HCN tracer with full treatment of the loss processes generally agree well with ACE-FTS measurements, as long as we use recent laboratory values for the atmospheric loss reactions. Diagnosis of the individual loss terms shows that decay of the HCN profile in the upper stratosphere is due mainly to the O(&lt;sup&gt;1&lt;/sup&gt;D) sink. In order to test the magnitude of the tropospheric OH sink and the magnitude of the ocean sink, we also show the comparisons of the model tracers with surface-based observations. The implications of our results for understanding HCN and its variability are then discussed.&lt;/p&gt;

scholarly journals Epithelial Cell Chirality Revealed by Three-Dimensional Spontaneous Rotation

2018 ◽  
Vol 115 (48) ◽  
pp. 12188-12193 ◽  
Author(s):  
Amanda S. Chin ◽  
Kathryn E. Worley ◽  
Poulomi Ray ◽  
Gurleen Kaur ◽  
Jie Fan ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Cell Polarity ◽  
Three Dimensional ◽  
Intrinsic Property ◽  
Cell Aggregates ◽  
Mechanistic Studies ◽  
Directional Bias ◽  
Self Organized ◽  
Dependent Cell

Our understanding of the left–right (LR) asymmetry of embryonic development, in particular the contribution of intrinsic handedness of the cell or cell chirality, is limited due to the confounding systematic and environmental factors during morphogenesis and a ack of physiologically relevant in vitro 3D platforms. Here we report an efficient two-layered biomaterial platform for determining the chirality of individual cells, cell aggregates, and self-organized hollow epithelial spheroids. This bioengineered niche provides a uniform defined axis allowing for cells to rotate spontaneously with a directional bias toward either clockwise or counterclockwise directions. Mechanistic studies reveal an actin-dependent, cell-intrinsic property of 3D chirality that can be mediated by actin cross-linking via α-actinin-1. Our findings suggest that the gradient of extracellular matrix is an important biophysicochemical cue influencing cell polarity and chirality. Engineered biomaterial systems can serve as an effective platform for studying developmental asymmetry and screening for environmental factors causing birth defects.

QUANTUM COMPUTING WITH NON-ABELIAN QUASIPARTICLES

2007 ◽  
Vol 21 (08n09) ◽  
pp. 1372-1378 ◽  
Author(s):  
N. E. BONESTEEL ◽  
L. HORMOZI ◽  
G. ZIKOS ◽  
S. H. SIMON
Keyword(s):  
Dimensional Space ◽  
Quantum Hall ◽  
Three Dimensional ◽  
Fractional Quantum ◽  
Fractional Quantum Hall ◽  
Quantum Operations ◽  
Topological Quantum ◽  
Dimensional Space Time ◽  
Two Space Dimensions ◽  
Topological Quantum Computation

In topological quantum computation quantum information is stored in exotic states of matter which are intrinsically protected from decoherence, and quantum operations are carried out by dragging particle-like excitations (quasiparticles) around one another in two space dimensions. The resulting quasiparticle trajectories define world-lines in three dimensional space-time, and the corresponding quantum operations depend only on the topology of the braids formed by these world-lines. We describe recent work showing how to find braids which can be used to perform arbitrary quantum computations using a specific kind of quasiparticle (those described by the so-called Fibonacci anyon model) which are thought to exist in the experimentally observed ν = 12/5 fractional quantum Hall state.

A Vector Normalized Method-Assisted 3D-QSA2R Model and Its Application in the Molecular Modification of PCBs with Higher Flame Retardancy and Lower Toxicity

2021 ◽  
Vol 13 (1) ◽  
pp. 80-87
Author(s):  
Minghao Li ◽  
Yu Li
Keyword(s):  
Flame Retardancy ◽  
Flame Retardants ◽  
Polychlorinated Biphenyl ◽  
Three Dimensional ◽  
Predictive Ability ◽  
Energy Functional ◽  
Long Distance ◽  
Molecular Modification ◽  
And Control ◽  
Physical And Chemical

Flame retardants are widely used in many materials and products, and there is a pressing need to enhance the performance of flame retardants while lowering their toxicity. In this paper, using polychlorinated biphenyl flame retardants as an example, a three-dimensional quantitative structure-double-activity relationship (3D-QSA2R) model, with the double activities of flame retardancy and toxicity, was constructed by introducing a vector normalized method to achieve the goal of environmental risk management and control the sources of chemicals. The results showed that the 3D-QSA2R model has good robustness and strong predictive ability. PCB-209 was used as a target molecule for the contour map analysis and molecular modification. The comprehensive values (C) of six novel PCB-209 molecules were increased by up to 53.61%. The physical and chemical parameters (frequency and Gibbs free energy), functional properties (stability and insulation) and the other three POP properties of the novel PCB-209 molecules showed that the Cl atom substitution reaction of PCB209 molecules could occur and exist stably in the environment. With improvement in stability, the insulation of six novel PCB-209 molecules was not influenced after modification, and the environmental persistence, bioconcentration and long-distance migration of six novel PCB-209 molecules were increased up to 99.47%, 15.29% and 100.9%, respectively. The flame retardancy and toxicity of the new molecules were verified by Gaussian software and the EPI database, respectively. The single activity verification values of flame retardancy and toxicity followed the trend of C values predicted by the double-activity 3D-QSA2R model established in this paper. The ratio between the two single activities of the new PCB-209 molecule generally conformed to the weight setting, which satisfies the purpose of setting the weight as the main way to improve the efficacy of flame retardants.

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