The mechanics of cilia and flagella: What we know and what we need to know

Cytoskeleton, Journal Year: 2024, Volume and Issue: 81(11), P. 648 - 668

Published: May 23, 2024

In this review, we provide a condensed overview of what is currently known about the mechanical functioning flagellar/ciliary axoneme. We also present list 10 specific areas where our current knowledge incomplete and explain benefits further experimental investigation. Many physical parameters axoneme its component parts have not been determined. This limits ability to understand how structure contributes in several regards. It restricts mechanics contribute regulation motor function. confines three-dimensional workings various beating modes are accomplished. Lastly, it prevents accurate computational modeling three-dimensions.

Language: Английский

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Chemomechanical model of sperm locomotion reveals two modes of swimming

Physical Review Fluids, Journal Year: 2023, Volume and Issue: 8(11)

Published: Nov. 15, 2023

We present a chemomechanical model to analyze the propulsion of mammalian spermatozoa. The accounts for motor kinetics, flagellar deformations, and hydrodynamics suspending fluid. Simulations demonstrate spontaneous oscillations leading realistic swimming patterns. Notably, velocity exhibits two distinct peaks as function activity molecular motors. These are characterized by waveforms trajectories. Our findings contribute deeper understanding biophysical mechanisms involved in sperm locomotion.

Language: Английский

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Viscous Loading Regulates the Flagellar Energetics of Human and Bull Sperm

Small Methods, Journal Year: 2023, Volume and Issue: 8(7)

Published: Dec. 22, 2023

Abstract The viscoelastic properties of the female reproductive tract influence sperm swimming behavior, but exact role these rheological changes in regulating energetics remains unknown. Using high‐speed dark‐field microscopy, flagellar dynamics free‐swimming across a physiologically relevant range viscosities is resolved. A transition from 3D to 2D slither under an increased viscous loading revealed, absence any geometrical or chemical stimuli. This species‐specific, aligning with viscosity variations within each species’ tract. Despite substantial drag increase, slithering maintain steady speed wide (20–250 and 75–1000 mPa s for bull human sperm) by dissipating over sixfold more energy into fluid without elevating metabolic activity, potentially altering mechanisms dynein motor activity. energy‐efficient motility mode ideally suited environment

Language: Английский

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Twist - torsion coupling in beating axonemes

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: March 18, 2024

Abstract Motile cilia and flagella are ubiquitous cell appendages whose regular bending waves pump fluids across tissue surfaces enable single-cell navigation. Key to these functions their non-planar waveforms with characteristic torsion. It is not known how torsion, a purely geometric property of the shape, related mechanical deformations axoneme, conserved cytoskeletal core flagella. Here, we assess torsion twist in reactivated axonemes isolated from green alga Chlamydomonas reinhardtii . Using defocused darkfield microscopy beat-cycle averaging, resolve 3D shapes axonemal waveform nanometer precision at millisecond timescales. Our measurements reveal hetero-chiral propagating base tip peak-to-peak amplitude 22 º/µm. To investigate if observed results twist, attach gold nanoparticles measure its cross-section rotation during beating. We find that locally, co-rotates plane. This co-rotation presents first experimental evidence for twist-torsion coupling indicates propagate along axoneme work thus links shape deformation beating axonemes, informing models motor regulation beat motile cilia.

Language: Английский

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The cooperative impact of flow and viscosity on sperm flagellar energetics in biomimetic environments

Cell Reports Physical Science, Journal Year: 2023, Volume and Issue: 4(11), P. 101646 - 101646

Published: Nov. 1, 2023

Complex rheological properties of the female reproductive tract serve as a long-range guidance mechanism for sperm. However, conventional microscopy methods and population-level studies have restricted our understanding combined effects flow viscosity on sperm flagellar beating behavior at single-cell level. Here, using microfluidics, we study individual dynamics within physiologically relevant range shear rate. Our results indicate that an increase in rate from 0 to 6 s−1 75 mPa s reduces curvature by 20%, while peak energy occurs 3 s−1—a favorable rheotaxis. Viscosity has more dominant influence than waveform, synergistic effect promotes energy-efficient behavior. findings provide new insights into complex interplay between environment function facilitating fertilization.

Language: Английский

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Swimming by spinning: spinning-top type rotations regularize sperm swimming into persistently symmetric paths in 3D

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2023, Volume and Issue: unknown

Published: July 16, 2023

Abstract Sperm modulate their flagellar symmetry to navigate through complex physico-chemical environments and achieve reproductive function. Yet it remains elusive how sperm swim forwards despite the inherent asymmetry of several components that constitutes engine. Despite critical importance symmetry, or lack it, on navigation its physiological state, there is no methodology date can robustly detect state beat in free-swimming 3D. How does symmetric progressive swimming emerge even for asymmetric beating, beating (a)symmetry be inferred experimentally? Here, we numerically resolve fluid mechanics around asymmetrically spermatozoa. This reveals spinning critically regularizes into persistently paths 3D, allowing any imperfections beat. The orientation three-dimensions, not path, inform beat, eliminating need tracking flagellum We report a surprising correspondence between movement spinning-top experiments, indicating drives “spinning-top” type rotations during swimming, this parallel mere analogy. These results may prove essential future studies role microorganisms micro-robots, as body detection has been vastly overlooked favour path detection. Altogether, rotation provide foolproof mechanism forward propulsion nature would otherwise possible flagella with broken symmetry.

Language: Английский

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The human sperm head spins with a conserved direction during swimming in 3D

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2022, Volume and Issue: unknown

Published: Nov. 29, 2022

Abstract In human sperm, head spinning is essential for sperm swimming and critical fertilization. Measurement of has not been straightforward due to its symmetric morphology, translucent nature fast 3D motion driven by helical flagellum movement. Microscope image acquisition mostly restricted 2D single focal plane images limited position tracing, in absence orientation rotation 3D. To date, reported be mono or bidirectional, even intermittently changing direction. This variety direction, however, appears contradict observations conserved beating the flagellum. Here, we reconcile these directly measuring movement freely with multi-plane 4D microscopy. We show that microscopy unable distinguish direction sperm. evaluated 409 spermatozoa four different conditions: non-capacitating capacitating solutions, both aqueous viscous media. All spermatozoa, regardless experimental conditions spun counterclockwise (CCW) as seen from head-to-tail. Head was suppressed 57% media, though, interestingly, they recovered CCW after incubation within same medium. Our conserved, when non-spin, indicating presence a robust persistent driving mechanism powering flagellum, thus importance future motility assessments, reproduction research microorganism self-organised swimming.

Language: Английский

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Fluid flow reconstruction around a free-swimming sperm in 3D

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: June 1, 2024

We investigate the dynamics and hydrodynamics of a human spermatozoa swimming freely in 3D. simultaneously track sperm flagellum head orientation laboratory frame reference via high-speed high-resolution 4D (3D+t) microscopy, extract flagellar waveform relative to body reference, as seen from that translates rotates with Numerical fluid flow reconstructions motility are performed utilizing experimental 3D waveforms, excellent accordance between predicted observed kinematics. The reconstruction accuracy is validated by directly comparing three linear angular velocities measurements. Our microhydrodynamic analysis reveals novel pattern, characterized pair vortices circulate opposition each other along cell. Finally, we show counter-vortices not unique beat, can be reproduced idealised models, thus suggesting fundamental structure for free-swimming propelled beating flagellum.

Language: Английский

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Sperm quality analyzer: A portable LED array microscope with dark‐field imaging

Bioengineering & Translational Medicine, Journal Year: 2024, Volume and Issue: 9(6)

Published: Aug. 2, 2024

Abstract Sperm quality analysis plays an important role in diagnosing infertility, which is widely implemented by computer‐assisted sperm (CASA) of sperm‐swimming imaging from commercial phase‐contrast microscopy. A well‐equipped microscope comes with a high cost, increasing the burden assessment, and it also occupies large volume. For point‐of‐care testing (POCT) quality, these factors are confronted challenges low‐cost portable instruments. In this study, encoded light‐emitting diode (LED) array illumination employed to achieve multicontrast for analysis. This microscopy has dimensions 16.5 × 14.0 25.0 cm, its dark‐field (DF) provides high‐contrast image data suitable CASA. According DF imaging, we developed software LabCASA, can used assess motility characteristics sperm. Compared TrackMate, difference parameters our was less than 10% coefficient variation (CV). The vary chamber temperature, further confirms reliability system imaging. strong robustness tracking sperm's motion under different microscopes. assessment parameters, work at lower cost plastic structure. POCT analysis, highly cost‐effective resource‐constrained circumstances.

Language: Английский

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Swimming by Spinning: Spinning‐Top Type Rotations Regularize Sperm Swimming Into Persistently Progressive Paths in 3D

Advanced Science, Journal Year: 2024, Volume and Issue: unknown

Published: Dec. 18, 2024

Abstract Sperm swimming is essential for reproduction, with movement strategies adapted to specific environments. navigate by modulating the symmetry of their flagellar beating, but how they swim forward asymmetrical beats remains unclear. Current methods lack ability robustly detect state in free‐swimming spermatozoa, despite its importance understanding sperm motility. This study uses numerical simulations investigate fluid mechanics beats. Results show that rotation regularizes motion, allowing persistently progressive even Crucially, 3D head orientation, rather than path, provides critical insight into state. rotations during closely resemble spinning‐top dynamics, precession driven helical beating flagellum. These results may prove future studies on role microorganisms and artificial swimmers, as body orientation detection has been largely overlooked favor path analysis. Altogether, this rotational mechanism a reliable solution propulsion navigation nature, which would otherwise be challenging flagella broken symmetry.

Language: Английский

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