Mechanics of Vorticella Contraction

Misra, Gaurav; Dickinson, Richard B.; Ladd, Anthony J. C.

doi:10.1016/j.bpj.2010.03.023

Cited by 26 publications

(36 citation statements)

References 32 publications

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“…In a variety of designs to generate movement at cellular and molecular levels, one of the fastest cellular mechanics is found in stalked protozoans such as single-celled Vorticella sp. 1 – 10 . It has been pointed out that the cell motility of Vorticella sp.…”

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confidence: 99%

Contraction behaviors of Vorticella sp. stalk investigated using high-speed video camera. I: Nucleation and growth model

et al. 2012

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The contraction process of living Vorticella sp. has been investigated by image processing using a high-speed video camera. In order to express the temporal change in the stalk length resulting from the contraction, a damped spring model and a nucleation and growth model are applied. A double exponential is deduced from a conventional damped spring model, while a stretched exponential is newly proposed from a nucleation and growth model. The stretched exponential function is more suitable for the curve fitting and suggests a more particular contraction mechanism in which the contraction of the stalk begins near the cell body and spreads downwards along the stalk. The index value of the stretched exponential is evaluated in the range from 1 to 2 in accordance with the model in which the contraction undergoes through nucleation and growth in a one-dimensional space.

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mentioning

confidence: 99%

Contraction behaviors of Vorticella sp. stalk investigated using high-speed video camera. I: Nucleation and growth model

et al. 2012

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“…After coiling, the stalk recovers its straightened shape relatively more slowly than the contraction. The recovery is due to the unbinding of the calcium from the spasmin and the elastic recovery of the stalk sheath, as confirmed by numerical simulations . High‐speed videography of the stalk contraction shows that the Vorticella head does not rotate significantly during contraction indicating the process conserves the linking number.…”

Section: Contractile Helical Fibers In a Compliant Matrixmentioning

confidence: 60%

“…b) Simulations of the contraction of the Vorticella stalk due to the contraction of the spasmoneme that is helically wrapped around the stalk in the initial state. Reproduced with permission . Copyright 2010, Elsevier.…”

Section: Contractile Helical Fibers In a Compliant Matrixmentioning

confidence: 99%

Advanced Actuator Materials Powered by Biomimetic Helical Fiber Topologies

Spinks

2019

Advanced Materials

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where conventional mechanical drive systems, such as electric motors, are too large or too heavy. [13] Natural skeletal muscle is often used as a benchmark for comparing and evaluating synthetic artificial muscles. The three key attributes of any actuator are the force generated, the amount of movement produced, and the time taken to complete a full actuation cycle. Skeletal muscle, e.g., generates a blocked stress of ≈0.3 MPa, free strain of ≈20%, responds in ≈0.1 s, and has a density of 1037 kg m −3 . Combining these parameters gives a reasonable estimate of the peak powerto-weight ratio (PWR) for muscle at ≈300 W kg −1 . [14] The PWR for conventional motors, engines, and other actuators covers a wide range (1-10 4 W kg −1 ), and there is a rough scaling between weight and PWR. This scaling means that small motors are less powerful and at sizes of less than a few tens of grams, muscle outperforms any available engine or motor. This limitation is currently hampering the development of many needed technologies. For example, the current state-of-the-art, motor-driven prosthetic hands are impressive but still do not match the dexterity of a healthy human. In theory, low-profile and high PWR artificial muscles could replicate the full range of motion, grip types, and strengths of the hand. Recent demonstrations of artificial muscle powered robotic hands [15] highlight the need for improved actuator materials, fabrication strategies, and control processes. In fact, biomimetic actuators are yet to be developed that match all of the features of natural muscle including large stroke, high speed, efficiency, long operating life, silent operation, and safety for use in human contact. Great progress has been made in the development of artificial muscles, and the most recent significant example of twisted and coiled polymer fibers [16] exploits a helical fiber topology that has a similarity with many constructs found in nature. Helices are a recurring feature in many of nature's actuators, which poses the question of whether the helix introduces any particular mechanical advantage.The helix is a striking and ubiquitous feature in biology [17] with several examples illustrated in Figure 1. The double stranded DNA molecule is probably the most famous helix (or double helix), but similar structures pervade biology at all length scales from molecular to the macroscopic. Many protein molecules adopt an alpha-helix conformation and assemble into helical filaments, such as the thin filament in skeletal muscle.Helical constructs are ubiquitous in nature at all size domains, from molecular to macroscopic. The helical topology confers unique mechanical functions that activate certain phenomena, such as twining vines and vital cellular functions like the folding and packing of DNA into chromosomes. The understanding of active mechanical processes in plants, certain musculature in animals, and some biochemical processes in cells provides insight into the versatility of the helix. Most of these natural systems consist of helically orien...

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“…Ultrafast motility occurs at many length scales in nature, from large multicellular organisms such as a mantis shrimp and trap-jaw ants [1,2] to microscopic single cells such as Vorticella and nematocysts of jellyfish [3][4][5][6][7]. Mechanistic understanding how organisms achieve repeatable rapid motion, especially at small scales is an emerging area of interdisciplinary research with potential to advance our understanding of the biophysics of cellular actuators and motors, as well as inspire design of smallscale robots [8].…”

Section: Introductionmentioning

confidence: 99%

“…To the best of our knowledge, a physical mechanism of this same direction rotational-contraction remains elusive. It is worth noting that contraction is not symmetric -there is a short time delay between the start of the motion of each end due to the propagation of a Ca 2+ wave that travels along the cell body [4,5]. After the contraction, Spirostomum slowly returns to its original shape by elongation.…”

Section: Introductionmentioning

confidence: 99%

Biophysical mechanism of ultrafast helical twisting contraction in the giant unicellular ciliate Spirostomum ambiguum

Bhamla

2019

Preprint

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The biophysical mechanism of cytoskeletal structures has been fundamental to understanding of cellular dynamics. Here, we present a mechanism for the ultrafast contraction exhibited by the unicellular ciliate Spirostomum ambiguum. Powered by a Ca 2+ binding myoneme mesh architecture, Spirostomum is able to twist its two ends in the same direction and fully contract to 75% of its body length within five milliseconds, followed by a slow elongation mechanism driven by the uncoiling of the microtubules. To elucidate the principles of this rapid contraction and slow elongation cycle, we used high-speed imaging to examine the same-direction coiling of the two ends of the cell and immunofluorescence techniques to visualize and quantify the structural changes in the myoneme mesh, microtubule arrays, and the cell membrane. Lastly, we provide support for our hypotheses using a simple physical model that captures key features of Spirostomum's ultrafast twisting contraction. SIGNIFICANCEUltrafast movements are ubiquitous in nature, and some of the most fascinating ultrafast biophysical systems are found on the cellular level. Quantitative studies and models are key to understand the biophysics of these fast movements. In this work, we study Spirostomum's ultrafast contraction by using high-speed imaging, labeling relevant cytoskeletal structures, and building a physical model to provide a biophysical mechanism especially of the helical same direction twisting of this extremely large single cell organism. Deeper understanding of how single cells can execute extreme shape changes hold potential for advancing basic cell biophysics and also inspire new cellular inspired actuators for engineering applications.

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Mechanics of Vorticella Contraction

Cited by 26 publications

References 32 publications

Contraction behaviors of Vorticella sp. stalk investigated using high-speed video camera. I: Nucleation and growth model

Contraction behaviors of Vorticella sp. stalk investigated using high-speed video camera. I: Nucleation and growth model

Advanced Actuator Materials Powered by Biomimetic Helical Fiber Topologies

Biophysical mechanism of ultrafast helical twisting contraction in the giant unicellular ciliate Spirostomum ambiguum

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