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1
Miyata, Makoto, William S. Ryu, and Howard C. Berg. "Force and Velocity of Mycoplasma mobile Gliding." Journal of Bacteriology 184, no. 7 (April 1, 2002): 1827–31. http://dx.doi.org/10.1128/jb.184.7.1827-1831.2002.
Повний текст джерелаАнотація:
ABSTRACT The effects of temperature and force on the gliding speed of Mycoplasma mobile were examined. Gliding speed increased linearly as a function of temperature from 0.46 μm/s at 11.5°C to 4.0 μm/s at 36.5°C. A polystyrene bead was attached to the tail of M. mobile using a polyclonal antibody raised against whole M. mobile cells. Cells attached to beads glided at the same speed as cells without beads. When liquid flow was applied in a flow chamber, cells reoriented and moved upstream with reduced speeds. Forces generated by cells at various gliding speeds were calculated by multiplying their estimated frictional drag coefficients with their velocities relative to the liquid. The gliding speed decreased linearly with force. At zero speed, the force measurements extrapolated to 26 pN at 22.5 and 27.5°C. At zero force, the speed extrapolated to 2.3 and 3.3 μm/s at 22.5 and 27.5°C, respectively—the same speeds as those observed for free gliding cells. Cells attached to beads were also trapped by an optical tweezer, and the stall force was measured to be 26 to 28 pN (17.5 to 27.5°C). The gliding speed depended on temperature, but the maximum force did not, suggesting that the mechanism is composed of at least two steps, one that generates force and another that allows displacement. Other implications of these results are discussed.
2
Bahlman, Joseph W., Sharon M. Swartz, Daniel K. Riskin, and Kenneth S. Breuer. "Glide performance and aerodynamics of non-equilibrium glides in northern flying squirrels ( Glaucomys sabrinus )." Journal of The Royal Society Interface 10, no. 80 (March 6, 2013): 20120794. http://dx.doi.org/10.1098/rsif.2012.0794.
Повний текст джерелаАнотація:
Gliding is an efficient form of travel found in every major group of terrestrial vertebrates. Gliding is often modelled in equilibrium, where aerodynamic forces exactly balance body weight resulting in constant velocity. Although the equilibrium model is relevant for long-distance gliding, such as soaring by birds, it may not be realistic for shorter distances between trees. To understand the aerodynamics of inter-tree gliding, we used direct observation and mathematical modelling. We used videography (60–125 fps) to track and reconstruct the three-dimensional trajectories of northern flying squirrels ( Glaucomys sabrinus ) in nature. From their trajectories, we calculated velocities, aerodynamic forces and force coefficients. We determined that flying squirrels do not glide at equilibrium, and instead demonstrate continuously changing velocities, forces and force coefficients, and generate more lift than needed to balance body weight. We compared observed glide performance with mathematical simulations that use constant force coefficients, a characteristic of equilibrium glides. Simulations with varying force coefficients, such as those of live squirrels, demonstrated better whole-glide performance compared with the theoretical equilibrium state. Using results from both the observed glides and the simulation, we describe the mechanics and execution of inter-tree glides, and then discuss how gliding behaviour may relate to the evolution of flapping flight.
3
Sabass, Benedikt, Matthias D. Koch, Guannan Liu, Howard A. Stone, and Joshua W. Shaevitz. "Force generation by groups of migrating bacteria." Proceedings of the National Academy of Sciences 114, no. 28 (June 27, 2017): 7266–71. http://dx.doi.org/10.1073/pnas.1621469114.
Повний текст джерелаАнотація:
From colony formation in bacteria to wound healing and embryonic development in multicellular organisms, groups of living cells must often move collectively. Although considerable study has probed the biophysical mechanisms of how eukaryotic cells generate forces during migration, little such study has been devoted to bacteria, in particular with regard to the question of how bacteria generate and coordinate forces during collective motion. This question is addressed here using traction force microscopy. We study two distinct motility mechanisms of Myxococcus xanthus, namely, twitching and gliding. For twitching, powered by type-IV pilus retraction, we find that individual cells exert local traction in small hotspots with forces on the order of 50 pN. Twitching bacterial groups also produce traction hotspots, but with forces around 100 pN that fluctuate rapidly on timescales of <1.5 min. Gliding, the second motility mechanism, is driven by lateral transport of substrate adhesions. When cells are isolated, gliding produces low average traction on the order of 1 Pa. However, traction is amplified approximately fivefold in groups. Advancing protrusions of gliding cells push, on average, in the direction of motion. Together, these results show that the forces generated during twitching and gliding have complementary characters, and both forces have higher values when cells are in groups.
4
Seto, Shintaro, Atsuko Uenoyama, and Makoto Miyata. "Identification of a 521-Kilodalton Protein (Gli521) Involved in Force Generation or Force Transmission for Mycoplasma mobile Gliding." Journal of Bacteriology 187, no. 10 (May 15, 2005): 3502–10. http://dx.doi.org/10.1128/jb.187.10.3502-3510.2005.
Повний текст джерелаАнотація:
ABSTRACT Several mycoplasma species are known to glide on solid surfaces such as glass in the direction of the membrane protrusion, but the mechanism underlying this movement is unknown. To identify a novel protein involved in gliding, we raised monoclonal antibodies against a detergent-insoluble protein fraction of Mycoplasma mobile, the fastest glider, and screened the antibodies for inhibitory effects on gliding. Five monoclonal antibodies stopped the movement of gliding mycoplasmas, keeping them on the glass surface, and all of them recognized a large protein in immunoblotting. This protein, named Gli521, is composed of 4,738 amino acids, has a predicted molecular mass of 520,559 Da, and is coded downstream of a gene for another gliding protein, Gli349, which is known to be responsible for glass binding during gliding. Edman degradation analysis indicated that the N-terminal region is processed at the peptide bond between the amino acid residues at positions 43 and 44. Analysis of gliding mutants isolated previously revealed that the Gli521 protein is missing in a nonbinding mutant, m9, where the gli521 gene is truncated by a nonsense mutation at the codon for the amino acid at position 1170. Immunofluorescence and immunoelectron microscopy indicated that Gli521 localizes all around the base of the membrane protrusion, at the “neck,” as previously observed for Gli349. Analysis of the inhibitory effects of the anti-Gli521 antibody on gliding motility revealed that this protein is responsible for force generation or force transmission, a role distinct from that of Gli349, and also suggested conformational changes of Gli349 and Gli521 during gliding.
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Miyata, M., William S. Ryu, and Howard C. Berg. "Force-velocity relationship of mycoplasma gliding." Seibutsu Butsuri 41, supplement (2001): S203. http://dx.doi.org/10.2142/biophys.41.s203_2.
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Kawanishi, Kengo, Daisuke Fukuda, Hiroyuki Niwa, Taisuke Okuno, Toshinori Miyashita, Takashi Kitagawa, and Shintarou Kudo. "Relationship between Tissue Gliding of the Lateral Thigh and Gait Parameters after Trochanteric Fractures." Sensors 22, no. 10 (May 19, 2022): 3842. http://dx.doi.org/10.3390/s22103842.
Повний текст джерелаАнотація:
Trochanteric fractures lead to severe functional deficits and gait disorders compared to femoral neck fractures. This study aims to investigate gait parameters related to gliding between tissues (gliding) after trochanteric fracture (TF) surgery. This study implemented a cross-sectional design and was conducted amongst patients who underwent TF surgery (n = 94) approximately three weeks post-trochanteric fracture surgery. The following parameters were evaluated: (1) gliding between tissues; (2) lateral femoral pain during loading; (3) maximum gait speed; (4) stride time variability and step time asymmetry as measures of gait cycle variability; (5) double stance ratio and single stance ratio for assessment of stance phase, (6) jerk; and (7) Locomotor rehabilitation index as a measure of force changes during gait. The gliding coefficient was significantly correlated with lateral femoral pain (r = 0.517), jerk root mean square (r = −0.433), and initial contact-loading response jerk (r = −0.459). The jerk of the force change value during gait was also effective in understanding the characteristics of the gait in the initial contact-loading response in patients with trochanteric fractures. Additionally, gliding is related not only to impairments such as pain but also to disabilities such as those affecting gait.
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Fu, S. C., L. K. Hung, Y. W. Lee, T. Y. Mok, and K. M. Chan. "Tendon adhesion measured by a video-assisted gliding test in a chicken model." Journal of Hand Surgery (European Volume) 36, no. 1 (September 3, 2010): 40–47. http://dx.doi.org/10.1177/1753193410381674.
Повний текст джерелаАнотація:
We developed a video-assisted gliding test to evaluate the gliding force and the flexion angle with unrestricted joint motion. Tendon adhesion was induced in a chicken model of flexor digitorum profundus (FDP) injury at the annular pulley region of the long toe. The chicken feet were harvested immediately after injury, and 2 weeks and 6 weeks after injury. During the gliding test, the injured FDP was pulled for 15 mm then returned to its initial position. The test was recorded using a video camera and registered to the gliding test mechanical data. The maximum flexion angle and gliding resistance were calculated. The maximum flexion angle was significantly decreased from 78 (SD 10) in controls to 42 (SD 22) in tendons with injury, while gliding resistance was significantly increased in week 2 (0.06, SD 0.05) and week 6 (0.07, SD 0.01) after injury.
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Carmigniani, R., L. Seifert, D. Chollet, and C. Clanet. "Coordination changes in front-crawl swimming." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, no. 2237 (May 2020): 20200071. http://dx.doi.org/10.1098/rspa.2020.0071.
Повний текст джерелаАнотація:
We report the evolution of the coordination with velocity in front-crawl swimming which is used in competitions over a large range of distances (from 50 m up to 25 km in open-water races). Inside this single stroke, top-level swimmers show different patterns of arm organization. At low velocities, swimmers select an alternated stroke with gliding pauses during their propulsion. The relative duration of the gliding pauses on a stroke cycle is independent of the velocity in this first regime. Above a critical velocity, the relative duration of the gliding pauses starts to decrease as speed increases. Above a second critical velocity, the gliding pauses disappear and the swimmers start to superpose their propulsion phases. These three regimes are first revealed experimentally and then studied theoretically. It appears that below the first critical velocity, swimmers use a constant coordination index and vary their speed by varying their propulsive force to minimize their cost of propulsion. For larger velocities, swimmers use their maximum propulsive force and vary their recovery time to increase further their speed. The physical model developed is general and could be applied to understand other modes of locomotion.
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Mizutani, Masaki, Isil Tulum, Yoshiaki Kinosita, Takayuki Nishizaka, and Makoto Miyata. "Detailed Analyses of Stall Force Generation in Mycoplasma mobile Gliding." Biophysical Journal 114, no. 6 (March 2018): 1411–19. http://dx.doi.org/10.1016/j.bpj.2018.01.029.
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Wong, Yoke-Rung, Ita Suzana Mat Jais, Min-Kai Chang, Beng-Hai Lim, and Shian-Chao Tay. "An Exploratory Study Using Semi-Tabular Plate in Zone II Flexor Tendon Repair." Journal of Hand Surgery (Asian-Pacific Volume) 23, no. 04 (November 15, 2018): 547–53. http://dx.doi.org/10.1142/s242483551850056x.
Повний текст джерелаАнотація:
Background: This study evaluated the feasibility of using a low-profile titanium (Ti) plate implant, also known as the Ti-button, for Zone II flexor tendon repair. We hypothesize that the use of the Ti-button can distribute the tensile force on the digital flexor tendons to achieve better biomechanical performance. Methods: Twenty lacerated porcine flexor tendons were randomly divided into two groups and repaired using Ti-button or 6-strand modified Lim-Tsai technique. Ultimate tensile strength, load to 2 mm gap force, and mode of failure were recorded during a single cycle loading test. We also harvested twelve fingers with lacerated flexor digitorum profundus tendons from six fresh-frozen cadaver hands and repaired the tendons using either Ti-button method or modified Lim-Tsai technique. A custom-made bio-friction measurement jig was used to measure the gliding resistance and coefficient of friction of the tendon sheath interface at the A2 pulley. Results: The ultimate tensile strength, load to 2 mm gap force, stiffness, and gliding resistance of the Ti-button repairs were 101.5 N, 25.7 N, 7.8 N/mm, and 2.2 N respectively. Ti-button repairs had significantly higher ultimate tensile strength and stiffness than the modified Lim-Tsai repair. However, Ti-button also increased the gliding resistance and coefficient of friction but there was no significant difference between the two repair techniques. Conclusions: Ti-button repair displayed comparable mechanical properties to the traditional repair in terms of 2-mm gap formation and gliding resistance, but with a stronger repair construct. Thus, this deepened our interest to further investigate the potential of using Ti-button implant in Zone II flexor tendon repair by studying both the mechanical and biochemical (tendon healing) properties in more in-depth.
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Vilas-Boas, J. Paulo, Lígia Costa, Ricardo J. Fernandes, João Ribeiro, Pedro Figueiredo, Daniel Marinho, António J. Silva, Abel Rouboa, and Leandro Machado. "Determination of the Drag Coefficient during the First and Second Gliding Positions of the Breaststroke Underwater Stroke." Journal of Applied Biomechanics 26, no. 3 (August 2010): 324–31. http://dx.doi.org/10.1123/jab.26.3.324.
Повний текст джерелаАнотація:
The purpose of the current study was to assess and to compare the hydrodynamics of the first and second gliding positions of the breaststroke underwater stroke used after starts and turns, considering drag force (D), drag coefficient (CD) and cross-sectional area (S). Twelve national-level swimmers were tested (6 males and 6 females, respectively 18.2 ± 4.0 and 17.3 ± 3.0 years old). Hydrodynamic parameters were assessed through inverse dynamics from the velocity to time curve characteristic of the underwater armstroke of the breaststroke technique. The results allow us to conclude that, for the same gliding velocities (1.37 ± 0.124 m/s), D and the swimmers’ S and CD values obtained for the first gliding position are significantly lower than the corresponding values obtained for the second gliding position of the breaststroke underwater stroke (31.67 ± 6.44 N vs. 46.25 ± 7.22 N; 740.42 ± 101.89 cm2 vs. 784.25 ± 99.62 cm2 and 0.458 ± 0.076 vs. 0.664 ± 0.234, respectively). These differences observed for the total sample were not evident for each one of the gender’s subgroups.
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Nan, Beiyan, Jigar N. Bandaria, Kathy Y. Guo, Xue Fan, Amirpasha Moghtaderi, Ahmet Yildiz, and David R. Zusman. "The polarity of myxobacterial gliding is regulated by direct interactions between the gliding motors and the Ras homolog MglA." Proceedings of the National Academy of Sciences 112, no. 2 (December 30, 2014): E186—E193. http://dx.doi.org/10.1073/pnas.1421073112.
Повний текст джерелаАнотація:
Gliding motility in Myxococcus xanthus is powered by flagella stator homologs that move in helical trajectories using proton motive force. The Frz chemosensory pathway regulates the cell polarity axis through MglA, a Ras family GTPase; however, little is known about how MglA establishes the polarity of gliding, because the gliding motors move simultaneously in opposite directions. Here we examined the localization and dynamics of MglA and gliding motors in high spatial and time resolution. We determined that MglA localizes not only at the cell poles, but also along the cell bodies, forming a decreasing concentration gradient toward the lagging cell pole. MglA directly interacts with the motor protein AglR, and the spatial distribution of AglR reversals is positively correlated with the MglA gradient. Thus, the motors moving toward lagging cell poles are less likely to reverse, generating stronger forward propulsion. MglB, the GTPase-activating protein of MglA, regulates motor reversal by maintaining the MglA gradient. Our results suggest a mechanism whereby bacteria use Ras family proteins to modulate cellular polarity.
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Håkansson, Sebastian, Hiroshi Morisaki, John Heuser, and L. David Sibley. "Time-Lapse Video Microscopy of Gliding Motility inToxoplasma gondii Reveals a Novel, Biphasic Mechanism of Cell Locomotion." Molecular Biology of the Cell 10, no. 11 (November 1999): 3539–47. http://dx.doi.org/10.1091/mbc.10.11.3539.
Повний текст джерелаАнотація:
Toxoplasma gondii is a member of the phylum Apicomplexa, a diverse group of intracellular parasites that share a unique form of gliding motility. Gliding is substrate dependent and occurs without apparent changes in cell shape and in the absence of traditional locomotory organelles. Here, we demonstrate that gliding is characterized by three distinct forms of motility: circular gliding, upright twirling, and helical rotation. Circular gliding commences while the crescent-shaped parasite lies on its right side, from where it moves in a counterclockwise manner at a rate of ∼1.5 μm/s. Twirling occurs when the parasite rights itself vertically, remaining attached to the substrate by its posterior end and spinning clockwise. Helical gliding is similar to twirling except that it occurs while the parasite is positioned horizontally, resulting in forward movement that follows the path of a corkscrew. The parasite begins lying on its left side (where the convex side is defined as dorsal) and initiates a clockwise revolution along the long axis of the crescent-shaped body. Time-lapse video analyses indicated that helical gliding is a biphasic process. During the first 180o of the turn, the parasite moves forward one body length at a rate of ∼1–3 μm/s. In the second phase, the parasite flips onto its left side, in the process undergoing little net forward motion. All three forms of motility were disrupted by inhibitors of actin filaments (cytochalasin D) and myosin ATPase (butanedione monoxime), indicating that they rely on an actinomyosin motor in the parasite. Gliding motility likely provides the force for active penetration of the host cell and may participate in dissemination within the host and thus is of both fundamental and practical interest.
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Morio, Hanako, Taishi Kasai, and Makoto Miyata. "Gliding Direction of Mycoplasma mobile." Journal of Bacteriology 198, no. 2 (October 26, 2015): 283–90. http://dx.doi.org/10.1128/jb.00499-15.
Повний текст джерелаАнотація:
ABSTRACTMycoplasma mobileglides in the direction of its cell pole by a unique mechanism in which hundreds of legs, each protruding from its own gliding unit, catch, pull, and release sialylated oligosaccharides fixed on a solid surface. In this study, we found that 77% of cells glided to the left with a change in direction of 8.4° ± 17.6° μm−1displacement. The cell body did not roll around the cell axis, and elongated, thinner cells also glided while tracing a curved trajectory to the left. Under viscous conditions, the range of deviation of the gliding direction decreased. In the presence of 250 μM free sialyllactose, in which the binding of the legs (i.e., the catching of sialylated oligosaccharides) was reduced, 70% and 30% of cells glided to the left and the right, respectively, with changes in direction of ∼30° μm−1. The gliding ghosts, in which a cell was permeabilized by Triton X-100 and reactivated by ATP, glided more straightly. These results can be explained by the following assumptions based on the suggested gliding machinery and mechanism: (i) the units of gliding machinery may be aligned helically around the cell, (ii) the legs extend via the process of thermal fluctuation and catch the sialylated oligosaccharides, and (iii) the legs generate a propulsion force that is tilted from the cell axis to the left in 70% and to the right in 30% of cells.IMPORTANCEMycoplasmas are bacteria that are generally parasitic to animals and plants. SomeMycoplasmaspecies form a protrusion at a pole, bind to solid surfaces, and glide. Although these species appear to consistently glide in the direction of the protrusion, their exact gliding direction has not been examined. This study analyzed the gliding direction in detail under various conditions and, based on the results, suggested features of the machinery and the mechanism of gliding.
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Ichikawa, Hiroshi, Hirofumi Shimojo, Yasuhiro Baba, Takao Mise, Rio Nara, and Yoshimitsu Shimoyama. "The Difference of Propulsive Force between Water Surface and Underwater Conditions in Flutter Kick Swimming." Proceedings 49, no. 1 (June 15, 2020): 167. http://dx.doi.org/10.3390/proceedings2020049167.
Повний текст джерелаАнотація:
This study investigates differences in propulsive force between the water surface and underwater conditions in the flutter kick swimming technique. The subjects were well-trained university male swimmers. A towing device was set up in a 25 m swimming pool to measure the towing force and velocity of the swimmer under two conditions: the swimmer was near the water surface and at a depth of 0.60 m. The swimmers performed the gliding trials and the kicking trials with maximum effort with five towing velocities from 1.2 to 2.4 m/s. The passive drag and the resultant force of the propulsive and drag forces in kick swimming were formulated, respectively. The propulsive force was calculated from the difference between the two formulas. A difference of the propulsive force under conditions in high swimming velocity was observed. This suggests that the water surface condition has advantages of raising the foot above water.
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URZAY, JAVIER. "Asymptotic theory of the elastohydrodynamic adhesion and gliding motion of a solid particle over soft and sticky substrates at low Reynolds numbers." Journal of Fluid Mechanics 653 (May 5, 2010): 391–429. http://dx.doi.org/10.1017/s0022112010000364.
Повний текст джерелаАнотація:
This analysis makes use of asymptotic analyses and numerical methods to address, in the limit of small Reynolds and ionic Péclet numbers and small clearances, the canonical problem of the forces exerted on a small solid spherical particle undergoing slow translation and rotation in an incompressible fluid moving parallel to an elastic substrate, subject to electric double-layer and van der Waals intermolecular forces, as a representative example of particle gliding and the idealized swimming dynamics of more complex bodies near soft and sticky surfaces in a physiological solvent. The competition of the hydrodynamic, intermolecular and surface-deformation effects induces a lift force, and drag-force and drift-force perturbations, which do not scale linearly with the velocities, and produce a non-additivity of the intermolecular effects by reducing the intensity of the repulsive forces and by increasing the intensity of the attractive forces. The lift force enhances a reversible elastohydrodynamic adhesion regime in both ionized and deionized solvents, in which lateral motion and lift-off from the substrate can occur. An irreversible elastohydrodynamic adhesion regime, produced by elastic instabilities in the form of surface bifurcations in the substrate, is found to exist for both positive and negative lift forces and is enhanced by small gliding velocities and large substrate compliances, for which critical thresholds are calculated for both ionized and deionized solvents. Elastohydrodynamic corrections are derived for the critical coagulation concentration of electrolyte predicted by the Derjaguin–Landau–Verwey–Overbeek (DLVO) standard theory of colloid stabilization. The corrected DLVO critical concentration is unable to describe the adhesion process when the substrate is sufficiently compliant or when the solvent is deionized. These effects may have consequences on the lateral motility and adhesion of small particles and swimming micro-organisms to soft and sticky substrates, in which the reversible or irreversible character of the adhesion process may be influenced not only by the solvent ionic strength, as described by the DLVO theory, but also by the motion kinematics and the substrate mechanical properties.
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Spormann, Alfred M. "Gliding Motility in Bacteria: Insights from Studies ofMyxococcus xanthus." Microbiology and Molecular Biology Reviews 63, no. 3 (September 1, 1999): 621–41. http://dx.doi.org/10.1128/mmbr.63.3.621-641.1999.
Повний текст джерелаАнотація:
SUMMARY Gliding motility is observed in a large variety of phylogenetically unrelated bacteria. Gliding provides a means for microbes to travel in environments with a low water content, such as might be found in biofilms, microbial mats, and soil. Gliding is defined as the movement of a cell on a surface in the direction of the long axis of the cell. Because this definition is operational and not mechanistic, the underlying molecular motor(s) may be quite different in diverse microbes. In fact, studies on the gliding bacterium Myxococcus xanthus suggest that two independent gliding machineries, encoded by two multigene systems, operate in this microorganism. One machinery, which allows individual cells to glide on a surface, independent of whether the cells are moving alone or in groups, requires the function of the genes of the A-motility system. More than 37 A-motility genes are known to be required for this form of movement. Depending on an additional phenotype, these genes are divided into two subclasses, the agl and cgl genes. Videomicroscopic studies on gliding movement, as well as ultrastructural observations of two myxobacteria, suggest that the A-system motor may consist of multiple single motor elements that are arrayed along the entire cell body. Each motor element is proposed to be localized to the periplasmic space and to be anchored to the peptidoglycan layer. The force to glide which may be generated here is coupled to adhesion sites that move freely in the outer membrane. These adhesion sites provide a specific contact with the substratum. Based on single-cell observations, similar models have been proposed to operate in the unrelated gliding bacteria Flavobacterium johnsoniae (formerly Cytophaga johnsonae), Cytophaga strain U67, and Flexibacter polymorphus (a filamentous glider). Although this model has not been verified experimentally, M. xanthus seems to be the ideal organism with which to test it, given the genetic tools available. The second gliding motor in M. xanthus controls cell movement in groups (S-motility system). It is dependent on functional type IV pili and is operative only when cells are in close proximity to each other. Type IV pili are known to be involved in another mode of bacterial surface translocation, called twitching motility. S-motility may well represent a variation of twitching motility in M. xanthus. However, twitching differs from gliding since it involves cell movements that are jerky and abrupt and that lack the organization and smoothness observed in gliding. Components of this motor are encoded by genes of the S-system, which appear to be homologs of genes involved in the biosynthesis, assembly, and function of type IV pili in Pseudomonas aeruginosa and Neisseria gonorrhoeae. How type IV pili generate force in S-motility is currently unknown, but it is to be expected that ongoing physiological, genetic, and biochemical studies in M. xanthus, in conjunction with studies on twitching in P. aeruginosa and N. gonorrhoeae, will provide important insights into this microbial motor. The two motility systems of M. xanthus are affected to different degrees by the MglA protein, which shows similarity to a small GTPase. Bacterial chemotaxis-like sensory transduction systems control gliding motility in M. xanthus. The frz genes appear to regulate gliding movement of individual cells and movement by the S-motility system, suggesting that the two motors found in this bacterium can be regulated to result in coordinated multicellular movements. In contrast, the dif genes affect only S-system-dependent swarming.
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Nan, B., J. Chen, J. C. Neu, R. M. Berry, G. Oster, and D. R. Zusman. "Myxobacteria gliding motility requires cytoskeleton rotation powered by proton motive force." Proceedings of the National Academy of Sciences 108, no. 6 (January 19, 2011): 2498–503. http://dx.doi.org/10.1073/pnas.1018556108.
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Nohguchi, Yasuaki. "A Mathematical Model for Instability in Snow Gliding Motion." Annals of Glaciology 13 (1989): 211–14. http://dx.doi.org/10.1017/s0260305500007916.
Повний текст джерелаАнотація:
In this paper a fundamental model is proposed to describe the time-dependent behaviour of uniform snow glide on an infinite slope. This model is composed both of a mechanical balance equation relating a driving force and a resistant force, and of a rate equation for a real contact area at the boundary. In the model, a steady motion of glide is described as a stable equilibrium of glide motion, and a non-steady motion is considered as a transient one not in equilibrium. Finally, the model is applied to a full-depth avalanche release caused by acceleration of snow glide. By comparing the model predictions with glide-velocity field data, a proper model of acceleration prior to full-depth avalanche release is determined. As a result, we can obtain the safety standards to be applied in the event of full-depth avalanches in terms of a glide velocity.
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Nohguchi, Yasuaki. "A Mathematical Model for Instability in Snow Gliding Motion." Annals of Glaciology 13 (1989): 211–14. http://dx.doi.org/10.3189/s0260305500007916.
Повний текст джерелаАнотація:
In this paper a fundamental model is proposed to describe the time-dependent behaviour of uniform snow glide on an infinite slope. This model is composed both of a mechanical balance equation relating a driving force and a resistant force, and of a rate equation for a real contact area at the boundary. In the model, a steady motion of glide is described as a stable equilibrium of glide motion, and a non-steady motion is considered as a transient one not in equilibrium. Finally, the model is applied to a full-depth avalanche release caused by acceleration of snow glide. By comparing the model predictions with glide-velocity field data, a proper model of acceleration prior to full-depth avalanche release is determined. As a result, we can obtain the safety standards to be applied in the event of full-depth avalanches in terms of a glide velocity.
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Tchoufag, Joël, Pushpita Ghosh, Connor B. Pogue, Beiyan Nan, and Kranthi K. Mandadapu. "Mechanisms for bacterial gliding motility on soft substrates." Proceedings of the National Academy of Sciences 116, no. 50 (November 25, 2019): 25087–96. http://dx.doi.org/10.1073/pnas.1914678116.
Повний текст джерелаАнотація:
The motility mechanism of certain prokaryotes has long been a mystery, since their motion, known as gliding, involves no external appendages. The physical principles behind gliding still remain poorly understood. Using myxobacteria as an example of such organisms, we identify here the physical principles behind gliding motility and develop a theoretical model that predicts a 2-regime behavior of the gliding speed as a function of the substrate stiffness. Our theory describes the elasto-capillary–hydrodynamic interactions between the membrane of the bacteria, the slime it secretes, and the soft substrate underneath. Defining gliding as the horizontal translation under zero net force, we find the 2-regime behavior is due to 2 distinct mechanisms of motility thrust. On mildly soft substrates, the thrust arises from bacterial shape deformations creating a flow of slime that exerts a pressure along the bacterial length. This pressure in conjunction with the bacterial shape provides the necessary thrust for propulsion. On very soft substrates, however, we show that capillary effects must be considered that lead to the formation of a ridge at the slime–substrate–air interface, thereby creating a thrust in the form of a localized pressure gradient at the bacterial leading edge. To test our theory, we perform experiments with isolated cells on agar substrates of varying stiffness and find the measured gliding speeds in good agreement with the predictions from our elasto-capillary–hydrodynamic model. The mechanisms reported here serve as an important step toward an accurate theory of friction and substrate-mediated interactions between bacteria proliferating in soft media.
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Wagner, Emilio, Pablo Wagner, Diego Zanolli, Rubén Radkievich, Gunther Redenz, and Rodrigo Guzman. "Biomechanical Evaluation of Circumtibial and Transmembranous Routes for Posterior Tibial Tendon Transfer for Dropfoot." Foot & Ankle International 39, no. 7 (March 12, 2018): 843–49. http://dx.doi.org/10.1177/1071100718760845.
Повний текст джерелаАнотація:
Background: Tibialis posterior tendon transfer is performed when loss of dorsiflexion has to be compensated. We evaluated the circumtibial (CT), above-retinaculum transmembranous (TMAR), and under-retinaculum transmembranous (TMUR) transfer gliding resistance and foot kinematics in a cadaveric foot model during ankle range of motion (ROM). Methods: Eight cadaveric foot-ankle distal tibia specimens were dissected free of soft tissues on the proximal end, applying an equivalent force to 50% of the stance phase to every tendon, except for the Achilles tendon. Dorsiflexion was tested with all of the tibialis posterior tendon transfer methods (CT, TMAR, and TMUR) using a tension tensile machine. A 10-repetition cycle of dorsiflexion and plantarflexion was performed for each transfer. Foot motion and the force needed to achieve dorsiflexion were recorded. Results: The CT transfer showed the highest gliding resistance ( P < .01). Regarding kinematics, all transfers decreased ankle ROM, with the CT transfer being the condition with less dorsiflexion compared with the control group (6.8 vs 15 degrees, P < .05). TMUR transfer did perform better than TMAR with regard to ankle dorsiflexion, but no difference was shown in gliding resistance. The CT produced a supination moment on the forefoot. Conclusion: The CT transfer had the highest tendon gliding resistance, achieved less dorsiflexion and had a supination moment. Clinical Relevance We suggest that the transmembranous tibialis posterior tendon transfer should be the transfer of choice. The potential bowstringing effect when performing a tibialis posterior tendon transfer subcutaneously (TMAR) could be avoided if the transfer is routed under the retinaculum, without significant compromise of the final function and even with a possible better ankle range of motion.
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de Koning, Jos J., Ruud W. de Boer, Gert de Groot, and Gerrit Jan van Ingen Schenau. "Push-Off Force in Speed Skating." International Journal of Sport Biomechanics 3, no. 2 (May 1987): 103–9. http://dx.doi.org/10.1123/ijsb.3.2.103.
Повний текст джерелаАнотація:
In speed skating, performance is related to the product of the amount of work per stroke and the stroke frequency. Work per stroke is dependent on the component of the push-off force in the direction perpendicular to the gliding direction of the skate. The push-off force at different velocities was measured in three trained speed skaters. The results showed that the peak push-off force and mean force do not change at different velocities, and that the stroke time was decreased at higher velocities. It can be concluded that these speed skaters regulate their velocity not by changing the push-off force but by changing their stroke time. The shape of push-off–time curves is dependent on push-off technique and differs during straight lane and curve skating.
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Uenoyama, Atsuko, and Makoto Miyata. "Identification of a 123-Kilodalton Protein (Gli123) Involved in Machinery for Gliding Motility of Mycoplasma mobile." Journal of Bacteriology 187, no. 16 (August 15, 2005): 5578–84. http://dx.doi.org/10.1128/jb.187.16.5578-5584.2005.
Повний текст джерелаАнотація:
ABSTRACT Mycoplasma mobile glides on a glass surface in the direction of its tapered end by an unknown mechanism. Two large proteins, Gli349 and Gli521, were recently reported to be involved in glass binding and force generation/transmission, respectively, in M. mobile gliding. These proteins are coded tandemly with two other open reading frames (ORFs) in the order p123-gli349-gli521-p42 on the genome. In the present study, reverse transcriptase PCR analysis suggested that these four ORFs are transcribed cistronically. To characterize the p123 gene coding a 123-kDa protein (Gli123) of 1,128 amino acids, we raised polyclonal antibody against the Gli123 protein. Immunoblotting for Gli123 revealed that Gli123 was missing in a mutant strain, m12, which was previously isolated and characterized by a deficiency in glass binding. Sequencing analysis showed a nonsense mutation at the 523rd amino acid of the protein in the m12 mutant. Immunofluorescence microscopy with the polyclonal antibody showed that Gli123 is localized at the head-like protrusion's base, the cell neck, which is specialized for gliding, as observed for Gli349 and Gli521. Localization of the gliding proteins, Gli349 and Gli521, was disturbed in the m12 mutant, suggesting that Gli123 is essential for the positioning of gliding proteins in the cell neck.
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Hall, K., D. Cole, Y. Yeh, and R. J. Baskin. "Kinesin force generation measured using a centrifuge microscope sperm-gliding motility assay." Biophysical Journal 71, no. 6 (December 1996): 3467–76. http://dx.doi.org/10.1016/s0006-3495(96)79542-5.
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Read, Nicholas, Simon Connell, and David G. Adams. "Nanoscale Visualization of a Fibrillar Array in the Cell Wall of Filamentous Cyanobacteria and Its Implications for Gliding Motility." Journal of Bacteriology 189, no. 20 (August 10, 2007): 7361–66. http://dx.doi.org/10.1128/jb.00706-07.
Повний текст джерелаАнотація:
ABSTRACT Many filamentous cyanobacteria are motile by gliding, which requires attachment to a surface. There are two main theories to explain the mechanism of gliding. According to the first, the filament is pushed forward by small waves that pass along the cell surface. In the second, gliding is powered by the extrusion of slime through pores surrounding each cell septum. We have previously shown that the cell walls of several motile cyanobacteria possess an array of parallel fibrils between the peptidoglycan and the outer membrane and have speculated that the function of this array may be to generate surface waves to power gliding. Here, we report on a study of the cell surface topography of two morphologically different filamentous cyanobacteria, using field emission gun scanning electron microscopy (FEGSEM) and atomic force microscopy (AFM). FEGSEM and AFM images of Oscillatoria sp. strain A2 confirmed the presence of an array of fibrils, visible as parallel corrugations on the cell surface. These corrugations were also visualized by AFM scanning of fully hydrated filaments under liquid; this has not been achieved before for filamentous bacteria. FEGSEM images of Nostoc punctiforme revealed a highly convoluted, not parallel, fibrillar array. We conclude that an array of parallel fibrils, beneath the outer membrane of Oscillatoria, may function in the generation of thrust in gliding motility. The array of convoluted fibrils in N. punctiforme may have an alternative function, perhaps connected with the increase in outer membrane surface area resulting from the presence of the fibrils.
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Gusnowski, Eva M., and Martin Srayko. "Visualization of dynein-dependent microtubule gliding at the cell cortex: implications for spindle positioning." Journal of Cell Biology 194, no. 3 (August 8, 2011): 377–86. http://dx.doi.org/10.1083/jcb.201103128.
Повний текст джерелаАнотація:
Dynein motors move along the microtubule (MT) lattice in a processive “walking” manner. In the one-cell Caenorhabditis elegans embryo, dynein is required for spindle-pulling forces during mitosis. Posteriorly directed spindle-pulling forces are higher than anteriorly directed forces, and this imbalance results in posterior spindle displacement during anaphase and an asymmetric division. To address how dynein could be asymmetrically activated to achieve posterior spindle displacement, we developed an assay to measure dynein’s activity on individual MTs at the embryo cortex. Our study reveals that cortical dynein motors maintain a basal level of activity that propels MTs along the cortex, even under experimental conditions that drastically reduce anaphase spindle forces. This suggests that dynein-based MT gliding is not sufficient for anaphase spindle-pulling force. Instead, we find that this form of dynein activity is most prominent during spindle centering in early prophase. We propose a model whereby different dynein–MT interactions are used for specific spindle-positioning tasks in the one-cell embryo.
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Abd El-Latief, Mahmoud E., Khairy Elsayed, and Mohamed Madbouli Abdelrahman. "Aerodynamic study of the corrugated airfoil at ultra-low Reynolds number." Advances in Mechanical Engineering 11, no. 10 (October 2019): 168781401988416. http://dx.doi.org/10.1177/1687814019884164.
Повний текст джерелаАнотація:
In this study, Aeshna cyanea dragonfly forewing mid-cross-section corrugated airfoil was simulated at ultra-low Reynolds number. The corrugated airfoil was compared with its smooth counterpart to study the effect of the corrugations upon the aerodynamic performance. Unsteady two-dimensional laminar flow was solved using FLUENT. This study was divided into gliding phase and flapping phase. In the gliding phase, the corrugated airfoil produced a higher lift force with respect to the profiled airfoil at both tested Reynolds numbers ([Formula: see text], [Formula: see text]) with comparable drag coefficient for all the tested angles of attack. In the flapping phase, both the corrugated airfoil and the flat-plate have a very similar flow behavior which yields a very similar aerodynamic performance at Re[Formula: see text]. A structural analysis was performed to compare the corrugated airfoil with the flat-plate. The analysis revealed the superiority of the corrugated airfoil over the flat-plate in decreasing the deflection under the applied load. The reduced frequency was varied to study its impact on the aerodynamic performance. By increasing the reduced frequency, the thrust and the lift forces increased by [Formula: see text]% and [Formula: see text]%, respectively. Any increase in the reduced frequency will increase lift and thrust forces, but the propulsive efficiency will deteriorate.
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Shi, Xing, Xianwen Huang, Yao Zheng, and Susu Zhao. "Effects of cambers on gliding and hovering performance of corrugated dragonfly airfoils." International Journal of Numerical Methods for Heat & Fluid Flow 26, no. 3/4 (May 3, 2016): 1092–120. http://dx.doi.org/10.1108/hff-10-2015-0414.
Повний текст джерелаАнотація:
Purpose – The purpose of this paper is to explore the effects of the camber on gliding and hovering performance of two-dimensional corrugated airfoils. While the flying mechanism of natural flyers remains a myth up to nowadays, the simulation serves as a minor step toward understanding the steady and unsteady aerodynamics of the dragonfly flight. Design/methodology/approach – The lattice Boltzmann method is used to simulate the flow past the cambered corrugated dragonfly airfoil at low Reynolds numbers. For gliding flight, the maximum camber, the distance of the location of maximum camber point from the leading edge and Reynolds number are regarded as control variables; for hovering flight, the maximum camber, the flapping amplitude and trajectory are considered as control variables. Then corresponding simulations are performed to evaluate the implications of these factors. Findings – Greater gliding ratio can be reached by increasing the maximum camber of the dragonfly wing section. When the location of the maximum camber moves backward along the wing chord, large scale flow separation can be delayed. These two effects result in better gliding performances. For hovering performances, it is found that for different flapping amplitudes along an inclined plane, the horizontal force exerted on the airfoils increases with the camber, and the drag growths first but then drops. It is also found that the elliptic flapping trajectory is most sensitive to the camber of the cambered corrugated dragonfly wing section. Originality/value – The effects of the camber on gliding and hovering performance of the cambered dragonfly wing section are explored in detail. The data obtained can be helpful when designing micro aerial vehicles.
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Matúš, Ivan. "Biomechanická analýza štartových skokov v plávaní." Studia sportiva 8, no. 1 (July 14, 2014): 109–25. http://dx.doi.org/10.5817/sts2014-1-12.
Повний текст джерелаАнотація:
Presented research comes up with results representing a role of speed-force and timing parameters in four start types at the track of 7.5 m and 10 m distance. Eighteen performance male swimmers (age 23.4±2.1), specialists in sprint event, participated in this study. We noticed the highest measured vertical force in swimming starts with rearward stretch (ZŠSN, AŠSN) in both track distances. For the horizontal force in the tracks of both distances we noticed the highest values of maximum force in grab starts (ZŠS, ZŠSN), but the average values were the highest in the track starts (AŠSN, AŠS). From the timing parameters on the starting block, the shortest reaction time was measured in swimming starts with rearward stretch (ZŠSN, AŠSN). The shortest movement and starting reaction time from the starting block was measured in the swimming start with rearward stretch (ZŠSN, AŠSN) in both track distances. The shortest time of a flight and gliding phase for the track of 7.5 m and 10 m distance we measured in the track start with rearward. Difference between the first and the second fastest time in the track of 7.5 m distance to 0,02 s, but the track of 10 m distance was doubled. On the basis of these results we recommend to swimmer sprinters to use mainly the track start with rearward. The statistical significance of differences in speed-force parameters pointed on the differences between the four types of swimming starts. In all types of the starts were shown close relations between the track time for 7.5 m and 10 m distance, horizontal force parameters and the time of the flight and gliding phase.
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Wagner, Emilio, Pablo Wagner, Diego Zanolli de Solminihac, Cristian Ortiz, Andres Keller Díaz, Ruben Radkievich, Gunther Redenz Gallardo, and Rodrigo Guzman-Venegas. "Posterior tibial tendon transfer." Foot & Ankle Orthopaedics 2, no. 3 (September 1, 2017): 2473011417S0004. http://dx.doi.org/10.1177/2473011417s000400.
Повний текст джерелаАнотація:
Category: Ankle, Basic Sciences/Biologics, Tendon Transfer, Dropfoot Introduction/Purpose: Posterior tibial tendon transfer (PTTT) is performed for a variety of pathologies where loss of dorsiflexion is compensated by the transfer, e.g. cavus foot, neurologic foot (dropfoot), etc. Transfers can be performed subcutaneously through a circumtibial way or deeply through the interosseous membrane (transmembranous). The latter is classically routed above the extensor retinaculum. We evaluated the circumtibial (CT), above-retinaculum transmembranous (ART) and below-retinaculum transmembranous (BRT) transfers gliding resistance and kinematics in a cadaveric model during ankle range of motion (ROM). Our first hypothesis was that the CT would be the transfer with more gliding resistance and with more kinematic alteration. Our second hypothesis was that the ART would not show significant differences against the BRT transfer. Methods: 8 cadaveric foot- ankle – distal tibia were prepared, identifying all extensor and flexor tendons proximally. The skin and subcutaneous tissue were kept intact. Each specimen was mounted on a special frame, and luminous markers were attached to the skin to adapt it to the Oxford Foot Model. A dead weight equal to 50% of the stance phase force was applied to each tendon, except for the Achilles tendon. Each specimen served as its own control, testing dorsiflexion when pulling the tibialis anterior (TA), recording the kinematics and gliding resistance. Then, dorsiflexion was tested with the transfers already described (CT, ART and BRT PTTT). A 10-repetition cycle of dorsiflexion and plantarflexion was performed for each condition. The movement of the foot was recorded using high speed cameras, and the force needed to achieve dorsiflexion was registered in every cycle. Statistical analysis was performed using the SPSS software. Results: The circumtibial transfer showed the highest gliding resistance (p<0.05). The ART and BRT transfers increased the least the gliding resistance over the control, with no difference between them (p>0.05). Regarding kinematics, all transfers decreased ankle ROM, being the CT transfer the condition with less range of motion (-9 degrees, p<0.05). ART and BRT transfers did not show differences relative to ankle ROM among them. The CT transfer significantly produced more supination of the forefoot over the hindfoot (p<0.05). The ART and BRT transfers did not differ from the control group relative to supination/pronation. Finally all the transfers produced a significant abduction motion of the forefoot compared to the control, with no difference between them. Conclusion: The circumtibial transfer had the highest tendon gliding resistance and the worst kinematics of all transfers. It achieves less dorsiflexion and in an inverted position. Interestingly, there was minimal difference in gliding resistance between the above and below retinaculum transmembranous transfers. Per our results, we suggest that when performing a PTTT the transmembranous route should be the transfer of choice. The potential bowstringing effect which may be painful and not cosmetic for patients when performing a PTTT subcutaneously (ART) could be avoided if the transfer is routed under the retinaculum, without significant compromise of the final function.
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Huang, Jiafeng, Hyeung-Sik Choi, Mai The Vu, Dong-Wook Jung, Ki-Beom Choo, Hyun-Joon Cho, Phan Huy Nam Anh, et al. "Study on Position and Shape Effect of the Wings on Motion of Underwater Gliders." Journal of Marine Science and Engineering 10, no. 7 (June 28, 2022): 891. http://dx.doi.org/10.3390/jmse10070891.
Повний текст джерелаАнотація:
A typical structure of an underwater glider (UG) includes a pair of fixed wings, and the hydrodynamic force driving the glider forward as descending or ascending in the water is generated primarily by the fixed wings. In this paper, a simplified glider motion model was established to analyze the dynamics in an easier way, and whose simulation results do not differ from the original one. Also, in the paper, the effects of the wing position and wing shape on the UG to the motion were studied. Since no direct analytic approach cannot be performed, the case study of the effects of six different wing positions and three wing shapes on gliding performances which are gliding speed, gliding angle and gliding path were performed through computer simulation. The simulation results revealed that when the fixed wing is located far from the buoyancy center to the tail end, more traveling range is achieved with less energy. Also, effect of the shape difference of the wings were analyzed. Shape changes did not show much difference on the travelling performance of the UG. In addition to these, the transient mode of the UG was studied. To control this, the PID controller for the position of the mass shifter and piston were applied. By application of the PID controller to the linearized dynamics equations, it was shown that the transient behavior of the UG was quickly and steadily controlled.
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Stadler, Rachel V., Lauren A. White, Ke Hu, Brian P. Helmke, and William H. Guilford. "Direct measurement of cortical force generation and polarization in a living parasite." Molecular Biology of the Cell 28, no. 14 (July 7, 2017): 1912–23. http://dx.doi.org/10.1091/mbc.e16-07-0518.
Повний текст джерелаАнотація:
Apicomplexa is a large phylum of intracellular parasites that are notable for the diseases they cause, including toxoplasmosis, malaria, and cryptosporidiosis. A conserved motile system is critical to their life cycles and drives directional gliding motility between cells, as well as invasion of and egress from host cells. However, our understanding of this system is limited by a lack of measurements of the forces driving parasite motion. We used a laser trap to measure the function of the motility apparatus of living Toxoplasma gondii by adhering a microsphere to the surface of an immobilized parasite. Motion of the microsphere reflected underlying forces exerted by the motile apparatus. We found that force generated at the parasite surface begins with no preferential directionality but becomes directed toward the rear of the cell after a period of time. The transition from nondirectional to directional force generation occurs on spatial intervals consistent with the lateral periodicity of structures associated with the membrane pellicle and is influenced by the kinetics of actin filament polymerization and cytoplasmic calcium. A lysine methyltransferase regulates both the magnitude and polarization of the force. Our work provides a novel means to dissect the motile mechanisms of these pathogens.
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Reinemann, Dana N., Emma G. Sturgill, Dibyendu Kumar Das, Miriam Steiner Degen, Zsuzsanna Vörös, Wonmuk Hwang, Ryoma Ohi, and Matthew J. Lang. "Collective Force Regulation in Anti-parallel Microtubule Gliding by Dimeric Kif15 Kinesin Motors." Current Biology 27, no. 18 (September 2017): 2810–20. http://dx.doi.org/10.1016/j.cub.2017.08.018.
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Oliver, Tim, Olga J. Pletjuushkina, Juri M. Vasiliev, Micah Dembo, and Ken Jacobson. "Mapping traction forces generated by motile cells." Proceedings, annual meeting, Electron Microscopy Society of America 53 (August 13, 1995): 892–93. http://dx.doi.org/10.1017/s042482010014083x.
Повний текст джерелаАнотація:
In a continuing effort to understand how cell-generated traction forces are utilised for locomotion, we have applied our modified silicone rubber traction force assay to rapidly locomoting fish epidermal keratocytes executing turns and shape changes, and negotiating obstacles. The resulting maps show that these cells can redistribute tractions from the “steady-state” pattern (previously observed during unobstructed, gliding locomotion), into a variety of transient patterns, with lifetimes of less than 1 minute (Figs. 1-4). The map for a “steady state” locomoting keratocyte shows a maximum traction force density of ~5x10-5 dynes/μm (data not shown). This value was derived from cell-free experiments in which elastic films were manipulated with a pair of micronneedles. Such experiments, in which all forces were known, showed that both the magnitude and direction of traction forces applied to the film could be closely predicted, and that the Young’s modulus of elasticity for the silicone substratum could be calculated. The consequences for understanding the underlying molecular basis for shape change and cell motility from this type of analysis will be discussed.
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Jin, Hiroshi, Shunsuke Shimizu, Tadaharu Watanuki, Hirotoshi Kubota, and Kazutoshi Kobayashi. "Desirable Gliding Styles and Techniques in Ski Jumping." Journal of Applied Biomechanics 11, no. 4 (November 1995): 460–74. http://dx.doi.org/10.1123/jab.11.4.460.
Повний текст джерелаАнотація:
Desirable flight styles and techniques in ski jumping were calculated on the basis of the new aerodynamic force data for three styles: classic style, V style, and flat V style. In the V style and flat V style two skis are in a herringbone position in the frontal plane, whereas in the classic style the skis are parallel Flat V style is more flat in the sagittal plane than V Style. The most effective style was the flat V style if a ski jumper model did not change style during the gliding phase, which was the late part of flight phase (distance was 110 m). If the model changed flight style, the model that changed from classic style to V style at 1.3 s after takeoff or from flat V style to V style at 1.6 s could achieve 112.5 m. In addition, forward initial angular velocity was a positive factor to increase distance; in particular, the distance for the V style was sensitive to initial angular velocity.
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Schatten, Heide, David Sibley, and Hans Ris. "Low Voltage Field Emission Scanning Electron Microscopy Provides Structural Evidence For Actin-Sized Filaments In Toxoplasma Gondii." Microscopy and Microanalysis 5, S2 (August 1999): 1130–31. http://dx.doi.org/10.1017/s1431927600018973.
Повний текст джерелаАнотація:
The protozoan parasite Toxoplasma gondiiis an obligate intracellular parasite that exhibits gliding and twisting motility during cell locomotion and host cell invasion. By using molecular and genetic approaches it has been determined that actin and myosin are localized beneath the parasite plasma membrane and produce the force for motility and active penetration during host cell invasion. However, structural evidence for actin fibers beneath the plasma membrane is still missing. Recently Chavez et al. demonstrated actin-like filaments in isolated cytoskeletal complexes. Our aproach has been to remove the cell membrane with 0.15% Triton X-100 in cytoskeleton preserving buffer, followed by imaging with low voltage field emission SEM. As seen in Fig. I, we could demonstrate the subpellicle actin network in parasites invading a host cell (arrow). Fig. 2 shows a similar subsurface network of actin filaments in a parasite gliding on glass.
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Johansson, L. Christoffer. "Indirect estimates of wing-propulsion forces in horizontally diving Atlantic puffins (Fratercula arctica L.)." Canadian Journal of Zoology 81, no. 5 (May 1, 2003): 816–22. http://dx.doi.org/10.1139/z03-058.
Повний текст джерелаАнотація:
Instantaneous force production in wing-propelled diving Atlantic puffins (Fratercula arctica) was investigated using four birds for which instantaneous estimates of velocity and acceleration of the body were made. The quasi-steady resultant force acting on the body in the sagittal plane was calculated using acceleration reaction coefficients, buoyancy estimates, and drag coefficients taken from the literature and calculated, using two different methods, from a video sequence of a puffin gliding (CDw = 0.021 and 0.026, respectively). The forces calculated from the motion of the body coincide well with the wing-beat cycle, with a forward- and upward-directed force produced by the wings during the downstroke and a forward- and downward-directed force produced during the upstroke. The result suggests that a thrust force may also be produced during at least the lower-stroke reversal. This means either that there may exist some undescribed propulsive mechanism, possibly caused by an interaction of the wings beneath the body, or that the body drag coefficient may be overestimated. However, the body drag coefficient calculated in the study is close to the coefficients measured on dead birds. Furthermore, I conclude that the high reduced frequency (average 0.82) suggests a non-steady-state hydrodynamic mechanism of wing-propelled diving in puffins.
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Nakarmi, Kiran K., and Sikshya Prakash Shrestha. "Degloving Injury: Different Ways of Management." Journal of Nepalgunj Medical College 15, no. 1 (July 31, 2017): 54–55. http://dx.doi.org/10.3126/jngmc.v15i1.23565.
Повний текст джерелаАнотація:
Degloving injury involves shearing of the skin from the underlying tissue due to differential gliding in response to the tangential force applied to the surface of the body leading to disruption of all the blood vessels connected to skin. The flap of degloved skin has precarious blood supply making it almost impossible for the flap to survive. We describe two cases of degloving of thigh managed differently in different settings.
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Nakarmi, Kiran K., and Sikshya Prakash Shrestha. "Degloving Injury: Different Ways of Management." Journal of Nepalgunj Medical College 16, no. 1 (July 31, 2018): 76–77. http://dx.doi.org/10.3126/jngmc.v16i1.24237.
Повний текст джерелаАнотація:
Degloving injury involves shearing of the skin from the underlying tissue due to differential gliding in response to the tangential force applied to the surface of the body leading to disruption of all the blood vessels connected to skin. The flap of degloved skin has precarious blood supply making it almost impossible for the flap to survive. We describe two cases of degloving of thigh managed differently in different settings.
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Oliver, Tim, Micah Dembo, and Ken Jacobson. "Separation of Propulsive and Adhesive Traction Stresses in Locomoting Keratocytes." Journal of Cell Biology 145, no. 3 (May 3, 1999): 589–604. http://dx.doi.org/10.1083/jcb.145.3.589.
Повний текст джерелаАнотація:
Strong, actomyosin-dependent, pinching tractions in steadily locomoting (gliding) fish keratocytes revealed by traction imaging present a paradox, since only forces perpendicular to the direction of locomotion are apparent, leaving the actual propulsive forces unresolved. When keratocytes become transiently “stuck” by their trailing edge and adopt a fibroblast-like morphology, the tractions opposing locomotion are concentrated into the tail, leaving the active pinching and propulsive tractions clearly visible under the cell body. Stuck keratocytes can develop ∼1 mdyn (10,000 pN) total propulsive thrust, originating in the wings of the cell. The leading lamella develops no detectable propulsive traction, even when the cell pulls on its transient tail anchorage. The separation of propulsive and adhesive tractions in the stuck phenotype leads to a mechanically consistent hypothesis that resolves the traction paradox for gliding keratocytes: the propulsive tractions driving locomotion are normally canceled by adhesive tractions resisting locomotion, leaving only the pinching tractions as a resultant. The resolution of the traction pattern into its components specifies conditions to be met for models of cytoskeletal force production, such as the dynamic network contraction model (Svitkina, T.M., A.B. Verkhovsky, K.M. McQuade, and G.G. Borisy. 1997. J. Cell Biol. 139:397–415). The traction pattern associated with cells undergoing sharp turns differs markedly from the normal pinching traction pattern, and can be accounted for by postulating an asymmetry in contractile activity of the opposed lateral wings of the cell.
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de Boer, Ruud W., Paul Schermerhorn, Jan Gademan, Gert de Groot, and Gerrit Jan van Ingen Schenau. "Characteristic Stroke Mechanics of Elite and Trained Male Speed Skaters." International Journal of Sport Biomechanics 2, no. 3 (August 1986): 175–85. http://dx.doi.org/10.1123/ijsb.2.3.175.
Повний текст джерелаАнотація:
In speed skating, the amount of work per stroke is dependent on the component of the push-off force in the direction perpendicular to the gliding direction of the skate. One stroke consists of a gliding phase and a push-off phase in which the knee is explosively extended. Film and video analysis showed that the better skaters show a higher power production and no differences in stroke frequency. Differences in performance are related to differences in push-off mechanics. The faster skaters reach a higher angular velocity at the knee; the time during which the knee is extended is shorter. At the start of the push-off, the velocity of the body center of gravity in the horizontal direction is higher due to a passive falling movement in the frontal plane. It is concluded that the better skaters show a better timing that results in a more explosive and effective directed push-off.
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Chainok, Phornpot, Leandro Machado, Karla de Jesus, J. Arturo Abraldes, Márcio Borgonovo-Santos, Ricardo J. Fernandes, and João Paulo Vilas-Boas. "Backstroke to Breaststroke Turning Performance in Age-Group Swimmers: Hydrodynamic Characteristics and Pull-Out Strategy." International Journal of Environmental Research and Public Health 18, no. 4 (February 14, 2021): 1858. http://dx.doi.org/10.3390/ijerph18041858.
Повний текст джерелаАнотація:
We compared the hydrodynamic characteristics and pull-out strategies of four backstroke-to-breaststroke turning techniques in young swimmers. Eighteen 11 and 12-year-old swimmers participated in a 4 week intervention program including 16 contextual interference sessions. The hydrodynamic variables were assessed through inverse dynamics, and the pull-out strategy kinematics were assessed with tracking markers followed by 12 land cameras and 11 underwater cameras. Swimmers randomly completed sixteen 30 m maximal backstroke-to breaststroke-open, somersault, bucket and crossover turns (four in each technique) with a 3 min rest. The data showed higher drag force, cross-sectional area and drag coefficient values for the first (compared with the second) gliding position. The crossover turn revealed the highest push-off velocity (2.17 ± 0.05 m·s−1), and the somersault turn demonstrated the lowest foot plant index (0.68 ± 0.03; 68%), which could have affected the first gliding, transition and second gliding depths (0.73 ± 0.13, 0.86 ± 0.17 and 0.76 ± 0.17 m). The data revealed the consistency of the time spent (4.86 ± 0.98 s) and breakout distance (6.04 ± 0.94 m) among the four turning techniques, and no differences were observed between them regarding time and average velocity up to 7.5 m. The hydrodynamic characteristics and pull-out strategy of the backstroke-to-breaststroke turns performed by the age group swimmers were independent of the selected technique.
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Kusumadewi, An-Nissa, Lisda Damayanti, Rukiah, and Risdiana. "Factors Affecting the Attractive Force of Dental Magnetic Attachment: A Literature Review for Guiding Dentists in Clinical Application." International Journal of Dentistry 2022 (June 14, 2022): 1–9. http://dx.doi.org/10.1155/2022/9711285.
Повний текст джерелаАнотація:
Aim. The aim of this review is to get a comprehensive description of the factors that may influence the attractive force of the dental magnetic attachment. Background. Dental magnetic attachment is a term for a magnet used as an overdenture retainer. Magnets that are widely used are permanent magnets such as neodymium iron boron (NdFeB) and samarium cobalt (SmCo). Theoretically, the magnetic attractive force in a permanent magnet has a constant retentive force, and the magnitude of the force will not decrease over time. However, several studies revealed that the magnetic attractive force can be decreased, resulting in the failure of overdenture retention. Some of the factors of reduced magnetic attraction that have been studied are corrosion and temperature. There are no articles that specifically review the factors that can influence magnetic attraction. Review Results. A total of 25,880 articles were obtained during a search on 3 journal databases: PubMed (2,647), ScienceDirect (23,184), and Scopus (229). From those publications, 15 articles reported relevant outcome data that were then extracted. Magnetic attractive force can be influenced by temperature, corrosion, keeper surface morphology, type of magnet, keeper-assembly size combination, inclination, insertion-removal cycle, gliding/loading cycle, number of magnets, crosshead speed, and force direction. Conclusion. Many factors can affect the magnetic attraction force of the dental magnetic attachment. Corrosion is the most likely factor to occur because the dental magnetic attachment is always in the oral environment which contains corrosive saliva and is susceptible to damage due to mastication forces.
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Hemami, Hooshang. "Toward a Computational Model of the Upper Extremity." Mechanical Engineering Research 7, no. 2 (November 29, 2017): 40. http://dx.doi.org/10.5539/mer.v7n2p40.
Повний текст джерелаАнотація:
A basic 22-segment model of the upper extremity is formulated that can allow computational testing of hypotheses about the control and coordination of the upper extremity by the central nervous system. The formulation allows for further analytical, anatomical, physiological, and bio-mechanical expansion and improvement of the model. It allows for inclusion of all passive structures: ligaments, membranes, soft tissues, and cartilages. The formulation is based on the state space formulation of the Newton-Euler method applied to multi-body systems. Extensive use is made of three-segment rigid body modules, constraints, reduction of dimensionality, projection, and matrices of large dimensions.An example, gliding motion of a rigid body on a circular surface (as in wiping a dish with a pre-specified force of contact) shows the application of some of the concepts and feasibility of the developed routines. The control is based on analogous strategies in living systems where co-activation of agonist-antagonist muscular systems and precise reference inputs implement the desirable trajectories of motion and where an integral feedback of the force implements the desired forces of contact.
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Zot, Henry G., P. Bryant Chase, Javier E. Hasbun, and Jose R. Pinto. "Mechanical contribution to muscle thin filament activation." Journal of Biological Chemistry 295, no. 47 (September 8, 2020): 15913–22. http://dx.doi.org/10.1074/jbc.ra120.014438.
Повний текст джерелаАнотація:
Vertebrate striated muscle thin filaments are thought to be thermodynamically activated in response to an increase in Ca2+ concentration. We tested this hypothesis by measuring time intervals for gliding runs and pauses of individual skeletal muscle thin filaments in cycling myosin motility assays. A classic thermodynamic mechanism predicts that if chemical potential is constant, transitions between runs and pauses of gliding thin filaments will occur at constant rate as given by a Poisson distribution. In this scenario, rate is given by the odds of a pause, and hence, run times between pauses fit an exponential distribution that slopes negatively for all observable run times. However, we determined that relative density of observed run times fits an exponential only at low Ca2+ levels that activate filament gliding. Further titration with Ca2+, or adding excess regulatory proteins tropomyosin and troponin, shifted the relative density of short run times to fit the positive slope of a gamma distribution, which derives from waiting times between Poisson events. Events that arise during a run and prevent the chance of ending a run for a random interval of time account for the observed run time distributions, suggesting that the events originate with cycling myosin. We propose that regulatory proteins of the thin filament require the mechanical force of cycling myosin to achieve the transition state for activation. During activation, combinations of cycling myosin that contribute insufficient activation energy delay deactivation.
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Vincent, Maxence S., Caterina Comas Hervada, Corinne Sebban-Kreuzer, Hugo Le Guenno, Maïalène Chabalier, Artemis Kosta, Françoise Guerlesquin, et al. "Dynamic proton-dependent motors power type IX secretion and gliding motility in Flavobacterium." PLOS Biology 20, no. 3 (March 25, 2022): e3001443. http://dx.doi.org/10.1371/journal.pbio.3001443.
Повний текст джерелаАнотація:
Motile bacteria usually rely on external apparatus like flagella for swimming or pili for twitching. By contrast, gliding bacteria do not rely on obvious surface appendages to move on solid surfaces. Flavobacterium johnsoniae and other bacteria in the Bacteroidetes phylum use adhesins whose movement on the cell surface supports motility. In F. johnsoniae, secretion and helicoidal motion of the main adhesin SprB are intimately linked and depend on the type IX secretion system (T9SS). Both processes necessitate the proton motive force (PMF), which is thought to fuel a molecular motor that comprises the GldL and GldM cytoplasmic membrane proteins. Here, we show that F. johnsoniae gliding motility is powered by the pH gradient component of the PMF. We further delineate the interaction network between the GldLM transmembrane helices (TMHs) and show that conserved glutamate residues in GldL TMH2 are essential for gliding motility, although having distinct roles in SprB secretion and motion. We then demonstrate that the PMF and GldL trigger conformational changes in the GldM periplasmic domain. We finally show that multiple GldLM complexes are distributed in the membrane, suggesting that a network of motors may be present to move SprB along a helical path on the cell surface. Altogether, our results provide evidence that GldL and GldM assemble dynamic membrane channels that use the proton gradient to power both T9SS-dependent secretion of SprB and its motion at the cell surface.
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Kawai, M., T. Kido, M. Suzuki, and S. Ishiwata. "The effect of temperature on gliding force between reconstituted thin filament and heavy meromyosin molecules." Seibutsu Butsuri 43, supplement (2003): S147. http://dx.doi.org/10.2142/biophys.43.s147_2.
Повний текст джерела
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Tucker, VA. "Gliding flight: speed and acceleration of ideal falcons during diving and pull out." Journal of Experimental Biology 201, no. 3 (February 1, 1998): 403–14. http://dx.doi.org/10.1242/jeb.201.3.403.
Повний текст джерелаАнотація:
Some falcons, such as peregrines (Falco peregrinus), attack their prey in the air at the end of high-speed dives and are thought to be the fastest of animals. Estimates of their top speed in a dive range up to 157 m s-1, although speeds this high have never been accurately measured. This study investigates the aerodynamic and gravitational forces on 'ideal falcons' and uses a mathematical model to calculate speed and acceleration during diving. Ideal falcons have body masses of 0.5-2.0 kg and morphological and aerodynamic properties based on those measured for real falcons. The top speeds reached during a dive depend on the mass of the bird and the angle and duration of the dive. Given enough time, ideal falcons can reach top speeds of 89-112 m s-1 in a vertical dive, the higher speed for the heaviest bird, when the parasite drag coefficient has a value of 0.18. This value was measured for low-speed flight, and it could plausibly decline to 0.07 at high speeds. Top speeds then would be 138-174 m s-1. An ideal falcon diving at angles between 15 and 90 degrees with a mass of 1 kg reaches 95 % of top speed after travelling approximately 1200 m. The time and altitude loss to reach 95 % of top speed range from 38 s and 322 m at 15 degrees to 16 s and 1140 m at 90 degrees, respectively. During pull out at top speed from a vertical dive, the 1 kg ideal falcon can generate a lift force 18 times its own weight by reducing its wing span, compared with a lift force of 1.7 times its weight at full wing span. The falcon loses 60 m of altitude while pulling out of the dive, and lift and loss of altitude both decrease as the angle of the dive decreases. The 1 kg falcon can slow down in a dive by increasing its parasite drag and the angle of attack of its wings. Both lift and drag increase with angle of attack, but the falcon can cancel the increased lift by holding its wings in a cupped position so that part of the lift is directed laterally. The increased drag of wings producing maximum lift is great enough to decelerate the falcon at -1.5 times the acceleration of gravity at a dive angle of 45 degrees and a speed of 41 m s-1 (0.5 times top speed). Real falcons can control their speeds in a dive by changing their drag and by choosing the length of the dive. They would encounter both advantages and disadvantages by diving at the top speeds of ideal falcons, and whether they achieve those speeds remains to be investigated.
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Videler, J., and P. Kamermans. "Differences between upstroke and downstroke in swimming dolphins." Journal of Experimental Biology 119, no. 1 (November 1, 1985): 265–74. http://dx.doi.org/10.1242/jeb.119.1.265.
Повний текст джерелаАнотація:
Steady swimming movements of dolphins were recorded in a search for direct evidence of asymmetry between upstrokes and downstrokes. Kinematic swimming and gliding data from frame-by-frame analysis of cine pictures taken at constant frame rates with a camera in a fixed position are presented. We estimated the propulsive forces generated by the tail blade with a simple hydrodynamic model. Dolphins accelerate during the downstroke and decelerate during the upstroke: the net hydrodynamic force in the animal is always positive during the downstroke and negative during the upstroke. Both parts of the stroke cycle are equally long. The propulsive forces of downstrokes are on average larger than the forces of the upstrokes. Occasionally the average forces within an upstroke are greater than within a downstroke of the same sequence. Our data suggest that the drag on the body during the upstroke exceeds the drag in the course of the downstroke. The specific swimming speed or stride length of dolphins swimming at low speeds is about 0.9 body lengths per tail beat.