Literature on cilia

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  • Structure and function of mammalian cilia, Peter Satir et al. (2008)
    TitleStructure and function of mammalian cilia
    AuthorsPeter Satir, Søren Christensen
    PublicationHistochemistry and Cell Biology
    DateJune 16, 2008
    AbstractIn the past half century, beginning with electron microscopic studies of 9 + 2 motile and 9 + 0 primary cilia, novel insights have been obtained regarding the structure and function of mammalian cilia. All cilia can now be viewed as sensory cellular antennae that coordinate a large number of cellular signaling pathways, sometimes coupling the signaling to ciliary motility or alternatively to cell division and differentiation. This view has had unanticipated consequences for our understanding of developmental processes and human disease.
  • An Integrative Computational Model of Multiciliary Beating, Xingzhou Yang et al. (2008)
    TitleAn Integrative Computational Model of Multiciliary Beating
    AuthorsXingzhou Yang, Robert Dillon, Lisa Fauci
    PublicationBulletin of Mathematical Biology
    DateMay 04, 2008
    AbstractThe coordinated beating of motile cilia is responsible for ovum transport in the oviduct, transport of mucus in the respiratory tract, and is the basis of motility in many single-celled organisms. The beating of a single motile cilium is achieved by the ATP-driven activation cycles of thousands of dynein molecular motors that cause neighboring microtubule doublets within the ciliary axoneme to slide relative to each other. The precise nature of the spatial and temporal coordination of these individual motors is still not completely understood. The emergent geometry and dynamics of ciliary beating is a consequence of the coupling of these internal force-generating motors, the passive elastic properties of the axonemal structure, and the external viscous, incompressible fluid. Here, we extend our integrative model of a single cilium that couples internal force generation with the surrounding fluid to the investigation of multiciliary interaction. This computational model allows us to predict the geometry of beating, along with the detailed description of the time-dependent flow field both near and away from the cilia. We show that synchrony and metachrony can, indeed, arise from hydrodynamic coupling. We also investigate the effects of viscosity and neighboring cilia on ciliary beat frequency. Moreover, since we have precise flow information, we also measure the dependence of the total flow pumped per cilium per beat upon parameters such as viscosity and ciliary spacing.
  • Bio-inspired electric cilia development for biomedical applications: use of ionic electro-active polymer, nanowire arrays, and micro-stereo-lithography, Hargsoon Yoon et al. (2007)
    TitleBio-inspired electric cilia development for biomedical applications: use of ionic electro-active polymer, nanowire arrays, and micro-stereo-lithography
    AuthorsHargsoon Yoon, Vasuda Ramachandran, Devesh C. Deshpande, Vijay K. Varadan
    DateApril 06, 2007
    Proceedings TitleNanosensors, Microsensors, and Biosensors and Systems 2007
    Conference NameNanosensors, Microsensors, and Biosensors and Systems 2007
    PlaceSan Diego, California, USA
  • Active micromixer based on artificial cilia, Vinayak V. Khatavkar et al. (2007)
    TitleActive micromixer based on artificial cilia
    AuthorsVinayak V. Khatavkar, Patrick D. Anderson, Jaap M. J. den Toonder, Han E. H. Meijer
    PublicationPhysics of Fluids
    AbstractWe propose a design for an active micromixer that is inspired by the motion of ciliated micro-organisms occurring in nature. The conceptual design consists of an array of individually addressable artificial cilia in the form of microactuators covering the channel wall. The microactuators can be set into motion by an external stimulus such as an electric or a magnetic field, inducing either a primary or secondary motion in the surrounding fluid. To validate the concept and to help to design the precise mixer configuration, we developed a computational fluid-structure model. This model is based on a fictitious domain method that couples the microactuator motion to the concomitant fluid flow, fully capturing the mutual fluid-structure interactions. The simulated flow patterns resulting from the motion of single and multiple actuated elements (in a microchannel filled with a Newtonian fluid) under the action of a time-periodic forcing function are analyzed using dynamical systems theory to quantify the mixing efficiency. The results show that with a proper actuation scheme, two microactuators placed on the same wall of a microchannel can indeed induce effective mixing by chaotic advection; their distance should be small, but collisions should be avoided, and they can be actuated in a rather broad regime around 90° out of phase. Placing actuators on opposite walls also induces exponential stretching in the fluid, but if their length is relatively small, of the order of 20% of the channel height, mixing effectiveness is higher when they are arranged on the same wall
  • Mechanical Properties and Consequences of Stereocilia and Extracellular Links in Vestibular Hair Bundles, Jong-Hoon Nam et al. (2006)
    TitleMechanical Properties and Consequences of Stereocilia and Extracellular Links in Vestibular Hair Bundles
    AuthorsJong-Hoon Nam, John R. Cotton, Ellengene H. Peterson, Wally Grant
    PublicationBiophysical Journal
    DateApril 15, 2006
    AbstractAlthough knowledge of the fine structure of vestibular hair bundles is increasing, the mechanical properties and functional significance of those structures remain unclear. In 2004, Bashtanov and colleagues reported the contribution of different extracellular links to bundle stiffness. We simulated Bashtanov's experimental protocol using a three-dimensional finite element bundle model with geometry measured from a typical striolar hair cell. Unlike any previous models, we separately consider two types of horizontal links: shaft links and upper lateral links. Our most important results are as follows. First, we identified the material properties required to match Bashtanov's experiment: stereocilia Young's modulus of 0.74 GPa, tip link assembly (gating spring) stiffness of 5300 pN/microm, and the combined stiffness of shaft links binding two adjacent stereocilia of 750 [~] 2250 pN/microm. Second, we conclude that upper lateral links are likely to have nonlinear mechanical properties: they have minimal stiffness during small bundle deformations but stiffen as the bundle deflects further. Third, we estimated the stiffness of the gating spring based on our realistic three-dimensional bundle model rather than a conventional model relying on the parallel arrangement assumption. Our predicted stiffness of the gating spring was greater than the previous estimation.
  • The importance of being cilia, David Brinley (2005)
    TitleThe importance of being cilia
    AuthorDavid Brinley
    PublicationHHMI Bulletin
    DateSeptember 2005
    AbstractOn the surface of nearly every cell in the body is a slender protuberance called the primary cilium. Although ubiquitous, the primary cilium was long considered—with a few exceptions—to be a largely useless evolutionary vestige, destined to go the way of the tailbone and the wisdom tooth. But now we know that cilia are functioning organelles, essential to normal development and health.
  • Primary cilia: new perspectives, Denys Wheatley (2004)
    TitlePrimary cilia: new perspectives
    AuthorDenys Wheatley
    PublicationCell Biology International
  • Mechanosensory Transduction in "Sensory" and "Motile" Cilia, Michael L. Wiederhold (2003)
    TitleMechanosensory Transduction in "Sensory" and "Motile" Cilia
    AuthorMichael L. Wiederhold
    PublicationAnnual Review of Biophysics and Bioengineering
  • Mechanics of Motor Proteins and the Cytoskeleton, J Howard (2002)
    TitleMechanics of Motor Proteins and the Cytoskeleton
    AuthorJ Howard
    PublicationApplied Mechanics Reviews
    DateMarch, 2002
  • The Speed of a Protozoan, Ross Krupnik (2000)
    TitleThe Speed of a Protozoan
    AuthorRoss Krupnik
    AbstractThe Physics Factbook™ is an encyclopedia of scientific essays written by high school students that can be used by anybody. It is an exercise in library research methods in which students are sent out in search of a measurement with the intent of having them find more than just a number with a unit. It is an ongoing project with no foreseeable end date or limits.
  • Cilia and Flagella: Structure and Movement (Chapter 19.4), Harvey Lodish et al. (2000)
    TitleCilia and Flagella: Structure and Movement (Chapter 19.4)
    AuthorsHarvey Lodish, Arnold Berk, Lawrence S. Zipursky, Paul Matsudaira, David Baltimore, James Darnell
    PlaceNew York
    PublisherW.H. Freeman and Company
  • Flexural Rigidity of Echinoderm Sperm Flagella, Sumio Ishijima et al. (1994)
    TitleFlexural Rigidity of Echinoderm Sperm Flagella
    AuthorsSumio Ishijima, Yukio Hiramoto
    PublicationCell Structure and Function
    AbstractThe stiffness (flexural rigidity) of live sperm flagella, Triton-demembranated flagella (axonernes), trypsin-digested axonemes, and doublet microtubules of the axonemes in echinoderms was determined from the relationship between their deformation when a stream of medium was applied and the viscous resistance of the medium acting on the flagellum. The stiffness of the flagellum beating in seawater was 5.8×10-21 Nm2 for bending in the direction perpendicular to the beating plane and 4.2×10-22 Nm2 for bending within the beating plane. A similar difference in stiffness from the difference in bending directions was found in reactivated flagella with 1 Mm ATP. The stiffness of live flagella immobilized in CO2-saturated seawater and axonemes in ATP-free medium was similar to that of beating flagella for bending in the direction perpendicular to the beating plane. The stiffness of motionless flagella significantly decreased with erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) and vanadate. The trypsin-digestion of motionless axonemes did not change their stiffness. The stiffness of doublet microtubules was 1.4 ×10-23 Nm2 in 0.1 mM ATP medium and 6.1×10-23 Nm2 in ATP-free medium. These results suggest that doublet pairs lying parallel to the beating plane of the flagellum retain fewer cross-bridges than doublet pairs lying perpendicular to the beating palne.
  • Stiffness of sensory-cell hair bundles in the isolated guinea pig cochlea, David Strelioff et al. (1984)
    TitleStiffness of sensory-cell hair bundles in the isolated guinea pig cochlea
    AuthorsDavid Strelioff, Åke Flock
    PublicationHearing Research
    DateJuly 1984
    AbstractStiffness of hair bundles on cochlear hair cells was measured in turns 2, 3 and 4 of isolated preparations of the guinea-pig organ of Corti maintained in tissue culture medium. Defined as the force required to produce a linear 1.0 [mu]m deflection of the hair-bundle tip, stiffness is greater for deflection in the excitatory than in the inhibitory direction. The excitatory-to-inhibitory ratio for inner hair cells (IHC) is significantly lower than the ratio for outer hair cells (OHC). Hair-bundle stiffness decreases radially from the first to third rows of OHC. Over the measurement range of 9.0-18.0 mm from the stapes hair-bundle stiffness decreases much more for OHC (88-97%) than for IHC (50%). Although an increase in hair-bundle length with distance from the stapes accounts for some of the observed stiffness decrease, the major decrease is due to an increase in compliance of the sensory-hair attachment to the hair-cell surface.
  • Direct Measurements of the Stiffness of Echinoderm Sperm Flagella, Makato Okuno et al. (1979)
    TitleDirect Measurements of the Stiffness of Echinoderm Sperm Flagella
    AuthorsMakato Okuno, Yukio Hiramoto
    PublicationJournal of Experimental Biology
    DateApril 1, 1979
    Abstract1. The stiffness (flexural rigidity) of some echinoderm sperm flagella was measured, using a flexible glass microneedle.2. Values of 0.3-1.5 x 10-21 N m2 were obtained for the stiffness of live flagella which were immobilized with CO2-saturated sea water.3. The immobilized live flagellum was uniform in stiffness along its entire length, except in a particular plane of imposed bending in which flexible regions were observed.4. Demembranated flagella (Hemicentrotus pulcherrimus) in an ATP-free solution were about ten times stiffer (1.1 x 10-20 N m2) than immobilized live ones (0.5-0.9 x 10-21 N m2). The stiffness was decreased by addition of ATP to the solution and became equivalent to that of live ones when the solution contained 10 mM ATP.5. In the demembranated flagella, the effects of ADP and ATP on the stiffness were similar. Other nucleotide phosphates and inorganic phosphate did not reduce the stiffness.6. Young's modulus of microtubules is estimated to be 2.5 x 109 Nm2 on the basis that the microtubules have no tight connexion with one another in immobilized live flagella.
  • Fluid transport by cilia between parallel plates, N. Liron (1977)
    TitleFluid transport by cilia between parallel plates
    AuthorN. Liron
    PublicationJournal of Fluid Mechanics
    DateSeptember 8 1977
    AbstractThe problem of fluid transport by cilia is investigated using the Green's function for a Stokeslet between two parallel plates. The discrete-cilia approach is used in building the model, and a readily usable expression for the velocities is obtained. Dependence on the direction of the metachronal wave and on time is not averaged out. Velocity fields, pressure fields and fluxes due to a single Stokeslet and to an infinite line of Stokeslets are discussed. It is found that the flux associated with Stokeslets in between two parallel plates is always zero, in contrast to a Stokeslet parallel to, and above, one plate. In the model one also has to add a plane Poiseuille flow, which incorporates non-zero flux. The flow due to the Stokeslet solution imposes a positive pressure gradient downstream, and the Poiseuille flow a negative pressure gradient. Calculated velocity profiles, in the pumping range, are seen to be time-independent in the centre of the channel and vary between a negative parabolic profile and a plug flow. The reason for these profiles and some possible biological applications are discussed.
  • Fluid Mechanics of Propulsion by Cilia and Flagella, C. Brennen et al. (1977)
    TitleFluid Mechanics of Propulsion by Cilia and Flagella
    AuthorsC. Brennen, H. Winet
    PublicationAnnual Review of Fluid Mechanics
  • The distribution, activity, and function of the cilia in the frog brain, Deborah J. Nelson et al. (1974)
    TitleThe distribution, activity, and function of the cilia in the frog brain
    AuthorsDeborah J. Nelson, Ernest M. Wright
    PublicationJ Physiol
    DateNovember 1, 1974
    Abstract1. The distribution, activity, and function of the cilia in the brain was studied using in vitro preparations of the frog choroid plexuses and ependyma. 2. Scanning electron microscopy revealed that twenty to forty cilia, about 20 microm long, project from the cells of the choroidal epithelium and ependyma into the ventricular system of the brain. 3. These cilia beat at a constant frequency which ranged from 5 to 20 c/s. Ciliary activity was enhanced by ATP, cyclic AMP, theophylline, and acetylcholine, and was depressed by DNP, IAA, Ni2+, La3+, and Co2+. 4. Ciliary motion produced a flow of c.s.f. over the surface of the cells lining the ventricles, and in the choroid plexus this flow reduced the effective thickness of the unstirred layer adjacent to the epithelium by about 100 microm. 5. These results are discussed in relation to the factors that control the frequency of ciliary beating, and the role of the cilia in the circulation of the c.s.f.
  • Flexural Rigidity and Elastic Constant of Cilia, Shoji A. Baba (1972)
    TitleFlexural Rigidity and Elastic Constant of Cilia
    AuthorShoji A. Baba
    PublicationJournal of Experimental Biology
    DateApril 1, 1972
    Abstract1. The flexural rigidity of the large abfrontal cilia of Mytilus has been measured with a flexible glass micro-needle.2. The same cilium has similar values to the flexural rigidity irrespective of the phases of beat cycle (including the recovery phase) and of the direction of force applied.3. The values of 3-13 x 10-9 dyne. cm2 have been obtained for the flexural rigidity of compound cilia of various sizes; 2-3 x 10-10 dyne.cm2 for that of the component cilia.4. The Young's modulus of the microtubule is estimated to be 5-9 x 1010 dyne/cm2 on the basis that the outer doublet microtubules are tightly connected with one another.
  • Elastic Properties of the Sea Urchin Sperm Flagellum, Robert Rikmenspoel (1966)
    TitleElastic Properties of the Sea Urchin Sperm Flagellum
    AuthorRobert Rikmenspoel
    PublicationBiophysical Journal
    DateJuly 1, 1966
    AbstractThe theory of flexural vibrations in thin rods, applied to the movement of flagella, has been extended to include an investigation of the influence of the boundary conditions on the theoretical waveforms. It was found that for flagella which are flexible enough, the flexibility can be estimated solely from the wavelength of the wave traveling in it. This can be expected to hold for those flagella which do not possess a fibrous sheath. The bending moment in flagella in which the ampitude of the wave is maintained as the wave travels distally is almost completely produced by active contractile elements. This means that the active bending moment can be estimated from the radius of curvature of the flagellum and the stiffness. The above findings were applied to the case of the sea urchin sperm flagellum. One finds that the stiffness of the flagellum is caused mainly by the nine longitudinal fibers which must have a Young's modulus of slightly less than 108dyne/cm2. The longitudinal fibers need to develop a tension of 1.6 x 108dyne/cm2 to account for the bending moment in the flagellum. These two figures are in line with those found for muscle fibers.