How cilia beat

Mitchison, Tim; Mitchison, Hannah M.

doi:10.1038/463308a

Cited by 73 publications

(47 citation statements)

References 12 publications

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“…The coupling of these three physical phenomena leads to the emergence of complex flagellar waveforms, which were examined in detail through numerical simulations for a large spectrum of internal shear wavenumber, k, sperm compliance, Sp, and different boundary conditions. While weakly nonlinear analyses (Hilfinger et al 2009;Mitchison & Mitchison 2010) support the use of geometrically linear elasticity theory in recent models of flagellar dynamics (Camalet et al 1999;Camalet & Jü licher 2000;Riedel-Kruse et al 2007;Fu et al 2008), we have demonstrated that the linear theory can be unreliable in general. On varying the internal shear wavenumber k and the sperm compliance, Sp, the linear theory yields inaccurate predictions for reasonably large values of Sp and a wide range of wavenumbers k ( figure 4a,b).…”

Section: Discussionmentioning

confidence: 99%

“…Although the sliding filament mechanism has been successful in explaining flagellar bending, there is a limited quantitative understanding of the regulation and nature of the internal shear stress f, which represents the coupling between the dynein molecular motor activity and the passive cross-linking proteins within the flagellum (Brokaw 2009;Mitchison & Mitchison 2010). There have been several attempts to explain the observed flagellar beat via different shear-control hypotheses dictating the regulation of internal shear f (Brokaw 1971(Brokaw , 1975(Brokaw , 2009Hines & Blum 1978;Lindemann & Kanous 1995;Camalet et al 1999;Camalet & Jü licher 2000;Mitchison & Mitchison 2010), although comparison with experiments has only become possible recently (Riedel-Kruse et al 2007). Here, it is beyond the scope of the study to consider detailed assessments of the internal shear regulation and the difficulties associated with dynein control mechanisms.…”

Section: Geometrically Nonlinear Theory: Equation Of Motionmentioning

confidence: 99%

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Nonlinear instability in flagellar dynamics: a novel modulation mechanism in sperm migration?

Gadêlha

Gaffney

Smith

et al. 2010

J. R. Soc. Interface.

109

148

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Throughout biology, cells and organisms use flagella and cilia to propel fluid and achieve motility. The beating of these organelles, and the corresponding ability to sense, respond to and modulate this beat is central to many processes in health and disease. While the mechanics of flagellum -fluid interaction has been the subject of extensive mathematical studies, these models have been restricted to being geometrically linear or weakly nonlinear, despite the high curvatures observed physiologically. We study the effect of geometrical nonlinearity, focusing on the spermatozoon flagellum. For a wide range of physiologically relevant parameters, the nonlinear model predicts that flagellar compression by the internal forces initiates an effective buckling behaviour, leading to a symmetry-breaking bifurcation that causes profound and complicated changes in the waveform and swimming trajectory, as well as the breakdown of the linear theory. The emergent waveform also induces curved swimming in an otherwise symmetric system, with the swimming trajectory being sensitive to head shape-no signalling or asymmetric forces are required. We conclude that nonlinear models are essential in understanding the flagellar waveform in migratory human sperm; these models will also be invaluable in understanding motile flagella and cilia in other systems.

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Section: Discussionmentioning

confidence: 99%

Section: Geometrically Nonlinear Theory: Equation Of Motionmentioning

confidence: 99%

Nonlinear instability in flagellar dynamics: a novel modulation mechanism in sperm migration?

Gadêlha

Gaffney

Smith

et al. 2010

J. R. Soc. Interface.

109

148

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“…IgG titer (Log10) 2 Level of Cytokine IL-5 (pg/ml) In serum 3 After stimulation 4 Booster doses containing either a GC (GC-GC and GC-GC-GC) or a native polysaccharide of Pn14PS (PS) (GC-PS, GCGC-PS, and GC-PS-PS) were injected at Weeks 5 and 10. 2 ELISA was employed to measure specific anti-Pn14PS IgG antibodies, and expressed as the log10 of the sera dilution 3 Cytokine levels in sera from mice receiving booster injection.…”

Section: Immunizationmentioning

confidence: 99%

“…2 ELISA was employed to measure specific anti-Pn14PS IgG antibodies, and expressed as the log10 of the sera dilution 3 Cytokine levels in sera from mice receiving booster injection. Sera were collected on Day 1 after the primary immunization 4 Splenocytes were isolated 7 days after the first booster injection.…”

Section: Immunizationmentioning

confidence: 99%

“…He discovered that (i) small organic molecules with a simple structure, such as phenyl arsonates and nitrophenyls, do not provoke antibodies by themselves, but (ii) if those molecules are attached covalently, by simple chemical reactions, to a protein carrier, then antibodies against those small organic molecules are evoked. Since their introduction, these haptencarrier complexes have become excellent tools to elucidate the role of different antigenreactive cells in the immune response [2]. The key players in this immunological process are thymus-derived T cells and bone marrow-derived B cells.…”

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confidence: 99%

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The Future of Synthetic Carbohydrate Vaccines: Immunological Studies on Streptococcus pneumoniae Type 14

Safari¹,

Rijkers²,

Snippe³

2012

The Complex World of Polysaccharides

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Additional information is available at the end of the chapter http://dx.doi.org/10.5772/48326 IntroductionStudies on synthetic carbohydrates to be used as potential vaccine candidates for polysaccharide encapsulated bacteria were started in the mid-1970s. They were the logical follow-up to studies being performed at that time on the immunogenicity of antigens composed of carrier proteins and synthetic hapten groups. Hapten-carrier complexes were first introduced in immunology by Karl Landsteiner in the early 1900s [1]. He discovered that (i) small organic molecules with a simple structure, such as phenyl arsonates and nitrophenyls, do not provoke antibodies by themselves, but (ii) if those molecules are attached covalently, by simple chemical reactions, to a protein carrier, then antibodies against those small organic molecules are evoked. Since their introduction, these haptencarrier complexes have become excellent tools to elucidate the role of different antigenreactive cells in the immune response [2]. The key players in this immunological process are thymus-derived T cells and bone marrow-derived B cells. The former group of lymphoid cells is responsible for various phenomena of cell-mediated immunity, e.g. delayed hypersensitivity, allograft-, and graft-versus-host reactions, and reacts with specific determinants on the carrier protein (T cell epitopes). The latter group of lymphoid cells (B cells) give rise to the precursors of antibody-secreting cells, and reacts with both the carrier protein and the synthetic haptenic determinants. This results in antibody formation to both the carrier and the hapten.The reason to apply the above concepts and techniques to carbohydrate antigens was to address an immunological problem: polysaccharide molecules are classified as so-called thymus-independent (TI) antigens, because they do not require T cells to induce an immune response of B cells. As a result, the antibodies formed are mainly of the IgM class and have aThe Complex World of Polysaccharides 618 low avidity. Moreover, no immunological memory is generated and the antigens are poorly immunogenic in infants. Latter characteristic has major implications for development of vaccines against polysaccharide encapsulated bacteria. It was hypothesized that by linking small carbohydrates (oligosaccharides) to a carrier protein, the immunogenic behavior would change to that of a thymus-dependent (TD) antigen. Therefore, the studies of both Goebel [3,4] and Campbell and Pappenheimer [5], who first isolated the antigenic determinant of Streptococcus pneumoniae type 3, were combined and extended. The hapteninhibition studies by Mage and Kabat [6] demonstrated that the antibody-combining site of type 3 pneumococcal polysaccharide consists of two to three cellobiuronic acid units. In the dextran-anti-dextran system extensively studied by Kabat and colleagues [7] the upper size limit of the antibody-combining site appeared to be a hexa-or heptasaccharide and the lower limit was estimated to be somewhat larger than a monosac...

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Cilia

Hilton¹,

Quarmby²

2011

Cellular Domains

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How cilia beat

Cited by 73 publications

References 12 publications

Nonlinear instability in flagellar dynamics: a novel modulation mechanism in sperm migration?

Nonlinear instability in flagellar dynamics: a novel modulation mechanism in sperm migration?

The Future of Synthetic Carbohydrate Vaccines: Immunological Studies on Streptococcus pneumoniae Type 14

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