Mechanoelectrical Transduction By Hair Cells

Howard, J

doi:10.1146/annurev.biophys.17.1.99

Cited by 19 publications

(18 citation statements)

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“…In such a short period, the movement of one amyloplast should be very slight (0.019 mm, Driss-Ecole et al 2000a) and the potential energy dissipated by its displacement (2.1 ¿ 10 ª21 J, Driss-Ecole et al 2000a) not sufficient to trigger a response since it is similar to the thermal noise (2 ¿ 10 ª21 J; Björkman 1988). However, the potential energy of the 20 amyloplasts of the statocyte (42 ¿ 10 ª21 J) should be just enough to induce a stimulus (for instance to open a mechano-sensitive Ca 2π channel which requires 35 ¿ 10 ª21 J; Howard et al 1988). This result indicates that at least for the threshold stimuli the statoliths which are enmeshed in the actin network (Driss-Ecole et al 2000b) must exert altogether forces on the site of attachment of the microfilaments to the plasma membrane or that the protoplast itself could play the role of graviperceptor (Wayne andStaves 1996, Perbal 1999).…”

Section: Resultsmentioning

confidence: 99%

The dose–response curve of the gravitropic reaction: a re‐analysis

Perbal

Jeune

Lefranc

et al. 2002

Physiologia Plantarum

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The dose-response curve of the gravitropic reaction is often used to evaluate the gravisensing of plant organs. It has been proposed (Larsen 1957) that the response (curvature) varies linearly as a function of the logarithm of the dose of gravistimulus. As this model fitted correctly most of the data obtained in the literature, the presentation time (tp, minimal duration of stimulation in the gravitational field to induce a response) or the presentation dose (dp, minimal quantity in g.s of stimulation to induce a response) were estimated by extrapolating down to zero curvature the straight line representing the response as a function of the logarithm of the stimulus. This method was preferred to a direct measurement of dp or tp with minute stimulations, since very slight gravitropic response cannot be distinguished from the background oscillations of the extremity of the organs. In the present review, it is shown that generally the logarithmic model (L) does not fit the experimental data published in the literature as well as the hyperbolic model (H). The H model in its simplest form is related to a response in which a ligand-receptor system is the limiting phase in the cascade of events leading to the response (Weyers et al. 1987). However, it is demonstrated that the differential growth, responsible for the curvature (and the angle of curvature), would vary as a hyperbolic function of the dose of stimulation, even if several steps involving ligand-receptor systems are responsible for the gravitropic curvature. In the H model, there is theoretically no presentation time (or presentation dose) since the curve passes through the origin. The value of the derivative of the H function equals a/b and represents the slope of the cune at the origin. It could be therefore used to estimate gravisensitivity. This provides a measurement of graviresponsiveness for threshold doses of stimulation. These results imply that the presentation time (or presentation dose) derived from the L model cannot be used anymore as an estimate of gravisensitivity. On the contrary, the perception time (minimal duration of a repeated stimulation which induces a response), which is less than 1 s, should be related to the perception of gravity. The consequences of these results on the mode of action and the nature of graviperception are discussed.

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Section: Resultsmentioning

confidence: 99%

The dose–response curve of the gravitropic reaction: a re‐analysis

Perbal

Jeune

Lefranc

et al. 2002

Physiologia Plantarum

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“…o At a moderate light-adaptation state (Figure 7-figure supplement 2), the intracellular pupil 70 mechanism has reduced light input and the rhabdomere lengths should occupy a position (or set-point), which allows further contractions to light increments (cf. hair cells in the inner ear (Howard et al, 1988)). However, here, R1-R6s' acceptance angles would still be broader for flashes with 500 ms intervals.…”

Section: R1-r6 Acceptance Angles Are Much Broader Than the Theoreticamentioning

confidence: 99%

Microsaccadic sampling of moving image information providesDrosophilahyperacute vision

Juusola

Dau

Song

et al. 2016

Preprint

173

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Small fly eyes should not see fine image details. Because flies exhibit saccadic visual behaviors and their compound eyes have relatively few ommatidia (sampling points), their photoreceptors would be expected to generate blurry and coarse retinal images of the world. Here we demonstrate that Drosophila see the world far better than predicted from the classic theories. By using electrophysiological, optical and behavioral assays, we found that R1-R6 photoreceptors' encoding capacity in time is maximized to fast high-contrast bursts, which resemble their light input during saccadic behaviors. Whilst over space, R1-R6s resolve moving objects at saccadic speeds beyond the predicted motion-blur-limit. Our results show how refractory phototransduction and rapid photomechanical photoreceptor contractions jointly sharpen retinal images of moving objects in space-time, enabling hyperacute vision, and explain how such microsaccadic information sampling exceeds the compound eyes' optical limits. These discoveries elucidate how acuity depends upon photoreceptor function and eye movements.

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“…For small inclination angles of the sporangiophore of 1-2°, the gravitropic stimuli are, according to the sine law, 1.7-3.4 9 10 À2 g, which is just above the absolute gravitropic threshold, and thus above the thermal noise (see above). Energy of about 10 À16 J could be sufficient to open 10 6 mechanosensitive Ca 2+ channels (Howard et al 1988). Such considerations appear relevant, particularly in view of the observation that gravireception of the sporangiophore correlates with specific ion fluxes in the growing zone ( Zivanovi c 2005( Zivanovi c , 2012.…”

Section: Criteria For Gravisusceptorsmentioning

confidence: 99%

The sporangiophore of Phycomyces blakesleeanus: a tool to investigate fungal gravireception and graviresponses

Galland

2013

Plant Biol J

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The giant sporangiophore of the single-celled fungus, Phycomyces blakesleeanus, utilises light, gravity and gases (water and ethylene) as environmental cues for spatial orientation. Even though gravitropism is ubiquitous in fungi (Naturwissenschaftliche Rundschau, 1996, 49, 174), the underlying mechanisms of gravireception are far less understood than those operating in plants. The amenability of Phycomyces to classical genetics and the availability of its genome sequence makes it essential to fill this knowledge gap and serve as a paradigm for fungal gravireception. The physiological phenomena describing the gravitropism of plants, foremost adherence to the so-called sine law, hold even for Phycomyces. Additional phenomena pertaining to gravireception, specifically adherence to the novel exponential law and non-adherence to the classical resultant law of gravitropism, were for the first time investigated for Phycomyces. Sporangiophores possess a novel type of gravisusceptor, i.e. lipid globules that act by buoyancy rather than sedimentation and that are associated with a network of actin cables (Plant Biology, 2013). Gravitropic bending is associated with ion currents generated by directed Ca(2+) and H(+) transport in the growing zone (Annals of the New York Academy of Sciences, 2005, 1048, 487; Planta, 2012, 236, 1817). A set of behavioural mutants with specific defects in gravi- and/or photoreception allowed dissection of the respective transduction chains. The complex phenotypes of these mutants led to abandoning the concept of simple linear transduction chains in favour of interacting networks with molecular modules of physically interacting proteins.

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Mechanoelectrical Transduction By Hair Cells

Cited by 19 publications

References 0 publications

The dose–response curve of the gravitropic reaction: a re‐analysis

The dose–response curve of the gravitropic reaction: a re‐analysis

Microsaccadic sampling of moving image information providesDrosophilahyperacute vision

The sporangiophore of Phycomyces blakesleeanus: a tool to investigate fungal gravireception and graviresponses

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