The Experts below are selected from a list of 204 Experts worldwide ranked by ideXlab platform
Dolores Bozovic - One of the best experts on this subject based on the ideXlab platform.
-
Motion of the Otolithic Membrane in the bullfrog sacculus
2015Co-Authors: Sebastiaan W. F. Meenderink, Dolores BozovicAbstract:Accessory structures that overlie the sensory epithelia of the various inner ear organs play an important role in the transduction of mechanical perturbations by the underlying hair cells. It imposes a load (mass, offset in position) on individual hair bundles and is the medium that mechanically couples multiple hair bundles. Also, it may provide a preferred directionality of motion across the macula. In this manuscript, we present results on the mechanical properties of the Otolithic Membrane (OM) from the American bullfrog sacculus. Experiments were performed in which the motion of the OM, in response to a mechanical stimulus, was determined over an extended 2-D area. We find that the OM moves in phase with the stimulus, preferentially in the same direction as the applied stimulus. The decay in response amplitude is consistent with the OM being a homogeneous elastic material.
-
Coupling and Elastic Loading Affect the Active Response by the Inner Ear Hair Cell Bundles
2013Co-Authors: Clark Elliott Strimbu, Lea Fredrickson-hemsing, Dolores BozovicAbstract:Active hair bundle motility has been proposed to underlie the amplification mechanism in the auditory endorgans of nonmammals and in the vestibular systems of all vertebrates, and to constitute a crucial component of cochlear amplification in mammals. We used semi-intact in vitro preparations of the bullfrog sacculus to study the effects of elastic mechanical loading on both natively coupled and freely oscillating hair bundles. For the latter, we attached glass fibers of different stiffness to the stereocilia and observed the induced changes in the spontaneous bundle movement. When driven with sinusoidal deflections, hair bundles displayed phase-locked response indicative of an Arnold Tongue, with the frequency selectivity highest at low amplitudes and decreasing under stronger stimulation. A striking broadening of the mode-locked response was seen with increasing stiffness of the load, until approximate impedance matching, where the phase-locked response remained flat over the physiological range of frequencies. When the Otolithic Membrane was left intact atop the preparation, the natural loading of the bundles likewise decreased their frequency selectivity with respect to that observed in freely oscillating bundles. To probe for signatures of the active process under natural loading and coupling conditions, we applied transient mechanical stimuli to the Otolithic Membrane. Following the pulses, the underlying bundles displayed active movement in the opposite direction, analogous to the twitches observed in individual cells. Tracking features in the Otolithic Membrane indicated that it moved in phase with the bundles. Hence, synchronous active motility evoked in th
-
Active hair bundle movement under the Otolithic Membrane.
2013Co-Authors: Clark Elliott Strimbu, Lea Fredrickson-hemsing, Dolores BozovicAbstract:(A)Traces of twitches in underlying hair bundles evoked by a series of 5 ms pulses delivered to the Otolithic Membrane in the excitatory (top) and inhibitory (bottom) directions. The command signals were half-cycles of a 100 Hz sine wave and are shown below the traces. (B) With the transduction channels blocked with 20 M gentamicin, the active movement was abolished. The probe had a stiffness of = 1200 N/m. (C) and (D) Average traces for the bundle movement shown in panels A and B. (E) The averaged traces obtained from 1 m aluminum oxide beads dispersed on the Otolithic Membrane of the same preparation. (F) Average traces of a pit boundary measured in a different preparation. In both E and F, the Otolithic Membrane was entrained by the active bundle movement at the end of the applied pulse. The stimulus fiber used on the sample in panel F had a stiffness of = 1400 N/m. In C, E, and F the exponential fits (red lines) from which the recovery times were extracted, have been overlaid on the traces. (G) Response of a hair bundle which showed a 15 nm twitch in response to sinusoidal pulses. (H) +10 A transepithelial electric current had little effect on either phase-locked amplitude or the twitch for both stimuli. (I) −10 A current reduced the magnitude of the twitch to 10 nm for positive deflections but had a negligible effect for negative displacements. In G, H, and I the average traces have been plotted below the raw data.
-
Coupling of active hair bundles by the Otolithic Membrane broadens the response to sinusoidal stimulation.
2013Co-Authors: Clark Elliott Strimbu, Lea Fredrickson-hemsing, Dolores BozovicAbstract:(A) A top-down view of a 15050 m area of the saccular epithelium with the Otolithic Membrane removed. The linear response function averaged over the four bundles in the corners of the white square is shown in panel C (the central bundle was partially occluded by an otolith). The tallest row of stereocilia appear as elongated bright features. The kinociliary bulbs (indicated by arrows) appear as grey circles to the right of the stereocilia. Scale bar: 10 m. (B) Normalized linear response functions for three hair bundles coupled to the Otolithic Membrane. The mean and standard deviation at each frequency were computed from a digitally resampled trace on a cycle-by-cycle basis over the 1 s recording. When the Otolithic Membrane was removed from this sample, 84% of bundles exhibited spontaneous oscillations demonstrating that the active process was maintained throughout the measurement. C. Ensemble-averaged ( = 4) linear response function of bundles coupled to the Otolithic Membrane from the preparation shown in panel A. Filled squares: the average response was essentially flat across the physiological range of frequencies. Open circles: Blocking the transduction channels with 20 M gentamicin had little effect on the response at low frequencies; the response was modestly reduced at frequencies above 150 Hz. With the Otolithic Membrane removed, 90% of the bundles in this preparation oscillated spontaneously. All recordings were taken at 1000 fps.
-
Experimental setup.
2013Co-Authors: Clark Elliott Strimbu, Lea Fredrickson-hemsing, Dolores BozovicAbstract:(A) Top-down view of a freestanding hair bundle with a glass probe (black line positioned vertically across the image) attached to the tallest row of stereocillia. Because of light piping, the stereocillia appear much brighter than the background. Scale bar: 2.5 m. (B) Schematic diagram showing a side view of a hair bundle with a probe attached. The piezoelectric actuator displaces the probe's base in the direction of the bundle's axis of sensitivity indicated by the arrow in the figure. (C) Top-down view of hair bundles coupled to the Otolithic Membrane. The pits in the Membrane into which the bundles protrude give rise to the bright ellipses around each bundle. The shadow of the probe's tip has been highlighted with the dashed line. Scale bar: 5 m. (D) Schematic diagram of a side view of hair bundles coupled to the Otolithic Membrane and stimulated with a probe. In the actual experiment, the probe's tip is embedded a few microns into the Otolithic Membrane. Note than in C and D, the probes have not been drawn to scale; in particular, the cantilever arms are typically a few hundred microns in length.
Ian S. Curthoys - One of the best experts on this subject based on the ideXlab platform.
-
The new vestibular stimuli: sound and vibration—anatomical, physiological and clinical evidence
Experimental Brain Research, 2017Co-Authors: Ian S. CurthoysAbstract:The classical view of the otoliths—as flat plates of fairly uniform receptors activated by linear acceleration dragging on otoconia and so deflecting the receptor hair bundles—has been replaced by new anatomical and physiological evidence which shows that the maculae are much more complex. There is anatomical spatial differentiation across the macula in terms of receptor types, hair bundle heights, stiffness and attachment to the overlying Otolithic Membrane. This anatomical spatial differentiation corresponds to the neural spatial differentiation of response dynamics from the receptors and afferents from different regions of the Otolithic maculae. Specifically, receptors in a specialized band of cells, the striola, are predominantly type I receptors, with short, stiff hair bundles and looser attachment to the overlying otoconial Membrane than extrastriolar receptors. At the striola the hair bundles project into holes in the Otolithic Membrane, allowing for fluid displacement to deflect the hair bundles and activate the cell. This review shows the anatomical and physiological evidence supporting the hypothesis that fluid displacement, generated by sound or vibration, deflects the short stiff hair bundles of type I receptors at the striola, resulting in neural activation of the irregular afferents innervating them. So these afferents are activated by sound or vibration and show phase-locking to individual cycles of the sound or vibration stimulus up to frequencies above 2000 Hz, underpinning the use of sound and vibration for clinical tests of vestibular function.
-
The new vestibular stimuli: sound and vibration-anatomical, physiological and clinical evidence.
Experimental brain research, 2017Co-Authors: Ian S. CurthoysAbstract:The classical view of the otoliths—as flat plates of fairly uniform receptors activated by linear acceleration dragging on otoconia and so deflecting the receptor hair bundles—has been replaced by new anatomical and physiological evidence which shows that the maculae are much more complex. There is anatomical spatial differentiation across the macula in terms of receptor types, hair bundle heights, stiffness and attachment to the overlying Otolithic Membrane. This anatomical spatial differentiation corresponds to the neural spatial differentiation of response dynamics from the receptors and afferents from different regions of the Otolithic maculae. Specifically, receptors in a specialized band of cells, the striola, are predominantly type I receptors, with short, stiff hair bundles and looser attachment to the overlying otoconial Membrane than extrastriolar receptors. At the striola the hair bundles project into holes in the Otolithic Membrane, allowing for fluid displacement to deflect the hair bundles and activate the cell. This review shows the anatomical and physiological evidence supporting the hypothesis that fluid displacement, generated by sound or vibration, deflects the short stiff hair bundles of type I receptors at the striola, resulting in neural activation of the irregular afferents innervating them. So these afferents are activated by sound or vibration and show phase-locking to individual cycles of the sound or vibration stimulus up to frequencies above 2000 Hz, underpinning the use of sound and vibration for clinical tests of vestibular function.
A. Campos - One of the best experts on this subject based on the ideXlab platform.
-
Electron probe microanalysis of gentamicin-induced changes on ionic composition of the vestibular gelatinous Membrane.
Hearing Research, 1994Co-Authors: Jose A. Lopez-escamez, F.j. Cañizares, P.v. Crespo, J.m. Baeyens, A. CamposAbstract:Abstract Gentamicin-induced changes in ionic composition in the Otolithic Membrane of adult OF1 mice were evaluated in the gelatinous layers of the saccule and utricle by quantitative electron probe X-ray microanalysis. The Otolithic Membranes were plunge-frozen and freeze-dried to prevent the redistribution of elements. Quantitative analysis was carried out with an energy dispersive detector using the peak-to-background ( P B ) ratio method and different salts dissolved in dextran as standards to calibrate the P B ratio against the concentration of the elements P, S and K in the microprobe. Gentamicin selectively decreased the concentrations of P (P
-
Electron probe microanalysis of gentamicin-induced changes on ionic composition of the vestibular gelatinous Membrane.
Hearing research, 1994Co-Authors: J A López-escámez, F.j. Cañizares, P.v. Crespo, J.m. Baeyens, A. CamposAbstract:Gentamicin-induced changes in ionic composition in the Otolithic Membrane of adult OF1 mice were evaluated in the gelatinous layers of the saccule and utricle by quantitative electron probe X-ray microanalysis. The Otolithic Membranes were plunge-frozen and freeze-dried to prevent the redistribution of elements. Quantitative analysis was carried out with an energy dispersive detector using the peak-to-background (P/B) ratio method and different salts dissolved in dextran as standards to calibrate the P/B ratio against the concentration of the elements P, S and K in the microprobe. Gentamicin selectively decreased the concentrations of P (P < 0.001) and S (P < 0.01) in the gelatinous Membrane of the saccule, and had no effect in the utricle. The concentration of K also increased in the utricular gelatinous Membrane (P < 0.05). The mechanism of ototoxicity in the gelatinous Membrane is unknown, but the ability of aminoglycosides to block calcium channels may induce disturbances in the ionic equilibrium of the endolymphatic fluid, and thus affect the biochemical composition of the gelatinous Membrane. This technique can be useful to evaluate the distribution of ions in the process of drug-induced ototoxicity.
-
Gentamicin ototoxicity in otoconia: quantitative electron probe X-ray microanalysis.
Acta oto-laryngologica, 1994Co-Authors: A. Campos, Jose A. Lopez-escamez, F.j. Cañizares, P.v. Crespo, J.m. BaeyensAbstract:Chronic gentamicin ototoxicity was evaluated in the Otolithic Membrane of adult OF1 mice at the otoconial layer of the saccule and utricle by quantitative electron probe X-ray microanalysis of Ca and K. The Otolithic Membranes were plunge-frozen and freeze-dried. The analysis was carried out with an energy dispersive detector using the peak-to-background ratio method and different inorganic salts of Ca and K as standards to calibrate the microprobe. Ca and K in the otoconia are related via a linear function in both the saccule and the utricle. This association is not maintained after exposure to gentamicin, which suggests that this aminoglycoside antibiotic interferes with the Ca — K equilibrium in the otoconia. A dose of 200 mg/kg gentamicin twice a day for 5 days did not affect Ca in the mineral phase of the otoconia, but did increase K in both saccular (p < 0.05) and utricular (p < 0.01) otoconia. These increases in K may reflect a modification in the composition of the endolymph, resulting from cellul...
-
Standards for quantification of elements in the Otolithic Membrane by electron probe X-ray microanalysis: Calibration curves and electron beam sensitivity
Journal of Microscopy, 1993Co-Authors: Jose A. Lopez-escamez, F.j. Cañizares, P.v. Crespo, A. CamposAbstract:An absolute quantitative standardization technique has been developed to measure Ca and K weight fractions (WF) in the Otolithic Membrane of the saccule and utricle by scanning electron microscopy and electron probe X-ray analysis using the peak-to-background (P/B) ratio method. Microcrystalline salt standards were used to calibrate Ca and K K alpha P/B or Y = (P/B).Z2/A (Z = atomic number; A = atomic weight) against WF at 10, 15, 20 and 25 kV accelerating voltage. The effect of voltage on the calibration, plotting the coefficient of correlation (r) as a function of voltage, was not dependent on the voltage in the range 10-25 kV for Ca standards. K standards were also independent when P/B was corrected for Z2/A. Background counts in the otoconia (Bo) were obtained at 5, 25, 50, 100, 200 and 500 s and used to test the electron beam sensitivity of saccular and utricular otoconia. Bo was not dependent on the spectra acquisition time, with the exception of Bo under K alpha K peak in the saccule at 10 kV. Ca and K WF were determined at 10, 15, 20 and 25 kV in the saccule and utricle, showing similar values regardless of the voltage used. This method of calibration offers several advantages, such as stability, homogeneity, known composition of the standards, high reproducibility at different voltages even without Z2/A correction and the similarity between the otoconia and crystal standards. We recommend the application of this method for other elements and biomineral systems.
-
Electron probe microanalysis of the Otolithic Membrane. A methodological and quantitative study.
Scanning microscopy, 1992Co-Authors: Jose A. Lopez-escamez, F.j. Cañizares, P.v. Crespo, A. CamposAbstract:The effect of tissue preparation on calcium and potassium weight percent in the otoconial layer in the utricle and saccule was studied in four groups of OF1 mice with electron probe X-ray microanalysis. Glutaraldehyde and freeze-drying, glutaraldehyde and air-drying, air-drying, and cryo-fixation and freeze-drying were compared. Ca and K changed significantly in the utricle depending on the method used (P < 0.001), and K changed significantly in the saccule (P < 0.001). We chose cryo-fixation with freeze-drying for the quantitative analysis of the Otolithic Membrane because this method provided the highest values of Ca and K with minimum loss of Ca and K. Microcrystalline salt standards mounted on scanning electron microscopy holders were used for the quantification of Ca and K by the peak-to-local-background (P/B) ratio method. The P/B ratio in standards with reproducible results, when plotted against weight percent, gave a straight line for Ca (r = 0.99, P < 0.001) and K (r = 0.98, P < 0.001). The Ca and K weight percent in otoconia showed similar frequency distributions in the utricle and saccule.
Valeri Goussev - One of the best experts on this subject based on the ideXlab platform.
-
Transversal Otolithic Membrane Deflections Evoked by the Linear Accelerations
International Journal of Biology, 2019Co-Authors: Valeri GoussevAbstract:Considered is the model of the transversal utricle Membrane deflections evoked by the linear accelerations. The basic idea underlying this consideration is that the linear accelerations can cause both longitudinal and transversal deformations when acting along the Membrane in the buckling way. The real 3D utricle Membrane structure was simplified by considering its middle section and evaluating its elastic properties in 2D space. The steady state transversal deflections along the Membrane are analytically evaluated and numerically simulated using the 2D elasticity theory. The transversal deflections are found to be more expressive and stronger as compared to the conventional longitudinal deformations. The maxima of longitudinal deformations and transversal deflections are observable in different regions of the utricle Membrane. The revealed properties could be used for explanation of the transduction processes in the otolith organ. Based on the implemented modeling approach the new Otolithic Membrane mechanical properties are discussed and new explanations for the available experimental data are given.
-
Transversal Otolithic Membrane deflections evoked by the linear accelerations
2019Co-Authors: Valeri GoussevAbstract:Considered is the model of the transversal utricle Membrane deflections evoked by the linear accelerations. The real 3D utricle Membrane structure was simplified by considering its middle section and evaluating its elastic properties in 2D space. The steady state transversal deflections along the Membrane are analytically evaluated and numerically simulated using the 2D elasticity theory. The transversal deflections are found to be more expressive and stronger as compared with the conventional longitudinal deformations. The revealed properties could be used for explanation of the transduction processes in the otholith organ. Based on the implemented modeling approach the new Otolithic Membrane mechanical properties are discussed and new explanations for the available experimental data are given.
D. V. Lychakov - One of the best experts on this subject based on the ideXlab platform.
-
Evolution of Otolithic Membrane. Structure of Otolithic Membrane in Amphibians and Reptilians
Journal of Evolutionary Biochemistry and Physiology, 2004Co-Authors: D. V. LychakovAbstract:Otolithic Membrane of utricles, saccules, and lagena of amphibians ( Bufo bufo , Xenopus laevis , Rana temporaria ) and reptiles ( Teratoscincus scincus , Agama sanguinolenta , Ophisaurus apodus , Caiman crocodilus ) were studied using light and scanning electron microscopy. Otolithic Membrane in various Otolithic organs in all studied animals was found to differ by shape, size, structure, and composition of otoconia. Otolithic Membrane of utricle of amphibians and reptiles represents a thin plate of non-uniform structure. Otolithic apparatus in saccule represents a large cobble-stone-like conglomerate of otoconia. Otolithic Membrane of lagena looks like a bent plate and is poorly differentiated in amphibians, but well differentiated in reptiles. Thus, transition of vertebrates to the earth surface was accompanied by a fundamental reorganization of Otolithic Membrane structure. Otolithic Membrane containing constantly growing large otolith (in fish) was replaced by a thin structurally differentiated Otolithic Membrane that ceases its growth at early stages of ontogenesis. However, this replacement did not occur simultaneously in all Otolithic organs. The changes initially involved Otolithic Membrane of utricle. Saccule of amphibians and reptiles has a typical compositional otolith. In the course of further phylogenetic development of tetrapods the process of structural differentiation of Otolithic Membrane was enhanced and otoliths were completely lost. In parallel, there proceeded a process of replacement of prismatic and spindle-shaped aragonitic otoconia by calcitic barrel-shaped otoconia. The data obtained confirm our hypothesis put forward earlier about two directions of evolution of Otolithic Membrane.
-
Otolithic apparatus in Black Sea elasmobranchs
Fisheries Research, 2000Co-Authors: D. V. Lychakov, A Boyadzhieva-mikhailova, I Christov, I.i EvdokimovAbstract:Abstract Using light, transmission and scanning electron microscopy, and morphometry, we examined the Otolithic organs of 25 Raja clavata (35–93 cm), 12 Dasyatis pastinaca (34–50 cm), and two Squalus acanthias specimens (100 and 145 cm). In D. pastinaca all three Otolithic Membranes merge into one another, and the Otolithic apparatus as a whole is relatively poorly developed. In R. clavata and S. acanthias the large saccular Otolithic Membrane and the small lagenar Otolithic Membrane are continuous. The mass of the Otolithic Membrane and the length of the animal are power related. The otoconia of rays tend to be lemon shaped or spherical. The dogfish has large, cuboidal (parallelepiped-shaped) endogenous otoconia, exogenous sand grains, and crystal-containing globules. The size of the endogenous otoconia does not depend on the size of the animals. No specialized zones were found in rays either on the surface or inside the Otolithic Membranes containing otoconia of one type or size. The data indicate that the mass of the Otolithic apparatus in rays increases on account of the formation of new otoconia. The Otolithic apparatus of the dogfish can also increase in mass by addition of small grains of sand, which enter the labyrinth and are incorporated into the Otolithic Membrane.
