scholarly journals Low-frequency sound affects active micromechanics in the human inner ear

2014 ◽  
Vol 1 (2) ◽  
pp. 140166 ◽  
Author(s):  
Kathrin Kugler ◽  
Lutz Wiegrebe ◽  
Benedikt Grothe ◽  
Manfred Kössl ◽  
Robert Gürkov ◽  
...  
Keyword(s):  
Inner Ear ◽  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Low Frequency ◽  
Short Exposure ◽  
Low Frequencies ◽  
Spontaneous Otoacoustic Emissions ◽  
Human Cochlea ◽  
Human Hearing ◽  
The Impact

Noise-induced hearing loss is one of the most common auditory pathologies, resulting from overstimulation of the human cochlea, an exquisitely sensitive micromechanical device. At very low frequencies (less than 250 Hz), however, the sensitivity of human hearing, and therefore the perceived loudness is poor. The perceived loudness is mediated by the inner hair cells of the cochlea which are driven very inadequately at low frequencies. To assess the impact of low-frequency (LF) sound, we exploited a by-product of the active amplification of sound outer hair cells (OHCs) perform, so-called spontaneous otoacoustic emissions. These are faint sounds produced by the inner ear that can be used to detect changes of cochlear physiology. We show that a short exposure to perceptually unobtrusive, LF sounds significantly affects OHCs: a 90 s, 80 dB(A) LF sound induced slow, concordant and positively correlated frequency and level oscillations of spontaneous otoacoustic emissions that lasted for about 2 min after LF sound offset. LF sounds, contrary to their unobtrusive perception, strongly stimulate the human cochlea and affect amplification processes in the most sensitive and important frequency range of human hearing.

scholarly journals Calcium Modulates the Frequency and Amplitude of Spontaneous Otoacoustic Emissions in the Bobtail Skink

2004 ◽  
Vol 92 (5) ◽  
pp. 2685-2693 ◽  
Author(s):  
Geoffrey A. Manley ◽  
Ulrike Sienknecht ◽  
Christine Köppl
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Calcium Concentration ◽  
Chelating Agent ◽  
Lizard Species ◽  
Spontaneous Otoacoustic Emissions ◽  
Active Processes

Active processes in the inner ear of lizards can be monitored using spontaneous otoacoustic emissions (SOAE) measured outside the eardrum. In the Australian bobtail lizard, SOAE are generated by an active motility process in the hair-cell bundle. This mechanism has been shown to be sensitive to the calcium-chelating agent 1,2-bis(o-aminophenoxy)ethane- N,N,N′,N′-tetraacetic acid and is presumed to be related to the calcium-sensitive transduction-channel motor implicated in other nonmammalian hair cell systems. In studies of frog saccular and turtle auditory papillar hair cells in vitro, the frequency and amplitude of bundle oscillations depend on the concentration of calcium in the bathing solutions. In the present study, the calcium concentration in the endolymph was changed in vivo in the Australian bobtail lizard Tiliqua rugosa, and SOAE were monitored. Glass pipettes with large tips and containing different calcium concentrations in their fluids were introduced into scala media, and their contents were allowed to passively flow into the endolymph. Low calcium concentrations resulted in a downward shift in the frequency of SOAE spectral peaks and generally an increase in their amplitudes. Calcium concentrations >2 mM resulted in increases in frequency of SOAE peaks and generally a loss in amplitude. These frequency shifts were consistent with in vitro data on the frequencies and amplitudes of spontaneous oscillation of hair cell bundles and thus also implicate calcium ions in the generation of active motility in nonmammalian hair cells. The data also suggest that in this lizard species, the ionic calcium concentration in the cochlear endolymph is ≥1 mM.

Spontaneous otoacoustic emissions (SOAE) changes in testicular cancer patients treated with cisplatin: A pilot study of whether the acute ototoxic effect of cisplatin treatment can be detected

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 15581-15581
Author(s):  
K. Biro ◽  
L. Noszek ◽  
P. Prekopp ◽  
K. Vehovszky ◽  
E. Nemeth ◽  
...  
Keyword(s):  
Testicular Cancer ◽  
Inner Ear ◽  
Cancer Patients ◽  
Cumulative Dose ◽  
Otoacoustic Emissions ◽  
Control Group ◽  
Spontaneous Otoacoustic Emissions ◽  
Number Of Patients ◽  
Detailed Medical History ◽  
Acute Changes

15581 Background: We studied the acute ototoxic effect of cisplatin in testicular cancer patients with two highly sensitive new methods for detecting high frequency hearing loss: distorsion product otoacoustic emissions (DPOAE), and spontaneous otoacoustic emissions (SOAE). Methods: Checking the acute effect, 32 (63 ears) testicular cancer patients (median age: 33 years, range: 16–59 years) were measured on the first day of their first cycle and after one week of their last cycle of cisplatin treatment. 20 mg/m2 cisplatin was administered for five days, in BEP chemotherapy regimen. The patients got on the average 2.19 cycles (2–3 cycles). We also measured the SOAE of ten healthy control persons (without chemotherapy) matching sex and age distribution of this group. A detailed medical history evaluated audiological risk factors and hearing problems. Tympanometry, DPOAE and SOAE were measured, to detect the acute changes in the inner ear after low cumulative dose of cisplatin treatment. Paired t-test, and sign test was used for statistical analysis. Results: The DPOAE did not show any changes close after cisplatin treatment (average: 2.19 cycles, 2–3 cycles), similarly to our earlier results with pure tone audiometry (PTA) and transiently evoked otoacoustic emission (TOAE). But the SOAE showed significant, early changes in incidence, shape and amplitude, in the treated group. 66% of the SOAE changed after treatment (p=0,006). In the control group (20 ears) the SOAE never changed in a three months period. (It behaves as a fingerprint) Conclusions: DPOAE did not change significantly after 2 or 3 cycles of cisplatin treatment, similarly to our earlier results with PTA, and TOAE, but the change of the SOAE-incidence, shape and amplitude close after cisplatin treatment shows acute changes in the inner ear function (first described in the literature) after administration of low cumulative dose of cisplatin. This case is the first indication of the possible clinical relevance of SOAE. Our observation has to be confirmed in further studies, with larger number of patients. No significant financial relationships to disclose.

scholarly journals Static length changes of cochlear outer hair cells can tune low-frequency hearing

2017 ◽  
Author(s):  
Nikola Ciganović ◽  
Rebecca L. Warren ◽  
Batu Keçeli ◽  
Stefan Jacob ◽  
Anders Fridberger ◽  
...  
Keyword(s):  
Inner Ear ◽  
Hair Cells ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Frequency Selectivity ◽  
Apical Region ◽  
Low Frequencies ◽  
Inner Hair Cells ◽  
Length Changes ◽  
The Brain

AbstractThe cochlea not only transduces sound-induced vibration into neural spikes, it also amplifies weak sound to boost its detection. Actuators of this active process are sensory outer hair cells in the organ of Corti, whereas the inner hair cells transduce the resulting motion into electric signals that propagate via the auditory nerve to the brain. However, how the outer hair cells modulate the stimulus to the inner hair cells remains unclear. Here, we combine theoretical modeling and experimental measurements near the cochlear apex to study the way in which length changes of the outer hair cells deform the organ of Corti. We develop a geometry-based kinematic model of the apical organ of Corti that reproduces salient, yet counter-intuitive features of the organ’s motion. Our analysis further uncovers a mechanism by which a static length change of the outer hair cells can sensitively tune the signal transmitted to the sensory inner hair cells. When the outer hair cells are in an elongated state, stimulation of inner hair cells is largely inhibited, whereas outer hair cell contraction leads to a substantial enhancement of sound-evoked motion near the hair bundles. This novel mechanism for regulating the sensitivity of the hearing organ applies to the low frequencies that are most important for the perception of speech and music. We suggest that the proposed mechanism might underlie frequency discrimination at low auditory frequencies, as well as our ability to selectively attend auditory signals in noisy surroundings.Author summaryOuter hair cells are highly specialized force producers inside the inner ear: they can change length when stimulated electrically. However, how exactly this electromotile effect contributes to the astonishing sensitivity and frequency selectivity of the inner ear has remained unclear. Here we show for the first time that static length changes of outer hair cells can sensitively regulate how much of a sound signal is passed on to the inner hair cells that forward the signal to the brain. Our analysis holds for the apical region of the inner ear that is responsible for detecting the low frequencies that matter most in speech and music. This shows a mechanisms for how frequency-selectivity can be achieved at low frequencies. It also opens a path for the efferent neural system to regulate hearing sensitivity.

R449 – The Role of DPZF in Inner Ear Development and Function

2008 ◽  
Vol 139 (2_suppl) ◽  
pp. P195-P195
Author(s):  
Gao Xia
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Inner Ear ◽  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Auditory Brainstem ◽  
Auditory Brainstem Responses ◽  
Inner Ear Development ◽  
Scanning Electron

Problem The dendritic cell-derived BTB/POZ zinc finger (DPZF) protein belongs to the C2H2 zinc finger protein transcription factor family. It is localized on chromosome 3 and widely expressed in hematopoietic tissues, including human dendritic cells (DC), monocytes, B cells and T cells. DPZF null mice (DPZF-/-) exhibit a circling phenotype, suggestive of an inner ear defect. Here, we present our work on the role of DPZF in hearing defects. Methods We used auditory brainstem responses (ABR) and distortion production otoacoustic emissions (DPOAEs) to test the hearing function of DPZF-/- mice, then gross observation and histopathology analysis including serial sections and scanning electron microscopy were performed to exam the cochlea of DPZF-/- mice. Results Auditory brainstem responses (ABR) and distortion production otoacoustic emissions (DPOAEs) showed that DPZF-/-mice were completely deaf. Disorganized and fewer hair cells of the Corti organ in DPZF-/- mice were identified by scanning electron microscopy. Besides, although the hair cells of the utricle and saccule were grossly normal, the stereocilia were greatly reduced in number. Further more, lipofuscin was seen in the stria vascularis with the amount of which increased with age. Conclusion The impaired hearing and balance function and the morphological abnormalities of inner ears are caused by the deletion of DPZF gene. Significance DPZF gene may participates in regulating inner ear development and the DPZF null mice may serve as a new disease model of hearing loss. Support This work was supported by the ground of Jiangsu Province Famous Doctor Project(RC2007010).

scholarly journals The Impact of the Treatment Method of Root Crops on Micro flora during their Storage

2019 ◽  
Vol 9 (1) ◽  
pp. 4273-4278
Keyword(s):  
Magnetic Induction ◽  
Treatment Time ◽  
Low Frequency ◽  
Treatment Method ◽  
Integrated Treatment ◽  
Low Frequencies ◽  
Anaerobic Microorganisms ◽  
Root Crops ◽  
Different Temperatures ◽  
The Impact

The study aims at determining the effect of the treatment method of root crops before storage, as well as storage parameters, on the dynamics of their microflora, namely, the quantity of bacterial microflora, mesophilic aerobic and optionally anaerobic microorganisms (MAaOAM), as well as molds. When storing garden carrot at t = +(2±1) °C (during 56 days), the amount of bacterial microflora of the samples subjected to integrated treatment decreased by 2.5 times by the end of storage; the number of mold fungi decreased twice compared to the control. When storing garden carrot at t = +(25±1) °C (for 21 days) the amount of bacterial microflora in the samples treated by electromagnetic fields of extremely low frequencies (with the following parameters: frequency – 28 Hz, the treatment time – 5 min, the magnetic induction – 12 mTl), and by Vitaplan biologic preparation (at the concentration of 106 CFU/g, and in the amount of 2.5 ml/kg), decreased by 2.1 times, while the number of mold fungi reduced by 1.5 times. When storing garden beet at t = +(2±1) °C for 56 days, the amount of bacterial microflora of samples, subjected to integrated treatment for 5 min at a frequency of 15, 24, and 30 Hz, and magnetic induction of 9 mTl, as well as treatment with Bactofit biological preparation (at the concentration of 106 CFU/g in amount of 2.5 ml/kg), decreased by 1.5 times compared to the control, while the number of mold fungi decreased by 2.3 times. When storing garden beet at t = +(25±1) °C (for 21 days), the quantity of bacterial microflora of samples, subjected to integrated treatment, was by 2.8 times lower compared to the control, while the number of mold fungi reduced by 1.8 times. It has been revealed that the integrated treatment of root crops with biopreparations and extremely low frequency (ELF) electric and magnetic fields (EMF) more effectively inhibits the development of pathogenic microflora compared to treatment only with biopreparations or treatment only by ELF-EMF. Significant retardation of growth rates was revealed in both bacterial and fungal pathogenic microflora during storage of root crops at different temperatures.

scholarly journals Fast adaptation of cooperative channels engenders Hopf bifurcations in auditory hair cells

2021 ◽  
Author(s):  
Francesco Gianoli ◽  
Brenna Hogan ◽  
&Eacutemilien Dilly ◽  
Thomas Risler ◽  
Andrei S Kozlov
Keyword(s):  
Inner Ear ◽  
Hair Cells ◽  
Current Model ◽  
Low Frequency ◽  
Reaction Rates ◽  
Hopf Bifurcations ◽  
Active Process ◽  
Auditory Hair Cells ◽  
Cycle Basis ◽  
Vestibular Hair Cells

Since the pioneering work of Thomas Gold published in 1948, it has been known that we owe our sensitive sense of hearing to a process in the inner ear that can amplify incident sounds on a cycle-by-cycle basis. Termed the active process, it uses energy to counteract the viscous dissipation associated with sound-evoked vibrations of the ear's mechanotransduction apparatus. Despite its importance, the mechanism of the active process and the proximate source of energy that powers it have remained elusive—especially at the high frequencies characteristic of mammalian hearing. This is partly due to our insufficient understanding of the mechanotransduction process in hair cells, the sensory receptors and amplifiers of the inner ear. It has previously been proposed that a cyclical binding of Ca2+ ions to individual mechanotransduction channels could power the active process. That model, however, relied on tailored reaction rates that structurally forced the direction of the cycle. Here, we ground our study on our previous model of hair-cell mechanotransduction, which relied on the cooperative gating of pairs of channels, and incorporate into it the cyclical binding of Ca2+ ions. With a single binding site per channel and reaction rates drawn from thermodynamic principles, our model shows that hair cells behave as nonlinear oscillators that exhibit Hopf bifurcations, dynamical instabilities long understood to be signatures of the active process. Using realistic parameter values, we find bifurcations at frequencies in the kilohertz range with physiological Ca2+ concentrations. In contrast to the myosin-based mechanism, responsible for low-frequency relaxation oscillations in the vestibular hair cells of amphibians, the current model relies on the electrochemical gradient of Ca2+ as the only energy source for the active process and on the relative motion of cooperative channels within the stereociliary membrane as the single mechanical driver. Equipped with these two mechanisms, a hair bundle proves capable of operating at frequencies in the kilohertz range, characteristic of mammalian hearing.

scholarly journals Neutral stability curves of low-frequency Görtler flow generated by free-stream vortical disturbances

2018 ◽  
Vol 845 ◽  
Author(s):  
Samuele Viaro ◽  
Pierre Ricco
Keyword(s):  
Vortex Flow ◽  
Free Stream ◽  
Low Frequency ◽  
Neutral Stability ◽  
Flow Conditions ◽  
Low Frequencies ◽  
Transition Prediction ◽  
Neutral Curves ◽  
The Impact ◽  
Inviscid Instability

The neutral curves of the boundary layer Görtler-vortex flow generated by free-stream disturbances, i.e., curves that distinguish the perturbation flow conditions of growth and decay, are computed through a receptivity study for different Görtler numbers, wavelengths, and low frequencies of the free-stream disturbance. The perturbations are defined as Klebanoff modes or strong and weak Görtler vortices, depending on their growth rate. The critical Görtler number below which the inviscid instability due to the curvature never occurs is obtained and the conditions for which only Klebanoff modes exist are thus revealed. A streamwise-dependent receptivity coefficient is defined and we discuss the impact of the receptivity on the $N$-factor approach for transition prediction.

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