• Proceedings of the KSME Conference
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• 2007.05a
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• pp.405-408
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• 2007

Vestibular hair cells, the sensory receptors of vestibular organs, selectively amplify miniscule stimuli to attain high sensitivity. Such selective amplification results in compressive nonlinear sensitivity, which plays an important role in expanding dynamic range while ensuring robustness of the system. In this study, negative stiffness mechanism, a mechanism responsible for the selective amplification by vestibular hair cells, is applied to a simple mechanical system consisting of an array of inverted pendulums. The structure and working principle of the system have been inspired by gating spring hypothesis proposing that opening and closing of transduction channels contributes to the global stiffness of vestibular hair bundle. Parameter study was carried out to analyze the effect of each parameter on the compressive nonlinearity of suggested model.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.9
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• pp.190-199
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• 2014

In this paper, the vestibular hair bundle feature model and integrated vestibular hair cell model were proposed. In conventional modeling studies of vestibular system, only partial mechanisms were modeled, such as the characteristics of the vestibular hair bundles without external forces or the action potential of synapse, and the study about action potential of vestibular afferent considering the characteristics of the vestibular hair bundle was not performed. The proposed integrated vestibular hair cell model reflects external forces considering negative stiffness features of each hair bundles with different regularities of hair cells and our model was compared with conventional model without external forces. As a result, irregular afferent and intermediate afferent with high ratio of firing frequency variations to the changes of external stimulation had small width of negative stiffness section, but the width of the negative stiffness of regular afferent with low ratio was similar to that of conventional negative stiffness features. And the proposed integrated vestibular hair cell model showed almost same results with conventional data with animal experiments in 11 chosen frequency bands. It is verified that our proposed hair bundle feature model is adequately modeled.

• Molecular & Cellular Toxicology
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• v.4 no.3
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• pp.177-182
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• 2008

Caveolin proteins are mediators of cell death or the survival of injured cells, and they are inhibitors of various signaling pathways. The expression of caveolin-, which is involved in the protein kinase A (PKA) signaling pathway, was examined in the differentiated mouse vestibular cell line UB/UE-1 after gentamicin ototoxicity. Caveolae in the vestibular hair cell of healthy guinea pigs were observed through an electron microscope. UB/UE-1 cells were cultured at 95% $CO_2$ with 5% $O_2$ at $33^{\circ}C$ for 48 hours and at 95% $CO_2$ with 5% $O_2$ at $39^{\circ}C$ for 24 hours for differentiation. Cells were treated with 1 mM gentamicin, 0.02 mM H89 (PKA inhibitor), and then incubated for 24 hours. Caveolin-1 expression was examined by western blotting and PKA activity by a $PepTag^{(R)}$ assay. Caveolae were observed in the vestibular hair cells of healthy guinea pigs by electron microscopy. Caveolin-1 was expressed spontaneously in differentiated UB/UE-1 cells and increased after gentamicin treatment. PKA was also over-activated by gentamicin treatment. Both gentamicin-induced caveolin-1 expression and PKA over-activation were inhibited by H89. These results indicate that gentamicin-induced caveolin-1 expression is mediated by the PKA signaling pathway. We conclude that caveolae/ caveolin activity, induced via a PKA signaling pathway, may be one of the mechanisms of gentamicin-induced ototoxicity.

• The Korean Journal of Physiology and Pharmacology
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• v.7 no.2
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• pp.85-89
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• 2003

The basic mechanism for the excitation of the peripheral vestibular receptors following acute hypotension induced by sodium nitroprusside (SNP) or hemorrhage was investigated in anesthetized rats. Electrical activity of the afferent vestibular nerve was measured after pretreatment with kynurenic acid, an NMDA receptor antagonist. The activity of the vestibular nerve at rest following acute hypotension induced by SNP or simulating hemorrhage was a greater increase than in control animals. The gain of the vestibular nerve with sinusoidal rotation following acute hypotension increased significantly compared to control animals. The acute hypotension induced by SNP or hemorrhage did not change the activity of the afferent vestibular nerve after kynurenic acid injection. These results suggest that acute hypotension produced excitation of the vestibular hair cells via glutamate excitotoxicity in response to ischemia.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.4
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• pp.363-368
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• 2018

Hypotension is one of the potential causes of dizziness. In this review, we summarize the studies published in recent years about the electrophysiological and pharmacological mechanisms of hypotension-induced dizziness and the role of the vestibular system in the control of blood pressure in response to hypotension. It is postulated that ischemic excitation of the peripheral vestibular hair cells as a result of a reduction in blood flow to the inner ear following hypotension leads to excitation of the central vestibular nuclei, which in turn may produce dizziness after hypotension. In addition, excitation of the vestibular nuclei following hypotension elicits the vestibulosympathetic reflex, and the reflex then regulates blood pressure by a dualcontrol (neurogenic and humoral control) mechanism. In fact, recent studies have shown that peripheral vestibular receptors play a role in the control of blood pressure through neural reflex pathways. This review illustrates the dual-control mechanism of peripheral vestibular receptors in the regulation of blood pressure following hypotension.

• Korean Journal of Otorhinolaryngology-Head and Neck Surgery
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• v.56 no.12
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• pp.749-753
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• 2013

Basically stem cells have characteristics of multi-potency, differentiation into multiple tissue types, and self-renew through proliferation. Recent advances in stem cell biology can make identifying the stem-cell like cells in various mammalian tissues. Stem cells in various tissues can restore damaged tissue. Stem cells from the adult nervous system proliferate to form clonal floating colonies called spheres in vitro, and recent studies have demonstrated sphere formation by cells in the tympanic membrane, vestibular system, spiral ganglion, and partly in the organ of Corti. The presence of stem cells in the ear raises the possibilities for the regeneration of the tympanic membrane & inner ear hair cells & neurons. But the gradual loss of stem cells postnatally in the organ of Corti may correlate with the loss of regenerative capacity and limited hearing restoration. Future strategies using endogenous stem cells in the ear can be the another treatment modality for the patients with intractable inner ear diseases.

• The Journal of Korean Physical Therapy
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• v.12 no.1
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• pp.41-47
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• 2000

BACKGROUND AND PURPOSE. The purpose of this study is to investigate the effect of the disturbed vision on the gait distance parameters on the healthy young population. SUBJECTS. Twenty four healthy college aged individuals are randomly assigned to both a condition with a strobe light and the other condition without a strobe light. METHODS. The instrumentation used for gait analysis is the GaitRite electronic walkway system with a personal IBM computer. The examiner naked all the subjects to walk 6 times on the gait mat without the strobe light and. 6 times on the mat with the strobe light. The first 4 trials were practice and the last two trials were recorded in both conditions. The gait parameters analyzed were as follows : velocity, cadence, step length, and heel to heel base of support. RESULTS. Paired samples t-test used for this study did not found any significant differences between the two conditions because the p-values that were analyzed on the experiment were Utter than 0.05. The gait parameters that were analyzed included cadence, velocity, left and right heel to heel base of support, and left and right step length. DISCUSSION AND CONCLUSION. Based on this population, the condition of disturbed vision via the effect of the strobe light was not significantly challenging to compromise the body's sensory systems. However, in the elderly population, these systems can undergo age related changes. Visual changes rapidly decline in people 60 to 80 years of age and changes in the vestibular system include $20-40\%$ reduction in hair cells.