• Journal of Audiology & Otology
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• v.23 no.2
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• pp.69-75
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• 2019

Background and Objectives: The antioxidant ebselen will be able to limit or prevent the ototoxicity arising from 2-hydroxypropyl-β-cyclodextrin (HPβCD). Niemann-Pick Type C (NPC) disease is a disorder of lysosomal storage manifested in sphingolipidosis. Recently, it was noted that experimental use of HPβCD could partially resolve the symptoms in both animals and human patients. Despite its desirable effect, HPβCD can induce hearing loss, which is the only major side effect noted to date. Understanding of the pathophysiology of hearing impairment after administration of HPβCD and further development of preventive methods are essential to reduce the ototoxic side effect. The mechanisms of HPβCD-induced ototoxicity remain unknown, but the resulting pathology bears some resemblance to other ototoxic agents, which involves oxidative stress pathways. To indirectly determine the involvement of oxidative stress in HPβCD-induced ototoxicity, we tested the efficacy of an antioxidant reagent, ebselen, on the extent of inner ear side effects caused by HPβCD. Materials and Methods: Ebselen was applied prior to administration of HPβCD in mice. Auditory brainstem response thresholds and otopathology were assessed one week later. Bilateral effects of the drug treatments also were examined. Results: HPβCD-alone resulted in bilateral, severe, and selective loss of outer hair cells from base to apex with an abrupt transition between lesions and intact areas. Ebselen co-treatment did not ameliorate HPβCD-induced hearing loss or alter the resulting histopathology. Conclusions: The results indirectly suggest that cochlear damage by HPβCD is unrelated to reactive oxygen species formation. However, further research into the mechanism(s) of HPβCD otopathology is necessary.

• Korean Journal of Audiology
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• v.23 no.2
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• pp.69-75
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• 2019

Background and Objectives: The antioxidant ebselen will be able to limit or prevent the ototoxicity arising from 2-hydroxypropyl-β-cyclodextrin (HPβCD). Niemann-Pick Type C (NPC) disease is a disorder of lysosomal storage manifested in sphingolipidosis. Recently, it was noted that experimental use of HPβCD could partially resolve the symptoms in both animals and human patients. Despite its desirable effect, HPβCD can induce hearing loss, which is the only major side effect noted to date. Understanding of the pathophysiology of hearing impairment after administration of HPβCD and further development of preventive methods are essential to reduce the ototoxic side effect. The mechanisms of HPβCD-induced ototoxicity remain unknown, but the resulting pathology bears some resemblance to other ototoxic agents, which involves oxidative stress pathways. To indirectly determine the involvement of oxidative stress in HPβCD-induced ototoxicity, we tested the efficacy of an antioxidant reagent, ebselen, on the extent of inner ear side effects caused by HPβCD. Materials and Methods: Ebselen was applied prior to administration of HPβCD in mice. Auditory brainstem response thresholds and otopathology were assessed one week later. Bilateral effects of the drug treatments also were examined. Results: HPβCD-alone resulted in bilateral, severe, and selective loss of outer hair cells from base to apex with an abrupt transition between lesions and intact areas. Ebselen co-treatment did not ameliorate HPβCD-induced hearing loss or alter the resulting histopathology. Conclusions: The results indirectly suggest that cochlear damage by HPβCD is unrelated to reactive oxygen species formation. However, further research into the mechanism(s) of HPβCD otopathology is necessary.

• Journal of Biomedical Engineering Research
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• v.28 no.6
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• pp.732-743
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• 2007

Background noise is one of the major complaints of not only hearing impaired persons but also normal listeners. This paper describes the results of two experiments in which speech recognition performance was determined for listeners with normal hearing and sensorineural hearing loss in noise environment. First, we compared speech enhancement algorithms by evaluation speech recognition ability in various speech-to-noise ratios and types of noise. Next, speech enhancement algorithms by reducing background noise were presented and evaluated to improve speech intelligibility for sensorineural hearing impairment listeners. We tested three noise reduction methods using single-microphone, such as spectrum subtraction and companding, Wiener filter method, and maximum likelihood envelop estimation. Their responses in background noise were investigated and compared with those by the speech enhancement algorithm that presented in this paper. The methods improved speech recognition test score for the sensorineural hearing impaired listeners, but not for normal listeners. The results suggest the speech enhancement algorithm with the loudness compression can improve speech intelligibility for listeners with sensorineural hearing loss.

• Biomolecules & Therapeutics
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• v.24 no.3
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• pp.328-337
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• 2016

We examined whether wogonin (WO) improved hippocampal neuronal activity, behavioral alterations and cognitive impairment, in rats induced by administration of trimethyltin (TMT), an organotin compound that is neurotoxic to these animals. The ability of WO to improve cognitive efficacy in the TMT-induced neurodegenerative rats was investigated using a passive avoidance test, and the Morris water maze test, and using immunohistochemistry to detect components of the acetylcholinergic system, brain-derived neurotrophic factor (BDNF), and cAMP-response element-binding protein (CREB) expression. Rats injected with TMT showed impairments in learning and memory and daily administration of WO improved memory function, and reduced aggressive behavior. Administration of WO significantly alleviated the TMT-induced loss of cholinergic immunoreactivity and restored the hippocampal expression levels of BDNF and CREB proteins and their encoding mRNAs to normal levels. These findings suggest that WO might be useful as a new therapy for treatment of various neurodegenerative diseases.

• Journal of Photoscience
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• v.1 no.1
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• pp.9-14
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• 1994

Exposure of isolated intact mitochondria to near UV to visible light resulted in not only loss of respiration, the most well-documented phenomenon regarding phototoxic effects in the respiring organelles, but also lipid peroxidation of membranes and mitochondrial swelling; these turned out to be O$_2$-dependent and thus prevented by anaerobiosis, enhanced by a partial deuteration of the suspension medium, and suppressed by the presence of a singlet oxygen ($^1O_2$) scavenger. Measurements of the spectral dependence of such detrimental effects of light on mitochondrial structure and function revealed that all the resulting spectra bear a significant resemblance to the action spectrum for photogeneration of $^1O_2$ from mitochondrial membranes, which in turn carries the spectral characteristics of light absorption by mitochondrial Fe-S centers. Futhermore, destructing the Fe-S centers by a mercurial treatment of mitochondria brought about a striking reduction of the light-induced membrane peroxidation and swelling of mitochondria. These results are consistent with the suggestion that the impairment of functional, structural integrity of mitochondria caused by strong irradiation is directly related to the production of $^1O_2$ in mitochondria, photosensitized by the Fe-S centers. This paper also presents kinetic data which indicate that, among various membrane-bound protein systems associated with mitochondrial energy metabolism, the respiratory chain is the primary target for photodamage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4C
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• pp.433-439
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• 2007

This paper derives an approximate expression for the output SINR(Signal to Interference plus Noise Ratio) of Applebaum type adaptive array under the scenario of the interferer's proximity to the desired signal. The approximation is made in terms of array geometry, the arrival direction of desired signal and that of an interfering signal. An interferer in the close proximity of target signal is shown to drastically impair the away performance. An approximate expression for interferer arrival direction which results in a predetermined performance loss is also obtained in terms of array configurations. Proposed approximation agrees with the computer calculated performance impairment when the two signals are apart by less than eight degrees. The allowable proximity of the interfering signal increases with the number of array elements.

• Speech Sciences
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• v.12 no.4
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• pp.197-202
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• 2005

The cochlear implantation(CI) as an useful tool for aural rehabilitation in bilateral severe to profound hearing impairment. However, CI prefer to usually one ear in spite of bilateral hearing impaired. because of the various characteristics of hearing loss, the hearing conservation for the future possibility, and socioeconomic condition of hearing impaired person and their families. The unilateral CI has limitations such as a directional loss, a difficult speech understanding in noise and a neural plasticity. These limitations will be overcome by hearing aid(HA) which is familiar with hearing impairer. but HA fitting for bimodal-binaural hearing are difficult because the difference output characteristic of HA and CI. This study will be confirm realities of use of HA in unilateral cochlear implantee. For this goal, 25(m:f=10:15) child participated who are used to HA for 1 to 17 months. We had telephone interviews with their mother about use of HA, change of auditory performance and own voice. As the results, hearing threshold levels of unimplanted ear, the use of a appropriate HA, implanted and aided hearing threshold level(HTL) are must be considered for successful biomodal-binaural hearing. Especially, implanted and aided HTL should be very useful parameter for a prediction of HA effect and a criterion of selection for bilateral cochlear implantation.

• Journal of Audiology & Otology
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• v.25 no.1
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• pp.8-13
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• 2021

Background and Objectives: In 2013, the Singapore government reviewed and expanded the Senior Mobility Fund (SMF) to provide subsidy for assistive devices, including hearing aids (HA). While SMF has improved accessibility to HA, its impact on HA acquisition has not been determined. The study aims to elucidate the influence of SMF on HA acquisition and the relationship between financial funding and compliance to HA use. Subjects and Methods: Retrospective review of 643 patients seen between January 2017 to January 2018 at the earnose and throat specialist outpatient clinic, who were referred for a hearing aid evaluation. Of the 643 patients, 109 patients with baseline hearing handicap (HH) scores recorded, and no formal diagnosis of cognitive impairment were included. The patients were grouped according to SMF eligibility and clinical data were obtained. Results: The odds ratio for acquiring HA was significantly higher with SMF, regardless of HH scores. When looking at actual degree of hearing loss (DHL), HA uptake was significantly higher in the least severe of DHL categories. There is no relationship between SMF and compliance to HA use. However, HH score is positively correlated with data log in regression analyses. Conclusions: SMF appears to influence HA acquisition. Especially in financially funded patients with low self-perceived HH, the benefits of HA may be underappreciated given the few hours of HA use. Further studies are warranted to investigate the impact of financial funding on outcomes of HA users to help policy planners and clinicians be prudent in the utilization of SMF.

• Korean Journal of Audiology
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• v.25 no.1
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• pp.8-13
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• 2021

Background and Objectives: In 2013, the Singapore government reviewed and expanded the Senior Mobility Fund (SMF) to provide subsidy for assistive devices, including hearing aids (HA). While SMF has improved accessibility to HA, its impact on HA acquisition has not been determined. The study aims to elucidate the influence of SMF on HA acquisition and the relationship between financial funding and compliance to HA use. Subjects and Methods: Retrospective review of 643 patients seen between January 2017 to January 2018 at the earnose and throat specialist outpatient clinic, who were referred for a hearing aid evaluation. Of the 643 patients, 109 patients with baseline hearing handicap (HH) scores recorded, and no formal diagnosis of cognitive impairment were included. The patients were grouped according to SMF eligibility and clinical data were obtained. Results: The odds ratio for acquiring HA was significantly higher with SMF, regardless of HH scores. When looking at actual degree of hearing loss (DHL), HA uptake was significantly higher in the least severe of DHL categories. There is no relationship between SMF and compliance to HA use. However, HH score is positively correlated with data log in regression analyses. Conclusions: SMF appears to influence HA acquisition. Especially in financially funded patients with low self-perceived HH, the benefits of HA may be underappreciated given the few hours of HA use. Further studies are warranted to investigate the impact of financial funding on outcomes of HA users to help policy planners and clinicians be prudent in the utilization of SMF.

• Biomolecules & Therapeutics
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• v.31 no.2
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• pp.148-160
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• 2023

Depression is a neuropsychiatric disorder associated with persistent stress and disruption of neuronal function. Persistent stress causes neuronal atrophy, including loss of synapses and reduced size of the hippocampus and prefrontal cortex. These alterations are associated with neural dysfunction, including mood disturbances, cognitive impairment, and behavioral changes. Synaptic plasticity is the fundamental function of neural networks in response to various stimuli and acts by reorganizing neuronal structure, function, and connections from the molecular to the behavioral level. In this review, we describe the alterations in synaptic plasticity as underlying pathological mechanisms for depression in animal models and humans. We further elaborate on the significance of phytochemicals as bioactive agents that can positively modulate stress-induced, aberrant synaptic activity. Bioactive agents, including flavonoids, terpenes, saponins, and lignans, have been reported to upregulate brain-derived neurotrophic factor expression and release, suppress neuronal loss, and activate the relevant signaling pathways, including TrkB, ERK, Akt, and mTOR pathways, resulting in increased spine maturation and synaptic numbers in the neuronal cells and in the brains of stressed animals. In clinical trials, phytochemical usage is regarded as safe and well-tolerated for suppressing stress-related parameters in patients with depression. Thus, intake of phytochemicals with safe and active effects on synaptic plasticity may be a strategy for preventing neuronal damage and alleviating depression in a stressful life.