Objective Verification of Acute Tinnitus and Validation of Efficacy of Systemic Steroids in Rats.

BACKGROUND: This study was performed to identify acute tinnitus and evaluate the efficacy of steroids for noise-induced acute tinnitus by measuring the gap-prepulse inhibition of the acoustic startle (GPIAS) value in an animal model. METHODS: Nineteen rats (the noise group [n = 7] and the noise + dexamethasone [DEX] group [n = 12]) were exposed to narrow-band noise centered at 16 kHz from a sound generator for 4 hours. The noise + DEX group received intraperitoneal steroid administration daily for 5 days (1.5 mg/kg/day) after completing noise exposure. Auditory brainstem response and GPIAS value were measured just prior to, and 1 day after noise exposure and on days 1 and 10 days after completing steroid administration. The changes in cochlear structure were evaluated by histological analysis. RESULTS: The threshold shift was checked 1 and 10 days after intraperitoneal steroid injection, and no differences in threshold shift were observed between the two groups in each frequency except for 32 kHz 1 day after steroid injection. The mean GPIAS value in the noise + DEX group (36.4% ± 14.1%) was significantly higher than that in the noise group (16.4% ± 18.8%) 10 days after intraperitoneal steroid administration (P = 0.017). There were no pathological changes associated with noise trauma in the two groups as determined on hematoxylin and eosin and immunohistochemical staining. CONCLUSION: An acute tinnitus model with minimal structural changes by noise exposure was set up, and used to verify tinnitus objectively by measuring the GPIAS value. Steroid therapy for control of tinnitus was validated in this animal model.

Memantine Attenuates Salicylate-induced Tinnitus Possibly by Reducing NR2B Expression in Auditory Cortex of Rat.

Memantine, a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, suppresses the release of excessive levels of glutamate that may induce neuronal excitation. Here we investigated the effects of memantine on salicylate-induced tinnitus model. The expressions of the activity-regulated cytoskeleton-associated protein (ARC) and tumor necrosis factor-alpha (TNFα) genes; as well as the NMDA receptor subunit 2B (NR2B) gene and protein, were examined in the SH-SY5Y cells and the animal model. We also used gap-prepulse inhibition of the acoustic startle reflex (GPIAS) and noise burst prepulse inhibition of acoustic startle, and the auditory brainstem level (electrophysiological recordings of auditory brainstem responses, ABR) and NR2B expression level in the auditory cortex to evaluate whether memantine could reduce salicylate-mediated behavioral disturbances. NR2B was significantly upregulated in salicylate-treated cells, but downregulated after memantine treatment. Similarly, expression of the inflammatory cytokine genes TNFα and immediate-early gene ARC was significantly increased in the salicylate-treated cells, and decreased when the cells were treated with memantine. These results were confirmed by NR2B immunocytochemistry. GPIAS was attenuated to a significantly lesser extent in rats treated with a combination of salicylate and memantine than in those treated with salicylate only. The mean ABR threshold in both groups was not significant different before and 1 day after the end of treatment. Additionally, NR2B protein expression in the auditory cortex was markedly increased in the salicylate-treated group, whereas it was reduced in the memantine-treated group. These results indicate that memantine is useful for the treatment of salicylate-induced tinnitus.

The Relationship between Epidemiologic Factors and Usage Pattern of Hair Care Products in Korea.

BACKGROUND: For hair care products that are used almost everyday, it is important to estimate the cumulative dosage of long-term exposure and to assess the effects on the human body. Little data are available to evaluate actual daily usage in Asian populations. OBJECTIVE: Reliable exposure data for hair care products is essential to conduct safety assessments. METHODS: We evaluated the actual usage pattern and amounts by checking the daily log over a 2-week period, to obtain all the data regarding the participants' hair care preferences. And, statistical analyses were conducted to analyze the daily use amount (g/d) and daily usage per hair length (g/cm/d), and other variables by sex, age group, and hair oiliness. RESULTS: Throughout this study, we found that female users consumed significantly larger daily amounts of shampoo and rinse. Male groups used more hair gel and spray than female groups. Interestingly, all the hair care products studied scored higher levels of usage among men when calibrated per unit length. Koreans tend to use lesser amount of rinse although their hairs are usually thicker than the Western hairs. CONCLUSION: This study provides exposure information for commonly used hair care products, which will be useful for risk assessment purposes.

Effects of transient auditory deprivation during critical periods on the development of auditory temporal processing.

OBJECTIVES: The central auditory pathway matures through sensory experiences and it is known that sensory experiences during periods called critical periods exert an important influence on brain development. The present study aimed to investigate whether temporary auditory deprivation during critical periods (CPs) could have a detrimental effect on the development of auditory temporal processing. MATERIALS AND METHODS: Twelve neonatal rats were randomly assigned to control and study groups; Study group experienced temporary (18-20 days) auditory deprivation during CPs (Early deprivation study group). Outcome measures included changes in auditory brainstem response (ABR), gap prepulse inhibition of the acoustic startle reflex (GPIAS), and gap detection threshold (GDT). To further delineate the specific role of CPs in the outcome measures above, the same paradigm was applied in adult rats (Late deprivation group) and the findings were compared with those of the neonatal rats. RESULTS: Soon after the restoration of hearing, early deprivation study animals showed a significantly lower GPIAS at intermediate gap durations and a larger GDT than early deprivation controls, but these differences became insignificant after subsequent auditory inputs. Additionally, the ABR results showed significantly delayed latencies of waves IV, V, and interpeak latencies of wave I-III and wave I-V in study group. Late deprivation group didn't exhibit any deterioration in temporal processing following sensory deprivation. CONCLUSION: Taken together, the present results suggest that transient auditory deprivation during CPs might cause reversible disruptions in the development of temporal processing.

The effects of postnatal phthalate exposure on the development of auditory temporal processing in rats.

OBJECTIVE: The central auditory pathway is known to continue its development during the postnatal critical periods and is shaped by experience and sensory inputs. Phthalate, a known neurotoxic material, has been reported to be associated with attention deficits in children, impacting many infant neurobehaviors. The objective of this study was to investigate the potential effects of neonatal phthalate exposure on the development of auditory temporal processing. METHODS: Neonatal Sprague-Dawley rats were randomly assigned into two groups: The phthalate group (n = 6), and the control group (n = 6). Phthalate was given once per day from postnatal day 8 (P8) to P28. Upon completion, at P28, the Auditory Brainstem Response (ABR) and Gap Prepulse Inhibition of Acoustic Startle response (GPIAS) at each gap duration (2, 5, 10, 20, 50 and 80 ms) were measured, and gap detection threshold (GDT) was calculated. These outcomes were compared between the two groups. RESULTS: Hearing thresholds by ABR showed no significant differences at all frequencies between the two groups. Regarding GPIAS, no significant difference was observed, except at a gap duration of 20 ms (p = 0.037). The mean GDT of the phthalate group (44.0 ms) was higher than that of the control group (20.0 ms), but without statistical significance (p = 0.065). Moreover, the phthalate group tended to demonstrate more of a scattered distribution in the GDT group than the in the control group. CONCLUSION: Neonatal phthalate exposure may disrupt the development of auditory temporal processing in rats.

Compressed single pixel imaging in the spatial frequency domain.

We have developed compressed sensing single pixel spatial frequency domain imaging (cs-SFDI) to characterize tissue optical properties over a wide field of view ( 35 ?? mm × 35 ?? mm ) using multiple near-infrared (NIR) wavelengths simultaneously. Our approach takes advantage of the relatively sparse spatial content required for mapping tissue optical properties at length scales comparable to the transport scattering length in tissue ( l tr ? 1 ?? mm ) and the high bandwidth available for spectral encoding using a single-element detector. cs-SFDI recovered absorption ( ? a ) and reduced scattering ( ? s ? ) coefficients of a tissue phantom at three NIR wavelengths (660, 850, and 940 nm) within 7.6% and 4.3% of absolute values determined using camera-based SFDI, respectively. These results suggest that cs-SFDI can be developed as a multi- and hyperspectral imaging modality for quantitative, dynamic imaging of tissue optical and physiological properties.

Trans-canal laser irradiation reduces tinnitus perception of salicylate treated rat.

The aim of this study was to find out the effect of low-level laser therapy (LLLT) on salicylate-induced tinnitus in the rat model. Fourteen Sprague-Dawley rats (8 weeks; 240-280 gm) were divided into 2 groups (study group, control group). Rats of both groups were treated with 400 mg/kg/day of sodium salicylate for 8 consecutive days. Tinnitus was monitored using GPIAS (Gap Prepulse Inhibition of Acoustic Startle) 2 h after first salicylate treatment, and every 24 h during 9 days of treatment. Rats in laser group were irradiated to each ear with wavelength of 830 nm diode laser (165 mW/cm(2)) for 30 min daily for 8 days. During salicylate treatment, rats of study group irradiated with low level laser showed significantly higher GPIAS values throughout the experiment. Therapeutic effect of LLLT is demonstrated in animal tinnitus model by means of GPIAS. Further experimental studies are needed to find possible mechanisms and better methods to improve LLLT efficacy.

Parameter optimization for applying the prepulse gap paradigm to humans.

BACKGROUND AND OBJECTIVES: Turner and colleagues introduced a new method that can detect tinnitus in animals. The stimulus is composed of a small background noise that is identical to the pitch of the tinnitus and a large pulse noise that can evoke a startle response. In normal rats, the gap decreases the startle reflex. However, in tinnitus rats, the gap does not decrease the startle reflex. The goal of this study was to optimize the stimulation paradigm so that the prepulse inhibition of N1-P2 amplitude would be maximized in the normal human subjects. SUBJECTS AND METHODS: Seven normal control subjects without tinnitus were recruited. The stimulus was composed of two different sounds: the softer background noise and the louder pulse noise. A 50 msec silent gap was inserted before the pulse noise as the gap condition (G condition) but not in the no-gap condition (N condition). The averaged amplitude of the N1-P2 cortical response was recorded for the G and N conditions. RESULTS: The G/N ratio was the smallest when the gap was 20 msec prior to the pulse noise. The G/N ratio was 84.8±16.8% with the Hanning window and 78.5±5.9% without the window. The G/N ratio was 91.1±24.9%, 78.0±5.4%, and 79.0±18.1% when the intensity of the background noise was 10, 20, and 32 dB SL, respectively. When the intensity of the background noise was 20 and 32 dB SL, the N1-P2 amplitude of the G condition was significantly smaller than that of the N condition. CONCLUSIONS: The optimal stimulus should be composed of the 1 kHz pulse noise without Hanning window. The intensity of the background noise should be 20 dB HL and the location of the gap should be 20 msec prior to the pulse noise. It seems that with these optimized parameters we could expect a 78.0% inhibition of N1-P2 amplitude in normal subjects without tinnitus.

Comparisons of electromagnetic and piezoelectric floating-mass transducers in human cadaveric temporal bones.

Electromagnetic floating-mass transducers for implantable middle-ear hearing devices (IMEHDs) afford the advantages of a simple surgical implantation procedure and easy attachment to the ossicles. However, their shortcomings include susceptibility to interference from environmental electromagnetic fields, relatively high current consumption, and a limited ability to output high-frequency vibrations. To address these limitations, a piezoelectric floating-mass transducer (PFMT) has recently been developed. This paper presents the results of a comparative study of these two types of vibration transducer developed for IMEHDs. The differential electromagnetic floating-mass transducer (DFMT) and the PFMT were implanted in two different sets of three cadaveric human temporal bones. The resulting stapes displacements were measured and compared on the basis of the ASTM standard for describing the output characteristics of IMEHDs. The experimental results show that the PFMT can produce significantly higher equivalent sound pressure levels above 3 kHz, due to the flat response of the PFMT, than can the DFMT. Thus, it is expected that the PFMT can be utilized to compensate for high-frequency sensorineural hearing loss.

Discovery of Maritrema jebuensis n. sp. (Digenea: Microphallidae) from the Asian Shore Crab, Hemigrapsus sanguineus, in Korea.

Maritrema spp. (Digenea: Microphallidae) are parasites of birds, but have not been found in the Republic of Korea. In this study, metacercariae of Maritrema sp. were discovered in the Asian shore crab, Hemigrapsus sanguineus, caught in the mud-flats of Jebu-do, Hwasung-gun, Gyeonggi-do, and the adult flukes were confirmed by experimental infection into mice. Based on the symmetric ribbon-like vitellarium, adult flukes of Maritrema sp. were identified, but did not belong to previously described species in terms of the following morphologic characteristics: ceca reaching to the lateral wall at the anterior border of the ovary; ventral sucker larger than oral sucker; a prominent metraterm; and vitellarium forming a complete ring. Hence, we named this microphallid M. jebuensis n. sp. after the island where the second intermediate hosts were collected. From this study, it has been shown that Maritrema sp. is distributed in Korea and transmitted by the Asian shore crab, H. sanguineus.

Efficacy of transnasal nebulized surfactant on experimental otitis media with effusion in guinea pig.

OBJECTIVE: Recently experimental trials have demonstrated that nebulized natural surfactant is effective in the treatment of experimental otitis media with effusion (OME). Two methodologically incomplete studies using animal models of induced OME have reported that nebulized surfactant can improve Eustachian tube function. There have been no reports that investigated the efficacy of the nebulized surfactant for OME using analysis of tympanic membrane vibration. In this study, we evaluated the therapeutic effect of nebulized natural surfactant by investigation of tympanic membrane vibration. MATERIALS AND METHODS: The guinea pigs (n=20) were divided into three groups. Four normal guinea pigs without any treatment were used as normal controls. Sixteen pigs were given experimental OME in both ear and then divided into two groups. The OME model of guinea pig was created by transbullar injection 10 microl of lipopolysaccharide in saline. Experimental group 1 (n=8) was nebulized phosphate buffered saline (PBS). Experimental group 2 (n=8) was nebulized natural bovine surfactant. The transnasal nebulization was repeated for 7 days in both experimental groups. On the 8th day, both experimental groups and normal control group were measured the tympanic membrane vibration by laser Doppler vibrometer (LDV), and additionally histopathologic observation was performed by scanning electron microscope (SEM). RESULTS: The TM vibration velocity in nebulized PBS group showed significantly reduced mainly at low frequencies. However, nebulized natural surfactant group recovered the reduction of tympanic membrane vibration. In nebulized PBS group, SEM showed severe thickened subepithelial layer and hyperplasia of gland structure. However, in nebulized natural surfactant group, SEM showed the reduced the thickness of subepithelial layer and the loss of glandular hyperplasia. CONCLUSION: From our results, the nebulized natural surfactant is postulated to be effective in the treatment of intractable OME in animal model. The measurement of tympanic membrane vibration for analysis of middle ear mechanics was significantly corresponding to the middle ear mucosal changes. LDV is a useful tool for investigate the therapeutic effect of nebulized surfactant in experimental OME. With supporting clinical studies, nebulization of natural surfactant may become noninvasive treatment of OME in future.

The effect of increased inner ear pressure on tympanic membrane vibration.

BACKGROUND & OBJECTIVE: It has been suggested that increased inner ear pressure can affect the stiffness of the tympano-ossicular conductive system. However, the published literature contains few studies on changes of middle ear mechanics caused by increased inner ear pressure. In this study, we evaluated the effects of increased inner ear pressure on tympanic membrane vibration in guinea pigs using a laser Doppler vibrometer (LDV). MATERIALS AND METHODS: We used 10 male guinea pigs (weighing 250 g each) with normal eardrums and Preyer reflexes were used for the experiment. Inner ear pressure was modified by two approaches--directly via a tube placed in the inner ear (n=5) and indirectly via a tube placed in the subaracnoid space (n=5). Slow uniform pressure (microl/min) was infused until constant pressure was maintained. At this time, an artificial endolymph or perilymph was injected with a constant pressure of 100 and 300 mm H2O. We measured the umbo velocity using a LDV. RESULTS: A positive pressure load decreased the umbo vibration at low frequencies but did not change the umbo vibration at mid and high frequencies. The umbo velocity had a greater reduction for an endolymphatic pressure load than for a perilymphatic pressure load. The largest change in velocity was noted at a frequency of 0.1 kHz. There was no significant change in velocity at higher frequencies, except for 5 kHz. CONCLUSION: LDV is a good tool to analyze middle ear function and it has the potential indirectly to diagnose an increase in endolymphatic or perilymphatic pressure.

The use of piperacillin-tazobactam coated tympanostomy tubes against ciprofloxacin-resistant Pseudomonas biofilm formation: an in vitro study.

BACKGROUND AND OBJECTIVE: Bacterial biofilm formation has been implicated in the high rate of persistent otorrhea after tympanostomy tube insertion. It has been suggested that the tube material may be an important factor in the development of otorrhea. Recently we reported the presence of ciprofloxacin-resistant Pseudomonas aeruginosa (CRPA) biofilms on infected tympanostomy tubes following the use of intractable post-tympanostomy tubes and the onset of otorrhea. In this study, we have evaluated the resistance of piperacillin-tazobactam coated with chitosan on a tympanostomy tube to prevent CRPA biofilm formation in vitro. MATERIALS AND METHODS: Three sets each of piperacillin-tazobactam coated silicone tubes (n=5), commercial silver-oxide coated silicone tubes (Activent, Silic) (n=5) and control uncoated tympanostomy tubes (Paparella type 1) (n=5) were processed for evaluation. The piperacillin-tazobactam coated tympanostomy tubes were compared with the silver-oxide coated tubes and the uncoated control tubes for resistance to CRPA biofilm formation after in vitro incubation. RESULTS: Scanning electron microscopy showed that the surface of the silver-oxide coated tube (Activent) formed a thick biofilm with crusts as well as an uncoated tube. In contrast, the surface of a piperacillin-tazobactam coated tympanostomy tube showed virtually no CRPA biofilm formation. CONCLUSION: The piperacillin-tazobactam coated tympanostomy tube showed resistance to CRPA biofilm formation. The piperacillin-tazobactam coating may be useful to reduce CRPA biofilm formation; however, further in vivo studies are necessary.

Tegumental ultrastructure of adult Gynaecotyla squatarolae (Digenea: Microphallidae).

Gynaecotyla squatarolae (Digenea: Microphallidae) adult flukes were recovered from experimental chicks at day 4-6 post-infection and their tegumental ultrastructure was observed with a scanning electron microscopy. They were pyriform in shape, and their anterior halves were concaved ventrally. The whole body surface was covered with tegumental spines, which were wide and 16-17 digitated between oral and ventral suckers. The density of spines and number of digits decreased posteriorly. The oral sucker was subterminal and the excretory pore was at the posterior end of the worm. Two ventral suckers were similar in appearance and protruded near midline of the worm. The genital atrium was dextral to the small ventral sucker. The dorsal surface was covered with tegumental spines, but the spines were sparser than on the ventral surface. On the middle portion of the dorsal surface, a small opening presumed to be the Laurer's canal was seen. From these findings, it has been confirmed that the adult G. squatarolae has unique characteristics in the surface ultrastructure.

Antibacterial effect of octylcyanoacrylate against methicillin-resistant Staphylococcus aureus isolates from patients with chronic suppurative otitis media.

UNLABELLED: There has been a steady increase in the number of cases of methicillin-resistant Staphylococcus aureus (MRSA) otorrhea; this is a growing medical concern. For otological surgery in children, octylcyanoacrylate can be an alternative method of closure for surgical incisions. Recent in vitro studies have shown that octylcyanoacrylate is effective as an antimicrobical barrier. To date, there have been only rare reports on the antibacterial effect of octylcyanoacrylate against MRSA. The purpose of this study is to determine the antimicrobial effects of octylcyanoacrylate against the MRSA that was isolated from patients with chronic suppurative otitis media. MATERIALS AND METHODS: Clinical MRSA (n=20) bacteria and methicillin-sensitive SA (MSSA) (n=20) were obtained from patients. The susceptibilities to various antibiotics were determined by disk diffusion method. RESULTS: MSSA was sensitive to octylcyanoacrylate. The antibacterial activity of octylcyanoacrylate was weak against MRSA. CONCLUSION: Our results demonstrated that octylcyanoacrylate has slight antibacterial activity against MRSA.

Fabrication and optimal design of differential electromagnetic transducer for implantable middle ear hearing device.

A differential electromagnetic transducer (DET), with similar frequency characteristics to those of a normal middle ear, is designed and implemented for use in an implantable middle ear hearing device (IMEHD). To optimize the characteristics of the DET that depend on the electromagnetically forced vibration, a theoretical analysis is conducted to design the vibrating part. The electromagnetic force of the DET is simulated according to the design parameters of the coil size using a finite element analysis (FEA). As a result, the maximal vibration force is achieved when the optimal length and thickness of the cylindrical coil is 70% of the length of the magnets and 56% of their radius. The vibration characteristics of the DET are then simulated when applying the maximal force. The optimally designed DET is implemented using MEMS technology and vibration experiments carried out with the fabricated DET in an unloaded state. The vibrating displacement of the DET is about 200 nm within a range between 0.1 and 1.5 kHz when a current of 1 mA(rms) is applied to the coil. To investigate the usefulness of the DET, in vitro and in vivo experiments are conducted using the ossicular chain of a cadaver and guinea pig, and the results verify that the implemented DET performs well as a transducer for an IMEHD.