No Reduction in the 226-Hz Probe Tone Acoustic Reflex Amplitude Following Severe Inner Hair Cell Loss in Chinchillas.

The relationship between the middle ear acoustic reflex (AR) and inner hair cell (IHC) loss is currently unknown. Given that IHC are believed to convey nearly all acoustic information to the central auditory nervous system, it has been assumed that loss of IHC would significantly impact the AR. To evaluate this relationship, we assessed the presence and amplitude of the AR in chinchillas before and after treatment with carboplatin, an anticancer drug that reliably and selectively destroys IHC in this species.

A missense mutation in causes hippocampal learning deficits in mice.

Although a wide variety of genetic tools has been developed to study learning and memory, the molecular basis of memory encoding remains incompletely understood. Here, we undertook an unbiased approach to identify novel genes critical for memory encoding. From a large-scale, in vivo mutagenesis screen using contextual fear conditioning, we isolated in mice a mutant, named , with spatial learning deficits.

Effect of Selective Carboplatin-Induced Inner Hair Cell Loss on Temporal Integration in Chinchillas.

Integration of acoustic information over time is essential for processing complex stimuli, such as speech, due to its continuous variability along the time domain. In both humans and animals, perception of acoustic stimuli is a function of both stimulus intensity and duration. For brief acoustic stimuli, as duration increases, thresholds decrease by approximately 3 dB for every doubling in duration until stimulus duration reaches 500 ms, a phenomenon known as temporal integration.

Audiogenic Seizures in the Knock-Out Mouse Are Induced by Deletion in Subcortical, VGlut2-Expressing Excitatory Neurons and Require Deletion in the Inferior Colliculus.

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and the leading monogenetic cause of autism. One symptom of FXS and autism is sensory hypersensitivity (also called sensory over-responsivity). Perhaps related to this, the audiogenic seizure (AGS) is arguably the most robust behavioral phenotype in the FXS mouse model-the knock-out (KO) mouse.

Ephrins and Ephs in cochlear innervation and implications for advancing cochlear implant function.

Objectives/hypothesis: Determine if the neuronal pathfinding cues resulting from Eph/ephrin interaction in the inner ear play a role in establishing the tonotopic innervation of the cochlea.

Study Design: Protein expression of Ephs and ephrins was evaluated in the inner ear of mice and chicks. Subsequently, in vitro, in vivo, and functional electrophysiologic studies were performed to indicate that Ephs and ephrins play a role regulating the normal innervation patterns in the mouse inner ear.

Hearing loss is an early consequence of Npc1 gene deletion in the mouse model of Niemann-Pick disease, type C.

Niemann-Pick disease, type C1 (NPC1) is a rare lysosomal lipidosis that is most often the result of biallelic mutations in NPC1, and is characterized by a fatal neurological degeneration. The pathophysiology is complex, and the natural history of the disease is poorly understood. Recent findings from patients with NPC1 and hearing loss suggest that multiple steps along the auditory pathway are affected.

Ototopic applications of povidone iodine/dexamethasone in the rat.

Hypothesis: Repeated applications of low-concentration povidone iodine (PI) combined with dexamethasone (Dex) through a tympanic membrane ventilation tube will not cause ototoxic changes in the rat.

Background: Otitis externa (OE) and acute otitis media (AOM) are 2 of the most common otologic disorders requiring outpatient antibiotic treatment. The development of topical treatments that are easy to administer would help to limit systemic exposure to antibiotics in these patients.

Cochlear implant device failure secondary to cholesterol granuloma-mediated cochlear erosion.

Study Design: Case report.

Setting: A tertiary care pediatric hospital.

Patient: A 7-year-old boy complained of retroauricular pain 3.

Effects of cochlear drilling with Piezosurgery Medical device in rats.

Objectives/hypothesis: Drilling on the otic capsule for cochleostomy should be less traumatic to the cochlea with the Piezosurgery Medical device (PZ) than with a standard diamond drill (DD). "Soft" cochleostomy is used for preservation of residual hearing in cochlear implant patients. PZ drilling can be used for accurate cochleostomy placement with minimal soft-tissue damage and may be superior for atraumatic drilling on the cochlea, as compared with a DD.

Comparison of systemic and otic administration of ofloxacin.

Objectives: To assess the feasibility of delivering ofloxacin across the intact tympanic membrane; to compare middle ear bioavailability of ofloxacin after otic and systemic administrations; to determine distribution of otically delivered ofloxacin to other tissues.

Study Design: A prospective, controlled animal study.

Methods: Rats underwent surgery wherein the middle ear cavity was opened and filled with saline.

Ototoxicity of topical azithromycin solutions in the guinea pig.

Objective: To investigate possible ototoxic effects of topical azithromycin (AZ) in the guinea pig.

Design: A prospective, controlled animal study.

Setting: The University of Texas Southwestern Medical Center at Dallas.

Controlled release of hepatocyte growth factor from a bovine acellular scaffold for vocal fold reconstruction.

A bovine acellular scaffold was found to facilitate tissue remodeling in a rat model of vocal fold injury, whereas hepatocyte growth factor (HGF) has been shown to have an antiscarring effect in the larynx. This study examined the loading and release kinetics of HGF in vitro, and the potential of the acellular scaffold as a timed-release system for the delivery of HGF in vivo. Bilateral wounds were created in the posterior vocal folds of 20 rats, with HGF-loaded acellular scaffolds implanted into the wounds unilaterally, and scaffolds without HGF implanted into the contralateral vocal folds as control.

Biofilm presence in humans with chronic suppurative otitis media.

Objective: To study the presence of biofilm formation in humans with chronic suppurative otitis media (CSOM).

Study Design: Cross-sectional study.

Setting: Tertiary academic hospital.

A bovine acellular scaffold for vocal fold reconstruction in a rat model.

With a rat model of vocal fold injury, this study examined the in vivo host response to an acellular xenogeneic scaffold derived from the bovine vocal fold lamina propria, and the potential of the scaffold for constructive tissue remodeling. Bilateral wounds were created in the posterior vocal folds of 20 rats, and bovine acellular scaffolds were implanted into the wounds unilaterally, with the contralateral vocal folds as control. The rats were humanely sacrificed after 3 days, 7 days, 1 month, and 3 months, and the coronal sections of their larynges were examined histologically.

Cochlear neuronal tracing for frequency mapping with DiI, NeuroVue, and Golgi methods.

Conclusions: Labeling experiments using NeuroVue Red dye allowed us to demonstrate individual afferent fiber tracks in the cochlea from the synaptic region of the inner hair cell in the organ of Corti (OC) to the spiral ganglion in Rosenthal's canal. Further optimization is necessary to obtain 3-dimensional (3D) neural distribution in the apical region for frequency mapping.

Objectives: We intend to develop a method by which the radial fibers of the spiral ganglion (SG) can be individually visualized and tracked in 3D from the base to the apex of the cochlea.

A mouse model with postnatal endolymphatic hydrops and hearing loss.

Endolymphatic hydrops (ELH), hearing loss and neuronal degeneration occur together in a variety of clinically significant disorders, including Meniere's disease (MD). However, the sequence of these pathological changes and their relationship to each other are not well understood. In this regard, an animal model that spontaneously develops these features postnatally would be useful for research purposes.

Development of outer hair cells in Ames waltzer mice: mutation in protocadherin 15 affects development of cuticular plate and associated structures.

The Ames waltzer (av) mouse mutant harbors a mutation in the protocadherin 15 gene (Pcdh15) and is a model for deafness in Usher syndrome 1F and nonsyndromic deafness DFNB23. Mutation in Pcdh15 affects stereocilia morphogenesis and polarity. Disruptions of apical cellular components in outer hair cells have also been described in av mutants.

Progression of inner ear pathology in Ames waltzer mice and the role of protocadherin 15 in hair cell development.

The Ames waltzer (av) mouse mutant exhibits auditory and vestibular abnormalities resulting from mutation of protocadherin 15 (Pcdh15). Ames waltzer has been identified as an animal model for inner ear pathology associated with Usher syndrome type 1F. Studies correlating anatomical phenotype with severity of genetic defect in various av alleles are providing better understanding of the role played by Pcdh15 in inner ear development and of sensorineural abnormalities associated with alterations in Pcdh15 protein structure as a result of gene mutation.

Bacterial biofilm formation on a human cochlear implant.

Objective: To report the characteristics of a bacterial biofilm from the surface of a cochlear implant.

Background: Bacterial biofilm formation on implanted devices causes intractable infections and device extrusions necessitating device removal, with loss of function. More information is needed about biofilm characteristics and interactions with the implant surface before better treatments can be designed.

Characterization of vestibular dysfunction in the mouse model for Usher syndrome 1F.

The deaf-circling Ames waltzer (av) mouse harbors a mutation in the protocadherin 15 (Pcdh15) gene and is a model for inner ear defects associated with Usher syndrome type 1F. Earlier studies showed altered cochlear hair cell morphology in young av mice. In contrast, no structural abnormality consistent with significant vestibular dysfunction in young av mice was observed.

Cochlear degeneration in leigh disease: histopathologic features.

Objective: To describe pathologic findings from temporal bones acquired from an infant with Leigh disease.

Study Design: Retrospective case review.

Materials And Methods: Temporal bones were taken at autopsy from an 8-month-old infant with Leigh disease.

Histopathological basis of hearing impairment in Wolf-Hirschhorn syndrome.

Objectives/hypothesis: To perform histological examination of temporal bones acquired from an infant with Wolf-Hirschhorn syndrome with an emphasis on identifying abnormalities that might be responsible for hearing impairment in this disorder.

Study Design: Retrospective case review.

Methods: Temporal bones were taken at autopsy from a 10-month-old infant with Wolf-Hirschhorn syndrome.