Search

Objective: Multi-centre collaborative study to develop and refine the design of a prototype thin perimodiolar cochlear implant electrode array and to assess feasibility for use in human subjects.Study Design: Multi-centre temporal bone insertion studies.Materials and Methods: The modiolar research array (MRA) is a thin pre-curved electrode that is held straight for initial insertion with an external sheath rather than an internal stylet. Between November 2006 and February 2009, six iterations of electrode design were studied in 21 separate insertion studies in which 140 electrode insertions were performed in 85 human temporal bones by 12 surgeons. These studies aimed at addressing four fundamental questions related to the electrode concept, being: (1) Could a sheath result in additional intra-cochlear trauma? (2) Could a sheath accommodate variations in cochlea size and anatomies? (3) Could a sheath be inserted via the round window? and (4) Could a sheath be safely removed once the electrode had been inserted? These questions were investigated within these studies using a number of evaluation techniques, including X-ray and microfluoroscopy, acrylic fixation and temporal bone histologic sectioning, temporal bone microdissection of cochlear structures with electrode visualization, rotational tomography, and insertion force analysis.Results: Frequent examples of electrode rotation and tip fold-over were demonstrated with the initial designs. This was typically caused by excessive curvature of the electrode tip, and also difficulty in handling of the electrode and sheath. The degree of tip curvature was progressively relaxed in subsequent versions with a corresponding reduction in the frequency of tip fold-over. Modifications to the sheath facilitated electrode insertion and sheath removal. Insertion studies with the final MRA design demonstrated minimal trauma, excellent perimodiolar placement, and very small electrode dimensions within scala tympani. Force measurements in temporal bones demonstrated negligible force on cochlear structures with angular insertion depths of between 390 and 450°.Conclusion: The MRA is a novel, very thin perimodiolar prototype electrode array that has been developed using a systematic collaborative approach. The different evaluation techniques employed by the investigators contributed to the early identification of issues and generation of solutions. Regarding the four fundamental questions related to the electrode concept, the studies demonstrated that (1) the sheath did not result in additional intra-cochlear trauma; (2) the sheath could accommodate variations in cochlea size and anatomies; (3) the sheath was more successfully inserted via a cochleostomy than via the round window; and (4) the sheath could be safely removed once the electrode had been inserted. [ABSTRACT FROM AUTHOR]

Purpose : This study describes sources of COVID-19 vaccine information and COVID-19 knowledge among sexual and gender minority (SGM) adults in New York City (NYC). Methods : A sample of 986 SGM adults in NYC completed an online survey between June 25 and December 1, 2021. Participants indicated their top three sources of COVID-19 vaccine information from a list of 10 options. Participants were also categorized into low or high COVID-19 knowledge using a 14-item questionnaire. We described knowledge sources, then conducted bivariate and multivariable logistic regression to identify characteristics associated with greater knowledge. Results : The mean age of participants was 29 years (range 18-68 years). Only 12.5% identified their health care provider as a main COVID-19 vaccine information source. Social media (54.9%) and TV news channels (51.4%) were most reported as a main COVID-19 vaccine information source. COVID-19 vaccine knowledge was moderate, with four of eight questions showing correct responses in approximately 70% or more participants. In the multivariable logistic regression model, having at least some college education (adjusted odds ratio [aOR]: 2.34, 95% confidence interval [CI]: 1.55-3.52), attaining a master's degree (aOR: 3.28, 95% CI: 1.93-5.57), reporting a household income of $25,000-$49,999 per year (aOR: 1.68, 95% CI: 1.14-2.46), and having health insurance (aOR: 2.12, 95% CI: 1.51-2.96) were significantly associated with high COVID-19 knowledge. Conclusion : Our sample demonstrated high levels of COVID-19 knowledge, particularly among educated individuals and those with health insurance. Primary access to health information was through social media and TV news channels.

Background: Population-level research evaluating HIV-related stigma among countries with varied national HIV prevalence is scarce. To better understand HIV-related stigma and mitigate its potential negative effects, it is necessary to evaluate its relationship with HIV prevalence, as well as the mechanisms that influence it. This study aimed to analyze how HIV-related stigma correlates with subnational HIV prevalence in three African countries with varied HIV epidemics., Methods: This paper used data from the nationally representative Population-based HIV Impact Assessment (PHIA) surveys conducted from 2015-2017 in Malawi, Zambia, and Tanzania. Each country's sub-national geographic divisions were used to categorize them as low (0-5.4%), middle (5.5-11.2%), and high (11.3-17.1%) HIV prevalence regions in the main analysis. Questions from the survey stigma module were used to measure HIV-related stigma. Logistic regression and multilevel models were performed to assess the associations between the level of sub-national HIV prevalence and HIV-related stigma measures among persons living with, and without, HIV., Results: The results show that the odds of people living without HIV expressing stigmatizing behavior towards PLWH was significantly lower in regions of middle (OR = 0.80, 90%CI = (0.68-0.96)) and high (OR = 0.65, 90%CI = (0.53-0.80)) HIV prevalence when compared to low prevalence regions. The odds of reporting discriminatory attitudes were also lower for those in middle (OR = 0.87, 90%CI = (0.78-0.98)) and high (OR = 0.64, 90%CI = (0.56-0.73)) HIV prevalence regions compared to others. Living in middle and high HIV prevalence regions was associated with lower odds of expressing prejudice toward PLWH (OR = 0.84, 90%CI = (0.71-0.99) and OR = 0.60, 90%CI = (0.45-0.80), respectively) among people living without HIV. Notably, PLWH living in high prevalence regions had higher odds of reporting internalized stigma (OR = 1.48, 90%CI = (1.02-2.14)) compared to those living in low prevalence regions., Conclusions: The results indicate that among people not living with HIV, subnational HIV prevalence was negatively associated with discriminatory attitudes and prejudice towards PLWH, but HIV prevalence was positively associated with self-reported internalized stigma among PLWH. These results provide insight on how resources could be invested to reduce HIV related stigma among both PLWH and those not living with HIV., (© 2023. BioMed Central Ltd., part of Springer Nature.)

Dysregulated neutrophilic inflammation can be highly destructive in chronic inflammatory diseases due to prolonged neutrophil lifespan and continual release of histotoxic mediators in inflamed tissues. Therapeutic induction of neutrophil apoptosis, an immunologically silent form of cell death, may be beneficial in these diseases, provided that the apoptotic neutrophils are efficiently cleared from the tissue. Previous research in our group identified ErbB inhibitors as able to induce neutrophil apoptosis and reduce neutrophilic inflammation both in vitro and in vivo . Here, we extend that work using a clinical ErbB inhibitor, neratinib, which has the potential to be repurposed in inflammatory diseases. We show that neratinib reduces neutrophilic migration o an inflammatory site in zebrafish larvae. Neratinib upregulates efferocytosis and reduces the number of persisting neutrophil corpses in mouse models of acute, but not chronic, lung injury, suggesting that the drug may have therapeutic benefits in acute inflammatory settings. Phosphoproteomic analysis of human neutrophils shows that neratinib modifies the phosphorylation of proteins regulating apoptosis, migration, and efferocytosis. This work identifies a potential mechanism for neratinib in treating acute lung inflammation by upregulating the clearance of dead neutrophils and, through examination of the neutrophil phosphoproteome, provides important insights into the mechanisms by which this may be occurring., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Herman, Wright, Marriott, McCaughran, Bowden, Collins, Renshaw and Prince.)

Background: Animal models for chronic multichannel cochlear implant stimulation and selective neuronal activation contribute to a better understanding of auditory signal processing and central neural plasticity., New Method: This paper describes the design and surgical implantation of a multichannel cochlear implant (CI) system for chronic use in the free-moving gerbil. For chronic stimulation, adult-deafened gerbils were connected to a multichannel commutator that allowed low resistance cable rotation and stable electric connectivity to the current source., Results: Despite the small scale of the gerbil cochlea and auditory brain regions, final electrophysiological mapping experiments revealed selective and tonotopically organized neuronal activation in the auditory cortex. Contact impedances and electrically evoked auditory brainstem responses were stable over several weeks demonstrating the long-term integrity of the implant and the efficacy of the stimulation., Comparison With Existing Methods: Most animal models on multichannel signal processing and stimulation-induced plasticity are limited to larger animals such as ferrets, cats and primates. Multichannel CI stimulation in the free-moving rodent and evidence for selective neuronal activation in gerbil auditory cortex have not been previously reported., Conclusions: Overall, our results show that the gerbil is a robust rodent model for selective and tonotopically organized multichannel CI stimulation. We anticipate that this model provides a useful tool to develop and test both passive stimulation and behavioral training strategies for plastic reorganization and restoration of degraded unilateral and bilateral central auditory signal processing in the hearing impaired and deaf central auditory system., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A method involving headspace solid-phase microextraction (HS-SPME) and comprehensive two-dimensional gas chromatography (GC×GC) coupled to time-of-flight mass spectrometry (TOFMS) was developed and applied to evaluate profiles of volatile compounds present in mainstream tobacco smoke particulate matter trapped on glass fiber filters. Six SPME fibers were tested for the extraction capacities toward selected compounds, showing the best results for the polyacrylate fiber. The optimization of the extraction conditions was carried out using multivariate response surface methodology. Two cigarette types differing in a filter design were analyzed using optimized conditions. A template was built in order to generate comprehensive chemical information, which conceded obtaining consistent information across 24 chromatograms. Principal component analysis (PCA) allowed a clear differentiation of the studied cigarette types. Fisher ratio analysis allowed identification of compounds responsible for the chemical differences between the cigarette samples. Of the selected 143 most important ones, 134 analytes were reduced by the active carbon filter, while for nine, classical cellulose acetate filter was more efficient., (Copyright © 2014 Elsevier B.V. All rights reserved.)

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. The current study was undertaken to determine the auditory phenotype in the Npc1 (nih) mutant mouse model, to extend analyses to histologic evaluation of the inner ear, and to compare our findings to those reported from human patients. Auditory testing revealed a progressive high-frequency hearing loss in Npc1 (-/-) mice that is present as early as postnatal day 20 (P20), well before the onset of overt neurological symptoms, with evidence of abnormalities involving the cochlea, auditory nerve, and brainstem auditory centers. Distortion product otoacoustic emission amplitude and auditory brainstem response latency data provided evidence for a disruption in maturational development of the auditory system in Npc1 (-/-) mice. Anatomical study demonstrated accumulation of lysosomes in neurons, hair cells, and supporting cells of the inner ear in P30 Npc1 (-/-) mice, as well as increased numbers of inclusion bodies, myelin figures, and swollen nerve endings in older (P50-P70) mutant animals. These findings add unique perspective to the pathophysiology of NPC disease and suggest that hearing loss is an early and sensitive marker of disease progression.

Purpose: Validation of a novel minimally invasive, image-guided approach to implant electrodes from three FDA-approved manufacturers-Medel, Cochlear, and Advanced Bionics-in the cochlea via a linear tunnel from the lateral cranium through the facial recess to the cochlea., Methods: Custom microstereotactic frames that mount on bone-implanted fiducial markers and constrain the drill along the desired path were utilized on seven cadaver specimens. A linear tunnel was drilled from the lateral skull to the cochlea followed by a marginal, round window cochleostomy and insertion of the electrode array into the cochlea through the drilled tunnel. Post-insertion CT scan and histological analysis were used to analyze the results., Results: All specimens ([Formula: see text]) were successfully implanted without visible injury to the facial nerve. The Medel electrodes ([Formula: see text]) had minimal intracochlear trauma with 8, 8, and 10 (out of 12) electrodes intracochlear. The Cochlear lateral wall electrodes (straight research arrays) ([Formula: see text]) had minimal trauma with 20 and 21 of 22 electrodes intracochlear. The Advanced Bionics electrodes ([Formula: see text]) were inserted using their insertion tool; one had minimal insertion trauma and 14 of 16 electrodes intracochlear, while the other had violation of the basilar membrane just deep to the cochleostomy following which it remained in scala vestibuli with 13 of 16 electrodes intracochlear., Conclusions: Minimally invasive, image-guided cochlear implantation is possible using electrodes from the three FDA-approved manufacturers. Lateral wall electrodes were associated with less intracochlear trauma suggesting that they may be better suited for this surgical technique.

Objective: This study was performed to investigate the vascular structures of the cochlea that are potentially vulnerable to mechanical trauma during cochlear implant surgery., Background: Despite improvements in surgical technique and electrode design, residual hearing is lost in a significant percentage of cochlear implant patients. Although a variety of factors may contribute, it is widely believed that mechanical trauma plays an important role. This study focused on the vasculature of scala tympani and its potential susceptibility to injury during implant surgery., Methods: Anatomic study of normal human temporal bones prepared by either conventional cross sectioning or by microdissection for examination by light or scanning electron microscopy., Results: Blood vessels located at or near the perilymphatic surface of scala tympani are predominately of the venous type, and they are situated so as to be at risk for trauma during implantation. Those vessels include veins on the lateral wall and floor of scala tympani, the modiolar wall and the undersurface of the osseous lamina and basilar membrane., Conclusion: Injury or occlusion of blood vessels associated with scala tympani may adversely affect inner ear function, potentially contributing to hearing loss following cochlear implantation.

Comprehensive 2D GC coupled to time-of-flight mass spectrometry was applied for the characterization of the particulate phase of mainstream tobacco smoke particulate. Five 3R4F research cigarettes were smoked on a rotary smoking machine under standardized conditions, total particular matter was collected on Cambridge filter pads and extracted using methanol-based liquid extraction and dynamic headspace (DHS) approaches. Automated peak finding and mass spectral deconvolution combined with scripting and manual revision of library hits were used to evaluate the library search results. The revised peak table contained nearly 1800 individual compounds for the DHS sample and over 900 for the solvent extracted sample. These methods of extraction were shown to be complementary, leading to only 11% of repeated analytes, and their combination gave rise to a list of almost 2500 individual compounds., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This report provides an overview of many research projects conducted by the Dallas Cochlear Implant Program, a joint enterprise between the University of Texas at Dallas, the University of Texas Southwestern Medical Center, and Children's Medical Center. The studies extend our knowledge of factors influencing communication outcomes in users of cochlear implants. Multiple designs and statistical techniques are used in the studies described including both cross sectional and longitudinal analyses. Sample sizes vary across the studies, and many of the samples represent large populations of children from North America. Multiple statistical techniques are used by the team to analyze outcomes. The team has provided critical information regarding electrode placement, signal processing, and communication outcomes in users of cochlear implants., (American Academy of Audiology.)

Hypothesis: The goal of this human temporal bone study was to assess the safety and efficacy of round window insertion of the Cochlear Contour Advance electrode and identify any anatomic obstacles that may affect its insertion., Background: Minimizing intracochlear trauma during electrode insertion reduces the risk of losing residual hearing. The Contour Advance electrode is designed for insertion via an anteroinferior cochleostomy, in which drilling causes a degree of inner ear trauma. If consistently successful round window insertions are possible with this electrode, it would allow for better perimodiolar positioning in the basal turn and greater likelihood of hearing preservation., Methods: A total of 16 human temporal bone round window insertions with the Contour Advance electrode were performed at the University of Melbourne and Southwestern Medical Center, Dallas. Surgeons' observations, fluoroscopy, histology and anatomic dissections were analyzed., Results: Successful full insertions of the electrode with minimal resistance and good perimodiolar placement were achieved in less that 50% of cases in the Melbourne series and in two-thirds of cases in the Dallas series. A common finding by both centers was obstruction of electrode entry at the anteroinferior margin of the round window, which prevented optimal scala tympani positioning and often resulted in intracochlear trauma., Conclusion: The anteroinferior region of the round window bony margin influences the trajectory of insertion of the relatively large Contour Advance electrode as well as physically obstructing and distorting the array. A pure round window insertion is not predictable and reliable enough to be a recommended approach for this electrode.

Cochlear implantation is a procedure performed to treat profound hearing loss. Accurately determining the postoperative position of the implant in vivo would permit studying the correlations between implant position and hearing restoration. To solve this problem, we present an approach based on parametric Gradient Vector Flow snakes to segment the electrode array in post-operative CT. By combining this with existing methods for localizing intra-cochlear anatomy, we have developed a system that permits accurate assessment of the implant position in vivo. The system is validated using a set of seven temporal bone specimens. The algorithms were run on pre- and post-operative CTs of the specimens, and the results were compared to histological images. It was found that the position of the arrays observed in the histological images is in excellent agreement with the position of their automatically generated 3D reconstructions in the CT scans.

Objectives/hypothesis: We have previously described a novel, automated, nonrigid, model-based method for determining the intrascalar position of cochlear implant (CI) electrode arrays within human temporal bones using clinically available, flat-panel volume computed tomography (fpVCT). We sought to validate this method by correlating results with anatomic microdissection of CI arrays in cadaveric bones., Study Design: Basic science., Methods: Seven adult cadaveric temporal bones were imaged using fpVCT before and after electrode insertion. Using a statistical model of intracochlear anatomy, an active shape model optimization approach was employed to identify the scalae tympani and vestibuli on the preintervention fpVCT. The array position was estimated by identifying its midline on the postintervention scan and superimposing it onto the preintervention images using rigid registration. Specimens were then microdissected to demonstrate the actual array position., Results: Using microdissection as the standard for ascertaining electrode position, automatic identification of the basilar membrane coupled with postintervention fpVCT for electrode position identification accurately depicted the array location in all seven bones. In four specimens, the array remained within the scala tympani; in three, the basilar membrane was breached., Conclusions: We have anatomically validated this automated method for predicting the intrascalar location of CI arrays using CT. Using this algorithm and pre- and postintervention CT, rapid feedback regarding implant location and expected audiologic outcomes could be obtained in clinical settings.

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., Participants: Twenty-three pigmented guinea pigs were given single, unilateral middle ear applications of a solution containing 3% (n = 3), 2% (n = 5), 1% (n = 5), or 0.5% (n = 5) AZ or saline (n = 5). The contralateral ear served as the untreated control., Main Outcome Measures: The animals were observed for behavioral changes for 2 weeks and then humanely killed. The ears were processed for anatomical evaluation. Morphologic changes were analyzed by quantitation of middle ear changes and cochlear inner and outer hair cell loss. Statistical analysis was performed to examine effects by dose., Results: Analysis revealed extensive middle and inner ear changes associated with all formulations of AZ. Moderate correlation was found between the extent of middle ear changes and AZ concentration (r(2) = 0.59), whereas a strong correlation was seen between inner ear damage and AZ concentration (r(2) = 0.94). Both inner and outer hair cells were affected, with inner hair cell damage consistently greater than outer hair cell damage., Conclusions: The results of this study demonstrate that ototopical AZ can cause middle ear changes and significant hair cell loss in the guinea pig. This finding, together with previous clinical reports, indicates that topical AZ should be used with caution in the clinical setting.

Usher syndrome 3A (USH3A) is an autosomal recessive disorder characterized by progressive loss of hearing and vision due to mutation in the clarin-1 (CLRN1) gene. Lack of an animal model has hindered our ability to understand the function of CLRN1 and the pathophysiology associated with USH3A. Here we report for the first time a mouse model for ear disease in USH3A. Detailed evaluation of inner ear phenotype in the Clrn1 knockout mouse (Clrn1(-/-)) coupled with expression pattern of Clrn1 in the inner ear are presented here. Clrn1 was expressed as early as embryonic day 16.5 in the auditory and vestibular hair cells and associated ganglionic neurons, with its expression being higher in outer hair cells (OHCs) than inner hair cells. Clrn1(-/-) mice showed early onset hearing loss that rapidly progressed to severe levels. Two to three weeks after birth (P14-P21), Clrn1(-/-) mice showed elevated auditory-evoked brainstem response (ABR) thresholds and prolonged peak and interpeak latencies. By P21, approximately 70% of Clrn1(-/-) mice had no detectable ABR and by P30 these mice were deaf. Distortion product otoacoustic emissions were not recordable from Clrn1(-/-) mice. Vestibular function in Clrn1(-/-) mice mirrored the cochlear phenotype, although it deteriorated more gradually than cochlear function. Disorganization of OHC stereocilia was seen as early as P2 and by P21 OHC loss was observed. In sum, hair cell dysfunction and prolonged peak latencies in vestibular and cochlear evoked potentials in Clrn1(-/-) mice strongly indicate that Clrn1 is necessary for hair cell function and associated neural activation.

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. A search for such a model led us to the Phex Hyp-Duk mouse, a mutant allele of the Phex gene causing X-linked hypophosphatemic rickets. The hemizygous male (Phex Hyp-Duk/Y) was previously reported to exhibit various abnormalities during adulthood, including thickening of bone, ELH and hearing loss. The reported inner-ear phenotype was suggestive of progressive pathology and spontaneous development of ELH postnatally, but not conclusive. The main focuses of this report are to further characterize the inner ear phenotype in Phex Hyp-Duk/Y mice and to test the hypotheses that (a) the Phex Hyp-Duk/Y mouse develops ELH and hearing loss postnatally, and (b) the development of ELH in the Phex Hyp-Duk/Y mouse is associated with obstruction of the endolymphatic duct (ED) due to thickening of the surrounding bone. Auditory brainstem response (ABR) recordings at various times points and histological analysis of representative temporal bones reveal that Phex Hyp-Duk/Y mice typically develop adult onset, asymmetric, progressive hearing loss closely followed by the onset of ELH. ABR and histological data show that functional degeneration precedes structural degeneration. The major degenerative correlate of hearing loss and ELH in the mutants is the primary loss of spiral ganglion cells. Further, Phex Hyp-Duk/Y mice develop ELH without evidence of ED obstruction, supporting the idea that ELH can be induced by a mechanism other than the blockade of longitudinal flow of endolymphatic fluid, and occlusion of ED is not a prerequisite for the development of ELH in patients.

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. Organization of stereocilia and cell polarization may be dependent on proper orientation of structural components residing in the apical portion of the cell during development. We used electron and immunofluorescent microscopy to examine structural maturation of outer hair cells in av3J mice with emphasis on the fonticulus, basal body/centriole complex, actin mesh, and the microtubule network during initiation of bundle organization, between embryonic day (E) 16.5 and postnatal day 5 (P5). We found major ultrastructural rearrangements near the hair cell surface in av3J mice. Earliest changes were in kinocilia, basal body, and stereocilia positioning and microtubule arrangement once the kinocilia had lateralized to the side of the cell (between E16.5 and postnatal day [P] 0, before cuticular plate formation and stereocilia elongation). By P0, the developing fonticulus in av mice appeared enlarged, with a normal vesicle density. Stereocilia bundle disorganization increased after P0, with disruptions of the actin mesh within the cuticular plate. These observations support the hypothesis that mutations in Pcdh15 in av3J mice adversely affect coordinated maturation of apical cell components, resulting in disturbed stereocilia bundle polarity in av mice., ((c) 2008 Wiley-Liss, Inc.)

We have characterized a new allele of the protocadherin 15 gene (designatedPcdh15(av-6J)) that arose as a spontaneous, recessive mutation in the C57BL/6J inbred strain at Jackson Laboratory. Analysis revealed an inframe deletion in Pcdh15, which is predicted to result in partial deletion of cadherin domain (domain 9) in Pcdh15. Morphologic study revealed normal to moderately defective cochlear hair cell stereocilia in Pcdh15(av-6J) mutants at postnatal day 2 (P2). Stereocilia abnormalities were consistently present at P5 and P10. Degenerative changes including loss of inner and outer hair cells were seen at P20, with severe sensory cell loss in all cochlear turns occurring by P40. The hair cell phenotype observed in the 6J allele between P0 and P20 is the least severe phenotype yet observed in Pcdh15 alleles. However, young Pcdh15(av-6J) mice are unresponsive to auditory stimulation and show circling behavior indicative of vestibular dysfunction. Since these animals show severe functional deficits but have relatively mild stereocilia defects at a young age they may provide an appropriate model to test for a direct role of Pcdh15 in mechanotransduction.

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. In this work we present new findings on inner ear pathology in four alleles of av mice with differing mutations of Pcdh15 as well as varying alterations in inner ear morphology. Two alleles with in-frame deletion mutations (Pcdh15 (av-J) and Pcdh15 (av-2J)) and two presumptive functional null alleles (Pcdh15 (av-3J) and Pcdh15 (av-Tg)) were studied. Light and electron microscopic observations demonstrated that the severity of cochlear and vestibular pathology in these animals correlates positively with the extent of mutation in Pcdh15 from embryonic day 18 (E18) up to 12 months. Electron microscopic analysis of immature ears indicated early abnormalities in the arrangement of stereocilia and the inner and outer hair cell cuticular plates, stereocilia rootlets, and the actin meshwork within the cuticular plate. In severe cases, displacement of the kinocilium and alterations in the shape of the cuticular plate was also observed. Mice harboring in-frame deletion mutations showed less disorganization of stereocilia and cuticular plates in the organ of Corti than the presumptive functional null alleles at P0-P10. A slower progression of pathology was also seen via light microscopy in older animals with in-frame deletions, compared to the presumptive functional null mutations. In summary, our results demonstrate that mutation in Pcdh15 affects the initial formation of stereocilia bundles with associated changes in the actin meshwork within the cuticular plate; these effects are more pronounced in the presumed null mutation compared to mutations that only affect the extracellular domain. The positive correlation of severity of effects with extent of mutation can be seen well into adulthood.

Laser Capture Microdissection (LCM) allows microscopic procurement of specific cell types from tissue sections that can then be used for gene expression analysis. We first tested this method with sections of adult mouse inner ears and subsequently applied it to human inner ear sections. The morphology of the various cell types within the inner ear is well preserved in formalin fixed paraffin embedded (FFPE) sections, making it easier to identify cell types and their boundaries. Recovery of good quality RNA from FFPE sections can be challenging, however, recent studies in cancer research demonstrated that it is possible to carry out gene expression analysis of FFPE material. Thus, a method developed using mouse FFPE tissue can be applied to human archival temporal bones. This is important because the majority of human temporal bone banks have specimens preserved in formalin and a technique for retrospective analysis of human archival ear tissue is needed. We used mouse FFPE inner ear sections to procure distinct populations of cells from the various functional domains (organ of Corti, spiral ganglion, etc.) by LCM. RNA was extracted from captured cells, amplified, and assessed for quality. Expression of selected genes was tested by RT-PCR. In addition to housekeeping genes, we were able to detect cell type specific markers, such as Myosin 7a, p27(kip1) and neurofilament gene transcripts that confirmed the likely composition of cells in the sample. We also tested the method described above on FFPE sections from human crista ampullaris. These sections were approximately a year old. Populations of cells from the epithelium and stroma were collected and analyzed independently for gene expression. The method described here has potential use in many areas of hearing research. For example, following exposure to noise, ototoxic drugs or age, it would be highly desirable to analyze gene expression profiles of selected populations of cells within the organ of Corti or spiral ganglion cells rather than a mixed population of cells from whole inner ear tissue. Also, this method can be applied for analysis of human archival ear tissue.

The development of hybrid electroacoustic devices has made conservation of residual hearing an important goal in cochlear implant surgery. Our laboratory has recently conducted anatomical studies directed toward better understanding mechanisms underlying loss of residual hearing associated with electrode insertion. This paper provides an overview of observations based on microdissection, scanning electron microscopy and temporal bone histology relating to inner ear injury that may occur during implant surgery. Trauma to cochlear structures including lateral wall tissues, the basilar membrane, the osseous spiral lamina and the modiolus is considered in relation to the implications of specific types of injury for hearing preservation. These findings are relevant to the design of future implant devices and to various important issues regarding the surgical technique used for implantation, including the possible use of the round window as a portal of entry for electrode insertion.

Objective: This report describes a temporal bone microdissection method for laboratory evaluation of cochlear implant electrodes., Design: Anatomic study of human temporal bones., Methods: Implant electrodes from three manufacturers were inserted into temporal bones which were processed and dissected so as to visualize spatial relationships between the electrodes and sensorineural structures of the cochlea., Results and Conclusion: Images are presented illustrating perimodiolar and lateral wall electrode arrays after insertion into the human cochlea and functional characteristics of the two electrode types are discussed. Temporal bone microdissection permits direct, three-dimensional study of inner ear structures and is an effective method for evaluation of the insertional properties of cochlear implant electrodes. Copyright (c) 2005 John Wiley & Sons, Ltd.

Objective: To clarify the anatomic characteristics, cause, and surgical outcomes relating to fixation of the stapes footplate in children., Study Design: Retrospective case review and four-center histopathologic study of temporal bones., Setting: Tertiary referral center., Patients: We reviewed charts and histologic specimens from 12 children, aged 7 to 13 years, who underwent surgery for footplate fixation. We also studied stapes footplates in 288 temporal bones from 181 children ranging from newborn (20-44 weeks of gestation) to 13 years of age., Main Outcome Measure: Anomalies of the stapes footplate in children., Results: The average age of diagnosis of hearing loss was 6.6 years. Criteria for a diagnosis of otosclerosis were progression of a conductive hearing loss and an intraoperative finding of fixation of the anterior stapediovestibular joint in five patients. In contrast, a nonhomogeneous, thickened, fixed footplate and the absence of an annular ligament were indicators of congenital fixation in six children. In one child, there was neither new bone from the otic capsule nor any obvious otosclerotic foci. In the temporal bone study, 17 of 181 (9.4%) children had anomalies of the stapes footplates, with ankylosis in 4 (2.2%). In two subjects (1.1%), there was an otosclerotic focus not in contact with the stapes footplate., Conclusion: Children younger than 6 years with various congenital anomalies are more likely to have congenital footplate fixation, which will present intraoperatively as a thickened footplate with a partial or absent annular ligament. Children older than 6 years with progressive conductive hearing loss are more likely to have otosclerosis, which presents as fixation of the anterior stapediovestibular joint. The difference in surgical outcomes is probably related to different degrees of footplate abnormality.

Objective: To evaluate temporal bone histopathology in infants with congenital heart defects (CHD)., Study Design and Setting: A retrospective review of our temporal bone collection was conducted to identify temporal bones acquired from infants with CHD. Subjects were divided into nonsyndromic and syndromic CHD groups. The presence of temporal bone abnormalities and the incidence of abnormalities that may result in hearing impairment were determined., Results: Thirty-eight temporal bones obtained from 16 infants with nonsyndromic CHD and 4 with syndromic CHD were evaluated. Nonsyndromic CHD cases had abnormalities such as a mesenchymal remnant, malformed stapes, persistent stapedial artery, shallow round window, dehiscent facial nerve canal, short cochlea, strial basophilic deposits, deformity of the spiral ligament, bulging Reissner's membrane, hypoplastic lateral semicircular canal, and cupular deposits. Syndromic CHD cases had abnormalities including narrow round window niche, facial canal dehiscence, strial basophilic deposits and cysts, and outer hair cell loss. Middle and inner ear abnormalities that may impair hearing were observed in 6 subjects with nonsyndromic CHD and in 1 subject with syndromic CHD., Conclusions: A wide variety of temporal bone defects were documented in infants with CHD. Congenital middle and inner ear abnormalities should be anticipated in the hearing assessment and otologic surgery of infants with CHD.

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. Light and scanning electron microscopic studies showed that vestibular hair cells from presumptive null alleles Pcdh15(av-Tg) and Pcdh15(av-3J) are morphologically similar to vestibular sensory cells from control littermates, suggesting that the observed phenotype in these alleles might be a result of a central, rather than peripheral, defect. In the present study, a combination of physiologic and anatomic methods was used to more thoroughly investigate the source of vestibular dysfunction in Ames waltzer mice. Analysis of vestibular evoked potentials and angular vestibulo-ocular reflexes revealed a lack of physiologic response to linear and angular acceleratory stimuli in Pcdh15 mutant mice. Optokinetic reflex function was diminished but still present in the mutant animals, suggesting that the defect is primarily peripheral in nature. These findings indicate that the mutation in Pcdh15 results in either a functional abnormality in the vestibular receptor organs or that the defects are limited to the vestibular nerve. AM1-43 dye uptake has been shown to correlate with normal transduction function in hair cells. Dye uptake was found to be dramatically reduced in Pcdh15 mutants compared to control littermates, suggesting that the mutation affects hair cell function, although structural abnormalities consistent with significant vestibular dysfunction are not apparent by light and scanning electron microscopy in the vestibular neuroepithelia of young animals.

Objective: To describe temporal bone histopathology in an infant with partial trisomies of chromosomes 13 and 14., Methods: Temporal bones were taken at autopsy from a 7-day-old neonate who has both partial trisomy 13 and partial trisomy 14. The right temporal bone was embedded in celloidin and sections were cut for microscopic examination. The left temporal bone was studied by microdissection. The middle ear was examined and the inner ear sensory organs dissected for study by light microscopy., Results: The external auditory canal was stenotic in both ears. Remnants of mesenchymal tissue were present in the middle ear cavity. The middle ear ossicles were normal except that both stapes were malformed with a single crus and a small footplate. Both facial nerve canals were dehiscent in the region of the oval window. The cochlea was malformed bilaterally; a scala communis was present and the basilar membrane was abnormally short. No loss of sensory cells was observed in either cochlea. Blood vessels were found traversing scala vestibuli and there were cystic lesions in the stria vascularis and spiral ligament. In the middle cochlear turn, the bony wall of scala vestibuli and the osseous spiral lamina were covered by a substantial layer of connective tissue which appeared to be an extension of the spiral ligament. This is an unusual finding which, to the authors' knowledge, has not been previously reported. In the vestibular apparatus a wide communication was present between the saccule and utricle., Conclusions: As this study demonstrates, abnormalities of the external, middle, and inner ear may occur in cases of partial trisomy 13 and partial trisomy 14. Both temporal bone findings and clinical features in partial trisomy 13 and partial trisomy 14 to some degree overlap with those of trisomy 13, partial trisomy 13 and partial trisomy 14.

Mutation in the protocadherin 15 (Pcdh15) gene causes hair cell dysfunction and is associated with abnormal stereocilia development. We have characterized the first allele (Pcdh15(av-nmf19)) of Ames waltzer (av) obtained by N-ethyl-N-nitrosourea (ENU) mutagenesis. Pcdh15(av-nmf19) was generated in the Neuroscience Mutagenesis Facility (NMF) at The Jackson Lab (Bar Habor, USA). Pcdh15(av-nmf19) mutants display circling and abnormal swimming behavior along with lack of auditory-evoked brainstem response at the highest intensities tested. Mutation analysis shows base substitution (A--> G) in the consensus splice donor sequence linked to exon 14 resulting in the skipping of exon 14 and the splicing of exon 13-15. This results in the introduction of a stop codon in the coding sequence of exon 15 due to shift in the reading frame. The effect of nmf19 mutation is expected to be severe since the expressed Pcdh15 protein is predicted to truncate in the 5th cadherin domain. Abnormalities of cochlear hair cell stereocilia are apparent in Pcdh15(av-nmf19) mutants near the time of birth and by about P15 (15 days after birth) there is evidence of sensory cell degeneration. Disorganization of outer hair cell stereocilia is observed as early as P2. Inner hair cell stereocilia are also affected, but less severely than those of the outer hair cells. These results are consistent with characteristics of the mutation in the Pcdh15(av-nmf19) allele and they support our previous finding that Protocadherin 15 plays an important role in hair-bundle morphogenesis.

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. The right temporal bone was studied by microdissection. The middle ear was examined and the inner ear sensory organs dissected for study by light microscopy. The left temporal bone was embedded in celloidin, and sections were cut for microscopic examination., Results: Middle ear structures were normal bilaterally. There was, however, evidence of otitis media in both middle ears, which was more severe on the left side. Inner and outer hair cell loss, patchy degeneration of organ of Corti, and loss of nerve fibers in the osseous spiral lamina were found in the basal and middle turns of both cochleas. Basophilic deposits in the stria vascularis were observed in the apical portion of the left cochlea., Conclusions: Inner ear sensorineural degeneration may occur in Leigh disease. Possible cochlear dysfunction caused by the degenerative changes needs to be considered in the hearing assessment of patients with Leigh disease.

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. The right-side temporal bone was studied by microdissection. The middle ear was examined, and the inner ear sensory organs dissected for study by light microscopy. The left-side temporal bone was embedded in celloidin, and sections were cut for microscopic examination., Results: Chronic otitis media was observed in both ears. Inflammation, effusion, and adhesions were present in the middle ear space. The malleus was malformed, and the chorda tympani nerve was found to pass through the bone of the malleus bilaterally. There was an area of sharply defined outer hair cell loss in the lower basal turn of the right-side organ of Corti, and defects were noted in the bone of the apical osseous spiral lamina in both cochleae., Conclusion: In addition to the presence of otitis media, the likelihood of congenital abnormalities of the middle and inner ear should be considered in the assessment of patients with Wolf-Hirschhorn syndrome with hearing impairment.

A recessive deafness mutation in the mouse arose spontaneously and was identified in a colony segregating a null allele of the gastrin-releasing peptide receptor (Grpr) locus. Auditory-evoked brain stem response measurements revealed deafness in 7-week-old affected mice. By linkage analyses, the mutant phenotype was mapped near marker D10Mit186 and the protocadherin gene Pcdh15. As shown by complementation testing, the new mutation is allelic with Ames waltzer (Pcdh15(av)). Sequencing mutant-derived brain Pcdh15 cDNAs identified the insertion of a cytosine residue at nucleotide position c2099 (2099insC), which results in a frame-shift and premature stop codon. Abnormal stereocilia on inner and outer hair cells of the organ of Corti were identified by scanning electron microscopy as early as postnatal day 0 and cross-sectional histology revealed severe neuroepithelial degeneration in cochleas of 30-50-day-old mutants. The new allele of Ames waltzer, designated Pcdh15(av-Jfb), may aid in studying the histopathology associated with Usher syndrome type 1F, which is caused by a functional null allele of PCDH15.

The neuroepithelia of the inner ear contain hair cells that function as mechanoreceptors to transduce sound and motion signals. Mutations affecting these neuroepithelia cause deafness and vestibular dysfuction in humans. Ames waltzer (av) is a recessive mutation found in mice that causes deafness and a balance disorder associated with the degeneration of inner ear neuroepithelia. Here we report that the gene that harbours the av mutation encodes a novel protocadherin. Cochlear hair cells in the av mutants show abnormal stereocilia by 10 days after birth (P10). This is the first evidence for the requirement of a protocadherin for normal function of the mammalian inner ear.

Products currently used as injectable soft tissue replacement materials in the dermatologic, plastic and reconstructive, and urological fields exhibit several shortfalls including reactivity, migration, rapid degradation, and necessity of a donor site. This study examines the feasibility of providing a particulate acellular human dermal matrix for injection as a soft tissue replacement material that addresses many of these issues. Animal feasibility studies tested differences in implant performance related to processing techniques, matrix concentration, and volume of the collagen matrix to be injected. Results demonstrated that processing techniques that involve shearing and tearing of the dermal collagen matrix resulted in frayed and damaged collagen bundles and led to rapid resorption or loss of the implant, when injected subcutaneously in a rat model. Processing the collagen matrix in liquid nitrogen resulted in less damage to the collagen matrix and exhibited longer persistence, when compared to the damaged collagen matrix. This particulate matrix also exhibits rapid repopulation by host cells that should enhance revascularization and remodeling. The particulate nature of this processed dermal matrix allows for easy delivery of concentrations up to 330 mg/mL, which exceeds that of other currently used products. This increased concentration should allow for decreased need of "overcorrection" and repeated injections., (Copyright 2000 John Wiley & Sons, Inc. Biomed Mater Res (Appl Biomater) 58: 10-15, 2001)

This report presents new findings regarding a recessive insertional mutation in the transgenic line TgN2742Rpw that causes deafness and circling behavior in mice homozygous for the mutation. The mutant locus was mapped to a region on mouse chromosome 10 close to three spontaneous recessive mutations causing deafness: Ames waltzer (av), Waltzer (v), and Jackson circler (jc). Complementation testing revealed that the TgN2742Rpw mutation is allelic with av. Histological and auditory brainstem response (ABR) evaluation of animals that have the new allele balanced with the av(J) allele (called compound heterozygotes, TgN2742Rpw/av(J)) supports our genetic analysis. ABR evaluation shows complete absence of auditory response throughout the life span of TgN2742Rpw/av(J) compound heterozygotes. Scanning electron microscopy revealed abnormalities of inner and outer hair cell stereocilia in the cochleae of TgN2742Rpw mutants at 10 days after birth (DAB). The organ of Corti subsequently undergoes degeneration, leading to nearly complete loss of the cochlear neuroepithelium in older mutants by about 50 DAB. The vestibular neuroepithelia remain morphologically normal until at least 30 DAB. However, by 50 days, degenerative changes are evident in the saccular macula, which progresses to total loss of the saccular neuroepithelium in older animals. The new allele of av reported here will be designated av(TgN2742Rpw).

Objective: To develop an animal model for testing efficacy of anti-inflammatory drugs designed to treat external ear canal (EAC) disease., Methods: Histological and morphometric methods were used to characterize EAC inflammation produced by topical application of tetradecanoylphorbol acetate (TPA) in mice. The effects of both single and repeated TPA applications were studied. A treatment trial was performed to evaluate the effects of a ciprofloxacin/hydrocortisone suspension on TPA-induced EAC inflammation. In 10 animals, two bilateral applications of TPA were made, spaced 24 hours apart. Immediately after the second TPA application, otic suspension was applied unilaterally four times over a 48-hour period. The contralateral EACs were left untreated to provide TPA-only controls., Results: Twenty-four hours after a single TPA application, EAC skin showed polymorphonuclear (PMN) leukocyte infiltration, vascular dilation, and thickening of the dermis and epidermis. Dermal and epidermal thickening were more pronounced after two TPA applications and PMN leukocyte infiltration remained high 48 hours after a second TPA placement. After treatment with the otic suspension, PMN leukocyte counts were reduced by an average of 76% relative to EACs that received TPA only. There was also statistically significant reduction of dermal swelling and a trend toward reduced epidermal thickness. Vascular dilation was clearly reduced as well EACs that received four applications of the suspension alone showed no adverse effects compared with those that received saline., Conclusion: TPA-induced inflammation of the mouse EAC provides a suitable model for testing the therapeutic efficacy of anti-inflammatory agents being considered for clinical use.

This article describes a new recessive insertional mutation in the transgenic line TgN2742Rpw that causes deafness and circling behavior in mice. Histologic analysis revealed virtually complete loss of the cochlear neuroepithelium (the organ of Corti) in adult mutant mice. In association with the neuroepithelial changes, there is a dramatic reduction of the cochlear nerve supply. Adult mutants also show morphological defects of the vestibular apparatus, including degeneration of the saccular neuroepithelium and occasional malformation of utricular otoconia. Audiometric evaluations demonstrated that the mice displaying the circling phenotype are completely deaf. Molecular analysis of this mutant line revealed that the transgenic insertion occurred without creating a large deletion of the host DNA sequences. The mutant locus was mapped to a region on mouse chromosome 10, where other spontaneous, recessive mutations causing deafness in mice have been mapped.

Hyaluronic acid is a glycosaminoglycan (GAG) which has been demonstrated by biochemical and histochemical methods to be present in inner ear fluids and tissues. However, consistent labeling of hyaluronic acid or other GAGs in inner ear fluid compartments in histologic sections has not been previously reported. Staining and characterization of GAGs in the normal inner ear fluids of humans and guinea pigs are described in this report. It was initially observed that alcian blue produces dense staining of the endolymphatic and perilymphatic fluid compartments in celloidin embedded material. Results obtained with alcian blue were subsequently compared to staining obtained with hematoxylin/eosin and periodic acid/Schiff base. Enzyme digestion was also performed with testicular hyaluronidase (bovine and ovine), streptomyces hyaluronidase, chondroitase ABC, and alpha-amylase. Results of the differential staining and enzyme digestion studies suggest that the substances in inner ear fluids that stain with alcian blue are a combination of chondroitin sulfate-4, -5 and/or -6 and hyaluronic acid.

It is widely believed that congenital cholesteatoma originates from epidermoid cell rests in the temporal bone. Congenital cholesteatomas of the anterior-superior middle ear may arise from such a rest, known as the epidermoid formation (EF), which has been described by Michaels and others. The EF is thought to disappear by 33 weeks' gestation in most cases; however, if it persists beyond fetal life, it may provide a nidus for cholesteatoma formation. The authors studied human temporal bones from individuals ranging from 20 weeks' gestation to 5 years of age to investigate pre- and postnatal occurrence of the EF. A total of 106 temporal bones were surveyed; 76 of these were fetal specimens and 30 were postnatal. EFs were present in 14 (18.4%) of the fetal specimens; they were identified in four (13.3%) of the postnatal temporal bones, with the oldest being 2 years, 7 months of age. Multiple EFs within a single temporal bone were also present in some cases. Although the EFs were composed of cells morphologically identical to those of the external ear canal epidermis, none of the specimens showed keratinization. These findings support the contention that EFs do occasionally persist into postnatal life and may be a source of cholesteatoma. However, a clear transition from epidermoid formation to unequivocal cholesteatoma has not yet been demonstrated.

External ear development is a lengthy and complex process that extends from early embryonic life until well into the postnatal period. Initial development of the auricle and external auditory canal during the fourth and fifth weeks of gestation is closely associated with anatomical changes involving the pharyngeal arch apparatus of the human embryo. The auricle and external canal are well formed by the time of birth but do not attain their full size and adult configuration until about 9 years of age. Sebaceous and modified apocrine glands, which are responsible for cerumen production, begin their development at about 5 months gestation in association with hair follicles in the outer portion of the external canal. Although they appear anatomically mature before birth, these glands do not reach full functional capacity until puberty.

Electrocochleography (ECochG) was used to evaluate cochlear function in guinea pigs with experimentally induced endolymphatic hydrops (ELH) before and after osmotic dehydration with either glycerol or urea. We surgically induced ELH in the right ears of 9 guinea pigs, while the right ears of 6 guinea pigs received a sham operation. The left ears of the 15 animals constituted the normal group. Eight weeks after surgery, summating potential (SP) and action potential (AP) amplitudes were measured prior to and following the administration of glycerol or urea. The SPs and SP/AP ratios were reduced in all groups, with no significant differences among groups or between dehydrating agents. Some of the hydropic ears, however, did show an increased AP threshold and a recruitment effect. In measurements from 6 additional animals, serum osmolarity increased more with urea than with glycerol. The guinea pig model remains valuable for investigation of ELH, even though it differs in significant respects from ELH in humans.