Power wheelchair usage and repair are associated: a retrospective analysis.

Purpose: This study evaluates the effect of power wheelchair telemonitoring and battery charging training on user charging behavior and repair measures and assesses the relationship between wheelchair usage and repair measures to support technician-led servicing.Methods: This is a retrospective analysis of two matched cohorts with a total of n=237 users from the NHS service dataset. In the training cohort, a wheelchair usage telemonitoring device monitored the battery usage of n=119 power wheelchair users for 12 months. Users whose battery charging behavior was not optimal were instructed on appropriate charging practices. Wheelchair usage parameters of wheelchair drive and power time every month were used to predict repairs and associated costs.Results: Fifty-four out of 119 users in the training cohort did not charge batteries regularly and were instructed on appropriate charging. Twenty-six of them changed their behavior and charged their batteries every night. This cohort experienced reduced battery repairs by 18%, wheelchair repairs by 11%, and repair costs by £3,092 compared to a matched standard care cohort (n=118). User age and drive time were associated with repair measures. Drive time predicted time-to-failure for wheelchair parts and classified failure risk with the area under the receiver operating characteristic curve as 0.71 (95% CI 0.61 to 0.82; p<.001). Conclusions: By leveraging the significant relationships between wheelchair usage and repairs, wheelchair users at risk of part failures can be identified, and technician-led servicing tools for proactive interventions can be developed. Wheelchair battery health telemonitoring and instructing users on appropriate battery charging reduced repairs and associated costs.

Proactive wheelchair servicing by repair technicians in collaboration with wheelchair users safeguards users against critical part failures and minimises repair-related operating costs for service providers.Providers should leverage wheelchair telemonitoring technologies and related research outputs to improve repair services and support their clients' continued mobility and community participation.It is important that healthcare plans and policies recognise the benefits of proactive wheelchair servicing and use data as a tool to allocate device usage and performance-based reimbursements.

Effects of the WHO 8-step wheelchair-service-delivery process on wheelchair users in El Salvador: a cohort study.

PURPOSE: To test the hypotheses that, after the delivery of manual wheelchairs following the WHO 8-step service-delivery process, wheelchair-related health and quality of life, wheelchair skills, wheelchair use, and poverty probability would improve; and that the number of wheelchair repairs required, adverse events, caregiver burden, and the level of assistance provided would decrease. METHODS: This was a longitudinal, prospective within-subject study including 247 manual wheelchair users, and 119 caregivers, in El Salvador who received a wheelchair following the WHO 8-step process as well as maintenance reminders. Outcome measurements were performed via structured questionnaires and dataloggers at the initial assessment, at wheelchair delivery, and at 3- and 6-month follow-up. RESULTS: Significant improvements in wheelchair-related health indicators (all with p < 0.004) and quality of life (p = 0.001), and a significant reduction in national and "extreme" poverty probability (p = 0.004 and p = 0.012) were observed by six months. Wheelchair use significantly decreased (p = 0.011 and p = 0.035) and wheelchair skills increased (p = 0.009). Caregiver burden did not change (p = 0.226) but the number of activities of daily living (ADLs) that required no assistance significantly increased (p = 0.001) by three months and those who required complete assistance decreased (p = 0.001). No changes were observed in wheelchair repairs (p = 0.967) and breakdowns over time with new wheelchairs. CONCLUSIONS: Wheelchair service delivery using the WHO 8-step process on manual wheelchair users in El Salvador has positive effects on health and quality of life, wheelchair skills, caregiver assistance levels, and poverty. Further research is needed to determine the relative contributions of the intervention components.Implications for RehabilitationProviding manual wheelchairs using the 8-step process of the WHO has benefits on health and quality of life, wheelchair skills, caregiver assistance levels, and poverty.The WHO 8-steps service delivery process for manual wheelchairs can be used in less-resourced settings.

A descriptive analysis of wheelchair repair registry data.

Wheeled mobility and seating (WMS) devices allow users to achieve greater mobility independence. Previous studies determined that 53% of wheelchair users required one or more repairs over a 6-month period; however, there are a limited number of studies that have evaluated types of repairs. The purpose of this study was to describe the types of manual wheelchair, power wheelchair, and scooter repairs within the Wheelchair Repair Registry (WRR) and examine the association between WMS devices and the frequency of repairs. A dataset of 4,645 devices distributed in the United States was collected from equipment suppliers who performed and logged community-based wheelchair repair services. The results demonstrated common repairs found across devices were within the wheels/tires/forks and batteries/cables categories. Device type was the most significant predictor of variance in the number of repairs. Customizable manual wheelchairs, tilt-in-space, Groups 2 & 3 power wheelchairs, and scooters were associated with higher number of repairs compared to non-customizable manual wheelchairs, pediatric, heavy-duty manual wheelchairs, and Group 4 power wheelchairs. The higher failure rate found in specific devices may be associated with a population of more active users, environment/conditions where equipment is used, time spent in equipment, additional features on device, or lower durability.

Accelerated wear testing shows that thermoplastic bushings could be a cost-effective and durable alternative to traditional bearings for wheelchair caster use.

Introduction: Wheelchair caster bearings often suffer high-risk failures that lead to adverse consequences such as user injuries, suggesting that design improvements are necessary. This study aimed to compare thermoplastic bushings to standard roller bearings for potential improvements in durability and cost-effectiveness. Methods: The durability and cost-effectiveness of two thermoplastic bushing models and two metallic ball-bearing models were tested using a standard lab-based accelerated wear testing protocol. Bushings and bearings were installed on a standard 8″ caster, and four samples per model underwent testing (16 total samples). Results: All failures were experienced by the stem rolling element. The thermoplastic bushings experienced higher mean durability than the standard ball-bearings. There were significant differences in durability across the tested models, F(3,12) = 3.88, p = 0.04. The durability of thermoplastic bushing #2 was higher than the standard type ZZ shielded deep groove ball bearings, p < 0.05. There were significant differences in cost-effectiveness across the tested models, F(3,12) = 7.64, p = 0.004. The cost-effectiveness of both thermoplastic bushings were significantly higher compared to type 2RS sealed deep groove bearings, p < 0.05. Conclusions: The use of thermoplastic bushings can lower product cost and potentially reduce caster failures in the community that are associated with adverse consequences including user injuries.

Older Wheelchair Users Recommend Age-Friendly Design Improvements to a Wheelchair Maintenance App: Mixed Methods Development Study.

BACKGROUND: Wheelchair part failures have doubled over the past decade. Preventative wheelchair maintenance reduces wheelchair failures and prevents user consequences. We are developing a smartphone app called WheelTrak, which alerts users when maintenance is required, to encourage maintenance practices and compliance. OBJECTIVE: This mixed methods study aimed to develop a wheelchair maintenance app using broad stakeholder advice and investigate older adults' interaction experience with the app and their perceived barriers to and facilitators of maintenance. METHODS: Interviews were conducted with stakeholders, including mobility device users, to generate needs statements and app specifications. The app was designed in 2 stages. Stage 1 involved the development of the app according to the specifications and evaluation of the app interface by lead users. Stage 2 included the revision of the app screens and manual functionality testing. Usability testing and semistructured interviews were conducted with older wheelchair and scooter users. The System Usability Scale was used to measure app usability. RESULTS: Interviews with power and manual wheelchair users (37/57, 65%), wheelchair service providers (15/57, 26%), manufacturers (2/57, 4%), seating and mobility researchers (1/57, 2%), and insurance plan providers (2/57, 4%) informed the needs and specifications of the app technology. The 2-stage development process delivered a fully functional app that met the design specifications. In total, 12 older adults (mean age 74.2, SD 9.1 years; n=10, 83% women; and n=2, 17% men) participated in the usability testing study. Of the 12 participants, 9 (75%) agreed to use WheelTrak for preventative maintenance. WheelTrak scored an average System Usability Scale score of 60.25 (SD 16). Four overarching themes were identified: WheelTrak app improvements, barriers to maintenance, consequences related to mobility device failure, and smart technology use and acceptance. Older adults preferred the simplicity, readability, personalization, and availability of educational resources in the app. Barriers to maintenance pertained to health issues and lack of maintenance knowledge among older adults. Facilitators of maintenance included notification for maintenance, app connectivity with the service provider, reporting of device failure, and the presence of a caregiver for maintenance. CONCLUSIONS: This study highlighted age-friendly design improvements to the app, making it easy to be used and adopted by older wheelchair users. The WheelTrak app has close to average system usability. Additional usability testing will be conducted following app revision in the future.

A cross-sectional descriptive analysis of complex rehabilitation technology (CRT) supplier opinions on the current state of wheelchair repair services.

PURPOSE: It is documented that wheelchair failures occur frequently, repair times are lengthy, and users often experience adverse consequences. This study aims to gather evidence on efficiency of current wheelchair repair processes from the perspective of complex rehabilitation technology (CRT) suppliers who perform repairs within the United States. MATERIALS AND METHODS: A 20 statement survey was developed to identify barriers and facilitators related to wheelchair repairs across the domains of administrative and operational factors as well as to identify future opportunities for improvement. Key statements in these areas included time to perform a repair, documentation requirements, tracking repair progress, reimbursement, technician competency, emerging strategies and preventative maintenance. The online survey was broadly disseminated to a nationwide network of CRT suppliers for data collection. RESULTS: A total of 127 responses were received. Results showed that administrative statements received the lowest scores while those statements dealing with future opportunities received the highest scores. Areas of the industry that suppliers were in most disagreement with included wait time for insurance approval, reimbursement for parts, reimbursement for technician travel time and lack of coverage for preventative maintenance. Telehealth system usage, preventative maintenance coverage, tracking repairs and repair scheduling were future opportunities that suppliers were in most agreement with. CONCLUSIONS: Administrative issues exist in the CRT industry due to restrictive insurance policies associated with repairs and maintenance. Future opportunities to improve the process exist including payment models and the application of telehealth, device monitoring and service-based performance incentives to reduce adverse consequences to the user. Implications for rehabilitationHighlights the direct importance and barriers faced within the wheelchair repair industry by CRT suppliers.In a sample of CRT suppliers, there is agreement there exists many administrative and operational issues related to wheelchair repairs.There is agreement among survey respondents of opportunities to investigate further telehealth and remote strategies, preventative maintenance coverage and online tracking for wheelchair repairs.

Community-based wheelchair caster failures call for improvements in quality and increased frequency of preventative maintenance.

STUDY DESIGN: Secondary data analysis of wheelchair failures and service repair logs from a network of wheelchair suppliers. OBJECTIVE: To determine the frequency of wheelchair caster failures and service repairs across wheelchair manufacturers and models and investigate the relationships between them. SETTING: Wheelchair caster failures and service repairs occurred in the community. METHODS: Reported caster failure types were classified based on the risk they pose for user injuries and wheelchair damage. Caster failures experienced by users of tilt-in-space and ultralightweight manual wheelchair models and Group 2, 3 and 4 power wheelchair models between January 2017 and October 2019 were analyzed using Chi-Square tests for independence. Correlational analysis of failures and service repairs was performed. RESULTS: A total of 6470 failures and 151 service repairs reported across four manufacturers and five models were analyzed. Failure types were significantly associated with manufacturers and models, respectively. Users of tilt-in-space wheelchairs, who require greater seating support, experienced twice the proportion of high-risk caster failures than the ultralightweight manual wheelchair users. Similarly, Group 3 and 4 power wheelchair users, who have complex rehabilitation needs, experienced 15-36% more high-risk failures than Group 2 users. Service repairs negatively correlated with high-risk manual wheelchair caster failures. CONCLUSIONS: Wheelchair users who have greater seating and complex rehabilitation needs are at a higher risk for sustaining injuries and secondary health complications due to frequent caster failures. The study findings call for significant reforms in product quality and preventative maintenance practices that can reduce wheelchair failures and user consequences.

Rolling resistance of casters increases significantly after two years of simulated use.

INTRODUCTION: Manual wheelchair propulsion is associated with upper limb pain and injury, and clinical guidelines recommend minimizing propulsive force to lower health risks. One of the strategies to reduce propulsive force is by minimizing rolling resistance (RR). Product testing studies suggest that RR of casters is affected by wear and tear which could have implications on the health risk of wheelchair users. The study will investigate the relationship between caster RR and environmental exposure using standard testing protocols. METHODS: RR of ten casters representing a range of diameters for different models of wheelchairs were measured before and after environmental exposure that includes corrosion, shock and abrasion simulating two years of community use. RESULTS: Four casters exhibited failures during durability testing, one catastrophically. Increases to RR after corrosion, shock and abrasion exposure were statistically significant using mixed-effects modeling, and four casters had increased RR greater than 20%. CONCLUSIONS: Many of the casters evaluated exhibited increased RR forces and failure after environmental exposure. Improved caster design and use of corrosion resistant materials may reduce these failures. In addition, modification of the provision process could include replacement casters to reduce failures and avoid breakdowns that leave manual wheelchair users stranded or injured.

Exploratory investigation of the outcomes of wheelchair provision through two service models in Indonesia.

The World Health Organization (WHO) estimates that only 17-37% of the approximately 77 million people who need a wheelchair have access to one. Many organizations are trying to address this need through varying service delivery approaches. For instance, some adhere to WHO's recommended 8-steps service approach while others provide wheelchairs with little to no service. There is limited and sometimes conflicting evidence of the impact of the WHO's recommendations on the outcomes of wheelchair provision. To help build this evidence, we \explored outcomes of two groups of users who received their wheelchairs through two service models over time. The 8-Steps group (n = 118) received a wheelchair selected from a range of models from service providers trained using the WHO process, and the standard of care (SOC) group (n = 24) received hospital-style wheelchairs and without clinical service. Interviews were conducted at baseline and at follow-up 3 to 6 months after provision, to collect data about wheelchair usage, satisfaction, skills, maintenance and repairs, and life satisfaction. Across-group statistical comparisons were not appropriate due to significant differences between groups. In general, participants used their wheelchairs every day but reported very low mobility levels (<500 meters for the 8-steps group, and <100 meters for the SOC group.) The 8-steps group used their wheelchair for either between 1-3 hours per day, or more than 8 hours per day. The SOC used it between 1 and 3 hours per day. Overall, wheelchair usage and wheelchair skills decreased over the 3- to 6-month data collection timeline. Wheelchair breakdowns were common in both groups emphasizing the need for maintenance, occurring more frequently in the 8-Steps (28.8%) compared to the SOC group (8%), and emphasizing the need for maintenance services. No significant differences were found when comparing device satisfaction across wheelchairs types. Our results emphasize the need for routine maintenance to address frequent wheelchair breakdowns. Our results also demonstrate a large disparity in several outcome variables across groups which motivates future studies where across-group comparisons are possible.

Development of a Wheelchair Repair Registry.

OBJECTIVE: To describe the development of a wheelchair repair registry from large datasets to attain an understanding of wheelchair failures and service repairs. DESIGN: Guidelines for registry development were applied and anchored around Labor-Tracker, a web-based information management system for wheelchair suppliers to manage and track wheelchair repairs. The registry was designed using online analytical processing, allowing for rapid data queries from multiple dimensions that enable complex data analysis and discovery. SETTING: The Wheelchair Repair Registry (WRR) was developed through an industry and academic collaboration whereby repair data were collected in the field, entered into the Labor-Tracker system, deidentified, and then transferred to the registry and made available for analyses. PARTICIPANTS: Wheelchair supplier service technicians reported data from repair services provided to individuals who use power wheelchairs, manual wheelchairs, and scooters. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Wheelchair failure and repair data, including variables related to scheduling, equipment information (eg, manufacturer, model, serial number, purchase date), labor, parts, and reasons for repairs. RESULTS: The WRR was developed to analyze wheelchair repairs and failures from the Labor-Tracker system. Currently, the registry has more than 60,000 repairs conducted on more than 5000 wheelchair devices from 25 manufacturers. The devices include 60% power wheelchairs, 35% manual wheelchairs, and 5% scooters. CONCLUSIONS: The WWR creates opportunities to apply large-data analytical methodologies that will serve to inform quality standards, practice, equipment selection, preventative maintenance routines, product design, and policy.

Design and evaluation of a laboratory-based wheelchair castor testing protocol using community data.

Wheelchair castors fail frequently causing physical, social and economic consequences for wheelchair users. These failures occur in spite of established wheelchair test methods and regulations, suggesting that the existing tests may not be sufficient to screen poorly designed castors. An expert stakeholder group, convened by the International Society of Wheelchair Professionals (ISWP), noted castor failures as a high priority and recommended that a new castor testing system should be developed. In a previous study, the effect of shock exposure on castor durability was studied. The current paper extends the previous work and focuses on the development of a castor testing protocol based on shock, corrosion and abrasion exposure data collected in the community. The testing protocol was applied to 8 different castor models tested under four conditions: shock, corrosion + shock, abrasion + shock and abrasion + corrosion + shock. For each model, a total of n = 8 samples were evaluated across the four conditions. Results demonstrate that corrosion and abrasion reduced castor durability between 13% to 100% depending on the model. Importantly, the inclusion of corrosion and abrasion resulted in changes in the failure modes for 75% of the tested models and two-thirds of the altered failure modes are associated with increased risk of injury for wheelchair users. These results suggest that corrosion and abrasion present in the community reduce castor durability, thus supporting their inclusion in the castor testing protocol and potentially other wheelchair standards.

Development, reliability, and piloting of a wheelchair caster failure inspection tool (C-FIT).

Introduction: Wheelchair casters fail frequently in the field causing multiple user consequences and wheelchair breakdowns. To inform caster design improvement, there exists no validated tools that can collect caster failures. This need motivated the development of a user-reported, caster failure inspection tool (C-FIT).Methods: To develop C-FIT, a multistep design and testing approach was used which included face validity testing, test-retest reliability testing and expert review. Reliability testing was conducted with two independent cohorts of wheelchair professionals who inspected caster failures physically and online through pictures. The tool was revised based on testing outcomes and expert feedback. For preliminary data collection and evaluating usability, C-FIT was piloted at wheelchair service centers in Scotland, Indonesia and Mexico.Results: Caster failure items reported in the literature were screened to develop the initial list of C-FIT items. Face validity testing conducted through surveys with wheelchair experts (n = 6) provided 14 items for C-FIT inclusion. The test-retest reliability was found to be high for 10 items with physical failure inspections (n = 12). For each of these items, 75% or more participants had substantial to almost perfect agreement scores (κ = 0.6-1.0). Lower reliability scores were found with online failure inspections (n = 11). C-FIT received positive usability feedback from study participants and data collectors in the field. Pilot field data (n = 31) included comprehensive details about failures useful for manufacturers, designers and researchers to improve caster designs.Conclusions: The C-FIT tool developed in this study has substantial reliability and can be used for documenting caster failures at wheelchair service centers.Implications for rehabilitationCollecting data on caster failures is an important first step to inform design improvements and caster quality testing methods.The caster failure inspection tool is a reliable tool that can be used during wheelchair repair and servicing to collect caster failures in a standardized way.The failure data can be used by wheelchair manufacturers, designers, technicians and researchers to develop reliable caster designs. Wheelchair providers can select caster designs based on context of use.

Development of wheelchair caster testing equipment and preliminary testing of caster models.

BACKGROUND: Because of the adverse environmental conditions present in less-resourced environments (LREs), the World Health Organization (WHO) has recommended that specialised wheelchair test methods may need to be developed to support product quality standards in these environments. A group of experts identified caster test methods as a high priority because of their common failure in LREs, and the insufficiency of existing test methods described in the International Organization for Standardization (ISO) Wheelchair Testing Standards (ISO 7176). OBJECTIVES: To develop and demonstrate the feasibility of a caster system test method. METHOD: Background literature and expert opinions were collected to identify existing caster test methods, caster failures common in LREs and environmental conditions present in LREs. Several conceptual designs for the caster testing method were developed, and through an iterative process using expert feedback, a final concept and a design were developed and a prototype was fabricated. Feasibility tests were conducted by testing a series of caster systems from wheelchairs used in LREs, and failure modes were recorded and compared to anecdotal reports about field failures. RESULTS: The new caster testing system was developed and it provides the flexibility to expose caster systems to typical conditions in LREs. Caster failures such as stem bolt fractures, fork fractures, bearing failures and tire cracking occurred during testing trials and are consistent with field failures. CONCLUSION: The new caster test system has the capability to incorporate necessary test factors that degrade caster quality in LREs. Future work includes developing and validating a testing protocol that results in failure modes common during wheelchair use in LRE.

Developing product quality standards for wheelchairs used in less-resourced environments.

BACKGROUND: Premature failures of wheelchairs in less-resourced environments (LREs) may be because of shortcomings in product regulation and quality standards. The standards published by the International Organization for Standardization (ISO) specify wheelchair tests for durability, safety and performance, but their applicability to products used in the rugged conditions of LREs is unclear. Because of this, wheelchair-related guidelines published by the World Health Organization recommended developing more rigorous durability tests for wheelchairs. OBJECTIVES: This study was performed to identify the additional tests needed for LREs. METHODS: First, a literature review of the development of ISO test standards, wheelchair standards testing studies and wheelchair evaluations in LREs was performed. Second, expert advice from members of the Standards Working Group of the International Society of Wheelchair Professionals (ISWP) was compiled and reviewed. RESULTS: A total of 35 articles were included in the literature review. Participation from LREs was not observed in the ISO standards development. As per wheelchair testing study evidence, wheelchair models delivered in LREs did not meet the minimum standards requirement. Multiple part failures and repairs were observed with reviewed field evaluation studies. ISWP experts noted that several testing factors responsible for premature failures with wheelchair parts are not included in the standards and accordingly provided advice for additional test development. CONCLUSION: The study findings indicate the need to develop a wide range of tests, with specific tests for measuring corrosion resistance of the entire wheelchair, rolling resistance of castors and rear wheels, and durability of whole wheelchair and castor assemblies.

Design and focus group evaluation of a bed-integrated weight measurement system for wheelchair users.

Regular weight monitoring is known to help with weight management, which is an important part of maintaining a healthy, active lifestyle. Unfortunately, weight monitoring is challenging for wheelchair users because the few scales that are available are expensive and very large. Consequently, wheelchair users typically learn their weight at infrequent visits to their healthcare providers, which likely contributes to higher prevalence of obesity-related health risks among this population. In this article, we describe the design and development of the Embedded Scale, or E-Scale, which is a bed-integrated bodyweight measuring system that allows a user to measure and track their weight. The E-Scale team followed a standard product development approach to build the E-Scale prototype. Bench testing results indicate that the performance of the prototype is on par with commercially available wheelchair scales (capacity = 1,200 lbs, accuracy = 1.73 lbs, and precision = ± 0.35 lbs over one-fourth rated capacity). Institutional Review Board (IRB)-approved focus groups with 20 Veterans who use wheelchairs for mobility were conducted to gather feedback about the design, which was very positive. Development and testing results suggests the E-Scale technology is feasible and may provide a valuable tool to help wheelchair users manage their weight.

APOL1 variants increase risk for FSGS and HIVAN but not IgA nephropathy.

A chromosome 22q13 locus strongly associates with increased risk for idiopathic focal segmental glomerulosclerosis (FSGS), HIV-1-associated nephropathy (HIVAN), and hypertensive ESRD among individuals of African descent. Although initial studies implicated MYH9, more recent analyses localized the strongest association within the neighboring APOL1 gene. In this replication study, we examined the six top-most associated variants in APOL1 and MYH9 in an independent cohort of African Americans with various nephropathies (44 with FSGS, 21 with HIVAN, 32 with IgA nephropathy, and 74 healthy controls). All six variants associated with FSGS and HIVAN (additive ORs, 1.8 to 3.0; P values 3 × 10(-2) to 5 × 10(-5)) but not with IgA nephropathy. In conditional and haplotype analyses, two APOL1 haplotypes accounted for virtually all of the association with FSGS and HIVAN on chromosome 22q13 (haplotype P value = 5.6 × 10(-8)). To assess the role of MYH9 deficiency in nephropathy, we crossbred Myh9-haploinsufficient mice (Myh9(+/-)) with HIV-1 transgenic mice. Myh9(+/-) mice were healthy and did not demonstrate overt proteinuria or nephropathy, irrespective of the presence of the HIV-1 transgene. These data further support the strong association of genetic variants in APOL1 with susceptibility to FSGS and HIVAN among African Americans.

Temporary reduction of distortion product otoacoustic emissions (DPOAEs) immediately following auditory brainstem response (ABR).

The hearing status of an experimental animal is typically assessed in the laboratory setting by the combined use of auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAEs), carried out in succession, with the former assay preceding the latter. This study reports a cautionary finding that the use of this accepted regimen yields a reduced DPOAE response. When the DPOAEs were performed after ABR testing, transient reduction of the DPOAE amplitudes was observed at all frequencies in both the inbred, C57/B6 and FVB/N, and the outbred, SW mouse strains. DPOAEs were reduced post-ABR in multiple mouse strains which suggests that this finding is not strain-specific but a general consequence of the preceding ABR analysis. The reduction in DPOAE was temporary: when re-tested at one hour, DPOAE amplitudes recovered to pre-ABR levels. In contrast to the ABR's impact on DPOAE response, ABR thresholds were not altered or reduced when preceded immediately by DPOAE measurements. The molecular alterations underlying the ABR-induced transient reduction of DPOAE remain to be determined. To investigate the potential role of reactive oxygen species in post-ABR DPOAE reduction, transgenic mice over-expressing SOD1, the cytoplasmic enzyme critical for removal of superoxide radicals were subjected to the same auditory testing regimen. Similar to their wild type littermates, the SOD1 transgenic mice also demonstrated post-ABR DPOAE reduction, and thus do not support a role for superoxide radicals in transient reduction of DPOAE. While toxic noise exposure is known to negatively impact OAE, transient decrease in DPOAE levels following standard ABR assay has not been previously described. A practical outcome from this study is a recommendation for reversal of the traditional order for carrying out auditory tests, with the OAE measurements preceding ABR assessment, thus ensuring that the DPOAE response is unaffected.

In vitro expression and characterization of MYH9 mutant alleles linked to hereditary hearing loss.

OBJECTIVE: To assess whether MYH9 mutant alleles linked to hereditary hearing loss induce disruption of cellular functions and associated phenotype following transient expression within cultured human cell lines. STUDY DESIGN: Dominantly inherited MYH9 mutant alleles, MYH9(R702C) and MYH9(R705H), were integrated within eukaryotic expression vector and then transfected into cultured human cell lines for transient expression and analysis. The transfected cells were assessed for transgene-induced alterations of the cellular phenotype, including NMHC-IIA-dependent cell shape, actin cytoskeleton integrity, and inhibition of cytokinesis. SETTING: Laboratories of Molecular Otology and Molecular Genetics at the New York University School of Medicine. SUBJECTS AND METHODS: HeLa and MDA-MB-231 cultured cell lines were transiently transfected with an expression vector carrying a wild type or mutant MYH9 alleles, linked to nonsyndromic and syndromic hearing loss. Expression of exogenous transgene product was detected with antibodies directed toward its N-terminal HA tag, and transfection efficiency was greater than 95 percent. Host cells were characterized for cell shape, integrity of actin-myosin cytoskeleton, and nuclear status before and after transfections via immunofluorescence. RESULTS: MDA-MB-231 cells transfected with MYH9(R705H) but not MYH9(R702C) were found to have a greater than two-fold increase in cells with filopodia and a ten-fold increase in proportion of cells with multiple nuclei, indicating inhibition of cytokinesis, relative to the control cells transfected with wild type MYH9. Actin cytoskeleton configuration within MDA-MB-231 cells was unaffected by expression of MYH9(R702C) or MYH9(R705H). Unlike MDA-MB-231 cells, HeLa cells were refractory to MYH9(R705H) and MYH9(R702C). CONCLUSIONS: MYH9(R705H)-induced altered phenotype of the MDA-MB-231 cell line supports the pathogenicity of the mutation and represents a suitable assay system for identification and characterization of its dysfunction.

Clinical and molecular genetic analysis of a family with macrothrombocytopenia and early onset sensorineural hearing loss.

A kindred with inherited macrothrombocytopenia (MTCP) and sensorineural hearing loss (SNHL) from Ghent, Belgium was identified. Currently, joint expression of MTCP and hearing loss are linked to mutations within MYH9 only. Thus, we tested the hypothesis that a mutation within MYH9 is responsible for the autosomal dominant inheritance of MTCP and hearing loss in the Ghent family. A mutation screen of MYH9 coding region including its intron-exon junctions, as well as common hearing loss genes GJB2, GJB3, and GJB6, was performed. However, no pathogenic sequence alteration was identified. Patients' leukocytes were determined to be normal for NMMHC-A distribution via immunofluorescence analysis and free of Döhle body-like inclusions, identified as aggregates of mutant NMHC-IIA in MYH9 disorders. Also, western blot analysis with anti-NMHC-IIA antibody identified a single 220 kDa immunoreactive band with normal expression level of NMHC-IIA within the platelets and leukocytes of the affected family members. The immunoblot analysis eliminates the possibility of a large deletion within MYH9 that can escape detection by direct sequencing. Collectively, these results suggest that molecular genetic etiology of the Ghent family disorder may be due to as yet unidentified gene whose mutation(s) yields a phenocopy of the MYH9-related disease.

MYH9-siRNA and MYH9 mutant alleles: expression in cultured cell lines and their effects upon cell structure and function.

MYH9 encodes a class II nonmuscle myosin heavy chain-A (NMHC-IIA), a widely expressed 1960 amino acid polypeptide, with translated molecular weight of 220 kDa. From studies of type II myosin in invertebrates and analogy with the skeletal and smooth muscle myosin II, NMHC-IIA is considered to be involved in diverse cellular functions, including cell shape, motility and division. The current study assessed the consequences of two separate, naturally occurring MYH9 dominant mutant alleles, MYH9(R702C) and MYH9(R705H) linked to syndromic and nonsyndromic hearing loss, respectively, upon diverse NMHC-IIA related functions in two separate cultured cell lines. MYH9-siRNA-induced inhibition of NMHC-IIA in HeLa cells or HEK293 cells resulted in alterations in their shape, actin cytoskeleton and adhesion properties. However, HeLa or HEK293 cells transfected with naturally occurring MYH9 mutant alleles, MYH9(R702C) or MYH9(R705H), as well as in vitro generated deletion derivatives, MYH9(DeltaN592) or MYH9(DeltaC570), were unaffected. The effects of MYH9-siRNA-induced suppression underline the critical role of NMHC-IIA in maintenance of cell shape and adhesion. However, the results also indicate that the NMHC-IIA mutants, R702C and R705H do not inactivate or suppress the endogenous wild type NMHC-IIA within the HeLa or HEK293 cell assay system.