Probabilities of Isolated and Co-Occurring Vestibular Disorder Symptom Clusters Identified Using the Dizziness Symptom Profile

OBJECTIVES

Dizziness is among the most common reasons people seek medical care. There are data indicating patients with dizziness, unsteadiness, or vertigo may have multiple underlying vestibular disorders simultaneously contributing to the overall symptoms. Greater awareness of the probability that a patient will present with symptoms of co-occurring vestibular disorders has the potential to improve assessment and management, which could reduce healthcare costs and improve patient quality of life. The purpose of the current investigation was to determine the probabilities that a patient presenting to a clinic for vestibular function testing has symptoms of an isolated vestibular disorder or co-occurring vestibular disorders.

DESIGN

All patients who are seen for vestibular function testing in our center complete the dizziness symptom profile, a validated self-report measure, before evaluation with the clinician. For this retrospective study, patient scores on the dizziness symptom profile, patient age, and patient gender were extracted from the medical record. The dizziness symptom profile includes symptom clusters specific to six disorders that cause vestibular symptoms, specifically: benign paroxysmal positional vertigo, vestibular migraine, vestibular neuritis, superior canal dehiscence, Meniere disease, and persistent postural perceptual dizziness. For the present study, data were collected from 617 participants (mean age = 56 years, 376 women, and 241 men) presenting with complaints of vertigo, dizziness, or imbalance. Patients were evaluated in a tertiary care dizziness specialty clinic from October 2020 to October 2021. Self-report data were analyzed using a Bayesian framework to determine the probabilities of reporting symptom clusters specific to an isolated disorder and co-occurring vestibular disorders.

RESULTS

There was a 42% probability of a participant reporting symptoms that were not consistent with any of the six vestibular disorders represented in the dizziness symptom profile. Participants were nearly as likely to report symptom clusters of co-occurring disorders (28%) as they were to report symptom clusters of an isolated disorder (30%). When in isolation, participants were most likely to report symptom clusters consistent with benign paroxysmal positional vertigo and vestibular migraine, with estimated probabilities of 12% and 10%, respectively. The combination of co-occurring disorders with the highest probability was benign paroxysmal positional vertigo + vestibular migraine (~5%). Probabilities decreased as number of symptom clusters on the dizziness symptom profile increased. The probability of endorsing vestibular migraine increased with the number of symptom clusters reported.

CONCLUSIONS

Many patients reported symptoms of more than one vestibular disorder, suggesting their symptoms were not sufficiently captured by the symptom clusters used to summarize any single vestibular disorder covered by the dizziness symptom profile. Our results indicate that probability of symptom clusters indicated by the dizziness symptom profile is comparable to prior published work on the prevalence of vestibular disorders. These findings support use of this tool by clinicians to assist with identification of symptom clusters consistent with isolated and co-occurring vestibular disorders.

Self-Reported Symptoms of Vertigo and Imbalance Are Prevalent Among Adults With Chronic Moderate-Severe Traumatic Brain Injury: A Preliminary Analysis

PURPOSE

Dizziness and imbalance are common symptoms during the acute phase of traumatic brain injury (TBI). However, there is evidence to suggest that these symptoms persist into the chronic phase of injury. Few prospective studies have examined the frequency and type of dizziness and imbalance in adults with chronic moderate-severe TBI. The aim of this preliminary analysis was to investigate the prevalence of these symptoms in adults with chronic moderate-severe TBI.

METHOD

Twenty-four adults with chronic moderate-severe TBI and a group of 19 age-, sex-, and education-matched noninjured comparison participants were recruited. Self-reported dizziness and imbalance were measured using a modified version of a standard case history form. Significant associations between group (TBI group or noninjured comparison [NC] participants) and self-reports of dizziness, imbalance, and related symptoms (endorsed "yes" or "no") were explored.

RESULTS

The TBI group most reported lightheadedness (75%), vertigo (38%), and imbalance and/or falling (46%). The most common related symptom reported by the TBI group was headache (63%) and nausea (46%). Significant associations revealed that the TBI group responded "yes" in higher percentages than the NC group across all categories (dizziness, imbalance, and related symptoms). There were no statistically significant relationships among dizziness, imbalance, or headache symptoms within the TBI group.

CONCLUSIONS

These preliminary findings suggest that dizziness and imbalance are prevalent in adults with chronic moderate-severe TBI. Persistent vertiginous symptoms may point to an underlying vestibular impairment. However, further research is needed to characterize vestibular function in chronic moderate-severe TBI.

Applying the Hearing Aid Fitting Standard to Selection for Adults

The recent hearing aid fitting standard for adults outlines the minimum practice for audiologists fitting adult patients with hearing loss. This article focuses on three items of the standard (5, 6, and 7), which focus on the selection of unilateral/bilateral hearing aids, hearing aid style, and coupling, in addition to feature selection. The standard emphasizes that decisions around these three aspects should be recommended for a patient in an individualized manner, based on their needs assessment. For these decisions, the needs assessment might include measures of speech-in-noise ability, social network size, patient preference, and a trial period. Additional elements could include assessments of manual dexterity, binaural interference, and attitude toward hearing aids. However, there are a multitude of ways to practice clinically and still meet the items outlined in the standard. As long as the selection decisions consider individualized patient factors and are capable of meeting validated prescriptive targets, a clinician would be meeting the adult hearing aid fitting minimum standard guidance. In addition, despite the large number of past studies supporting these standards, additional, high-quality research including randomized, controlled, clinical trials are still needed to further support appropriate minimum standard recommendations.

Effects of Lifestyle Modification on Vestibular Migraine

OBJECTIVE

To evaluate effects of lifestyle modification on symptoms of dizziness and headache in patients diagnosed with definite vestibular migraine.

STUDY DESIGN

Prospective within-participants repeated-measures study.

SETTING

Otolaryngology tertiary care.

PARTICIPANTS

Twenty-eight adults with definite vestibular migraine who were willing to be treated without pharmacological intervention.

INTERVENTIONS

Information and instructions were provided on lifestyle modification; participants were instructed to improve restful sleep, exercise, eat at regulated mealtimes, and avoid dietary triggers. Participants were asked to maintain the modifications for at least 60 days.

MAIN OUTCOME MEASURES

Two self-report inventories were used pre- and post-intervention to evaluate participants' perceived dizziness handicap and headache disability using the Dizziness Handicap Inventory and Headache Disability Inventory, respectively. Questions were also used to evaluate the extent to which participants reported compliance with lifestyle factors pre- and post-intervention.

RESULTS

Significant improvement was observed after the lifestyle intervention with mean improvements in Dizziness Handicap Inventory and Headache Disability Inventory of 14.3 points. As a group, improvement in restful sleep was related to improvement in both dizziness and headache symptoms. At the individual participant level, 39% and 18% of participants reported significant reduction in dizziness handicap and headache disability, respectively.

CONCLUSIONS

Lifestyle modifications are an effective intervention for symptoms of dizziness and headache in participants with definite vestibular migraine. Participants who reported a larger increase in restful sleep were more likely to also report larger improvements in dizziness handicap and headache disability. Effect sizes using the current intervention were comparable or better than some reported pharmacological interventions but less than others. Our lifestyle modification intervention produced significant improvement in dizziness for a larger percentage of individual participants and in headache for a similar percentage of participants compared to data reported with other lifestyle modification interventions. Lifestyle modifications, especially restful sleep, have the potential to reduce the impact of vestibular migraine on patients' lives, with limited risk.Clinical Trials Registration: NCT03979677.

Automated Audiometry in Quiet and Simulated Exam Room Noise for Listeners with Normal Hearing and Impaired Hearing

BACKGROUND

 Up to 80% of audiograms could be automated which would allow more time for provision of specialty services. Ideally, automated audiometers would provide accurate results for listeners with impaired hearing as well as normal hearing. Additionally, accurate results should be provided both in controlled environments like a sound-attenuating room but also in test environments that may support greater application when sound-attenuating rooms are unavailable. Otokiosk is an iOS-based system that has been available for clinical use, but there are not yet any published validation studies using this product.

PURPOSE

 The purpose of this project was to complete a validation study on the OtoKiosk automated audiometry system in quiet and in low-level noise, for listeners with normal hearing and for listeners with impaired hearing.

RESEARCH DESIGN

 Pure tone air conduction thresholds were obtained for each participant for three randomized conditions: standard audiometry, automated testing in quiet, and automated testing in noise. Noise, when present, was 35 dBA overall and was designed to emulate an empty medical exam room.

STUDY SAMPLE

 Participants consisted of 11 adults with hearing loss and 15 adults with normal hearing recruited from the local area.

DATA COLLECTION AND ANALYSIS

 Thresholds were measured at 500, 1000, 2000, and 4000 Hz using the Otokiosk system that incorporates a modified Hughson-Westlake method. Results were analyzed using descriptive statistics and also by a linear mixed-effects model to compare thresholds obtained in each condition.

RESULTS

 Across condition and participant group 73.6% of thresholds measured with OtoKiosk were within ± 5 dB of the conventionally measured thresholds; 92.8% were within ± 10 dB. On average, differences between tests were small. Pairwise comparisons revealed thresholds were ∼3.5-4 dB better with conventional audiometry than with the mobile application in quiet and in noise. Noise did not affect thresholds measured with OtoKiosk.

CONCLUSIONS

 The OtoKiosk automated hearing test measured pure tone air conduction thresholds from 500 - 4000 Hz at slightly higher thresholds than conventional audiometry, but less than the smallest typical 5 dB clinical step-size. Our results suggest OtoKiosk is a reasonable solution for sound booths and exam rooms with low-level background noise.

Case Study: Depersonalization and Vestibular Impairment

BACKGROUND

 We describe herein the case of a patient whose primary complaints were episodic vertigo and "depersonalization," a sensation of detachment from his own body.

PURPOSE

 This case study aims to further clinical knowledge and insight into the clinical evaluation of vertiginous patients with complaints of depersonalization.

RESEARCH DESIGN

 This is a case study.

DATA COLLECTION AND ANALYSIS

 A retrospective chart review of vestibular function testing done on a vertiginous patient with complaints of depersonalization was performed.

RESULTS

 Vestibular function testing revealed absent cervical and ocular vestibular evoked myogenic potentials on the left side with normal vHIT or video Head Impulse Test, videonystagmography, and rotational chair results, suggesting peripheral vestibular impairment isolated to the left saccule and utricle.

CONCLUSION

 The otolith end organ impairment explains the patient's postural deviation to the left side during attempts to ambulate. We recommend that clinicians should be attentive to patient complaints of depersonalization and perform vestibular evoked myogenic potential testing to determine whether evidence of at least a unilateral peripheral otolith end organ impairment exists.

Multiple Co-Occurring Vestibular Disorders Identified Using the Dizziness Symptom Profile

Purpose The purpose of the current investigation was to determine the interrelations among vestibular disorders from a data set generated from the patient perspective as compared to previous data generated from the physician's perspective. Method The data for the current investigation originated from a previously published study describing the development of the Dizziness Symptom Profile (DSP; Jacobson et al., 2019). The DSP is a 31-item patient self-report tool designed to help primary care physicians in the development of a differential diagnosis using the patient's level of agreement with each dizziness and symptom-related statement. Responses to these items converge on common vestibular diagnoses and were previously found to agree with ear specialist differential diagnoses 70.3% of the time. Data were collected for 131 subjects (M _age = 56.7 years, 72 women) seen for evaluation in a tertiary dizziness specialty clinic. For this study, the data were analyzed using descriptive statistics to determine the frequency of single diagnoses, multiple diagnoses, co-occurring diagnoses, and patterns of co-occurrence. Results Results indicated that 52.7% of patients endorsed a single vestibular diagnosis and 47.3% endorsed two or more vestibular diagnoses. Benign paroxysmal positional vertigo (BPPV) and vestibular migraine were the most common single diagnoses and also the most common co-occurring diagnoses. As the number of diagnoses endorsed on the DSP increased, so did the percentage of time that BPPV and vestibular migraine would occur. Conclusions Results support and extend the work of others but using data generated from the perspective of the patient. A slight majority of patients endorsed a single disorder, but almost as many patients endorsed more than one vestibular diagnosis. BPPV and vestibular migraine were the most common single vestibular diagnoses and also the most common co-occurring vestibular diagnoses; vestibular migraine was more common when multiple diagnoses were endorsed. Results suggest it is common for patients to volunteer symptoms that cannot be explained by a single vestibular diagnosis. This finding is in agreement with physician-generated diagnosis data. Clinicians should consider the possibility of co-occurring diagnoses in complicated patients or in patients who are not responding optimally to management of a single vestibular disorder. The DSP is a tool that encourages clinicians to consider multiple co-occurring vestibular disorders as the source of patient complaints.

Efficacy of a New Treatment Maneuver for Posterior Canal Benign Paroxysmal Positional Vertigo

Existing treatment maneuvers for posterior canal benign paroxysmal positional vertigo (PC-BPPV) include the Semont liberatory maneuver (SLM) and canalith repositioning maneuver (CRM). Independent investigations reveal that these maneuvers provide an excellent outcome for most patients. However, certain aspects of these maneuvers, such as hyperextension of the neck for CRM and brisk lateral motion for the SLM, are contraindicated for patients with vertebrobasilar insufficiency, cervical spondylosis, back problems, and so forth. A hybrid approach, the Gans repositioning maneuver (GRM) was developed for use with these patients. The purpose of this project was to assess efficacy of the GRM for treatment of PC-BPPV. Two-hundred seven participants were enrolled in this prospective study. All participants were treated with the GRM. Six different clinicians performed the treatments. Participants returned for follow-up at one-week intervals until it was determined that the PC-BPPV was clear. On average, 1.25 GRM treatments were required to resolve the PC-BPPV. The majority of the participants (80.2%) were cleared with one GRM treatment, and 95.6% were clear after two treatments. Recurrence rate was 5%. There was no difference in outcome based on clinician. The GRM is an efficacious treatment maneuver for PC-BPPV and may be preferential for use in patients with neck, back, hip, and/or mobility issues that contraindicate the use of SLM or CRM.

Treatment of Benign Paroxysmal Positional Vertigo: Necessity of Postmaneuver Patient Restrictions

Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo, resulting from migration of otoconia into the semicircular canals. Several treatment methods involving positioning maneuvers that return the otoconia to the utricle have been described. Following treatment, most patients are provided with a variety of activity restrictions. Previous studies suggest that, overall, BPPV treatment may be successful without these restrictions. The purpose of this study was to determine the necessity of postmaneuver restrictions using an experimental and control group with participants matched for age, gender, involved ear, and symptoms. A canalith repositioning maneuver was used to treat the BPPV. During postmaneuver instruction, the 21 participants assigned to the restricted group were provided with typical activity restrictions. Twenty-one participants assigned to the nonrestricted group were given no postmaneuver restrictions. Only one participant in the restricted group and two participants in the nonrestricted group were not clear at the one-week follow-up appointment. Results indicated that postmaneuver restrictions do not improve treatment efficacy.

A factor analytic assessment of the English translation of the neuropsychological vertigo inventory (NVI)

Purpose

Vestibular impairments have been associated with a variety of cognitive deficits, most notably deficits in visuo-spatial memory. The Neuropsychological Vertigo Inventory (NVI) was developed to measure self-reported cognitive deficits in patients with dizziness and/or vertigo. The original French language version of the NVI includes 28 items and 7 subscales. The purpose of the present investigation was to determine whether the statistical assessment of an English language version supported the presence of the same cognitive constructs as the French version of the NVI.

Method

The English language adaptation of the NVI (referred to here as the NVIe) was administered to an unselected sample of 280 patients that were being evaluated for dizziness and/or vertigo in a tertiary care dizziness clinic. The individual item scores from the NVIe were subjected to an exploratory factor analysis (EFA).

Results

The results of the data analysis supported a 22-item NVIe consisting of 4 constructs: affective state, temporal memory, spatial memory, visual spatial cognition.

Conclusions

The NVIe is a new tool for screening cognitive constructs that may be affected by vestibular impairments. Prior to clinical implementation of the NVIe, additional studies of reliability and convergent validity are needed.

Short Communication: The Belly-Tendon Derivation Yields Superior Ocular Vestibular Evoked Myogenic Potential Amplitudes in a Normal Pediatric Sample

Purpose The purpose of the investigation was to determine whether the "belly-tendon" electrode derivation produced ocular vestibular evoked myogenic potentials (oVEMPs) in children that were superior to those recorded with the infraorbital-chin electrode derivation. Method This was a prospective observational study using a sample of convenience at a tertiary care medical center. Subjects were 13 children between the ages of 5 and 12 years. We compared the latency of the N1 wave and the N1-P1 peak-to-peak amplitude for the belly-tendon electrode derivation to the infraorbital-chin electrode derivation. Results The belly-tendon electrode derivation was associated with superior N1-P1 amplitudes compared to the infraorbital-chin electrode derivation. However, the large amplitude was also associated with greater variability compared to the infraorbital-chin derivation. There were no significant electrode derivation-based differences in N1 latency. Additionally, there was no predictable relationship between age and oVEMP amplitude. Conclusion As shown previously in adults, the belly-tendon electrode derivation produces significantly larger oVEMP amplitudes compared to the infraorbital-chin electrode derivation.

Evaluation of pediatric glioma outcomes using intraoperative MRI: a multicenter cohort study

BACKGROUND

The use of intraoperative MRI (iMRI) during treatment of gliomas may increase extent of resection (EOR), decrease need for early reoperation, and increase progression-free and overall survival, but has not been fully validated, particularly in the pediatric population.

OBJECTIVE

To assess the accuracy of iMRI to identify residual tumor in pediatric patients with glioma and determine the effect of iMRI on decisions for resection, complication rates, and other outcomes.

METHODS

We retrospectively analyzed a multicenter database of pediatric patients (age ≤ 18 years) who underwent resection of pathologically confirmed gliomas.

RESULTS

We identified 314 patients (mean age 9.7 ± 4.6 years) with mean follow-up of 48.3 ± 33.6 months (range 0.03-182.07 months) who underwent surgery with iMRI. There were 201 (64.0%) WHO grade I tumors, 57 (18.2%) grade II, 24 (7.6%) grade III, 9 (2.9%) grade IV, and 23 (7.3%) not classified. Among 280 patients who underwent resection using iMRI, 131 (46.8%) had some residual tumor and underwent additional resection after the first iMRI. Of the 33 tissue specimens sent for pathological analysis after iMRI, 29 (87.9%) showed positive tumor pathology. Gross total resection was identified in 156 patients (55.7%), but this was limited by 69 (24.6%) patients with unknown EOR.

CONCLUSIONS

Analysis of the largest multicenter database of pediatric gliomas resected using iMRI demonstrated additional tumor resection in a substantial portion of cases. However, determining the impact of iMRI on EOR and outcomes remains challenging because iMRI use varies among providers nationally. Continued refinement of iMRI techniques for use in pediatric patients with glioma may improve outcomes.

Anterior Canal benign paroxysmal positional Vertigo following surgical Management of superior canal dehiscence

OBJECTIVE

Benign paroxysmal positional vertigo (BPPV) is a common post-surgical finding in patients managed for superior semicircular canal dehiscence (SSCD). The posterior semicircular canal has been reported as the involved canal in the majority of cases of post-surgical BPPV, with only two cases reported of lateral canal involvement. The objective of this report is to present a case in which an anterior semicircular canal BPPV response was identified in a patient following surgical management for SSCD.

METHOD

This case report presents an adult with residual dizziness following surgical management of SSCD and vestibular rehabilitation therapy (VRT). During subsequent evaluation of vestibular function, a transient and torsional, down-beating nystagmus was provoked along with vertigo during Dix-Hallpike positioning to the right. This was consistent with BPPV affecting the left superior (anterior) semicircular canal.

RESULTS

The patient was treated with a repositioning maneuver to manage anterior semicircular canal BPPV and no nystagmus response was recorded with post-repositioning Dix-Hallpike test. Review of radiographic images, obtained prior to vestibular function testing, showed a hyperintensity in the area of the left anterior semicircular canal ampulla. It was felt this was likely a bone chip from the SSCD repair that was pushing against the ampulla with further mobile debris within the canal.

CONCLUSION

It is reported that BPPV is a common complication in patients surgically managed for SSCD. Posterior semicircular canal BPPV is reported most often, with a couple of cases of lateral semicircular canal BPPV also reported. As far as we are aware, the current case represents the first report of anterior semicircular canal BPPV in this type of patient.

Management of Recurrent Vestibular Neuritis in a Patient Treated for Rheumatoid Arthritis

PURPOSE

This clinical report is presented to describe how results of vestibular function testing were considered along with other medical history to develop a management plan that was ultimately successful.

METHOD

The patient underwent audio-vestibular assessment including comprehensive audiogram, videonystagmography, cervical vestibular evoked myogenic potential, and postural stability testing.

RESULTS

Results from initial testing were most consistent with uncompensated peripheral vestibular dysfunction affecting the right superior vestibular nerve. These results, considered along with history and symptoms, supported vestibular neuritis. After a second vertigo event, we became concerned about the potential temporal association between the patient's rheumatoid arthritis treatment and symptom onset. It is established that treatment for rheumatoid arthritis can exacerbate latent viral issues, but this has not specifically been reported for vestibular neuritis. There are reports in the literature in which patients successfully used viral suppressant medication to decrease viral activity while they were able to continue benefiting from immunosuppressive therapy. We hypothesized that, if the current patient's vestibular neuritis events were related to her treatment for rheumatoid arthritis, she may also benefit from use of viral suppressant medication while continuing her otherwise successful immunosuppressive intervention.

CONCLUSIONS

Patients treated with biologic disease-modifying antirheumatic drugs are more susceptible to viral issues, and this may include vestibular neuritis. For the current case, identifying this possibility and recommending viral suppressant medication allowed her to continue with successful treatment of rheumatoid arthritis while avoiding additional vertigo events.

Teaching Patient-Centered Counseling Skills for Assessment, Diagnosis, and Management of Benign Paroxysmal Positional Vertigo

Audiologists are an integral part of the management of those with dizziness and vestibular disorders. However, little research has been performed on counseling approaches for patients who present with dizziness as a primary concern. Accordingly, it is important that audiology students are provided with didactic and experiential learning opportunities for the assessment, diagnosis, and management of this population. Benign paroxysmal positional vertigo is the most common vestibular disorder among adults. Doctor of Audiology students, at a minimum, should be provided with learning opportunities for counseling patients with this particular disorder. Implementation of patient-centered counseling is applied across various parts of the patient encounter from initial intake to treatment and patient education. The purpose of this article is to present the available evidence and to apply widely accepted theories and techniques to counseling those with benign paroxysmal positional vertigo. Didactic resources and experiential learning activities are provided for use in coursework or as a supplement to clinical education.

Correction of metopic synostosis utilizing an in situ bandeau approach

Metopic craniosynostosis is a common growth disturbance in the infant cranium, second only to sagittal synostosis. Presenting symptoms are usually of a clinical nature and are defined by an angular forehead, retruded lateral brow, bitemporal narrowing, and a broad-based occiput. These changes create the pathognomonic trigonocephalic cranial shape. Aesthetic in nature, these morphological changes do not constitute the only developmental issues faced by children who present with this malady. Recent studies and anecdotal evidence have also demonstrated that children who present with metopic synostosis may face issues with respect to intellectual and/or psychological development. The authors present an elegant approach to the surgical reconstruction of the trigonocephalic cranium using an in situ bandeau approach.

Rodent toxicity and nongenotoxic carcinogenesis: knowledge-based human risk assessment based on molecular mechanisms

It is necessary to determine whether chemicals or drugs have the potential to pose a threat to human health. Chemicals that can damage DNA are detected in short-term assays, but the detection of nongenotoxic carcinogens relies upon bioassays in laboratory animals. However, there are marked differences between rodents and humans in response to nongenotoxic carcinogens, which makes the relevance of rodent data to human risk assessment questionable. Here, we address the background issues concerning rodent nongenotoxic carcinogenesis and then focus upon peroxisome proliferators, chloroform, and dioxins as examples of toxicants that cause rodent-specific oxidative stress, cell proliferation, and the suppression of apoptosis. In the case of peroxisome proliferators and dioxins, this response is receptor-mediated. The evidence presented suggests that, at least for some toxicants, the molecular mechanisms of the rodent carcinogenic responses do not operate in humans; this is discussed in the context of human risk assessment. Finally, consideration is given to incorporating mechanism-based information into risk assessment for regulatory purposes.

Guided plate wave scattering at vertical stiffeners and its effect on source location

This paper examines guided wave transmission characteristics of plate stiffeners and their influence on the performance of acoustic noise source location. The motivation for this work is the detection of air leaks in manned spacecraft. The leaking air is turbulent and generates noise that can be detected by a contact-coupled acoustic array to perform source location and find the air leak. Transmission characteristics of individual integral stiffeners are measured across a frequency range of 50-400kHz for both high and low aspect-ratio rectangular stiffeners, and comparisons are made to model predictions which display generally good agreement. It is demonstrated that operating in frequency ranges of high plate wave stiffener transmission significantly improves the reliability of noise source location in the plate. A protocol is presented to enable the selection of an optimal frequency range for leak location.

Differentiation of migrainous positional vertigo (MPV) from horizontal canal benign paroxysmal positional vertigo (HC-BPPV)

This article presents an approach to differentiation of migrainous positional vertigo (MPV) from horizontal canal benign paroxysmal positional vertigo (HC-BPPV). Such an approach is essential because of the difference in intervention between the two disorders in question. Results from evaluation of the case study presented here revealed a persistent ageotropic positional nystagmus consistent with MPV or a cupulolithiasis variant of HC-BPPV. The patient was treated with liberatory maneuvers to remove possible otoconial debris from the horizontal canal in an attempt, in turn, to provide further diagnostic information. There was no change in symptoms following treatment for HC-BPPV. This case was diagnosed subsequently as MPV, and the patient was referred for medical intervention. Treatment has been successful for 22 months. Incorporation of HC-BPPV treatment, therefore, may provide useful information in the differential diagnosis of MPV and the cupulolithiasis variant of HC-BPPV.

Prevalence of vestibulopathy in benign paroxysmal positional vertigo patients with and without prior otologic history Prevalencia de vestibulopatía en pacientes con vértigo postural paroxístico benigno (BPPV), con y sin historia previa de patología otológica

The purpose of this study was to determine the prevalence of reduced or absent labyrinthine reactivity (vestibulopathy) in two groups of participants with posterior canal BPPV. One group had prior diagnosis of otologic disease (positive history group). No one in the second group had ever been diagnosed with otologic disease (negative history group). Caloric responses were retrospectively analyzed for the two groups. Patients with a positive history exhibited a greater prevalence of vestibulopathy than patients with a negative history. The positive history group, on average, also exhibited a larger unilateral weakness than those patients in the negative history group. We conclude that patients with BPPV and a history of otologic disease are more likely to present with vestibulopathy, than patients with BPPV and no history of otologic disease. This finding supports the benefit of complete vestibular evaluation in patients with BPPV to ensure comprehensive and successful treatment outcome.

Comparison of horizontal and vertical dynamic visual acuity in patients with vestibular dysfunction and nonvestibular dizziness

Blurred vision with head movement is a common symptom reported by patients with vestibular dysfunction affecting the vestibulo-ocular reflex (VOR). Impaired VOR can be measured by comparing visual acuity in which there is no head movement to visual acuity obtained with head movement. A previous study demonstrated that dynamic visual acuity (DVA) testing using vertical head movement revealed deficits in impaired VOR. There is evidence that horizontal head movement is more sensitive to impaired VOR. The objective of this investigation was to compare horizontal and vertical DVA in participants with normal vestibular function (NVF), impaired vestibular function (IVF), and participants with nonvestibular dizziness (NVD). Participants performed the visual acuity task in a baseline condition with no movement and also in two dynamic conditions, horizontal head movement and vertical head movement. Horizontal DVA was twice as sensitive to impaired VOR than vertical DVA. Results suggest that horizontal volitional head movement should be incorporated into tasks measuring functional deficits of impaired VOR.

An Adaptive Clinical Test of Temporal Resolution

Purpose

It has been recommended that diagnostic and screening test batteries for auditory processing disorder (APD) include a measure of temporal gap detection using broadband noise stimuli. Although psychophysical laboratory procedures exist for the measurement of temporal resolution, none are clinically feasible. This study was designed to obtain preliminary data on a new clinical measure of gap detection, the Adaptive Test of Temporal Resolution (ATTR).

Method

The ATTR, a currently available clinical test (Random Gap Detection Test), and a standard psychophysical laboratory procedure were used to measure gap detection thresholds (GDTs) from a group of 30 young adults with normal hearing.

Results

Mean ATTR GDTs were 2.2 ms, consistent with GDTs measured using the psychophysical laboratory procedure (3.2 ms) and significantly smaller than those measured using the Random Gap Detection Test (7.0 ms).

Conclusions

Because it incorporates standard adaptive psychophysical methodology in a computer application that can be used on any desktop computer but does not depend on specialized hardware for application, the ATTR promises to be a clinically feasible addition to the APD test battery.

Computerized dynamic visual acuity with volitional head movement in patients with vestibular dysfunction

OBJECTIVES

Patients with uncompensated vestibular dysfunction frequently report blurred vision during head movement, a symptom termed oscillopsia. One way to measure the functional deficit associated with an impaired vestibulo-ocular reflex is by comparing visual acuity from a baseline condition in which there is no head movement to visual acuity obtained during a dynamic condition with head movement. A previously described test incorporated a treadmill upon which patients walked during assessment of visual acuity. The objective of the current investigation was to evaluate an alternative method of assessing dynamic visual acuity that uses volitional head movement instead of walking on a treadmill.

METHODS

Fifteen participants with normal vestibular function and 16 participants with impaired vestibular function were enrolled. All participants performed the visual acuity task under baseline conditions with no movement and also under dynamic conditions that included 1) walking on a treadmill and 2) volitionally moving their head in the vertical plane.

RESULTS

No difference in performance was observed between the treadmill task and the volitional head movement task. Participants with impaired vestibular function performed more poorly under the dynamic conditions than did participants with normal vestibular function.

CONCLUSIONS

The results suggest that the volitional head movement paradigm may be useful in identification of patients with functional deficits of the vestibulo-ocular reflex.

Effects of age and hearing loss on gap detection and the precedence effect: narrow-band stimuli

Deficits in temporal resolution and/or the precedence effect may underlie part of the speech understanding difficulties experienced by older listeners in degraded acoustic environments. In a previous investigation, R. Roberts and J. Lister (2004) identified a positive correlation between measures of temporal resolution and the precedence effect, specifically across-channel gap detection (as measured dichotically) and fusion. Across-channel gap detection may also be measured using frequency-disparate markers. Thus, the present investigation was designed to determine if the relation is specific to dichotic gap detection or may generalize to all types of across-channel gap detection. Gap-detection thresholds (GDTs) for fixed-frequency and frequency-disparate markers and lag-burst thresholds (LBTs) were measured for 3 groups of listeners: young with normal hearing sensitivity (YNH), older with normal hearing sensitivity (ONH), and older with sensorineural hearing loss (OIH). Also included were conditions of diotic and dichotic GDT. Largest GDTs were measured for the frequency-disparate markers, whereas largest LBTs were measured for the fixed-frequency markers. ONH and OIH listeners exhibited larger frequency-disparate and dichotic GDTs than YNH listeners. Listener age and hearing loss appeared to influence temporal resolution for frequency-disparate and dichotic stimuli, which is potentially important for the resolution of timing cues in speech. Age and hearing loss did not significantly influence fusion as measured by LBTs. Within each participant group, most GDTs and LBTs were positively, but not significantly, correlated. For all participants combined, across-channel GDTs and LBTs were positively and significantly correlated. This suggests that the 2 tasks may rely on a common across-channel temporal mechanism.

Effects of age and hearing loss on gap detection and the precedence effect: broadband stimuli

Older listeners with normal-hearing sensitivity and impaired-hearing sensitivity often demonstrate poorer-than-normal performance on tasks of speech understanding in noise and reverberation. Deficits in temporal resolution and in the precedence effect may underlie this difficulty. Temporal resolution is often studied by means of a gap-detection paradigm. This task is similar to binaural fusion paradigms used to measure the precedence effect. The purpose of this investigation was to determine if within-channel (measured with monotic and diotic gap detection) or across-channel (measured with dichotic gap detection) temporal resolution is related to fusion (measured with lag-burst thresholds; LBTs) under dichotic, anechoic, and reverberant conditions. Gap-detection thresholds (GDTs) and LBTs were measured by means of noise-burst stimuli for 3 groups of listeners: young adults with normal-hearing sensitivity (YNH), older adults with normal-hearing sensitivity (ONH), and older adults with impaired-hearing sensitivity (OIH). The GDTs indicated that across-channel temporal resolution is poorer than within-channel temporal resolution and that the effects of age and hearing loss are dependent on condition. Results for the fusion task indicated higher LBTs in reverberation than for the dichotic and anechoic conditions, regardless of group, and no effect of age or hearing loss for the nonreverberant conditions. However, higher LBTs were observed in the reverberant condition for the ONH listeners. Further, there was a correlation between across-channel temporal resolution and fusion in reverberation. Gap detection and fusion may not necessarily reflect the same underlying processes; however, across-channel gap detection may influence fusion under certain conditions (i.e., in reverberation).

Effects of reverberation on fusion of lead and lag noise burst stimuli

The purpose of this investigation was to determine the effects of reverberation on the precedence effect by obtaining thresholds for perception of leading and lagging noise burst stimuli as separate auditory events. In Experiment 1, lag burst thresholds for 4-ms noise bursts were measured in a simulated reverberant and anechoic environment for nine subjects with normal hearing at presentation levels of 10, 20, and 30 dB SL. Results indicated that lag burst thresholds obtained in the reverberant environment were higher than those obtained in the anechoic environment, with no effect of sensation level. In Experiment 2, three new stimulus conditions, two monaural and one binaural control, were employed. For one monaural condition, the stimuli were equal in level and for the other, the leading stimulus was more intense than the lagging stimulus. For the binaural control condition, the stimuli were presented from a perceived spatial location of 0 degrees azimuth. In the monaural and binaural control conditions, lag burst thresholds were lower than those obtained in the reverberant environment of Experiment 1. There was no difference between lag burst thresholds obtained in either environment for the monaural and binaural control conditions compared to the anechoic condition of Experiment 1. Results of Experiment 2 indicate that the higher lag burst thresholds observed in Experiment 1 are not fully explained by a peripheral masking effect.

Speech Perception Benefits From Sound Field FM Amplification

The effects of sound field FM amplification (SFA) on speech perception performance were investigated in this 2-year study. Kindergarten children with normal hearing were randomly assigned to a treatment group, which comprised 7 classrooms that had SFA systems installed in them, and to a control group, which comprised another 7 classrooms that did not have any amplification available. The children were followed from the beginning of kindergarten through the end of first grade. Improvements in speech perception performance were measured for both groups, with the treatment group demonstrating progress much sooner than the control group. However, this difference was not apparent by the end of the study. The only significant difference measured between the treatment and control groups was that the treatment group performed significantly better than the control group when the stimuli were presented with SFA for the treatment group and without SFA for the control group. The teachers who used SFA enjoyed using amplification in their classrooms and felt that their students enjoyed using it as well.

Effects of Noise and Reverberation on the Precedence Effect in Listeners With Normal Hearing and Impaired Hearing

The purpose of this study was to determine the effects of reverberation and noise on the precedence effect in listeners with hearing loss. Lag burst thresholds (LBTs) for 4-ms noise bursts were obtained for 2 groups of participants: impaired hearing and normal hearing. Data were collected in reverberant and anechoic environments in quiet and noise, at sensation levels of 10, 20, 30, 40, and 50 dB. Results indicated a significant effect of reverberation on LBTs for both participant groups. LBTs increased with sensation level in the reverberant environment and decreased with increasing sensation level in the anechoic environment. There was no effect of hearing loss on LBTs. When the change in LBT due to noise was compared, the effect of noise depended on group and environment, with a greater effect of noise on the performance of listeners with impaired hearing. It is likely that the ability to fuse direct sounds and early reflections is degraded in listeners with impaired hearing and that this contributes to the difficulties experienced by these listeners in reverberation and noise.

An animal evaluation of a paste of chitosan glutamate and hydroxyapatite as a synthetic bone graft material

The objective of this study was to develop a synthetic bone graft in a paste form. Reported here are the results of the evaluation of a paste of chitosan glutamate (Protosan) and hydroxyapatite (referred to as a paste) used in a critical size defect model in rats. Eight-millimeter--diameter cranial defects were made in rat calvaria following a protocol approved by the animal review committee. Five groups were studied: (1) empty control, (2) defect filled with paste only, (3) defect filled with the paste containing bone-marrow aspirate, (4) defect filled with paste containing BMP-2, and (5) defect filled with paste containing osteoblasts cultured from bone-marrow aspirate. The sacrifice intervals were 9 and 18 weeks. Calvaria containing the defect were harvested, and the bone mineral density (BMD) was determined by dual energy X-ray absorptiometry. Push-out strength measurements were also performed. The BMD values of empty control were significantly lower than those of other groups at both 9 and 18 weeks. The mechanical properties, that is, push-out strengths and area under the push-out load and displacement were not significantly different between the samples. Histological examination of Goldner-trichromestained undecalcified sections showed the presence of mineralized bone spicules in the defect areas that were more prominent in those filled with paste and osteoblasts cultured from bone-marrow aspirate. Hence, this study demonstrated that the paste of chitosan glutamate and hydroxyapatite-containing osteoblasts cultured from bone-marrow aspirate would be an effective material to repair bone defects.

PPAR alpha and the regulation of cell division and apoptosis

Peroxisome proliferators (PPs) such as the hypolipidaemic drug, nafenopin and the phthalate plasticiser 2-diethylhexylphthalate induce rodent hepatocyte cell proliferation and suppress apoptosis leading to tumours. PPs act via the nuclear hormone receptor peroxisome proliferator activated receptor alpha (PPAR alpha) which directly regulates genes implicated in the response to PPs such as the peroxisomal gene acyl CoA oxidase. As expected for xenobiotics that perturb proliferation, PPs alter expression of cell cycle regulatory proteins. However, the ability to alter expression of cyclins and cyclin-dependent kinases is shared by physiological hepatic mitogens such as epidermal growth factor and is thus unlikely to be specific to the PP-induced aberrant growth associated with hepatocarcinogenesis. Recent evidence suggests that the response of hepatocytes to PPs is not only dependent upon PPAR alpha but also on the trophic environment provided by nonparenchymal cells and by cytokines such as tumour necrosis factor alpha. Additionally, the ability of PPs to suppress apoptosis and induce proliferation depends upon survival signalling mediated by p38 mitogen activated protein kinase. The cross talk between PPAR alpha-mediated transcription, survival signalling and cell cycle will be discussed with particular emphasis on relevance to toxicology.

Effects of hearing loss on echo thresholds

OBJECTIVE

The purpose of this investigation was to determine the effects of hearing loss on the perception of echoes.

DESIGN

Echo thresholds were measured for eight listeners with normal hearing and nine listeners with impaired hearing. Pairs of 4-msec noise bursts were presented to each listener with onset-to-onset delays ranging from 2 to 16 msec. Echo thresholds were obtained at signal presentation levels of 10, 20, 30, 40, and 50 dB SL.

RESULTS

Results revealed differences between the psychometric functions of the two subject groups. Psychometric functions of the subjects with impaired hearing indicated higher echo thresholds than for the subjects with normal hearing. In addition, echo thresholds at 10 dB SL were significantly higher than echo thresholds measured at 40 dB SL for both subject groups.

CONCLUSION

Listeners with impaired hearing exhibit higher echo thresholds than listeners with normal hearing. The higher echo thresholds for listeners with impaired hearing may account, at least in part, for difficulty on tasks such as localization in everyday listening environments.

Randomized clinical trial of laparoscopic versus open abdominal rectopexy for rectal prolapse

BACKGROUND

The objectives of this study were to compare both subjective clinical outcomes and the objective stress response of laparoscopic and open abdominal rectopexy in patients with full-thickness rectal prolapse. Abdominal rectopexy for patients with rectal prolapse is well suited for a laparoscopic approach as no resection or anastomosis is necessary.

METHODS

Forty patients with a full-thickness rectal prolapse were randomized before operation to a laparoscopic group and an open group. They agreed to conform to a clinical pathway (CP) of liquid diet (CP1) and full mobility (CP2) on day 1, solid diet (CP3) on day 2 and discharge (CP4) before day 5. Their compliance was monitored by an assessor blinded to the operative group, who also rated pain and mobility. Patient-controlled morphine use was documented. Neuroendocrine and immune stress response and respiratory function were measured.

RESULTS

Some 75 per cent of all clinical pathway objectives of early recovery were achieved in the laparoscopic group compared with 37 per cent in the open group (P < 0.01). Significant differences in favour of laparoscopy were noted with regard to narcotic requirements, and pain and mobility scores. Differences in objective measures of stress response favouring laparoscopy were found for urinary catecholamines, interleukin 6, serum cortisol and C-reactive protein. No differences were noted in respiratory function but significant respiratory morbidity was greater in the open group (P < 0.05). None of the measured outcomes, subjective or objective, favoured the open group apart from operating time, which was significantly shorter (153 versus 102 min; P < 0.01).

CONCLUSION

This study has demonstrated significant subjective and objective differences in favour of a laparoscopic technique for abdominal rectopexy. The advantages were all short term but no evidence of any adverse effect on longer-term outcomes was observed.

Scientific analysis of the proposed uses of the T25 dose descriptor in chemical carcinogen regulation

The uncertainties that surround the methods used for risk assessment of exposure to carcinogens have been highlighted by a recent document advocating an approach based on the T25 dose (the dose giving a 25% incidence of cancer in an appropriately designed animal experiment). This method relies on derivation of the T25 dose then assesses risk at the exposure dose using proportionality provided by a linear extrapolation (T25/linear). To promote discussion of the scientific issues underlying methods for the risk assessment of chemical carcinogens, the European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) hosted a one-day workshop in Brussels on 10 November 2000. Several invited presentations were made to participants, including scientists from regulatory authorities, industry and academia. In general, it was felt that there was sufficient basis for using the T25 dose as an index of carcinogenic potency and hence as part of the hazard assessment process. However, the use of the T25 in risk assessment has not been validated. The T25/linear and other extrapolation methods based on metrics such as LED 10 assume linearity which may be invalid. Any risk calculated using the T25/linear method would provide a precise risk figure similar to the output obtained from the Linearised Multistage (LMS) method formerly used by the Environmental Protection Agency (EPA) in the United States of America. Similarity of output does not provide validation but rather reflects their reliance on similar mathematical approaches. In addition to the T25 issue, evidence was provided that using two separate methods (linearised non-threshold model for genotoxic carcinogens; no-observable-effect level with a safety factor (NOEL/SF) method for all other toxicity including non-genotoxic carcinogens) is not justified. Since the ultimate purpose of risk assessment is to provide reliable information to risk managers and the public, there was strong support at the workshop for harmonisation of approaches to risk assessment for all genotoxic and nongenotoxic carcinogens. In summary, the T25 method has utility for ranking potency to focus efforts in risk reduction. However, uncertainties such as the false assumption of precision and non-linearity in the dose-response curve for tumour induction raise serious concerns that caution against the use of T25/linear method for predicting human cancer risk.

Results following trapeziometacarpal arthroplasty of the thumb

A retrospective follow-up study was performed on patients with degenerative joint disease (DJD) who underwent trapeziometacarpal arthroplasty of the thumb with 3-week immobilization and without the use of K-wire fixation. Pre- and post-operative pain, activities of daily living (ADLs), grip strength, and pinch strength were compared. Data were collected on 25 hands in 23 patients, 7 hands with full trapezium resections and 18 with hemi-trapezium resections. The median age was 60 years, with a range of 39 to 73 years, and the median follow-up period was 1 year 11 months, with a range of 3 months to 11 years. Grip and pinch strength were measured pre- and postoperatively. Pain was assessed on a visual analog scale (VAS), and ADLs were assessed by means of a 15-item survey. Both pain and ADLs were evaluated postoperatively with recall of preoperative status. Following surgery, all thumbs were immobilized in a static splint for 3 weeks and then allowed progressive use. Median improvements in hemi-trapezium resections included grip, 22.5 lb; pinch, 4.7 lb; and ADLs, 33%. Pain was reduced a median of 7.0 cm on the VAS. Median improvements in full trapezium resection included grip, 29.5 lb; pinch, 0 lb; ADLs, 60%; and pain reduction, 8 cm on the VAS. This follow-up study suggests that satisfactory results can be achieved in pain reduction, strength, and ADLs with an immobilization period of only 3 weeks and without the use of K-wires following carpometacarpal (CMC) arthroplasty.

A comparison of breast cancer secondary prevention activities and satisfaction with access and communication issues in women 50 and over

BACKGROUND

Between 1950 and 1990, the incidence of breast cancer increased about 52% and the mortality rate increased 4%. Prevention programs (mammograms and clinical breast exams) can positively affect both cost control and mortality rates. Balancing the costs of preventive screening against the potential savings is a part of an ongoing debate centering on the age at which women should have yearly mammograms. Yet, if all agencies agree that women aged 50 and over should receive yearly mammograms, then why are so many women aged 50 and over not being screened?

METHODS

Using previously validated instruments, this study surveyed residents of Spokane County, Washington. Respondents (1,850 returned of 2,600) were compared over time by demographic characteristics and by insurance type to identify any significant differences between those who had preventative screens and those who did not. Issues involving access to screening and communication with healthcare providers were also examined.

RESULTS

Factors that affect whether women receive preventative screening include insurance type, provider type, long waiting times, and poor communication among the doctor, the staff, and the patient.

CONCLUSION

The most important determinant to whether preventative screening is being conducted is the relationship between the patient and their healthcare provider.

Role of cytokines in non-genotoxic hepatocarcinogenesis: cause or effect?

Chemicals with the potential to cause cancer through damaging DNA can be readily identified in a range of in vitro screens that detect genotoxicity. However, many carcinogens are non-genotoxic yet cause rodent tumours, particularly in the liver. Some non-genotoxic carcinogens such as the peroxisome proliferators (PPs) act directly to cause liver growth and proliferation, whereas others such as carbon tetrachloride cause liver damage, followed by regenerative hyperplasia. Current data support a role for cytokines such as tumour necrosis factor alpha (TNFalpha) and interleukin 1 (IL1) in hepatocarcinogenesis. However, these data give rise to conflicting hypotheses; in some experimental models, TNFalpha appears to mediate damage, whereas in others it is postulated to play a role in tissue repair. Recently, we have shown that TNFalpha acting via TNFalpha receptor 1 and p38 MAP kinase suppresses hepatocyte apoptosis. However, when new protein synthesis is disabled, TNFalpha becomes a death signal. An understanding of the role of cytokines in rodent hepatocarcinogenesis will allow the development of markers that can be used to identify, at an early stage, those chemicals with the potential to induce rodent tumours.

Identification of a possible association between carbon tetrachloride-induced hepatotoxicity and interleukin-8 expression

Hepatotoxicants can elicit liver damage by various mechanisms that can result in cell necrosis and death. The changes induced by these compounds can vary from gross alterations in DNA repair mechanisms, protein synthesis, and apoptosis, to more discrete changes in oxidative damage and lipid peroxidation. However, little is known of the changes in gene expression that are fundamental to the mechanisms of hepatotoxicity. We have used DNA microarray technology to identify gene transcription associated with the toxicity caused by the hepatotoxicant carbon tetrachloride. Labeled poly A+ RNA from cultured human hepatoma cells (HepG2) exposed to carbon tetrachloride for 8 hours was hybridized to a human microarray filter. We found that 47 different genes were either upregulated or downregulated more than 2-fold by the hepatotoxicant compared with dimethyl formamide, a chemical that does not cause liver cell damage. The proinflammatory cytokine interleukin-8 (IL-8) was upregulated over 7-fold compared with control on the array, and this was subsequently confirmed at 1 hour and 8 hours by Northern blot analyses. We also found that carbon tetrachloride caused a time-dependent increase in interleukin-8 protein release in HepG2 cells, which was paralleled by a decrease in cell viability. These data demonstrate that carbon tetrachloride causes a rapid increase in IL-8 mRNA expression in HepG2 cells and that this increase correlates with a later and significant increase in the levels of interleukin-8 protein. These results illustrate the potential of microarray technology in the identification of novel gene changes associated with toxic processes.

PPAR alpha-mediated responses in the rodent liver: a holistic biochemical view

Carcinogenesis through the direct action of genotoxic, DNA damaging chemicals is an established and well-studied paradigm. As yet there are no short term tests available for non-genotoxic rodent carcinogens that do not damage DNA but cause liver tumours in long term rodent bioassays. A key aim is to develop short term in vitro screens for the detection of nongenotoxic carcinogens, and this requires knowledge of the mode or mechanism of action of this class of chemicals. The largest and most chemically diverse family of non-genotoxic hepatocarcinogens is the peroxisome proliferators (PPs) such as hypolipidaemic fibrate drugs, plasticizers used in clingwrap/medical tubing and certain pesticides and solvents. PPs mediate their biological responses via activation of the transcription factor PPAR alpha (peroxisome proliferator activated receptor alpha), a member of the nuclear hormone receptor superfamily. PPAR alpha activation is responsible for the pleiotropic effects of PPs in rodent liver such as the induction of enzymes of the b-oxidation pathway, hepatocyte DNA synthesis, liver enlargement and tumourigenesis. Although much is known, we are far from defining the key cell cycle regulating targets of PPs, due perhaps to past limitations of technology. The technology of proteomics allows quantitative measurement of the expression levels of potentially thousands of individual genes at the protein level on exposure to toxic insult. This is predicted to revolutionise the way many biological systems are investigated. Here we review the current knowledge of proteins involved in the response to peroxisome proliferators and describe the impact of proteomics in this field.

Role of hepatic non-parenchymal cells in the response of rat hepatocytes to the peroxisome proliferator nafenopin in vitro

Induction of liver cancer by peroxisome proliferators such as nafenopin is frequently associated with increased liver growth, increased DNA synthesis and suppression of apoptosis. The cytokine, tumour necrosis factor alpha (TNF alpha), and non-parenchymal liver cells have been implicated in mediating the hepatic response to peroxisome proliferators. Here, we have investigated the dependency of the hepatocyte response to peroxisome proliferators on non-parenchymal cells, a major source of hepatic cytokines. Addition of non-parenchymal cells, or conditioned medium from non-parenchymal cell cultures, increased DNA synthesis (220% and 270% of control, respectively) and suppressed transforming growth factor beta(1)-induced hepatocyte apoptosis (32% and 54% of control, respectively). Removal of non-parenchymal cells from normal hepatocyte cultures prevented both the nafenopin- and TNF alpha-induced increase in DNA synthesis and suppression of hepatocyte apoptosis; this response was restored by returning non-parenchymal cells to the purified hepatocytes. TNF alpha was detected in the medium of non-parenchymal cell (3-15 pg/ml) and normal hepatocyte cultures (25-100 pg/ml) by bioassay using L929 cells. However, the contribution of TNF alpha released from non-parenchymal cells was small compared with that released spontaneously by hepatocytes. Nafenopin significantly increased the release of TNF alpha from non-parenchymal cells to 56 +/- 18 pg/ml, but had little effect on TNF alpha release by hepatocytes. However, the concentration of exogenous TNF alpha required to elicit a response in hepatocytes was 100 pg/ml and above. These data provide evidence that hepatic non-parenchymal cells are permissive for the growth response of hepatocytes in vitro to peroxisome proliferators and this may be mediated, at least in part by TNF alpha. However, the levels of TNF alpha released spontaneously or in response to peroxisome proliferators are insufficient per se to induce a growth response.