Complex Mixture Analysis of Emerging Contaminants Generated from Coal Tar- and Petroleum-Derived Pavement Sealants: Molecular Compositions and Correlations with Toxicity Revealed by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry.

Pavement sealants are of environmental concern because of their complex petroleum-based chemistry and potential toxicity. Specifically, coal tar-derived sealants contain high concentrations of toxic/carcinogenic polycyclic aromatic hydrocarbons (PAHs) that, when weathered, can be transferred into the surrounding environment. Previous studies have demonstrated the effects of coal tar sealants on PAH concentration in nearby waterways and their harmful effects in aquatic ecosystems.

Time-dependent molecular progression and acute toxicity of oil-soluble, interfacially-active, and water-soluble species reveals their rapid formation in the photodegradation of Macondo Well Oil.

Photodegradation is a significant weathering process that transforms spilled oil, yet, the fate, degradation rate, and molecular transformations that occur through photoinduced pathways remain relatively unknown. The molecular complexity combined with the increased polarity of photoproducts challenges conventional analytical techniques. Here, we catalogue the molecular progression of photochemical transformation products of Macondo Well Oil by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS).

The MOC reflex during active listening to speech.

Purpose: The purpose of this study was to test the hypothesis that active listening to speech would increase medial olivocochlear (MOC) efferent activity for the right vs. the left ear.

Method: Click-evoked otoacoustic emissions (CEOAEs) were evoked by 60-dB p.

TEOAE suppression in adults with learning disabilities.

The presentation of contralateral noise during the recording of transient evoked otoacoustic emissions (TEOAEs) reduces the amplitude of the TEOAE in normally-hearing adults. This is known as TEOAE suppression. The present study investigated TEOAE suppression in 18 adults with learning disabilities (LDs) compared to 18 adults without LDs.

Comparison of transient evoked otoacoustic emissions and distortion product otoacoustic emissions when screening hearing in preschool children in a community setting.

Objective: The first purpose of this study was to compare transient evoked otoacoustic emissions (TEOAE) with distortion product otoacoustic emissions (DPOAE) to determine if they resulted in equivalent signal-to-noise ratios (SNRs) when used for hearing screening in a preschool population in a community setting. The second purpose was to determine if the OAE methods would result in equivalent pass/refer rates. The third purpose was to determine the agreement between the pass/refer rates from a tympanometric screening and the pass/refer rates from each OAE method.

Do children and adults with language impairment recognize prosodic cues?

Purpose: Prosodic cues are used to clarify sentence structure and meaning. Two studies, one of children with specific language impairment (SLI) and one of adults with a history of learning disabilities, were designed to determine whether individuals with poor language skills recognize prosodic cues on par with their normal-language peers.

Method: Participants were asked to determine whether low-pass filtered sentences matched unfiltered target sentences.

A comparison of two methods of hearing screening in the preschool population.

Unlabelled: The outcome of hearing screening using conventional pure tone behavioral testing was compared with the outcome employing measures of transient otoacoustic emissions (TEOAEs) in a preschool population under conditions typical of educational settings. Two hundred children ranging in age from 2 years 1 month to 5 years 10 months were screened. Nearly equal numbers of children were referred from the two types of screening activities.

The effect of noise bandwidth on the contralateral suppression of transient evoked otoacoustic emissions.

The purpose of this study was to determine whether the bandwidth or loudness of a contralateral stimulus is the most important factor in evoking suppression of transient evoked otoacoustic emissions (TEOAEs). TEOAEs were measured in both ears of 10 women in quiet and in the presence of one of three contralateral noise bands; narrow band (NB), wide band (WB) and equalized (EQ), all centered at 2000 Hz. The NB (100 Hz bandwidth) and WB (2200 Hz bandwidth) noises were presented at 60 dB SPL.

Distortion product otoacoustic emissions created through the interaction of spontaneous otoacoustic emissions and externally generated tones.

Spontaneous otoacoustic emissions (SOAEs) and external tones (XTs) were used as primaries f2 and f1, respectively (frequency of f2 > f1) to create 2f1--f2 distortion product otoacoustic emissions (DPOAEs). Amplitude and frequency of the SOAEs, XTs, and DPOAEs were recorded by placing a sensitive microphone in the ear canal and extracted using fast Fourier transform analysis. XTs were presented to ten ears at SOAE/f1 ratios between 1.

Multichannel waveforms and topographic mapping of the auditory brainstem response under common stimulus and recording conditions.

Topographic representation of brain electrical activity may be employed to provide information about excitation patterns and symmetry of responses to sensory stimulation. The present investigation describes the waveforms and topographic distribution of the auditory brainstem response (ABR) in normal-hearing and neurologically-normal women during several stimulus and recording conditions using a multiple electrode array. Acoustic stimuli were rarefaction clicks presented monaurally at five intensities.

Detection of hearing loss in young children and adults using otoacoustic emissions.

Measures of transient evoked otoacoustic emission (TEOAE) reproducibility were obtained for 506 ears of 260 children and young adults. Frequency-specific and whole reproducibility data were obtained using ILO88 hardware and software (version 3.92), and were analyzed with respect to pure tone threshold and emmittance data for the same ears.

Conductive hearing loss in bighorn sheep.

In January 1993 we simulated a conductive hearing loss in three Mexican bighorn sheep (Ovis canadensis mexicana) by placing bone wax or saline solution in their ear canals. Our objective was to test whether lesions of the external auditory canal caused by psoroptic mites (Psoroptes ovis) may lead to conductive hearing loss in bighorn sheep. We assessed the effects of these manipulations using the auditory brainstem response test.

A nicotinic-like receptor mediates suppression of distortion product otoacoustic emissions by contralateral sound.

The purpose of this investigation was to provide in vivo pharmacologic characterization of a cholinergic receptor mediating the suppressive effects of medial olivocochlear (MOC) efferent activation. MOC neurons were activated by contralateral sound and the resulting suppression of ipsilateral distortion product otoacoustic emissions (DPOAEs) was monitored before and after intracochlear perfusions of cholinergic antagonists. Results revealed a dose-dependent blockade of contralateral suppression of DPOAEs by a wide variety of nicotinic and muscarinic cholinergic receptor antagonists, as well as by non-traditional antagonists of cholinergic activity.

Contralateral sound suppresses distortion product otoacoustic emissions through cholinergic mechanisms.

Presentation of an acoustic signal to one ear can suppress sound-evoked activity recorded at the opposite ear. The suppression appears to be mediated by medial olivocochlear (MOC) efferent neurons synapsing with outer hair cells (OHCs) and acting through the MOC neurotransmitter, acetylcholine (ACh). The purpose of the present investigation was to study the suppression of distortion product otoacoustic emissions (DPOAEs) by contralateral sound and to examine whether the suppression could be blocked by known antagonists of olivocochlear (OC) efferent activity.

Intracochlear application of acetylcholine alters sound-induced mechanical events within the cochlear partition.

Activation of olivocochlear (OC) efferent fibers has been suggested to alter micromechanical events occurring within the cochlear partition, possibly through an effect of the efferent neurotransmitter (acetylcholine; ACh) on outer hair cells (OHCs). Based on the widely-accepted assumption that otoacoustic emissions reflect OHC activity, we investigated the in vivo influence of ACh on OHCs by studying alterations in emission amplitude with local ACh application. Distortion product otoacoustic emissions (DPOAEs) were measured in anesthetized guinea pigs before, during, and after intracochlear application of ACh (250 microM) with the cholinesterase inhibitor, eserine (20 microM).

Otoacoustic Emissions.

Otoacoustic emissions are low-intensity sounds that are produced in the cochlea and transmitted through the middle ear apparatus to the ear canal. They can be detected and extracted from the background noise in the ear canal through the use of a sensitive microphone and selective filtering or averaging techniques. The technical aspects of emission recording are very similar to those associated with the detection and capture of auditory evoked potentials.

Reliability of spontaneous otoacoustic emission suppression tuning curve measures.

The purpose of this investigation was to study the reliability of spontaneous otoacoustic emission (SOAE) suppression tuning curve (STC) measurements. Two repetitions of an SOAE STC, using a 4-dB suppression criterion, were obtained from 5 subjects who exhibited stable SOAE level (SD less than or equal to 1.5 dB) and SOAE frequency (+/- 5 Hz).

A phase II study of alpha-difluoromethylornithine (DFMO) for the treatment of metastatic melanoma.

Difluoromethylornithine (DFMO) is an irreversible enzyme-activated inhibitor of ornithine decarboxylase, a key enzyme in polyamine synthesis. We have screened for potential anti-cancer activity of DFMO using a clonogenic assay, which suggested that melanoma might have sensitivity to this agent. Accordingly, we have performed a phase II trial of DFMO (2 g/m2 po q 8 h) in 24 patients, 21 of whom were evaluable for response.

Effect of ibuprofen upon hearing in the guinea pig.

The authors investigated the effect of varying doses of ibuprofen upon the hearing of guinea pigs monitored with brain stem-evoked response procedures. In daily dosages comparable on a weight basis to therapeutic levels in humans, ibuprofen was found not to have significant effects on response threshold or latency characteristics.

Electrophysiologic response audiometry: state of the art.

Electrophysiologic response audiometry (ERA) is based upon recording neuroelectric potentials from sites extending from the cochlea to the cortex. These recordings rely on the use of averaging computers to extricate desired neuroelectric responses from the ongoing background electrical activity of the human auditory system and brain. The different neuroelectric responses are distinguished by response latency, response waveform, and probable site of origin.

Cochlear implants: technical and clinical implications.

Recent investigations using animal models and human subjects have helped to define the limits which are achievable in terms of information transfer with single-channel electrical stimulation of the auditory nerve. These studies are reviewed, and presented as a context for a description of the development of an implantable multiple-electrode multiplexing system which may provide control for several stimulus channels. While such a device may enable the stimulation of small segments of the auditory nerve independently, it does not contain any means of complex stimulus analysis and recording.