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Biomedical subjects

A J Klein

Publications and source records attributed to A J Klein.

At least 19 recordsLinked to original sources
PubMed2000

Antioxidant enzymes are induced during recovery from acute lung injury.

OBJECTIVE: To determine the contribution of the pulmonary antioxidant defense enzymes of the hexose monophosphate (HMP) shunt and glutathione systems to recovery from oxidant-mediated lung injury in an animal model shown to closely resemble the clinical syndrome of acute respiratory distress syndrome. DESIGN: Prospective, controlled laboratory study on phorbol myristate acetate (PMA)-induced lung injury in rabbits. SETTING: Animal research laboratory. SUBJECTS: Rabbits were injected with PMA (80 microg/kg) for 3 consecutive days. Control animals received normal saline. MEASUREMENTS AND MAIN RESULTS: Lungs were harvested at 24, 48, 72, and 96 hrs (n = 5/time point) after PMA injection or after the third injection of normal saline in control animals (n = 6). The cytosolic fraction from lung and bronchial alveolar lavage (BAL) fluid was used for measurements of HMP shunt and glutathione enzymes. Pulmonary activity peaked at 48 hrs post-PMA injury with a 40% increase in glucose-6-phosphate dehydrogenase activity and a 32% increase in 6-phosphogluconate dehydrogenase activity over control levels. BAL activity was maximal at 72 hrs with an increase of 98% in glucose-6-phosphate dehydrogenase and 346% in 6-phosphogluconate dehydrogenase activities. Glutathione peroxidase was maximally induced by 77% at 48 hrs in BAL and by 107% at 24 hrs in lung. Glutathione reductase activity did not increase significantly in either lung or BAL. CONCLUSIONS: The observed induction of the antioxidant enzymes in response to PMA suggests that both the HMP shunt and the glutathione systems contribute to the recovery phase of oxidant-mediated lung injury. The inability of natural host defenses to regenerate reduced glutathione may explain failure of recovery from acute respiratory distress syndrome and suggests an avenue for clinical intervention.

Animals↗
PubMed1999

Hearing loss.

Hearing loss may be caused by either a conductive problem, such that the sound waves do not reach the tympanic membrane, ossicles or inner ear, or a sensorineural problem, in which the cochlea and/or auditory nerve are somehow damaged. A combination of the above may also occur. The various causes of hearing loss and the options in treatment will be presented.

Cochlear Nerve↗
PubMed1999

Hearing aids.

The first step in the hearing aid fitting and selection process is to determine the patient's hearing disability, motivation, lifestyle, finances, and cosmetic concerns. Most hearing impairments can be helped with a modern hearing aid. With a symmetric hearing loss, a binaural fitting provides the most benefit and should be attempted initially. The binaural fitting may not be successful in cases with large asymmetries in auditory function. The advances in electronic technology, such as the digital hearing aid, are moving faster than the research to determine which is the most effective signal processing method. The near future should yield more significant improvements in hearing aids that will provide a better quality of life of the hearing-impaired population.

Attitude to Health↗
PubMed1999

Traumatic hematuria in patients with polycystic kidney disease.

Autosomal dominant polycystic kidney disease (PKD) is the most prevalent hereditary disorder in this country and a common cause of chronic renal failure. Patients frequently present with hematuria as the initial manifestation of PKD. We describe a patient with gross hematuria after blunt trauma who was found to have previously undiagnosed PKD. We review present diagnostic and treatment modalities and suggest potential management strategies for surgeons caring for patients presenting with traumatic hematuria and PKD.

Adult↗
PubMed1999

Hearing-aid-processed tone pips: electroacoustic and ABR characteristics.

The auditory brainstem response (ABR) recorded while wearing a hearing aid may supply supplemental information about the benefit and appropriateness of the hearing aid for certain infants. The purposes of this study were (1) to determine the effects of different output limiting circuits on the acoustics of tone-pip stimuli used for ABR recordings and (2) assess how changes in hearing-aid-processed stimuli affect ABR characteristics. Electroacoustic input/output functions to tone-pip stimuli were constructed for three different output limiting circuits (wide dynamic range compression, output compression, and linear with peak clipping) available in a programmable hearing aid. Wave V latency and amplitude functions were then measured to the same stimuli and hearing aid settings in five normal-hearing adults. Electroacoustic results showed that none of the output limiting circuits, including linear peak clipping, were effectively activated by tone pips compared to the hearing aid performance to continuous tones. Aided wave V latency and amplitude functions were asymptotic to high stimulus levels, suggesting that cochlear output was in saturation.

Acoustics↗
PubMed1997

Cognitive, adaptive, and behavioral characteristics of Williams syndrome.

Williams syndrome is a genetic disorder linked to cognitive and behavioral patterns of varying consistency; this study was conducted to clarify further the strengths and weaknesses of children with Williams syndrome. Fifteen subjects with the characteristic features of Williams syndrome were evaluated using the Stanford-Binet Intelligence Scale for Children, Fourth Edition; the Vineland Adaptive Behavior Scales, Interview Edition; and the Child Behavior Checklist. Cognitive skills ranged from the Moderate Range of Mental Retardation to the Low Average range, with relative strengths in nonverbal and quantitative reasoning. Adaptive skills were delayed, with strengths in communication and socialization. Behaviorally, clinically significant levels of attention problems, borderline-significant levels of social and thought problems, and significantly low levels of social contacts and structured activities were found. In contrast to the findings of many other studies of Williams syndrome, language skills and short-term memory skills were weak. Children with Williams syndrome may present a more evenly developed intellectual profile, with verbal and nonverbal skills being commensurate. In conclusion, a variety of cognitive, adaptive, and behavioral patterns have been shown to be possible in Williams syndrome; therefore, a single predictable cognitive or behavioral phenotype cannot be assumed.

Activities of Daily Living↗
PubMed1997

Pass/fail rates for repeated click-evoked otoacoustic emission and auditory brain stem response screenings in newborns.

The click-evoked otoacoustic emission (EOAE) recording procedure is a simple and quick test to perform. Some suggest that the EOAE is a more efficient newborn hearing screening procedure than the auditory brain stem response (ABR). However, one shortcoming of the EOAE is a high false-positive rate in newborns, which is attributed to ear-canal debris. The purposes of this study were to assess the initial pass/fail rates of ABR and EOAE measurements and the effectiveness of repeated EOAE measurements as a method of reducing the false-positive rate. Fifty healthy, low-risk newborns sequentially underwent ABR, repeated EOAE, otoscopy, EOAE, and ABR if necessary. The initial ABR passing rate was 98%, whereas the EOAE passing rate was 61%. The EOAE passing rate improved with each retest and approximated the ABR rate by the fourth test. EOAE failures and the overall level of the EOAE were found to be significantly related to the amount of ear-canal debris. These results indicate that some newborns will require four or more tests before they eventually pass. Further study is needed to determine the overall cost-effectiveness of the EOAE as compared with the ABR before specific recommendations for a universal hearing screening program are proposed.

Age Factors↗
PubMed1995

Distance from an intrauterine hydrophone as a factor affecting intrauterine sound pressure levels produced by the vibroacoustic stimulation test.

OBJECTIVE: The purpose of this study was to determine whether intrauterine sound pressure levels produced by vibroacoustic stimulation were associated with distance from an intrauterine hydrophone in human parturients and to evaluate the effects of distance on the spectrum of the stimulus. STUDY DESIGN: Measurements of intrauterine sound were taken in eight volunteer parturients in normal active-phase labor by use of an intrauterine hydrophone. Vibroacoustic stimulation was performed on the maternal abdomen directly overlying the hydrophone; at distance of 5, 10, 15, 20, and 25 cm from the hydrophone; and at the maternal sternum. Intrauterine sound pressure levels were tape-recorded for later analysis. Fetal heart rate and fetal movement were assessed with each vibroacoustic stimulation. Spectral analyses were performed by taking the fast Fourier transform of the tape-recorded stimulation at each position. RESULTS: Analysis of variance with repeated measures indicated a statistically significant decrease (F = 4.1, p = 0.004) in the sound pressure levels as distance increased. Spectral analysis indicated large variability between and within subjects. CONCLUSION: Sound exposure of the fetal ear is on average decreased as the distance between the ear and the vibroacoustic stimulation is increased. The spectrum of the stimulus produced with vibroacoustic stimulation is highly variable.

Acoustic Stimulation↗
PubMed1995

Confidence limits for maximum word-recognition scores.

Clinical judgments are often made regarding whether maximum word-recognition scores (PBmax) are appropriate in relation to degree of sensorineural hearing loss. In order to determine if word recognition is significantly poorer than expected, it is necessary to consider the lower boundary of PBmax associated with a particular degree of hearing loss for speech materials commonly used to measure word recognition. The purpose of this experiment was to define a confidence limit for PBmax from Northwestern University Test #6 (NU-6) word-recognition scores obtained from a large group of young and aged subjects with confirmed cochlear hearing loss. Word-recognition scores at several speech levels were obtained from 407 ears with a wide range of pure-tone averages. Because the characteristics of the distribution of maximum scores are not known, a procedure was developed using computer simulations to approximate the distribution of word-recognition scores corresponding to PBmax and determine the 95% confidence limit (CL). Results of the simulation were confirmed by comparing means and standard deviations of PBmax derived from experimental and simulation data. Percentages of young and aged subjects with scores outside the 95% CL are equal to their proportions in the entire subject sample. If PBmax determined from a score-level psychometric function is poorer than the 95% CL, PBmax may be considered "disproportionately" poor in relation to the degree of hearing loss. One score measured at a single arbitrary suprathreshold level that is poorer than the 95% CL suggests that the score may underestimate PBmax and that word recognition should be measured at additional levels to obtain a more reasonable estimate of the listener's maximum word-recognition score.

Adult↗
PubMed1993

Minimal upward spread of masking: correlations with speech and auditory brainstem response masked thresholds.

Much less than predicted upward spread of masking, termed undermasking, was previously noted in three elderly listeners, who are the focus of this report. Three aspects of undermasking were studied: Reliability, facilitation of speech recognition in noise, and correlation with physiological measurements. The masker was a 90-dB-SPL 1-kHz low-pass-filtered noise. Reliability of undermasking was assessed from serial measurements made over an approximately 2-year interval. Masked speech thresholds were measured with an adaptive procedure for two types of stimuli: spondaic words and the California Consonant Test. Subjects with undermasking had substantially lower masked speech thresholds than either audiometrically matched elderly subjects or young, normal-hearing subjects. It appears that undermasking is a stable characteristic that provides the listener with exceptionally good communication abilities in noise. Finally, a strong positive correlation was observed between the masked auditory brainstem response (wave V) threshold and the masked behavioral threshold, suggesting that the mechanism producing undermasking is in the auditory periphery.

Acoustic Stimulation↗
PubMed1992

Infant screening.

Explore the source record for details and available documents.

Acoustic Impedance Tests↗
PubMed1992

The effects of stimulus rate on detectability of the auditory brain stem response in infants.

This study was undertaken to determine the feasibility of using a fast stimulus rate for auditory brain stem response (ABR) hearing screening in infants. Eighty-four neonates and infants with postconceptional ages (PCA) from 30 to 78 weeks with clear ABRs to click rate of 40/sec at 30 dB HL were retested at 90/sec. Ninety-two percent of infants with PCA > 42 weeks had a clearly identifiable ABR at the 90/sec rate. In contrast, 71% of the infants with PCA between 37 and 42 weeks, and only 50% of the infants with PCA < 37 weeks, had clearly identifiable ABRs at 90/sec. Thus, a 90/sec stimulus rate was not practical on infants < 43 weeks PCA. Accordingly, ABR detectability was assessed to 40 dB clicks at 70/sec compared to the 40/sec rate on 20 infants between 33 and 42 weeks PCA. ABRs were detectable on 85% of this group, which suggests that these parameters may be more reasonable, but further data are needed. ABR measures for hearing screening on infants > 42 weeks and children can be satisfactorily performed at stimulus rates up to 90/sec; however, infants who fail the screening when using a fast stimulus rate should have a repeated measurement at a slower rate to rule out a false positive result.

Acoustic Stimulation↗
PubMed1991

Occupational hearing conservation.

Chronic exposure to high-intensity noise can produce permanent hearing loss, the amount of which depends on noise intensity, temporal and spectral characteristics, and the length of exposure. OSHA regulates workplace noise exposure in accordance with the Hearing Conservation Amendment of 1983. When noise levels equal or exceed an 85 dBA time-weighted average (TWA), the employer is required to provide annual audiometric screening. When noise levels exceed 90 dBA TWA, the worker's exposure must be reduced by engineering methods, administrative changes, or personal hearing protectors. If a worker demonstrates a standard (significant) threshold shift (10 dB or greater increased average hearing threshold at 2, 3, and 4 kHz in either ear) that is attributed to noise, the worker's exposure must be further reduced by one of the aforementioned methods.

Ear Protective Devices↗
PubMed1990

Hyperacusis and otitis media in individuals with Williams syndrome.

Williams syndrome is characterized by cardiac defects, varying degrees of physical and developmental delay, stellate eye pattern, possible elevated serum calcium level, and elfin/pixie facial features. A problem perhaps unique to these children is hyperacusis that can be severe enough to disrupt many routine daily activities. Parental questionnaires were used to determine the prevalence of hyperacusis and otitis media in individuals with Williams syndrome. Prevalences of 95% for hyperacusis and 61% for otitis media were found. This was significantly higher than in the general population. Despite the prevalence of hyperacusis, parents of these children were not counseled about management of the problem. The audiologist may become involved with Williams syndrome patients through hearing assessment and management, parental counseling, and research.

Adolescent↗
PubMed1990

Upward spread of masking, hearing loss, and speech recognition in young and elderly listeners.

Upward spreading of masking, measured in terms of absolute masked threshold, is greater in hearing-impaired listeners than in listeners with normal hearing. The purpose of this study was to make further observations on upward-masked thresholds and speech recognition in noise in elderly listeners. Two age groups were used: One group consisted of listeners who were more than 60 years old, and the second group consisted of listeners who were less than 36 years old. Both groups had listeners with normal hearing as well as listeners with mild to moderate sensorineural loss. The masking paradigm consisted of a continuous low-pass-filtered (1000-Hz) noise, which was mixed with the output of a self-tracking, sweep-frequency Bekesy audiometer. Thresholds were measured in quiet and with maskers at 70 and 90 dB SPL. The upward-masked thresholds were similar for young and elderly hearing-impaired listeners. A few elderly listeners had lower upward-masked thresholds compared with the young control group; however, their on-frequency masked thresholds were nearly identical to the control group. A significant correlation was found between upward-masked thresholds and the Speech Perception in Noise (SPIN) test in elderly listeners.

Adolescent↗
PubMed1989

Assessing speech recognition in noise for listeners with a signal processor hearing aid.

Hearing aids with signal processors use advanced circuitry to enhance speech recognition in noise. The effectiveness of these processors has not been well established. The purpose of this study was to evaluate performance on a speech recognition in noise task for listeners wearing a Zeta signal processor aid with the processor turned on and with the processor turned off. In addition, comparisons were made to performance while unaided and aided with a conventional hearing aid. A simple adaptive procedure and a psychometric function were the procedures used. Results for normal-hearing subjects indicate performance was usually better without a hearing aid. Performance when aided was similar for the processor on and the conventional aid. Performance in both of these conditions was clearly better than with the signal processor off. Although results for the hearing-impaired subjects varied widely, there was a trend for better performance with the conventional aid and with the signal processor on than for the signal processor off condition.

Adaptation, Physiological↗
PubMed1987

Effect of signal temporal shaping on the frequency specificity of the action potential in gerbils.

We examined the effects of temporal shaping of a tone burst on the frequency specificity of evoked responses in gerbils. Frequency specificity was assessed by means of whole-nerve action potential (AP) tuning curves (APTCs). The envelopes of the onset and offset portions of the AP-eliciting tone burst (or probe) were either a linear or nonlinear (1/4 sine) function of time. At probe frequencies of 1, 4 and 8 kHz, APTCs in the two envelope conditions were similar in shape and had equally narrow tips. This was true at both low (40-50 dB SPL) and high (70-75 dB SPL) probe levels. It suggests that tone bursts in the two envelope conditions evoke AP responses that are equally frequency specific. Despite these similarities, a notable difference in the two conditions was found at high probe levels. Specifically, raising the level of an 8-kHz probe from 40 to 70 dB SPL resulted in a downward shift of the APTC tip frequency, and this shift was greater for probes with linear on-off envelopes than for those with nonlinear on-off envelopes. This result suggests that of the two waveform shapes, the nonlinear envelope is likely to produce responses at frequencies closer to the nominal signal frequency. Reducing the rise-fall time of the probe from 2.0 to 0.75 ms caused the tip of the 8-kHz APTC to undergo an even greater displacement in frequency, indicating a greater 'off-frequency' response for briefer rise times.

Action Potentials↗