Biomedical subjects

W Melnick

Publications and source records attributed to W Melnick.

7 recordsLinked to original sources

PubMed1992

[Cystic tumor of the mediastinum of digestive origin. Apropos of a new case. Diagnostic and pathogenic hypotheses].

An incidental discovery of a posterior and inferior mediastinal cyst-like opacity allowed us to diagnose a pulmonary sequestration in a 45-year old woman. The operative findings showed an hour-glass tumor of the inferior mediastinum with an abdominal prolongation attached by a stalk onto the top of the stomach. These findings made us change our diagnosis in favour of an abdomino-thoracic gastric duplication. This new hypothesis was not confirmed by the results of the pathological report which revealed two kinds of tissue; intestinal in the abdomen and broncho-pulmonary in the chest. Two diagnoses where then proposed: complex hamartoma or mediastinal bronchogenic cyst. The pathogenic interpretation in such cases is still very controversial. English authors are prone to classify them as broncho-pulmonary foregut malformations. Macroscopic and microscopic data of the specimen led us to consider our case-report to be a foregut malformation.

Angiography↗

PubMed1991

Human temporary threshold shift (TTS) and damage risk.

Information regarding the relation of human temporary threshold shift (TTS) to properties of steady-state and intermittent noise published since the 1966 appearance of the CHABA damage risk contours is reviewed. The review focuses on results from four investigative areas relevant to potential revision of the CHABA contours including effects of long-duration exposure and asymptotic threshold shifts (ATS); equivalent quiet and/or safe noise levels; effects of intermittency; and use of noise-induced temporary threshold shift (NITTS) to predict susceptibility to noise-induced permanent threshold shift (NIPTS). These data indicate that two of three major postulates on which the original contours were based are not valid. First, recovery from TTS is not independent of the conditions that produced the TTS as was assumed. Second, the assumption that all exposures that produce equal TTS2 are equally hazardous is not substantiated. The third postulate was that NIPTS produced by 10 years of daily exposure is approximately equal to the TTS2 produced by the same noise after an 8-h exposure. Based upon several TTS experiments showing that TTS reaches an asymptote after about 8 h of exposure, the third CHABA postulate can be reworded to state the hypothesis that ATS produced by sound of fixed level and spectrum represents an upper bound on PTS produced by that sound regardless of the exposure duration or the number of times exposed. This hypothesis has a strong, logical foundation if ATS represents a true asymptote for TTS, not a temporary plateau, and if threshold shifts do not increase after the noise exposure ceases.

Auditory Fatigue↗

PubMed1991

Hearing compensation evaluation.

Compensation claims for hearing loss are increasing. Physicians and audiologists supply necessary information regarding probable cause and amount of loss for evaluating these claims. Compensable hearing loss can arise from several sources. The principal activity has been claims based on industrial noise exposure. Compensation evaluation is considered as a consequence of noise-induced hearing loss, but the evaluation procedure is applicable regardless of the cause of hearing loss.

Audiometry↗

PubMed1979

Reflex threshold shift in chinchillas following a prolonged exposure to noise.

The acoustic reflex is considered to reduce transmission across the middle ear and thereby protect the inner ear from intense sounds. The dynamic properties of this reflex seem to be a function of the duration of the eliciting stimulus. Assessment of the protective action afforded by middle-ear muscle contractions for long-term noise exposures requires the knowledge of how these dynamic properties change under such conditions. Round window electrodes were implanted in eight chinchillas. Changes in the threshold of the acoustic reflex were measured during an eight-hour exposure at 95 dB SPL to an octave-band noise centered at 0.5 kHz. The criterion measure of the acoustic reflex was a change in the amplitude of the cochlear microphonic generated by a 0.5 kHz eliciting tone. Thresholds of the acoustic reflex increased systematically throughout the noise exposure up to approximately 14 dB after 8 hours. The time course of the changes in the threshold of the acoustic reflex was nearly identical to the time course of behaviorally measured changes in the auditory sensitivity as reported by Carder and Miller (1972).

Acoustic Stimulation↗

PubMed1979

Audiometers.

Explore the source record for details and available documents.

Audiometry↗

PubMedDate not supplied

Temporary threshold shift following 24-hour noise exposure.

Nine men were exposed to 24 hours of continuous noise in a sound field. The noise was an octave band centered at 4 kHz at levels 80 and 85 dB. Hearing thresholds were measured monaurally at 11 test frequencies ranging from 250 to 10000 Hz before, during, and after exposure. Temporary threshold shift (TTS) reached maximum levels at 8 to 12 hours of exposure. Maximum TTS occurred at 4 and 6 kHz. Mean asymptomtic threshold shifts (ATS) resulting from the 80 dB exposure level were 9.3 dB for 4 kHz and 7.2 dB for 6 kHz. For the 85 dB noise level, these threshold shifts were 17.8 dB and 14.6 dB respectively. The increase in ATS with increase of noise level for these two frequencies could be fitted with a straight line having a slope of 1.6.

Auditory Threshold↗

PubMedDate not supplied

Asymptotic threshold shift in people with sensorineural hearing loss.

Twelve men with mild to moderate sensorineural hearing loss in the frequency range of 3 to 6 kHz were exposed to 24 hours of continuous noise. The noise was an octave band centered at 4 kHz at a level of 85 dB. Hearing thresholds were measured monaurally at 11 test frequencies ranging from 250 to 10,000 Hz prior to exposure and at selected intervals during and after exposure. Temporary threshold shift (TTS) development followed a similar time course to that observed in normal hearing subjects, asymptotic levels being reached between 8 and 12 hours of noise exposure. Maximum TTS occurred at 4 and 6 kHz. The amount of TTS was less for the subjects with sensorineural hearing loss than for people with normal hearing. However, the sound pressure level required to detect pure tone (shifted thresholds) following noise exposure was greater in the group with hearing loss than was measured in the normal hearing subjects. Within the limits of this experiment, a sensorineural hearing loss does seem to exert a significant effect on change in hearing sensitivity resulting from noise exposure.

Auditory Threshold↗