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Biomedical subjects

R Probst

Publications and source records attributed to R Probst.

At least 109 records · Page 6Linked to original sources
PubMed1988

Spontaneous otoacoustic emissions in a nonhuman primate. II. Cochlear anatomy.

Both cochleas of a rhesus monkey exhibiting stable spontaneous and stimulus-frequency emissions were evaluated histologically using surface-preparation methods to determine if certain features of these emissions could be related to structural properties of the organ of Corti (OC). The comprehensive assessment included preparation of routine cytocochleograms and a detailed study of the arrangement of cochlear sensory cells, best revealed by the precise positional relationships between stereocilia bundles, in selected areas representing low-, medium-, and high-frequencies. Several additional measurements were made in an area extending from about 25-60% distance from the apex, which was estimated to encompass the cochlear region where emissions were generated. These quantifications included measures, in both micrometers and Hertz, of the distances between irregularities in the lateral border of the OC due to a sporadically occurring fourth row of outer hair cells (OHCs). Measures, in micrometers, of the changes in the radial extent of the corresponding OC in the presence or absence of this extra fourth row of OHCs were also made. A final measure within low-, medium-, and high-frequency OC regions consisted of describing the angles that the tips of the stereocilia bundles were displaced from an axis parallel to the tunnel of Corti. For comparative purposes, similar plots were made in comparable regions of the OC in the normal and experimental cochleas of three additional rhesus monkeys in which one ear had been systematically exposed to noise. In the emitting-monkey cochlea, there was a mild loss of sensory cells scattered throughout the OC which was generally greater for the OHCs. No evidence of small circumscribed lesions, defined as a loss of more than four adjacent hair cells, was found. The most striking observation which varied in degree across the three other monkeys was a generalized irregularity in the cellular organization of the OHC region which was most pronounced in the low- and midfrequency regions of the OC. The notable cellular disorganization specific to the apical half of the cochlea was reflected by an increased variance in the distribution of deviation angles measured for corresponding stereocilia bundles. Outer hair cells in the remaining basal region of the OC were arranged in three regular rows with the usual stereocilia orientation.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustics↗
PubMed1987

Acoustic distortion products in rabbit ear canal. I. Basic features and physiological vulnerability.

In contrast to evoked otoacoustic emissions, acoustic distortion products (DPs) recorded from the ear canal are present at predictable frequencies with respect to their primary tones, f1 and f2. Such specificity may provide detailed frequency-place information concerning the functional state of limited regions of the organ of Corti following experimental intervention. However, to date, it is not clear whether emitted DPs solely reflect activity at the basilar-membrane regions of primary tones or if the remote DP site makes a significant contribution to the emitted signal measured in the ear canal. We have investigated a number of the general features of acoustic-DP generation in the rabbit so that, in later experiments, the contributions of specific basilar-membrane regions involved in generating these DPs can be identified using techniques designed to manipulate their normal properties. The first report describes the outcome of systematic manipulations of a number of stimulus conditions and alterations to the physiological state of the cochlea by exposure to fatiguing sound or anoxia. Experimental findings for the 2f1-f2 DP showed that, in general, the relations of the levels and frequency of the primary tones to DP magnitude were consistent with previously published data from other mammalian species. Additional observations for other odd-order intermodulation DPs at the 3f1-2f2 and 2f2-f1 frequencies suggested that the basic attributes of the acoustic DPs were similarly affected by systematic manipulation of the basic parameters of the primary tones and the general metabolic state of the cochlea. General anesthesia, however, did not affect DP amplitude. A companion paper describes the results of a series of subsequent experiments using response-suppression, interfering-tone, and temporary threshold shift techniques which address more directly the issue of which basilar-membrane sites contribute to the generation of different acoustic DPs.

Anesthesia, General↗
PubMed1987

Acoustic distortion products in rabbit ear canal. II. Sites of origin revealed by suppression contours and pure-tone exposures.

Previous work on acoustic distortion products (DPs) recorded from the ear canal has not established unequivocally whether emitted DPs principally reflect basilar-membrane nonlinearities at the frequency sites of the primary tones, f1 and f2, or if the DP-frequency place itself makes a significant contribution to the emitted response. Results from some studies on acoustic emissions attribute generation of the emitted DP almost exclusively to the regions of maximum primary-tone interaction, while the findings of other investigations implicate reemission of the response from the DP locus as a significant contributor to response magnitude. Using suppression, interfering tones, and temporary threshold shift (TTS) procedures, the work reported here was designed to establish more definitively the precise contributions of the basilar-membrane regions involved in generating acoustic DPs in rabbits. Suppression tuning curves and interfering-tone experiments indicated that for the DP at 2f1-f2, regions near the f1 or f2 frequencies were the major contributors to the emitted response. However, for the higher-frequency DP at 2f2-f1, the basilar-membrane region just basal to the DP site was implicated as the generator. Following brief episodes of TTS at frequencies related to either the DP or the primary tones, the locus of the exposure stimulus that most effectively reduced the magnitude of the 2f1-f2 response also implicated the region of maximal primary-tone interaction in the generation of the acoustic DP. In contrast, for the DP at 2f2-f1, basilar-membrane sites nearer the DP were identified as the primary contributors to the emitted response. Both sets of results imply that different DPs recorded from the ear canal may originate from unique regions of primary-tone interaction along the basilar membrane.

Acoustic Stimulation↗
PubMed1986

Spontaneous, click-, and toneburst-evoked otoacoustic emissions from normal ears.

Evoked and spontaneous otoacoustic emissions were recorded bilaterally in a group of normal subjects (n = 14) using clicks and tonebursts at four frequencies (0.5, 1, 1.5, and 3 kHz). All ears (n = 28) demonstrated evoked emissions, but not to every stimulus type. The 0.5-kHz toneburst evoked emissions in only 10 (36%) ears, the 1.5-kHz toneburst in all ears, and the remaining stimuli in at least 80% of ears. Two distinct patterns of evoked emissions were identified. Five (18%) ears showed short, broadband click-evoked emissions lasting less than 20 ms after stimulus onset. In these ears, toneburst-evoked emissions were often more prominent than click-evoked emissions and no spontaneous emissions were detected. Twenty-three (82%) ears showed click-evoked emissions lasting longer than 20 ms poststimulus onset. Spectral analysis of these emissions demonstrated several (2-10) narrow frequency peaks. Highly similar peaks were present in the spectra of toneburst-evoked emissions within the range of toneburst spectra. Spontaneous emissions were recorded in 12 of the 23 ears. In these ears, at the frequencies of spontaneous emissions, prominent peaks in both click- and toneburst-evoked emission spectra were always present. Otoacoustic emission characteristics correlated significantly between the ears of individual subjects inferring that a symmetrical cochlear mechanism generates otoacoustic emissions.

Acoustic Stimulation↗
PubMed1985

Construction and experimental application of a catheter for selective arterial kidney perfusion in situ.

In order to improve dog kidney perfusion in situ with a protective solution, a perfusion catheter was constructed which allowed continuous pressure measurement in the center of the catheter tip during perfusion. Using this catheter, the equilibration of the extracellular space with a protective solution (HTK solution) was found to be pressure dependent. Continuous pressure and resistance control is therefore a prerequisite for reliable organ protection.

Animals↗
PubMed1985

Spontaneous otoacoustic emissions in the nonhuman primate: a survey.

A number of reports have described a relatively high incidence of spontaneous otoacoustic emissions (SOAEs) in recordings made from the sealed human ear canal. Our attempt to detect similar emissions in 122 presumably normal-hearing ears from 61 monkeys revealed SOAEs in 5% of the primates and 2.5% of the ears tested.

Animals↗
PubMed1983

Electrocochleography: using extratympanic or transtympanic methods?

The advantages and disadvantages of the transtympanic and extratympanic methods for recording electrocochleographic potentials (ECochG) are discussed. Our extra-tympanic method (adapted from Coats) and some results are presented. We conclude that for broad clinical application an ear canal surface electrode is the method of choice for recording ECochG, unless the primary question is one of threshold measurement. If the registration of brainstem potentials from the vertex does not show a potential I, we recommend simultaneous recording of ECochG by an extratympanic method with earphones.

Audiometry↗
PubMed1983

[Neuro-otologic findings in the Wernicke-Korsakoff syndrome].

The Wernicke-Korsakoff syndrome is induced by thiamine deficiency. It occurs mainly in subjects with chronic alcoholism. It begins with an acute phase (Wernicke's encephalopathy) and changes to a chronic phase, which is characterized by a symptomatology varying from subclinical findings to a fully developed Korsakoff psychosis. We examined otoneurologically eight patients with Wernicke-Korsakoff syndrome. The examination included: clinical status, caloric stimulation, optokinetic nystagmus, pure tone audiogram (air- and bone conduction), speech audiogram, and brain-stem auditory evoked potentials. The typical findings of the chronic phase are: gaze nystagmus and reduced gain of the optokinetic nystagmus. In five of seven patients OK gain was reduced by more than two standard-deviations. The other examinations including brain-stem potentials did not reveal any specific findings. The symptomatology of the acute phase is well known: nystagmus (mostly lateral gaze nystagmus) and reduced by caloric responses. Early diagnosis of a Wernicke-Korsakoff syndrome is of great importance since its treatment is simple and efficient. The results of a thorough neuro-otologic examination are of considerable diagnostic value, particularly during the chronic phase of the disease.

Adult↗
PubMed1976

[Change of working place in occupational noise].

Nowadays noise in industry cannot be eliminated by technical means alone. Therefore, exposed workers have to wear an ear protector to prevent the occurrence of deafness caused by professional noise. Patients with chronic otitis media and permanent or intermittent otorrhea should avoid the prolonged use of ear protectors. On principle, such patients are not allowed to work in a noisy environment (inaptitude for noisy employment/change of occupation) unless the contraindication for use of ear protectors can be eliminated by therapeutic means (such as operation).

Cerebrospinal Fluid Rhinorrhea↗