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PubMed2006

Resorption of gas trapped in body cavities: comparison of alveolar and pleural space with inner ear and paranasal sinuses.

This paper describes our attempt to devise a short text aimed at improving students' understanding of gas resorption in body cavities. Students are expected to understand the mechanisms behind paranasal sinusitis, otitis media, closed pneumothorax, and atelectasis of collapsed lung tissue, all used as examples. On the basis of the interpretation that during pneumothorax resorption, gas diffuses down pressure gradients into the blood, students are encouraged to calculate tables of pressure gradients for the above-mentioned pathological conditions. After answering a few questions, students need to analyze and eventually accept the following conclusion: in cases of air trapping in collapsible body cavities, all gases will be fully reabsorbed without pain. Air trapping in bone cavities leads only to partial reabsorption of gases and results in subatmospheric intracavity pressure. Partial vacuum causes painful mucosal edema and free fluid secretion.

Absorption↗
PubMed2006

Molecular and physiological bases of the K+ circulation in the mammalian inner ear.

Endolymph, the extracellular solution in cochlea, contains 150 mM K(+) and exhibits a potential of approximately +80 mV relative to neighboring extracellular spaces. This unique situation, essential for hearing, is maintained by K(+) circulation from perilymph to endolymph through the cochlear lateral wall. Recent studies have identified ion-transport molecules involved in the K(+) circulation and their pathophysiological relevance.

Animals↗
PubMedDate not supplied

New approach for 3D imaging and geometry modeling of the human inner ear.

Obtaining high-resolution three-dimensional (3D) geometry data performs a necessary assumption for modeling cochlear mechanics. Preferably this procedure has to be done noninvasively to preserve the original morphology. Depending on the actual application, various levels of spatial resolution and tissue differentiation should be reached. Here a new approach is presented which allows 3D imaging of temporal bone specimens with intact regions of interest and spatial resolution currently in the 10-microm range, but providing capabilities for future enhancements down to the submicron level. The technique is based on microtomography by X-rays or synchrotron radiation respectively. The structural data are reconstructed and converted to geometry data by 3D image processing, and eventually transferred into simulation environments, e.g., Finite Element Analysis, but may also be used for general visualization tasks in research, clinics, and education.

Computer Simulation↗
PubMedDate not supplied

Ultrastructural evidence for protection of the outer hair cells of the inner ear during intense noise exposure by application of the organic calcium channel blocker diltiazem.

Outer hair cells could be protected during intense noise exposure by the application of the calcium channel blocker diltiazem given before and after noise treatment. After various experimental approaches, the ultrastructural morphology was analysed for the different animal populations in the basal part of the second turn of the cochlea, which was the most destroyed area after an acute noise trauma caused by a gun shot (sound pressure at the ear drum 156 dB, frequency maximum between 4 and 6 kHz). Compared to untreated control specimens (experimental animal group I), the outer hair cells in the basal part of the second turn of the cochlea were mostly destroyed without any diltiazem application but after intense noise exposure (group II) or when the calcium channel blocker was given only before (group III) or only after an intense noise exposure (group IV). Only cellular debris of these receptor cells could be identified within this region of the cochlea at the electron-microscopic level. After diltiazem application before and after the intensive noise exposure (group V), the general morphology of the tissue was much better conserved and almost no destroyed outer hair cells were found. But nevertheless, the electron-microscopic analysis revealed that the cellular fine structure was altered. Compared to untreated control specimens, small invaginations were sometimes seen in the basolateral membranes of outer hair cells, and also the cuticular structures of the Deiters cells forming the lamina reticularis bulged into the outer hair cells. To get more information about possible physiological alterations, the amounts of precipitable calcium within the outer hair cells were determined by an image-processing system for the five different populations (groups I-V). The values obtained were compared to the calcium content in specimens which had received diltiazem without any additional noise exposure (group VI) and with an animal population which was exposed to a pure tone for 5 min at 90 dB (group VII). The results are discussed in respect of outer hair cell protection preventing morphological damage and/or physiological alterations.

Acute Disease↗
PubMedDate not supplied

Age-related hearing changes and effects of exotoxin on inner ear function in aging rat. A frequency-specific auditory brainstem response study.

Frequency-specific auditory brainstem responses to tone bursts (2-31.5 kHz) and tuning curves were recorded in 8 male rats during their entire life. No significant threshold elevation occurred during the 1st year. Mean age at onset of hearing loss was 20 months, with individual variations ranging from 14 up to 23 months. In most animals, threshold elevations were limited to 20 and 31.5 kHz. At age of 18-23 months, 3 rats were treated with Pseudomonas aeruginosa exotoxin A. After instillation, threshold elevation occurred at all frequencies, followed by near-total recovery at low frequencies, but only partial reversibility at high frequencies. It is concluded that aging-related hearing changes in Sprague-Dawley albino rats start at different ages, particularly comprising high frequencies and encroaching on the middle and low areas with increasing age.

Aging↗
PubMed2006

Benign paroxysmal positioning vertigo: a disease explainable by inner ear mechanics.

Many arguments give evidence that benign paroxysmal positioning vertigo, one of the most frequent kinds of vertigo, can be reduced to mechanical processes in the vestibular part of the labyrinth. Based on the assumption that otoliths have departed from their normally fixed position in the otolithic membrane and travel in the semicircular canals, clinical observations find their explanation. Latency between the onset of a head movement and the beginning of the vertiginous sensation, its duration and the nystagmic pattern provoked by specific head movements are in good correlation with the canalith hypothesis. Further arguments are the successful treatment by liberatory maneuvers, the relatively high number of recurrences and the change of the affected canal.

Ear, Inner↗