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At least 631 records · Page 35Linked to original sources
PubMed1976

Endolymphatic hydrops: mechanical causes of hearing loss.

An explanation for the mechanical origin of the hearing loss in endolymphatic hydrops is presented that is based on studies in mechanical cochlear models. An elastic bias of the basilar membrane and/or a mass loading of the cochlear duct account for the low-frequency hearing loss, diplacusis, and even-harmonic distortion. In addition, the static shearing displacement between the tectorial membrane and the organ of Corti, caused by the displacement of the basilar membrane, may partially decouple the hair cells from the tectorial membrane, an event that would explain the tinnitus, recruitment, and perhaps even the disportional loss of speech intelligibility associated with endolymphatic hydrops.

Basilar Membrane↗
PubMed1976

[Morbus Menière and acousticus-neurinoma (author's transl)].

It is questionable whether a hydrops endolymphaticus can develop on the basis of an acousticus-neurinoma. Histological evidence is also lacking. The fact that an acousticus-neurinoma can very rarely lead to the classical symptoms of Menière's disease has practical consequences. If a significant decrease in caloric function and an asymmetry in the inner ear ducts exist, a meato-cisternography is indicated. In the meato-cisternogramme typical filling defects are found; but also in 50% of the patients with Menière's disease, certain types of filling defects are seen. This observation suggests that perhaps other pathological processes in the inner ear duct provoke symptoms similar to those of Menière's disease. In our patient material we have indications that isolated intrameatal liquor circulation disturbances and intrameatal angioma are much more often associated with the clinical symptoms of Meniere's disease than an acousticus neurinoma.

Ear Neoplasms↗
PubMed1985

The effect of glycerol on cochlear function and ionic concentration.

The use of glycerol continues to be a popular clinical test for diagnosing reversible hearing loss in patients with Meniere's disease, although its mechanism of action remains obscure. The purpose of this investigation was to study experimentally the alterations in the ionic composition and function of the cochlea which occur following glycerol administration. Immediate decreases in inner ear pressure and increases in AP threshold were seen. Delayed decreases in the endocochlear potential with increases in inner ear electrolytes occurred. However, we were unable to find any substantial changes in inner ear oxygen concentrations. Our findings support the concept that the principal action of glycerol is in osmotic reduction of inner ear pressure.

Action Potentials↗
PubMed1980

[Mezlocillin pharmacokinetics and otitis media (author's transl)].

The results of experimental investigations on the pharmacokinetics of mezlocillin in the perilymph after i.m. injection of 200 mg per kg in the guinea pig are represented graphically. A retention of this new acylureidopenicillin in the inner ear, similar to that of the aminoglycoside antibiotics, is observed. The consideration of the mezlocillin perilymph concentrations that resemble those of gentamicin on a weight for weight basis and the clinically equivalent dosages of these two antibiotics show clearly that the perilymph concentrations of mezlocillin, that may be clinically reached, are many times higher than those of gentamicin. Finally, the prophylactic and therapeutic importance of the mezlocillin perilymph concentrations for infectious inner ear complications caused by the usual bacteria of the acute otitis media or the problem germs of chronic otitis media is discussed.

Animals↗
PubMed1980

Endocochlear potential and potassium concentration in endolymph and perilymph of the chinchilla.

Guinea pigs and chinchillas were studied for EP and potassium concentrations in scala media and scala tympani using potassium-sensitive microelectrodes. Response of EP to 3 min anoxia was strikingly different in these two species. On the other hand, the resting values for EP and potassium concentrations in endolymph and perilymph were not significantly different. These findings suggest that the different response to anoxia in these two species is due to differences in permeability of the cochlear partitions to the ions.

Animals↗
PubMed1985

Freeze-fracture studies on the perilymph-endolymph barrier in experimentally induced hydrops.

A double-blind study was performed on nine pigmented guinea pigs which were unilaterally operated on in order to create an endolymphatic hydrops. After 12-18 months, both inner ears of the animals were removed and investigated by the freeze-fracture technique. The ultrastructure of the epithelial cells lining the endolymphatic compartment of the cochlea and the vestibular apparatus was analyzed. Special attention was directed to possible changes of the tight junctions (zonulae occludentes) in these sites. The number and depth of strands between the cells of sensory and non-sensory epithelia of both operated and unoperated sides were compared by an examiner unaware of the operated side. After the code of double-blind study was broken, it was found that there were no significant differences between the operated and the unoperated ears. These results are discussed in relation to the late DC-potential decrease in experimentally induced hydrops.

Animals↗
PubMed1979

Development of endolymph during maturation of the mammalian inner ear. A preliminary report.

The development of the elemental composition in the endolymphatic space was investigated during embryologic and early post natal maturation of the CBA/CBA mouse. At birth the elemental distribution was similar in the endo- and perilymphatic spaces. Mature composition of endolymph was reached 6--8 days post partum. The maturation of endolymph corresponded well in time with the morphological maturation of the stria vascularis.

Age Factors↗
PubMed1987

Organic acid transport into the cochlear perilymph.

The passage of exogenous organic and inorganic substances from blood into perilymph is likely to be controlled by the blood-perilymph barrier. This report reviews published data on the transfer of ten exogenous organic acids from the blood into the perilymph of experimental animal models. Although the range of the molecular weights of these acids is within half an order of magnitude, major differences exist in the perilymph concentration as a percentage of simultaneous serum concentration. Furthermore, these studies show that, contrary to previous suggestions, non-ototoxic compounds can achieve marked concentration gradients within the perilymph.

Acids↗
PubMed1987

The effect of round window membrane rupture on endolymphatic and perilymphatic pressures.

We used a guinea pig model to investigate the effect of round window membrane rupture on endolymphatic and perilymphatic pressures under conditions known to increase these pressures: anoxia, hypercapnia, increased intracranial pressure, and occlusion of the vein of the cochlear aqueduct. When the round window membrane was not ruptured, increases in endolymphatic pressure paralleled the perilymphatic pressure following exposure to each of the experimental conditions. After the round window membrane had been ruptured, however, no increases in perilymphatic pressure or endolymphatic pressure were seen. These results suggest that endolymphatic pressure is dependent on perilymphatic pressure, even when the round window membrane is ruptured.

Animals↗
PubMed1977

[Active otosclerosis of the stapes footplate: histological and clinical aspects of its influence on the perilymph (author's transl)].

Pathologic capillaries are usually seen in the center of an otospongious process. Next to obliteration, dilatation and increased permeability a loss of basement membrane structure is evident. Around the capillaries exists a wide network of mesenchymal cells which have a glycogen like mass within the cytoplasm; glycogen can be delivered into the extracellular fluidspace. Free erythrocytes are located around many vessels. Near the margin of the lacunae decalcificated areas are seen; in the center of these areas osteocytes undergo lysis; they show intracytoplasmatic deposits of apatite which we assume to be located within the mitochondria. The collagen structure in the neighbourhood of the osteocytes seems to be damaged. Once the resorptive process has reached the perilymphatic surface of the footplate there comes to an connection between the otospongiotic lacunae and the vestibule. Free erythrocytes, glycogen like drops and lysosomes are delivered into the perilymph. Comparing the histological results with the operative results in patients with floride otosclerosis we conclude that operation should be done as early as possible to prevent damage from the inner ear, caused by the continuous intoxication of the perilymph from the otosclerotic focus.

Bone Resorption↗
PubMed1980

The blood-perilymph barrier.

Freeze fracture replicas of the guinea pig inner ear were studied under the electron microscope to define the blood-perilymph barrier morphologically. This barrier is represented basically by the continuous endothelium of the inner ear capillaries. The endothelial cells contain only a few micropinocytotic vesicles in contrast to those of the stria vascularis vessels. The cochlear plexus also exhibits some special differences. Tight junctions of the continuous mesothelial type connect the endothelial cells of the inner ear capillaries. Cell membranes of these cells possess a lower particle density than those of the stria vascularis vessels. In general, the blood-perilymph barrier is morphologically similar to the blood-brain barrier.

Animals↗
PubMed1981

[Postmortem changes in the perilymphatic lactate and pyruvate concentrations of guinea pigs. (author's transl)].

Lactate and pyruvate of perilymph (PL) were studied 30, 60, and 120 min postmortem. During this period the mean lactate concentration of scala tympani and scala vestibuli increased from 4.8 mmol/l found intravitally to 17.8 and 15.1 mmol/l, respectively, whereas pyruvate decreased from an average of 0.33 to 0.10 mmol/l (fig. 1). These inverse changes of concentration yield postmortem lactate/pyruvate quotients which are more than one order of magnitude higher than the quotients found intravitally (Table 1). In comparative tests of blood samples carried out 30, 60, and 120 min after the sampling (Fig.1), the lactate increase was found to be markedly lower than in postmortem PL. The substantial metabolite changes in PL seem to be caused by glycolytic activity of all cochlear structures that are in direct contact with PL. The decrease of pyruvate level is probably due to a shift of the lactate-pyruvate equilibrium (lactate dehydrogenase system) in PL. The blood vessels in the perilymphatic space can be neglected as postmortem metabolite source of PL.

Animals↗