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PubMed2001

Electron microscopic studies of ion- and H2O-transporting epithelial cells in the horizontal ampulla of the pigeon.

Earlier morphological studies of the epithelial structure in the semicircular canals of mammals have focused on the sensory cells of the crista ampullaris. This report draws attention to the fact that there exist at least seven further cell types in the horizontal ampulla walls of pigeon with various functions; the role of ion- and H2O-transporting epithelial cells is dealt with here in detail. While the dark cells appear to play a decisive role in the regulation of ionic composition, the cells in the planum semilunatum may transport H2O and assist in the regulation of endolymph volume. In addition, protein-secreting structures are located in the apical region of the cells of the planum semilunatum. The question whether the proteins are dispersed in the endolymph or contribute to cupula formation remains unclear. The morphology and possible functions of these two cell types are discussed on the basis of electron microscopic results.

Animals↗
PubMed2005

Morphological aspects of potassium flow in the semicircular canal ampulla of the pigeon.

Potassium ions are a prerequisite for the development and regulation of sensory cell stimulation in the inner ear. From the potassium-rich endolymph the ions flow into the sensory cells apically and are released basolaterally. After transport pathways of various lengths potassium is released again into the endolymph - in the cochlea by marginal cells of the stria vascularis, in the vestibular labyrinth by dark cells. While this long recycling pathway is relatively well-known in the cochlea, few studies have been conducted on the semicircular canal ampullae (SCCA) where its morphological basis is largely unknown. According to the present electron microscopic findings, potassium ions are initially released into the extracellular space during stimulation of the sensory cells and then absorbed by supporting and light cells. Finally they are transported transcellularly over numerous very long gap junctions into the region of the dark cells. From here they move to an extracellular compartment, which is more or less completely sealed off basally by basal plates of the light cells. Apically the intercellular space between light and dark cells is sealed by junctional complexes. This newly identified space in the SCCA corresponds to the extracellular compartment between the marginal and intermediate cells in the stria vascularis. At both sites, the cochlea and the SCCA, this probably serves as a regulatory valve, reservoir or storage space, particularly for potassium ions. It is likely that the different morphology of the ion transport pathways is related to the different flow levels of potassium ions expressed by the different levels of the so-called endocochlear potential and concomitant movement of other ions in the cochlea and SCCA.

Animals↗
PubMedDate not supplied

Afferent and efferent nerve terminal degeneration in the guinea-pig cochlea following atoxyl administration.

Atoxyl causes destruction of both afferent and efferent nerve endings. Degeneration of afferent nerve terminals occurred even though the adjacent hair cell had a normal ultrastructure. The degeneration of the efferent nerve endings took place at the same time as the adjacent cell disintegration. Earlier studies on the effects of atoxyl have shown that it also induces damage to the stria vascularis and Reissner's membrane, thus interfering with endolymph metabolism (Anniko & Wersäll, 1975; Anniko, 1975a, b). The afferent nerve terminals may be more sensitive to changes in the environment (endolymph) than are the surrounding structures, including efferent nerve endings, hair cells and supporting structures, and would therefore be the first structures to disintegrate.

Aniline Compounds↗
PubMed1984

Pathogenesis of Meniere's disease and Meniere's syndrome.

Meniere's disease can only be studied in patients, since it does not occur spontaneously in animals nor can it be induced in them. However, aspects of the disease such as endolymphatic hydrops can be usefully studied in animals. A study of the natural history (epidemiology) of Meniere's disease demonstrated the three major symptoms (triad) to be vestibular symptoms, auditory symptoms, and aural pressure. Bilaterality occurs in at least one out of 3 patients, and may approach 50% over full lifespans. Aural pressure (74.1%) was common, as was positional vertigo (85.9%) during and/or between attacks. Clinical variants such as vestibular Meniere's disease could persist for 25 years or more. Understanding the pathogenesis of Meniere's requires a study of known and unknown causes. In this study, Meniere's disease (cause unknown) was differentiated from Meniere's syndrome (cause known). Meniere's disease or syndrome can occur years after some inciting cause; thus all forms of Meniere's can be considered to have a delayed onset. Meniere's syndrome can occur as a sequel to syphilis, otosclerosis, infection (for example otitis media), or trauma. Endolymphatic hydrops explained on the basis of quantity and quality of endolymph is found in all forms of Meniere's disease and syndrome. Representative cases and pathological examples are discussed. Hydrops of the pars inferior (cochlear duct and saccule) is the most important finding in Meniere's disease. In some (but not most) cases, ruptures of the membranes are seen. The saccule can distend into the lateral semicircular canal. Symptomatic attacks are explained on the basis of both physical and biochemical phenomena. This study discusses concepts of pathogenesis of the disease, finding both theories of longitudinal (slow) and radial (fast) flow to be operational. Longitudinal flow, however, appears to be more important than radial flow, especially in advanced Meniere's where perilymph in the scala vestibuli and vestibule disappears and is replaced by membranous labyrinth. Meniere's disease (idiopathic) and Meniere's syndrome (cause known) probably occur as a result of endolymphatic absorptive dysfunction (the site being endolymphatic duct and sac). Hypocellularity of the mastoid and periaqueductal air cells, hypodevelopment of Trautmann's triangle, and anterior displacement of the lateral sinus are likely to be important findings associated with developmentally dysfunctional absorption of endolymph.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1984

Pathogenesis of experimental endolymphatic hydrops.

The protein content and the d.c. potential of the endolymph differs in the various parts of the endolymphatic space (cochlea, utricle, semicircular canals and endolymphatic sac) as also does the ion composition (chloride, potassium, sodium). 12 months after obliteration of the endolymphatic sac and duct in guinea pigs the d.c. potential falls, whereas, the sodium activity increases. The endolymphatic hydrops is not caused by an increased colloid osmotic pressure. The increased water-binding capacity of the cochlear endolymph is correlated with the increased Na+ activity.

Animals↗
PubMedDate not supplied

Caloric stimulation of the vestibular system of the pigeon under minimal influence of gravity.

Vestibular microphonics in response to acoustical stimulation were recorded in cochlea-deprived pigeons. Endolymph flow in the semicircular canals alters this response. A caloric stimulus was applied to the horizontal canal or the posterior vertical canal close to the ampulla. To minimize the influence of gravity, the canal being studied was positioned in the horizontal plane. Local temperature changes were generated with an electrically heated miniature copper probe, producing an approximately trapezoidal temperature profile. Because of the opposite hair cell polarization in the horizontal and the vertical ampulla, we could prove that the observed effects were of (hydro-)mechanical origin and were not caused by a direct effect of sensory epithelium temperature change. The first effect of temperature increase was an utriculopetal endolymph flow, as predicted by the 'expansion theory'.

Acoustic Stimulation↗
PubMedDate not supplied

Effects of carbon dioxide in the middle ear cavity upon the cochlear potentials and cochlear pH.

To elucidate the effects of CO2 in the middle ear upon the cochlea, measurements were made of the cochlear potentials (compound action potential and endocochlear potential) and of the pH of the inner ear fluids and the organ of Corti. Gas containing CO2 did not affect the AP threshold, except for a slight decrease in AP threshold elicited by an 8 kHz tone burst with 10% CO2 flow. The EP did not vary with CO2 gas. The CO2 gas mixture reduced the pH in perilymph significantly, by 0.11 +/- 0.05 with 5% CO2 and by 0.17 +/- 0.04 with 10% CO2, in comparison with 100% N2. The CO2 gas slightly but significantly decreased the endolymph pH, by 0.05 +/- 0.04 with 5% CO2 and by 0.09 +/- 0.06 with 10% CO2. The removal of perilymph led to a greater acidification of endolymph with CO2 gas. Acidification of the organ of Corti was also noted with the CO2 gas flush. These findings indicate that CO2 in the middle ear influences the acid-base regulation of inner ear fluids and the cochlear function.

Animals↗
PubMedDate not supplied

Electrocochleography in an experimental animal model of acute endolymphatic hydrops.

A reliable animal model of acute type of endolymphatic hydrops was made with injection of artificial endolymph into the cochlear duct. In 12 animals without Reissner's membrane rupture, the endolymphatic potentials (EP) were kept normal after injection of artificial endolymph, but their electrocochleography (ECoG) showed as: a rise of summating potentials (SP) amplitude, a decrease of action potentials (AP) amplitude, an increase of SP/AP ratio, as well as a delay of N1 latency. In 7 animals with membrane rupture, the EP significantly decreased. ECoG showed as: a decrease of hearing function in all test frequencies, a distortion of SP-AP wave and even a loss of AP. Based on the results of our experiment it can be assumed that the dominant -SP may be seen in the acute stage of endolymphatic hydrops without a rupture of Reissner's membrane. Therefore, the dominant -SP may only be of value in the clinical diagnosis during episodic vertigo and fluctuating hearing loss of Meniere's disease.

Action Potentials↗
PubMed1997

An electrophysiological study of the effects of acute methylmercury chloride exposure on the function of the guinea pig cochlea.

The inner ear function of methylmercury chloride (MMC)-exposed guinea-pigs was examined in this study. Previous studies which investigated the function of the eighth cranial nerve and Corti-organ using cochlear microphonics (CM), compound action potential (CAP) and measurement of endocochlear potential (EP) reported ototoxicity following experimental exposure to MMC. In this report, the effect of MMC on the cochlea and the eighth cranial nerve were investigated systematically by measuring CM, action potential (AP), EP and K+ ion concentration of the endolymph. Guinea-pigs were injected with 5 mg/kg MMC (using 0.2% solution) twice a week for 1-3 weeks. The maximum output voltage of AP was decreased by injection of MMC (5 mg/kg x 6). A decrease in the CM maximum output voltage and the elevation of CM pseudothreshold was seen after MMC injection. Changes in EP during 3 min anoxia were observed, especially a decrease in the absolute value of the negative potential. The endolymph K+ ion concentration remained unchanged. These findings indicate that the diffusion potentials decreased and at the same time was reduced the maximum output voltage in CM induced by MMC injection (5 mg/kg x 6) in this experiment.

Action Potentials↗
PubMed1997

Two-phase endolymphatic hydrops: a new dynamic guinea pig model.

The classical guinea pig model for Meniere's disease, in which endolymphatic hydrops was achieved by destruction of the endolymphatic sac and obliteration of the endolymphatic duct, is a non-physiological profound model with shortcomings in relation to Meniere's disease as seen in patients. We developed a more subtle animal model; the two-phase endolymphatic hydrops. This model is based on a combination of chronic endolymphatic sac dysfunction, induced by slight destruction of the most distal part of the endolymphatic sac, and acute stress-induced endolymph production by stimulation of the Na/K-ATPase in the stria vascularis with aldosterone. Light microscopy of the fluid compartments of four groups of cochleas was used to examine them for the presence of endolymphatic hydrops: i) Normal (control) cochleas showed no hydrops; ii) some of the non-operated (no destruction) aldosterone-treated cochleas showed small degrees of hydrops mainly present in the basal turns; iii) mild dissection of the endolymphatic sac without administration of aldosterone produced a hydrops which was mainly present in the cochlear apex; iv) combination of chronic endolymphatic sac dysfunction and acute attacks of endolymph production by aldosterone administration revealed the most severe degrees of hydrops in all cochlear windings, damage to cochlear structures, and cellular disturbances of the epithelial lining of the endolymphatic sac. This new model may represent a more physiologic and dynamic approach to Meniere's disease and may explain the etiology of many symptoms in patients such as the fluctuant nature and the types of sensoneuronal hearing losses.

Aldosterone↗
PubMed1991

[Electron microscopic study on inner ear barotrauma: with emphasis on the cochlear damage].

In order to investigate inner ear barotrauma, guinea pigs were subjected to rapid decompression between 2 absolute pressure (ATA) and 1 ATA in a chamber. After pressure loading and observation for absence of Preyer's reflex, they were sacrificed immediately, 1 day, 1 week and 1 month later, respectively. Then, morphological changes of the organ of Corti and stria vascularis were studied under TEM and SEM. The immediate features noted were fracture of stereocilia with minimal intracellular changes. One day later, there was marked degeneration of outer hair cells and expansion of supporting cells. The damage to stereocilia clearly preceded morphological alterations within hair cell bodies and cannot be interpreted as arising secondary to hair cell degeneration. Most of outer hair cells eventually disappeared and were replaced by supporting cells. Inner hair cells degenerated slowly; 1 month later, some of them remained almost intact, despite disappearance of stereocilia. The continuity of reticular lamina was maintained not only immediately but also through the period of hair cell degeneration, thus preventing any leakage of endolymph into the organ of Corti. There was reversible dendritic swelling of inner hair cells immediately following the trauma. No changes of stria vascularis were observed over passage of time. The mechanism of hair cell damage due to inner ear barotrauma is presumed to be a deformity of the organ of Corti caused by pressure discrepancy between perilymph and endolymph resulting in an injury to stereocilia.

Animals↗
PubMed1976

Experiments on the mechanism of Ménière attacks.

The pattern of response decline following semicircular canal stimulation corresponds to a mechanical process. This process is the elastic recoil of the hairs of the sensory cells. The response decline is the same, whether the endolymph-cupula system is patent or mechanically maintained in a displaced position. The role of the bending of the entire cupula as the principle factor is excluded for the response and its decline. Repeated endolymph displacements immediately after each decline of response always result in an equal response and its decline. This rules out the depletion of a chemical mediator as a cause for the response decline. Indentations of the sidewalks of the ampulla result in reactions suggesting that the ampulla is filled with a loose gel secreted by the planum semilunatum cells.

Action Potentials↗
PubMedDate not supplied

[Some peculiarities of the environment surrounding mechano- and electroreceptors of the acoustico-lateral system in the ray Raja clavata].

Studies have been made on the degree of binding of potassium ions, the content of free calcium ions and glycosaminoglycans in the fluid surrounding mechano- and electroreceptors of the acoustico-lateral system of the ray Raja clavata as well as on the electrical phenomena in potassium hyaluronate solutions and solutions of the fluids investigated. Comparative electrometric and chemical analyses indicate that bound potassium ions amount to 36.4% in the endolymph jelly, 39.6% in the Lorenzini jelly and 21.9% in the canal fluid. Calcium level in the fluids studied amounts to 3.6-4.1 mequiv./l which is similar to that in the sea water (3.4 mequiv./l). Glycosaminoglycan content is equal to 0.30 +/- 0.02% in the endolymph jelly, 0.21 +/- 0.03% in the canal fluid and 2.79 +/- 0.28% in the ampullary jelly (per wet solution). Some characteristics of the "displacement potentials" in potassium hyaluronate solutions and Lorenzini jelly solutions were obtained. Possible role of these potentials in the activity of ampullary structures of the lateral line organ is discussed.

Animals↗
PubMed2002

[Na transport in the cochlea of mammals].

Endolymph, the fluid that bathes the apical side of the inner ear sensory cells, is a K-rich and Na-poor fluid. In the cochlea, various epithelial transport systems involved in the transport of Na from the apical endolymphatic to the basolateral perilymphatic compartments have been identified: basolateral Na+, K(+)-ATPase, apical non selective cationic channels, Na+/H+ exchanger, and ENaC epithelial Na channel. These transporters may be involved in physiological and pathological processes in which endolymph Na concentration is high.

Animals↗
PubMed1992

Changes in hyaluronan synthesis by in vitro cultured endolymphatic sac cells.

The endolymphatic sac (ELS) has been implicated in the maintenance of endolymph volume and pressure in the membranous labyrinth through fluid resorption and secretion of osmotically active substances, known as glycosaminoglycans (GAGs). To assess whether the ELS cells synthesize the GAG, hyaluronan (HA), and to further elucidate the secretory function of the ELS, a series of experiments were carried out on in vitro tissue-cultured, fetal murine ELSs. In phase 1 of the investigation, the ELSs that were attached to a small portion of the posterior labyrinth, were resected from whole otocyst specimens and studied in tissue culture. This model was chosen to determine whether a change in endolymph homeostasis affects ELS activity. Radiolabeled 14C glucose incorporation was used to evaluate HA synthesis by ELS cells when cultured in vitro. Approximately 43 percent of the incorporated 14C glucose radiolabel was digested by Streptomyces hyaluronidase (an HA-specific hyaluronidase), suggesting HA synthesis by sac cells. In phase 2 of our experiments, the ELSs were not resected from the otocysts. Instead, they were left attached to intact membranous labyrinths, and whole otocysts were cultured. Studies analogous to those of phase 1, assessing the ability of the ELS cells to incorporate 14C glucose into HA, were performed on these specimens. Streptomyces hyaluronidase treatment of these ELS specimens resulted in a reduction in the removal of radiolabel. Therefore, the ELS cells of intact otocysts incorporated less 14C glucose into HA when compared to the ELS cells of the resected specimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[Electrocochleography in experimental animal model with acute hydrolabyrinth].

A desirable animal model of acute hydrolabyrinth was made by injecting artificial endolymph into the cochlear duct of guinea pigs. In 12 animals with intact Reissner membranes, the endolymphatic potential kept normal after injection of artificial endolymph, but their ECochG showed a rise of SP amplitude, a decrease in AP amplitude, an increase of SP/AP ratio, and a delay of N1 latency. In 7 animals with ruptured membranes, the EP significantly decreased. ECochG showed a decrease in hearing in all test frequencies, a distortion of SP-AP wave or even a loss of AP. Based on the results of our experiment, it can be assumed that the dominant -SP may be seen in the acute stage of endolymphatic hydrops without a rupture of Reissner membrane. Therefore, the dominant -SP may only be of value in the clinical diagnosis during an episodic vertigo and fluctuating hearing loss in Ménière disease.

Animals↗
PubMed1990

[Ways of increasing the effectiveness of the treatment of male patients with genital tuberculosis].

Endolymphic therapy proved to be a considerable resource for the rise in the treatment efficacy of specific inflammatory diseases of the male genital organs without adding to the antituberculous drug dosage. Indirect endolymphic chemotherapy appears to be more accessible and not labour-intensive, instead it can increase the efficacy of a conservative therapy of men with genital tuberculosis. Besides, it seems to be promising in relation to the preservation of fertility after tuberculous epididymitis.

Adult↗
PubMed1986

[Approaches to the control of lymphogenic metastatic spread of tumors].

Lymphopoiesis stimulating drugs were injected into the blood of rabbits bearing Brown-Pearce transplantable tumor. It was found that treatment with mannitol targeted on osmoregulation mechanisms and terrilytin--on blood and lymph coagulation intensified the lymphogenic migration of tumor cells. When used in an experimental series involving endolymphic transplantation of tumor cells, the said drugs promoted tumor cell passage from lymph to blood, which resulted in an increased number of metastasis-bearing animals. It was also found that the promoting effect may be counteracted by preliminary endolymphic injection of a fat-soluble antitumor preparation. Lymphopoiesis and lymph flow stimulation in conjunction with thoracic duct draining may be used for removal of tumor cells from the lymphatics.

Amylases↗