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At least 469 records · Page 26Linked to original sources
PubMed1987

Vasopressin entry into the inner ear fluids of the rat.

The entry of arginine-vasopressin (AVP) and sucrose into cochlear endolymph, perilymph of scala vestibuli (PLV), perilymph of scala tympani (PLT), and cisternal cerebrospinal fluid (CSF) was studied, in anesthetized rats, after the administration into the cerebral lateral ventricle of a 10 microliter solution containing the radioactive tracers. Both tracers were detected in PLV, PLT, and CSF but not in endolymph. Monoexponential decay curves were calculated for PLV, PLT, and CSF, and for each tracer no difference was found between the regression lines calculated for the different fluids. These results indicate that (i) injection into the cerebral lateral ventricle is a useful tool to study the permeability of the cochlear epithelium to different solutes and (ii) no specific transport system exists for AVP across the cochlear epithelium, suggesting that AVP may exert its effect via the perilymphatic side of the stria vascularis.

Animals↗
PubMedDate not supplied

Glycerol effects on the perilymphatic and cerebro-spinal fluid pressure.

Glycerol has been injected intravenously in guinea pig and its effects on the pressure in the cochlear fluids have been studied. Simultaneously, arterial and cerebro-spinal pressures have been recorded. Glycerol lowered the intracochlear as well as cerebro-spinal and blood pressures, the latter only temporarily. Different possible mechanisms for the glycerol effect on the intracochlear pressure and its transient effect on hearing in Menière's disease are discussed.

Animals↗
PubMed2006

Cochlea's graded curvature effect on low frequency waves.

In the ear, sound waves are processed by a membrane of graded mechanical properties that resides in the fluid-filled spiral cochlea. The role of stiffness grading as a Fourier analyzer is well known, but the role of the curvature has remained elusive. Here, we report that increasing curvature redistributes wave energy density towards the cochlea's outer wall, affecting the shape of waves propagating on the membrane, particularly in the region where low frequency sounds are processed.

Animals↗
PubMed1976

[Causal therapy for diseases of the inner ear? (author's transl)].

The examples of sudden deafness and Meniere's Disease are used to discuss the possibilities of causal therapy for inner ear dysfunctions. In sudden deafness, etiological and therapeutic considerations are focused on the problem of disorders of the arterial and venous microcirculation, contributing to oxygen deprivation of the organ of Corti. Disruption of the arterial microcirculation leads to irreversible damage of the sensory organ within minutes and non-responsiveness to therapy, whereas even serious venous circulation disturbances can be treated successfully within days after onset of the acute disease. While knowledge of pathological changes in sudden deafness is still limited, temporal bone studies in Meniere's disease provides important information on its pathogenesis. Many authors have described enlargement of the cochlear duct as evidence for endolymphatic hydrops. Maximum enlargement of the endolymphatic system disrupts the membrane system which separates endo- from perolymph, and can be confirmed by histologic examination. This indicates that a change of the ionic concentration in the inner ear fluids is responsible for inner ear dysfunction. Thus, the acute Meniere attack can be explained as a consequence of the "burst hydrops." Because of the still unknown etiology of hydrops, only its consequences can be treated at the present time: i.c., immediate removal of the toxic potassium concentration from the perilymph by increasing the microcirculation of the inner ear before irreversible damage occurs.

Deafness↗
PubMedDate not supplied

Element content of intracochlear fluids, outer hair cells, and stria vascularis as determined by energy-dispersive roentgen ray analysis.

Roentgen ray spectrometry was used to obtain element spectra from isolated samples of perilymph, endolymph, outer hair cells, and stria vascularis obtained by microdissection from the freeze-dried inner ears of chinchillas. The spectra of perilymph and endolymph residues indicated that no cross-contamination of the two cochlear fluids occurs during freeze-drying or sampling. The spectra of outer hair cells suggested that the extracellular fluid in the organ of Corti spaces is similar to perilymph in its ionic content. The spectra of stria vascularis samples indicated low sodium and high phosphorus contents. Energy-dispersive roentgen ray analysis of freeze-dried inner ears appears to be a promising method for low-contamination measurement of ion distribution in the cochlea.

Animals↗
PubMedDate not supplied

Investigations on the critical perilymphatic pressure value causing round window membrane rupture in anesthetized cats.

Increasing perilymphatic fluid pressure was found to be an important factor in the etiology of round window membrane rupture. The critical pressure, causing membrane rupture was determined in anesthetized cats. Its value was found to be in the range 10--30 mmHg (x+/-S.E.M.=23.4+/-17.1). This value was compared with the pressure increases caused by thoracic and abdominal compression, cervical strangulation, forced Trendelenburg position, coughing and sneezing.

Anesthesia↗
PubMed1982

Amino acid profiles in inner ear fluids and cerebrospinal fluid.

The levels of 19 amino acids in utricular endolymph, vestibular and cochlear perilymph, and cerebrospinal fluid of guinea pigs were determined using gradient elution reverse phase high performance liquid chromatography of the o-phthaldialdehyde-ethanethiol adducts with fluorescence detection. Aspartate and glutamate were significantly higher in endolymph than in perilymph, in agreement with earlier results on cochlear fluids based on enzymatic fluorometric techniques. All other amino acids tested were significantly lower in the endolymph, in most cases by an order of magnitude. Vestibular perilymph and perilymph of scala vestibuli are virtually identical. Amino acid levels were all higher in perilymph of scala vestibuli than in cerebrospinal fluid; two by an order of magnitude. All differences were statistically significant, with the exception of aspartate. Amino acid levels in perilymph of scala tympani were highly variable dependent upon sampling technique, and no definite values are therefore presented. Comparisons with results from other laboratories, technical pitfalls, and possible implications and interpretations of the results are presented.

Amino Acids↗
PubMed1988

Secretion of endolymph by semicircular canals of the shark.

The semicircular canals of the vestibular labyrinth of the dogfish shark, Squalus acanthias, may serve as a simple in vitro system for the study of the ionic transport mechanisms involved in endolymph formation. Electron microscopy showed that the epithelium was made up of at least three distinct cell types divided into separate regions running the length of the canals. Secretion of endolymph was studied in isolated canals by the split droplet method; when the lumens of the canals were filled with shark Ringer a potassium-rich fluid was secreted into the lumen at a rate of 0.34 microliter.cm-2.min-1. The K concentration of the secreted fluid averaged 112 mM; the calculated rate of K secretion was 2.3 mumol.cm-2.h-1, comparable to recent measurements in mammalian utricle. Fluid secretion was dependent on active transport and was inhibited by ouabain, bumetanide, or methazolamide in the external bathing solution. Fluid secretion was unaffected by the K channel blocker, Ba, in the luminal droplet or by the adenylate cyclase stimulator, forskolin, in the external bathing solution. For electrophysiological analysis, isolated canals were perfused in a chamber designed for voltage/current clamping; an axial wire was inserted into the canal lumen and constant-current pulses were passed to determine tissue resistance. When the luminal fluid was high-K Ringer, transepithelial potential difference was -1.1 mV (lumen negative) and resistance 37 omega.cm2. Dilution and bi-ionic potential measurements showed that the epithelium of the canals exhibited only slight cation selectivity. These results are consistent with a model for endolymph secretion involving cotransport secondary to the ion gradients created by the Na+-K+-ATPase.

Animals↗
PubMed1975

Maximum compliance and the symptom of fullness in Meniere disease.

The symptom of fullness in Meniere disease was investigated in relation to measurements of maximum compliance (Cm) at the eardrum. The symptom of fullness is considered to be related to an increase in inner ear fluid pressure in Meniere disease. The Cms between ears were measured and compared for 36 patients with Meniere disease and the symptom of fullness in only one ear (full ear). A comparison of the Cm between the full ear and nonfull ear showed that the Cm was reduced for 32 of the patients. The data were interpreted as indicating that the Cm can be affected by pathological mechanical changes in the inner ear.

Compliance↗
PubMed1987

Fluid flow in the cochlear aqueduct and cochlea-hydrodynamic considerations in perilymph fistula, stapes gusher, and secondary endolymphatic hydrops.

There is convincing evidence that the cochlear aqueduct is normally patent in humans and is of relatively constant size. It probably plays an important role in the balance between the perilymphatic, endolymphatic, and cerebrospinal fluid pressures. The flow rate of liquids through tubes is a linear function of pressure, viscosity, and length of the tube but is a fourth degree power function of the radius of the lumen. For this reason, the radius is the most critical factor determining the flow rate. Small variations in size of the cochlear aqueduct can cause very large variations in flow rate through it.

Cochlea↗
PubMed1975

[The significance of inner ear fluid (perilymph) in forensic medicine (author's transl)].

An original method for collecting the perilymph in the inner ear by chiselling the pyramid of the temporal bone is presented; From 300 to 350 mul of fluid may be obtained each time. Various types of determination were performed on 399 human cadavers. The alcohol level was tested in 140 cases, the ABO(H) group antigens were determined in 89 cases, the phenotypes of the gamma-globulin (1) group system in 152 cases, and the alpha1-antitrypsin (Pi) system in 18 cases. Determinations of the alcohol level in the perilymph has been confirmed to be useful, as they allow not only determination of the degree of intoxication in cadavers in an advanced state of decomposition, but also by comparing the alcohol concentration in the cerebrospinal fluid, the vitreous humour, and the blood, the phases of elimination and absorption of alcohol may be more precisely determined. It was also found that the perilymph is a good medium for the determination of the group antigens of the red blood-cells and the gamma-globulin system, the serum and the alpha1-antitrypsin enzyme. These data suggest that the method may be more widely used in various forensic medical tests.

Forensic Medicine↗
PubMedDate not supplied

Sodium loading of inner ear fluids.

A slow intracarotid infusion of hypertonic sodium chloride solution, 350 mEq/L, and potassium chloride, 5 mEq/L, was used to increase serum sodium chloride over a 90-minute period in 85 cats. A slow, steady rise in serum sodium occurred, which reached almost 208 mEq/L at the end of 90 minutes. A concomitant rise in sodium occurred in the cerebrospinal fluid and perilymph. In contrast, the sodium showed only a transient slight increase in the cochlear and vestibular endolymph. Endolymph potassium appeared to rise in order to balance out the increase in sodium concentration of the surrounding and extracellular fluids. The ratio of sodium to potassium ions in both the endolymph and perilymph compartment remained relatively constant before and after the infusion with hypertonic NaCl. After infusion, the total concentration of ions in endolymph was similar to that of perilymph. These experiments indicate that the endolymph compartment has a built-in mechanism for maintaining a low-sodium concentration while keeping ionic balance with the surrounding perilymph and serum.

Animals↗
PubMed1983

[Effects of bilateral nephroadrenectomy on the composition of perilymphatic fluid in the rat].

The examination of osmolality and ionic composition of plasma and perilymphatic liquid of nephroadrenectomized rats was performed by systematic methods. Significant increases in osmolality, Na and K concentrations were found in perilymph of nephroadrenectomized animals. The functional importance of these findings is evaluated, and the influence of blood labyrinth barrier and osmotic mechanisms on these results is discussed. Simultaneously, the possibility that similar mechanisms might be involved in the pathogenesis of Meniere's disease is pointed out. A possible route on pathogenical and clinical studies in labyrinth pathology is enhanced.

Adrenalectomy↗
PubMed2004

Cochlear aqueduct flow resistance depends on round window membrane position in guinea pigs.

The resistance for fluid flow of the cochlear aqueduct was measured in guinea pigs for different positions of the round window membrane. These different positions were obtained by applying different constant pressures to the middle ear cavity. Fluid flow through the aqueduct was induced by small pressure steps superimposed on these constant pressures. It was found that the resistance for fluid flow through the aqueduct depended on the round window position but not on flow direction. The results can be explained by special fibrous structures that connect the round window with the entrance of the aqueduct. It was also found that the equilibrium inner ear pressure depends on middle ear pressure, indicating that the aqueduct does not connect the inner ear with a cavity with constant pressure.

Animals↗
PubMedDate not supplied

Accuracy of an automatic impedance apparatus in a population with secretory otitis media: principles in the evaluation of tympanometrical findings.

INTRODUCTION: The primary demand for a screening procedure for secretory otitis media (SOM) is to identify an objective test with sufficient sensitivity and specificity to meet the needs of the screening program. This study was designed to estimate the value of a portable automatic impedance apparatus to meet these needs. SUBJECTS AND METHODS: Two hundred twenty children with unilateral or bilateral SOM were evaluated in a double-blind, cross-sectional study. All have fulfilled two of the following three criteria for surgical intervention: (1) SOM by physical examination, (2) greater than 20 dB hearing impairment, and/or (3) adenoid symptoms. All ears were evaluated using tympanometry, following which myringotomy was performed. RESULTS: Otomicroscopy showed fluid behind the tympanic membrane in 393 ears. All underwent myringotomy. Thirteen percent (51 ears) were empty. Of the otomicroscopic findings consistent with SOM, 82% had B curves, 6% had C2 curves, 8% had C1 curves, and 4% had A curves. Both C2 and B curves were considered abnormal. Sensitivity of the apparatus is 94.4% and of the specificity is 52.9%. There was no statistical correlation between tympanometrical findings and fluid viscosity. RESULTS: A test intended for screening has to be simple, easy, and quick to perform. Furthermore, the test should have high sensitivity. The automatic impedance apparatus is able to meet these demands; however, the individual results have to be confirmed by another method, eg, otomicroscopy, pure-tone audiometry, and/or manual tympanometry.

Acoustic Impedance Tests↗
PubMedDate not supplied

Cochlear fluid balance. A clinical/research overview.

Stria edema, and in some cases atrophy, follows osmotic agents, loop-inhibiting diuretics, acoustic trauma, and rupture of Reissner's membrane. All have in common an imbalance of fluid and electrolytes in the cochlear duct. The glycerol test causes temporary improvement in hearing in Menière's disease. Glycerol causes stria edema and collapse of Reissner's membrane in the chinchilla. Stria edema, as well as stria atrophy, are found in Menière's disease. Metabolic manipulation of the stria might be that the best approach in the search for successful treatment of Menière's disease.

Adenylyl Cyclase Inhibitors↗
PubMed1982

Intracochlear microprobe analysis.

Energy dispersive x-ray analysis (EDXA) or "microprobe analysis" provides cochlear physiologists with a means of accurately assessing relative ionic concentrations in selected portions of the auditory mechanism. Rapid freezing followed by lyophilization allows the recovery of fluid samples in crystalline form not only from perilymphatic and endolymphatic spaces, but also from much smaller subregions of the cochlea. Because samples are examined in a solid state, there is no risk of diffusion into surrounding or juxtaposed fluids. Samples of cochlear tissues may also be evaluated without the danger of intercellular ionic diffusion. During direct visualization by scanning electron microscopy, determination of the biochemical makeup of the material being examined can be simultaneously, assuring the source of the data collected. Other potential advantages and disadvantages of EDXA are reviewed. Initial findings as they relate to endolymph, perilymph, stria vascularis, and the undersurface of the tectorial membrane are presented.

Cochlea↗
PubMed1981

Passage of albumin from the middle ear to the inner ear in otitis media in the chinchilla.

A study of the permeability of the middle ear-inner ear interface for macromolecules was carried out in chinchillas with open and obstructed eustachian tubes utilizing tritiated human serum albumin and immunoelectrophoresis. Tritiated albumin was placed in the round window niche area or normal animals and animals in which the eustachian tubes had been obstructed for 24 hours or 14 days. The tritiated albumin was allowed to remain in the middle ear cavity for 24 hours, Samples of middle ear effusion, perilymph, blood and cerebrospinal fluid were collected and measured for radioactivity. Radioactivity was demonstrated in the perilymph. Samples of middle ear effusions and perilymph were also studied by immunoelectrophoresis with goat antihuman albumin. Albumin placed in the round window niche of an experimental animal could be recovered unchanged in the perilymph. The results suggest a pathophysiologic explanation for the association of otitis media and sensorineural hearing loss or endolymphatic hydrops.

Animals↗