Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Labyrinthine Fluids”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMedDate not supplied

Effect of glycerol on inner ear fluid electrolytes and osmolalities in guinea pigs.

Endolymph of the scala media (SM) and perilymph of the scala vestibuli (SV) and scala tympani (ST) were collected from the basal turn of anesthetized guinea pigs before and after intravenous administration of glycerol (3 g/kg). Sound-evoked responses were recorded during the test periods. Blood, CSF, and perilymph of the ST were also collected continuously after the injection. The osmolalities and chloride concentrations of the collected samples were determined. In another experiment, the continuous changes of potassium and chloride concentrations in endolymph and perilymph of the ST before and after the injection were measured by ion-selective electrodes. The osmolalities in CSF and perilymph lagged behind the increase in serum osmolality. The osmolalities in endolymph and perilymph increased gradually after the injection, reached maximum values after 90 minutes, and then decreased. The changes in chloride and potassium concentrations in endolymph and perilymph had similar tendencies. But the increases in chloride concentrations in perilymph of the SV and ST were much less than that in endolymph. We propose that most of the osmolality increase in perilymph is due to glycerol or other osmotically active substances and that the osmolality increase in endolymph is due to water shift.

Animals↗
PubMed2002

Change of guinea pig inner ear pressure by square wave middle ear cavity pressure variation.

The inner ear fluid pressure of guinea pigs was measured during square wave middle ear cavity pressure variation. Time constants were derived for the slopes of the inner ear pressure recovery curves after middle ear pressure change. A "single exponential" function did not fit well and therefore more complicated functions were used for this purpose. For middle ear pressure increasing from zero to a few centimetres of water, returning to zero again, decreasing from zero to minus a few centimetres of water and then returning to zero again, time constants for the inner ear pressure recovery curves were on average 15.0, 8.6, 2.5 and 2.5 s, respectively. The results could not be described using a linear model with constant window membrane compliance and cochlear aqueduct flow resistance. A possible explanation for the large difference in time constants for positive or negative middle ear pressure changes is a dependence on aqueduct flow resistance or round window membrane position.

Animals↗
PubMed1989

Effects of nitrogen mustard-N-oxide on ionic activities of inner ear fluid and ionic permeabilities of the cochlear partition in the guinea pig.

The effect of nitrogen mustard-N-oxide (NMO) on the endocochlear potential (EP) was investigated from the aspect of the ion concentrations and permeabilities in the cochlea. Compared with the untreated animals, in NMO-treated animals 20 to 30 hours after administration, the EP was decreased (30.8 +/- 3.5 mV in NMO versus 82.4 +/- 1.6 mV in control), the K+ concentration in perilymph of the scala tympani was increased (8.2 +/- 1.0 mM versus 5.3 +/- 0.7 mM), the K+ concentration in endolymph was decreased (128.5 +/- 10.6 mM versus 157.9 +/- 7.9 mM), and the Na+ concentration in endolymph was increased (9.6 +/- 3.6 mM versus 2.5 +/- 0.4 mM). The permeability coefficient for Na+ of the cochlear partition in the NMO-treated animals significantly decreased, while that for Cl- significantly increased. The negative EP, which presumably exists in the normal state, diminished further (-2.7 mV versus -27.8 mV), and the calculated electrogenic potential of the EP was depressed remarkably (33.5 mV versus 110.2 mV). The results suggest that the effects of NMO involved changes in ion permeabilities of the partition and the inhibition of electrogenic transport processes in the cochlea.

Animals↗
PubMed2003

Otoacoustic emissions from residual oscillations of the cochlear basilar membrane in a human ear model.

Sounds originating from within the inner ear, known as otoacoustic emissions (OAEs), are widely exploited in clinical practice but the mechanisms underlying their generation are not entirely clear. Here we present simulation results and theoretical considerations based on a hydrodynamic model of the human inner ear. Simulations show that, if the cochlear amplifier (CA) gain is a smooth function of position within the active cochlea, filtering performed by a middle ear with an irregular, i.e., nonsmooth, forward transfer function suffices to produce irregular and long-lasting residual oscillations of cochlear basilar membrane (BM) at selected frequencies. Feeding back to the middle ear through hydrodynamic coupling afforded by the cochlear fluid, these oscillations are detected as transient evoked OAEs in the ear canal. If, in addition, the CA gain profile is affected by irregularities, residual BM oscillations are even more irregular and tend to evolve towards self-sustaining oscillations at the loci of gain irregularities. Correspondingly, the spectrum of transient evoked OAEs exhibits sharp peaks. If both the CA gain and the middle-ear forward transfer function are smooth, residual BM oscillations have regular waveforms and extinguish rapidly. In this case no emissions are produced. Finally, and paradoxically albeit consistent with observations, simulating localized damage to the CA results in self-sustaining BM oscillations at the characteristic frequencies (CFs) of the sites adjacent to the damage region, accompanied by generation of spontaneous OAEs. Under these conditions, stimulus-frequency OAEs, with typical modulation patterns, are also observed for inputs near hearing threshold. This approach can be exploited to provide novel diagnostic tools and a better understanding of key phenomena relevant for hearing science.

Basilar Membrane↗
PubMed2004

Four antibiotic-resistant Streptococcus pneumoniae clones unrelated to the pneumococcal conjugate vaccine serotypes, including 2 new serotypes, causing acute otitis media in southern Israel.

This study examined the prevalence of antibiotic-resistant clones that belong to serotypes not included in the pneumococcal conjugate vaccines and that cause a significant percentage of acute otitis media (AOM) in children in southern Israel. During 1998-2001, 2467 pneumococcal isolates, obtained from middle-ear fluid of children <3 years old with AOM, were characterized by antimicrobial susceptibility testing, serotype testing, and pulsed-field gel electrophoresis. Non-vaccine type (NVT) strains constituted 477 (19%) of the 2467 isolates, of which 173 (36%) belonged to only 4 serotypes: 35B, 33F, 21, and 15B/C. For serotype 35B, 47 (96%) of 49 strains were penicillin nonsusceptible, and 93% constituted a single clone; for serotype 33F, 31 (82%) of 38 strains were penicillin nonsusceptible, and 95% constituted a single clone; for serotype 21, 38 (93%) of 41 strains were penicillin nonsusceptible, and 93% constituted a single clone; for serotype 15B/C, 22 (49%) of 45 strains were penicillin nonsusceptible, and 42% constituted a single clone. Two of these clones have not been described elsewhere. The high prevalence of NVT clones should increase the awareness of the potential for replacement of the vaccine strains with these NVT antibiotic-resistant strains.

Acute Disease↗
PubMed1986

Ionic environment of cochlear hair cells.

The scala media of the adult cochlea in mammals comprises a morphologically closed compartment sealed with tight junctions of the intermediate to tight types. The unique ionic composition of endolymph is maintained by the stria vascularis through active reabsorption of sodium and active secretion of potassium against ionic gradients. The subtectorial space is only a partially closed compartment which communicates with the endolymph via holes in the tectorial membrane at its outer insertion to the organ of Corti. Hardesty's membrane divides the subtectorial space into two compartments: one facing the surfaces of inner hair cells and one facing the surfaces of outer hair cells. In the study of comparative anatomy, hair cells, e.g. in the lizard, basilar papilla are of two types: those covered with a tectorial membrane and those being free-standing lacking the tectorial membrane. The ionic environment of the hair cell surface seems to be the same, independent of whether covered with a tectorial membrane or not. The tectorial membrane itself is semipermeable to ions in the endolymphatic space. Only the surface structures of the hair cell with the sensory hairs facing the subtectorial space are exposed to the high concentration of potassium, whereas the remaining parts of the hair cell are surrounded by a fluid having a more normal extracellular type of ionic composition (cortilymph/perilymph). During embryonic development the ionic composition of endolymph develops in parallel with the morphologic maturation of the stria vascularis. A completely mature composition of endolymph is reached before any electrophysiological potentials in the cochlea can be elicited. The sensory hair surface of hair cells has reached a mature morphology prior to the maturation of endolymph. In several species the tectorial membrane is morphologically only partially mature when the increase of the potassium concentration of endolymph starts. Drugs primarily affecting the stria vascularis causing a transient change of the ionic composition of endolymph result in a transient dysfunction of inner ear potentials. If the ionic changes persist for longer time, morphological changes can occur in both the stria vascularis and the hair cells of the organ of Corti. Whether such changes are primarily caused by the ototoxic drug itself or by changes in the ionic composition of endolymph has to be explored further.

Animals↗
PubMed1984

Effects of glycerol on the inner ear fluid electrolytes of guinea pigs--oral and intravenous administration.

Under sodium pentobarbital anesthesia (25-35 mg/kg), serum, CSF and inner ear fluids from scala tympani perilymph, scala vestibuli perilymph, and scala media endolymph were collected from normal guinea pigs after the oral administration of glycerol (50%, 12 ml/kg) or the intravenous injection of glycerol (1.0 ml/kg). The sodium and potassium concentrations were assessed by microflame photometry. The electrolyte dynamics of the inner ear fluids were compared after these two routes of administration. Serum: There was no significant change in Na or K levels after either route of administration. CSF: The Na concentration increased rapidly after both intravenous and oral administrations of glycerol and remained high until the end of the experiment. The K concentration did not change significantly after intravenous injection. Scala tympani perilymph: The Na concentration increased transiently, after intravenous glycerol, while after oral administration it increased slowly and steadily. The K concentration increased only after oral administration. Scala vestibuli perilymph: The Na level increased slowly and steadily only after oral administration of glycerol, and the K level increased slightly after intravenous injection. Scala media endolymph: No changes in the K level occurred after either route of administration. After oral administration the Na level increased. These experiments show that dehydration persists longer after oral than after intravenous administration of glycerol. In the diagnosis of Meniere's disease, oral administration of glycerol is more effective than intravenous injection.

Administration, Oral↗
PubMed1987

Facilitated transfer of glucose from blood into perilymph in the rat cochlea.

The transport of glucose into cochlear endolymph, perilymph of scala vestibuli and perilymph of scala tympani, and cerebrospinal fluid (CSF) was studied after intravenous administration of tracers of D-glucose, L-glucose, and 3-O-methyl-D-glucose in anesthetized rats. The data showed that D-glucose concentrations in perilymph of scala vestibuli, perilymph of scala tympani, and CSF were approximately 50%, and in endolymph less than 10%, that in plasma; D-glucose concentration in perilymph of scala vestibuli, perilymph of scala tympani, and CSF increased as a linear function of that in plasma; D-glucose entry into perilymph of scala vestibuli, perilymph of scala tympani, and CSF was more rapid than that of L-glucose; after infusion of 3-O-methyl-D-glucose, but not after that of mannitol, both the D-glucose concentration ratio of perilymph over plasma and D-glucose transfer into perilymph were lowered. These results indicate that D-glucose enters into perilymph of scala vestibuli by a facilitated transport, possibly located at the blood-perilymph barrier.

3-O-Methylglucose↗
PubMed1981

Cochlear model including three-dimensional fluid and four modes of partition flexibility.

The WKB solution is developed for the analysis of a straight box cochlear model which includes four modes of partition displacement, simulating the motion of the bony shelf and arches of Corti, as well as the pectinate zone of the basilar membrane. The theory is similar to that previously used for the 1-mode model with scalar quantities now replaced by 4-vectors. Calculations are carried out for the guinea pig cochlea with stiffness computed mainly from the anatomy and assumed physiological values for the materials. Results show that the stiffness is such that the amplitude and phase of the basilar membrane response are not significantly altered from those given by the 1-mode model. For primates and some other mammals, the bony shelf is substantially weaker than in the guinea pig and causes a much more rapid accumulation of phase along the basilar membrane. Thus, with anatomically and physiologically consistent parameters, the model yields good correlation in phase and amplitude with the in vivo measurements which have been made in the squirrel monkey by Rhode [J. Acoust. Soc. Am. 64, 158-176 (1978)] as well as in the guinea pig by Wilson and Johnstone [J. Acoust. Soc. Am. 57, 705-723 (1975)] and Rhode [Basic Mechanisms in Hearing (Academic, New York, 1973), pp. 49-63].

Animals↗
PubMed1991

Pathophysiology of inner ear fluid imbalance.

Maintenance of homeostasis of inner ear fluids and biochemical integrity of inner ear tissue are essential for proper functioning of the auditory and vestibular end organs. Although various regulatory mechanisms exist in a different portion of the labyrinth, the inner ear is known to respond to systemic challenges. The association of Meniere's syndrome with an imbalance of inner ear fluid homeostasis has been hypothesized for the past century. Among many factors, the effects of hormonal imbalance on inner ear fluid composition and inner ear function have however scarcely been studied. The purpose of this study was to explore the relationship between the autonomic nervous system and inner ear function and possible mechanisms of functional disturbances in an experimental condition. An infusion of supraphysiologic amounts of epinephrine, a stress related hormone, resulted in an elevation of osmolality in serum and perilymph. Furthermore, the infusion of epinephrine resulted in elevation of threshold, prolongation of latency, and depression of amplitude in the compound action potential of the auditory nerve. These findings were most marked at high frequencies. We hypothesized that the epinephrine-induced hearing loss was brought about by an increase in perilymphatic osmolality, as well as by the ionic imbalance caused by the osmotic gradient. Since emotional stress has been implicated as a mechanism of inducing a Meniere's attack, evaluation of the relationship between the autonomic system and cochlear function may contribute to the understanding of possible mechanisms of inner ear dysfunction caused by hormonal imbalances.

Animals↗
PubMed1978

The effects of indomethacin on inner ear fluids and morphology.

Metabolic disturbances may affect inner ear fluid homeostasis in various ways. The membrane sodium-potassium pump must play a role in this homeostasis, and as this pump derives energy from A.T.P. it may also depend somewhat on the presence of prostaglandins, through their stimulatory effect on the adenylate cyclase system. Salicylates suppress prostaglandins; and Indomethacin is even more potent in this respect. Could the temporary ototoxic effects of salicylates and Indomethacin be due to prostaglandin suppression? Further, could energy system problems involving prostaglandins be related to the development of endolymphatic hydrops? These questions prompted this study. Sublethal doses of Indomethacin were given to 14 guinea pigs in order to maximally suppress prostaglandins. Samples of perilymph and endolymph were analyzed for sodium and potassium concentrations and compared to normal controls. No significant differences were found in either acute (two to 24 hour) or chronic (three week) experiments. Light microscopic examination of serially sectioned cochleae in similarly treated animals showed, in a few cases, somewhat questionable distension of Reissner's membrane. Electron microscopy or the organ of Corti did not demonstrate any abnormalities. The study suggests that Indomethacin does not produce significant inner ear electrolyte shifts or endolymphatic distension, at least over the short term.

Animals↗
PubMed1976

[Formation of the inner ear lymphs. Permeability of inner ear membranes (author's transl)].

1. The endolymphatic system is morphologically a close system. The inner surface of the wall is tightly lined with an epithelium of ectodermal origin. The perilymphatic spaces are enlarged intercellular spaces which are built from the embryonic mesenchyme. 2. The perilymph ist an ultrafiltrate of plasma. There is probably a flow from the cerebrospinal fluid which is constantly renewed. The diffusion in the perilymph is dependent on the concentration and the size of the molecules. The endolymph is mainly a perilymph-filtrate. The "secretory" epithelia (e.g. stria vascularis cells and other tissues) of the endolymphatic system perform an important role to sustain the potassium and sodium concentrations. The ionic concentrations regulate the water movement also the volume of the endolymphatic spaces. They are maintained by anoxy-sensitive pumps. 3. The DC potential within the endolymphatic spaces represents the movement of certain electrical charge through membranes. By applying various inhibitors it is possible to distinguish the pumping mechanisms, and to observe the continuous changes of potassium and sodium concentrations with Na+ specific electrodes and K+ specific electrodes. There are probably three interdependent sources of driving-forces: a. A positively electrogenic K+-pump which is anoxia-sensitive and can be inhibited by Ethacrynic acid. This mechanism is more active in stria cells and less so in utricle and saccule. b. A negatively electrogenic Na+-K+ exchange-pump in all parts of the endolymphatic spaces is inhibited by Ouabain or anoxia. c. The passive diffusion of potassium-ions from endolymph to perilymph results an electro-negative effect.

Animals↗
PubMed1989

Kinetic experiments with radionuclides concerning the perilymph-blood barrier in a guinea pig model.

Since 1950 many animal radiotracer experiments have been performed to study inner ear kinetics. For the most part in these studies, radionuclides were applied systemically, following which a discontinuous probing of inner ear fluids or of inner ear tissues was done. Two techniques have been developed in the Section for Experimental Otorhinolaryngology of the University of Würzburg. These have been adapted to the direct and continuous measurements of inner ear efflux kinetics for several hour periods. For this purpose, only a tiny amount of radiotracer need be applied directly to the inner ear. Experiments were done on the anesthetized guinea pig as an animal model. In the first technique, a collimator-detector system is focused precisely on the cochlea, which had been quickly resealed after application of the radionuclide bolus via two small holes in the basal turn of the cochlea. The second technique makes use of a perilymph cycling system, whereby a small outer volume includes a microcuvette with a so-called artificial round window. By this latter cycling technique, perilymph clearance kinetics of all kinds of radiotracers--with the exception of tritium labelled ones--can be measured. Calculations from clearance kinetics show that quite small particles with particle weights up to 100, such as the chlorine anion and the potassium cation, as well as urea, glycerol, pyruvate, and lactate, exhibit perilymphatic half-lives varying from 45 to 60 min. These half-live data are plausible in regard to cochlear blood flow measured previously via an independent technique developed by Angelborg et al.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

[Sisomycin pharmacokinetics in the perilymph and blood serum--an approach to predicting its ototoxic effect].

To elucidate the possibility of predicting the level of aminoglycoside antibiotic penetration into the fluids of the internal ear by the antibiotic blood levels, the pharmacokinetics of sisomicin in the perilymph and blood serum was studied on guinea pigs. The antibiotic was administered to the animals subcutaneously in doses of 50, 100 and 200 mg/kg. On the basis of the comparison of the sisomicin concentrations in the perilymph normalized against the dose it was concluded that the pharmacokinetics of sisomicin in the perilymph and blood serum of the animals was linear. Comparison of the areas under the curves of the antibiotic concentration versus time in the perilymph (AUCp) and blood serum (AUCs) showed that the tissue availability of the antibiotic in this study characterized by its penetration into the perilymph and defined by the ratio of the AUCp to AUCs amounted to 55 per cent. In a two-compartment model it was not possible to predict the antibiotic levels in the perilymph by concentrations in the blood. However, by the antibiotic blood levels it was possible to characterize in a complex the pharmacokinetic behaviour of the antibiotic in the perilymph by predicting the areas under the respective curves of the antibiotic concentration versus time. The proportional relation between the values of the AUCp and AUCs suggested that the level of the antibiotic penetration into the internal ear and consequently the intensity of the potential ototoxic effect could be more reliably predicted not by separate values of the antibiotic concentration but by the areas under curves of aminoglycoside concentrations versus time.

Animals↗
PubMed1980

A cylindrical cochlea model: the bridge between two and three dimensions.

In this paper the response is studied of a linear two-channel of the cochlea with a circular cross-section. In conformity with anatomical data the basilar membrane occupies only a small fraction of the width of the cochlear partition separating the channels. Fluid displaced by the membrane will move mainly in the longitudinal (x) direction, the remainder is assumed to occur only in the radial (r) direction. In this way the major effect of three-dimensional fluid movement is built in, yet the mathematical treatment can proceed as in two-dimensional theory. The problem can be solved by analytical means when the membrane is taken as completely described by the mechanical impedance z(x) and the functional form of z(x) is simplified to a sufficient degree. Near the locus of resonance z(x) is nearly a linear function of x. For this case - the straight-line approximation of z(x) - the solution of the problem is straightforward. The response of this three-dimensional model is found to have characteristics about midway between those of one- and two-dimensional models. The same general properties are found when a better approximation - the hyperbolic approximation - of z(x) is introduced. In the resonance region the computed response for this model agrees excellently with experimental data, much better than for a two-dimensional model. A noteworthy feature of the three-dimensional response is that in the resonance region the response is well elevated above its course in the remainder of the cochlea (where wave propagation can be regarded as one-dimensional model). In this respect the three-dimensional response differs fundamentally from that of the two-dimensional model. This property is also found in certain experimental data, and from the present results this feature can be interpreted as specific for a three-dimensional structure. Further work should be directed at other three-dimensional structures in which the basilar membrane also occupies a small fraction of the width of the cochlear partition, and at more elaborate types of model.

Basilar Membrane↗
PubMed1976

[Comparative studies of lactate concentration in the perilymph, blood and cerebrospinal fluid of normal and sound exposed guinea pigs (author's transl)].

The paper deals with comparative studies of lactate concentration in the perilymph (PL) of scala tympani and of scala vestibuli, arterial and venous blood, serum and cerebrospinal fluid (CSF) of normal and sound exposed guinea pigs, special consideration having been given to possible sources of error in the methods employed. Lactate was determined enzymatically using a micromodification of the Boehringer UV-test combination adapted to 1 mul PL. The lactate concentrations in the PL of scala tympani and scala vestibuli did not differ significantly. The mean values amounted to 4.5-5.2 mM/l in the case of the opened and of the unopened subarachnoid space (Table 1). The lactate concentrations in the PL of both cochlea scales were significantly higher already ten minutes post-mortem. In the exposure experiments the animals were unilaterally exposed to sound for 1 h in an acoustically isolated system using a wide-band noise at an intensity of 120 dB SPL for one series and 2-kHz pure-tone at intensities of 112 and 122 dB SPL for two other series. We did not detect any changes in the lactate concentrations neither in the PL nor in the blood and in the CSF, following sound exposure (Table 2 and 3). The lactate concentrations of arterial and venous blood and CSF did not differ significantly. The mean values amounted to 1.4-1.8 mM/l (Table 2). However, if blood was not deproteinized or centrifuged immediately after being taken, the lactate concentration increased markedly. A comparison of the present results has shown that the lactate concentration in the PL is about three times as high as in blood and in CSF. This difference in concentration suggests that the PL lactate is of intracochlear origin and that glycolytic processes take place in the inner ear also under normal conditions. Systematic studies of additional metabolic parameters must be conducted before a definitive physiological interpretation of the present analytical results can be given.

Animals↗