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At least 55 records · Page 3Linked to original sources
PubMed1978

Chemical composition in various compartments of inner ear fluid.

Sodium, potassium, chloride, glucose and total protein were determined in samples of scala vestibuli perilymph, scala tympani perilymph, CSF, cochlear endolymph and utricular endolymph from normal cats. Small but significant differences were evident in the concentrations of sodium and potassium between the scala vestibuli and scala tympani perilymph. It was also apparent that each compartment of endolymph has different values for sodium and potassium concentrations. Compared with the endolymph, the perilymph was found to contain a higher concentration of glucose and total protein. These findings are discussed from the view point of biological significance.

Cerebrospinal Fluid↗
PubMed1988

Barrier systems in the inner ear.

Because of the highly complicated function of the central nervous system and sensory organs, barrier systems have necessarily developed to ensure stability of the extracellular fluids bathing these organs. Several barrier systems which can influence the composition of the inner ear fluids are discussed. They are the 1) blood-labyrinth barrier, 2) cerebrospinal fluid-labyrinth barrier, and 3) middle ear-labyrinth barrier. The experimental data are shown to indicate that these barriers serve to protect the inner ear through selective permeability. Arachidonic acid metabolites, particularly compounds of the prostaglandin series, were identified in perilymph, and were increased by the administration of stress-related hormones, and decreased after aspirin injection. The inner ear fluid composition responds to the changes of the surrounding fluid containing compartments. However, the degree of response appears to depend on the level of changes induced in the surrounding compartments. The concept of a threshold concentration of toxic substances in middle ear effusion to induce inner ear damage is also proposed.

Body Fluid Compartments↗
PubMed1990

Cochlear and cerebrospinal fluid pressure: their inter-relationship and control mechanisms.

The patency of the cochlear aqueduct is a key factor in intra-cochlear hydromechanics. If patent, the cerebrospinal fluid (CSF) provides the reference pressure for the perilymph and also to a large extent the endolymph, since Reissner's membrane can only withstand a relatively small pressure differential. The aqueduct often becomes sealed as a natural process of ageing. In this instance the reference pressure is from a source, its position unknown, within the boundaries of the cochlea itself. Relatively large and rapid changes in the cerebrospinal fluid pressure may result from everyday events such as coughing (ca. 175 mm saline) and sneezing (ca. 250 mm saline). The resistive nature of the cochlear aqueduct and the mechanical compliance of the cochlear windows are probably important factors in limiting the amount of stress, and therefore possible damage, which may occur to the cochlea and cochlear windows for a given pressure change within the CSF system. A narrow aqueduct and compliant cochlear windows reduce the risk of structural damage. In practice, this should mean that the risk of structural damage will be increased by any process which reduces the compliance of one or both of the cochlear windows, for example, extremes of middle ear pressure perhaps brought about by Eustachian tube dysfunction or rapid barometric pressure changes. Techniques are now available which provide non-invasive indirect measures of perilymphatic pressure and CSF-perilymphatic pressure transfer. The tympanic membrane displacement measurement technique has been used to provide reliable measures of perilymphatic pressure and CSF-perilymphatic pressure transfer on an individual subject basis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Effect of peroral glycerol administration on inner ear fluid electrolytes of guinea pigs.

After the oral administration of 50% glycerol (12 mL/kg), serum, CSF and inner ear fluids from scala tympani perilymph, scala vestibuli perilymph, and scala media endolymph were collected from normal guinea pigs under sodium pentobarbital anesthesia (25-35 mg/kg). The sodium and potassium concentrations were determined by microflame photometry. Increases in sodium concentrations were found in CSF, scala tympani perilymph, scala vestibuli perilymph, and cochlear endolymph. No significant change was observed in the serum. These sodium increases were considered to be due to the dehydration caused by the osmotic action of glycerol. Potassium concentration was increased only in scala tympani perilymph. Oral administration of glycerol was found to be more gradual and effective in dehydration compared to intravenous injection.

Administration, Oral↗
PubMed1977

Labyrinth and cerebral-spinal fluid pressure changes in guinea pigs and monkeys during simulated zero G.

This study was undertaken to explore the hypothesis that shifts of body fluids from the legs and torso toward the head contribute to the motion sickness experienced by astronauts and cosmonauts. The shifts in body fluids observed during zero-G exposure were simulated by elevating guinea pigs' and monkeys' torsos and hindquarters. Cerebral-spinal fluid pressure was recorded from a transducer located in a brain ventricle; labyrinth fluid pressure was recorded from a pipette cemented in a hole in a semicircular canal. An anticipated divergence in cerebral-spinal fluid pressure and labyrinth fluid pressure during torso elevation was not observed. The results of this study do not support a fluid shift mechanism of zero-G-induced motion sickness. However, a more complete test of the fluid shift mechanism would be obtained if endolymph and perilymph pressure changes were determined separately; we have been unable to perform this test to date.

Animals↗
PubMed1977

[Determination of the perilymph density in the cochlea of guinea pigs (author's transl)].

The perilymph density of the sc. tympani, sc. vestibuli and the density of liquor cerebrospinalis in guinea-pigs are measured by determination from mass and volume of the fluid column in a glass capillary tube. For the density of perilymph in sc. vest. a value of (formula: see text) in sc. tymp. a value of (formula: see text), and for liquor a value of (formula: see text) was obtained.

Animals↗
PubMed1986

Possible implication of an efferent neuropathy in vestibular upset.

This essay examines two possible mechanisms whereby a neuropathy affecting the efferent vestibular innervation may cause incoordination of vestibular afferent input to the Vestibular Integrating Centres: firstly, by loss of the normal fine control of afferent impulses; secondly, by a disruption of the sodium-potassium pump mechanism that maintains the ionic stability of the inner ear fluids.

Humans↗
PubMed1987

Na and nonelectrolyte entry into inner ear fluids of the rat.

Kinetics of hydrophilic solute entry into endolymph (EL), perilymph (PL), and cerebrospinal fluid (CSF) were studied after intravenous administration (sodium, urea, glycerol, mannitol, sucrose) and cerebral lateral ventricle injection (urea, sucrose) of tracers in anesthetized rats. Samples of cochlear EL, PL of scala vestibuli (PLV), PL of scala tympani (PLT), and cisternal CSF were obtained. The data showed slow entry of tracers in PLV, PLT, and CSF as follows: Na greater than urea greater than mannitol approximately sucrose; slower entry of mannitol and sucrose in PLT and CSF than in PLV; 1 h delayed peak of radioactivity in PLV compared with the immediate peaks in PLT and CSF after CSF injection, and the value of PLV peak was 13% that in CSF; extremely slow entry of nonelectrolytes in EL. These results indicate that PLV originates mainly from plasma across a blood-perilymph barrier that restricts the entry of small hydrophilic solutes. The blood-perilymph barrier is most likely composed of an endothelial barrier associated with an epithelial secretion. The latter could be located at the vasculo-epithelial zone of the spiral limbus.

Animals↗
PubMed1976

Quantitative assessment of perilymph sources.

The problem of the perilymph origin--influx of cerebrospinal fluid (CSF) versus ultrafiltration within the cochlea--cannot be solved by mere qualitative proofs of tracer passage through the cochlear aqueduct. In order to gain quantitative data on the possible perilymph sources, an experimental study was designed to follow the time course of dye concentrations in the cisternal CSF and in the perilymph after tracer injection into the CSF at the vertex. By comparing the resulting concentration peaks in both fluids, the mean peak of the perilymph tracer concentrations was found to reach 36% of the maximum CSF concentration only. It is concluded that the local perilymph production within the cochlea exceeds the influx of CSF by a ratio of about 2:1. A working hypothesis of the double perilymph origin is discussed.

Animals↗
PubMedDate not supplied

[Protein study on perilymph susbstitution during cerebrospinal fluid flow through cochlear aqueduct].

Total protein contents in the perilymphy of Scala vestibuli and Scala tympani as well as in the cerobrospinal fluid (CSF) of guinea-pigs were determined, by which specimens were taken under the following various conditions: With or without subarachnoidal puncture before perilymph collection, by varying the amount of perilymph taken from Scala tympani, by fractionating collection and under post mortem condition. The results suggest that under physiological conditions the CSF also flows through the cochleae aqueduct and the protein concentration in the Scala tympani decreases especially in the basal winding. Because the protein content in CSF is inaverage four times lower than in fluids of the inner ear it is of preference to consider the question of connection between the CSF and the fluids of the inner ear. In the specimens taken the blood contamination was estimated on the basisof erythrocytes in the connection capillaries under microscope. The protein content in the perilymph of Scala vestibuli was found significantly higher in relation to perilymph of Scala tympani.

Animals↗
PubMed1988

Volume flow rate of perilymph in the guinea-pig cochlea.

The rate of longitudinal flow of perilymph has been measured using an ionic tracer technique. Spread of the tracer trimethylphenylammonium (TMPA) along the perilymphatic scalae was monitored with ion-selective microelectrodes following injection of a minute bolus (approximately 50 nl) of 150 mM TMPAC1 one turn away. This amount of TMPA had virtually no toxic effect on cochlear function. The spread of tracer by longitudinal volume flow and passive diffusion were separated by comparing tracer movements in both apical and basal directions along the scalae in two groups of animals. Experimental findings were compared with a mathematical model which combined diffusion and volume flow. Our results demonstrated that when electrodes were completely sealed into the cochlea, the rate of longitudinal volume flow in scala tympani was extremely slow, approximately 1.6 nl/min in the apical direction. Longitudinal flow was not detectable in scala vestibuli. When the otic capsule was perforated, flow rates of over 1 microliter/min were recorded in scala tympani, probably as a result of cerebrospinal fluid entry through the cochlear aqueduct. When the cochlea was sealed (with recording electrodes in place) and cerebrospinal fluid pressure was released, there was no significant basally-directed flow of perilymph in scala tympani. These findings support the concept that perilymph composition is maintained by local, cochlear mechanisms which do not involve longitudinal volume flow. They provide strong evidence that perilymph is not secreted in one region and resorbed at a spatially distant site.

Action Potentials↗
PubMedDate not supplied

Perilymph production and cochlear blood flow.

In rodents at least, the main sources of the perilymph fluid are (1) influx of CSF through the cochlear aqueduct, and (2) blood flow dependent local production within the cochlea. Experimental data are presented that give a ratio of 22:78 percent for those sources. The perilymph production thus derives mainly from the cochlear blood flow. It is concluded that measurements of the perilymph production can be used as indirect measurements of the inner ear blood flow under various experimental conditions. Two experimental examples are referred to.

Acidosis, Respiratory↗
PubMedDate not supplied

Cerebrospinal fluid absorption in the rabbit. Inner ear pathways.

Fifteen adult rabbits were perfused intrathecally with horseradish peroxidase (HRP) for 20-30 min under conditions that prevented any increase in cerebrospinal fluid (CSF) pressure. Histologic and ultrastructural examination of the cochlea disclosed HRP deposits along the cochlear and vestibular branches of the auditory nerve and beyond their ganglia, in a) epineural and perineural spaces; b) intraneural spaces reaching the membrane of myelinated axons via nodes of Ranvier; and c) extending beyond the epineurium into area lymphatics. HRP was also found in the basilar membrane, along with deposits in the scalae tympani, vestibuli, media and the spiral ligament. The endolymph also received HRP which followed vestibular nerve fibers and penetrated between sustentacular and hair cells of the cristae ampullaris and both maculae. HRP permeated interendothelial spaces lining the modiolus to reach the scala vestibuli lymphatics close to all the above areas were also permeated by HRP, but the inner tunnel was devoid of the marker.

Absorption↗
PubMed1979

[Blockage of cochlear aqueduct for examination of perilymph (guinea pig) (author's transl)].

To prevent the perilymph (guinea pig) from contamination with CSF during the sampling the aqueductus cochleae (AC) was blocked by injection of tissue adhesive into the meningeal aperture. The control of an exact blockage of AC was carriedout by examination of perilymph-outflow after opening the cochlea (injection of fluorescein-Na into the CSF-space), analysis of perilymph-protein-concentration, macroscopic and microscopic examination of the temporal bones. In all cochleae we have found the same morphological structures, notwithstanding whether the AC was blocked (for a time from 30 min to 7 weeks) or not: The cochlear aqueduct is filled with a mesh of mesenchymal tissue, which grows more dense towards the cochlear aperture andcontinues into the round window membrane. From scala tympani the AC is always limited by one layer of cells forming a sort of membrane (under light microscope). It seems possible that CSF moves in the inner of the round window membrane between AC and subepithelian space of middle ear mucosa, whereas perilymph of scala tympani is not in direct contact with the flow of CSF. The scala tympanic side of the round window membrane may be a big area for diffusion and there also may be an exchange between CSF and perilymph. The outflow of CSF into the cochlea after experimental opening of the cochlea is an artifact, caused by damage of pressure equilibration between CSF-space and cochlea. 30 min and 5--7 weeks after blockage no morphologicaland electrophysiological alterations from those of the control ears were to be seen. The protein concentration, however, increased significantly 5--7 weeks after blockage from normally about 200 mg/100 ml toalmost the double especially in the scala tympani (see Table 1).

Action Potentials↗