Concentrations of inorganic ions in guinea-pig inner ear fluids. I. Concentrations of potassium and sodium in cochlear and utricular endolymph.
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Animals↗
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Presence of Chlamydia trachomatis in tympanocentesis fluid assessed by immunofluorescence microscopy and cell culture.
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Cells, Cultured↗
Sodium and potassium changes in inner ear fluids. An in vivo study with glass microelectrodes.
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Animals↗
Pathology of Ménière's disease as it relates to the sac and tack procedures.
The rationale for endolymphatic sac and tack operations is to prevent the further accumulation of endolymph, the former by draining endolymph into extralabyrinthine tissues and the latter by shunting endolymph into the perilymphatic space. While the basic concepts are reasonable enough, the probability of achieving these objectives seems remote. There appears to be adequate clinical evidence, however, to show that these procedures are of therapeutic value in selected cases. It is tempting to speculate that these surgical insults to the labyrinth, with the associated inflammatory and biochemical changes, alter the function of cells which control fluid physiology and thus improve the symptoms of Ménière's disease.
Adult↗
Congenital perilymphatic fistula: a prospective study in infants and children.
A 3-year prospective study of 244 children (aged 5 months to 17 years) with sensorineural hearing loss of unknown cause revealed that 57 children (23%) had radiographic evidence of abnormalities of the temporal bone, detected by computed tomography scan, and/or progression of sensorineural hearing loss. Of these 57 children, 42 (74%) underwent surgical exploration, with 15 children (26%) of this subgroup demonstrating active congenital perilymphatic fistula. The prevalence of congenital perilymphatic fistula in a large, closely monitored population of children with unexplained sensorineural hearing loss appears to be at least 6% (15 of 244 children). The incidence may be higher because some congenital perilymphatic fistulae may leak intermittently and not be observed during middle ear surgery. Therefore, in children with suspected sensorineural hearing loss, early and frequent audiological evaluations should be made to rule out progressive/fluctuating sensorineural hearing loss. These children should also have radiographic imaging of their temporal bone by computed tomography scan. The use of both methods is the best indicator for congenital perilymphatic fistula.
Adolescent↗
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↗
Physical properties of fluids and structures of vestibular apparatus of the pigeon.
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Acceleration↗
Production of endolymph in the semicircular canal of the frog Rana esculenta.
The mechanisms of secretion of endolymph were studied in vitro in the isolated inner ear of the frog. Prior to in vitro experiments, the composition of perilymph was evaluated in vivo and compared to that of plasma. Composition of perilymph resembled that of an extracellular fluid, although Na and Cl concentrations were higher and K concentration was lower in perilymph than in plasma water. No difference in Ca and Mg concentrations was observed between these two fluids. Osmolality averaged 227 mosmol/kg H2O in perilymph and 183 mosmol/kg H2O in plasma. Endolymph in frog inner ear corresponded in chemical pattern to mammalian endolymph. K and Na concentrations in endolymph collected from the ampulla of the posterior vertical semicircular canal averaged 121.1 mM and 2.5 mM, respectively. Osmolality of endolymph was 237 mosmol/kg H2O. K and Na concentrations were unaltered when inner ears were incubated for 24 h either at 15 degrees C or at 4 degrees C. Addition of ouabain (10(-4) M) to the perilymph-like bathing solution altered greatly Na and K composition of endolymph after incubation for 3 h at 15 degrees C. The Na and K concentration gradients between endolymph and the bath were abolished after incubation for 24 h. Ligatures of the posterior vertical semicircular canal were performed at different sites to isolate some parts of the canal, i.e. the ampulla and the non-ampullar duct. K concentration in the ampulla after incubation for 24 h remained as high as 20 times that in the bath. This K gradient was abolished in the presence of ouabain (10(-4) M). High K concentration could be maintained in the non-ampullar part of the semicircular canal only if the latter communicated with the ampulla. It is concluded that endolymph is actively secreted into the ampulla of the semicircular canal. Na+-K+-activated ATPase in the ampullar dark cells may energize the ouabain sensitive ionic transports that are involved in the production of endolymph. Endolymph secreted into the ampulla would spread intraluminally to account for the high K and low Na concentrations of the fluid which fills the non-secretory part of the semicircular canal.
Animals↗
Development of pressure monitoring and controlling system for quantitative analysis of experimentally induced perilymph fistula.
The cause of perilymph fistula, a subgroup of sudden deafness, has not been clearly understood. To study its etiology quantitatively, the inner ear pressure monitoring system with a computer controlled pressurizing device and three types of low-pressure monitoring sensors was constructed and utilized in ex vivo experiments using white guinea pigs. Hypothesizing that cerebrospinal pressure increases cause rupture of the round window membrane, direct and indirect pressurization to cerebrospinal region and simultaneous measurement of inner ear and cerebrospinal pressures were carried out. Ruptures of the round window membranes were seen in the experiments with direct saline infusion into the cochlea when the increment of inner ear pressure exceeded 500 mmH2O. There was no sign of rupture when squeezing abdomen was employed as an indirect pressurization, although cerebrospinal pressure increased.
Animals↗
Expression of G protein alpha subunits in the lateral wall of the rat cochlea.
Expression of five G protein alpha subunits was investigated in the rat cochlea by reverse transcription-polymerase chain reaction (RT-PCR) in order to understand their role in the cochlear signal transduction mechanisms. Immunohistochemical techniques were employed to study their distribution in the lateral wall of the cochlea. Total RNA was extracted with guanidine thiocyanate from cochleas and brains of 14-21-day-old rats. The extract was treated with DNase to degrade genomic DNA. After RT, the resulting cDNA was amplified by PCR using primers specific for the nucleotide sequences representing alpha subunits of heterotrimeric G proteins. The results indicated that mRNA for all five alpha subunits was expressed in the brain and cochlear samples. For immunohistochemical localization, temporal bones of 6-week-old rats were fixed in 4% paraformaldehyde and 0.1% glutaraldehyde and processed for embedding in paraffin wax. The dewaxed, midmodiolar sections of the cochlea were incubated with subunit-specific polyclonal antibodies. The pattern of immunoreactivity varied for the five G protein alpha subunits studied in the stria vascularis and spiral ligament. The significance of these findings and the role of G protein alpha subunits in cochlear fluid homeostasis are discussed.
Animals↗
Prediction of the characteristics of two types of pressure waves in the cochlea: theoretical considerations.
The aim of this study was to predict the characteristics of two types of cochlear pressure waves, so-called fast and slow waves. A two-dimensional finite-element model of the organ of Corti (OC), including fluid-structure interaction with the surrounding lymph fluid, was constructed. The geometry of the OC at the basal turn was determined from morphological measurements of others in the gerbil hemicochlea. As far as mechanical properties of the materials within the OC are concerned, previously determined mechanical properties of portions within the OC were adopted, and unknown mechanical features were determined from the published measurements of static stiffness. Time advance of the fluid-structure scheme was achieved by a staggered approach. Using the model, the magnitude and phase of the fast and slow waves were predicted so as to fit the numerically obtained pressure distribution in the scala tympani with what is known about intracochlear pressure measurement. When the predicted pressure waves were applied to the model, the numerical result of the velocity of the basilar membrane showed good agreement with the experimentally obtained velocity of the basilar membrane documented by others. Thus, the predicted pressure waves appeared to be reliable. Moreover, it was found that the fluid-structure interaction considerably influences the dynamic behavior of the OC at frequencies near the characteristic frequency.
Animals↗
X-ray microanalysis of fluid spaces in the frozen cochlea.
The cochlea is quick-frozen and then opened while under liquid nitrogen to expose the scalae of all turns in the mid-modiolar section. Still under liquid nitrogen, the cochlea is transferred to the cold stage of a pre-vacuum chamber especially constructed for attachment to the scanning electron microscope. Under partial vacuum, it is moved to the cold stage in the high vacuum chamber of a field-emission scanning electron microscope. Energy dispersive X-ray analysis demonstrates the relative levels of sodium, potassium, and chlorine in the fluid spaces of the cochlea.
Animals↗
Detection of endotoxin in ear specimens from patients with chronic otitis media by means of the limulus amebocyte lysate test.
The limulus amebocyte lysate (LAL) test is the most sensitive procedure for the detection of endotoxic lipopolysaccharides. The test was applied to middle ear fluids, cholesteatomas, and granulation tissue specimens from 31 patients in parallel with bacteriologic examination. The LAL test and bacteriologic examination yielded concordant results with 26 out of 28 specimens. A positive LAL test was obtained with 11 specimens containing endotoxin-producing organisms. The test became positive within 60 min of incubation in 10 out of 11 specimens and in 1 specimen between 1 and 24 h, suggesting that, in the majority of specimens, endotoxin was present in the specimen itself and that the result was not due to the in vitro multiplication of the microorganisms. All negative tests remained negative for 24 h. It is conceivable that endotoxin present in ear fluids may contribute to the pathologic changes in chronic otitis media.
Adolescent↗
Biochemical parameters of guinea pig perilymph sampled according to scala and following sound presentation.
Guinea pigs were exposed to sound varying from 2 to 8 kHz in frequency and 80-100 dB (SPL) in intensity for periods of 1 hr. The biochemical parameters, glucose, sodium, total protein, and the glycolytic enzymes, aldolase, phosphohexose isomerase, and total LDH as well as isozymes of the latter were ascertained for blood serum, perilymph, and, in some instances, cerebrospinal fluid. The three enzymes occurred at lower levels in perilymph as compared to blood serum. Except for a small difference in serum total protein, sound presentation incurred no significant effect on any of the above parameters. Definite differences in several metabolites were discerned for perilymph sampled according to scala and which were independent of the respective acoustical treatments. Thus, as compared to the scale tympani, the scala vestibuli perilymph displayed a higher glucose content and a diminished total LDH level and of the latter isozymes, LDH(1) ranged lower and LDH(2), higher. As further evidence pointing to cerebrospinal fluid as the possible origin of perilymph, similarities in glucose contents and LDH isozyme patterns were noted for both fluids.
Animals↗
Perilymphatic fistula in the guinea pig.
Clinical reports on perilymphatic fistulae (PLF) of the round window membrane (RWM) have shown different degrees of hearing loss. However, the hearing can also be entirely unaffected. Experimentally induced PLF of the RWM in animals showed results similar to those of the clinical reports, although some researchers have concluded that perforation of the RWM per se does not necessarily induce significant hearing loss. The purpose of the present study was to clarify if, and how, PLF of RWM in the guinea pig actually affects the auditory action potentials. During 1 h of observation following perforation of the RWM, the immediate and continuous effect of the PLF was evaluated. In more than 50% of the animals, different amounts of threshold shift were obtained. In another group of guinea pigs an attempt was made to clarify the findings by reducing the cerebrospinal fluid pressure before perforating the RWM.
Animals↗
Effect of opening and draining the cochlea.
The WKB approximation was used in calculations of the pure-tone response of a two-dimensional inviscid model of the human cochlea and a three-dimensional inviscid model of the guinea pig cochlea. The common experimental procedure of opening the scala tympani was simulated. Basilar membrane displacement was unaffected at and beyond the peak, but was slightly lower pre-peak. The peak location shifted to a significant extent apically only when the fluid level in the scala tympani was lowered to less than 1/10 of normal depth.
Animals↗
Lymphocytic streaming as an indicator of inner ear compartmentalization.
Despite a great deal of anatomic and physiologic data in animals, controversy still exists over whether or not the perilymphatic space in man is directly connected to the intracranial space via a patent cochlear aqueduct or other fluid channel. Human physiologic data are limited, indirect, and conflicting. Anatomic and pathologic data have heretofore been inadequate for answering the question convincingly. The temporal bones of a 19-year-old woman with central nervous system lymphoblastic leukemia are discussed. The passive-appearing movement of lymphoblasts between cerebrospinal fluid and perilymphatic spaces suggests both a functionally patent cochlear aqueduct and alternate pathways.
Adult↗
Experimental study of nystagmus induced by injecting various solutions into the middle ear cavity.
Injecting of various solutions into the middle ear cavity of cats and rabbits provoked certain characteristic types of nystagmus which resembled caloric nystagmus or clinical cases of peripheral vestibular disorders. Solutions with different degrees of specific gravity, osmotic effect and ion composition were used in this study. Direction-changing positional nystagmus, irritative nystagmus, and paralytic nystagmus were elicited according to the physical or chemical properties of each solution. Histological findings showed mild changes in the perilymphatic space and/or in the endolymphatic space in the period with some characteristic types of nystagmus. Infiltration of the substances into the inner ear fluids from the middle ear cavity via a round window membrane were probably responsible for these types of nystagmus.
Animals↗