Pulmonary delivery of d-methionine is associated with an increase in ALCAR and glutathione in cochlear fluids.

In animals, hearing loss resulting from cochlear mechanosensory cell damage can be mitigated by antioxidants such as d-methionine (d-met) and acetyl-l-carnitine (ALCAR). The systemic routes of administration of these compounds, that must of necessity transit trough the cochlear fluids, may affect the antioxidant levels in the cochlea and the resulting oto-protective effect. In this study, we analyzed the pharmacokinetics of [(14)C]d-met in the cochlea and four other tissues after intratracheal (IT), intranasal (IN), and oral by gavage (OG) administration and compared it to intravenous administration (IV). We then analyzed the effect of these four routes on the antioxidant content of the cochlear fluids after d-met or ALCAR administration, by liquid chromatography/mass spectrometry. Our results showed that the concentration of methionine and ALCAR in cochlear fluids significantly increased after their respective systemic administration. Interestingly, d-met administration also contributed to an increase of ALCAR. Our results also showed that the delivery routes differently affected the bioavailability of administered [(14)C]d-met as well as the concentrations of methionine, ALCAR and the ratio of oxidized to reduced glutathione. Overall, pulmonary delivery via IT administration achieved high concentrations of methionine, ALCAR, and oxidative-related metabolites in cochlear fluids, in some cases surpassing IV administration, while IN route appeared to be the least efficacious. To our knowledge, this is the first report of the direct measurements of antioxidant levels in cochlear fluids after their systemic administration. This report also demonstrates the validity of the pulmonary administration of antioxidants and highlights the different contributions of d-met and ALCAR allowing to further investigate their impact on oxidative stress in the cochlear microenvironment.

[Clinical and anatomical features of the middle ear in the premature infants at different gestational time].

The objective of the present study was to analyse anatomical features of the middle ear in the premature infants of different gestational age. Materials from 100 still-born and live-born babies (200 temporal bones) were available for the investigation. The study has revealed a number of distinctive clinical and morphological peculiarities in the structure of tympanic membranes in both the prematurely born infants depending on the gestational age and in the full-term babies. The fluid from the tympanic cavity was found to contain human beta-chorionic gonadotropin.

Aquaporins and Meniere's disease.

PURPOSE OF REVIEW: Review of the role of aquaporins in inner ear homeostasis and potential role in the pathogenesis of Meniere's disease. RECENT FINDINGS: Recent findings include the immunolocalization of aquaporins in the inner ear of mouse, rat, and human to cell types that are likely to undergo high ionic perturbances (e.g. potassium flux) and to putative areas of endolymph resorption or cycling. SUMMARY: The expression of aquaporins and related proteins in the human cochlea and vestibular periphery resembles the distribution found in animal models, suggesting a critical role of aquaporins in inner ear water homeostasis and their potential role in the pathogenesis of Meniere's disease.

A new immunohistochemical method for the detection of gentamicin in inner ear fluid compartments.

A new method was developed for frozen section detection of antigens that natively occur in the cochlear peri- and endolymph. A combination of immuno-histochemistry and immunoblot assay enabled topological and quantitative detection of small and hydrophilic molecules (such as the aminoglycoside antibiotics) in frozen sections of the inner ear compartments (scala tympani, scala vestibuli and cochlear duct). A selective localization is possible in the peri- and endolymphatic region of each coil of the cochlea. During sectioning of the cochlea, a small piece of a nitrocellulose membrane is placed to the surface of the intersection and briefly warmed. The sections are cut, simultaneously attached to a nitrocellulose membrane on which the aminoglycoside antibiotics remain adsorbed without any fixation procedure. Using this method, immunoincubation to detect gentamicin was performed in a way usually done in western blot analysis. Results with two different enzyme reactions with the enzyme conjugated to a second antibody (i.e., dye as substrate and the chemiluminescence detection system) are presented and compared. This histoimmunoblot assay provides a general non-radioactive and sensitive immunohistochemical tool for the localization of compounds occurring in extracellular body fluid compartments. For inner ear research this method now enables the investigation of the penetration and distribution of therapeutics in peri- and endolymphatic sites and can even be applied to separately quantifying concentrations of a substance in different coils of the same cochlear section.

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.

Ionic activities of the inner ear fluid and ionic permeabilities of the cochlear duct in endolymphatic hydrops of the guinea pig.

Ionic activities (K+, Na+, and Cl-) of the perilymph and endolymph of the basal turn were measured using ion-selective microelectrodes in experimentally induced endolymphatic hydrops of the guinea pig. Three months following the obstruction of the endolymphatic duct and sac, the endocochlear potential (EP) of hydroptic ears was measured at 59.7 +/- 9.6 mV (N = 12) which was significantly lower than the EP of the contralateral control ears (84.4 +/- 2.8 mV, N = 12). A paired t-test (P greater than 0.05) showed no significant differences of ion concentrations of the inner ear fluid between the hydroptic and contralateral ears. Ion permeabilities of the cochlear duct following anoxia were calculated according to the Nernst-Planck equation. Comparing hydroptic and normal ears following anoxia, a statistically significant decrease was observed in the permeability coefficients for K+. Similarly, K+ conductance was significantly lower in the hydroptic ears than in the normal ears. Total conductance of the cochlear duct, defined as the sum of each ion conductance, was 0.560 siemens in the normal ears and 0.217 siemens in the hydroptic ears. On the basis of the Goldman-Hodgkin-Katz equation, preexisting negative EP in the normal state was calculated to be -24.5 mV in normal ears and -21.4 mV in hydroptic ears. Therefore, the positive component of the EP was 108.9 mV in normal ears and 81.1 mV in hydroptic ears. These findings suggest that the pathophysiology of hydrops involves changes in K+ permeability and the inhibition of the electrogenic transport processes.

Concentration of salicylate in serum and perilymph of the chinchilla.

The concentration of salicylate in serum and perilymph was measured in chinchillas after intraperitoneal administration of sodium salicylate. Serum salicylate concentration peaked 2 to 4 hours after a single injection. Clearance was approximately complete after 16 hours. The within-subject variability of serum concentration 4 hours after injection was very low. Subject weight significantly affected serum salicylate concentration, with heavier animals showing higher serum levels. The relationship of perilymph to serum salicylate concentration was approximately linear, with a high correlation between measures.

Electrochemical aspects of cations in the cochlear hair cell of the chinchilla: a cellular model of the ion movement.

The dc potential and ion composition (K+, Na+, and Ca++) in the hair cells of the cochlea were examined using ion-selective microelectrodes. The K+, Na+, and Ca++ concentrations were 124.0 +/- 29.8 mM, 6.9 +/- 4.1 mM, and 1.7 +/- 1.4 microM in the hair cells, respectively. The electrochemical potential gradients for K+, Na+, and Ca++ across the apical membranes of the hair cells were calculated to be 160.0 +/- 29.8 mV, 87.6 +/- 27.0 mV, and 194.4 +/- 35.2 mV, respectively. Those for K+, Na+, and Ca++ across the basolateral membranes of the hair cells were -12.6 +/- 33.3 mV, 126.8 +/- 28.3 mV, and 170.8 +/- 30.1 mV, respectively. These findings were discussed in light of the transport mechanism necessary to maintain the ionic composition of hair cells.

Effect of high perilymphatic potassium concentration on the guinea pig vestibular sensory epithelium.

The 'rupture theory' has been proposed to explain the vertiginous attack of Meniere's disease, and the high perilymphatic potassium concentration was thought to be the most important factor in this theory. In this investigation, potassium ion was introduced through the round window into the perilymphatic space in guinea pigs by means of iontophoresis, to investigate the effect of high perilymphatic potassium concentrations on the vestibular sensory epithelium, histochemically. Following the iontophoretic procedure, spontaneous nystagmus was observed, directed toward the iontophoretic side (irritative nystagmus) for the first 10 min, and then toward the unaffected side (paralytic nystagmus) for 24 h. Both these nystagmus types were quite reversible and left no morphological change in sensory cells. However, histochemical analysis revealed an increased ATPase activity during the irritative nystagmus and decreased ATPase activity during the paralytic nystagmus in the synaptic area between the hair cells and the nerve endings of the vestibular sensory epithelium on the iontophoretic side. Judging by these results, high perilymphatic potassium concentration is assumed to affect the synaptic area of the sensory epithelium, leading to reversible nystagmus.

[Effects of mannitol on the fluids of the internal ear. Use in the treatment of deafness]. / Effets du mannitol sur les liquides de l'oreille interne. Application au traitement des surdités.

The action of mannitol upon the inner ear fluids was studied experimentally by means of kinetics of mannitol entry into cochlear perilymph and endolymph in rats. A daily two hours infusion of 10% mannitol induces an osmotic water flow from cochlear fluids toward plasma. Following this therapeutic protocol, progressive, non-tumoral sensorineural hearing loss is enhanced in 32% of the cases. The rate of hearing improvement is larger than 50% in case of Ménière's disease. For sudden hearing loss, 75% of the cases are improved by mannitol, and 92% of the cases when the delay between the hearing loss onset and the mannitol therapy is less than two weeks. Sudden hearing loss should be considered as a sensory emergency.

Peptides of the otosclerotic perilymph examined by analytical isotachophoresis.

Perilymphs of normal and otosclerotic origin were separated chromatographically on a Sephadex G-25 microcolumn. Peptide composition of the perilymphs was compared by capillary analytical isotachophoresis in the molecular mass range 0.3-5 kD. Otosclerotic perilymph samples contain a heterogeneous, UV-absorbing peptide subfraction which is not detected in the normal perilymph. Normal and otosclerotic perilymph, furthermore, contain four common subfractions detected in twice the normal concentration in the otosclerotic perilymph. These ITP subfractions are degraded during acid hydrolysis (6 M HCI). On the contrary, otosclerosis is a deficient state compared with the normal, as the number of peptides or oligoglycopeptides is twice as high in normal as in otosclerotic perilymph, beside the otosclerosis specific peptides.

Transport characteristics of the blood--perilymph barrier.

The inner ear must maintain a delicate homeostasis to preserve high sensitivity to acoustic and vestibular inputs. Various experimental conditions were imposed upon chinchillas to help identify these homeostatic mechanisms for the inner ear fluids. Radioactive ions (sodium, chloride, and calcium) pass into perilymph more slowly than they pass into cerebrospinal fluid or aqueous humor. The concentration of glucose in perilymph relative to that in serum was found to be quite constant (about 45 per cent) over a wide range of serum values (130-943 mg/dl) generated by continuous intravenous infusion. The transport of albumin into perilymph was very slight after injection of the radioactive protein intravenously. Osmotic agents cause an efflux of water from perilymph into a relatively hypertonic circulating blood, resulting in a secondary elevation of perilymph osmolarity. Recent findings relating to cyclic AMP metabolism and the possible role of this second messenger in the regulation of inner ear fluid metabolism are discussed. A new hypothesis that excess cyclic AMP in the inner ear may be related to endolymphatic hydrops is presented.

[Antibacterial therapy in surgery of the inner and middle ear. A study of co-trimoxazole penetration into the perilymph (author's transl)]. / Intérêt de l'antibiothérapie dans la chirurgie de l'oreille moyenne et de l'oreille interne. Etude de la diffusion de l'association sulfaméthoxazole-triméthoprime dans la perilymphe.

Studies of the type presented here have rarely been undertaken and should be useful in surgery and pathology of the inner and middle ear. Samples of perilymph were collected during stapedectomy in patients with otosclerosis. In view of the very small volume of perilymph obtainable from each patient's vestibule (2 to 4 microliter), the only assay method that could be used to measure drug levels was thin layer chromatography on silica gel. Despite pooling of the perilymphs of 5 patients, trimethoprim (TMP) levels could not be measured but the authors were able to demonstrate that sulfamethoxazole (SMZ) does penetrate into the perilymph. Since the TMP-SMZ combination (co-trimoxazole) is active against the pathogens usually encountered in middle ear fluids, it is concluded that the drug could be of benefit in the treatment of middle and inner ear infections or after surgical operations on this area.

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.

Perilymph penetration of methotrexate in cats.

The perilymph of the inner ear has recently been suggested as a site of frequent leukemic or lymphomatous infiltrates. Experimental evidence supports the existence of barrier mechanisms and explains the attenuated entry of several substances, including chemotherapeutic agents, from either the cerebrospinal fluid or blood into theperilymph. The present study describes the attenuated entry of methotrexate into the perilymph compartment of experimental animals following intrathecal or iv administration.

Physiology and chemistry of cerebrospinal fluid, aqueous humor and endolymph in Squalus acanthias.

By means of the appropriate isotopes injected into the spiny dogfish, Squalus acanthias, the transfer of all major ions into cerebrospinal fluid (CSF), aqueous humor (A) and endolymph (E) was studied. In addition, the effect of raising pCO2 in sea-water upon HCO3- concentration of these fluids was measured. In the several types of experiments, acetazolamide or methazolamide was used to inhibit completely carbonic anhydrase. The rates of fluid formation and ion transfer in CSF and A were fairly close, but those for E were far slower. The general pattern of ion transport in the three fluids were the same, Na+ (or Na+ + K+ in E) entry greater than Cl - entry, and the difference was HCO3-. The greater rate constants for HCO3-, increase in its entry rate by elevation of pCO2, and inhibition of its appearance by the sulfonamides, show that this is a special case of transport; the ion is formed in secretory cells from gaseous CO2 + OH-. Secretory cells at sites of formation of all the fluids contain both carbonic anhydrase and Na+-K+-ATP-ase, which subserve HCO3- formation and Na+ (or K+) transport. Comparison of these results with studies in mammals show that the vertebrate pattern for secretion of these three fluids is well established in the elasmobranch.

Rates of ion movement from plasma to endolymph in the dogfish.

The rates of movement of Na+, Rb+, Cl- and HCO3- from plasma to endolymph were studied in the elasmobranch fish, Squalus acanthias, by use of the appropriate isotopes. Rb+ was used as a marker for K+. The half-times to equilibrium for Na+, Rb+ and Cl- were about 100 hours; for HCO3- it was 6 hours. The equilibrium ratios, endolymph/plasma, are Na+ 0.87, K+ 26, Cl- 1.37, HCO3- 1.47. Carbonic anhydrase inhibition decreased the rate of HCO3- accumulation, suggesting that the process is actually the formation of endolymphatic HCO3- from plasma or tissue CO2. Increase in plasma pCO2 elevates endolymph HCO3- concentration. The secretory tissue contains carbonic anhydrase and Na-K-ATPase. These and other data suggest that a dominant feature of endolymph chemistry may be HCO3- formation linked in some fashion with K+ transport, through rates catalyzed by these two enzymes.

The transport of radioactive labelled sodium ions at the round window. Corroboration of the mechanism of "Arslan's operation" for morbus Menière.

Radioactive-labelled sodium does not penetrate via the round window in the inner ear of guinea-pigs. The findings reported confirm the mechanism assumed by Arslan for his "osmotic induction" surgery in the treatment of morbus Menière.