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At least 253 records · Page 14Linked to original sources
PubMed1983

Gentamicin persistence in rat endolymph and perilymph after a two-day constant infusion.

The kinetics of gentamicin in the inner ear fluids of rats were studied up to 15 days after cessation of a 2-day constant infusion of 10 micrograms/min. In endolymph, the concentration of gentamicin persisted at about 1 microgram/ml for up to 15 days, precluding the determination of the half-life of the drug in this fluid. In perilymph, gentamicin cleared more slowly than after a shorter period of infusion. These results suggest that the tissues of the inner ear could bind the aminoglycoside and then slowly release it into the surrounding fluids.

Animals↗
PubMed1995

Glycolipidic component of the epithelial cell coat of the endolymphatic sac.

The endolymphatic sac (ES) is thought to synthesize and secrete glycoconjugates such as sulfated glycoproteins into the endolymphatic lumen. Ganglioside Gm1 is a specialized glycolipid containing one sialic acid molecule, which is generally found in the outer leaflet of the cell membrane. This glycolipid, which is known to be a specific receptor for cholera toxin (CT), acts as a membrane transducer and is involved in the modulation of cell metabolism, growth and regeneration. In the present study we identified Gm1 by studying the distribution of the FITC-labeled CT-subunit B in the ES epithelium of adult guinea pigs. Our findings indicate the presence of this ganglioside in the ES, with a predominant localization in the basolateral aspect of the epithelial cell layer. No detectable differences between ES cell types could be identified, whilst the ES distal and intermediate portions showed more reactivity than the proximal portion. This study, which represents the first description of a lipidic glycoconjugate component in the ES, provides evidence in support of the role of the ES in the turnover and regulation of inner ear fluids.

Animals↗
PubMed1982

[Effect of nitrous oxide inhalation anesthesia on sero-mucous secretions of the tympanum].

It is known that nitrous oxide anaesthesia results in an increase of the middle ear pressure. The aim of this project was to find out, if an increase of the middle ear pressure due to high concentration of nitrous oxide could lead to evacuation of the seromucoid secretion through the Eustachian tube. In 37 children (64 ears) scheduled for myringotomy, tympanograms were performed immediately before and during anaesthesia, the middle ear fluid was confirmed by myringotomy and, if any, sucked out. Both the comparison of the tympanograms prior and during the anaesthesia and the results of myringotomy led to a conclusion, that, in general, nitrous oxide anaesthesia induces no evacuation of middle ear fluid via the Eustachian tube.

Acoustic Impedance Tests↗
PubMed1976

Lactic dehydrogenase of fetal ear fluids under ambient and high-intensity sound.

Lactic dehydrogenase (LDH) was determined in the fluids of the inner ear scalae and the middle ear cavity of fetal guinea pigs near term. Scalar dissimilarities in prenatal perilymph and distinctions between fetal and maternal perilymph suggest functional differentiation between the antenatal scalae vestibuli and tympani, elevated glycolytic activity in the prenatal vestibular channel and primarily aerobic processes in fetal perilymph although anaerobic metabolism is also evident. Disparities between fetal middle ear fluid and prenatal perilymph as well as maternal serum indicate that the former medium is probably not directly derived from either of the latter sources. After experimental treatment consisting of the presentation of high-intensity sound to gravid animals, the total LDH activity of the fetal middle ear fluid decreased.

Acoustic Stimulation↗
PubMed1982

Immunologic study on the inner ear. Immunoglobulins in perilymph.

The immunoglobulin composition of perilymph (PL) was measured using electroimmunodiffusion, and transfer of serum antibodies to PL was studied using a passive hemagglutination test in chinchillas and guinea pigs. The mean values of IgG an albumin in PL were two to four times greater than those in CSF. In guinea pigs, IgA was found in 93% of the PL and 32% of the CSF samples, but in chinchillas only trace amounts of IgA were found in 50% of the PL and 15% of the CSF samples. No IgM was detected in PL or CSF of either species. This study suggests that a greater portion of the immunoglobulins in PL probably is derived from perilymphatic blood vessels as a filtrate and that the perilymphatic inner ear immune system is independent from that of the CSF.

Animals↗
PubMed2003

Aquaporin-mediated fluid regulation in the inner ear.

1. The sensory functions of the inner ear (hearing and balance) critically depend on the precise regulation of two fluid compartments of highly desparate ion composition, i.e., the endolymph and the perilymph. 2. The parameters volume, ion composition, and pH need to be held at homeostasis irrespective of the hydration status of the total organism. 3. Specific cellular water channels, aquaporins, have been shown to be essential for the fluid regulation of several organs, e.g., kidney, lung, and brain. 4. Because of functional similarities of water regulation in the kidney and inner ear this review initially summarizes some aquaporin functions in the kidney and then focuses on 6 out of 11 mammalian aquaporins that are present in the inner ear (AQP1-6). 5. Their potential role in the inner ear fluid control will be discussed on the basis of the respective expression patterns and individual pore properties. 6. Further, a working model is presented of how the endolymphatic sac may contribute to inner ear fluid regulation.

Animals↗
PubMed1982

X-ray analysis of biological fluids: contribution of microdroplet technique to biology.

Electron probe analysis by x-ray spectrometry is used in biology for simultaneous determination of the concentrations of any elements with a higher atomic number than that of carbon in single samples with volumes of 0.01 to 0.5 nl. In this technique, deposits prepared from identical volumes of biological fluids and standard solutions are totally covered by the electron beam, and the measured x-ray intensities for each element directly compared. The possibility of intensity quantification depends on the thinness of the dried deposits obtainable by various preparatory techniques. Factors affecting the accuracy of the results include droplet stability under the electron beam, the identity of the degree of oxidation of the elements in biological fluids and standards, sample mass thickness, beam voltage, and matrix effects. Minimum detectable concentrations in the 0.05 mmol.l-1 range are now achievable. This technique is the only one applicable in cases where available volumes are too small to determine the concentrations of several elements on the same sample (for instance of Na, Mg, S, P, Cl, K, Ca, Fe and Co), or even to determine the concentration of a single element (e.g. Mg). Although the droplet technique has so far mainly been used in renal physiology, it has also been applied in reproductive and digestive physiology. Isolated cells are analyzed according to the same principle of totally covering the cell by the electron beam. During the last decade, the vast increase in the relevant literature has testified to the contribution of the microdroplet technique to various fields of biology.

Absorption↗
PubMedDate not supplied

Effect of increased perilymphatic pressure on endocochlear potential.

A study was done to determine how increased fluid pressure in the inner ear influences cochlear blood flow. Hydrostatic pressure was applied to the scala vestibuli or scala tympani in guinea pigs. Endocochlear potential, which is sensitive to the lack of oxygen, was measured through the round window membrane or through the stria vascularis. Cochlear blood flow was confirmed by intravenous injection of India ink. When the perilymphatic pressure was raised to a relatively high level, endocochlear potential decreased, ina similar way as in response to anoxia, because of the cessation of the cochlear blood flow. This change was completely reversible upon applications of pressure for brief periods of time. We consider that the cochlear blood flow ceases when the fluid pressure reaches the level of intracochlear arterial pressure.

Animals↗