Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Endolymph”

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 631 records · Page 35Linked to original sources
PubMed1979

The uptake of methyl mercury in guinea pig cochlea in relation to its ototoxic effect.

Guinea pigs were treated for 7 days by daily subcutaneous injection of methyl mercury chloride labeled with 14C, the total dose of which was 17 mg Hg/kg. In these animals the cochlear microphonics and whole-nerve action potentials were suppressed in the basal turn but there was no marked losses in the third turn of the cochlea. The endocochlear potential was not decreased in magnitude. At the end of the treatment there was no accumulation of mercury in the perilymph, endolymph and cerebrospinal fluid. Uptake and elimination of mercury in the cochlear fluids were studied in guinea pigs which were treated by a single intravenous injection of 203Hg-labeled methyl mercury, the dose of which ranged from 0.2 to 17 mg Hg/kg. The results indicated that mercury concentration ratio of the blood relative to cochlear fluids was comparable with the blood to plasma ratio reported previously. In contrast to lack of accumulation in the extra cellular environment, it is likely that tissues of the sensory end organs in the cochlea accumulated methyl mercury.

Action Potentials↗
PubMedDate not supplied

Elemental composition of individual cells and tissues in the cochlea.

Localization of elements at the cellular and sub-cellular levels was performed with the energy dispersive X-ray microanalysis technique, using shock-frozen, freeze-dried and araldite-embedded mouse (CBA/CBA) cochleae sectioned dry. Anatomical identification occurred in the STEM (scanning transmission electron microscopy) mode. In inner hair cell stereocilia the K/Na ratio was 70:1 but only 20:1 in the cytoplasm. In outer hair cell cytoplasm the K/Na ratio was 11:1 while the ratio in stereocilia was similar to that in inner hair cells. Ca was identified in stereocilia and the upper part of the cytoplasm of both outer and inner hair cells. The elemental composition in the subtectorial space is endolymph-like and that in the inner tunnel of the organ of Corti is similar to extracellular fluid. Considerable regional differences in elemental composition occur in the tectorial membrane with regard to P, K and Ca. The highest concentration of Ca occurs in the basal part of the tectorial membrane towards the sensory hairs. The highest concentration of K occurs in the basal and outer parts whereas the middle part of the tectorial membrane contains low levels of both K and Ca. The elemental composition changes in two main directions: 1) from the limbal (growing) region to the tip of the tectorial membrane, and, 2) from upper to lower surfaces. The three cell types of the stria vascularis differ considerably in elemental composition. The highest concentration of K occurs in marginal cells. The basal cells contain more K than do the intermediate cells. A significantly higher concentration of Ca, Cl and Na occurs in marginal cell cytoplasm than in any other cell type in the stria vascularis.

Animals↗
PubMedDate not supplied

The early postnatal development of the cochlear vasculature in the gerbil.

The blood vessels of the cochlea were studied from birth up to adult age in the gerbil. Even at birth the principal vascular arrangement could be identified in the external wall. However, the early circulatory mainstream appeared even more predominantly radial apico-basal over radiating arterioles-arteriovenous anastomoses-collecting venules than at later stages. At birth, only small sections of capillaries could be observed in the stria vascularis. Stria vascularis achieved its adult vascular appearance rapidly between 8-10 days after birth (DAB). The rapid development of stria vascularis immediately preceded the development of cochlear function and may have been related to the development of the ionic composition of endolymph. At birth the vessel of the basilar membrane showed many large vascular connections with the collecting venules in the scala tympani of the external wall but very few supplying and draining ramifications on the medial side of the vessel. This suggests that the vessel of the basilar membrane originates from the external wall vessels, not from the spiral lamina vessels as has previously been supposed. The peripheral vascular connections degenerated rapidly after birth. The vessel, being very large at birth, degenerated completely by 15 to 20 DAB, ultimately disappearing in the basal turn. The degeneration suggests that its major importance may be during embryonic stages, with great probability for the development of the organ of Corti.

Aging↗
PubMedDate not supplied

Pigmented epithelial cells of the membranous saccular wall of the chinchilla.

The posterior-superior portion of the membranous wall of the chinchilla saccule is lined by pigmented epithelial cells which contain golden brown granules having three components (lipid droplets, granular matrix, and dense globules). Histochemical and electronmicroscopic studies indicate that the dense component is a form of melanin. The pigmented cells show morphological features suggestive of fluid transport function; they are also involved in decalcification and phagocytosis of otoconial crystals. These findings provide evidence that the saccular wall epithelium plays an active role in regulating endolymph composition and in clearance of debris from the endolymphatic space.

Animals↗
PubMedDate not supplied

Effect of labyrinthectomy on the endolymphatic sac. A histological, ultrastructural and computer-aided morphometric investigation in the mouse.

A time sequence study of the effect of hemilabyrinthectomy on the endolymphatic sac was performed in mice. Light and transmission electron microscopy of the sac showed significant morphological changes of the epithelial lining and adjacent structures. Initially (2 and 4 days post-labyrinthectomy) the sac lumen was collapsed, but later (7 days post-labyrinthectomy) it was dilated or 'ballooned' and filled with a darkly staining homogeneous substance. This substance, which has been identified histochemically as a proteoglycan, appeared to be secreted from the epithelium of the endolymphatic sac. This finding suggests that the endolymphatic sac may be capable both of absorbing and of secreting endolymph.

Animals↗
PubMedDate not supplied

Whole-body autoradiography of [3H]dihydrostreptomycin in guinea pigs and rats: the labelling of the inner ear in relation to other tissues.

[3H]Dihydrostreptomycin was given intramuscularly to young pigmented guinea pigs and rats. Whole-body autoradiography, combined with densitometric measurement of the blackening of the autoradiograms, and liquid scintillation counting were used to determine the levels of radioactivity in the inner ear in relation to blood and other tissues. It was found that there was an accumulation of radioactivity in the perilymph of both the cochlear and vestibular parts of the labyrinth. The labelling of the endolymph was weak. The levels of radioactivity in the membranous linings of the labyrinth including the areas covered with the neuroepithelial structures, were about the same as in the perilymph. The general distribution pictures were characterized by a localization of radioactivity in extracellular tissues, such as cartilages and connective tissues and by strong labelling of the kidney cortex. The preferential uptake in the perilymph indicates a route by which the inner ear hair cells can be exposed to high levels of aminoglycoside antibiotics.

Animals↗
PubMedDate not supplied

Cytochemical identification of secreted carbohydrates in the endolymphatic sac.

Carbohydrate complexes were investigated in the murine endolymphatic sac by means of histochemical techniques in normal untreated animals as well as after ethacrynic acid treatment. The light epithelial cells were classified into three different types: normal, granular and vacuolar. The granular and vacuolar cells were believed to secrete glycoproteins and/or proteoglycans, the presence of which was closely correlated with the component of the precipitate in the lumen of the endolymphatic sac. This finding suggested that the light cells not only absorb endolymph but may also be involved with secretory activity. Such a dual modality in function may have several important implications, since it suggests that the endolymphatic sac has both absorptive and secretory functions.

Animals↗
PubMed1988

Possible role of Ca ions in the vestibular system.

The Ca++ messenger system is nearly universally present in the control of cell functions by extracellular messengers. It elicits different kinds of responses: either brief, as in neurotransmission and in skeletal muscle contraction, or sustained, as in smooth muscle contraction and in the regulation of transepithelial transport systems. In this latter function the Ca++ messenger system interacts with other cellular modulation systems such as cAMP production and arachidonic acid cascade. In the vestibular apparatus, the Ca++ messenger system is involved in the transduction processes in that it controls both the release of neurotransmitter at the basal pole of the hair cell and the electrical resonance of the cell. It also figures in the contractile properties of cochlear outer hair cells. The Ca++ messenger system as well as adenylate cyclase and prostaglandins may play an important role in the modulation of endolymph secretion.

Animals↗
PubMed1989

An electron microscopic study of the function of the root cells in the external spiral sulcus of the cochlea.

The ultrastructure of the area of the external spiral sulcus of the cochlea was studied in 15 hamsters. Intravital fixation with glutaraldehyde was followed by osmium citrate fixation and embedding in araldite. The endolymphatic surface of the external spiral sulcus is nearly completely covered by Claudius cells under which the root cells are situated. These epithelial cells are composed of bundles (roots), which protrude into the connective tissue of the spiral ligament in a tree-like fashion, forming primary, secondary, and tertiary branches. The basement membrane is a reliable landmark in this complex region, serving as a differentiating zone between the root cells and the mesenchymal tissue. Two different types of root cells are found. There are organelle rich "dark" cells and "light" cells which contain only a few cell organelles. All types of transitional forms between these two cell types are found, which can be interpreted as an expression of different metabolic activity of the same cell type. Between the root cells are seen extracellular clefts into which the "dark" cells, with their high synthetic and secretory activity, expel their secretions. These clefts lead to the endolymphatic space. A continuous production and secretion of part of the endolymph by the root cells is very likely. The anchoring of fibrils at the basement membrane of the root cell bundles, and their continuity with the basilar membrane leads to the assumption that this whole system may act as a mechanical pump. At high sound pressure levels, the strong vibration of the basilar membrane may lead to a locally and temporarily enhanced secretion of substances from the root cells into the cochlear duct.

Animals↗
PubMedDate not supplied

Long-term treatment with chlorthalidone reduces experimental hydrops but does not prevent the hearing loss.

Long-term treatment of guinea pigs with the diuretics chlorthalidone and acetazolamide, following the experimental obstruction of the endolymphatic duct, was assessed using chronically implanted round window cochlear electrodes. The diuretic chlorthalidone appeared to curb the progressive low-frequency sensitivity loss during the first 4 weeks following surgery, as compared with animals receiving the diuretic acetazolamide or no treatment. However, this apparent beneficial effect decreased after 4 weeks and was not apparent at 14 weeks post-induction. On the other hand, morphological control at the end of 14 weeks confirmed a marked reduction in hydrops in the chlorthalidone-treated animals. The data clearly demonstrate a dissociation between hydrops and the development of hearing loss and suggest that the augmenting endolymph volume is only one of several contributing factors to the deteriorating auditory function in experimental hydrops.

Acetazolamide↗
PubMed1991

Carbohydrates in the guinea pig stria vascularis demonstrated with lectin-gold techniques.

Soybean agglutinin (SBA), Helix pomatia agglutinin (HPA), Ricinus communis agglutinin-II (RCA-II), Limax flavus agglutinin (LFA) and wheat germ agglutinin (WGA) were employed to determine the localization of specific carbohydrates on thin sections of lowicryl K4M embedded guinea pig striae vasculares using the lectin-gold and glycoprotein-gold techniques. SBA, HPA and RCA-II gold labeling was observed in many of the cytoplasmic vesicles, endosomes and apical tubules located in the supranuclear region as well as on the microvilli and micropinocytotic invaginations of the luminal plasma membrane of the marginal cells. LFA labeling was found on the basal plasma membrane of the marginal cells as well as in the basement membrane of the perivascular spaces. WGA binding sites were detected along the plasma membrane of all types of cells constituting the stria vascularis. Our present results revealed that the membranes of internalization and many of the cytoplasmic vesicles, endosomes and apical tubules in the supranuclear region of the marginal cells are associated together and it is suggested that these structures may be related to the regulation of endolymph.

Animals↗
PubMed1991

Modelling the action of caloric stimulation of vestibule. III. Caloric nystagmus induced by osmotic pressure variation.

The properties of the membranous wall of the semi-circular canal and of the labyrinthine fluids give as a result the inflating pressure of this inflatable structure. The difference of osmotic pressure between perilymph and endolymph, which is involved in this problem, depends on temperature. Therefore, a caloric stimulation leads to a change in the inflating pressure. A numerical model, similar to the model used to study the effects of relative volume variations, gives a quantitative estimation of the transcupular pressure arising in a horizontal semi-circular canal (i.e. without gravity dependent effects) during a caloric stimulation, according to the inflating pressure change. As a consequence, it appears that rotational and caloric stimulations are not quite similar. The caloric stimulation leads not only to a transcupular pressure difference but also to a change in inflating pressure. As a result of the change in inflating pressure, the stiffness of the cupula varies. This modifies the gain and the dynamics of the vestibulo-ocular reflex, and may explain the asymmetry between hot and cold stimulations.

Caloric Tests↗
PubMed1991

Ototoxic effect of potassium canrenoate on the guinea pig cochlea.

Potassium canrenoate (PC) is a diuretic with antialdosterone action, reducing the reabsorption of sodium in the efferent renal tubules. This drug has been reported to damage only the marginal cells of the stria vascularis in the cochlea. The perilymphatic space of the guinea pig cochlea was perfused with an artificial perilymph containing 5 x 10(-3) M potassium canrenoate. Following the onset of perfusion, the endocochlear dc potential (EP) gradually declined to around 10 mV but did not become negative even when the perfusion was continued. A similar decrease in EP was observed in kanamycin-deafened guinea pigs. When the respirator was turned off and perfusion discontinued, a large negative EP appeared during 5 min of anoxia in normal guinea pigs but not in the kanamycin-deafened guinea pigs. The decreased EP recovered to preanoxic level after resumption of ventilation. The cochlear microphonics (CM) also gradually declined in parallel with the EP. The summating potential (SP) showed only a minor change. The potassium ion activity in the endolymph decreased slightly but the sodium ion activity remained unchanged during perfusion. These findings suggest that the main target of the PC is the cells of the stria vascularis.

Animals↗
PubMed1993

Menière's disease and autoimmunity: clinical study and survey.

In order to clarify whether autoimmune mechanisms form part of the etiopathogenesis of Meniere's disease, sera and endolymphatic sac tissues from 30 patients with Meniere's disease were analyzed according to the clinical criteria for autoimmune diseases stated by Mackay & Burnet. Several cases showed hyper gamma-globulinemia, antibody elevation to Type II collagen in the serum and endolymph, positive staining to immunoglobulins and C3 or infiltration of immuno-competent cells in the endolymphatic sac, good response to prednisolone and combination with systemic immune disorders. Other examinations showed a significant elevation of OKT 4/8 ratio and a decrease of OKT8-positive cells, and elevated levels of circulating immune complex and antiviral antibody titers. It is suggested that certain cases of Meniere's disease may have an altered immunological background, which may be attributed to an autoimmune mechanism dependent on humoral and/or cellular responses.

Adult↗
PubMed1995

Atypical "reversed" paroxysmal positioning nystagmus in benign paroxysmal positional vertigo.

An atypical paroxysmal positioning nystagmus (PPNy), "reversed" in its directional components, is a rare finding in patients suffering from benign paroxysmal positioning vertigo (BPPV). It poses problems of pathophysiogenetic interpretation, differential diagnosis with a CNS lesion and therapeutic strategy. Such a finding was observed in 7 patients (out of a total of 450 BPPV) and took on the typical PPNy pattern after repeated diagnostic manoeuvres. These aspects are incompatible with the "heavy cupula" mechanism (cupulolithiasis) and are better explained by the presence of "free endolymph aggregates" (canalolithiasis) within the posterior semicircular canal (p.s.c). Moreover, canalolithiasis would also permit a more convincing interpretation of all the clinical findings observed in typical p.s.c.-BPPV.

Adult↗
PubMed1995

In vitro electrogenic K secretion in the frog semicircular canal: absence of effect of streptomycin.

In vitro, the frog semicircular canal secretes an endolymph-like fluid, i.e. a K-rich, positively polarized fluid. This electrogenic K secretion involved basolateral Na+, K(+)-ATPase and Na-K-Cl co-transporter and a luminal protein possessing sulfhydryl groups blocked by N-ethylmaleimide. Streptomycin, an ototoxic antibiotic, is known to block the non-specific mechano-dependent channels in the sensory cells of the ampulla of the semicircular canal. The aim of the present study was to investigate the possible effect of streptomycin on the K fluxes in the ampulla of the semicircular canal. The posterior frog semicircular canal was isolated and the lumen was filled with perilymph-like solution containing or not containing 0.5 mM streptomycin. The luminal K concentration and the transepithelial potential were measured and the unidirectional K fluxes calculated. The K influxes (into the lumen, pmoles/min/mm2) were 114 +/- 25.9 and 111 +/- 3.2 (mean +/- SE, n = 3) in the absence and presence of streptomycin, respectively. The transepithelial potential was not altered (4.0 +/- 1.08 mV versus 3.4 +/- 1.03 mV, n = 3). When ouabain (10(-3)M) was added to the basolateral solution together with luminal streptomycin, no further alteration occurred as compared with the effect of ouabain alone. These results suggest that in these conditions, the sensory organ does not have a major role in the endolymphatic K secretion in the ampulla of the frog semicircular canal.

Animals↗
PubMed1996

Contributions of single semicircular canals to caloric nystagmus as revealed by canal plugging in rhesus monkeys.

We demonstrated specific responses from the anterior and the posterior semicircular canal to irrigation of the outer ear canal with cold water in the Rhesus monkey. This required i) three-dimensional analysis of the evoked eye movements in the planes of the semicircular canals (canal plane vectors, CPV); ii) assessing these CPV responses in eight different head positions relative to gravity; iii) comparing the responses in 6 normal animals (12 ears) with responses after selective plugging of pairs of semicircular canals (all, both lateral, and right anterior + left posterior). The results showed: i) Irrigation of the outer ear canal with cold water induces thermoconvection also in the posterior and anterior semicircular canals. This can be inferred from the sinusoidal modulation of eye movement components with changes in position of the corresponding semicircular canal plane relative to gravity; ii) Specific vertical canal responses occur exclusively in the direction of the corresponding semicircular canal, though they are superimposed with response components of other origin, one probably related to endolymph shift in the lateral semicircular canal; iii) before possible clinical application, these different response components of vertical canals will need to be determined in humans.

Animals↗
PubMedDate not supplied

Increased fatigue of cochlear potentials after injection of KCl solution in the perilymph.

Cochlear microphonics (CM), action potentials (AP) and endochochlear potential (EP) were recorded on guinea pigs. The introduction of a small quantity of KCl solution (0.1 N) in the perilymph provoked a moderate decrease of CM and AP. During the period of depressed but stable amplitude, the presentation of intense sounds provoked an exaggerated susceptibility to fatigue and a delayed recovery. Similar changes were observed in the evolution of EP. However, the recovery was slower for EP than for CM. The results, as a whole, suggest that the fatigue which is manifested in the depression of cochlear potentials is related to a leakage of potassium ions from endolymph to fluids spaces within the organ of Corti.

Acoustic Stimulation↗