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At least 649 records · Page 36Linked to original sources
PubMed1983

Surface view of strial vessel, prominence vessel, and external sulcus cells as revealed by scanning electron microscopy.

The stria vascularis and the spiral prominence in the lateral cochlear wall were observed with scanning electron microscopy (SEM) after dissolving out the epithelial layer and the basement membrane by tryptic digestion and HCl hydrolysis. The external sulcus cells have regularly arranged pegs and a fine basal interdigitation on the cell surface. The strial vessel and the spiral prominence vessel could be visualized well and the characteristic surface view of their periendothelial cells presented. The former has cytoplasmic processes with a fine branching appearance similar to red coral and the latter has bulged popcorn like processes. Their functional significance is discussed.

Animals↗
PubMed1988

Magnesium ion activity in the mammalian endolymph measured with ion-selective microelectrodes.

The free Mg++ concentration in endolymph was measured with Mg++-selective microelectrodes based on the neutral ligand ETH 1117. The property of Mg++ microelectrodes was obtained from calibration solutions, containing various Mg++ concentrations with the background electrolytes resembling endolymph. The range between 10 and 0.1 mM Mg++ concentrations changed the potentials of Mg++ microelectrodes by 14.4 +/- 3.0 mV. The endocochlear potential and the Mg++ concentration in the endolymph were 82.0 +/- 5.0 mV and 0.77 +/- 0.29 mM in the guinea pig, and 84.4 +/- 4.9 mV and 1.12 +/- 0.24 mM in the chinchilla, respectively. These results are discussed in the light of the dependence of Na+, K+-ATPase and its interaction with Ca++.

Animals↗
PubMed1985

A new theory for thermal influences on endolymphatic flow.

We applied thermal stimuli to the partly isolated posterior canal of the bullfrog half-head preparation. Warming or cooling stimuli to the canal side changed the activity of the semicircular nerve. Our results suggest that changes in the endolymphatic density might be responsible for convection flow in the semicircular canal as well as calorically induced nystagmus.

Animals↗
PubMed1985

An experimental study on the physiological significance of the mode of cupular movement.

Isolated frog posterior semicircular canals were used. The ampullary nerve action potentials were recorded under three kinds of cupular movement, i.e., swing-door deflection, "cupula fixation-1" and "cupula fixation-2". Cupula fixation-1 was achieved by immobilizing the central top portion of the cupula, while cupula fixation-2 was achieved by immobilizing the entire top of the cupula. Cupula fixation-1 resulted in action potentials which were comparable to those of the swing-door deflection in terms of the maximum spike count and the stimulus-response curve. Cupula fixation-2 resulted in potentials with the maximum spike count comparable to the swing-door deflection; however, the response increase rate was very low. The time courses of the potentials in those cases of cupula fixation-1 and -2 were extremely short (about 2-3s) when compared to that of the swing-door deflection. These findings suggest that the swing-door deflection is physiologically more relevant in giving the optimum increase in response rate, as well as maintaining the time course of the tonic response.

Animals↗
PubMed1986

Inhibition of myosin light-chain kinase activity in the organ of Corti by 0.3-5 kilodalton substances of the otosclerotic perilymph.

The guinea pig organ of Corti contains myosin light-chain kinase (MLCK) activity. The upper and lower most parts of the cochlea do not show significantly different activities of the enzyme, which is Ca2+ and calmodulin-dependent. Short-term noise exposure does not cause a significant change. 0.3-5 Kilodalton substances of the otosclerotic perilymph, separated by SG-25 column chromatography, inhibit the MLCK activity in in vitro organ of Corti preparations. This inhibitory action of the perilymph substances can also be observed with the purified MLCK of turkey gizzard. The activity of the enzyme can be specifically inhibited by cyclic AMP-dependent protein kinase.

Animals↗
PubMed1988

The basement membrane and associated structures in the murine endolymphatic sac.

The ultrastructure of the basement membrane of the murine endolymphatic sac was studied under various experimental conditions in labyrinthectomized and ethacrynic acid-treated animals and was compared with normal anatomy. The basement membrane was clearly visualized after staining with ruthenium red or dialyzed iron. The basement membrane of the murine sac consists of two different layers: the lamina rara and the lamina densa. It demarcates the border between the epithelial cells and the subepithelial connective tissue. Our findings suggest that the basement membrane acts as a physical support to the epithelium in the endolymphatic sac. The basement membrane also shows a dynamic capacity to form a new basement membrane, with the result that the lateral intercellular space between contiguous epithelial cells may be integrated with the subepithelial space. This system is believed to act as a macromolecular and bulk water transport system. In the subepithelial space, collagen, reticular and elastic fibrils are found having a close relationship to the basement membrane. The elastic fibres are presumed to play a role in the pressure-regulating mechanism in the endolymphatic sac.

Animals↗
PubMed1977

Sources of endolymph and EP. Does the perilymph or Reissner's membrane influence the ionic content of the endolymph and EP?

The source of EP and the production of the endolymph are often considered to be at the stria vascularis. However, the significance of Reissner's membrane in maintaining the ionic composition of the endolymph cannot be ruled out. We perfused the entire perilymphatic space of guinea pigs with paraffin oil to determine the effects on the endolymph and perilymph. After 1 and 2 h the endolymph was removed from the second turn and the ionic concentration of these samples was measured by flamephotometry. The results revealed no significant changes in Na+ and K+ concentration as compared to normal endolymph. EP was measured from the second turn under an equivalent experimental condition. During 1 h of oil perfusion, EP remained fairly constant. From these experiments we surmise that perilymph and Reissner's membrane do not influence the ionic composition of the endolymph and EP during 1 or 2 h of our experiments.

Animals↗
PubMed1979

Alteration of oxidative enzymes (LDH and MDH) in perilymph after noise exposure.

Chinchillas were exposed to noise (123 dB, 1/2 h, 700--2800 Hz). The activity of lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) was studied immediately after exposure or 1, 7, 14, 21, or 28 days later. LDH activity in perilymph doubled immediately after exposure, gradually decreasing to control values in about a month. The activity of MDH not only doubled immediately after the exposure but continued to rise for at least another 24 h, reaching a peak value of 3.5 times normal at 24 h. The activity was still 1.6 times normal even after a month of recovery. The enzyme activity of serum and CSF remained within the control range throughout the experimental period except for an initial increase of serum enzyme activity due to anesthetic. The results demonstrate that the morphological changes induced by a noise exposure that is known to produce permanent threshold shift (PTS) are reflected in a significant elevation of oxidative enzymes in perilymph. Possible mechanisms of the elevation of enzymes in perilymph are discussed.

Animals↗
PubMed1988

Simultaneous investigations of elemental changes in individual cells of the stria vascularis and in endolymph.

Using the microprobe for energy dispersive X-ray microanalysis, the elemental compositions of both the individual cells of the stria vascularis and of the endolymph were followed simultaneously under normal conditions and after the administration of 120 mg/kg ethacrynic acid (EA). Marginal cells and intermediate cells showed reversible increases in potassium and decreases in sodium concentrations. Shifts in the ionic composition of endolymph occurred later than after elemental changes in the strial cells. The present results indicate that the marginal and the intermediate cells are the primary target for EA-induced ototoxicity. However, generalized toxic effects of EA are also indicated, with a general leakage of different elements occurring during the 30-60 min period after EA administration.

Animals↗