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At least 19 recordsLinked to original sources
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↗
PubMed1978

A correlation of the effects of normoxia, hyperoxia and anoxia on PO2 of endolymph and cochlear potentials.

Change in PO2 in endolymph, endocochlear potentials and cochlear microphonics have been tested in normoxia, hyperoxia and anoxia on 24 guinea pigs. The polarographic method and construction of oxygen-sensitive microelectrodes is described in detail. The normal level of PO2 in endolymph vaires between 20 and 30 mm Hg. One-minute anoxia induced by breathing 100% N2 caused a decline in PO2, EP and CM, but during recovery only PO2 returned with over-correction to the preexposure level. Hyperoxia evoked by breathing 100% oxygen failed to increase the cochlear potentials and the PO2 in the endolymph. This suggests that vasoconstriction most likely occurs proximal to the capillaries bed of the stria vascularis.

Animals↗
PubMedDate not supplied

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.

Acetazolamide↗
PubMed1979

Development of endolymph during maturation of the mammalian inner ear. A preliminary report.

The development of the elemental composition in the endolymphatic space was investigated during embryologic and early post natal maturation of the CBA/CBA mouse. At birth the elemental distribution was similar in the endo- and perilymphatic spaces. Mature composition of endolymph was reached 6--8 days post partum. The maturation of endolymph corresponded well in time with the morphological maturation of the stria vascularis.

Age Factors↗
PubMed1976

Effects of cholera toxin on cochlear endolymph production: model for endolymphatic hydrops.

To evaluate a possible role for adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] and adenosine 3':5'-cyclic monophosphate in the secretion of endolymph, we studied the effect of an intra-scala media injection of purified cholera toxin (an adenylate cyclase stimulant) on cochlear endolymph volume, endolymphatic potential, and endolymphatic Na and K concentrations.

Adenylyl Cyclases↗
PubMed1976

Propranolol antagonism to the effect of furosemide on the compostion of endolymph in guinea pigs.

Furosemide, administered intravenously (50 mg/kg) to guinea pigs, caused an increase in the sodium concentration and a decrease in the potassium concentration of endolymph, and a fall in the endolymphatic potential. The furosemide-induced electrolyte changes were prevented by pretreatment of five guinea pigs with propranolol given intravenously (2 mg/kg). The fall in the endolymphatic potential was not prevented by propranolol. Local administration of furosemide to the perilymphatic or endolymphatic space caused a fall in the endolymphatic potential, but had no effect upon the concentrations os sodium and potassium of endolymph. These studies provide additional information suggesting the mutual independence of the endolymphatic potential and sodium and potassium concentration gradients.

Animals↗
PubMed1977

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.

Adenosine Triphosphatases↗
PubMed1979

Effects of noise on cochlear potentials and endolymph potassium concentration recorded with potassium-selective electrodes.

Guinea pig cochleas were exposed to either broad-band noise at intensities between 95 and 115 dBA or octave-band noise centered at 380 Hz or 4.2 kHz at intensities between 115 and 125 dB SPL. Cochlear microphonics (CM), summating potentials (SP) and action potentials (AP) were recorded from differential electrodes in the perilymphatic scalae between successive 20-min periods of noise exposure. The endocochlear potential (EP) and endolymph potassium concentration [Kendo+] were recorded continuously from scala media using double-barreled potassium-sensitive electrodes. It was found that the initial exposure to noise at 115 dBA produced considerable suppression of the CM and AP, while the EP and [Kendo+] were elevated above their normal values. When animals previously treated with kanamycin were subjected to the same level of noise exposure no systematic increase in either EP ro [Kendo+] was observed. After prolonged exposure to 380 Hz octave-band noise at 125 dB SPL, a slow decline of EP and [Kendo+] was observed. The relationships between the changes in EP, [Kendo+] and CM are discussed.

Animals↗
PubMedDate not supplied

Ionic composition of the endolymph and sensory transduction in labyrinthine organs.

The role of various ions in stimuli conversion has been investigated in isolated frog semicircular canals, by replacing the endolymph with solutions deprived in turn of Na+, K+, Cl- and Ca++. Mechanical and electrical stimuli were employed and slow ampullar and nerve potentials were recorded, together with the afferent discharge of impulses in the eighth nerve. The results support evidence that K+ is the carrier of the receptor current, as postulated in Davis' hypothesis, while Ca++ is essential in the processes which allow the current to be modulated during cupula deflections and therefore endon hair cells with mechanical sensitivity.

Acoustic Stimulation↗
PubMedDate not supplied

Effect of intracochlear aminooxyacetic acid on cochlear potentials and endolymph composition.

Summary--Aminooxyacetic acid (AOAA; 1 MM) when perfused through the scala tympani of guinea pigs produced a biphasic reduction in the endocochlear potential, together with a shift in the input-output functions of the cochlear microphonics and the compound action potential of the cochlear nerve. Since the ionic (Na+, K+) content of the scala media was not alerted, it appears that such changes did not underlie the reduction recorded in the endocochlear potential. The negative direct current potential recorded in the organ of Corti did not appear to be affected by the drug. Attempts to antagonize the effects of AOAA with pyridoxine failed.

Acetates↗
PubMedDate not supplied

Alternobaric effects on the endolymph.

Hearing loss and vertigo experienced as a result of environmental pressure change has been the subject of many superficial inquiries. The mechanism of these conditions remains obscure. In human volunteers and a rhesus monkey, the effects of intratympanic as well as ear canal pressure changes on the endolymphatic system were measured using electronystagmography (ENG). For the monkey histological evaluation of the pressure effects on auditory structures was performed. We were unable to cause any ENG effects on the monkey neither did we produce intracochlear pathology. The data obtained in humans using a similar approach are presented and explanations for the mechanism related to hearing loss and vertigo in barotrauma are discussed.

Air Pressure↗