PubMed Health⌕ Search

Biomedical subjects

E Ferrary

Publications and source records attributed to E Ferrary.

At least 19 recordsLinked to original sources
PubMed1992

Changes in the electrochemical composition of cochlear fluids after intracisternal application of doxorubicin in the rat.

Since doxorubicin (Adriamycin) is known to bind on membranous negative surface charges, its effect on the electrochemical composition of the cochlear fluids was studied in rats. Doxorubicin was infused into the cerebrospinal fluid via the lateral cerebral ventricle. The endocochlear resting potential was recorded, and endolymph and perilymph of the scala vestibuli were collected from the basal cochlear turn before and 1, 2, and 4 h after the drug application. Na+, K+, and Cl- concentrations and osmolality of the endolymph and perilymph were measured in 1 nl aliquots. In perilymph, Cl- concentration increased 4 h after doxorubicin treatment to reach a concentration 8 mM higher than recorded initially. In endolymph, the endocochlear potential decreased by 5 mV/h while its K+ concentration and osmolality increased by about 3 mM/h and 4 mosmol/kg H2O per hour, respectively. These results suggest that the negative surface charges demonstrated on Reissner's membrane may play a role in the homeostasis of endolymph.

Animals↗
PubMed1992

Secretion of endolymph by the isolated frog semicircular canal.

Secretion of endolymph is localized in some structures of the inner ear, namely the stria vascularis in the cochlea and the dark cells in the vestibule and in the lower vertebrate inner ear. In isolated semicircular canal it is possible to study separately the endolymphatic composition in the ampulla, which contains the dark cells, and in its non-ampullar part, which is devoid of these cells. Further, in vitro preparation of the semicircular canal provides access to both faces of the epithelium so that different agents can be applied separately to the apical or to the basolateral membranes of the epithelium. In this structure, the following results were obtained: i) in vitro, the semicircular canal secreted a K-rich, positively polarized fluid; ii) this fluid was secreted only in the ampulla of the semicircular canal; iii) the secretion of endolymph was dependent on basolateral Na+, K(+)-ATPase, inhibited by ouabain, and basolateral Na-K-Cl co-transporter, inhibited by bumetanide; iv) approximately 60% of luminal Na absorption occurred across a luminal Na channel inhibited by amiloride; v) the permeability of the paracellular pathway of the semicircular canal epithelium was 7.10(-7) cm/s. These results indicate that endolymph secretion involves basolateral Na+, K(+)-ATPase and Na-K-Cl co-transporter. An Na channel has been shown at the apical membrane.

Animals↗
PubMed1992

Time-related alteration of endolymph composition in an experimental model of endolymphatic hydrops.

The electrochemical changes of the inner ear fluids were studied in the guinea pig during the development of endolymphatic hydrops in an experimental model of Meniere's disease obtained by the blockage of the vestibular aqueduct. The endocochlear potential (first and third turns) was recorded, and the sodium, potassium, and chloride concentrations, and osmolality of the endolymph (first and third turns) and perilymph were determined at different intervals from 2 to 24 weeks after the induction of the hydrops. The development of hydrops was monitored by the compound action potential once a week during the observation period. In normal, nonoperated guinea pigs, longitudinal endolymphatic gradients of endocochlear potential, potassium and chloride concentrations, and osmolality, increasing from the apex to the base of the cochlea, were observed. After 2 weeks of hydrops, no alteration of this pattern was detected. After 6 and 9 weeks of hydrops, a progressive decrease of endocochlear potential, potassium and chloride concentrations, and osmolality was noticed at the first turn (6 and 9 weeks) and then at the third turn (9 weeks) which resulted in the disappearance of longitudinal gradients. At 24 weeks, the endocochlear potential was still diminished by 60%, whereas potassium and chloride concentrations and osmolality increased as compared to 9-week values but remained lower than in controls. The changes in composition of endolymph induced by the development of the hydrops could be related to the progressive alteration of the ionic permeability of the cochlear epithelium, which should be localized at the distended Reissner's membrane.

Action Potentials↗
PubMed1991

Antidiuretic hormone stimulation of adenylate cyclase in semicircular canal epithelium.

Basal adenosine 3',5'-cyclic monophosphate (cAMP) content and the modulation of its production were studied in the frog's semicircular canal epithelium. This epithelium secretes endolymph, a K(+)-rich, positively polarized fluid. The basal cAMP content measured by microradioimmunoassay was 244 +/- 14.2 fmol/structure per 5 min (n = 30). This content was increased about 8 times by 10(-5) M forskolin. Vasotocin, the frog antidiuretic hormone, increased the cAMP production by factors of 1.3 and 3.3 at concentrations of 10(-8) M and 10(-7) M, respectively. This stimulatory effect of vasotocin was blunted by the addition of alpha 2-adrenergic agonists, such as 10(-8) M-10(-5) M norepinephrine, in the presence of 10(-5) M propranolol, or 10(-5) M clonidine. Prostaglandin E2 at a concentration of 10(-8) M, which did not affect the cAMP production, did not modify the response to vasotocin. Glucagon (10(-6) M), calcitonin (10(-6) M), and parathyroid hormone (10 units/ml) did not affect the cAMP content. Prostaglandin E2 (10(-7) M) and the beta-adrenergic agonist isoproterenol (10(-6) M) stimulated the cAMP production by a factor of 1.6. These results indicate that the frog semicircular canal is a target of both vasotocin and catecholamines and that catecholamines through alpha 2-receptors modulate vasotocin-induced cAMP generation. Further, this interaction might be of physiological relevance in the modulation of ion transport in this structure.

Adenylyl Cyclases↗
PubMed1991

Antidiuretic-hormone-induced morphological changes in the ampullary epithelium of the frog semicircular canal.

Morphological changes induced by in vitro treatment with arginine-vasotocin, the frog antidiuretic hormone, were studied in the ampullary epithelium of the frog semicircular canal. Morphological changes appeared only in the apical side of the dark cells, while the basal part of these cells and the other cells lining the semicircular canal did not show any change. Changes consisted of the appearance of numerous small vesicles in the apical cytoplasm and the development of microvilli on the apical plasma membrane of the dark cells. These results suggest that arginine-vasotocin could play a role in the regulation of endolymph section.

Animals↗
PubMed1991

Adenylate cyclase in the semicircular canal. Hormonal stimulation and ultrastructural localization.

The modulation of the cyclic AMP (cAMP) production and the cytochemical localization of adenylate cyclase were studied in isolated semicircular canal epithelium of the frog. The basal cAMP content, as measured by radioimmunoassay, was 344 +/- 37.8 fmoles/structure/5 min (mean +/- SEM, n = 41). This content was increased 6- to 8-fold by forskolin (10(-7) M to 10(-5) M). Among the tested drugs, only prostaglandin E2, isoproterenol, and vasotocin increased the cAMP production: 1.7-fold by prostaglandin E2 (1.5 X 10(-7) M) and isoproterenol (10(-6) M), and 1.3- and 3.3-fold by vasotocin at 10(-8) M and 10(-7) M, respectively. The addition of alpha 2-adrenergic agonists blunted the stimulatory effect of vasotocin. The adenylate cyclase was evidenced in both the basolateral and apical membranes of the dark cells. Vasotocin stimulated only the apical adenylate cyclase of dark cells. These results indicated that the adenylate cyclase located in the apical dark cells of the semicircular canal was stimulated by the antidiuretic hormone which may be involved in the regulation of the endolymph secretion.

Adenylyl Cyclases↗
PubMed1991

[Experimental endolymphatic hydrops. Biochemical data in the guinea pig].

The electrochemical and osmotic composition of the inner ear fluids has been studied during experimental endolymphatic hydrops in guinea pig. The data showed that the modifications of the electrochemical composition of endolymph has been detected only after more than 2 weeks after the hydrops induction. The endocochlear potential, the K and Cl concentrations, and the osmolality progressively decreased between 6 and 9 weeks of hydrops. The longitudinal gradients disappeared. After 24 weeks of hydrops, the endocochlear potential was 50% of the initial value whereas the K and Cl concentrations and the osmolality were higher than that measured at 9 weeks but remained lower than contralateral, normal values. These results suggest that the alterations of the electrochemical and osmotic composition of endolymph that were observed during the evolution of experimental endolymphatic hydrops in guinea pig are related to an alteration of the permeabilities of the Reissner's membrane induced by an increase of hydrostatic pressure.

Animals↗
PubMed1990

Adenylate cyclase and carbonic anhydrase in the semicircular canal epithelium of the frog Rana esculenta. An ultrastructural cytochemical localization.

Because the secretion of endolymph has been localized in the ampullar part of the frog semicircular canal, we attempted to determine by cytochemical methods the ultrastructural localization of two enzymes that are assumed to play a role in endolymph secretion: carbonic anhydrase and adenylate cyclase. Functionally, the epithelium of the frog semicircular canal can be schematically divided into three areas: sensory (crista ampullaris), secretory (dark cells), and non-sensory and nonsecretory (transitional and undifferentiated cells) areas. Carbonic anhydrase activity was widely distributed in dark cells. Dark cell labeling disappeared in the presence of acetazolamide. The other cells of the canal did not show any carbonic anhydrase labeling except for the supporting cells of the sensory cells. Adenylate cyclase activity was found on the basolateral and apical membranes of dark cells, and on the apical membrane of sensory cells; weak labeling was also observed in the other epithelial cells. In the apical membrane of the dark cells, adenylate cyclase labeling was dependent on the presence of vasotocin, the frog antidiuretic hormone. The dark cells of the frog semicircular canal thus possess the enzyme equipment needed for the secretion of endolymph and its possible hormonal regulation.

Adenylyl Cyclases↗
PubMed1989

Sodium transfer from endolymph through a luminal amiloride-sensitive channel.

An in vitro preparation of frog semicircular canal was devised to study the mechanisms of Na transport across the labyrinthine epithelium. When the lumen of the semicircular canal was filled with perilymph-like solution, the structure was able to secrete K into and to absorb Na from the lumen and to generate a lumen-positive transepithelial potential. When the lumen of the semicircular canal was filled with endolymph-like solution, the electrochemical composition of the luminal fluid was partly maintained up to 2 h. In this last experimental condition net and unidirectional fluxes were calculated in absence or presence of transport inhibitors, separately for the ampulla and for the nonampullar part of the canal. Amiloride (10(-5) M) but not dimethyl amiloride (10(-5) M) inhibited 60% of the unidirectional Na efflux out of endolymph; this Na efflux decrease resulted in an increase of the inward net Na flux. The net Na flux was also increased after abluminal application of ouabain (10(-3) M), furosemide (10(-4) M), and bumetanide (10(-6) M). This study validates this isolated preparation as a suitable tool for the study of endolymph secretion, confirms that the secretion of endolymph is achieved in the ampulla, and provides evidence for an apical amiloride-sensitive Na channel through which Na is transferred out of endolymph along an electrochemical gradient provided by the activity of the abluminal Na+-K+-ATPase.

Amiloride↗
PubMed1988

Ultrastructural study of the semicircular canal cells of the frog Rana esculenta.

The ultrastructure of the nonsensory cells (dark cells, transitional cells, and undifferentiated cells) of the frog semicircular canal was studied by using transmission electron microscopy in an attempt to correlate the structure with the functions of these epithelial cells. All the nonsensory cells were linked by tight junctions and desmosomes; this suggested that there is little paracellular ionic transport from perilymph to endolymph. In the dark cell epithelium, the apical intercellular spaces were dilated; in the basal part, numerous basolateral plasma membrane infoldings, containing mitochondria, delimited electron-lucent spaces. The undifferentiated cells and the transitional cells were devoid of any basal membrane infolding. Surrounding the semicircular canal, very flattened and interdigitated mesothelial cells constituted a thin multilayer tissue which limited the perilymphatic space. The morphological aspect of the dark cells suggests that they may play a role in the secretion and/or in the reabsorption of endolymph, which bathes the apical pole of these cells. The undifferentiated and transitional cells can play a role in the maintenance of the endolymphatic ionic composition because of their apical tight junctions and desmosomes.

Animals↗
PubMed1988

Calcium and the inner ear fluids.

Total calcium (Ca) concentration in inner ear fluids was determined by fluorimetry, emission and absorption spectrophotometry, and electron probe analysis. The ionized Ca was measured with selective microelectrodes. In perilymph, the total Ca concentration (1.2 mM) was similar to the ultrafiltrable Ca concentration in plasma. The fraction of ionized Ca was 80%. In endolymph, a total Ca concentration of 0.5 mM contrasted with a reported ionized Ca concentration of 0.02 mM, which suggests, as a working hypothesis, that most of the Ca could exist as bicarbonate and/or phosphate undissociated salts. The decrease in the endocochlear potential induced an increase of the ionized fraction of the Ca. The electrochemical potential of Ca across the perilymph-endolymph barrier implies an active entry of Ca into the endolymph.

Calcium↗
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↗
PubMed1987

Prostaglandins in the semicircular canal of the frog.

The synthesis of prostaglandins by ampulla and duct tissue isolated from the frog posterior semicircular canal was investigated in vitro. Ampulla and duct produced PGE2 (9 and 6 pg/structure, respectively) and prostacyclin (26 and 12 pg/structure). In the ampulla, prostaglandins mostly originated from the part containing dark and sensory cells and was not altered by 10(-3) M streptomycin. Prostaglandin levels were time-dependent and temperature-dependent. Arachidonic acid (3 X 10(-5) M) stimulated PGI2 synthesis by ampulla and duct (by 11.4 and 17 times) and PGE2 synthesis by 50 times in both structures. Ionophore A23187 stimulated ampulla and duct PGI2 synthesis (by 4.8 and 5.6 times) and PGE2 synthesis (by 2.4 and 1.8 times). Subcutaneous 100 mg/kg aspirin reduced PGI2 and PGE2 synthesis (ampulla: -87%, -33%; duct: -100%, -33%). Indomethacin (10(-6) M), in vitro, decreased PGI2 and PGE2 synthesis (ampulla: -47%, -47%; duct; -22%, -77%). Within 3 h, aspirin (5 X 10(-6) M) or arachidonic acid (2 X 10(-5) M) did not change Na and K concentrations in endolymph. It is concluded that frog inner ear produces PGI2 and PGE2, mostly from the part containing the dark cells, and that prostaglandins could be involved in the physiology of inner ear.

Animals↗
PubMed1987

Vasopressin entry into the inner ear fluids of the rat.

The entry of arginine-vasopressin (AVP) and sucrose into cochlear endolymph, perilymph of scala vestibuli (PLV), perilymph of scala tympani (PLT), and cisternal cerebrospinal fluid (CSF) was studied, in anesthetized rats, after the administration into the cerebral lateral ventricle of a 10 microliter solution containing the radioactive tracers. Both tracers were detected in PLV, PLT, and CSF but not in endolymph. Monoexponential decay curves were calculated for PLV, PLT, and CSF, and for each tracer no difference was found between the regression lines calculated for the different fluids. These results indicate that (i) injection into the cerebral lateral ventricle is a useful tool to study the permeability of the cochlear epithelium to different solutes and (ii) no specific transport system exists for AVP across the cochlear epithelium, suggesting that AVP may exert its effect via the perilymphatic side of the stria vascularis.

Animals↗
PubMed1987

Na and nonelectrolyte entry into inner ear fluids of the rat.

Kinetics of hydrophilic solute entry into endolymph (EL), perilymph (PL), and cerebrospinal fluid (CSF) were studied after intravenous administration (sodium, urea, glycerol, mannitol, sucrose) and cerebral lateral ventricle injection (urea, sucrose) of tracers in anesthetized rats. Samples of cochlear EL, PL of scala vestibuli (PLV), PL of scala tympani (PLT), and cisternal CSF were obtained. The data showed slow entry of tracers in PLV, PLT, and CSF as follows: Na greater than urea greater than mannitol approximately sucrose; slower entry of mannitol and sucrose in PLT and CSF than in PLV; 1 h delayed peak of radioactivity in PLV compared with the immediate peaks in PLT and CSF after CSF injection, and the value of PLV peak was 13% that in CSF; extremely slow entry of nonelectrolytes in EL. These results indicate that PLV originates mainly from plasma across a blood-perilymph barrier that restricts the entry of small hydrophilic solutes. The blood-perilymph barrier is most likely composed of an endothelial barrier associated with an epithelial secretion. The latter could be located at the vasculo-epithelial zone of the spiral limbus.

Animals↗
PubMed1987

Facilitated transfer of glucose from blood into perilymph in the rat cochlea.

The transport of glucose into cochlear endolymph, perilymph of scala vestibuli and perilymph of scala tympani, and cerebrospinal fluid (CSF) was studied after intravenous administration of tracers of D-glucose, L-glucose, and 3-O-methyl-D-glucose in anesthetized rats. The data showed that D-glucose concentrations in perilymph of scala vestibuli, perilymph of scala tympani, and CSF were approximately 50%, and in endolymph less than 10%, that in plasma; D-glucose concentration in perilymph of scala vestibuli, perilymph of scala tympani, and CSF increased as a linear function of that in plasma; D-glucose entry into perilymph of scala vestibuli, perilymph of scala tympani, and CSF was more rapid than that of L-glucose; after infusion of 3-O-methyl-D-glucose, but not after that of mannitol, both the D-glucose concentration ratio of perilymph over plasma and D-glucose transfer into perilymph were lowered. These results indicate that D-glucose enters into perilymph of scala vestibuli by a facilitated transport, possibly located at the blood-perilymph barrier.

3-O-Methylglucose↗