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Patrick Payan - One of the best experts on this subject based on the ideXlab platform.

  • characterization and variations of organic parameters in teleost fish Endolymph during day night cycle starvation and stress conditions
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2006
    Co-Authors: Marielle Guibbolini, Gil Borelli, Fabrice Priouzeau, N Mayergostan, Denis Allemand, Helene De Pontual, Patrick Payan
    Abstract:

    The aim of the present work was to examine the modifications of the organic composition of fish Endolymph under environmental conditions (day-night cycle, starvation and Cl2-stress) known to modify otolith growth. Endolymph electrophoretic patterns were compared. An antibody raised against the trout otolith organic matrix allowed examining the variations of organic matrix precursors in the Endolymph under the above conditions. Western blot analysis showed bands around 60-80 kDa. A 50% decrease of immunolabelling was observed during the night whereas increases were seen after starvation (factor 3) or stress (factor 2) suggesting that these variations could be related to the organic matrix deposit. A factor retarding in vitro CaCO3 crystallization (FRC) was shown to co-precipitate with Endolymph proteins and its apparent molecular mass (determined by measuring the activity after electro elution of gel electrophoresis) was estimated around 20 kDa. The FRC activity was stable during day-night cycle whereas it decreased by 70% and nearly 100% under starvation and stress respectively. These results suggest that the FRC, although retarding in vitro crystallization, plays a major role in the process of otolith calcification and that the decreases measured after starvation and stress are responsible for the decreases of the otolith growth. The variations of these two parameters (precursors and FRC) could contribute for the changes in the microstructure of the otolith

  • Endolymph chemistry and otolith growth in fish
    Comptes Rendus Palevol, 2004
    Co-Authors: Patrick Payan, Helene De Pontual, Gilles Bœuf, N Mayergostan
    Abstract:

    Abstract Otoliths are composed of 99% CaCO3 in the aragonite form which is deposited daily onto an organic matrix. The mineralisation process takes place in an acellular medium, the Endolymph, which is secreted by the inner-ear epithelium. The present review is mostly devoted to ionic and organic Endolymph components (concentration and spatial distribution) in relation to otolith growth, with a special interest to the ionic supply from plasma to Endolymph and to the biochemical relationships between Endolymph and otolith matrix. To cite this article: P. Payan et al., C. R. Palevol 3 (2004).

  • effects of stress on plasma homeostasis Endolymph chemistry and check formation during otolith growth in rainbow trout oncorhynchus mykiss
    Canadian Journal of Fisheries and Aquatic Sciences, 2004
    Co-Authors: Patrick Payan, A Edeyer, H. De Pontual, Gil Borelli, Gilles Boeuf, N Mayergostan
    Abstract:

    This is the first study in which the effects of an external stress were analysed at different levels: plasma ho meostasis, Endolymph chemistry, and otolith growth. Stress was applied to rainbow trout (Oncorhynchus mykiss) by exposure to Cl2 gas. In the plasma of Cl2-stressed trout, Na+ and Cl– decreased (70 mmol·L–1) and K+ increased (2.0 mmol·L–1), whereas total Ca was unchanged. A slight hypercapny (+2.4 mmHg (1 mmHg = 133.322 Pa)) was observed related to a significant rise (40%) in total CO2 without pH variation. In the Endolymph, Na+ and Cl– also decreased, whereas other parameters (K+, PO43–, Mg, and, peculiarly, total Ca) remained stable. The important effect provoked by Cl2 stress in Endolymph was an increase of proteins (factor of 2.6) and total CO2 (factor of 3.1) concentrations at the proximal side of the Endolymph. The stress induced a decrease in otolith growth rate and produced a discontinuity (check) in the microstructure pattern of the otolith characterized by a large D zone. The variations...

  • daily variations of Endolymph composition relationship with the otolith calcification process in trout
    The Journal of Experimental Biology, 2003
    Co-Authors: Gil Borelli, H. De Pontual, Fabrice Priouzeau, N Mayergostan, Marielle Guibbolini, Denis Allemand, Sandrine Puverel, Eric Tambutte, Patrick Payan
    Abstract:

    Ionic and organic parameters of the otolith calcification process in the trout Oncorhynchus mykiss were analysed in plasma and Endolymph over the day:night cycle. Plasma pH remained constant and total CO2 concentration was significantly lower (by 21%) during the day than at night. Calcifying parameters (total CO2, total calcium concentration) were measured in the proximal and distal Endolymphs and were unchanged in the latter during the day:night cycle, but fluctuated in the former. Non-collagenous protein and collagen concentrations in Endolymph were higher (1.5- and 10-fold, respectively) during the day than at night. As there was no change in total calcium concentration, we propose that Ca2+ increases during the dark period and was maximal by the end of the night when the total CO2 concentration has also increased (by 14%). Measurements of Endolymph pH in situ revealed significant differences between samples from proximal and distal Endolymph (7.38 and 7.87, respectively), but no variation between values obtained during the day and at night. Thus, the saturation state of aragonite (Sa) in the proximal Endolymph should fluctuate around unity during the day:night cycle, and CaCO3 precipitation should occur when supersaturation is reached. The electrophoretic pattern of proximal Endolymph showed variations in both major and minor components. Immunoblotting of Endolymph, using a rabbit antiserum raised against the otolith soluble organic matrix revealed an increase in the expression of two proteins (65 kDa and 75 kDa) during the day period. We propose that organic matrix and calcium carbonate deposition on the otolith vary antiphasically: organic matrix deposition begins by the end of the day period, when the concentration of organic precursors is maximal in the Endolymph, whereas CaCO3 precipitation starts once the solubility of CaCO3 is exceeded.

  • otolith growth in trout oncorhynchus mykiss supply of ca2 and sr2 to the saccular Endolymph
    The Journal of Experimental Biology, 2002
    Co-Authors: Patrick Payan, H. De Pontual, Gil Borelli, Fabrice Priouzeau, G Bœuf, N Mayergostan
    Abstract:

    SUMMARY Kinetic and pharmacological characteristics of Ca 2+ fluxes across the saccular epithelium of trout were studied using a perfused isolated inner ear. 45 Ca 2+ influx from the Ringer solution to the Endolymph was 3-4 nmoles h -1 μl -1 Endolymph, which corresponds to a global turnover rate of the Endolymph calcium of 200 % h -1 . Ca 2+ entry into the proximal Endolymph was faster than into the distal fluid. Net Ca 2+ movement across the saccular epithelium depended on the direction and intensity of the chemical gradient of calcium between the Ringer solution and the Endolymph. Increasing the calcium concentration in the Ringer solution up to 4.4 mmol l -1 provoked an accumulation of Ca 2+ in both proximal and distal Endolymphs, and equilibrium was reached about 30 min after the beginning of perfusion. Perfusion with calcium-free Ringer partially emptied the proximal compartment of calcium, whereas the calcium levels in the distal Endolymph did not vary during 70 min of perfusion. Verapamil (10 -5 mol l -1 ) and cyanide (CN, 10 -3 mol l -1 ) did not modify the accumulation of Ca 2+ within the Endolymph in the presence of a favourable calcium chemical gradient. Furthermore the relationship between Ca 2+ net fluxes and the chemical calcium gradient across the saccular epithelium was linear, indicating a passive diffusional mechanism via a paracellular pathway. Similar relationships were found for Sr 2+ fluxes across the saccular epithelium in the presence of positive chemical gradients (1, 2 and 4 mmol l -1 Sr 2+ ). In vivo experiments in which trout were intraperitoneously injected with CaCl 2 solution confirmed the tight relationship between the calcium levels in plasma and Endolymph (both proximal and distal). Sampling proximal and distal Endolymphs in trout and turbot saccules revealed a decreasing proximo—distal calcium gradient in Endolymph of both fish species. The present results strongly suggest that the Endolymph is supplied with Ca 2+ and Sr 2+ via a paracellular pathway located in the proximal area of the saccular epithelium.

N Mayergostan - One of the best experts on this subject based on the ideXlab platform.

  • characterization and variations of organic parameters in teleost fish Endolymph during day night cycle starvation and stress conditions
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2006
    Co-Authors: Marielle Guibbolini, Gil Borelli, Fabrice Priouzeau, N Mayergostan, Denis Allemand, Helene De Pontual, Patrick Payan
    Abstract:

    The aim of the present work was to examine the modifications of the organic composition of fish Endolymph under environmental conditions (day-night cycle, starvation and Cl2-stress) known to modify otolith growth. Endolymph electrophoretic patterns were compared. An antibody raised against the trout otolith organic matrix allowed examining the variations of organic matrix precursors in the Endolymph under the above conditions. Western blot analysis showed bands around 60-80 kDa. A 50% decrease of immunolabelling was observed during the night whereas increases were seen after starvation (factor 3) or stress (factor 2) suggesting that these variations could be related to the organic matrix deposit. A factor retarding in vitro CaCO3 crystallization (FRC) was shown to co-precipitate with Endolymph proteins and its apparent molecular mass (determined by measuring the activity after electro elution of gel electrophoresis) was estimated around 20 kDa. The FRC activity was stable during day-night cycle whereas it decreased by 70% and nearly 100% under starvation and stress respectively. These results suggest that the FRC, although retarding in vitro crystallization, plays a major role in the process of otolith calcification and that the decreases measured after starvation and stress are responsible for the decreases of the otolith growth. The variations of these two parameters (precursors and FRC) could contribute for the changes in the microstructure of the otolith

  • Endolymph chemistry and otolith growth in fish
    Comptes Rendus Palevol, 2004
    Co-Authors: Patrick Payan, Helene De Pontual, Gilles Bœuf, N Mayergostan
    Abstract:

    Abstract Otoliths are composed of 99% CaCO3 in the aragonite form which is deposited daily onto an organic matrix. The mineralisation process takes place in an acellular medium, the Endolymph, which is secreted by the inner-ear epithelium. The present review is mostly devoted to ionic and organic Endolymph components (concentration and spatial distribution) in relation to otolith growth, with a special interest to the ionic supply from plasma to Endolymph and to the biochemical relationships between Endolymph and otolith matrix. To cite this article: P. Payan et al., C. R. Palevol 3 (2004).

  • effects of stress on plasma homeostasis Endolymph chemistry and check formation during otolith growth in rainbow trout oncorhynchus mykiss
    Canadian Journal of Fisheries and Aquatic Sciences, 2004
    Co-Authors: Patrick Payan, A Edeyer, H. De Pontual, Gil Borelli, Gilles Boeuf, N Mayergostan
    Abstract:

    This is the first study in which the effects of an external stress were analysed at different levels: plasma ho meostasis, Endolymph chemistry, and otolith growth. Stress was applied to rainbow trout (Oncorhynchus mykiss) by exposure to Cl2 gas. In the plasma of Cl2-stressed trout, Na+ and Cl– decreased (70 mmol·L–1) and K+ increased (2.0 mmol·L–1), whereas total Ca was unchanged. A slight hypercapny (+2.4 mmHg (1 mmHg = 133.322 Pa)) was observed related to a significant rise (40%) in total CO2 without pH variation. In the Endolymph, Na+ and Cl– also decreased, whereas other parameters (K+, PO43–, Mg, and, peculiarly, total Ca) remained stable. The important effect provoked by Cl2 stress in Endolymph was an increase of proteins (factor of 2.6) and total CO2 (factor of 3.1) concentrations at the proximal side of the Endolymph. The stress induced a decrease in otolith growth rate and produced a discontinuity (check) in the microstructure pattern of the otolith characterized by a large D zone. The variations...

  • daily variations of Endolymph composition relationship with the otolith calcification process in trout
    The Journal of Experimental Biology, 2003
    Co-Authors: Gil Borelli, H. De Pontual, Fabrice Priouzeau, N Mayergostan, Marielle Guibbolini, Denis Allemand, Sandrine Puverel, Eric Tambutte, Patrick Payan
    Abstract:

    Ionic and organic parameters of the otolith calcification process in the trout Oncorhynchus mykiss were analysed in plasma and Endolymph over the day:night cycle. Plasma pH remained constant and total CO2 concentration was significantly lower (by 21%) during the day than at night. Calcifying parameters (total CO2, total calcium concentration) were measured in the proximal and distal Endolymphs and were unchanged in the latter during the day:night cycle, but fluctuated in the former. Non-collagenous protein and collagen concentrations in Endolymph were higher (1.5- and 10-fold, respectively) during the day than at night. As there was no change in total calcium concentration, we propose that Ca2+ increases during the dark period and was maximal by the end of the night when the total CO2 concentration has also increased (by 14%). Measurements of Endolymph pH in situ revealed significant differences between samples from proximal and distal Endolymph (7.38 and 7.87, respectively), but no variation between values obtained during the day and at night. Thus, the saturation state of aragonite (Sa) in the proximal Endolymph should fluctuate around unity during the day:night cycle, and CaCO3 precipitation should occur when supersaturation is reached. The electrophoretic pattern of proximal Endolymph showed variations in both major and minor components. Immunoblotting of Endolymph, using a rabbit antiserum raised against the otolith soluble organic matrix revealed an increase in the expression of two proteins (65 kDa and 75 kDa) during the day period. We propose that organic matrix and calcium carbonate deposition on the otolith vary antiphasically: organic matrix deposition begins by the end of the day period, when the concentration of organic precursors is maximal in the Endolymph, whereas CaCO3 precipitation starts once the solubility of CaCO3 is exceeded.

  • otolith growth in trout oncorhynchus mykiss supply of ca2 and sr2 to the saccular Endolymph
    The Journal of Experimental Biology, 2002
    Co-Authors: Patrick Payan, H. De Pontual, Gil Borelli, Fabrice Priouzeau, G Bœuf, N Mayergostan
    Abstract:

    SUMMARY Kinetic and pharmacological characteristics of Ca 2+ fluxes across the saccular epithelium of trout were studied using a perfused isolated inner ear. 45 Ca 2+ influx from the Ringer solution to the Endolymph was 3-4 nmoles h -1 μl -1 Endolymph, which corresponds to a global turnover rate of the Endolymph calcium of 200 % h -1 . Ca 2+ entry into the proximal Endolymph was faster than into the distal fluid. Net Ca 2+ movement across the saccular epithelium depended on the direction and intensity of the chemical gradient of calcium between the Ringer solution and the Endolymph. Increasing the calcium concentration in the Ringer solution up to 4.4 mmol l -1 provoked an accumulation of Ca 2+ in both proximal and distal Endolymphs, and equilibrium was reached about 30 min after the beginning of perfusion. Perfusion with calcium-free Ringer partially emptied the proximal compartment of calcium, whereas the calcium levels in the distal Endolymph did not vary during 70 min of perfusion. Verapamil (10 -5 mol l -1 ) and cyanide (CN, 10 -3 mol l -1 ) did not modify the accumulation of Ca 2+ within the Endolymph in the presence of a favourable calcium chemical gradient. Furthermore the relationship between Ca 2+ net fluxes and the chemical calcium gradient across the saccular epithelium was linear, indicating a passive diffusional mechanism via a paracellular pathway. Similar relationships were found for Sr 2+ fluxes across the saccular epithelium in the presence of positive chemical gradients (1, 2 and 4 mmol l -1 Sr 2+ ). In vivo experiments in which trout were intraperitoneously injected with CaCl 2 solution confirmed the tight relationship between the calcium levels in plasma and Endolymph (both proximal and distal). Sampling proximal and distal Endolymphs in trout and turbot saccules revealed a decreasing proximo—distal calcium gradient in Endolymph of both fish species. The present results strongly suggest that the Endolymph is supplied with Ca 2+ and Sr 2+ via a paracellular pathway located in the proximal area of the saccular epithelium.

John E Demott - One of the best experts on this subject based on the ideXlab platform.

  • ionic and potential changes of the Endolymphatic sac induced by Endolymph volume changes
    Hearing Research, 2000
    Co-Authors: Alec N Salt, John E Demott
    Abstract:

    Abstract The Endolymphatic sac (ES) is believed to be the locus for Endolymph volume regulation in the inner ear. It has recently been shown that induced Endolymph volume changes in the cochlea result in anatomical changes in the ES, suggesting that function of the sac varies according to Endolymph volume status. In the present study we have recorded luminal concentrations of K + and Na + from the ES and the Endolymphatic sac potential (ESP) during cochlear Endolymph volume changes. ES recordings were made by an extradural approach, thereby preserving normal cerebrospinal fluid resting pressure. Cochlear Endolymph volume changes were generated by performing injections or withdrawals through a pipette inserted into Endolymph by a round window approach. The pre-treatment concentrations of K + and Na + in the ES were found to be 8.4 mM (S.D. 3.3, n =8) and 128.6 mM (S.D. 18.4, n =10) respectively, and the mean ESP was 14.4 mV (S.D. 5.2, n =18). Endolymphatic injections were found to produce a sustained increase in the K + content of the ES by an average of 19.9 mM and to decrease Na + by 30.7 mM measured 50 min after the start of injection. The time for K + increase to occur was found to correlate with the injected volume, with larger injected volumes producing a more rapid increase. Endolymphatic withdrawals were found to induce a slow decline in Endolymphatic K + by an average of 3.4 mM measured at 50 min after withdrawal, although no significant change of Na + was detected. Volume-induced ESP changes were highly variable. Injections produced a small increase in the mean ESP and withdrawals produced a small decrease but neither change was statistically significant and some animals showed potential changes in the opposite direction. These data show that a change in cochlear Endolymph volume status results in a physiologic response of the ES which is sustained for a considerable period. If the ES plays a part in the restoration of normal Endolymph volume, this process appears to proceed slowly, based on the prolonged time courses of ionic changes observed.

  • morphological changes of the Endolymphatic sac induced by microinjection of artificial Endolymph into the cochlea
    Hearing Research, 1999
    Co-Authors: Helge Raskandersen, D Baggersjoback, John E Demott, Alec N Salt
    Abstract:

    Abstract Morphological changes of the Endolymphatic sac were analyzed in guinea pigs following microinjection of artificial Endolymph into the cochlea or withdrawal of a quantity of native Endolymph. Injections were performed into the second turn of scala media with a micro-pump at a rate of 60–100 nl/min, lasting for a period of 4, 7.5, 15 or 18 min. In withdrawal experiments, Endolymph was aspirated from the second cochlear turn over a period of 8 min. For each procedure the contralateral (non-treated) ear served as a histological control. Following artificial Endolymph injections of 7.5 min or more there was an almost total absence of the normal intraluminal homogeneous substance (HS) on the injected side. Our observations suggest that the disappearance of the HS occurs by both enzymatic and macrophagic activity. After Endolymphatic withdrawals the ES was found to contain increased amounts of HS. The results could suggest that the volume of fluid in the ES, and hence the volume of the entire membranous labyrinth, may be regulated by a dynamic relationship between active secretion and enzymatic degradation of a lumen-expanding substance that is intimately related to the intraluminal macrophages. The exact mechanism governing these regulatory systems, and their relationship to ion and water movements across the epithelium of the sac, remain to be elucidated.

  • longitudinal Endolymph movements and endocochlear potential changes induced by stimulation at infrasonic frequencies
    Journal of the Acoustical Society of America, 1999
    Co-Authors: Alec N Salt, John E Demott
    Abstract:

    The inner ear is continually exposed to pressure fluctuations in the infrasonic frequency range (< 20 Hz) from external and internal body sources. The cochlea is generally regarded to be insensitive to such stimulation. The effects of stimulation at infrasonic frequencies (0.1 to 10 Hz) on endocochlear potential (EP) and Endolymph movements in the guinea pig cochlea were studied. Stimuli were applied directly to the perilymph of scala tympani or scala vestibuli of the cochlea via a fluid-filled pipette. Stimuli, especially those near 1 Hz, elicited large EP changes which under some conditions exceeded 20 mV in amplitude and were equivalent to a cochlear microphonic (CM) response. Accompanying the electrical responses was a cyclical, longitudinal displacement of the Endolymph. The amplitude and phase of the CM varied according to which perilymphatic scala the stimuli were applied to and whether a perforation was made in the opposing perilymphatic scala. Spontaneously occurring middle ear muscle contractions were also found to induce EP deflections and longitudinal Endolymph movements comparable to those generated by perilymphatic injections. These findings suggest that cochlear fluid movements induced by pressure fluctuations at infrasonic frequencies could play a role in fluid homeostasis in the normal state and in fluid disturbances in pathological states.

  • longitudinal Endolymph movements induced by perilymphatic injections
    Hearing Research, 1998
    Co-Authors: Alec N Salt, John E Demott
    Abstract:

    Abstract Endolymph movements and endocochlear potential (EP) changes were measured during disturbances of perilymphatic pressure, induced by injecting artificial perilymph into scala tympani (ST) or scala vestibuli (SV) of the guinea pig cochlea. Injections were performed either with or without an outlet made in the opposite perilymphatic scala. Injections into ST without an outlet induced large pressure changes but virtually no Endolymph movement or EP change. Injection at the same rate into ST with an outlet in SV produced smaller pressure changes which were accompanied by a basally-directed displacement of Endolymph and significant EP changes. The magnitude of Endolymph displacements and EP changes varied as a function of injection rate. Injections into SV, either with or without an outlet in ST, produced apically-directed Endolymph displacement and EP changes. For the SV injections without an outlet, the cochlear aqueduct and round window are likely to provide an outlet and compliance, permitting flow along the perilymphatic scalae to occur even when no ST outlet was provided. We conclude that Endolymph movements are not dependent on the absolute pressure of the perilymph, but instead occur when small, sustained pressure gradients are present across the cochlear partition, corresponding to times when perilymph flow is induced. This study demonstrates that in the normal, sealed cochlea, Endolymph and EP are insensitive to fluid injections into ST, but are sensitive to fluid injections into SV. Endolymph movements are therefore unlikely to be generated by cerebrospinal fluid pressure fluctuations (such as those produced by respiration, posture changes, coughing, sneezing, etc) which are transmitted to ST by the cochlear aqueduct.

  • longitudinal Endolymph flow associated with acute volume increase in the guinea pig cochlea
    Hearing Research, 1997
    Co-Authors: Alec N Salt, John E Demott
    Abstract:

    Endolymph volume disturbances were induced by microinjections of artificial Endolymph into the second turn of the guinea pig cochlea at rates less than 60 nl/min. Induced longitudinal movements and area changes of Endolymph were quantified in the basal turn using an ionic flow marker technique. Tetramethylammonium (TMA) was used as a flow marker by iontophoresing it into Endolymph in micromolar amounts. TMA movements in the apical and basal directions were monitored by ion-selective electrodes. Changes in Endolymph flow and cross-sectional area of scala media were derived using a mathematical model to interpret the recorded tracer time courses. The model was validated by performing comparable volume injections and flow measurements in fine-diameter plastic tubes. The rate of flow of Endolymph measured prior to injection was close to zero, in agreement with prior studies. Based on the injection of different volumes into Endolymph over a 15 min period, we found that injection of up to 80 nl of artificial Endolymph into the second turn would not induce flow in the basal turn. However, above this amount, flow towards the base increased at a rate which correlated with the injected volume, with Endolymph moving basally by a distance of 0.0067 mm/nl of artificial Endolymph injected. Flow rates measured in the third turn, on the apical side of the injection were far lower and showed characteristics consistent with there being no outlet at the apex. These results suggest that small volume disturbances are corrected locally in the cochlea, but larger disturbances produce a longitudinal flow of Endolymph out of the cochlea which represents a significant mechanism contributing to homeostasis. It can be concluded that structures outside the cochlea, such as the Endolymphatic sac, do play a role in the correction of Endolymph volume disturbances. Although the maintenance of Endolymph composition is dominated by local ion transport mechanisms, the capacity of these local mechanisms to maintain normal Endolymph volume appears to be limited.

Alec N Salt - One of the best experts on this subject based on the ideXlab platform.

  • ionic and potential changes of the Endolymphatic sac induced by Endolymph volume changes
    Hearing Research, 2000
    Co-Authors: Alec N Salt, John E Demott
    Abstract:

    Abstract The Endolymphatic sac (ES) is believed to be the locus for Endolymph volume regulation in the inner ear. It has recently been shown that induced Endolymph volume changes in the cochlea result in anatomical changes in the ES, suggesting that function of the sac varies according to Endolymph volume status. In the present study we have recorded luminal concentrations of K + and Na + from the ES and the Endolymphatic sac potential (ESP) during cochlear Endolymph volume changes. ES recordings were made by an extradural approach, thereby preserving normal cerebrospinal fluid resting pressure. Cochlear Endolymph volume changes were generated by performing injections or withdrawals through a pipette inserted into Endolymph by a round window approach. The pre-treatment concentrations of K + and Na + in the ES were found to be 8.4 mM (S.D. 3.3, n =8) and 128.6 mM (S.D. 18.4, n =10) respectively, and the mean ESP was 14.4 mV (S.D. 5.2, n =18). Endolymphatic injections were found to produce a sustained increase in the K + content of the ES by an average of 19.9 mM and to decrease Na + by 30.7 mM measured 50 min after the start of injection. The time for K + increase to occur was found to correlate with the injected volume, with larger injected volumes producing a more rapid increase. Endolymphatic withdrawals were found to induce a slow decline in Endolymphatic K + by an average of 3.4 mM measured at 50 min after withdrawal, although no significant change of Na + was detected. Volume-induced ESP changes were highly variable. Injections produced a small increase in the mean ESP and withdrawals produced a small decrease but neither change was statistically significant and some animals showed potential changes in the opposite direction. These data show that a change in cochlear Endolymph volume status results in a physiologic response of the ES which is sustained for a considerable period. If the ES plays a part in the restoration of normal Endolymph volume, this process appears to proceed slowly, based on the prolonged time courses of ionic changes observed.

  • morphological changes of the Endolymphatic sac induced by microinjection of artificial Endolymph into the cochlea
    Hearing Research, 1999
    Co-Authors: Helge Raskandersen, D Baggersjoback, John E Demott, Alec N Salt
    Abstract:

    Abstract Morphological changes of the Endolymphatic sac were analyzed in guinea pigs following microinjection of artificial Endolymph into the cochlea or withdrawal of a quantity of native Endolymph. Injections were performed into the second turn of scala media with a micro-pump at a rate of 60–100 nl/min, lasting for a period of 4, 7.5, 15 or 18 min. In withdrawal experiments, Endolymph was aspirated from the second cochlear turn over a period of 8 min. For each procedure the contralateral (non-treated) ear served as a histological control. Following artificial Endolymph injections of 7.5 min or more there was an almost total absence of the normal intraluminal homogeneous substance (HS) on the injected side. Our observations suggest that the disappearance of the HS occurs by both enzymatic and macrophagic activity. After Endolymphatic withdrawals the ES was found to contain increased amounts of HS. The results could suggest that the volume of fluid in the ES, and hence the volume of the entire membranous labyrinth, may be regulated by a dynamic relationship between active secretion and enzymatic degradation of a lumen-expanding substance that is intimately related to the intraluminal macrophages. The exact mechanism governing these regulatory systems, and their relationship to ion and water movements across the epithelium of the sac, remain to be elucidated.

  • longitudinal Endolymph movements and endocochlear potential changes induced by stimulation at infrasonic frequencies
    Journal of the Acoustical Society of America, 1999
    Co-Authors: Alec N Salt, John E Demott
    Abstract:

    The inner ear is continually exposed to pressure fluctuations in the infrasonic frequency range (< 20 Hz) from external and internal body sources. The cochlea is generally regarded to be insensitive to such stimulation. The effects of stimulation at infrasonic frequencies (0.1 to 10 Hz) on endocochlear potential (EP) and Endolymph movements in the guinea pig cochlea were studied. Stimuli were applied directly to the perilymph of scala tympani or scala vestibuli of the cochlea via a fluid-filled pipette. Stimuli, especially those near 1 Hz, elicited large EP changes which under some conditions exceeded 20 mV in amplitude and were equivalent to a cochlear microphonic (CM) response. Accompanying the electrical responses was a cyclical, longitudinal displacement of the Endolymph. The amplitude and phase of the CM varied according to which perilymphatic scala the stimuli were applied to and whether a perforation was made in the opposing perilymphatic scala. Spontaneously occurring middle ear muscle contractions were also found to induce EP deflections and longitudinal Endolymph movements comparable to those generated by perilymphatic injections. These findings suggest that cochlear fluid movements induced by pressure fluctuations at infrasonic frequencies could play a role in fluid homeostasis in the normal state and in fluid disturbances in pathological states.

  • longitudinal Endolymph movements induced by perilymphatic injections
    Hearing Research, 1998
    Co-Authors: Alec N Salt, John E Demott
    Abstract:

    Abstract Endolymph movements and endocochlear potential (EP) changes were measured during disturbances of perilymphatic pressure, induced by injecting artificial perilymph into scala tympani (ST) or scala vestibuli (SV) of the guinea pig cochlea. Injections were performed either with or without an outlet made in the opposite perilymphatic scala. Injections into ST without an outlet induced large pressure changes but virtually no Endolymph movement or EP change. Injection at the same rate into ST with an outlet in SV produced smaller pressure changes which were accompanied by a basally-directed displacement of Endolymph and significant EP changes. The magnitude of Endolymph displacements and EP changes varied as a function of injection rate. Injections into SV, either with or without an outlet in ST, produced apically-directed Endolymph displacement and EP changes. For the SV injections without an outlet, the cochlear aqueduct and round window are likely to provide an outlet and compliance, permitting flow along the perilymphatic scalae to occur even when no ST outlet was provided. We conclude that Endolymph movements are not dependent on the absolute pressure of the perilymph, but instead occur when small, sustained pressure gradients are present across the cochlear partition, corresponding to times when perilymph flow is induced. This study demonstrates that in the normal, sealed cochlea, Endolymph and EP are insensitive to fluid injections into ST, but are sensitive to fluid injections into SV. Endolymph movements are therefore unlikely to be generated by cerebrospinal fluid pressure fluctuations (such as those produced by respiration, posture changes, coughing, sneezing, etc) which are transmitted to ST by the cochlear aqueduct.

  • longitudinal Endolymph flow associated with acute volume increase in the guinea pig cochlea
    Hearing Research, 1997
    Co-Authors: Alec N Salt, John E Demott
    Abstract:

    Endolymph volume disturbances were induced by microinjections of artificial Endolymph into the second turn of the guinea pig cochlea at rates less than 60 nl/min. Induced longitudinal movements and area changes of Endolymph were quantified in the basal turn using an ionic flow marker technique. Tetramethylammonium (TMA) was used as a flow marker by iontophoresing it into Endolymph in micromolar amounts. TMA movements in the apical and basal directions were monitored by ion-selective electrodes. Changes in Endolymph flow and cross-sectional area of scala media were derived using a mathematical model to interpret the recorded tracer time courses. The model was validated by performing comparable volume injections and flow measurements in fine-diameter plastic tubes. The rate of flow of Endolymph measured prior to injection was close to zero, in agreement with prior studies. Based on the injection of different volumes into Endolymph over a 15 min period, we found that injection of up to 80 nl of artificial Endolymph into the second turn would not induce flow in the basal turn. However, above this amount, flow towards the base increased at a rate which correlated with the injected volume, with Endolymph moving basally by a distance of 0.0067 mm/nl of artificial Endolymph injected. Flow rates measured in the third turn, on the apical side of the injection were far lower and showed characteristics consistent with there being no outlet at the apex. These results suggest that small volume disturbances are corrected locally in the cochlea, but larger disturbances produce a longitudinal flow of Endolymph out of the cochlea which represents a significant mechanism contributing to homeostasis. It can be concluded that structures outside the cochlea, such as the Endolymphatic sac, do play a role in the correction of Endolymph volume disturbances. Although the maintenance of Endolymph composition is dominated by local ion transport mechanisms, the capacity of these local mechanisms to maintain normal Endolymph volume appears to be limited.

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  • characterization and variations of organic parameters in teleost fish Endolymph during day night cycle starvation and stress conditions
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2006
    Co-Authors: Marielle Guibbolini, Gil Borelli, Fabrice Priouzeau, N Mayergostan, Denis Allemand, Helene De Pontual, Patrick Payan
    Abstract:

    The aim of the present work was to examine the modifications of the organic composition of fish Endolymph under environmental conditions (day-night cycle, starvation and Cl2-stress) known to modify otolith growth. Endolymph electrophoretic patterns were compared. An antibody raised against the trout otolith organic matrix allowed examining the variations of organic matrix precursors in the Endolymph under the above conditions. Western blot analysis showed bands around 60-80 kDa. A 50% decrease of immunolabelling was observed during the night whereas increases were seen after starvation (factor 3) or stress (factor 2) suggesting that these variations could be related to the organic matrix deposit. A factor retarding in vitro CaCO3 crystallization (FRC) was shown to co-precipitate with Endolymph proteins and its apparent molecular mass (determined by measuring the activity after electro elution of gel electrophoresis) was estimated around 20 kDa. The FRC activity was stable during day-night cycle whereas it decreased by 70% and nearly 100% under starvation and stress respectively. These results suggest that the FRC, although retarding in vitro crystallization, plays a major role in the process of otolith calcification and that the decreases measured after starvation and stress are responsible for the decreases of the otolith growth. The variations of these two parameters (precursors and FRC) could contribute for the changes in the microstructure of the otolith

  • effects of stress on plasma homeostasis Endolymph chemistry and check formation during otolith growth in rainbow trout oncorhynchus mykiss
    Canadian Journal of Fisheries and Aquatic Sciences, 2004
    Co-Authors: Patrick Payan, A Edeyer, H. De Pontual, Gil Borelli, Gilles Boeuf, N Mayergostan
    Abstract:

    This is the first study in which the effects of an external stress were analysed at different levels: plasma ho meostasis, Endolymph chemistry, and otolith growth. Stress was applied to rainbow trout (Oncorhynchus mykiss) by exposure to Cl2 gas. In the plasma of Cl2-stressed trout, Na+ and Cl– decreased (70 mmol·L–1) and K+ increased (2.0 mmol·L–1), whereas total Ca was unchanged. A slight hypercapny (+2.4 mmHg (1 mmHg = 133.322 Pa)) was observed related to a significant rise (40%) in total CO2 without pH variation. In the Endolymph, Na+ and Cl– also decreased, whereas other parameters (K+, PO43–, Mg, and, peculiarly, total Ca) remained stable. The important effect provoked by Cl2 stress in Endolymph was an increase of proteins (factor of 2.6) and total CO2 (factor of 3.1) concentrations at the proximal side of the Endolymph. The stress induced a decrease in otolith growth rate and produced a discontinuity (check) in the microstructure pattern of the otolith characterized by a large D zone. The variations...

  • daily variations of Endolymph composition relationship with the otolith calcification process in trout
    The Journal of Experimental Biology, 2003
    Co-Authors: Gil Borelli, H. De Pontual, Fabrice Priouzeau, N Mayergostan, Marielle Guibbolini, Denis Allemand, Sandrine Puverel, Eric Tambutte, Patrick Payan
    Abstract:

    Ionic and organic parameters of the otolith calcification process in the trout Oncorhynchus mykiss were analysed in plasma and Endolymph over the day:night cycle. Plasma pH remained constant and total CO2 concentration was significantly lower (by 21%) during the day than at night. Calcifying parameters (total CO2, total calcium concentration) were measured in the proximal and distal Endolymphs and were unchanged in the latter during the day:night cycle, but fluctuated in the former. Non-collagenous protein and collagen concentrations in Endolymph were higher (1.5- and 10-fold, respectively) during the day than at night. As there was no change in total calcium concentration, we propose that Ca2+ increases during the dark period and was maximal by the end of the night when the total CO2 concentration has also increased (by 14%). Measurements of Endolymph pH in situ revealed significant differences between samples from proximal and distal Endolymph (7.38 and 7.87, respectively), but no variation between values obtained during the day and at night. Thus, the saturation state of aragonite (Sa) in the proximal Endolymph should fluctuate around unity during the day:night cycle, and CaCO3 precipitation should occur when supersaturation is reached. The electrophoretic pattern of proximal Endolymph showed variations in both major and minor components. Immunoblotting of Endolymph, using a rabbit antiserum raised against the otolith soluble organic matrix revealed an increase in the expression of two proteins (65 kDa and 75 kDa) during the day period. We propose that organic matrix and calcium carbonate deposition on the otolith vary antiphasically: organic matrix deposition begins by the end of the day period, when the concentration of organic precursors is maximal in the Endolymph, whereas CaCO3 precipitation starts once the solubility of CaCO3 is exceeded.

  • otolith growth in trout oncorhynchus mykiss supply of ca2 and sr2 to the saccular Endolymph
    The Journal of Experimental Biology, 2002
    Co-Authors: Patrick Payan, H. De Pontual, Gil Borelli, Fabrice Priouzeau, G Bœuf, N Mayergostan
    Abstract:

    SUMMARY Kinetic and pharmacological characteristics of Ca 2+ fluxes across the saccular epithelium of trout were studied using a perfused isolated inner ear. 45 Ca 2+ influx from the Ringer solution to the Endolymph was 3-4 nmoles h -1 μl -1 Endolymph, which corresponds to a global turnover rate of the Endolymph calcium of 200 % h -1 . Ca 2+ entry into the proximal Endolymph was faster than into the distal fluid. Net Ca 2+ movement across the saccular epithelium depended on the direction and intensity of the chemical gradient of calcium between the Ringer solution and the Endolymph. Increasing the calcium concentration in the Ringer solution up to 4.4 mmol l -1 provoked an accumulation of Ca 2+ in both proximal and distal Endolymphs, and equilibrium was reached about 30 min after the beginning of perfusion. Perfusion with calcium-free Ringer partially emptied the proximal compartment of calcium, whereas the calcium levels in the distal Endolymph did not vary during 70 min of perfusion. Verapamil (10 -5 mol l -1 ) and cyanide (CN, 10 -3 mol l -1 ) did not modify the accumulation of Ca 2+ within the Endolymph in the presence of a favourable calcium chemical gradient. Furthermore the relationship between Ca 2+ net fluxes and the chemical calcium gradient across the saccular epithelium was linear, indicating a passive diffusional mechanism via a paracellular pathway. Similar relationships were found for Sr 2+ fluxes across the saccular epithelium in the presence of positive chemical gradients (1, 2 and 4 mmol l -1 Sr 2+ ). In vivo experiments in which trout were intraperitoneously injected with CaCl 2 solution confirmed the tight relationship between the calcium levels in plasma and Endolymph (both proximal and distal). Sampling proximal and distal Endolymphs in trout and turbot saccules revealed a decreasing proximo—distal calcium gradient in Endolymph of both fish species. The present results strongly suggest that the Endolymph is supplied with Ca 2+ and Sr 2+ via a paracellular pathway located in the proximal area of the saccular epithelium.

  • biochemical relationships between Endolymph and otolith matrix in the trout oncorhynchus mykiss and turbot psetta maxima
    Calcified Tissue International, 2001
    Co-Authors: Gil Borelli, H. De Pontual, N Mayergostan, Gilles Boeuf, Patrick Payan
    Abstract:

    This paper compares the organic compositions of the otolith and Endolymph of trout and turbot. Irrespective of the method of demineralization (0.5 M EDTA or acetic acid), trout otoliths were found to be largely composed of proteins (48%), collagens (23%), and proteoglycans (29%). Collagen was only detectable in the EDTA-insoluble (0.30 microg/mg) and in the acetic acid-soluble fractions (0.53 microg/mg). The same compounds were found in the Endolymph but in different proportions (proteins 85%, collagens 12%, and proteoglycans 3%). It was shown that the distribution of these compounds was not uniform within the Endolymph. Proteins, collagens, and amino acids were 4, 10, and 3 times, respectively, more concentrated in the proximal (facing the macula) than the distal side whereas proteoglycans were 10 times more concentrated at the distal side. SDS PAGE analyses of proximal and distal samples of Endolymph showed similar patterns suggesting that the spatial gradient of protein is quantitative and not qualitative. SDS PAGE comparison of Endolymph and otolith samples showed only two proteins with similar molecular weights. We propose that collagen and protein gradients are involved in the organic matrix formation and otolith calcification process. Endolymphs from both trout and turbot display inhibitions of in vitro calcification although these inhibitions were 50 and 80 times, respectively, less than that of the otoliths. The inhibitory factor probably plays a significant role in the regulation of otolith calcification.