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C J Dechesne

Publications and source records attributed to C J Dechesne.

At least 19 recordsLinked to original sources
PubMed2001

Development of the rat efferent vestibular system on the ground and in microgravity.

We investigated whether plastic changes occurred in the organization of the vestibular efferent network in the rat utricle during a 17-day episode of microgravity, from postnatal (PN) day 8 to PN23, and on return to earth on PN25. We also determined the normal pattern of efferent development from birth to PN25. Immunofluorescence experiments were performed with a specific biochemical marker of the efferent system, the calcitonin gene-related peptide (CGRP), and vibratome sections of the utricles were analyzed by laser scanning confocal microscopy. At birth, a few efferent fibers were detected beneath the sensory epithelium. These then massively invaded the epithelium between PN2 and PN4. At the time of launch, PN8, most fiber paths in the utricular epithelium, after following transient courses (towards the epithelial surface for example) returned to the base and were stabilized in the lower part of the epithelium, in which they established synaptic contacts with sensory cells, except at a few immature locations. The main difference between this stage (on PN8) and subsequent more mature stages was the lower density of fibers and synapses in the utricle. The maturation of the vestibular efferent system was similar in microgravity and on the ground. Thus, maturation of the efferent system between PN8 and PN23 was not sensitive to a change in gravitational environment. These results suggest that periods of microgravity at earlier stages are required to identify critical periods in peripheral vestibular system development.

Animals↗
PubMed2001

Contribution of the plasmalemma to Ca2+ homeostasis in hair cells.

Calcium influx through transduction channels and efflux via plasmalemmal Ca(2+)-ATPases (PMCAs) are known to contribute to calcium homeostasis and modulate sensory transduction in vertebrate hair cells. To examine the relative contributions of apical and basolateral pathways, we analyzed the calcium dynamics in solitary ciliated and deciliated guinea pig type I and type II vestibular hair cells. Whole-cell patch-clamp recordings demonstrated that these cells had resting potentials near -70 mV and could be depolarized by 10-20 mV by superfusion with high potassium. Fura-2 measurements indicated that ciliated type II cells and deciliated cells of either type had low basal [Ca(2+)](i), near approximately 90 nm, and superfusion with high potassium led to transient calcium increases that were diminished in the presence of Ca(2+) channel blockers. In contrast, measurements of type I ciliated cells, hair cells with large calyceal afferents, were associated with a higher basal [Ca(2+)](i) of approximately 170 nm. High-potassium superfusion of these cells induced a paradoxical decrease in [Ca(2+)](i) that was augmented in the presence of Ca(2+) channel blockers. Optical localization of dihydropyridine binding to the kinocilium suggests that they contain L-type calcium channels, and as a result apical calcium influx includes a contribution from voltage-dependent ion channels in addition to entry via transduction channels localized to the stereocilia. Eosin block of PMCA significantly altered both [Ca(2+)](i) baseline and transient responses only in ciliated cells suggesting that, in agreement with immunohistochemical studies, PMCA is primarily localized to the bundles.

Animals↗
PubMed2000

Distribution of frequenin in the mouse inner ear during development, comparison with other calcium-binding proteins and synaptophysin.

Frequenin is a calcium-binding protein previously implicated in the regulation of neurotransmission. We report its immunocytochemical detection in the mouse inner ear, in the adult, and during embryonic (E) and postnatal (P) development. The distribution of frequenin was compared with those of other calcium-binding proteins (calbindin, calretinin, parvalbumin) and synaptophysin. In the adult mouse inner ear, frequenin immunostaining was observed in the afferent neuronal systems (vestibular and cochlear neurons, their processes and endings) and in the vestibular and cochlear efferent nerve terminals. Frequenin colocalized with synaptophysin in well characterized presynaptic compartments, such as the vestibular and cochlear efferent endings, and in putative presynaptic compartments, such as the apical part of the vestibular calyces. Frequenin was not found in vestibular hair cells and in cochlear inner and outer hair cells. During development, frequenin immunoreactivity was first detected on E11 in the neurons of the statoacoustic ganglion. On E14, frequenin was detected in the afferent neurites innervating the vestibular sensory epithelium, along with synaptophysin. On E16, frequenin was detected in the afferent neurites below the inner hair cells in the organ of Corti. The timing of frequenin detection in vestibular and cochlear afferent neurites was consistent with their sequences of maturation, and was earlier than synaptogenesis. Thus in the inner ear, frequenin is a very early marker of differentiated and growing neurons and is present in presynaptic and postsynaptic compartments.

Aging↗
PubMed2000

Developmental study of rat vestibular neuronal circuits during a spaceflight of 17 days.

The aim of this study was to investigate the potential plasticity of the vestibular system, in structural and biochemical terms, at the level of the gravity receptors (the sensory hair cells), the primary neurons relaying the sensory signals (the vestibular ganglion neurons) and their projections into the vestibular nuclei. We studied the biochemical differentiation of the sensory cells and of the vestibular ganglion by investigating which calcium-binding proteins were present. We studied the development of peripheral synaptic connections of the efferent system by investigating the distribution of CGRP (calcitonin-gene related-peptide) and we also studied the cerebellar synaptic connections in the vestibular nuclei, as identified by the presence of calbindin. Putative changes were studied after a 17-day episode of microgravity (Neurolab STS-90), in developing rats between postnatal days 8 and 25. The extent to which these changes could be caused by alterations in gravity was determined by examining sensory and nervous structures not involved in gravity detection, the cochlea and the cochlear nuclei.

Acoustic Maculae↗
PubMed1997

Rab3A immunolocalization in the mammalian vestibular end-organs during development and comparison with synaptophysin expression.

Rab proteins are essential for membrane vesicle docking and fusion and for transport vesicle formation at the presynaptic membrane, a step in the release of neurotransmitters. The vestibular sensory epithelia contain three types of synapses: afferent terminals, efferent endings and possible synaptic contacts between the apex of the afferent nerve calyces and the sensory cells. We report an immunocytochemical codetection of rab3A and synaptophysin in the vestibular end-organs of mouse, between fetal day 14 and adult, and of rat during the postnatal development. During mouse fetal development, rab3A appeared in afferent neurites on F16, and in sensory cells on F19. This was respectively two and five days later than the appearance of synaptophysin-IR in the same compartments. During the late postnatal development and in the adult sensory epithelia, rab3A and synaptophysin were strongly detected in nerve terminals of efferent and possibly afferent nature and in the upper part of the nerve calyces. The presence of rab3A in the nerve calyces is consistent with the putative secretory function of the calyx. In addition, rab3A immunostaining was also present in the sensory cells together with a faint synaptophysin-IR, that had not been described in previous reports [Scarfone, E., Demêmes, D. and Sans, A. J. Neurosci., 11 (1991) 1173-1181.]. The presence of these two proteins in the sensory cells supports the existence of a synaptic vesicle cycle in these cells.

Animals↗
PubMed1995

Cellular and subcellular localization of AMPA-selective glutamate receptors in the mammalian peripheral vestibular system.

The cellular and subcellular distribution of AMPA-selective glutamate receptors in the mammalian peripheral vestibular system was examined using antibodies against peptides corresponding to the C-terminal portions of AMPA receptor subunits: GluR1, GluR2/R3 and GluR4. The light and electron microscopic immunocytochemical studies were carried out on Vibratome sections of rat and guinea pig vestibular sensory epithelial and ganglia. In the epithelium, GluR1 subunit immunoreactivity appeared as accumulations of patches outlining the baso-lateral periphery of the type I sensory cells. The GluR1-immunoreactive microareas were postsynaptically distributed on the membranes of calyceal afferent fibers. GluR2/R3 immunoreactivity was present in the sensory cells. GluR4 was not detected. In the vestibular ganglion, the neurons were densely stained with antibodies to GluR2/R3 and GluR4. The fibroblasts and the Schwann cells were also intensely stained with antibodies to GluR2/R3 and GluR4. In the sensory cells, the AMPA receptors, GluR2/R3, may function as (1) autoreceptors controlling afferent neurotransmitter release or (2) 'postsynaptic' receptors activated by the neurotransmitter release of the afferent calyx. The detection of GluR1 at postsynaptic sites in the afferent fibers provides anatomical evidence for the role of glutamate as a neurotransmitter of sensory cells. In the ganglion neurons, GluR2/R3 and GluR4 may represent reserve intracytoplasmic pools of receptor subunits in transit to the postsynaptic sites. In the Schwann cells, GluR2/R3 and GluR4 may be involved in neuronal-glial signalling at the nodes of Ranvier.

Animals↗
PubMed1994

Development of calretinin immunoreactivity in the mouse inner ear.

Calretinin is a calcium-binding protein of the EF-hand family. It has been previously identified in particular cell types of adult guinea pig, rat, and chinchilla inner ear. Development of calretinin immunoreactivity in the mouse inner ear was investigated from embryonic day 13 (E13) to the adult stage. In the adult mouse vestibule, calretinin immunoreactivity was present in the same structures as described for the rat and guinea pig: the population of afferent fibers forming calyx units and a small number of ganglion neurons. The earliest immunoreactivity was found at E17 in vestibular hair cells (VHCs), then, at E19, in afferent fibers entering the sensory epithelia and in rare ganglion neurons. At postnatal day 4 (P4), a few vestibular nerve fibers and ganglion neurons were reactive. From this stage until P14, immunoreactivity developed in the calyx units and disappeared from VHCs. At P14, immunostaining was adult-like. In the adult mouse cochlea, immunoreactivity was present in the same cell populations as described in the rat: the inner hair cells (IHCs) and most of Corti's ganglion neurons. Calretinin immunoreactivity appeared at E19-P0 in IHCs and ganglion neurons of the basal turn. At P1, outer hair cells (OHCs) of the basal turn were positive. Calretinin immunoreactivity then appeared in IHCs, OHCs, and ganglion neurons of the medial turn, then of the apical turn. At P4, all IHCs and OHCs and most of the ganglion neurons were immunostained. Immunoreactivity gradually disappeared from the OHCs starting at P10 and, at P22, only IHCs and ganglion neurons were positive. The sequences of appearance of calretinin were specific to each cell type of the inner ear and paralleled their respective maturation. Calretinin was transiently expressed in VHCs and OHCs.

Animals↗
PubMed1994

Characterization of different neuron populations in mouse statoacoustic ganglion cultures.

Statoacoustic ganglion (SAG) cells were grown in primary culture and the appearance of different neuronal phenotypes was investigated. Analysis criteria were shape, size and staining for the immunocytochemical markers: neurofilament proteins (NF-200 kDa), neuron-specific enolase (NSE), calretinin, a calcium-binding protein and substance P, a neurotransmitter. Cultures were prepared from dissociated SAG cells of 13 gestation-day-old mouse embryos. Neurons were identified and counted after 7 days in vitro. At this stage, neurons were organized in small clusters forming an extensive network of neurites grown on a layer of fibroblasts and glia. Most neurons identified by NF or NSE immunoreactivity showed a typical adult-like bipolar profile. The diameters of the neurons were between 5.62 and 17.00 microns and displayed a normal distribution (mean: 10.6 microns). Two distinct subpopulations were identified by the expression of calretinin and substance P. Calretinin-immunoreactive neurons were large and very rare and had a mean diameter of 11.3 microns; the distribution of substance P was more extensive than that of calretinin and identified a population of small neurons with a mean diameter of 8.9 microns. The distributions of these two markers in SAG cultures were consistent with in vivo results. In conclusion, dissociated SAG cell cultures appear to be a suitable model for analyzing the development of the immunocytochemical and functional characteristics of the neurons of this inner ear ganglion.

Animals↗
PubMed1994

Neurofilament proteins form an annular superstructure in guinea-pig type I vestibular hair cells.

Neurofilaments, the neuron-specific intermediate filaments, are composed of three immunochemically distinct subunits: NF-L, NF-M and NF-H that can be either phosphorylated or unphosphorylated. In mammals, the distribution of these subunits has been described in vestibular ganglion neurons, but there are no reports on the presence of neurofilaments in vestibular hair cells. We investigated, by immunocytochemistry, neurofilaments in vestibular hair cells from rat and guinea-pig using antibodies against the three subunits and to dephosphorylated NF-H (clone SMI 32, recognizes also NF-M on immunoblots), on Vibratome sections of the vestibular end-organs and on isolated hair cells. Various immunostaining protocols were used, as appropriate for the method of observation: laser scanning confocal microscopy (immunofluorescence) and transmission electron microscopy (immunoperoxidase, pre-embedding technique). In rat and guinea-pig cristae and utricles, neurofilament immunoreactivity was observed in axons inside and below the sensory epithelia. In guinea-pig, in addition to this staining, intensely immunoreactive annular structures were found in the basal regions of hair cells. These rings were detected with anti-NF-L, -NF-M and -dephosphorylated NF-H/M antibodies, but not with anti-phosphorylation-independent NF-H. Ring-containing hair cells were present in all regions of the sensory epithelia but were more abundant in the peripheral areas. All levels of observation (Vibratome and thin sections, and isolated hair cells) showed that only the guinea-pig type I hair cells contained a neurofilament ring. High-resolution observations showed that the ring was located below the nucleus, often close to smooth endoplasmic reticulum and the cell membrane.

Animals↗
PubMed1993

Localization of calretinin mRNA in rat and guinea pig inner ear by in situ hybridization using radioactive and non-radioactive probes.

The localization of calretinin mRNA was studied in the rat and guinea pig inner ear by in situ hybridization, and compared to the distribution of the protein previously examined by immunocytochemistry. Radioactive and non-radioactive in situ hybridization (ISH) were performed using oligonucleotide probes labelled with 35S or digoxigenin. Radioactive ISH was more sensitive than non-radioactive ISH. In cochlear and vestibular ganglia, calretinin mRNA was localized in subpopulations of neurons with patterns of distribution similar to those shown by immunocytochemistry. By contrast, the observations in the sensory epithelia differed with the two techniques, ISH revealing less positive structures than immunocytochemistry. Rat inner hair cells and guinea pig inner hair cells, Hensen's cells and Deiters cells, which had been described strongly immunoreactive, appeared positive with radioactive but not with non-radioactive ISH. On the other hand, rat vestibular type II hair cells and guinea pig interdental cells of the spiral limbus which were faintly immunoreactive were not positive with both ISH techniques.

Animals↗
PubMed1993

Different calcium-binding proteins identify subpopulations of vestibular ganglion neurons in the rat.

Vestibular neurons were studied by cytochrome oxidase (CO) histochemistry and by immunocytochemistry using antibodies against parvalbumin (PV), calbindin (CaBP), calretinin (CaR) and 160 KD neurofilament protein (NF). All the neurons present a high level of CO activity and a high content of PV. CaBP and CaR are restricted to a specific population of about 16% of the neurons and are among the largest ones. The latter neurons also have a high density of NF 160 KD protein. In conclusion the biochemical characteristics of the vestibular ganglion neurons are discussed in relation to their morphological and physiological properties.

Animals↗
PubMed1992

Identification of neuron subpopulations in the rat vestibular ganglion by calbindin-D 28K, calretinin and neurofilament proteins immunoreactivity.

Immunocytochemical and morphometric analyses were combined to demonstrate the presence of neuron subpopulations in the rat vestibular ganglion. Monoclonal antibodies reacting with neurofilament proteins (NF), calbindin-D 28K (CaBP) and calretinin (CaR) were used. Three subpopulations were identified: (1) CaBP- and CaR-positive neurons were the largest neurons (16%) and they were also highly NF-immunoreactive; (2) exclusively NF-positive neurons; (3) unlabelled neurons, representing about two-thirds of the population.

Animals↗
PubMed1992

Calretinin immunoreactivity in chinchilla and guinea pig vestibular end organs characterizes the calyx unit subpopulation.

Immunohistochemical investigations with calretinin, a neuronal calcium binding protein, were made in the vestibular end organs of five guinea pigs and one chinchilla. A specific pattern of immunoreactivity of afferent nerve fibers was found. Immunostaining was restricted to thick fibers innervating the apex of the cristae or the striola of the utricular macula. A study of serial sections revealed that the stained afferents gave rise to calyx endings, but not to collaterals containing bouton endings. The results are consistent with the conclusion that, of the three classes of fibers defined by Fernández et al. (1988, 1990), only calyx units are calretinin immunoreactive. A count of the number of labelled fibers in the chinchilla crista suggests that the entire population of calyx units is immunoreactive. The conclusion is surprising since the physiology of calyx units does not differ qualitatively from that of other afferents (Baird et al. 1988; Goldberg et al. 1990). The presence of this protein in the calyx neurons may be related to specific post-synaptic functions of this type of afferents.

Animals↗
PubMed1992

Expression of heat shock protein, HSP72, in the guinea pig and rat cochlea after hyperthermia: immunochemical and in situ hybridization analysis.

The induction of the heat shock protein, HSP72, was studied in the cochlea of guinea pigs and rats subjected to a hyperthermic stress. Analyses were done by immunoblotting and immunocytochemistry at 6 and 12 h after heat shock, using a commercially available monoclonal antibody (Amersham), and by in situ hybridization 1 h after heat shock using an oligonucleotide probe. In guinea pig immunoblots of the cochlea, HSP72 was present in both unstressed and heat stressed animals and immunocytochemistry did not reveal any difference of staining between them. As opposed to guinea pig, HSP72 was not found in unstressed rat cochlea. Heat shock induced HSP72 expression in most inner ear tissues of the rat examined by immunoblotting. Immunocytochemistry and in situ hybridization localized HSP72 synthesis in ganglion neurons, Schwann cells, spiral limbus, spiral ligament and stria vascularis. The strongest immunoreactivity and highest density of silver grains were seen in the stria vascularis. All blood vessels were strongly immunoreactive and were outlined with silver grains. These results show that HSP72 synthesis can be induced by hyperthermia in rat cochlea and suggest that this protein could be a useful marker for assessment of the effects of specific stresses in this organ.

Animals↗
PubMed1991

Identification and ultrastructural localization of a calretinin-like calcium-binding protein (protein 10) in the guinea pig and rat inner ear.

Calretinin has been identified as a brain specific calcium-binding protein which appears as a prominent protein in the cochlear nucleus. We identified and localized calretinin in the guinea pig and rat inner ear using polyclonal antibodies. Immunoblot analyses of guinea pig and rat auditory nerve homogenates revealed an immunoreactive band migrating with the same molecular weight as the purified protein, at Mr = 29 k. Immunocytochemistry was carried out at the light and electron microscope levels. In the guinea pig cochlea, inner hair cells, Deiters' cells, Hensen's cells and interdental cells of the spiral limbus were stained. Most of the cochlear ganglion cells were immunostained. In the guinea pig vestibular organs, the staining was exclusively neuronal and localized in large nerve fibers and nerve calices of the apex of the cristae. Only some vestibular ganglion cells were stained. In the rat cochlea, inner hair cells and most of the ganglion neurons were immunoreactive. In the rat vestibule, large nerve fibers and calices were stained as were some type II hairs cells. Only some vestibular ganglion cells were reactive. Electron microscopic observations of immunostained guinea pig cochlea and vestibule showed that the staining was cytosolic. In addition, specific sub-localization was also found in the apical portion of the nerve calices in association with microvesicles. These results describe the discrete localization of calretinin in the cochlea and in the vestibular receptors and suggest a function associated with biochemical regulations at the level of microvesicles in vestibular afferent neurons.

Animals↗
PubMed1991

Identification and localization of a kainate binding protein in the frog inner ear by electron microscopy immunocytochemistry.

A kainate binding protein (KBP) was studied in Rana pipiens inner ear using monoclonal and polyclonal antibodies against affinity purified KBP from frog brain. The KBP identified and analyzed in inner ear tissue homogenates, with one- and two-dimensional immunoblots, was similar to the affinity purified KBP and to the antibody-identified frog brain KBP. As brain KBP, inner ear KBP had 5 main components in the molecular weight dimension, centered at Mr = 48,000; however, inner ear KBP had a greater abundance of the higher molecular weight components. Light and electron microscopy observations showed KBP immunostaining at two locations: (1) in the dendrites of the eight nerve afferent fibers contacting sensory hair cells, with the postsynaptic density being more intensely stained; and (2) on the cytoplasmic membrane of fibroblasts present in the inner ear connective tissue which displayed intense immunostaining. The presence of kainate (KA) binding sites in the inner ear was assessed using in vitro receptor autoradiography. [3H]KA binding sites were found in connective tissue areas confirming the immunocytochemistry results. The postsynaptic localization of the KBP in afferent endings, strongly supports it as being a component of the KA receptor complex. However, its presence on fibroblasts situated in the inner ear connective tissue makes its function hypothetical. The dual presence of the KBP on non-neuronal cells as well as at postsynaptic membrane sites suggests the existence of a family of proteins involved in KA binding and KA receptors with a complex organization.

Afferent Pathways↗
PubMed1990

Antibodies to a C-terminal peptide of the rat brain glutamate receptor subunit, GluR-A, recognize a subpopulation of AMPA binding sites but not kainate sites.

Antibodies were made to a thirteen amino acid synthetic peptide corresponding to the C-terminal portion of the glutamate (glu) receptor, GluR-A. The immunoprecipitation of kainic acid (KA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) binding sites by the anti-peptide antibodies was studied using a detergent-solubilized preparation of rat brain membranes. Under these conditions a subpopulation of AMPA binding sites was recognized by the antibodies, but no KA binding sites were recognized. Scatchard analysis of this subpopulation of AMPA binding sites yields a curvilinear plot which fits a two-site model with dissociation constants of 4.6 and 323 nM. These studies show that the glu receptor complex, GluR-A, binds AMPA but not KA and suggest that (i) the binding sites for these two ligands reside on different proteins, and (ii) the KA receptor identified physiologically is not equivalent to the KA binding sites identified with 3H-labelled KA.

Amino Acid Sequence↗