Maduración postnatal del receptor acústico de la rata

Fac. de MedicinaTRUEProQuestpu

Maduración postnatal del receptor acústico de la rata

Fac. de MedicinaTRUEProQuestpu

Ultrastructural morphology and protein content of the internal organic material of rat otoconia

Otoconia taken from the maculae of the saccule and utricle of the rat inner ear were investigated using transmission electron microscopy (TEM). Their ultrastructure was compared using various decalcification techniques. Similar preparations were analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to assess their protein constituents. TEM results show loss of organic material during prolonged decalcification. This is not seen in samples decalcified overnight. The SDS-PAGE results show that rat otoconia contain a major broad band of 90-100 kDa, a major thin band of 56 kDa, and three other bands of 33, 45, and 50 kDa. The band of 56 kDa may be associated with the surface of the otoconia.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26205/1/0000285.pd

Role for a Novel Usher Protein Complex in Hair Cell Synaptic Maturation

The molecular mechanisms underlying hair cell synaptic maturation are not well understood. Cadherin-23 (CDH23), protocadherin-15 (PCDH15) and the very large G-protein coupled receptor 1 (VLGR1) have been implicated in the development of cochlear hair cell stereocilia, while clarin-1 has been suggested to also play a role in synaptogenesis. Mutations in CDH23, PCDH15, VLGR1 and clarin-1 cause Usher syndrome, characterized by congenital deafness, vestibular dysfunction and retinitis pigmentosa. Here we show developmental expression of these Usher proteins in afferent spiral ganglion neurons and hair cell synapses. We identify a novel synaptic Usher complex comprised of clarin-1 and specific isoforms of CDH23, PCDH15 and VLGR1. To establish the in vivo relevance of this complex, we performed morphological and quantitative analysis of the neuronal fibers and their synapses in the Clrn1−/− mouse, which was generated by incomplete deletion of the gene. These mice showed a delay in neuronal/synaptic maturation by both immunostaining and electron microscopy. Analysis of the ribbon synapses in Ames waltzerav3J mice also suggests a delay in hair cell synaptogenesis. Collectively, these results show that, in addition to the well documented role for Usher proteins in stereocilia development, Usher protein complexes comprised of specific protein isoforms likely function in synaptic maturation as well

Maturation des elements sensorinerveux de la cochlee

SIGLEINIST T 77334 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Synaptophysin immunoreactivity in the cat cochlear nuclei

The presence of synaptophysin, a presynaptic ca2+ binding glycoprotein, has been analyzed in the cochlear nucleus complex of the adult cat using an antisynaptophysin monoclonal antibody. Synaptophysin immunoreactivity was differently distributed between regions of cochlear nuclei. Terminal boutons contacting directly with neurons (cell bodies and dendrites) or in the neuropil of ventral and dorsal cochlear nuclei appeared immunostained. In the ventral cochlear nucleus, synaptophysin-labelled boutons were clearly defined in contact with spherical, globular, multipolar, octopus and cochlear-nerve root neurons. However, the dorsal cochlear nucleus showed a dense immunostained network of synaptophysin-labelled puncta, inside which some neuron cell bodies were observed. The present findings show a differential distribution of synaptophysin- immunostained boutons between the ventral and the dorsal cochlear nuclei of the cat. The present description of the different synaptophysin-labelled terminal boutons in the cochlear nuclei complex and their pattern of distribution, will be useful for further studies on development, degeneration or regeneration of the peripheral auditory pathway

Synaptophysin immunoreactivity in the cat cochlear nuclei

The presence of synaptophysin, a presynaptic ca2+ binding glycoprotein, has been analyzed in the cochlear nucleus complex of the adult cat using an antisynaptophysin monoclonal antibody. Synaptophysin immunoreactivity was differently distributed between regions of cochlear nuclei. Terminal boutons contacting directly with neurons (cell bodies and dendrites) or in the neuropil of ventral and dorsal cochlear nuclei appeared immunostained. In the ventral cochlear nucleus, synaptophysin-labelled boutons were clearly defined in contact with spherical, globular, multipolar, octopus and cochlear-nerve root neurons. However, the dorsal cochlear nucleus showed a dense immunostained network of synaptophysin-labelled puncta, inside which some neuron cell bodies were observed. The present findings show a differential distribution of synaptophysin- immunostained boutons between the ventral and the dorsal cochlear nuclei of the cat. The present description of the different synaptophysin-labelled terminal boutons in the cochlear nuclei complex and their pattern of distribution, will be useful for further studies on development, degeneration or regeneration of the peripheral auditory pathway

Transitional expression of OX-2 and GAP-43 glycoproteins in developing rat cochlear nerve fibers

The OX-2 and GAP-43 glycoproteins are two proteins involved in neuronal cell-to-cell interaction and/or growing of dendrites and axons. Therefore, for the auditory receptor the expression of these proteins could provide information on the afferent and eff e r e n t nerve fiber organization. The expression and distribution of OX-2 and GAP-43 were analyzed during the auditory receptor development and maturation (from embryonic day E13 to postnatal day P22). Both glycoproteins were early recognized in the cochleae of E13 rats. Then, they slowly but progressively disappeared, being absent when the animals reached the P22 postnatal day. At E13, a weak OX-2 expression was restricted to the perikaryon of the spiral ganglion neurons, while in the same period a strong GAP-43 immunostaining was found in both the neuronal perikaryon and the neurites. During the rat embryonic period (E13 to birth) the expression of both glycoproteins appeared progressively restricted to the neurites. During the rat postnatal period (P0 to P22), OX-2 and GAP-43 exhibited a dissimilar distribution pattern. The OX-2 glycoprotein appeared in the afferent, efferent and fibers of the auditory nerve, while the GAP- 43 glycoprotein only appeared in the efferent nerve fibers. Present data suggest that OX-2 and GAP-43 could act as two complementary glycoproteins during the development, organization, and maturation of the cochlear nerve fibers. While both glycoproteins could participate in axonal growing and orientation, OX-2 could also be involved in a similar process for auditory dendrites