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Biomedical subjects

M Lavigne-Rebillard

Publications and source records attributed to M Lavigne-Rebillard.

17 recordsLinked to original sources
PubMed1997

Identification of preferentially expressed cochlear genes by systematic sequencing of a rat cochlea cDNA library.

107 expressed sequence tags (ESTs) from a rat cochlea cDNA library were identified by systematic sequencing coupled to database selection and RT-PCR analysis of novel sequences. This approach led us to select a clone, pCO8, showing no significant homology with any database sequence, that corresponds to a mRNA whose expression is restricted to the cochlea, except for traces detected in brain. Additional clones with novel sequences enriched in the cochlea were also found. ESTs bearing significant homologies with database sequences (63 out of 107) were classified according to the putatively encoded protein. They include tissue-specific genes not previously described in the cochlea as well as known genes from other species. We performed in situ hybridization in cochlear tissues to localize the pCO8 mRNA and that of clone pCO6 which is 100% homologous to the delayed rectifier potassium channel drk1. We found that both mRNAs were exclusively expressed in the cellular body of the primary auditory neurons from the spiral ganglion of the cochlea. These results indicate that this approach is an efficient way to identify novel genes that could be of importance in cochlear function.

Animals↗
PubMed1995

Molecular cloning and expression of alpha parvalbumin in the guinea pig cochlea.

We have cloned and sequenced an alpha parvalbumin cDNA from the guinea pig cochlea. The deduced amino acid sequence shows greater identity with the rabbit sequence (86.3%) than with other mammalian sequences (< 82%). Using in situ hybridization and immunohistochemistry, alpha parvalbumin mRNA and protein were found in primary auditory neurons and inner hair cells, in agreement with RT-PCR data showing alpha parvalbumin mRNA expression in the spiral ganglion and the organ or Corti.

Amino Acid Sequence↗
PubMed1993

Changes in 2f1-f2 distortion product otoacoustic emissions following alterations of cochlear metabolism.

This paper summarizes the results obtained from investigations in which distortion product otoacoustic emissions (DPOAEs) were studied together with other cochlear physiological parameters. The cochlear metabolism was subjected to three different experimental conditions: guinea pigs were either submitted to hypoxia, to an intra-cochlear perfusion of ouabain or to an intra-cochlear perfusion of naloxone. The data show that DPOAEs remain affected for a certain time after the metabolic perturbations were removed. The comparison of the behaviour of DPOAEs and of other cochlear parameters gives good indications on the way these different experimental procedures affect the functioning of the cochlea during and after their application.

Acoustic Stimulation↗
PubMed1992

Development of the human stria vascularis.

Fifteen human fetal cochleas were investigated by light microscopy and transmission electron microscopy in order to observe the development of the stria vascularis. The earliest signs of strial cell differentiation take place during the 11th week of gestation. Subsequently, the first stages of the stria vascularis development occur quickly. At week 14 the three types of cells, namely, marginal, intermediate and basal cells are discernable. Moreover at this stage, signs of specific activity are already present. The adult-like appearance of the stria vascularis is reached by week 21 but its maturation is completed only during the last trimester of pregnancy. This is in good agreement both with the development of the organ of Corti structures and with the maturation of the human auditory function.

Adult↗
PubMed1992

Effect of reversible hypoxia on the compared time courses of endocochlear potential and 2f1-f2 distortion products.

In order to study the effects of a controlled hypoxia on the cochlear active mechanisms, the 2f1-f2 distortion product (DP) and the endocochlear potential (EP) were recorded simultaneously in the same ear, in guinea pigs artificially respired with gas mixtures containing different percentages of oxygen. The data show an important difference in the behavior of the two parameters. While the EP undergoes a reduction of amplitude starting shortly after the establishment of the hypoxia, reaches a steady state, and recovers monotonically after a return to normoxic conditions, the time course of the DP is more complex. Its level also declines shortly after the beginning of the hypoxia though it slightly lags behind the EP decline. After switching back to normoxic conditions, the DP rises with an eventual delay with respect to the EP, overshoots, and then dramatically falls again. A slow recovery subsequently takes place and normal values are reached within 5 to 10 min. These results indicate a certain independence of the DP versus the EP. During the exposure to hypoxic conditions, differences in the time course and in the variation of amplitude of the two recorded parameters seem to indicate that the DPs could be more related to the OHC physiology than to the EP. The DP post-hypoxia effect observed after a return to normoxic conditions, indicates that a normal EP is not sufficient for the generation of normal DPs. Different hypotheses which could explain the DP post-hypoxia effect are discussed.

Acoustic Stimulation↗
PubMed1992

Development of neurosensory structures in the human cochlea.

The present paper summarizes the main stages in the maturation of the cochlear neurosensory structures in humans. New trends in the field of the functional development of the cochlea, as well as some recent experimental data are also discussed.

Cell Differentiation↗
PubMed1991

Development of the human cochlea.

This paper summarizes the most recent findings dealing with the anatomical development of the human cochlea, and especially with ultrastructural data from both scanning and transmission electron microscopic studies. It also briefly reviews physiological findings and attempts to specify the timing of the main developmental events, i.e. the onset of function, the acquisition of adult properties, and the sensitive periods.

Cochlea↗
PubMed1990

Auditory hair cells in human fetuses: synaptogenesis and ciliogenesis.

This paper brings together the most recent findings concerning the development of human fetus cochlear hair cells, as observed using transmission and scanning electron microscopy (TEM and SEM). Specific attention is drawn to the formation of synapses and the growth of stereocilia. In both types of hair cells, synaptogenesis begins before ciliogenesis (week 10 of gestation versus week 12). In the inner hair cell (IHC), an adultlike stage is seen around week 15 for synapses, but not before week 22 for stereocilia. In the outer hair cell (OHC), both synapses and stereocilia are not yet fully mature at week 22. Classic gradients of maturation are found: a base-to-apex gradient, and an IHC-to-OHC gradient. By comparing these results with the anatomical and functional data on cochlear development in laboratory mammals, the onset of cochlear function in the human fetus can be estimated to occur around week 18. The completion of cochlear maturation based upon the same anatomical criteria should occur about 10 weeks later.

Cilia↗
PubMed1988

Appearance and distribution of neuron-specific enolase and calbindin (CaBP 28 kDa) in the developing human inner ear.

The onset and development of neuron-specific enolase (NSE) and calbindin immunoreactivities were studied in the inner ear of human fetuses aged from 6-7 to 14 weeks of gestation. NSE occurred very early in ganglion neurons. Its appearance in vestibular sensory cells at 8 weeks coincided with the formation of the first afferent synapses, and showed an apex/base gradient in the cristae. Calbindin was found in vestibular ganglion neurons at 6-7 weeks and in the cochlear ganglion neurons at 8-9 weeks. Vestibular sensory cells and the whole ventral wall of the cochlear duct were stained from 8-9 weeks. At 14 weeks, calbindin staining occurred only in the sensory cells of the cochlear neuroepithelium. Non-neuronal secretory structures, i.e. Kölliker's organ and some cells of the transitional zone of the utricle, were also reactive. Staining appeared in Kölliker's organ with a base to apex gradient and disappeared from it with an internal to external gradient. Calbindin appeared in vestibular sensory cells later than NSE staining, synapse formation and sensory hair bundle differentiation. By contrast in the cochlea, calbindin staining appeared in the neuroepithelium before sensory cell differentiation, but remained only in the hair cells after they had differentiated and been contacted by the afferent fibers.

Antibodies↗
PubMed1987

Surface aspects of the developing human organ of Corti.

Thirteen cochleas from human fetuses ranging in age from week 9 to week 22 were observed by scanning electron microscopy. The classical 'base-to-apex' and 'internal-to-external' gradients of maturation were confirmed by surface observations of the developing organ of Corti. The tectorial membrane begins to be secreted around week 9, i.e. 2 weeks before the onset of the ciliogenesis. Its structure appears to be first amorphous and then fibrillar. The surface of the organ of Corti looks mature around week 22, but, in fact, its complete maturation, especially at outer hair cell level, probably occurs during the last trimester of pregnancy.

Cell Differentiation↗
PubMed1986

Development of the auditory hair cell surface in human fetuses. A scanning electron microscopy study.

Thirteen human fetal cochleas were investigated by scanning electron microscopy. Our observations concentrated on the hair cell surface. Ciliogenesis appeared to start during the 11th week of gestation on the inner hair cells (IHCs) and one week later on the outer hair cells (OHCs). The earliest stages of stereociliary development were similar on both types of cell and were characterized by the presence of round bundles of cilia arising from the surrounding microvilli. A three-dimensional V-shaped arrangement suddenly appeared, accompanied by the disappearance of short cilia on the internal side. Between the 20th and the 22nd weeks of gestation, both types of hair cell had an adult stereociliary pattern, i.e. a rectilinear arrangement on IHCs and W-shaped on OHCs. However, there were signs of immaturity, such as a disarray of OHCs and the presence of the kinocilium, suggesting that the surface of the auditory hair cells achieves its maturation during the last trimester of pregnancy.

Cell Membrane↗
PubMed1985

The very distal part of the basilar papilla in the chicken: a morphological approach.

The very distal part of the chicken basilar papilla was investigated by light and electron (scanning and transmission) microscopy. The rostral tip of the basilar papilla has a lenticular area with atypical sensory hair cells which are more similar to vestibular than to auditory cells. The structure of the lenticular area appears to be suitable for vestibular function or, more likely, for auditory perception at very low frequencies. Several hypotheses can be proposed to explain this very peculiar portion of the avian cochlea. It is difficult to consider it a continuously growing area since it remains stable in adulthood. A better explanation would be that there is an incomplete ontogenetic or phylogenetic process.

Animals↗
PubMed1985

Early stages of innervation and sensory cell differentiation in the human fetal organ of Corti.

Early development of the human organ of Corti was investigated at the light and electron microscopic level. In 9-week fetal material the cochlea was completely coiled and nerve fibers penetrated into an undifferentiated Corti's primordium. By week 10 a single cell in radial sections, presumed to be the inner hair cell (IHC), could be found with many nerve fibers surrounding and contacting its base. It is possible to identify outer hair cells by the end of the 11th week while IHC development continues. During the 12th week stereocilia appear on IHCs and synaptic specializations could be found at the junctions between both types of hair cell and afferent dendrites. The first appearance of the efferent fibers beneath IHCs were also observed during week twelve.

Cell Differentiation↗
PubMed1985

[Development of the internal ear during the 1st trimester of pregnancy. Differentiation of the sensory cells and formation of the 1st synapses].

The inner ear of seventeen embryos, aged from 7 to 14 weeks after the fecondation, was investigated by optic and electron (transmission and scanning) microscopy. The timing of the first stages of the auditory and vestibular human receptor development is similar to the timing reported in animal studies, the vestibular epithelium development preceding by 2 to 3 weeks the cochlear development. The nerve fibers enter the sensory epithelia before the hair cell differentiation was histologically observed. At 9 weeks in the vestibular organs and 11 weeks in the cochlea, the hair cells are well differentiated and they exhibit typical synapses with nerve endings. Very early in the embryonic life, the auditory and vestibular receptors start their maturation and establish their connections with the peripheral and central nervous system; this indicates that the third month of pregnancy is a particularly sensitive period as far as the inner ear development is concerned.

Cell Communication↗
PubMedDate not supplied

Hair cell innervation in the fetal human cochlea.

Twelve cochleas from human fetuses ranging in age from 13 to 22 gestational weeks were investigated by transmission electron microscopy in order to follow the development of hair cell innervation. First, we were able to confirm the two general gradients of cochlear maturation, i.e. 'internal-to-external' and 'base-to-apex'. In the 14th week of gestation, the inner hair cell pattern of innervation was almost mature, with well formed afferent synapses and axo-dendritic efferent contacts. At the outer hair cell level, only afferents, probably both spiral and radial ones, were present up to week 16. At week 22, axo-somatic synapses were observed between the medial efferents and the outer hair cells, but they were not yet completely mature. At this stage the myelination had begun within the spiral lamina fibres. These findings confirmed that the different stages of synaptogenesis in the human cochlea are similar to that described in other mammals, and thus the same kind of functional relationships could be proposed.

Cochlea↗