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A Sans

Publications and source records attributed to A Sans.

At least 91 records · Page 5Linked to original sources
PubMed1986

Immunocytochemical detection of vitamin D-dependent calcium-binding protein (CaBP-28K) in vestibular sensory hair cells and vestibular ganglion neurones of the cat.

Vestibular sensory hair cells, afferent fibres and vestibular ganglion neurones of the cat are intensely labelled by a specific antibody to rat kidney vitamin D-dependent calcium-binding protein (CaBP-28K). Type I hair cells are more weakly CaBP immunoreactive than type II hair cells. Ganglion neurones also present a differential staining. The presence of calcium-binding protein in sensory hair cells could be of interest for the understanding of transductional mechanisms.

Animals↗
PubMed1986

Freeze-fracture study of the vestibular hair cell surface during development.

The ciliary arrangement and external surface of the vestibular receptor cell were studied in their immature stages. In the first stages, immature stereocilia are similar to the microvilli of the adjacent supporting cells. Later, when the cilia grow, a geometric arrangement of the stereocilia occurs, while the peripheral microvilli disappear. The size of the hair cell apex increases. The biggest and more bulbous cells correspond to type I hair cells, but in the newborn cat it is difficult to distinguish accurately type II flat hair cells from immature hair cells.

Animals↗
PubMed1986

In vitro electrophysiological study of spontaneous activity in neonatal mouse vestibular ganglion neurons during development.

Spontaneous discharges from vestibular ganglion neurons have been studied in mice between 0 and 10 days in freshly isolated in vitro preparations. The vestibular ganglion neurons were electrophysiologically active at birth with irregular activities. From the 3rd day. the activities could be divided into irregular and regular discharging units based on the coefficient of variation of their interspike intervals. This study provides two criteria for maturation of vestibular activities: a decreasing number of irregular units with age and an increase of the spontaneous discharge frequencies.

Action Potentials↗
PubMed1986

Microtubule organization and synaptogenesis in the vestibular sensory cells.

Microtubule organization in type I hair cells has been investigated during the synaptogenesis of vestibular receptors in mammals. The different steps in the maturation of the synapse between the hair cell and the nerve chalice were: a slight symmetrical membrane densification; the appearance of synaptic bodies alongside microtubules closely associated with densified presynaptic membranes; the disappearance of synaptic bodies and the persistence of microtubules. During this development, microvesicules were never seen to be associated with microtubules.

Animals↗
PubMed1986

Effects of hypothyroidism on postnatal development in the peripheral vestibular system.

The morphogenetic effects of congenital hypothyroidism on the development of rat vestibular receptor cells and ganglia were investigated by transmission electron microscopy. Vestibular ganglia are especially immature and characterized by an absence of a myelin sheath around the perikarya. The type I hair cells have a delayed development in their innervation. The last cells to differentiate and the last synaptic contacts to develop are the most affected. The most remarkable result of hypothyroidism is the persistent immaturity of the synaptic contacts.

Animals↗
PubMed1986

[Demonstration and localization of synapsin I in vestibular receptors in the cat: immunocytochemical study].

The presence and localization of synapsin I, a neuron-specific phosphoprotein, was investigated in the cat vestibular epithelium, using a rabbit antisynapsin I anti-serum. The staining was performed by immunofluorescence or by a peroxidase-antiperoxidase (PAP) technique. A strong immunoreactivity was observed with both methods. This immunoreactivity appeared as spherical patches distributed in the lower part of the epithelium. This distribution pattern is very similar to that of the efferent synaptic endings which form axodendritic synapses with the afferent nerve chalice of type I hair cells, or axosomatic synapses with type II hair cells. Some of the nerve chalices were also labelled; in this case, the immunoreactivity was more evident with PAP staining. These results thus suggest the presence of large amounts of synapsin I in the vestibular efferent nerve endings. These endings are known to be filled with numerous synaptic vesicles. This localization of synapsin I is well correlated with previous work that report a close association between synapsin I and small synaptic vesicles. The presence of synapsin I in sensory endings such as the afferent nerve chalices was unexpected and is under investigation.

Animals↗
PubMed1985

Onset and development of neuron-specific enolase immunoreactivity in the peripheral vestibular system of the mouse.

The development of neuron-specific enolase (NSE) immunoreactivity in mouse sensory and ganglion vestibular cells was studied from gestation day 14 to adulthood. NSE staining appeared sequentially in these structures with a pattern that closely paralled their maturation sequences. The onset of NSE reactivity, at gestation day 15, in ganglion cells was concomitant with the formation of contacts between the afferent fibers and sensory cells, and was observed in hair cells, at gestation day 17, during the period in which the first synaptic structures form. The development of NSE staining in the cristae revealed an apex-base and axial gradients of maturation.

Animals↗
PubMed1985

Pathological changes during the development of the vestibular sensory and ganglion cells of the Bronx waltzer mouse. Scanning and transmission electron microscopy.

Vestibular receptors and ganglia of homozygous Bronx waltzer (bv/bv) mice were investigated by scanning and transmission electron microscopy at various stages between 3 days and 90 days after birth. Scanning electron microscopy revealed that there was already a considerable lack of hair bundles in the maculae utriculi, as well as in the cristae ampullares by the 3rd day after birth. During development, the growth of the remaining hair bundles was observed but the most of them exhibited morphological abnormalities. Transmission electron microscopy revealed early degeneration of sensory cells followed by delayed maturation of the remaining sensory cells. The sensory cells which seem unaffected displayed immature features in adult animals. In type I hair cells, the calyces were incomplete, contacts between the cell and the afferent calyces were immature and synaptic bodies persisted. In some type II hair cells, there was an abnormal overabundance of afferent nerve endings, which implies that these type II cells could be immature type I cells. Immature features were also observed in the vestibular ganglia, particularly the absence of the myelin sheath around the perikarya. We discuss the relationship between these vestibular morphogenetic abnormalities and those described in the cochlear system.

Animals↗
PubMed1985

Early development of vestibular receptors in human embryos. An electron microscopic study.

The development of the vestibular receptors in 7 to 9-week-old human embryos was investigated by light, scanning and transmission electron microscopy. The greater part of the vestibular epithelium is undifferentiated in the 7-week-old embryo. It is composed of polystratified epithelial cells. Some afferent endings are found at the base of the epithelial cells but no synaptic specializations are detected. A few afferent endings reach the upper part of the epithelium. Thus, at this stage the fibers are present in the vestibular epithelium before the differentiation of the sensory cells. The apical pole of the epithelial cells presents basal bodies linked with striated rootlets and other typical vestibular epithelium cell structures. Short hair bundles are found in a very small part of the vestibular epithelium. At 8-9 weeks of gestation, numerous nerve endings surround the base of the sensory cells. Densifications of the pre- and postsynaptic membranes and synaptic bodies are seen. The newly afferented cells present polarized hair bundles. We suspect that the hair cells are important for the guidance of afferent terminals perhaps even before their morphological differentiation.

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↗
PubMed1984

New ultrastructural features in the vestibular labyrinth of the toadfish, Opsanus tau.

Electron microscopy of the toadfish vestibular labyrinth demonstrated the usual cytoarchitectural efferent-hair cell organization with type II hair cells having efferent synaptic terminals directly onto the hair cell bodies. Additional, unexpected findings were: direct efferent-afferent synapses; and two types of synaptic vesicles either found both in the same efferent terminals or in two separate classes of efferent terminals.

Afferent Pathways↗
PubMed1984

Evidence for an organized lattice in the intercellular space of vestibular sensory cat epithelia.

The intracellular space between sensory hair cells and nerve endings and between supporting cells of the vestibular epithelia in the cat contains a fine network of microstructures arranged obliquely between the cell membranes of adjacent cells. In situ immersion-perfusion fixation, electron microscopy complemented by lanthanum negative-contrast and freeze-fracture methods suggest that these intercellular structures are tubular with an external diameter between 3 and 6 nm and an internal diameter of 1.5 nm. They could serve as intercytoplasmic tunnels. We discuss the evidence concerning the analogy between the present microchannels and the passageways regularly arranged in the intercellular space of gap-junctions which would permit the transport of low molecular weight substances from one cell to other.

Animals↗
PubMed1984

Evidence for glutamate as a neurotransmitter in the cat vestibular nerve: radioautographic and biochemical studies.

Evidence that glutamate acts as a neurotransmitter in vestibular nerve fibers was sought (1) by electron microscope radioautographic identification of the uptake sites of [3H]-glutamic acid after incubation of slices of cat vestibular nuclei, and (2) by measuring changes in sodium-dependent high affinity glutamate uptake in nerve endings containing homogenates from normal and deafferented vestibular nuclei 8 to 11 days after unilateral vestibular nerve lesion. Electron microscopic radioautography revealed that glutamate had been taken up by numerous nerve endings projecting over the whole vestibular nuclear complex. The biochemical approach indicated that after section of the vestibular nerve, a significant decrease in high affinity glutamate uptake occurred in the vestibular nuclei, which lost their exclusively ipsilateral projection. This decrease varied from one area of the deafferented vestibular nuclei to another, reaching -58% in the lateral area of the central part corresponding to the ventral lateral vestibular nucleus and the rostral part of the descending vestibular nucleus. It is concluded that glutamate (or aspartate) is used by the vestibular nerve fibers as a neurotransmitter in the vestibular nuclei.

Animals↗
PubMed1984

The pattern of ciliary development in fetal mouse vestibular receptors. A qualitative and quantitative SEM study.

The development of vestibular receptors in the mouse was studied by scanning electron microscopy between the 13th gestation day to birth. On the 13th gestation day, the utricle was entirely covered with microvilli, which were often grouped around small kinocilia at the center of the macula. The vertical cristae were not clearly differentiated at this stage. On the 15th gestation day, the opposite orientation of ciliary tufts in the utricle indicated the beginnings of the striola. During the whole period studied, gradients in differentiation of ciliary tufts were observed between the center and the periphery of the utricle, and the top and base of the cristae. The auxiliary structures (otolithic membrane and cupula) began to appear at the same time as the first ciliary tufts differentiated. Otoliths, still immature, were only observed as from the 16th gestation day. Differentiation of ciliary tufts on the utricle appeared to be progressive during the fetal period. However, between the 16th and 17th gestation days, a pause in the differentiation of ciliary tufts was registered. A day later, there was a pause in the increase of the utricular sensory surface, which coincided with a temporary stabilization of the decrease in the thickness of the sensory epithelium.

Acoustic Maculae↗
PubMed1984

The efferent vestibular system in the cat: a horseradish peroxidase and fluorescent retrograde tracers study.

Neurons of the efferent vestibular system were investigated in the cat using retrograde axonal transport of horseradish peroxidase and fluorescent retrograde double labelling techniques. The number of efferent neurons was clearly higher than previously reported. A three dimensional reconstruction of the location of these neurons showed that they constitute a single group and did not give evidence of an eventual specialization based on neuron subpopulations. However, a study of cross-sectional areas of the horseradish peroxidase-labelled efferent neurons detected that the ipsilateral population contained a larger number of small neurons than the contralateral one. Double labelling by means of either 4',6-diamidino-2- phenylindol 2HCl in combination with horseradish peroxidase or Fast Blue in combination with Nuclear Yellow showed that 20% of efferent neurons project to both labyrinths. Such a high percentage raises the question of the role of these double-projecting cells and the specificity of their branching on vestibular receptors. This study expands previous work in the cat demonstrating that a much greater number of efferent neurons exists than had hitherto been assumed, among them 20% have both crossed and uncrossed projections.

Animals↗
PubMed1984

[Method for in vitro recording of vestibular neurons of the inner ear during postnatal development in the mouse].

Unitary recordings of spontaneous activity were performed from vestibular ganglion perikaria and axons of Mouse inner ear explants. The latter were from 1-11 day postnatal mice and were maintained in vitro at 37 degrees C, in a defined bathing medium. Spontaneous action potentials were obtained at each developmental stage and presented the distinctive features of the in vivo recorded activities during normal development. On the 3rd day post partum the recorded activities were of the immature type, with slow irregular discharge frequencies. In ganglia 3 to 9 days post partum the spike frequencies increased and the discharges exhibited 3 distinct firing patterns. This electrophysiological maturation of vestibular receptors is discussed in comparison with the morphological maturation of the vestibular organ during the same postnatal period.

Action Potentials↗