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Biomedical subjects

A Sans

Publications and source records attributed to A Sans.

At least 109 records · Page 6Linked to original sources
PubMed1983

Selective retrograde labelling of vestibular efferent neurons with [3H]choline.

Following administration of [3H]choline in the lateral semicircular canal of the cat labyrinth, bidirectional axoplasmic transport [3H]choline and its derivatives was shown by radioautography in the vestibular system. Light-microscopic radioautographs exhibited various patterns of radioautographic labelling. First, a diffuse reaction was observed in vestibular nuclei representing anterograde-labelled, vestibular nerve endings. Second, a heavy labelling limited to perikarya was detected in efferent vestibular neurons and corresponded to retrograde transport. The anterograde migration of [3H]choline is known to be non-selective and is related to synthesis of phospholipids, non-diffusable molecules. In contrast, the retrograde perikaryal labelling seems highly selective and related to the cholinergic specificity of the transmitter. The selectivity of such labelling offers a further possibility of identifying cholinergic neurons and is additional evidence that cholinergic mechanisms are involved in the efferent vestibular control.

Animals↗
PubMed1982

[In vitro organotypic development of the vestibular sensory epithelium of the embryonic mouse otocyst. A morphological and autoradiographic study (author's transl)].

The cytogenesis of the two cell populations of the vestibular sensory epithelium-hair cells and supporting cells-was investigated in explanted Mouse embryo otocysts using tritiated thymidine autoradiography. The otocysts were explanted on the 13th day of gestation and grown in vitro for 7 days. A close in vitro and in vivo correspondence was found in the cytodifferentiation of the sensory epithelium. At different times after explanation, a single administration of tritiated thymidine was added to the otocysts. The time schedule of the hair cell generation in the explants was essentially different from that observed during normal development. In contrast, the time schedule of the supporting cell generation was only mildly altered. The data suggest that the generative processes of the two cell populations are influenced differently, depending on their later specific differentiation.

Animals↗
PubMed1982

Analysis of temporal and spatial patterns of rat vestibular hair cell differentiation by tritiated thymidine radioautography.

The location in time and space of the terminal mitoses of type I and type II sensory hair cells (HCI and HCII) of the developing crista ampullaris in rat lateral semicircular canal and macula utriculi was determined by radioautographs of specimens exposed to tritiated thymidine from the 13th to the 20th day of gestation. Qualitative analysis and statistical treatment of the percentages of labeled HCI and HCII show that the terminal mitoses occur first in the macula utriculi with a maximum percentage of the 14th day of gestation, for the HCI, and on the 15th day of gestation, for the HCII. In the lateral crista, the maximum percentage of labeled HCI occurs on the 17th and 18th day of gestation and on the 19th day of gestation for the HCII. A spatial distribution of this labeling activity is also described: the older cells are located at the top of the crista and at the level of the striola of the macula utriculi while the younger cells are found at the bottom of the crista and on the sides of the utricle. A study of the vestibular receptors in the fetuses shows that synaptic contacts already exist on the 18th day of gestation in the macula utriculi at the level of the striola and on the 19th day at the top of the crista; the cells situated on the periphery are still immature. The first hair cells to undergo their terminal mitoses are, therefore, connected first. These results also suggest that the two types of cells are genetically programmed and that the HCI start functioning first during the development of the labyrinth.

Acoustic Maculae↗
PubMed1981

High resolution radioautographic study of the inner ear following in vivo tritiated deoxyglucose administration.

Light and high resolution radioautography were performed on cat and guinea pig inner ear after an in vivo administration of tritiated deoxyglucose and conventional histological treatments. In the guinea pig cochlea a diffuse radioautographic reaction product appeared on all the neurosensory and surrounding structures, with a more intense labelling of stria vascularis and Reissner's membrane. In the cat vestibular organ a diffuse reaction was also noted, with an intense clear-cut labelling of some dark cells at the base of the lateral crista and on some cells limiting the endolymphatic space, opposite the utricular macula. At the EM level, the silver grain distribution preferentially appeared to be localized on the cytoplasmic glycogen granules. In addition, some sensory cells were densely marked, the silver grains neither occurring on the nucleus nor on the surrounding nerve calyx, and rarely upon the mitochondria. These data indicate that using classical histological treatments, it is possible to retain a part of the radioactive molecules around the injection site. The possible physiological meaning of the selective labeling of some cellular and subcellular compartments is discussed.

Animals↗
PubMed1980

[Cellular detection of the in vivo incorporation of tritiated 2-deoxyglucose. Radioautographic study in the inner ear].

Inner ear injection of (3H) deoxyglucose was followed by in situ glutaraldehyde fixation and, after removal, by traditional preparation of the tissue for electron microscopy. Radioautography of semi-thin sections revealed preferential tracer accumulation in metabolically active structures such as the cochlear stria vascularis and the dark cells surrounding the basis of the vestibular cristae. Furthermore, in the vestibule, the perikaryon of some sensory cells was intensely labelled. These results show that an in vivo injection of deoxyglucose, followed by conventional histological processing can be used to mark active cells at both cellular and subcellular levels.

Animals↗
PubMed1980

Control of the vestibular nerve activity by the efferent system in the cat.

The effect of vestibular efferent system stimulation on the vestibular action potential (VAP) recorded after brief mechanical ampullopetal stimulation of the lateral canal crista was studied in the cat. When an inhibitory action was recorded it had an effect on the VAP component N2 potential and was also characterized by a positive post potential. When stimulation seemed to have no effect, computer averaging showed a weak facilitating action affecting the N1 potential. The hypothesis of a double efferent system is discussed.

Animals↗
PubMed1979

A new stimulation technique of the crista ampullaris of the lateral canal in the adult cat: study of the action potential of the vestibular nerve.

The stimulation of the crista ampullaris of the lateral canal by a short ampullopetal liquid flux produces on the pre-ganglionic vestibular fibres the appearance of a bimodal action potential. The amplitude of this action potential increases with the intensity of the stimulation. This stimulation also provokes the birth of an evoked potential at the level of the vestibular nuclei as well as an ocular jerk.

Action Potentials↗
PubMed1979

Morphological changes in afferent vestibular hair cell synapses during the postnatal development of the cat.

In the course of postnatal development in the cat, there is a decrease of about 93% in the total number of synaptic bodies (synaptic balls and synaptic bars) in type I hair cells. In type II hair cells, there is no change in the number of synaptic balls. Simultaneously, the length of specialized neuroepithelial contact increases by approximately 300% during type I hair cell maturation. Only the synaptic bars displaying a polylamellar ultrastructure persist in the type I hair cells of the adult animal. It is suggested that the afferent vestibular synapses of the type I hair cell are transformed during ontogeny.

Animals↗
PubMed1977

Synaptogenesis of the efferent vestibular nerve endings of the cat: ultrastructural study.

The maturation of the innervation of the sensory hair cells of the cristae ampullares was studied in the newborn cat. The essential characteristics of the adult are already present in the type II cells at this age. The type I cells on the contrary reveal different degrees of maturation. It was observed that in the immature stages the efferent endings which were already filled with synaptic vesicles were in direct contact with the membrane of the sensory cell. The nerve chalice as it settles into place breaks this contact and simultaneously a synapse is created between the efferent endings and the afferent chalice.

Animals↗
PubMed1976

The structural maturation of the stato-acoustic nerve in the cat.

The maturation of the stato-acoustic nerve in the cat was studied by light and electron microscopy from the fetal stage to the adult. Measurement of the outer diameter of the fibers and the study of the myelination process revealed that myelination begins earlier for the vestibular nerve than for the cochlear nerve: by the fifty-third day of gestation 64% of the vestibular fibres have already passed the promyelin stage whereas for the cochlear nerve this promyelin stage begins for the majority of fibers on the fifty-seventh gestation day. Afterward, maturation proceeds more rapidly for the cochlear nerve. In the case of both nerves, maturation is still incomplete at two months of age. Concerning the relationship between the thickness of the myelin sheath and the axoplasmic diameter, there is already a good correlation by the fifty-seventh day of gestation in the vestibular nerve, whereas it appears several days after birth in the cochlear nerve.

Age Factors↗
PubMed1976

[Postnatal maturation of vestibular nuclei in the cat: histological study by the Golgi-Cox method (author's transl)].

Postnatal maturation of vestibular nuclei in the cat was studied from both the qualitative and quantitative points of view, following impregnation of the sections by the Golgi-Cox method. Three principal data arise from our results. (1) The different vestibular neurones undergo significant growth during the first two weeks of extra-uterine life: during this time, the progressive disappearance of dendritic growth cones and filopodia, an increase in area and volume of the perikarya as well as that of dendritic fields are remarkable; the smallest neurones completing their maturation before the largest. (2) Average sized neurones of the superior vestibular nucleus show a significant increase in the number of dendritic spines between birth and the age of 3 days. (3) On the 12th day, a decrease in the number of dendritic spines is noted. This decrease is accompagnied by a modification in spine density along the dendrites.

Animals↗