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Biomedical subjects

A Sans

Publications and source records attributed to A Sans.

At least 127 records · Page 7Linked to original sources
PubMed1976

A vestibulothalamic pathway: electrophysiological demonstration in the cat by localized cooling.

Localized cooling was used in the search for vestibulothalamic pathways and a study was made of its effect on the activity of the thalamic neurons brought into action by stimulation of the vestibular nerve. Two cell populations were identified by their distinctive latencies in the ventral part of the posterior thalamus. Short latency responses were transmitted monosynaptically by means of a direct controlateral pathway whose course was identified. For long latency responses, the hypothesis of a polysynaptic path seems probable.

Animals↗
PubMedDate not supplied

Development of vestibular receptor surfaces in human fetuses.

The development of human vestibular receptors was studied between the 7th and 14th gestational weeks using scanning electron microscopy. The development phase appeared to last longer than previously described. At 7 weeks, no receptors were individualized, the vestibular epithelium was plicated, and scarce nascent hair bundles could be seen grouped in a small area. At 8 weeks, all receptors were well differentiated. Modifications in crista shapes were evaluated qualitatively and quantitatively along the length of their profile. Their growth occurred in two quick steps with a pause between the 9th and 12th weeks, during which growth slowed and a transformation occurred. In the utricle, the epithelium decreased in thickness, and this process underwent a pause between the 8th and 11th weeks. These results demonstrate pauses in the maturation process of the vestibular receptors and show that the utricles develop one week in advance of the cristae. At 14 weeks, all receptors had an adult profile, but the cristae had only reached 55 per cent of their adult size. The ciliary apparatus appeared to be nearly mature in the utricle but was still growing in the cristae. The differentiation of ciliary tufts in the cristae displayed an apex-base gradient. These developmental patterns were compared with those described in the mouse.

Adult↗
PubMedDate not supplied

Action of glutamate in the cat labyrinth.

Glutamate solutions of either 50 mM applied on the membranous labyrinth or 1 mM perfused into the lateral canal in cats increased spontaneous and stimulus-evoked activity of vestibular neurons. Kainic acid (10(-4) M) perfused into the labyrinth produced a depolarizing action on vestibular afferents. These results indicate that glutamate could be an excitatory neurotransmitter at the synapse between vestibular hair cells and afferent nerve fibers in the cat.

Action Potentials↗
PubMedDate not supplied

Embryonic and postnatal development of afferent innervation in cat vestibular receptors.

The maturing process of afferent innervation of the vestibular sensory cells in the cat was studied during both the fetal and postnatal stages. Although the type II cells from the 36th day of gestation already have an innervation similar to that found in the adult, it is not the same for the type I receptor cells. Only 75% have a complete innervation from the 7th postnatal day onwards. Most often, the formation of a continuous nerve calyx is caused by the fusion of the neighbouring membranes of the different dendritic elements belonging to the same neuron. Following the polyneuronal innervation of certain type I cells, numerous competition phenomena can be seen between the fibre endings coming from different neurons. The hypothesis that, during ontogenesis, type I cell innervation passes through a stage which corresponds to type II cell innervation is presented in the Discussion.

Afferent Pathways↗
PubMedDate not supplied

Organization and density of microtubules in the vestibular sensory cells in the cat.

In the vestibular receptors, the cytoplasmic hair cell microtubules manifest a particular affinity for the membraneous areas juxtaposed to an afferent nerve terminal. Moreover, their number is greater in the type I cells, which possess larger neuro-epithelial surface contacts than either in the type II cells or in the supporting cells. In the discussion, two hypotheses are proposed according to the results; the first concerns the structural role of the cytoskeleton and the second suggests its participation in sensory transduction.

Animals↗