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PubMed1986

Cholinergic innervation of the rat's labyrinth.

Efferent vestibular and cochlear neurons were identified in the rat's brain stem by retrograde labelling with True Blue (TB) or wheat germ agglutinin - horseradish peroxidase (WGA-HRP) injected into the utricle. Such cells were found at the same locations described in 1983 by White and Warr (ipsilateral superior olivary nucleus (LSO), bilateral latero-ventral nucleus of the trapezoid body (LTz) bilateral group E medial and lateral to the genu facialis) and, in addition, bilaterally in the caudal pontine reticular nucleus (CPR) at the level of the descending facial nerve. Cholinergic neurons were identified by counterstaining sections containing TB filled perikarya for acetylcholinesterase (AChE) following pretreatment with diisopropylfluorophosphate (DFP) or choline acetyltransferase (ChAT), by immunohistochemistry with highly specific monoclonal antibodies. Many, but not all, vestibular efferent cell bodies located in group E were shown to be cholinergic. These and other recently published data suggest that the efferent octavus system may consist of a number of chemically distinct cell groups.

Acetylcholinesterase↗
PubMed1988

Excitatory input to burst neurons from the labyrinth and its mediating pathway in the cat: location and functional characteristics of burster-driving neurons.

1. Spikes of single neurons were recorded extracellularly in the cat prepositus hypoglossi nucleus and the underlying reticular formation and were identified as type II neurons by horizontal rotation. Among these neurons, those activated by contralateral vestibular nerve stimulation with short latencies (1.5-3.0 ms) were selected for further study. 2. A class of these identified neurons was antidromically activated from the contralateral excitatory burst neuron (EBN) area immediately rostral to the abducens nucleus. Systematic tracking for antidromic stimulation revealed a wide distribution of effective spots in and near the EBN area, with varied latencies and thresholds, suggesting terminal branching in that area. The same neurons were also antidromically activated from the contralateral inhibitory burst neuron (IBN) area, the region near the midline, and the nucleus reticularis tegmenti pontis. 3. These neurons exhibited a characteristic firing pattern related to nystagmus: with contralateral rotation the firing rate gradually increased during the slow phase (type II response) and further steeply increased in a burst fashion before and during the contraversive quick phase. Since the time of occurrence of burst activity in these neurons was similar to that of contralateral ENBs and IBNs that received their axonal projection, it is suggested that they send excitatory input to burst neurons, and can thus be called burster-driving neurons (BDNs). 4. Intracellular study revealed that stimulation of the BDN area produced monosynaptic EPSPs in contralateral EBNs. The monosynaptic connection of BDNs with EBNs was confirmed by detecting unitary extracellular synaptic currents of EBNs with the spike-triggered averaging technique. 5. In contrast to BDNs, another class of nystagmus-related type II neurons in the prepositus hypoglossi and medullary reticular formation showed a discharge pattern similar to that of abducens motoneurons on the same side. None of them was antidromically activated from the contralateral pontine reticular formation including the EBN area. Some neurons responded antidromically to stimulation of the ipsilateral dorsomedial pontine reticular formation. 6. In conclusion, the input from the horizontal canal during rotation reaches the contralateral prepositus hypoglossi nucleus and the underlying reticular formation through the vestibular nuclei, and a class of neurons in these structures (BDNs) responds to the canal input in a burst fashion following a tonic type II activity. The axons of BDNs cross the midline and monosynaptically excite EBNs on the side of the canal stimulated.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Permeability studies of the guinea pig placental labyrinth. III. Tracer studies of the materno-fetal barrier.

The permeability of the materno-fetal barrier in the chorioallantoic placenta was studied in guinea pigs with gestation at term applying a variety of electron-opaque tracers via maternal circulation. None of the tracers tested was seen permeating the syncytiotrophoblast in the materno-fetal direction up to a 20 min interval when the fine structure of the placenta was satisfactorily preserved. The lanthanum chloride, cationized ferritin and horseradish peroxidase bound to the trophoblast surface, apparently due to electrostatic forces more than to specific receptors, and no uptake of these probes was detected in the cytoplasm. Albumin-colloidal gold complex, also used as a tracer, yielded similar results. As reported in other species with more complex syncytiotrophoblastic organization, this layer investing maternal lacunae is a highly selective permeability barrier.

Animals↗
PubMed1983

[Experimental studies on the effect of labyrinth anesthesia].

Injection of tetracaine into the tympanic cavity inhibits, independently of histologic lesions of the round window membrane, the active electrogenic pump in the stria vascularis cells. The DC potential in the endolymph is reduced with increasing doses of tetracaine, while the K+-Cl- activity is unchanged for 120 min. This drug does not alter the permeability of Reissner's membrane. Near the stria vascularis area, the oxygen pressure in the endolymph increases significantly after the effects of 4% tetracaine.

Anesthesia, Local↗
PubMed1982

[The early development of the labyrinth (author's transl)].

The developmental kinetics of the inner ear of 2- to 30-mm embryos are examined. The development of the inner ear can be shown as being constructively correlated with the development of the brain and thus being an ontogenic requisite for the structural development of the embryo. The development kinetic findings, as shown here, demonstrate that the functions of the inner ear have already started during its development and differentiation.

Auditory Pathways↗
PubMed1992

Anatomic variations of surgical importance in ethmoid labyrinth and sphenoid sinus. A study of radiological anatomy.

The present study was performed on axial and coronal CT scans of 100 patients, most of whom were affected by nasal polyposis. Five observers had to analyse the radiograms and answer a questionnaire including the following items: presence of a supraorbital recess; identification of anterior and posterior ethmoidal canals; dehiscences in the lamina papyracea; pneumatized middle turbinate; presence of a sphenomaxillary plate; presence of Haller's cells; presence of Onodi's cells; relationships of the optic canal; relationships of the internal carotid artery; relationships of the maxillary nerve; relationships of the vidian nerve; level difference between the ethmoid roof and nasal vault; depth of the sphenoethmoidal recess. The data obtained were compared with those drawn from anatomical studies. The fair agreement between them proves the value of CT as an alternative method for studying paranasal sinuses anatomy.

Ethmoid Bone↗
PubMed1997

The frontal sinus and the ethmoidal labyrinth.

In the "standard" anatomic description, the frontal bone and cribriform plate of the ethmoid bone form the base of the anterior cranial fossa. We studied the development of the ethmoidal bone as well as its relations to the frontal bone in macerated disarticulated skull bones and macerated skull bases of 35 individuals between 9 and 35 years of age. In 19 cases the ethmoidal cells were completely or partly uncovered by the frontal bone. In 6 of 19 cases the frontal bone did not cover any of the ethmoidal cells; in 10 further cases the frontal bone covered only the anterior and in 3 cases the anterior and middle ethmoidal cells. In a 60-year-old subject the ethmoidal cells were incorporated in the base of the anterior cranial fossa, a rare finding. Thus, a depressed lamina cribrosa is not the only danger in ethmoidectomy. Based on the present data ethmoidal cells uncovered by the frontal bone may involve a serious risk during ethmoidectomy even if the surgeon remains lateral to the insertion of the middle concha. The discrepancy between common descriptions of this region and our own findings may be related to imprecise data concerning the life stage of the cases described in the literature.

Adolescent↗
PubMed1978

[The influence of alcohol on central nervous compensating mechanisms following labyrinthic lesions (author's transl)].

The influence of alcohol on mechanisms compensating for labyrinthine lesions was studied in 180 guinea-pigs. The animals were subjected to either unilateral or to successive bilateral labyrinthectomy which was induced by an injection of chloroform into the middle ear. No significant influences of alcohol on vestibular compensation were found up to alcohol levels of 1g/kg. Dosages higher than 2 g/kg exerted inhibitory effects on compensation after unilateral labyrinthectomy. Compensation after successive bilateral labyrinthine lesions could not clearly be influenced. In animals which had achieved natural compensation after labyrinthectomy alcohol dosages of 0,5--1 g/kg re-elicited some of the formerly present symptoms. The data presented are interpreted with regard to their significance for the action of alcohol patients with cerebral dysfunction.

Animals↗