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Results for “Organ of Corti”

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At least 19 recordsLinked to original sources

PubMed1975

[Functional survival of the human Corti organ after dissection of the eight nerve (author's transl)].

The behaviour of the functional unit haircell - peripheral neurit before and after the dissection of the cochlear nerve in two cases of cerebello-pontine angle tumors is described. An immediate alteration does not seem to be found when the blood supply via internal acoustic meatus is not severed. The survival time after the dissection of the acoustic nerve is somewhat more than seven weeks. This is longer than related morphological findings indicate in the cat where the morphological survival time of fibre population I (95% of all fibres) is not more than four weeks. On the other hand, morphological survival time of fibre population II (5% of all fibres) in cat is up to 14 months. The functional survival time in man under pure tumor pressure is longer than 10 years. Discrepancies between morphological and functional findings may indicate that morphological and functional behaviour do not necessarily coincide.

Adult↗

PubMed1978

[Population of hair cells in the Corti's organ of shrews].

In shrews (family Soricidase) the organ of Corti was examined by means of the surface specimen technique. The analysis of the qualitative deviations from the normal cellular pattern of Corti organ was based on more than 160 ears of shrews (Sorex araneus, S. minutus, Neomys fodiens, and Crocidura suaveolens). The dislocation, rotation, malformation of hair cells, and one finding of the giant outer hair cell are described. The quantitative analyses of the population of hair cells are based on 61 ears of Sorex araneus divided into 2 age groups. The mean values of aplasias and of missing and supernumerary hair cells in dependence on individual rows and half-turns of cochlea are given. The loss of hair cells depends on the age of the animal. The findings of aplasias and supernumerary outer hair cells (especially those of atypical 4th row) are relatively frequent in shrews. The organ of Corti in shows has a very regular arrangement; deviations of all types are scant and thus we may hold the ideal cochleogram for the norm. The found deviations seem to have no functional meaning.

Age Factors↗

PubMedDate not supplied

Ultrastructural changes of the nerve elements following disruption of the organ of Corti. I. Nerve elements in the organ of Corti.

3-137 days after disruption of the guinea pig organ of Corti by perilymphatic perfusion with 20% streptomycin (SM), ultrastructural changes of the nerve fibers in the organ were observed. Most of nerve fibers began to degenerate after a latent period of 4 days. On the other hand, a number of fibers survived reactively enlarged and later developed into myelinated and unmyelinated fibers by becoming enclosed in Schwann cells which entered the organ of Corti through the habenula perforata. Regeneration and sprouting of the surviving nerve fibers also occurred. The fibers became mature, but atrophied after 60 days and then gradually disappeared. The regenerating fibers were mainly of the myelinated and unmyelinated efferent type. Retrograde degeneration occurred in both afferent and efferent fibers. In the less damaged organ of Corti perfused with 2% SM or Ringer's solution, Schwann cell invasion was not found.

Animals↗

PubMed1979

Ultrastructural changes of the nerve elements following disruption of the organ of Corti. II. Nerve elements outside the organ of Corti.

Various stages of changes in the nerve fibers, spiral ganglion cells, and satellite cells from the guinea pig cochlea 3 to 137 days after perilymphatic perfusion with streptomycin solution (2 and 20%) were observed electron microscopically. Initially, the axoplasms of the cochlear nerve fibers became swollen or pyknotic. Then, the axons disappeared and myelin lamellae disrupted. The Schwann cells shrank and degenerated, though their basement membranes survived for a time. Regeneration of the cochlear nerve fibers began with extension of axonal sprouts into the tube of the basement membrane and surviving Schwann cells, which still contained myelin debris. Only one of the axonal sprouts matured for myelination. These regenerating cochlear nerve fibers were found in the osseous spiral lamina, modiolus and internal auditory meatus, but these fibers atrophied and disappeared afterward. Retrograde degeneration occurred in the olivo-cochlear bundle. Some of the efferent myelinated fibers also showed temporary regeneration.

Animals↗

PubMedDate not supplied

Cochlear nerve projections following organ of corti destruction.

Experimental organ of Corti destruction results in (1) secondary loss of all type I spiral ganglion neurons, (2) development of type III spiral ganglion neurons, (3) degeneration of most cochlear nerve myelinated fibers, and (4) terminal degeneration in the ventral and dorsal cochlear nuclei. The first signs of degenerative changes occur by eight days after organ of Corti destruction and degeneration debris remains until 28 weeks after destruction.

Animals↗

PubMedDate not supplied

The efferent innervation in the region of inner hair cells in the organ of Corti.

The efferent innervation of the inner hair cells in Corti's organ of the laboratory rat and of a bat was investigated with help of histochemical staining of the inner spiral bundle. The area of acetylcholinesterase-positive fibres in the inner spiral bundle regions was measured. The bulk of the efferent fibres lie in the middle part of the cochlea. Towards the apical and lower basal turns a distinct decrease in the number of fibres was observed.

Acetylcholinesterase↗

PubMed1976

[Thermal noise of Corti's organ hair cells].

Thermal agitation of the hair cells stereocilia of Corti organ is estimated. It is shown that with threshold sound stimulus the signal-to-noise ratio for single stereocilium and for single hair cell is less than 1. Some methods are proposed for signal-noise discrimination.

Auditory Perception↗

PubMed1979

Noise-noise effect upon the spreading of the posttraumatic progressive necrosis in the organ of Corti.

Progressive necrosis of the organ of Corti caused by a disturbance of the ionic composition of the Cortilymph resulting from the infiltration of endolymph into the organi of Corti after traumatization of its barrier against the scala media, is greatly intensified by posttraumatic stimulation with noise of physiological intensities. This effect is attributed to oscillation of the cochlear partition, with resultant greater blending of the Cortilymph and the endolymph. Stimulation augments necrosis fourfold towards the base of the cochlea and twofold towards the helicotrema. Posttraumatic stimulation is one of the factors which markedly potentiate the regressive effect of acoustic trauma.

Acoustic Stimulation↗

PubMed1977

Freeze-fracture studies on the synapses in the organ of Corti.

Receptoneural junctions and synapses in the organ of Corti of the chinchilla have been examined with the freeze-fracture technique. The presynaptic membranes at the receptoneural junctions of inner and outer hair cells have many structural features in common with membranes found at chemical synapses outside the organ of Corti. However, the membranes of the postsynaptic afferent terminals are quite different depending on whether they are part of an inner or outer hair cell synapse. These differences in the distribution of intramembrane particles suggest that the transmitters, or transmitter actions, may be different at these two synapses. The distribution of particles in the postsynaptic membrane at efferent synapses with outer hair cell differs from that in the postsynaptic membrane at efferent synapses with afferent terminals or fibers, suggesting that transmitter actions at these locations could also differ.

Animals↗

PubMedDate not supplied

Scanning electron microscopic study of the organ of Corti in normal and sound-damaged guinea pigs.

A method was evolved by which the organ of Corti could be examined in its entirety with the scanning electron microscope, the organ meanwhile retaining its spiral form. This made it possible to assess traumatic effects on the cochlea and qualify lesions in terms of extent, localization and pattern. It was also found possible eventually to cut the same specimen into sections for cellular and subcellular studies. The number of guinea pigs examined totalled 91, divided into three groups. The first group was used to study the anatomy of the organ of Corti with special reference to normal variations and artifacts. Unmistakable indications were found that the longest stereocilia of the inner hair cells are linked to the tectorial membrane. The animals of the second group were exposed to pure tones of high intensity, whereupon, lesions of the organ of Corti were described according to intensity, time, and frequency. Three different types of otologic drills were used to perform mastoidectomies on temporal bones and on the cadaver. The noise produced was analyzed as to intensity and frequency range. It was found that the drill with the lowest rpm (and highest torque) produced the highest noise intensities, at levels which can be traumatic to the human organ of hearing. The animals of the third group were exposed to the amplified noise produced by otologic drills of three different types. The resulting lesions in the organ of Corti were examined by the method described for scanning electron microscopy and compared. In spite of the wide variation in individual lesions, patterns of degeneration of three different types could be distinguished. The high-speed and the very-high-speed drill inflicted less damage on the organ of Corti than the low-speed drill. It is therefore advised to refrain from using the latter drill in prolonged operations.

Animals↗

PubMed1977

Scanning electron microscopy of the nerves within the organ of Corti.

A method of studying the innervation inside the organ of Corti is presented. Rabbits, guinea pigs and chinchillas were fixed with perfusion of the perilymphatic spaces. The cochleas were dissected according to the surface specimen technique and the specimens critical point dried, coated with gold and studied in the SEM. The final dissection into the planes of the fluid spaces of the organ of Corti was done in the dry state using especially sharpened watch makers forceps and razor blade knives. The course of the afferent and efferent innervation is described and differences between the species illustrated. Small high nerve endings on the outer hair cell degenerate after cutting the efferent nerve supply by dividing the vestibular nerve indicating their efferent nature.

Animals↗

PubMed1975

Tissue culture of the organ of Corti and the isolated hair cells from the newborn guinea pig.

The organ of Corti and isolated hair cells from newborn guinea pig were cultured with the Rose chamber method. The hair cells could be maintained for more than 20 days after explantation when the organ of Corti was cultured as a whole, though the isolated hair cells swelled and degenerated within about 13 hours after explantation. By comparison between the tissue culture of the hair cells with the organ of Corti and isolated hair cell culture, the following conclusions were reached: (1) There are some functional correlations concerning the nutritional requirements and cell metabolism between the hair cells and the supporting cells in addition to the structural correlations. (2) There are no distinct fundamental differences between both inner and outer hair cells about their affectability as a single cell level.

Animals↗

PubMedDate not supplied

Distribution of cyclic nucleotides in the organ of Corti.

Recent developments in radioimmunoassay technology have made possible measurements of cyclic nucleotides in individual specimens of the organ of Corti and its subdivisions. Steep longitudinal and transverse gradients of glycogen are known to exist in the organ of Corti of the guinea pig, with preferential accumulation in the outer hair cells of the apical turns. However, no significant longitudinal gradient of cyclic AMP was detectable in the organ of Corti, and the concentration of the compound was found to be nearly equal in the inner and outer hair cell layers. This is indirect evidence against the concept that cyclic AMP plays a role as "second messenger" in the control of glycogen metabolism of the organ of Corti. By contrast, the concentration of cyclic GMP was found to be consistently higher in the inner layer than in the outer layer of the organ of Corti, and to increase significantly in basal direction. This trend is remarkably similar to the distribution patterns of acetylcholinesterase, which may be considered as indirect evidence in favor of a possible role of cyclic GMP in the mediation of cholinergic effects.

Acetylcholinesterase↗

PubMedDate not supplied

Intercellular fluid pathways in the organ of Corti of cat and man.

The intercellular junctions in the organ of Corti of cat and man were examined with the electron microscope. In contrast to the zone of tight junctions, or zonulae occludentes, which were present at the surface of cells lining the scala media, there was no tight junctional specialization among the cells of the tympanic lamina, perilymphatic lining cells of the scala vestibuli, basal processes of the supporting cells of the organ of Corti or cells of the spiral limbus and spiral ligament. These findings suggest the possibility of fluid continuity between the scala vestibuli and scala tympani all along the cochlear duct. Morphological evidence for an intercellular diffusion barrier was present only at the endolymphatic surfaces of the cochlear duct and between the processes of the basal cells of the stria vascularis in cat and man.

Animals↗

PubMedDate not supplied

Organ of Corti in the human fetus: scanning and transmission electronmicroscope studies.

The organ of Corti in the five-month human fetus was studied by transmission and scanning electronmicroscopy. Differentiation of the surface organization of the organ of Corti into a single row of inner and three to four rows of outer hair cells was complete at this stage except at the apical end. The morphological aspects of the hair bundles changed with maturation of the sensory cells; the inner hair cells preceded the outer hair cells in cytodifferentiation at a given location.

Cell Differentiation↗

PubMed1977

[To Wittmaack's theory of "hearing without the organ of Corti" (author's transl)].

1911 Wittmaack had shown by experiments in cats that the organ of Corti is independent from the cochlear nerve but dependent from a normal internal auditory artery. Similar findings he could observe in his temporal bone collection in cases of acoustic nerve tumors. On the other hand many human cases with the compression phenomenon of the organ of Corti had intact cochlear nerve fibers and neurons, and nearly normal hearing. Thus Wittmaack concluded that some parameters of hearing are transmitted by the nerve endings in the organ of Corti without the haircells. This hypothesis is discussed by means of examples of Wittmaack's temporal bone collection in the light of our present knowledge.

Cochlea↗

PubMed1975

Mechanism of sound susceptibility in organ of Corti - inference of contrary recruitment phenomenon (hypothesis) and the application to diagnosis -.

In order to make the mechanism concerned with the sound-susceptibility in the organ of Corti clear, we observed the organ of Corti with the phase-contrast microscope, after the microdissection of the cochleae in human, dogs, guinea pigs and hamsters by Engstroöm's surface preparation technique. As a result, we have formulated a hypothesis for the mechanism of the sound-susceptibility in the organ of Corti. Further, we have inferred the contrary recruitment phenomenon (hypothesis), by explaining theoretically such a clinical fact as the recruitment phenomenon or the cochlear hearing loss by applying our first formula of hypothesis. Finally, we described the application of the contrary recruitment phenomenon (hypothesis) to the early discovery or diagnosis of the false normal ear or cochlea, in other words, latent hearing loss.

Acoustic Stimulation↗

PubMed1979

Intracellular potential changes of Corti's organ with anoxia.

Intracellular measurements of the resting cell membrane potentials of guinea pig Corti's organ were made in order to determine the sensitivity of this cell potential to anoxic hypoxia (a lowered oxygen state due to lack of respiratory oxygen) and to establish differences according to cell types or morphologic regions of the sensory epithelium. The negative cell potentials measured from successful electrode penetrations were found to be relatively more stable and resistant to change during a 120-s period of anoxia than was the positive endocochlear potential. The intracellular resting potentials were also much slower to recover after resumption of respiration. Data obtained from various cells in two different regions of Corti's organ is receiving oxygen from both the perilymph and the endolymph. An iontophoretic dye-marking technique was used to label some experimental cells for later histologic identification.

Action Potentials↗