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- Liu, Wei, et al.
(författare)
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Spike Generators and Cell Signaling in the Human Auditory Nerve : An Ultrastructural, Super-Resolution, and Gene Hybridization Study
- 2021
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Ingår i: Frontiers in Cellular Neuroscience. - : Frontiers Media S.A.. - 1662-5102. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Background: The human auditory nerve contains 30,000 nerve fibers (NFs) that relay complex speech information to the brain with spectacular acuity. How speech is coded and influenced by various conditions is not known. It is also uncertain whether human nerve signaling involves exclusive proteins and gene manifestations compared with that of other species. Such information is difficult to determine due to the vulnerable, "esoteric," and encapsulated human ear surrounded by the hardest bone in the body. We collected human inner ear material for nanoscale visualization combining transmission electron microscopy (TEM), super-resolution structured illumination microscopy (SR-SIM), and RNA-scope analysis for the first time. Our aim was to gain information about the molecular instruments in human auditory nerve processing and deviations, and ways to perform electric modeling of prosthetic devices.Material and Methods: Human tissue was collected during trans-cochlear procedures to remove petro-clival meningioma after ethical permission. Cochlear neurons were processed for electron microscopy, confocal microscopy (CM), SR-SIM, and high-sensitive in situ hybridization for labeling single mRNA transcripts to detect ion channel and transporter proteins associated with nerve signal initiation and conductance.Results: Transport proteins and RNA transcripts were localized at the subcellular level. Hemi-nodal proteins were identified beneath the inner hair cells (IHCs). Voltage-gated ion channels (VGICs) were expressed in the spiral ganglion (SG) and axonal initial segments (AISs). Nodes of Ranvier (NR) expressed Nav1.6 proteins, and encoding genes critical for inter-cellular coupling were disclosed.Discussion: Our results suggest that initial spike generators are located beneath the IHCs in humans. The first NRs appear at different places. Additional spike generators and transcellular communication may boost, sharpen, and synchronize afferent signals by cell clusters at different frequency bands. These instruments may be essential for the filtering of complex sounds and may be challenged by various pathological conditions.
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| 3. |
- Rask-Andersen, Helge, et al.
(författare)
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Nerve fibre interaction with large ganglion cells in the human spiral ganglion : A TEM study
- 1997
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Ingår i: Auris, nasus, larynx. - 0385-8146 .- 1879-1476. ; 24:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- A TEM study was performed on freshly fixed human spiral ganglions (HSG) biopsied during skull base surgery. Well preserved tissue specimens were obtained for ultrastructural analysis. The investigation revealed that nerve fibres frequently form contacts with the large ganglion cells (type I cells). In the areas of contact, membrane specializations occurred, consisting of symmetric or asymmetric densities often alternating from one cell to the other with a reduced intercellular distance (approximately 10 nm). High power TEM showed the intercellular cleft to contain an extra dense line resulting in a pentalaminar structure. The dense line appeared on the side of the membrane protein concentration. Protein densities jutted into the cytoplasm along the intracellular face spreading into a diffuse cytoplasmic web physically related to accumulating mitochondria. This indicated a concentration of oxygen-dependent metabolic activity in these regions. It is believed that the nerve junctions are involved in electric transmission between type I ganglion cells. The neural junctions were morphologically different from synaptic contacts between small human ganglion cells (type II cells) and nerve fibres which have been suspected of sharing the olivocochlear bundle as their origin.
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| 8. |
- Tylstedt, Sven, et al.
(författare)
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Neural interaction in the human spiral ganglion : A TEM study
- 1997
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Ingår i: Acta Oto-Laryngologica. - : Informa UK Limited. - 0001-6489 .- 1651-2251. ; 117:4, s. 505-512
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Tidskriftsartikel (refereegranskat)abstract
- A TEM study was performed on freshly fixed human spiral ganglions (HSG) collected during skull base surgery. This technique gives well preserved tissue for ultrastructural analysis. Unlike spiral ganglion cells in mature animals so far studied, most HSG cells lack a myelin coat, but are surrounded by a thin rim of Schwann cell (SC) cytoplasm. In the region of maximal innervation density (upper basal and middle turn), HSG cells were frequently ensheathed by the same Schwann cell, forming a "unit-like" structure. In this region the cells often showed signs of physical interaction where the SCs were frequently incompletely developed ("gaps") so that the cell membranes of adjacent ganglion cells (sometimes as many as four in one section plane) were in direct apposition. In one thin section as many as 20 of 100 ganglion cells were found to face the cell membrane, at any point, of an adjacent cell. At these "gaps" in the SC, complexes of cell membrane specializations occurred between individual HSG cells. The same nerve junctions were also found between unmyelinated nerve fibres and the body of large ganglion cells. Our findings may challenge the view that afferent information in the acoustic nerve is conveyed uninterrupted to the CNS at the level of the spiral ganglion.
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| 9. |
- Tylstedt, Sven, 1969-
(författare)
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The Human Spiral Ganglion
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Our knowledge of the fine structure of the Human Spiral Ganglion (HSG) is still inadequate and new treatment techniques for deafness using electric stimulation, call for further information and studies on the neuronal elements of the human cochlea. This thesis presents results of analyses of human cochlear tissue and specimens obtained during neurosurgical transpetrosal removal of life-threatening meningeomas. The use of surgical biopsies produced a well-preserved material suitable for ultrastructural and immunohistochemical studies on the human inner ear. The SG was studied with respect to fine structure, using TEM technique and the immunostaining pattern of synaptophysin, which is an integral membrane protein of neuronal synaptic vesicles. The immunostaining patterns of the tight junctional protein ZO-1 and the gap junctional proteins Cx26 and Cx43 in the human cochlea were also studied. The ultrastructural morphology revealed an absence of myelination pattern in the HSG, thus differing from that in other species. Furthermore, formation of structural units as well as signs of neural interaction between the type 1 neurons could be observed. Type 1 cells were tightly packed in clusters, sharing the ensheathment of Schwann cells. The cells frequently made direct physical contact in Schwann cell gaps in which membrane specializations appeared. These specializations consisted of symmetrically or asymmetrically distributed filamentous densities along the apposed cell membranes. The same structures were also present between individual unmyelinated nerve fibres and the type 1 cells. Synapses were observed on the type 2 neurons, with nerve fibres originating from the intraganglionic spiral bundle. Such synapses, though rare, were also observed on the type 1 cells. The ultrastructural findings were confirmed by the synaptophysin study. A 3-D model of a Schwann cell gap between two type 1 cells was constructed, describing the distribution pattern of membrane specializations. In the immunohistochemical studies on the human cochlea, ZO-1 was expressed in tissues lining scala media, thus contributing to the formation of a closed compartment system, important for the maintenance of the specific ionic composition of the endolymph. Protein Cx26 could be identified in non-sensory epithelial cells of the organ of Corti, in connective tissue cells of the spiral ligament and spiral limbus, as well as in the basal and intermediate cell layers of stria vascularis. Cx26 in this region may be involved in the recycling of potassium. Protein Cx43 stained weakly in the spiral ligament, but intense staining in the SG may indicate that gap junctions exist between these neurons. A different functional role for the HSG can be assumed from the morphological characteristics and the signs of a neural interaction between the SG cells. This might be relevant for neural processing mechanisms in speech coding and could have implications for cochlear implant techniques.
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