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The pre- and post-somatic segments of the human type I spiral ganglion neurons--structural and functional considerations related to cochlear implantation.

Liu W, Edin F, Atturo F, Rieger G, Löwenheim H, Senn P, Blumer M, Schrott-Fischer A, Rask-Andersen H, Glueckert R - Neuroscience (2014)

Bottom Line: These segments were found surrounded by non-myelinated Schwann cells (NMSCs) showing strong intracellular expression of laminin-β2/collagen IV.Their BMs express laminin-β2/collagen IV and reaches the BM of the sensory epithelium at the habenula perforata.We speculate that the NMSCs protect SGNs from further degeneration following dendrite loss.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgical Sciences, Head and Neck Surgery, Section of Otolaryngology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden; Department of Otolaryngology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden. Electronic address: lwoo24@gmail.com.

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Light and transmission electron microscopy of the human spiral ganglion. (A) Light microscopy of a semi-thin section from the second turn of the cochlea sectioned perpendicular to the long axis of the modiolus (upper inset). Several type I SGNs lie typically close to each other and share SGCs. Sometimes a thin rim of their cytoplasm jams itself between (middle arrow, right inset). SGCs are surrounded by a basement membrane whenever facing extra-cellular tissue. Filled arrows show AISs. Cochlea was fixed in glutaraldehyde according M&M (normal audiogram). Toluidine/osmium. Na-EDTA decalcification (section thickness approx. 1 μm). AIS, axonal initial segment. (B) TEM demonstrating AIS junction at nerve cell body in a cell cluster. There is incongruence in the basement membrane (BM) lining. Inset confirms that neural cell bodies face each other without a limiting SGC cell. The cell membranes show electron-dense specializations. (C) TEM of corresponding area shown in A (upper filled arrow). A satellite glial cell (SGC) surrounds several type I nerve bodies. The group of cells is surrounded by a basement membrane.
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f0005: Light and transmission electron microscopy of the human spiral ganglion. (A) Light microscopy of a semi-thin section from the second turn of the cochlea sectioned perpendicular to the long axis of the modiolus (upper inset). Several type I SGNs lie typically close to each other and share SGCs. Sometimes a thin rim of their cytoplasm jams itself between (middle arrow, right inset). SGCs are surrounded by a basement membrane whenever facing extra-cellular tissue. Filled arrows show AISs. Cochlea was fixed in glutaraldehyde according M&M (normal audiogram). Toluidine/osmium. Na-EDTA decalcification (section thickness approx. 1 μm). AIS, axonal initial segment. (B) TEM demonstrating AIS junction at nerve cell body in a cell cluster. There is incongruence in the basement membrane (BM) lining. Inset confirms that neural cell bodies face each other without a limiting SGC cell. The cell membranes show electron-dense specializations. (C) TEM of corresponding area shown in A (upper filled arrow). A satellite glial cell (SGC) surrounds several type I nerve bodies. The group of cells is surrounded by a basement membrane.

Mentions: Well preserved human SGNs were obtained and verified with LM, TEM and SEM (Figs. 1, 4 and 5A). Most type I SGNs were unmyelinated and lacked expression of MBP (Figs. 1 and 2A). Instead they were surrounded by SGCs whose extracellular surface was covered by a BM (Figs. 1 and 2A–C, E, F, 3). Their cell nuclei were often crescent-like. Many type I SGNs formed clusters and were jointly surrounded by SGCs and a distinct BM (Fig. 1). The continuous BM co-expressed the β2 isoform of laminin heterotrimeric complex and collagen type IV (Figs. 2 and 3). The BM surrounded the neurons from the spiral ganglion (SG) to the nerve entry in the sensory organ (habenula perforata) and stained positive for both markers (Fig. 2D). The BM also formed a thin sheet lining the short canal into the sensory organ (habenular canal) which coalesced with the BM of the sensory epithelium. The peripheral axons (or dendrites) lost their myelin sheath beneath the inferior canal opening of the habenula perforata (Fig. 2D). Dendrites and axons of the type I SGNs were bordered by MBP-positive, myelinating Schwann cells. The pre- and post-somal segments however, were mostly bordered by unmyelinated Schwann cells (MBP-negative). The non-myelinated zones varied considerably in length but could be up to 50 microns (Fig. 2A, E). Typically, as opposed to the SGCs, the NMSCs showed rich expression of intracellular laminin-β2 and collagen IV (Figs. 2E, F, and 3). This contrasted to the SGCs that showed no such expression. The NMSCs extended to the poles of the cell soma. Their cell nuclei were often round compared to the crescent shape of the SGCs nuclei.


The pre- and post-somatic segments of the human type I spiral ganglion neurons--structural and functional considerations related to cochlear implantation.

Liu W, Edin F, Atturo F, Rieger G, Löwenheim H, Senn P, Blumer M, Schrott-Fischer A, Rask-Andersen H, Glueckert R - Neuroscience (2014)

Light and transmission electron microscopy of the human spiral ganglion. (A) Light microscopy of a semi-thin section from the second turn of the cochlea sectioned perpendicular to the long axis of the modiolus (upper inset). Several type I SGNs lie typically close to each other and share SGCs. Sometimes a thin rim of their cytoplasm jams itself between (middle arrow, right inset). SGCs are surrounded by a basement membrane whenever facing extra-cellular tissue. Filled arrows show AISs. Cochlea was fixed in glutaraldehyde according M&M (normal audiogram). Toluidine/osmium. Na-EDTA decalcification (section thickness approx. 1 μm). AIS, axonal initial segment. (B) TEM demonstrating AIS junction at nerve cell body in a cell cluster. There is incongruence in the basement membrane (BM) lining. Inset confirms that neural cell bodies face each other without a limiting SGC cell. The cell membranes show electron-dense specializations. (C) TEM of corresponding area shown in A (upper filled arrow). A satellite glial cell (SGC) surrounds several type I nerve bodies. The group of cells is surrounded by a basement membrane.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4300406&req=5

f0005: Light and transmission electron microscopy of the human spiral ganglion. (A) Light microscopy of a semi-thin section from the second turn of the cochlea sectioned perpendicular to the long axis of the modiolus (upper inset). Several type I SGNs lie typically close to each other and share SGCs. Sometimes a thin rim of their cytoplasm jams itself between (middle arrow, right inset). SGCs are surrounded by a basement membrane whenever facing extra-cellular tissue. Filled arrows show AISs. Cochlea was fixed in glutaraldehyde according M&M (normal audiogram). Toluidine/osmium. Na-EDTA decalcification (section thickness approx. 1 μm). AIS, axonal initial segment. (B) TEM demonstrating AIS junction at nerve cell body in a cell cluster. There is incongruence in the basement membrane (BM) lining. Inset confirms that neural cell bodies face each other without a limiting SGC cell. The cell membranes show electron-dense specializations. (C) TEM of corresponding area shown in A (upper filled arrow). A satellite glial cell (SGC) surrounds several type I nerve bodies. The group of cells is surrounded by a basement membrane.
Mentions: Well preserved human SGNs were obtained and verified with LM, TEM and SEM (Figs. 1, 4 and 5A). Most type I SGNs were unmyelinated and lacked expression of MBP (Figs. 1 and 2A). Instead they were surrounded by SGCs whose extracellular surface was covered by a BM (Figs. 1 and 2A–C, E, F, 3). Their cell nuclei were often crescent-like. Many type I SGNs formed clusters and were jointly surrounded by SGCs and a distinct BM (Fig. 1). The continuous BM co-expressed the β2 isoform of laminin heterotrimeric complex and collagen type IV (Figs. 2 and 3). The BM surrounded the neurons from the spiral ganglion (SG) to the nerve entry in the sensory organ (habenula perforata) and stained positive for both markers (Fig. 2D). The BM also formed a thin sheet lining the short canal into the sensory organ (habenular canal) which coalesced with the BM of the sensory epithelium. The peripheral axons (or dendrites) lost their myelin sheath beneath the inferior canal opening of the habenula perforata (Fig. 2D). Dendrites and axons of the type I SGNs were bordered by MBP-positive, myelinating Schwann cells. The pre- and post-somal segments however, were mostly bordered by unmyelinated Schwann cells (MBP-negative). The non-myelinated zones varied considerably in length but could be up to 50 microns (Fig. 2A, E). Typically, as opposed to the SGCs, the NMSCs showed rich expression of intracellular laminin-β2 and collagen IV (Figs. 2E, F, and 3). This contrasted to the SGCs that showed no such expression. The NMSCs extended to the poles of the cell soma. Their cell nuclei were often round compared to the crescent shape of the SGCs nuclei.

Bottom Line: These segments were found surrounded by non-myelinated Schwann cells (NMSCs) showing strong intracellular expression of laminin-β2/collagen IV.Their BMs express laminin-β2/collagen IV and reaches the BM of the sensory epithelium at the habenula perforata.We speculate that the NMSCs protect SGNs from further degeneration following dendrite loss.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgical Sciences, Head and Neck Surgery, Section of Otolaryngology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden; Department of Otolaryngology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden. Electronic address: lwoo24@gmail.com.

Show MeSH
Related in: MedlinePlus