Schwann cell

Schottky mechanism Schott nomenclature Schradan [152-16-9] Schreibersite [12424-46-3] Schugi mixer Schulze-Hardy rule Schwann cells Schwarzembergite Schwenzfeier process Science policy... 

When large areas of the membrane are depolarized in this manner, the electrochemical disturbance propagates in wave-like form down the membrane, generating a nerve impulse. Myelin sheets, formed by Schwann cells, wrap around nerve fibers and provide an electrical insulator that surrounds most of the nerve and greatly speeds up the propagation of the wave (signal) by allowing ions to flow in and out of the membrane... 

Opportunistic infection, eg. CMV Progressive polyradiculopathy AIDS Acute, subacute Multiple, asymmetric mononeuropathies, usually painful CMV infection, Schwann cell infection demyelinating neuropathy... 

Fig. 4.4 Simplified hypothesis of the mechanism of gpI20-induced dorsal root gangUon (DRG) neurotoxicity. CXCR4 binding on Schwann cells by SDF-Ia or gpI20 results in the release of RANTES, which induces tumor necrosis factor (TNF)-a production by DRG neurons, and subsequent TNFRl-mediated neurotoxicity in an autocrine/paracrine fashion. Reproduced with permission of John Wiley Sons, Inc. (Keswani et al. 2003b)...

In the periphery PROG and PREG may well have an important trophic action since their production in Schwann cells has been shown to result in increased myelin synthesis in regenerating rat sciatic nerve and cultured dorsal root ganglia (see Koenig et al. 1995). 

Koenig, HE, Schumacher, M, Ferzaz, B, DeThi, A, Ressouches, A, Gennoun, R, Jung-Tester, L, Robel, P, Akwa, Y and Baulieu, EE (1995) Progesterone S5mthesis and myelin formation by Schwann cells. Science 286 1500-1503. 

The afferent fibres differ in their conduction velocity and degree of myelination, and can be distinguished by their diameter. The large diameter A S-fibres are myelinated by Schwann cells and hence have a fast conduction velocity. This group of nerve fibres innervates receptors in the dermis and is involved in the transmission of low-threshold, non-noxious information, such as touch. The A5-fibre is less densely myelinated and conveys both non-noxious and noxious sensory information. The unmyelinated C-fibre conveys high-threshold noxious inputs and has the slowest conduction velocity of all three fibre types. 

Myelin A segmented laminated lipoprotein sheath formed by glial cells (oligodendrocytes and Schwann cells). It is wrapped round the axon and acts as a biological insulating material. 

Schwann cells (grey cells) and regenerating axons... 

Fig. 3. Flalf smooth (top) and half 10/20/3 pm patterned laminin coated (200 pg/mL) PDLA solvent-cast substrate with Dil-labeled neurons and Schwann cells showing nonaligned and aligned cells, respectively. Bar = 50 pm. [Reproduced with permission from Miller et al. (2001a).]...

Schwann cells incorporated in a collagen matrix and injected into PLLA conduits were found to demonstrate comparable SFI values compared to isograft controls, but showed a statistically lower number of axons for both the high and low density Schwann cells groups and the collagen samples compared to the isograft controls (Evans et al., 2002). These results can be explained by a simple reaction diffusion model (Rutkowski and Heath, 2002b) described earlier. 

Poly(alpha-hydroxy acids) with seeded Schwann cells or Schwann cell grafts were also found to be effective candidates for spinal cord... 

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