Analysis Tools
nervous system
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• onion bulb structures are seen indicating myelin degeneration and regeneration
• however, stacking of myelin sheaths in compact myelin is unaffected
• noncompact myelin structures are more abundant
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• myelin sheaths are thicker at P15 and P30 and myelin continues to grow radially such that the mean myelin area in peripheral nerves at P90 is increased 6-fold
• increase in myelin thickness is particularly pronounced in small-diameter fibers
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• increase in the diameter of sciatic nerves due to massive hypermyelination and reduced axonal packing
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• myelination begins prematurely and mice show continuous myelin growth
• increase in the number of myelinated fibers per field at P0
• myelin abnormalities are seen at P30-P90 but not at P15, indicating that they result from massive hypermylination
• treatment with the mTORC1 inhibitor everolimus dampens myelin growth in the nerves of mutants and completely rescues the decreased axonal packing
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• ratio of compound action potentials in myelinated A and nonmyelinated C fibers (A/C fiber waves) is reduced and there is a reduction in numbers of active mechanoreceptive units after P60 indicating that many myelinated axons are not conducting
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• D-hair mechanoreceptors show increased conduction velocities at P30, however no differences were seen after P60
• however, conduction velocities of other mechanosensory fibers are unchanged
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