Segmental demyelination

Windebank AJ, McCall JT, Hunder HG, et al. 1980. The endoneurial content of lead related to the onset and severity of segmental demyelination. J Neuropathol Exp Neurol 39 692-699. 

The response of the axon to loss of myelin is instructive. In the trembler mutant mouse, the axon undergoes a continuing cycle of partial myelination followed by demyelin-ation. The result is a thin or absent peripheral myelin sheath and a reduction in axonal caliber (Fig. 8-6). Remarkably, this reduction in axonal caliber is highly localized to segments of axon with disrupted myelin. 

The most hydrophobic integral membrane proteins can be extracted into organic solvents such as mixtures of chloroform and methanol. One such proteolipid protein, the 23.5-kDa lipophilin, accounts for over half the protein of myelin.57 182 The purified protein from rat brain contains 66% of nonpolar amino acids and six molecules of covalently bound palmitic acid and other fatty acids per peptide chain in thioester linkage to cysteine side chains. This protein evidently has four transmembrane helical segments with the six fatty acid chains incorporated into the membrane bilayer. It also has cytoplasmic and extracellular loops, one of which binds inositol hexakisphosphate (Ins P-6). (Fig. 11-9).183 The myelin proteolipid is an essential component of the myelin sheath and defects in this protein are associated with some demyelinating diseases57 which are discussed in Chapter 30. 

Pale coat color, axonal degeneration -motor and sensory, limited segmental demyelination pit (71-73)... 

Dyck, P.J., O Brien, P.C., Ohnishi, A. (1977). Lead neuropathy 2. Random distribution of segmental demyelination among old intemodes of myelinated fibers. J. Neuropathol. Exp. Neurol. 36 570-5. 

Figure 20.1. Hypotlietical scheme of tlie immune response in acute inflammatory demyelinadng polyiadiculoneuiopatliy (AIDP) Inflammatory cells migrate from die systemic immune compartment dnough die damaged blood-nei ve banier into die endoneuiium. Inflammatory infiltrates, which contain T-lymphocytes and macrophages cause marked segmental demyelination and secondary axonal degeneradon (B B-cell T T-cell M0 Macrophage).

Acute oral parenteral tellurium intoxication in animals results in restlessness, tremor, diminished reflexes, paralysis, convulsions, somnolence, coma, and death. Hematuria was prompt and occurred in all animals. Exposure of weanling rats to a diet containing elemental tellurium results in a peripheral neuropathy characterized by segmental demyelination and minimal axonal degeneration. It is noteworthy that functional recovery occurred despite... 

In diabetic patients, the incidence of clinically manifested deficits in peripheral nervous system function increases with duration of disease and is approx 50% after 25 yr of disease. The resulting diabetic neuropathies comprise a group of distinct disorders that can affect both somatic and autonomic nerves, the most common of which is symmetric sensory polyneuropathy. Clinical signs of overt human diabetic neuropathy include decreases in nerve conduction velocity and action potential amplitude and in resistance to ischemic conduction failure. These abnormalities may be accompanied by sensory deficits and, in some cases, severe pain. In diabetes of long standing, morphological deterioration is evident, and both nerve fiber loss and segmental demyelination may occur. 

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