Sciatic nerve myelin

The results of JT-ray diffraction studies on frog sciatic nerve myelin have indicated that the major glycoprotein is inserted into the extracellular half of the myelin bilayer and that it extends into the extracellular space. Various glycopeptides containing L-fucose and 2-acetamido-2-deoxy-D-glucose, but no neuraminic acid, have been isolated from garfish olfactory nerve. ... 

A glycoprotein isolated from rabbit sciatic nerve myelin contained 6.3% carbohydrate in the form of a nonasaccharide unit composed of residues of D-mannose (3), 2-acetamido-2-deoxy-D-glucose (3), iV-acetylneuraminic acid (1), D-galactose (1), and L-fucose (1). Treatment of sciatic nerve myelin with trypsin releases a glycoprotein fragment (mol. wt. 1.9 x 10 ) with a higher content of hydrophobic amino-acid residues than the former glycoprotein. ... 

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). 

Taylor, K.S., G.D. Waller, and L.A. Crowder. 1987. Impairment of a classical conditioned response of the honey bee (Apis mellifera L.) by sublethal doses of synthetic pyrethroid insecticides. Apidologie 18 243-252. Theophilidis, G., M. Benaki, and E. Papadopoulu-Mourkidou. 1997. Neurotoxic action of six pyrethroid insecticides on the isolated sciatic nerve of a frog (Rana ridibunda). Comp. Biochem. Physiol. 118C 97-103. Tippe, A. 1987. Evidence for different mechanisms of action of the three pyrethroids, deltamethrin, cypermethrin, and fenvalerate, on the excitation threshold of myelinated nerve. Pestic. Biochem. Physiol. 28 67-74. 

In affected cats and hens, extensive damage is observed in the spinal cord and sciatic nerves damage to the myelin sheath and Schwann cells... 

In contractile experiments the time from the stimulation of the nerve to the CMAP recorded in muscle provides an estimate of NCV. The length of the nerve from the stimulating electrode to the muscle can simply be measured and divided by the time. However, the time recorded in this way includes the delay for synaptic transmission, which may be increased in models with synaptic defects. If this is a concern or if the only parameter desired is NCV, then the measurement can be obtained non-invasively with a relatively simple setup (e.g., (3)). Using the sciatic nerve, NCV can be calculated by measuring the latency of compound motor action potentials recorded in the muscle of a rear paw. Action potentials are produced by subcutaneous stimulation at two separate sites proximal stimulation at the sciatic notch and distally at the ankle. NCV is then calculated by using the two latencies and conduction distance. Decreases in nerve conduction velocity most often reflect defects in myelination, but may also be the result of changes in internodal distance, decreased axon diameters, or altered excitability. 

Basic protein P2 has a molecular weight of 15 kDa and is a member of a family of cytoplasmic lipid-binding proteins. Unlike other myelin proteins, its quantitative expression varies greatly according to species, ranging from less than 1% in rodent sciatic nerves up to 5-14% in human, bovine, and rabbit nerve. P2 is located on the cytoplasmic side of compacted regions of myelin. 

After exposure to 3300 ppm tellurium in the diet for 5 months, rats were markedly impaired in their ability to learn a sequence of behavioral tasks. The administration of 500-3000 ppm tellurium through the diet to pregnant rats resulted in a high incidence of hydrocephalic offspring. Neonatal rats exposed to tellurium via the mother s milk from the day of birth until killing at 7, 14, 21, or 28 days of age developed Schwann cell and myelin degeneration in the sciatic nerves at each age studied. In the central nervous system (CNS), hypomyelination of the optic nerves was demonstrated at 14, 21, and 28 days of age. 

Martini R, Schachner M. 1988. Immunoelectron microscopic localization of neural cell adhesion molecules (LI, N-CAM, and myelin-associated glycoprotein) in regenerating adult mouse sciatic nerve. J CeU Biol 106 1735-1746. 

Notest aData for compounds 3 and 4 taken from ref. 263 data for compound 10 taken from ref. 266. bRats with lesioned sciatic nerves were treated with the indicated compounds, and sacrificed on the 18th day of the experiment. Axonal diameter and cross-sectional area were quantitated by anti-neurofilament staining, and myelin levels were quantitated by myelin basic protein-immunoreactive stain density. 

Also significant was the demonstration that the compounds did not appear to affect healthy nerves. Experiments with protein growth factors have shown that they may induce abnormal neuronal sprouting.267 Treatment with 40 mg/kg/day, sc, of 10 for 18 days did not cause abnormal axonal growth or altered myelination patterns in the sciatic nerves of healthy, nonlesioned rats. 

Schafers M, Geis C, Svensson C I, et al. (2003). Selective increase of tumour necrosis factor-alpha in injured and spared myelinated primary afferents after chronic constrictive injury of rat sciatic nerve. Euro. J. Neurosci. 17 791-804. 

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