tellurium and Diabetic-Neuropathies

Neuropathy in animals is either genetically determined or is provoked by chemical compounds or physical injury. Diabetes in mice and rats may be spontaneous or induced, but a true copy of diabetic neuropathy in man is not yet available. Painful neuropathy occurs after nerve constriction or neuroma formation. A mouse mutant with delayed Wallerian degeneration demonstrates the pivotal role of this process for the regeneration of injured axons. Surprisingly, the neurotoxic effect of cisplatin which is severe in cancer patients has not yet unambiguously been reproduced in animals. Genetically determined diseases in mutants or transgenic animals may affect the myelination of peripheral axons. 'Trembler mice' are deficient in myelin and possibly correspond to CMT IA in man. The relation of sensory neuronopathies in mice, rats and dogs to human diseases is not yet clear. Motor neuronopathies in experimental animals have attracted much interest, because the recent discovery of motoneuronotrophic factors has raised high hopes. Most of the mutants described have not been appropriately studied, and the mouse mutant 'motoneurone disease' (mnd) eventually was found to have Batten's disease. None of the few more thoroughly studied models is probably a copy of human disease, although they may none the less help to test new therapies.

Topics: Animals; Antineoplastic Agents; Cisplatin; Diabetic Neuropathies; Dogs; Hereditary Sensory and Autonomic Neuropathies; Humans; Male; Mice; Nerve Degeneration; Nerve Regeneration; Peripheral Nerves; Radioisotopes; Rats; Tellurium

Demyelination is a prominent feature in nerve biopsies of patients with diabetic neuropathy. The mechanism is unknown because diabetic rodents, unlike humans, do not consistently develop segmental demyelination. We examined how diabetes influences toxicant-induced demyelination, remyelination, Schwann cell nerve growth factor receptor (p75) expression, and endoneurial macrophage apolipoprotein E (apo E) synthesis in diabetic rats. Postnatal day 17 (P17) rats were given 110 mg/kg streptozotocin intraperitoneally and then fed a diet containing metallic tellurium (Te) from P20 to P27 to induce demyelination. Transverse electron micrographs and immunostained longitudinal cryosections were prepared from sciatic nerve during demyelination and remyelination. Diabetic rats had a mean serum glucose concentration of 490 mg/dl and consumed equivalent doses of peroral Te. The number of demyelinated fibers in electron micrographs was increased significantly by 17% (P < .0011). Endoneurial density of p75-stained Schwann cells was increased in diabetic rats in proportion to the increased number of injured internodes. Density of apo E- and ED1-positive macrophages also was significantly increased in diabetes. There was no delay in macrophage myelin clearance. and remyelination was not compromised. Increased Schwann cell vulnerability to stress, by increasing the turnover rate of myelinated units, may explain why myelin defects accumulate after long-standing diabetes.

Topics: Animals; Apolipoproteins E; Demyelinating Diseases; Diabetes Mellitus, Experimental; Diabetic Neuropathies; Female; Macrophages; Male; Metabolic Clearance Rate; Myelin Proteins; Nerve Regeneration; Rats; Receptor, Nerve Growth Factor; Receptors, Nerve Growth Factor; Schwann Cells; Tellurium; Up-Regulation