Effect of pyrithiamine on rat sciatic nerve. (II) Morphological changes during the last stages of thiamine deficiency
Oguchi, E.; Okazaki, M.; Noumi, M.; Sakamoto, K.
Nihon Yakurigaku Zasshi. Folia Pharmacologica Japonica 76(7): 567-580
1980
ISSN/ISBN: 0015-5691 PMID: 7215995 Document Number: 154922
Under light microscopy and EM, morphological changes in the rat sciatic nerve were observed during the last stages of a thiamine deficient state induced by pyrithiamine (PT: 50 .mu.g/100 g .times. 11 days) and thiamine deficient diet (TDD) in which rats experimenced severe tetanic convulsions. Experiments used normal control, PT (PT treated rats) and PTD (PT treated rats fed TDD) groups. Grossly, 4 of 9 rats in the PTD group had severe tetanic convulsions on the 12th day and there were no neurologic signs in the PT group. Microscopically, many myelinated axons in the animals in the PT group showed shrinkage with myelin ovoids and folds, but in the PTD group, there was swelling and shrinkage. Despite the difference in general symptoms between the PT and PTD groups, axonal degeneration in both groups, as determined EM, was almost to the same degree and the convulsed rats in the PTD group showed the severest changes in the myelin sheath. These ultrastructural changes included swelling or vacuolation of Schwann cells, axonal degeneration with the appearance of a myelin-like structure, collection of neurotubules or vacuoles, invasion of Schwann cell and/or myelin fragments into the periaxonal space and active phagocytosis by the macrophages. PT apparently directly affects the nervous system; the dysfunction of the sciatic nerve following PT-induced thiamine deficiency originates from the CNS.