Pathologic study on tissue anomalies in the developing brain

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It has been well known that in endemic cretinism, the outstanding symptoms are dwarfism, deafness, and mental retardation. The propose of the present study was to examine pathomorphologic changes of brains in endemic cretinism patients and experimental cretin rats.1. Histopathological study was made on cerebellar cortex of six patients with endemic cretinism in Jixian village, Heilongjiang, China. Examination revealed increased density of granule cells and sparse myelin sheath in the granular layer. Immunohistochemistry, showed lowered reactivity to myelin basic protein in the deep molecular layer and granular layer of cerebellum. Increased density of granule cells in the patients seems to be related to underdevelopment of cerebellar glomeruli and deficient myelination in the granular layer.2. Experiment was performed on iodine deficient rats fed in Jiamusi with a diet made of the local agricultural products and drinking water from an area of high incidence of endemic cretinism. Experi … More ments were made also in Kochi using antithyroid drug, thiamazole. The mother rats were fed with the deficient diet during pregnancy and after delivery. Their offsprings fed on the same diet were sacrificed on day 1-one year of The experiments.(1) Light microscopy showed lower synaptophysin reactivity in the granule cell layer and increased density of granule cells in hypothyroid rates as compared to normal rats. Electron microscopy exhibited reduced density and number of ethanolic phosphotungstic acid-positive syanptic junctions in the cerebellar glomeruli. This finding seems to be related to lowered synaptophysin immunoreactivity.(2) Iodine deficiency led to a sluggish development and cellular degeneration of cochlear structures. These changes might be related to the pathogenesis of deafness of human endemic cretinism.3. The results suggest that iodine deficiency or hypothyroidism has effcts on cellular differentiation of cerebellar cortex end inner ear. Further studies are required to assess the full effects of iodine deficiency on the brain development. Less