EFFECT OF THYMOSIN FRACTION-5 (TF5) ON EARLY NEUROEMBRYOGENESIS IN THE NEWT TRITURUS-CRISTATUS

Thymosin fraction five (TF5), a well-characterized immunoregulatory th ymic preparation, has been reported to stimulate corticotropin (ACTH) release. The present study explores the morphogenetic role of TF5 on e arly stages of nerve tissue formation during embryogenesis. In vivo TF 5-treatment of newt embryos during neurulation results in stimulation of the process expressed at a macro-microscopical level by emphasizing the embryo's relief and by accelerating the neural tube closure. The stimulating effect of TF5 on neurulation is manifested ultrastructural ly by enhanced apical endocytosis, a well-developed contractile microf ilamentous layer, increased apical intercellular junctions and changes of the cytoplasmic organelles linked with the protein synthesis. The polymorphism of mitochondria and the morphological expression of enhan ced yolk material assimilation confirm the idea of TF5-stimulating eff ect on the neuroepithelial cells.