Effect of thymosin fraction five (TF5) on early neuroembryogenesis in the newt Triturus cristatus

Thymosin fraction five (TF5), a well-characterized immunoregulatory thymic preparation, has been reported to stimulate corticotropin (ACTH) release. The present study explores the morphogenetic role of TF5 on early stages of nerve tissue formation during embryogenesis. In vivo TF5-treatment of newt embryos during neurulation results in stimulation of the process expressed at a macro-microscopical level by emphasizing the embryo' relief and by accelerating the neural tube closure. The stimulating effect of TF5 on neurulation is manifested ultrastructurally by enhanced apical endocytosis, a well-developed contractile microfilamentous 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 enhanced yolk material assimilation confirm the idea of TF5-stimulating effect on the neuroepithelial cells.