DER EINFLUSS DES RADIOAKTIVEN PHOSPHORS (P32) AUF WACHSTUM UND DIFFERENZIERUNG DER KAULQUAPPEN VON RANA TEMPORARIA

Histochemical studies were conducted on tadpoles reared from eggs in water containing 100 to 1500 mC P/sup 32/- phosphate. At the highest dose the first detectable change was decreased RNA-staining granules and increased vacuolation of the yolk. The cell nuclei of the neural tube showed bluish staining with methyl green-pyronin rather than the greenish color of controls. The liver showed marked changes, including atrophy and uneven thickness of liver cell trabeculae, granulated or vacuolated parenchymal cells, and absence of RNA in their cytoplasm. Nuclei showed irregular staining and pyknosis. Regressive changes were found in the thyroid. Other organs also showed atrophic alterations. Growth of the animals was retarded, their motility was depressed, and death occurred with the highest doses. It is suggested that many of the changes can be attributed to impairment of protein synthesis presumably as a result of a primary action of P/sup 32/ on DNA and RNA replication. The cytoplasm rather than the nucleus appears to be the site of initial action of P/sup 32/, and injury to cytoplasmic enzyme systems may be of basic importance in its action. (H.H.D.)