Number of somatic and germ cells during early stages of gonadal development in frog larvae treated with zinc sulphate.

ZnSO treatment of early frog tadpoles resulted, initially, in a mitotic stimulation of primordial germ cells. In later larval stages, ZnSO was responsible for the atresy of gonads in which germ cell and medullary cell numbers sharply decreased. At the same time, very few germ cells entered the meiotic prophase, while the degeneration of some of them was observed. Our results are discussed in connection with previous findings about the influence of Zn on cellular proliferation.