On the fine Structure of Paracentrotus Lividus Permanent Blastulae Obtained after Treatment with 5-Bromodeoxyuridine: (5-bromodeoxyuridine/sea urchin embryos/ultrastructure).

This work reports some observations on the fine structure of the different types of Paracentrotus lividus permanent blastulae obtained after treatment with BUdR. Some permanent blastulae appeared similar to normal early mesenchyme blastulae and at the ultrastructural level they did not show any particular differences compared with the normal embryos. The only remarkable fact was that nucleoli often displayed the fibrous portion still abundant. Other permanent blastulae showed the blastocoel partially or completely, invaded by cells and it was often very difficult to recognize the embryo polarity. In these embryos, at the ultrastructural level, the most striking effects were observed in the blastocoelic cells. On the basis of the results reported in this paper and of the data already existing in the literature about the effects of BUdR on sea urchin embryos, the possibility is discussed that the drug might affect selectively some steps essential for the realizing of the embryo differentiation.