Protein Synthetic Activities during Spermiogenesis in the Sea Urchin: An high Resolution Autoradiographic Study of 3H-Leucine Incorporation

Protein synthetic activity has been studied during spermiogenesis of Paracentrotus lividus by high-resolution autoradiography using ³H-leucine as a labeled precursor. Under the adopted experimental conditions ³H-leucine is incorporated during the whole spermiogenesis period. The early spermatid is the most active stage and it shows labeling over the nucleus, the cytosol and the mitochondria. Nuclear ³H-leucine incorporation progressively decreases as spermiogenesis proceeds. Cytosol labeling shows similar values at early and intermediate spermatid and it undergoes a considerable decreases at late spermatid. Mitochondrial grain density increases from early to intermediate spermatid and it remains almost constant at late spermatid.
Our results are compared with the data reported for other animal groups and possible functions of the observed protein synthesis are discussed.     

On the fine Structure of Paracentrotus Lividus Permanent Blastulae Obtained after Treatment with 5-Bromodeoxyuridine

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.     

Cortical modifications in Paracentrotus lividus eggs after ammonia activation

We have shown by electron microscopy that ammonia activation of Paracentrotus lividus eggs alters the inner ultrastructure of cortical granules. If activated eggs are inseminated, they fail to undergo a typical cortical reaction.