MITOCHONDRIAL MASS, DISTRIBUTION AND ACTIVITY DURING SEA URCHIN OOGENESIS

The sea urchin egg is a favourite model for studies of the molecular biology and physiology of fertilization and early development, yet we know sparingly little of its oocytes and of mitochondria behaviour during oogenesis. The process of oogenesis in most echinoderms is asynchronous so each ovary lobe has hundreds of oocytes at all stages of development. At the beginning of oogenesis, the oocyte is about 10 µm in diameter. During the vitellogenic phase of oogenesis, the oocyte accumulate yolk proteins and grow to ten times their original size to 80 to 100 µm in sea urchins. The oocyte, arrested at the prophase of the first meiotic division, is apparent with its large nucleus, the germinal …

Hsp56 protein and mRNA distribution in normal and stressed P. lividus embryos

It was previously demonstrated that Paracentrotus lividus Hsp56 mitochondrial chaperonin is con- stitutively expressed during development, that it increases after heat-shock and cadmium treatment, and that it has a specific territorial distribution, both in normal and heat-shocked embryos, as shown by immunolocalization experiments. In this work, we analyzed by Western blot the territorial distribution of the protein in plutei exposed to heat-shock or sublethal cadmium concentrations, and we found that Hsp56 increases in both ectodermal and en- dodermal cells. Moreover, by “in situ” hybridization, we looked at Hsp56 mRNA during normal development and under stress conditions. We found that th…

Cadmium accumulation induces apoptosis in P. Lividus embryos