Transformation of follicular epithelium during the previtelogenesis in the Ceratophrys cranwelli

LEONARDI, SOFÍA; VILLECCO, EVELINA; SÁNCHEZ, SARA

Tafi del Valle, Tucumán

Congreso; XXI Annual Scientific Meeting of Tucumán Society Biology; 2004

Asociación de Biología de Tucumán

In the follicles previtellogenic of C. cranwelli ovaries, the follicle cells-oocyte interactions are intense. The follicular epithelium shows two types of cells, one of them displays utrastructural features indicative of synthetic activity, including large amounts of free ribosomes, glycogen, rough endoplasmic reticulum and particle-filled vesicles. Autoradiographic study with [3H]adenosine showed that they are involved in an intense synthesis of RNA. Ultrastructural observations, pulse-chasse experiments and ultrastructural RNA localization with RNase-gold complexes showed that particles of ribonucleoprotein are transferred to the oocyte, which incorporates them into cortical vesicles. In the late previtellogenic follicles, these cells undergo regression showing the typical features of apoptosis: the shrinkage of the nucleus and cytoplasm, the condensation of chromatin, blebbings of the nuclear membrane and an extensive vacuolization of the cytoplasm. The nucleases are activated and consequently DNA fragmentation occurs, revealed by in situ nick translation technique (TUNEL). This nuclear material is engulfed by the oocyte and in the cortex appear apoptotic bodies among the cortical vesicles. The results indicated that during previtellogenesis, some follicular cells regress via apoptosis transfering to the oocyte RNA and DNA.