Based on their chromatin organization, antral oocytes can be classified into two classes, namely surrounded nucleolus (SN, chromatin forms a ring around the nucleolus), and not surrounded nucleolus (NSN, chromatin has a diffuse pattern). Oocytes of both classes are capable of meiotic resumption, but while SN oocytes, following fertilization, develop to term, NSN oocytes never develop beyond the two-cell stage. A recent study has shown that the position of the germinal vesicle (GV) can be used as a morphological marker predictive of oocyte meiotic competence, i.e. oocytes with a central GV have a higher meiotic competence than oocytes with an eccentric GV. In the present study, we have associated both markers with the aim of identifying, with more accuracy, the oocytes' developmental competence. Following their isolation, antral oocytes were classified on the basis of both SN and NSN chromatin configuration and their GV position, matured to metaphase II and fertilized in vitro. We demonstrated that the position of the GV is a good marker to predict the oocytes' developmental competence, but only when associated with the observation of the chromatin organization.
Michele Bellone, Maurizio Zuccotti, Carlo Alberto Redi and Silvia Garagna
Valeria Merico, Juan Pablo Luaces, Luis Francisco Rossi, Paola Rebuzzini, Maria Susana Merani, Maurizio Zuccotti and Silvia Garagna
In nature, mammalian seasonal breeders undergo spermatogenetic arrest during the non-breeding season. In the large hairy armadillo Chaetophractus villosus, testis regression initiates with immature post-meiotic germ cells sloughing into the tubule lumen and continues with the death of the remaining spermatocytes. At the end of the regression period, only spermatogonia and Sertoli cells persist in the seminiferous epithelium. It has been suggested that cell sloughing is determined by changes in the adhesion complexes between Sertoli cells and spermatids, which are mediated by low intra-testicular testosterone levels. By immunofluorescence and Western blotting we studied key proteins of the N-cadherin/N-cadherin and A6B1-integrin/laminin interlocks that contribute to the complex Sertoli/spermatid adhesion system throughout the eight stages of the seminiferous epithelium cycle in the comparison between active and regressing testes. In active testis, B1-integrin, laminin G3, N-cadherin, B-catenin, P-B-catenin-Tyr654, FAK, P-FAK-Tyr397, SRC, P-SRC-Tyr416 proteins present a spermatogenetic cycle-dependent localisation pattern, unmaintained in regressing testes. In the latter, quantitative variations and changes in the phosphorylation state of protein FAK, SRC and B-catenin contribute to the disassembly of the N-cadherin/N-cadherin and A6B1-integrin/laminin interlocks, thus promoting the massive release of immature spermatids.