Maturation competence and chromatin behaviour in growing and fully grown cattle oocytes.

Chromatin configurations of cattle oocytes from different follicle sizes were classified in three chromatin categories. Early diplotenes, dictyate-like structures, more progressed diplotenes and early diakinesis and metaphases were found. In follicle group A (0.4-0.9 mm) immature diplotenes predominated (82.3%), and a rather low maturation competence was observed (12.1%). With increasing follicle size the maturation competence was improved to 47.8% metaphases II in follicle group C (3-8 mm). Impressive CMA3 positive blocks were visualized especially in early diplotenes. Heterochromatic CMA3 positive clusters surrounded the nucleolus.