[Nuclear structures at late stages of Rana temporaria oogenesis. II. Autoradiographic data]

Seasonal dynamics of RNA synthesis in the nuclei of 3rd year vitellogenetic oocytes of Rana temporaria has been studied by autoradiography. The nucleoli and chromosomes exhibit the highest level of RNA synthesis in summer, when lampbrush chromosomes are well developed, and multiple nucleoli start moving away from the nuclear membrane. The weakening of RNA synthesis is observed in autumn, when the nuclear structures assemble in the centre of the nucleus to form the karyosphere. The synthesis level is the lowest in winter, and increases in spring. The karyosphere of Rana temporaria is involved in protein metabolism of oocytes. Possible reasons of the seasonal RNA synthesis dynamics by the oocyte nuclei are discussed.