The fate and role of macromolecules synthesized during mammalian oocyte meiotic maturation . I . Autoradiographic topography of newly synthesized RNA and protein in the germinal vesicle of the pig and rabbit

a more advanced stage of this process in vitro or in vivo. Some oocytes were maintained thereafter in a cold medium to trace the metabolism of the labelled protein. In addition to uridine3Hincorporation into the nucleolus and nucleoplasm, during pig oocyte maturation it was found that an intensive RNA synthesis site appeared in association with condensing chromocentres of the GV II. A considerable proportion of oocytes from slaughterhouse material did not show intensive GV activity in RNA synthesis during maturation in vitro. In the pig and rabbit oocyte it was shown that the newly synthesized 3Hlysi nelabelled protein accumulated to a high degree in the GV and in the nucleolus. The labelled protein accumulated in the GV up to the stage of GV IV (pig) and persisted during the chase period in the ooplasm ; it was found to be associated with chromosomes of metaphase I (pig) or metaphase II (rabbit) of the meiotic division. The process of protein accumulation in the GV was not influenced by meiotic arrest during oocyte culture in autologous follicular fluid. A similar accumulation of the label in the GV was detected in oocytes which were cultured in a medium enriched by 35 S-methionine.