Nucleolar changes in the oocytes of newborn rats treated with follicle stimulating hormone (FSH)

: In the ovaries of newborn rats the exogenous follicle stimulating hormone (FSH) given in a large dose leads to the appearance of uncommon structures in the nucleoli of the oocytes. Fuzzy filaments sometimes with chiasma-like connections appear and ring-like structures in connection with, or independent of, the nucleoli are seen. The results demonstrate the possible appearance of a morphological response of oocytes to FSH prior to any detectable biochemical or receptor binding evidence.