INFREQUENT STRUCTURES IN CATTLE OOCYTES

Uncommon and controversial structures in cattle oocytes were studied i n dominant and subordinate follicles of unstimulated Bos taurus and ze bu (Bos indicus), and in FSH-stimulated B. taurus cattle, before or af ter administration of cloprostenol. Growing oocytes were very rare in follicles more than or equal to 5 mm in diameter. For the first time, special vesicles that may be involved in cortical granule synthesis we re observed. Classical rough endoplasmic reticulum was very rare in un stimulated oocytes, but was seen at superovulation. Vacuolation of the nucleolus was a common feature in dominant oocytes that were collecte d after cloprostenol injection, except in superovulated cattle. Annula te lamellae were very rare or absent in oocytes of B. taurus, while th ey were more frequent in zebu oocytes.