Annals of the New York Academy of Sciences, Vol 442, Issue 1 251-264, Copyright © 1985 by New York Academy of Sciences
The origin and distribution of cortical granules in human oocytes with reference to Golgi, nucleolar, and microfilament activity
A. H. Sathananthan, S. C. Ng, C. M. Chia, H. Y. Law, W. R. Edirisinghe and S. S. Ratnam
The origin and distribution of cortical granules were investigated in human
preovulatory oocytes at various phases of maturation. Twenty-five oocytes
obtained from unstimulated small antral follicles and from stimulated large
antral and mature follicles were examined by transmission electron
microscopy. Ovarian stimulation in women was accomplished by administering
Clomid followed by hMG or hCG or both. Small antral follicle oocytes were
dissected from ovarian biopsies, while the other oocytes were recovered by
laparoscopy. Some oocytes were allowed to mature in Ham's F-10 or
Whittingham's T-6 media before routine fixation in glutaraldehyde/osmium.
Cortical granules originate from typical, hypertrophic Golgi complexes
during early maturation and continue till its completion. Evidently there
are two waves of cortical granule synthesis, the first more prolific than
the second. The first occurred in small antral follicle oocytes, when there
was a peak in Golgi activity, and the second was observed at the germinal
vesicle stage, particularly at the onset of resumption of meiosis. Golgi
complexes became progressively scarce as oocytes completed first
maturation. Golgi membranes were also involved in the formation of
lysosomes. A well-defined band of microfilaments was detected in small
antral follicle oocytes which seemed to prevent the cortical granules,
organized in a single layer, from migrating to the periphery. This band
gradually became disorganized at the germinal vesicle stage as oocytes
resumed meiosis, when cortical granules were apparently migrating to the
surface. Metaphase I and mature oocytes had one to three discontinuous
layers of cortical granules beneath the oolemma. The general organization
of oocytes was also investigated and the roles of the nucleolus and
endoplasmic reticulum in relation to Golgi activity and cell secretion were
discussed.
