Prostaglandin F2α Causes Fast Degenerative Changes in Ovulated Mouse Oocytes.

The effects of prostaglandin F2α on the cytoskeleton and membrane organelles of oocytes was investigated by culturing ovulated mouse oocytes in its presence (50 or 100 ng/ml) for 3 h. Tubulin, fibrillar actin, membranes and chromatin were visualized by specific antibodies, phalloidin, lipophilic dye DiOC6 and Hoechst 33342, respectively. Control oocytes were characterized by a meiotic spindle with chromosomes aligned at its equator, and a cortical layer of microfilaments with an actin cap. Intracellular membranes were localized mostly in the central region in metaphase I and in a broader volume, but still excluding the cell periphery, in metaphase II, and were slightly concentrated around the chromosomes. In oocytes treated with 50 ng/ml prostaglandin, cortical actin staining was diminished, the membrane distribution was clustered, and chromosomes showed signs of misalignment despite the apparently preserved spindle. In cells treated with 100 ng/ml prostaglandin, both the spindle and the actin cortex had degenerated or disappeared as microscopic objects. Metaphase plates were on average broader and more disorganized than in the 50 ng/ml group, and the distribution of membrane organelles had become uniform. These effects, to our knowledge observed for the first time, did not require presence of the cumulus during the incubation. They could be regarded as acceleration of the oocyte postovulatory aging, in which cytoskeletal deterioration seemed to have a leading role.

Dynamics of Lamins B and A/C and Nucleoporin Nup160 during Meiotic Maturation in Mouse Oocytes.

This study was aimed at elucidating the fate of three important nuclear envelope components - lamins B and A/C and nucleoporin Nup160, during meiotic maturation of mouse oocytes. These proteins were localized by epifluorescence and confocal microscopy using specific antibodies in oocytes at different stages from prophase I (germinal vesicle) to metaphase II. In immature germinal vesicle oocytes, all three proteins were detected at the nuclear periphery. In metaphase I and metaphase II, lamin B co-localized with the meiotic spindle, lamin A/C was found in a diffuse halo surrounding the spindle and to a lesser degree throughout the cytoplasm, and Nup160 was concentrated to the spindle poles. To our knowledge, this is the first report on nucleoporin localization in mammalian oocytes and the first successful detection of lamins in mature oocytes. While the distribution patterns of both lamins closely paralleled the respective stages of mitosis, Nup160 localization in metaphase oocytes corresponded to that in mitotic prometaphase rather than metaphase. The peculiar distribution of this nucleoporin in oocytes may reflect its role in meiosis-specific mechanisms of spindle assembly and its regulation.

[Investigation of cytokeratin and vimentin intermediate filaments in polycystic ovaries (PCOS) -- presence and specific structure of Balbiani body in primordial follicles].

Despite of the importance of cytoskeletal proteins for ovarian function and pathology, very few studies have addressed the presence and distribution of these proteins in polycystic ovaries. We investigated sections of human polycystic ovarian tissue for vimentin and a set of cytokeratins by epifluorescence. The studied proteins showed strong colocalization. Positive reaction was detected in two main ovarian compartments: with weak intensity in follicular cells and very strong in perinuclear position in oocytes of primordial follicles. Epifluorescent study of the oocytes from primordial follicles allowed us to identify the immunopositive structure in oocytes as Balbiani body, a transient organelle responsible for establishing oocyte polarity and ooplasm gradients in nonmammalian vertebrates. Our results suggest functional interaction of different types of cytoplasmic intermediate filament proteins in polycystic ovaries and a possible importance of the Balbiani body for human oogenesis in norm and pathology.