Polysaccharide Complexes in Full-Grown Oocytes of the Newt, Pleurodeles, and Changes in their Distribution During Progesterone-Induced Maturation

Immature full-grown oocytes of Pleurodeles waltlii contain large amounts of small electron-dense polysaccharidic granules. These granules lack a limiting membrane, and have a dense but heterogeneous matrix and an apparent diameter of 24–36 nm. Their structure, organization and distribution strongly suggest that they are glycogen granules. On the other hand, mature oocytes both after oviposition or 22–24 hr after in vitro progesterone stimulation contain no polysaccharide granules or complexes. During the first 9–10 hr after hormonal stimulation, granules were abundant and present both individually and as large strands occupying most of the space between the organelles. Granules were frequently found packed together and arranged in regularly arrayed stacks within large subcortical ant cortical vacuoles. Between 4 and 6 hr after progesterone addition, oocytes released the contents of vacuoles to the outside. Between about 11 and 14 hr after progesterone addition, oocytes still contained large amounts of polysaccharide complexes, but the vacuoles were empty. From about 15 hr after progesterone treatment until the end of maturation, the complexes progressively disappeared from the cytoplasm, coincident with the detachment of the follicle cell layer from the oocytes and a reduction in the number and size of microvilli.