Figure 5

Sequential stages of the oocyte-nest assembly and Balbiani body formation. A) A group of primary follicles in various stages of formation. Note adjacent venule (v). B) Early stage (see arrow in A) shows the oocyte during entrance into the CK+ (brown color) nest with nest wall (w) and inverted "gates" (g). Cytokeratin+ material appears to enter the nucleus (black arrowhead) and traces (white arrowhead) are visible around the nucleolus (x). Note a lack of Balbiani body. C) More advanced stage (white arrow in A) shows the oocyte nucleus (dotted line) adjacent to the nest wall (just opposite to the closing gate), embraced by intraooplasmic extensions (arrows). The Balbiani body (asterisk) appears to reside within the nucleus (dotted line), and small proportion of the ooplasm (dashed line) is still outside of the complex. D) Completed formation of primary follicle (arrowhead in A) shows closed gate ('g'), CK+ Balbiani body at the opposite side, adjacent to the nest wall, oocyte nucleus free of CK staining, and a single CK+ intraooplasmic extension (arrow) from the nest side. A follicle top (ft) from an adjacent follicle is also visible. CK18 immunostaining, hematoxylin counterstain.