Ascaris oocytes: ultrastructural and immunocytochemical changes during passage through the oviduct

Slender, bipolar, immature, Ascaris suum oocytes assume a smooth, spherical configuration as they traverse the oviduct. The present investigation was conducted to determine if this morphological alteration might be accompanied by changes in surface membranes. Immunocytochemical studies were conducted utilizing (1) fluorescein-labeled, sheep, anti-rabbit IgG, (2) Sternberger's unlabeled, antibody-enzyme technique, (3) ferritin-labeled, sheep, anti-rabbit IgG, and (4) an immunobead, labeled-antibody technique. These procedures clearly demonstrated that the surface of both immature and mature oocytes possessed different specific antigens. It is assumed that this acquisition of new antigens (or the loss of older ones) by the mature oocyte is somehow related to a conditioning phenomenon which prepares the oocyte for fertilization.