CONFOCAL SCANNING LASER MICROSCOPY OF THE FOLLICULAR EPITHELIUM IN OVARIOLES OF THE STICK INSECT CARAUSIUS-MOROSUS

Ovarian follicles of the stick insect Carausius morosus were analyzed by confocal laser microscopy and immunocytochemistry with a view to st udying cell polarity in the follicular epithelium. Such probes as anti -alpha-tubulin antibodies and Rh-phalloidin were employed to establish how the follicle cell cytoskeleton changes during ovarian development . Data show that alpha-tubulin prevails over the basal end, while F-ac tin appears more abundant along the apical end of the follicle cells. This finding was further corroborated by immunogold cytochemistry, sho wing that label along the basal end is primarily associated with micro tubules, while that along the apical end is due to follicle cell micro villi interdigitating with the oocyte plasma membrane. A monoclonal an tibody specifically raised against a vitellin polypeptide was used to investigate the role the follicular epithelium might play in relation to vitellogenin (Vg) uptake by the oocyte. Data show that under these conditions label is restricted to the intercellular channels of the fo llicular epithelium, thus providing further support to the notion that Vg enters the oocyte through the extracellular pathway leading from t he basement lamina to the oocyte surface. By contrast, the use of a mo noclonal antibody raised against a fat-body-derived protein of 85 kDa that is specifically sulfated within the follicle cells provides evide nce for the existence of an alternative way of gaining access to the o ocyte surface, that is by transcytosis through the follicular cell epi thelium. These findings confirm our earlier observations on stick inse ct ovarioles whereby polarization in the follicular epithelium is prim arily addressed to sustain a transcytotic vesicular traffic between op posite poles of the follicle cell of Vg toward the oocyte surface.