Formation of new plasma membrane during the first cleavage cycle in the egg of Xenopus laevis: an immunocytological study.

Polyclonal antibodies (IS1) reacting specifically with plasma membrane proteins of the Xenopus oocyte were used to study the formation of new plasma membrane in cleavage furrows. Membrane precursors were detected in the inner cytoplasm, then under the plasma membrane of the animal hemisphere and finally on the furrow's edges. Cycloheximide and colchicine caused abnormal distribution of stained material. IS1 antibodies conjugated to colloidal gold, were used to examine the local insertion of membrane precursors into the furrow region by electron microscopy. Membrane precursors were only detected in intracytoplasmic vesicles that fused with the plasma membrane at the edges of the furrow walls. Arrays of microtubules may guide membrane precursors to the site of their insertion in the furrow walls.