Fig. 5.

Inhibiting protein tyrosine phosphatases (PTPs) with PAO stops loss of multidrug efflux transport activity in the micromeres. (A) Relative amount of intracellular calcein of the sea urchin micromeres compared with the rest of the embryo [n=3×≥10 (batches × embryos), ±s.e.m.] during treatment with inhibitors of transcription (ActD), Golgi traffic (BfA), endocytosis (CdCl₂ and PAO) and exocytosis (Wort). Asterisk indicates values significantly different from control (ANOVA, P≤0.5). Treatment with PAO stops the loss of multidrug efflux, and postponing PAO treatment until 50 minutes after the appearance of the micromeres does not stop the loss of efflux transport [PAO (50)]. (B) Representative MIPs of calcein accumulation in embryos treated with DMSO, PAO and PAO (50). (C) MIPs showing the cumulative amount of rhodamine dextran and CTB-positive endosomes in micromeres and macromeres for embryos treated with DMSO or PAO for 80 minutes after their appearance. Scale bars: 10 μm.