Fig. 11

RGD inhibits the effect of T4 in Pisaster ochraceus larvae. T4 binds to gut and somatocoel in P. o. larvae. Larvae were exposed for 90 min prior to fixation. Exposure to T4 increases MAPK phosphorylation in the midgut and somatocoel. Larvae were stained with Hoechst 33342 (blue; nuclei), rhodamine-conjugated T4 (red; T4-binding sites), and an antibody for phosphorylated MAPK (green, P-MAPK). Exposure to T4 and RGD peptide increases binding locations for T4 in the midgut. Arrowheads (▶) indicate T4 binding or MAPK phosphorylation in the gut wall. Arrows indicate T4 binding or MAPK phosphorylation outside the gut wall. A-A′′ Control larva, from left to right: Combined image, T4-binding sites, MAPK phosphorylation. T4-binding locations are visible in and adjacent to the gut. B-B′′ T4-exposed larva, from left to right: Combined image, T4-binding sites, MAPK phosphorylation. T4-binding locations are visible in and adjacent to the gut, especially adjacent to the somatocoel. Regions of increased MAPK phosphorylation correspond roughly with T4-binding sites. C–C′′ RGD and T4-exposed larva, from left to right: Combined image, T4-binding sites, MAPK phosphorylation. T4-binding sites are present in the gut wall, but effects of T4 on MAPK phosphorylation are reduced. There is an increase of T4-binding sites in RGD-exposed larvae. s: Somatocoel. Gut: midgut