Fig. 5

Putative MAPK-P and T4-binding site distribution in Strongylocentrotus purpuratus gastrulae. Gastrulae were exposed for 90 min prior to fixation. Gastrulae were stained with Hoechst 33342 (blue; nuclei), rhodamine-conjugated T4 (red; T4-binding sites), and an antibody for phosphorylated MAPK (green, P-MAPK). Fluorescent debris exterior to gastrula was removed. A T4 increases MAPK intensity in S. p. larvae (n = 4, p < 0.05; significant differences exist between cell types with no shared letter). This effect may be partially inhibited by RGD peptide (p < 0.05). The increase in MAPK phosphorylation is present in PMCs, but not SMCs or the coelomic pouch (n = 4, p < 0.05). Both SMCs and the coelomic pouch presented with a high degree of MAPK phosphorylation in both the T4-exposed and control groups. B Maximum intensity projection of confocal fluorescent image of S. p. gastrula. C–C‴ Focal slice of gastrula showing primary mesenchyme cells (PMCs) and lower archenteron. Arrowheads (▶) PMCs. PMCs display greater T4 binding and MAPK phosphorylation than surrounding cells. Ventrolateral clusters have formed (vlc). D–D‴ Focal slice of gastrula showing tip of the archenteron and developing coelomic pouches, as well as secondary mesenchyme cells (SMCs). Arrowheads (▶) identify SMCs. SMCs and the coelomic pouches display greater MAPK phosphorylation than surrounding cells. T4 binding is slightly elevated in regions near the tip of the archenteron and small protein clusters in SMCs. c: Coelomic pouch, ar: Archenteron (gut), pmc: primary mesenchyme cells, smc: secondary mesenchyme cells, vlc: ventrolateral cluster