Fig. 4

Histology of zebrafish at 4 days of development. Shown are transversal sections of zebrafish at 4 days of development stained with toluidine blue. At the one-cell stage, zebrafish embryos were either injected with a control morpholino (control) or with the cypher-MO (MO). a and b show a comparison of more anterior somites of control and MO injected embryos. Large lacunae (La) are shown within the compartments of skeletal muscle in cypher-MO injected zebrafish (b and j). Transversal sections through more caudal regions are shown in c and d, these show the more posterior somites. g and h sections show the heart, with markedly enlarged and thinned pericardium (pc) and the thinned ventricular wall (vw) in the cypher-MO injected embryos (h). g and h are not absolutely comparable in scale in order to be able to show the enlarged pericardium in h. Shown in e and f are higher magnification pictures (40×) of the ventricles of either control or MO injected embryos, respectively. The ventricular wall (vw) is marked and is thinned in the cypher-MO injected embryos (f) compared to the control (e). Higher magnification (100× oil emersion) pictures of the anterior somites shown ir MO injected embryos, respectively. The ventricular wall (vw) is marked and is thinned in the cypher-MO injected embryos (f) compared to tr MO injected embryos, respectively. The ventricular wall (vw) is marked and is thinned in the cypher-MO injected embryos (f) compared to tn a and b are shown in i and j. Large lacunae (LA) in the m