The ability of cells and
latex beads to become incorporated into the cranial region of embryos after microinjection into the amniotic cavity was studied. Premigratory neural crest cells isolated from the lateral margins of the neuroepithelium, 3T3 fibroblast cells or H35
hepatoma cells were labelled with
WGA-gold conjugates, and were then microinjected into the amniotic cavity of embryos with two to three somites in vitro.
Latex beads were similarly microinjected into different groups of embryos. Incorporation of injected cells or
latex beads was found in the neural crest of the midbrain and the hindbrain of 5-20% of the recipients 4 h after microinjection. At 6 and 12 h, increasingly more embryos (20-77%) were observed with labelled cells or
latex beads in the crest region. While
hepatoma cells and
latex beads were restricted to the crest region, injected neural crest cells and fibroblasts were also found in the lateral mesenchyme, bounded laterally by the surface ectoderm and medially by the closing neural tube. By 24 h after microinjection, the injected cells or
latex beads were found in 50-80% of the recipients. Neural crest cells and fibroblasts, which showed similar patterns of distribution in the embryos, were located on the dorsal aspect of the neural tube, the lateral mesenchyme, the pharyngeal arches and the regions for ganglia.
Hepatoma cells and
latex beads were limited to the dorsal regions of the neural tube. When microinjection was carried out in embryos with seven to eight somites, incorporation of cells or
latex beads was found in 44-75% of embryos, but no dispersion of the incorporated cells or
latex beads into the mesenchyme was found 24 h after microinjection. Incorporation and dispersion of cells and
latex beads were not observed when embryos with 18-20 somites were used as recipients. The present study showed that neural crest or fibroblast cells when injected into the amniotic cavity could be incorporated into the neural crest, and then undergo migration along the neural crest pathways, whereas
hepatoma cells and
latex beads could only be incorporated. The incorporation and migration of the exogenous tissues are related to the formation and the accessibility of the neural crest in the recipients.