These can be placed over the embryo or adjacent to the embryo exactly as described in Subheading 3.1.1., but beads are also ideal for inserting into the embryo and were originally used for inserting into the anterior margin of the chick limb bud (27). In this case:
1. Window the eggs at the appropriate stage, e.g., stage 20.
2. Tear all the membranes above the limb bud. This is usually the right limb bud owing to the turning of the embryo, but not always.
3. With a tungsten needle, make a slit between the AER and the mesenchyme from the apex of the bud to the anterior margin.
4. Stretch the AER away from the mesenchyme to expand it, but do not break it.
5. With the AER pulled away with a needle, take a bead with a pair of fine forceps, place it into the gap between the AER and the mesenchyme, and release the AER. The bead will stay in place as the AER contracts.
6. Seal the eggs and replace in the incubator.
Was this article helpful?