Folding stages

At 16 h post the initial culture, use 10% oxygen to gas the embryos that were at late head fold stage at the beginning of the culture use 20% oxygen to gas the embryos that had achieved somite stage when put into the culture. 

Fig. 12.3. Stages in the development of the chick embryo, (a) Blastoderm before invagination of the mesoderm, (b) Blastoderm after the formation of the primitive streak and Henson s node, mesoderm cells forming from the epiblast. (c) Neural fold stage, (d) Differentiation of the somites into sderoderm, myotome and dermatome.

Exencephaly and associated eye defects were edso observed in rat embryos surviving culture in vitro for 48 h on serum from cadmium-treated rats. Since the embryos were explanted at head-fold stage, the culture test period overlapped with the gestational ages challenged in the in utero studies reported by Barr. Exencephaly was not seen in the in utero studies, but eye... 

Neural plate stage Neural fold stage... 

V (the potential) is identified with the enthalpy, i.e. the number n of base pairings (contacts), and T corresponds to the entropy. At each stage in the folding process, as many as possible new favourable intramolecular interactions are fonned, while minimizing the loss of confonnational freedom (the principle of sequential minimization of entropy loss, SMEL). The entropy loss associated with loop closure is (and the rate of loop closure exp... 

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