Hormonal control of differentiation at a biochemical level is exemplified by studies on amphibian and insect metamorphosis. However, Hinni & Watterson (1963) have reviewed the literature and presented new data on another developmental system with potential for analysis of hormone action. Chicken embryos at 33–36 h of incubation can be ‘hypophysectomized’ by partial decapitation, the prosencephalic and anterior part of the mesencephalic areas being removed. Absence of the pituitary primordium prevents the formation of a pituitary gland. Such embryos that continue to develop are noticeably smaller and show retardation in the development of bones, feathering, and several epithelial structures by 2 weeks of incubation. These ‘hypophysectomized’ embryos have an increased mortality, especially in the third week of incubation; the few that escape this ‘phenocritical period’ never hatch and remain in ovo days after the normal time of hatching.
Huntingtin regulates Ca2+ chemotaxis and K+-facilitated cAMP chemotaxis, in conjunction with the monovalent cation/H+ exchanger Nhe1, in a model developmental system: Insights into its possible role in Huntington׳s disease