Causes of windowing-induced dysmorphogenesis (neural tube defects and early amnion deficit spectrum) in chicken embryos.

Previous reports suggest that windowing the shells of chicken eggs during the first day of incubation frequently results in dysmorphogenesis of the central nervous system. We report here data that further delineate the neural tube defects associated with this animal model. In addition, we describe another birth defect syndrome associated with windowing: the early amnion deficit spectrum (EADS). Several components of the egg are altered structurally by windowing: the shell, outer and inner shell membranes, yolk, and air space at the blunt end of the egg. A new air space is formed over the embryo as the original one at the blunt end is obliterated. A series of studies (pH, oxygen and carbon dioxide tensions, relative humidity, temperature, and deformation of the yolk documented with magnetic resonance imaging) examining individual steps of the windowing procedure and additional techniques that stimulate windowing suggest that mechanical stress causes isolated neural tube defects and dehydration causes amnion defects. These amnion defects are associated with other embryonic abnormalities suggestive of deformations consistent with EADS.