Formation of the chick heart is initiated when paired regions of the mesoderm migrate to a specific region in the primitive head. Certain cells eventually form a pair of endocardiac tubes that become the lining of the heart, while the remaining precardiac mesoderm ultimately differentiates into the myocardium. Fibronectin is suspected as a crucial component of the migratory process. Very few investigations have been conducted on the relationship between cell motility and microgravity.

The primary objectives of this investigation were to determine the effect of altered gravity on the production and distribution of fibronectin, an extracellular matrix glycoprotein, during embryonic development of the chick heart, and to ascertain the extent to which these alterations affect myogenesis or morphogenesis. A microgravity bioreactor vessel, originally designed by NASA as a low-shear culture system, was employed to culture the cellular expiants in a simulated microgravity environment. Fertile, White-Leghorn chicken eggs were incubated at 38°C for 32 hours in a humidified egg incubator.