Programmed cell death or apoptosis occurs in many tissues during normal development and in the normal homeostasis of adult tissues. Apoptosis also plays a significant role in abnormal development and disease. Increased interest in apoptosis and cell death in general has resulted in the development of new techniques and the revival of old ones. Each assay has its advantages and disadvantages that can render it appropriate and useful for one application, but inappropriate or difficult to use in another. Understanding the strengths and limitations of the assays would allow investigators to select the best methods for their needs.

Apoptosis peaks within the cardiac outflow tract (OFT) myocardium during chick development (stage 30-31) and coincides with dramatic remodeling of the OFT 4. Apoptosis was assayed by TUNEL, Annexin V, transmission electron microscopy, and Lysotracker Red (Fig. 1-4). These assays reveal that as many as 92% of the apoptotic cells express cardiomyocyte markers. The timing of apoptosis suggests that it may occur to allow proper alignment of the great vessels over their respective ventricles. Our current aims are to determine the consequences of disturbing OFT cardiomyocyte cell death to heart morphogenesis and to elucidate the cellular and molecular components that initiate and regulate this high level of apoptosis.To enhance apoptosis in the OFT myocardium, recombinant adenoviruses were injected into the pericardial space to deliver the gene for the death ligand Fas-L to the cardiomyocytes of chicken embryos prior to the stages when OFT remodeling occurs.