Fig. 2. Flow cytometric analysis of FITC-Annexin V-PI stained hemocytes incubated in the presence of 1 µM NA for 0, 6, 12 and 24 hours. Region R1 includes viable cells, which excude PI and are negative for FITC-Annexin V binding. Region R2 includes apoptotic cells, which are FITC-Annexin V positive but impermeable to PI, and region R3 includes non-viable, necrotic or late apoptotic cells, which are positive for FITC-Annexin V staining and for PI uptake. The number of apoptotic cells increases over time and reaches about 16% of the total number of cells after 24 hours of exposure to 1 µM NA. One representative experiment out of three is shown.