Fig. 4. ADA activity of salivary homogenates of P. duboscqi. A cuvette containing 20 µM adenosine in PBS was scanned at 3 min intervals for 30 min following addition of salivary homogenate equivalent to 0.2 pairs of salivary gland from P. duboscqi (A) and P. papatasi (B). (C) Differential spectra of the data in (A) obtained by subtracting each scan from the scan at time zero. The arrows indicate the direction of change of the spectrum over time.