Dose-dependent effect of mCMV-infection on embryonic SMG development. E15+6 SMGs infected with 10,000 PFU mCMV (A) exhibit modest β-gal staining (viral presence) in the periphery, whereas SMGs infected with 50,000 PFU mCMV (B) exhibit staining almost completely throughout the gland. No β-gal staining is seen in control (CONT) SMGs. Bar:50 μm C. Relative to controls, there are significant (P < 0.01) declines in the size of mCMV-infected SMGs (as measured by area); this decline is dose dependent (P < 0.01). Comparisons of control and infected SMGs were based on matched pairs (right v. left in the same embryo). Samples sizes for each bar ranged from 6 to 29 matched pairs. True differences were determined by matched-pairs t-test. See text for details.