(A) Zymography showing gelatinase activity in tissue lysates from nonlesional (N) and lesional (L) lung tissue obtained from calves 6 days after challenge with M. haemolytica. Lysis bands representing both progelatinase A and B and activated gelatinase A (MMP-2) and B (MMP-9) are more prominent in samples from lesion areas of lung. (B) Densitometric analysis of zymography from lesion and nonlesion areas of lungs from six animals. Open bar, mean density (± SEM) of gelatinases in nonlesional tissue; filled bar, mean density (± SEM) of gelatinases in lesional tissue; *, significantly higher levels compared to nonlesional tissue for each enzyme (P < 0.05); †, significantly higher levels of progelatinase B than active gelatinase B in nonlesional tissue (P < 0.05); ††, significantly higher levels of progelatinase A than active gelatinase A in lesional tissue (P < 0.05). Gel, gelatinase; Pro Gel, progelatinase.