FIG. 4.

Pathogenic and asymptomatic carrier isolates of H. somnus induce internucleosomal DNA fragmentation in bovine endothelial cells. Bovine pulmonary artery endothelial cells (5 × 10⁵) were incubated for 6 h at 37°C (5% CO₂) with H. somnus isolates (649, 8025, 2336, 127P, and 129Pt) at an MOI of 10:1 DNA (5 μg) was loaded into a 1.5% agarose gel as described in Materials and Methods. Lane 1, 200-bp DNA molecular weight marker; lane 2, DNA from untreated endothelial cells; lane 3, DNA from endothelial cells treated with 200 nM staurosporine (positive control); lanes 4 to 8, DNA from endothelial cells incubated with H. somnus isolates 649, 8025, 2336, 127P, and 129Pt, respectively. Note the presence of a DNA ladder in all of the H. somnus-treated samples and in the staurosporine control. These data represent one of three independent experiments that were performed.