Histopathology of mCMV-infected E15 + 6 SMGs. A, B. E15 + 6 SMGs have achieved the Terminal Bud Stage, consisting of ductal and terminal bud epithelia (e) which surround distinct lumina. The epithelial component is embedded in loosely-packed mesenchyme (m) sparsely populated by fibroblasts (arrows). C, D. E15 + 6 SMGs infected with 100,000 PFU mCMV exhibit a marked decrease in branching epithelia and greatly dilated lumina (*); clusters of large, basophilic, pleiomorphic cells, often with inclusion bodies (arrowheads), are seen in peripherally-localized mesenchyme (double arrows); centrally-localized cells retain their fibroblastic morphology (m). Bar: A, C: 100 μm; B, D: 20 μm.