β-Gal activity is retained in platelets of the inducible Tet-on/off double-transgenic mouse model. (A) β-Galactosidase expression in platelets. To demonstrate the feasibility of retaining the expression of transgenes (β-gal in this case) after megakaryocytes fragmented into platelets, we isolated platelets from plasma of double-transgenic mice with Tet-on/off conditions along with age- and sex-matched wild-type mice. Shown are phase-contrast micrographs at × 60 objective of platelets stained for β-galactosidase activities. (B-C) Usage of the double-transgenic model (PF4-tTA-VP16/CMV–Aurora-B/β-gal no. 41/42) to trace platelets at sites of accumulation. Identifying and quantifying platelet accumulation at sites of injury or stress is a goal common to various experimental pursuits. As a model system, we used endotoxic shock using LPS injection as detailed in “Materials and methods.” Shown are livers, lungs, and spleen stained for β-gal activity. Whole tissues (B) as well as tissue sections (C) (spleen and liver shown as representatives) displayed accumulated platelets. Thin sections were stained only with eosin and visualized by light phase contrast; × 60 original magnification. Arrows indicate areas of platelet accumulation. Images were captured using an Olympus ×70 microscope with Hamamatsu CCD camera C4742-95. Images were acquired with Openlab 3.1.2 software.