UV light photography of microvascular EC stained with DAPI/sulforhodamine. Microvascular EC of pulmonary and dermal lineages were exposed to a 1:100 dilution of normal plasma or plasma from individuals with childhood/diarrhea-associated HUS or TTP for 18 hours. Cells were harvested and stained with DAPI and sulforhodamine 101, as described in the text. Apoptotic cells show DNA in two compartments: intense blue staining of fragmented nuclear material, (or apoptotic bodies) and dispersed DNA outside of the nucleus, inferred from the uniformity of the blue or violet (red/blue) hue of the cytoplasm. In contrast, intact cells show red cytoplasmic staining, with uniformly blue nuclei.