A and B show human aortic smooth muscle cells that were incubated with LDL that had been given a net positive charge by covalent linkage with N,N-dimethyl-1,3-propanediamine. After 19 days in culture, the cells were examined either with polarizing microscopy (A) or stained with oil red O and hematoxylin (B). Note that the smooth muscle cell in A shows inclusions that exhibit birefringence with typical formée crosses indicative of liquid crystals of cholesteryl esters as shown in the inset. Parallel dishes of cells incubated with native LDL in the same experiment showed no birefringence and no oil red O staining. Original magnification: ×525 (A); ×3,520 (A, inset); ×600 (B). C and D show the pale color and fat-laden histology of the enlarged fatty liver from a mouse expressing a transgene encoding the nuclear form of SREBP-1a. The liver sample in D was stained with Sudan IV, which stains fatty inclusions orange. Original magnification, ×378.