Images labeled with facpia are Ptk2 rat kangaroo endothelial cells stained with fluorescein phalloidin (to stain actin filaments) and propidium iodide (to stain DNA and chromosomes).  PtK cells are tissue culture cells used in the study of mitosis because they do not round up, but remain relatively flat in tissue culture when undergoing mitosis. First image: metaphase spindle showing one section through the middle of the spindle showing actin filaments associated with chromosomes.  Second image: same spindle, but with a second fluorescein section approximately 5 mm below the first added to the image to show the actin filaments in the cells near the substratum.  Dr. Matthew J. Schibler, Carol Moss Spivak Cell Imaging Facility, UCLA Brain Research Institute.