A comparison of two methods of preparing cells or nuclei for high-resolution microspectrophotometry

Suspensions of isolated mouse thymus cells were subjected to two preparative methods: either they were dropped through several mm of 9:1 v/v ethanol-acetic acid fixative, allowed to stand for 1hr and then processed for staining; or they were fixed, passed through a graded ethanol series to 70% ethanol, centrifuged on to slides in a modified Shandon cytocentrifuge and then carried wet into the staining procedure. All preparations were stained by the Feulgen reaction and evaluated by high-resolution microspectrophotometry. While the two preparative procedures yielded similar results, there appeared to be less variability in the data obtained from the centrifuged cell populations.