The University of Toledo

Vickers M85 Microdensitometer

The Vickers M85 Microdensitometer remains the most accurate instrument ever built for the measurement of the DNA content of single cells fixed onto slides. The nuclei of the cells to be studied are specifically stained for DNA by the Feulgen reaction. The Vickers instrument makes 50,000 point absorbance measurements over each individual nucleus with a 0.2 μm scanning spot in 5 seconds. The light wavelengths and optical settings of the measurements are selected to minimize glare and refractive errors. The separate point measurements are integrated to determine the cellular DNA values.

This microscope has been in continuous use since 1978 and has provided data for 33 basic science publications, including (1) The definitive technical papers on how to measure cellular DNA content with absorption cytometry; (2) The first reports that cancer-cell DNA synthesis varies according to tumor growth conditions and (3) The effects of tumor-cell DNA content on the survival of pancreatic cancer patients.

Non-DNA synthesizing cells in white and cells making DNA in black.	Feulgen stained autoradiograph of normal and DNA synthesizing cells (black dots).