A Quantitative Study of the Cytoplasm of Ascites Tumour Cells in Mice

Abstract

ABSTRACT This paper describes how a combination of microspectroscopy and interference microscopy has been used to investigate the composition of the cytoplasm of fresh ascites tumour cells of mice. The accuracy of the microspectroscopic method will be very dependent on the standard absorption curves used (i.e. results obtained from dilute nucleic acid and protein solutions of known concentration), and particular attention has therefore been given to this aspect of the investigation. Thus, the standard protein absorption curve has been derived in two ways, first from a certain assumed amino-acid composition, and secondly by a method involving the optical density and refractive index of the ascitic fluid itself. Both methods are shown to result in similar cellular analyses. The cytoplasm of the ascites cell can be divided broadly into two regions—a granular zone of comparatively low ultra-violet absorption, and a peripheral region possessing greater absorption, but with little structure visible by the optical microscope. Absorption measurements at 257 and 275 mμ show that, despite the difference in ribonucleic acid content in these two regions, the protein concentrations are approximately the same. For comparison with these microspectroscopic results, optical retardations have been measured in the identical regions of the same ascites cells. Total dry mass concentrations, evaluated interferometrically, were found to be in good agreement with the sum of the nucleic acid and protein weights, these being obtained from the ultraviolet results. This indicates that the ultra-violet absorption of the cytoplasm of the fresh ascites cell is not grossly different from that to be expected from its extracted nucleic acid and protein components. It is stressed that the material used in this investigation was in many ways suitable for quantitative absorption measurements and equally consistent results should not be expected from all other types of cells, particularly those measured after fixation rather than in a fresh condition.