PROBLEMS CONCERNING THE QUALITY OF DNA MEASUREMENTS ON FEULGEN-STAINED IMPRINTS - A STUDY OF 5 FIXATION TECHNIQUES

Feulgen-stained mt liver imprints were investigated, and hepatocytes, lymphocytes and granulocytes were measured. Additionally, chicken eryt hrocytes placed on the slides were measured as an external DNA standar d. The imprints were treated according to five different fixation prot ocols. The measured integrated optical density (IOD) was normalized ac cording to the leukocytes and afterwards scaled according to the diplo id hepatocytes. The mean IOD, coefficient of variation (CV), standard error of the mean (SEM) and IOD ratios of distinct cell groups were ca lculated. The CV of the IOD for hepatocytes was slightly better for ai r-dried preparations. If was larger for leukocytes than for hepatocyte s and worst for chicken erythrocytes. The SEM of hepatocytes did not s how remarkable differences between the fixation groups; in general it was near 1%. In all cases the IOD ratios of 2c, 4c and 8c hepatocytes reasonably well followed the expected ratio of 1 : 2:4 except for wet, formalin-fixed hepatocytes (3.8). Tire ratios of leucocytes to 2c hep atocytes were about 1.0 for air-dried preparations but considerably lo wer (0.85) for wet fixation in formalin. The IOD ratios of chicken ery throcytes to 2C hepatocytes varied from 0.33 to 0.35. Tire deviation o f the ratios of single specimens from the estimated mean of a fixation group are described.