[Quantitative limits of the Feulgen reaction: analysis of interference caused by dehistonization and denaturation and renaturation treatments].

The Feulgen reaction intensity (measured with a microdensitometer Vickers M86 on the nucleus of erytrocytes of Xenopus laevis Daud.) is increased after dehistonization according to Brody (1974) only if the dehistonization is made before the fixation in acetic acid. The denaturation and renaturation treatments which should act specifically on the screws of the DNA and therefore should not affect the Feulgen reaction, act in a specific manner, probably going away another histonic components. On the dehistonized material the action of the hydrolysis of the Feulgen reaction would add up to that implicit in the dehistonization treatment and would cause a rapid fall of the values for loss of material as consequence of depolymerization facts, according to Andersson and Kjellstrand (1975). The successive renaturation treatment both on dehistonized and on non dehistonized material does not change significantly the values precedently obtained and this confirms the idea that the rilevability of the Feulgen reaction is not influenced by the treatments "per se" but by the deep "touching" of the chromatin components.