The Feulgen hydrolysis kinetics in the midgut cell classes of the stick insect Bacillus rossius: a computer analysis

In the midgut epithelium of the walking stick insect Bacillus rossius, nuclei belong to two main cytological categories: nuclei with ordinary chromatin (ON) showing a polyploid series of Feulgen-DNA contents (2, 4, 8, 16C) and nuclei with DNA-RNA bodies (NWB) varying from 9 to 34C. Cells with ON are either small basal or large secretory elements, while those with NWB always belong to the second type. The Feulgen kinetics profiles obtained after formalin fixation, as well as their least squares fit by computer analysis, have shown that with increasing ploidy both the aldehydic group availability and the resistance to depolymerization increase in the genomes of ON; on the contrary, NWB have a depurination rate and resistance to depolymerization significantly lower than the ON. The kind and magnitude of the changes observed, while suggesting a gradually different DNA-protein relationship with increasing ploidy and concurrent maturation of ON, also indicate a deeper chromatin reorganization for NWB.