A study on macronuclear chromatin structure in Colpoda inflata (Protozoa, Ciliophora) by means of image analysis.

Resting encystment is a reversible cytodifferentiation phenomenon regularly taking place during the life cycle of Colpodidae. The encystment involves regulation of the macronuclear DNA content, accomplished via chromatin extrusion and DNA synthesis mechanisms. An analysis of macronuclear chromatin texture was carried out in Colpoda inflata logarithmically growing cells, pre-cystic cells, and increasingly aging resting cysts after Feulgen staining. Morphometric and densitometric parameters as well as Markovian chromatin texture variables were utilised for image analysis. Moreover, univariate and multivariate analyses were applied both to macronuclei and to their chromatin extrusion bodies. The results show that structural variations in chromatin appear under macronuclear functional activity conditions, suggesting a dynamic state of chromatin texture throughout a long-term resting encystment.