[Blood serum as a factor of chromatin condensation in trisomy-21 (Down's syndrome)].

The influence of blood sera from patients with Down's syndrome and healthy ones, and different serum fractions on the structure of the deoxyribonucleoprotein systems (DNP-system) has been studied. It was demonstrated that non-fractionated sera of the patients produce a condensation effect on the DNP-system in contradistinction to the sera from healthy people. The analysis of the action of single serum fractions showed that different condensation effect results from the activity of high molecular nondialysable thermosensitive components whose action disappears at gel-filtration of serum proteins. A possibility of the humoral control over chromatin structural organization in vivo is discussed in terms of the evidence on the similarity of serum proteins and chromosomal nonhistone proteins.