[Analysis of changes in the structural state of chromatin in Down's disease]

Dependence of optic density (lambda = 260 nm) of human lymphocyte nuclear chromatin on temperature under normal conditions and in Down's disease was studied. The low temperature (t approximately 70 degrees C) absorption maximum, absent in the nuclei of lymphocytes in patients with Down's disease, was characteristic of the lymphocyte nuclei of healthy donors. Analysis of the mentioned correlation for individual regions of the nucleus demonstrated the presence of at least two types of regions, i.e. with and without the low temperature absorption maximum. There were more regions of the latter type in Down's disease in comparison with the normal.