Age-dependent alterations of DNA synthesis. Terminal deoxynucleotidyl transferase and DNA polymerase activities in bone marrow subpopulations from mice

Abstract The decrease of functional capacity of cellular immunity during ageing seems to be due to cellular changes of stem cells, particularly in the growth properties and the cell density in T-cell subsets. We approached this problem at the molecular biological level by quantifying the key enzymes necessary for DNA synthesis in bone marrow cells from mice: deoxynucleotidyl transferase (TdT) and DNA polymerase α. The bone marrow cells were fractionated on a discontinuous bovine serum albumin density gradient and the extractable enzyme activities (expressed per 10 8 nucleated cells in the respective fraction) were determined. TdT activity was found to decrease markedly during ageing. Mature…