Altered conformation and increased strand breaks in neuronal and astroglial DNA of aging rat brain.

Melting temperatures (Tm) of the DNA isolated from young, adult, and old rat brain neurons and astrocytes were recorded under different conditions. There was a rise in Tm and decrease in hyperchromicity in the old when compared to the young and adult. Single and double strand breaks were assessed by using nick translation type incubation of DNA with E. coli Pol I and addition of nucleotides at the terminal 3'-OH by calf thymus terminal deoxynucleotidyl transferase. Results show that DNA from old brain cells is more compact in conformation. However, there is also an increase in the number of single and double strand breaks with age in both neuronal and astroglial DNA.