A study on chromatin conformation in hypothalamus and pituitary neuronal nuclei of elderly rats / 中华老年医学杂志

ABSTRACT

Objective To observe the characteristics of chromatin conformation in hypothalamus and pituitary gland of rats with different ages (16 17 weeks and 100 105 weeks of age). Methods Micrococcal nuclease (MCN) and deoxyribonuclease I ( DNase I) were used as the probe to differentiate chromatin conformation and agarose gel electrophoresis and polyacrylamide gel electrophoresis (PAGE) were employed to investigate the changes of chromatin conformation in rats with different ages. Results Chromatin DNA of hypothalamus and pituitary gland in old rats existed a repeat length (nucleosome core and linker region) of (190?7)bp and (171?8)bp, and in young rats (193?9)bp and (170?5)bp respectively. PAGE showed that DNase I cleaved nucleosome DNA at 10 bp intervals and the cleavage patterns were the same in all ages of rats; comparison of DNA fragments digested by DNase I in young and old rats showed that less fragments with lower base pair were produced in old rats. Conclusions (1) No aging related changes were observed with the repeat length of chromatin nucleosome DNA in hypothalamus and pituitory gland, but there was difference depending on tissues. (2) The chromatin DNA mainly existed in B type of duplex conformation and contained similar super helical structure of solenoid in hypothalamus. (3) Further experiments showed that the chromatin DNA in hypothalamus and pituitary gland from elderly rats was more resistent to DNase I digestion.