title: Structural and replicative forms of mitochondrial DNA from human leukocytes in relation to age.
abstract: The structure and replication of human leukocyte mitochondrial DNA (mtDNA) was investigated in healthy young adult males (23--37 years old), middle-aged males (42--52 years old) with secondary polycythemia, and elderly males (80--89 years old) who exhibited different degrees of age-related disease syndromes. The distribution of the various cell types within the white cell population was within normal limits in all samples. Total mtDNA was isolated in ethidium bromide--CsCl gradients and examined by electron microscopy after spreading by the aqueous and formamide techniques. The individual frequencies of catenated forms ranged from 2 to 6% but showed relatively little change (declining slightly) with age. The individual frequencies of circular dimers varied from 0 to 0.1% in the young adult and polycythemic groups and in 10 out of 12 elderly individuals. One elderly individual had a circular dimer frequency of 0.3% (including a circular molecular of tetramer size) and another had 4.5%. This finding suggest that agerelated cellular pathology may exist in the blood-forming system in some cases. The mode of replication of leukocyte mtDNA agrees well with that described for mouse L cells. There was no evidence of aberrant mtDNA replication as a result of aging.
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging; D004261:DNA Replication; D004270:DNA, Circular; D004272:DNA, Mitochondrial; D006801:Humans; D007962:Leukocytes / Q000648:ultrastructure*; D008297:Male; D008875:Middle Aged; D008928:Mitochondria / Q000648:ultrastructure; D011086:Polycythemia / Q000097:blood
chemical_list: D004270:DNA, Circular; D004272:DNA, Mitochondrial