The apparent paradox of heightened adrenal corticosteroid levels associated with reduction in the competence of the body's defensive apparatus to cope with exposure to new microbial antigens is considered. The question is asked how this lowered defensive capability, which occurs in the face of a threat to body integrity, is consistent with Cannon's principals of the "wisdom of the body." The suggestion is offered that the immunologic response to self-antigens exposed by disease or trauma may be suppressed by corticosteroid to offset the likelihood of autoimmune attack.
Isotopic labeling of the DNA of blood cells has provided an important technique for obtaining information about the cytokinetics of white cells. It has been assumed that the DNA label is stable within a given lineage of cells. However, several papers have indicated reincorporation of tritiated thymidine (H3Tdr)-labeled deoxyribonucleic acid (H3DNA) of cells during catabolism by other proliferating cells. The tritiated thymidine is originally incorporated during DNA synthesis (I-6). Most interpretations of this finding have assumed that it is not the result of radiobiological artifact due to the isotope. Aside from the significance of this finding in terms of interpretation of data pertaining to cell renewal, life span, and possible transformation of blood cells into different morphological entities (7), the possibility of the DNA within cells being unstable has many other implications.The biochemistry of the transfer of DNA label remains to be elucidated. Hamilton (8), whose work in leukemic subjects led him to propose that DNA reutilization might occur within lymphatic tissue, believed that his data favored the reincorporation of fragments of DNA polymer rather than mononucleotides or nucleosides resulting from DNA breakdown. He pointed out that the earlier works of Ottesen (9) and Osgood et al. (10) were also consistent with this view.On the other hand, Robinson and Brecher have recently reported strong evidence suggesting that reincorporation of the DNA label in blood cells by rapidly growing liver cells occurs after breakdown of DNA to a nucleoside level (11).
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