The data revealed that DNA damage in neighboring tumor cells could be detected within min and that a maximum level was reached in min.Although the net level of DNA breaks diminished after that time, considerable damage still remained even after min of coincubation.The data represent the slopes of the elution profiles obtained in two separate experiments. It was found was completely effective in preventing detectable DNA damage.Superoxide dismutase, and the hydroxyl radical scavenger mannitol was noninhibitory.The results represent the averages of at least two separate experiments that repair commenced immediately after addition of catalase with no apparent lag time but that complete of min.This rate of repair was more than three times slower than that found for repair of damage from either M HO or rad equivalents of irradiation; the latter two types of damage were reproducibly repaired at nearly identical rates, with repair occurring in min and complete repair achieved in min. None of the treatments was found to be lethal for RIMPC cells in culture. However, physiological stimuli are expected to act in vivo; these may include complement factors and immune complexes that may be abundant in an inflamed tissue.In the mouse plasmacytomagenesis system, it has yet to be determined whether ingestion of oils by neutrophils and macrophages may stimulate the oxidative burst or whether other constituents of the oil granuloma may accomplish this.Under the experimental conditions tested herein, DNA damage is detected within min after addition of PMA and persists for more than min thereafter.This result is similar to that obtained in mouse epidermal cells. It should be noted that because these experiments are carried out at C, the level of strand breaks found at any time reflects a balance between damage and repair in the target cells.Nonetheless, even after damage is stopped, complete restitution of the DNA to control levels of alkaline elution is achieved only after several hours of continued incubation of the target cells. This rate of repair is significantly slower than that observed for repair of a similar level of strand breaks induced in the same cells by yirradianon. Prolonged formation of DNA strand breaks and slow repair of those breaks for whatever reason may provide lengthy opportunity for potentially mutagenic secondary changes to develop in the chromatin. Moreover, adaptative processes such as induction of antioxidant enzymes or changes in membrane permeability may enhance die cells survivability and subsequent susceptibility to undergo malignant transformation. Thus, time is a critical component of me hypothesis that chronic inflammation causes chromosomal abnormalities and tumorigenesis.After min, jgml catalase was added to the mixtures and the cells were further incubated for the times indicated in the figure.On the basis of numerous experiments, we have made E.It is highly possible that cellular defence and repair mechanisms vary from cell to cell and distinguish different cell types.We found an average of inhibition of SSB formation in four separate experiments.In addition, SOD has been found to inhibit phagocyte induced chromosomal abberrations in mixed leukocyte cultures. As HO and O can give rise to hydroxyl radicals and singlet oxygen in the presence of metal ions such as iron that hydroxyl radicals form in the vicinity of the neutrophil.