Time-Resolved Oxygen Effects in Irradiated Bacteria and Mammalian Cells: A Rapid-Mix Study

Fast Kinetics of the Oxygen Effect in Irradiated Mammalian Cells

“…however, the millisecond lifetimes obtained using the gas-explosion apparatus are supported by similar values obtained in this laboratory using the quite different liquid-mixing technique (Shenoy et al 1975) .…”

“…7 µM . This value is only about 5 per cent of the K value for V79 379A cells irradiated with a single pulse (Shenoy et al 1975) and as such would have little effect on the results presented in this paper .…”

“…marcescens (Weiss, Ling, Epp, Santomasso and Heslin 1975) . A continuous-flow, liquid-mixing and irradiation technique with a time resolution of 3 ms has been used to study oxygen-effect kinetics in V79 Chinese hamster cells and in S. marcescens (Shenoy, Asquith, Adams, Michael and Watts 1975) . With this liquid-mixing technique, the behaviour of mammalian cells was found to be quite different from that of bacteria, showing two time-resolved stages of the effect of oxygen mixed with the cells milliseconds before irradiation .…”

The changing paradigm of tumour response to irradiation

“…Detailed studies demonstrated that the effect was largely due to direct interaction of oxygen with radiation-induced radicals on the DNA-preventing rapid chemical repair of the radical by antioxidant molecules such as sulphydryls (2SH0). 45 The level of oxygen required for an observed decrease in radiation response was less than about 10 mmHg, but full resistance was not observed until oxygen levels were below approximately 0.5 mmHg. Studies indicated that the levels of free sulfhydryls (e.g.…”

Rapid-mix Studies on the Anomalous Radiosensitization of Mammalian Cells by 5-chloro-1-methyl-4-nitromidazole

“…Since it is known (Shenoy, Asquith, Adams, Michael and Watts 1975) that oxygen itself does not sensitize if added 5 ms after irradiation (a timescale over which CMNI-is stable, Clarke and Wardman 1980) then, provided 02 is not itself toxic, the amount of sensitization by the drug might be reduced if this mechanism is important .…”