Studies on the mechanism of action of ionizing radiations; inhibition of enzymes by X-rays

Comportamento Dell'Attivita’ Deidrogenasica in Seguito alla Irradiazione nel Sarcoma 180 del Topo e Nell'Adenocarcinoma di Walker del Ratto

In mice and rats bearing Sarcoma 180 and Walker adenocarcinoma (respectively radiosensitive and radioresistant according to earlier experiments) the dehydrogenasic activity has been determined « in vitro » after irradiation of the neoplasms. No variation of the dehydrogenasic activity was observed after irradiation in Walker adenocarcinoma; while a moderate but evident dehydrogenase diminution is observed in sarcoma 180. On the basis of the obtained results some considerations are exsposed on the different biochemical behaviour between radiosensitive and radioresistant biological substrates.

The effect of x-radiation on the oxygen uptake of embryonate eggs

Groups of 10 day old embryonate eggs were given 250, 500, 750, and 1000 r of x-radiation, and oxygen consumption determinations were made subsequently at various intervals during a period of 90 hours. In general, the effect of radiation was moderately stimulatory, but after 90 hours the respiratory rates of the 250 and 1000 r groups were well below those of the control groups. The most striking effect, noted in 3 separate experiments, was the occurrence of a "3 step staircase" type of oxygen consumption curve in all irradiated groups, the levelling off periods apparently occurring between the 4th and 14th, the 24th and 36th, and the 42nd and 66th hours after exposure. These curves were in striking contrast to those shown by groups of non-irradiated eggs, which were practically of the straight line type.