C3H mice aged 56-70 days, weighing 27-37 g. were used throughout this experiment. A transplantable fibrosarcoma arising spontaneousely from C3H mice was used. For experiment, 104 tumor cells suspended in 0.025 ml of saline solution were injected into the cerebral hemisphere by a 26 gauge needle with a micrometer syringe under nembutal anesthesia.
Whole brain irradiation was performed at 7 days after injection of the tumor cells and the radiation doses were 2, 000 and 20, 000 rads, respectively. The feature of x-rays were 200 kVp, 20 mA, 0.5 mm Cu + 0.5 mm Al filtration and TSD 20 cm. The dose-rate was 340-360 R/min.
The articles of this study were as follows:a) Determination of LD50 values for the mice, tumor-bearing in the brain or non-tumor-bearing; and b) Observation of clinical features and gross autopsy findings of the mice following irradiation.
The LD50 values for 2, 000 rad irradiation in the tumor-bearing or non-tumor-bearing mice were 10.9 and 11.4 days, respectively. LD50 values of 3.7 days and 4.3 days were the results for the tumor-bearing and non-tumorbearing mice irradiated by 20, 000 rad, respectively. On the other hand, the LD50 value for the control group, i.e. non-irradiated mice, was 6.7 days.
At postmortem examinations, gastrointestinal bleeding was observed frequently in mice bearing tumor in the brain.
Whole brain irradiation is effective to prolong the life of tumor-bearing mice. However, in some instances, deaths have occurred earlier in tumor-bearing mice compared to the control group.
