Effects of surgery on remaining brain tumor cells (author's transl)

Abstract

9L tumor cells were transplanted into the left lobe of the brain in Fischer 344 rats. In one group, the brain tumor was grossly removed from the rats microsurgically on the 14th to 18th day after transplantation (operated group). These rats were decapitated 1, 6, 24, or 48 hr after surgery, having received 250 μc 3H-thymidine (3H-TdR) intraperitoneally 30 min before sacrifice. Both frontal lobes (operated left side and non-operated normal side) were removed and DNA was extracted using a modified Schmidt-Thannhauser method. 3H activity was then measured with a liquid scintillation spectrometer (LSC) to determine the 3H-TdR uptake into the DNA of the remaining tumor cells. A second group of rats which did not undergo tumor removal (non-operated group) received the same dosage of 3H-TdR 30 min before decapitation; the brain was removed postmortem, the tumor was then removed from the brain, and the same extraction procedures and uptake measurements were performed. For comparison of the two groups, the relative increased radioactivity (RIRA) in the brain was determined as a ratio of the counts per gram (cpg) in the tissue of the left lobe, from which tumor was removed, to the cpg in the normal right lobe. RIRA in the non-operated group was 5.7, indicating that the 3H-TdR uptake of tissue in the left lobe, which contained some remaining tumor cells, was 5.7 times higher than that in the normal lobe. In the operated group, RIRA was 1.5 and 1.7 respectively in the rats sacrificed 1 and 6 hr after surgery, which indicated that remaining tumor cells had virtually ceased to proliferate; however, in rats sacrificed 24 hr after surgery, RIRA was 4.9, which approached the same level as that in the non-operated group. In the rats sacrificed 48 hr after surgery, RIRA was as high as 9.5. These results showed that for at least 6 hr after surgery there was almost no proliferation, but by 24 hr after surgery, active division of the remaining tumor cells had resumed. To confirm both 3H-TdR perfusion in the tissue and tissue permeability, a third group consisting of operated rats received 3H-TdR and 14C-urea before being decapitated. Both frontal lobes were lyophilized and activities of the 3H and 14C were measured with LSC. During an observation time of up to 48 hr, there was no significant fluctuation in the level of available 3H-TdR in tissue or in the tissue permeability, as indicated by 14C-urea space.