A study of the immunosuppressive activity of methylene dimethane sulphonate (MDMS) in relation to its effectiveness as an anti-tumour agent

Influence of tumour volume and cell kinetics on the response of the solid Yoshida sarcoma to hyperthermia (42 degrees C)

The cytokinetic response of the solid Yoshida sarcoma to hyperthermia was examined at two tumour volumes, 1.0-1.5 ml and 3.0-3.5 ml. The tumour, growing on the feet of rats, was heated at 42 degrees C for 1 h by water-bath immersion. The larger tumour grew more slowly than the smaller one (doubling time 144 h vs 36 h) due to a halving in growth fraction from 67.8 to 39.6% and an increase in cell-loss factor from 59 to 75.9%. Cell cycle and phase times were similar at both volumes. The effect of heat on the population kinetics at both volumes was similar but complex, and involved delayed cell death after up to 10 mitoses. Initial cell killing and blockade of cell-cycle progression (0-24 h) was followed by recovery of proliferation due to recruitment of cells from the non-proliferative compartment, cell cycle and phase times remaining unaltered. From 48 h, the proliferation rate declined progressively, and tumours were completely necrotic 7-8 days after heat. The damaging effects of heat were at least as severe in the large tumours with a low labelling index and small growth fraction as in the smaller tumours with a much larger compartment of proliferating cells and shorter doubling time. The results imply that there may be no simple relationship between proliferative status and thermosensitivity of a tumour, and illustrate the difficulty in predicting tumour response to heat on the basis of cytokinetic studies.

Changes in NMR relaxation times of adjacent muscle after implantation of malignant and normal tissue

In separate experiments, normal foreign tissue and malignant tumour were implanted s.c. into the rat thigh. NMR T1 values of the adjacent normal muscle, resulting from local inflammatory reactions or from malignant invasion, were measured. Elevations in T1 of the underlying muscle occurred within 24 h in both experiments, and it is believed these were caused by rapid inflammatory and immunological reactions to the implants. However the T1 values of muscle samples adjacent to the non-malignant implants decreased during the 11 days after implantation, dropping to values within the normal range. In the second experiment there was progressive malignant invasion into the normal adjacent tissue and the elevated T1 values were maintained throughout the 12-day period. The effects of the implantation on tissue water content are discussed in relation to NMR T1 relaxation times, and the relevance to whole-body NMR imaging of elevated T1 values due to nonmalignant pathological states is considered.

Electron spin resonance study of changes during development of solid Yoshida tumour. I: Ascorbyl radical

The ascorbyl radical concentration has been observed, by means of electron spin resonance spectroscopy, in the blood and spleen of female Wistar rats carrying a Yoshida tumour. The ascorbyl radical concentration of the tumour tissue itself was studied as the tumour was developing, and as it was regressing after treatment with methylene dimethane sulphonate. Changes in the concentration of this radical may be related to host tumour reactions.