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Biologic effects of hyperthermia (42 degrees-44 degrees C) and radiation on SGC-7901 were studied quantitatively and morphologically. Action of hyperthermia and radiation on the population and subpopulation of cells was monitored by cell growth curve and colony counts. The results show that both hyperthermia (43 degrees C for 30 min) and radiation (500 rad) can cause the cell kill and growth curve decrease but the cells still tend to proliferate. The synergistic action of heat plus radiation is demonstrated when they are given in the interval of 30 min. The thermal enhance rate was 1.27 and 1.37 for survival rate down to 2% and 5%. The concentration of potassium ions in the media is increased with cell kill after heat and radiation. The damage from heating appears like a direct kill or immediate death, the damage from radiation reveals delayed or metabolic death. Partial and transitory redistribution of cell cycle occurs following heating or radiation. Delayed division is more marked following heating than radiation. The synchronization effect may be used to hit the cycling tumor cells in the most radiosensitive phase.

Different characteristic damages of the SGC-7901 gastric adenocarcinoma cells were studied by electron microscopy 1, 36, 72, 96 and 120 hours after heating and radiation in vitro. The visible damages, such as the enlarged mitochondria, increase of lysosomes and perichromatin granules could be shown 1 hour after heating (43 degrees C for 30 min) but no visible damages of the cells were shown until 36 hours following radiation (500 rad). In order to study the ultrastructural changes of the gastric cancer cells in mitosis after heating and radiation, we have used the new method of ultrastructural research in selecting and observing the M cell in vitro and found loosened structure of chromosome and disappearance of microtubules 1 hour following hyperthermia. At the same time, no apparent abnormalities of the mitotic cells were observed after radiation. It is the chief cause of division delay in heat injured cells. However, the chromosomes and microtubules of the new mitotic cells could recover 36 hours after heating (43 degrees C for 30 min). After radiation, the giant cells and abnormal morphologic changes of cells gradually increase and the living cells decrease. Unexpectedly, the division of a few giant cells is observed 72 hours after heating and radiation.