The effect of heat on the clonogenicity of bovine aortic endothelial (BAE) cells in vitro was measured. Continuous heating of cells at 43 degrees C or 43.5 degrees C produced survival curves exhibiting thermoresistant tails. When heated at 44 degrees C the survival curve of BAE cells was exponential except for a small shoulder. The BAE cells heated at 44 degrees C and 45 degrees C had D0 values of 33 min and 19 min, respectively. The development of thermotolerance in BAE cells was studied by measuring the sensitivity of cells to a 44 degrees C heating at various times following a priming heat treatment at 43 degrees C or 44 degrees C for 30 min. The thermotolerance ratio in BAE cells preheated at 43 degrees C for 30 min reached a peak of 3.8 at 3 h and declined to 1.9 at 24 h after the prime heating. After prime heating at 44 degrees C for 30 min the thermotolerance ratio increased rapidly to 5.4 in 5 h, remained elevated at 12 h and then declined to a value of 2.1 at 24 h. Thermotolerance in endothelial cells may be partially responsible for the thermotolerance in blood vessels of normal tissues and tumours.
The growth parameters and radiosensitivity of normal rat intestinal epithelial cells, IEC-17, were studied. The cells were cultured by standard methods and exposed to an array of doses (1-12 Gy) of 250 kVp X rays. The survival curves generated exhibited no initial shoulder and were bimodal. The Do of the first component was about 0.2 Gy and the second component. 5.0 Gy. The ability of this cell line to repair sublethal lesions was examined by fractionation studies; repair was completed within 60 min after the first dose. When Chinese hamster ovary (CHO) cells were grown under the same conditions used for the IEC-17 cells and then irradiated with single doses, a typical survival curve with a Do of 1.4 Gy was obtained. The survival curves obtained for the IEC-17 cell line are consistent with the response of a morphologically distinct single population containing two functionally separate types of cells.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.