Scanning electron microscopic (SEM) analyses of cultured human embryo fibroblasts were performed 10 minutes, 1, 4 and 24 hours after X-irradiation with 2.5 Gy. Marked surface changes were observed 10 minutes and 1 hour after irradiation. These include the appearances of filopodia and lamellipodia as well as of plasma bridges connecting the detached membranes with the substrate. Initial signs of surface restoration, however, could be observed 4 hours after irradiation, while the full restoration of the confluent monolayer seemed to be completed at 24 hours. These observations as well as those obtained 1 hour after smaller and larger doses than above, i.e. 0.25 and 5 Gy, suggest that the early and temporary functional membrane alterations demonstrated previously by lectin-binding technique are in good agreement with well-defined micromorphological phenomena.

View full abstract

Nineteen radiation-induced and one spontaneously developed transformed foci were cloned from mouse 10T½: cells. Each clone was grown with normal 10T½: cells, and typing (types II and III) was carried out by making reference to the description of Reznikoff et al. Morphological characteristics of foci and their response to co-cultured normal counterparts are described. Some in vitro properties of the clones were examined and the relationship to each focus type is discussed. A reduced serum requirement of transformed clones was not recognized. Soft agar colonies were produced exclusively by type III clones. Tumorigenicity testing of the clones revealed that 93% of type III clones were tumorigenic upon inoculation into syngeneic mice in an immunosuppressed condition. From these findings, it can be concluded that the tumorigenic potential of radiation-induced transformed cells can be predicted from the ability of the cells to form colonies in agar.

View full abstract

Role of Ca ion in development of radiation damage of rat thymocytes was examined. Free DNA release, an expression of chromatin degradation, and the percentage of erythrosin B stained (dead) cells were increased after incubation of 1000 R X-irradiated thymocytes with normal Ca-containing medium. Incubation of the irradiated cells with Ca ion-depleted medium resulted in marked depression of free DNA release as well as of development of cell death. It was concluded from these results that Ca-dependent process(es) was involved in rat thymocyte interphase death.

View full abstract