ABSTRACT
Chinese hamster ovary cells grown in vitro were treated with bleomycin or irradiated with high doses of 60Co gamma rays (200 and 400 Gy). DNA strand breaks in single cells were analysed by using our newly introduced microelectrophoretic technique. Bleomycin seems to act in a selective manner so that in some cells the DNA is heavily degraded while in others there is only moderate or no measurable damage. In contrast, a uniform response was found after gamma irradiation. To achieve the same magnitude of DNA fragmentation as in the most severely bleomycin-damaged cells, irradiation with more than 200 Gy is required. Some 8000 double-strand breaks per cell are produced by 200 Gy which will convert the molecular weight of the DNA to the range of 10(8)-10(9) dalton, and free migration of DNA fragments occurs during electrophoresis. We include also a detailed study of the DNA migration pattern following doses of 0-100 Gy gamma rays.
Subject(s)
Bleomycin/toxicity , Cobalt Radioisotopes , DNA Damage , DNA/radiation effects , Animals , Cricetinae , DNA/drug effects , Gamma Rays , In Vitro TechniquesABSTRACT
Aspiration biopsy specimens were taken from malignant tumours--1 Hodgkin's lymphoma, 3 non-Hodgkin lymphomas, 1 squamous cell carcinoma and 1 adenocarcinoma-before and after irradiation. Individual cells were analysed by micro-electrophoresis, a new technique which estimates radiation-induced DNA strand breaks. The cells were embedded in agarose gel; after lysis of the cells in a neutral detergent solution, an electric field (5 V/cm) was applied for five minutes. DNA showed a tendency to migrate, some cell diameters, and was more pronounced in irradiated than in control cells. The DNA migration was evaluated by a microscope photometer which estimated the fluorescence in cells stained with acridine orange. This technique was found to be suitable for human material in vivo as only a few cells are needed and no radioactive prelabelling is necessary.
Subject(s)
Adenocarcinoma/genetics , Carcinoma, Squamous Cell/genetics , DNA/radiation effects , Hodgkin Disease/genetics , Lymphoma, Non-Hodgkin/genetics , Adenocarcinoma/radiotherapy , Adult , Aged , Biopsy, Needle , Carcinoma, Squamous Cell/radiotherapy , Electrophoresis , Female , Hodgkin Disease/radiotherapy , Humans , Lymphoma, Non-Hodgkin/radiotherapy , Male , Microchemistry/methods , Middle AgedABSTRACT
Mammalian cells were after irradiation suspended in melted agarose, and casted on microscope slides. The slides were after gelling at 0 degree C immersed in a neutral detergent solution which lysed the cells. A weak electric field (5 V/cm) was then applied over the gel for 5 minutes. The DNA in the gel was stained with the fluorescent dye acridine orange and gives a green emission in a microscope photometer. DNA had migrated towards the anode and this migration was more pronounced in irradiated than in control cells. The differences in migration pattern were quantitatively measured. The lower detection limit was below 0.5 Gy and a plateau in the dose-effect curve was reached at about 3 Gy. In repair experiments residual DNA damage could be observed after postirradiation incubation for 60 minutes. The advantages of the method is: no radioactive labelling and only a few number of cells is required.
