Effects of ionizing radiations on the mitotic activity and deoxyribonucleic acid of fibroblasts cultivated in vitro (in French)
Effects of x rays were studied on chick embryo fibroblasts cultivated by the hanging drop method, using hard, soft, and half-soft x rays (200-100 kv) and a dose of 400 r. With hard (200-kv) x rays only, 2 different rates were used for 400 r, and effect of other doses (100, 200, and 800 r) was compared. Growth was studied by mitotic index and surface area measurements, for times up to 14 hours after irradiation, on fixed cells. DNA content was estimated in individual nuclei by cytophotometry after Feulgen staining. Incorporation of tritiated thymidine was studied by autoradiography for different periods after irradiation of fibroblasts cultures. Mitotic activity was suppressed immediately under all conditions of irradiation. After 400 r, mitoses took place again four hours after hard rays, eight hours after soft rays, and no longer after half-soft rays. Rates of irradiation had no influence (30 or 200 r/min at 260 kv). The percentage of nuclei with a DNA content between two and four units, corresponding to diploid and tetraploid nuclei, was increased during the first four hours after irradiation and nearly fell to zero 12 and 14 hours after irradiation. Histograms were normal and were comparable with controls; neither the quality nor intensity of x rays seemed to influence the results. After 800 r, there were no more values between two and four units DNA but tetraploid values decreased 15 hr after irradiation, which was interpreted as an inhibition of the synthesis. During the first four hours after irradiation at 400 r, the mean value of DNA, estimated for 100 nuclei was increased and reached 150% of the controls. It then decreased gradually and was comparable to controls at 12 and 14 hours after irradiation. Neither quality nor intensity of x rays influenced these results. The effect was proportional to dose up to 400 r. Tritiated thymidine was incorporated into more nuclei during the first two hours after irradiation; during the following hours, less nuclei synthesized DNA. Incorporation of tritiated thymidine in irradiated nuclei (number of grains per nucleus) was less than in controls. The moderate dose of 400 r permitted demonstration of the effect of x rays on cells which were in the presynthesis stage. These cells initiate DNA synthesis earlier than without irradiation. However, the DNA which synthesized under these conditions may be abnormal and cells which have produced this DNA may disappear afterwards.
- Research Organization:
- Universite, Liege
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-18-011723
- OSTI ID:
- 4107003
- Journal Information:
- Experimental Cell Research, Vol. 28, Issue 3; Other Information: Orig. Receipt Date: 31-DEC-64; ISSN 0014-4827
- Country of Publication:
- Country unknown/Code not available
- Language:
- French
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