Abstract
A selective portion of HeLa cells in culture was irradiated with a heterochromatic ultraviolet-microbeam (about 2μ in diameter) mainly for 25 seconds, using a high-pressure mercury arc lamp (Toshiba 80 watt) as an irradiation source, and biochemical effects on the RNA, DNA and protein synthesis were exmained by autoradiography, labeling with each tritiated precursor at various intervals, respectively. The results showed that the irradiation at a nuclear or extra-nucleolar nuclear site rapidly caused the inhibition of RNA synthesis which was partly restored in 3-4 hours and mostly for 24 hours after the irradiation. However, the inhibition of DNA synthesis developed fully for several hours after the irradiation and was not restored within a period of 12 hours. The experimental results also showed that the protein synthesis was resistant to the irradiation of any cellular area at the doses employed.
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