An investigation of environmental radiation and dosimetry was carried out in the high background radiation area of Guangdong Province of China. The surface soil of the high background and control areas were analysed by both radiochemical procedure and gamma ray spectrometry. The results revealed that the concentrations of uranium and radium are about 5 times higher than those in the control area, and the thorium has a higher value in the high background area, about 6-7 times more than that in the control area. The higher content of natural radionuclides in this area raised the environmental radiation level. Environmental cumulative exposures and resultant inhabitant exposure rates were measured in the high background area with Photoluminescent dosimeters and TLD CaSO₄(Dy), and an average figure of 300 mR/yr for the inhabitants was estimated (110 mR/yr for those in the control area). To determine the internal doses resulting from the deposition of natural radionuclides in the body tissue, we compared the data obtained by different methods and procedures adopted in this investigation. The results obtained by measurements of ²²²Rn and ²²⁰Rn in the exhaled breath of healthy inhabitants, by radiochemical analyses of the adults'' teeth, from dietary investigation and of radiochemical analyses of foodstuff and drinking water suggested that the activity concentrations of 226Ra and 228Ra in human bones in the high background area are about 3-5 times higher than that in the control area. After comparing these data, annual absorbed doses of red bone marrow and bone surface from ²²⁶Ra and ²²⁸Ra were estimated.

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Distribution of the absorbed RF power in a phantom was measured by scanning the thermocouple immediately after RF-irradiation of 13.56 MHz; a phantom used was composed of 2.0 W/W % agar, 0.5 W/W % NaCI and 97.5 W/W % distilled water and equivalent to high water content tissue both in the electric conductivity and the dielectric constant. Absorbed RF power at the midpoint on the central axis of the phantom decreased exponentially in accordance with increasing in its thickness. And the decrease at the midpoint was more remarkable at the RF electrodes got smaller. Relationship between relative absorbed RF power at the midpoint to that at 1 cm in the depth and relative thickness of the phantom to the diameter of electrodes was shown as a sort of exponential function regardless the diameter of electrodes. The effective heating diameter at the midpoint was equal to the diameter of electrode if the thickness of phantom was smaller than the diameter of electrode, while the effective heating diameter became larger than the diameter of electrode as the thickness of phantom became larger than the diameter of electrode.

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A culture system was established in which haemopoietic stem cells can undergo a recovery proliferation after a depletion of the stem cells, completely in vitro. To elucidate the source of the stimulatory factors, normal bone marrow cells were overlayed on top of the irradiated adherent ‘stromal’ cell colonies in the bone marrow cell culture. This stimulated the proliferation of haemopoietic stem cells in the cultured cells in suspension.
The present results indicate that the stromal cells produce factors which stimulate stem cell proliferation. Whether the stimulation is evoked by direct cell-cell interactions or by humoral factors is as yet to be studied.

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T4-phages were irradiated by UV-light and phage-specific mRNAs were extracted from Escherichia coli B_B-1 cells at various periods of infection. The RNAs were fractionated by methylated albumin-coated kieselguhr (MAK) column chromatography into characteristic sizeclasses. With UV-irradiated phages the last-eluted mRNA component of high molecular weight disappeared preferentially after the middle stage of infection but not at the early stage. However, quite the contrasted changes in the last-eluted, phage-specific component in chromatographic profiles were observed in E. coli cells irradiated by UV-light before infection of normal phages. Some unstable proteins might be responsible for the UV-induced, selective inhibition of high molecular weight mRNA synthesis in bacterial cells.

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The chromosome aberrations (chromosome bridges) were observed at the blastula stage of Oryzias eggs treated in the following three manners, 1) incubated in HTO (0-10 Ci/1) and in ⁹⁰Sr-⁹⁰Y (0-1, 000 μCi/1), 2) irradiated continuously with γ-rays (0-74 rad/h), 3) given single doses of X-rays (0-500 R), All the treatments were initiated immediately after fertilization (at the one-cell stage). and the continuous irradiation time was eight hours at 26°C. The frequencies of chromosome bridges increased significantly when the eggs were treated with solutions of concentrations higher than 0.5 Ci/1 (>19 rad) for HTO and 100 μCi/1(>58 rad) for ⁹⁰Sr-⁹⁰Y, or were irradiated with γ-rays of 78 rad or more, or were given single doses more than 100R of X-rays. Comparing the continuous irradiation experiments, it is considered that β-rays from tritium are more effective than the other radiations in inducing chromosome aberrations. Hatchability of Oryzias eggs irradiated with X-rays at the one-cell stage was checked and the dose required for 50% killing of embryos was estimated at 360R.

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Two kinds of samples have been tested to investigate the adsorption of plutonium in soil under natural conditions. In a soil sample containing only about 5% of organic materials, no significant leaching of plutonium was observed with three kinds of extractants, namely, 1N-ammonium acetate, 5%-EDTA and 0.1N-sodium citrate, while some plutonium was leached with 0.1N-citric acid. The results of solubility tests made with natural soil organic acids, namely, humic and fulvic acids, showed that solubilization of plutonium by these acids is unlikely to occur in this soil sample. On the other hand, in another soil sample rich in organic materials (about 50%), significant leaching of plutonium was observed with all the extractants tested. The leaching of plutonium was especially very high with 0.1N-sodium citrate (about 60%) ; sodium citrate showing an initial pH of 8.4 probably solubilized some of organic materials present. Experiments made on extraction of organic materials with alkali solution also suggested that as much as 60-70% of plutonium in this soil sample was associated with some organic acids, whose carbon content was assumed to be 30-40% of the total organic carbon in the soil sample. This finding is very important from a view point of the uptake of plutonium by plant because plutonium associated with such organic acids is presumed to exist abundantly in cultivated soils which are quite rich in organic materials.

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The intracellular pH of unfertilized eggs and those at early prophase was measured using labeled dimethyloxazolidinedione. The pH was not altered by agents which induce mitotic delay but was decreased slightly by lowering extracellular pH which reduces mitotic delay. The evidence suggests that the effect of the agents causing mitotic delay may not be mediated by changes in intracellular pH, but the reduction by low pH of mitotic delay may be mediated by it.

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