Metabolic peculiarity of 134Cs and its radioimmunotoxicological effect on central and peripheral immune cells

A fitted equation with least square method to describe the retention of ^134Cs in whole body is obtained by a whole body counter.That is R(t)=18.04exp(-9.3175t) 45.13exp(-0.0423t),where R(t) is in %,and t in d.The equationn consists of two half-life components,the fast component is T1/2=0.07d,and the slow is T1/2=16.14d,Study on the localization of ^134Cs at cellular level was carried out by freezing microautoradiography.The results indicate of ^134Cs at cellular level was carried out by freezing microautoradiography.The results indicate that ^134Cs was chiefly in ionizing form accumulated in red as well as white blood cells.In bone marrow cells ^134Cs predominantly deposited in young cells and less in mature cells.Distribution of ^134Cs penetrated quickly into the tissue cells.The observation of investigating radioimmunotoxicological effect induced by ^134Cs shows that the inhibition of thymocytes is higher than bone marrow cells,the spleen T lynmphocytes are more sensitive to ^134Cs than B lymphocytes and lymphocytes of peripheral immune cells are more sensitive to radiation than central immune cells.     

NASOPHARYNGEAL CARCINOMA RADIOSENSITIVITY PREDICTION BY CYTOKINESIS—BLOCK MICRONUCLEUS ASSAY

Cytokinesis-block micronucleus method is used to evaluate the radiosensityvity of a nasopharyngeal carcinoma cell line(CNE-1) and biopsies obtained from 31 patients with nasopharyngeal carcinoma,The number of micronuclei increases with the radiation dose.A good correlation was found between the radiosensitivity determined by the micro-nucleus assay and that measured by the colony-forming assay in CNE-1 cell line(r=-0.998).Moreover,the results of micronucleus assay for tumor cells from biopsies of patients with primary carcinoma look promising for the prediction of tumor radiosensitivity.These results are encouraging but need to be confirmed with a larger number of patients with a longer follow-up.     

Estimation of the Lyman-α signal of the EFILE diagnostic under static or radiofrequency electric field in vacuum

The electric field induced Lyman-α emission diagnostic aims to provide a non intrusive and precise measurement of the electric field in plasma, using a beam of hydrogen atoms prepared in the metastable 2 s state. The metastable particles are obtained by means of a proton beam extracted from a hydrogen plasma source, and neutralised by interaction with vaporised caesium.When a 2 s atom enters a region where an electric field is present, it undergoes a transition to the2 p state(Stark mixing). It then quickly decays to the ground level, emitting Lyman-α radiation,which is collected by a photomultiplier. The 2 s→2 p transition rate is proportional to the square of the magnitude of the electric field, and depends on the field oscillation frequency(with peaks around 1 GHz). By measuring the intensity of the Lyman-α radiation emitted by the beam it is possible to determine the magnitude of the field in a defined region. In this work, an analysis of the behaviour of the diagnostic under static or radiofrequency electric field is presented. Electric field simulations obtained with a finite element solver of Maxwell equations, combined with theoretical calculations of the Stark mixing transition rate, are used to develop a model for the interpretation of photomultiplier data. This method shows good agreement with experimental results for the static field case, and allows to measure the field magnitude for the oscillating case.     

ONE CASE OF LEUKEMIA INDUCED BY ^60Co ACCIDENT

The peripheral blood lymphocyte chromosomes in a case of 60Co γ rays accident were examined at 2.5h after exposure.The frequency of the dicentrics plus centric rings was 89% and exposure dose was estimated to be 4.78 (4.53-4.88)GY.The examinations of lymphocyte chromosome aberration within follow-up 12a showed that the incidence of Dic R reduced with lg regrssion(r=-0.9895).While the number of ceels with stable aberration remained unchanged and showed a tendency to increase.During the period of leukemia,bone marrow cell chromosome aberrations were studied by method of G-banding.Of 13 cells observed,4 cells belonged to normal karyotypes.Among 9 aberration cells,12 aberrations were detected.The majority of which were classified as translocation,deletion and inversion,Numeric aberrations were-9,12,20-,22,-y.This case suggested that acute lymphocytic leukemia was induced after radiation accident.     

Semaphorin3B modulates radiosensitivity of human glioma U-87MG cells

This study was to determine the Semaphorin3B(SEMA3B) role in glioma cells responding to irradiation. Two glioma cell lines,which were used here was wild-type p53(U-87MG),and the other was harboring mutated p53 (U-251).The SEMA3B mRNA could be detected in the two cell lines.The expression level of SEMA3B mRNA was higher in U-87MG cells than in U-251 cells,and increased with time in U-87MG cells after irradiation.Knockdown of SEMA3B expression by shRNA decreased the radiosensitivity of U-87MG cells,this may be associated with the increased G2 accumulation after irradiation.In addition,G2 accumulation after irradiation was enhanced in SEMA3B low-expressing U-87MG cells.These results showed that the SEMA3B was implicated in glioma cells responding to irradiation.     

Effects of ELF magnetic fields exposure with or without X-rays on in-duction of kinetochore positive and negative micronuclei in CHO cells

Extremely low frequency magnetic field (ELFMF) produced by power lines and household electric appli-ances has been associated with increased incidence of cancers, as was suggested by several epidemiological stud-ies[1]. To test the genotoxic effects of ELFMF, the induction of micronuclei by exposure to ELFMF and/or X-rayswas investigated by cytokinesis-block method in cultured Chinese Hamster Ovary (CHO) cells. Approximately4×105 cells were plated in 10cm dishes, following exposure to…     

Comparison of DNA double—strand breaks induced by ^16O^8＋ in deproteinized DNA and intact cells

The yield of DNA double-strand breaks(DSBs) is sure to be influenced by the environment around DNA molecule.Inverse pulsed-field gel electrophoresis(PIGE)has been applied to compared the sensitivity of B16 cells and their DNA in DSBs induced by 75MeV/u 16O^8 beam.Results show that the percentages of DNA released from the plug(PR)in both kinds of the samples increase with the dose and approach a similar quasi-threshold of about 81%.A simple new equation was presented to calculated the break level of DNA molecules.Within a certain dose,the relationship between the break level and the dose is linear.THe yield of DSBs in deproteinized DNA was 1.11DSBs/100Mbp/Gy,while that in intact cells was 0.60DSBs/100Mbp/Gy.it is testified that deproteinized DNA is more sensitive to oxygen ions irradiation than intact cells.     

Heat Transfer During Radio Frequency Inductively Coupled Plasma Deposition of Tungsten

Particle melting and substrate temperature are important in controlling deposited density and residual stress in thermal plasma deposition of refractory materials. In this paper, both the heating and cooling behaviours of tungsten particles inside a radio frequency inductively coupled plasma （ICP） and the plasma heat flux to the substrate were investigated. The distribution of the plasma-generated heat on device, powder injection probe, deposition chamber, and substrate was determined by measuring the water flow rate and the flow-in and flow-out water temperatures in the four parts. Substrate temperature was measured by a two-colour pyrometer during the ICP deposition of tungsten. Experimental results show that the heat flux to the substrate accounts for about 20% of the total plasma energy, the substrate temperature can reach as high as 2100 K, and the heat loss by radiation is significant in the plasma deposition of tungsten.     

Increased radiosenstivity of human nasopharyngeal carcionma cells by coixenolide under hypoxic condition

Objective:to study the effect of coixenolide (CXL) on irradiation of human nasophyaryngeal carcinoma cell line CNE-2Z in the absence of oxygen,Methods: Microcolony formation assay was used for determining the sensitivity of CNE-2Z to γ-ray in vitro,Results:When CNE-2Z was treated with 10^-7--10^-6 mol/L of CXL,CXL shifted the radiation dose-survival curve to the left,with the decrease of D0,Dq and N values,Radiation dose reduced 10.07%-35.69% at D37 level,the sensitizing enhancement ratios(SER) were 1.07-1.43 and 1.16-1.72 at D0 and Dq levels respectively.Conclusion:CXL increase susceptibility of CNE-2Z to ray under hypoxic condition by the mechanism of inhibiting its sublethal damgae repair.Subject words Nasopharyngeal neoplasm;Coixenolide;Radiosensitzation;Hypoxic irradiation.     

Studies on apoptosis in bone tumor cells induced by 153Sm

The apoptosis in human bone tumor cells induced by internal irradiation with ^153Sm was studied. The morphological changes in bone tumor cells were observed by electronic and fluorescent microscopy, as well as DNA agarose gel eletrophoresis. DNA chain fragmentation, microautoradiographic tracing and the inhibition rate of proliferation in bone tumor cells exposed to ^153Srn with different duration time were examined. It was demonstrated that the bone tumor cells exposed to ^153Sm displayed nuclear fragmentation, pyknosis, margination of condensed chromatin, and formation of membrane bounded apoptotic bodies, whereas the percentage of DNA chain fragmentation of bone tumor cells increases in direct proportion to the duration of irradiation with ^153Sm, as well as DNA ladder formation in apoptotic cells. Also a marked inhibition effect of proliferation in bone tumor cells after exposure with ^153Sm was observed.     

Estimation of the resident＇s additional dose in bone-coal mining areas of the five provinces

This paper introduces the resident＇s additional dose in bone-coal mining areas. The increase of the annual additional effective doses accepted by the residents living in the carbide-brick houses, the staffs working in the carbide-brick houses and the miners working in the bone-coal mining areas of Hubei, Hunan, Jiangxi, Zhejiang and Anhui Provinces is caused by the rising of environmental radioactive level. The investigation of natural background radiation in the bone-coal mining areas indicated that both mining and utilizing bone-coal cause the rise of environmental radioactive level. The ranges of the annual additional effective dose accepted by the residents, staffs and miners is 1.9-6.8 mSv, 0.5-2.0 mSv and 8.2-71 mSv, and with an average of 3.8 mSv, 1 mSv and 40 mSv, respectively. The annual additional effective doses accepted by part residents and staffs exceed the dose limit of 1 mSv for public exposure, and part miners exceed the dose limit of 20 mSv for occupational exposure. And the contribution of dose caused by inhaled radon to the total additional effective dose is over 76%.     

Development of a dose-adjustable α-particle irradiation facility for radiobiological studies

Bystander effects induced by low-dose or low dose-rate radiation have put a great challenge to the traditional model for radiation protection. In order to get a better assessment of the adverse effects of radiation, especially the low-dose radiation risk in environment, a radioactive irradiation facility, by which the dose and dose-rate to the biological targets can be controlled by rotating the sample bracket and changing the space between the radioactive source and the targets, was developed. The energy of our α-radioactive source (^241Am) is measured averagely 3.5 MeV at the position of the irradiated sample. The dose rate was measured by using a silicon surface barrier detector and a CR39 particle track detector. A dose rate ranging from 0.045 cGy/s to 1.07 cGy/s can be obtained by changing the space length from the radioactive source to the sample dish.     

Fast inactivation of microbes and degradation of organic compounds dissolved in water by thermal plasma

The multifunctionality and the advantages of thermal plasma for the fast inactivation of viable cells and degradation of organic compounds dissolved in waste water are presented.A complete bacterial inactivation process was observed and studied using a thermal plasma treatment source with very short application times,in particular for Staphylococcus aureus bundle spore survival.The survival curves and analyses of the experimental data of the initial and final densities of S.aureus bacteria show a dramatic inhibitory effect of the plasma discharge on the residual bacteria survival ratio.As the exposure time increased,the inactivation process rate increased for direct exposure more than it did for indirect exposure.The evaluation of direct and indirect exposure was based on the analysis of the ultraviolet spectrum from the absorbance spectra of the organic compound dye called benzene sulfonate(C_(16)H_(11)N_2Na O_4S)and of viable cells called S.aureus.Organic compounds were degraded and viable cells were killed in a short time by thermal plasma.Moreover,analyses of total carbon,total organic carbon,and total inorganic carbon showed a fast decrease in organically bound carbon,however,this was not as fast as the absorbance spectra revealed by the exposure time increasing more for direct exposure than indirect exposure.After 100 s of exposure to the organic compound dye the removal had a maximun of 40%for samples with indirect exposure to the plasma and a maximum of 90%for samples with the direct exposure.For both samples,where some organic contaminants still remained in treated water,four electrolytes(KCl,Na Cl,Na_2SO_4,and CH_3COONa)were added to be effective for complete sterilization,reaching a purity of 100%.A proposal is made for an optimized thermal plasma water purification system(TPWPS)to improve fast inactivation of microbes and the degradation of organic compounds dissolved in water(especially for direct exposure rather than indirect exposure)using a hybrid plasma torch with an electrical power of 125 kW(500 V–250 A)producing a high-temperature(10 000 K–19 000 K)plasma jet with a maximum gas consumption of 28 mg s~(-1).     

Feasibility study on determining the conventional true value of gamma-ray air kerma in a minitype reference radiation

A minitype reference radiation(MRR) with dimensions of only 1 m × 1 m × 1 m has been developed for the in situ calibration of photon dosimeters.The present work conducts a feasibility study on determining the conventional true value of gamma-ray air kerma at the point of test in the MRR.Owing to its smaller dimensions,the scattered gamma-rays in the MRR are expected to induce a non-negligible interference with the radiation field compared with conditions in the standard reference radiation stipulated by ISO4037-1 or GB/T12162.1.A gamma-ray spectrometer was employed to obtain the spectra of scattered gamma-rays within the MRR,and the feature components of the spectra were extracted by principal component analysis to characterize the interference of a dosimeter probe in the radiation field.A prediction model of the CAK at the point of test was built by least squares support vector machine based on the feature component data obtained from nine sample dosimeters under five different dose rates.The mean prediction error of the CAK prediction model was within ±4.5%,and the maximum prediction error was about ±10%.     

Environmental radioactivity level at a mantle factory in eastern Zhejiang

The Y radiation level, alpha potential energy of thoron and alpha surface contamination level at a mantle factory in the east of Zhejiang Province are reported. The measured results show that the additional annual effective dose equivalent absorbed by the worker in some workshops of the factory was higher than 15 mSv-management limit. The alpha surface contamination on the workers' hands in some workshops was 10 times more than the management limit of National Standard (0.04 Bq/cm2). The mantle factory s main danger to body was internal irradiation of a rays from thoron aerosol.     

RADIOACTIVITY LEVEL OF RESIDENTIAL AREAS AROUND XINJIANG NUCLEAR TESTING SITE AND ESTIMATED POPULATION DOSE

Results are reported on a research for the radioactive level in the investigation region and the control region around the Xinjiang Nuclear Testing Site from 1982 to 1987. There are no significant differences on the land γ radiation level, nor in the radioactive level in the soil, food and water between the two regions. The distribution and transfer of 90Sr, 137Cs and Pu in various kinds of soil are also discussed. It is estimated that the effective dose equivalent of radiation, undergone by the residents around the Testing Site is only 2.9% of that of natural radiation taken yearly by people in normal areas.     

Application of CCD Cameras to Investigations of Mixing on Boundaries of a Thermal Plasma Jet

Mixing of a thermal plasma jet with the surrounding atmosphere was studied using two CCD cameras （PCO SensiCam） situated detecting simultaneously the radiation of argon and nitrogen. The evaluation of image differences between two records showed that the location of regions on plasma jet boundaries characterised by stronger nitrogen radiation changes with the plasma flow rate. Close-to-laminar flow results in a small mixing rate and consequently low nitrogen optical emission on plasma jet boundaries. The increase of the flow rate leads to the formation of a relatively thick and stable layer on the boundaries characterised by strong nitrogen radiation. Further enhancement of the flow rate results in the formation of unstable regions of excited nitrogen molecules moving along the jet.     

Microarray screening of differentially expressed genes in DCX transfected U87 cells before and after irradiation

Radiation therapy plays a critical role in the treatment of neurogliocytoma and it is known that doublecortin (DCX)-transfected U87 cells can inhibit tumor cell growth. Microarray analysis to screen for differentially expressed genes in DCX-transfected U87 cells before and after radiation uncovered DCX-related genes, the functions of DCX, and downstream genes in radiation therapy of neurogliocytoma. Stably transfected U87 cells were constructed (DCX-U87) and the differentially expressed genes were screened by microarray analysis to compare U87 cells with DCX-U87 cells in both non-irradiated and irradiated conditions. Cells were irradiated using 60Co γ-ray at a dose rate of 1.0 Gy/min. Mean values were subject to paired comparison analysis and genes with a p-value of less than 0.05 were analyzed. Differentially expressed genes can correlate with radiation sensitivity and DCX transfection. DCX and SPN proteins in DCX-U87 cells were detected by two groups of 0 and 10 Gy, but not the U87 cells, and their expression levels were higher in the 10 Gy group than in the 0 Gy group. The differential gene expression in DCX-U87 cells before and after radiation is helpful for future investigations into the mechanisms of radiation therapy in neurogliocytoma cells.     

NATURAL BACKGROUND RADIOACTIVITY LEVELS IN THE TERRESTRIAL ENVIRONMENT OF HONG KONG

This paper analyses and summarizes the natural radionuclide contents of soil and building materials, radon concentrations and the penetrating radiation levels in Hong Kong. From these, a thorough and objective assessment for the terrestrial background irradiation level of Hong Kong was made. Finally, the annual effective dose equivalent received by Hong Kong people due to the natural background irradiation was calculated to be 3.2 mSv.     

Calculation of Plasma Radiation in Electrothermal-Chemical Launcher简

A numerical model of radiation has been adopted for electrothermM-chemical （ETC） launcher, in which Monte Carlo method and statistical physics are employed to simulate the process of a capillary plasma source in an ETC launcher. The effect on propellant grains with different average absorption coefficients is discussed. The plasma-propellant interaction is also discussed when combined with a thermal model. Results show that the strong instantaneous radiation is responsible for the transmission of energy to the propellant grains leading to ignition. The efficiency of energy absorption in the propellant bed always maintains a high level. Radiant energy caused by plasma is concentrated around the plaslna injector. And the ＂hot zone＂ efficiency is mainly affected by the properties of propellant grains within a small field around the plasma injector.