Feasibility study of in vivo fingernail dosimetry by electron paramagnetic resonance / 中华放射医学与防护杂志

Objective To explore the feasibility of EPR in vivo fingernail dosimetry to address the difficulty in separating mechanically induced signals from fingernail EPR dosimetry for need of nuclear medical emergency aid.Methods Using the specially designed EPR in vivo measurement system,uncut fingernails were measured to obtain the characteristics of EPR signal without mechanically induced signals.The in vivo fingernail experiment was carried out to evaluate the impact of in vivo condition on the spectra.Actual in vivo measurement experiment was conducted to evaluate the interference of the in vivo condition on EPR spectra.Results The background signal distribution of uncut fingernails was obtained and background signals had no significant difference between male and female(P＞0.05).The dose response curve in the range of 2-10 Gy was established,and the half-life of the fingernail radiation-induced signal was approximately 5 d.The water treatment combined with temperature-changing was established for restoring the background signal.EPR signal obtained after restoring treatment has no significant difference with background signal (P＞ 0.05).The EPR spectra of in vivo fingernails were obtained.Conclusions The EPR spectra without mechanically induced signals can be acquired by this method.The feasibility of the in vivo fingernail EPR dosimetry is preliminarily verified.

Stability of carbonate hydroxyapatite dosimeter material / 军事医学

Objective To develop a promising type of radiation dosimeter based on doped hydroxyapatite,and to study the stability of dosimetric characteristics indepth.Methods The samples prepared by stereotyping techniques were stored under different temperatures,humidity and illumination conditions after 60Co γ-ray irradiation.Electron spin resonance (ESR) technique was used to quantitatively measure the radiation-induced free radical signal.Results The signal change was less than 3% when the dosimeter was preserved at 4℃ or room temperature within 3 months in the experiment.At 40℃,the signal changed by about 13%,but at room temperature with the humidity less than 36%,the signal changed less than 2%.The change rose to about 8% when humidity was 76%.However,no significant decay of signal strength occurred at relatively high temperatures and under high humidity conditions.When the samples were stored under average illumination of 1600 lux or in a light-resistant container,the signal changes were less than 3.8% or 3.4% respectively.Long-term stability inspection at room temperature suggested a signal change within 4.8%.Conclusion The dosimetric properties of the material don't change significantly below room temperature in a natural environment and exhibit good stability over long-term storage.The free radical signal is not influenced drastically by relatively strong light exposure.However,a high temperature or a highly humid environment may have some effect on the measurement process,which should be taken into consideration in further applications.

Enamel dose calculation by electron paramagnetic resonance spectral simulation technique / 中华放射医学与防护杂志

Objective To optimize the enamel electron paramagnetic resonance (EPR) spectral processing by using the EPR spectral simulation method to improve the accuracy of enamel EPR dosimetry and reduce artificial error.Methods The multi-component superimposed EPR powder spectral simulation software was developed to simulate EPR spectrum models of the background signal(BS) and the radiation- induced signal (RS) of irradiated enamel respectively.RS was extracted from the multi-component superimposed spectrum of irradiated enamel and its amplitude was calculated.The dose-response curve was then established for calculating the doses of a group of enamel samples.The result of estimated dose was compared with that calculated by traditional method.Results BS was simulated as a powder spectrum of gaussian line shape with the following spectrum parameters:g =2.00 35 and Hpp =0.65 - 1.1 mT,RS signal was also simulated as a powder spectrum but with axi-symmetric spectrum characteristics.The spectrum parameters of RS were:g(1) =2.0018,g (11) =1.996 5,Hpp =0.335 - 0.4 mT.The amplitude of RS had a linear response to radiation dose with the regression equation as y =240.74x + 76 724 ( R2 =0.9947 ).The expectation of relative error of dose estimation was 0.13.Conclusions EPR simulation method has improved somehow the accuracy and reliability of enamel EPR dose estimation.

Application of ESR imaging technique in studying of skin-penetration properties of nitroxide free radical / 生物医学工程学杂志

A set of L-band electron spin resonance imaging (ESRI) equipment suitable for biological species was developed and an ESRI experiment model for viable skin samples was established. The mechanic process of nitroxide free radical TEMPO (2,2, 6, 6-tetramethyl-1-piperidinyloxy) penetrating through skin sample and the spin density distribution of TEMPO after it interacted with skin sample were detected by the developed ESRI method. Skin samples were extracted from mice back. The experimental samples were prepared by cutting the skin pieces into square shape of 2 x 2 cm2 and then the samples were divided into three groups by treating them with three different methods: Method A, simple treatment by simply cutting the hair; method B, 8% Na2S depilation treatment for 10 min; method C, 8% Na2S depilation and then 5% pancreatic digestion treatment for 2 hours. The liposoluble solvent DMSO (dimethyl sulfoxide) and distilled water were used as two kinds of solvent for the TEMPO liquor. The results indicated that the skin-penetration properties of TEMPO were significantly different among samples treated with different methods and the surface cornifin of skin offered remarkable resistance to TEMPO. The TEMPO liquor of water could hardly penetrate through skins, whereas about 20%-30% of the original TEMPO compounds that solved in liposoluble solvent DMSO could penetrate through the skin sample treated with method C after 16 hours of interaction. Furthermore, the penetration rate of TEMPO through the skin tissue was a strong time dependent process. The preliminary application results suggested that ESRI technique could provide an effective and applicable method for dynamically researching skin-penetration properties of some special kinds of materials such as paramagnetic compounds.

The effects of electromagnetic pulse on fluidity and lipid peroxidation of mitochondrial membrane / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the effects of intense electromagnetic pulse(EMP) on the biological effects of mitochondrial membrane.</p><p><b>METHOD</b>Rat liver mitochondrial suspension was exposed to EMP at 60 kV/m level. The changes of membrane lipid fluidity and membrane protein mobility were detected by ESR and spin label technique. Malondialdehyde(MDA) was detected by spectrophotometer.</p><p><b>RESULTS</b>The mobility of membrane protein decreased significantly(P < 0.05). Correlation time (tau c) of control group was (0.501 +/- 0.077) x 10(-9)s, and tau c of EMP group was (0.594 +/- 0.049) x 10(-9)s, indicating that the mobility of protein was restricted. The fluidity of mitochondrial membrane increased significantly(P < 0.05) at the same time. Order parameter(S) of mitochondrial membrane lipid in control group was 0.63 +/- 0.01, while S of EMP group was 0.61 +/- 0.01(P < 0.05). MDA decreased significantly.</p><p><b>CONCLUSION</b>The mobility and lipid peroxidation of mitochondrial membrane may be disturbed after EMP exposure.</p>

Effect of extraneous sugar on the reactive oxygen species metabolism of strept ococcus mutans / 实用口腔医学杂志

Objective:To study the effect of extraneous sugar on rea ct ive oxygen species metabolism of Streptococcus mutans. Methods: Electron spin resonance (ESR) method was used to measure reactive oxygen spe cies of Streptococcus mutans incubated in the different sugar incubation con ditions. Results:With the increase of glucose at 0.0062~0.05 mo l/L, the quantities of reactive oxygen species produced by Streptococcus mutan s increased and increased to the maximum when Streptococcus mutans were in cubated in different sugar culture fluids within 2 h. All kinds of sugar promote d reactive oxygen species metabolism of Streptococcus mutans. Conclu sion:Extraneous sugar promotes reactive oxygen species metabolism of Streptococcus mutans.