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Estimates of Space Radiation Exposure to Astronauts Using Male Voxel Model Based on MRI

Xianghong JIA ; Feng XU ; Zengxin HUANG ; Duicai LV ; Zhi ZENG ; Junli LI

Space Medicine & Medical Engineering.2008;21(4):299-303.

Objective To predict the astronaut organs radiation exposure and related health risks in the space radiation environment, the calculated method is studied. Methods A male voxel human model based on MRI and radiation data bank was build. The calculation was carried out with Monte Carlo particle transporting program GEANT4. Results The organ absorbed dose distribution and the effec-tive doses to the model in isotropic proton fields with energies ranges from 10 MeV to 500 MeV were obtained. Conclusion Based on the Chinese astronaut voxel model and the data set of proton spectrum measured in the space cabin, the cumulated dose in the model is gotten. The calculated skin dose is about 148.6 μGy/d, which is within in the range of 100 -300 μGy/d, published by USA and Russia.

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Analysis of Kaolin Intake in Rats Subjected to Different Motion Stimulations

Wenbo KANG ; Yulin DONG ; Fuxing ZHANG ; Jinlian LI ; Yunqing LI

Space Medicine & Medical Engineering.2008;21(2):79-83.

Objective To analyze the efficacy of kaolin intake amount as an index for motion sickness (MS)induced by different motion patterns stimulating the vestibular receptors of rats.Methods Rats were randomly divided into 5 groups.Three groups were subjected to one of the following stimulations,respectively-linear acceleration along either the interaural axis(IA)or body axis (AP),and double rotation(DR)stimulation.Other 2 groups were used as control.Kaolin intake was recorded for consecutive 6 d,3 d before and 3 d after stimulation,and the data were statistically analyzed.Results It was found that:1)following IA,AP and DR stimulations,25%,17% and 58% of the rats in each group increased mean kaolin intake by 1 g in the 3 d phase post-stimulation compared with that in the same duration of pre-stimulation,respectively;2)in contrast to some prewous reports,the present observation showed that high Ievel of kaolin intake post-stimulation may persist for more than one day.Conclusion All 3 tvpes of stimulation methods can serve as ways of specifically stimulating vestibular end-organs to induce kaolin intake increase,and double rotation iS the most effective.

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Intervention of Ciliary Neurotrophic Factor on Weightlessness-Induced Muscle Atrophy and Myofiber Phenotype Transition

Peng ZHANG ; Hongju LIU ; Minghao YANG ; Li LI ; Xin GE ; Xiang LI ; Xu WANG ; Ming FAN ; Xiaoping CHEN

Space Medicine & Medical Engineering.2008;21(3):240-244.

Objective To investigate the intervention of ciliary enurotrophic factors(CNTF)on weightlessness-induced muscle atrophy and its myofiber phenotype transition.Methods Tail-suspended (hindlimb unloading)of adult male Wistar rats were used to create the mode J of weightlessness-induced muscle atrophy.The effect of CNTF treatment on weightlessness-induced muscle atrophy and its myofiber phenotype transition was determined by analyzing the expression changes of MHCI/IIb and p130 or Myf5 with RT-PCR and Western blot.Results CNTF treatment in vivo markedly reversed weightlessness-induced muscle weight IOSS selectively in the slow-twitch muscle soleus.Moreover,during tail suspension,soleus weight loss and myofiber phenotype transition indicated that CNTF treatment could sigificantly attenuate the weight loss and slow to fast myofiber phenotrype transition in soleus compared with control(CNTF untreated and tail suspended).Furthermore,it was showed that the CNTF-induced intervention effect was associated with the protein level upregulation of muscle satellite cell-specific markers,P130 and Myf5.The satellite cell pool in CNTFtreated soleus was increased.Conclusion It iS firstly demonstrated that CNTF can attenuate weightlessness-induced muscle atrophy and its myofiber phenotype transition to be through the increase of satellite cell pool in soleus.

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Chronotherapy by Ribozyme Targeted to Telomerase in Nude Mice with a Transplanted Tumor: Model for Human Hepatic Cancer

Yi QU ; Zhengrong WANG ; Chaomin WAN ; Xiang HUANG ; Dezhi MU ; Cornelissen GERMAINE ; Halberg FRANZ

Space Medicine & Medical Engineering.2008;21(1):1-5.

Objective To investigate therapeutic autcomes of using telomerase inhibitors to treat cancer at the presumably most and least opportune circadian stages basing on our earlier study. Methods Twenty-four BALB/C nude mice were synchronized to a regimen of LD12:12 for 4 wk. Hepatic cancer cells (SMMC-7721) were implanted into both flanks of each mouse.Two weeks after transplantation,the hTERT-5'RZ was used to treat the hepatic cancer transplanted into the nude mice daily for two weeks,the injection times being either 9 or 21 HALO.Results The tumorinhibition ratio of mice treated at 21 HALO (65%) was statistically significantly higher than that of mice treated at 9 HALO (48%). Telomerase activity was also reduced to a greater extent in mice treated withhTERT-5'RZ at 21 than at 9 HALO, that was at the time of maximal circadian telomerase activity. Conclusion Injection of ribozyme targeted to telomerase during the tumor's DNA synthesis is associated with a betterinhibition of tumor growth and a better therapeutic outcome in hepaticcancer.

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Identification of Model Parameters Basing on Matched Processing between Simulated and Recorded sEMG Signals

Qiang LI ; Jihai YANG ; Zhangyan ZHAO ; Xuezhong CHU ; Xiang CHEN ; Zhi LOU

Space Medicine & Medical Engineering.2007;20(6):391-397.

Objective To identify the model parameters of surface Electromyography (sEMG) by comparison between simulated and recorded signals. Methods A physiological model of sEMG signal was established basing on several logical hypothetical conditions, such as motor unit action potentials (MUAP), motor unit recruitment and firing behavior caused by excitation, architecture of volume conductor and other simulated factors. According to the matched shapes between the simulated and recorded sEMG signals, a group of model parameters was obtained; according to the similar power spectrum variations of real sEMG signals, decreased muscle fiber conduction velocity (MFCV) was applied to simulate the sEMG signals of the fatigued muscle. Results The experimental results showed that the simulated superimposed MUAP shapes could be matched with the recorded MUAPs satisfactorily by adjusting some proper physiological parameters of the model. When the MFCV of each fiber was assumed to decrease, the mean and median frequency (MNF, MDF) of the simulated sEMG signals declined, and this phenomenon was very similar to that of the recorded sEMG signals and could be used to interpret the muscle fatigue process. Conclusion This model provides an effective approach to simulate real sEMG signals, and the simulated signals can also be used to help the analysis of recorded sEMG signals.

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Effects of Psoralen on ADR Multidrug Resistance and Ca2+ Concentration in MCF-7/ADR Cells

Tiange CAI ; Yu CAI ; Shaolei YU ; Xiaozhen FENG

Space Medicine & Medical Engineering.2007;20(5):313-316.

Objective To research the reversal effects of psoralen on multidrug resistant action and its influence on intracellular Ca2+ concentration in MCF-7/ADR cells and to explore its possible mechanisms of reversing multidrug resistance (MDR). Methods The inhibitory effects of psoralen on the viability of MCF-7/ADR cells were determined with MTT assay, intracellular adriamycin (ADR) concentration was assayed with HPLC and the intracellular Ca2+ concentrations in different incubative duration were detected with confocal microscope. Results Psoralen from 1 to 20 μmol/L reduced the value of IC50 of ADR in MCF-7/ADR cells, enhanced accumulation of ADR and influenced Ca2+ concentration with a negative correlation in different duration (24 h, 48 h and 96 h). Conclusion Psoralen can reverse MDR in MCF-7/ADR cells and its mechanism may be related to the increase of the intracellular accumulation of ADR by enhancing the intracellular Ca2+ concentration.

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An Accurately Represented Finite Element Model of Lumbar Motion Segment

Yaosheng LIU ; Qixin CHEN ; Fangcai LI ; Xiaojun TANG ; Jie FANG ; Shenghui LIAO ; Shice YU

Space Medicine & Medical Engineering.2007;14(2):79-86.

Objective To construct a detailed, 3-dimensional, anatomically accurate finite element (FE) model of lumbar L4-L5 segment from CT data with a new kind of computer aided design (CAD) method. Methods A modified "no-seed region segmentation" was done to extract the interest region in the CT scan images and produce a binary image. "Best cross-section planes" accounting for the preferential direction dictated by lumbar spine were placed on the initial iso-surface model, forming a "non-regular piecewise subspace". This subspace and the embedded iso-surface mode were transformed by local affine transforms to a "regular subspace", in which a surface mesh of high quality was generated quickly. Finally a reverse transform procedure was employed to recover the shape feature of the lumbar surface mesh of lumbar L4-L5 in the original 3-dimensional space, which was then imported into ANSYS for the 3-dimensional FE mesh construction. Results All complicated anatomical features of the L4-L5 segment were explicitly represented in the unprecedented finite element model. The predicted results for compression, flexion and extension correlated well with experimental data under similar loading configurations. Conclusion The presented CAD method containing advanced algorithm implements fast and accurate simulation of such complicated geometry with fine mesh representation for lumbar FE analysis.

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Relationship between Polymorphism of Pulmonary Surfactant Protein A Gene and Adaptation to Hypobaric Hypoxia

Shengwei WANG ; Xuechuan SUN ; Kunxiang LIU

Space Medicine & Medical Engineering.2007;20(4):235-239.

Objective To investigate the relation between polymorphisms of pulmonary surfactant protein A gene and adaptation to hypobaric hypoxia. Methods The genotype proportions and allel frequencies of 86 Tibetan mountaineers and 90 sea-level Hans were examined with polymerase chain reaction-sequence specific primer(SSP-PCR) reaction for surfactant protein A gene. Results The constituent ratio of A/A,A/G and G/G genotypes in A1-aa62 locus and C/C,A/C and A/A genotypes in A2-aa223 locus showed significant statistic difference between highland group and the sea-level control group(P＜0.05). A1-aa62 G/G and A2-aa223 A/C genotype demonstrated high odds ratio in Tibetan mountaineers. Moreover, the comparisons of genotypes and alleles in A1-219 locus showed no significant difference between the plateau group and the sea-level Han control(P＞0.05). Conclusion The single-nucleotide polymorphisms(SPN) in SP-A1aa62 and SP-A2aa223 may be associated with the adaptation to hypobaric hypoxia.

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A Scoring Method for Quantitative Assessment of Cardiovascular Health Status Based on Non-linear Parameters

Xia LI ; Jing BAI ; Xun JIN ; Zhiying REN

Space Medicine & Medical Engineering.2007;20(1):1-6.

Objective To study a scoring method for assessing function status of cardiovascular system quantitatively. Methods First, exercise heart rate variability (EHRV) was obtained from the primary dynamic electrocardiogram (ECG) recorded during exercise testing. Then appropriate entropy, relative complexity, and other three parameters extracted from poincare dispersed-dot plot were extracted from the EHRV. Discriminant analysis was used to classify two extreme groups.Results Based on the values of two groups from the discriminant formula, a scoring formula was proposed and four ranks were divided according to different score domains. A novel scoring method was established. To validate the proposed scoring method, 60 middle-aged hypertensives, 50 elder subjects and 110 young healthy subjects were examined and scored. Conclusion Scores of 220 subjects are consistent with their real health status. The proposed scoring method reflects the status of the subject's cardiovascular system effectively.

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Effects of Psoralen on Improving Chemotherapeutics Drug's Concentration of HL60 Cells

Yu CAI ; Shaolei YU

Space Medicine & Medical Engineering.2006;19(6):391-393.

Objective To determine the reversal effect of psoralen on multidrug resistance (MDR) in the harringtonine (HT)-resistant leukemic cell line HL60/HT. Method The modulating effect of psoralen on MDR in HL60 and HL60/HT cells were determined by the measurement of cell growth and viability via MTT assay. High performance liquid chromatography(HPLC) was used to analyze intracellular HT concentrations in HL60/HT and HL60 cells treated with psoralen. Result Psoralen from 1 to 20 μmol/L could reduce the value of IC50 to HT and enhance the accumulation of HT in HL60/HT cells. Conclusion Psoralen can reverse MDR of HL60/HT cells and is a potential modulator of MDR.

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