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Study on Stochastic Resonance of Electrical Sense based on Psychophysical Experiments.

Space Medicine & Medical Engineering.2006;0(04):-.

Objective To investigate the change of threshold of electrical sense through experiments in the presence of electrical noise according to stochastic resonance phenomenon that has been observed in somatosensory system.Method Psychophysical experiments were carried out using both single stimulus method based on random-gradient method and one-interval-forced-choice method.The glabrous skin of human fingers was choosed as the experimental objects,which was stimulated by square wave electrical signal mixed with electrical noise.Result The corresponding threshold of electrical sense can be reduced by the effect of external electrical noises.Conclusion Although electrical sense is not natural sense,stochastic resonance can occur in it, and effect of noise on enhancing this sense can be implemented by controlling external noises.

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Model Reseach of Effects of Defibrillation Waveform on Action Potential Duration.

Xiaodong HAN ; Zhenning NIE ; Zuxiang FANG ; Cuiwei YANG ; Xiaomei WU

Space Medicine & Medical Engineering.2006;0(04):-.

Objective To explore the mechanism underlying the superiority of the biphasic waveform to monophasic waveform in defibrillation.Method The Luo-Rudy model was adjusted so that it could be used to study defibrillation.Based on the adjusted model the effects of different defibrillation waveforms on cell action potential duration(APD) were studied.Result Biphasic electrical field pulse extended the APD longer than that with monophasic one.Moreover,biphasic waveforms with different strengths could prolong the APD almost equally,while monophasic pulses with different strengths showed different ability to prolong the APD and the spatial distribution of the APD became dispersed.It was also found that the strength of electrical fields pulse contributed much to the change of APD while the duration showed little effect.Conclusion The clinical superiority of biphasic pulses to monophasic pulses in defibrillation is resulted from its ability to prolong the time course of the APD and more importantly,it causes even spatial distribution of the APD.

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Preventive Effects of Iptakalim on Brain Edema Caused by Acute Hypobaric Hypoxia in Rats.

Hualing ZHU ; Hai WANG

Space Medicine & Medical Engineering.2006;0(04):-.

Objective To investigate the preventive effect of iptakalim hydrochloride(Ipt) on brain edema in rats after exposure to simulated high altitude and the mechanisms involved.Method Adult Wistar rats were randomly divided into normoxic control group,simulated plateau acute hypoxia group simulated 8 000 m for 8 h and three Ipt taking groups which were pretreated with 2, 4 and 8 mg(kg?d) of Ipt respectively for 7d before exposure to hypoxia.Water content was determined by the wet-dry method;Na~+,K~+,Ca~(2+) and Mg~(2+) content in the cortex was detected with all atomic absorption spectrophotometer;inorganic phosphorus standardization was applied to decide the activities of Na~+/K~+-ATPase,Ca~(2+)-ATPase and Mg~(2+)-ATPase;Occludin and AQP4 gene expression were determined by RT-PCR.Result The water content was increased and the concentration of Na~+ and Ca~(2+),the activities of Na~+/K~+-ATPase,Ca~(2+)-ATPase and Mg~(2+)-ATPase and the gene expression of the Occludin and AQP4 were all down-regulated in acute hypoxia group compared with normoxic control group.And these changes could be significantly relieved by pretreatment with Ipt.Conclusion Ipt can prevent the occurrence of brain edema caused by acute hypobaric hypoxia possibly related to the effect on water content,electrolytes concentration,ATPase activity and gene expressions of aquaporin and tight junction proteins.

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Effects of +Gz Exposures on Expression of HSP70 Protein in Rat Hippocampus.

Lei HAN ; Xiqing SUN ; Minggao LI ; Guixi MA

Space Medicine & Medical Engineering.2006;0(04):-.

Objective To observe changes of expression level of HSP70 protein in rat hippocampus after exposure to +Gz of different magnitudes and to investigate the machanism of HSP70 protein induced by +Gz exposure.Method One hundred rats were divided into: control group,+2 Gz group,+6 Gz group and +10 Gz group.The experimental rats were exposed to +2 Gz,+6 Gz and +10 Gz for 3 min respectively.The rats were killed 6 h,1 d,2 d,4 d,6 d after exposure and brain specimens were made for examination under microscope.The changes of HSP70 protein expression level were determined with immunohistochemical technology.Result The HSP70 protein expression level in the 3 experimental groups were significantly higher than that in control group.It began to rise 6 h after exposure,reached the peak after 1 d,and resumed to normal 6 d after exposure.The expression level was the highest in +6 Gz group and the lowest in +10 Gz group.Conclusion +Gz exposure can induce obvious changes of HSP70 protein expression level and the most prominent changes are found in rats after exposure to +6 Gz group.

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Effects of Hindlimb-unloading on Diameter of Intrafusal Fibers and Capsule at Equatorial Region of Rat Soleus Muscle Spindle.

Yongjin ZHU ; Sudi WU ; Xiaoli FAN ; Xinai SONG ; Linping XU

Space Medicine & Medical Engineering.2006;0(04):-.

Objective To observe the changes of diameter of intrafusal fibers and capsule at equatorial region of rat soleus muscle spindle caused by hindlimb-unloading.Method Tail-suspended female rats were used as the model of hindlimb-unloading,all rats were randomly divided into 4 groups according to body weight.The four groups were exposed to tail-suspension for: 7 d,14 d,28 d and 0 d,respectively.The diameter of intrafusal fibers and capsule of single muscle spindle was measured and analyzed.Result The diameter of intrafual fibers,including nuclear-bag fibers and nuclear-chain fibers, were reduced slightly in both 7 d group and 28 d group and obviously reduced in 14 d group.The capsule diameter at equatorial region was obviously reduced in 7 d group.Conclusion Hindlimb-unloading can obviously reduce the diameters of intrafusal fibers and capsule at equatorial region of rat soleus muscle spindle.

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Effects of Intermittent Head-up Tilt on the Endothelin Expression and Morphological Changes of Artery during Simulated Weightlessness in Rabbits.

Xiqing SUN ; Bing WANG ; Huipin SUN ; Fei SHI ; Jie GENG ; Fourth THE

Space Medicine & Medical Engineering.2006;0(04):-.

Objective To observe the effects of intermittent 45? head-uptilt on endothelin(ET-1) expression and morphological changes of femoral and carotid arteries in rabbits induced by 21 d simulated weightlessness.Method Twenty-four healthy male rabbits were randomly divided into control group,simulated weightlessness group and countermeasure group,8 rabbits in each group.The simulated weightlessness group kept head-down tilt for 21 d.The countermeasure group was exposed to 45? head-up tilt for 2 h every day during 21 d head-down tilt.After 21 d experiment,structure of femoral artery and carotid artery were studied and ET-1 expression was tested by immunohistochemical method.Result Detachment of endothelial cells in femoral artery,necrosis of smooth muscle cells and decreased ET-1 expression were found in animals in the simulated weightlessness group,and the vessel wall became thinner.While hyperplasia of endothelial cells and thickened internal elastic lamina of the carotid artery were also observed.No significant changes were observed in femoral artery and carotid artery in animals of the countermeasure group.ET-1 expression decreased in femoral artery but increased in carotid artery in animals of the simulated weightlessness group,but no significant change was found in both femoral and carotid arteries in animals of the countermeasure group as compared with those in the control group.Conclusion Twenty-one days simulated weightlessness may induce an atrophic change and decreased ET-1 expression in femoral artery,and hyperplastic change and increased ET-1 expression in carotid artery in rabbits.Two-hour 45? head-up tilt every day may partly counteract the change in femoral artery and carotid artery induced by simulated weightlessness.

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Effects of Microgravity on Human Spatial Orientation in Space Flight

Jian SONG ; Xufeng LIU ; Danmin MIAO

Space Medicine & Medical Engineering.2006;0(05):-.

In the researches of space flight,studies of the effects of microgravity on visual orientation were relatively few.This paper reviews recent progress on this topic.It surveys the spatial orientation problems encountered in spaceflight including 0-G inversion illusions,visual reorientation illusions,EVA height vertigo,and spatial memory problems described by astronauts.A vector model for sensory cue interaction was briefly described.

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Development of Controlled Ecological Life-support System in Russia

Hong LIU ; Chengying YU ; Liping PANG ; Jun WANG

Space Medicine & Medical Engineering.2006;0(05):-.

Controlled Ecological Life-support System(CELSS)is one of the key technologies that must be solved before founding permanent base in space such as Lunar or Mars base.After discussing with Russian experts and analysing the data,the author introduced something important about CELSS in Russia,including research methods,achievements and problems to be solved urgently.In the end a proposal for developing CELSS research in China was given based on them.

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Design of a Wearable Respiratory Inductive Plethysmograph and Its Applications

Zhengbo ZHANG ; Mengsun YU ; Ruoxin LI ; Taihu WU ; Jialong WU

Space Medicine & Medical Engineering.2006;0(05):-.

Objective To develop a new type of respiratory inductive plethysmograph to achieve high signal-noise rate(SNR)and low system power cost,and also to eliminate the cross-talk between chest and abdominal band sensors.Method Either of the two bands was powered by a very high power oscillator in a very short time,and these two bands were switched on in turn.The sensor structure of the respiratory inductive plethysmograph was modified so that these two bands could be embeded in a shirt conveniently.Result With these new designs,the cross-talk between these two bands was greatly eliminated and high SNR and low system power cost were achieved.This new wearable respiration monitoring system is easy to use,and can be used for long time and ambulatory monitoring.Conclusion This new system meets the design requirement with excellent performance.With this new wearable respiration monitoring system,non-invasive measurement of ventilation and non-intrusive detection of sleep apnea event can be achieved.

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sEMG Dynamics of Muscle Fatigue Induced by Maximal Voluntary Isometric Contractions

Haihong ZHANG ; Jian WANG ; Zhen YANG

Space Medicine & Medical Engineering.2006;0(05):-.

Objective To investigate the effect of muscle fatigue on linear and nonlinear dynamics of sEMG from biceps brachii during maximal voluntary isometric contractions.Method Ten young volunteers subjects performed non-fatiguing isometric contractions with four load levels and fatiguing maximal voluntary isometric contractions.Linear and nonlinear analysis were used to examine the sEMG signals and the changes of sEMG signals when MVC decreased to levels of 80% MVC,70% MVC,60%MVC and 50%MVC compared with the signals of sEMG during non-fatiguing contractions.Result Statistical analyses revealed that AEMG and %DET were significantly higher at fatigue states than those at non fatigue states,while MPF and C(n)were significantly lower than those at non fatigue states.With the development of muscle fatigue,MPF and %DET significantly decreased during maximal effort,while AEMG and %DET stayed stable.The interaction of load level and fatigue state for AEMG,MPF and C(n)were significant.Conclusion MPF and C(n)significantly decrease during maximal voluntary isometric contractions.sEMG dynamics between fatigue state and non-fatigue state is significantly different.

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