Study On The Damage And Mechanism Of Mouse Body In Simulated Space Sub-magnetic Environment

Many vertebrates,such as migratory birds and sea turtles,are able to sense the earth's magnetic field,for positional and directional information during their long-distance migrations.It has been established that eliminating the local GMF,i.e.hypomagnetic field,interferes with many aspects of life functions.The magnetic field intensity in outer space is far less than geomagnetic filed(GMF),which belongs to HMF.Space scientists paid more attention to biological effect of HMF in 1960s.Animal experiments show that the HMF exposure has adverse effects on the processes of embryonic development and the brain functions.Consecutive HMF exposure leads to increased abnormality in newt and Xenopus laevis.Alterations of the vocal behavior and circadian activity rhythm,dysfunction in the learning and memory ability,and reduction in stress-induced analgesia have been observed in the HMF-exposed animals.It is even reported that short-term HMF exposure can disrupt human cognitive processes.Given that the HMF is an essential environmental factor of outer space,increasing attentions have been paid to the studies on the biological effects of the HMF for the life support and health care of the astronauts in the recent decades.But the biological effects on mammals are still not clear,which may provide more reference to health care of astronauts.Previous studies in our lab have demonstrated that elimination of GMF may lead to structural and functional abnormalities at molecular,cellular,organism levels.For example,HMF exposure leads to malformations of Xenopus laevis development,promoting proliferation of SH-SY5Y and inducing improper assembly of tublin.So,in this work,we studied the effects of HMF on mental and physical health of adult C57 mice.In this experiment,two systems shielding geomagnetic field were used:3-axis Helmholtz coils system and Permalloy tank system.Experiments aimed at short-term effects and long-term effects were performed respectively.Open-field test and elevated plus maze test were used to test that whether the mice became anxiety.The oxidative stress level in brain,liver and serum was assessed through the parameters of TAC,SOD,CAT and MDA.SOD protein level was determemed by ELISA.The structure of SOD was detected with intrisct fluroscence and circular dichroism.Results showed that 3-days HMF exposure increases anxious behavior in adult C57 mice.The mood wing induced by hypomagnetic in mammals was first reported in this paper.Besides,it was proved that Cu/Zn-SOD can response to HMF directly in vivo and in vitro,which may lead to oxidative stress in organism finally.But this influence in the activity of Cu/Zn-SOD was not associated with the structure of it for no difference was observed in circular dichroism of Cu/Zn-SOD incubated in HMF.Long-term HMF(30 days)effects on adult C5 7 mice were also explored in this experiment.The body weight,food and water assuming were recorded in these thirty days.The athletic ability of the mice was assessed with open field,rota rod and tread mill tests.The learning and memory ability was detected with morris mater maze.Their whole blood was collected for the detection of blood routine;serum was analysied for the ion concentration with ICP-AES.H2O2 level,SOD activity and CAT activity in serum was measured with kits.Results showed that the HMF-exposed mice required more rest and their mean velocities were significant decreased in open field test,and the duration of continuous operation in treadmill was reduced.However,the performances in the rota rod were the same with the GMF control.These results indicate that HMF exposure weakens the athletic activity,but not balanced capacity.The body weight increase of the HMF-exposed mice was slower than the control from day 14 to day 24 while water and food assuming was the same with control.Blood routine analysis showed that the concentration of neutrophil granulocyte was significantly increased after one-month HMF exposure.However,no significant change was observed in serum microelements and the oxidative stress indexes.We can draw a preliminary conclution that short-term HMF would cause oxidative stress in adult C57 mice,and induced anxiety-like behaviors meanwhile;all these may result from Cu/Zn-SOD,which responsed to HMF directly.Then activity of total SOD would back to normal for its compensatory mechanisms,along with oxidative stress and anxiety-like behavior disappeared.As exposure time prolonged,the damage would be irreversible.After 30 consecutive days HMF exposure,the body weight,athletic ability and blood system were all abnormal,and it's still hard to confirm the exact target in this effect.Further investigations at histological and cellular level under this system would provide useful data for the mechanism of the HMF effect and contribute to the development of the counteractive strategy of the adverse HMF effect.