Objective　To observe rat plasma angiotensin Ⅱ (AⅡ) content change after exposed to infrasound. Methods　Infrasound was exposed to rats for 1,7,14,21 d and two hours every time in a day. After half, six, twelve, eighteen and twenty-four hours, AⅡcontent change was observed. Results　After exposed to infrasound for 1 d,AⅡcontent continued to increase in the next twenty-four hours compared to control group (P<0.01).After infrasound exposure for 7 d,AⅡ began to increase after half hour compared to control group(P<0.01), reached maximum at twelve hours, then began to decrease and turned less than that in the control group at twenty-four hours(P<0.05).After infrasound exposure for 14 d, AⅡ increased significantly compared to the control group(P<0.01).At six hours and twelve hours,there was no significant difference(P>0.05),it increased notably at eighteen hours and twenty-four hours(P<0.01).After infrasound exposure for 21 d, AⅡ began to increase at half hour compared to the contol group(P<0.05),reached maximum at twelve hours,then began to decrease and showed no significant difference at twenty-four hours(P>0.05).Conclusion　After infrasound exposure, there was irregular change of rat plasma AⅡ content at different times.

Objective To investigate the effects of 8Hz infrasound on spatial learning ability of rats and its the underlying mechanism. Methods Forty male SD rats were randomly divided into a control group and an experiment group (consisting of the 8Hz, 90dB, 100dB and 130dB subgroups). The experimental subgroups were exposed to 8Hz, 90dB, 100dB or 130dB infrasound for 2 hours daily, respectively, for a total of 6 days. All of the rats were taken out of the infrasonic depot once a day and given Morris maze training. And at last the brain of the rats were harvested and treated with immunohistochemical staining for detection of ryanodine receptor (RyR). The content of RyR in hippocampi and temporal cortex were detected under an optical microscope. Results The rats in the 8Hz, 90dB, 100dB and 130dB subgroups showed prolonged latency in Morris training ( P =0.010, P =0.001 and P = 0.000 ). The hippocampi and temporal cortex of rats in 8Hz, 90dB, 100dB and 130dB subgroups showed less positive neurons of RyR ( P =0.000). There was a negative correlation between the latency period of rats finding the hidden platform and the content of RyR in hippocampus and temporal cortex. Conclusion Infrasound of 8Hz, 90dB, 100dB and 130dB could decrease the spatial learning ability of rats, and this was possibly related to the reduce of RyR in hippocampus and temporal cortex.

Objective To study the effect of 8Hz infrasound on the expression of 5-HTR of hippocampus and temporal cortex in rats. Methods SD rats were exposed to 8Hz, 90dB,100dB or 130dB infrasound, respectively for 2 hours daily. Then the rats' brains were taken and given stained immunohistochemically for (5-hydroxy tryptamine receptor,5-HTR). The content of 5-HTR in hippocampus and temporal cortex were detected under an optical microscope. Results The animals in the infrasound groups had less expression of 5-HTR in hippocampus and temporal cortex, and the least were at the 35th day for 90dB group and 100dB group and the 28th day for 130dB group (P

Objective To observe the expression of polysialic acid-neural cell adhesion molecule (PSA-NCAM) in the rat hippocampus after infrasound exposure. Methods Ninety-six Sprague-Dawley rats were random-ized into a 16 Hz 130 dB infrasound exposure group (n =72) and a control group (n =24). Rats of the infrasound exposure group were exposed to 16 Hz 130 dB infrasound in a barochamber 2 h/d for 1, 7, 14 and 21 d. The rats' brains were removed and immunohistochemieal methods were used to detect the expression of PSA-NCAM in the hip-pocampus on the 1st, 7th, 14th, and 21st day during treatment and on the lat, 7th, and 14th day after the treatment ended. Results The expression of PSA-NCAM in the rats' hippocampuses increased after exposure for 1 d, reached its peak at the 14th day, then had decreased by the 21st day but remained at a higher level than in the controls (P≤ 0.05). Conclusion The expression of PSA-NCAM in the rat hippocampus is increased by exposure to 16 Hz 130 dB infrasound, but the levels recover somewhat after infrasound exposure ends. lnfrasound could induce neural injury and promote the migration of neural stem cells. PSA-NCAM might participate in the repair of neural injuries re-suiting from infrasound exposure.

Objective To study the effect of 16 Hz infrasound on the proliferation of the neural stem cells in rats' hippocampus.Methods72 SD rats were randomized into 16 Hz-130 dB infrasound exposure group(n=24),16 Hz-90 dB infrasound exposure group(n=24)and control group(n=24).Rats of the infrasound exposure groups were exposed to 16Hz 90dB/130dB infrasound barochamber system,2 h/d for 1 d,7 d,14 d,or 21 d.Their brains were removed and anti-nestin immunohistochemistry was used to observe the neural stem cells in rats' hippocampus.ResultsThe expression of nestin in rats' hippocampus increased after exposure for once and increased with the exposure time.It reached its peak on the 14th day,decreased on the 21st day but remained higher level.The reaction of 90 dB group was weaker than that of 130 dB group.ConclusionThe brain injuries result from 16 Hz infrasound exposure can enhance the proliferation of neural stem cells in rats' hippocampus which might participate in the repair of neural injuries.

Objective To explore the effects of infrasound frequency and intensity on gastric emptying in rats. Methods One hundred and forty rats were randomly divided into a control group, and groups receiving 8 Hz-90 dB, 8 Hz-130 dB and 16 Hz-130 dB infrasound. Another 70 rats were randomly divided into a control group and an exposure group continuously stimulated with infrasound at 8 Hz and 130 dB. The control group again was not exposed. The gastric emptying rate of the rats in all the groups was tested at different time points. Results ①Compared with the control group, gastric emptying rate decreased significantly after exposure to infrasound for 7 or 14 days. After exposure for 1 day, no significant difference was found. After exposure for 7 , 14, 21 or 28 days, gastric emptying decreased significantly more in the 8 Hz-130 dB group than in the 8 Hz-90 dB group or the control group. ②Compared with the controls, gastric emptying decreased in the 16 Hz-130 dB group after exposure for 1 , 7 and 14 days, but there was no significant difference between these two groups after 21 or 28 days. Gastric emptying decreased significantly more at 8 Hz-130 dB than at 16 Hz-130 dB after exposure for 14 or 28 days.③Gastric emptying tended to recover after exposure of 14 days to 8 Hz-130 dB infrasound, but compared with the controls, gastric emptying was still reduced after exposure had been stopped for 1 , 7 , 14, 21 and 28 days. Conclusion Infrasound at 8 Hz-90 dB, 8 Hz-130 dB or 16 Hz-130 dB can restrain stomach emptying. The extent of the reduction is closely related to the frequency, intensity and exposure time. Gastric emptying tends to recover after infra-sound exposure is stopped.

Objective To further investigate the threshold value and the dose-effect relationship of infrasound on the rat pallium, and to observe the effects on the pallium's ultrastructure. Methods Rats were exposed to 16 Hz, 90 dB infrasound for 2 hours daily. With a transmission electron microscope, changes in the ultrastructure of the cortex of the rats' parietal lobes were observed 2 hours, 3 days and 7 days after the treatment. Results There were no changes in the ultrastructure of the pallium in rats which had been exposed for 7 days or 14 days. Denaturation appeared when the rats had been exposed for 21 days, 28 days or 35 days. Denaturation become more serious as the exposure time increased beyond 21 days. Denaturation and damage gradually returned to normal with time after exposure. Conclusion 16 Hz, 90 dB infrasound exposure over an extended time may cause denaturation and other changes in the ultrastructure of the pallium in rats. Such changes can return to normal with time.

Objective To observe the effects of infrasound on the expression of inducible nitric oxide synthase(iNOS)and endothelial nitric oxide synthase(eNOS)in gastric tissues in rats.Methods The study consisted of a total of 210 SD rats.Of them,140 rats were randomly divided into 8 Hz-90 dB,8 Hz-130 dB and 16 Hz-130 dB experimental groups and a control group A.The experimental groups were exposed to infrasound with different frequencies and intensities,2h/d.After exposure for 1,7,14,21 and 28 days,7 rats randomly selected from each group underwent an examination of the expression of iNOS and eNOS in gastric tissues.The other 70 rats were randomly divided into a control group B and an exposure group continuously stimulated by infrasound with 8 Hz-130 dB for 14 days,2 h/d,and after stopping exposure for 1,7,14,21 and 28 days;the same indexes were detected in 7 rats randomly selected from each group.Results ① Compared with that in the control group A,the expression of iNOS in gastric tissues significantly increased in 8 Hz-90 dB group after exposure for 14 and 21 days,in 8 Hz-130 dB group after exposure for 7,14,21 and 28 days and in 16 Hz-130 dB group after exposure for 7 and 14 days(P

0.05),but there are increases of that in 90dB/7d ( P 0.05). Conclusion The results showed that 8Hz, 90dB/130dB infrasound definitely induced increases of apoptosis ratio in the hippocampus cells after certain time of exposure, suggesting that there are damages occurred by infrasound field with 90dB or 130dB and some adaptation of the hippocampal cells ensued after a certain period of time.

Objective To observe the effects of infrasound on rat myocardial cells and to study its underlying mechanism. Methods One hundred Sprague-Dawley rats were divided into a normal control group and a infrasound exposure group, composed of various subgroups subject to exposure to infrasound for 2 hours daily for 1 d,7 d,14 d,21 d,and 28 d, respectively. The ultra-microstructure and apoptosis of the rat myocardial cells were observed, and SOD and MDA were measured. Results After exposure to infrasound, significant ultra-microstructural impairment and increased apoptosis of the myocardial cells were observed in the infrasound exposure group as compared to those of the normal control group,(P