| As the audible sound and ultrasound, infrasound is a mechanical vibration wave with frequency in range of 0.0001 to 20Hz. With the physical characteristics of less attenuation in long distance spreading and strong penetration, infrasound is harmful to human and leads to body dysfunction or a even severe damage when the intensity comes to a enough certain degree. So people are becoming increasingly aware of the importance in studying the mechanisms of the occurrence, spreading, biological effects and preventive measures of the infrasound.Infrasound is existed widely in nature. It can be detected in our living condition, productive and military environments. In recent years many developed counties throw into a great amount of manpower and money in studying biological effects of infrasound, also they are gradually paying much attention to infrasound doing as a new concept weapon. Articles and reports about the infrasound are being increased year by year.However, the low density infrasound maybe has good effects in medical just like other physiology agents. Some reports founded the low density infrasound can be used in treatment for ametropia, keratitis, anorexia. Being a mechanical wave, infrasound as an elastic spring forces produces a mechanical stress which something likes a pull and press alternately forces. As we kone, bone is very sensitive to strain, it can gain modeling when in the adapted strain windows, but no article about the low density infrasound on bone can be seen in present.In the thesis, we observed the effects of bone modeling by low density infrasound on osteoporosis rats, and then to investigate the cellular proliferation , ALP activity , osteocalin (OCN) synthesis, extracelllular matrix(OPN/ ON ) mRNA level and cytoskeletal F actin expresion in vitro, to explore the infrasound signal transduction pathway into intracellular caused the bio-effects.This thesis is composed of four parts as follow: Part one: Effect of infrasound for the prevention of osteoporosis in orchiectomized SD ratsObjective:To determine the preventive effects of lower density infrasound pressure on bone loss in orchiectomied rats. Method: divided 32 SD male rats into the control group, osteoporosis group, 4Hz infrasound group and 20Hz infrasound group. The rats in last 3 groups had been orchiectomied. Every group was expoused under infrasound of 4, and 20Hz individually 100dB output 30min each day while the control group and the osteoporosis group no infrasound output. After 12 weeks ( every group expoused 5d per week ), we observed the change of serum osteocalcin (OCN), bone mineral density (BMD), mineralization rate (MAR) and hisomorphometric measurement and calculations of distal femur with imaging analysis process.Result: The osteoporosis group was obversly decresed in MAR and hisomorphometric measurement and calculations of distal femur than the control group (p<0.05 ). There was significantly increased in MAR and trabecular area, trabecular thickness, trabecular number in 4 Hz groups vs the osteoporosis group (p<0.05 ). In 4Hz group the serum osteocalcin also increased but no significant difference with the osteoporosis group. But in 20Hz group there were only increased in trabecular thickness, trabecular number ( p<0.05 ), the other measurement were no any differences with the osteoporosis group (p>0.05 ). There were no significant chang in BMD among the osteoprosis group and infrasound groups (p>0.05 ).Part two: Effect on biological characteristics of Osteoblast-like cells exposed by infrasound in vitroObjective:To determine the effects of infrasound pressure on biological characteristics of ostoblast-like cells,MC3T3-E1,in vitro.Method: After primary culture, and devided into 4 groups, the osteoblast-like cells, MC3T3-E1,were exposed by infrasound with intensity output of 100dB and frequency of 4, 12 and 20Hz individually for 30min each day. The cellular proliferation was detected by cell counting method. Biochemical analysis and radio-immunological method were used to measure alkaline phosphatease activity (ALP) and osteocalin (OCN) synthesis after 5 days.Result: The cell proliferation in experimental groups showed obviously faster than that in control group. The cell concentration in 4 and 12Hz groups was significantly increased from the 3rd day than in control group(p<0.05). Anyway, the same tendency could be observed in 20Hz group till the 5th day (p<0.05). There were not any differences between control group and experimental groups in ALP activity(p>0.05). The secretion of OCN was greatly increased in experimental groups(p<0.01).Part three: Effects of infrasound on osteonectin and osteopontin mRNA level of osteoblast-like cells MC3T3 in vitroObjective: To determine the effects of lower density infrasound pressure on osteopontin(OPN) and osteonectin(ON)mRNA level of osteoblast-like cells MC3T3.Method: After primary culture, the cells were exposed by infrasound with intensity output of 100dB and frequency of 4, 12 and 20Hz individually for 30min each day. After the 3rd day, .Result: Those infrasound exposured groups were significantly increased in the mRNA level of ON and OPN vs. the control group in 2h and 4h (p<0.05). There was no any differences between every groups and the control group in 8h in the mRNA level of OPN and ON (p>0.05).Part four: The effect of low density infrasound on filament F- actin of osteoblast MC3T3Objective:To study the alterations in expression of F-actin of osteoblast MC3T3 exposed by low density infrasound.Methods: After the primary cultured on coverglass , and divided into four groups just like the experiment part three, the cells in experimental groups were exposed by infrasound with intensity output of 100dB and frequency of 4Hz, 12Hz and 20Hz individually for 30min/d. The cells in control group were managed in the same environment as experimental groups with intensity output of 0dB. Laser scanning confocal microscope was used to examine the changes of F-actin after immunofluorescent staining and the photos were taken for further analysis of the cells` average fluorescence by spectrofluorimetric quantification.Results: In control group, most fluorescein-labelled substance was in diffusion states. Less actin filaments were tenuously short without direction. Correspondingly F-actin in the cells of experimental groups was thick long and showed in longitudinal arrangement after the exposure. The intensity of fluorescence was significantly increased. In every experiment group, there was a membrane-like boundary strong fluorescence. . More F-actin expression in experimental groups were being kept obviously increasing in 2h , 4h and 8h than the control group (p<0.05). However, there was not any significantly different in F-actin expression between the experimental groups ( p>0.05). Anyway cells in experimental groups showed a synchronous change.Conclusion:1. It could prevent bone loss in orchiectomied rats by expoused with 4 Hz/100dB infrasound 30min/d. There was significantly increased in MAR and trabecular area, trabecular thickness, trabecular number in 4Hz/100dB groups vs the osteoporosis group.2. It could promote proliferation of the osterblast-like cells by exposured with 4Hz/100dB infrasound for 30min each day in vitro. and promote secretion of the cells by 20Hz/100dB infrasound for 30min/d.3. The infrasound of 4Hz/100dB, 12Hz/100dB and 20Hz/100dB, 30min/d could promote the mRNA level of 0PN and 0N. This effects at last for 4 hours. There were no obviously different among 4Hz, 12Hz and 20Hz.4. F-actin expression can be increased in osteoblast MC3T3 exposed 30min/d with infrasound whioch intensity output of 100dB and frequency of 4Hz, 12Hz, 20Hz . The expression increasing of F-actin still can be founded in 8h after exposed under the low density infrasound.5. No special frequency effects can be founded in those cells-cultured expriments.
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