Objective To observe the effect of high positive acceleration(+Gz) environment on dental implant osseointegration in a rabbit model and to investigate its mechanism.Methods Forty-eight New Zealand white rabbits were r...Objective To observe the effect of high positive acceleration(+Gz) environment on dental implant osseointegration in a rabbit model and to investigate its mechanism.Methods Forty-eight New Zealand white rabbits were randomly divided into 6 groups. The rabbit’s mandibular incisors were extracted and 1 implant was placed in each socket immediately. After 1 week of rest, the rabbits were exposed to a high +Gz environment, 3 times a week. The rabbits were sacrificed at 3 weeks(2 weeks +Gz exposure), 5 weeks(4 weeks +Gz exposure), and 12 weeks(4 weeks +Gz exposure and 7 weeks normal environment) after surgery, respectively. Specimens were harvested for micro-CT scanning, histological analysis, and real-time polymerase chain reaction examination.Results Compared with those in the control group, the mRNA expression levels of bone morphogenetic protein-2(BMP-2), osteopontin(OPN), and transforming growth factor-β1(TGF-β1)were significantly lower(P < 0.05), while the mRNA expression level of receptor activator of nuclear factor κB ligand(RANKL) and the RANKL/osteoprotegerin(OPG) ratio were significantly higher(P < 0.05)at 3 weeks;values of bone volume fraction, trabecular number, bone-implant contact(BIC), and TGF-β1 and OPG mRNA expression levels were significantly lower(P < 0.05), and the value of trabecular separation, RANKL mRNA expression level and RANKL/OPG ratio were significantly higher(P < 0.05) at 5 weeks;and the value of BIC was still significantly lower(P < 0.05) at 12 weeks in the experimental group.Conclusion Early exposure to the high +Gz environment after implant surgery might have an adverse effect on osseointegration, and its mechanism could be related to the inhibition of osteoblast activity and promotion of osteoclast activity.展开更多
BACKGROUND Exposure to high sustained +Gz(head-to-foot inertial load) is known to have harmful effects on pilots' body in flight. Although clinical data have shown that liver dysfunction occurs in pilots, the prec...BACKGROUND Exposure to high sustained +Gz(head-to-foot inertial load) is known to have harmful effects on pilots' body in flight. Although clinical data have shown that liver dysfunction occurs in pilots, the precise cause has not been well defined.AIM To investigate rat liver function changes in response to repeated +Gz exposure.METHODS Ninety male Wistar rats were randomly divided into a blank control group(BC group, n = 30), a +6 Gz/5 min stress group(6 GS group, n = 30), and a +10 Gz/5 min stress group(10 GS group, n = 30). The 6 GS and 10 GS groups were exposed to +6 Gz and +10 Gz, respectively, in an animal centrifuge. The onset rate of +Gz was 0.5 G/s. The sustained time at peak +Gz was 5 min for each exposure(for 5 exposures, and 5-min intervals between exposures for a total exposure and non-exposure time of 50 min). We assessed liver injury bymeasuring the portal venous flow volume, serum alanine aminotransferase(ALT)and aspartate aminotransferase(AST), liver tissue malondialdehyde(MDA), Na+-K+-ATPase, and changes in liver histology. These parameters were recorded at 0 h, 6 h, and 24 h after repeated +Gz exposures.RESULTS After repeated +Gz exposures in the 6 GS and the 10 GS groups, the velocity and flow signal in the portal vein(PV) were significantly decreased as compared to the BC group at 0 h after exposure. Meanwhile, we found that the PV diameter did not change significantly. However, rats in the 6 GS group had a much higher portal venous flow volume than the 10 GS group at 0 h after exposure. The 6 GS group had significantly lower ALT, AST, and MDA values than the 10 GS group 0 h and 6 h post exposure. The Na^+-K^+-ATPase activity in the 6 GS group was significantly higher than that in the 10 GS group 0 h and 6 h post exposure.Hepatocyte injury, determined pathologically, was significantly lower in the 6 GS group than in the 10 GS group.CONCLUSION Repeated +Gz exposures transiently cause hepatocyte injury and affect liver metabolism and morphological structure.展开更多
BACKGROUND： Both animal experiments and clinical studies have shown that basic fibroblast growth factor （bFGF） and danshen （Salvia miltiorrhiza） can exhibit protective effects on ischemia-reperfusion cerebral inj...BACKGROUND： Both animal experiments and clinical studies have shown that basic fibroblast growth factor （bFGF） and danshen （Salvia miltiorrhiza） can exhibit protective effects on ischemia-reperfusion cerebral injury. OBJECTIVE： To test whether bFGF and danshen can protect cerebral injury induced by exposure to repeated, high, positive acceleration （＋Gz） in an animal model and to analyze the possible mechanisms. DESIGN, TIME AND SETTING： Randomized controlled animal study. The experiment was performed at the Research Center for Molecular Biology, Air-force General Hospital of Chinese PLA from April to August 2000. MATERIALS： A total of 20 clean grade, healthy, Sprague Dawley rats of both genders, weighing （200 ± 15） g, were provided by our experimental animal center. Rats were randomly divided into 5 groups： the control group, ＋Gz exposure group, bFGF group, danshen group, and saline group, with 4 animals per group. bFGF （Beijing Bailuyuan Biotechnology Co. Ltd.） and danshen solution （Shanghai Zhongxi Pharmaceutical Co. Ltd.） were used. METHODS： All rats were fixed on a rotary arm of a centrifugal apparatus （2 m in radius） with their heads oriented towards the center of the apparatus. Except for rats in the control group, the value of ＋Gz exposure was ＋14 Gz with an acceleration rate of 1.5 G/s. The peak force lasted for 45 seconds. ＋Gz exposure was performed three times with intervals of 30 minutes. Rats in the control group received the same ＋Gz procedure, but the G value was ＋1 Gz. Rats in bFGF group and danshen group were intraperitoneally injected with 100 μg/kg bFGF or 15 g/kg danshen solution, respectively, at 30 minutes prior to centrifugation and immediately after centrifugation. Rats in saline group were injected with the same volume of saline. Six hours after exposure, rats were decapitated. One hemisphere was preserved in liquid nitrogen for RNA extraction and the other was processed for apoptosis detection. MAIN OUTCOME MEASURES： mRNA levels of bcl-2 and p53 were measured by semi-quantitative reverse-transcription polymerase chain reaction. Apoptotic cell death was detected by terminal deoxynuleotidyl transferase-mediated dUTP nick end labeling. RESULTS： Changes in mRNA expression of bcl-2 and p53 and apoptotic cells were observed in rat brain six hours after repeated ＋Gz exposures, bFGF and danshen were able block the changes of bcl-2 and p53 expression and inhibit apoptotic cell death. CONCLUSION： The data suggest that apoptosis and changes in bcl-2 and p53 expression in the rat brain can be induced by repeated ＋Gz exposures. Apoptosis is, therefore, one of the molecular mechanisms of brain damage induced by repeated ＋Gz exposures, bFGF and danshen were of the equal potency in preventing brain injury induced by repeated ＋Gz exposures.展开更多
基金financially supported by China Postdoctoral Science Foundation [No.2016M592971]Logistics Department of the Chinese People’s Liberation Army [No.AKJ15J003]
文摘Objective To observe the effect of high positive acceleration(+Gz) environment on dental implant osseointegration in a rabbit model and to investigate its mechanism.Methods Forty-eight New Zealand white rabbits were randomly divided into 6 groups. The rabbit’s mandibular incisors were extracted and 1 implant was placed in each socket immediately. After 1 week of rest, the rabbits were exposed to a high +Gz environment, 3 times a week. The rabbits were sacrificed at 3 weeks(2 weeks +Gz exposure), 5 weeks(4 weeks +Gz exposure), and 12 weeks(4 weeks +Gz exposure and 7 weeks normal environment) after surgery, respectively. Specimens were harvested for micro-CT scanning, histological analysis, and real-time polymerase chain reaction examination.Results Compared with those in the control group, the mRNA expression levels of bone morphogenetic protein-2(BMP-2), osteopontin(OPN), and transforming growth factor-β1(TGF-β1)were significantly lower(P < 0.05), while the mRNA expression level of receptor activator of nuclear factor κB ligand(RANKL) and the RANKL/osteoprotegerin(OPG) ratio were significantly higher(P < 0.05)at 3 weeks;values of bone volume fraction, trabecular number, bone-implant contact(BIC), and TGF-β1 and OPG mRNA expression levels were significantly lower(P < 0.05), and the value of trabecular separation, RANKL mRNA expression level and RANKL/OPG ratio were significantly higher(P < 0.05) at 5 weeks;and the value of BIC was still significantly lower(P < 0.05) at 12 weeks in the experimental group.Conclusion Early exposure to the high +Gz environment after implant surgery might have an adverse effect on osseointegration, and its mechanism could be related to the inhibition of osteoblast activity and promotion of osteoclast activity.
文摘BACKGROUND Exposure to high sustained +Gz(head-to-foot inertial load) is known to have harmful effects on pilots' body in flight. Although clinical data have shown that liver dysfunction occurs in pilots, the precise cause has not been well defined.AIM To investigate rat liver function changes in response to repeated +Gz exposure.METHODS Ninety male Wistar rats were randomly divided into a blank control group(BC group, n = 30), a +6 Gz/5 min stress group(6 GS group, n = 30), and a +10 Gz/5 min stress group(10 GS group, n = 30). The 6 GS and 10 GS groups were exposed to +6 Gz and +10 Gz, respectively, in an animal centrifuge. The onset rate of +Gz was 0.5 G/s. The sustained time at peak +Gz was 5 min for each exposure(for 5 exposures, and 5-min intervals between exposures for a total exposure and non-exposure time of 50 min). We assessed liver injury bymeasuring the portal venous flow volume, serum alanine aminotransferase(ALT)and aspartate aminotransferase(AST), liver tissue malondialdehyde(MDA), Na+-K+-ATPase, and changes in liver histology. These parameters were recorded at 0 h, 6 h, and 24 h after repeated +Gz exposures.RESULTS After repeated +Gz exposures in the 6 GS and the 10 GS groups, the velocity and flow signal in the portal vein(PV) were significantly decreased as compared to the BC group at 0 h after exposure. Meanwhile, we found that the PV diameter did not change significantly. However, rats in the 6 GS group had a much higher portal venous flow volume than the 10 GS group at 0 h after exposure. The 6 GS group had significantly lower ALT, AST, and MDA values than the 10 GS group 0 h and 6 h post exposure. The Na^+-K^+-ATPase activity in the 6 GS group was significantly higher than that in the 10 GS group 0 h and 6 h post exposure.Hepatocyte injury, determined pathologically, was significantly lower in the 6 GS group than in the 10 GS group.CONCLUSION Repeated +Gz exposures transiently cause hepatocyte injury and affect liver metabolism and morphological structure.
文摘BACKGROUND： Both animal experiments and clinical studies have shown that basic fibroblast growth factor （bFGF） and danshen （Salvia miltiorrhiza） can exhibit protective effects on ischemia-reperfusion cerebral injury. OBJECTIVE： To test whether bFGF and danshen can protect cerebral injury induced by exposure to repeated, high, positive acceleration （＋Gz） in an animal model and to analyze the possible mechanisms. DESIGN, TIME AND SETTING： Randomized controlled animal study. The experiment was performed at the Research Center for Molecular Biology, Air-force General Hospital of Chinese PLA from April to August 2000. MATERIALS： A total of 20 clean grade, healthy, Sprague Dawley rats of both genders, weighing （200 ± 15） g, were provided by our experimental animal center. Rats were randomly divided into 5 groups： the control group, ＋Gz exposure group, bFGF group, danshen group, and saline group, with 4 animals per group. bFGF （Beijing Bailuyuan Biotechnology Co. Ltd.） and danshen solution （Shanghai Zhongxi Pharmaceutical Co. Ltd.） were used. METHODS： All rats were fixed on a rotary arm of a centrifugal apparatus （2 m in radius） with their heads oriented towards the center of the apparatus. Except for rats in the control group, the value of ＋Gz exposure was ＋14 Gz with an acceleration rate of 1.5 G/s. The peak force lasted for 45 seconds. ＋Gz exposure was performed three times with intervals of 30 minutes. Rats in the control group received the same ＋Gz procedure, but the G value was ＋1 Gz. Rats in bFGF group and danshen group were intraperitoneally injected with 100 μg/kg bFGF or 15 g/kg danshen solution, respectively, at 30 minutes prior to centrifugation and immediately after centrifugation. Rats in saline group were injected with the same volume of saline. Six hours after exposure, rats were decapitated. One hemisphere was preserved in liquid nitrogen for RNA extraction and the other was processed for apoptosis detection. MAIN OUTCOME MEASURES： mRNA levels of bcl-2 and p53 were measured by semi-quantitative reverse-transcription polymerase chain reaction. Apoptotic cell death was detected by terminal deoxynuleotidyl transferase-mediated dUTP nick end labeling. RESULTS： Changes in mRNA expression of bcl-2 and p53 and apoptotic cells were observed in rat brain six hours after repeated ＋Gz exposures, bFGF and danshen were able block the changes of bcl-2 and p53 expression and inhibit apoptotic cell death. CONCLUSION： The data suggest that apoptosis and changes in bcl-2 and p53 expression in the rat brain can be induced by repeated ＋Gz exposures. Apoptosis is, therefore, one of the molecular mechanisms of brain damage induced by repeated ＋Gz exposures, bFGF and danshen were of the equal potency in preventing brain injury induced by repeated ＋Gz exposures.
