Effects of driving behavior on real-world emissions of particulate matter, gaseous pollutants and particle-bound PAHs for diesel trucks.

This study employed a portable emissions measurement system to investigate the effects of vehicle attributes, driving behavior, and road grade on real-world emissions of particulate matter (PM), regulated gaseous pollutants, and particle-bound polycyclic aromatic hydrocarbons (PAHs) for old-model diesel trucks (model year 1995-2006, 6.7-35.0 metric ton) with little to no tailpipe emission control. The rated power of engines was a major determinant of the distance-specific emission factors of PM, particle-bound PAHs, and most gaseous pollutants. However, the engine size was unrelated to the total hydrocarbon emission factor and the benzo[a]pyrene equivalent (BaPeq) emission factor of PAHs. Aggressive (AG) and normal (NR) driving behaviors were quantitatively defined with a relative positive acceleration. The emission factors of PM, CO2, and THC were significantly different (p < 0.05) between the AG and NR driving modes. AG driving caused an average increase in emissions of PM, CO2, NOx, and particle-bound PAHs by 122%, 56%, 15%, and 128%, respectively, compared to the respective emissions under the NR mode. The BaPeq emission factor of PAHs in the AG mode was more than 10 times that in the NR mode. The road gradient (ranging from -9.3% to 9.0% over the test route) had significant impacts on the emissions of PM, CO2, and NOx. PM, CO2, and NOx emission factors increased by 109%, 168%, and 160%, respectively, in the >6% grade bin and decreased by 95%, 91%, and 90%, respectively, in the equivalent negative-grade bin, implying that the decrease in emissions on negative road slopes may not compensate for the increase in emissions on the equivalent positive road slopes despite the road slope being compensated. The findings of this study will be valuable for developing air quality management strategies and furthering scientific knowledge on the complex interplay of different variables that affect real-world emissions of on-road vehicles.

Effect of High Positive Acceleration (+Gz) Environment on Dental Implant Osseointegration:A Preliminary Animal Study.

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-ß1 (TGF-ß1) 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-ß1 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.

Positive acceleration adaptive training attenuates gastric ischemia-reperfusion injury through COX-2 and PGE2 expression.

The mechanism involved in the effects of positive acceleration adaptive training (PAAT) on gastric ischemia-reperfusion injury (GI-RI) has not been fully characterized. The aim of the present study was to investigate the effects of PAAT in attenuating GI-RI in a rat model. The inflammatory factor and caspase-3 levels were measured using ELISA kits. A western blot assay was used to analyze tumor necrosis factor-α (TNF)-α, tumor necrosis factor receptor 1 (TNFR1), tumor necrosis factor-related apoptosis inducing ligand (TRAIL), death receptor (DR) 4, DR5, cyclooxygenase (COX)-2, COX-1 and prostaglandin E2 (PGE2) protein expression levels. It was revealed that PAAT could alleviate GI-RI and inflammatory factor levels in a rat model. PAAT suppressed TNF-α and TNFR1 protein expression levels, inhibited TRAIL, DR4, DR5, COX-2 and PGE2 protein expression levels; however, it did not have an effect on COX-1 protein expression in the model of GI-RI. The data indicated that the effects of PAAT attenuated GI-RI through the downregulation of COX-2 and PGE2 expression.

Effects of positive acceleration (+Gz stress) on liver enzymes, energy metabolism, and liver histology in rats.

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 (6GS group, n = 30), and a +10 Gz/5min stress group (10GS group, n = 30). The 6GS and 10GS 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 by measuring 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 6GS and the 10GS 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 6GS group had a much higher portal venous flow volume than the 10GS group at 0 h after exposure. The 6GS group had significantly lower ALT, AST, and MDA values than the 10GS group 0 h and 6 h post exposure. The Na+-K+-ATPase activity in the 6GS group was significantly higher than that in the 10GS group 0 h and 6 h post exposure. Hepatocyte injury, determined pathologically, was significantly lower in the 6GS group than in the 10GS group. CONCLUSION: Repeated +Gz exposures transiently cause hepatocyte injury and affect liver metabolism and morphological structure.

Effect of High Positive Acceleration (+Gz) Environment on Dental Implant Osseointegration:A Preliminary Animal Study / 生物医学与环境科学（英文）

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.

Repeated positive acceleration exposure exacerbates endothelial dysfunction in high-fat-diet-induced hyperlipidemic rats.

INTRODUCTION: It remains unclear whether exposure to repeated positive acceleration (+Gz) can exacerbate endothelial dysfunction on the basis of hyperlipidemia. The aim of this study was to investigate the effect of repeated +Gz exposure on endothelial function in high-fat-diet-induced hyperlipidemic rats. MATERIAL AND METHODS: Male Sprague-Dawley rats were randomly divided into control, repeat +Gz exposure, high-fat diet (HFD), and +Gz + HFD groups. The rats in the +Gz group were exposed to +Gz and the rats in the HFD group were fed a diet with 2% cholesterol. The rats in the +Gz + HFD group received both the +Gz exposure and HFD. Eight weeks later, the endothelium-dependent relaxation of the aorta was tested and the ultrastructure of the endothelial cells was observed using transmission electron microscopy. Quantitative real-time polymerase chain reaction and Western blot were used to detect the mRNA and protein expression of endothelial function-associated proteins. RESULTS: Repeated +Gz exposure elevated the serum level of LDL-C in HFD rats. In the +Gz + HFD rats, the ACh-induced relaxation in the aorta rings was significantly attenuated and the endothelial cells of the aorta were dramatically damaged compared with HFD rats. Nitric oxide content and eNOS expression in the aortic tissue were markedly decreased and the oxidative stress was more serious in the +Gz + HFD rats compared with HFD rats. In addition, repeated +Gz exposure significantly increased serum ox-LDL level and LOX-1 expression in the aorta of HFD rats, thereby activating NF-κB p65 and upregulating the expression of interleukin 6, ICAM-1 and VAP-1. CONCLUSIONS: Repeated +Gz exposure promotes endothelial dysfunction in HFD-induced hyperlipidemic rats.

Metabolomics reveals positive acceleration(+Gz)-induced metabolic perturbations and the protective effect of Ginkgo biloba extract in a rat model based on ultra high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry.

Positive acceleration (+Gz) in the head-to-foot direction generated by modern high-performance fighter jets during flight maneuvers is characterized by high G values and a rapid rate of acceleration, and is often long in duration and a repeated occurrence. The acceleration overload far exceeds the pilot's physiological tolerance limits and causes considerable strain on several organ systems. Despite the importance of monitoring pathophysiological alterations related to +Gz exposure, we lack a complete explanation of the pathophysiology of +Gz exposure. Ginkgo biloba extract (GBE) is a classic traditional Chinese medicine (TCM) that might exert a protective effect against +Gz exposure. However, its mechanism remains unclear. Here, a metabolomics approach based on ultra high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOFMS) was used to characterize +Gz-induced metabolic fluctuations in a rat model and to evaluate the protective effect of GBE. Using partial least-squares discriminant analysis for the classification and selection of biomarkers, eighteen serum metabolites related to +Gz exposure were identified, and were found to primarily involve the fatty acid ß-oxidation pathway, glycerophospholipid metabolism, phospholipid metabolism, bile acid metabolism, purine metabolism and lysine metabolism. Taking these potential biomarkers as screening indexes, we found that GBE could reverse the pathological process of +Gz exposure by partially regulating the perturbed fatty acid ß-oxidation pathway, glycerophospholipid metabolism, purine metabolism and lysine metabolism. This indicates that UHPLC-Q-TOFMS-based metabolomics provides a powerful tool to reveal serum metabolic fluctuations in response to +Gz exposure and to study the mechanism underlying TCM.

Effects of positive acceleration exposure on intestinal mucosal barrier and sIgA level in rats / 解放军医学杂志

Objective To explore the effect of positive acceleration (+Gz) on immune barrier of intestinal mucosa in rats. Methods Thirty two male SD rats were randomly divided into 4 groups (8 each): Group A (control group), Group B (+5Gz group), Group C (+10Gz group) and Group D (repeated exposure group). The animal centrifuge was used to simulate the exposure of acceleration. Group A was no disposed. +5Gz group and +10Gz group were subjected to centrifugal force of +5Gz and +10Gz respectively for 5min; repeated exposure group was continuously exposed to 1.5min under +5Gz value, 2min under +10Gz value and 1.5min under +5Gz. All groups were exposed to the respective acceleration once daily for 5 days. The damage of intestinal mucosa was observed by light microscopy after the experiment was finished, and the content of sIgA in intestinal mucosa was detected by ELISA. Results Except for group A, intestinal mucosal injury was observed in the other three groups. Group D was shown as the most serious one, followed by group C and group B. Compared with group A, the level of sIgA was significantly lower in other three groups (P<0.05). The level of sIgA in group C was significantly lower than that in group B (P<0.05) and higher than that in group D (P<0.05). Conclusion +Gz exposure can result in intestinal injury and weaken the function of immune barrier of intestinal mucosa in rats.

Low G preconditioning reduces liver injury induced by high +Gz exposure in rats.

AIM: To investigate the effect of repeated lower +Gz exposure on liver injury induced by high +Gz exposure in rats. METHODS: Sixty male Wister rats were randomly divided into a blank control group, a low G preconditioning group (LG) (exposed to +4 Gz/5 min per day for 3 d before +10 Gz/5 min exposure), and a +10 Gz/5 min group (10G) (n = 20 in each group). Blood specimens and liver tissue were harvested at 0 h and 6 h after +10 Gz/5 min exposure. Liver function was analyzed by measuring serum alanine transaminase (ALT) and aspartate aminotransferase (AST) levels, and liver injury was further assessed by histopathological observation. Malondialdehyde (MDA), superoxide dismutase (SOD) and Na(+)-K(+)-ATPase were determined in hepatic tissue. RESULTS: The group LG had lower ALT, AST, and MDA values at 0 h after exposure than those in group 10G. SOD values and Na(+)-K(+)-ATPase activity in the LG group were higher than in group 10G 0 h post-exposure. Hepatocyte injury was significantly less in group LG than in group 10G on histopathological evaluation. CONCLUSION: It is suggested that repeated low +Gz exposure shows a protective effect on liver injury induced by high +Gz exposure in rats.

Cellular electrophysiologic mechanisms of tachyarrhythmia in rabbits induced by positive acceleration / 军事医学

Objective To investigate the effect of positive acceleration (+Gz) on monophasic action potential duration of 90%repolarization( MAPD90 ) and transmural dispersion of repolarization ( TDR) in ventricles of rabbits and to explore the cellular electrophysiologic mechanism of tachyarrhythmia induced by positive acceleration .Methods Twenty-four healthy, male New Zealand white rabbits were randomly and equally divided into control group and +Gz group.The +Gz group rabbits were given +8 Gz exposure, 1 min a time, 3 times a day,and a total of 7 days.The two groups were subjec-ted to Holter monitoring at the same time to observe the incidence of tachyarrhythmia .Using the monophasic action potential ( MAP) recording technology , the MAP of the left ventricle was recorded while MAPD 90 and TDR were measured .By using Burst stimulation method , the right ventricular anterior wall of the rabbits was stimulated , and the incidence of tachya-rrhythmia was observed .Results The Holter record showed that the incidence of tachyarrhythmias in +Gz group was 55%(6/11), but the control group did not have any case of tachyarrhythmias .Compared with the control group ,MAPD90 of en-docardial and epicardial cells was significantly decreased in the +Gz group, while MAPD90 of middle myocardial cells did not change significantly ,but TDR was increased obviously .Four rabbits in +Gz group suffered from tachyarrhythmias dur-ing Burst stimulation ,and the incidence of tachyarrhythmias was 40% ( 4/10 ) .Conclusion +Gz exposure can increase the incidence of tachyarrhythmias .The shortened MAPD90 of ventricular muscle cells and the increased TDR may be the cell electrophysiological mechanisms of tachyarrhythmias induced by +Gz.

Review of positive acceleration exposure-induced myocardial and brain injuries in animals and the mechanisms / 中国比较医学杂志

The prevention of myocardial and brain dysfunction induced by positive acceleration (+Gz) exposure is the focus in the field of aerospace medicine research topic .The characteristics and mechanisms that +Gz exposure caused damages to vital organs such as heart and brain remain to be further elucidated .The research literature about +Gz acceleration exposure-induced heart and brain injuries in experimental animals and its mechanisms at home and abroad was reviewed in this paper .

Effect of repeated and prolonged +Gz exposure on endocrine function of vessel in a rabbit model of atherosclerosis / 解放军医学杂志

Objective To investigate the effect of repeated and prolonged +Gz exposure on endocrine function of vessel in a rabbit model of atherosclerosis. Methods Twenty-four male New Zealand white rabbits were used to establish the model of atherosclerosis, and then randomly divided into control group and +Gz exposure group (12 each). Animals in control group underwent no +Gz exposure, while those in +Gz exposure group underwent +Gz exposure for 4, 8, and 12 weeks respectively (4 animals at each time point), and 4 animals from each group were sacrificed at each time point. The levels of angiotensin II (Ang II), endothelin (ET), heme oxygenase-1 (HO-1), carbon monoxide (CO) and cyclic guanosine-3', 5'-monophosphate (cGMP) were measured by radioimmunoassay and biochemical method, and the ultrastructure of aortic intima was examined by electron microscopy. Results Along with the prolongation of +Gz exposure, the contents of Ang II, ET, HO-1, CO and cGMP were increased in +Gz exposure group (P<0.05), but the increase stopped at the 12th week, and no obvious change in the above indices was observed in control group (P=0.05). The foam cells and collagen content under the aortic intima and in the shallow layer of aortic media were slightly increased in control group, but the foam cells and the interstitial collagen fibers were greatly increased after +Gz exposure for 8 and 12 weeks as compared with that in control group. Conclusion Repeated and prolonged +Gz exposure may induce the production of Ang II and ET, increase the secretion of HO-1, CO and cGMP, thus play a potential role in protecting the vessels from further injuries.

Effect of repeated and prolonged +Gz exposure on endocrine function of vessel in a rabbit model of atherosclerosis / 解放军医学杂志

Objective To investigate the effect of repeated and prolonged +Gz exposure on endocrine function of vessel in a rabbit model of atherosclerosis. Methods Twenty-four male New Zealand white rabbits were used to establish the model of atherosclerosis, and then randomly divided into control group and +Gz exposure group (12 each). Animals in control group underwent no +Gz exposure, while those in +Gz exposure group underwent +Gz exposure for 4, 8, and 12 weeks respectively (4 animals at each time point), and 4 animals from each group were sacrificed at each time point. The levels of angiotensin II (Ang II), endothelin (ET), heme oxygenase-1 (HO-1), carbon monoxide (CO) and cyclic guanosine-3', 5'-monophosphate (cGMP) were measured by radioimmunoassay and biochemical method, and the ultrastructure of aortic intima was examined by electron microscopy. Results Along with the prolongation of +Gz exposure, the contents of Ang II, ET, HO-1, CO and cGMP were increased in +Gz exposure group (P<0.05), but the increase stopped at the 12th week, and no obvious change in the above indices was observed in control group (P=0.05). The foam cells and collagen content under the aortic intima and in the shallow layer of aortic media were slightly increased in control group, but the foam cells and the interstitial collagen fibers were greatly increased after +Gz exposure for 8 and 12 weeks as compared with that in control group. Conclusion Repeated and prolonged +Gz exposure may induce the production of Ang II and ET, increase the secretion of HO-1, CO and cGMP, thus play a potential role in protecting the vessels from further injuries.

Effects of positive acceleration on the metabolism of endogenous carbon monoxide and serum lipid in atherosclerotic rabbits.

BACKGROUND: Atherosclerosis (AS) is caused mainly due to the increase in the serum lipid, thrombosis, and injuries of the endothelial cells. During aviation, the incremental load of positive acceleration that leads to dramatic stress reactions and hemodynamic changes may predispose pilots to functional disorders and even pathological changes of organs. However, much less is known on the correlation between aviation and AS pathogenesis. METHODS AND RESULTS: A total of 32 rabbits were randomly divided into 4 groups with 8 rabbits in each group. The control group was given a high cholesterol diet but no acceleration exposure, whereas the other 3 experimental groups were treated with a high cholesterol diet and acceleration exposure for 4, 8, and 12 weeks, respectively. In each group, samples of celiac vein blood and the aorta were collected after the last exposure for the measurement of endogenous CO and HO-1 activities, as well as the levels of total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C). As compared with the control group, the endocardial CO content and the HO-1 activity in aortic endothelial cells were significantly elevated at the 4th, 8th, and 12th weekend, respectively (P < 0.05 or <0.01). And these measures tended upward as the exposure time was prolonged. Levels of TC and LDL-C in the experimental groups were significantly higher than those in the control group, presenting an upward tendency. Levels of TG were found significantly increased in the 8-week-exposure group, but significantly declined in the 12-week-exposure group (still higher than those in the control group). Levels of the HDL-C were increased in the 4-week-exposure group, declined in the 8-week-exposure group, and once more increased in the 12-week-exposure group, without significant differences with the control group. CONCLUSIONS: Positive acceleration exposure may lead to a significant increase of endogenous CO content and HO-1 activity and a metabolic disorder of serum lipid in high-cholesterol diet-fed rabbits, which implicates that the acceleration exposure might accelerate the progression of AS.

Biomechanics in aviation / 医用生物力学

Pilots are usually under various different mechanical loads during flights, which can affect their musculoskeletal and cardiovascular system and even bring them injuries. Biomechanics mainly studies the mechanics and mechanobiology in medicine and biology. Aviation biomechanics studies the physiological response to different complicated mechanical loads during flights and the countermeasures. The research fields of aviation biomechanics include: mechanical loads on human body injury and related countermeasures, durative loads, vibration and noise on the physiological effects of human body and related comtermeasures, etc.

Hyperbaric oxygen preconditioning ameliorates high positive acceleration exposure-induced impairment of learning and memory in rats / 中华行为医学与脑科学杂志

Objective To explore the effect of hyperbaric oxygen (HBO) preconditioning on learning and memory damage induced by high positive acceleration( + Gz) exposure in rats.Methods Thirty-two male Sprague-Dawley rats were randomly divided into four groups with 8 in each group: control group( Con), + Gz group,HBO group and HBO-+ Gz group.Rats of Con group were given 5d( 1 ATA ,21% O2, 1h/d); Rats of + Gz group was exposed to + 10Gz for 5 min; HBO group were only given 5d (2.5 ATA, 100% O2,1 h/d); HBO-+ Gz group were given HBO 5 consecutive days,and then suffered +Gz exposure.Morris water maze was used to observe the navigation and probe capabilities of rats.Results In the spatial acquisition test,there exist significant difference among these groups(F(3.28) = 5.325, P＜ 0.01 ).Compared with the control group, the escape latency increased significantly in the + Gz group and HBO-+ Gz group (P＜0.05) while had no difference in HBO group.HBO-+ Gz group had significantly shorter escape latency than + Gz group (P＜0.05).In the probe test,compared with the control group, + Gz group and HBO-+ Gz group had a longer percentage in the target quadrant( (43.71 ± 3.29 ) %vs (28.65 ±1.00)%, P＜0.05;(43.71 ±3.29)% vs (37.17 ±0.98)%, P＜0.05)),and HBO-+Gz group was better than + Gz group.Conclusion HBO preconditioning may have a protective effect on the impairment of learning and memory caused by + Gz exposure in rats.

The Effect of +Gz Acceleration on Intraocular Pressure / 항공우주의학회지

BACKGROUND: The physiological change of positive acceleration is primarily focused on the hydrostatic column effects that are associated with acceleration exposures. IOP values during positive acceleration is reduced according to this theory. However, the first trial of IOP measurement during positive acceleration showed that there were no significant changes in IOP values during the +2G phase of parabolic flight. In addition, IOP study during centrifuge exposures showed that there were significant increases in IOP during +2Gz and +3Gz. Therefore, the purpose of this study is to investigate the effect of positive acceleration on IOP. METHODS: The data from 4 normal subjects (2 men and 2 women) were included in this study. The baseline IOPs of subjects were within normal range. The subjects did not wear anti-G suits and use anti-G maneuver during the acceleration exposure. Pressure phosphene tonometer was used to measure IOP. To minimize the difference between the Goldmann tonometer and the pressure phosphene tonometer, IOPs were measured in subjects for 1 week prior to this study. IOP measurements of protocol 1 were obtained with pressure phosphene tonometer at +1Gz (baseline), +2Gz, +3Gz, +4Gz, and again at +1Gz (post). IOP measurements of protocol 2 were obtained at + 1Gz (baseline), +3Gz, and again at +1Gz (post). IOP measurements of protocol 3 were obtained at + 1Gz (baseline), +4Gz, and again at +1Gz (post). A total of 55 IOP measurements for each subject were made. RESULTS: The result showed that there was a significant difference in the means of IOP in protocol 1, 2, and 3 (P<0.05). But, they did not show an increasing or decreasing trend according to increase in acceleration. In particular, subject 1 showed that there was significant decrease of IOP in protocol 1, 2, and 3 compared to the baseline IOP measurements during positive acceleration(P<0.05). Based on symptom questionnaire and VTR review, variable body contractions may affect the IOP measurements during acceleration. There were significant differences in the means of IOP among variable body contractions in subject 1 when compared to the baseline IOP measurements. CONCLUSIONS:Persistent decreases of IOP in subject 1 suggest that the mechanism of IOP changes under positive acceleration could be explained by the hydrostatic column effect. In addition, interpretation for IOP measurements under positive acceleration should be cautious due to variable muscle contraction.

Effects of +Gz Exposures on Expression of HSP70 Protein in Rat Hippocampus / 航天医学与医学工程

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.

Changes of Hippocampus Somatostatin and Learning Ability in Rats after+Gz Exposure / 航天医学与医学工程

Objective To investigate changes of learning ability and somatostatin (SS) changes after positive acceleration (+Gz) exposures. Mehtod Eighty male SD rats were randomly divided into 3groups: control group(Con), +6 Gz/3 min group ( +6 Gz), and +10 Gz/3 min group ( +10 Gz),8 rats in each group. Changes of learning ability in rats were observed at 0 d, 2 d, 4 d and 6 d after + Gz exposure. SS in hippocampus was measured by RIA at 0 d, 2 d and 4 d after + Gz exposures ( there were 8 rats every time, in each group). Result In Y-maze test,number of correct response decreased significantly (P ＜0.01 ), and total reaction time increased significantly(P ＜0.01 ) in +6Gz and +10 Gz groups as compared with control group; number of correct response and total reaction time in +10 Gz group changed significantly at 0 d(P ＜0.01 or P ＜0.05) as compared with +6Gz group. RIA showed that, content of SS in hippocampus declined at 0 d and 2 d(P ＜0.05 or P ＜0.01) in +6 Gz and + 10 Gz groups as compared with control group. Conclusion + Gz exposure could impair learning ability of rats, and inhibit expression of SS in hippocampus.

Effects of +3Gz, +2Gz, and -1Gz on Intraocular Pressure (IOP)

BACKGROUND: Pilots of tactical aircraft are exposed to sustained accelerations ranging from -1Gz to +9Gz. Pilots are routinely exposed to +2 and +3Gz. It has been known that chronic elevations in intraocular pressure (IOP) are associated with the development of visual impairments, which could lead to a damage of optic nerve fibers with subsequent visual field defects. This IOP alteration may be caused by body fluid shifts resulting from acceleration forces. The IOP, theoretically, will be increased under negative Gz acceleration resulting from cephalad shift of body fluid and should not be increased under positive Gz accelerations according to hydrostatic column effects. However, there is little research regarding intraocular pressure changes during acceleration forces. Therefore, this study was designed to evaluate IOP effects of exposure to +2 Gz, +3 Gz, and -1Gz environments. METHODS: Intraocular pressures were measured on 3 subjects (2 men and 1 woman) during +2Gz, +3Gz, and -1Gz centrifuge exposures on the Dynamic Environment Simulator (DES) centrifuge. Two IOP measurements were obtained with the Ocuton S self-tonometer at +1Gz (Pre-baseline), +2Gz, +3Gz, -1Gz, and again at +1Gz (Post-baseline). A total 60 measures were obtained under +1Gz, + 2Gz, + 3Gz, and -1Gz. RESULTS: The result showed that there was a significant difference in the means for percent change of IOP from pre-baseline to +2Gz, +3Gz, and -1Gz. The mean IOP increased by 19.5% during +2Gz acceleration when compared to pre-baseline (16.3 vs. 19.5 mmHg, P=0.0001). The mean IOP of +3Gz level was 30.2% higher than that of pre-baseline level (16.3 vs. 21.2 mmHg, P=0.0001). The mean of IOP increased 127.9% during -1Gz when compared to baseline values (16.3 vs. 37.1 mmHg, P=0.0001). However, there was no significant difference in IOP between pre-baseline and post-baseline (16.3 vs. 16.0 mmHg, P=0.4261). There were significant differences, in percent change from pre-baseline, among the +2Gz, +3Gz, and -1Gz conditions {F (2,18)=152.05, P=0.0001}. There was a significant difference in the means of IOP at +2Gz and -1Gz (19.5 vs. 37.1 mmHg, P=0.0001). There was a significant difference in the means of IOP at +3Gz and -1Gz (21.2 vs. 37.1 mmHg, P=0.0001). There was a marginal significance in the means of IOP at +2Gz and +3Gz (P=0.0321). CONCLUSION: The conclusion of this study was that significant increases in IOP were found during +2Gz and +3Gz as well as -1Gz when compared to pre-baseline IOP values. These findings suggest that a rise of IOP during +2Gz and +3Gz cannot be explained by the hydrostatic column effects that are associated with acceleration exposure.