Objective To observe pre-syncopal limited tolerance and cardiovascular responses to head-up tilt combined with lower body negative pressure (HUT/LBNP) following exposure to head-down tilt (HDT, -1 Gz). Method Exposures to HUT/LBNP (-60 mmHg) in control session (without preceding 30 s -1 Gz treatment) and in simulated push-pull effect (PPE) session (with preceding 30 s -1 Gz treatment) were performed in 8 healthy adults. The changes of hemodynamic parameters were monitored by electrical impedance instrument during the experiments. Result The mean endurance time in presyncopal symptom limited HUT/LBNP in control session and in simulated PPE session were 8.4±2.1 min and 4.5±2.4 min, respectively, the two means were significantly different (P< 0.01). In simulated PPE session, as compared with baseline, heart rate (HR) during HDT was significantly lowered (P<0.01), while stroke volume (SV) and cardiac output (CO) were increased significantly (P<0.01). During HUT/LBNP, the increased percentage (relative to baseline) of HR in PPE session was lower than these in control session (P<0.05); the decreased percentages of SV and CO during HUT/LBNP in PPE session were both higher than those in control session (P<0.05). During HUT/LBNP, arterial pulse pressure (PP) of control session was significantly decreased than the value of baseline value (P<0.05); Total peripheral resistance (TPR) of PPE session was significantly increased than baseline value (P<0.05). Conclusion Tolerance time before the appearance of presyncopal symptoms during HUT/LBNP decreases and cardiovascular responses to HUT/LBNP are impaired, preceding exposure to HDT.

BACKGROUND: Cleistocalyx operculatus is a dried alsbastrum of myrtle. It is reported that cleistocalyx operculatus extracts can improve cardiac contraction through inhibiting the activity of Na+/K+-ATPase, and decrease rate of contraction. Do cleistocalyx operculatus extracts have the biological activity of antioxidation?OBJECTIVE: To observe the effects of cleistocalyx operculatus on oxidative injury of PC12 nerve cells induced by H2O2.DESIGN: Non-randomized controlled study.SETTING: State Key Laboratory of Bioreactor Engineering, New World Institute of Biotechnology, East China University of Science and Technology.MATERIALS: The experiment was conducted at New World Institute of Biotechnology, State Key Laboratory of Bioreactor Engineering of East China University of Science and Technology, from May to November 2002.Eight adult male Kunming mice were selected. PC12 nerve cells were supplied by Shanghai Cell Institute of the Chinese Academy of Sciences.METHODS: Model of oxygenic injury of PC12 nerve cells was estabPC12 cells were cultured in 96-well plates. Cleistocalyx operculatus was diluted with RPMI1640 culture medium into five concentrations of 0.001,0.01, 0.1, 0.5 and 1 g/L with 3 wells in each concentration; each well had 2×103 cells. Blank control group, or non-drug culture medium group, was set. Under the standard condition, cells were cultured for 48 hours and ascells were inoculated in 96-well plate with the density of 2×103 for 24-hour wall adhering, and then divided into normal control group (normal cell without H2O2 or cleistocalyx operculatus extracts), 0, 0.01, 0.1, 0.5 and 1 g/L cleistocalyx operculatus. Cells in all groups except normal control group were treated with 200 μmol/L H2O2 at 37℃ for 3 hours, then cleistocalyx operculatus of various concentrations was added and survival rate was asfree radicals: PC12 cells with oxygen-derived free radicals were treated in the same way as done for cell survival rate assay and measured with CDCFH staining method.fect of cleistocalyx operculatus extracts on intracellular and extracellular oxygen-derived free radicals in PC12 nerve cells induced by oxidative injury.operculatus could protect nerve cells; however, at 0.055-1.00 g/L the effect on cell growth did not significantly differ from that of blank control extracts had no protective effect on the injury of PC12 nerve cells induced by H2O2. At 1.00 g/L, it had strong plerosis for oxidative injury of PC12 and extracellular oxygen-derived free radicals in PC12 nerve cells was increased; however, at 0.01 g/L concentration of cleistocalyx operculatus extracts, the level was lower than that in model group.dation of membrane lipid of hepatic microsome, but also protect against oxcleistocalyx operculatus extracts is related to its concentration. At 1.00 g/L,it has great capacity of oxidation plerosis, and at 0.01 g/L it can decrease the level of oxygen-derived free radicals inside and outside cells.

Objective The aim of this study was to determine whether psychomotor performance and visual reaction time were affected by acute exposure to mild or moderate hypoxia. Method Eighteen healthy male volunteers performed finger tapping, simple reaction time(SRT) and 4-choice reaction time(CRT) tests at simulated altitude of 300 m (control),2800 m, 3600 m and 4400 m for 1 h in a hypobaric chamber. Result SaO2 decreased from 98%(control) to 90%,82% and 74% respectively at the various altitudes. All the performance parameters showed no significant change after exposure to 2800 m for 1 h relative to ground level(P>0.05). However the mean reaction time of 4-CRT under 3600 m prolonged and performance decreased as compared with baseline value(P<0.05), and the performance decreased further under 4400 m(P<0.01). No significant difference was found in finger tapping and SRT even under exposure to 4400 m for 1 h.Furthermore, no decrease in correct rate were observed at any altitude (P>0.05). Conclusion The results from this study demonstrated that there were no measurable impairment of visual reaction time and psychomotor performance under exposure to an altitude of 2800 m for 1 h. However, adverse effects on psychomotor performance were observed under 3600 m and over.