Biomedical subjects

Xi-qing Sun

Publications and source records attributed to Xi-qing Sun.

10 recordsLinked to original sources

PubMed2003

[Development and application of self-powered short arm human centrifuge].

OBJECTIVE: To present the development and application of a self-powered short arm human centrifuge. METHOD: Self-powered short arm human centrifuge consisted of human power, adjustable resistance trig, short arm and supporting construction parts. It was driven by human power. The short arm turned around the supporting part so artificial gravity is produced. The physical load can be adjusted by the adjustable resistance part. G-level depends on the rotative velocity of the central shaft. Nine healthy male volunteers received self-powered short arm human centrifuge training for 5 min per day with rotative velocity of 30-34 r min-1 for 7 d. Cardiac pumping function was measured before and after training. RESULT: Heart rate (HR) decreased significantly while left ventricular ejection time (LVET) increased significantly after 3 d training, and HR and LVET changed further after 7 d training. Stroke volume increased significantly only after 7 d training. CONCLUSION: Self-powered short arm human centrifuge combines artificial gravity and exercise and included other advantages of safety and economy of construction. Cardiac pumping function could be improved by 7 d training. It may be used for anti-G physiological training or as a countermeasure to counteract the effect of microgravity.

Adaptation, Physiological↗

PubMed2003

[Effects of +Gz exposure time on memory and behavior in rats].

OBJECTIVE: To explore the effect of +Gz exposure time on memory and behavior in rats. METHOD: Twenty-four male SD rats were randomly divided into control group (A), +10 Gz/3 min group (B) and +10 Gz/5 min group (C). Rats in group A and B were exposed to +10 Gz for 3 min or 5 min respectively. Changes of memory and behavior in rats were observed after +Gz exposure. RESULT: As compared with control, percentage of right reflex decreased significantly and reaction time lengthened significantly immediately, 1 d, 2 d, 4 d and 6 d after +10 Gz/5 min exposure (P<0.01); reaction time lengthened significantly immediately and 2 d after +10 Gz/3 min exposure (P< 0.01). As compared with +10 Gz/3 min, percentage of right reflex decreased significantly and reaction time lengthened significantly at 1 d, 2 d, 4 d and 6 d after +10 Gz/5 min exposure (P<0.01). As compared with control and +10 Gz/3 min, time stayed in center grille lengthened significantly immediately after +10 Gz/5 min exposure (P<0.01); balancing function decreased significantly immediately and 2 d after +10 Gz/5 min exposure (P< 0.01). CONCLUSION: It is suggested that +10 Gz/ 3 min exposure may induce a provisional disturbance in memory function and a change in behavior in rats, and +10 Gz/5 min exposure may induce a sustained disturbance in memory function and an obvious change in behavior in rats.

Acceleration↗

PubMed2003

[Weightlessness or weightlessness simulation and vascular remodeling].

Weightlessness is inavoidable during spaceflight. It brings profound physiological effects on human body. Vascular remodeling is one of the important changes of cardiovascular system caused by weightlessness or simulated weightlessness. The paper summarized the studies on the effects of weightlessness or weightlessness simulation on vascular remodeling in recent years. The emergence and development of the concept of vascular remodeling were briefly reviewed. The advances of study on vascular remodeling in recent years was briefly discussed with the points focused on the effects of weightlessness or weightlessness simulation on cardiovascular remodeling and its mechanism. It is proposed that cardiovascular remodeling might be important in studying the causes of orthostatic intolerance after spaceflight.

Adaptation, Physiological↗

PubMed2002

[Effects of repeated +Gz exposures on the expression of c-fos protein in rabbit brain].

OBJECTIVE: To investigate the effect of repeated +Gz exposures on the expression and distribution of c-fos protein immunoreactivity in rabbit brain. METHOD: Twenty rabbits were divided randomly into 4 groups (n=5 in each group). Animals were anesthetized and then exposed to +4 Gz until 30 s after the arterial pressure at eye level dropped to 0 kPa. The exposure was repeated for 3 times with 30 min intervals. The expression of c-fos protein in rabbit brain was examined at 0 h, 1 h and 6 h after +Gz exposure by immunohistochemistry method. RESULT: c-fos protein was obviously expressed in cortex, the third ventricle, hippocampus and dentate gyrus immediately after repeated +Gz exposures, and strongly expressed 1 h after the exposure, and then had a tendency to decrease 6 h after the exposure. CONCLUSION: Three +Gz exposures may cause time-dependent c-fos expression in rabbit brain, which may be involved in +Gz-induced brain damage.

Aerospace Medicine↗

PubMed2002

[Effects of lower body negative pressure in the first and last week during 21 d head-down bed rest on orthostatic tolerance and cardiac function].

OBJECTIVE: To investigate the changes of orthostatic tolerance and cardiac function during 21 d head-down tilt (HDT) bed rest and effect of lower body negative pressure (LBNP) in the first and the last weeks in humans. METHOD: Twelve healthy male volunteers were exposed to -6 degrees HDT bed rest for 21 d. Six subjects received -30 mmHg LBNP sessions for 1 h/d from the 1st to the 7th day and from the 15th to the 21st day of the HDT, and the other six who did not receive LBNP served as control. Orthostatic tolerance was assessed by means of standard tilt test. The cardiac pumping function and cardiac systolic function were measured before and during HDT. RESULT: Before HDT, all the subjects in the two groups completed the tilt tests. After 10 d and 21 d of HDT, all the subjects of the control group and one subject of the LBNP group could not complete the tilt test due to presyncopal or syncopal symptoms. The mean time of upright standing in the control group (15.0 +/- 3.2 min) was significantly shorter than those in the LBNP group (19.7 +/- 0.9 min). The stroke volume and cardiac output decreased significantly in the control group on days 3 and 10 of HDT, but remained unchanged throughout HDT in the LBNP group. A significant increase in preejection period (PEP)/left ventricular ejection time (LVET) was observed on days 3 and 14 of HDT in both groups. The PEP/LVET in the LBNP group was significantly lower than those in the control group on days 3 of HDT, while LVET in LBNP group was significantly higher than those in the control group on days 3, 7 and 14 of HDT. CONCLUSION: It is suggested that the brief daily LBNP sessions in the first and the last weeks were effective in preventing orthostatic intolerance and the reduction of cardiac pumping function and cardiac systole function induced by 21 d HDT bed rest.

Adult↗

PubMed2002

[Upright tilt table testing and syncope evaluation].

Syncope is a state of unconsciousness, the process of syncope is sudden and transient. Transient and widespread cerebral ischemia/hypoxia are the reasons of syncope. Sixty percent to seventy percent of the patients suffering from syncope have no categorical reasoning, although lots of assisted examinations had been carried out. Those syncope are called unexplained syncope or unknown origin syncope. Basic upright tilt table test, as well as isoproterenol tilt table test, is a quite effective diagnostic technique for unexplained syncope. This paper reviewed the value of upright tilt [correction of tile] table test in diagnosing unexplained syncope. The method of experiment, information of it's clinical application and points for attention with test were also introduced.

Brain Ischemia↗

PubMed2002

[Change of cerebral blood flow velocity during 4 d head-down tilt bed rest].

Objective. To investigate the change of cerebral blood flow velocity during 4 d head-down tilt (HDT) bed rest in humans. Method. Eight healthy male volunteers were exposed to -6 degrees HDT bed rest for 4 d. Orthostatic tolerance was assessed by means of standard tilt test. Cerebral blood flow velocity in the right middle cerebral artery was measured by transcranial Doppler sonography before HDT (supine), on days 1, 3 and 4 of HDT and on day 2 post HDT. Result. After 4 d HDT, the frequency of orthostatic intolerance was significantly higher than those before HDT (P<0.05). The systolic, diastolic and mean blood velocities in the middle cerebral artery tended to decrease on days 1 and 3 of HDT, and decreased significantly on day 4 of HDT, compared with pre-HDT, and returned to basal levels on day 2 post HDT. The mean arterial blood pressure and diastolic blood pressure increased significantly, while the body weight decreased significantly during HDT. Conclusion. It is suggested that 4 d HDT may decrease cerebral blood flow velocity and increase the frequency of orthostatic intolerance. This decrease of cerebral blood flow velocity may be partially responsible for the increased risk of orthostatic intolerance.

Adult↗

PubMed2002

[Changes of serum alkaline phosphatase and electrolytes during 21 d head down bed-rest].

Objective. To investigate the effect of simulated weightlessness on serum alkaline phosphatase (ALP), calcium, magnesium, chlorine and phosphorus. Method. 6 healthy males, aged 24.8 +/- 6.1, were exposed to -6 degrees HDT bed rest for 21 d. Activity of serum alkaline phosphatase, serum contents of calcium (Ca), magnesium (Mg), chlorine (Cl) and phosphorus (P) ions were assayed before HDT (d-3), on the 3rd, 10th and 21st day during HDT and after HDT (d+2). Ca was measured by methyl thymol blue method, P was determined with ultraviolet spectrophotography, determination of Mg and Cl were made with enzyme method, ALP was examined with 4-nitrobenzene phosphate method. Result. Serum Ca2+ levels were significantly higher at d10, d2l and d+2 than the value of d-3 (P<0.01). P3+ levels declined significantly on d2l as compared with d-3 (P<0.01). During the HDT and after HDT, Mg2+ declined to a level below that before HDT (P<0.05 or P<0.01). Cl- were significantly higher at d2l and d+2 than the value of d-3 (P<0.01). ALP level was higher on d2l than on d-3 (P<0.01). Conclusion. 21 d HDT induced increase of Ca, Cl, ALP, and decline of Mg and P. The changes may reflect the imbalance of metabolism.

Adult↗

PubMed2002

[Effects of simulated microgravity on cardiovascular function and counter effect of lower body negative pressure].

Studies on effect of simulated microgravity on cardiovascular function and counter effect of lower body negative pressure (LBNP) in recent years were summarized. The mechanism of simulated microgravity induced orthostatic intolerance may involve the reduction of cardiovascular function and cerebral blood flow, and endocrine changes. The significance of mathematical model in the study of mechanism of microgravity induced orthostatic intolerance was also discussed. The counter effect of LBNP was emphasized.

Bed Rest↗

PubMed2002

[Influences of repeated lower +Gz exposures on high +Gz exposure induced brain injury in rats].

Objective. To explore the influence of repeated lower +Gz exposures on high +Gz exposure induced brain injury in rats. Method. Forty SD male rats were randomly divided into control group (5 rats), +10 Gz/5 min group (5 rats) +4 Gz exposure one time, three times and five times group (10 rats each group). After 1 d or 6 d of +4 Gz exposure each group were exposed to +10 Gz again. Three days after +10 Gz exposure the neuron damage was observed by light microscope in HE stained section. Result. There was no brain damage after repeated +4 Gz/3 min exposure 5 times so it was reasonable to use this exposure intensity as ischemia stimulation. +10 Gz/5 min exposure could result in irreversible neuron damage such as neuron degeneration and coagulation necrosis. The experiment results suggested that after +10 Gz/5 min exposure there were degenerated neurons in cortex, hippocampus and thalamus. The number of degenerated neurons were obviously decreased in cortex, hippocampus and thalamus when exposed to +10 Gz/5 min again after repeated +4 Gz/3 min 3-5 times. Conclusion. The degree of neuron damage was obviously slight at the time of exposure to +10 Gz/5 min again after repeated +4 Gz/3 min 3-5 times. The ischemia tolerance at the time of exposure to +Gz was similar to other brain ischemia.

Animals↗