[A study on pathological changes of brain after high +Gx exposure in rhesus monkey].

OBJECTIVE: To study the pathological morphological changes of cerebral cortex and hippocampi in rhesus monkey caused by +Gx exposure, and to explore the relation between +Gx level and pathological changes. METHOD: Healthy rhesus monkeys were randomly divided into one control group and three experimental groups (+15 Gx, +18 Gx, +21 Gx). Monkeys in each group were exposed to the corresponding level of +Gx, after that, the required tissue was qualitatively studied on the basis of pathological morphology. RESULT: 1) Different morphology changes were observed in pyramidal neurons and astrocytes in the cerebral cortex and hippocampi by light microscopy. The higher the +Gx level, the more the changes were observed. In addition, the trauma was more serious in the hippocampi. 2) Chromatin marginating, karyotheca fold, apoptosis body and swollen mitochondria with blurred cristae were observed in pyramidal cell under electron microscope after +Gx exposure, and degenerative changes were also observed in some cases after higher +Gx. CONCLUSION: High level of +Gx causes acute pathological trauma of brain tissues in rhesus monkey, and consanguineous relationship exists between pathological changes and level of +Gx.

[A study on training method for increasing adaptability to blood redistribution in human].

OBJECTIVE: To verify validity of the increase in adaptability of blood redistribution in human body with repeated body position change training and to find preferable training method for increasing astronaut's adaptability of blood redistribution. METHOD: Twelve subjects were randomly divided into group A and B. Six subjects in each group were trained with mode A and B repeated position change (9 times in 11 d) respectively. Their head-down tilt (HDT -30 degrees/30 min) tolerance and orthostatic tolerance were determined before and after training to verify training effects. RESULT: 1) Two kinds of repeated body position change training modes increased all subjects' HDT tolerance. Compared with pre-training, during HDT test subjects' symptom scores in group B were significantly lower than those in group A (P<0.05) and after training decreasing magnitude of heart rate in group B increased significantly (P<0.01). Then mode B to be preferable training method in increasing HDT tolerance was suggested. 2) Two kinds of training modes improved all subjects' orthostatic tolerance. Compared with pre-training, during orthostatic tolerance test increasing magnitude of mean arterial blood pressure in group B increased significantly (P<0.05) and a trend of increasing magnitude of heart rate in group B was appeared smaller than in group A (P<0.10). Mode B to be preferable training method in increasing orthostatic tolerance was suggested too. CONCLUSION: Repeated body position change training could increase adaptability to blood redistribution in human body. Mode B was preferable training method and would be hopeful to be used in astronaut training.

[Effects of repeated body position change training for human orthostatic tolerance].

OBJECTIVE: To verify the validity that repeated position change training can increase human orthostatic tolerance and to explore its mechanism. METHOD: Six subjects were trained with repeated position change for 11 d according to a protocol of alternative head-down and head-up tilts, each set of training lasted for about 35 min. Their orthostatic tolerances were determined before and after training. RESULT: Compared with the data before training, subjects' symptom scores during orthostatic tolerance test after training decreased significantly (4.50 +/- 1.05 vs. 2.83 +/- 1.60, P<0.05), magnitude of the increased heart rate increase lowered significantly [(29.3 +/- 4.3) bpm vs. (13.5 +/- 7.5) bpm, P<0.01], magnitude of mean arterial blood pressure augmentation increased significantly [(4.8 +/- 4.4) mmHg vs. (9.0 +/- 3.0) mmHg, P<0.05] and cardiovascular response index decreased significantly (34.42 +/- 5.00 vs. 22.33 +/- 8.27, P<0.01). In brief, the responses to orthostatic stress were improved after training. CONCLUSION: Repeated alternative body position change training can increase human orthostatic tolerance. This kind of training is promising for pilot, especially astronaut training.

[Effects of +Gx stress on contractility of rat diaphragm and its mechanism].

Objective. To observe the effect of sustained +Gx exposure on contractility of rat diaphragm and explore its mechanism. Method. Forty-two male Wistar rats were randomly divided into control group (underwent +1 Gx exposure, n=21) and experiment group (underwent +15 Gx for 3 min, n=21). The tension of rat diaphragm in vivo, contents of nucleoside phosphates and lactic acid in diaphragm and ultrastructure of diaphragm were measured and observed respectively. Result. 1) Compared with pre- +Gx, low-frequency tension of diaphragm of experiment group decreased significantly (P<0.01), whereas high-frequency tension did not significantly decrease after +Gx (P>0.05). As to the control group, however, the tension of diaphragm tested at a wide range of frequencies was almost unchanged (P>0.05). 2) Compared with control group, ATP decreased (P<0.01), while ADP and lactic acid contents in diaphragm increased significantly (P<0.05 and P<0.01) after +Gx in experiment group. In addition, ratios of ADP/AMP and AMP/ATP increased significantly (P<0.01). 3) After +Gx exposure, hypoxic changes in ultrastructure of rat diaphragm occurred in experiment group, but not in control group. Conclusion. Sustained +Gx exposure could cause diaphragm muscle fatigue, which was possibly due to changes in energy metabolism and ultrastructure of rat diaphragm induced by hypoxia under +Gx stress.

[Study on anti +Gx respiratory maneuver and its training method].

Objective. To study the anti +Gx respiratory maneuver and its training method. Method. Seven young male subjects undertook the anti +Gx respiratory maneuver training. Their +Gx tolerances were examined on human centrifuge before and after training. The change of respiratory type, breath rate, electrocardiogram, heart rate, arterial oxygen saturation (SaO2), subjective symptom and vision were real-time monitored during the +Gx tolerance examination. Result. Compared with pre-training, the +Gx tolerance increased after training (P<0.05). Dyspnea and chest pain disappeared or obviously lightened and the magnitude of decrease of SaO2 decreased significantly (P<0.05). Conclusion. The above results suggested that the anti +Gx respiratory maneuver can effectively eliminate or alleviate dyspnea and chest pain induced by +Gx stress and increase human +Gx tolerance.

[Effects of +Gx load on energy metabolism of brain tissue in rats].

Objective. To observe the changes of energy metabolism of brain tissue in rats under +Gx loads, and to explore its possible role in changes of brain function and work efficiency induced by +Gx stress. Method. Forty-five male Wistar rats were randomly divided into control, +5 Gx, +10 Gx, +15 Gx and +20 Gx group. Each group was exposed to the corresponding G value for 3 min. After that, cortical adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and lactic acid (LA) content, lactate dehydrogenase (LDH) activity were measured. Result. Compared with the control group, the cortical (LA) content increased significantly after +5 Gx, +10 Gx, +15 Gx and +20 Gx exposure (P<0.01). Cortical ADP content and ratio of ADP/AMP and AMP/ATP increased significantly after +10 Gx, +15 Gx and +20 Gx exposure (P<0.01), whereas ATP content, energy charge and LDH activity decreased significantly (P<0.05 or 0.01). Cortical AMP content increased significantly after +15 Gx and +20 Gx exposure (P<0.05 and 0.01). Conclusion. It is suggested that +Gx load can result in obvious depression of brain energy metabolism, which could be an important reason for the change of brain function and work efficiency induced by +Gx stress.