[Regulative effects of Chinese herb-compound on blood rheology and circulatory system of rabbits under simulated weightlessness].

OBJECTIVE: To investigate effects of Chinese herb-compound on blood rheology and circulatory system of rabbits under simulated weightlessness in order to provide bases for protecting against the influence of simulated weightlessness on cardiovascular function. METHOD: Rabbits were exposed to head-down tilt (HDT -20 degrees) for 9 d to simulate weightlessness. The effect of Chinese herb-compound on indices related to blood rheology, blood-fat and orthostatic tolerance in these rabbits were examined. RESULT: After head-down tilt, hematocrit value and red blood cells deformability decreased significantly; cholesterol and low density lipoprotein increased markedly; plasma fibrinogen content and triglyceride showed increasing trend. Administration of the Chinese herb-compound didn't improve the blood rheology indices, but showed a trend to decrease triglyceride and to inhibit the increase of cholesterol. In the head-up tilt (HUT) plus lower body negative pressure (LBNP) experiment, orthostatic tolerance time of the rabbits in the control group decreased, and myocardial ischemic changes in ECG, such as dropped ST segment, inverse T wave, and arrhythmia were observed. While in the Chinese herb-compound group, the heart rate of the rabbits kept smooth, ischemic changes in ECG were not clear, and orthostatic tolerance time increased. CONCLUSION: The Chinese herb-compound shows an effect of preventing orthostatic tolerance from decreasing, and improves blood-fat metabolism. It regulates different human systems on the whole, and increases ability of adaptation to ill environment.

[Changes of reactivity of rabbit femoral venous rings after 21 d simulated weightlessness].

OBJECTIVE: To study the effects of simulated weightlessness on reactivity of leg veins. METHOD: Vascular bathing technique was used to measure the contractile responses of rabbit femoral venous rings to Ht, PE and KCl, and the dilatory responses to ACh and SNP after horizontal confinement or head-down tilt confinement for 21 d. RESULT: After simulated weightlessness for 21 d, the contractile response of rabbit femoral venous rings to higher concentrations of PE and KCl decreased significantly (P<0.05); the contractile response to Ht also decreased, but not significantly (P>0.05); the dilatory responses to ACh and SNP did not change significantly in both groups. CONCLUSION: Contractile response of rabbit femoral vein decreased after simulated weightlessness for 21 d, which might partly explain the occurrence of orthostatic intolerance in men after space flight.

[Expectation of the study of weightlessness physiology in the 21st century].

Weightlessness physiology is an applied subject to study the influence of weightlessness on human body, the mechanism of the changes and countermeasures. This paper introduces the effects of weightlessness on human physiological system, and on the basis of the general research situation of weightlessness physiology at home and abroad, the research goal, the division of research stages and implement methods of our country in the 21st century are proposed.

[Preliminary study on protecting effect of two kinds of Chinese medical herbs on changes of three physiology systems in suspended rats].

Objective. To observe the protecting effect of two kinds of Chinese medical herbs on changes of blood circulation, muscle and skeletal systems in tail suspended rats. Method. Changes of blood circulation, muscle and skeletal systems in tail suspended rats (n=15), Chinese medical herb group 1 (n=15) and Chinese medical herb group 2 (n=15) after 30 d tail suspension were compared with those in control group rats (n=15). Result. Two kinds of Chinese medical herbs have obvious effect on improving the condition of blood circulation, and have some effects on improving the muscle and skeletal systems in tail suspended rats. Conclusion. Chinese medical herbs have a good prospect of being used in space flight, and further studies are needed.

[Changes of leg compliance during weightlessness or simulated weightlessness].

Weightlessness or simulated weightlessness causes increase of leg compliance. It leads to more blood pooling in the legs and less blood returning to the heart during orthostatic test, which may partly explain the occurrence of orthostatic intolerance induced by weightlessness or simulated weightlessness. This article is a review covering published materials about the methods of measurement, mechanisms and countermeasures of the increase of leg compliance during weightlessness or simulated weightlessness.

[Effects of weightlessness on baroreflex function].

The declination of baroreceptor reflex function is one of the important factor causing orthostatic intolerance after space flight. The change of baroreceptor reflex function during weightlessness and simulated weightlessness is introduced, and the influence of elevatory upper body blood pressure and electrolyte changes caused by weightlessness on baroreflex function are analyzed.