Catecholamines and their enzymes in discrete brain areas of rats after space flight on biosatellites Cosmos

The activity of the catecholaminergic system was measured in the hypothalamus of rats which had experienced an 18.5-19.5-day-long stay in the state of weightlessness during space flights on board Soviet biosatellites of the type Cosmos. In the first two experiments, Cosmos 782 and 936, the concentration of norepinephrine and the activities of synthesizing enzymes tyrosine hydroxylase and dopamine-beta-hydroxylase and of the degrading enzyme monoamine oxidase were measured in the total hypothalamus. None of the given parameters was changed after space flight. In the light of the changes of these parameters recorded after exposure to acute stress on Earth, this finding indicates that long-term state of weightlessness does not represent an intensive stressogenic stimulus for the system studied. In the space experiment Cosmos 1129, the concentration of norepinephrine, epinephrine, and dopamine was studied in isolated nuclei of the hypothalamus of rats within 6-10 hr following return from space. Norepinephrine was found to be significantly reduced in the arcuate nucleus, median eminence and periventricular nucleus, epinephrine in the median eminence, periventricular and suprachiasmatic nuclei, whereas dopamine was not significantly changed after space flight. The decreased catecholamine levels found in some hypothalamic nuclei of rats which had undergone space flight indicate that no chronic intensive stressor could have acted during the flight, otherwise the catecholamine concentration would have been increased in the nuclei. The decreased levels must have been induced by the effect of a stressogenic factor acting for a short time only, and that either during the landing maneuver or immediately after landing. Thus long-term exposure of the organism to the state of weightlessness does not represent a stressogenic stimulus for the catecholaminergic system in the hypothalamus, which is one of the regulators of the activation of neuroendocrine reactions under stress.     

Study of physiological effects of weightlessness and artificial gravity in the flight of the biosatellite Cosmos-936.

In the 18.5-day flight of the Soviet biosatellite Cosmos-936 (3-22, August 1977) com-parative investigations of the physiological effects of prolonged weightlessness (20 rats) and artificial gravity of 1 g (10 rats) were carried out. Throughout the flight artificial gravity was generated by means of animal rotation in two centrifuges with a radius of 320mm. Postflight examination of animals and treatment of the flight data were performed by Soviet scientists in collaboration with the specialists from Bulgaria, Czechoslovakia, the German Democratic Republic, Hungary, Poland, Rumania, France and the U.S.A. During the flight the total motor activity of the weightless rats was higher and their body temperature was lower than those of the centrifuged animals. Postflight examination of the weightless rats showed a greater percentage of errors during maze an increase in water intake and a decrease in diuresis; a fall of the resistance of peripheral red cells; an increase in the conditionally pathogenic microflora in the mouth; a decrease of oxygen consumption, carbon dioxide production and energy expenditures; a drop in the static physical endurance; a decline in the capacity to keep balance on the rail; an increase in the latent period of the lifting reflex, etc. The centrifugal animals displayed lesser or no change of the above type. These findings together with the biochemical and morphological data give evidence that during and after flight adaptive processes in the centrifuged rats developed better.     

Effects of long-duration space flight on target acquisition

The purpose of the study was to explore the effects of long-duration space flight on the acquisition of specific visual targets in the horizontal plane. Seven cosmonauts (4 high performance pilots and 3 non-pilots) who had flown between 186–198 days on Mir served as subjects. Baseline testing was performed 4 times prior to launch and 4 times following landing at different intervals totrack recovery. During testing the subjects were required to acquire targets that were randomly presented with both a head and eye movement using a time optimal strategy. Prior to flight two unique head movement strategies, related primarily to piloting experience, were used for target acquisition. Non-pilots employed a Type-I strategy consisting of high velocity head movements with large peak amplitudes, while high performance pilots used primarily low velocity, small amplitude head movements (Type-II) to acquire the targets (p<0.02). For both strategies peak head velocities increased as the angular distance to the target increased (p<0.01) resulting in greater discrimination between strategies for the 60° targets. While preflight eye velocity between strategies did not reach statistical significance, postflight testing revealed a decrease in eye velocity for Type-I compared with their preflight performance (p<0.02) for the 60° targets. Postflight, the Type-I group showed a decrease in head velocity (p<0.20) while the Type-II group compensated by increasing head velocity (p<0.02). Variability for both of the head and eye parameters tended to increase postflight for both types of strategies.     

Adaptation of neuromuscular activation patterns during treadmill walking after long-duration space flight

The precise neuromuscular control needed for optimal locomotion, particularly around heel strike and toe off, is known to he compromised after short duration (8- to 15-day) space flight. We hypothesized here that longer exposure to weightlessness would result in maladaptive neuromuscular activation during postflight treadmill walking. We also hypothesized that space flight would affect the ability of the sensory-motor control system to generate adaptive neuromuscular activation patterns in response to changes in visual target distance during postflight treadmill walking. Seven crewmembers, who completed 3- to 6-month missions, walked on a motorized treadmill while visually fixating on a target placed 30 cm (NEAR) or 2 m (FAR) from the subject's eyes. Electronic foot switch data and surface electromyography were collected from selected muscles of the right lower limb. Results indicate that the phasic features of neuromuscular activation were moderately affected and the relative amplitude of activity in the tibialis anterior and rectus femoris around toe off changed after space flight. Changes also were evident after space flight in how these muscles adapted to the shift in visual target distance.     

Effects of prolonged space flight on rat skeletal muscle

The effect of a 20-day space flight on water, Na+, K+, Mg2+, Ca2+ and glycogen contents as well as on activities of glycogen metabolism enzymes--glycogen synthetase and glycogen phosphorylase--of rat skeletal muscles was studied. This data is regarded as an integral test characterizing the state of contractile tissue of the animals at the final stage of flight aboard biosatellites. The measurements indicate that there were no significant changes of cations and glycogen contents nor of the enzymic activities in fast-twitch muscles during the 20-day spaceflight. At the same time dehydration in these muscles was observed, which disappeared on the 25th postflight day. In slow-twitch antigravitational skeletal muscle (m. soleus) there was a decrease of K+ and increase of Na+ in the tissue contents. The changes disappeared at the end of the on-earth readaptation period. From the pattern of these observations, we can conclude that the 20-day space flight leads to some reversible biochemical changes of the rat skeletal muscles. A conclusion can be drawn about necessity of creating, aboard the spaceship, an artificial load on antigravitational skeletal muscles.     

Prevention of space flight induced soft tissue calcification and disuse osteoporosis.

This paper emphasizes the devastating effects of displacement of calcium during space flight, due to increased bone turnover.     

Assessment of the efficacy of medical countermeasures in space flight

Changes in body fluids, electrolytes, and muscle mass are manifestations of adaptation to space flight and readaptation to the 1-g environment. The purposes of this paper are to review the current knowledge of biomedical responses to short- and long-duration space missions and to assess the efficacy of countermeasures to 1-g conditioning. Exercise protocols, fluid hydration, dietary and potential pharmacologic measures are evaluated, and directions for future research activities are recommended.     

The role of HZE particles in space flight: results from spaceflight and ground-based experiments.

Selected results from experiments investigating the potentially specific radiobiological importance of the cosmic HZE (= high Z, energetic) particles are discussed. Results from the Biostack space flight experiments, which were designed to meet the experimental requirements imposed by the microdosimetric nature of this radiation field, clearly indicate the existence of radiation mechanisms which become effective only at higher values of LET (linear energy transfer). Accelerator irradiation studies are reviewed which conform with this conjecture. The recently discovered production of "micro-lesions" in mammalian tissues by single HZE particles is possibly the most direct evidence. Open questions concerning the establishment of radiation standards for manned spaceflight, such as late effects, interaction with flight dynamic parameters, and weightlessness, are indicated.     

Reflections on human presence in space.

Humankind's exploration of Space has until now been understood as analogous to that of planet Earth: sending out crews to far-off, unknown lands in the hope of finding supplies of food, water or energy along with shelter and living-space. But Space is turning out to be much less hospitable than our earthly milieu in terms of resources as well as energy costs. It seems appropriate to ask what level of adaptation is needed for humans to travel and live in the cosmos, and to assess if the next logical step should necessarily be a programme of conquest analogous to that of the Moon--for example, towards Mars. Should we not rather be making more use of Earth's immediate neighbourhood, namely the sphere of a million of kilometres we call "Greater Earth"? In the same way, it is appropriate to ask questions about the conception of human beings which will from now on sustain the conquest of Space. The astronaut of the last forty years is the direct heir of the explorers of Ancient and Modern times; now, through the influence of science and technology, humanity has been put "into motion" not only geographically, but also in its most essential foundations: culture, psychology, philosophy. If the development of telepresence technology now gives us the ability to talk about a "Greater Human Being", it is chiefly through freedom of choice for oneself, for humanity and even for Earth.     

Walter Hohmann's contributions towards space flight: an appreciation on the occasion of the centenary of his birthday

In 1923 Hermann Oberth published his book “Die Rakete zu den Planetenräumen” (The Rocket into Planetary Space), in 1924 Max Valier's book “Der Vorstoss in den Weltenraum” (The Advance into Space) appeared while in the U.S.A. already in 1919 Robert H. Goddard reported on his rocket experiments. Altogether different from the publications just mentioned was a book entitled “Die Erreichbarkeit der Himmelskörper” (The Attainability of Celestial Bodies) published in 1925. Its author was Dr.-Ing. Walter Hohmann, born 18 March 1880, civil engineer for the city authorities of Essen, who had already made, during World War I, calculations as to the amount of fuel, initial mass and flight time necessary for flights from the Earth to other planets. The transfer trajectories investigated by Hohmann and today attributed with his name have a great practical significance for space flight onto the present. In the lecture a critical appreciation of Hohmann's work is given.     

Survival of rock-colonizing organisms after 1.5 years in outer space

Cryptoendolithic microbial communities and epilithic lichens have been considered as appropriate candidates for the scenario of lithopanspermia, which proposes a natural interplanetary exchange of organisms by means of rocks that have been impact ejected from their planet of origin. So far, the hardiness of these terrestrial organisms in the severe and hostile conditions of space has not been tested over extended periods of time. A first long-term (1.5 years) exposure experiment in space was performed with a variety of rock-colonizing eukaryotic organisms at the International Space Station on board the European EXPOSE-E facility. Organisms were selected that are especially adapted to cope with the environmental extremes of their natural habitats. It was found that some-but not all-of those most robust microbial communities from extremely hostile regions on Earth are also partially resistant to the even more hostile environment of outer space, including high vacuum, temperature fluctuation, the full spectrum of extraterrestrial solar electromagnetic radiation, and cosmic ionizing radiation. Although the reported experimental period of 1.5 years in space is not comparable with the time spans of thousands or millions of years believed to be required for lithopanspermia, our data provide first evidence of the differential hardiness of cryptoendolithic communities in space.     

Male and female characteristics in vestibular testing: a step toward the selection of the best participants for space flight

Vestibular disturbances in connection with space flight were reported by a majority of participating astronauts and cosmonauts. These include motion sickness symptoms in the first few days of the space flight, as well as standing, gait and orientation disturbances after the return to Earth. The Aerospace Medical Community has been trying to select those people that are particularly adapted to the above stresses or that can be further adapted through training programs. As the circle of selectees extends to women, the problem arises as to whether differences between men and women exist under the conditions of space flight. In seeking answers to this question we studied a group of 42 women and 44 men, who were further subdivided according to their subjective motion sickness sensitivity, as determined by a questionnaire. Using this material, 26 men and 22 women were designated as motion sickness resistant, and 18 men and 20 women were designated as nonresistant. The vestibular test battery given these test subjects consisted of caloric, rotatory, optokinetic, vestibulo-spinal and vestibulo-vegetative testing. Because of the mixed orthostatic and vestibular problems seen after space flights, we also studied the response of the vestibular apparatus during peripheral blood pooling as induced by lower body negative pressure. The collected historical and test data are analyzed in this paper with emphasis on the relationship to motion sickness tendency.     

Cardiac arrhythmias in space. Role of vagotonia.

Rhythm disorders observed in space have always been minor but they are not unfrequent. They include: ventricular or supra-ventricular extrasystoles, nodal arrhythmias, auriculo-ventricular conduction disorders. There are several etiopathogenetic hypotheses: a strict selection must permit its elimination of an underlying heart disease; the potassium deficiency is often advanced but its role is not certain; the role of catecholamines is also discussed; the role of hypervagotony is extensively analysed as great clinical and electro-cardiographic evidence speaks for it. It can induce disorders which are more serious than those observed so far, particularly fibrillation or intermittent atrial flutter; weightlessness itself could partly condition the vagotonic state; and the effects of fluid shifts are also discussed from this point of view. The possible therapies for various atrial, nodal, ventricular disorders are reviewed, with greater detail for vagal atrial arrhythmias.     

美国空间态势感知能力研究

增强空间态势感知能力是空间资源开发、空间安全、空间控制以及利用空间实施军事行动的关键。分析了美国天基空间目标监视的现状及动态,在此基础上讨论了空间目标探测领域所涉及到的各种关键技术及相应的需求方向,为发展天基空间目标监视系统提供了有益参考。     

Pathophysiology of motor functions in prolonged manned space flights.

The influence of weightlessness on different parts of the motor system have been studied in crew members of 140 and 175 days space flights. It has been shown that weightlessness affects all parts of the motor system including (i) the leg and trunk muscles, in which severe atonia, a decrease of strength and an increase of electromyographic cost of contraction have been observed, (ii) the proprioceptive elements and the spinal reflex mechanisms in which decreased thresholds accompanied by decreases of maximal amplitude of reflexes and disturbances in cross reflex mechanisms have been found. and (iii) the central mechanisms that control characteristics of postural and locomotor activities. The intensities and durations of disturbances of different parts of the motor system did not correlate to each other, but did correlate with prophylactic activity during space flight. The data suggest a different nature of disturbances caused by weightlessness in different parts of the motor system.     

固体动能拦截器助推段飞行方案研究

针对三维空间内的高速飞行目标,提出了一种可用于固体动能拦截器助推段的导引方法。建立了固体动能拦截器与目标的相对运动关系模型,分析确定了转移轨道的约束条件,并在此基础上推导出转移轨道的轨道根数计算方法。同时根据拦截器的待增速度给出了助推器推力矢量方向的确定方法。仿真结果表明,该方法能有效实现固体动能拦截器助推段的制导控制。     

空间可充气气球应用研究

简述了空间可充气结构的国外应用情况及可充气结构的导弹诱饵和气球卫星,介绍了可充气气球的设计特点,包括采用压力刚化铝箔的刚化结构、充气装置和释放装置,分析了太空环境中原子氧和紫外线辐射对可充气刚化气球的影响程度。