Effects of long-term space flights on organization of horizontal gaze fixation reaction

Results of Russian-Austrian space experiment "Monimir" which was a part of international space program "Austromir" are presented in this paper. Characteristics of horizontal gaze fixation reaction (hGFR) to visual targets were analyzed. Seven crewmembers of "Mir" space station expeditions took part in the experiment. Experiments were carried out 4 times before space flight, 5 times in flight and 3-4 times after landing. There were revealed significant alterations in characteristics of gaze fixation reaction during flight and after its accomplishing, namely: an increase of the time of gaze fixation to the target, changes of eye and head movements' velocity and increase of the gain of vestibular-ocular reflex, that pointed out to the disturbances of the control mechanisms of vestibular-ocular reflex in weightlessness caused by changes of vestibular input's activity. There was discovered also the difference in the strategies of adaptation to microgravity conditions among the cosmonauts of flight and non-flight occupation: in the first group exposure to weightlessness was accompanied by gaze hypermetry and inhibition of head movements; in the second one--on the contrary--by increase of head movement velocity and decrease of saccades' velocity.     

Alterations of characteristics of horizontal gaze fixation reaction in long-term space flights

The study was performed to explore effects of long-duration SF on the characteristics of horizontal gaze fixation reaction (hGFR). Changes in GFR observed in long-duration space flight (SF) point out to serious disturbances of the VOR system due to, apparently, altered vestibular activity. Two strategies of reaction adaptation to the microgravity conditions were discovered in cosmonauts of civic occupations and pilots.     

Countermeasures for long-term space flights, lessons learned from the Russian space program

Physical exercises (PE) constitute the most important part of the Russian countermeasure system which is proved to be highly successful in fighting negative effects of weightlessness on the physiological systems of the body. To control the intensity and volume of the workload and also specific features of the regimens used by cosmonauts during SF there were provided monthly 3-days recordings of cosmonaut training sessions with the subsequent downlinking of the obtained information to the ground control center. Additionally once a month cosmonauts performed a fitness test that was composed of 11 minutes of locomotion on the passive treadmill including slow, middle range and maximal running. The results of 3-days recordings and fitness test allowed to evaluate correctly effectiveness of PE protocols used by cosmonauts and to form recommendations for their corrections. The effectiveness of the onboard exercise program after SF was evaluated based on results of detailed studies of alterations that were recorded in different parts of sensory-motor system.     

Some magnetic-biological problems of distant and long-term space flights

Some magnetobiological problems of orbital (in the geomagnetic field--GMF) and interplanetary (in hypomagnetic conditions) flights are considered. The influence of electromagnetic fields (EMF) created by systems and equipment of the space vehicle (SV) are touched also. A level of the geomagnetic field (GMF) onboard during the orbital flights is discussed. Its periodic variations onboard owing to movement of SV on an orbit are analyzed. The reader's attention in attracted to the papers by R.M. Baevsky et al. in which the influence of magnetic storms and periodic variations of GMS on the cardiovascular system of astronauts onboard are shown. Possible ways and mechanisms of the influence are discussed. The wrong assertions in a number of works namely that at orbital flights an appreciable electrical field is induced in an organism of an astronaut in a space-craft and the electrical field may by responsible for some biological impacts are analyzed. The situation at the future in the terplanetary flights (for example Martian missions) when a crew and biological objects for a long time will be in the interplanetary magnetic field (by several orders less then GMF) is considered. As applied to the flights the opportunities of generation onboard the "artificial" GMF are outlined. The ensuing biological and technical questions are discussed.     

The volume of extracellular fluid under conditions of long-term space flights

The volume of extracellular fluid (the bromine space) was determined in 18 cosmonauts 30 days before the start of a space flight and on the first day after landing. The duration of space flights on the Mir orbital station was from 126 to 438 days. Moreover, the volume of extracellular fluid was determined in seven cosmonauts directly during long-term space flights approximately two weeks before landing. After long-term space flights, the volume of extracellular fluid was decreased in all cosmonauts studied. The bromine space volume was significantly decreased compared to its initial preflight value. A decrease in the volume of extracellular fluid was caused not only by the reduction in the dense mass of the body but also by its dehydration. These processes developed independently of the duration of weightlessness but are mainly determined by the individual features of human beings.     

Psychophysiological issues of manned space flights

The article deals with some issues of psychophysiological support (PPS) of manned space flights discussed with Academician O.G. Gazenko. It has been shown that even at the initial stages of development of space flights (SFs), monitoring and evaluation of the mental state and working capacity of crew members were regarded as the key components of PPS and merited special comprehensive studies with the development of associated methods. The polyeffectors method for recording physiological functions, such as electrocardiogram, electroencephalogram, and skin-galvanic reaction, was recognized as a potent tool in gathering information for the assessment of the current state of health. In the period of the performance of long-term orbital flights, starting with the 96-day flight of Yu. Romanenko and G. Grechko, the system of psychological support developed at the Institute for Biomedical Problems (IBMP), under the leadership of Gazenko was introduced into PPS, and then used in all flights of the stations Salyut and Mir, and now at the International Space Station. Evidently, the use of this system made a significant contribution to the PPS and maintenance of health and working efficiency of crews.     

Changes in the gaze fixation reaction in rhesus monkeys during the initial stage of water immersion

The gaze fixation reaction was studied in three rhesus monkeys before and during thermoneutral (34.5 degrees C) water immersion to the mid-chest level. The angular vestibulo-ocular reflex gain increased and the head angular velocity decreased significantly in all monkeys in 5 h after the start of immersion. Additionally, one animal was immersed to the neck level. Two hours in the condition of more pronounced support deprivation decreased significantly angular velocity of the head but not increased the angular vestibulo-ocular reflex gain. Therefore, support deprivation act upon the head movement control first.     

Intensity of lipid peroxidation and antioxidant protection system indices during re-adaptation period after long-term space flights at the international space station

In the blood serum of seventeen members of crews which participated in 14 orbital expeditions to the International Space Station with the duration of 125 to 217 days, during the pre-flight period and on the day of landing on the 1st, 7th and 14th days of the rehabilitation period (RP) the content of LPO products was determined, namely diene conjugates (DC), malon dialdehyde (MDA), shiffbases (SB) and the main lipid oxidant - tocopherol (TP). The group of astronauts who made landing in the Space Shuttle spacecraft (8 persons) and the group of astronauts who accomplished space mission in the Soyus TM spacecraft (9 persons) demonstrated a decrease in DC and MDA levels with a rise in TF concentration in the course of the rehabilitation period. Changes in the group of the American spacecraft astronauts were more pronounced. LPO inhibition during the rehabilitation period is recognized [treated] as an adequate reaction to the stress caused by re-adaptation to the ground conditions. Also are discussed probable mechanisms of intergroup differencies in LPO intensity degree: biomembrane phase state changing under the influence of overloads during de-orbiting and stress response intensity during landing in different types of spacecraft.     

Lipid peroxidation rate and the antioxidant protection system during the readaptation period after long-term space flights on board the International Space Station

The content of lipid peroxidation (LPO) products (diene conjugates (DC), malondialdehyde (MDA), Schiff bases (SB), and tocopherol (TP, a main lipid antioxidant) were measured in blood serum of 17 astronauts taking part in long-term (125–217 days) missions on board the International Space Station (ISS) during the preflight period, on the day of the landing, and on the 7th and 14th days after landing (the rehabilitation period, RP). A decrease in the DC and MDA levels against a background of an increase in TP has been found in a group of eight astronauts after landing on board the Space Shuttle spacecraft and a group of eight astronauts after a space flight on board the Soyuz TM in the course of RP. The changes in measured indices were more pronounced in the group of astronauts after the space flight on board the Space Shuttle spacecraft. Inhibition of LPO during RP was regarded as an adequate response to readaptation stress to the conditions on earth. The possible mechanisms of differences in the efficiency of LPO inhibition between groups are discussed: the changes in the biomembrane phase state under the conditions of deceleration load during disorbiting and the stressful reaction to landing on board different spacecrafts.     

The influence of space flights on water-electrolytes turnover and its regulation

A study of water-electrolyte exchange, the condition of water milieu of the organism, and the volume- and electrolyte homeostasis regulation in space flights, and also in postflight period has shown the important role of the water-salt homeostasis in adaptation of the human and animal organism to weightlessness. Obviously, downturn of food consumption, renal excretion and the intestine output seem to be caused by suppression of activity of mechanisms of ion deposition. The most intensive changes of the liquid milieu volumes occur in the first days of weightlessness or in its ground simulation. And, with prolonged duration, the changes of extracellular liquid volume and the volume of plasma do not extend. After termination of long space flights, activation of renin-aldosterone systems occurs as well as a decrease in efficiency of antidiuretic hormone, misbalance of pressor/unpressor prostanoids. In the period of re-adaptation after space flights, development of desensitization of kidneys to endogenous ADH occurs. This is the basis for researches directed to improvement of the existing scheme of correction of the hydrogenous status of the astronaut organism in the closing stage of flight.     

Effect of space flight factors on health of cosmonauts in the near and late term after space flights

Cytogenetical studies of cosmonauts' peripheral blood lymphocytes after space flights on MIR orbital station showed a statistically significant increase in the yields of radiation-induced chromosomal aberrations. However, similar studies with in vitro irradiation of biological objects with accelerated charged particles are of great importance for elucidation of the nature of cytogenetical damage induced in vivo. It is also important to investigate the structure of cosmonatus' diseases over their life, in particular, lens opacities and oncological diseases. Thus, the purpose of the investigations planned is to study cytogenetical damage in blood lymphocytes from cosmonauts after space flights on the ISS in vivo, as well as in donor blood lymphocytes after in vitro exposure to accelerated charged particles. The tasks of the project are as follows: determination of the yields and types of chromosomal aberrations in cosmonauts' blood lymphocytes before and after space flights, comparative studies of biological effects induced in vitro by different types of ionizing radiation in human blood lymphocytes in ground experiments, assessment of cytogenetical risks, analysis of the structure of cosmonatus' diseases comparing with that of whole population, study of the mortality and frequency of cataracts and oncological diseases in cosmonauts. The results to be obtained will be used for setting of health norms applied to the influence of radiations of different types, and for elaboration of measures to reduce health risks from space flight factors.     

Effect of artificial gravitation on the skeletal musculature of rats during space flights]

Comparative morphological and histochemical investigation of the rat skeletal muscles after a 18.5 days flight in the space ship "Cosmos-936" under conditions of weightlessness and artificial gravitation created by means of a centrifuge has demonstrated that weightlessness creates muscular atrophy, with fibres of different types affected in different muscles. The greatest changes take place in the soleus muscle. Metabolic disorders in the muscular tissue are manifested as an excessive deposition of glycogen and an increased content of phospholipids in it. The artificial gravitation favourably affects the state of the skeletal musculature preventing the development of metabolic disorders, though it does not completely avert the appearance of atrophic processes in it.     

Immune system of Russian cosmonauts after orbital space flights

This article is an overview of the results of studies of the immune systems of cosmonauts. The use of a systematic approach to evaluating various components of the immune system made it possible to identify a number of characteristics of adaptive change, including the quantitative and functional changes of the innate and adaptive immunity. The most important ones are the changes in the system of signaling pattern recognition receptors (Toll-like receptors, TLRs), which manifest themselves as a decrease in the content and cytokine-producing ability of monocytes and granulocytes expressing TLR2, TLR4, and TLR6, as well as in the suppression of the functional potential of natural killer (NK)- and T-cell components of adaptive immunity and are discussed.     

The system of preventive measures in long space flights

The article summarizes the results of the development of preventive measures (PMs) performed by the team headed by Academician O.G. Gazenko (winner of the State Prize), as well as some data obtained in the following years at the Institute of Biomedical Problems of the Russian Academy of Sciences, where these measures were further developed. The system of prevention of adverse changes in the body of cosmonauts, which was first developed in Russia, provided successful implementation of long-term space flights (SFs) on board series of orbital stations (OSs) Salyut and the station Mir, which lasted from 64 to 438 days. This system includes performing physical exercises on a treadmill and bicycle ergometer, axial loading along the longitudinal axis of the human body by means of a Penguin suit, application of negative pressure to the lower part of the body by means of a pneumatic-vacuum spacesuit Chibis, and some other means. This system proved to be highly efficient, preventing or considerably decreasing the negative effects of microgravity throughout and after prolonged space flights.     

Smooth pursuit deficits in space flights of variable length

The maintenance of stable vision is a primary function of the neurovestibular and sensory-motor systems. There is, however, strong evidence suggesting that space flight results in a modification of the central nervous system and subsequent control of ocular-motor responses. These changes effect those neural mechanisms which are responsible for holding images steady on the retina during brief, self-initiated, head rotations or during the voluntary pursuit of moving targets. Recent studies have shown significant saccadic intrusions in both of these experimental paradigms, including an inability to null the vestibulo-ocular reflex (VOR) during the head/eye pursuit task. The maintenance of vision, while not entirely stable, both inflight and immediately postflight is now believed to be due to neural strategies that evolve for the purpose of assisting in directing the moving target onto the retina.     

Effects of long-term space flight on erythrocytes and oxidative stress of rodents

Erythrocyte and hemoglobin losses have been frequently observed in humans during space missions; these observations have been designated as "space anemia". Erythrocytes exposed to microgravity have a modified rheology and undergo hemolysis to a greater extent. Cell membrane composition plays an important role in determining erythrocyte resistance to mechanical stress and it is well known that membrane composition might be influenced by external events, such as hypothermia, hypoxia or gravitational strength variations. Moreover, an altered cell membrane composition, in particular in fatty acids, can cause a greater sensitivity to peroxidative stress, with increase in membrane fragility. Solar radiation or low wavelength electromagnetic radiations (such as gamma rays) from the Earth or the space environment can split water to generate the hydroxyl radical, very reactive at the site of its formation, which can initiate chain reactions leading to lipid peroxidation. These reactive free radicals can react with the non-radical molecules, leading to oxidative damage of lipids, proteins and DNA, etiologically associated with various diseases and morbidities such as cancer, cell degeneration, and inflammation. Indeed, radiation constitutes on of the most important hazard for humans during long-term space flights. With this background, we participated to the MDS tissue-sharing program performing analyses on mice erythrocytes flown on the ISS from August to November 2009. Our results indicate that space flight induced modifications in cell membrane composition and increase of lipid peroxidation products, in mouse erythrocytes. Moreover, antioxidant defenses in the flight erythrocytes were induced, with a significant increase of glutathione content as compared to both vivarium and ground control erythrocytes. Nonetheless, this induction was not sufficient to prevent damages caused by oxidative stress. Future experiments should provide information helpful to reduce the effects of oxidative stress exposure and space anemia, possibly by integrating appropriate dietary elements and natural compounds that could act as antioxidants.     

Responses of collicular fixation neurons to gaze shift perturbations in head-unrestrained monkey reveal gaze feedback control

A prominent hypothesis in motor control is that endpoint errors are minimized because motor commands are updated in real time via internal feedback loops. We investigated in monkey whether orienting saccadic gaze shifts made in the dark with coordinated eye-head movements are controlled by feedback. We recorded from superior colliculus fixation neurons (SCFNs) that fired tonically during fixation and were silent during gaze shifts. When we briefly (相似文献