The physiological analysis of the possible reasons of hypoxemia in weightlessness

In spaceflight at cosmonauts decrease of oxygen partial pressure in capillary blood on 12-30% in comparison with preflight values is revealed. The analysis of the possible reasons and mechanisms of hypoxemia in weightlessness is carried out. On the basis of this analysis the conclusion becomes that the principal cause of oxygen partial pressure decrease in blood of cosmonauts at microgravity, with the big degree of probability, is venoarterial bypassing. It is connected with increasing of venous blood passage through lungs, without full gas exchange in capillaries of small circulation circle.     

Orientation of Paramecium under the conditions of weightlessness

A cell culture of Paramecium with a precise negative gravitaxis was exposed to 4 x l0(-6) g during a parabolic flight of a sounding rocket for 6 min. Computer image analysis revealed that without gravity stimulus the individual swimming paths remained straight. In addition, three reactions could be distinguished. For about 30 s, paramecia maintained the swimming direction they had before onset of low gravity. During the next 20 s, an approximate reversal of the swimming direction occurred. This period was followed by the expected random swimming pattern. Similar behavior was observed under the condition of simulated weightlessness on a fast-rotating clinostat. Control experiments on the ground under hyper-gravity on a low-speed centrifuge microscope and on a vibration test facility proved that the observed effects were caused exclusively by the reduction of gravity.     

Swimming velocity of Paramecium under the conditions of weightlessness

During the 6 min-lasting "free-fall conditions" (4 x 10(-6) g) of the parabolic flight of a sounding rocket Paramecium aurelia cells showed an increase of 7.5 % in their mean swimming velocity. A detailed analysis revealed that the kinetic response was transient: after 3 min the velocity decreased to the speed of the former horizontal swimming at 1 g. Control experiments simulating the influence of vibration and hypergravity during launch of the rocket lead to the conclusion that the increase of the velocity during the parabolic flight was exclusively induced by the transition to 0 g. An increased velocity was also observed under the condition of simulated weightlessness on a fast-rotating clinostat microscope.     

Phenomenology of spatial illusory reactions under conditions of weightlessness

Sensory interaction and sensory adaptation in short- and long-lasting space flights (SF) and the dynamics of stability of adaptive shifts were studied by the phenomenology of spontaneous and visually induced illusory reactions. It was shown that perceptive impairment developed during the initial adaptation to microgravity should be considered regular reactions of sensory systems under given environmental conditions rather than special features of the individuals examined. The classification of spontaneous illusory reactions (SIR) under conditions of microgravity and the results of investigation of the vertical vection (vection is a visual illusion evoked by the optokinetic stimulation) are presented. The following previously unknown phenomena were registered for the first time: inversion of the vertical vection illusion (VVI) evoked by vertical and sinusoidal optokinetic stimulation, impairment of perception of the body schema during VVI, change in the character of VVI, and development of VVI asymmetry. During long-lasting existence under conditions of weightlessness the anomalous perceptive reactions continued to be registered episodically (the period of adaptation was replaced by that of deadaptation). A hypothesis was suggested for the possible mechanisms of the phenomena found. [Translated from Fiziologiya Cheloveka, vol. 21, no. 4, p. 50-62, July-August, 1995]     

The development OF THE vestibular apparatus under conditions of weightlessness]

The spawn of the aquarium fish Brachydanio rerio was developing during 5--6 days under conditions of weightlessness (first on board the spaceship "Sojuz-16", then in the space station "Salut-4") in special aquariums "EMKON", in thermostable installations. Electron microscopically the embryos were found to have a well developed labyrinth in early developmental histologically and cytologically differentiated receptory structures of the macula utriculi and macula saccili. In contrast to controls, the experimental animals showed certain alterations in the otolite organization. In similar experiments the embryos of clawed frog Xenopus laevis in the stage of the tail bud were also placed in special containers "EMKON" and thermostable apparatus "Biotherm-4" and by the spaceship "Sojuz-17" were brought to the space station "Salut-4", where it stayed for 16 days. The initial embryos had already had a well developed acoustic vesicle with macula communis. Inspite of the preliminary load by start acceleration and staying under conditions of weightlessness, they reached the general development fairly similar to controls. As it was shown electron microscopically their labyrinth had highly histologically and cytologically differentiated structures. However, a disturbance of the development of the otolithic membrane and otoconia should be noted. The alterations observed in the otolithic membrane organization in experimental fishes and frogs may be explained by general disorders in calcium metabolism.     

Physiological and proteomic analysis of young rice leaves grown under nitrogen-starvation conditions

Rice grown in anaerobic waterlogged soil accumulates ammonium as a major source of nitrogen (N). We have compared the physiological symptoms of rice seedlings subjected to N-starvation stress with those receiving sufficient N, based on measurements of shoot/root length and weight and an analysis of protein expression patterns. N starvation marginally increased root growth but notably decreased shoot biomass. N uptake was reduced by >50% in the roots and shoots of N-starved seedlings. To better understand the mechanism of N starvation in rice, we performed a comparative proteome analysis of proteins isolated from rice leaves. Twenty-five differentially expressed proteins were analyzed by matrix-assisted laser desorption/ionization time-of-flight (TOF) mass spectrometry and electron spray ionization quadrupole TOF. Functional analysis of the N-starvation response proteins suggested their involvement in protein synthesis and fate, metabolism, and defense. These results indicate that these proteins may play important roles in regulating the plant’s complex adaptation responses for N use during N starvation. The proteins may be useful for further characterization of protein function in plant N nutrition.     

Motion sickness in lower vertebrates: Studies in weightlessness and under normal conditions

This review presents both literature data and results of our own studies aimed at finding out if lower vertebrates are susceptible to motion sickness. In our experiments, fish and amphibians were submitted to motion for 2 h and longer on a centrifuge (f = 0.25 Hz, a _centrifugal = 0.144 g) and on a parallel swing (f = 0.2 Hz, a _horizontal = 0.059 g). The performed studies did not revealed in 4 fish species and in toads any single feature characteristic of motion sickness (sopite syndrome, pre-vomiting behavior or emesis). At the same time, in toads, the characteristic stress reaction appeared (escape reaction, increase of urination frequency, worsening of appetite) as well as some other responses not associated with motion sickness (synchronized head swinging, eye retraction). In trout fry, the used stimulation promoted division of individuals into groups differing by locomotor reaction to stress as well as individuals with a well-pronounced compensatory response that we called the otolithotropic reaction. Our conclusions are confirmed by analysis of results obtained by other authors. Therefore, the lower vertebrates, unlike mammals, are not susceptible to motion sickness either under terrestrial conditions or under conditions of weightlessness. Based on available experimental data and theoretical concepts of mechanism of development of the motion sickness, which have been formulated in several hypotheses (the hypothesis of discoordination, Treisman’s hypothesis, resonance hypotheses), there is put forward the synthetic hypothesis of sopite that is of conceptual values. According to this hypothesis, the unusual stimulation producing sensory-motor or sensory-sensory discoordinations or action of vestibular and visual stimuli of frequency of about 0.2 Hz is perceived by the CNS as poisoning and causes the corresponding reactions. The sopiting is, in fact, a side effect of technological evolution. It is suggested that in the lower vertebrates, unlike mammals, there is absent a hypothetic vomiting center, therefore, they are not submitted to motion sickness.     

Proteomic analysis of pulmonary tissue in tail-suspended rats under simulated weightlessness

Weightlessness affects lung function and even causes certain damages to pulmonary tissue. This study used rat tail-suspension model to simulate the physiological effects of weightlessness and investigate the alterations of lung proteome, to reveal the mechanism of lung injury under weightlessness condition. Twenty male Sprague-Dawley rats were randomly divided into two groups: tail-suspended and control. Protein samples from pulmonary tissue of tail-suspended and control groups were separated by two-dimensional (2D) gel electrophoresis and analyzed with ImageMaster 2D elite software. Differentially expressed proteins were identified by high definition mass spectrometry (HDMS) in combination with database searching. Seventeen differentially expressed proteins were identified, among which 13 proteins were upregulated, and four proteins downregulated. The functions of these identified proteins can be classified into six classes related to: metabolism, oxidative stress, cellular functions, cytoskeletal proteins, signal tranduction, and protein degradation. They are mainly related to cellular energy metabolism, stress and inflammatory response, cell injury and repair, intracellular signal transduction, and other cellular functions, playing important roles in weightlessness-induced lung injury.     

Synthesis of putrescine under possible primitive earth conditions

The synthesis of putrescine was accomplished by decarboxylation of L-orithine when this amino acid was heated in aqueous solution and in the absence of oxygen. Chromatographic, radioisotopic, and enzymatic techniques were used to demonstrate that one mole of non-radioactive putrescine and one mole of¹⁴CO₂ was formed during the heating of L-(1-¹⁴C)-ornithine. This work indicates that the synthesis of putrescine can occur starting with ornithine and in conditions that are presumed could have existed on the primitive Earth. The possible significance of these results in the prebiotic molecular evolution is briefly discussed.     

Synthesis of phosphatidylethanolamine under possible primitive earth conditions

Summary The synthesis of phosphatidylethanolamine was accomplished when a mixture of phosphatidic acid, ethanolamine, and cyanamide at pH 7.3 was taken to dryness and heated at temperatures ranging from 25 to 60°C for 6 h. Chromatographic, enzymatic, and chemical techniques were used to identify and confirm that phosphatidylethanolamine had been formed. This work indicates that the synthesis of this compound can occur starting with precursors and conditions that are presumed to have existed on the primitive Earth.     

Stress under normal conditions, hypokinesia simulating weightlessness, and during flights in space

Stress due to intensive mental work under normal conditions was compared to stress under a sharp limitation of motor activity (hypokinesia), simulating weightlessness on the human body. Mental stress causes typical alterations of cerebral circulation under normal conditions: increase of blood flow in the supramarginal and angular gyri of the parietal lobe, in the frontal lobe, and in the superior temporal gyrus of the left hemisphere, and changes in cardiac activity and in the tonus of vessels. Dynamics of human stress reactions, among other features of this process, is best reflected in the parameters of a electrocardiogram, a rheoencephalogram, and total peripheric vascular resistance. An increase in the latter is an informative index of stress development. Human reaction to stress under hypokinesia and during flights in space have specific features. Prolonged hypokinesia causes an imbalance in an organism's control systems, specifically depressor reactions are distorted. In the context of hypokinesia, anxiety and mental stress lose their adaptive nature to a large extent. They provoke disturbances of the heartbeat and hypertensive reactions. A whole complex of factors affects the living organism during space flights. An imbalance of the body's control systems, emotional and physical overloads, which arise episodically, changes in electrolyte and energetic metabolism, and alterations in the head vessels increase the probability of reactions to stress and reinforce their effect. Stress can be retarded by using on elaborated system of preventive measures which includes physical training, psychological support of astronauts and, to some degree, reduction of the hypothalamus adrenergic centers' tonus through muscle relaxation. Astronauts' reactions to being in space occur during flights under heavy loading tests and in emergency situations. Weightlessness does not generate stress when one has adapted to it. Returning from weightlessness to the Earth's gravitation causes stress. After prolonged flights, stress associated with readaptation to the Earth's gravitation is atypical in character (increase of sympatoadrenalic system activity against the background of a reduction in hypothalamo-hypophysial system activity). We explain the voltage decrease of the T-wave of the electrocardiogram, the phenomenon repeatedly occurring both during prolonged space flights and under hypokinesia, by a lowering of cardiomyocytes, energetic potential due to hypokalemia, insufficient glucose usage, and a decrease in the coupling of oxidative phosphorylation processes. [Translated from Fiziologiya Cheloveka, vol. 22, no. 2, 1996, p. 10-19]     

Longterm conditions of mimicked weightlessness influences the cytoskeleton in thyroid cells

Weightlessness influences the human immune and hormone system, reduces bone mass, leads to muscle atrophy and cardiac atrophy. Effects on control mechanisms for proliferation, programmed cell death and differentiation are well documented. The principal aim of this study was to investigate changes of the cytoskeleton in thyroid cells cultured in vector-averaged gravity under clinostat rotation. After 12 hours the formation of multicellular spheroids started. An increase of extracellular matrix proteins and beta 1-integrin was observed. Laser scanning confocal microscopy of ML-1 follicular thyroid carcinoma cells and normal thyroid HTU-5 cells immunostained with anti-cytokeratin to demonstrate these intermediate filaments revealed that cytokeratin filaments extended from centers, were thickened, coalesced and shortened as compared to control cells. Moreover, vimentin was highly disorganized. The vimentin network formed a coiled aggregate closely associated with the nucleus. Western blot analyses of talin, alpha- and beta-tubulin showed a clear increase of these proteins in cells cultured under simulated 0 g. Our data suggest that the effects of microgravity on cultured human thyroid cells are accompanied by noticeable functional cellular changes. Future studies to clarify the pathway that regulate the observed integrin activation and the mechanisms by which they function have to be performed.     

Population extinctions in the Italian diurnal lepidoptera: an analysis of possible causes

In depth studies of patterns of extinction are fundamental to understand species vulnerability, in particular when population extinctions are not driven by habitat loss, but related to subtle changes in habitat quality and are due to ‘unknown causes’. We used a dataset containing over 160,000 non-duplicate individual records of occurrence (referred to 280 butterflies and 43 zygenid moths), and their relative extinction data, to carry out a twofold analysis. We identified ecological preferences that influence extinction probability, and we analysed if all species were equally vulnerable to the same factors. Our analyses revealed that extinctions were non-randomly distributed in space and time, as well as across species. Most of the extinctions were recorded in 1901–1950 and, as expected, populations at their range edges were more prone to become extinct for non-habitat-related causes. Ecological traits were not only unequally distributed between extinction and non-extinction events, but also not all ecological features had the same importance in driving population vulnerability. Hygrophilous and nemoral species were the most likely to experience population losses and the most prone to disappear even when their habitat remained apparently unchanged. Species vulnerability depends on both ecological requirements and threat type: in fact, each species showed a distinct pattern of vulnerability, depending on threats. We concluded that the analysis may be an important step to prevent butterfly declines: species that are strongly suffering due to ‘unknown changes’ are in clear and urgent need of more detailed auto-ecological studies.     

A possible influence of extracellular polysaccharides on the analysis of intracellular metabolites from Trichoderma harzianum grown under carbon-limited conditions

Intracellular metabolites were evaluated during the continuous growth of Trichoderma harzianum P49P11 under carbon-limited conditions. Four different conditions in duplicate were investigated (10 and 20 g/L of glucose, 5.26/5.26 g/L of fructose/glucose and 10 g/L of sucrose in the feed). Differences in the values of some specific concentrations of intracellular metabolites were observed at steady-state for the duplicates. The presence of extracellular polysaccharide was confirmed in the supernatant of all conditions based on FT-IR and proton NMR. Fragments of polysaccharides from the cell wall could be released due to the shear stress and since the cells can consume them under carbon-limited conditions, this could create an unpredictable carbon flow rate into the cells. According to the values of the metabolite concentrations, it was considered that the consumption of those fragments was interfering with the analysis.     

A possible route for the formation of protoprotein and its microspheres from primitive gases under possible prebiotic conditions

In this study, a possible reaction pathway for the formation of protein-like copolyamino acids from gaseous starting materials is presented. The sequence of the reaction pathway is composed of four steps. These are a) formation of fumaronitrile, b) hydrolysis of fumaronitrile to thermal precursors of aspartic acid such as ammonium fumarate or malate, c) thermal copolycondensation of the precursors of aspartic acids with various amino acids (s), and d) formation of microspheres from the copolyamino acids. The steps b), c) and d) were demonstrated experimentally in this study. The materials and the conditions used in this study could be regarded as prebiological. The thermal copolycondensation is also a convenient synthetic method of aspartic acid containing copolyamino acids.