Cardiovascular Function in Humans Using Thigh Cuffs during Seven Days of Simulated Microgravity

Data are summarized on changes in the human cardiovascular system associated with the use of cuffs during seven days of antiorthostatic hypokinesia simulating weightlessness. Eight subjects participated in two series of experiments, of which one was carried out with and the other (the control) without cuffs wrapped snugly around the upper third of the thighs. The parameters of the systemic hemodynamics, the cardiac function, and the hemodynamics of the cervicocephalic region and the lower limbs recorded under control and experimental conditions were analyzed. Without cuffs, changes in the hemodynamics during antiorthostatic hypokinesia were caused by displacement of body fluids in the cranial direction. The subjects responded favorably to the use of cuffs during antiorthostatic hypokinesia: most of their hemodynamic parameters remained at the baseline level, and signs of venous stasis in the cervicocephalic region were alleviated. Although the leg veins were distended in subjects wearing thigh cuffs during antiorthostatic hypokinesia, no pathological changes in the veins were detected during or after the experiment. Cuff usage during antiorthostatic hypokinesia lasting for seven days did not produce a cumulative effect on the cardiovascular system. These results justify the use of thigh cuffs in the initial period of adaptation to simulated or real weightlessness.     

Adaptation of the water-electrolyte metabolism to space flight and at its imitation

A fifty-year study of water-electrolyte metabolism, the condition of the water medium of the body, and hormonal regulation during space flights and the postflight period or their on-ground modeling (hypokinesia, bed rest, immersion, etc.) has shown the important role of water-salt homeostasis in adaptation of the human and animal body to weightlessness. It has been revealed that, in weightlessness, the conditions for the development of a negative balance of a liquid (hydrohydration) and basic electrolytes are created. After termination of long space flights, attributes of the development of adaptive reactions, compensating for the loss of extracellular liquid volume come to light. In order to assess the state of the kidneys and water-electrolyte metabolism in cosmonauts and investigators, functional load tests, and special methods of diagnostics were developed. This is the basis for the research aimed at improving the scheme of correction of the water balance of the body of cosmonauts at different stages of a flight.     

Physical working capacity and factors responsible for it after exposure to 120-day antiorthostatic hypokinesia

The effect of 120-day antiorthostatic hypokinesia on human physical working capacity and functional state was studied. The study revealed two adaptation phases: the first phase is characterized by a significant decrease in working capacity and the second by relative readaptation. However, the unfavorable effect of 120-day antiorthostatic hypokinesia was evident as a decrease in the effectiveness of function of the cardiorespiratory system that increased the physiological cost of physical work.     

The problem of estimation of the organism adaptable opportunities under stressful influences

The human organism testing in conditions of modern scientific and technical progress constant stressful influences (industrial, social, psycho-emotional) was carried out for continuous adaptation to the environment: changing of the level of functioning of separate systems and a corresponding tension of regulatory mechanisms occurred. In the article, theoretical bases and methodology of studying the adaptable capacities of the organism are considered. The prenosological diagnostics was used for studying functional conditions on the verge of norm and pathology. The heart rate variability analysis was used based on mathematical model of functional conditions. Concrete technologies and results of evaluation of the adaptation capacities of the organism in space and aviation medicine are presented as well as in applied physiology.     

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]     

Fluid electrolyte changes in trained subjects after water loading and during restriction of muscular activity and chronic hyperhydration

The objective of this investigation was to determine fluid electrolyte changes after water-loading tests and during hypokinesia (decreased number of km taken per day) and daily intake of fluid and salt supplementation (FSS). The studies during hypokinesia (HK) were performed for 364 d on 30 endurance-trained male volunteers in the age range of 23–26 yr, with an average peak oxygen uptake, POU, of 64 mL/kg/min. All volunteers were divided into three equal groups: 10 volunteers were placed on a continuous regime of exercise of 14.4 km/d and served as control subjects (CS); 10 volunteers were submitted to continuous HK without FSS and were considered as the unsupplemented hypokinetic subjects (UHS); and 10 volunteers were under continuous HK and FSS and were considered as the supplemented hypokinetic subjects (SHS). For the simulation of the hypokinetic effect, the UHS and SHS groups were kept continuously under an average of 2.7 km/d for the duration of the study. Prior to exposure to HK, the two groups of volunteers were on the same exercise regime as the control group. During a 60-d preexperimental period and during the remainder of the study, water-loading tests with a water load of 20 mL/kg body wt/min were performed, and urinary and plasma electrolytes (sodium, potassium, calcium, and magnesium) were measured. In the SHS group, urinary excretion of electrolytes and plasma electrolyte content decreased, while in the UHS these values increased after water loading tests and during HK. Based on the obtained data, it is concluded that chronic hyperhydration may be used to prevent or minimize urinary and plasma electrolyte changes in endurance-trained volunteers after water-loading tests and during prolonged restriction of muscular activity.     

Electrophysiological Mechanisms of Adaptation Processes

A systemic analysis of the relationships between electrophysiological parameters of the cardiovascular and respiratory systems during adaptation processes has been performed in order to study some electrophysiological mechanisms of stress. Studies were performed in subjects with various circulatory disorders and in healthy subjects at rest and during exercise; in skilled and apprentice workers at an electronics plant; and in students under examination stress. It is demonstrated that determining the set of parameters of the integrated cardiac–respiratory–hemodynamic system is necessary but not sufficient for diagnosing stress and its individual stages. The main characteristic is the degree of harmony in the ratios between these parameters, i.e., the balance of relationships between subsystems; the ratios thereby serve as new diagnostic signs of the functional state of the body. A resonance–wave model of stress is proposed. This model forms a basis for the assessment of stress during its development, with the stages of strain and overstrain being regarded as stages of the positive dynamics of adaptation syndrome provided that self-regulation is preserved during the progress of these stages, i.e., resonance is formed. In the case of disharmonic ratios between electrophysiological parameters and imbalance of their relationships, the stages of adaptation processes differ in the degree of deviation from invariant ratios between parameters.     

Fibrillin-1, a calcium binding protein of extracellular matrix

Fibrillin-1 is a large extracellular matrix glycoprotein which assembles to form 10-12 nm microfibrils in extracellular matrix. Mutations in the human fibrillin-1 gene (FBN-1) cause the connective tissue disease Marfan syndrome and related disorders, which are characterised by defects in the skeletal, cardiovascular and ocular systems of the body. Fibrillin-1 has a striking modular organisation which is dominated by multiple tandem repeats of the calcium binding epidermal growth factor-like (cbEGF) domain. This review focuses on recent studies which have investigated the structural and functional role of calcium binding to cbEGF domains in fibrillin-1 and 10-12 nm microfibrils.     

Efficacy of the Combined Use of Negative Pressure on the Lower Part of the Body and Negative-Pressure Respiration under Simulated Microgravity

The efficacies of the standard procedure for application of negative pressure on the lower part of the body (NPLB) and a combination of NPLB and negative-pressure respiration (NPR) during a simulated last stage of a spaceflight under conditions of antiorthostatic hypokinesia (ANOH, –6°) and isolation for 7 days have been compared in the course of three series of tests involving six volunteers in an EU-100 pressurized chamber. After the end of the 7-day ANOH and isolation, episodes of orthostatic disorders were observed in all six subjects in the first series of tests (the control series) and in four subjects in the second series (NPLB). In the third series (NPLB + NPR), orthostatic disorders, if any, were slight. Two main conclusions have been made. First, ANOH combined with isolation in a small chamber may be used to simulate the effects of the combined factors of spaceflight on humans in order to obtain model gravitational circulatory disorders. Second, the combined use of NPLB + NPR under these conditions may be effective for the prevention of orthostatic circulatory disorders in humans.     

Activity of the Sympathoadrenal System during Adaptation of the Human Body to Living Inside an Isolated Object

Changes in the activity of the sympathoadrenal systems of three healthy volunteers during their adaptation to living and working inside an isolated facility were studied. The living conditions and the professional activities of the subjects examined simulated those typical of cosmonauts during long-term spaceflight. The activities of the sympathoadrenal and serotonin- and histaminergic systems were assessed through relative rates of synthesis, inactivation, and metabolism. The subjective tolerance to the complex of experimental conditions was evaluated with a feeling–activity–mood test. It was shown that, while a human lives and works inside an isolated facility, adaptive changes in some parameters of the sympathoadrenal and histaminergic systems proceed through specific temporal phases. Among the rates of synthesis, inactivation, and metabolism, the most significant phase-related changes were observed in parameters of the metabolic activity. Apparently, the metabolic activity of the liver and other tissues affecting the blood levels of catecholamines and other biogenic amines is a leading mechanism of those phase-related changes in transmitter systems that are evident during human adaptation to complicated living conditions. For many of the metabolic parameters tested, rates of change were either independent of other experimental conditions or showed a less significant dependence on conditions than on phase-related factors.     

An inhibitor of free radical processes decreases the rate of protein synthesis in gunshot wound tissues and decelerates the general adaptation syndrome

The dynamics of total protein and procollagen biosynthesis was studied in the muscle tissue in gunshot wound during the natural healing and after treatment with antioxidant (AO) 2,6-di-tert-butyl-4-methylphenol (BHT). AO treatment considerably decreased the rate of both total protein and procollagen synthesis in the muscle on the third day of healing. BHT notably decreased protein biosynthesis and inhibited corticosteroid production as measured from the electron spin resonance (ESR) signal of reduced adrenodoxin. AO treatment also decreased the rate of protein biosynthesis in bone marrow, thymus, and spleen. The decreased functional activity of the endocrine and immune systems suggests that AO considerably decelerates the systemic body response (general adaptation syndrome) to acute wound. Lipid peroxide radicals and the products of lipid hydroperoxide degradation are proposed as the primary mediators of the body response to stress.     

Bioimpedance analysis of fluids and body composition under the conditions of short-term space flight or hypokinesia

Hydration status of humans was assessed by means of bioimpedancemetry on board the space station or under the conditions of antiorthostatic hypokinesia (AOSH). Water compartments of the body were decreased in a cosmonaut at the seventh day of a ten-day-long flight to the same degree as in a group of six testers by the seventh day of AOSH (?8°): the amount of total body fluids and intracellular and extracellular volumes were decreased by 5.6–6.5% as compared to the baseline level. The changes in body composition of a cosmonaut during flight were similar to the changes observed in testers during AOSH: lean body weight, which was determined by bioimpedancemetry, was insignificantly decreased, whereas the adipose component of body weight was, on the contrary, increased. It was concluded that the hydration level of the human body was decreased and the amount of body fat was increased during a short-term space flight. It was also shown that the hydration status and composition of the human body were changed in a similar way under the conditions of both AOSH and space flight, which indicates that this ground-based model is adequate for simulation of hydration changes caused by microgravity.     

Fundamental and applied objectives of investigation in dry immersion

The results of extended comparative research in the effect of hypogravity on the motor system in space flights and ground-based experiments have shown that “dry” immersion (DI) is the most adequate model of microgravity—the time of development, and the volume and depth of structural and functional motor disorders in DI are very close to what is observed in real microgravity. The high intensity and speed of development of hypogravity effects during immersion hypokinesia in comparison with bed rest hypokinesia, differing from DI only by the level of support deafferentation, promoted an insight into the leading (triggering) role of support lessness in the genesis of microgravity-induced syndromes of muscular deconditioning and hypogravitational ataxia. The involvement and pathways of support afferentation within the muscular system were experimentally studied and verified. The mechanisms of the development of changes in the activity of the system mechanisms remain much less investigated. These issues, as well as some new approaches for the elimination of the negative effects of hypogravity, were the subjects of investigation in the program of a complex dry immersion experiment, the results of which are presented in this issue of the journal.     

A period of urgent postnatal adaptation as a critical stage of human ontogenesis

The infant's state immediately after delivery is characterized by critical shifts of homeostasis parameters: decompensated mixed acidosis, pathologic indices of gaseous blood condition (arterial hypoxemia and hypercapnia), spontaneous postnatal hypothermia. Qualitative change of functional systems after delivery is accompanied by expressed tense of adaptation and regulation mechanisms and by centralization of cardiac rhythm control. The use of mathematical analysis of cardiac rhythm made it possible to find out that the change of degree of adaptation tense in the process- of postnatal period obeys the exponential dependence; moreover, the duration of transitional process of healthy newborns is 1 hour, but it considerably increases in case of hypoxia. After comparison of cardiac rhythm indices of these two groups of newborns it has been pointed out that mechanisms of adaptation after delivery are equal and they are based on the growing activity of central regulation processes. The dynamics of transitional process such as the period of postnatal adaptation indicates the reserve possibilities of infant and helps to reveal pre-nosological forms of disadaptational syndrome.     

The water-salt balance and renal function in space flights and in model experiments

Study of a condition of mineral and water-electrolyte metabolism, function of kidneys, and their hormonal regulation during model experiments (hypokinesia, bed rest, immersion etc.), and also in space flights and in readaptation period, has shown a major role of water-electrolyte homeostasis during general adaptation of humans and animals to new conditions of life and to conditions of weightlessness in particular. The change in regulation of volumes of fluid milieu in an initial period of weightlessness was shown to be the consequence of redistribution of blood and hemodynamics of the shifts resulting in change of production of volume-regulation hormones, formation of negative water balance, and redistribution of fluid in the organism among various fluid compartments. At later stages of flight or long-term hypokinesia, a change of water-electrolyte homeostasis occurs with a decrease in the kidneys excretion of sodium, and diuresis, but with an increased excretion of calcium and production of ADH and RAAS hormones. Following returning to earth gravitation, the majority of astronauts have adaptive reactions, compensating for the loss extracellular fluid and mineral substances and formation of "earth" water-electrolyte homeostasis. For estimation of water-electrolyte homeostasis and the functions of kidneys in astronauts, various functional loading tests have been developed. The developed system of preventive maintenance is successfully used for abolition of adverse changes at various stages of space flight and in readaptation period.     

Psychophysiological condition of first-year students with different levels of physical activity

The psychophysiological condition of first-year students (males) going or not going in for sport in the course of training was investigated. Baevskii’s method was used to determine the level of stress of regulatory mechanisms. The functional level of the nervous system, the stability of neural responses, and the level of functional abilities of the developed functional system were evaluated using the variation chronoreflexometric method. It was established that an improvement in the mental capacity parameters (increased mental capacity, reduction in the number of errors, an increase in the level of functional abilities, and shortening of the latent period of visuomotor response) was accompanied by an increase of stress of the body regulatory systems, which was more marked in individuals with a low level of physical activity. This fact indicates that physical activity reduces the cost of the adaptation of the body to permanently changing environmental conditions. The optimal human adaptive systemic reactions are ensured by the dynamic interaction of the functional systems forming complex correlations in the somatic, autonomic, motor, and psychoemotional spheres of the body’s activity.     

蝶形花亚科植物花部适应机制与传粉系统

蝶形花亚科(Papilionoideae)植物种类丰富、繁育系统多样,与其传粉者关系密切,主要表现在花部适应与传粉系统的形成。蝶形花形态复杂,为完全花,花萼、花瓣5基数,花萼呈箭头状,相邻花瓣螺旋轮生,旗瓣较大位于最外边,两片翼瓣紧贴旗瓣着生并包裹两片合生的龙骨瓣,龙骨瓣内包裹着雌、雄蕊,雌蕊位于正中央,雄蕊轮生,构成二体雄蕊(多数9+1,少数5+5)。对蝶形花亚科植物的花部特征、传粉功能群、酬物与传粉系统构建进行了回顾,重点论述了蝶形花形态和化学组成与传粉系统的进化关系以及花粉呈现机制。其中,泛化的传粉系统以蜂媒传粉为主,同时存在鸟媒传粉、蝙蝠传粉和松鼠传粉等方式,花部结构和传粉者的相互选择和相互适应推动了传粉系统的演化。花粉释放是体现蝶形花植物与其传粉功能群相互作用的重要方面,二者协同进化形成了以下4种花粉呈现机制:弹花机制、活塞机制、瓣膜机制和毛刷机制。蝶形花的花部特征与传粉功能群的相互作用形成相应的传粉系统,而传粉系统是执行传粉功能的重要集合体,各个构件的相互协调和适应保证了蝶形花亚科植物传粉过程的顺利完成。     

ComorbiditéS associées au trouble déficit de l’attention avec hyperactivité : Données épidémiologiques et implications thérapeutiques

ADHD has become one of the most frequent cause of referrals for children’ behaviour disorders. ADHD is a prevalent psychiatric condition affecting 5% to 9% of school-age children with regards to DSM-IV R diagnostic criteria. In addition, according to the results of different epidemiological studies, patients with ADHD very often experience comorbid conditions in 50% to 90% of the cases. The most frequent comorbidities include externalised disorders, (oppositional defiant disorder, conduct disorders), learning disorders, internalised disorders (anxiety, depression) and tics (chronic motor tics, Tourette’s syndrome). Given their negative impact on the outcome of ADHD in terms of affective and social functioning, and of social and school adaptation, these comorbid conditions should be carefully and systematically searched, even without any actual complaint. Although management of comorbid psychiatric conditions is never simple nor straightforward, therapeutic option should be considered taking into consideration both management of ADHD and specificity of these comorbidities.     

Human developmental disorders and the Sonic hedgehog pathway

Sonic hedgehog (Shh) is a morphogen that is crucial for normal development of a variety of organ systems, including the brain and spinal cord, the eye, craniofacial structures, and the limbs. Mutations in the human SHH gene and genes that encode its downstream intracellular signaling pathway cause several clinical disorders. These include holoprosencephaly (HPE, the most common anomaly of the developing forebrain), nevoid basal cell carcinoma syndrome, sporadic tumors, including basal cell carcinomas, and three distinct congenital disorders: Greig syndrome Pallister–Hall syndrome, and isolated postaxial polydactyly. These conditions caused by abnormalities in the SHH pathway demonstrate the crucial role of SHH in complex developmental processes, and molecular analyses of these disorders provide insight into the normal function of the SHH pathway in human development.     

Arm lengths and arm reaches: some interrelationships of structural and functional body dimensions

Structural measurements of the human body have for the most part been of little practical use as indicators of such functional body dimensions as arm reaches. These dimensions, which define the area around the body to which a person can reach given certain specified conditions and constraints are often critical for the design and layout of workspaces. However, they are relatively difficult and time-consuming to obtain, usually requiring specially constructed measuring systems for each differing design situation, as well as resurveys for each physically distinct population. An alternate approach, described here, investigates the interrelationships between these two classes of measurements with the aim of predicting functional reaches from structural body dimensions. In the present study traditional structural measurements and 117 functional arm reaches were obtained on 100 subjects. Correlations between the two types of measures are reported. Regression equations are presented which can predict functional arm reaches from two structural body dimensions on anthropometrically differing populations under a fixed set of workspace conditions.