Gravitational Unloading Research Articles

Application of lactoferrin for the prevention and restoration of bone tissue in Wistar rats under conditions of hindlimb unloading

The influence of gravitational unloading (antiorthostatic suspension) and subsequent recovery on the mineral density and mechanical properties of the femoral and tibial bones of Wistar rats was studied with oral administration of a biotechnological analog of human lactoferrin (200 mg/kg) derived from the milk of producer goats. Bone mineral density was determined by dual-energy X-ray absorptiometry, and strength and stiffness were assessed through three-point bending tests. It was shown that gravitational unloading for 21 days led to a decrease in the mineral density of the tibial and femoral bones. The administration of lactoferrin did not significantly affect the mineral density or projected area of the studied bones. No statistically significant differences in mechanical stiffness were found between the experimental groups, but after readaptation, the ultimate strength was significantly higher in the groups that received lactoferrin. Thus, the obtained results may indicate the potential of lactoferrin preparations as prophylactic agents for maintaining bone strength. At the same time, maintaining bone mineral density under deficit-stimulating conditions requires consideration of alternative dosages and delivery methods of the drug.

The change in Baroreflex Regulation of Heart Rhythm after “Dry” Immersion Appears during Orthostasis, but not Lower Body Negative Pressure Test

The ratio of low-frequency (LF, ~0.1 Hz) waves of RR interval duration (RRI) and systolic blood pressure (SAP) reflects the cardiac baroreflex sensitivity (BRS). Gravitational unloading (GU) may alter BRS during the passive orthostatic test (HUT) and lower body negative pressure (LBNP) test. Both effects cause blood redistribution to the lower body, but HUT is accompanied by greater unloading of sinocarotid baroreceptors than LBNP and activation of the vestibulosympathetic reflex but GU effects on BRS in these tests have not been directly compared previously. In this study we tested the hypothesis that the effect of “dry” immersion (DI, on-ground model of GU) on BRS in the same subjects will be more pronounced during HUT than during LBNP, which causes a comparable decrease in stroke volume. Nine healthy men participated in two test sessions (before and after 7-day DI) consisting of five 3-min HUT (65°) and five 3-min LBNP (–35 mmHg) with averaging the parameters in each test. Wavelet analysis was used to determine the amplitude of the RRI and SAP waves in the range of 0.05–0.13 Hz. The amplitude of LF waves of SAP increased in both tests, after DI - more significantly in HUT. The amplitude of LF RRI waves decreased in the two tests; the degree of decrease did not differ between tests and did not change under the influence of DI. The α-coefficient (the ratio of the amplitudes of RRI and SAP LF waves) decreased equally in the two tests before DI, but after DI, the degree of α-coefficient reduction increased in HUT test but did not change in LBNP test. Thus, the effect of DI on BRS is evident in HUT, but not in LBNP, which may be explained by the more pronounced influence of HUT on the mechanisms of neural control of heart rhythm.

Muscle stiffness indicating mission crew health in space

Muscle function is compromised by gravitational unloading in space affecting overall musculoskeletal health. Astronauts perform daily exercise programmes to mitigate these effects but knowing which muscles to target would optimise effectiveness. Accurate inflight assessment to inform exercise programmes is critical due to lack of technologies suitable for spaceflight. Changes in mechanical properties indicate muscle health status and can be measured rapidly and non-invasively using novel technology. A hand-held MyotonPRO device enabled monitoring of muscle health for the first time in spaceflight (> 180 days). Greater/maintained stiffness indicated countermeasures were effective. Tissue stiffness was preserved in the majority of muscles (neck, shoulder, back, thigh) but Tibialis Anterior (foot lever muscle) stiffness decreased inflight vs. preflight (p < 0.0001; mean difference 149 N/m) in all 12 crewmembers. The calf muscles showed opposing effects, Gastrocnemius increasing in stiffness Soleus decreasing. Selective stiffness decrements indicate lack of preservation despite daily inflight countermeasures. This calls for more targeted exercises for lower leg muscles with vital roles as ankle joint stabilizers and in gait. Muscle stiffness is a digital biomarker for risk monitoring during future planetary explorations (Moon, Mars), for healthcare management in challenging environments or clinical disorders in people on Earth, to enable effective tailored exercise programmes.

ИЗМЕНЕНИЕ ФАЗОВЫХ СООТНОШЕНИЙ КОЛЕБАНИЙ АРТЕРИАЛЬНОГО ДАВЛЕНИЯ И СЕРДЕЧНОГО РИТМА ПРИ ОРТОСТАЗЕ: ВЛИЯНИЕ ГРАВИТАЦИОННОЙ РАЗГРУЗКИ

Investigation of the amplitude characteristics of arterial pressure (AP) and heart rate (HR) within the low-frequency (LF) band (baroreflex waves, ~ 0.1 Hz) and high-frequency (HF) band (breathing rate) is commonly used to asses the cardiovascular system functioning. This work was concerned with the effects of 7-d dry immersion (DI) (period of distinct hemodynamic shifts) on the phase characteristics of AP and HR oscillations within the LF and HF bands during the orthostatic test. Eight young healthy male subjects were exposed to the passive tilt test, i.e. 15 min in supine position followed by 15-min tilt at 60°. During the test, ECG, AP and breathing rate were registered continuously; breathing rate was set by the vocal command from PC. Breathing control and data analysis were performed using a specially developed program. It was found that orthostasis increased synchronization of the AP and HR oscillations within the LF band and also reduced the phases difference (temporal shift) between the oscillations within the HF band. Disappearance of these changes after DI reflects deterioration of the cardiac rhythm control by the nervous system. The comprehensive analysis of the AP and HR phase relations within the LF and HF bands can be useful for assessing changes in nervous regulation of the heart during gravitational unloading, diagnostics of orthostatic instability due to cardiovascular diseases, and developing methods of prevention.

Influence of Gravitational Unloading on the Dynamics of Blood Redistribution during Orthostasis: The Study by Near-Infrared Spectroscopy

We studied the effects of long-term anti-orthostatic hypokinesia (head-down bed rest—BR, a model of gravitational unloading) on the dynamics of orthostasis-induced changes in the content of total (THb), deoxygenated (HHb), and oxygenated (OHb) hemoglobin in the calf at the level of the gastrocnemius muscle medial head using near-infrared spectroscopy. In seven young men, 2–4 days before and on the 19th day of BR, a passive head-up tilt test was performed (15 min in the supine position, then 15 min at 65°). After BR, there was an increase in heart rate and a decrease in stroke volume in the supine position, as well as more pronounced changes in these parameters during orthostasis. Blood pressure in the supine position and orthostasis did not change after BR. THb content increased gradually during orthostasis and reached a plateau by the end of the test; after BR, an increase in the half-rise time and a twofold increase in the plateau level were observed. Tissue HHb content by the end of the tilt test also increased after BR. The dynamics of OHb before BR was more complicated: this indicator grew, reached a maximum during a minute, and then gradually decreased to half of the maximum by the end of the test. After BR, the dynamics of OHb changed drastically: the signal increased gradually and reached a level that was twice the peak value of OHb content before BR. The results allow us to conclude that exposure to BR weakens the compensatory constriction of calf vessels during tilt test; consequently, it is followed by higher blood accumulation in calf vascular bed, which, in turn, leads to smaller SV during orthostasis.

Influence of Gravitational Unloading on the Dynamics of Blood Redistribution During Orthostasis: The Study by Near-Infrared Spectroscopy

The effects of long-term anti-orthostatic hypokinesia (bed rest – BR, a model of gravitational unloading) on the dynamics of orthostasis-induced changes in the content of total (THb), deoxygenated (HHb), and oxygenated (OHb) hemoglobin in the calf at the level of the gastrocnemius muscle medial head were studied using the near-infrared spectroscopy. In seven young men, 2−4 days before and on the 19th day of BR, a passive head-up tilt test was performed (15 min in the supine position, then 15 min at 65°). After BR, there was an increase in heart rate and a decrease in stroke volume in the supine position, as well as more pronounced changes in these parameters during orthostasis. Blood pressure in the supine position and orthostasis did not change after BR. THb content increased gradually during orthostasis and reached a plateau by the end of the test; after BR, an increase in the half-rise time and a two-fold increase in the plateau level were observed. Tissue HHb content by the end of the tilt test also increased after BR. The dynamics of OHb before BR was more complicated: this indicator grew, reached a maximum during a minute, and then gradually decreased to half of the maximum by the end of the test. After BR, the dynamics of OHb changed drastically: the signal increased gradually and reached a level that was twice the peak value of OHb content before BR. The results allow us to conclude that exposure to BR weakens the compensatory constriction of calf vessels during tilt test; consequently, it is followed by higher blood filling of calf vascular bed, which, in turn, leads to smaller SV during orthostasis.

The Effect of Spontaneous Neuromuscular Activity on the Development of Atrophy of the Functionally Unloaded &lt;i&gt;m. soleus&lt;/i&gt;

It is well known that the inactivity of mammalian skeletal muscles leads to the cessation of their electrical activity and is accompanied by atrophic changes in muscle fibers. However, it has been repeatedly noted that starting from the 3rd day of functional unloading, spontaneous rhythmic neuromuscular activity appears, which is the result of a decrease in the expression of the potassium chloride co-transporter KCC-2 in neurons of the lumbar spinal cord. A decrease in the expression of KCC-2 and the onset of autonomous electrical activity of the unloaded muscle can be prevented by the administration of the neuroleptic prochlorperazine. Thus, the aim of this study was to evaluate the structural and signaling effects of the reduced spontaneous activity of the unloaded m.soleus. It was found that daily administration of prochlorperazine to rats under conditions of 7-day simulated gravitational unloading prevented a decrease in the content of the main markers of ribosome biogenesis (c-Myc, 18S rRNA and 28S rRNA), and also partially prevented a decrease in the cross-sectional area of fast and slow muscle fibers in the m.soleus. Morphofunctional changes caused by a decrease of spontaneous activity of the unloaded muscle were accompanied by complete or partial prevention of activation of key proteolytic markers expression (MuRF-1, MAFbx/atrogin-1, ubiquitin). Thus, we assume that spontaneous neuromuscular activity may be a factor that augments muscle atrophy during the first week of functional unloading.

SPATIO-TEMPORAL PATTERNS OF CORTICAL-MUSCULAR INTERACTION DURING LOCOMOTION

The paper considers the synergetic effects manifested at the cortical and muscular levels during locomotor activity showed in conditions of horizontal hanging of the lower extremities. The analysis of the synergies’ spatio-temporal structure was carried out using the data matrix factorization methods. It was found out the control of the movements’ structure is mainly realized through the three muscle synergies. The activity synchronization of the motor, associative, visual and sensorimotor regions of the cortex bilateral part is due to the specifics of performing locomotion in conditions of gravitational unloading and the associated features of receptor signaling. The identified components indicating synchronization of different areas of the right and left cortex may reflect the control processes associated with the control of alternate activation of the flexor and extensor muscles of the contralateral limb during locomotion. The data on the cortical activity spatial-temporal structuring indicate the separate management of muscle synergies through synchronization of cortical commands and the temporary organization of muscle synergies in the frequency ranges 0.30 to 8.00 Hz. Such patterns may reflect the activity of the rhythm-generating mechanism involved in the management of cyclic locomotor activity.

Perception of length and orientation in dry immersion.

How does gravity (or lack thereof) affect sensory-motor processing? We analyze sensorimotor estimation dynamics for line segments with varying direction (orientation) in a 7-day dry immersion (DI), a ground-based model of gravitational unloading. The measurements were carried out before the start of the DI, on the first, third, fifth and seventh days of the DI, and after its completion. At the memorization stage, the volunteers led the leading hand along the visible segment on a touchscreen display, and at the reproduction stage they repeated this movement on an empty screen. A control group followed the same procedure without DI. Both in the DI and control groups, when memorizing, the overall error in estimating the lengths and directions of the segments was small and did not have pronounced dynamics; when reproducing, an oblique effect (higher variability of responses to oblique orientations compared to cardinal ones) was obtained. We then separated biases (systematic error) and uncertainty (random error) in subjects' responses. At the same time, two opposite trends were more pronounced in the DI group during the DI. On the one hand the cardinal bias (a repulsion of orientation estimates away from cardinal axes) and, to a small extent, the variability of direction estimates decreased. On the other hand, the overestimation bias in length estimates increased. Such error pattern strongly supports the hypotheses of the vector encoding, in which the direction and length of the planned movement are encoded independently of each other when the DI disrupts primarily the movement length encoding.

Simulated microgravity leads to altered intracellular calcium homeostasis and protein expression in C2C12 cultures.

Skeletal muscle has the role to maintain body posture against a constant gravitational load. During aging, in low physical activity or even in spaceflight, the muscle mass is decreasing, resulting in impaired myogenesis and regeneration. The cytoskeleton, mechanosensitive ion channels, and calcium homeostasis play crucial role in maintaining normal myogenic processes. Simulated microgravity (SM) with 3D clinorotation is one of the accepted techniques to model gravitational unloading in vitro. C2C12 mouse myoblast cell line is a verified in vitro model system of myogenesis. Using RPM 2.0, a Random Positioning Machine as a partial g simulator, by randomly rotating the accommodated experiment package around the Earth's gravity vector, we are able to investigate alteration of physiological processes caused by SM. In our experiments, territorial gravity is compared to 0 g, respectively. However, fusion of myoblasts was preserved with SM, the formation of myotubes was different as compared to the control environment. Expression of Myosin Heavy Chain 2 (MYH2) protein, which is an important structural protein and a marker molecule of myotube differentiation program, was significantly reduced in samples kept in RPM. Immunocytochemistry of myogenic cultures revealed decreased size and average nuclei content in differentiated myotubes. The expression level of Piezo1 channels, which are mechanically activated cation channels are also decreased under SM. Altered calcium transients evoked by KCl have been observed in myotubes formed under simulated microgravity. Our results are in coherence with the recently published data. Our future goal is to analyze the architecture of cytoskeletal Septin7 protein and investigate how intracellular calcium concentrations and mechanotransduction is regulated by Piezo1 channels under microgravity condition.

ИССЛЕДОВАНИЕ СОКРАТИТЕЛЬНОЙ АКТИВНОСТИ ПОРТАЛЬНОЙ ВЕНЫ МЫШИ В ПОЛЕТНОМ ЭКСПЕРИМЕНТЕ «БИОН-М2»: ОБОСНОВАНИЕ АКТУАЛЬНОСТИ И РАЗРАБОТКА ЭКСПЕРИМЕНТАЛЬНОЙ МОДЕЛИ

Redistribution of blood in the vascular system in the condition of gravitational unloading causes changes in venous blood flow inboth humans and laboratory animals; however, dependence of these changes on the alterationsin contractile activity of venous walls and mechanisms involved are not sufficientlyexplored. Purpose of the work is to design an experimental setupand procedure for studying the effects of microgravity on the venous vesselsin mouse, the most common object of animalspace experiments. The proposed procedure consists of recording the contractile activity of the longitudinal smooth layer of the portal vein wall, and itschanges due to actionof pharmacological agents. Frequency of venous contraction changes in response to different factors more significantly than the contraction amplitude and tone level. The resultswill serve as a basis for developing an optimal protocol of studying the mechanisms of changes in venous contractility in mice as part of space experiment BION-M2.

ВКЛАД mTORC1 И GSK-3 В РЕГУЛЯЦИЮ БИОГЕНЕЗА РИБОСОМ В ПОСТУРАЛЬНОЙ МЫШЦЕ КРЫСЫ В УСЛОВИЯХ МОДЕЛИРУЕМОЙ МИКРОГРАВИТАЦИИ

The investigation was aimed to reveal a potential role of mechanistic target of rapamycin (mTORC1) and glycogen synthase kinase (GSK-3) in the regulation of ribosome biogenesis and protein synthesis in rat soleus muscle during simulated gravitational unloading. Wistar rats were subject to 7-day tail-suspension (hindlimb unloading) and treated with rapamycin (mTORC1 inhibitor) or AR-A014418 (GSK-3 inhibitor). Protein synthesis was measured with SUnSET. Phosphorylation of glycogen synthase-1 (GS-1) and ribosomal protein S6 (rpS6) was measured with the use of Western-blotting. Levels of 28S and 18S rRNA were determined using agarose gel electrophoresis. Expression of 47S pre-rRNA and c-Myc was assessed with RT-PCR. Gravitational unloading led to an increase in phosphorylation of GS-1 (a marker of GSK-3 activity) and inhibited phosphorylation of rpS6 (a marker of mTORC1 activity), expression of the ribosome biogenesis markers (total RNA РНК, 28S and 18S rRNA, 47S pre-rRNA, с-Myc) and protein synthesis in soleus muscle. GSK-3 inhibition prevented an increase in GS-1 phosphorylation and, partly, a reduction in the markers of both ribosomal biogenesis and protein synthesis. The mTORC1 inhibitor contributed to the phospho-rpS6 reduction but did not substantially influence the parameters of translational capacity and protein synthesis. To sum up, unlike mTORC1, an elevated GSK-3 activity can contribute to the inhibition of ribosome biogenesis and protein synthesis in rat soleus muscle under 7-day gravitational unloading.

NAIAD-2020: Characteristics of Motor Evoked Potentials After 3-Day Exposure to Dry Immersion in Women.

As female astronauts participate in space flight more and more frequently, there is a demand for research on how the female body adapts to the microgravity environment. In particular, there is very little research on how the neuromuscular system reacts to gravitational unloading in women. We aimed to estimate changes in motor evoked potentials (MEPs) in the lower leg muscles in women after 3-day exposure to Dry Immersion (DI), which is one of the most widely used ground models of microgravity. Six healthy female volunteers (mean age 30.17 ± 5.5 years) with a natural menstrual cycle participated in this experiment. MEPs were recorded from the gastrocnemius and soleus muscles twice before DI, on the day of DI completion, and 3 days after DI, during the recovery period. To evoke motor responses, transcranial and trans-spinal magnetic stimulation was applied. We showed that changes in MEP characteristics after DI exposure were different depending on the stimulation site, but were similar for both muscles. For trans-spinal stimulation, MEP thresholds decreased compared to baseline values, and amplitudes, on the contrary, increased, resembling the phenomenon of hypogravitational hyperreflexia. This finding is in line with data observed in other experiments on both male and female participants. MEPs to transcranial stimulation had an opposing dynamic, which may have resulted from the small group size and large inter-subject variability, or from hormonal fluctuations during the menstrual cycle. Central motor conduction time remained unchanged, suggesting that pyramidal tract conductibility was not affected by DI exposure. More research is needed to explore the underlying mechanisms.

NOS-dependent effects of plantar mechanical stimulation on mechanical characteristics and cytoskeletal proteins in rat soleus muscle during hindlimb suspension.

The study was aimed at investigating the mechanisms and structures which determine mechanical properties of skeletal muscles under gravitational unloading and plantar mechanical stimulation (PMS). We hypothesized that PMS would increase NO production and prevent an unloading-induced reduction in skeletal muscle passive stiffness. Wistar rats were hindlimb suspended and subjected to a daily PMS and one group of stimulated animals was also treated with nitric oxide synthase (NOS) inhibitor (L-NAME). Animals received mechanical stimulation of the feet for 4h a day throughout 7-day hindlimb suspension (HS) according to a scheme that mimics the normal walking of the animal. Seven-day HS led to a significant reduction in soleus muscle weight by 25%. However, PMS did not prevent the atrophic effect induced by HS. Gravitational unloading led to a significant decrease in maximum isometric force and passive stiffness by 38% and 31%, respectively. The use of PMS prevented a decrease in the maximum isometric strength of the soleus muscle. At the same time, the passive stiffness of the soleus in the PMS group significantly exceeded the control values by 40%. L-NAME (NOS inhibitor) administration attenuated the effect of PMS on passive stiffness and maximum force of the soleus muscle. The content of the studied cytoskeletal proteins (α-actinin-2, α-actinin-3, desmin, titin, nebulin) decreased after 7-day HS, but this decrease was successfully prevented by PMS in a NOS-dependent manner. We also observed significant decreases in mRNA expression levels of α-actinin-2, desmin, and titin after HS, which was prevented by PMS. The study also revealed a significant NOS-dependent effect of PMS on the content of collagen-1a, but not collagen-3a. Thus, PMS during mechanical unloading is able to maintain soleus muscle passive tension and force as well as mRNA transcription and protein contents of cytoskeletal proteins in a NOS-dependent manner.

Cytoskeletal Remodeling Mimics Endothelial Response to Microgravity.

Mechanical cues contribute to the maintenance of a healthy endothelium, which is essential for vascular integrity. Indeed endothelial cells are mechanosensors that integrate the forces in the form of biochemical signals. The cytoskeleton is fundamental in sensing mechanical stimuli and activating specific signaling pathways. Because the cytoskeleton is very rapidly remodeled in endothelial cells exposed to microgravity, we investigated whether the disruption of actin polymerization by cytochalasin D in 1g condition triggers and orchestrates responses similar to those occurring in micro- and macro-vascular endothelial cells upon gravitational unloading. We focused our attention on the effect of simulated microgravity on stress proteins and transient receptor potential melastatin 7 (TRPM7), a cation channel that acts as a mechanosensor and modulates endothelial cell proliferation and stress response. Simulated microgravity downregulates TRPM7 in both cell types. However, 24 h of treatment with cytochalasin D decreases the amounts of TRPM7 only in macrovascular endothelial cells, suggesting that the regulation and the role of TRPM7 in microvascular cells are more complex than expected. The 24 h culture in the presence of cytochalasin D mimics the effect of simulated microgravity in modulating stress response in micro- and macro-vascular endothelial cells. We conclude that cytoskeletal disruption might mediate some effects of microgravity in endothelial cells.

The functional state of the neuromotor system during hypogravity in a rat. Support load effects

The main goal of the research was to estimate the morpho-functional condition of the neuromotor apparatus of the rat soleus muscle under simulated gravitational unloading, as well as under simulated gravitational unloading combined with the action of axial load and support reaction force. Model experiments were performed on male laboratory rats weighing 190-210 g in strict accordance with the accepted bioethical standards. Gravitational unloading was simulated by the antiorthostatic hanging method. Within 7 and 35 days. For the action of the support load, the animals were placed daily on a hard horizontal surface for 90 minutes. The H-reflex and the M-wave of the soleus muscle were recorded; the threshold, maximum amplitude, latency and duration of the evoked potentials were determined. Muscle wet and dry weights were also evaluated. We found that during simulated gravitational unloading occurs an increase in the reflex activity of the m. soleus motoneurons, reduces the reliability of neuromuscular transmission, and initiates atrophic processes. Periodic application of a support load under conditions of short-term (but not long-term) simulated hypogravity prevents alteration in the central and peripheral parts of the neuromuscular apparatus of the rat soleus muscle.

Investigation of the process of gravitational unloading of energy willow cuttings in conditions of static and dynamic arch formations

Investigation of the process of gravitational unloading of energy willow cuttings in conditions of static and dynamic arch formations

Alternative Splicing of Titin mRNA in Rat Soleus after Seven-Day Gravitational Unloading

Alternative Splicing of Titin mRNA in Rat Soleus after Seven-Day Gravitational Unloading

Impact of Aquafitness Training on Physical Condition of Early Adulthood Women

Background. The physical benefits of fitness for middle-aged women are well-known. Unlike the usual training sessions, aquafitness occupies a special place among the types of health-related exercise training. Its health-enhancing effect results from the activation of the body's functional systems, the gravitational unloading of the musculoskeletal system, high energy expenditures, and overall body hardening effect. &#x0D; The objective of this study was to evaluate the health-enhancing effects of an aquafitness program on the functional indicators and physical fitness of early adulthood women. &#x0D; Materials and methods. Theoretical analysis and generalization of scientific and methodological literature, anthropometric techniques, pedagogical methods, and methods of mathematical statistics were used. The functional status of the body was assessed with the indices characterizing the function of the cardiorespiratory system, which are commonly used. The study was conducted at the Sport Life fitness club, Chernivtsi. The study involved 48 women aged 21-31 with an average age of 26.3 years. The subjects took part in a six-month aquafitness program consisting of 60-min sessions, three times a week. The program was developed by the authors and included aquatic stretching, body shaping and bodybuilding exercise, aquadance, aquatic gymnastics, and aqua tae-bo. &#x0D; Results. After participation in the exercise program: vital capacity increased from 45.96±4.69 to 48.88±0.68; strength index increased from 35.80±1.07 to 43.26±0.71; Robinson's index increased from 85.72±12.34 to 89.63±10.11; Shtange test increased from 30.28±10.32 to 37.78±12.34; Hench test changed from 16.48±4.24 to 25.19±4.58; Kerdo index decreased from 5.23±0.74 to 0.88±0.38; and Rufier's test decreased from 12.21±4.26 to 8.03±2.14. The assessment of somatic health of the women showed a significant improvement (p&lt;0.05). Positive changes in the autonomic system were detected.&#x0D; Conclusion. The developed aquafitness program can be an effective tool for health improvement and body weight management in early adulthood women.

Jumping at a chance to control cerebral blood flow in astronauts.

Jumping at a chance to control cerebral blood flow in astronauts.