Space life sciences: search for signatures of life, and space flight environmental effects on the nervous system.
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Animals↗
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Living in space: scientific, medical and cultural implications. A selection of papers presented at the 14th IAA Humans in Space Symposium.
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Adaptation, Physiological↗
Effect of lower body negative pressure on orthostatic tolerance and cardiac function during 21 days head-down tilt bed rest.
The purpose of the present study was to investigate the changes of orthostatic tolerance and cardiac function during 21 d head-down tilt (HDT) bed rest and effect of lower body negative pressure in the first and the last week in humans. Twelve healthy male volunteers were exposed to -6 degrees HDT bed rest for 21 d. Six subjects received -30 mmHg LBNP sessions for 1 h per day from the 1st to the 7th day and from the 15th to the 21st day of the HDT, and six others served as control. Orthostatic tolerance was assessed by means of standard tilt test. Stroke volume (SV), cardiac output (CO), preejection period (PEP) and left ventricular ejection time (LVET) were measured before and during HDT. Before HDT, all the subjects in the two groups completed the tilt tests. After 10 d and 21 d of HDT, all the subjects of the control group and one subject of the LBNP group could not complete the tilt test due to presyncopal or syncopal symptoms. The mean upright time in the control group (15.0 +/- 3.2 min) was significantly shorter than those in the LBNP group (19.7 +/- 0.9 min). SV and CO decreased significantly in the control group on days 3 and 10 of HDT, but remained unchanged throughout HDT in the LBNP group. A significant increase in PEP/LVET was observed on days 3 and 14 of HDT in both groups. The PEP/LVET in the LBNP group was significantly lower on day 3 of HDT, while LVET in the LBNP group was significantly higher on days 3, 7 and 14 of HDT than those in the control group. The results of this study suggest that brief daily LBNP sessions used in the first and the last weeks of 21 d HDT bed rest were effective in diminished the effect of head-down tilt on orthostatic tolerance, and LBNP might partially improve cardiac pumping function and cardiac systole function.
Adult↗
The response of Dahl salt-sensitive and salt-resistant female rats to a space flight model.
Vitamin D metabolism in the Dahl salt-sensitive (S) rat, a model of salt-induced hypertension, differs from that in the Dahl salt-resistant (R) rat. We have tested the hypothesis that differences in vitamin D metabolism would render the Dahl S rat more susceptible than the Dahl R rat to the effects of a space flight model. Dahl female rats were tail suspended (hind limb unloaded) for 28 days, while fed a low salt (3 g/kg sodium chloride) diet. Plasma 25-OHD concentrations of S rats were significantly lower than that of R rats. Plasma 1,25-(OH)2D concentration was 50% lower in unloaded than in loaded S rats, but was unaffected in unloaded R rats. The left soleus muscle weight and breaking strength of the left femur (torsion test) were 50% and 25% lower in unloaded than in loaded S and R rats. The mineral content of the left femur, however, was significantly lower (by 11%) only in unloaded S rats. We conclude that female S rats are more vulnerable than female R rats to decreases in plasma 1,25-(OH)2D concentration and femur mineral content during hind limb unloading, but equally vulnerable to muscle atrophy and reduced breaking strength of the femur.
Animals↗
[Application of fractal dimension in heart rate variability analysis during head-down tilt].
OBJECTIVE: The paper applies the fractal dimension to heart rate variability (HRV), and discusses the changes of the fractal dimension of cardiovascular system during head down tilt (HDT). METHOD: ECG of 10 subjects were recorded during HDT, the experiment was repeated in each subject. Fractal dimension was used to analyze the HRV. RESULT: Compared to supine before HDT, the standard deviation of all normal to normal RR intervals (SDNN) at 15-20 min, 20-25 min, 25-30 min and restoration increased significantly; the root mean square of successive differences between adjacent normal cycles (rMSSD) at 20-25 min increased significantly; the fractal dimension at 0-5 min, 5-10 min, 10-15 min, 20-25 min, 25-30 min and restoration increased significantly. CONCLUSION: The result shows that HRV and the nonlinearity of cardiovascular system increase during HDT. It is feasible that the fractal dimension can be used for analyzing HRV.
Cardiovascular Physiological Phenomena↗
Artificial gravity.
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Adaptation, Physiological↗
Small step or giant leap? Human locomotion on Mars.
Human locomotion on Mars will be considerably different from on Earth. Optimum walking speeds will be approximately 30% lower and transitioning from a walk to a run will occur at a speed 25% slower. Peak vertical forces will be reduced by as much as 50%, and although ground contact time will remain constant with locomotion in 1 g, stride length and stride time will increase. During running on Mars airborne time will increase by approximately 80% in comparison to running on the Earth. On Mars, half as much energy will be required to travel the equivalent distance on Earth and it will be 65% more economical to run rather than to walk. Crews will, therefore, find themselves using a loping gait--a running-like action, with a slight upper body lean and an extended aerial phase, an unfamiliar gait in terrestrial locomotion.
Astronauts↗
Fate of allelopathic substances in space--allelopathy of velvet bean plant and gravity.
Interactions between organisms and species have been long known. It has not been known that the interactive phenomena (allelopathy) may (or may not) differ in space from those on earth. We have studied the gravitational effects on allelopathy by exposing a plant-plant system to pseudo-microgravity, which was generated by a 3D-clinostat. We hypothesized that allelopathy would be modified under altered gravity. L-DOPA (L-3,4-dihydroxyphenylalanine) is known to be the major substance in the allelopathy of velvet bean, released from its root. It has been found that there have been some differences of the allelopathic action of velvet bean plant under pseudo-microgravity. Biosynthesis, release, transport and sensing mechanism associated with allelopathy might be affected by gravity.
Levodopa↗
Graviregulation mechanism of woody stem growth on earth.
We have been studied the weeping habit of Japanese flowering cherry tree in the field of Tama Forest Science Garden, Forestry and Forest Products Research Institute at the foot of Mt. Takao. Since cherry trees at various age were the materials for our plant physiology experiments, our studies were conducted in the fields where we experienced certain difficulties. Even under such difficult environment that was rather unexpected and uncontrollable, we could obtain fruitful results on the growth of cherry tree, and found them scientifically significant, especially in terms of biological effects of gravity on earth. Moreover an interesting interaction of cherry tree with various kinds of birds was also observed.
Biomechanical Phenomena↗
Role of gravity in mammalian development: effects of hypergravity and/or microgravity on the development of skeletal muscles.
Effects of hindlimb suspension or exposure to 2-G between postnatal day 4 and month 3 and of 3-month recovery at 1-G environment on the characteristics of rat hindlimb muscles were studied. Pronounced growth inhibition was induced by unloading, but not by 2-G loading. It is suggested that the development and/or differentiation of soleus muscle fibers are closely associated with gravitational loading. The data indicated that gravitational unloading during postnatal development inhibits the myonuclear accretion in accordance with subnormal numbers of both mitotic active and quiescent satellite cells. Even though the fiber formation and longitudinal fiber growth were not influenced, cross-sectional growth of muscle fibers was also inhibited in association with lesser myonuclear domain and DNA content per unit volume of myonucleus. Unloading-related inhibition was generally normalized following the recovery.
Animals↗
Responses of neuromuscular systems under gravity or microgravity environment.
Hindlimb suspension of rats induces induces fiber atrophy and type shift of muscle fibers. In contrast, there is no change in the cell size or oxidative enzyme activity of spinal motoneurons innervating muscle fibers. Growth-related increases in the cell size of muscle fibers and their spinal motoneurons are inhibited by hindlimb suspension. Exposure to microgravity induces atrophy of fibers (especially slow-twitch fibers) and shift of fibers from slow- to fast-twitch type in skeletal muscles (especially slow, anti-gravity muscles). In addition, a decrease in the oxidative enzyme activity of spinal motoneurons innervating slow-twitch fibers and of sensory neurons in the dorsal root ganglion is observed following exposure to microgravity. It is concluded that neuromuscular activities are important for maintaining metabolism and function of neuromuscular systems at an early postnatal development and that gravity effects both efferent and afferent neural pathways.
Afferent Pathways↗
The change of HSP47, collagen specific molecular chaperone, expression in rat skeletal muscle may regulate collagen production with gravitational conditions.
It is well known that unloading of skeletal muscle with spaceflight leads skeletal muscle atrophy. However, it remains unclear how the extracellular matrix within the muscle and the connective tissues such as tendon and ligament respond to reduced mechanical load including microgravity, although they have been thought to play important roles in both the transmission of force and the signal transduction between cells and tissues. Type-I collagen and type-IV collagen, both of the major components of extracellular matrix and connective tissues. We focused on change of these collagen synthesis with mechanical load. To obtain an insight into the effects of gravitational changing on the protein metabolism of collagen in skeletal muscle during mechanical unloading, reloading after unloading, we investigated changes in the amount of Heat shock protein 47 (HSP47), has been postulated to be a collagen-specific molecular chaperone localized in the ER (Nagata et al, 1992). Western blot analysis revealed that HSP47 in rat soleus muscle decreases at 5 days after hindlimb suspension (HS). On the other hand, HSP47 in rat soleus muscle increases at 5 days after hypergravity (HG) induced by the centrifugation. RT-PCR analysis showed HSP47 mRNA decreased with HS earlier, as compared with collagen type-I and type-IV mRNA. From these results, the amount of HSP47 changing by gravitational condition may effect on signal transfers in the primary stage of adaptation and the change of HSP47 expression in skeletal muscle may regulate collagen production with gravitational conditions.
Animals↗
Global and temporal regulation of gene expression in Xenopus kidney cells in response to presumed microgravity generated by 3D clinostats.
We documented changes in morphology and gene expression of the renal epithelial cell line A6 derived from Xenopus leavis adult kidney induced by long-term culturing with three dimensional clinostats. An oligo microarray analysis on A6 cells showed that mRNA levels of 52 out of 8091 genes were significantly altered in response to clinorotation. Upregulation or downregulation of gene expression became evident on day 8 and day 10 while there was no significant change on day 5. However, on day 15, expression of 18 out of 52 genes resumed to the levels similar to its original levels while remaining 33 genes maintained altered levels of expression. Quantitative analyses of gene expression by real-time PCR confirmed that changes in mRNA levels of selected genes were found only under clinorotation but not under hypergravity (7 G) and ground control (1 G). Morphological changes including loss of dome-like structures, disassembly of E-cadherin adherence junctions and disassembly of cortical actin were also observed over 10 days of culturing with clinorotation. The results revealed genes which expression was altered specifically in A6 cells cultured under clinorotation.
Actins↗
Distribution of L-DOPA in the root of velvet bean plant (Mucuna pruriens L.) and gravity.
Velvet bean (Mucuna pruriens L.) has been found that the degree of suppression on the lettuce root growth by velvet bean was less on the 3D-clinorotation. The number and growth of adventitious root in velvet bean differed among the clinostated and control group. L-DOPA (L-3,4-dihydroxyphenylalanine) is known to be the major substance in the allelopathy of velvet bean plant, released from its root. Since L-DOPA is a precursor of melanin pigment, and is easily converted to melanin by oxidation, locality of L-DOPA production in the plant body can be seen through pigmentation. The amount of L-DOPA was analyzed by HPLC and LC-ESI/MS. The distribution of L-DOPA in the root was different among the ground control condition and pseudo-microgravity.
Gravitation↗
Modulation of cell mutability by serum factors from volunteers who experienced head-down-tilt bed rest.
Head-down-tilt bed rest (BR) is utilized to mimic a microgravity environment. In this study, we examined whether the modulating activity of serum factors on cell mutability was changed in seventeen volunteers subjected to BR. For comparison, serum was comparatively obtained from seven volunteers who experienced the parabolic flight (PF). Cultured human cells were treated with serum and then irradiated with UV or X-ray. Mutagenicity was estimated by identification of K-ras codon 12 base substitution mutation, following PCR and differential dot-blot hybridization. Modulating activity was detected in one sample from each of post-BR and post-PF serum.
Bed Rest↗
[Establishment of COL1A1-EGFP stably transfected ROS17/2.8 cell lines].
OBJECTIVE: To obtain ROS17/2.8 cell lines which were stably expressing EGFP reporter gene drived by COL1A1 promoter. METHOD: A 3.6 Kb COL1A1 promoter from rat was cloned into pMD-18-T vector by PCR. This amplified promoter vector was digested to get several different length fragments which were then fused with EGFP reporter gene to construct eukaryotic expression vectors. ROS17/2.8 cell was stably transfected with these vectors by LipofectAMINE(TM) and selected by G418. RESULT: The COL1A1-EGFP stably transfected cell lines were established. CONCLUSION: The cell lines will be useful for studying the effects of microgravity on the activity of COL1A1 promoter and expression of gene related with bone form.
Alkaline Phosphatase↗
[Role of ROK in contraction of rat femoral arteries after 14 d tail suspension].
OBJECTIVE: To determine the role of Rho associated kinase (ROK) in contraction of rat femoral arteries after 14 d tail suspension. METHOD: Male Wistar rats were randomly divided into control group (CON) and 14 d -30 degrees tail suspension group (TS14d). Analysis was performed on the contractile responses of perfused femoral arterial rings from both TS14d and CON rats to KCl, phenylephrine (PE), and U-46619 in the presence of Y-27632. RESULT: Arterial rings from TS14d rats displayed a reduced contractile response to KCl and PE but not significantly to U-46619. In the response to KCl, Y-27632 caused a concentration-dependent relaxation and significantly larger decrease of contraction in tissues from TS14d rats. Y27632 nearly abolished the tonic component of KCl-induced contraction when its dose was increased from 10(-6)mol/L to 10(-5) mol/L. It had also an inhibitive effect on the PE and U-46619-induced contraction and caused significantly larger decrease in U-46619 but not in KCl or PE induced contraction in tissues from TS14d rats. CONCLUSION: ROK activity may be enhanced and play a compensational role in rat femoral arteries after TS14d.
15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
[Effects of nifedipine on myosin heavy chain (MHC) isoforms transition in unloaded soleus].
OBJECTIVE: To observe the effects of nifedipine, a blocker of L-type Ca2+ channel, on soleus weight and expression of myosin heavy chain (MHC) isoforms in control and tail-suspended rats. METHOD: Animals were treated with nifedipine at a dose of 10 mg/kg per day in drinking water for 1 or 2 weeks. The expression of MHC isoform protein was observed by SDS-polyacrylamide gel electrophoresis at 4 degrees C. The expression of MHC mRNA was detected by RT-PCR. RESULT: The relative weight (muscle weight/body weight) of soleus muscle was decreased by 39.5% and 51.7% in 1 and 2 weeks of tail-suspended group respectively, but no changes in extensor digitorum longus (EDL) weight was found. The relative weight of soleus and EDL in 1 or 2 weeks of nifedipine treated control group showed no changes as compared with the untreated control group. The relative weight of soleus in 1 or 2 weeks of nifedipine treated tail-suspension group decreased by 36.6% or 52.0%, respectively, as compared with control, but there was no difference between tail-suspension group with or without nifedipine treatment. The expression of MHC I, IIa mRNA and protein could be detected in control soleus with or without nifedipine treatment. The expression MHC I, IIa, IIx and IIb mRNA was detected in 1 or 2 weeks of unloaded soleus with or without nifedipine treatment. Nifedipine inhibited the expression of II type MHC mRNA in unloaded soleus and expression of MHC IIa protein in control and unloaded soleus. CONCLUSION: Nifedipine can not resist atrophy of unloaded soleus, but inhibit the transition of MHC from slow to fast isoforms at the transcription level.
Animals↗