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The peripheral vestibular organs are sensors for linear acceleration (gravity and head tilt) and rotation,and turn them into nerve signals that travel to the central nervous system to regulate physiological functions, which play an important role in regulating body stability, ocular movement, autonomic nerve activity, arterial pressure, body temperature, as well as muscle and bone metabolism. The effect of gravity on these functions can be attributed to high plasticity of the vestibular system. In this review, changes in vestibular-related physiological functions induced by the hypergravity and microgravity were introduced, including arterial pressure,muscle and bone metabolism, feeding behavior and body temperature, with the aim to better understand the physiological function of vestibular in adaption to special gravity environment.
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Microgravity is a typical feature of the space. A large number of space flights and foundation simulation experiments have shown that cells show typical biological characteristics of aging, such as reduced cell proliferation and cell cycle arrest under microgravity or simulated microgravity. However, the molecular mechanism by which microgravity or simulated microgravity affects cellular senescence is not well understood. Understanding the mechanism controlling cellular senescence induced by microgravity environment is helpful for exploring anti-aging strategies and targeted interventions in space. In recent years, domestic and foreign scholars have carried out a number of researches and explorations on the effect of microgravity and simulated microgravity on cellular senescence as well as the related mechanisms. In this review, the latest research progress of this filed was summarized.
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ABSTRACT Objectives: The effects of weightlessness on the liver were studied using a tail suspension (TS) male mouse model. Methods: The effects of 0-, 2- and 4-week TS (CON, TS2 and TS4 groups) on glycogen and lipid content, as well as on the molecular processes of the synthesis and degradation pathways, were examined. Results: (1) The number of glycogenosomes under ultrastructure and the glycogen content were considerably larger in the TS4 group than in the other two groups. (2) In the TS4 group, glycogen synthase activity remained constant while glycogen phosphorylase activity dropped, indicating that glycogen breakdown was reduced. (3) The livers of the TS2 group had the highest lipid and triglyceride content, indicating lipid buildup in the liver at this time. (4) In the TS2 group, the activities of the fatty acid synthesis-related factors acetyl-CoA carboxylase and fatty acid synthase increased, while hepatic lipase decreased, indicating that lipid synthesis increased, while decomposition decreased. (5) In the TS2 group, the protein expression of glucose transporters 1 and 2 increased. Conclusions: From TS2 weeks to TS4 weeks, the main energy consumption mode in the livers of mice transitioned from glucose metabolism to lipid metabolism as glucose use decreased. Level of evidence II; Comparative prospective study.
RESUMEN Objetivos: Se estudiaron los efectos de la antigravedad en el hígado utilizando un modelo de ratón macho en prueba de suspensión de la cola (TS, tail suspension). Métodos: Se examinaron los efectos de la TS a las 0, 2 y 4 semanas (grupos CON, TS2 y TS4) sobre el contenido de glucógeno y lípidos, así como sobre los procesos moleculares de las vías de síntesis y degradación. Resultados: (1) El número de glucogenosomas ultraestructurales y el contenido de glucógeno fueron expresivamente más altos en el grupo TS4 que en los otros dos grupos. (2) En el grupo TS4, la actividad de la glucógeno sintasa se mantuvo constante, mientras que la actividad de la glucógeno fosforilasa disminuyó, lo que indica que la degradación del glucógeno se redujo. (3) Los hígados del grupo TS2 presentaron el mayor contenido de lípidos y triglicéridos, lo que indica la acumulación de lípidos en el hígado en ese momento. (4) En el grupo TS2, la actividad de los factores relacionados con la síntesis de ácidos grasos acetil-CoA carboxilasa y ácido graso sintasa aumentó, mientras que la lipasa hepática disminuyó, indicando que la síntesis de lípidos aumentó mientras que la descomposición disminuyó. (5) En el grupo TS2, la expresión proteica de los transportadores de glucosa 1 y 2 aumentó. Conclusiones: Desde la semana TS2 hasta la semana TS4, el principal modo de consumo de energía en el hígado de los ratones pasó del metabolismo de la glucosa al metabolismo de los lípidos a medida que disminuía el uso de la glucosa. Nivel de Evidencia II, Estudio retrospectivo comparativo.
RESUMO Objetivos: Os efeitos da antigravidade no fígado foram estudados usando um modelo de camundongo macho com a suspensão pela cauda (TS, tail suspension). Métodos: Foram examinados os efeitos da TS em 0, 2 e 4 semanas (grupos CON, TS2 e TS4) sobre o conteúdo de glicogênio e lipídios, bem como nos processos moleculares das vias de síntese e degradação. Resultados: (1) O número de glicogenossomos ultraestruturais e o teor de glicogênio foram expressivamente maiores no grupo TS4 do que nos outros dois grupos. (2) No grupo TS4, a atividade de glicogênio sintase permaneceu constante, enquanto a atividade de glicogênio fosforilase caiu, indicando que a degradação do glicogênio foi reduzida. (3) Os fígados do grupo TS2 tiveram o maior teor lipídico e de triglicérides, indicando acúmulo de lipídios no fígado no momento. (4) No grupo TS2, a atividade dos fatores relacionados com a síntese de ácidos graxos acetil-CoA carboxilase e ácido graxo sintase aumentaram, enquanto a lipase hepática diminuiu, indicando que a síntese de lipídios aumentou, enquanto a decomposição diminuiu. (5) No grupo TS2, a expressão proteica dos transportadores de glicose 1 e 2 aumentou. Conclusões: De TS2 semanas para TS4 semanas, o principal modo de consumo de energia no fígado de camundongos passou do metabolismo da glicose para o metabolismo lipídico, à medida que o uso de glicose diminuiu. Nível de evidência II, Estudo retrospectivo comparativo.
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The damage caused by space microgravity environment to the body systems of astronauts directly affects their work efficiency.This paper reviewed previous studies on the effects of space microgravity environment and ground simulated microgravity environment on cognition and emotion, potential mechanisms and interventions. It was found that a microgravity environment led to dysfunction in learning, memory, spatial orientation and other aspects, and caused anxiety and depression. The mechanisms of cognitive and emotional impairment associated with microgravity environment are complex, including neuronal damage, brain structure changes, neurotransmitter disorders, synaptic dysfunction, oxidative stress injury, and energy metabolism disorders. Pharmacological approaches such as natural extracts, physical interventions such as repetitive transcranial magnetic stimulation, and new therapies such as probiotics were expected to reduce cognitive impairment and mood disorders caused by microgravity exposure. With the development of aerospace medicine in China, the potential mechanism and interventions of microgravity environment on cognitive and emotional impairment remain to be further studied.
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Objective@#Exposure to microgravity results in postflight cardiovascular deconditioning in astronauts. Vascular oxidative stress injury and mitochondrial dysfunction have been reported during this process. To elucidate the mechanism for this condition, we investigated whether mitochondrial oxidative stress regulates calcium homeostasis and vasoconstriction in hindlimb unweighted (HU) rat cerebral arteries.@*Methods@#Three-week HU was used to simulate microgravity in rats. The contractile responses to vasoconstrictors, mitochondrial fission/fusion, Ca @*Results@#An increase of cytoplasmic Ca @*Conclusion@#The present results suggest that mitochondrial oxidative stress enhances cerebral vasoconstriction by regulating calcium homeostasis during simulated microgravity.
Subject(s)
Animals , Male , Rats , Calcium/metabolism , Cerebral Arteries , Homeostasis , Mitochondria/physiology , Myocytes, Smooth Muscle/physiology , Oxidative Stress , Rats, Sprague-Dawley , Vasoconstriction/physiology , Weightlessness SimulationABSTRACT
Se presenta este artículo de revisión con base en la evidencia científica actual sobre medicina espacial enfocada en fisiología humana y sus contramedidas. Por lo cual se realizó una búsqueda bibliográfica no sistemática de artículos científicos y libros de investigación en inglés-español de los últimos 7 años, que detallan su aplicación en seres humanos, modelos murinos y experimentos in vitro. Se tomaron en cuenta las condiciones del ambiente espacial como microgravedad y radiación que producen considerables cambios fisiológicos en el sistema cardiovascular (redistribución de líquidos, remodelación cardiovascular, arritmias); nervioso (sensitivomotores, neurosensoriales, neurovestibulares); respiratorio (cambios de volúmenes y capacidades); renal (litiasis); musculoesquelético (atrofia muscular, osteoporosis); hematológico (anemia); inmunológico (desregulación inmune) y digestivo (alteración de la microbiota intestinal). Además, existen procesos biológicos, moleculares y genéticos aún por explorar, para conocer y mitigar los mecanismos inciertos desencadenados en ambientes extremos y peligrosos. Por lo tanto, es una prioridad desarrollar e implementar contramedidas para reducir los efectos nocivos en la salud, con el objetivo de garantizar la adaptación, seguridad y performance del astronauta durante futuros viajes espaciales.
This Review Article is presented based on current scientific evidence on space medicine focused on human physiology and its countermeasures. Therefore, a non-systematic bibliographic search of scientific articles and research books in English-Spanish of the last 7 years was carried out, detailing their application in humans, murine models and in vitro experiments. The conditions of the space environment such as microgravity and radiation that produce considerable physiological changes in the cardiovascular system (redistribution of fluids, cardiovascular remodeling, arrhythmias) were taken into account; nervous (sensorimotor, neurosensory, neurovestibular); respiratory (volume and capacity changes); renal (lithiasis); musculoskeletal (muscular atrophy, osteoporosis); hematological (anemia); immunological (immune dysregulation) and digestive (intestinal microbiota disorder). In addition, there are biological, molecular and genetic processes still to be explored, in order to know and mitigate the uncertain mechanisms triggered in extreme and dangerous environments. Therefore, it is a priority to develop and implement countermeasures to reduce the harmful effects on health, with the aim of guaranteeing the astronaut's adaptation, safety and performance during future space flights.
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Objective To analyze the biomechanical effects of gravity loading countermeasure garment on human lumbar intervertebral disc in microgravity environment. Methods Based on CT images of a healthy adult volunteer, the finite element model of L4-5 vertebrae was established. Through the empty load and 400 N axial loading for 4 hours on lumbar finite element model, the biomechanical effect of the non-intervention and gravity loading countermeasure garment were simulated respectively in microgravity environment. Results The central pore pressure, radial displacement and water content of the human lumbar intervertebral disc increased with time in microgravity environment. In the case of wearing gravity loading countermeasure garment, the central pore pressure, axial stress, radial displacement and water content of the lumbar intervertebral disc were reduced after 72 hours of cyclic loading compared with the non-intervention group. Conclusions Wearing gravity loading countermeasure garment can help astronauts to prevent the adverse effects of microgravity on the spine to some extent in microgravity environment.
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Objective To investigate the effect of microgravity on MC3T3-E1 osteoblast differentiation. Methods The differential miRNA and mRNA expression profiling of MC3T3-E1 cells during exposure to microgravity were established by RNA transcriptome sequencing technology (RNA-seq). The RNA sequencing results were validated using quantitative real-time polymerase chain reaction (q-PCR). Bioinformatic analyses were applied for further study of these differentially expressed miRNAs and mRNAs. Results Compared with control (CON) group, A total of 1 912 coding transcripts and 160 miRNAs were detected along with osteogenic differentiation in simulated microgravity (SMG) group. Bioinformatic analysis revealed 10 core regulatory genes including 7 mRNAs and 3 miRNAs. Based on the analysis and verification, one miRNA, miR-9_6666-5p, was identified, which might play an important role in osteogenic differentiation process under microgravity. Conclusions The process of osteoblast differentiation was repressed under microgravity which might be related to the changed expression profile of miRNA/mRNA. The research findings can contribute to the better understanding of the molecular mechanisms of mRNA and miRNAs in osteogenic differentiation and bone formation under the microgravity condition.
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@#AIM: To observe changes in the flash electroretinogram(ERG)and retinal microcirculation in mice suspended by their tails, an animal model that simulates cephalad movement of bodily fluids under conditions of microgravity.<p>METHODS: Thirty-six adult male C57BL/6J mice(36 eyes)were randomly divided into three experimental groups and three control groups. Mice in the experimental groups were tail-suspended for 15d(Group one), tail-suspended for 30d(Group two), or tail-suspended followed by returning to normal position for 30d(Group three). Three control groups were similarly fixed with a harness but kept in the normal position for corresponding periods of 15, 30, and 60d. The mice were immediately examined using scotopic ERG(including oscillatory potentials \〖OPs\〗)and fundus fluorescein angiography(FFA)<i>in vivo</i>, and subsequently sacrificed to analyze the retinal histology(methods including immunohistochemistry and TUNEL staining)<i>in vitro</i>. Independent sample <i>t</i>-test was used for data comparison between the same time-point groups.<p>RESULTS: Following 15-days' tail-suspension, scotopic ERG showed a decline in OPs, but not in the b-wave; the second OP(O2)showed an amplitude of 197±33μV, which was about 60% of the control level(<i>t</i>=-5.938, <i>P</i><0.001). Following 30-days' tail-suspension, ERG recovered, with O2 showing an average value of 264±39μV; when compared to the corresponding control group(308±41μV), no significant difference was observed(<i>t</i>=-1.887, <i>P</i>>0.05). Morphologically, only the 15-days' tail-suspended mice showed FFA with microvascular dilation and tortuosity. Rhodopsin and cone-opsin were almost normal and no apoptotic-positive signals were detected in the retinas of the three tail-suspended groups.<p>CONCLUSION: Simulating cephalad shifting of bodily fluids as under microgravity, using short-term tail-suspension can affect rodent ERG and retinal microcirculation; however, the change is reversible with no obvious permanent injury observed in the retinas.
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After a short summary of the multifactorial models of maximal O2 consumption (VO2max) limitation, microgravity exposure is discussed as a convenient experimental condition to test these models. The following points are highlighted: 1) The decrease of (VO2max) in microgravity concerns specifically exercise performed in upright posture upon resumption of gravity exposure; 2) The decrease of (VO2max) after microgravity exposure has two components: one is fast and is related to cardiovascular adaptation, the other is slow and is related to the development of muscle atrophy; 3) (VO2max) does not decrease during microgravity or in supine posture upon resumption of gravity exposure, if the time in microgravity is sufficiently short; 4) cardiovascular oxygen transport accounts for 70% of (VO2max) limitation also after microgravity exposure.
Luego de un breve resumen de los modelos multifactoriales de la limitación del consumo máximo de oxígeno (VO2max), se analiza la exposición a la microgravedad como condición experimental conveniente para evaluar tales modelos. Se destacan los siguientes aspectos: 1) El decrecimiento en la microgravedad tiene que ver específicamente con los ejercicios realizados en posición vertical después de reanudar la exposición a la gravedad; 2) El decrecimiento posterior a la exposición a la microgravedad tiene dos componentes: uno es rápido y está relacionado con la adaptación cardiovascular, el otro es lento y está relacionado con la aparición de la atrofia muscular; 3) No decrece durante la microgravedad o en posición supina después de reanudarse la exposición a la gravedad, siempre que el tiempo transcurrido en microgravedad sea suficientemente corto; 4) el transporte de oxígeno cardiovascular representa el 70 % de la limitación también después de la exposición a la microgravedad.
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Maintaining health in microgravity and overcoming environmental hazards such as cosmic radiation are essential for long-term space flight. Recent studies have focused on the involvement of hypoxia-inducible factor (HIF)-1 in altered gravity using cell-based or in vivo mouse model systems. HIF-1alpha and its target downstream gene expression are differentially expressed in hypergravity and microgravity. Nevertheless, underlying molecular mechanism of HIF-1alpha involvement is still unclear. Herein, we analyzed the 2019 Science paper by Garrett-Bakelman and coauthors in which NASA performed multidimensional analyses of long-term human spaceflight in identical twin astronauts. Correlations were found between the expression of HIF-1alpha related cytokines and prolonged space flight. We hypothesize that HIF-1alpha is a molecular target for the development of therapeutics to prevent the detrimental effects of microgravity and cosmic radiation on astronauts during long-term space flight.
Mantener la salud en microgravedad y superar los peligros ambientales como la radiación cósmica son esenciales para los vuelos espaciales a largo plazo. Estudios recientes se han centrado en la participación del factor inducible por hipoxia (HIF) -1 en la gravedad alterada utilizando sistemas de modelos de ratones basados en células o in vivo. HIF-1alpha y su expresión génica secuencial objetivo se expresan diferencialmente en hipergravedad y microgravedad. Sin embargo, el mecanismo molecular subyacente de la participación de HIF-1alpha aún no está claro. Aquí, analizamos el artículo de Ciencia de 2019 de Garrett-Bakelman y coautores en el que la NASA realizó análisis multidimensionales de vuelos espaciales humanos a largo plazo en astronautas gemelos idénticos. Se encontraron correlaciones entre la expresión de citoquinas relacionadas con HIF-1alpha y el vuelo espacial prolongado. Presumimos que HIF-1alpha es un objetivo molecular para el desarrollo de terapias para prevenir los efectos perjudiciales de la microgravedad y la radiación cósmica en los astronautas durante los vuelos espaciales a largo plazo.
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Objective: To investigate the effects of RCCS simulated microgravity on the metabolism of the human keratinocyte cell line HaCaT. Methods: The rotary cell culture system (RCCS) was used to simulate the microgravity environment, and HaCaT cells were cultured in vitro and divided randomly into simulated microgravity group (SMG) and normal gravity group (NG). The two group HaCaT cells were collected respectively after 1 d, 2 d and 3 d culture, and the samples were analyzed by LC/MS metabolomics. The differential metabolites between the SMG and NG cells were identified with partial least squares discriminant analysis ((O)PLS-DA), and the data were input into the KEGG database for the construction and functional analysis of metabolic pathways. Results: Comparing to NG cells, after 1 d culture, there were 74 different metabolites in SMG cells, among which 16 were up-regulated and 58 were down-regulated; after 2 d culture, there were 89 different metabolites, among which 15 were up-regulated and 74 down-regulated; after 3d culture, there were 100 different metabolites, of which 23 were up-regulated and 77 were down-regulated. The differentially expressed 49 metabolites (VIP>1 and P<0.05) after 3 d were set as target metabolites, within which the sphingosine, glutamate, and docosapentaenoic acid were down-regulated, and dehydrated sorbitol was up-regulated. KEGG analysis indicated that the metabolic pathways involved were amino acid metabolism, lipid metabolism, cell proliferation and apoptosis, substance transport, catabolism, and signal transduction. Conclusion: RCCS simulated microgravity may have significant impacts on keratinocyte metabolism mainly involving metabolites such as sphingolipids and glutamate as well as the related signaling pathways.
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Objective To study the effect of simulated microgravity on activity of the store-operated calcium (SOC) channels in osteocytes and its possible mechanism, so as to elucidate the potential mechanism of weightlessness bone loss. Methods Osteocytes (MLO-Y4) as the experimental subjects were divided into simulated microgravity (SM) group and normal gravity group (CON). After rotating for 24 h and 48 h, confocal microscope was used to detect the intracellular calcium ion concentration level to reflect activity of the SOC channels after thapsigargin (TG)-induced endoplasmic reticulum (ER) depletion. Immunofluorescence staining was used to observe the distribution of ER membrane protein IP3R and spectrin membrane skeleton, in order to preliminarily explore the possible mechanism of functional changes of SOC channels. Results During the period of calcium release from ER, ［Ca2+］i had no significant difference between SM group and CON group for 24 h and 48 h; while during the period of extracellular calcium influx by SOC channels, ［Ca2+］i of SM group had significant differences in the first 4 minutes for 24 h, as well as in the whole time for 48 h. Compared with CON group, the spectrin membrane skeleton of SM group was gathered at the rim of membrane, while ER membrane protein IP3R of SM group was gathered at the nuclear envelope of ER. These two tendencies were more obvious for 48 h. Conclusions The stimulated microgravity could inhibit activity of SOC channels in osteocytes. Changes in the distribution of the spectrin membrane skeleton and ER membrane protein IP3R under the simulated microgravity might reduce the activity of SOC channels by affecting the conformation coupling process between the membrane and ER.
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OBJECTIVE@#To explore the dynamic impacts of simulated microgravity (SM) on different vital brain regions of rats.@*METHODS@#Microgravity was simulated for 7 and 21 days, respectively, using the tail-suspension rat model. Histomorphology, oxidative stress, inflammatory cytokines and the expression of some key proteins were determined in hippocampus, cerebral cortex and striatum.@*RESULTS@#21-day SM decreased brain derived neurotrophic factor and induced neuron atrophy in the cerebral cortex. Strong oxidative stress was triggered at day 7 and the oxidative status returned to physiological level at day 21. Inflammatory cytokines were gradually suppressed and in striatum, the suppression was regulated partially through c-Jun/c-Fos.@*CONCLUSION@#The results revealed that the significant impacts of SM on rat brain tissue depended on durations and regions, which might help to understand the health risk and to prevent brain damage for astronauts in space travel.
Subject(s)
Animals , Male , Rats , Brain , Metabolism , Pathology , Brain-Derived Neurotrophic Factor , Metabolism , Cytokines , Metabolism , Oxidative Stress , Proto-Oncogene Proteins c-fos , Metabolism , Proto-Oncogene Proteins c-jun , Metabolism , Random Allocation , Weightlessness SimulationABSTRACT
In this study, we aim to investigat the effect of microgravity on osteoblast differentiation in osteoblast-like cells (MC3T3-E1). In addition, we explored the response mechanism of nuclear factor-kappa B (NF-κB) signaling pathway to "zero- " in MC3T3-E1 cells under the simulated microgravity conditions. MC3T3-E1 were cultured in conventional (CON) and simulated microgravity (SMG), respectively. Then, the expression of the related osteoblastic genes and the specific molecules in NF-κB signaling pathway were measured. The results showed that the mRNA and protein levels of alkaline phosphatase (ALP), osteocalcin (OCN) and type Ⅰ collagen (CoL-Ⅰ) were dramatically decreased under the simulated microgravity. Meanwhile, the NF-κB inhibitor α (IκB-α) protein level was decreased and the expressions of phosphorylation of IκB-α (p-IκB-α), p65 and phosphorylation of p65 (p-p65) were significantly up-regulated in SMG group. In addition, the IL-6 content in SMG group was increased compared to CON. These results indicated that simulated microgravity could activate the NF-κB pathway to regulate MC3T3-E1 cells differentiation.
Subject(s)
Animals , Mice , 3T3 Cells , Cell Differentiation , NF-kappa B , Physiology , Osteoblasts , Signal Transduction , Weightlessness SimulationABSTRACT
The rotary cell culture system(RCCS)was used to simulate the microgravity environment, and FRTL-5 cells were divided into simulated microgravity group(SMG)and normal gravity group(NG). FRTL-5 cells were harvested after treatment for 6, 12, 24, and 36 h, the cell viability was measured by MTT assay, and the cells cycles were detected by flow cytometry. The ultrastructure of FRTL-5 cells was observed under laser confocal microscope with FITC-labeled technique. The MTT assay showed that the proliferation of FRTL-5 cells was significantly inhibited after RCCS treatment for 6, 12, 24, and 36h compared with NG(P<0.05), in which the most obvious effect was observed at 24h. The flow cytometry showed that the proportion of FRTL-5 cells at G1 stage in RCCS group was increased significantly after 6, 12, 24, and 36h compared with NG(P<0.05), while the proportion of FRTL-5 cells at S stage was decreased significantly(P<0.05)except that cultured with RCCS for 6 h. The proportion of FRTL-5 cells at G2/M stage was decreased in early phase(6-12 hours)of RCCS culture, with the lowest at 12h and transient increase at 24h of RCCS culture. The laser confocal microscope revealed that there were local microfilament depolymerization, tension fibers decrease, structure disorder, cellular pseudopodia reduction, and irregular shape among FITC-labeled FRTL-5 cells cultured with RCCS for 36h. (Chin J Endocrinol Metab, 2018, 34: 598-601)
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MicroRNA (miRNA) is a kind of important gene expression regulatory molecules during biological process, but its regulation mechanism in metabolic process of bone tissues has not been completely clarified. In this review, the regulation of miRNA on osteoblast differentiation in microgravity environment was discussed. The positive and negative regulation of miRNA was summarized, respectively, with focus on introducing the mechanism of different genes. Some miRNA molecules that have important effects on bone metabolism under microgravity were enumerated. MiRNA plays an important role in regulating and controlling bone metabolic diseases in microgravity environment, and its related studies are significant for the prevention and treatment of bone loss induced by weightlessness.
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To study the effect of microgravity on peripheral oxygen saturation (SpO ) in rats, tail-suspended rats were applied to simulate microgravity environment. SpO and arterial oxygen saturation (SaO ) were measured by pulse oximeter and arterial blood gas analyzer (ABGA) respectively on the 14th day, 21st day and 28th day in tail-suspended group and control group. Paired -test shows that SpO was significantly lower than SaO in tail-suspended group on the 14th day ( < 0.05), the 21st day ( < 0.05) and the 28th day ( < 0.01). The ANOVA results shows that modeling time had significant effect on SpO value but no effect on SaO value in tail-suspended group. These results indicate that pulse oximeter may be not suitable for oxygen saturation test in microgravity environment.
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OBJECTIVE@#To better understand the pathological causes of bone loss in a space environment, including microgravity, ionizing radiation, and ultradian rhythms.@*METHODS@#Sprague Dawley (SD) rats were randomly divided into a baseline group, a control group, a hindlimb suspension group, a radiation group, a ultradian rhythms group and a combined-three-factor group. After four weeks of hindlimb suspension followed by X-ray exposure and/or ultradian rhythms, biomechanical properties, bone mineral density, histological analysis, microstructure parameters, and bone turnover markers were detected to evaluate bone loss in hindlimbs of rats.@*RESULTS@#Simulated microgravity or combined-three factors treatment led to a significant decrease in the biomechanical properties of bones, reduction in bone mineral density, and deterioration of trabecular parameters. Ionizing radiation exposure also showed adverse impact while ultradian rhythms had no significant effect on these outcomes. Decrease in the concentration of the turnover markers bone alkaline phosphatase (bALP), osteocalcin (OCN), and tartrate-resistant acid phosphatase-5b (TRAP-5b) in serum was in line with the changes in trabecular parameters.@*CONCLUSION@#Simulated microgravity is the main contributor of bone loss. Radiation also results in deleterious effects but ultradian rhythms has no significant effect. Combined-three factors treatment do not exacerbate bone loss when compared to simulated microgravity treatment alone.
Subject(s)
Animals , Biomechanical Phenomena , Bone Density , Physiology , Bone Resorption , Metabolism , Femur , Metabolism , Hindlimb Suspension , Rats, Sprague-Dawley , Tibia , Metabolism , Ultradian Rhythm , Weightlessness Simulation , X-RaysABSTRACT
Objective To investigate the effects of simulated microgravity by RCCS on proliferation and cell cytoskeleton of human HaCaT keratinocyte. Methods The rotary cell culture system (RCCS) was used to simulate the microgravity environment, and human HaCaT keratinocytes were divided randomly(random number) into the simulated microgravity group (SMG) and normal gravity group (NG). HaCaT cells in the two groups were harvested respectively after 32, 36 and 42 h culture. The HaCaT cells proliferation and cycles were detected by flow cytometry, the concentration of hb-EGF in supernatant was detected by ELISA, and the cell cytoskeleton was observed after 42 hours' culture under laser confocal microscope with FITC-labeled technique. SPSS 23.0 statistical software was used for statistical analysis, and P <0.05 was considered statistically significant. Results The flow cytometry showed that the proportions of human HaCaT keratinocytes in G1 and G2/M phases were increased while the proportion of HaCaT cells in S stage was decreased significantly after 32, 36 and 42 h RCCSculture compared with those in the normal gravity group. The HaCaT cells in G1 stage were declined along with incubation time. ELISA results showed that the hb-EGF concentration in HaCaT supernatant under simulated microgravity culture for 24 and 36 h was lower than that in the normal control group (P<0.01). The laser confocal microscope revealed that the HaCaT fluorescence intensity was decreased,and there were disordered microfilaments, structural ambiguity, pseudopodia reduction and irregularshape among FITC-labeled HaCaT cells cultured 42 h in RSSC compared with the normal gravity group.Conclusions RCCS simulated microgravity environment could inhibit the cell cycle transformation and proliferation of human HaCaT keratinocyte, affect the keratinocyte-secreting function, and induce alterations of the cell cytoskeleton.