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Objective To observe the effect of simulated microgravity on the photopic negative response (PhNR) of full-field flash ERG in adult mice.Methods In an experimental study,forty-eight adult male C57BL/6J mice (48 eyes) were randomly divided into model and control groups.Model mice were further divided into three subgroups of 8 each:tail-suspended for 15 days (subgroup A),tail-suspended for 30 days (subgroup B),and tail-suspended for 30 days followed by returning to normal position for 30 days (subgroup C).The three control subgroups were similarly fixed with a harness but kept in the normal position for corresponding periods of 15,30,and 60 days.The mice were immediately examined using ERG-PhNR,flash VEP,OCT and visually-guided behavior in vivo,and subsequently sacrificed to analyze the retinal histology in vitro.PhNR amplitude was measured from baseline to PhNR trough.N1 peak-time and N1-P1 amplitude of VEP was analyzed.The escape duration was used to quantitatively evaluate the visual function of mice.In addition,inner retinal thickness was analyzed by OCT imaging.Data were compared by the independent sample t-test.Results PhNR amplitude in the model subgroup A was obviously lower than the corresponding control subgroup,the difference was statistically significant (t=-3.196,P＜0.01).There was no significant difference in PhNR amplitude between the model subgroup B or C and the corresponding control subgroup (t=-1.976,0.285;P＞0.05).There was no significant difference in FVEP N1 peak-time or N1-P1 amplitude between any of the three model subgroups and the corresponding control subgroup (P＞0.05).There was no significant difference in OCT-measured inner retinal thickness between any of the three model subgroups and the corresponding control subgroup (t=-0.461,2.073,-0.402;P＞0.05).The three model subgroups showed almost normal retinal structure,including the retinal ganglion cell,inner pexiform layer,inner nuclear layer,outer plexiform layer,outer nuclear layer,ellipsoid zone and RPE.There was no significant difference in visually-guided escape time between any of the three model subgroups and the corresponding control subgroup (t=-0.637,-0.955,1.297;P＞0.05).Conclusion Via tail-suspension,short-term simulated microgravity can affect the PhNR of flash ERG;however,the change is reversible and does not affect visual function of mice.
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Objective: To observe the morphological changes on cochlear hair cells of rats in simulated weightlessness and inboard noise and to investigate the different changes in three turns of hair cells.Methods: Thirty-two healthy SD rats, all males, were randomly divided into four groups: control group, weightlessness group, noise group and weightlessness+noise groups (n=8).Then rats were exposed to-30° head down tilt as simulated weightlessness and inboard noise including steady-state noise which was (72±2) dB SPL and impulse noise up to 160 dB SPL in spaceship environment.The control group was kept in normal condition for 8 weeks.Bilateral auditory brainstem response (ABR) thresholds were tested before and after exposure respectively, and immunofluorescence staining and scanning electron microscopy (SEMs) of basilar membrane were applied after exposure.Results: ABR threshold shifts of each group were higher after exposure.There was difference between ABRs of the experiment groups before and after exposure (Pnoise group>weightlessness group>control group and the damage degree of the four turns of hair cells: basal turn>mid turn>top turn.Conclusion: The rats exposed to the above environment for 2 weeks displayed obvious changes in cochlea morphology, and the weightlessness+noise group had the most obvious damage.
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Objective To investigate the effects of simulated microgravity by rotary cell culture system (RCCS) on expression profiles of miRNA in mouse fibroblasts L929 cell line.Methods L929 cells were cultured in vitro and divided into simulated microgravity (SMG) group and normal gravity (NG) group according to the simple random method.Samples of two groups were collected on 7th day of culture and the total RNAs were extracted,labeled,and hybridized in sequence.Feature Extraction Software was used to collect the array images and get raw data,which were analyzed by Genespring Software.Differentially expressed miRNAs were identified and then validated by qRT-PCR.Target genes of differentially expressed miRNAs were predicted by the databases of Targetscan and microRNAorg,and the intersections of databases were identified as potential regulatory target genes.Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) analysis were applied to determine the roles of these target genes.Relevant biological functions and/or signaling pathways of the regulated genes especially related with wound healing process were categorized based on their enrichments.Then integration predictions of the miRNA and mRNA expression profiles had been proposed to refine the functional miRNA-mRNA relationships.The miRNA-mRNA functional network and miRNA-mRNA control network were constructed.Results Four miRNA genes were up-regulated significantly including mmumiR-669j,-122-5p,-30a-3p,-6516-3p,among which mmu-miR-669j was up-regulated at 52.84 folds with the greatest significance (P ＜ 0.05).Seventeen miRNA genes were down-regulated significantly including mmu-miR-21a-3p,-miR-28a-5p,-218-5p,-210-3p,-miR-19a-3p,-miR-31-3p,and-miR-19b-3p,among which mmu-miR-28a-5p was down-regulated at 15.47 folds with the greatest significance (P ＜ 0.05).The qRT-PCR showed a high concordance with the microarray results (P ＜ 0.05).Target gene prediction and functional enrichment analysis suggested that a variety of biological processes and signaling pathways involved in wound repair were significantly enriched (P ＜ 0.05).Function network and regulation network of miRNA-mRNA covered all the differentially expressed miRNAs,which suggested that miR-21 a-3p and predicted target gene Smad3 might play an important role in wound healing under microgravity.Conclusions Simulated microgravity by RCCS can significantly affect the expression of stress-related miRNAs in mouse fibroblasts L929.The miRNA target gene prediction and functional enrichment analysis based on gene chip technology may provide theoretical basis for illustrating the mechanism and management of weightlessness stress injury.
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OBJECTIVE To investigate the effects of simulated noise-weightlessness combined factors on auditory brainstem response thresholds and the cochlear structure after a medium-long term (2-8 weeks). METHODS Healthy adult rats were randomly divided into male/female experimental and control groups. The male and female experimental groups were exposed to simulated noise-weightlessness environment and exerted impulse noise exposure at the end. Auditory brainstem response (ABR) threshold was recorded at the beginning, the 2nd, 4th and 8th weeks and after impulse noise exposure exerting. The cochlea was also examined by scanning electron microscopy each time after ABR threshold record. RESULTS ABR thresholds in experimental groups after impulse noise exposure were significantly increased (P<0.05). Female experimental group were lower than those of the male experimental group at 2 and 4 weeks (P<0.05). Scanning electron microscope observation showed that the inner and outer hair cell were losing and lodging, and the longer exposed to the compound factors, the heavier pathological changes observed on the cochlear hair cell. CONCLUSION Noise-weightlessness combined factors can cause the morphology and function damage of rat cochlear in medium-long term. The damage of impulse noise was more than steady noise on rat auditory function. Sex differences was also observed. Rat cochlear hair cell pathological changes increased with the exposed time.
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Objective To investigate the effect of simulated microgravity on growth , morphology, protein expression and virulence gene expression of Klebsiella pneumoniae (KPN).Methods KPN was divided into simulated microgravity group and control group in the experiment .The former group was in the ambient of simulated microgravity in a clinostat .The bacterial growth curves , morphologyical changes in electron microscopy , and protein expression were detected by SELDI-TOF-MS, and the expression of 4 virulence genes(ureA,wabG,uge and fimH) by real-time fluorescence quantitative PCR (RT-PCR) in both groups.Results Compared with the control group , the growth of KPN under simulated microgravity was accelerated , and the total bacterial count increased in microgravity group .The bacterial morphology in microgravity group was changed under scanning electron microscopy (SEM), and thinner and longer bacteria were increased .The transmission electron microscopy ( TEM) analysis revealed increase in cytoplasmic granular substance in microgravity group .Proteome analysis showed that the expression of 18 proteins was changed , half of which up-regulated and the rest were down-regula-ted.Those 18 proteins were searched in the protein library .And 21 proteins of a similar molecular mass were retrieved ,13 of which,proteins with known functions ,were closely related to bacterial life activities .RT-PCR results showed that four virulence genes of KPN were down-regulated.Conclusion Upon exposure to simulated microgravity , the growth and repro-duction of KPN are accelerated and enhanced .The bacterial morphology is changed .The strain′s protein expression and four virulence genes expressionare also changed .Therefore,microgravity can change the characteristics of KPN .
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Objective To investigate the effects of simulated null gravity on the secretion of adrenomedullary hormones and miRNA-375 expression in rats. Method Fifty-six healthy adult male Wistar rats were randomly divided into 7 experimental groups (8 each), including suspension for 6h, 12h, 1d, 3d, 5d, 7d and 0h (control). Tail-suspension was used to establish the weightlessness animal model according to Morey-Holton's method. At the end of the experiment, the blood samples were obtained from the postorbitor vein, and the bilateral adrenal glands were harvested. The serum concentrations of catecholamines were determined by radioimmunological analysis. The expression of TH mRNA and miRNA-375 were assessed by quantitative RTPCR. TH protein in adrenal medulla was assayed using Western blotting analysis and immunohistochemistry. Results(1) The serum concentrations of rat's adrenomedullary hormones fluctuated obviously during the period of tail-suspension simulated weightlessness, with a temporary decline during 6-12h, followed by a sharp increase with a peak value on the 3rd day of suspension. (2) RT-PCR assay showed that TH mRNA expression in adrenal medulla of rats also fluctuated obviously, with a temporary decline at 6h and then elevated with a peak value at 1 day of suspension, followed by a downward trend forming a trough value on 5d of suspension. The immunohistochemistry showed that TH protein was stained as brown particles and the cytoplasm of adrenal medulla was stained deeply on 3d of suspension. (3) RT-PCR assay revealed that the expression of miRNA-375 in adrenal medulla increased temporarily at 6h of suspension, and it decreased significantly during 12h to 3d of suspension compared with that of control group (P<0.05). The miRNA-375 expression was up-regulated again during sustained suspension with a significant increase on 7d of experiment compared with that of control group (P<0.05). Conclusion The simulated weightlessness could affect the secretion of hormone of adrenal medulla in rats, and it may be related to the regulation of TH through miRNA-375 messenger network.
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Objective To explore the effect of weightlessness simulation on processing speed of mental rotation of males in 72 h head-down tilt,in order to further reveal human performance changes caused by weightlessness.Methods During 72 h weightlessness simulation (9 am day 1 to 9 pm day 4,head-down tilt started from 9 pm day 1),16 male subjects were processed speed of rotation data byhand picture mental rotation (test 8 times),using self cross-references design,and the variation of processing speed of mental rotation by duration was analyzed.Results The linear regression analysis showed,the reaction time of each time point for each subject as the independent variable,the angle of rotation as the dependent variable,with the extension of simulated weightlessness time.The intercept(constant term of the regression equation),indicating the processing speed of non-rotation,were gradually increased with HDT time,but didn(t) reached significantly difference (F(3,14) =0.551,P =0.650) ;the slope(Regression coefficient of the regression equation),indicating the processing speed of rotation.were gradually increased with HDT time,and reached the significantly difference (F(3,14) =4.338,P =0.009).The value of intercept and slope was like upside-down U in three days,and reached the highest value at day 2.Conclusion Weightlessness simulation have affection on the speed of mental rotation,especially on the rotation speed.
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Osteoblasts are the most important mechanoreceptive and osteogenic cells. The loss of bone in microgravity is mainly due to the dysfunction of osteoblasts. Research on osteoblast cytology under simulated weightlessness has made great progress in recent years. Current experiments are focusing on the changes in the cellular proliferation, differentiation,apoptosis, function and signal transduction in osteoblasts. This paper reviews the progress of the studies in this field.
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A remodelação óssea pode ser estimulada por forças mecânicas presentes nas atividades físicas normais. Neste trabalho foi analisado o comportamento mecânico do terço proximal de fêmur de ratas submetidas à suspensão pela cauda e posterior treinamento em esteira. Sessenta e seis ratas da raça Wistar foram usadas. Primeiramente os animais foram criados por noventa dias e divididos em cinco grupos (dois controles e três experimentais). Os animais do grupo Controle I foram sacrificados com 118 dias de idade. No grupo S (suspenso) os animais foram suspensos pela cauda por 28 dias e sacrificados. No grupo Controle II os animais foram sacrificados com 139 dias de idade. No grupo S-L (suspenso-liberado) as ratas foram liberadas 21 dias após a suspensão. No grupo S-T (suspenso-treinado) após o período de suspensão os animais passaram por treinamento em esteira durante 21 dias. Para análise do comportamento mecânico do osso foi aplicada uma força vertical na cabeça femoral até a ruptura. A fratura foi analisada por raios-X. A suspensão causou um decréscimo da força máxima e, o treinamento e a liberação após a suspensão causaram a recuperação das propriedades mecânicas. Mas, o padrão de fratura não apresentou diferença entre os grupos experimentais.
Bone remodeling can be stimulated by mechanical forces present in normal physical activities. In the present research, we investigated the mechanical behavior of the proximal femur of rats previously maintained in tail suspension and later, submitted to physical exercise on a treadmill. Sixty-six Wistar rats were used. Firstly, the animals were raised until the age of ninety days and then divided into five groups (two control groups and three experimental groups). The animals allocated to Control I group were killed at 118 days of age. In the S group, the animals were suspended by tail for 28 days. In Control II group, the animals were killed at 139 days of age. In group S-L (suspended and released) the rats were kept free for 21 days after tail suspension. In group S-T (suspended and trained), after tail suspension period, the rats were trained in a treadmill for 21 days. For analysis of the mechanical behavior of the bone, force was applied on the femoral head until failure. The fracture was evaluated by x-ray. Suspension caused a decrease of the maximum load and, treadmill training and post-suspension release caused the recovery of mechanical properties. But, the fracture line pattern did not show any difference among the experimental groups.
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Animals , Female , Rats , Bone Remodeling , Femur , Physical Conditioning, Animal , Weightlessness Simulation , Biomechanical Phenomena , Rats, WistarABSTRACT
Objective To set up a simple method to measure the SR Ca2+ release function in skeletal muscle strips.Methods The time from peak tension to 75 % relaxation(TR75) during intermittent tetanic contraction(fatigue contraction) of isolated musculus soleus strips was analyzed.It was prolonged rapidly,and then shortened slowly.The ratio of maximal TR75 to initial TR75(R-TR75) indicated a balance between SR Ca2+ release and uptake.If the SR Ca2+-ATPase(SERCA) activity and inhibition extent of SERCA in fatigue contraction were identical,R-TR75 should be an index for SR Ca2+ release function.Results Higher stimulation voltage or 5 mmol/L caffeine perfusion which increased the SR Ca2+ release channel open probability induced an increase of R-TR75 from 2.5 in control to 3.0.On the contrary,inhibition of SR Ca2+ release with 5 mmol/L magnesium sulfate perfusion significantly decreased R-TR75.Inhibition of SR Ca2+ release by metabolites during fatigue contraction was recovered slowly.So R-TR75 at the second fatigued contraction was reduced after 5 or 10 min of recovery,but no significant difference after 60 min of recovery.During intermittent tetanic contraction R-TR75 was increased to be 2.9 times of normal in unloaded soleus.Conclusion The above results suggest that R-TR75 during muscle strip fatigue contraction without any change of SERCA activity can indirectly reflected SR Ca2+ release function.In 2-week unloaded soleus,the enhanced R-TR75 indicates an increase in SR Ca2+ release function.
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Objective To investigate the protective effects of Digoxin on cardioventricular function in rats after simulated weightlessness.Methods Eighty rats were divided randomly into 5 groups:control(Con)group,tail-suspended+sham feeding(TS+SF)group,tail-suspended+Digoxin 2 wk(TS+D2)group and tail-suspended+Digoxin 3 wk(TS+D3)group.The TS+SF group was given the distilled water.At the end of tail-suspended for 3 weeks,the heart function of 10 rats in each group was examined with echocardiography.The level of atrial natriuretic polypeptide(ANP)in serum was measured with immunoradiometric assay in other 6 rats.Results Compared with TS+SF group,the contractile function of LV improved in TS+D2 and TS+D3 groups(P0.05).Conclusion Digoxin can improve muscle contractile and blood ejection of LV and retard the tendency of atrophy in simulated weightlessness.
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Objective To observe the changes in excitability of alpha-motoneuron responding to the muscle spindles afferent excitability in the model rats and explore whether the changes in this excitability to be changed as high frequency sinusoidal vibration acted on the soleus muscle.Methods The simulated weightlessness model was created by the tail-suspension.Mechanical vibrations at a frequency of 100 Hz with amplitude of 0.3 mm were acted on soleus muscle.The electromyogram of soleus muscle evoked by electrical stimulation of the sciatic nerve was recorded in control rats and HS rats.Results It was showed that HS and HFV did not influence the tendency of changes in amplitude of H reflex when the stimulation intensity increased.However,after 14-day HS,mean maximal motor response(Mmax)and mean maximal monosynaptic reflex/Mmax(Hmax/Mmax)both significantly decreased,respectively(P0.05).Conclusion It is suggested that HS should lead to the decrease in motoneurons excitability which is resulted from the reduction of muscle spindle afferent.HFV acted on soleus muscle of rats can improve the excitability of alpha-motoneurons in spinal cord during hindlimb suspension.
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Objective To explore changes of local renin-angiotensin system(RAS)in renal tissue of rat during short-and mid-term tail suspension,as well as their relations with humoral regulation and renal function induced by real or simulated weightlessness.Methods 1-and 4-week(wk)tail-suspended rat model were used to simulate short-and mid-term weightlessness,respectively.Reverse transcriptase polymerase chain reaction(RT-PCR)was carried out to examine the mRNA expression of components of local RAS in renal tissue.Results Except for angiotensin Ⅱ receptor type 2(AT2),all of the other components of local RAS,including angiotensinogen(AGT),renin,angiotensin converting enzyme(ACE),angiotensin Ⅱ receptor type 1a(AT1a)and angiotensin Ⅱ receptor type 1b(AT1b),were found their expression in renal tissue of Sprague-Dawley rats.After 1 wk of tail suspension,mRNA expression of renin in renal tissue increased significantly(P
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Objective To investigate effects of Taikong Yangxin Prescription on left ventricular pump and contract function in rat after tail suspension.Methods Twenty four male Sprague-Dawley(SD)rats were randomly and divided into three groups:(A)normal control group,(B)tail-suspension group and(C)Chinese herb compound group(taking Taikong Yangxin Prescription and tail suspension).The left ventricular functions in rats were examined by echocardiography separately after 7 d and 28 d tail-suspension.Results After 28 d of tail-suspension,as compared with the tail-suspension group,LVDD in Chinese herb compound group increased significantly(P
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Objective To study changes of dielectric properties of gastrocnemius caused by simulated weightlessness.Methods Male Sprague-Dawley rats tail suspended for 10 wk were observed together with its normal control.AC impedance of isolated gastrocnemius was measured with an impedance analyzer(Agilent 4294A).Effects of simulated weightlessness on electric properties of cells in isolated rat sural muscle were also observed by analyzing the dielectric numerical characters of the dielectric spectra,the Cole-Cole plots,spectrum of loss factor and loss tangent,as well as spectrum of conductivity imaginary part.Results It was found that simulated weightlessness could induce certain changes:both relative permittivity at low frequency ?L and relative permittivity increment ??,as well as conductivity at high frequency ?h and conductivity increment ?? were all reduced.The first characteristic frequency fC1 decreased,while the second characteristic frequency fC2 increased.Peak of loss factor,peak of loss tangent and the maximum of conductivity imaginary part were also reduced.Conclusion Changes of dielectric property of gastrocnemius induced by simulated weightlessness can be observed effectively by frequency domain impedance technique.
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Objective To compare the morphological differences in soleus between tail-suspended and 30-month-old rats.Methods Fourty-two male rats were randomly divided into seven groups:5 d,7 d and 14 d tail-suspended and their synchronous control groups,30-month-old group.The cross-sectional area(CSA)and percentage of MHC Ⅰ/Ⅱ fibers were measured in immunohistochemically stained sections and CSA was normalized by body weight.Results Wet weight,relative wet weight,CSA and normalized CSA in unloaded soleus decreased significantly as compared with the synchronous control.The percentage of MHC Ⅰ fibers decreased,but that of MHC Ⅱ fibers increased in unloaded soleus.The wet weight and CSA of soleus in 30-month-old rats increased,but the relative wet weight and normalized CSA reduced significantly as compared with 14-day synchronous control.The relative wet weight and normalized CSA of soleus in 30-month-old rat were similar to that of 14 d tail-suspended group.The percentage of MHC Ⅰ/Ⅱ fibers of soleus in 30-month-old rat and in 5 d,7 d,and 14 d of synchronous control groups kept constant value.Conclusion It's suggested that the atrophic process of soleus is slower in 30-month-old rats than that in the tail-suspended rates.The reduction of soleus relative wet weight and normalized CSA appears early in aged rats,but the absolute and relative wet weight of soleus decrease simultaneously in tail-suspended rats.
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Objective To study the effects of choline chloride on activities of myosin adenosine triphosphatase (mATPase) of muscle fibres and muscle atrophy in tail-suspended rats. Method Twenty-four adult female Sprague-dawley rats were averagely divided into 3 groups matched for body mass:control group(CON),tail suspension group(TS) and tail suspension group associated with choline chloride(TS+Cch).Weightlessness was simulated by 14 d tail suspension of rats;gastric lavage with choline chloride was given to 1/2 of the rats during tail suspension (15 mg/kg body weight.i.g.).Activities of myosin adenosine triphosphatase (mATpase) of intrafusal and extrafusal fibres in soleus (SOL) muscle were determined by Ca 2+-ATPase method.Paraffin sections of the soleus muscle were prepared by routine histochemistry method. Result After tail suspension for 14 d it was found: 1) percentage of type Ⅱ fibre in SOL of rats treated with choline chloride decreased distinctly as compared with that in the untreated rats (P
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Objective To study the changes of gene and protein expressions of key components of renin-angiotensin system (RAS) in myocardium of simulated weightless rats. Method Tail-suspended rats were adopted as animal model of simulated weightlessness. RT-PCR and Western blot analysis were performed to examine mRNA and protein expressions in rat myocardium, respectively. Result After 1 week tail-suspension,no obvious changes in angiotensinogen (AGT), angiotensin converting enzyme (ACE), 1a and 1b subtype of type 1 angiotensin Ⅱ receptor (AT 1aand AT 1b), key components of RAS in myocardium were observed. But after 4 weeks tail-suspension, the expressions of AGT mRNA and higher molecular weight band of AGT protein increased significantly (P
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Objective To study the protective effects of vitamin E(VE) on injury to male reproductive function in tail-suspended rats. Method Thirty adult male Spraque-Dawley(SD) rats were randomly divided into three groups:control, TS (tail-suspension) and VE+TS groups. TS and VE+TS groups were tail-suspended for 14 d,and VE was given orally to VE+TS group during tail-suspension. After the treatment, weight and morphology of testes, quality and amount of sperm, as well as serum hormones were observed. Result As compared with the control group, weight of testes, quantity and quality of sperm, as well as serum testosterone decreased significantly in TS group (P
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Objective To observe the effects of intermittent 45? head-uptilt on endothelin(ET-1) expression and morphological changes of femoral and carotid arteries in rabbits induced by 21 d simulated weightlessness.Method Twenty-four healthy male rabbits were randomly divided into control group,simulated weightlessness group and countermeasure group,8 rabbits in each group.The simulated weightlessness group kept head-down tilt for 21 d.The countermeasure group was exposed to 45? head-up tilt for 2 h every day during 21 d head-down tilt.After 21 d experiment,structure of femoral artery and carotid artery were studied and ET-1 expression was tested by immunohistochemical method.Result Detachment of endothelial cells in femoral artery,necrosis of smooth muscle cells and decreased ET-1 expression were found in animals in the simulated weightlessness group,and the vessel wall became thinner.While hyperplasia of endothelial cells and thickened internal elastic lamina of the carotid artery were also observed.No significant changes were observed in femoral artery and carotid artery in animals of the countermeasure group.ET-1 expression decreased in femoral artery but increased in carotid artery in animals of the simulated weightlessness group,but no significant change was found in both femoral and carotid arteries in animals of the countermeasure group as compared with those in the control group.Conclusion Twenty-one days simulated weightlessness may induce an atrophic change and decreased ET-1 expression in femoral artery,and hyperplastic change and increased ET-1 expression in carotid artery in rabbits.Two-hour 45? head-up tilt every day may partly counteract the change in femoral artery and carotid artery induced by simulated weightlessness.