Weightlessness during space mission results in atrophic changes in those muscles which have maximum weight bearing function and consist primarily of slow twitch fibres. In the present study an animal ...model was designed to evaluate the effects of 15 days of hindlimb unloading (HU) in rats by tail suspension on the (i) weight of gastrocnemius (G), plantaris (P), both predominantly having fast twitch fibres and soleus (S) muscle, predominantly having fast twitch fibres and (ii) contractile properties viz peak twitch contraction (Pt) and peak tetanic contraction (Po) of GPS muscle. HU rats showed significant weight reductions of G (-17.9%), P (-13.3%) and S (-41.2%) muscles. Pt and Po were also reduced in HU group but when these were expressed per gm of GPS muscle, no significant changes in Pt and Po were observed. These findings confirm that HU in rats result in maximum atrophic change in those muscles which have predominantly slow twitch fibres and reductions in contractile properties of muscles are in proportion to reduction in muscle weight. Also, HU by tail suspension provides a good ground based model for developing the deconditioning of muscles as applicable to weightlessness of space and offers a scope for the development of various countermeasures.
The microgravity environment of spaceflight leads to a series of changes in the human blood system. The aim of the present study was to examine the influence of simulated microgravity on the ...differentiation of CD34+ cells and to explore whether transcription factor GATA-1, required for the terminal differentiation of committed erythroid progenitor cells, is involved in this process.
CD34+ cells were cultured in the simulated microgravity conditions created by a rotary cell-culture system (RCCS). The effects of simulated microgravity on the differentiation and apoptosis of CD34+ cells were analyzed using flow cytometry and propidium iodide (PI) staining, respectively. Expression of GATA-1 mRNA in CD34+ cells was determined by real-time quantitative PCR.
In the RCCS group, GlyA+ (glycophorin A) expression was lower and CD33+ expression higher than in the 1-g liquid control group (22.21% +/- 3.02% and 60.05% +/- 3.08%, vs. 52.12% +/- 1.92% and 18.87% +/- 1.41%, respectively). The proportion of differentiated cells in the 1-g methylcellulos e group (Gly+% = 54.39% +/- 2.86%, CD33+% = 21.09% +/- 3.19%) was similar to that in the 1-g liquid control group. As shown by real-time quantitative PCR, the relative expression of GATA-1 mRNA in the RCCS group was only 20% of that in the -g control group. CONCLUSIONSs: The differentiation of CD3+ cells, and especially erythroid differentiation, was inhibited by simulated microgravity by a mechanism that appears to involve the suppression of GATA-1 mRNA expression. The results of this study may be useful in understanding the critical effect of simulated microgravity on the pathogenesis of space anemia.
The present study was undertaken to determine the effect of simulated microgravity on the testis of the rats and to evaluate the possibility of spermatogenesis failure in space environment. ...Fifty-four adult male albino rats were used in this study. They were divided equally into intact control, stress control and experimental groups. The rats of the intact control group (Group Ia) were kept without intervention. The rats of both the stress control and experimental groups were subjected to inguinal canal ligation and tail-suspension. In the stress control group (Group Ib) the hindlimbs were not elevated above the floor of the housing units whereas in the experimental groups the hindlimbs were elevated for one week (Group II) and six weeks (Group III), respectively. In a third experimental group (Group IV) the rats were hindlimb-suspended for six weeks followed by another six weeks without suspension to allow recovery. Prior to sacrifice, the animals were weighed and anesthetized, and the testes were excised and weighed. Testicular specimens were processed for histological, histochemical and morphometric studies. The results of the present study revealed that only after six weeks of hindlimb-suspension, the rats showed a significant decline in testicular weight compared with the control groups. Histologically, few abnormalities were observed in some seminiferous tubules in one-week hindlimb-suspended group. Spermatogenesis was significantly reduced by six-week of hindlimb-suspension marked by atrophy of the testes and loss of all germ cells, except a few spermatogonia. Spermatogenesis was partially restored in the recovery group. In all groups the appearance of Sertoli cells remained the same. Proliferation of Leydig cells was observed in the experimental groups. It is concluded that spermatogenesis is severely inhibited by six weeks of hindlimb-suspension and that it is partially restored following six weeks of recovery. This study provides further insights regarding the serious effects of long-term exposure to microgravity on the testes of mammals, including human beings.
This study was designed to examine the effect of non-weight-bearing conditions and the systemic influences of simulated microgravity on rat hindlimb muscles. For this purpose, rats were suspended ...(SUS) in a head-down position (45 degrees) with the left hindlimb non-weight bearing (NWB) and the right hindlimb bearing 20% of presuspension body mass (WB). Weight bearing by the SUS-WB limb was accomplished by using a platform connected to a rod in sleeve, cable, and pulley apparatus to which weight could be added. Rats (250-325 g) were assigned to SUS or cage control (CC) conditions for 14 days. The angle between the foot and leg for SUS-WB and CC remained similar (20-30 degrees) throughout the experiment while the SUS-NWB hindlimbs extended to approximately 140 degrees by day 12. On day 14, the soleus, plantaris, and gastrocnemius muscles from the SUS-NWB limbs exhibited significantly lower (P < or = 0.05) masses than presuspension mass values (29, 11, and 21%, respectively). Weight bearing by the SUS-WB limbs prevented the loss of mass by these muscles. In separate groups of SUS and CC rats, 2-deoxyglucose uptake during hindlimb perfusion was significantly higher in both SUS-NWB and SUS-WB hindlimbs at 24,000 microU/ml of insulin compared with CC for all the muscles examined (21-80%). In addition, extracellular space (ml/g) was significantly greater in the soleus muscles from both the SUS-NWB and SUS-WB hindlimbs (64%) compared with CC muscles.
Sarcomere disruptions are observed in the adductor longus (AL) muscles following voluntary reloading of spaceflown and hindlimb suspension unloaded (HSU) rat, which resemble lesions in eccentrically ...challenged muscle. We devised and tested an eccentric contraction (ECCON) test system for the 14-day HSU rat AL. Six to 7 hours following ECCON, ALs were fixed to allow immunostaining and electron microscopy (EM). Toluidine blue-stained histology semithin sections were screened for lesion density (#/mm2). Serial semithin sections from the ECCON group were characterized for myosin immunointensity of lesions. Five myofibrillar lesion types were identified in histological semithin sections: focal contractions; wide A-bands; opaque areas; missing A-bands; and hyperstretched sarcomeres. Lesion density by type was greater for ECCON than NonECCON ALs (P< or =0.05; focal contractions and opaque regions). Lesion density (#-of-all-five-types/mm2) was significantly different (ECCON: 23.91+/-10.58 vs. NonECCON: 5.48+/-1.28, P< or =0.05; ECCON vs. SHAM: 0.00+/-0.00; P< or = 0.025). PostECCON optimal tension decreased (Poi-drop, 17.84+/-4.22%) and was correlated to lesion density (R2=0.596), but prestretch tension demonstrated the highest correlation with lesion density (R2=0.994). In lesions, the darkly staining A-band lost the normally organized thick filament alignment to differing degrees across the different lesion types. Ranking the five lesion types by a measure of lesion length deformation (hypercontracted to hyperstretched) at the light microscopy level, related to the severity of thick filament registry loss across the lesion types at the electron microscopic level. This ranking suggested that the five lesion types seen in semithin sections at the light level represented a lesion progression sequence and paralleled myosin immunostaining loss as the distorted A-band filaments spread across the hyperlengthening lesion types. Lesion ultrastructure indicated damage involved calcium homeostasis loss (focal contraction lesions) and "thick-filament-centering" failure of titin (wide A-band lesions) in the early stages of lesion development.
Hindlimb unloading has proven to be an effective model for studying the physiological effects of spaceflight. However, using current methodologies, maintenance of adult rats in hindlimb unloading for ...long periods is challenging. Therefore, our goal was to develop a technique allowing long-term hindlimb unloading in adult rats.
Adult male Sprague Dawley rats were assigned to control (C), control pinned (CP), and hindlimb unloaded (HU) groups. All rats were anesthetized and a stainless steel needle was inserted through the skin in the ventral side of the tail of CP and HU groups. A cable was inserted through the needle, wrapped around to the dorsal side, secured, and stabilized with casting tape. HU rats were hindlimb suspended for 28 d by attaching the cable to an adjustable bar, resulting in a 30 degrees head-down tilt, and were monitored for health status and bodyweight. Fecal corticosterone levels were used as a stress index. Hindlimb muscles and adrenals were weighed.
Attrition due to animals slipping from their tail harness was eliminated. HU animals lost 9.9% bodyweight within the first 6 d of hindlimb unloading, but maintained that bodyweight the remaining 22 d. Stress levels, as measured by fecal corticosterone and adrenal weights, were not elevated significantly during suspension and muscle weights were decreased significantly.
Results indicate that this method is suitable for long-term hindlimb unloading of adult rats, providing an alternative approach to study loss of musculoskeletal mass in simulated microgravity.
Provider: Czech digital library/Česká digitální knihovna - Institution: Academy of Sciences Library/Knihovna Akademie věd ČR - Data provided by Europeana Collections- Ho Nguyen Quynh Chi, Hoang Nghia ...Son, Doan Chinh Chung, Le Dinh Huan, Tran Hong Diem, Le Thanh Long.- Obsahuje bibliografii- The cytoskeleton plays a key role in cellular proliferation, cellshape maintenance and internal cellular organization. Cells are highly sensitive to changes in microgravity, which can induce alterations in the distribution of the cytoskeletal and cell proliferation. This study aimed to assess the effects of simulated microgravity (SMG) on the proliferation and expression of major cell cycle-related regulators and cytoskeletal proteins in human umbilical cord mesenchymal stem cells (hucMSCs). A WST-1 assay showed that the proliferation of SMG-exposed hucMSCs was lower than a control group. Furthermore, flow cytometry analysis demonstrated that the percentage of SMG-exposed hucMSCs in the G0/G1 phase was higher than the control group. A western blot analysis revealed there was a downregulation of cyclin A1 and A2 expression in SMG-exposed hucMSCs as well. The expression of cyclin-dependent kinase 4 (cdk4) and 6 (cdk6) were also observed to be reduced in the SMG-exposed hucMSCs. The total nuclear intensity of SMG-exposed hucMSCs was also lower than the control group. However, there were no differences in the nuclear area or nuclear-shape value of hucMSCs from the SMG and control groups. A western blot and quantitative RT-PCR analysis showed that SMG-exposed hucMSCs experienced a downregulation of β-actin and α-tubulin compared to the control group. SMG generated the reorganization of microtubules and microfilaments in hucMSCs. Our study supports the idea that the downregulation of major cell cycle-related proteins and cytoskeletal proteins results in the remodeling of the cytoskeleton and the proliferation of hucMSCs.- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
Provider: - Institution: - Data provided by Europeana Collections- Berlin, Medizinische Fakultät Charité - Universitätsmedizin Berlin, Habilitationsschr., 2007- All metadata published by Europeana ...are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
Exposure to actual or simulated weightlessness is known to induce orthostatic intolerance in humans. Many different methods have been suggested to counteract orthostatic hypotension. The repetitive ...or prolonged application of lower body negative pressure (LBNP) has shown beneficial effects to counter orthostatic intolerance, but devoting so much time to countermeasures is not compatible with space mission objectives or costs. The purpose of the present study was to assess the effects of brief LBNP sessions against orthostatic intolerance during a 21-d head-down tilt (HDT) bed rest.
There were 12 healthy male volunteers who were exposed to -6 degrees HDT bed rest for 21 d. Six subjects received -30 mm Hg LBNP sessions for 1 h x d(-1) from day 15 to day 21 of the HDT, and six others served as control. Orthostatic tolerance was assessed by means of standard tilt test.
Before HDT, all the subjects in the two groups completed the tilt tests. After 21 d of HDT, five 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 13.0 +/- 4.0 min) was significantly shorter (p < 0.05) than that in the LBNP group (19.0 +/- 2.2 min). Body weight decreased significantly in the control group during HDT, while increasing significantly on day 21 of HDT in the LBNP group. Urine volume increased on days 15-21 of HDT in the control group, but remained unchanged throughout HDT in the LBNP group. A significant decrease in cardiac output and cardiac index, and a significant increase in total peripheral resistance, pre-ejection period, plasma renin activity, aldosterone, and prostaglandin 12 were observed during HDT in both groups. There were no significant differences in these parameters between the two groups.
Brief daily LBNP sessions were effective in preventing orthostatic intolerance induced by 21 d HDT bed rest. However, it did not improve cardiac pump and systolic functions and did not preserve volume regulating hormones.
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