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At least 1,045 records · Page 58Linked to original sources
PubMed2002

[Effects of +Gx load on energy metabolism of brain tissue in rats].

Objective. To observe the changes of energy metabolism of brain tissue in rats under +Gx loads, and to explore its possible role in changes of brain function and work efficiency induced by +Gx stress. Method. Forty-five male Wistar rats were randomly divided into control, +5 Gx, +10 Gx, +15 Gx and +20 Gx group. Each group was exposed to the corresponding G value for 3 min. After that, cortical adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and lactic acid (LA) content, lactate dehydrogenase (LDH) activity were measured. Result. Compared with the control group, the cortical (LA) content increased significantly after +5 Gx, +10 Gx, +15 Gx and +20 Gx exposure (P<0.01). Cortical ADP content and ratio of ADP/AMP and AMP/ATP increased significantly after +10 Gx, +15 Gx and +20 Gx exposure (P<0.01), whereas ATP content, energy charge and LDH activity decreased significantly (P<0.05 or 0.01). Cortical AMP content increased significantly after +15 Gx and +20 Gx exposure (P<0.05 and 0.01). Conclusion. It is suggested that +Gx load can result in obvious depression of brain energy metabolism, which could be an important reason for the change of brain function and work efficiency induced by +Gx stress.

Acceleration↗
PubMed2002

[Construction of a cDNA subtractive library of rat brain after repeated +Gz exposure].

Objective. To construct a cDNA subtractive library of rat brain after repeated + Gz exposures with suppression subtractive hybridization (SSH). Method. Wistar [correction of Wister] rats were randomly divided into control group and repeated +Gz exposure group. Using an animal centrifuge, control rats were exposed to +1 Gz and exposure rats were exposed to +10 Gz for three times, each for 1 min with 30 min interval in between. Brains were taken 6 h after the last centrifuge run and Poly (A) + RNA were isolated. Moreover, single-strand cDNAs and double-strand cDNAs were synthesized in turn. After Rsa I enzyme restriction, +Gz exposure rat brain cDNAs were divided into two groups and ligated to the specific adaptor 1 and adaptor 2R, respectively. Then +Gz exposure rat brain cDNAs were hybridized with the control rat brain cDNA twice and underwent nested PCR twice. The PCR product was ligated with T/A plasmid vectors to set up the subtractive library. Result. The cDNA subtractive library of rat brain after repeated +Gz exposures with high subtractive efficiency was set up successfully. Conclusion. The highly efficient cDNA subtractive library may provide a solid foundation for screening and cloning differentially expressed genes in rat brain after repeated exposures to +Gz.

Animals↗
PubMed2002

[Review of influence of landing impact on human body (correction of boby) and its medical evaluation].

Landing impact is the dynamic factor that manned spaceship will inevitably meet after the mission has been completed, and impact force may cause damages to human tissues [correction of tissuses] and organs, even death. This paper described the characteristics of pathological and dynamic response of human body to landing impact, and discussed various related factors such as impact angle, fetters, design of cushion, harness and terrain condition. Medical evaluation of +Gx, +Gz, +/- Gy impacts were summarized.

Aerospace Medicine↗
PubMed2001

Changes in gene expression and signal transduction in microgravity.

Studies from space flights over the past three decades have demonstrated that basic physiological changes occur in humans during space flight. These changes include cephalic fluid shifts, loss of fluid and electrolytes, loss of muscle mass, space motion sickness, anemia, reduced immune response, and loss of calcium and mineralized bone. The cause of most of these manifestations is not known and until recently, the general approach was to investigate general systemic changes, not basic cellular responses to microgravity. This laboratory has recently studied gene growth and activation of normal osteoblasts (MC3T3-El) during spaceflight. Osteoblast cells were grown on glass coverslips and loaded in the Biorack plunger boxes. The osteoblasts were launched in a serum deprived state, activated in microgravity and collected in microgravity. The osteoblasts were examined for changes in gene expression and signal transduction. Approximately one day after growth activation significant changes were observed in gene expression in 0-G flight samples. Immediate early growth genes/growth factors cox-2, c-myc, bcl2, TGF beta1, bFGF and PCNA showed a significant diminished mRNA induction in microgravity FCS activated cells when compared to ground and 1-G flight controls. Cox-1 was not detected in any of the samples. There were no significant differences in the expression of reference gene mRNA between the ground, 0-G and 1-G samples. The data suggest that quiescent osteoblasts are slower to enter the cell cycle in microgravity and that the lack of gravity itself may be a significant factor in bone loss in spaceflight. Preliminary data from our STS 76 flight experiment support our hypothesis that a basic biological response occurs at the tissue, cellular, and molecular level in 0-G. Here we examine ground-based and space flown data to help us understand the mechanism of bone loss in microgravity.

Animals↗
PubMed2001

Enhancement of protease activity involved in modulation of cell mutability by microgravity stress in UVC-irradiated human cells.

It is an intriguing question whether gravity-changing stress modulates human cell mutability. To resolve this problem, it is necessary to determine the cellular events leading to modulation. We previously detected protease activation just after UV (UVC, principally 254 nm wavelength) irradiation followed by hypomutability in cultured human cells. We here investigated whether UV-activated protease activity is affected in human UVAP-1 cells exposed to gravity-changing stress prior to UV irradiation.

Cell Line↗
PubMed2001

Effect of gravity change on thrombopoiesis in mice.

It is reported that the stay in the space develops anemia, thrombocytopenia, and altered function and structure of red blood cell. The mechanism of these abnormalities was not clarified yet. Therefore, it is necessary to elucidate the mechanism of the effect of the gravity change on the thrombocytopoiesis, which plays the important role for the hemostasis, using animal models. The cloning of thrombopoietin (TPO), followed by the analysis of TPO and c-mpl (its cellular receptor) knockout mice confirmed its role as the primary regulator of thrombopoiesis. TPO has been shown to stimulate both megakaryocyte colony growth from marrow progenitor cells and the maturation of immature megakaryocyte to form functional platelet. This process includes the massive cytoskeletal rearrangement, such as proplatelet formation and fragmentation of proplatelet. In this study we have focused on the thrombopoiesis in mice those were exposed to gravity change by parabolic flight (PF).

Animals↗
PubMed2001

Reflex response changes during hyper and microgravity.

This paper reports the quantitative evaluation of the H-reflex exhibited by parabolic flight with exposure to micro and high-gravity. With respect to previous findings in parabolic flights and short-term space missions, the analysis focused on reflex activity in weightlessness. The aim of this study was to investigate the effect of gravity on H-reflex and motor evoked potentials (MEP) in soleus muscle (SOL) during parabolic flight.

Adult↗
PubMed2003

Cerebral blood flow during acceleration in flight measured with SPECT.

INTRODUCTION: Positive pressure breathing for G-protection (PBG) reduces the need for fighter pilots to use the fatiguing anti-G straining maneuver (AGSM) so that they can better endure high acceleration (+Gz). The aim of the study was to determine the differences in cerebral blood flow during flight with an extended-coverage anti-G suit (ECGS) with AGSM or with PBG. METHODS: Subjects were eight male members of the Finnish Air Force. Each was studied in the laboratory at +1 Gz and then during two identical flights in the back seat of the BAe Hawk Mk 51 jet trainer at +6 Gz, first with AGSM and second with PBG (24 mmHg). Regional cerebral blood flow (rCBF) was measured by injecting (99 m) Tc-ECD for deposition at +6 Gz, then scanning the subject in the laboratory an hour later using single photon emission computed tomography (SPECT). RESULT: The rCBF was 30% below baseline for both the AGSM and PBG. CONCLUSIONS: PBG maintained CBF at +6 Gz without the need for the fatiguing AGSM.

Adult↗
PubMed1970

Specific problems of physical training of cosmonauts.

Physical fitness and--closely related to it--physiological aspects of physical condition are very important in the elevation of the tolerance level to harmful effects of surrounding factors. To improve the possibilities of withstanding the factors of spaceflight, the cosmonauts undergo special training. Among the training methods there is a physical training program that is planned in relation to the general fitness of the cosmonaut. The following problems will be discussed, based on results obtained by the Polish Institute of Aviation Medicine: 1) The specific future of a physical training program. 2) The results of physiological research in a specifically elevated tolerance level to hypoxia and acceleration. 3) The possibilities of extension of physical training taking into account other flight factors.

Acceleration↗
PubMedDate not supplied

[Neuroprotective properties of pyroglutamic acid in combination with pyrrolidone].

A new drug composition containing pyroglutamic acid and pyrrolidone produces a significant effect on the cerebral circulation in rats with global recurrent brain ischemia and in a model ischemic state under high radial gravitational overload. In the former case, the new drug increases the blood circulation in rats with the global ischemic damage to a greater extent than in the intact control group. Pretreatment with the pyroglutamic acid--pyrrolidone composition produced a 2-2.5-fold increase in the survival of rats in the ischemic state caused by the radial gravitational overload. The data obtained show evidence of a substantial neuroprotector action of the new drug composition.

Animals↗
PubMed2003

Endurance and performance during multiple intense high +Gz exposures with effective anti-G protection.

BACKGROUND: In many high-intensity wartime scenarios, pilots may be required to fly multiple, strenuous missions during the same day. HYPOTHESIS: New anti-G protection allows fighter pilots to endure multiple high +G, exposures during several sorties in a limited time interval. METHODS: Nine well-trained centrifuge subjects were exposed to tactical aerial combat maneuvers using balanced pressure breathing during G (PBG) and an extended coverage anti-G suit. The centrifuge exposures consisted of five simulated sorties during a 4-h period, each consisting of four engagements with rapid onset cycles (6 G x s(-1)) varying between +4 G, and -9 GC. The subjects executed a tracking task before, during, and after each engagement and verbally indicated their effort level. Neck muscle strength was measured before and after the test. RESULTS: Seven of the nine subjects could endure all five sorties during the 4-h period. On a scale from 0 (no effort) to 11 (maximum possible effort), highest effort level during runs varied from 5.5 to 11 units (mean 8.7). Maximal heart rate varied from 140-173 bpm (mean 159) and minimum finger oxygen saturation from 75-93% (mean 88). Maximal peripheral and central light-loss varied from 0 to 100% (mean 71 and 40, respeclively). Three G-LOCs (two in the same subject) and four cases of near loss of consciousness occurred. The general fatigue recovery time varied from 9 to 48 h (mean 21). The tracking tests showed that performance deteriorated significantly during all G exposures; the neck muscle contraction was impaired by 12% (p = 0.035) after the C exposures. CONCLUSION: It is possible to train subjects to withstand five simulated flight sorties during a 4-h period with a total of up to 80 peaks to +9 Gz and 80 peaks to +8 Gz using PBCG and an extended coverage anti-G suit.

Aerospace Medicine↗
PubMed2002

Decreased platelet level in peripheral blood of mice by microgravity.

It is reported that the stay in the space develop anemia, throbocytopenia, and altered function and structure of red blood cell. The mechanism of these abnormalities was not clarified yet. TPO has been shown to stimulate both megakaryocyte colony growth from marrow progenitor cells and the maturation of immature megakaryocyte to form functional platelet. This process include massive cytoskeletal rearrangement, such as proplatelet formation and fragmentation of proplatelet. Our previous reports (Fuse and Sato, 2001, Fuse et al, 2001) showed an inverse relationship between decreased platelet count and increased TPO concentrations in peripheral blood of mouse was induced by parabolic flight (PF). We have studied which gravity change during PF involved this phenomenon.

Animals↗
PubMed2000

Daily head-up tilt, standing or centrifugation can prevent vasoreactivity changes in arteries of simulated weightless rats.

Artificial gravity will be considered for long-duration spaceflight missions. Recent studies have shown that continuous exposure to gravity does not appear necessary to prevent the adverse effects of weightlessness, instead intermittent exposure may suffice. Vernikos et al reported that 1 G intermittent exposures with and without walking exercise was effective in preventing physiologic deconditioning with 4-d, -6 degrees bedrest, and standing at 1 G was most effective in preventing orthostatic intolerance. Our previous work has demonstrated differential adaptational changes in structure, function, and innervation state of arterial vasculature in different body regions of rat during simulated weightlessness and further suggested that these changes might be one of the most important mechanisms accounting for postflight orthostatic intolerance. We therefore designed the present study involving a comprehensive evaluation of the effect of intermittent G exposure in preventing the differential functional changes of the arteries at the end of 3-wk head-down tail suspension in rats to answer the following questions: (1) do intermittent G exposure have counteracting effect in preventing differential functional changes in arterial vasculature with tail-suspension? (2) among the treatments used in the present study, i.e., head-up tilt (HUT), standing (STD), and centrifugation (CEN), what kind of exposure is more effective? (3) how much time in daily 1 G exposure is needed to maintain the normal (1 G) vascular responsiveness?

Adaptation, Physiological↗
PubMed2000

Altered gravity modulates prostaglandin H synthase in human K562 cells.

In this study, we extended our previous observations on the effects of altered gravity on the "lipoxygenase pathway", by ascertain the possible role of the force of gravity in modulating the activity and expression of PHS in human erythro-leukemia K562 cells.

Arachidonate 5-Lipoxygenase↗
PubMed2000

Influence of repetitive Gz acceleration on structural and metabolic profile of m. vastus lateralis in monkeys exposed to 30 day bedrest.

It was shown that changes in structural and metabolic indices of extensor muscles of the lower extremities were usually found in man after exposure to space flight or to bed rest. Similar changes were also observed in monkeys, space-flown on "Kosmos" biosatellites. Response to weightlessness and to restraint was found to be different in m. soleus and in m. vastus lateralis. Therefore, it is important to study structural and metabolic changes of m. vastus lateralis fibers under conditions of gravitational unloading in monkeys, who have motor apparatus similar to that of man, and are much more fruitful object of research. It is assumed that artificial gravity can serve as a countermeasure, aimed at diminishing effects of gravitational unloading. We have studied the effect of repeated gravity overloading, created by means of a centrifuge, on structural and metabolic indices of monkey m. vastus lateralis at the background of 30 day head down tilt bed rest (BR).

Acceleration↗
PubMed2000

Search for gravity-responsive genes by PCR-based mRNA differential display in human cells.

Mechanisms of molecular responses of human cells to gravity change and/or space radiation are one of the most important physiological problems in space science. We have previously reported that expression levels of several genes are changed in cultured human cells after UVC irradiation, and a few of those genes are responsible for UVC sensitivity. In this study, to find candidates for genes that play roles in susceptibility of human cells to gravity stressors, including those responsible for genetic stability in humans, we analyzed genes expressed differentially after gravity stress in human cells, using a PCR-based mRNA differential display (D.D.) method. Cells used were RSa and its variant cell lines, with discrepant sensitivity to radiation cell-killing and mutagenicity [correction of mutagenecity].

Cell Line↗
PubMed2003

[The use of gravitation overloading in the treatment of obliterative atherosclerosis of lower extremity arteries].

The article sums up results of treatment of 152 patients with obliterating atherosclerosis of the lower extremity arteries which were exposed to 2-3 G gravitation overloading made in a centrifuge of a short radius in direction head--pelvis. The gravitation overloading in the regimen followed were not found to have negative effects of central hemodynamics. Peripheral circulation was noted to considerably improve which is confirmed: 1) by clinical data showing 2-5 times longer distance of painless walking; 2) by the data of ultrasound dopplerography manifested as larger volume rate of blood flow and regional perfusion index; 3) by thermographic explorations evidencing the recovery of the thermoprophile of the legs and feet. Thus, the application of gravitation overloading is a new effective method of conservative treatment of patients with the pathology in question.

Aged↗