Effects of hypergravity on the gene expression of the hypothalamic feeding-related neuropeptides in mice via vestibular inputs.

The effects of hypergravity on the gene expression of the hypothalamic feeding-related neuropeptides in sham-operated (Sham) and vestibular-lesioned (VL) mice were examined by in situ hybridization histochemistry. Corticotrophin-releasing hormone (CRH) in the paraventricular nucleus was increased significantly in Sham but not in VL mice after 3 days of exposure to a 2 g environment compared with a 1 g environment. Significant decreases in pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript and significant increases in neuropeptide Y, agouti-related protein in the arcuate nucleus and orexin in the lateral hypothalamic area were observed in both Sham and VL mice. After 2 weeks of exposure, CRH and POMC were increased significantly in Sham but not in VL mice. After 8 weeks of exposure, the hypothalamic feeding-related neuropeptides were comparable between Sham and VL mice. These results suggest that the hypothalamic feeding-related neuropeptides may be affected during the exposed duration of hypergravity via vestibular inputs.

Psychophysiological responses of artificial gravity exposure to humans.

AIM: The aim of this study was to determine psychophysiological responses and cognitive performance after a single bout of artificial gravity, in order to investigate its use as a potential holistic countermeasure for long-duration human space flight, considering mental health. METHODS: Sixteen male participants were exposed to two different hypergravity protocols in a randomized order, one providing a constant +2 Gz environment for 30 min, the other providing participants for five times with repeated 3-min intervals of +2 Gz and rest, respectively. EEG was recorded prior, during and after AG. In addition, self-reported mood and cognitive performance was assessed before and after AG exposure. EEG data were analyzed using standardized brain electromagnetic tomography (sLORETA). RESULTS: Beta-1 EEG activity (12-18 Hz) was decreased in the left middle frontal gyrus after the continuous profile. Participants' motivation decreased after continuous artificial gravity, while perceived physical state was increased. The intermittent profile did not induce any changes in the observed parameters. Cognitive performance was not affected by either of both profiles. CONCLUSION: The continuous profile induced neurophysiological changes, which are considered with negative affect and withdrawal related motivation, according to the model of frontal asymmetry. This notion was further confirmed by decreases in self-reported mood after continuous AG. Therefore, the continuous profile would not be appropriate for the human space flight program. Intermittent AG did not induce any psychophysiological changes and might therefore provide a more appropriate approach as a countermeasure for further investigations.

Electroacupuncture pretreatment ameliorates hypergravity-induced impairment of learning and memory and apoptosis of hippocampal neurons in rats.

High-sustained positive acceleration (+Gz) exposures might lead to impairment in cognitive function. Our previous studies have shown that electroacupuncture (EA) pretreatment can attenuate transient focal cerebral ischemic injury in the rats. In this study we aimed to investigate whether EA pretreatment could ameliorate the impairment of learning and memory induced by a sustained +Gz exposure. Using the centrifuge model, rats of experimental groups were exposed to +10 Gz for 5 min. Morris water maze was used for assessing the cognitive ability, and the apoptotic hippocampal CA1 pyramidal neuronal cells were evaluated by caspase-3 activity and TUNEL staining. Our results showed that +Gz exposure significantly caused pyramidal neuronal damage, increased neuronal apoptosis and caspase-3 activity in hippocampal CA1 region, as well as resulted in an impairment of spatial learning and memory, as compared to the sham group animals. Furthermore, the EA pretreatment significantly attenuated the neuronal apoptosis, preserved neuronal morphology and inhibited the caspase-3 activity in hippocampal CA1 region resulted from +Gz exposure. The EA pretreatment also ameliorated the learning and memory function in rats exposed to +Gz. These findings indicate that EA pretreatment provides a novel method to prevent the cognitive damage caused by +Gz, which could significantly protect neuronal damage and impairment of learning and memory.

Effects of hypergravity on histamine H1 receptor mRNA expression in hypothalamus and brainstem of rats: implications for development of motion sickness.

CONCLUSION: The study findings suggest that histamine was released from the axon terminals in the hypothalamus and brainstem and the released histamine activated post-synaptic H1 receptors there, resulting in the development of motion sickness. OBJECTIVES: We first examined which subtype of post-synaptic histaminergic receptor was responsible for the development of motion sickness. We then examined whether H1 receptors were up-regulated in various areas of the rat brain after 2 G hypergravity load, because the stimulation of H1 receptor was reported to up-regulate the level of H1 receptor protein expression through augmentation of H1 receptor mRNA expression. MATERIALS AND METHODS: For this purpose, we used an animal model of motion sickness, using pica (eating non-nutritive substances such as kaolin), as a behavioral index in rats. RESULTS: After 2 G hypergravity load, rats ate a significant amount of kaolin, indicating that they suffered from motion sickness. The hypergravity-induced kaolin intake was suppressed by mepyramine, but not by terfinadine or zolantizine. This finding indicates that cerebral post-synaptic H1 but not H2 or peripheral H1 receptors play an important role in the development of motion sickness. The expression of H1 receptor mRNA was up-regulated in the hypothalamus and brainstem, but not in the cerebral cortex after 2 G hypergravity load in rats.

An electrical muscle stimulation suit for increasing blood pressure.

BACKGROUND: Electrical muscle stimulation (EMS) is used to strengthen muscles in rehabilitation of patients and for training of athletes. Voluntary muscle straining and an inflated anti-G suit increase the arterial blood pressure (BP) and give a pilot G protection during increased +Gz. This study's aim was to measure whether BP also increases with EMS of lower body muscles. METHODS: A suit with new cloth electrodes sewn into the garment was developed. There were 12 subjects who were tested in sitting position during 3 conditions with 10 consecutive periods of EMS, inflated anti-G suit (GS), or lower body muscle anti-G straining maneuvers (AGSM). BP was continuously measured noninvasively. RESULTS: The means of the baseline systolic BP, before each of the test conditions, were 127 +/- 16, 128 +/- 1, and 145 +/- 14 mmHg for GS, AGSM, and EMS, respectively. During inflation of the GS, execution of the AGSM, and EMS, mean systolic BP during the first 10 s was 143 +/- 15, 146 +/- 13, and 150 +/- 13 mmHg, respectively, with no statistical difference between the conditions. The corresponding mean resting heart rate before each test was 57-63 bpm for all conditions. During the test periods with GS, AGSM, and EMS, heart rate was 59 +/- 11, 79 +/- 16, and 61 +/- 15 bpm, respectively, with statistical differences (P < 0.001) between AGSM and the other two conditions. CONCLUSION: EMS created similar BP as GS and AGSM at 1 G and also had higher pre- and post-control values. Further studies are required to evaluate if this principle may be used for G protection of pilots.

[Evaluation of +Gz tolerance following simulation of 8-hr flight].

Tolerance of +Gz (head-pelvis) centrifugation of pilots was evaluated following simulation of a long flight on single-seat fighter. The experiment involved 5 test-subjects who were exposed to +Gz before and after simulated 8-hr flight with a growth gradient of 0.1 u/s without anti-g suits and muscles relaxed; in addition, limiting tolerance of intricate profile +Gz loads of 2.0 to 9.0 units with a growth gradient of 1.0 u/s of test-subjects in anti-g suits (AGS) with a change-over pressure valve in the peak mode using muscle straining and breathing maneuvers. To counteract the negative effects of extended flight, various seat configurations: with a back inclination at 30 degrees to the +Gz vector and changeable geometry with a back inclination at 55 degrees to the vector. The other counter-measures applied were cool air shower, suit ventilation, physical exercises, lower body massage with AGS, electrostimulation of the back and lumber region, profiling of the supporting and soft parts of the seat, and 30-s exposure to +5 Gz. Hemodynamic and respiration parameters as well as body temperature were measured in the course of 8 hrs of flight and during and shortly after centrifugation. According to the results of the investigation, seat inclination at 55 degrees to the +Gz vector and tested system of countermeasures prevent degradation of tolerance of large (9 u.) loads following 8-hr flight simulation with the use of the modern anti-g gear,

[Influences of repeated lower +Gz exposures on high +Gz exposure induced brain injury in rats].

Objective. To explore the influence of repeated lower +Gz exposures on high +Gz exposure induced brain injury in rats. Method. Forty SD male rats were randomly divided into control group (5 rats), +10 Gz/5 min group (5 rats) +4 Gz exposure one time, three times and five times group (10 rats each group). After 1 d or 6 d of +4 Gz exposure each group were exposed to +10 Gz again. Three days after +10 Gz exposure the neuron damage was observed by light microscope in HE stained section. Result. There was no brain damage after repeated +4 Gz/3 min exposure 5 times so it was reasonable to use this exposure intensity as ischemia stimulation. +10 Gz/5 min exposure could result in irreversible neuron damage such as neuron degeneration and coagulation necrosis. The experiment results suggested that after +10 Gz/5 min exposure there were degenerated neurons in cortex, hippocampus and thalamus. The number of degenerated neurons were obviously decreased in cortex, hippocampus and thalamus when exposed to +10 Gz/5 min again after repeated +4 Gz/3 min 3-5 times. Conclusion. The degree of neuron damage was obviously slight at the time of exposure to +10 Gz/5 min again after repeated +4 Gz/3 min 3-5 times. The ischemia tolerance at the time of exposure to +Gz was similar to other brain ischemia.

[Study on anti +Gx respiratory maneuver and its training method].

Objective. To study the anti +Gx respiratory maneuver and its training method. Method. Seven young male subjects undertook the anti +Gx respiratory maneuver training. Their +Gx tolerances were examined on human centrifuge before and after training. The change of respiratory type, breath rate, electrocardiogram, heart rate, arterial oxygen saturation (SaO2), subjective symptom and vision were real-time monitored during the +Gx tolerance examination. Result. Compared with pre-training, the +Gx tolerance increased after training (P<0.05). Dyspnea and chest pain disappeared or obviously lightened and the magnitude of decrease of SaO2 decreased significantly (P<0.05). Conclusion. The above results suggested that the anti +Gx respiratory maneuver can effectively eliminate or alleviate dyspnea and chest pain induced by +Gx stress and increase human +Gx tolerance.

[Experimental studies of the protective effects of basic fibroblast growth factor and Radix Salviae Miltiorrhizae on brain injury in rats caused by repeated exposures to +Gz].

Objective. To investigate the preventive and theralseutive (therapeutic) effects of basic fibroblast growth factor (bFGF) and Radix Salviae Miltiorrhizae (RSM) on brain injury caused by repeated +Gz exposures. Method. bFGF and RSM were injected intraperitoneally into SD rats before and after repeated +Gz exposures. The contents of excitatory amino acids (EAAs), nitric oxide (NO) and the number of cell apoptosis in the brain were measured, and were compared to those of the control group and normal saline (NS) group. Result. The contents of EAAs, NO and the number of cell apoptosis were significantly higher in repeated +Gz exposures group than those in control group. The values were markedly lower in bFGF and RSM group than those in repeated +Gz exposures group and NS group. Conclusion. bFGF and RSM showed distinct preventive and therapeutic effect on the brain injury induced by repeated +Gz exposures.

[Effect of hypergravity on the oxidative-antioxidative status of rats]. / Okysniuval'no-antyoksydantnyi status shchuriv za umov hiperhravitatsii.

The adaptogenic and antioxidant properties of new Ukrainian plant drug "Poliphytolum" was investigated on the model of stress, which was caused of hypergravitation 2 and 5 N.m2/kg2 action. It was established that hypergravitation makes typical stressory disturbances in oxidative homeostasis. The normalization action of "Polyphytolum" on lipid peroxidation is more strong in liver, spleen and blood, and less more--in brain. It may be caused of low level the drug in the brain tissue.

Manipulating the arterial pressure to prevent G-LOC.

NASA: I shall make an attempt to categorize--from a physiologist's point of view--the procedures that can be used to manipulate the arterial pressure at head level, assuming that for all practical purposes this is the critical variable in cerebral perfusion.^ieng