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Motion-Induced Nausea and Vomiting
Published in John Kucharczyk, David J. Stewart, Alan D. Miller, Nausea and Vomiting: Recent Research and Clinical Advances, 2017
Space motion sickness, also referred to by the National Aeronautices and Space Administration (NASA) as part of a space adaptation syndrome, is generally thought to be a special form of terrestial motion sickness because of the similarity of symptoms and because it is elicited or exacerbated by head movements.70,86,89–91 Motion sickness is also a common consequence of exposure to force environments greater than the terrestial level of 1 G.90,92,93 Susceptibility to space sickness has yet to be reliably predicted either by ground-based tests or by exposure to brief periods of weightlessness during parabolic flight.70,94,95 About one half of all astronauts and cosmonauts develop symptoms of space motion sickness which can appear within minutes following launch and usually disappear after the first 3 to 4 days of space flight; i.e., about one half of shuttle astronauts are sick for almost one half of a typical 7 to 9 day mission.70,91,95,96 One cosmonaut experienced symptoms until day 14 in space.91 Space motion sickness was not reported in the Mercury and Gemini programs, probably due mainly to relatively confined crew compartments that restricted head movement.6,97 Motion sickness may also be expected to occur on long duration space flights if a portion of a future spacecraft is rotated for the purpose of creating artificial gravity or when the craft re-enters a strong gravitational field (such as that of Mars). Postflight symptoms of motion sickness have been reported.91
Simulation of the mechanical behavior of osteons using artificial gravity devices in microgravity
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Hao Zhang, Hai-Ying Liu, Chun-Qiu Zhang, Zhen-Zhong Liu, Wei Wang
There is a three-dimensional network throughout osteons that is called the lacunar-canalicular system (LCS). Osteocytes are deeply embedded in the lacunae, on which many synapses pass through the canaliculi to connect with adjacent osteocytes, forming a complex network of osteocytes. Osteocytes regulate bone remodeling by sensing the fluid shear stress (FSS) and other physical information in the LCS caused by external loads, which promotes dynamic regulation of bone mass (Chen and Huo 2017). Although the LCS, the structure of osteocytes and the negative feedback process can prevent unnecessary energy consumption under the reduced load conditions experienced in microgravity, it leads to a large amount of bone loss. During space flight, physical exercise and nutritional supplementation are often used with the aim of reducing bone loss; however, research has found the effect was not significant (Miao et al. 2017). With the increasing distance of human exploration in space, long-term space flight is inevitable. Osteoporosis has become one of the urgent problems in aviation medicine. Artificial gravity (AG) devices aim to simulate Earth-like gravitational acceleration during space flight. As a result, the flow and mechanical properties of the fluid in LCS will return to levels common on the Earth’s surface, thus effectively preventing the loss of bone mass.
Spaceflight-Associated Neuro-ocular Syndrome (SANS): a review of proposed mechanisms and analogs
Published in Expert Review of Ophthalmology, 2020
Peter Wojcik, Shehzad Batliwala, Tyler Rowsey, Laura A. Galdamez, Andrew G. Lee
Environmental factors unique to the ISS (e.g., higher levels of CO2 and radiation) have been proposed to contribute to SANS. CO2 levels aboard the ISS are almost 10 times those found on Earth [29]. Exposure to increased CO2 environments causes vasodilation of cerebral vasculature-increasing flow and blood volume potentially exacerbating ICP [47]. Hypercapnic environments such as on the ISS can increase IOP – a frequent marker for ICP [8]; however, recent HDT tests with CO2 as a dependent variable showed no changes to either jugular filling [48] or ICP [49]. Aboard the ISS, astronauts are subjected to increased levels of ambient radiation. Terrestrially, radiation is known to create cotton wool spots/RNFL infarcts [31]. Murine mouse models have been used for years to evaluate the effects of cosmic radiation on the mouse retina. Enucleated mouse eyes following radiation exposure and hind limb unloading show increased apoptosis of retinal endothelial cells alongside increased inflammatory markers such as endothelial nitric oxide synthase with a dose-dependent response to radiation exposure [50,51]. Moreover, inflammation was more pronounced when radiation was paired with hind limb unloading to simulate microgravity offloading. Similar studies following spaceflight show similar degree and specificity of cellular apoptosis with artificial gravity endowing a protective effect with reduced inflammation and apoptosis [52]. Radiation may explain some of the features of SANS such as cotton wool infarcts and ODE through endothelial damage; however, terrestrial radiation retinopathy in humans is characterized by cotton wool spots as well as hard exudates, hemorrhages, microaneurysms, and telangiectasias [53] which have not been in SANS. More studies are needed to properly identify if this is an independent factor for the cotton wool spots seen in SANS.
Simulation study on the effect of resistance exercise on the hydrodynamic microenvironment of osteocytes in microgravity
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Hai-Ying Liu, Chao-Hui Zhao, Hao Zhang, Wei Wang, Qing-Jian Liu
Previous studies have only focused on the effects of macroscopic mechanical stimulation and nutrition on the markers of human bone remodeling. The research has suggested that long-duration high-resistance training combined with dietary changes can significantly increase bone formation markers (Smith et al. 2012). A short-arm centrifuge was used to apply 1×g artificial gravity (five min per treatment, six times daily for five days) to eleven subjects lying in a bed with their heads tilted downward, and bone resorption was not reduced by the application of this artificial gravity (Rittweger et al. 2015). Other research has shown that high-resistance exercises combined with vibration can reduce bone mass loss in subjects with long-term head-down bed rest (Belavy et al. 2011). The above studies showed that high-load strength training of lower limbs can inhibit bone mass loss to some extent. Therefore, we hypothesized that interstitial fluid flow driven by dynamic loads and arterial pressure in microgravity can compensate for the insufficient mechanical stimulation on osteocytes caused by the loss of gravity, so as to promote osteocytes to utilize their biological functions and reduce disuse osteoporosis after long-term space flight in astronauts. The LCS filled with tissue fluid is deeply buried in the bone matrix, and the diameter of canaliculi where the osteocytes processes are located is only a few hundred nanometers (You et al. 2004; Pazzaglia et al. 2012). It has been impossible to study the hydrodynamic behaviors in the LCS and stress on osteocytes in vivo owing to the limitation of experimental techniques, but application of the finite element method can address this deficiency. A finite element model of a single osteocyte was established and used to simulate the shear stress (>0.8 Pa) on the surface of osteocytes and the flow velocity of the surrounding fluid (380–79 μm·s−1) when the strain of bone was the limit state which reach pathological bone remodeling threshold (3000 με) of the Earth’s gravity field (Verbruggen et al. 2014). The liquid flow field in the LCS was also simulated within microgravity and high G environments (Zhao et al. 2020). However, compared with the Earth’s gravity field, the change in mechanical microenvironments of osteocytes in load-bearing bone caused by astronauts during resistance exercises in microgravity has not yet been reported.