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Effects of gravity on humans

Zeynep Masatli, Michael Nordine, Martina A Maggioni, Stefan Mendt, Ben Hilmer, Katharina Brauns, Anika Werner, Anton Schwarz, Helmut Habazettl, Hanns-Christian Gunga, Oliver S Opatz
Cardiovascular deconditioning occurs in astronauts during microgravity exposure, and may lead to post-flight orthostatic intolerance, which is more prevalent in women than men. Intermittent artificial gravity is a potential countermeasure, which can effectively train the cardiovascular mechanisms responsible for maintaining orthostatic integrity. Since cardiovascular responses may differ between women and men during gravitational challenges, information regarding gender specific responses during intermittent artificial gravity exposure plays a crucial role in countermeasure strategies...
2018: Frontiers in Physiology
Ievgen Levadnyi, Jan Awrejcewicz, Yan Zhang, Márcio Fagundes Goethel, Yaodong Gu
This study investigated the influence of human head impact on the severity of traumatic brain injury. Simulation of the dynamic impact of a human head was performed using FEM (finite element method) and employing HIC (Head Injury Criterion). The study of traumatic brain injury included impacts with the occiput, temporal, forehead, and parietal part of the head, and the impact velocity at the surface ranged from 1 to 7 m/s. The following characteristics were considered and analyzed in the simulation: duration of the impact, intracranial pressure, HIC, and change in accelerations at the center of gravity of the brain...
2018: Journal of Medical and Biological Engineering
Alex S Huang, Rafaella C Penteado, Sajib K Saha, Jian L Do, Phillip Ngai, Zhihong Hu, Robert N Weinreb
PURPOSE: To evaluate aqueous humor outflow (AHO) in intact eyes of live human subjects during cataract surgery using fluorescein aqueous angiography. METHODS: Aqueous angiography was performed in 8 live human subjects (56 - 86▒y old; 2 men and 6 women). After anesthesia, fluorescein (2%) was introduced into the eye (either alone or after indocyanine green [ICG; 0.4%]) from a sterile, gravity-driven constant-pressure reservoir. Aqueous angiographic images were obtained with a Spectralis HRA+OCT and FLEX module (Heidelberg Engineering)...
August 7, 2018: Journal of Glaucoma
Ying I Wang, Michael L Shuler
Microphysiological systems, also known as body-on-a-chips, are promising "human surrogates" that may be used to evaluate potential human response to drugs in preclinical drug development. Various microfluidics-based platforms have been proposed to interconnect different organ models and provide perfusion in mimicking the blood circulation. We have previously developed a pumpless platform that combines gravity-driven fluid flow and a rocking motion to create reciprocating flow between reservoirs for recirculation...
July 26, 2018: Lab on a Chip
Zachary Ray, Erik D Engeberg
Autonomously preventing grasped objects from slipping out of prosthetic hands is an important feature for limb-absent people since they cannot directly feel the grip force applied to grasped objects. Oftentimes, a satisfactory grip force in one situation will be inadequate in different situations, such as when the object is rotated or transported. Over time, people develop a grip reflex to prevent slip of grasped objects when they are rotated with respect to gravity by their natural hands. However, this reflexive trait is absent in commercially available prosthetic hands...
2018: Journal of Healthcare Engineering
Salman Faraji, Amy R Wu, Auke J Ijspeert
Since the advent of energy measurement devices, gait experiments have shown that energetic economy has a large influence on human walking behavior. However, few cost models have attempted to capture the major energy components under comprehensive walking conditions. Here we present a simple but unified model that uses walking mechanics to estimate metabolic cost at different speeds and step lengths and for six other biomechanically-relevant gait experiments in literature. This includes at various gait postures (e...
July 20, 2018: Scientific Reports
Dan Xu, Yu-Bing Guo, Min Zhang, Ye-Qing Sun
PURPOSE: Microgravity is known to cause endothelium dysfunction in astronauts returning from spaceflight. We aimed to reveal the regulatory mechanism in alterations of human endothelial cells after simulated microgravity (SMG). METHODS: We utilized the rotary cell culture system (RCCS-1) to explore the subsequent effects of SMG on human umbilical vein endothelial cells (HUVECs). RESULTS: SMG-treated HUVECs appeared obvious growth inhibition after return to normal gravity, which might be attributed to a set of responses including alteration of cytoskeleton, decreased cell adhesion capacity and increased apoptosis...
June 28, 2018: Chinese Journal of Traumatology, Zhonghua Chuang Shang za Zhi
Taghi Ramazanian, Julia A Müller-Lebschi, Min Yao Chuang, Anthony M Vaichinger, James S Fitzsimmons, Shawn W O'Driscoll
BACKGROUND: Long-term radiographic arthritis has been commonly reported after radial head excision. Concern over radial head arthroplasty may arise in certain situations including capitellar arthritis, radiocapitellar malalignment, and in young and active patients. We hypothesized that radial head excision increases coronoid contact pressures, which may at least be partially reduced by radiocapitellar Achilles tendon disc arthroplasty. METHODS: Coronoid and capitellar contact pressure was measured on 6 human cadaveric elbows on a custom-designed gravity-valgus simulator under passive flexion from 0° to 90°...
July 11, 2018: Journal of Shoulder and Elbow Surgery
Ajay K Verma, Da Xu, Michelle Bruner, Amanmeet Garg, Nandu Goswami, Andrew P Blaber, Kouhyar Tavakolian
Autonomic control of blood pressure is essential toward maintenance of cerebral perfusion during standing, failure of which could lead to fainting. Long-term exposure to microgravity deteriorates autonomic control of blood pressure. Consequently, astronauts experience orthostatic intolerance on their return to gravitational environment. Ground-based studies suggest sporadic training in artificial hypergravity can mitigate spaceflight deconditioning. In this regard, short-arm human centrifuge (SAHC), capable of creating artificial hypergravity of different g-loads, provides an auspicious training tool...
2018: Frontiers in Physiology
David Hauton, Clare J Ray
We describe a simple, cost-effective experiment to demonstrate cardiovascular integration of heart rate and blood pressure to accommodate the environmental and dietary factors of gravity and caffeine. Specific learning objectives associated with this include understanding the effects of posture on blood pressure and heart rate, coupled with the role of caffeine in modifying this response. Inclusion of ECG measurements, coupled with heart rate variability analysis, added a demonstration of the contribution made by the autonomic nervous system under these conditions...
September 1, 2018: Advances in Physiology Education
Akito Miura, Shinya Fujii, Masahiro Okano, Kazutoshi Kudo, Kimitaka Nakazawa
The capacity for auditory-motor coordination (AMC) is shared by several species, among which humans are most flexible in coordinating with tempo changes. We investigated how humans lose this tempo flexibility at their upper rate limit, and the effect of skill level on this phenomenon. Seven skilled street dancers, including a world champion, and ten non-dancers were instructed to bend their knees according to a metronome beat in a standing position at eight constant beat frequencies (3.8-5 Hz). Although maximum frequency of movement during the task was 4...
July 2, 2018: Journal of Experimental Biology
Nguk Ting Lo, Mohammad Abul Bashar Sarker, Yvonne Ai Lian Lim, Md Harun-Or-Rashid, Junichi Sakamoto
Providing safe drinking-water to human civilization is indispensable; it is one of the most cost-effective means of reducing the disease burden of diarrhea. Unfortunately, water supply quality monitoring from public water treatment plants (WTPs) is often neglected or taken for granted. To determine the produced water quality, WTPs in Sarawak, Malaysia were assessed for their protozoa removal ability. A self-administered questionnaire based on the regulations in the Drinking-water Standards for New Zealand (DWSNZ) was developed...
May 2018: Nagoya Journal of Medical Science
Joshua E Cinner, Eva Maire, Cindy Huchery, M Aaron MacNeil, Nicholas A J Graham, Camilo Mora, Tim R McClanahan, Michele L Barnes, John N Kittinger, Christina C Hicks, Stephanie D'Agata, Andrew S Hoey, Georgina G Gurney, David A Feary, Ivor D Williams, Michel Kulbicki, Laurent Vigliola, Laurent Wantiez, Graham J Edgar, Rick D Stuart-Smith, Stuart A Sandin, Alison Green, Marah J Hardt, Maria Beger, Alan M Friedlander, Shaun K Wilson, Eran Brokovich, Andrew J Brooks, Juan J Cruz-Motta, David J Booth, Pascale Chabanet, Charlotte Gough, Mark Tupper, Sebastian C A Ferse, U Rashid Sumaila, Shinta Pardede, David Mouillot
Coral reefs provide ecosystem goods and services for millions of people in the tropics, but reef conditions are declining worldwide. Effective solutions to the crisis facing coral reefs depend in part on understanding the context under which different types of conservation benefits can be maximized. Our global analysis of nearly 1,800 tropical reefs reveals how the intensity of human impacts in the surrounding seascape, measured as a function of human population size and accessibility to reefs ("gravity"), diminishes the effectiveness of marine reserves at sustaining reef fish biomass and the presence of top predators, even where compliance with reserve rules is high...
July 3, 2018: Proceedings of the National Academy of Sciences of the United States of America
Erica K Low, Egil Brudvik, Bradford Kuhlman, Paul F Wilson, Graça Almeida-Porada, Christopher D Porada
Astronauts on missions beyond low-Earth orbit are exposed to a hostile environment in which they are continually bombarded with unique high-energy species of radiation, while in conditions of microgravity (μG), which can alter radiation response and immunity. In the present studies, we examined the impact exposing human hematopoietic stem/progenitor cells (HSC) to μG had upon their capacity to repair DNA damage and their ability to generate immune cells critical for mounting an effective antitumor response...
July 16, 2018: Stem Cells and Development
Katja M Dockheer, Christopher J Bockisch, Alexander A Tarnutzer
Introduction: Verticality perception as assessed by the subjective visual vertical (SVV) is significantly biased by a rotating optokinetic stimulus. The underlying mechanisms of this effect remain open. Potentially, the optokinetic stimulus induces a shift of the internal estimate of the direction of gravity. This hypothesis predicts a shift of perceived vertical using other, non-vision dependent, paradigms as well. Alternatively, an optokinetic stimulus may only induce a shift of visual orientation, and so would be task specific...
2018: Frontiers in Neurology
Ning Guo, Xingyu Fan, Yuting Wu, Zhili Li, Shujuan Liu, Linjie Wang, Jie Yao, Yinghui Li
Long exposure to the microgravity will lead to muscle atrophy and bone loss. Treadmill exercise could mitigate the musculoskeletal decline. But muscle atrophy remains inevitable. The constraint loading applied on astronauts could affect the muscle force and its atrophy severity. However, the quantitative correlation between constraint loading mode and muscle forces remains unclear. This study aimed to characterize the influence of constraint loading mode on the lower limb muscle forces in weightless treadmill exercise...
2018: Journal of Healthcare Engineering
Sandra K Hnat, Ben J H van Basten, Antonie J van den Bogert
Force plates for human movement analysis provide accurate measurements when mounted rigidly on an inertial reference frame. Large measurement errors occur, however, when the force plate is accelerated, or tilted relative to gravity. This prohibits the use of force plates in human perturbation studies with controlled surface movements, or in conditions where the foundation is moving or not sufficiently rigid. Here we present a linear model to predict the inertial and gravitational artifacts using accelerometer signals...
June 25, 2018: Journal of Biomechanics
D S Tzeranis, I Panagiotopoulos, S Gkouma, G Kanakaris, N Georgiou, N Vaindirlis, G Vasileiou, M Neidlin, A Gkousioudi, V Spitas, G A Macheras, L G Alexopoulos
This work describes the design and validation of a novel device, the High-Throughput Degradation Monitoring Device (HDD), for monitoring the degradation of 24 soft tissue samples over incubation periods of several days inside a cell culture incubator. The device quantifies sample degradation by monitoring its deformation induced by a static gravity load. Initial instrument design and experimental protocol development focused on quantifying cartilage degeneration. Characterization of measurement errors, caused mainly by thermal transients and by translating the instrument sensor, demonstrated that HDD can quantify sample degradation with <6 μm precision and <10 μm temperature-induced errors...
June 6, 2018: Journal of Biomechanics
Mary E Ingle, Lidia Mínguez-Alarcón, Courtney C Carignan, Craig M Butt, Heather M Stapleton, Paige L Williams, Jennifer B Ford, Russ Hauser, John D Meeker
BACKGROUND: The use of PFRs has steadily increased as brominated compounds have been or are being phased out. Human exposure is widespread and animal studies have shown adverse impacts on male reproduction, but human data are lacking. OBJECTIVE: To study the associations between urinary concentrations of phosphorous-containing flame retardant (PFR) metabolites and semen parameters. METHODS: A subset of 220 men from an existing longitudinal cohort of couples were recruited from Massachusetts General Hospital fertility clinic between 2005 and 2015...
June 2018: International Journal of Hygiene and Environmental Health
O Kuldavletova, S Marie, P Denise, H Normand
NEW FINDINGS: What is the central question of this study? It is known that respiration is affected by graviceptors, but it remains unclear to what extent labyrinthine and non-labyrinthine graviceptors are involved in this process. What is the main finding and its importance? Our results suggest that the modulation of respiration is not a result of a simple reflex arc, but that it involves a higher integration of different types of receptors with variable contributions of either type of graviceptor among subjects...
July 2018: Experimental Physiology
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