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Venegas JM. Spaceflight-associated neuro-ocular syndrome: potential etiologies and connections to the glymphatic system. J Neurophysiol 2024; 131:785-788. [PMID: 38533966 DOI: 10.1152/jn.00056.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 03/25/2024] [Accepted: 03/26/2024] [Indexed: 03/28/2024] Open
Abstract
The etiology of spaceflight-associated neuro-ocular syndrome (SANS) is a developing field of research, with many current hypotheses receiving varying degrees of support. This syndrome affects ∼70% of astronauts both during and after long-duration space missions, resulting in impaired near vision and visual scotomas (blind spots). In this article, three prominent risk factors for SANS including zero gravity conditions, extraterrestrial hypercapnic environments, and individual genetic predisposition are described. These risk factors are then compared and their pathophysiological pathways are divided into five current hypotheses for the development of SANS. Finally, glymphatic system impairment is explored as a potential mutual end point for these pathways in the development of SANS.
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Affiliation(s)
- Joshua M Venegas
- Aerospace & Human Performance, Department of NeurologyThe Medical University of South CarolinaCharlestonSouth CarolinaUnited States
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段 雪, 韦 锦, 梁 安, 纪 雪. [Small tidal volume hyperventilation relieves intraocular and intracranial pressure elevation in prone spinal surgery: a randomized controlled trial]. NAN FANG YI KE DA XUE XUE BAO = JOURNAL OF SOUTHERN MEDICAL UNIVERSITY 2024; 44:660-665. [PMID: 38708498 PMCID: PMC11073951 DOI: 10.12122/j.issn.1673-4254.2024.04.06] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Indexed: 05/07/2024]
Abstract
OBJECTIVE To investigate the effects of different ventilation strategies on intraocular pressure (IOP) and intracranial pressure in patients undergoing spinal surgery in the prone position under general anesthesia. METHODS Seventy-two patients undergoing prone spinal surgery under general anesthesia between November, 2022 and June, 2023 were equally randomized into two groups to receive routine ventilation (with Vt of 8mL/kg, Fr of 12-15/min, and etCO2 maintained at 35-40 mmHg) or small tidal volume hyperventilation (Vt of 6 mL/kg, Fr of18-20/min, and etCO2 maintained at 30-35 mmHg) during the surgery. IOP of both eyes (measured with a handheld tonometer), optic nerve sheath diameter (ONSD; measured at 3 mm behind the eyeball with bedside real-time ultrasound), circulatory and respiratory parameters of the patients were recorded before anesthesia (T0), immediately after anesthesia induction (T1), immediately after prone positioning (T2), at 2 h during operation (T3), immediately after supine positioning after surgery (T4) and 30 min after the operation (T5). RESULTS Compared with those at T1, IOP and ONSD in both groups increased significantly at T3 and T4(P < 0.05). IOP was significantly lower in hyperventilation group than in routine ventilation group at T3 and T4(P < 0.05), and ONSD was significantly lower in hyperventilation group at T4(P < 0.05). IOP was positively correlated with the length of operative time (r=0.779, P < 0.001) and inversely with intraoperative etCO2 at T3(r=-0.248, P < 0.001) and T4(r=-0.251, P < 0.001).ONSD was correlated only with operation time (r=0.561, P < 0.05) and not with IOP (r=0.178, P>0.05 at T3; r=0.165, P>0.05 at T4). CONCLUSION Small tidal volume hyperventilation can relieve the increase of IOP and ONSD during prone spinal surgery under general anesthesia.
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Affiliation(s)
- 雪飞 段
- 南方医科大学附属广东省人民医院麻醉科, 广东 广州 510080Department of Anesthesiology, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou 510080, China
| | - 锦锋 韦
- 南方医科大学附属广东省人民医院麻醉科, 广东 广州 510080Department of Anesthesiology, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou 510080, China
| | - 安怡 梁
- 南方医科大学附属广东省人民医院眼科, 广东 广州 510080Department of Ophthalmology, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou 510080, China
| | - 雪霞 纪
- 南方医科大学附属广东省人民医院麻醉科, 广东 广州 510080Department of Anesthesiology, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou 510080, China
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Fois M, Diaz-Artiles A, Zaman SY, Ridolfi L, Scarsoglio S. Linking cerebral hemodynamics and ocular microgravity-induced alterations through an in silico-in vivo head-down tilt framework. NPJ Microgravity 2024; 10:22. [PMID: 38413627 PMCID: PMC10899661 DOI: 10.1038/s41526-024-00366-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 02/15/2024] [Indexed: 02/29/2024] Open
Abstract
Head-down tilt (HDT) has been widely proposed as a terrestrial analog of microgravity and used also to investigate the occurrence of spaceflight-associated neuro-ocular syndrome (SANS), which is currently considered one of the major health risks for human spaceflight. We propose here an in vivo validated numerical framework to simulate the acute ocular-cerebrovascular response to 6° HDT, to explore the etiology and pathophysiology of SANS. The model links cerebral and ocular posture-induced hemodynamics, simulating the response of the main cerebrovascular mechanisms, as well as the relationship between intracranial and intraocular pressure to HDT. Our results from short-term (10 min) 6° HDT show increased hemodynamic pulsatility in the proximal-to-distal/capillary-venous cerebral direction, a marked decrease (-43%) in ocular translaminar pressure, and an increase (+31%) in ocular perfusion pressure, suggesting a plausible explanation of the underlying mechanisms at the onset of ocular globe deformation and edema formation over longer time scales.
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Affiliation(s)
- Matteo Fois
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, Turin, 10129, Italy.
| | - Ana Diaz-Artiles
- Department of Aerospace Engineering, Texas A&M University, 3141 TAMU, College Station, TX, 77843-3141, USA
- Department of Kinesiology and Sport Management, Texas A&M University, 2929 Research Pkwy, College Station, TX, 77845, USA
| | - Syeda Yasmin Zaman
- Department of Aerospace Engineering, Texas A&M University, 3141 TAMU, College Station, TX, 77843-3141, USA
| | - Luca Ridolfi
- Department of Environmental, Land and Infrastructure Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, Turin, 10129, Italy
- PolitoBioMed Lab, Politecnico di Torino, Corso Duca degli Abruzzi 24, Turin, 10129, Italy
| | - Stefania Scarsoglio
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, Turin, 10129, Italy
- PolitoBioMed Lab, Politecnico di Torino, Corso Duca degli Abruzzi 24, Turin, 10129, Italy
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Xie Y, Fu Y, Shao Y, Qu L, Yang J, Yang C, Zhou K, Li K, Xu Z, Xu D, Cao K, Tian N, Lv K, Wang L, Wang Y, Wang N, Li Y. Quantitative ultrasound image assessment of the optic nerve subarachnoid space during 90-day head-down tilt bed rest. NPJ Microgravity 2024; 10:9. [PMID: 38233425 PMCID: PMC10794463 DOI: 10.1038/s41526-024-00347-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 01/03/2024] [Indexed: 01/19/2024] Open
Abstract
The elevation in the optic nerve sheath (ONS) pressure (ONSP) due to microgravity-induced headward fluid shift is the primary hypothesized contributor to SANS. This longitudinal study aims to quantify the axial plane of the optic nerve subarachnoid space area (ONSSA), which is filled with cerebrospinal fluid (CSF) and expands with elevated ONSP during and after head-down tilt (HDT) bed rest (BR). 36 healthy male volunteers (72 eyes) underwent a 90-day strict 6° HDT BR. Without obtaining the pre-HDT data, measurements were performed on days 30, 60, and 90 during HDT and at 6 recovery time points extended to 180-days (R + 180) in a supine position. Portable B-scan ultrasound was performed using the 12 MHz linear array probe binocularly. The measurements of the ONS and the calculation of the ONSSA were performed with ImageJ 1.51 analysis software by two experienced observers in a masked manner. Compared to R + 180, the ONSSA on HDT30, HDT60, and HDT90 exhibited a consistently significant distention of 0.44 mm2 (95% CI: 0.13 to 0.76 mm2, P = 0.001), 0.45 mm2 (95% CI: 0.15 to 0.75 mm2, P = 0.001), and 0.46 mm2 (95% CI: 0.15 to 0.76 mm2, P < 0.001), respectively, and recovered immediately after HDT on R + 2. Such small changes in the ONSSA were below the lateral resolution limit of ultrasound (0.4 mm) and may not be clinically relevant, possibly due to ONS hysteresis causing persistent ONS distension. Future research can explore advanced quantitative portable ultrasound-based techniques and establish comparisons containing the pre-HDT measurements to deepen our understanding of SANS.
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Affiliation(s)
- Yuan Xie
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China
| | - Yingdi Fu
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China
| | - Yaqi Shao
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China
| | - Lina Qu
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Jiangang Yang
- Xi'an No.1 Hospital; Shanxi Institute of Ophthalmology; Shanxi Key Laboratory of Ophthalmology; Clinical Research Center for Ophthalmology Diseases of Shanxi Province; the First Affiliated Hospital of Northwestern University, Xi'an, 710002, Shanxi Province, China
| | - Chengjia Yang
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Kun Zhou
- Xi'an No.1 Hospital; Shanxi Institute of Ophthalmology; Shanxi Key Laboratory of Ophthalmology; Clinical Research Center for Ophthalmology Diseases of Shanxi Province; the First Affiliated Hospital of Northwestern University, Xi'an, 710002, Shanxi Province, China
| | - Kai Li
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Zi Xu
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Dong Xu
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Kai Cao
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China
| | - Ning Tian
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China
| | - Ke Lv
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Linjie Wang
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Yaping Wang
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Ningli Wang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China.
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China.
| | - Yinghui Li
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China.
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Caddy HT, Kelsey LJ, Parker LP, Green DJ, Doyle BJ. Modelling large scale artery haemodynamics from the heart to the eye in response to simulated microgravity. NPJ Microgravity 2024; 10:7. [PMID: 38218868 PMCID: PMC10787773 DOI: 10.1038/s41526-024-00348-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 01/03/2024] [Indexed: 01/15/2024] Open
Abstract
We investigated variations in haemodynamics in response to simulated microgravity across a semi-subject-specific three-dimensional (3D) continuous arterial network connecting the heart to the eye using computational fluid dynamics (CFD) simulations. Using this model we simulated pulsatile blood flow in an upright Earth gravity case and a simulated microgravity case. Under simulated microgravity, regional time-averaged wall shear stress (TAWSS) increased and oscillatory shear index (OSI) decreased in upper body arteries, whilst the opposite was observed in the lower body. Between cases, uniform changes in TAWSS and OSI were found in the retina across diameters. This work demonstrates that 3D CFD simulations can be performed across continuously connected networks of small and large arteries. Simulated results exhibited similarities to low dimensional spaceflight simulations and measured data-specifically that blood flow and shear stress decrease towards the lower limbs and increase towards the cerebrovasculature and eyes in response to simulated microgravity, relative to an upright position in Earth gravity.
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Affiliation(s)
- Harrison T Caddy
- Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia and the UWA Centre for Medical Research, The University of Western Australia, Perth, WA, Australia
- School of Human Sciences (Exercise and Sport Sciences), The University of Western Australia, Perth, WA, Australia
| | - Lachlan J Kelsey
- Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia and the UWA Centre for Medical Research, The University of Western Australia, Perth, WA, Australia
- School of Engineering, The University of Western Australia, Perth, WA, Australia
| | - Louis P Parker
- FLOW, Department of Engineering Mechanics, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Daniel J Green
- School of Human Sciences (Exercise and Sport Sciences), The University of Western Australia, Perth, WA, Australia
| | - Barry J Doyle
- Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia and the UWA Centre for Medical Research, The University of Western Australia, Perth, WA, Australia.
- School of Engineering, The University of Western Australia, Perth, WA, Australia.
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Ustick JJ, Pardon LP, Chettry P, Patel NB, Cheng H. Effects of head-down tilt on optic nerve sheath diameter in healthy subjects. Ophthalmic Physiol Opt 2023; 43:1531-1539. [PMID: 37401194 PMCID: PMC10592427 DOI: 10.1111/opo.13200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 06/19/2023] [Accepted: 06/20/2023] [Indexed: 07/05/2023]
Abstract
PURPOSE Intracranial pressure increases in head-down tilt (HDT) body posture. This study evaluated the effect of HDT on the optic nerve sheath diameter (ONSD) in normal subjects. METHODS Twenty six healthy adults (age 28 [4.7] years) participated in seated and 6° HDT visits. For each visit, subjects presented at 11:00 h for baseline seated scans and then maintained a seated or 6° HDT posture from 12:00 to 15:00 h. Three horizontal axial and three vertical axial scans were obtained at 11:00, 12:00 and 15:00 h with a 10 MHz ultrasonography probe on the same eye, randomly chosen per subject. At each time point, horizontal and vertical ONSD (mm) were quantified by averaging three measures taken 3 mm behind the globe. RESULTS In the seated visit, ONSDs were similar across time (p > 0.05), with an overall mean (standard deviation) of 4.71 (0.48) horizontally and 5.08 (0.44) vertically. ONSD was larger vertically than horizontally at each time point (p < 0.001). In the HDT visit, ONSD was significantly enlarged from baseline at 12:00 and 15:00 h (p < 0.001 horizontal and p < 0.05 vertical). Mean (standard error) horizontal ONSD change from baseline was 0.37 (0.07) HDT versus 0.10 (0.05) seated at 12:00 h (p = 0.002) and 0.41 (0.09) HDT versus 0.12 (0.06) seated at 15:00 h (p = 0.002); mean vertical ONSD change was 0.14 (0.07) HDT versus -0.07 (0.04) seated at 12:00 h (p = 0.02) and 0.19 (0.06) HDT versus -0.03 (0.04) seated at 15:00 h (p = 0.01). ONSD change in HDT was similar between 12:00 and 15:00 h (p ≥ 0.30). Changes at 12:00 h correlated with those at 15:00 h for horizontal (r = 0.78, p < 0.001) and vertical ONSD (r = 0.73, p < 0.001). CONCLUSION The ONSD increased when body posture transitioned from seated to HDT position without any further change at the end of the 3 h in HDT.
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Affiliation(s)
| | - Laura P. Pardon
- University of Houston, College of Optometry, Houston, Texas, USA
| | - Pratik Chettry
- University of Houston, College of Optometry, Houston, Texas, USA
| | - Nimesh B. Patel
- University of Houston, College of Optometry, Houston, Texas, USA
| | - Han Cheng
- University of Houston, College of Optometry, Houston, Texas, USA
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7
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Robin A, Van Ombergen A, Laurens C, Bergouignan A, Vico L, Linossier MT, Pavy-Le Traon A, Kermorgant M, Chopard A, Py G, Green DA, Tipton M, Choukér A, Denise P, Normand H, Blanc S, Simon C, Rosnet E, Larcher F, Fernandez P, de Glisezinski I, Larrouy D, Harant-Farrugia I, Antunes I, Gauquelin-Koch G, Bareille MP, Billette De Villemeur R, Custaud MA, Navasiolava N. Comprehensive assessment of physiological responses in women during the ESA dry immersion VIVALDI microgravity simulation. Nat Commun 2023; 14:6311. [PMID: 37813884 PMCID: PMC10562467 DOI: 10.1038/s41467-023-41990-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 09/26/2023] [Indexed: 10/11/2023] Open
Abstract
Astronauts in microgravity experience multi-system deconditioning, impacting their inflight efficiency and inducing dysfunctions upon return to Earth gravity. To fill the sex gap of knowledge in the health impact of spaceflights, we simulate microgravity with a 5-day dry immersion in 18 healthy women (ClinicalTrials.gov Identifier: NCT05043974). Here we show that dry immersion rapidly induces a sedentarily-like metabolism shift mimicking the beginning of a metabolic syndrome with a drop in glucose tolerance, an increase in the atherogenic index of plasma, and an impaired lipid profile. Bone remodeling markers suggest a decreased bone formation coupled with an increased bone resorption. Fluid shifts and muscular unloading participate to a marked cardiovascular and sensorimotor deconditioning with decreased orthostatic tolerance, aerobic capacity, and postural balance. Collected datasets provide a comprehensive multi-systemic assessment of dry immersion effects in women and pave the way for future sex-based evaluations of countermeasures.
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Affiliation(s)
- Adrien Robin
- Univ Angers, CRC, CHU Angers, Inserm, CNRS, MITOVASC, Equipe CARME, SFR ICAT, F-49000, Angers, France.
| | | | - Claire Laurens
- Institute of Metabolic and Cardiovascular Diseases, INSERM, Paul Sabatier University, UMR1297, Toulouse, France
| | - Audrey Bergouignan
- Anschutz Health and Wellness Center, Division of Endocrinology, University of Colorado, Aurora, CO, USA
| | - Laurence Vico
- INSERM, University Jean Monnet, Mines Saint-Etienne, U 1059, Saint Etienne, France
| | | | - Anne Pavy-Le Traon
- Department of Neurology, CHU Toulouse and I2MC-INSERM 1297, Toulouse, France
| | - Marc Kermorgant
- Department of Neurology, CHU Toulouse and I2MC-INSERM 1297, Toulouse, France
| | - Angèle Chopard
- DMEM, Montpellier University, INRAE, Montpellier, France
| | - Guillaume Py
- DMEM, Montpellier University, INRAE, Montpellier, France
| | - David Andrew Green
- Centre of Human and Applied Physiological Sciences, King's College London, London, UK
| | - Michael Tipton
- Extreme Environments Laboratory, School of Sport, Health and Exercise Science, University of Portsmouth, Portsmouth, PO1 2EF, UK
| | - Alexander Choukér
- Laboratory of Translational Research Stress and Immunity, Department of Anesthesiology, Hospital of the Ludwig-Maximilians-University (LUM), Munich, Germany
| | - Pierre Denise
- Université de Caen Normandie, Inserm, COMETE U1075, CYCERON, CHU de Caen, F-14000, Caen, France
| | - Hervé Normand
- Université de Caen Normandie, Inserm, COMETE U1075, CYCERON, CHU de Caen, F-14000, Caen, France
| | - Stéphane Blanc
- DEPE-IPHC - Département Ecologie, Physiologie et Ethologie, Strasbourg, France
| | - Chantal Simon
- CarMeN Laboratory, INSERM 1060, INRA 1397, University Claude Bernard Lyon1, Human Nutrition Research Center Rhône-Alpes, Oullins, France
| | - Elisabeth Rosnet
- Faculty of Sport Sciences, Université de Reims Champagne-Ardenne, Reims, France
| | | | - Peter Fernandez
- INSERM, University Jean Monnet, Mines Saint-Etienne, U 1059, Saint Etienne, France
| | - Isabelle de Glisezinski
- Institute of Metabolic and Cardiovascular Diseases, INSERM, Paul Sabatier University, UMR1297, Toulouse, France
| | - Dominique Larrouy
- Institute of Metabolic and Cardiovascular Diseases, INSERM, Paul Sabatier University, UMR1297, Toulouse, France
| | - Isabelle Harant-Farrugia
- Institute of Metabolic and Cardiovascular Diseases, INSERM, Paul Sabatier University, UMR1297, Toulouse, France
| | - Inês Antunes
- Telespazio Belgium S.R.L. for the European Space Agency, Noordwijk, The Netherlands
| | | | | | | | - Marc-Antoine Custaud
- Univ Angers, CRC, CHU Angers, Inserm, CNRS, MITOVASC, Equipe CARME, SFR ICAT, F-49000, Angers, France.
| | - Nastassia Navasiolava
- Univ Angers, CRC, CHU Angers, Inserm, CNRS, MITOVASC, Equipe CARME, SFR ICAT, F-49000, Angers, France.
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Ong J, Tarver W, Brunstetter T, Mader TH, Gibson CR, Mason SS, Lee A. Spaceflight associated neuro-ocular syndrome: proposed pathogenesis, terrestrial analogues, and emerging countermeasures. Br J Ophthalmol 2023; 107:895-900. [PMID: 36690421 PMCID: PMC10359702 DOI: 10.1136/bjo-2022-322892] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 12/11/2022] [Indexed: 01/25/2023]
Abstract
Spaceflight associated neuro-ocular syndrome (SANS) refers to a distinct constellation of ocular, neurological and neuroimaging findings observed in astronauts during and following long duration spaceflight. These ocular findings, to include optic disc oedema, posterior globe flattening, chorioretinal folds and hyperopic shifts, were first described by NASA in 2011. SANS is a potential risk to astronaut health and will likely require mitigation prior to planetary travel with prolonged exposures to microgravity. While the exact pathogenesis of SANS is not completely understood, several hypotheses have been proposed to explain this neuro-ocular phenomenon. In this paper, we briefly discuss the current hypotheses and contributing factors underlying SANS pathophysiology as well as analogues used to study SANS on Earth. We also review emerging potential countermeasures for SANS including lower body negative pressure, nutritional supplementation and translaminar pressure gradient modulation. Ongoing investigation within these fields will likely be instrumental in preparing and protecting astronaut vision for future spaceflight missions including deep space exploration.
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Affiliation(s)
- Joshua Ong
- Michigan Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | | | | | | | - C Robert Gibson
- KBR, NASA Space Medicine Operations Division, Houston, Texas, USA
- South Shore Eye Center, League City, Texas, USA
| | | | - Andrew Lee
- Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, Texas, USA
- Center for Space Medicine, Baylor College of Medicine, Houston, Texas, USA
- The Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
- Departments of Ophthalmology, Neurology, and Neurosurgery, Weill Cornell Medicine, New York, New York, USA
- Department of Ophthalmology, University of Texas Medical Branch, Galveston, Texas, USA
- University of Texas MD Anderson Cancer Center, Houston, Texas, USA
- Texas A&M College of Medicine, Bryan, Texas, USA
- Department of Ophthalmology, The University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
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Corydon TJ, Schulz H, Richter P, Strauch SM, Böhmer M, Ricciardi DA, Wehland M, Krüger M, Erzinger GS, Lebert M, Infanger M, Wise PM, Grimm D. Current Knowledge about the Impact of Microgravity on Gene Regulation. Cells 2023; 12:cells12071043. [PMID: 37048115 PMCID: PMC10093652 DOI: 10.3390/cells12071043] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 03/24/2023] [Accepted: 03/25/2023] [Indexed: 03/31/2023] Open
Abstract
Microgravity (µg) has a massive impact on the health of space explorers. Microgravity changes the proliferation, differentiation, and growth of cells. As crewed spaceflights into deep space are being planned along with the commercialization of space travelling, researchers have focused on gene regulation in cells and organisms exposed to real (r-) and simulated (s-) µg. In particular, cancer and metastasis research benefits from the findings obtained under µg conditions. Gene regulation is a key factor in a cell or an organism’s ability to sustain life and respond to environmental changes. It is a universal process to control the amount, location, and timing in which genes are expressed. In this review, we provide an overview of µg-induced changes in the numerous mechanisms involved in gene regulation, including regulatory proteins, microRNAs, and the chemical modification of DNA. In particular, we discuss the current knowledge about the impact of microgravity on gene regulation in different types of bacteria, protists, fungi, animals, humans, and cells with a focus on the brain, eye, endothelium, immune system, cartilage, muscle, bone, and various cancers as well as recent findings in plants. Importantly, the obtained data clearly imply that µg experiments can support translational medicine on Earth.
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Affiliation(s)
- Thomas J. Corydon
- Department of Biomedicine, Aarhus University, Hoegh Guldbergs Gade 10, 8000 Aarhus, Denmark
- Department of Ophthalmology, Aarhus University Hospital, Palle Juul-Jensens Blvd. 99, 8200 Aarhus, Denmark
- Correspondence: ; Tel.: +45-28-992-179
| | - Herbert Schulz
- Department of Microgravity and Translational Regenerative Medicine, Medical Faculty, University Hospital Magdeburg, Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany
- Clinic for Plastic, Aesthetic and Hand Surgery, Medical Faculty, University Hospital Magdeburg, Otto von Guericke University, Leipziger Straße 44, 39120 Magdeburg, Germany
- Research Group ‘Magdeburger Arbeitsgemeinschaft für Forschung unter Raumfahrt-und Schwerelosigkeitsbedingungen’ (MARS), Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany
| | - Peter Richter
- Gravitational Biology Group, Department of Biology, Friedrich-Alexander University, 91058 Erlangen, Germany
| | - Sebastian M. Strauch
- Postgraduate Program in Health and Environment, University of Joinville Region, Joinville 89219-710, SC, Brazil
| | - Maik Böhmer
- Institute for Molecular Biosciences, Johann Wolfgang Goethe Universität, 60438 Frankfurt am Main, Germany
| | - Dario A. Ricciardi
- Institute for Molecular Biosciences, Johann Wolfgang Goethe Universität, 60438 Frankfurt am Main, Germany
| | - Markus Wehland
- Department of Microgravity and Translational Regenerative Medicine, Medical Faculty, University Hospital Magdeburg, Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany
- Clinic for Plastic, Aesthetic and Hand Surgery, Medical Faculty, University Hospital Magdeburg, Otto von Guericke University, Leipziger Straße 44, 39120 Magdeburg, Germany
- Research Group ‘Magdeburger Arbeitsgemeinschaft für Forschung unter Raumfahrt-und Schwerelosigkeitsbedingungen’ (MARS), Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany
| | - Marcus Krüger
- Department of Microgravity and Translational Regenerative Medicine, Medical Faculty, University Hospital Magdeburg, Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany
- Research Group ‘Magdeburger Arbeitsgemeinschaft für Forschung unter Raumfahrt-und Schwerelosigkeitsbedingungen’ (MARS), Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany
| | - Gilmar S. Erzinger
- Postgraduate Program in Health and Environment, University of Joinville Region, Joinville 89219-710, SC, Brazil
| | - Michael Lebert
- Gravitational Biology Group, Department of Biology, Friedrich-Alexander University, 91058 Erlangen, Germany
| | - Manfred Infanger
- Department of Microgravity and Translational Regenerative Medicine, Medical Faculty, University Hospital Magdeburg, Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany
- Clinic for Plastic, Aesthetic and Hand Surgery, Medical Faculty, University Hospital Magdeburg, Otto von Guericke University, Leipziger Straße 44, 39120 Magdeburg, Germany
- Research Group ‘Magdeburger Arbeitsgemeinschaft für Forschung unter Raumfahrt-und Schwerelosigkeitsbedingungen’ (MARS), Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany
| | - Petra M. Wise
- Department of Microgravity and Translational Regenerative Medicine, Medical Faculty, University Hospital Magdeburg, Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany
- Research Group ‘Magdeburger Arbeitsgemeinschaft für Forschung unter Raumfahrt-und Schwerelosigkeitsbedingungen’ (MARS), Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany
- The Saban Research Institute, Children’s Hospital Los Angeles, University of Southern California, 4650 Sunset Blvd, Los Angeles, CA 90027, USA
| | - Daniela Grimm
- Department of Biomedicine, Aarhus University, Hoegh Guldbergs Gade 10, 8000 Aarhus, Denmark
- Department of Microgravity and Translational Regenerative Medicine, Medical Faculty, University Hospital Magdeburg, Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany
- Clinic for Plastic, Aesthetic and Hand Surgery, Medical Faculty, University Hospital Magdeburg, Otto von Guericke University, Leipziger Straße 44, 39120 Magdeburg, Germany
- Research Group ‘Magdeburger Arbeitsgemeinschaft für Forschung unter Raumfahrt-und Schwerelosigkeitsbedingungen’ (MARS), Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany
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10
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Subramanian PS. Spaceflight-Associated Neuro-Ocular Syndrome and Increased Intracranial Pressure-Are We Closer to Understanding the Relationship? JAMA Ophthalmol 2023; 141:176-177. [PMID: 36602792 DOI: 10.1001/jamaophthalmol.2022.5686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Prem S Subramanian
- Departments of Ophthalmology, Neurology, and Neurosurgery, Sue Anschutz-Rodgers University of Colorado Eye Center, University of Colorado School of Medicine, Aurora.,Division of Ophthalmology, Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, Maryland
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11
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Fall DA, Lee AG, Bershad EM, Kramer LA, Mader TH, Clark JB, Hirzallah MI. Optic nerve sheath diameter and spaceflight: defining shortcomings and future directions. NPJ Microgravity 2022; 8:42. [PMID: 36202836 PMCID: PMC9537149 DOI: 10.1038/s41526-022-00228-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 09/12/2022] [Indexed: 11/24/2022] Open
Abstract
Neuro-ocular changes during long-duration space flight are known as spaceflight-associated neuro-ocular syndrome (SANS). The ability to detect, monitor, and prevent SANS is a priority of current space medicine research efforts. Optic nerve sheath diameter (ONSD) measurement has been used both terrestrially and in microgravity as a proxy for measurements of elevated intracranial pressure. ONSD shows promise as a potential method of identifying and quantitating neuro-ocular changes during space flight. This review examines 13 studies measuring ONSD and its relationship to microgravity exposure or ground-based analogs, including head-down tilt, dry immersion, or animal models. The goal of this correspondence is to describe heterogeneity in the use of ONSD in the current SANS literature and make recommendations to reduce heterogeneity in future studies through standardization of imaging modalities, measurement techniques, and other aspects of study design.
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Affiliation(s)
- Dylan A Fall
- Baylor College of Medicine and The Center for Space Medicine, Houston, TX, USA
| | - Andrew G Lee
- Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, TX, USA.,Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, USA.,Department of Ophthalmology, Weill Cornell Medicine, New York, NY, USA.,Department of Ophthalmology, University of Texas Medical Branch, Galveston, TX, USA.,University of Texas MD Anderson Cancer Center, Houston, TX, USA.,Texas A and M College of Medicine, Bryan, TX, USA
| | - Eric M Bershad
- Baylor College of Medicine and The Center for Space Medicine, Houston, TX, USA.,Department of Neurology, Baylor College of Medicine, Houston, TX, USA
| | - Larry A Kramer
- Department of Diagnostic and Interventional Imaging, University of Texas Health Science Center, Houston, USA
| | | | - Jonathan B Clark
- Baylor College of Medicine and The Center for Space Medicine, Houston, TX, USA
| | - Mohammad I Hirzallah
- Baylor College of Medicine and The Center for Space Medicine, Houston, TX, USA. .,Department of Neurology, Baylor College of Medicine, Houston, TX, USA.
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12
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Jasien JV, Laurie SS, Lee SMC, Martin DS, Kemp DT, Ebert DJ, Ploutz-Snyder R, Marshall-Goebel K, Alferova IV, Sargsyan A, Danielson RW, Hargens AR, Dulchavsky SA, Stenger MB, Macias BR. Noninvasive indicators of intracranial pressure before, during, and after long-duration spaceflight. J Appl Physiol (1985) 2022; 133:721-731. [PMID: 35861522 PMCID: PMC9484990 DOI: 10.1152/japplphysiol.00625.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 06/27/2022] [Accepted: 07/18/2022] [Indexed: 11/22/2022] Open
Abstract
Weightlessness induces a cephalad shift of blood and cerebrospinal fluid that may increase intracranial pressure (ICP) during spaceflight, whereas lower body negative pressure (LBNP) may provide an opportunity to caudally redistribute fluids and lower ICP. To investigate the effects of spaceflight and LBNP on noninvasive indicators of ICP (nICP), we studied 13 crewmembers before and after spaceflight in seated, supine, and 15° head-down tilt postures, and at ∼45 and ∼150 days of spaceflight with and without 25 mmHg LBNP. We used four techniques to quantify nICP: cerebral and cochlear fluid pressure (CCFP), otoacoustic emissions (OAE), ultrasound measures of optic nerve sheath diameter (ONSD), and ultrasound-based internal jugular vein pressure (IJVp). On flight day 45, two nICP measures were lower than preflight supine posture [CCFP: mean difference -98.5 -nL (CI: -190.8 to -6.1 -nL), P = 0.037]; [OAE: -19.7° (CI: -10.4° to -29.1°), P < 0.001], but not significantly different from preflight seated measures. Conversely, ONSD was not different than any preflight posture, whereas IJVp was significantly greater than preflight seated measures [14.3 mmHg (CI: 10.1 to 18.5 mmHg), P < 0.001], but not significantly different than preflight supine measures. During spaceflight, acute LBNP application did not cause a significant change in nICP indicators. These data suggest that during spaceflight, nICP is not elevated above values observed in the seated posture on Earth. Invasive measures would be needed to provide absolute ICP values and more precise indications of ICP change during various phases of spaceflight.NEW & NOTEWORTHY The current study provides new evidence that intracranial pressure (ICP), as assessed with noninvasive measures, may not be elevated during long-duration spaceflight. In addition, the acute use of lower body negative pressure did not significantly reduce indicators of ICP during weightlessness.
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Affiliation(s)
| | | | | | | | - David T Kemp
- University College London, London, United Kingdom
| | | | | | | | - Irina V Alferova
- Russian Federation State Research Center Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
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13
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Holmlund P, Støverud KH, Eklund A. Mathematical modelling of the CSF system: effects of microstructures and posture on optic nerve subarachnoid space dynamics. Fluids Barriers CNS 2022; 19:67. [PMID: 36042452 PMCID: PMC9426285 DOI: 10.1186/s12987-022-00366-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 08/18/2022] [Indexed: 11/21/2022] Open
Abstract
Background The pressure difference between the eye and brain in upright postures may be affected by compartmentalization of the optic nerve subarachnoid space (ONSAS). Both pressure and deformation will depend on the microstructures of the ONSAS, and most likely also on ocular glymphatic clearance. Studying these factors could yield important knowledge regarding the translaminar pressure difference, which is suspected to play a role in normal-tension glaucoma. Methods A compartment model coupling the ONSAS with the craniospinal CSF system was used to investigate the effects of microstructures on the pressure transfer through the ONSAS during a posture change from supine to upright body postures. ONSAS distensibility was based on MRI measurements. We also included ocular glymphatic flow to investigate how local pressure gradients alter this flow with changes in posture. Results A compartmentalization of the ONSAS occurred in the upright posture, with ONSAS porosity (degree of microstructural content) affecting the ONSAS pressure (varying the supine/baseline porosity from 1.0 to 0.75 yielded pressures between − 5.3 and − 2 mmHg). Restricting the minimum computed porosity (occurring in upright postures) to 0.3 prevented compartmentalization, and the ONSAS pressure could equilibrate with subarachnoid space pressure (− 6.5 mmHg) in \documentclass[12pt]{minimal}
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\begin{document}$$\le$$\end{document}≤ 1 h. The ocular glymphatics analysis predicted that substantial intraocular-CSF flows could occur without substantial changes in the ONSAS pressure. The flow entering the ONSAS in supine position (both from the intraocular system and from the cranial subarachnoid space) exited the ONSAS through the optic nerve sheath, while in upright postures the flow through the ONSAS was redirected towards the cranial subarachnoid space. Conclusions Microstructures affect pressure transmission along the ONSAS, potentially contributing to ONSAS compartmentalization in upright postures. Different pathways for ocular glymphatic flow were predicted for different postures.
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Affiliation(s)
- Petter Holmlund
- Department of Radiation Sciences, Radiation Physics, Biomedical Engineering, Umeå University, 901 87, Umeå, Sweden.
| | - Karen-Helene Støverud
- Department of Radiation Sciences, Radiation Physics, Biomedical Engineering, Umeå University, 901 87, Umeå, Sweden.,Department of Health Research, SINTEF Digital, Trondheim, Norway
| | - Anders Eklund
- Department of Radiation Sciences, Radiation Physics, Biomedical Engineering, Umeå University, 901 87, Umeå, Sweden.,Umeå Center for Functional Brain Imaging, Umeå University, 901 87, Umeå, Sweden
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14
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Yu JJ, Non AL, Heinrich EC, Gu W, Alcock J, Moya EA, Lawrence ES, Tift MS, O'Brien KA, Storz JF, Signore AV, Khudyakov JI, Milsom WK, Wilson SM, Beall CM, Villafuerte FC, Stobdan T, Julian CG, Moore LG, Fuster MM, Stokes JA, Milner R, West JB, Zhang J, Shyy JY, Childebayeva A, Vázquez-Medina JP, Pham LV, Mesarwi OA, Hall JE, Cheviron ZA, Sieker J, Blood AB, Yuan JX, Scott GR, Rana BK, Ponganis PJ, Malhotra A, Powell FL, Simonson TS. Time Domains of Hypoxia Responses and -Omics Insights. Front Physiol 2022; 13:885295. [PMID: 36035495 PMCID: PMC9400701 DOI: 10.3389/fphys.2022.885295] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Accepted: 05/24/2022] [Indexed: 02/04/2023] Open
Abstract
The ability to respond rapidly to changes in oxygen tension is critical for many forms of life. Challenges to oxygen homeostasis, specifically in the contexts of evolutionary biology and biomedicine, provide important insights into mechanisms of hypoxia adaptation and tolerance. Here we synthesize findings across varying time domains of hypoxia in terms of oxygen delivery, ranging from early animal to modern human evolution and examine the potential impacts of environmental and clinical challenges through emerging multi-omics approaches. We discuss how diverse animal species have adapted to hypoxic environments, how humans vary in their responses to hypoxia (i.e., in the context of high-altitude exposure, cardiopulmonary disease, and sleep apnea), and how findings from each of these fields inform the other and lead to promising new directions in basic and clinical hypoxia research.
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Affiliation(s)
- James J. Yu
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Amy L. Non
- Department of Anthropology, Division of Social Sciences, University of California, San Diego, La Jolla, CA, United States,*Correspondence: Amy L. Non, Tatum S. Simonson,
| | - Erica C. Heinrich
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, CA, United States
| | - Wanjun Gu
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States,Herbert Wertheim School of Public Health and Longevity Sciences, University of California, San Diego, La Jolla, CA, United States
| | - Joe Alcock
- Department of Emergency Medicine, University of New Mexico, Albuquerque, MX, United States
| | - Esteban A. Moya
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Elijah S. Lawrence
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Michael S. Tift
- Department of Biology and Marine Biology, College of Arts and Sciences, University of North Carolina Wilmington, Wilmington, NC, United States
| | - Katie A. O'Brien
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States,Department of Physiology, Development and Neuroscience, Faculty of Biology, School of Biological Sciences, University of Cambridge, Cambridge, ENG, United Kingdom
| | - Jay F. Storz
- School of Biological Sciences, College of Arts and Sciences, University of Nebraska-Lincoln, Lincoln, IL, United States
| | - Anthony V. Signore
- School of Biological Sciences, College of Arts and Sciences, University of Nebraska-Lincoln, Lincoln, IL, United States
| | - Jane I. Khudyakov
- Department of Biological Sciences, University of the Pacific, Stockton, CA, United States
| | | | - Sean M. Wilson
- Lawrence D. Longo, MD Center for Perinatal Biology, Loma Linda, CA, United States
| | | | | | | | - Colleen G. Julian
- School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Lorna G. Moore
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, Aurora, CO, United States
| | - Mark M. Fuster
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Jennifer A. Stokes
- Department of Kinesiology, Southwestern University, Georgetown, TX, United States
| | - Richard Milner
- San Diego Biomedical Research Institute, San Diego, CA, United States
| | - John B. West
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Jiao Zhang
- Department of Medicine, UC San Diego School of Medicine, San Diego, CA, United States
| | - John Y. Shyy
- Department of Medicine, UC San Diego School of Medicine, San Diego, CA, United States
| | - Ainash Childebayeva
- Department of Archaeogenetics, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - José Pablo Vázquez-Medina
- Department of Integrative Biology, College of Letters and Science, University of California, Berkeley, Berkeley, CA, United States
| | - Luu V. Pham
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, School of Medicine, Johns Hopkins Medicine, Baltimore, MD, United States
| | - Omar A. Mesarwi
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - James E. Hall
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Zachary A. Cheviron
- Division of Biological Sciences, College of Humanities and Sciences, University of Montana, Missoula, MT, United States
| | - Jeremy Sieker
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Arlin B. Blood
- Department of Pediatrics Division of Neonatology, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Jason X. Yuan
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Graham R. Scott
- Department of Pediatrics Division of Neonatology, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Brinda K. Rana
- Moores Cancer Center, UC San Diego, La Jolla, CA, United States,Department of Psychiatry, UC San Diego, La Jolla, CA, United States
| | - Paul J. Ponganis
- Center for Marine Biotechnology and Biomedicine, La Jolla, CA, United States
| | - Atul Malhotra
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Frank L. Powell
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Tatum S. Simonson
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA, United States,*Correspondence: Amy L. Non, Tatum S. Simonson,
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15
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Félix H, Oliveira ES. Non-Invasive Intracranial Pressure Monitoring and Its Applicability in Spaceflight. Aerosp Med Hum Perform 2022; 93:517-531. [DOI: 10.3357/amhp.5922.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
INTRODUCTION: Neuro-ophthalmic findings collectively defined as Spaceflight-Associated Neuro-ocular Syndrome (SANS) are one of the leading health priorities in astronauts engaging in long duration spaceflight or prolonged microgravity exposure. Though multifactorial in etiology,
similarities to terrestrial idiopathic intracranial hypertension (IIH) suggest these changes may result from an increase or impairing in intracranial pressure (ICP). Finding a portable, accessible, and reliable method of monitoring ICP is, therefore, crucial in long duration spaceflight. A
review of recent literature was conducted on the biomedical literature search engine PubMed using the search term “non-invasive intracranial pressure”. Studies investigating accuracy of noninvasive and portable methods were assessed. The search retrieved different methods that
were subsequently grouped by approach and technique. The majority of publications included the use of ultrasound-based methods with variable accuracies. One of which, noninvasive ICP estimation by optical nerve sheath diameter measurement (nICP_ONSD), presented the highest statistical correlation
and prediction values to invasive ICP, with area under the curve (AUC) ranging from 0.75 to 0.964. One study even considers a combination of ONSD with transcranial Doppler (TCD) for an even higher performance. Other methods, such as near-infrared spectroscopy (NIRS), show positive and promising
results [good statistical correlation with invasive techniques when measuring cerebral perfusion pressure (CPP): r = 0.83]. However, for its accessibility, portability, and accuracy, ONSD seems to present itself as the up to date, most reliable, noninvasive ICP surrogate and a valuable spaceflight
asset.Félix H, Santos Oliveira E. Non-invasive intracranial pressure monitoring and its applicability in spaceflight. Aerosp Med Hum Perform. 2022; 93(6):517–531.
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16
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Wostyn P, Mader TH, Gibson CR, Nedergaard M. Does Long-Duration Exposure to Microgravity Lead to Dysregulation of the Brain and Ocular Glymphatic Systems? Eye Brain 2022; 14:49-58. [PMID: 35546965 PMCID: PMC9081191 DOI: 10.2147/eb.s354710] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 04/27/2022] [Indexed: 02/05/2023] Open
Abstract
Spaceflight-associated neuro-ocular syndrome (SANS) has been well documented in astronauts both during and after long-duration spaceflight and is characterized by the development of optic disc edema, globe flattening, choroidal folds, and hyperopic refractive error shifts. The exact mechanisms underlying these ophthalmic abnormalities remain unclear. New findings regarding spaceflight-associated alterations in cerebrospinal fluid spaces, specifically perivascular spaces, may shed more light on the pathophysiology of SANS. The preliminary results of a recent brain magnetic resonance imaging study show that perivascular spaces enlarge under prolonged microgravity conditions, and that the amount of fluid in perivascular spaces is linked to SANS. The exact pathophysiological mechanisms underlying enlargement of perivascular spaces in space crews are currently unclear. Here, we speculate that the dilation of perivascular spaces observed in long-duration space travelers may result from impaired cerebral venous outflow and compromised cerebrospinal fluid resorption, leading to obstruction of glymphatic perivenous outflow and increased periarterial cerebrospinal fluid inflow, respectively. Further, we provide a possible explanation for how dilated perivascular spaces can be associated with SANS. Given that enlarged perivascular spaces in space crews may be a marker of altered venous hemodynamics and reduced cerebrospinal fluid outflow, at the level of the optic nerve and eye, these disturbances may contribute to SANS. If confirmed by further studies, brain glymphatic dysfunction in space crews could potentially be considered a risk factor for the development of neurodegenerative diseases, such as Alzheimer’s disease. Furthermore, long-duration exposure to microgravity might contribute to SANS through dysregulation of the ocular glymphatic system. If prolonged spaceflight exposure causes disruption of the glymphatic systems, this might affect the ability to conduct future exploration missions, for example, to Mars. The considerations outlined in the present paper further stress the crucial need to develop effective long-term countermeasures to mitigate SANS-related physiologic changes during long-duration spaceflight.
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Affiliation(s)
- Peter Wostyn
- Department of Psychiatry, PC Sint-Amandus, Beernem, Belgium
- Correspondence: Peter Wostyn, Department of Psychiatry, PC Sint-Amandus, Reigerlostraat 10, Beernem, 8730, Belgium, Tel +32-472713719, Fax +32-50-819720, Email
| | | | - Charles Robert Gibson
- Coastal Eye Associates, Webster, TX, USA
- KBR, NASA Space Medicine Operations Division, Houston, TX, USA
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, USA
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17
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Ong J, Tavakkoli A, Strangman G, Zaman N, Kamran SA, Zhang Q, Ivkovic V, Lee AG. Neuro-ophthalmic Imaging and Visual Assessment Technology for Spaceflight Associated Neuro-ocular Syndrome (SANS). Surv Ophthalmol 2022; 67:1443-1466. [DOI: 10.1016/j.survophthal.2022.04.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 04/15/2022] [Accepted: 04/18/2022] [Indexed: 12/11/2022]
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18
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Petersen LG, Whittle RS, Lee JH, Sieker J, Carlson J, Finke C, Shelton CM, Petersen JCG, Diaz-Artiles A. Gravitational effects on intraocular pressure and ocular perfusion pressure. J Appl Physiol (1985) 2022; 132:24-35. [PMID: 34762525 DOI: 10.1152/japplphysiol.00546.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Changes in the gravitational vector by postural changes or weightlessness induce fluid shifts, impacting ocular hemodynamics and regional pressures. This investigation explores the impact of changes in the direction of the gravitational vector on intraocular pressure (IOP), mean arterial pressure at eye level (MAPeye), and ocular perfusion pressure (OPP), which is critical for ocular health. Thirteen subjects underwent 360° of tilt (including both prone and supine positions) at 15° increments. At each angle, steady-state IOP and MAPeye were measured, and OPP calculated as MAPeye - IOP. Experimental data were also compared to a six-compartment lumped-parameter model of the eye. Mean IOP, MAPeye, and OPP significantly increased from 0° supine to 90° head-down tilt (HDT) by 20.7 ± 1.7 mmHg (P < 0.001), 38.5 ± 4.1 mmHg (P < 0.001), and 17.4 ± 3.2 mmHg (P < 0.001), respectively. Head-up tilt (HUT) significantly decreased OPP by 16.5 ± 2.5 mmHg (P < 0.001). IOP was significantly higher in prone versus supine position for much of the tilt range. Our study indicates that OPP is highly gravitationally dependent. Specifically, data show that MAPeye is more gravitationally dependent than IOP, thus causing OPP to increase during HDT and to decrease during HUT. In addition, IOP was elevated in prone position compared with supine position due to the additional hydrostatic column between the base of the rostral globe to the mid-coronal plane, supporting the notion that hydrostatic forces play an important role in ocular hemodynamics. Changes in OPP as a function of changes in gravitational stress and/or weightlessness may play a role in the pathogenesis of spaceflight-associated neuro-ocular syndrome.NEW & NOTEWORTHY Maintaining appropriate ocular perfusion pressure (OPP) is critical for ocular health. We measured the relative changes in intraocular and mean arterial pressures during 360° tilt and calculated OPP, which was elevated during head-down tilt and decreased during head-up tilt. Experimental data are also explained by our computational model. We demonstrate that OPP is more gravitationally dependent than previously recognized and may be a factor in the overall patho-etiology behind the weightlessness-induced spaceflight-associated neuro-ocular syndrome.
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Affiliation(s)
- Lonnie G Petersen
- Mechanical and Aerospace Engineering, Jacobs School of Engineering, University of California, San Diego, California.,Department of Radiology, School of Medicine, University of California, San Diego, California
| | - Richard S Whittle
- Department of Aerospace Engineering, Texas A&M University, College Station, Texas
| | - Justin H Lee
- Department of Radiology, School of Medicine, University of California, San Diego, California
| | - Jeremy Sieker
- Department of Radiology, School of Medicine, University of California, San Diego, California
| | - Joseph Carlson
- Department of Aerospace Engineering, Texas A&M University, College Station, Texas
| | - Colton Finke
- Department of Aerospace Engineering, Texas A&M University, College Station, Texas
| | - Cody M Shelton
- Department of Aerospace Engineering, Texas A&M University, College Station, Texas
| | - Johan C G Petersen
- Department of Anesthesiology, UC-Health, University of California, San Diego, California
| | - Ana Diaz-Artiles
- Department of Aerospace Engineering, Texas A&M University, College Station, Texas.,Department of Health and Kinesiology, Texas A&M University, College Station, Texas
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19
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Hearon CM, Dias KA, Babu G, Marshall JET, Leidner J, Peters K, Silva E, MacNamara JP, Campain J, Levine BD. Effect of Nightly Lower Body Negative Pressure on Choroid Engorgement in a Model of Spaceflight-Associated Neuro-ocular Syndrome: A Randomized Crossover Trial. JAMA Ophthalmol 2021; 140:59-65. [PMID: 34882176 DOI: 10.1001/jamaophthalmol.2021.5200] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Importance Astronauts returning from long-duration spaceflight experience ocular remodeling related to cephalad fluid shifts induced by microgravity. It is hypothesized that the absence of diurnal reductions in intracranial pressure in microgravity creates a low but persistent pressure gradient at the posterior aspect of the eye, which results in ocular remodeling and space-associated neuro-ocular syndrome (SANS) over many months. Objective To determine whether partial reintroduction of footward fluid shifts during simulated microgravity via lower body negative pressure (LBNP) during sleep attenuates choroid engorgement, an early marker of ocular remodeling related to SANS. Design, Setting, and Participants Between May 2019 and February 2020, participants with no major cardiovascular, kidney, or ophthalmic disease completed 3 days of supine (0°) bed rest with and 3 days without 8 hours of nightly LBNP in a randomized, crossover design. This single-center investigation took place at the UT Southwestern Medical Center. All analyses were conducted blinded to condition and time point. Interventions Eight hours of nightly LBNP (-20 mm Hg) vs no LBNP. Main Outcomes and Measures The primary outcome was the change in choroid area and volume after 3 days of bed rest measured by optical coherence tomography. Results Of 10 participants, 5 were female, the mean (SD) age was 29 (9) years, and the age range was 18 to 55 years. Central venous pressure increased from the seated to supine position (mean [SD], seated: -2.3 [2.0] vs supine: 6.9 [2.0] mm Hg; P < .001), leading to choroid engorgement over 3 days of bed rest (Δ area: +0.09 mm2 [95% CI, 0.04-0.13]; P = .001; Δ volume: +0.37 mm3 [95% CI, 0.19-0.55]; P = .001). Nightly LBNP caused a sustained reduction in supine central venous pressure (mean [SD], 5.7 [2.2] mm Hg to 1.2 [1.4 mm Hg]; P < .001) and attenuated the increase in choroid area (74%) (Δ: 0.02 mm2 [95% -0.02 to 0.06]; P = .01) and volume (53%) (Δ: 0.17 mm3 [95% CI, 0.01-0.34]; P = .05) compared with control. Conclusions and Relevance Nightly LBNP reinstated a footward fluid shift and mitigated the increase in choroid area and volume. LBNP during sleep may be an effective countermeasure for ocular remodeling and SANS during long-duration space missions.
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Affiliation(s)
- Christopher M Hearon
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas.,University of Texas Southwestern Medical Center, Dallas
| | - Katrin A Dias
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas.,University of Texas Southwestern Medical Center, Dallas
| | - Gautam Babu
- University of Texas Southwestern Medical Center, Dallas
| | | | - James Leidner
- Internal Medicine, Texas Health Presbyterian Hospital Dallas, Dallas
| | - Kirsten Peters
- University Medical Center, Radboud University, Nijmegen, the Netherlands
| | - Erika Silva
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas
| | - James P MacNamara
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas.,University of Texas Southwestern Medical Center, Dallas
| | | | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas.,University of Texas Southwestern Medical Center, Dallas
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20
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Mlinar T, Jaki Mekjavic P, Royal JT, Valencic T, Mekjavic IB. Intraocular pressure during handgrip exercise: The effect of posture and hypercapnia in young males. Physiol Rep 2021; 9:e15035. [PMID: 34665531 PMCID: PMC8525324 DOI: 10.14814/phy2.15035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 08/10/2021] [Accepted: 08/22/2021] [Indexed: 11/25/2022] Open
Abstract
PURPOSE As part of our investigations of intraocular pressure (IOP) as a potential contributing factor to the spaceflight-associated neuro-ocular syndrome using the 6° head-down tilt (6°HDT) bed rest experimental model, we compared the effect of rest and isometric exercise in prone and supine 6°HDT positions on IOP with that observed in the seated position. METHODS Ten male volunteers (age = 22.5 ± 3.1 yrs) participated in six interventions. All trials comprised a 10-min rest period, a 3-min isometric handgrip exercise at 30% of participant's maximum, and a 10-min recovery period. The trials were conducted under normocapnic (NCAP) or hypercapnic (FI CO2 = 0.01; HCAP) conditions, the latter mimicking the ambient conditions on the International Space Station. IOP, systolic and diastolic pressures, and heart rate (HR) were measured during the trials. RESULTS Isometric exercise-induced elevations in HR and mean arterial blood pressure. IOP in the prone 6°HDT position was significantly higher (p < 0.001) compared to IOP in supine 6°HDT position and seated trials at all time points. IOP increased with exercise only in a seated HCAP trial (p = 0.042). No difference was observed between trials in NCAP and HCAP. IOP in the prone 6°HDT position was constantly elevated above 21 mmHg, the lower limit for clinical ocular hypertension. CONCLUSIONS IOP in the prone 6°HDT position was similar to IOP reported in astronauts upon entering microgravity, potentially indicating that prone, rather than supine 6°HDT position might be a more suitable experimental analog for investigating the acute ocular changes that occur in microgravity.
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Affiliation(s)
- Tinkara Mlinar
- Department of Automation, Biocybernetics and RoboticsJozef Stefan InstituteLjubljanaSlovenia
- Jozef Stefan International Postgraduate SchoolLjubljanaSlovenia
| | - Polona Jaki Mekjavic
- Department of Automation, Biocybernetics and RoboticsJozef Stefan InstituteLjubljanaSlovenia
- Eye HospitalUniversity Medical CentreLjubljanaSlovenia
- Faculty of MedicineUniversity of LjubljanaLjubljanaSlovenia
| | - Joshua T. Royal
- Department of Automation, Biocybernetics and RoboticsJozef Stefan InstituteLjubljanaSlovenia
- Jozef Stefan International Postgraduate SchoolLjubljanaSlovenia
| | - Tamara Valencic
- Department of Automation, Biocybernetics and RoboticsJozef Stefan InstituteLjubljanaSlovenia
| | - Igor B. Mekjavic
- Department of Automation, Biocybernetics and RoboticsJozef Stefan InstituteLjubljanaSlovenia
- Department of Biomedical Physiology and KinesiologySimon Fraser UniversityBurnabyBritish ColumbiaCanada
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21
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Abstract
History books are rife with examples of the role of nutrition in determining either the success or the failure of human exploration on Earth. With planetary exploration in our future, it is imperative that we understand the role of nutrition in optimizing health before humans can safely take the next giant leaps in space exploration.
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Affiliation(s)
- Scott M Smith
- Human Health and Performance Directorate, NASA Johnson Space Center, Houston, Texas
| | - Sara R Zwart
- University of Texas Medical Branch, Galveston, Texas
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22
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Özelbaykal B, Öğretmenoğlu G, Tunçez IH. Ocular Outcomes in Healthy Subjects Undergoing a Short-Term Head-Down Tilt Test. Aerosp Med Hum Perform 2021; 92:619-626. [PMID: 34728026 DOI: 10.3357/amhp.5804.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
PURPOSE: This study aimed to examine the effect of head-down tilt (HDT) on vascular autoregulation in different age groups and determine its effects on intraocular pressure (IOP) and central corneal thickness (CCT).METHODS: Included were 43 eyes of 23 men. The optic nerve head and parafoveal vascular densities were measured by optical coherence tomography angiography before and after 20 min 10 HDT. Also, the study comprised an examination of the IOP and CCT in a subset of 8 participants (14 eyes) in the sitting position and during 15 min of 10 HDT.RESULTS: Grid-based inside disc all-vessel density (GBID) was statistically significantly lower after the HDT test in subjects under 30 yr (1.26). Whole image and peripapillary capillary vessel density (WICVD, PCVD), and whole image and peripapillary all-vessel density (WIAVD, PAVD) were significantly higher after the HDT test in subjects ages 30-39 yr (1.34, 2.16, 1.05, 1.72, respectively). Inside disc capillary, all-vessel density (IDCVD, IDAVD) and GBID were significantly higher after HDT in subjects over 40 yr (2.48, 2.15, 1.52, respectively). In a subset of eight participants, IOP was significantly higher (3.7 mmHg) and CCT was unchanged after 15 min of HDT.CONCLUSION: Our study showed that simulated microgravity induced optic nerve head vessel density at the inside disc area, especially in persons over 40 years. In addition, IOP was increased by HDT, although no change in CCT was observed.Özelbaykal B, Öğretmenoğlu G, Tunçez I.H. Ocular outcomes in healthy subjects undergoing a short-term head-down tilt test. Aerosp Med Hum Perform. 2021; 92(8):619-626.
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Affiliation(s)
| | - Gökhan Öğretmenoğlu
- Department of Ophthalmology, University of Health Sciences, Adana City Training and Research Hospital, Adana, Turkey
| | - I. Hakki Tunçez
- Department of Health Sciences, Konya Provincial Health Directorate, Konya, Turkey
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23
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Greenwald SH, Macias BR, Lee SMC, Marshall-Goebel K, Ebert DJ, Liu JHK, Ploutz-Snyder RJ, Alferova IV, Dulchavsky SA, Hargens AR, Stenger MB, Laurie SS. Intraocular pressure and choroidal thickness respond differently to lower body negative pressure during spaceflight. J Appl Physiol (1985) 2021; 131:613-620. [PMID: 34166098 DOI: 10.1152/japplphysiol.01040.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Spaceflight-associated neuro-ocular syndrome (SANS) develops during long-duration (>1 mo) spaceflight presumably because of chronic exposure to a headward fluid shift that occurs in weightlessness. We aimed to determine whether reversing this headward fluid shift with acute application of lower body negative pressure (LBNP) can influence outcome measures at the eye. Intraocular pressure (IOP) and subfoveal choroidal thickness were therefore evaluated by tonometry and optical coherence tomography (OCT), respectively, in 14 International Space Station crewmembers before flight in the seated, supine, and 15° head-down tilt (HDT) postures and during spaceflight, without and with application of 25 mmHg LBNP. IOP in the preflight seated posture was 14.4 mmHg (95% CI, 13.5-15.2 mmHg), and spaceflight elevated this value by 1.3 mmHg (95% CI, 0.7-1.8 mmHg, P < 0.001). Acute exposure to LBNP during spaceflight reduced IOP to 14.2 mmHg (95% CI, 13.4-15.0 mmHg), which was equivalent to that of the seated posture (P > 0.99), indicating that venous fluid redistribution by LBNP can influence ocular outcome variables during spaceflight. Choroidal thickness during spaceflight (374 µm, 95% CI, 325-423 µm) increased by 35 µm (95% CI, 25-45 µm, P < 0.001), compared with the preflight seated posture (339 µm, 95% CI, 289-388 µm). Acute use of LBNP during spaceflight did not affect choroidal thickness (381 µm, 95% CI, 331-430 µm, P = 0.99). The finding that transmission of reduced venous pressure by LBNP did not decrease choroidal thickness suggests that engorgement of this tissue during spaceflight may reflect changes that are secondary to the chronic cerebral venous congestion associated with spaceflight.NEW & NOTEWORTHY Spaceflight induces a chronic headward fluid shift that is believed to underlie ocular changes observed in astronauts. The present study demonstrates, for the first time, that reversing this headward fluid shift via application of lower body negative pressure (LBNP) during spaceflight may alter the ocular venous system, as evidenced by a decrease in intraocular pressure. This finding indicates that LBNP has the potential to be an effective countermeasure against the headward fluid shift during spaceflight, which may then be beneficial in preventing or reversing associated ocular changes.
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Affiliation(s)
| | - Brandon R Macias
- National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas
| | | | | | | | - John H K Liu
- Shiley Eye Institute, University of California, San Diego, California
| | - Robert J Ploutz-Snyder
- Applied Biostatistics Laboratory, School of Nursing, University of Michigan, Ann Arbor, Michigan
| | - Irina V Alferova
- Russian Federation State Research Center Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
| | | | - Alan R Hargens
- Altman Clinical and Translational Research Institute, University of California, San Diego, California
| | - Michael B Stenger
- National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas
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24
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Spaide RF, Gemmy Cheung CM, Matsumoto H, Kishi S, Boon CJF, van Dijk EHC, Mauget-Faysse M, Behar-Cohen F, Hartnett ME, Sivaprasad S, Iida T, Brown DM, Chhablani J, Maloca PM. Venous overload choroidopathy: A hypothetical framework for central serous chorioretinopathy and allied disorders. Prog Retin Eye Res 2021; 86:100973. [PMID: 34029721 DOI: 10.1016/j.preteyeres.2021.100973] [Citation(s) in RCA: 122] [Impact Index Per Article: 40.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 05/11/2021] [Accepted: 05/15/2021] [Indexed: 12/19/2022]
Abstract
In central serous chorioretinopathy (CSC), the macula is detached because of fluid leakage at the level of the retinal pigment epithelium. The fluid appears to originate from choroidal vascular hyperpermeability, but the etiology for the fluid is controversial. The choroidal vascular findings as elucidated by recent optical coherence tomography (OCT) and wide-field indocyanine green (ICG) angiographic evaluation show eyes with CSC have many of the same venous patterns that are found in eyes following occlusion of the vortex veins or carotid cavernous sinus fistulas (CCSF). The eyes show delayed choroidal filling, dilated veins, intervortex venous anastomoses, and choroidal vascular hyperpermeability. While patients with occlusion of the vortex veins or CCSF have extraocular abnormalities accounting for the venous outflow problems, eyes with CSC appear to have venous outflow abnormalities as an intrinsic phenomenon. Control of venous outflow from the eye involves a Starling resistor effect, which appears to be abnormal in CSC. Similar choroidal vascular abnormalities have been found in peripapillary pachychoroid syndrome. However, peripapillary pachychoroid syndrome has intervortex venous anastomoses located in the peripapillary region while in CSC these are seen to be located in the macular region. Spaceflight associated neuro-ocular syndrome appears to share many of the pathophysiologic problems of abnormal venous outflow from the choroid along with a host of associated abnormalities. These diseases vary according to their underlying etiologies but are linked by the venous decompensation in the choroid that leads to significant vision loss. Choroidal venous overload provides a unifying concept and theory for an improved understanding of the pathophysiology and classification of a group of diseases to a greater extent than previous proposals.
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Affiliation(s)
- Richard F Spaide
- Vitreous, Retina, Macula Consultants of New York, New York, NY, USA.
| | | | - Hidetaka Matsumoto
- Department of Ophthalmology, Gunma University Graduate School of Medicine, Japan.
| | | | - Camiel J F Boon
- Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands.
| | - Elon H C van Dijk
- Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands.
| | | | | | | | | | | | | | - Jay Chhablani
- University of Pittsburgh, UPMC Eye Center, Pittsburgh, PA, USA.
| | - Peter M Maloca
- Institute of Molecular and Clinical Ophthalmology Basel, Basel, Switzerland.
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25
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Chen Z, Stanbouly S, Nishiyama NC, Chen X, Delp MD, Qiu H, Mao XW, Wang C. Spaceflight decelerates the epigenetic clock orchestrated with a global alteration in DNA methylome and transcriptome in the mouse retina. PRECISION CLINICAL MEDICINE 2021; 4:93-108. [PMID: 34179686 PMCID: PMC8220224 DOI: 10.1093/pcmedi/pbab012] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 04/27/2021] [Accepted: 05/13/2021] [Indexed: 01/30/2023] Open
Abstract
Astronauts exhibit an assortment of clinical abnormalities in their eyes during long-duration spaceflight. The purpose of this study was to determine whether spaceflight induces epigenomic and transcriptomic reprogramming in the retina or alters the epigenetic clock. The mice were flown for 37 days in animal enclosure modules on the International Space Station; ground-based control animals were maintained under similar housing conditions. Mouse retinas were isolated and both DNA methylome and transcriptome were determined by deep sequencing. We found that a large number of genes were differentially methylated with spaceflight, whereas there were fewer differentially expressed genes at the transcriptome level. Several biological pathways involved in retinal diseases such as macular degeneration were significantly altered. Our results indicated that spaceflight decelerated the retinal epigenetic clock. This study demonstrates that spaceflight impacts the retina at the epigenomic and transcriptomic levels, and such changes could be involved in the etiology of eye-related disorders among astronauts.
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Affiliation(s)
- Zhong Chen
- Center for Genomics, School of Medicine, Loma Linda University, Loma Linda, CA 92350, USA
| | - Seta Stanbouly
- Center for Genomics, School of Medicine, Loma Linda University, Loma Linda, CA 92350, USA
| | - Nina C Nishiyama
- Division of Radiation Research, Department of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, CA 92354, USA
| | - Xin Chen
- Center for Genomics, School of Medicine, Loma Linda University, Loma Linda, CA 92350, USA
| | - Michael D Delp
- Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, FL 32306, USA
| | - Hongyu Qiu
- Center for Molecular and Translational Medicine, Institute of Biomedical Science, Georgia State University, Atlanta, GA 30303, USA
| | - Xiao W Mao
- Division of Radiation Research, Department of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, CA 92354, USA
| | - Charles Wang
- Center for Genomics, School of Medicine, Loma Linda University, Loma Linda, CA 92350, USA
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26
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Pardon LP, Cheng H, Chettry P, Patel NB. Optic Nerve Head Morphological Changes Over 12 Hours in Seated and Head-Down Tilt Postures. Invest Ophthalmol Vis Sci 2021; 61:21. [PMID: 33186468 PMCID: PMC7671873 DOI: 10.1167/iovs.61.13.21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Purpose The purpose of this study was to determine changes in optic nerve head (ONH) morphology in seated and 6° head-down tilt (HDT) postures over a 12-hour period. Methods Thirty eyes of 30 healthy human subjects (15 females) were included. Composite radial and circular optical coherence tomography (OCT) scans centered on the ONH, intraocular pressure (IOP), and optic nerve sheath diameter (ONSD) were acquired every two hours from 7 a.m. to 7 p.m. for both seated (n = 30) and HDT (n = 10) sessions. Global minimum rim width (BMO-MRW), total retinal thickness (TRT), retinal nerve fiber layer thickness (RNFLT), and Bruch's membrane opening (BMO) height were quantified. Results BMO-MRW decreased an average of 9.55 ± 8.03 µm (P < 0.01) over 12 hours in a seated position (range, -26.64 to +3.36 µm), and thinning was greater in females (-13.56 vs. -5.55 µm, P = 0.004). Modest decreases in TRT from the BMO to 500 µm (P < 0.04) and RNFLT for the 2.7, 3.5, and 4.2 mm circular scans (P < 0.02) were also observed. BMO-MRW thinning was not related to changes in IOP or ONSD (P = 0.34). In HDT, IOP and ONSD increased, BMO height moved anteriorly, and BMO-MRW thinning did not occur (P > 0.1). Conclusions The neuroretinal rim thins throughout the day in healthy individuals, and this change cannot be explained by changes in IOP or ONSD during the same time period. A HDT posture blunts the neuroretinal rim thinning observed in a seated position, suggesting a role of the translaminar pressure difference.
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Affiliation(s)
- Laura P Pardon
- University of Houston, College of Optometry, Houston, Texas, United States
| | - Han Cheng
- University of Houston, College of Optometry, Houston, Texas, United States
| | - Pratik Chettry
- University of Houston, College of Optometry, Houston, Texas, United States
| | - Nimesh B Patel
- University of Houston, College of Optometry, Houston, Texas, United States
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27
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Ong J, Lee AG, Moss HE. Head-Down Tilt Bed Rest Studies as a Terrestrial Analog for Spaceflight Associated Neuro-Ocular Syndrome. Front Neurol 2021; 12:648958. [PMID: 33841315 PMCID: PMC8032981 DOI: 10.3389/fneur.2021.648958] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Accepted: 03/01/2021] [Indexed: 01/16/2023] Open
Abstract
Astronauts who undergo prolonged periods of spaceflight may develop a unique constellation of neuro-ocular findings termed Spaceflight Associated Neuro-Ocular Syndrome (SANS). SANS is a disorder that is unique to spaceflight and has no terrestrial equivalent. The prevalence of SANS increases with increasing spaceflight duration and although there have been residual, structural, ocular changes noted, no irreversible or permanent visual loss has occurred after SANS, with the longest spaceflight to date being 14 months. These microgravity-induced findings are being actively investigated by the United States' National Aeronautics Space Administration (NASA) and SANS is a potential obstacle to future longer duration, manned, deep space flight missions. The pathophysiology of SANS remains incompletely understood but continues to be a subject of intense study by NASA and others. The study of SANS is of course partially limited by the small sample size of humans undergoing spaceflight. Therefore, identifying a terrestrial experimental model of SANS is imperative to facilitate its study and for testing of preventative measures and treatments. Head-down tilt bed rest (HDTBR) on Earth has emerged as one promising possibility. In this paper, we review the HDTBR as an analog for SANS pathogenesis; the clinical and imaging overlap between SANS and HDTBR studies; and potential SANS countermeasures that have been or could be tested with HDTBR.
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Affiliation(s)
- Joshua Ong
- University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Andrew G Lee
- Department of Ophthalmology, Houston Methodist Hospital, Houston, TX, United States.,Baylor College of Medicine and the Center for Space Medicine, Houston, TX, United States.,The Houston Methodist Research Institute, Houston Methodist Hospital, Houston, TX, United States.,Departments of Ophthalmology, Neurology, and Neurosurgery, Weill Cornell Medicine, New York, NY, United States.,Department of Ophthalmology, University of Texas Medical Branch, Galveston, TX, United States.,University of Texas MD Anderson Cancer Center, Houston, TX, United States.,Texas A and M College of Medicine, Bryan, TX, United States.,Department of Ophthalmology, The University of Iowa Hospitals and Clinics, Iowa City, IA, United States
| | - Heather E Moss
- Departments of Ophthalmology, Stanford University, Palo Alto, CA, United States.,Departments of Neurology & Neurosciences, Stanford University, Palo Alto, CA, United States
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28
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Liu X, Khodeiry MM, Lin D, Sun Y, Lin C, Feng W, Li J, Wang Y, Zhang Q, Cao K, Wang J, Wang N. The Association of Acute Cerebrospinal Fluid Pressure Reduction with Choroidal Thickness. Curr Eye Res 2021; 46:1193-1200. [PMID: 33517795 DOI: 10.1080/02713683.2021.1874024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
PURPOSE To investigate the changes in choroidal thickness (CT) after acute cerebrospinal fluid pressure (CSFP) reduction in human subjects. METHODS Before and 15 minutes after diagnostic lumbar puncture (LP), 44 patients underwent measurement of CT by swept-source optical coherence tomography. Thirty-two healthy volunteers imitated the body posture of LP procedure and underwent the same measurement before and 15 minutes after body posture change. RESULTS After CSFP reduction from 10.9 ± 2.1 mmHg at baseline to 8.1 ± 1.5 mmHg (p < 0.001), CT decreased in subfoveal region (p = 0.005), small to medium vessel layer (SMVL, p < 0.001), peripapillary regions in temporal (p = 0.001), nasal (p < 0.001), superior (p < 0.001) and inferior (p < 0.001), respectively. However, no significant change in CT in the control group after body posture change (all p > 0.05). A significant association between CSFP and the ratio of small to medium vessel layer to total choroidal thickness was found (p = 0.009). The CSFP reduction rate was associated with the change rate of SMVL to total CT portion, for each percent decrease in CSFP was associated with a decrease by 0.22% in the rate of SMVL to total CT portion (R2 = 0.125, p = 0.018). CONCLUSIONS A significant decrease in subfoveal CT, small to medium vessel layer and peripapillary region were observed following acute CSFP reduction. The CSFP reduction rate was associated with the change rate of small to medium vessel layer to total CT portion.
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Affiliation(s)
- Xiangxiang Liu
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Mohamed M Khodeiry
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, USA.,Research Institute of Ophthalamology, Giza, Egypt
| | - Danting Lin
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Yunxiao Sun
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Caixia Lin
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Wei Feng
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
| | - Jing Li
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Eye Institute, Beijing Ophthalmology and Visual Science Key Laboratory, Beijing, China
| | - Yaxing Wang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Eye Institute, Beijing Ophthalmology and Visual Science Key Laboratory, Beijing, China
| | - Qing Zhang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Eye Institute, Beijing Ophthalmology and Visual Science Key Laboratory, Beijing, China
| | - Kai Cao
- Beijing Eye Institute, Beijing Ophthalmology and Visual Science Key Laboratory, Beijing, China
| | - Jiawei Wang
- Department of Neurology and Medical Research Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Ningli Wang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Eye Institute, Beijing Ophthalmology and Visual Science Key Laboratory, Beijing, China
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29
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Murray KR, Wasef S, Edgell H. Ventilatory response to hypercapnia is increased after 4 h of head down bed rest. Sci Rep 2021; 11:2162. [PMID: 33495489 PMCID: PMC7835380 DOI: 10.1038/s41598-021-81837-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 01/12/2021] [Indexed: 11/15/2022] Open
Abstract
Head-down bed rest (HDBR) has previously been shown to alter cerebrovascular and autonomic control. Previous work found that sustained HDBR (≥ 20 days) attenuates the hypercapnic ventilatory response (HCVR); however, little is known about shorter-term effects of HDBR nor the influence of HDBR on the hypoxic ventilatory response (HVR). We investigated the effect of 4-h HDBR on HCVR and HVR and hypothesized attenuated ventilatory responses due to greater carotid and brain blood flow. Cardiorespiratory responses of young men (n = 11) and women (n = 3) to 5% CO2 or 10% O2 before and after 4-h HDBR were examined. HDBR resulted in lower HR, lower cardiac output index, lower common carotid artery flow, higher SpO2, and higher pulse wave velocity. After HDBR, tidal volume and ventilation responses to 5% CO2 were enhanced (all P < 0.05), yet no other changes in cardiorespiratory variables were evident. There was no influence of HDBR on the cardiorespiratory responses to hypoxia (all P > 0.05). Short-duration HDBR does not alter the HVR, yet enhances the HCVR, which we hypothesize is a consequence of cephalic CO2 accumulation from cerebral congestion.
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Affiliation(s)
- K R Murray
- School of Kinesiology and Health Science, York University, 355 Bethune College, 4700 Keele St, Toronto, ON, M3J 1P3, Canada
| | - S Wasef
- School of Kinesiology and Health Science, York University, 355 Bethune College, 4700 Keele St, Toronto, ON, M3J 1P3, Canada
| | - Heather Edgell
- School of Kinesiology and Health Science, York University, 355 Bethune College, 4700 Keele St, Toronto, ON, M3J 1P3, Canada. .,Muscle Health Research Centre, York University, Toronto, ON, Canada.
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Eye changes in space : New insights into clinical aspects, pathogenesis, and prevention. Ophthalmologe 2021; 118:96-101. [PMID: 33258060 DOI: 10.1007/s00347-020-01272-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
BACKGROUND More than ever research into changes in the eye caused by long-term space flight is becoming the focus of the international and national space agencies National Aeronautics and Space Administration (NASA), European Space Agency (ESA) and German Aerospace Center (DLR). In addition to space radiation-induced cataract formation considerable eye changes, summarized under space flight-associated neuro-ocular syndrome (SANS), can occur. OBJECTIVE This article gives an overview of the current state of research and future directions in the field of research concerned with ocular alterations in SANS and presents the relevance for terrestrial ophthalmological research. MATERIAL AND METHODS An analysis of existing publications on SANS in PubMed and reports on the risk of SANS published by the NASA of the USA was carried out. RESULTS The reasons for the development of the eye changes in space have not been clarified. Factors such as the increase in intracranial pressure, fluid shifts, hypercapnia and genetic factors are the subject of intensive research efforts. A terrestrial model for the induction of papilledema could be established (bed rest studies with -6° head-down tilt as a space analogue). Countermeasures for the development of eye changes, such as intermittent artificial gravity, are the subject of current research studies. CONCLUSION Research into SANS as part of bed rest studies will provide further important insights in the future for space research and also for terrestrial research. Clinical research projects can be derived from space research.
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Abstract
PURPOSE OF REVIEW Several decades of long duration space flight missions by the National Aeronautics and Space Administration has revealed an interesting and unique constellation of neuro-ophthalmic findings now called spaceflight associated neuro-ocular syndrome (SANS). The unique space environment of microgravity produces novel physiological changes and derangements that present a challenge to astronauts in current and future long duration space missions. Although the precise mechanism of SANS is not fully understood, in this review, we examine recent developments that may to help explain possible causes and potential countermeasures. RECENT FINDINGS The cause of SANS is still largely unknown. A growing body of evidence implicates multiple factors that contribute to the development of SANS including cephalad fluid shifts, increased intracranial pressure, venous/lymphatic stasis, inflammation, metabolism, axoplasmic stasis and radiation exposure. SUMMARY The pathologic mechanism behind SANS may be multifactorial and may be amenable to different countermeasures for prevention and management of SANS.
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32
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Laurie SS, Lee SMC, Macias BR, Patel N, Stern C, Young M, Stenger MB. Optic Disc Edema and Choroidal Engorgement in Astronauts During Spaceflight and Individuals Exposed to Bed Rest. JAMA Ophthalmol 2020; 138:165-172. [PMID: 31876939 DOI: 10.1001/jamaophthalmol.2019.5261] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Importance Optic disc edema develops in astronauts during long-duration spaceflight and is a risk for all future astronauts during spaceflight. Having a ground-based analogue of weightlessness that reproduces critical features of spaceflight-associated neuro-ocular syndrome will facilitate understanding, preventing, and/or treating this syndrome. Objective To determine whether the ocular changes in individuals exposed to an analogue of weightlessness are similar to the ocular changes in astronauts exposed to a duration of spaceflight comparable to this analogue of weightlessness. Design, Setting, and Participants This cohort study, conducted from 2012 to 2018, investigated 11 healthy test participants before, during, and after 30 days of strict 6° head-down tilt bed rest as well as 20 astronauts before and during approximately 30 days of spaceflight. Data were collected at NASA Johnson Space Center, the German Aerospace Center, and on board the International Space Station. Statistical analysis was performed from February 13 to April 24, 2019. Main Outcomes and Measures Peripapillary total retinal thickness and peripapillary choroid thickness quantified from optical coherence tomography images. Results Peripapillary total retinal thickness increased to a greater degree among 11 individuals (6 men and 5 women; mean [SD] age, 33.4 [8.0 years]) exposed to bed rest than among 20 astronauts (17 men and 3 women; mean [SD] age, 46.0 [6.0] years), with a mean difference between groups of 37 μm (95% CI, 13-61 μm; P = .005). Conversely, choroid thickness did not increase among the individuals exposed to bed rest but increased among the astronauts, resulting in a mean difference between groups of 27 μm (95% CI, 14-41 μm; P < .001). Conclusions and Relevance These findings suggest that strict head-down tilt bed rest produces a different magnitude of edema than occurs after a similar duration of spaceflight, and no change in choroid thickness. It is possible that a mild, long-term elevation in intracranial pressure experienced by individuals exposed to bed rest is greater than the intracranial pressure experienced by astronauts during spaceflight, which may explain the different severity of optic disc edema between the cohorts. Gravitational gradients that remain present during bed rest may explain the lack of increase in choroid thickness during bed rest, which differs from the lack of gravitational gradients during spaceflight. Despite the possibility that different mechanisms may underlie optic disc edema development in modeled and real spaceflight, use of this terrestrial model of spaceflight-associated neuro-ocular syndrome will be assistive in the development of effective countermeasures that will protect the eyes of astronauts during future space missions.
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Affiliation(s)
| | | | | | - Nimesh Patel
- College of Optometry, University of Houston, Houston, Texas
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Lawley JS, Babu G, Janssen SLJE, Petersen LG, Hearon CM, Dias KA, Sarma S, Williams MA, Whitworth LA, Levine BD. Daily generation of a footward fluid shift attenuates ocular changes associated with head-down tilt bed rest. J Appl Physiol (1985) 2020; 129:1220-1231. [PMID: 32940563 DOI: 10.1152/japplphysiol.00250.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Astronauts have presented with a constellation of visual changes referred to as spaceflight-associated neuro-ocular syndrome (SANS). However, neither have early markers of microgravity-induced optic remodeling been fully identified nor have countermeasures been developed. To identify early markers of SANS, we studied 10 subjects with optical coherence tomography and ultrasonography when upright and supine and again after 24 h of 6° head-down tilt (HDT) bed rest. Upon acute transition from the upright to the supine position, choroid area (2.24 ± 0.53 to 2.28 ± 0.52 mm2, P = 0.001) and volume (9.51 ± 2.08 to 9.73 ± 2.08 mm3, P = 0.002) increased. After 24 h of HDT bed rest, subfoveal choroidal thickness (372 ± 93 to 381 ± 95 µm, P = 0.02), choroid area (2.25 ± 0.52 to 2.33 ± 0.54 mm2, P = 0.08), and volume (9.64 ± 2.03 to 9.82 ± 2.08 mm3, P = 0.08) increased relative to the supine position. Subsequently, seven subjects spent 3 days in -6°HDT bed rest to assess whether low-level lower body negative pressure (LBNP) could prevent the observed choroidal engorgement during bed rest. Maintaining the -6° HDT position for 3 days caused choroid area (Δ0.11 mm2, P = 0.05) and volume (Δ0.45 mm3, P = 0.003) to increase. When participants also spent 8 h daily under -20 mmHg LBNP, choroid volume still increased, but substantially (40%) less than in the control trial (Δ0.27 mm3, P = 0.05). Moreover, the increase in choroid area was diminished (Δ0.03 mm2, P = 0.13), indicating that low-level LBNP attenuates the choroid expansion associated with 3 days of -6° HDT bed rest. These data suggest that low-level LBNP may be an effective countermeasure for SANS.NEW & NOTEWORTHY Choroid measurements appear to be sensitive to changes in gravitational gradients, as well as periods of head-down tilt (HDT) bed rest, suggesting that they are potential indicators of early ocular remodeling and could serve to evaluate the efficacy of countermeasures for SANS. Eight hours of lower body negative pressure (LBNP) daily attenuates the choroid expansion associated with 3 days of strict -6° HDT bed rest, indicating that LBNP may be an effective countermeasure for SANS.
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Affiliation(s)
- Justin S Lawley
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas.,Division of Physiology, Department of Sports Science, University of Innsbruck, Innsbruck, Austria
| | - Gautam Babu
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | | | - Lonnie G Petersen
- Department of Orthopedic Surgery, University of California San Diego, California
| | - Christopher M Hearon
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | - Katrin A Dias
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | - Satyam Sarma
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | - Michael A Williams
- Department of Neurology, University of Washington School of Medicine, Seattle, Washington.,Department of Neurological Surgery, University of Washington School of Medicine, Seattle, Washington
| | | | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
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Mader TH, Gibson CR, Barratt MR, Miller NR, Subramanian PS, Killer HE, Tarver WJ, Sargsyan AE, Garcia K, Hart SF, Kramer LA, Riascos R, Brunstetter TJ, Lipsky W, Wostyn P, Lee AG. Persistent Globe Flattening in Astronauts following Long-Duration Spaceflight. Neuroophthalmology 2020; 45:29-35. [PMID: 33762785 DOI: 10.1080/01658107.2020.1791189] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Posterior globe flattening has been well-documented in astronauts both during and after long-duration space flight (LDSF) and has been observed as early as 10 days into a mission on the International Space Station. Globe flattening (GF) is thought to be caused by the disc centred anterior forces created by elevated volume and/or pressure within the optic nerve sheath (ONS). This might be the result of increased intracranial pressure, increased intraorbital ONS pressure from compartmentalisation or a combination of these mechanisms. We report posterior GF in three astronauts that has persisted for 7 years or more following their return from LDSFs suggesting that permanent scleral remodelling may have occurred.
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Affiliation(s)
| | - C Robert Gibson
- Coastal Eye Associates, Webster, Texas, USA.,KBR, Houston, Texas, USA
| | | | - Neil R Miller
- Wilmer Eye Institute, The Johns Hopkins Hospital, Baltimore, Maryland, USA
| | - Prem S Subramanian
- Department of Ophthalmology, Sue Anschutz-Rodgers UCHealth Eye Center, University of Colorado School of Medicine, Aurora, Colorado, USA
| | | | | | | | | | - Stephen F Hart
- NASA Johnson Space Center, Space Medicine, Houston, Texas, USA
| | - Larry A Kramer
- Department of Diagnostic Imaging and Intervention, University of Texas Health Science Center, Houston, Texas, USA
| | - Roy Riascos
- Department of Diagnostic Imaging and Intervention, University of Texas Health Science Center, Houston, Texas, USA
| | | | | | - Peter Wostyn
- Department of Psychiatry, PC Sint-Amandus, Beernem, Belgium
| | - Andrew G Lee
- Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, Texas, USA.,Department of Ophthalmology, The University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA.,Departments of Ophthalmology, Neurology, and Neurosurgery, Weill Cornell Medicine, New York, New York, USA.,Department of Ophthalmology, University of Texas Medical Branch, Galveston, Texas, USA.,Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA.,Department of Ophthalmology; University of Texas MD Anderson Cancer Center, Houston, Texas, USA.,Department of Ophthalmology, Texas A and M College of Medicine, Bryan, Texas, USA
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35
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Abstract
Spaceflight-associated neuro-ocular syndrome (SANS) describes a series of morphologic and functional ocular changes in astronauts first reported by Mader and colleagues in 2011. SANS is currently clinically defined by the development of optic disc edema during prolonged exposure to the weightless (microgravity) environment, which currently occurs on International Space Station (ISS). However, as improvements in our understanding of the ocular changes emerge, the definition of SANS is expected to evolve. Other ocular SANS signs that arise during and after ISS missions include hyperopic shifts, globe flattening, choroidal/retinal folds, and cotton wool spots. Over the last 10 years, ~1 in 3 astronauts flying long-duration ISS missions have presented with ≥1 of these ocular findings. Commensurate with research that combines disparate specialties (vision biology and spaceflight medicine), lessons from SANS investigations may also yield insight into ground-based ocular disorders, such as glaucomatous optic neuropathy that may have the potential to lessen the burden of this irreversible cause of vision loss on Earth.
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36
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Wojcik P, Batliwala S, Rowsey T, Galdamez LA, Lee AG. Spaceflight-Associated Neuro-ocular Syndrome (SANS): a review of proposed mechanisms and analogs. EXPERT REVIEW OF OPHTHALMOLOGY 2020. [DOI: 10.1080/17469899.2020.1787155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Peter Wojcik
- Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, TX, USA
| | - Shehzad Batliwala
- Department of Ophthalmology, Dean McGee Eye Institute, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
| | - Tyler Rowsey
- College of Medicine, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
| | - Laura A. Galdamez
- Department of Emergency Medicine, Memorial Hermann The Woodlands, Shenandoah, TX, USA
| | - Andrew G. Lee
- Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, TX, USA
- Departments of Ophthalmology, Neurology, and Neurosurgery, Weill Cornell Medicine, New York, NY, USA
- Department of Ophthalmology, University of Texas Medical Branch, Galveston, TX, USA
- Department of Ophthalmology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Texas A and M College of Medicine, Bryan, TX, USA
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37
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Lee C, Rohr J, Sass A, Sater S, Zahid A, Macias B, Stenger MB, Samuels BC, Martin BA, Oshinski JN, Ethier CR. In vivo estimation of optic nerve sheath stiffness using noninvasive MRI measurements and finite element modeling. J Mech Behav Biomed Mater 2020; 110:103924. [PMID: 32957219 DOI: 10.1016/j.jmbbm.2020.103924] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Revised: 06/04/2020] [Accepted: 06/06/2020] [Indexed: 12/21/2022]
Abstract
The optic nerve sheath (ONS) is biomechanically important. It is acted on by tension due to ocular movements, and by fluid shifts and/or alterations in intracranial pressure (ICP) in human disease, specifically in pathologies leading to intracranial hypertension. It has also been hypothesized that the ONS is acted on by altered ICP in astronauts exposed chronically to microgravity. However, a non-invasive method to quantify ONS biomechanical properties is not presently available; knowledge of such properties is desirable to allow characterization of the biomechanical forces exerted on the optic nerve head and other ocular structures due to the ONS. Thus, the primary objective of this study was to characterize the biomechanical properties (stiffness) of the human ONS in vivo as a necessary step towards investigating the role of ICP in various conditions, including Spaceflight Associated Neuro-ocular Syndrome (SANS). We acquired non-invasive magnetic resonance imaging (MRI) scans of ostensibly healthy subjects (n = 18, age = 30.4 ± 11.6 [mean ± SD] years) during supine and 15-degree head-down-tilt (HDT) postures, and extracted ONS contours from these scans. We then used finite element modeling to quantify ONS expansion due to postural changes and an inverse approach to estimate ONS stiffness. Using this non-invasive procedure, we estimated an in vivo ONS stiffness of 39.2 ± 21.9 kPa (mean ± SD), although a small subset of individuals had very stiff ONS that precluded accurate estimates of their stiffness values. ONS stiffness was not correlated with age and was higher in males than females.
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Affiliation(s)
- Chanyoung Lee
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Jesse Rohr
- Department of Biological Engineering, University of Idaho, Moscow, ID, USA
| | - Austin Sass
- Department of Biological Engineering, University of Idaho, Moscow, ID, USA
| | - Stuart Sater
- Department of Biological Engineering, University of Idaho, Moscow, ID, USA
| | - Arslan Zahid
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, USA
| | - Brandon Macias
- Cardiovascular and Vision Laboratory, KBR, Houston, TX, USA
| | | | - Brian C Samuels
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Bryn A Martin
- Department of Biological Engineering, University of Idaho, Moscow, ID, USA
| | - John N Oshinski
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, USA
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA.
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Pandiarajan M, Hargens AR. Ground-Based Analogs for Human Spaceflight. Front Physiol 2020; 11:716. [PMID: 32655420 PMCID: PMC7324748 DOI: 10.3389/fphys.2020.00716] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 05/29/2020] [Indexed: 11/13/2022] Open
Abstract
This mini-review provides an updated summary of various analogs for adaptations of humans to the microgravity of space. Microgravity analogs discussed in this paper include dry immersion, wet immersion, unilateral lower-extremity limb suspension, head down tilt (HDT), and supine bed rest. All Earth-based analogs are imperfect simulations of microgravity with their own advantages and disadvantages. This paper compares these five frequently used microgravity analogs to offer insights into their usefulness for various physiological systems. New developments for each human microgravity analog are explored and advantages of one analog are evaluated against other analogs. Furthermore, the newly observed risk of Spaceflight Associated Neuro-Ocular Syndrome (SANS) is included in this mini review with a discussion of the advantages and disadvantages of each method of simulation for the relatively new risk of SANS. Overall, the best and most integrated analog for Earth-based studies of the microgravity of space flight appears to be head-down tilt bed rest.
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Affiliation(s)
- Meenakshi Pandiarajan
- Department of Orthopaedic Surgery, Altman Clinical and Translational Research Institute, University of California, San Diego, San Diego, CA, United States
| | - Alan R Hargens
- Department of Orthopaedic Surgery, Altman Clinical and Translational Research Institute, University of California, San Diego, San Diego, CA, United States
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Laurie SS, Christian K, Kysar J, Lee SMC, Lovering AT, Macias BR, Moestl S, Sies W, Mulder E, Young M, Stenger MB. Unchanged cerebrovascular CO 2 reactivity and hypercapnic ventilatory response during strict head-down tilt bed rest in a mild hypercapnic environment. J Physiol 2020; 598:2491-2505. [PMID: 32196672 DOI: 10.1113/jp279383] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 03/16/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Carbon dioxide levels are mildly elevated on the International Space Station and it is unknown whether this chronic exposure causes physiological changes to astronauts. We combined ∼4 mmHg ambient P C O 2 with the strict head-down tilt bed rest model of spaceflight and this led to the development of optic disc oedema in one-half of the subjects. We demonstrate no change in arterialized P C O 2 , cerebrovascular reactivity to CO2 or the hypercapnic ventilatory response. Our data suggest that the mild hypercapnic environment does not contribute to the development of spaceflight associated neuro-ocular syndrome. ABSTRACT Chronically elevated carbon dioxide (CO2 ) levels can occur in confined spaces such as the International Space Station. Using the spaceflight analogue 30 days of strict 6° head-down tilt bed rest (HDTBR) in a mild hypercapnic environment ( P C O 2 = ∼4 mmHg), we investigated arterialized P C O 2 , cerebrovascular reactivity and the hypercapnic ventilatory response in 11 healthy subjects (five females) before, on days 1, 9, 15 and 30 of bed rest (BR), and 6 and 13 days after HDTBR. During all HDTBR time points, arterialized P C O 2 was not significantly different from the pre-HDTBR measured in the 6° HDT posture, with a mean (95% confidence interval) increase of 1.2 mmHg (-0.2 to 2.5 mmHg, P = 0.122) on day 30 of HDTBR. Respiratory acidosis was never detected, although a mild metabolic alkalosis developed on day 30 of HDTBR by a mean (95% confidence interval) pH change of 0.032 (0.022-0.043; P < 0.001), which remained elevated by 0.021 (0.011-0.031; P < 0.001) 6 days after HDTBR. Arterialized pH returned to pre-HDTBR levels 13 days after BR with a change of -0.001 (-0.009 to 0.007; P = 0.991). Compared to pre-HDTBR, cerebrovascular reactivity during and after HDTBR did not change. Baseline ventilation, ventilatory recruitment threshold and the slope of the ventilatory response were similar between pre-HDTBR and all other time points. Taken together, these data suggest that the mildly increased ambient P C O 2 combined with 30 days of strict 6° HDTBR did not change arterialized P C O 2 levels. Therefore, the experimental conditions were not sufficient to elicit a detectable physiological response.
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Affiliation(s)
| | - Kate Christian
- Department of Human Physiology, University of Oregon, Eugene, OR, USA
| | - Jacob Kysar
- Department of Human Physiology, University of Oregon, Eugene, OR, USA
| | | | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, OR, USA
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40
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Elwy R, Soliman MA, Hasanain AA, Ezzat AA, Elbaroody M, Alsawy MF, El Refaee E. Visual changes after space flight: is it really caused by increased intracranial tension? A systematic review. J Neurosurg Sci 2020; 64:468-479. [PMID: 32347675 DOI: 10.23736/s0390-5616.20.04927-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
INTRODUCTION Spaceflight-Associated Neuro-ocular Syndrome (SANS) was linked to increased intracranial pressure (ICP) attributable to the combined effects of microgravity and environmental conditions encountered during spaceflight. Microgravity countermeasures as lower body negative pressure (LBNP) are potential interventions for SANS. Our aim is to provide a comprehensive qualitative analysis of literature contrasting simulation and spaceflight studies, focusing on the pathophysiology of SANS, and highlighting gaps in current knowledge. EVIDENCE ACQUISITION We systematically searched PubMed electronic database for English primary research published until February 2019 discussing intracranial changes in spaceflight or simulated microgravity, excluding animal and experimental studies. Two authors screened all the abstracts with a third author resolving disagreements. The full-text manuscripts were analyzed in pilot-tested tables. EVIDENCE SYNTHESIS Nineteen studies were reviewed; 13 simulation, and two out of six spaceflight studies were prospective. ICP changes were investigated in 11 simulation studies, where eight demonstrated a significant increase in ICP after variable periods of head-down tilt. three showed a significant increase in intraocular pressure (IOP) in conjunction with ICP elevation. With increasing ambient CO<inf>2</inf>: one showed an increase in IOP without further increase in ICP, while another showed a slight further decrease in ICP. LBNP demonstrated no significant effect on ICP in one and a decrease thereof in another study. After spaceflight, increased ICP on lumbar puncture was demonstrated in five studies. CONCLUSIONS Exposure to microgravity increases ICP possibly precipitating ocular changes. Whether other factors come into play is the subject of investigation. Further randomized studies and methods of direct ICP measurement during spaceflight are needed.
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Affiliation(s)
- Reem Elwy
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Mohamed A Soliman
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt - .,Department of Neurosurgery, Western University, London, ON, Canada
| | - Amr A Hasanain
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Ahmed A Ezzat
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Mohammad Elbaroody
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Mohamed F Alsawy
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Ehab El Refaee
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt.,Department of Neurosurgery, University Medicine Greifswald, Greifswald, Germany
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Händel A, Stern C, Jordan J, Dietlein T, Enders P, Cursiefen C. [Eye changes in space : New insights into clinical aspects, pathogenesis and prevention]. Ophthalmologe 2020; 117:721-729. [PMID: 32347333 DOI: 10.1007/s00347-020-01103-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
BACKGROUND More than ever research into changes in the eye caused by long-term space flight is becoming the focus of the international and national space agencies National Aeronautics and Space Administration (NASA), European Space Agency (ESA) and German Aerospace Center (DLR). In addition to space radiation-induced cataract formation considerable eye changes, summarized under space flight-associated neuro-ocular syndrome (SANS), can occur. OBJECTIVE This article gives an overview of the current state of research and future directions in the field of research concerned with ocular alterations in SANS and presents the relevance for terrestrial ophthalmological research. MATERIAL AND METHODS An analysis of existing publications on SANS in PubMed and reports on the risk of SANS published by the NASA of the USA was carried out. RESULTS The reasons for the development of the eye changes in space have not been clarified. Factors such as the increase in intracranial pressure, fluid shifts, hypercapnia and genetic factors are the subject of intensive research efforts. A terrestrial model for the induction of papilledema could be established (bed rest studies with -6° head-down tilt as a space analogue). Countermeasures for the development of eye changes, such as intermittent artificial gravity, are the subject of current research studies. CONCLUSION Research into SANS as part of bed rest studies will provide further important insights in the future for space research and also for terrestrial research. Clinical research projects can be derived from space research.
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Affiliation(s)
- A Händel
- Zentrum für Augenheilkunde, Universitätsklinik Köln, Kerpener Str. 62, 50937, Köln, Deutschland.
| | - C Stern
- Institut für Luft- und Raumfahrtmedizin, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Köln, Deutschland
| | - J Jordan
- Institut für Luft- und Raumfahrtmedizin, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Köln, Deutschland.,Lehrstuhl für Luft- und Raumfahrtmedizin, Universitätsklinik Köln, Köln, Deutschland
| | - T Dietlein
- Zentrum für Augenheilkunde, Universitätsklinik Köln, Kerpener Str. 62, 50937, Köln, Deutschland
| | - P Enders
- Zentrum für Augenheilkunde, Universitätsklinik Köln, Kerpener Str. 62, 50937, Köln, Deutschland
| | - C Cursiefen
- Zentrum für Augenheilkunde, Universitätsklinik Köln, Kerpener Str. 62, 50937, Köln, Deutschland
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Mekjavic IB, Amoaku W, Mlinar T, Jaki Mekjavic P. Hypercapnia augments resistive exercise-induced elevations in intraocular pressure in older individuals. Exp Physiol 2020; 105:641-651. [PMID: 32034962 DOI: 10.1113/ep088236] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Accepted: 02/07/2020] [Indexed: 12/13/2022]
Abstract
NEW FINDINGS What is the central question of this study? Astronauts on-board the International Space Station (ISS) perform daily exercises designed to prevent muscle atrophy and bone demineralization: what is the effect of resistive exercise performed by subjects while exposed to the same level of hypercapnia as on the ISS on intraocular pressure (IOP)? What is the main finding and its importance? The static exercise-induced elevation in IOP during 6° prone head-down tilt (simulating the headward shift of body fluids in microgravity) is augmented by hypercapnia and exceeds the ocular hypertension threshold. ABSTRACT The present study assessed the effect of 6° head-down (establishing the cephalad fluid displacement noted in astronauts in microgravity) prone (simulating the effect on the eye) tilt during rest and exercise (simulating exercise performed by astronauts to mitigate the sarcopenia induced by unloading of weight-bearing limbs), in normocapnic and hypercapnic conditions (the latter simulating conditions on the International Space Station) on intraocular pressure (IOP). Volunteers (mean age = 57.8 ± 6 years, n = 10) participated in two experimental sessions, each comprising: (i) 10 min rest, (ii) 3 min static handgrip exercise (30% max), and (iii) 2 min recovery, inspiring either room air (NCAP) or a hypercapnic mixture (1% CO2 , HCAP). We measured IOP in the right eye, cardiac output (CO), stroke volume (SV), heart rate (HR) and mean arterial pressure (MAP) at regular intervals. Baseline IOP in the upright seated position while breathing room air was 14.1 ± 2.9 mmHg. Prone 6° head-down tilt significantly (P < 0.01) elevated IOP in all three phases of the NCAP (rest: 27.0 ± 3.7 mmHg; exercise: 32.2 ± 4.8 mmHg; recovery: 27.4 ± 4.0 mmHg) and HCAP (rest: 27.3 ± 4.3 mmHg; exercise: 34.2 ± 6.0 mmHg; recovery: 29.1 ± 5.8 mmHg) trials, with hypercapnia augmenting the exercise-induced elevation in IOP (P < 0.01). CO, SV, HR and MAP were significantly increased during handgrip dynamometry, but there was no effect of hypercapnia. The observed IOP measured during prone 6° HDT in all phases of the NCAP and HCAP trials exceeded the threshold pressure defining ocular hypertension. The exercise-induced increase in IOP is exacerbated by hypercapnia.
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Affiliation(s)
- Igor B Mekjavic
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, Ljubljana, SI-1000, Slovenia.,Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, V51 1S6, Canada
| | - Winfried Amoaku
- Nottingham Eye Research Centre, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Tinkara Mlinar
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, Ljubljana, SI-1000, Slovenia.,International Postgraduate School Jozef Stefan, Jamova 39, Ljubljana, SI-1000, Slovenia
| | - Polona Jaki Mekjavic
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, Ljubljana, SI-1000, Slovenia.,Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, Ljubljana, SI-1000, Slovenia.,Faculty of Medicine, University of Ljubljana, Vrazov trg 2, Ljubljana, SI-1000, Slovenia
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Spaceflight associated neuro-ocular syndrome (SANS) and the neuro-ophthalmologic effects of microgravity: a review and an update. NPJ Microgravity 2020; 6:7. [PMID: 32047839 PMCID: PMC7005826 DOI: 10.1038/s41526-020-0097-9] [Citation(s) in RCA: 130] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 11/11/2019] [Indexed: 11/08/2022] Open
Abstract
Prolonged microgravity exposure during long-duration spaceflight (LDSF) produces unusual physiologic and pathologic neuro-ophthalmic findings in astronauts. These microgravity associated findings collectively define the “Spaceflight Associated Neuro-ocular Syndrome” (SANS). We compare and contrast prior published work on SANS by the National Aeronautics and Space Administration’s (NASA) Space Medicine Operations Division with retrospective and prospective studies from other research groups. In this manuscript, we update and review the clinical manifestations of SANS including: unilateral and bilateral optic disc edema, globe flattening, choroidal and retinal folds, hyperopic refractive error shifts, and focal areas of ischemic retina (i.e., cotton wool spots). We also discuss the knowledge gaps for in-flight and terrestrial human research including potential countermeasures for future study. We recommend that NASA and its research partners continue to study SANS in preparation for future longer duration manned space missions.
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Abstract
Many experiments have documented the response of intraocular pressure (IOP) to postural change. External forces caused by gravitational orientation change produce a dynamic response that is encountered every day during normal activities. Tilting the body at a small downward angle is also relevant to studying the effects of hypogravity (spaceflight), including ocular changes. We examined data from 36 independent datasets from 30 articles on IOP response to postural change, representing a total population of 821 subjects (≥1173 eyes) with widely varying initial and final postures. We confirmed that IOP was well predicted by a simple quantity, namely the hydrostatic pressure at the level of the eye, although the dependence was complex (nonlinear). Our results show that posturally induced IOP change can be explained by hydrostatic forcing plus an autoregulatory contribution that is dependent on hydrostatic effects. This study represents data from thousands of IOP measurements and provides insight for future studies that consider postural change in relation to ocular physiology, intraocular pressure, ocular blood flow and aqueous humor dynamics.
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45
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Kerscher SR, Schöni D, Neunhoeffer F, Wolff M, Haas-Lude K, Bevot A, Schuhmann MU. The relation of optic nerve sheath diameter (ONSD) and intracranial pressure (ICP) in pediatric neurosurgery practice - Part II: Influence of wakefulness, method of ICP measurement, intra-individual ONSD-ICP correlation and changes after therapy. Childs Nerv Syst 2020; 36:107-115. [PMID: 31392457 DOI: 10.1007/s00381-019-04336-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 07/30/2019] [Indexed: 12/30/2022]
Abstract
PURPOSE Previous studies correlating ultrasound (US)-based optic nerve sheath diameter (ONSD) and intracranial pressure (ICP) in children were performed under general anesthesia. To apply ONSD in daily clinical routine, it is necessary to investigate patients awake. It is furthermore essential for ICP-assessment with ONSD to know if ONSD-ICP correlation varies within individuals. In this study, we report on the influence of wakefulness, method of ICP measurement, intraindividual correlations, and dynamic changes of ONSD and ICP after ICP decreasing therapy. METHODS The overall study included 72 children with a median age of 5.2 years. US ONSD determination was performed immediately prior to invasive ICP measurement, and the mean binocular ONSD was compared to ICP. In 10 children, a minimum of 3 ONSD/ICP measurements were performed to investigate a correlation within subjects. In 30 children, measurements were performed before and after therapy. RESULTS Twenty-eight children were investigated awake with an excellent correlation of ONSD and ICP (r = 0.802, p < 0.01). In 10 children, at least three simultaneous ONSD and ICP measurements were performed. The intraindividual correlations were excellent (r = 0.795-1.0) however with strongly differing individual regression curves. The overall correlation within subjects was strong (r = 0.78, p < 0.01). After ICP decreasing therapy, all ONSD values decreased significantly (p < 0.01); however, there was no correlation between ∆ICP and ∆ONSD. CONCLUSION Awake investigation does not impair the correlation between ONSD and ICP. Even if there is a good overall ONSD-ICP correlation, every individual has its own distinctive and precise correlation line. The relationship between ONSD and ICP is furthermore not uniform between individuals. Strong ICP decreases can lead to smaller ONSD changes and vice versa. This should be kept in mind when using this technique in the clinical daily routine.
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Affiliation(s)
- Susanne R Kerscher
- Department of Neurosurgery, Pediatric Neurosurgery, University Hospital of Tuebingen, Hoppe-Seyler-Str.3, 72076, Tuebingen, Germany.
- Department of Neurosurgery, University Hospital of Tuebingen, Tuebingen, Germany.
| | - Daniel Schöni
- Department of Neurosurgery, University Hospital of Tuebingen, Tuebingen, Germany
- Department of Neurosurgery, University Hospital of Bern, Bern, Switzerland
| | - Felix Neunhoeffer
- Pediatric Intensive Care Unit, Childrens' Hospital, University Hospital of Tuebingen, Tuebingen, Germany
| | - Markus Wolff
- Department of Pediatric Neurology and Developmental Medicine, Childrens' Hospital, University Hospital of Tuebingen, Tuebingen, Germany
| | - Karin Haas-Lude
- Department of Pediatric Neurology and Developmental Medicine, Childrens' Hospital, University Hospital of Tuebingen, Tuebingen, Germany
| | - Andrea Bevot
- Department of Pediatric Neurology and Developmental Medicine, Childrens' Hospital, University Hospital of Tuebingen, Tuebingen, Germany
| | - Martin U Schuhmann
- Department of Neurosurgery, Pediatric Neurosurgery, University Hospital of Tuebingen, Hoppe-Seyler-Str.3, 72076, Tuebingen, Germany
- Department of Neurosurgery, University Hospital of Tuebingen, Tuebingen, Germany
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46
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Brain Physiological Response and Adaptation During Spaceflight. Neurosurgery 2019; 85:E815-E821. [DOI: 10.1093/neuros/nyz203] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 02/11/2019] [Indexed: 01/17/2023] Open
Abstract
Abstract
More than half of astronauts returning from long-duration missions on the International Space Station present with neuro-ocular structural and/or functional changes, including optic disc edema, optic nerve sheath distension, globe flattening, choroidal folds, or hyperopic shifts. This spaceflight-associated neuro-ocular syndrome (SANS) represents a major risk to future exploration class human spaceflight missions, including Mars missions. Although the exact pathophysiology of SANS is unknown, evidence thus far suggests that an increase in intracranial pressure (ICP) relative to the upright position on Earth, which is due to the loss of hydrostatic pressure gradients in space, may play a leading role. This review focuses on brain physiology in the spaceflight environment, specifically on how spaceflight may affect ICP and related indicators of cranial compliance, potential factors related to the development of SANS, and findings from spaceflight as well as ground-based spaceflight analog research studies.
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47
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Garrett-Bakelman FE, Darshi M, Green SJ, Gur RC, Lin L, Macias BR, McKenna MJ, Meydan C, Mishra T, Nasrini J, Piening BD, Rizzardi LF, Sharma K, Siamwala JH, Taylor L, Vitaterna MH, Afkarian M, Afshinnekoo E, Ahadi S, Ambati A, Arya M, Bezdan D, Callahan CM, Chen S, Choi AMK, Chlipala GE, Contrepois K, Covington M, Crucian BE, De Vivo I, Dinges DF, Ebert DJ, Feinberg JI, Gandara JA, George KA, Goutsias J, Grills GS, Hargens AR, Heer M, Hillary RP, Hoofnagle AN, Hook VYH, Jenkinson G, Jiang P, Keshavarzian A, Laurie SS, Lee-McMullen B, Lumpkins SB, MacKay M, Maienschein-Cline MG, Melnick AM, Moore TM, Nakahira K, Patel HH, Pietrzyk R, Rao V, Saito R, Salins DN, Schilling JM, Sears DD, Sheridan CK, Stenger MB, Tryggvadottir R, Urban AE, Vaisar T, Van Espen B, Zhang J, Ziegler MG, Zwart SR, Charles JB, Kundrot CE, Scott GBI, Bailey SM, Basner M, Feinberg AP, Lee SMC, Mason CE, Mignot E, Rana BK, Smith SM, Snyder MP, Turek FW. The NASA Twins Study: A multidimensional analysis of a year-long human spaceflight. Science 2019; 364:364/6436/eaau8650. [PMID: 30975860 DOI: 10.1126/science.aau8650] [Citation(s) in RCA: 427] [Impact Index Per Article: 85.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 02/28/2019] [Indexed: 12/11/2022]
Abstract
To understand the health impact of long-duration spaceflight, one identical twin astronaut was monitored before, during, and after a 1-year mission onboard the International Space Station; his twin served as a genetically matched ground control. Longitudinal assessments identified spaceflight-specific changes, including decreased body mass, telomere elongation, genome instability, carotid artery distension and increased intima-media thickness, altered ocular structure, transcriptional and metabolic changes, DNA methylation changes in immune and oxidative stress-related pathways, gastrointestinal microbiota alterations, and some cognitive decline postflight. Although average telomere length, global gene expression, and microbiome changes returned to near preflight levels within 6 months after return to Earth, increased numbers of short telomeres were observed and expression of some genes was still disrupted. These multiomic, molecular, physiological, and behavioral datasets provide a valuable roadmap of the putative health risks for future human spaceflight.
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Affiliation(s)
- Francine E Garrett-Bakelman
- Weill Cornell Medicine, New York, NY, USA.,University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Manjula Darshi
- Center for Renal Precision Medicine, University of Texas Health, San Antonio, TX, USA
| | | | - Ruben C Gur
- University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Ling Lin
- Stanford University School of Medicine, Palo Alto, CA, USA
| | | | | | - Cem Meydan
- Weill Cornell Medicine, New York, NY, USA.,The Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, New York, NY, USA
| | | | - Jad Nasrini
- University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | | | | | - Kumar Sharma
- Center for Renal Precision Medicine, University of Texas Health, San Antonio, TX, USA
| | | | - Lynn Taylor
- Colorado State University, Fort Collins, CO, USA
| | | | | | - Ebrahim Afshinnekoo
- Weill Cornell Medicine, New York, NY, USA.,The Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, New York, NY, USA
| | - Sara Ahadi
- Stanford University School of Medicine, Palo Alto, CA, USA
| | - Aditya Ambati
- Stanford University School of Medicine, Palo Alto, CA, USA
| | | | - Daniela Bezdan
- Weill Cornell Medicine, New York, NY, USA.,The Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, New York, NY, USA
| | | | - Songjie Chen
- Stanford University School of Medicine, Palo Alto, CA, USA
| | | | | | | | - Marisa Covington
- National Aeronautics and Space Administration (NASA), Houston, TX, USA
| | - Brian E Crucian
- National Aeronautics and Space Administration (NASA), Houston, TX, USA
| | | | - David F Dinges
- University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | | | | | | | | | | | | | | | | | - Ryan P Hillary
- Stanford University School of Medicine, Palo Alto, CA, USA
| | | | | | | | - Peng Jiang
- Northwestern University, Evanston, IL, USA
| | | | | | | | | | | | | | | | - Tyler M Moore
- University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | | | - Hemal H Patel
- University of California, San Diego, La Jolla, CA, USA
| | | | - Varsha Rao
- Stanford University School of Medicine, Palo Alto, CA, USA
| | - Rintaro Saito
- University of California, San Diego, La Jolla, CA, USA
| | - Denis N Salins
- Stanford University School of Medicine, Palo Alto, CA, USA
| | | | | | | | - Michael B Stenger
- National Aeronautics and Space Administration (NASA), Houston, TX, USA
| | | | | | | | | | - Jing Zhang
- Stanford University School of Medicine, Palo Alto, CA, USA
| | | | - Sara R Zwart
- University of Texas Medical Branch, Galveston, TX, USA
| | - John B Charles
- National Aeronautics and Space Administration (NASA), Houston, TX, USA.
| | - Craig E Kundrot
- Space Life and Physical Sciences Division, NASA Headquarters, Washington, DC, USA.
| | - Graham B I Scott
- National Space Biomedical Research Institute, Baylor College of Medicine, Houston, TX, USA.
| | | | - Mathias Basner
- University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
| | | | | | - Christopher E Mason
- Weill Cornell Medicine, New York, NY, USA. .,The Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, New York, NY, USA.,The Feil Family Brain and Mind Research Institute, New York, NY, USA.,The WorldQuant Initiative for Quantitative Prediction, New York, NY, USA
| | | | - Brinda K Rana
- University of California, San Diego, La Jolla, CA, USA.
| | - Scott M Smith
- National Aeronautics and Space Administration (NASA), Houston, TX, USA.
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Smith SM, Zwart SR. Spaceflight-related ocular changes: the potential role of genetics, and the potential of B vitamins as a countermeasure. Curr Opin Clin Nutr Metab Care 2018; 21:481-488. [PMID: 30169456 DOI: 10.1097/mco.0000000000000510] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW Within the last decade, it was realized that during and after long-duration spaceflight, some astronauts experience ophthalmic abnormalities including refractive changes, optic disc edema, globe flattening, choroidal folds, and cotton wool spots. Much research has been initiated and conducted, but little evidence is available to differentiate affected crewmembers. RECENT FINDINGS The first published data to distinguish between affected and nonaffected crewmembers identified biochemical differences in affected astronauts: one-carbon pathway metabolite concentrations were higher in these individuals than in nonaffected astronauts, even before flight. These data led to findings that genetics and B-vitamin status were predictors of the incidence of the ophthalmic abnormalities. A multihit hypothesis was developed, with genetics and B-vitamin status as two of several important elements that all contribute to endothelial dysfunction and ultimately to ophthalmic changes after flight. One of these contributing factors - response to carbon dioxide exposure - was recently documented to be affected by the same one-carbon pathway genetics. SUMMARY This line of research may help identify which astronauts are at risk of these ophthalmic changes, and allow targeted treatment. This research may have implications for clinical populations, including patients with polycystic ovary syndrome, that have similar biochemical, endocrine, and genetic characteristics, and it may shed light on why links between cardiovascular disease and the metabolites homocysteine and folate have been elusive and confounded.
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Affiliation(s)
- Scott M Smith
- NASA Lyndon B. Johnson Space Center, Houston, Texas, USA
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49
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Laurie SS, Vizzeri G, Taibbi G, Ferguson CR, Hu X, Lee SMC, Ploutz-Snyder R, Smith SM, Zwart SR, Stenger MB. Effects of short-term mild hypercapnia during head-down tilt on intracranial pressure and ocular structures in healthy human subjects. Physiol Rep 2017; 5:e13302. [PMID: 28611153 PMCID: PMC5471441 DOI: 10.14814/phy2.13302] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 05/04/2017] [Indexed: 01/23/2023] Open
Abstract
Many astronauts experience ocular structural and functional changes during long-duration spaceflight, including choroidal folds, optic disc edema, globe flattening, optic nerve sheath diameter (ONSD) distension, retinal nerve fiber layer thickening, and decreased visual acuity. The leading hypothesis suggests that weightlessness-induced cephalad fluid shifts increase intracranial pressure (ICP), which contributes to the ocular structural changes, but elevated ambient CO2 levels on the International Space Station may also be a factor. We used the spaceflight analog of 6° head-down tilt (HDT) to investigate possible mechanisms for ocular changes in eight male subjects during three 1-h conditions: Seated, HDT, and HDT with 1% inspired CO2 (HDT + CO2). Noninvasive ICP, intraocular pressure (IOP), translaminar pressure difference (TLPD = IOP-ICP), cerebral and ocular ultrasound, and optical coherence tomography (OCT) scans of the macula and the optic disc were obtained. Analysis of one-carbon pathway genetics previously associated with spaceflight-induced ocular changes was conducted. Relative to Seated, IOP and ICP increased and TLPD decreased during HDT During HDT + CO2 IOP increased relative to HDT, but there was no significant difference in TLPD between the HDT conditions. ONSD and subfoveal choroidal thickness increased during HDT relative to Seated, but there was no difference between HDT and HDT + CO2 Visual acuity and ocular structures assessed with OCT imaging did not change across conditions. Genetic polymorphisms were associated with differences in IOP, ICP, and end-tidal PCO2 In conclusion, acute exposure to mild hypercapnia during HDT did not augment cardiovascular outcomes, ICP, or TLPD relative to the HDT condition.
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Affiliation(s)
| | - Gianmarco Vizzeri
- Department of Ophthalmology and Visual Sciences, The University of Texas Medical Branch, Galveston, Texas
| | - Giovanni Taibbi
- Department of Ophthalmology and Visual Sciences, The University of Texas Medical Branch, Galveston, Texas
| | | | - Xiao Hu
- Department of Physiologic Nursing, University of California, San Francisco, San Francisco, California
| | | | - Robert Ploutz-Snyder
- University of Michigan School of Nursing Department of Applied Biostatistics Laboratory, Ann Arbor, Michigan
| | | | - Sara R Zwart
- Department of Preventive Medicine & Community Health, The University of Texas Medical Branch, Galveston, Texas
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