Dataset Information

Opposite response of blood vessels in the retina to 6° head-down tilt and long-duration microgravity.

ABSTRACT: The Spaceflight Associated Neuro-ocular Syndrome (SANS), associated with the headward fluid shifts incurred in microgravity during long-duration missions, remains a high-priority health and performance risk for human space exploration. To help characterize the pathophysiology of SANS, NASA's VESsel GENeration Analysis (VESGEN) software was used to map and quantify vascular adaptations in the retina before and after 70 days of bed rest at 6-degree Head-Down Tilt (HDT), a well-studied microgravity analog. Results were compared to the retinal vascular response of astronauts following 6-month missions to the International Space Station (ISS). By mixed effects modeling, the trends of vascular response were opposite. Vascular density decreased significantly in the 16 retinas of eight astronauts and in contrast, increased slightly in the ten retinas of five subjects after HDT (although with limited significance). The one astronaut retina diagnosed with SANS displayed the greatest vascular loss. Results suggest that microgravity is a major variable in the retinal mediation of fluid shifts that is not reproduced in this HDT bed rest model.

SUBMITTER: Taibbi G

PROVIDER: S-EPMC8516890 | biostudies-literature | 2021 Oct

REPOSITORIES: biostudies-literature

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Opposite response of blood vessels in the retina to 6° head-down tilt and long-duration microgravity.

Taibbi Giovanni G Young Millennia M Vyas Ruchi J RJ Murray Matthew C MC Lim Shiyin S Predovic Marina M Jacobs Nicole M NM Askin Kayleigh N KN Mason Sara S SS Zanello Susana B SB Vizzeri Gianmarco G Theriot Corey A CA Parsons-Wingerter Patricia P

NPJ microgravity 20211014 1

The Spaceflight Associated Neuro-ocular Syndrome (SANS), associated with the headward fluid shifts incurred in microgravity during long-duration missions, remains a high-priority health and performance risk for human space exploration. To help characterize the pathophysiology of SANS, NASA's VESsel GENeration Analysis (VESGEN) software was used to map and quantify vascular adaptations in the retina before and after 70 days of bed rest at 6-degree Head-Down Tilt (HDT), a well-studied microgravity ...[more]

PMID: 34650071

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Project description:Adverse cognitive and behavioral conditions and psychiatric disorders are considered a critical and unmitigated risk during future long-duration space missions (LDSM). Monitoring and mitigating crew health and performance risks during these missions will require tools and technologies that allow to reliably assess cognitive performance and mental well-being. Electroencephalography (EEG) has the potential to meet the technical requirements for the non-invasive and objective monitoring of neurobehavioral conditions during LDSM. Weightlessness is associated with fluid and brain shifts, and these effects could potentially challenge the interpretation of resting state EEG recordings. Head-down tilt bed rest (HDBR) provides a unique spaceflight analog to study these effects on Earth. Here, we present data from two long-duration HDBR experiments, which were used to systematically investigate the time course of resting state electrocortical activity during prolonged HDBR. EEG spectral power significantly reduced within the delta, theta, alpha, and beta frequency bands. Likewise, EEG source localization revealed significantly lower activity in a broad range of centroparietal and occipital areas within the alpha and beta frequency domains. These changes were observed shortly after the onset of HDBR, did not change throughout HDBR, and returned to baseline after the cessation of bed rest. EEG resting state functional connectivity was not affected by HDBR. The results provide evidence for a postural effect on resting state brain activity that persists throughout long-duration HDBR, indicating that immobilization and inactivity per se do not affect resting state electrocortical activity during HDBR. Our findings raise an important issue on the validity of EEG to identify the time course of changes in brain function during prolonged HBDR, and highlight the importance to maintain a consistent body posture during all testing sessions, including data collections at baseline and recovery.

Project description:BackgroundThe hemodynamic variations of cardiac and cerebral blood monitoring during pneumoperitoneum and head-down tilt position in general anesthetized elderly patients remain unresolved. We evaluated the time course of cerebral tissue oxygen saturation (SctO2) and cardiac output (CO) and investigated how the changes in hemodynamic values during the surgery would affect cerebral perfusion in elderly patients.MethodsIn this prospective observational study of 47 elderly patients (≥65 years old, American Society of Anesthesiologists Physical status I to III) undergoing laparoscopic colorectal radical resection with head-down position, SctO2 by near-infrared spectroscopy and arterial pressure-based cardiac output (APCO), Cardiac index (CI), stroke volume (SV), and SV index (SVI) according to FloTrac/Vigileo were measured at 9 time points. Heart rate (HR), mean arterial blood pressure (MAP), end-tidal carbon dioxide (ETCO2), bispectral index (BIS), central venous pressure (CVP), and ventilator settings were recorded. Results are reported as medians [95% confidence interval (CI)].ResultsHeart Rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), MAP, CO, CI, SV, SVI, and SctO2 before incision decreased significantly compared with the waking state (P<0.05). SBP, CO, CI, SV, and SVI before incision decreased significantly compared with induction and intubation (P<0.05). SBP, DBP, MAP, and CVP increased significantly after pneumoperitoneum and head-down tilt, and then decreased during the following hour. CO and SVI decreased, while CI and SV increased after pneumoperitoneum and head-down tilt. CO, CI, SV and SVI decreased at the following 20, 40, and 60 minutes respectively. SctO2 increased after pneumoperitoneum and head-down tilt and remained stable during the following hour. CVP decreased while CO, CI, SV, and SVI increased significantly at the end of pneumoperitoneum and head-down tilt (P<0.05). HR and MAP increased significantly at the end of surgery compared to at the end of pneumoperitoneum and head-down tilt (P<0.05). CI was associated with SctO2 as indicated by a Pearson r of 0.035 (P<0.05).ConclusionsAnesthesia, pneumoperitoneum, and head-down tilt affect cardiac function and cerebral perfusion in elderly patients. cardiac index independently affects elderly patients' cerebral blood flow.

Project description:Microgravity influences are prevalent during orbital flight and can adversely affect astronaut physiology. Notably, it may affect the physicochemical properties of saliva and the salivary microbial community. Therefore, this study simulates microgravity in space using a ground-based -6° head-down bed rest (HDBR) test to observe the effects of microgravity on oral salivary secretion function and the salivary microbiome. Sixteen healthy young male volunteers were recruited for the 15-day -6° HDBR test. Non-stimulated whole saliva was collected on day 1 (pre-HDBR), on days 5, 10, and 15 of HDBR, and day 6 of recovery. Salivary pH and salivary flow rate were measured, and the V3-V4 region of the 16S rRNA gene was sequenced and analyzed in 80 saliva samples. The results showed that there were no significant differences in salivary pH, salivary flow rate, and alpha diversity between any two time points. However, beta diversity analysis revealed significant differences between pre-HDBR and the other four time points. After HDBR, the relative abundances of Actinomyces, Parvimonas, Peptostreptococcus, Porphyromonas, Oribacterium, and Capnocytophaga increased significantly, whereas the relative abundances of Neisseria and Haemophilus decreased significantly. However, the relative abundances of Oribacterium and Capnocytophaga did not recover to the pre-HDBR level on day 6 of recovery. Network analysis revealed that the number of relationships between genera decreased, and the positive and negative correlations between genera changed in a complex manner after HDBR and did not reach their original levels on day 6 of recovery. PICRUSt analysis demonstrated that some gene functions of the salivary microbiome also changed after HDBR and remained significantly different from those before HDBR on day 6 of recovery. Collectively, 15 days of -6° HDBR had minimal effect on salivary secretion function but resulted in significant changes in the salivary microbiome, mainly manifested as an increase in oral disease-related bacteria and a decrease in oral health-related commensal bacteria. Further research is required to confirm these oral microbial changes and explore the underlying pathological mechanisms to determine the long-term effects on astronauts embarking on long-duration voyages to outer space.

Project description:BackgroundAdverse effects of spaceflight on sensorimotor function have been linked to altered somatosensory and vestibular inputs in the microgravity environment. Whether these spaceflight sequelae have a central nervous system component is unknown. However, experimental studies have shown spaceflight-induced brain structural changes in rodents' sensorimotor brain regions. Understanding the neural correlates of spaceflight-related motor performance changes is important to ultimately develop tailored countermeasures that ensure mission success and astronauts' health.MethodHead down-tilt bed rest (HDBR) can serve as a microgravity analog because it mimics body unloading and headward fluid shifts of microgravity. We conducted a 70-day 6° HDBR study with 18 right-handed males to investigate how microgravity affects focal gray matter (GM) brain volume. MRI data were collected at 7 time points before, during and post-HDBR. Standing balance and functional mobility were measured pre and post-HDBR. The same metrics were obtained at 4 time points over ~90 days from 12 control subjects, serving as reference data.ResultsHDBR resulted in widespread increases GM in posterior parietal regions and decreases in frontal areas; recovery was not yet complete by 12 days post-HDBR. Additionally, HDBR led to balance and locomotor performance declines. Increases in a cluster comprising the precuneus, precentral and postcentral gyrus GM correlated with less deterioration or even improvement in standing balance. This association did not survive Bonferroni correction and should therefore be interpreted with caution. No brain or behavior changes were observed in control subjects.ConclusionsOur results parallel the sensorimotor deficits that astronauts experience post-flight. The widespread GM changes could reflect fluid redistribution. Additionally, the association between focal GM increase and balance changes suggests that HDBR also may result in neuroplastic adaptation. Future studies are warranted to determine causality and underlying mechanisms.

Dataset Information

Opposite response of blood vessels in the retina to 6° head-down tilt and long-duration microgravity.

Publications

Opposite response of blood vessels in the retina to 6° head-down tilt and long-duration microgravity.

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