Volume 2 (2022): Issue 1 (January 2022)

Exposure to long-duration microgravity leads to ocular changes in astronauts, manifested by a variety of signs and symptoms during spaceflight that in some cases persist after return to Earth. These morphological and functional changes are only partly understood and are of occupational health relevance. To investigate further into the molecular basis of the changes occurring in ocular tissue upon exposure to spaceflight, eyes were collected from male C57BL/6 mice flown on STS-135 (FLT) on landing day or from their ground control counterparts maintained at similar conditions within the Animal Enclosure Module (AEM). One eye was fixed for histological sectioning while the contralateral eye was dissected to isolate the retina for gene expression profiling. 8-hydroxy-deoxyguanosine (8OHdG) staining showed a statistically significant increase in the inner nuclear layer of FLT samples compared to AEM. Gene expression analysis in isolated retina identified 139 differentially expressed genes in FLT compared to AEM control samples. The genes affected were mainly involved in pathways and processes of endoplasmic reticulum (ER) stress, inflammation, neuronal and glial cell loss, axonal degeneration, and herpes virus activation. These results suggest a concerted change in gene expression in the retina of mice flown in space, possibly leading to retinal damage, degeneration, and remodeling.

Space travel beyond the Earth’s protective magnetosphere risks exposing astronauts to ionizing radiation, such as that generated during a solar particle event (SPE). Ionizing radiation has well documented effects on blood cells and it is generally assumed that these effects contribute to the hematopoietic syndrome (HS), observed in animals and humans, following exposure to total body irradiation (TBI). The purpose of the current study was to assess the role of gender on the effects of gamma radiation on blood cells. C3H/HeN mice were irradiated with a ¹³⁷Cs gamma source. Radiation had similar effects on white blood cells (WBCs), lymphocytes, and granulocytes in male and female C3H/HeN mice, while red blood cell (RBC) counts and hematocrit values remained stable following radiation exposure. Non-irradiated male mice had 13% higher platelet counts, compared with their female counterparts, and showed enhanced recovery of platelets on day 16 following radiation exposure. Hence, gender differences influence the response of platelets to TBI exposure.

High charge (Z) and energy (E) (HZE) particles in deep space have significantly contributed to the biological effects of space radiation, although they only account for less than 1% of the galactic cosmic rays (GCR) particle fluxes. Previously we have shown that combined radiation exposure of 2-Gy proton (¹H) followed by 0.5-Gy iron (⁵⁶Fe) ion particles increase transformation in human colonic epithelial cells (HCEC CT7). The present study was undertaken to characterize if additional HZE ions, such as oxygen (¹⁶O) and silicon (²⁸Si) particles, also result in increased cell transformation. HCEC CT7 cells irradiated with 1-Gy ¹⁶O (250 MeV/nucleon), followed 24 hours later by 1-Gy ²⁸Si particle (300 MeV/nucleon), showed an increase in proliferation, anchorage-independent growth, migration, and invasion abilities compared to unirradiated controls. In addition, we found that the β-catenin pathway was activated and that subsets of DNA repair genes were under-expressed in these transformed cells. Pretreatment with the radioprotector, CDDO-Me, 18 hours before and during irradiation prevented the HZE-induced transformation. These results can be interpreted to suggest that the mixed radiation exposure of ¹⁶O followed by ²⁸Si has carcinogenic potential. Importantly, this transformation can be protected by CDDO-Me pre-treatment.

Astronauts traveling in space missions outside of low Earth orbit will be exposed for longer times to a microgravity environment. In addition, the increased travel time involved in exploration class missions will result in an increased risk of exposure to significant doses of solar particle event (SPE) radiation. Both conditions could significantly affect the number of circulating blood cells. Therefore, it is critical to determine the combined effects of exposure to both microgravity and SPE radiation. The purpose of the present study was to assess these risks by evaluating the effects of SPE-like proton radiation and/or microgravity, as simulated with the hindlimb unloading (HU) system, on circulating blood cells using mouse as a model system. The results indicate that exposure to HU alone caused minimal or no significant changes in mouse circulating blood cell numbers. The exposure of mice to SPE-like proton radiation with or without HU treatment caused a significant decrease in the number of circulating lymphocytes, granulocytes and platelets. The reduced numbers of circulating lymphocytes, granulocytes, and platelets, resulting from the SPE-like proton radiation exposure, with or without HU treatment, in mice suggest that astronauts participating in exploration class missions may be at greater risk of developing infections and thrombotic diseases; thus, countermeasures may be necessary for these biological endpoints.

Here we report on the science verification test (SVT) and the payload verification test (PVT) that we conducted in preparation for experiments evaluating the impact of microgravity on Arabidopsis thaliana root development and cellular structure. Hardware used for these experiments was the Advanced Biological Research System (ABRS) and Kennedy Space Center (KSC) fixation tubes (KFTs). A simple procedure to delay seed germination prior to installation on ABRS involved the construction of a metal box with a single far-red (FR) light-emitting diode (LED). The exposure of Petri dishes containing seeds (ecotype Columbia) to FR light immediately after planting and maintaining Petri dishes in the dark prevented seed germination until exposure to white light on ABRS. Additional tests revealed that germination can be delayed for up to 10 weeks with FR light treatment. Seedlings fixed in KFTs preloaded with glutaraldehyde for subsequent microscopy studies were not adequately preserved. We suspected that poor fixation was due to the extended contact of glutaraldehyde with oxygen while stored on KFTs, which likely contributed to fixative oxidation. During PVT, minor modifications to address fixation problems encountered during SVT included storing KFTs with glutaraldehyde at 4^o C in the dark, increasing glutaraldehyde concentration from 3% to 5%, and bubbling nitrogen (N₂) gas over the glutaraldehyde solution prior to loading the KFTs. These changes led to improvements in the quality of microscopic images. Lessons learned from SVT and PVT allowed us to optimize some of the preflight protocols needed to successfully implement Advanced Plant EXperiments (APEX) in space.

The leaf venation of angiosperms is key to their terrestirial dominance. These higher land plants include maple, corn, and ISS model organism Arabidopsis thaliana. The venation-dependent photosynthetic capacity of angiosperm leaves is largely responsible for terrestrial production of glucose and atmospheric _{oxygen, and may be fundamentally important to long-term space colonization. Leaf studies in orbit, where human-tended experiments are limited, can be enhanced by quantifying complex venation patterning. VESsel GENeration Analysis (VESGEN), a beta-level NASA software that analyzes vertebrate and human vascular branching for biomedical applications, is therefore being modified to map the branching venation patterns of dicot angiosperm leaves. By physiological branching rules, VESGEN decomposes a continuously connected vascular tree into its structural (dendritic) branching and reticulate (networked) capillary components.}

For an arabidopsis juvenile leaf flown on NASA Space Shuttle Mission (STS)-130, the venation patterning of larger structural vessel orders 1°-2° remained relatively constant compared to normal gravity (by vessel number density N_v, 1.24E-5/micron², and 1.29E-5/micron², respectively). However, as a measure of increased venation maturity, N_v of smaller reticulate orders ≥ 3° increased considerably from 7.7E-6/micron² in ground control to 1.74E-5/micron² in the STS-130 leaf. Vascular geometric complexity is another feature of plant development that is governed in part by changes in gene expression patterns responding to environmental influence. We therefore propose that the mapping of leaf venation patterns by VESGEN can provide additional insight into plant responses to the spaceflight environment.

Backlit droplet images are evaluated for droplet combustion experiments that have been performed on the International Space Station. The focus of the present analyses is on non-sooting or lightly-sooting droplets. The influences of diffraction, interference, and partial coherence on droplet images are considered via Fourier optics modeling. It is found that light diffraction at the droplet edge can contribute significantly to errors in droplet size measurements. Other error sources include background light variations and partial coherence effects. An image-processing algorithm is proposed to account for the effects of diffraction, partial coherence, and background light variations on measurements of droplet sizes.

Physiological deconditioning is a critical problem in space, especially during long-term missions. Resistance exercise, coupled with lower body negative pressure (LBNP), has been shown to be effective in counteracting some of the deconditioning related problems. This paper describes the development of a compact and effective resistance exercise machine that works within an existing environmentally controlled LBNP Box, and is designed to simulate both exercise and sitting, to decrease microgravity-induced deconditioning by simulating physiological and biomechanical features of upright exercise and daily activities. Theoretical calculations are carried out to determine whether kinematics, musculoskeletal loadings, and metabolic rate during supine exercise within the existing LBNP Box are similar to those of an upright posture in Earth gravity (1G).

Preliminary results show subjects that use the resistance machine presented in this paper will be able to elicit loads comparable to exercise on Earth, since the ground reaction forces are greater than their body weight (BW). The largest single-leg forces during resistance exercise are 1.16 BW (232 lbs) during supine position when γ, the angle between the horizontal and the ground pivot on the right side of the mechanism, equals 187 degrees and minimal at 0.68 BW (136 lbs) when γ equals 177 degrees. At the lowest setting of the machine, peak resistance of the foot pedal during the outward stroke is 196 lbf. This force, added to the force due to the 50 mmHg of negative differential pressure, gives a total force of 400 lb, which is 2 BW.

The results suggest that this machine can be used to collect and establish a database under both terrestrial conditions and microgravity environments, such as the International Space Station (ISS), to enhance medical researchers’ understanding of how LBNP paired with exercise impacts osteoporosis, orthostatic intolerance, and cardiovascular health.

In-flight resistive exercise workouts are performed on novel flywheel-based hardware. Designs of such workouts may be better served by measuring changes to lactate and testosterone values. To make workouts pertinent to μg they should utilize unique features of flywheel-based hardware, such as the option to exert eccentric torque. Our study compares changes to blood lactate and testosterone concentrations ([BLa^-], [T]) from leg press workouts that differ by contractile mode and work volume, on a flywheel ergometer. Subjects performed three workouts; two entailed two sets of concentric-eccentric (CE2) or concentric-only (CO2) actions. A third involved four sets of concentric-only actions (CO4). Workouts entailed eight-repetition sets with 90-second rest periods. Total work (TW) was quantified per workout. [T] were assessed, both pre- and post-exercise. [BLa^-] were measured pre- and at 0-, 5-, 10-, 15-, and 20-minutes post-exercise. TW was assessed with a one-way analysis of variance (ANOVA). [BLa^-] and [T] were evaluated with two- and three-factor ANOVAs, respectively. Scheffe’s test was our post-hoc. TW data had an inter-workout (CE2, CO4 > CO2) difference. [BLa^-] included a two-way interaction as CO4 workouts evoked higher post-exercise values. Results for [T] produced gender (men > women) and time (post > pre) main effects. Our results imply flywheel-based workouts with a large volume of concentric actions evoke no greater increase in [T] than workouts with only half the muscle shortening activity, despite attainment of higher TW and post-workout [BLa^-].

Weather balloon flights provide affordable access to a space-like environment for student research. Typical flights last for 2.0-2.5 hours and reach altitudes of approximately 30 km. Payloads are exposed to intense cosmic and ultraviolet radiation, temperatures below -60° C, and atmospheric pressures of approximately 0.01 atmospheres. We report on simple laboratory procedures intended primarily for high school and middle school students in studying the effects of high-altitude balloon flights on yeast and plant seeds. Saccharomyces cerevisiae, Raphanus sativus, and Brassica rapa were flown on two weather balloons inside and outside of payload containers to an altitude of approximately 27.5 km. After the flights the yeast cells were plated on YED media and incubated to assess survival and mutation rates. The seeds were planted to assess survival and variation in quantitative traits. We also discuss connections to disciplinary core ideas in the Next Generation Science Standards (NGSS) (NGSS Lead States, 2013) and provide an overview of further laboratory investigations designed to enhance students’ understanding of the effects of radiation on living organisms.