Volume 3 (2015): Issue 1 (July 2015)

Secretory proteins produced by salivary glands are stored in granules and released into saliva. Rodent salivary glands are a reliable experimental model because they are morphologically and functionally similar to those of humans. To determine if the effects of microgravity on secretory proteins are increased on extended flights, their expression in mouse parotid glands, morphological, immunocytochemical, and biochemical/molecular methods were employed. Acinar cells of STS-135 (13 day) and Bion-M1 (30 day) flight animals showed an increase of autophagy and apoptosis, while duct cells contained vacuoles with endocytosed proteins. In STS-135, decreases were seen in the regulatory subunit of type II protein kinase A (RII) by Western blotting, and demilune cell and parotid protein (DCPP) and α-amylase (p<0.01) by immunogold labeling, while proline-rich proteins (PRPs, p<0.001) and parotid secretory protein (PSP, p<0.05) were increased. These results suggest microgravity effects on secretion are function-dependent. Microarray analyses showed significant changes in the expression of a number of genes, including components of the cyclic-3’,5’,-adenosine monophosphate (cyclic AMP) signaling pathway. Compared to habitat ground controls, mice from both flights exhibited altered expression of cyclic AMP-specific phosphodiesterases, adenylate cyclase isoforms, and several A-kinase anchoring proteins. Bion-M1 flight mice showed increases in gene expression for lysozyme and amylase, a decrease in PRPs, and RII expression was unchanged from control values. Secretory protein expression is altered by travel in space, representing a reversible adjustment to microgravity conditions. Ultimately, the goal is to develop a test kit using saliva — an easily obtained body fluid — to assess the physiologic effects of travel in space.

It has been well documented that spaceflight has adverse effects on many tissues and systems throughout the body. Although this phenomenon is well documented, relatively little research has been done in the area of the female reproductive system. If spaceflight has harmful effects on the female reproductive system, the migration of the human species into space would be greatly compromised. The purpose of this study was to determine the effects of spaceflight on the thickness of the apical mucin layer in the vaginae of mice, as changes in this layer could have detrimental effects on sperm survival and, therefore, a profound impact on the animal’s ability to reproduce. This study examined the thickness of the vaginal mucin lining from female mice that were exposed to 13 days of spaceflight and their concomitant controls. The tissues were stained using a technique commonly used to localize and analyze mucin varieties. The tissue was qualitatively analyzed for the type of mucin produced (i.e., acidic, neutral, acidic/neutral mixture). Further, the tissue was quantitatively analyzed for the amount of mucins produced by measuring the thickness of the mucin layer. The results of this study indicate that spaceflight causes a thickening of the mucin lining of the vaginal canal. The results further indicate being housed in an Animal Enclosure Module also caused a thickening of the vaginal mucin layer — presumably due to internal cage environmental factors — but this effect was not as pronounced as that seen in the spaceflight mice.

Inversion is the regular position for bats at rest, but continuous inversion was expected to reverse the gravity vector exposure from feet-ward to head-ward and present hemodynamic challenges that induce remodeling of the aorta. There is paucity of information regarding the cardiovascular structural adaptations in bats engaged in regulating cranial or caudal blood redistribution in prolonged inversion. The aim of this study was to determine aortic adaptations in bats during prolonged inversion. Forty (40) bats were captured at Iwo, Osun State, Nigeria and randomly allocated into a normal control group and three test groups (n=10/group). The inversion period was not extended in control group A, but was maintained 8 days in B, 15 days in C, and 22 days in D. At the end of each inversion period, the bats were euthanized using intramuscular injection, and tissues were processed for Haematoxylin and Eosin, Orcein, and Van Gieson staining. Histological changes in the tunica media and adventitia were quantified, and the results were analyzed statistically. The ascending aorta exhibited thickening of the media and adventitia, whereas the abdominal aorta showed thinning of these regions. The changes increased in magnitude with longer periods of inversion. The histological stains indicated alterations in smooth muscle cells, collagen, and elastin content, consistent with predicted elevated pressure in the ascending and decreased pressure in the abdominal aortae. The vascular adaptation in bats may provide insights into suspected cardiovascular changes in astronauts during long-term spaceflight.

Tree fruits (e.g., apples, plums, cherries) are appealing constituents of a crew menu for long-duration exploration missions (i.e., Mars), both in terms of their nutritive and menu diversity contributions. Although appealing, tree fruit species have long been precluded as candidate crops for use in plant-based bioregenerative life support system designs based on their large crown architecture, prolonged juvenile phase, and phenological constraints. Recent advances by researchers at the United States Department of Agriculture (USDA) have led to the development of plum (Prunus domestica) trees ectopically over-expressing the Flowering Locus T-1 (FT1) gene from Populus trichocarpa (poplar). The transformed plants exhibit atypical phenotypes that seemingly eliminate the aforementioned obstacles to spaceflight. Here we demonstrate the FT1 expression system (FasTrack) and the resultant dwarf growth habits, early flowering, and continuous fruit production. The potential contribution of P. domestica as a countermeasure to microgravity-induced bone loss is also discussed.

The National Aeronautics and Space Administration (NASA) has plans to further their manned space exploration to Mars and possibly beyond. The potential toxicity of lunar and Martian dusts to astronauts is a big concern. Primary routes of exposure for astronauts are dermal contact, ocular contact, and inhalation. In this study, we focused on dermal contact exposure using human skin cells to investigate the cytotoxic and genotoxic effects of two fractions of lunar dust simulant (JSC-1A-vf, JSC-1A-f) and a Mars dust simulant (Mars-1A), and compared them to urban dust (urban particulate matter), as urban dust toxicity is better understood and thus, provides a good comparison. Our data show the three simulants and urban dust are cytotoxic to human skin cells. The JSC-1A-vf lunar dust simulant is more cytotoxic than the JSC-1A-f and urban dust. Urban dust cytotoxicity is similar to Mars dust simulant after 120 h exposure. All three dust simulants and urban dust show similar low genotoxicity effects. Our data suggest extraterrestrial dust can damage skin cells and may have the potential to be harmful to humans.

One of the challenges of human spaceflight in deep space is the harsh radiation environment. The current best practices for mitigating radiation are via design and multifunctional materials. There have been many studies over the years showing low-Z materials as the best radiation mitigators for spaceflight. In addition, there have recently been several studies investigating hydrogen-loading of materials for fuel cells. If it is possible to load a material with additional low-Z materials — such as hydrogen — it may be possible to increase the radiation mitigating potential of these materials. Thus, our work is focused on metal hydrides (MHs), metal organic frameworks (MOFs), and nanoporous carbon composites (CNTs) that can be loaded with hydrogen or methane for radiation mitigation. Our previous simulation work focused on hydrogen-loading only, and investigated the capability of these materials during a particularly hard solar particle event (SPE) in October 1989. In these simulations, we found 50% of the investigated carbon composites outperformed high-density polyethylene (HDPE) — the current standard for passive radiation shielding. We also found 10% of the investigated MOFs outperformed HDPE. Therefore, we wanted to continue our simulation study of these materials to determine whether they may also show improvement over HDPE in a galactic cosmic ray (GCR) environment. Furthermore, there are concerns with using hydrogen as a loading material — a result of its flammability and instability in thermal extremes. Thus, we are also considering methane-loading of the MOFs and CNTs. The details of this work will be discussed in the paper. Overall, the results showed several MOFs, CNTs, and MHs that performed very well when compared with our typical spacecraft material of aluminum and our standard shielding material of HDPE. This study also showed there is little difference in the dose between hydrogen-loaded and methane-loaded materials of the same base chemistry.