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NASA NTRS2011

Desert Rats 2010 Operations Tests: Insights from the Geology Crew Members

Desert Research and Technology Studies (Desert RATS) is a multi-year series of tests of NASA hardware and operations deployed in the high desert of Arizona. Conducted annually since 1997, these activities exercise planetary surface hardware and operations in relatively harsh conditions where long-distance, multi-day roving is achievable. Such activities not only test vehicle subsystems, they also stress communications and operations systems and enable testing of science operations approaches that advance human and robotic surface exploration capabilities. Desert RATS 2010 tested two crewed rovers designed as first-generation prototypes of small pressurized vehicles, consistent with exploration architecture designs. Each rover provided the internal volume necessary for crewmembers to live and work for periods up to 14 days, as well as allowing for extravehicular activities (EVAs) through the use of rear-mounted suit ports. The 2010 test was designed to simulate geologic science traverses over a 14-day period through a volcanic field that is analogous to volcanic terrains observed throughout the Solar System. The test was conducted between 31 August and 13 September 2010. Two crewmembers lived in and operated each rover for a week with a "shift change" on day 7, resulting in a total of eight test subjects for the two-week period. Each crew consisted of an engineer/commander and an experienced field geologist. Three of the engineer/commanders were experienced astronauts with at least one Space Shuttle flight. The field geologists were drawn from the scientific community, based on funded and published field expertise.

Bleacher, J. E.↗
NASA NTRS2011

Tools and Technologies Needed for Conducting Planetary Field Geology While On EVA: Insights from the 2010 Desert RATS Geologist Crewmembers

Observation is the primary role of all field geologists, and geologic observations put into an evolving conceptual context will be the most important data stream that will be relayed to Earth during a planetary exploration mission. Sample collection is also an important planetary field activity, and its success is closely tied to the quality of contextual observations. To test protocols for doing effective planetary geologic fieldwork, the Desert RATS (Research and Technology Studies) project deployed two prototype rovers for two weeks of simulated exploratory traverses in the San Francisco volcanic field of northern Arizona. The authors of this paper represent the geologist crewmembers who participated in the 2010 field test. We document the procedures adopted for Desert RATS 2010 and report on our experiences regarding these protocols. Careful consideration must be made of various issues that impact the interplay between field geologic observations and sample collection, including time management; strategies related to duplication of samples and observations; logistical constraints on the volume and mass of samples and the volume/transfer of data collected; and paradigms for evaluation of mission success. We find that the 2010 field protocols brought to light important aspects of each of these issues, and we recommend best practices and modifications to training and operational protocols to address them. Underlying our recommendations is the recognition that the capacity of the crew to "flexibly execute" their activities is paramount. Careful design of mission parameters, especially field geologic protocols, is critical for enabling the crews to successfully meet their science objectives.

Young, Kelsey↗
NASA NTRS2012

NASA's Desert RATS Science Backroom: Remotely Supporting Planetary Exploration

NASA's Desert Research and Technology Studies (Desert RATS) is a multi-year series of tests designed to exercise planetary surface hardware and operations in conditions where long-distance, multi-day roving is achievable. In recent years, a D-RATS science backroom has conducted science operations and tested specific operational approaches. Approaches from the Apollo, Mars Exploration Rovers and Phoenix missions were merged to become the baseline for these tests. In 2010, six days of lunar-analog traverse operations were conducted during each week of the 2-week test, with three traverse days each week conducted with voice and data communications continuously available, and three traverse days conducted with only two 1-hour communications periods per day. In 2011, a variety of exploration science scenarios that tested operations for a near-earth asteroid using several small exploration vehicles and a single habitat. Communications between the ground and the crew in the field used a 50-second one-way delay, while communications between crewmembers in the exploration vehicles and the habitat were instantaneous. Within these frameworks, the team evaluated integrated science operations management using real-time science operations to oversee daily crew activities, and strategic level evaluations of science data and daily traverse results. Exploration scenarios for Mars may include architectural similarities such as crew in a habitat communicating with crew in a vehicle, but significantly more autonomy will have to be given to the crew rather than step-by-step interaction with a science backroom on Earth.

Cohen, Barbara A.↗
NASA NTRS2012

Desert RATS 2011: Near-Earth Asteroid Human Exploration Operations

The Desert Research and Technology Studies (D-RATS) 2011 field test involved the planning and execution of a series of exploration scenarios under operational conditions similar to those that would be expected during a human exploration mission to a near-Earth asteroid (NEA). The focus was on understanding the operations tempo during simulated NEA exploration and the implications of communications latency and limited data bandwidth. Anchoring technologies and sampling techniques were not evaluated due to the immaturity of those technologies and the inability to meaningfully test them at D-RATS. Reduced gravity analogs and simulations are being used to fully evaluate Multi-Mission Space Exploration Vehicle (MMSEV) and extravehicular (EVA) operations and interactions in near-weightlessness at a NEA as part of NASA s integrated analogs program. Hypotheses were tested by planning and performing a series of 1-day simulated exploration excursions comparing test conditions all of which involved a single Deep Space Habitat (DSH) and either zero, one, or two MMSEVs; three or four crewmembers; one of two different communications bandwidths; and a 100-second roundtrip communications latency between the field site and Houston. Excursions were executed at the Black Point Lava Flow test site with a Mission Control Center and Science Support Room at Johnson Space Center (JSC) being operated with 100-second roundtrip communication latency to the field. Crews were composed of astronauts and professional field geologists and teams of Mission Operations, Science, and Education & Public Outreach (EPO) experts also supported the mission simulations each day. Data were collected separately from the Crew, Mission Operations, Science, and EPO teams to assess the test conditions from multiple perspectives. For the operations tested, data indicates practically significant benefits may be realized by including at least one MMSEV and by including 4 versus 3 crewmembers in the NEA exploration architecture as measured by increased Scientific Data Quality, EVA Exploration Time, Capability Assessment Ratings, and Overall Acceptability ratings by Crew, Mission Operations, Science, and Education & Public Outreach teams. A combination of text and voice was used to effectively communicate over the 100-second roundtrip communications latency and increased communication bandwidth yielded a small but practically significant improvement in Overall Acceptability as rated by the Science team, although the impact of bandwidth on scientific strategic planning was not assessed. No effect of increased bandwidth was observed with respect to Crew, Mission Operations, or EPO team ratings of Overall Acceptability.

Abercromby, Andrew↗
NASA NTRS2013

Overview of the Habitat Demonstration Unit Power System Integration and Operation at Desert RATS 2010

A habitat demonstration unit (HDU) was constructed at NASA Johnson Space Center (JSC) and designed by a multicenter NASA team led out of NASA Kennedy Space Center (KSC). The HDU was subsequently utilized at the 2010 Desert Research and Technology Studies (RATS) program held at the Black Point Lava Flow in Arizona. This report describes the power system design, installation and operation for the HDU. The requirements for the power system were to provide 120 VAC, 28 VDC, and 120 VDC power to the various loads within the HDU. It also needed to be capable of providing power control and real-time operational data on the load's power consumption. The power system had to be capable of operating off of a 3 phase 480 VAC generator as well as 2 solar photovoltaic (PV) power systems. The system operated well during the 2 week Desert RATS campaign and met all of the main goals of the system. The power system is being further developed to meet the future needs of the HDU and options for this further development are discussed.

Colozza, Anthony J.↗
NASA NTRS2014

Hindlimb Suspension as a Model to Study Ophthalmic Complications in Microgravity Status Report: Optimization of Rat Retina Flat Mounts Staining to Study Vascular Remodeling

Preliminary data from a prior tissue‐sharing experiment has suggested that early growth response protein‐1 (Egr1), a transcription factor involved in various stress responses in the vasculature, is induced in the rat retina after 14 days of hindlimb suspension (HS) and may be evidence that mechanical stress is occurring secondary to the cephalad fluid shift. This mechanical stress could cause changes in oxygenation of the retina, and the subsequent ischemia‐ or inflammation‐driven hypoxia may lead to microvascular remodeling. This microvascular remodeling process can be studied using image analysis of retinal vessels and can be then be quantified by the VESsel GENeration Analysis (VESGEN) software, a computational tool that quantifies remodeling patterns of branching vascular trees and capillary or vasculogenic networks. Our project investigates whether rodent HS is a valid model to study the effects of simulated‐weightlessness on ocular structures and their relationship with intracranial pressure (ICP). One of the hypotheses to be tested is that HS‐induced cephalad fluid shift is accompanied by vascular engorgement that produces changes in retinal oxygenation, leading to oxidative stress, hypoxia, microvascular remodeling, and cellular degeneration. We have optimized the procedure to obtain flat mounts of rat retina, staining of the endothelial lining in vasculature and acquisition of high quality images suitable for VESGEN analysis. Briefly, eyes were fixed in 4% paraformaldehyde for 24 hours and retinas were detached and then mounted flat on microscope slides. The microvascular staining was done with endothelial cell‐specific isolectin binding, coupled to Alexa‐488 fluorophore. Image acquisition at low magnification and high resolution was performed using a new Leica SP8 confocal microscope in a tile pattern across the X,Y plane and multiple sections along the Z‐axis. This new confocal microscope has the added capability of dye separation using the Linear Unmixing method and allows us to remove the autofluorescence originating from the photoreceptor layer. In summary, we have an improved method for studying the retinal microvasculature that will provide an increase in the quality of images captured and will be applied throughout the various animal cohorts of the recentlyinitiated study that will evaluate rodent HS as a model to study ophthalmic complications in microgravity.

Theriot, Corey A.↗
NASA NTRS2014

Persistent Expression Changes of Fibrosis-Related Genes in the Lung Tissues of Rats Exposed to Lunar Dust Particles

The Moon's surface is covered by a layer of fine, potential reactive dust. Lunar dust contain about 1‐2% of very fine respirable dust (less than 3 micrometers). The habitable area of any lunar landing vehicle and outpost would inevitably be contaminated with lunar dust that could pose a health risk. The purpose of the study is to evaluate the toxicity of Apollo moon dust in rodents to assess the health risk of dust exposures to humans. One of the particular interests in the study is to evaluate dust‐induced changes of the expression of fibrosis‐related genes, and to identify specific signaling pathways involved in lunar dustinduced toxicity. F344 rats were exposed for 4 weeks (6h/d; 5d/wk) in nose‐only inhalation chambers to concentrations of 0 (control air), 2.1, 6.8, 21, and 61 milligrams per cubic meters of lunar dust. Five rats per group were euthanized at 1 day, 1 week, 1 month, and 3 months after the last inhalation exposure. The bronchoalveolar lavage fluid (BALF) was collected by lavaging with phosphate‐buffered saline (PBS). A zymosan‐induced luminolbased chemiluminescence assay was used to assess the activity of BAL cells. The lavaged lung tissue was snap frozen in LN2 and total RNA was isolated using the Qigen RNeasy kit. The expression of 84 fibrosisrelated genes were analyzed using the RT2 Profiler PCR Array technique. The expression of 18 genes of interest were further measured using real‐time PCR technique in all the samples. 10 out of 18 genes of interest showed persistently significant expression changes in the local lung tissue exposed to lunar dust, indicating a prolonged proinflammatory response. The expressions of several of these genes were dose‐ and time‐dependent and were significantly correlated with other pathological parameters. The potential signaling pathways and upstream regulators were further analyzed using IPA pathway analysis tool based on the gene expression data. The data presented in this study, for the first time, explore the molecular mechanisms of lunar dust induced toxicity, contributing not only the risk assessment for future space exploration, but also understandings of the dust‐induced toxicity in humans on earth.

Zhang, Ye↗
NASA NTRS2017

Effects of 2G on Gene Expression of Stress-Related Hormones in Rat Placenta

Understanding the effects of spaceflight on mammalian reproductive and developmental physiology is important to future human space exploration and permanent settlement beyond Earth orbit. Fetal developmental programming, including modulation of the HPA axis, is thought to originate at the placental-uterine interface, where both transfer of maternal hormones to the fetus and synthesis of endogenous hormones occurs. In healthy rats, fetal corticosterone levels are kept significantly lower by 11BetaHSD-2, which inactivates corticosterone by conversion into cortisone. Placental tissues express endogenous HPA axis-associated hormones including corticotropin-releasing hormone (CRH), pre-opiomelanocortin (POMC), and vasopressin, which may contribute to fetal programming alongside maternal hormones. DNA methylase 3A, 11BetaHSD-2, and 11BetaHSD-1, which are involved in the regulation of maternal cortisol transfer and modulation of the HPA axis, are also expressed in placental tissues along with glucocorticoid receptor and may be affected by differential gravity exposure during pregnancy. Fetuses may respond differently to maternal glucocorticoid exposure during gestation through sexually dimorphic expression of corticosterone-modulating hormones. To elucidate effects of altered gravity on placental gene expression, here we present a ground-based analogue study involving continuous centrifugation to produce 2g hypergravity. We hypothesized that exposure to 2g would induce a decrease in 11BetaHSD-2 expression through the downregulation of DNA methylase 3a and GC receptor, along with concurrent upregulation in endogenous CRH, POMC, and vasopressin expression. Timed pregnant female rats were exposed to 2G from Gestational day 6 to Gestational day 20, and comparisons made with Stationary Control (SC) and Vivarium Control (VC) dams at 1G. Dams were euthanized and placentas harvested on G20. We homogenized placental tissues, extracted and purified RNA, synthesized cDNA, and quantified the expression levels of the genes of interest relative to the GAPDH housekeeping gene, using RT-qPCR and gene-specific cDNA probes. Elucidation of glucocorticoid transfer and synthesis in the placenta can provide new insights into the unique dynamics of mammalian development in microgravity and guide future multi-generational studies in space.

Benson, S.↗
NASA NTRS1994

Cytoplasm-to-myonucleus ratios and succinate dehydrogenase activities in adult rat slow and fast muscle fibers

The relationship between myonuclear number, cellular size, succinate dehydrogenase activity, and myosin type was examined in single fiber segments (n = 54; 9 +/- 3 mm long) mechanically dissected from soleus and plantaris muscles of adult rats. One end of each fiber segment was stained for DNA before quantitative photometric analysis of succinate dehydrogenase activity; the other end was double immunolabeled with fast and slow myosin heavy chain monoclonal antibodies. Mean +/- S.D. cytoplasmic volume/myonucleus ratio was higher in fast and slow plantaris fibers (112 +/- 69 vs. 34 +/- 21 x 10(3) microns3) than fast and slow soleus fibers (40 +/- 20 vs. 30 +/- 14 x 10(3) microns3), respectively. Slow fibers always had small volumes/myonucleus, regardless of fiber diameter, succinate dehydrogenase activity, or muscle of origin. In contrast, smaller diameter (< 70 microns) fast soleus and plantaris fibers with high succinate dehydrogenase activity appeared to have low volumes/myonucleus while larger diameter (> 70 microns) fast fibers with low succinate dehydrogenase activity always had large volume/myonucleus. Slow soleus fibers had significantly greater numbers of myonuclei/mm than did either fast soleus or fast plantaris fibers (116 +/- 51 vs. 55 +/- 22 and 44 +/- 23), respectively. These data suggest that the myonuclear domain is more limited in slow than fast fibers and in the fibers with a high, compared to a low, oxidative metabolic capability.

NASA Discipline Developmental Biology↗
NASA NTRS2003

Quantification of rat retinal growth and vascular population changes after single and split doses of proton irradiation: translational study using stereology methods

This study quantified architectural and population changes in the rat retinal vasculature after proton irradiation using stereology. A 100 MeV conformal proton beam delivered 8, 14, 20 and 28 Gy as single and split doses to the whole eye. The vascular networks were prepared from retinal digests. Stereological methods were used to obtain the area of the retina and unbiased estimates of microvessel/artery/vein endothelial, pericyte and smooth muscle population, and vessel length. The retinal area increased progressively in the unirradiated, age-matched controls and in the retinas irradiated with 8 and 14 Gy, indicating uniform progressive retinal growth. No growth occurred after 20 and 28 Gy. Regression analysis of total endothelial cell number in all vessels (arteries, veins and capillaries) after irradiation documented a progressive time- and dose-dependent cell loss occurring over 15 to 24 months. The difference from controls was significant (P<0.01) after 28 Gy given in single and split doses and after 20 Gy given as a split dose (P<0.05). Total vessel length in microvessel was significantly shortened at 20 and 28 Gy compared to that of controls (P<0.05). No evident dose recovery was observed in the endothelial populations after split doses. At 10 Gy, the rate of endothelial cell loss, a dose parameter used to characterize the time- and dose-dependent loss of the endothelial population, was doubled.

NASA Discipline Radiation Health↗
NASA NTRS2000

Disuse bone loss in hindquarter suspended rats: partial weightbearing, exercise and ibandronate treatment as countermeasures

The purpose of this study was to evaluate potential countermeasures for bone loss during long-term space missions in the hindquarter suspended rat, including partial weight bearing (surrogate for artificial gravity) episodic full weight bearing (2 hour/day full weight bearing) and treatment with the third generation bisphosphonate ibandronate (Roche). Graded mechanical loading was studied by housing the animals on a novel servo controlled force plate system which permitted the titration of mechanical force at varying frequency and amplitude and different levels of weight bearing. The force plate, which forms the cage floor, is a glass platform supported by an 18" diameter speaker cone filled with expanding polyurethane foam. An infrared optical sensor attached to the speaker cone yields a voltage linearly related to vertical displacement of the glass platform. The dynamic force on the paw was computed as a product of the apparent mass of the animal on the platform at rest and the acceleration of the platform determined from the second derivative of the optical sensor output. The mass of the animal on the platform was varied by adjusting tension on the tether suspending the animal. Mechanical impact loading was titrated with the force plate resonating at different frequencies, including 3 Hz and 16 Hz.

Non-NASA Center↗
NASA NTRS2001

Indomethacin attenuates post-suspension hypotension in Sprague-Dawley rats

Orthostatic hypotension is a serious condition that is sometimes manifested in astronauts during standing postflight. These observations may be related to impairment of autonomic function and/or excessive production of endothelium-dependent relaxing factors. To evaluate the role of the cyclooxygenase inhibitor indomethacin as a countermeasure against the post-suspension reduction in mean arterial pressure (MAP), we examined the cardiovascular responses to 7-day 30 degrees tail-suspension and a subsequent 6-hr post-suspension period in conscious male Sprague-Dawley rats. Indomethacin (2 mg/kg) or saline were administered intravenously prior to release from suspension and at 2 and 4 hrs post-suspension. Direct MAP and heart rate were determined prior to suspension, daily and every 2 hrs post-suspension. During suspension, MAP did not change, in contrast, during post-suspension; it decreased compared to parallel non-suspended, untreated animals. There were no significant changes in heart rate. The reduction in MAP post-suspension was associated with significant increases in plasma prostacyclin. Indomethacin attenuated the observed post-suspension reduction in MAP and reduced plasma prostacyclin levels. Also, the baroreflex sensitivity for heart rate was modified by indomethacin--the MAP threshold for baroreflex activation was raised and the effective MAP range expanded. Thus, the post suspension reduction in mean arterial pressure may be due to overproduction of vasodilatory prostaglandins and/or other endothelium-dependent relaxing factors and alteration in baroreflex activity.

NASA Discipline Cardiopulmonary↗
NASA NTRS2002

Differential half-maximal effects of human insulin and its analogs for in situ glucose transport and protein synthesis in rat soleus muscle

Analogs of human insulin have been used to discriminate between responses of metabolic and mitogenic (growth-related) pathways. This study compared the stimulatory effects of human insulin (HI) and 2 analogs (X2, B-Asp(9), B-Glu(27) and H2, A-His(8),B-His(4),B-Glu(10), B-His(27)) on glucose uptake and protein synthesis in rat soleus muscle in situ. Glucose uptake, estimated by intramuscular (IM) injection of 2-deoxy[1,2-3H]glucose with or without insulin, was maximally increased at 10(-6) mol/L for HI and X2 and 10(-7) mol/L for H2. HI had a larger effect (318%) than either X2 (156%) or H2 (124%). The half-maximal effect (ED(50)) values for HI, X2, and H2 were 3.3 x10(-8) mol/L, 1.7 x 10(-7) mol/L, and 1.6 x 10(-9) mol/L, respectively. Protein synthesis, estimated by protein incorporation of [(3)H]phenylalanine injected into muscles with or without insulin, was maximally increased at 10(-5) mol/L for HI and 10(-6) for X2 and H2. HI had a larger effect in stimulating protein synthesis (34%) than either X2 (25%) or H2 (19.8%). The ED(50) values for HI, X2, and H2 were 3.0 x 10(-7) mol/L, 3.2 x 10(-7) mol/L, and 1.0 x 10(-9) mol/L, respectively. The biological potency of each analog (ED(50)insulin/ED(50)analog) showed X2 to be less potent than HI for both glucose uptake (0.2) and protein synthesis (0.9), whereas H2 is more potent than HI with ratios of 20 and 300, respectively. These data suggest that this approach for studying insulin responsiveness in a single muscle in situ may be a useful tool for investigating insulin signaling in muscle in vivo. Copyright 2002, Elsevier Science (USA). All rights reserved.

NASA Discipline Developmental Biology↗
NASA NTRS2002

Post-suspension hypotension is attenuated in Sprague-Dawley rats by prostacyclin synthase inhibition

Cardiovascular deconditioning, sometimes manifested in astronauts during standing postflight, may be related to the impairment of autonomic function and/or excessive production of endothelium-dependent relaxing factors. In the present study, we examined the cardiovascular responses to 7-day 30 degrees tail-suspension and a subsequent 6-h post-suspension period in conscious male Sprague-Dawley rats to determine the role of prostacyclin in the observed post-suspension reduction in mean arterial pressure (MAP). The specific prostacyclin synthase inhibitor U-51605 (0.3 mg/kg), or saline, was administered intravenously prior to release from suspension and at 2 and 4 h post-suspension. During 7 days of suspension, MAP did not change, however, there was a post-suspension reduction in MAP which was associated with significant increases in plasma prostacyclin and nitric oxide. U-51605 attenuated the observed post-suspension hypotension and reduced plasma prostacyclin levels, but not nitric oxide levels. The baroreflex sensitivity for heart rate was modified by U-51605: increased MAP threshold and effective MAP range. Thus, the post-suspension reduction in mean arterial pressure may be due to overproduction of prostacyclin and/or other endothelium-dependent relaxing factors and alteration in baroreflex activity.

Non-NASA Center↗
NASA NTRS2002

Regulation of period 1 expression in cultured rat pineal

The aim of the present study was to investigate the in vitro expression of Period 1 (Per1), Period 2 (Per2) and arylalkylamine N-acetyltransferase (AA-NAT) genes in the rat pineal gland to understand the mechanism(s) regulating the expression of these genes in this organ. Pineals, when maintained in vitro for 5 days, did not show circadian rhythmicity in the expression of any of the three genes monitored. Norepinephrine (NE) induced AA-NAT and Per1, whereas its effect on Per2 was negligible. Contrary to what was observed in other systems, NE stimulation did not induce circadian expression of Per1. The effect of NE on Per1 level was dose- and receptor subtype-dependent, and both cAMP and cGMP induced Per1. Per1 was not induced by repeated NE - or forskolin - stimulation. Protein synthesis was not necessary for NE-induced Per1, but it was for reduction of Per1 following NE stimulation. Per1 transcription in pinealocytes was activated by BMAL1/CLOCK. Our results indicate that important differences are present in the regulation of these genes in the mammalian pineal. Copyright 2002 S. Karger AG, Basel.

NASA Discipline Space Human Factors↗
NASA NTRS2002

Inhibition of the active lymph pump by flow in rat mesenteric lymphatics and thoracic duct

There are only a few reports of the influence of imposed flow on an active lymph pump under conditions of controlled intraluminal pressure. Thus, the mechanisms are not clearly defined. Rat mesenteric lymphatics and thoracic ducts were isolated, cannulated and pressurized. Input and output pressures were adjusted to impose various flows. Lymphatic systolic and diastolic diameters were measured and used to determine contraction frequency and pump flow indices. Imposed flow inhibited the active lymph pump in both mesenteric lymphatics and in the thoracic duct. The active pump of the thoracic duct appeared more sensitive to flow than did the active pump of the mesenteric lymphatics. Imposed flow reduced the frequency and amplitude of the contractions and accordingly the active pump flow. Flow-induced inhibition of the active lymph pump followed two temporal patterns. The first pattern was a rapidly developing inhibition of contraction frequency. Upon imposition of flow, the contraction frequency immediately fell and then partially recovered over time during continued flow. This effect was dependent on the magnitude of imposed flow, but did not depend on the direction of flow. The effect also depended upon the rate of change in the direction of flow. The second pattern was a slowly developing reduction of the amplitude of the lymphatic contractions, which increased over time during continued flow. The inhibition of contraction amplitude was dependent on the direction of the imposed flow, but independent of the magnitude of flow. Nitric oxide was partly but not completely responsible for the influence of flow on the mesenteric lymph pump. Exposure to NO mimicked the effects of flow, and inhibition of the NO synthase by N (G)-monomethyl-L-arginine attenuated but did not completely abolish the effects of flow.

NASA Discipline Musculoskeletal↗
NASA NTRS2002

Effects of microgravity on myogenic factor expressions during postnatal development of rat skeletal muscle

To clarify the role of gravity in the postnatal development of skeletal muscle, we exposed neonatal rats at 7 days of age to microgravity. After 16 days of spaceflight, tibialis anterior, plantaris, medial gastrocnemius, and soleus muscles were removed from the hindlimb musculature and examined for the expression of MyoD-family transcription factors such as MyoD, myogenin, and MRF4. For this purpose, we established a unique semiquantitative method, based on RT-PCR, using specific primers tagged with infrared fluorescence. The relative expression of MyoD in the tibialis anterior and plantaris muscles and that of myogenin in the plantaris and soleus muscles were significantly reduced (P < 0.001) in the flight animals. In contrast, MRF4 expression was not changed in any muscle. These results suggest that MyoD and myogenin, but not MRF4, are sensitive to gravity-related stimuli in some skeletal muscles during postnatal development.

Non-NASA Center↗
NASA NTRS2002

Clinostat rotation induces apoptosis in luteal cells of the pregnant rat

Recent studies have shown that microgravity induces changes at the cellular level, including apoptosis. However, it is unknown whether microgravity affects luteal cell function. This study was performed to assess whether microgravity conditions generated by clinostat rotation induce apoptosis and affect steroidogenesis by luteal cells. Luteal cells isolated from the corpora lutea of Day 8 pregnant rats were placed in equal numbers in slide flasks (chamber slides). One slide flask was placed in the clinostat and the other served as a stationary control. At 48 h in the clinostat, whereas the levels of progesterone and total cellular protein decreased, the number of shrunken cells increased. To determine whether apoptosis occurred in shrunken cells, Comet and TUNEL assays were performed. At 48 h, the percentage of apoptotic cells in the clinostat increased compared with that in the control. To investigate how the microgravity conditions induce apoptosis, the active mitochondria in luteal cells were detected with JC-1 dye. Cells in the control consisted of many active mitochondria, which were evenly distributed throughout the cell. In contrast, cells in the clinostat displayed fewer active mitochondria, which were distributed either to the outer edge of the cell or around the nucleus. These results suggest that mitochondrial dysfunction induced by clinostat rotation could lead to apoptosis in luteal cells and suppression of progesterone production.

NASA Discipline Cell Biology↗