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At least 55 records · Page 3

Preflight studies on tolerance of pocket mice to oxygen and heat. I - Physiological studies

Tests were carried out on pocket mice to ascertain their tolerance to elevated oxygen pressures alone and to a combination of hyperoxia and heat in excess of that expected during the flight of the mice on Apollo XVII. The mice withstood oxygen partial pressures up to 12 psi at normal room temperature (24 C, 75 F) over a period of 7 days. A few mice previously exposed to increased PO2 died in the course of exposure to an oxygen pressure of 10 psi or 12 psi (517 mm or 620 mm Hg) for 13 d in ambient heat of 32 C (90 F). Supplemental vitamin E and physiological saline loading given prior to exposure had no apparent protective effect. The overall conclusion was that the pocket mice which were to go on Apollo XVII could readily survive the ambient atmosphere to which they would be exposed.

Leon, H. A.

Developmental and hematological responses to low level continuous exposure of nitrogen dioxide in mice

Young healthy mice were continuously exposed to 0ppm, 0.5ppm, 1.0ppm and 5ppm nitrogen dioxide gas for eight weeks. Nitrogen dioxide exposure for eight weeks decreased the average weight of mice, increased the average weight of lungs, heart, and brain and decreased the average weight of liver. Nitrogen dioxide exposure did not have any effects on the WBC and RBC in mice blood but it increased the HCT and HGB in mice blood. Nitrogen dioxide exposure increased the MCV and decreased the MCH and MCHC in mice blood.

Singh, J.

Test of the antiorthostatic suspension model on mice - Effects on the inflammatory cell response

The antiorthostatic suspension model was tested for use as a 1G model to study the effects of factors that will be encountered during space travel on inflammation. No differences were found in inflammatory cells induced in antiorthostatically suspended mice. However, the superoxide response (used for oxidative killing of bacteria such as S. aureus) was impaired in antiorthostatically oriented mice compared to control mice. Elevated corticosterone levels were found in antiorthostatically suspended mice, indicating that stress may be a factor in the model. If the stress factor of the model correlates with the physiological stress of space flight, antiorthostatic suspension may be an acceptable model for studying inflammatory responses in mice.

Rosenkrans, Charles F., Jr.

Estrous Cyclicity in Mice During Simulated Weightlessness

Hindlimb unloading (HU) is a rodent model system used to simulate weightlessness experienced in space. However, some effects of this approach on rodent physiology are under-studied, specifically the effects on ovarian estrogen production which drives the estrous cycle. To resolve this deficiency, we conducted a ground-based validation study using the HU model, while monitoring estrous cycles in 16-weeks-old female C57BL6 mice. Animals were exposed to HU for 12 days following a 3 day HU cage acclimation period, and estrous cycling was analyzed in HU animals (n=22), normally loaded HU Cage Pair-Fed controls (CPF; n=22), and Vivarium controls fed ad libitum (VIV; n=10). Pair feeding was used to control for potential nutritional deficits on ovarian function. Vaginal cells were sampled daily in all mice via saline lavage. Cells were dried and stained with crystal violet, and the smears evaluated using established vaginal cytology techniques by two individuals blinded to the animal treatment group. Estrous cyclicity was disrupted in nearly all HU and CPF mice, while those maintained in VIV had an average normal cycle length of 4.8+/- 0.5 days, with all stages in the cycle visibly observed. CPF and HU animals arrested in the diestrous phase, which precedes the pre-ovulatory estrogen surge. Additionally, infection-like symptoms characterized by vaginal discharge and swelling arose in several HU animals, which we suspect was due to an inability of these mice to properly groom themselves, and/or due to the change in the gravity vector relative to the vaginal opening, which prevented drainage of the lavage solution. Pair-feeding resulted in similar weight gains of HU and CPF (1.5% vs 3.0%, respectively). The current results indicate that pair-feeding controlled weight gain and that the HU cage alone influenced estrous cyclicity. Thus, longer acclimation needs to be tested to determine if and when normal estrous cycling resumes in non-loaded mice in HU cages prior to HU testing. Future studies might also examine whether modifications to the vaginal lavage procedure might prevent the onset of the infection-like symptoms, and allow estrous cyclicity to be measured in this model system. Research supported by NNX15AB48G to JST.

Hindlimb Unloading

Estrous Cyclicity of Mice During Simulated Weightlessness

Hindlimb unloading (HU) is a rodent model system used to simulate weightlessness experienced in space. However, some effects of this approach on rodent physiology are under-studied, specifically the effects on ovarian estrogen production which drives the estrous cycle. To resolve this deficiency, we conducted a ground-based validation study using the HU model, while monitoring estrous cycles in 16-weeks-old female C57BL6 mice. Animals were exposed to HU for 12 days following a 3 day HU cage acclimation period, and estrous cycling was analyzed in HU animals (n22), normally loaded HU Cage Pair-Fed controls (CPF; n22), and Vivarium controls fed ad libitum (VIV; n10). Pair feeding was used to control for potential nutritional deficits on ovarian function. Vaginal cells were sampled daily in all mice via saline lavage. Cells were dried and stained with crystal violet, and the smears evaluated using established vaginal cytology techniques by two individuals blinded to the animal treatment group. Estrous cyclicity was disrupted in nearly all HU and CPF mice, while those maintained in VIV had an average normal cycle length of 4.8 0.5 days, with all stages in the cycle visibly observed. CPF and HU animals arrested in the diestrous phase, which precedes the pre-ovulatory estrogen surge. Additionally, infection-like symptoms characterized by vaginal discharge and swelling arose in several HU animals, which we suspect was due to an inability of these mice to properly groom themselves, andor due to the change in the gravity vector relative to the vaginal opening, which prevented drainage of the lavage solution. Pair-feeding resulted in similar weight gains of HU and CPF (1.5 vs 3.0, respectively). The current results indicate that pair-feeding controlled weight gain and that the HU cage alone influenced estrous cyclicity. Thus, longer acclimation needs to be tested to determine if and when normal estrous cycling resumes in non-loaded mice in HU cages prior to HU testing. Future studies might also examine whether modifications to the vaginal lavage procedure might prevent the onset of the infection-like symptoms, and allow estrous cyclicity to be measured in this model system.

fertilit

Somatic Mutation in Mice on the International Space Station (ISS): Guanine Substitution Suggests Link to Cancer Risk

We conducted comprehensive analysis of single nucleotide somatic mutations in mice exposed to microgravity and other factors aboard the International Space Station (ISS), using data archived in GeneLab. Animals in the experimental cohort consisted of mice that spent 37 days on the ISS within the Rodent Habitat. Ground control animals consisted of mice of identical age, sex, strain, in a terrestrial Rodent Habitat controlled for temperature, humidity and carbon dioxide levels, to match ISS conditions as closely as possible. RNA extracted from eye, liver, skeletal muscle, and kidney tissue specimens was subjected to next-generation sequencing to acquire primary data. Our analysis employed cutting-edge software developed at NASA Ames Research Center, executed on the NASA Ames Supercomputer and on another high-performance computer, for accurate variant calling of single point mutations. ISS-flown mice exhibited a notably heightened level of somatic mutation compared to control mice. The degree of somatic mutation correlated with the degree of gene expression across the four tissue types, i.e., the greatest rate of mutation accumulation was seen in highly expressed genes. We discovered that guanine substitutions were the most common type of somatic mutation. This observation is consistent with the hypothesis that DNA mutation events stem from reactive oxygen/nitrogen/chlorine species-mediated guanine oxidation induced by the spaceflight environment. Since guanine oxidation is a prominent feature of the DNA mutation landscape that accompanies malignant transformation, our findings suggest a possible link between the spaceflight environment and cancer risk that is independent of radiation carcinogenesis.

ISS

Reduction of obesity, as induced by leptin, reverses endothelial dysfunction in obese (Lep(ob)) mice

Obesity is a major health care problem and is associated with significant cardiovascular morbidity. Leptin, a neuroendocrine hormone released by adipose tissue, is important in modulating obesity by signaling satiety and increasing metabolism. Moreover, leptin receptors are expressed on vascular endothelial cells (ECs) and mediate angiogenesis. We hypothesized that leptin may also play an important role in vasoregulation. We investigated vasoregulatory mechanisms in the leptin-deficient obese (ob/ob) mouse model and determined the influence of leptin replacement on endothelial-dependent vasorelaxant responses. The direct effect of leptin on EC nitric oxide (NO) production was also tested by using 4, 5-diaminofluorescein-2 diacetate staining and measurement of nitrate and nitrite concentrations. Vasoconstrictor responses to phenylephrine, norepinephrine, and U-46619 were markedly enhanced in aortic rings from ob/ob mice and were modulated by NO synthase inhibition. Vasorelaxant responses to ACh were markedly attenuated in mesenteric microvessels from ob/ob mice. Leptin replacement resulted in significant weight loss and reversal of the impaired endothelial-dependent vasorelaxant responses observed in ob/ob mice. Preincubation of ECs with leptin enhanced the release of NO production. Thus leptin-deficient ob/ob mice demonstrate marked abnormalities in vasoregulation, including impaired endothelial-dependent vasodilation, which is reversed by leptin replacement. These findings may be partially explained by the direct effect of leptin on endothelial NO production. These vascular abnormalities are similar to those observed in obese, diabetic, leptin-resistant humans. The ob/ob mouse may, therefore, be an excellent new model for the study of the cardiovascular effects of obesity.

NASA Program Biomedical Research and Countermeasur

A Simplified Model of Adenine-Induced Chronic Kidney Disease Using SKH1 Mice

Commonly used adenine-induced chronic kidney disease (CKD) murine models often employ C57BL/6 mice; however, this strain has inherent limitations due to its natural resistance to developing key pathological features of CKD, such as tubulointerstitial fibrosis and inflammation. There have been attempts to overcome these barriers by using multiple concentrations of adenine-supplemented diets or by performing prolonged experiments up to 20 weeks. Here, we demonstrate that SKH1 Elite mice develop clinically relevant CKD phenotypes (e.g., polyuria, proteinuria, inflammation, and renal fibrosis) over the course of only 6 weeks of low-dose (0.15%) adenine supplementation. As a docile, immunocompetent, and hairless strain, SKH1 Elite mice offer several logistical advantages over C57BL/6 mice, including ease of handling and the ability to study dermal conditions, which are often secondary to CKD.

60 APPLIED LIFE SCIENCES

2-deoxy-D-glucose-induced metabolic stress enhances resistance to Listeria monocytogenes infection in mice

Exposure to different forms of psychological and physiological stress can elicit a host stress response, which alters normal parameters of neuroendocrine homeostasis. The present study evaluated the influence of the metabolic stressor 2-deoxy-D-glucose (2-DG; a glucose analog, which when administered to rodents, induces acute periods of metabolic stress) on the capacity of mice to resist infection with the facultative intracellular bacterial pathogen Listeria monocytogenes. Female BDF1 mice were injected with 2-DG (500 mg/kg b. wt.) once every 48 h prior to, concurrent with, or after the onset of a sublethal dose of virulent L. monocytogenes. Kinetics of bacterial growth in mice were not altered if 2-DG was applied concurrently or after the start of the infection. In contrast, mice exposed to 2-DG prior to infection demonstrated an enhanced resistance to the listeria challenge. The enhanced bacterial clearance in vivo could not be explained by 2-DG exerting a toxic effect on the listeria, based on the results of two experiments. First, 2-DG did not inhibit listeria replication in trypticase soy broth. Second, replication of L. monocytogenes was not inhibited in bone marrow-derived macrophage cultures exposed to 2-DG. Production of neopterin and lysozyme, indicators of macrophage activation, were enhanced following exposure to 2-DG, which correlated with the increased resistance to L. monocytogenes. These results support the contention that the host response to 2-DG-induced metabolic stress can influence the capacity of the immune system to resist infection by certain classes of microbial pathogens.

Non-NASA Center

Effects of 2-deoxy-D-glucose administration on cytokine production in BDF1 mice

Physical exercise and diet changes have been shown to affect immune parameters, and similar effects are also induced by the administration of a nonmetabolizable glucose analog, 2-deoxy-D-glucose (2-DG). The present study was designed to characterize the effects of glucoprivation induced by 2-DG administration on concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6 in the blood and interferon-gamma (IFN-gamma), IL-2, and IL-4 in vitro production by partially purified T splenocytes in BDF1 mice. Mice (n = 8 per group) were injected intraperitoneally one or three times with 0, 500, 750, or 1000 mg/kg of 2-DG, and blood and spleens were collected 2 h after the last injection. Partially purified T splenocytes were cultured 24 h in the presence of concanavalin A (ConA). A significant increase in the corticosterone levels with the amount of 2-DG injected was observed after one or three injections (p<0.05). The amount of 2-DG injected was associated with an increase in TNF-alpha, IL-1beta, and IL-6 concentrations in the blood of mice after one or three injections of 2-DG (p<0.05). A significant decrease in in vitro proliferation of partially purified splenocytes in the presence of ConA was associated with a decrease in IFN-gamma production in the culture supernatants and an increase in IL-1 receptor expression on the cell surface (p<0.05).

NASA Discipline Regulatory Physiology

Macrophage cell lines derived from major histocompatibility complex II-negative mice

Two bone-marrow-derived macrophage cell lines, C2D and C2Dt, were isolated from major histocompatibility class II negative knock-out mice. The C2D cell line was stabilized by continuous culture in colony-stimulating factor-1 and the C2Dt cell line was transformed with SV40 virus large T antigen. These cells exhibited phenotypic properties of macrophages including morphology and expression of Mac 1 and Mac 2 cell surface molecules. These cells also had comparable growth to the bone-marrow-derived macrophage cell line B6MP102. These new cell lines were not spontaneously cytotoxic and were only capable of modest killing of F5b tumor cells when stimulated with LPS and interferon-gamma, but not when stimulated with LPS alone or with staphylococcal exotoxin. C2D and C2Dt cells phagocytosed labeled Staphylococcus aureus similarly to B6MP102 cells but less well than C2D peritoneal macrophages. These cell lines secreted interleukin-6, but not tumor necrosis factor or nitric oxide in response to LPS or staphlococcal enterotoxins A or B C2D(t) cells were tumorigenic in C2D and C57BL/6J mice but C2D cells were not. These data suggest that macrophage cell lines can be established from bone marrow cells of major histocompatibility complex II-negative mice.

NASA Discipline Musculoskeletal

Diet outperforms microbial transplant to drive microbiome recovery in mice

A high-fat, low-fibre Western-style diet (WD) induces microbiome dysbiosis characterized by reduced taxonomic diversity and metabolic breadth, which in turn increases risk for a wide array of metabolic, immune and systemic pathologies. Recent work has established that WD can impair microbiome resilience to acute perturbations such as antibiotic treatment, although little is known about the mechanism of impairment and the specific consequences for the host of prolonged post-antibiotic dysbiosis. Here, in this study, we characterize the trajectory by which the gut microbiome recovers its taxonomic and functional profile after antibiotic treatment in mice on regular chow (RC) or WD, and find that only mice on RC undergo a rapid successional process of recovery. Metabolic modelling indicates that a RC diet promotes the development of syntrophic cross-feeding interactions, whereas in mice on WD, a dominant taxon monopolizes readily available resources without releasing syntrophic byproducts. Intervention experiments reveal that an appropriate dietary resource environment is both necessary and sufficient for rapid and robust microbiome recovery, whereas microbial transplant is neither. Furthermore, prolonged post-antibiotic dysbiosis in mice on WD renders them susceptible to infection by the intestinal pathogen Salmonella enterica serovar Typhimurium. Our data challenge widespread enthusiasm for faecal microbiota transplant (FMT) as a strategy to address dysbiosis, and demonstrate that specific dietary interventions are, at a minimum, an essential prerequisite for effective FMT, and may afford a safer, more natural and less invasive alternative.

Kennedy, M. S. [University of Chicago, IL (United

Cellular signaling within aged skeletal muscle reveals a dysregulated stress-induced remodeling response following volumetric muscle loss in female mice

Severe muscle trauma disrupts endogenous repair mechanisms, producing chronic functional deficits that are incompletely characterized in aged populations. This study investigated inflammatory, molecular, and physiological responses to volumetric muscle loss in young adult and aged female mice. Serum cytokine profiling revealed elevated baseline inflammation in aged animals and a blunted response to injury, with cytokines such as IL-6 increasing 4.4-fold in young versus 1.8-fold in aged mice at day 3 compared to baseline. By day 28 post-injury, histological analyses showed comparable reductions in muscle size and increases in fibrosis across ages. Despite these similar tissue-level outcomes, age-dependent differences emerged in downstream functional and molecular responses. Muscle functional testing demonstrated persistent force deficits independent of age but altered muscle relaxation kinetics in aged mouse muscles (p < 0.001), suggesting dysregulated excitation-contraction coupling. Additionally, mice displayed age-associated differences in post-injury limb loading. Global proteomic analyses further confirmed age-associated enrichment of complement and antigen-processing pathways alongside metabolic dysfunction (p < 0.05). Phosphoproteomic profiling revealed reduced basal kinase activity in the muscles of aged mice yet exaggerated injury-induced phosphorylation of Mapk1-associated phosphosites, indicating a dysregulated stress response. Collectively, these findings suggest that aged murine muscles function within a heightened inflammatory and perturbed kinase-signaling environment that may hinder the coordination of regenerative programs, underscoring the need for regenerative strategies that address age-specific molecular contexts to improve functional recovery across the lifespan.

Habing, Krista M.

Hematologic changes in mice during and after exposure to severe hypobaric hypoxia

Exposing mice to an atmospheric pressure of 300 mm Hg for 16 d caused a variety of hematologic effects. Hematocrit increased rapidly in the first 8 d of exposure and slowly in the second 8 d. Reticulocyte counts rose above normal, peaked on day 8, and then fell rapidly toward the control level. Macrocytic erythrocytes, formed during exposure, remained macrocytic after the termination of exposure and after the loss of their reticulum. The posthypoxic mice proved sensitive for erythropoietin bioassay. Mice injected with normal dog serum showed a significantly higher incorporation of Fe-59 than control mice injected with physiologic saline. A reduction of the duration of exposure to 10 d resulted in only a slight decrease in the sensitivity of the mouse bioassay system. However, a 16-d exposure at a pressure of 360 mm Hg resulted in considerably less sensitive bioassay animals.

Huff, J. E.

Electrophoresis pattern of serum from mice exposed to different concentrations of sulfur dioxide

Three day old mice were continuously exposed to sulphur dioxide concentrations at 0ppm, 0.05ppm, 0.15ppm and 1ppm for eight weeks. At the end of the experiment, blood samples were collected and centrifuged for electrophoresis studies of the serum in 5 percent acrylamide gel. The length of bands of different serum proteins from the SO2 exposed mice was at a variance as compared with the length of bands from the control exposed mice and alpha-1 band seems to be missing from the serum of SO2 exposed mice.

Singh, J.

Treatment of trypanosome-infected mice with exogenous interferon, interferon inducers, or antibody to interferon

Earlier studies have demonstrated that mice resistant to Trypanosoma brucei rhodesiense (the B10.BR/SgSnJ strain) produces, upon infection by this parasite, two peaks of serum interferon (IFN), while the susceptible mice (C3HeB/FeJ) produces no IFN. In the present study, survival times were compared for B10.BR/SgSnJ, C3HeB/FeJ, and CBA/J (an intermediately resistant strain) mice that were injected, prior to infection with the parasite, with either of the following three preparations (1) IFN-gamma, (2) an antibody to IFN-gamma and (3) polyriboinosinic-polyribocytidylic acid (to induce IFN-alpha/beta). No effect on the survival times of mice by any of these preparations could be demonstrated, contrary to some previous reports.

Degee, Antonie L. W.

The Effects of Rm-CSF and Ril-6 Therapy on Immunosuppressed Antiorthostatically Suspended Mice

Antiorthostatically suspended mice had suppressed macrophage development in both unloaded and loaded bones, indicating a systemic effect. Bone marrow cells from those mice secreted less macrophage colony-stimulating factor (M-CSF) and interleukin-6 (IL-6) than did control mice. Because M-CSF and IL-6 are important to bone marrow macrophage maturation, we formulated the hypothesis that suppressed macrophage development occurred as a result of the depressed levels of either M-CSF or IL-6. To test the hypothesis, mice were administered recombinant M-CSF or IL-6 intraperitoneally. We showed that recombinant M-CSF therapy, but not recombinant IL-6 therapy, reversed the suppressive effects of orthostatic suspension on macrophage development. These data suggest that bone marrow cells that produce M-CSF are affected by antiorthostatic suspension and may contribute to the inhibited maturation of bone marrow macrophage progenitors.

Armstong, Jason W.

Pulmonary Toxicity Study of Lunar and Martian Dust Simulants Intratracheally Instilled in Mice

NASA is contemplating sending humans to Mars and the Moon for further exploration. The properties of Hawaiian and Californian volcanic ashes allow them to be used to simulate Martian and lunar dusts, respectively. NASA laboratories use these dust simulants to test performance of hardware destined for Martian or lunar environments. Workers in these test facilities are exposed to low levels of these dusts. The present study was conducted to investigate the toxicity of these dust simulants. Particles of respirable-size ranges of lunar simulant (LS), Martian simulant (MS), TiO2 (negative control) and quartz (positive control) were each intratracheally instilled (saline as vehicle) to groups of 4 mice (C57BL, male, 2-3 month old) at a single treatment of 1 (Hi dose) or 0.1 (Lo dose) mg/mouse. The lungs were harvested at the end of 7 days or 90 days for histopathological examination. Lungs of the LS-Lo groups had no evidence of inflammation, edema or fibrosis. The LS-Hi-7d group had mild to moderate acute inflammation, and neutrophilic and lymphocytic infiltration; the LS-Hi-90d group showed signs of chronic inflammation and some fibrosis. Lungs of the MS-Lo-7d group revealed mild inflammation and neutrophilic and lymphocytic infiltration; the MS-Lo-90d group showed mild fibrosis and particle-laden macrophages (PLM). Lungs of the MS-Hi-7d group demonstrated mild to moderate inflammation and large foci of PLM; the MS-Hi-90d group showed chronic mild to moderate inflammation and fibrosis. To mimic the effects of the oxidative and reactive properties of Martian soil surface, groups of mice were exposed to ozone (3 hour at 0.5 ppm) prior to MS dust instillation. Lung lesions in the MS group were more severe with the pretreatment. The results for the negative and positive controls were consistent with the known pulmonary toxicity of these compounds. The overall severity of toxic insults to the lungs were TiO2<LS<MS<Quartz. For the mice in the 90-d study, blood samples were taken for immunotoxicity study. Antinuclear antibodies (such as those against Golgi, kinetichore, and centromere) were detected in serum in a greater extent in mice treated with LS than those with quartz, suggesting that LS, like quartz, has the potential of inducing antoimmune disease.

Lam, Chiu-Wing