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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

New method for estimating bacterial cell abundances in natural samples by use of sublimation

We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500 degrees C for several seconds under reduced pressure. The sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approximately 10(5) to 10(9) E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DAPI (4,6-diamidino-2-phenylindole) staining.

Evaluation Studies↗
NASA NTRS2004

A New Method for Estimating Bacterial Abundances in Natural Samples using Sublimation

We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert were heated to a temperature of 500 C for several seconds under reduced pressure. The sublimate was collected on a cold finger and the amount of adenine released from the samples then determined by high performance liquid chromatography (HPLC) with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approx. l0(exp 5) to l0(exp 9) E. coli cell equivalents per gram. For most of these samples, the sublimation based cell counts were in agreement with total bacterial counts obtained by traditional DAPI staining. The simplicity and robustness of the sublimation technique compared to the DAPI staining method makes this approach particularly attractive for use by spacecraft instrumentation. NASA is currently planning to send a lander to Mars in 2009 in order to assess whether or not organic compounds, especially those that might be associated with life, are present in Martian surface samples. Based on our analyses of the Atacama Desert soil samples, several million bacterial cells per gam of Martian soil should be detectable using this sublimation technique.

Glavin, Daniel P.↗
DOE OSTI2018

A Novel In Situ Flamelet Tabulation Methodology for the Representative Interactive Flamelet Model

A priori flamelet tabulation methods have been used extensively to model premixed and non-premixed combustion in Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulations (LES). Pre-tabulation of flamelet libraries have led to significant cost reduction of CFD simulations. However, these tabulation methods rely on certain simplifying assumptions. The dimensionality of the flamelet manifolds and size of flamelet libraries are also constrained due to memory and computational limitations. This limits the applicability and predictive capability of flamelet models. The traditional representative interactive flamelet (RIF) approach with multiple flamelets on the other hand involves online solution of flamelet equations and presumed PDF integration at each computational cell making it attractive but computationally expensive and not suitable for LES with large cell counts. The current work discusses the development of a novel methodology that combines the advantages of an online flamelet solver along with the computational efficacy of tabulated models. The novel in situ tabulation approach consists of creating a flamelet table at each computational time step using the unsteady flamelet equations. The flamelets are then integrated in real time based on their respective scalar dissipation rate histories. This approach is capable of including history effects and unsteady chemical kinetic effects as it involves the online solution of unsteady flamelets. Implementation and comprehensive validation of the new framework is carried out against gas jet flames as well as spray flames at high pressures. The approach is first validated for a partially premixed methane gas-jet flame in a RANS framework. The temperature and species mass fractions are compared against experimental results at different locations of a lifted flame. The approach is able to capture the transient flame characteristics. The model is then validated against an n -dodecane spray flame at high pressures in a LES framework with a 103 species n -dodecane chemistry mechanism. The model is able to capture ignition delays and flame liftoff of the n -dodecane spray over varying ambient temperature conditions. Due to the offsetting of presumed PDF integration cost, the proposed framework is shown to be faster than the traditional RIF approach and the speedup over RIF increases with an increase in the cell count. Furthermore, this framework enables use of the RIF model for large cell count LES simulations.

42 ENGINEERING↗
NASA NTRS2001

Dose and dose rate effects of whole-body gamma-irradiation: I. Lymphocytes and lymphoid organs

The major goal of part I of this study was to compare varying doses and dose rates of whole-body gamma-radiation on lymphoid cells and organs. C57BL/6 mice (n = 75) were exposed to 0, 0.5, 1.5, and 3.0 Gy gamma-rays (60Co) at 1 cGy/min (low-dose rate, LDR) and 80 cGy/min (high-dose rate, HDR) and euthanized 4 days later. A significant dose-dependent loss of spleen mass was observed with both LDR and HDR irradiation; for the thymus this was true only with HDR. Decreasing leukocyte and lymphocyte numbers occurred with increasing dose in blood and spleen at both dose rates. The numbers (not percentages) of CD3+ T lymphocytes decreased in the blood in a dose-dependent manner at both HDR and LDR. Splenic T cell counts decreased with dose only in HDR groups; percentages increased with dose at both dose rates. Dose-dependent decreases occurred in CD4+ T helper and CD8+ T cytotoxic cell counts at HDR and LDR. In the blood the percentages of CD4+ cells increased with increasing dose at both dose rates, whereas in the spleen the counts decreased only in the HDR groups. The percentages of the CD8+ population remained stable in both blood and spleen. CD19+ B cell counts and percentages in both compartments declined markedly with increasing HDR and LDR radiation. NK1.1+ natural killer cell numbers and proportions remained relatively stable. Overall, these data indicate that the observed changes were highly dependent on the dose, but not dose rate, and that cells in the spleen are more affected by dose rate than those in blood. The results also suggest that the response of lymphocytes in different body compartments may be variable.

NASA Discipline Radiation Health↗
DOE OSTI2018

Extended live-tracking and quantitative characterization of wound healing and cell migration with SiR-Hoechst

Highlights: • SiR-Hoechst is a nuclear dye that enables cell tracking without affecting migration. • Single cell analysis provides multiple migration metrics during wound healing. • Cell density-based report of wound healing is less susceptible to subjective bias. • Cell directionality is an important contributor of early wound recovery. Cell migration is essential to many life processes, including immune response, tissue repair, and cancer progression. A reliable quantitative characterization of the cell migration can therefore aid in the high throughput screening of drug efficacy in wound healing and cancer treatments. In this work, we report what we believe is the first use of SiR-Hoechst for extended live tracking and automated analysis of cell migration and wound healing. We showed through rigorous statistical comparisons that this far-red label does not affect migratory behavior. We observed excellent automated tracking of random cell migration, in which the motility parameters (speed, displacement, path length, directionality ratio, persistence time, and direction autocorrelation) obtained closely match those obtained from manual tracking. We also present an analysis framework to characterize the healing of a scratch wound from the perspective of single cells. The use of SiR-Hoechst is advantageous for the crowded environments in wound healing assays because as long as cell nuclei do not overlap, continuous tracking can be maintained even if there is cell-cell contact. In this paper, we report wound recovery based on the number of cells migrating into the wound over time, normalized by the initial cell count prior to the infliction of the wound. This normalized cell count approach is impervious to operator bias during the arbitration of wound edges and is also robust against variability that arises due to differences in the cell density of different samples. Additional wound healing characteristics were also defined based on the evolution of cell speed and directionality during healing. Not unexpected, the wound healing cells exhibited much higher tendency to maintain the same migratory direction in comparison to the randomly migrating cells. The use of SiR-Hoechst thus greatly simplified the automation of single cell and whole population analysis with high spatial and temporal resolution over extended periods of time.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1989

Rapid enumeration of viable bacteria by image analysis

A direct viable counting method for enumerating viable bacteria was modified and made compatible with image analysis. A comparison was made between viable cell counts determined by the spread plate method and direct viable counts obtained using epifluorescence microscopy either manually or by automatic image analysis. Cultures of Escherichia coli, Salmonella typhimurium, Vibrio cholerae, Yersinia enterocolitica and Pseudomonas aeruginosa were incubated at 35 degrees C in a dilute nutrient medium containing nalidixic acid. Filtered samples were stained for epifluorescence microscopy and analysed manually as well as by image analysis. Cells enlarged after incubation were considered viable. The viable cell counts determined using image analysis were higher than those obtained by either the direct manual count of viable cells or spread plate methods. The volume of sample filtered or the number of cells in the original sample did not influence the efficiency of the method. However, the optimal concentration of nalidixic acid (2.5-20 micrograms ml-1) and length of incubation (4-8 h) varied with the culture tested. The results of this study showed that under optimal conditions, the modification of the direct viable count method in combination with image analysis microscopy provided an efficient and quantitative technique for counting viable bacteria in a short time.

Non-NASA Center↗
DOE OSTI2020

Genotypic and Phenotypic Characterization of Incompatibility Group FIB Positive Salmonella enterica Serovar Typhimurium Isolates from Food Animal Sources

Salmonella enterica is one of the most common bacterial foodborne pathogens in the United States, causing illnesses that range from self-limiting gastroenteritis to more severe, life threatening invasive disease. Many Salmonella strains contain plasmids that carry virulence, antimicrobial resistance, and/or transfer genes which allow them to adapt to diverse environments, and these can include incompatibility group (Inc) FIB plasmids. This study was undertaken to evaluate the genomic and phenotypic characteristics of IncFIB-positive Salmonella enterica serovar Typhimurium isolates from food animal sources, to identify their plasmid content, assess antimicrobial resistance and virulence properties, and compare their genotypic isolates with more recently isolated S. Typhimurium isolates from food animal sources. Methods: We identified 71 S. Typhimurium isolates that carried IncFIB plasmids. These isolates were subjected to whole genome sequencing and evaluated for bacteriocin production, antimicrobial susceptibility, the ability to transfer resistance plasmids, and a subset was evaluated for their ability to invade and persist in intestinal human epithelial cells. Results: Approximately 30% of isolates (n = 21) displayed bacteriocin inhibition of Escherichia coli strain J53. Bioinformatic analyses using PlasmidFinder software confirmed that all isolates contained IncFIB plasmids along with multiple other plasmid replicon types. Comparative analyses showed that all strains carried multiple antimicrobial resistance genes and virulence factors including iron acquisition genes, such as iucABCD (75%), iutA (94%), sitABCD (76%) and sitAB (100%). In 17 cases (71%), IncFIB plasmids, along with other plasmid replicon types, were able to conjugally transfer antimicrobial resistance and virulence genes to the susceptible recipient strain. For ten strains, persistence cell counts (27%) were noted to be significantly higher than invasion bacterial cell counts. When the genome sequences of the study isolates collected from 1998–2003 were compared to those published from subsequent years (2005–2018), overlapping genotypes were found, indicating the perseverance of IncFIB positive strains in food animal populations. This study confirms that IncFIB plasmids can play a potential role in disseminating antimicrobial resistance and virulence genes amongst bacteria from several food animal species.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1986

Reduction of spermatogonia and testosterone in rat testes flown on Space Lab-3

The effects of space flight on rat testes were investigated. The weight, spermatogonial cell count, and testosterone levels in six rats flown on Space Lab-3 were measured. It is observed that compared to ground control rats the average weight loss was 7.1 percent and the spermatogonial cell count decreased by 7.5 percent. The data reveal that the testosterone level for large control rats was 9.13 ng/ml and 0.31 ng/ml for flight rats; and 2.54 ng/ml and 0.233 ng/ml for smaller control and flight rats, respectively. It is noted that spermatogenesis and testosterone production are reduced during spaceflight.

Philpott, Delbert E.↗
DOE OSTI2019

A Handheld Medical Diagnostic Device for Harsh Environments

Medical diagnostic capabilities for extreme environments, are currently limited in nature to single marker type assays. We propose to develop a handheld device for medical diagnostics in extreme environments that provide sensitive and specific detection of biomarkers with an emphasis initially on radiation exposure. Such a device will have multiple uses, and will be easily adaptable to many applications. For example, first responders, the battlefield, in low resource settings in developing countries facing emerging disease outbreaks, and during long-duration space flights. To this end, we will develop highly adaptable microfluidic devices (cards) for profiling different biomarkers with an emphasis on those related to radiation exposure. We will leverage the previous centrifugal separator work from LLNL and Sandia National Laboratory. The radiation exposure biomarker work at LLNL will provide a biological platform for demonstrating the utility of the device. We will develop a fluidic system using a pump-less mechanical method (centrifugal) to move, control, order and layer fluids in the platform. This decreases complexity, while enabling simultaneous cell separation and plasma generation for two uses: the first is differential blood cell counts and the second is biomarker assay panels. This work will be accomplished in three Aims: Aim 1) Test multiplex microfluidic cards and integrated reader. Aim 2) Demonstrate system capabilities to take and process blood samples for multi-endpoint analysis. Aim 3) Test multiplex detection based on measuring differential blood cell counts, while measuring plasma protein biomarkers. The proposed work addresses the mission research challenge of chemical and biological countermeasure in that our work aims to provide new research capabilities to respond to man-made or natural outbreaks of pandemic diseases in particular in low resource and triage environments.

60 APPLIED LIFE SCIENCES↗
NASA NTRS2003

Polyomavirus JCV excretion and genotype analysis in HIV-infected patients receiving highly active antiretroviral therapy

OBJECTIVE: To assess the frequency of shedding of polyomavirus JC virus (JCV) genotypes in urine of HIV-infected patients receiving highly active antiretroviral therapy (HAART). METHODS: Single samples of urine and blood were collected prospectively from 70 adult HIV-infected patients and 68 uninfected volunteers. Inclusion criteria for HIV-infected patients included an HIV RNA viral load < 1000 copies, CD4 cell count of 200-700 x 106 cells/l, and stable HAART regimen. PCR assays and sequence analysis were carried out using JCV-specific primers against different regions of the virus genome. RESULTS: JCV excretion in urine was more common in HIV-positive patients but not significantly different from that of the HIV-negative group [22/70 (31%) versus 13/68 (19%); P = 0.09]. HIV-positive patients lost the age-related pattern of JCV shedding (P = 0.13) displayed by uninfected subjects (P = 0.01). Among HIV-infected patients significant differences in JCV shedding were related to CD4 cell counts (P = 0.03). Sequence analysis of the JCV regulatory region from both HIV-infected patients and uninfected volunteers revealed all to be JCV archetypal strains. JCV genotypes 1 (36%) and 4 (36%) were the most common among HIV-infected patients, whereas type 2 (77%) was the most frequently detected among HIV-uninfected volunteers. CONCLUSION: These results suggest that JCV shedding is enhanced by modest depressions in immune function during HIV infection. JCV shedding occurred in younger HIV-positive persons than in the healthy controls. As the common types of JCV excreted varied among ethnic groups, JCV genotypes associated with progressive multifocal leukoencephalopathy may reflect demographics of those infected patient populations.

Non-NASA Center↗
DOE OSTI2022

Long-Term and Low-Level Envelope C2V3 Stimulation by Highly Diverse Virus Isolates Leads to Frequent Development of Broad and Elite Antibody Neutralization in HIV-1-Infected Individuals

A minority of HIV-1-infected patients produce broadly neutralizing antibodies (bNAbs). Identification of viral and host correlates of bNAb production may help develop vaccines. We aimed to characterize the neutralizing response and viral and host-associated factors in Angola, which has one of the oldest, most dynamic, and most diverse HIV-1 epidemics in the world. Three hundred twenty-two HIV-1-infected adults from Angola were included in this retrospective study. Phylogenetic analysis of C2V3C3 env gene sequences was used for virus subtyping. Env-binding antibody reactivity was tested against polypeptides comprising the C2, V3, and C3 regions. Neutralizing-antibody responses were determined against a reference panel of tier 2 Env pseudoviruses in TZM-bl cells; neutralizing epitope specificities were predicted using ClustVis. All subtypes were found, along with untypeable strains and recombinant forms. Notably, 56% of the patients developed cross neutralizing, broadly neutralizing, or elite neutralizing responses. Broad and elite neutralization was associated with longer infection time, subtype C, lower CD4 + T cell counts, higher age, and higher titer of C2V3C3-specific antibodies relative to failure to develop bNAbs. Neutralizing antibodies targeted the V3-glycan supersite in most patients. V3 and C3 regions were significantly less variable in elite neutralizers than in weak neutralizers and nonneutralizers, suggesting an active role of V3C3-directed bNAbs in controlling HIV-1 replication and diversification. In conclusion, prolonged and low-level envelope V3C3 stimulation by highly diverse and ancestral HIV-1 isolates promotes the frequent elicitation of bNAbs. These results provide important clues for the development of an effective HIV-1 vaccine. Studies on neutralization by antibodies and their determinants in HIV-1-infected individuals have mostly been conducted in relatively recent epidemics caused by subtype B and C viruses. Results have suggested that elicitation of broadly neutralizing antibodies (bNAbs) is uncommon. The mechanisms underlying the elicitation of bNAbs are still largely unknown. We performed the first characterization of the plasma neutralizing response in a cohort of HIV-1-infected patients from Angola. Angola is characterized by an old and dynamic epidemic caused by highly diverse HIV-1 variants. Remarkably, more than half of the patients produced bNAbs, mostly targeting the V3-glycan supersite in HIV-1. This was associated with higher age, longer infection time, lower CD4 + T cell counts, subtype C infection, or higher titer of C2V3C3-specific antibodies relative to patients that did not develop bNAbs. These results may help develop the next generation of vaccine candidates for HIV-1.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Modeling the Effects of Morphine-Altered Virus Specific Antibody Responses on HIV/SIV Dynamics

Abstract Drugs of abuse, such as opiates, have been widely associated with enhancing HIV replication, accelerating disease progression and diminishing host-immune responses, thereby making it harder to effectively manage HIV infection. It is thus important to study the effects of drugs of abuse on HIV-infection and immune responses. Here, we develop mathematical models that incorporate the effects of morphine-altered antibody responses on HIV/SIV dynamics. Based on fitting the model to experimental data from simian immunodeficiency virus (SIV) infections in control and morphine-addicted macaques, we found that two of the most significant effects of virus specific antibodies are neutralizing viral particles and enhancing viral clearance. Using our model, we quantified how morphine alters virus-specific antibody responses, and how this alteration affects the key components of virus dynamics such as infection rate, virus clearance, viral load, CD4 + T cell count, and CD4 + T cell loss in SIV-infected macaques under conditioning with morphine. We found that in a subpopulation of SIV-infected morphine addicted macaques, the presence of drugs of abuse may cause significantly diminished antibody responses, resulting in more severe infection with increased SIV infectivity, a decreased viral clearance rate, increased viral load, and higher CD4 + T cell loss.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1996

Effects of substrates and phosphate on INT (2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl tetrazolium chloride) and CTC (5-cyano-2,3-ditolyl tetrazolium chloride) reduction in Escherichia coli

The effects of substrates of primary aerobic dehydrogenases, and inorganic phosphate on aerobic INT and CTC reduction in Escherichia coli were examined. In general, INT produced less formazan than CTC, but INT (+) cell counts remained near values of CTC (+) cells. INT and CTC (+) cell numbers were higher than plate counts on R2A medium using succinate, formate, lactate, casamino acids, glucose, glycerol (INT only) and no substrate. Formate resulted in the greatest amount of INT and CTC formazan. Reduction of both INT and CTC was inhibited above 10 mmol l-1 phosphate, and this appeared to be related to decreased rates of O2 consumption. Formation of fluorescent CTC (+), but not INT (+) cells was also inhibited in a concentration dependent manner by phosphate above 10 mmol l-1. From light microscopic observations it appeared CTC formed increasing amounts of poorly or non-fluorescent formazan with increasing phosphate. Therefore, use of phosphate buffer in excess of 10 mmol l-1 may not be appropriate in CTC and INT reduction assays.

NASA Program Environmental Health↗
NASA NTRS1992

Effects of isolation on interferon production and hematological and immunological parameters

A 27-year-old woman was maintained in an isolated state for 131 days in Carlsbad Caverns, New Mexico. Her diet was vitamin D-depleted. Determinations on the effects of such isolation on levels and activities of peripheral blood cells that are important for hematological homeostasis and immunological function were carried out. Throughout the duration of the study, the percentage of lymphoid cells that expressed CD3, CD4, CD8, CD19, Leu 8, and other markers remained relatively constant although the absolute numbers of these cells varied. Although the percentage of natural killer (NK) cells did not vary, the activity of these cells did change. NK cell activity became elevated as the isolation study progressed. Production of interferon-gamma (IFN-gamma) in response to mitogen stimulation was higher than expected throughout the isolation periods, but returned to the normal range after termination of the isolation. Red and white cell counts dropped significantly upon entering isolation, but soon returned to normal.

NASA Discipline Cell Biology↗
NASA NTRS1985

Hematologic parameters of astrorats flown on SL-3

Hematologic studies were performed on a group of large and small rats which were sacrificed after flying in life sciences shuttle engineering flight SL-3. The results are presented on flight (F) and control (C) 200 gm rats. The small flight animals demonstrated a significant increase in hematocrits, red blood cell counts, hemoglobins and peripheral blood percentages of neutrophils as well as a decrease in percentage of lymphocytes. Erythropoietin (Ep) determinations were similar for the two groups as were the bone marrow an spleen differential counts. In vitro cultures for erythroid colonies of bone marrow showed that in response to different doses of Ep, in all cases where differnces were statistically significant, the F rats had increased colony counts. The changes in red cell parameters could be caused by a decrease in plasma volume. However, no isotopic studies were possible on this flight and this lack points up the need for such studies to determine the red cell mass and plasma volume.

Lange, R. D.↗