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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Emission of nitric oxide (NO) from tropical forest soils and exchange of NO between the forest canopy and atmospheric boundary layers

Emissions of NO from soils in the Amazon rain forest were measured at 66 locations using an enclosure technique, and continuous vertical profiles of NO and O3 were measured between the ground and 41-m altitude. Fluxes of NO averaged 8.9 (+ or - 1.5) x 10 to the 9th molecules/sq cm per sec from the dominant (yellow clay) soils of the region, with larger fluxes observed from adjacent white sand soils. Fluxes from clay soils were lower by more than a factor of 5 than fluxes observed during the dry season at a nearby site. Low soil emission rates were reflected in lower concentrations of NO at the top of the forest canopy in the wet season, only 30-50 parts per trillion by volume during the daytime. The measured fluxes are consistent with chemical mass balances for NO within the forest canopy, calculated from the NO and O3 profiles taken at night, and with observations of NO between 150 and 5000 m altitude. Measurements of NO emission rates from soil plots fertilized using NaNO3, NH4Cl, or sucrose indicated that a reductive pathway (denitrification) may have been primarily responsible for production of the NO released by both clay and sand soils.

Bakwin, Peter S.↗
NASA NTRS1990

Radial spreading of viscous-gravity currents with solidifying crust

In the present investigation of solidifying-crust effects on the dynamics and surface morphology of radial viscous-gravity currents, polyethylene glycol inflows into the base of a tank holding a cold sucrose solution are used as analogs. As the radial current advanced away from the inlet, its surface solidified and deformed through a combination of folding anf fracturing. When cooling was sufficiently rapid, solid crust formed and caused the spreading rate to increase; progressively colder experiments revealed a sequence of surface morphologies resembling features of cooling lava flows and lava lakes, including multiarmed rift structures with shear offsets and bulbous lobate forms resembling pillow lavas on the ocean floor.

Fink, Jonathan H.↗
NASA NTRS1991

Photosynthetic reaction center complexes from heliobacteria

Photosynthetic reaction centers are pigment-protein complexes that are responsible for the transduction of light energy into chemical energy. Considerable evidence indicates that photosynthetic organisms were present very early in the evolution of life on Earth. The goal of this project is to understand the early evolutionary development of photosynthesis by examining the properties of reaction centers isolated from certain contemporary organisms that appear to contain the simplest photosynthetic reaction centers. The major focus is on the family of newly discovered strictly anaerobic photosynthetic organisms that are grouped with the gram-positive phylum of bacteria. The properties of these reactions centers suggest that they may be the descendants of an ancestor that also gave rise to Photosystem 1 found in oxygen-evolving photosynthetic organisms. Photoactive reaction center-core antenna complexes were isolated from the photosynthetic bacteria, Heliobacillus mobilis and Heliobacterium gestii, by extraction of membranes with Deriphat 160C followed by differential centrifugation and sucrose density gradient centrifugation. Other aspects of this investigation are briefly discussed.

Trost, J. T.↗
NASA NTRS1993

Experiments On Flow In A Coronary Artery

Report describes experiments on simulated flow of blood in atherosclerotic human coronary artery. Experiments performed on polyurethane cast made from S-shaped coronary artery of cadaver. Sucrose solution with viscosity of blood pumped through cast at physiologically realistic rates, and flow made pulsatile by mechanism alternately compressing and releasing elastic tube just upstream of cast.

Back, Lloyd H.↗
NASA NTRS1991

Relationship of area postrema to three putative measures of motion sickness

Although the rat has an incomplete emetic reflex, several species-specific responses to motion were proposed as measures of 'motion sickness' in rats. The purpose was to determine the dependence of these responses on one of several neural structures known to be essential to motion-induced vomiting in species with a complete emetic reflex. The Area Postrema (AP) was shown to play an important role in the production of motion sickness in vomiting species. The effects of thermo-cautery ablations of the AP on three different responses supposedly reflecting motion sickness in the rat were compared: conditioned taste aversion (CTA); drinking suppression; and fecal boli. Efficacy of the ablations was determined by subjecting ablated, sham-operated, and unoperated control animals to a CTA test which is known to require a functional AP. Animals with AP ablations failed to form CTA when 0.15 M LiCl was paired with a 10 percent sucrose solution, while sham-operated control subjects conditioned as well as the unoperated control subjects. The extent of the ablations was evaluated histologically at the end of the experiment. To determine the effects of the ablations on the measures of motion sickness, all animals were subjected to rotation for 30 min or 90 min on a platform displaced 20 deg from earth horizontal. Results indicate that ablation of AP in the rat has no effect on the formation of CTA to a 4 percent solution of cider paired with motion, on the suppression of drinking immediately after exposure to motion, or on the frequency of fecal boli during exposure to motion. This failure of AP ablations to eliminate the effects of motion on any of these responses discourages their use as equivalents of motion-induced vomiting. The appropriateness of other suggested measures, e.g., pica, remains untested but the dependence of such measures on stimulation more severe than commonly used in motion sickness research and the absence of a demonstration of their dependence on neural structures essential to motion sickness in vomiting species, suggest caution in the use of such responses. Further, until more is known about the neural structures underlying these putative measures, the rat will remain a questionable subject in which to study motion sickness.

R Sutton↗
NASA NTRS1988

Role of the area postrema in three putative measures of motion sickness in the rat

After thermal cauterization of the area postrema in rats, the absence of conditioned taste aversion of sucrose paired with lithium chloride (0.15M, 3.3 ml/kg) was used as a pharmacologic/behavioral index of area postrema damage. In a subsequent experiment the effects of area postrema lesions on three measures proposed as species-relevant measures of motion sickness were studied, using off-vertical rotation at 150 deg/s for either 30 or 90 min. Lesions of area postrema did not alter postrotational suppression of drinking or amount of defecation during motion. The initial acquisition of conditioned taste aversion to a novel cider vinegar solution paired with motion was not affected by lesioning of the area postrema, but these taste aversions extinguished more slowly in lesioned rats than in sham-operates or intact controls. Results are discussed in terms of proposed humoral factors which may induce motion sickness and in light of recent data on the role of the area postrema in similar measures in species possessing the complete emetic reflex.

Richard L Sutton↗
NASA NTRS1992

Presence of methyl sterol and bacteriohopanepolyol in an outer-membrane preparation from Methylococcus capsulatus (Bath)

Cytoplasmic/intracytoplasmic and outer membrane preparations of Methylococcus capsulatus (Bath) were isolated by sucrose density gradient centrifugation of a total membrane fraction prepared by disruption using a French pressure cell. The cytoplasmic and/or intracytoplasmic membrane fraction consisted of two distinct bands, Ia and Ib (buoyant densities 1.16 and 1.18 g ml (exp -1), respectively) that together contained 57% of the protein, 68% of the phospholipid, 73% of the ubiquinone and 89% of the CN-sensitive NADH oxidase activity. The only apparent difference between these two cytoplasmic bands was a much higher phospholipid content for Ia. The outer membrane fraction (buoyant density 1.23-1.24 g ml (exp -1)) contained 60% of the lipopolysaccharide-associated, beta-hydroxypalmitic acid, 74% of the methylsterol, and 66% of the bacteriohopanepolyol (BHP); phospholipid to methyl sterol or BHP ratios were 6:1. Methanol dehydrogenase activity and a c-type cytochrome were also present in this outer membrane fraction. Phospholipase A activity was present in borh the cytoplasmic membrane and outer membrane fractions. The unique distribution of cyclic triterpenes may reflect a specific role in conferring outer membrane stability in this methanotrophic bacterium.

Jahnke, Linda L.↗
NASA NTRS2002

Spirochaeta americana sp. nov.: A New Haloalkaliphilic, Obligately Anaerobic Spirochete Isolated from Soda Mono Lake, California

A novel obligately anaerobic, mesophilic, haloalkaliphilic spirochete, strain ASpG1, was isolated from sediments of the alkaline, hypersaline Mono Lake in California, U.S.A. The gram-negative cells are motile and spirochete-shaped with sizes of 0.22 x 10-15 micron. Growth was observed over the temperature range of 10 C to 44 C (optimum 37 C), NaCl concentration range of greater than 1 - 12 % (wt/vol) (optimum 3%), and pH range 7.5 - 10.5 (optimum pH 9.5). The novel isolate is strictly alkaliphilic, requires high concentrations of carbonate in the medium, and is capable of utilizing D-glucose, fructose, maltose, sucrose, starch, and D-mannitol. Main end products of glucose fermentation are: H2, acetate, ethanol, and formate. Strain AspG1 is resistant to kanamycin, but sensitive to chloramphenicol, gentamycin and tetracycline. The G+C content of its DNA is 58.5 mol%. On the basis of its physiological and molecular properties, the isolate appears to be a novel species among the genus Spirochaeta; and the name Spirochaeta americana sp. nov., is proposed for the taxon (type strain ASpG1(sup T) = ATCC BAA_392(sup T) = DSMZ 14872(sup T)).

Hoover, Richard B.↗
NASA NTRS2002

Spirochaeta Americana Sp. Nov., A new Haloalkaliphilic, Obligately Anaerobic Spirochete Isolated from Soda Mono Lake in California

A novel obligately anaerobic, mesophilic, haloalkaliphilic spirochete, strain ASpG1(sup T), was isolated from sediments of the alkaline, hypersaline Mono Lake in California, U.S.A. The Gram-negative cells are motile and spirochete-shaped with sizes of 0.2 - 0.22 X 8-15 microns. Growth was observed over the following ranges: temperature 10 C to 44 C; optimum +37 C; NaCl concentration 2 - 12 % (w/v); optimum NaCl3 % and pH 8 - 10.5; optimum pH 9.5. The novel isolate is strictly alkaliphilic, requires high concentrations of carbonate in the medium, and is capable of utilizing D-glucose, fructose, maltose, sucrose, starch, and D-mannitol. The main end products of glucose fermentation are: H2, acetate, ethanol, and formate. Strain ASpG(sup T) is resistant to kanamycin, and rifampin, but sensitive to chloramphenicol, gentamycin and tetracycline. The G+C content of its DNA is 58.5 mol%, genome size is 2.98 x l0(exp 9) Daltons, Tm of the genomic DNA is 68 +/- 2 C, and DNA-DNA hybridization with the most closely related species, Spirocheta alkalica Strain Z-7491(sup T), exhibited 48.7% homology. On the basis of its physiological and molecular properties, the isolate appears to be a novel species of the genus Spirochaeta; and the name Spirochaeta americana sp. nov., is proposed for the taxon (type strain ASpG1(sup T) = ATCC BAA-392(sup T) = DSMZ 14872(sup T)).

Hoover, Richard B.↗
NASA NTRS2003

Spirochaeta Americana sp. Nov., A New Haloalkaliphilic, Obligately Anaerobic Spirochaete Isolated from Soda Mona Lake in California

A novel, obligately anaerobic, mesophilic, haloalkaliphilic spirochaete, strain ASpG1(sup T), was isolated from sediments of the alkaline, hypersaline Mono Lake in California, USA. Cells of the Gram-negative strain were motile and spirochaete-shaped with sizes of 0.2-0.22 x 8-18 microns. Growth of the strain was observed between 10 and 44 C (optimum 37 C), in 2-12% (w/v) NaCl (optimum 3 % NaCl) and between pH 8 and 10.5 (optimum pH 9.5). The novel strain was strictly alkaliphilic, required high concentrations of carbonates in the medium and was capable of utilizing D-glucose, fructose, maltose, sucrose, starch and D-mannitol. End products of glucose fermentation were H2, acetate, ethanol and formate. Strain ASpG1(sup T) was resistant to kanamycin and rifampicin, but sensitive to gentamicin, tetracycline and chloramphenicol. The G + C content of its DNA was 58.5 mol%. DNA-DNA hybridization analysis of strain ASpG1(sup T) with its most closely related species, Spirochaeta alkalica Z-7491(sup T) revealed a hybridization value of only 48.7 %. On the basis of its physiological and molecular properties, strain ASpG1(sup T) appears to represent a novel species of the genus Spirochaeta, for which the name Spirochaeta americana is proposed (type strain ASpG1(sup T) = ATCC 13AA-392(sup T) = DSM 14872(sup T)).

Hoover, Richard B.↗
NASA NTRS2003

Spirochaeta americana sp. nov., a new haloalkaliphilic, obligately anaerobic spirochaete isolated from soda Mono Lake in California

A novel, obligately anaerobic, mesophilic, haloalkaliphilic spirochaete, strain ASpG1(T), was isolated from sediments of the alkaline, hypersaline Mono Lake in California, USA. Cells of the Gram-negative strain were motile and spirochaete-shaped with sizes of 0.2-0.22 x 8-18 microm. Growth of the strain was observed between 10 and 44 degrees C (optimum 37 degrees C), in 2-12% (w/v) NaCl (optimum 3% NaCl) and between pH 8 and 10.5 (optimum pH 9.5). The novel strain was strictly alkaliphilic, required high concentrations of carbonates in the medium and was capable of utilizing D-glucose, fructose, maltose, sucrose, starch and D-mannitol. End products of glucose fermentation were H2, acetate, ethanol and formate. Strain ASpG(T) was resistant to kanamycin and rifampicin, but sensitive to gentamicin, tetracycline and chloramphenicol. The G + C content of its DNA was 58.5 mol%. DNA-DNA hybridization analysis of strain ASpG1(T) with its most closely related species, Spirochaeta alkalica Z-7491(T), revealed a hybridization value of only 48.7%. On the basis of its physiological and molecular properties, strain ASpG1(T) appears to represent a novel species of the genus Spirochaeta, for which the name Spirochaeta americana is proposed (type strain ASpG1(T) =ATCC BAA-392(T) = DSM 14872(T)).

Sodium Chloride/metabolism↗
NASA NTRS2003

Increased Agrobacterium-mediated transformation and rooting efficiencies in canola (Brassica napus L.) from hypocotyl segment explants

An efficient protocol for the production of transgenic Brassica napus cv. Westar plants was developed by optimizing two important parameters: preconditioning time and co-cultivation time. Agrobacterium tumefaciens-mediated transformation was performed using hypocotyls as explant tissue. Two variants of a green fluorescent protein (GFP)-encoding gene--mGFP5-ER and eGFP--both under the constitutive expression of the cauliflower mosaic virus 35S promoter, were used for the experiments. Optimizing the preconditioning time to 72 h and co-cultivation time with Agrobacterium to 48 h provided the increase in the transformation efficiency from a baseline of 4% to 25%. With mGFP5-ER, the transformation rate was 17% and with eGFP it was 25%. Transgenic shoots were selected on 200 mg/l kanamycin. Rooting efficiency was 100% on half-strength Murashige and Skoog medium with 10 g/l sucrose and 0.5 mg/l indole butyric acid in the presence of kanamycin.

NASA Discipline Life Sciences Technologies↗
NASA NTRS2002

A microarray immunoassay for simultaneous detection of proteins and bacteria

We report the development and characterization of an antibody microarray biosensor for the rapid detection of both protein and bacterial analytes under flow conditions. Using a noncontact microarray printer, biotinylated capture antibodies were immobilized at discrete locations on the surface of an avidin-coated glass microscope slide. Preservation of capture antibody function during the deposition process was accomplished with the use of a low-salt buffer containing sucrose and bovine serum albumin. The slide was fitted with a six-channel flow module that conducted analyte-containing solutions over the array of capture antibody microspots. Detection of bound analyte was subsequently achieved using fluorescent tracer antibodies. The pattern of fluorescent complexes was interrogated using a scanning confocal microscope equipped with a 635-nm laser. This microarray system was employed to detect protein and bacterial analytes both individually and in samples containing mixtures of analytes. Assays were completed in 15 min, and detection of cholera toxin, staphylococcal enterotoxin B, ricin, and Bacillus globigii was demonstrated at levels as low as 8 ng/mL, 4 ng/mL, 10 ng/mL, and 6.2 x 10(4) cfu/mL, respectively. The assays presented here are very fast, as compared to previously published methods for measuring antibody-antigen interactions using microarrays (minutes versus hours).

Non-NASA Center↗
NASA NTRS2002

Transcriptional control of monolignol biosynthesis in Pinus taeda: factors affecting monolignol ratios and carbon allocation in phenylpropanoid metabolism

Transcriptional profiling of the phenylpropanoid pathway in Pinus taeda cell suspension cultures was carried out using quantitative real time PCR analyses of all known genes involved in the biosynthesis of the two monolignols, p-coumaryl and coniferyl alcohols (lignin/lignan precursors). When the cells were transferred to a medium containing 8% sucrose and 20 mm potassium iodide, the monolignol/phenylpropanoid pathway was induced, and transcript levels for phenylalanine ammonia lyase, cinnamate 4-hydroxylase, p-coumarate 3-hydroxylase, 4-coumarate:CoA ligase, caffeoyl-CoA O-methyltransferase, cinnamoyl-CoA reductase, and cinnamyl alcohol dehydrogenase were coordinately up-regulated. Provision of increasing levels of exogenously supplied Phe to saturating levels (40 mm) to the induction medium resulted in further up-regulation of their transcript levels in the P. taeda cell cultures; this in turn was accompanied by considerable increases in both p-coumaryl and coniferyl alcohol formation and excretion. By contrast, transcript levels for both cinnamate 4-hydroxylase and p-coumarate 3-hydroxylase were only slightly up-regulated. These data, when considered together with metabolic profiling results and genetic manipulation of various plant species, reveal that carbon allocation to the pathway and its differential distribution into the two monolignols is controlled by Phe supply and differential modulation of cinnamate 4-hydroxylase and p-coumarate 3-hydroxylase activities, respectively. The coordinated up-regulation of phenylalanine ammonia lyase, 4-coumarate:CoA ligase, caffeoyl-CoA O-methyltransferase, cinnamoyl-CoA reductase and cinnamyl alcohol dehydrogenase in the presence of increasing concentrations of Phe also indicates that these steps are not truly rate-limiting, because they are modulated according to metabolic demand. Finally, the transcript profile of a putative acid/ester O-methyltransferase, proposed as an alternative catalyst for O-methylation leading to coniferyl alcohol, was not up-regulated under any of the conditions employed, suggesting that it is not, in fact, involved in monolignol biosynthesis.

NASA Discipline Plant Biology↗
NASA NTRS2001

Evidence of root zone hypoxia in Brassica rapa L. grown in microgravity

A series of experiments was conducted aboard the U.S. space shuttle and the Mir space station to evaluate microgravity-induced root zone hypoxia in rapid-cycling Brassica (Brassica rapa L.), using both root and foliar indicators of low-oxygen stress to the root zone. Root systems from two groups of plants 15 and 30 d after planting, grown in a phenolic foam nutrient delivery system on the shuttle (STS-87), were harvested and fixed for microscopy or frozen for enzyme assays immediately postflight or following a ground-based control. Activities of fermentative enzymes were measured as indicators of root zone hypoxia and metabolism. Following 16 d of microgravity, ADH (alcohol dehydrogenase) activity was increased in the spaceflight roots 47% and 475% in the 15-d-old and 30-d-old plants, respectively, relative to the ground control. Cytochemical localization showed ADH activity in only the root tips of the space-grown plants. Shoots from plants that were grown from seed in flight in a particulate medium on the Mir station were harvested at 13 d after planting and quick-frozen and stored in flight in a gaseous nitrogen freezer or chemically fixed in flight for subsequent microscopy. When compared to material from a high-fidelity ground control, concentrations of shoot sucrose and total soluble carbohydrate were significantly greater in the spaceflight treatment according to enzymatic carbohydrate analysis. Stereological analysis of micrographs of sections from leaf and cotyledon tissue fixed in flight and compared with ground controls indicated no changes in the volume of protoplast, cell wall, and intercellular space in parenchyma cells. Within the protoplasm, the volume occupied by starch was threefold higher in the spaceflight than in the ground control, with a concomitant decrease in vacuolar volume in the spaceflight treatment. Both induction of fermentative enzyme activity in roots and accumulation of carbohydrates in foliage have been repeatedly shown to occur in response to root zone oxygen deprivation. These results indicate that root zone hypoxia is a persistent challenge in spaceflight plant growth experiments and may be caused by microgravity-induced changes in fluid and gas distribution.

long duration↗
NASA NTRS1998

Gravity and light control of the developmental polarity of regenerating protoplasts isolated from prothallial cells of the fern Ceratopteris richardii

A procedure has been developed for isolating protoplasts from prothalli of Ceratopteris richardii which can be cultured and are capable of regeneration. Protoplasts were isolated from 2-week-old gametophytes in a medium containing wall-digesting enzymes in 0.5 M sucrose, followed by purification of the released protoplasts by floating them up into a 0.5 M sorbitol layer. Regeneration occurred over a period of 10-24 days, and, under optimal osmotic conditions, followed the developmental pattern seen during spore germination, in that the first division gave rise to a primary rhizoid. Thus, prothallial protoplasts are comparable to germinating spores as suitable models for studies of developmental polarity in single cells. As in germinating spores, the polarity of development in regenerating protoplasts is influenced by the vectors of gravity and unilateral light. However, the relative influence of light in fixing this polarity is greater in regenerating protoplasts, while in germinating spores, the influence of gravity is greater.

NASA Discipline Plant Biology↗
NASA NTRS1990

Somatic embryogenesis of carrot in hormone-free medium: external pH control over morphogenesis

Cultures of preglobular stage proembryos (PGSPs) were initiated from mechanically wounded mature zygotic embryos of carrot, Daucus carota, on a hormone-free, semisolid medium. These PGSPs have been maintained and multiplied for extended periods without their progression into later embryo stages on the same hormone-free medium containing 1 mM NH4+ as the sole nitrogen source. Sustained maintenance of cultures comprised exclusively of PGSPs was dependent on medium pH throughout the culture period. Best growth and multiplication of PGSP cultures occurred when the pH of unbuffered, hormone-free medium fell from 4.5 to 4 over a 2-week period or when buffered medium was titrated to pH 4. If the hormone-free medium was buffered to sustain a pH at or above 4.5, PGSPs developed into later embryo stages. Maintenance with continuous multiplication of PGSPs occurred equally well on medium containing NH4+ or NH4+ and NO3-, but growth was poor with NO3- alone. Additional observations on the effects of medium components such as various nitrogen sources and levels, sucrose concentration, semisolid supports, type of buffer, borate concentration, activated charcoal, and initial pH that permit optimum maintenance of the PGSPs or foster their continued developmental progression into mature embryos and plantlets are reported. The influence of the pH of the hormone-free medium as a determinant in maintaining cultures as PGSPs or allowing their continued embryonic development are unequivocally demonstrated by gross morphology, scanning electron microscopy, and histological preparations.

NASA Discipline Number 29-20↗
NASA NTRS1992

Effect of pH on subunit association and heat protection of soybean alpha-galactosidase

Soybeans contain the enzyme alpha-galactosidase, which hydrolyzes alpha-1, 6 linkages in stachyose and raffinose to give sucrose and galactose. We have found that galactose, a competitive product inhibitor of alpha-galactosidase, strongly promotes the heat stability of the tetrameric form of the enzyme at pH 4.0 and at temperatures of up to 70 degrees C for 60 min. Stachyose and raffinose also protect alpha-galactosidase from denaturation at pH 4.0 although to a lesser extent. Glucose and mannose have little effect. At pH 7.0 the enzyme is a monomer, and galactose has no effect on the heat stability of the enzyme. In the absence of heat protection of the enzyme by added sugars, a series deactivation mechanism was found to describe the deactivation data. In comparison, a unimolecular, non-first order deactivation model applies at pH 4.0, where heat protection effects were observed. At a temperature above 60 degrees C, simple deactivation is a suitable model. The results suggest that alpha-galactosidase conformation and heat stability are directly related.

Non-NASA Center↗