SEARCH · PubMed Health

Results for “Yucca”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMedDate not supplied

Effect of heterogeneity on radionuclide retardation in the alluvial aquifer near Yucca Mountain, Nevada.

The U.S. Department of Energy is currently studying Yucca Mountain, Nevada, as a potential site for a geological high-level waste repository. In the current conceptual models of radionuclide transport at Yucca Mountain, part of the transport path to pumping locations would be through an alluvial aquifer. Interactions with minerals in the alluvium are expected to retard the downstream migration of radionuclides, thereby delaying arrival times and reducing ground water concentrations. We evaluate the effectiveness of the alluvial aquifer as a transport barrier using the stochastic Lagrangian framework. A transport model is developed to account for physical and chemical heterogeneities and rate-limited mass transfer between mobile and immobile zones. The latter process is caused by small-scale heterogeneity and is thought to control the macroscopic-scale retardation in some field experiments. A geostatistical model for the spatially varying sorption parameters is developed from a site-specific database created from hydrochemical measurements and a calibrated modeling approach (Turner and Pabalan 1999). Transport of neptunium is considered as an example. The results are sensitive to the rate of transfer between mobile and immobile zones, and to spatial variability in the hydraulic conductivity. Chemical heterogeneity has only a small effect, as does correlation between hydraulic conductivity and the neptunium distribution coefficient. These results illustrate how general sensitivities can be explored with modest effort within the Lagrangian framework. Such studies complement and guide the application of more detailed numerical simulations.

Actinoid Series Elements↗

PubMed1997

Factors limiting microbial growth and activity at a proposed high-level nuclear repository, yucca mountain, nevada.

As part of the characterization of Yucca Mountain, Nev., as a potential repository for high-level nuclear waste, volcanic tuff was analyzed for microbial abundance and activity. Tuff was collected aseptically from nine sites along a tunnel in Yucca Mountain. Microbial abundance was generally low: direct microscopic cell counts were near detection limits at all sites (3.2 x 10(sup4) to 2.0 x 10(sup5) cells g(sup-1) [dry weight]); plate counts of aerobic heterotrophs ranged from 1.0 x 10(sup1) to 3.2 x 10(sup3) CFU g(sup-1) (dry weight). Phospholipid fatty acid concentrations (0.1 to 3.7 pmol g(sup-1)) also indicated low microbial biomasses; diglyceride fatty acid concentrations, indicative of dead cells, were in a similar range (0.2 to 2.3 pmol g(sup-1)). Potential microbial activity was quantified as (sup14)CO(inf2) production in microcosms containing radiolabeled substrates (glucose, acetate, and glutamic acid); amendments with water and nutrient solutions (N and P) were used to test factors potentially limiting this activity. Similarly, the potential for microbial growth and the factors limiting growth were determined by performing plate counts before and after incubating volcanic tuff samples for 24 h under various conditions: ambient moisture, water-amended, and amended with various nutrient solutions (N, P, and organic C). A high potential for microbial activity was demonstrated by high rates of substrate mineralization (as much as 70% of added organic C in 3 weeks). Water was the major limiting factor to growth and microbial activity, while amendments with N and P resulted in little further stimulation. Organic C amendments stimulated growth more than water alone.

Journal Article↗

PubMed1999

Effect of Yucca schidigera on ruminal fermentation and nutrient digestion in heifers.

In a replicated 3 x 3 Latin square experiment, six heifers (443 +/- 6.1 kg) fed a 61% barley grain:39% alfalfa silage diet (DM basis) were given intraruminal doses of powdered Yucca schidigera (YS). Doses of 0 (control), 20, or 60 g/d were given at 0800 daily. Ruminal content was sampled 0, 2, 4, and 6 h after dosing. Acidity, concentrations of reducing sugars, free amino acids, and peptides in the rumen were not affected (P > .05) by YS. Relative to control, ruminal ammonia concentration was reduced (P < .05) 2 h after YS dosing. Ruminal propionate concentration was increased (P < .05) by YS. Protozoal numbers in the rumen were lower (P < .05) with YS than without. Yucca did not affect (P > .05) rate or extent of in situ DM degradability. Fibrolytic, amylolytic, and proteolytic activities in ruminal contents were similar among treatments (P > .05). Dry matter intake, apparent digestibilities of DM, NDF, and CP, nitrogen balance, and microbial protein synthesis in the rumen were not affected (P > .05) by treatment. The effect of YS on ruminal ammonia concentration likely resulted from a decreased concentration of protozoa and, presumably, from ammonia binding by YS. The effect on ruminal propionate was probably a result of a selective inhibitory effect of YS on rumen microbial species.

Animals↗

PubMed2025

The auxin gatekeepers: Evolution and diversification of the YUCCA family.

The critically important YUCCA (YUC) gene family is highly conserved and specific to the plant kingdom, primarily responsible for the final and rate-limiting step for indole-3-acetic acid (IAA) biosynthesis. IAA is an essential phytohormone, involved in virtually all aspects of plant growth and development. In addition, IAA is involved in fine-tuning plant responses to biotic and abiotic interactions and stresses. While the YUC gene family has significantly expanded throughout the plant kingdom, a detailed analysis of the evolutionary patterns driving this diversification has not been performed. Here, we present a comprehensive phylogenetic analysis of the YUC family, combining YUCs from species representing key evolutionary plant lineages. The evolutionary history of YUCs is complex and suggests multiple recruitment events via horizontal gene transfer from bacteria. We identify and hierarchically classify the YUC family into an early diverging grade, five distinct classes and 41 subclasses. Angiosperm YUC diversity and expansion are explained in the context of protein sequence conservation, as well as spatial and gene expression patterns. The presented YUC gene landscape offers new perspectives on the distribution and evolutionary trends of this crucial family, which facilitates further YUC characterization within plant development and response to environmental change.

Indoleacetic Acids↗

PubMed2004

Liquid chromatography/tandem mass spectrometry of unusual phenols from Yucca schidigera bark: comparison with other analytical techniques.

Qualitative and quantitative analyses of phenolic compounds are of interest for both medicinal and food plants. In the present work, the phenolic fraction from Yucca schidigera, a plant bearing the GRAS (Generally Recognized as Safe) label approved by the US Food and Drug Administration, was studied. Crude extracts of Y. schidigera bark were investigated by liquid chromatography/UV spectrophotometry with diode-array detection, liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) and liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS), in order to develop and optimize simple and rapid techniques to determine both stilbenes and yuccaols for the purposes of quality control of collected material. With optimal LC and MS conditions, stilbenes and yuccaols were quantified with all the proposed methods and the results were compared. Sensitivity was evaluated and the results indicated that MS/MS detection in the multiple reaction monitoring mode is easily applicable to this plant and allows the rapid and direct identification and quantification of these peculiar compounds in crude plant extracts.

Chromatography, Liquid↗

PubMed2005

Antifungal activity of steroidal glycosides from Yucca gloriosa L.

The antifungal activity of a crude steroidal glycoside extract from Yucca gloriosa flowers, named alexin, was investigated in vitro against a panel of human pathogenic fungi, yeasts as well as dermatophytes and filamentous species. The minimal inhibitory concentration (MIC) was determined by an agar dilution method. Alexin had a broad spectrum of antifungal activity, found to reside entirely in the spirostanoid fraction. The major tigogenyl glycosides, yuccaloeside B and yuccaloeside C, exhibited MICs between 0.39 and 6.25 microg[sol ]mL for all the tested yeast strains except for two (C. lusitaniae and C. kefyr). They were also active against several clinical Candida isolates known to be resistant to the usual antifungal agents. The MICs for the dermatophytes were between 0.78 and 12.5 microg[sol ]mL. The most sensitive filamentous species was A. fumigatus (MIC = 1.56 microg[sol ]mL). For most of the strains, the MICs of both glycosides were similar to those of the reference antifungal agent.

Antifungal Agents↗

PubMed2006

The influence of interaction type and feeding location on the phylogeographic structure of the yucca moth community associated with Hesperoyucca whipplei.

The interactions between herbivorous insects and their host plants have been central in generating diversification in both groups. We used a community of four yucca moth species, monophagous on the host plant Hesperoyucca whipplei (Agavaceae), to examine how the type of interaction and where insects feed within a plant influence phylogeographic structure of herbivorous insects. These four species included two fruit-feeders, one mutualistic and one commensalistic, and two commensalistic stalk-feeders. Surveys based on mtDNA cytochrome oxidase I sequence data demonstrated that the moth species differed in phylogeographic history. Populations of the mutualist pollinator, Tegeticula maculata, exhibited the most subdivision in comparison to the three commensal Prodoxus species (both genera in Lepidoptera, Prodoxidae). Feeding location was also correlated with differences in phylogeographic history through its influence on population sizes and the probability of gene flow. The results suggest that both the outcome of interactions and where insects feed may influence population structure.

Animals↗

PubMed2003

Antioxidant and insect growth regulatory activities of stilbenes and extracts from Yucca periculosa.

The methanol extract from the bark of Yucca periculosa F. Baker afforded 4,4'-dihydroxstilbene, resveratrol and 3,3',5,5'-tetrahydroxy-4-methoxystilbene and had growth regulatory activity against the Fall Army worm (Spodoptera frugiperda J.E. Smith, Lepidoptera:Noctuidae) an insect pest of corn. The most active compound was 3,3',5,5'-tetrahydroxy-4-methoxystilbene which had significant effects at 3 microg/g in diets. In addition to the inhibitory activity on bleaching of crocin induced by alkoxyl radicals, these compounds also demonstrated scavenging properties toward 2,2-diphenyl-1-picrylhydrazyl in TLC autographic and spectrophotometric assays. Our results indicate that these compounds could be involved in interference of sclerotization and moulting. These compounds appear to have selective effects on the pre-emergence metabolism of the insect. The results were fully comparable to known natural insect growth inhibitors such as gedunin and Cedrela extracts and have had a possible role as natural insecticidal agents.

Animals↗

PubMed2002

Anti-platelet effects of different phenolic compounds from Yucca schidigera Roezl. bark.

Resveratrol (3,4',5-trihydroxystilbene) has been reported to have a variety of anti-inflammatory, anti-carcinogenic, anti-fungal and anti-platelet effects. It occurs naturally in different medicinal plants. Recently, resveratrol and other related phenolic compounds including trans-3,3',5,5'-tetrahydroxy-4'-methoxystilbene and yuccaols A and C were isolated from the bark of Yucca schidigera. The aim of the present study was to evaluate in vitro the effects of these compounds on platelet aggregation induced by thrombin and ADP. Pretreatment of platelets with resveratrol or other tested phenolics (1-25 microg/ml) slightly reduced platelet aggregation stimulated by 5 microM ADP (P < 0.05) or 10 microM ADP (P < 0.005). The comparison of the inhibitory effects of tested compound in thrombin-induced platelet aggregation revealed that phenolic showed even stronger antiplatelet actions than resveratrol. These compounds also had an inhibitory effect on the thrombin-induced enzymatic platelet lipid peroxidation determined as the level of thiobarbituric acid reactive substances.

Adenosine Diphosphate↗

PubMedDate not supplied

Evaluation of the mutagenic activity of phenolics from the bark of Yucca schidigera Roezl.

The mutagenic activity of yuccaols A, B, and C, trans-resveratrol and trans - 3.3',5.5'-tetrahydroxy -4'-methoxystilbene was tested by the Ames method with Salmonella typhimurium strains TA97, TA98, TA100, TA102 in the absence and presence of metabolic activation (S9 fraction). These phenolic compounds have been isolated and identified from the hark of Yucca schidigera. All of them were found to be non-toxic and non-mutagenic for testing doses in any of the S. typhimurium strains.

Animals↗

PubMed1991

12-Keto steroidal glycosides from the caudex of Yucca gloriosa.

Eight new steroidal glycosides, tentatively named YS-VI, -VII, -VIII, -IX, -X, -XI, -XII and -XIII were isolated from the caudex of Yucca gloriosa along with P-1, YG-2 and YG-3 previously obtained from flowers. The structures of five of these compounds were elucidated as mexogenin 3-O-beta-D-glucopyranosyl-(1----2)-beta-D-galactopyranoside (YS-VI), gloriogenin 3-O-beta-D-glucopyranosyl-(1----2)-[beta- D-glucopyranosyl-(1----3)]-beta-D-glucopyranoside (YS-VII) and 3-O-beta-D-glucopyranosyl-(1----2)-[beta-D-glucopyranosyl)-(1----3)]- beta-D-galactopyranoside (YS-VIII), manogenin 3-O-beta-lycotetraoside (YS-IX) and 3-O-alpha-L-rhamnopyranosyl-beta-lycotetraoside (YS-X), respectively, on the basis of chemical and spectral evidence.

Carbohydrate Sequence↗

PubMed1991

12-Hydroxy steroidal glycosides from the caudex of Yucca gloriosa.

The structures of the new steroidal saponins (tentatively named YS-XI, -XII and -XIII) have been isolated from the caudex of Yucca gloriosa and characterized as 3-O-beta-D-glucopyranosyl-(1----2)-beta-D-galactopyranosyl 5 beta- (25R)-spirostan-3 beta, 12 beta-diol, 3-O-beta-D-glucopyranosyl-(1----2)- [beta-D-glucopyranosyl-(1----3)]-beta-D-glucopyranosyl 5 beta- (25R)-spirostan-3 beta, 12 beta-diol and 3-O-beta-D-glucopyranosyl-(1----2)- beta-D-galactopyranosyl 5 beta-(25R)-spirostan-2 beta,3 beta,12 beta-triol, respectively.

Acetylation↗

PubMed1992

A spirostanol glycoside from Yucca aloifolia.

From an ethanolic extract of the influorescence of Yucca aloifolia a new spirostanol glycoside has been isolated and characterized as 3-O[(alpha-L-rhamnopyranosyl(1----3)-beta-D-xylopyranosyl(1----2))(beta- D-glucopyranosyl(1----3)-beta-D-glucopyranosyl(1----3)-beta-D-glucopy ranosyl]-25R,5 alpha-spirostan-2 alpha, 3 beta-diol.

Carbohydrate Sequence↗

PubMed2004

Transport of radon gas into a tunnel at Yucca Mountain--estimating large-scale fractured tuff hydraulic properties and implications for the operation of the ventilation system.

Radon gas concentrations have been monitored as part of the operation of a tunnel (the Exploratory Studies Facility-ESF) at Yucca Mountain to ensure worker safety. The objective of this study was to examine the potential use of the radon data to estimate large-scale formation properties of fractured tuffs. This objective was examined by developing a numerical model, based upon the characteristics of the ESF and the Topopah Spring welded (TSw) tuff unit, capable of predicting radon concentrations for prescribed ventilation conditions. The model was used to address two specific issues. First, it was used to estimate the permeability and porosity of the fractures in the TSw at the length scale of the ESF and extending tens of meters into the TSw, which surrounds the ESF. Second, the model was used to understand the mechanism leading to radon concentrations exceeding a specified level within the ESF. The mechanism controlling radon concentrations in the ESF is a function of atmospheric barometric fluctuations being propagated down the ESF along with ventilated air flow and the slight suction induced by the ventilation exhaust fans at the South Portal of the ESF. These pressure fluctuations are dampened in the TSw fracture continuum according to its permeability and porosity. Consequently, as the barometric pressure in the ESF drops rapidly, formation gases from the TSw are pulled into the ESF, resulting in an increase in radon concentrations. Model calibration to both radon concentrations measured in the ESF and gas-phase pressure fluctuations in the TSw yielded concurrent estimates of TSw fracture permeability and porosity of 1 x 10(-11) m2 and 0.00034, respectively. The calibrated model was then used as a design tool to predict the effect of adjusting the current ventilation-system operation strategy for reducing the probability of radon gas concentrations exceeding a specified level.

Air Movements↗

PubMed2005

Scoping analyses of geochemical sealing of early cracks in a waste container and associated drip shield, Yucca Mountain, Nevada.

Early after final emplacement of the nuclear waste containers at the proposed Yucca Mountain, Nevada, high-level-waste repository, tiny cracks (less than 200 microm wide, 1 to 2 cm deep, and a few centimeters long at most) could appear in the containers and in the drip shield protecting them. Modeling calculations were performed to understand how fast those cracks could be sealed. Under dripping conditions, they are expected to be bridged with water. If cracks are located in the drip shield, any further dripping on the waste containers located underneath will be limited. If cracks are located in a container, potentially harmful radionuclides could only travel by diffusion. In addition, water-bridged cracks will be sealed through at least two processes: precipitation of calcite with minor silica following evaporative concentration of the water residing in the cracks and continuous corrosion of the crack walls. The sealing rate is calculated as the intersection of the time of emergence of the cracks, the water dripping rate, and the decreasing evaporation rate. The evaporative driving force declines as short-lived radioactive elements, having given up much of the heat affecting the repository, are progressively depleted from the waste. Depending on the crack initiation time and environmental conditions, crack sealing varies from a few tens of years to a few thousand years. Because environmental conditions in the vicinity of the cracks and at the crack scale have not been produced, a parametric method scaling drift scale conditions is used.

Calcium Carbonate↗

PubMed2001

Application of MS and NMR to the structure elucidation of complex sugar moieties of natural products: exemplified by the steroidal saponin from Yucca filamentosa L.

An approach, using well characterized procedures, is presented that should be of general applicability for the structural elucidation of complex sugar moieties of natural products. The methods used are exemplified by the structure elucidation of a new gitogenin-based steroidal saponin that has a strong leishmanicidal activity similar to preparations used in clinical practice and has been isolated by bioactivity-guided fractionation of the ethanolic extract of Yucca filamentosa L. leaves. The saponin has been characterized as 3-O-((beta-D-glucopyranosyl-(1-->3)- beta-D-glucopyranosy-(1-->2))(alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->3))-beta-D-glucopyranosyl-(1-->4)-beta-D-galactopyranosyl)-25R,5alpha-spirostan-2alpha,3beta-diol.

Biological Products↗

PubMedDate not supplied

The ameliorating effect of Yucca schidigera extract on canine and feline faecal aroma.

Addition of Yucca schidigera extract (YSE) products to canine or feline diets improved the character and reduced the intensity of faecal aroma as monitored by a human panel. The general condition of the animals was not adversely affected as monitored by faecal pH, food retention time, and blood cell counts. Blood urea increased significantly in YSE-treated cats, possibly due to the saponins of YSE affecting gut wall permeability. This finding contrasts with previously published reports of a reduction in blood urea on the addition of sarsaponin (from YSE) to rat diets and of YSE products to poultry and cattle diets.

Analysis of Variance↗

PubMedDate not supplied

The effect of Yucca schidigera extract on canine and feline faecal volatiles occurring concurrently with faecal aroma amelioration.

Addition of Yucca schidigera extract (YSE) products to canine or feline diets improved faecal aroma as monitored by a human panel. Odour port-gas chromatography (GC) indicated different odour component types in dog faecal volatiles and, in particular, 'faecal'-type odours due to methyl sulfides. GC-mass spectrometry demonstrated several chemical compound classes present in faecal volatiles and quantitation in the cat indicated apparently significant changes in the concentrations of several compounds on YSE treatment, although these were not necessarily aroma components. The potential for direct YSE alteration of aroma perception in a mixture of volatiles, possibly by binding, was demonstrated.

Animals↗