Bioguided Fractionation and Isolation of an Antiplasmodial Saponin from the Roots of Nauclea xanthoxylon (A.Chev.) Aubrév. (Rubiaceae)

The root extract of Nauclea xanthoxylon (A.Chev.) Aubrév. displayed significant 50 % inhibition concentration (IC₅₀s) of 0.57 and 1.26 μg/mL against chloroquine resistant and sensitive Plasmodium falciparum (Pf) Dd2 and 3D7 strains, respectively. Bio-guided fractionation led to an ethyl acetate fraction with IC₅₀s of 2.68 and 1.85 μg/mL and subsequently, to the new quinovic acid saponin named xanthoxyloside ( 1 ) with IC₅₀s of 0.33 and 1.30 μM, respectively against the tested strains. Further compounds obtained from ethyl acetate and hexane fractions were the known clethric acid ( 2 ), ursolic acid ( 3 ), quafrinoic acid ( 4 ), quinovic acid ( 5 ), quinovic acid 3-O-β-D-fucopyranoside ( 6 ), oleanolic acid ( 7 ), oleanolic acid 3-acetate ( 8 ), friedelin ( 9 ), β-sitosterol ( 10a ), stigmasterol ( 10b ) and stigmasterol 3-O-β-D-glucopyranoside ( 11 ). Their structures were characterised with the aid of comprehensive spectroscopic methods (1 and 2D NMR, Mass). Bio-assays were performed using nucleic acid gel stain (SYBR green I)-based fluorescence assay with chloroquine as reference. Extracts and compounds exhibited good selectivity indices (SIs) of >10. Significant antiplasmodial activities measured for the crude extract, the ethyl acetate fraction and xanthoxyloside ( 1 ) from that fraction can justify the use of the root of N. xanthoxylon in ethnomedicine to treat malaria.     

BLOEM: A spatially explicit model of bioenergy and carbon capture and storage,applied to Brazil

Bioenergy could play a major role in decarbonizing energy systems in the context of the Paris Agreement. Large-scale bioenergy deployment could be related to sustainability issues and requires major infrastructure investments. It, therefore, needs to be studied carefully. The Bioenergy and Land Optimization Spatially Explicit Model (BLOEM) presented here allows for assessing different bioenergy pathways while encompassing various dimensions that influence their optimal deployment. In this study, BLOEM was applied to the Brazilian context by coupling it with the Brazilian Land Use and Energy Systems (BLUES) model. This allowed investigating the most cost-effective ways of attending future bioenergy supply projections and studying the role of recovered degraded pasture lands in improving land availability in a sustainable and competitive manner. The results show optimizing for limiting deforestation and minimizing logistics costs results in different outcomes. It also indicates that recovering degraded pasture lands is attractive from both logistics and climate perspectives. The systemic approach of BLOEM provides spatial results, highlighting the trade-offs between crop allocation, land use and the logistics dynamics between production, conversion, and demand, providing valuable insights for regional and national climate policy design. This makes it a useful tool for mapping sustainable bioenergy value chain pathways.     

SAR in rats exposed in 2,450-MHz circularly polarized waveguides

Average specific absorption rates (SARs) for live rats exposed in 2,450-MHz circularly polarized waveguides were estimated from the total system loss determined from measurements using five power meters, and a correction factor representing actual SAR/apparent SAR. The actual SAR was measured by twin-well calorimetry and the apparent SAR by power meters. Values were obtained for carcasses of various body masses for five orientations. The average SAR with free movement in the cages changed less than threefold as the rats grew from 200 to 700 g. The ratio of peak to average SAR in the body was less than 3. These results indicate relatively constant energy disposition in rats exposed in the circularly polarized waveguide.     

Studies on the size,location and turnover of calcium pools accessible to growing Tetrahymena cells

Tetrahymena pyriformis cells in the logarithmic phase of growth accumulate 2.5–3.75 times as much calcium per unit volume as is present in the growth medium. It appears that most of this calcium is stored in a non-ionic form, with approximately 30% existing in the cilia, near its site of action in effecting ciliary reversal. The exchange of extracellular ⁴⁵Ca²⁺ with the major internal pools is extremely rapid, exhibiting a $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ of less than 0.5 h. Sites located on the cilia are responsible for 35–50% of Ca²⁺ influx, with the remainder entering through other positions on the cell surface.     

A stochastic model of a temperature-dependent population

The theoretical basis is developed for a population model which allows the use of constant temperature experimental data in predicting the size of an insect population for any variable temperature environment. The model is based on a stochastic analysis of an insect's mortality, development, and reproduction response to temperature. The key concept in the model is the utilization of a physiological time scale. Different temperatures affect the population by increasing an individual's physiological age by differing rates. Conditions for the temperature response properties are given which establish the validity of the model for variable temperature regimes. These conditions refer to the relationship between chronological and physiological age. Reasonable agreement between the model and field populations demonstrates the practicality of this approach.     

Atomic scale structure and functional models of voltage-gated potassium channels.

Recent mutagenesis experiments have confirmed our hypothesis that a segment between S5 and S6 forms the ion selective portion of voltage-gated ion channels. Based on these and other new data, we have revised previous models of the general folding pattern of voltage-gated channel proteins and have developed atomic scale models of the entire transmembrane region of the Shaker A K+ channel. In these models, the ion selective region is a beta-barrel that spans the outer half of the membrane. The inner half of the pore is larger. The voltage-dependent conformational changes of activation gating are modeled to occur by the "helical screw" mechanism, in which the four S4 segments move along and rotate about their axes. These changes are followed by a voltage-independent conformational change, in which the segments linking S4 to S5 move from blocking the intracellular entrance of the pore to forming part of the lining of the large inner portion of the pore. The NH2-terminal of the protein was modeled as an alpha-helix that plugs the intracellular half of the pore to inactivate the channel.     

A new species of Ionactis (Asteraceae: Astereae) from Southern Nevada and an overview of the genus

Ionactis caelestis Leary & Nesom is a new species known from a single population that occurs on the Aztec Sandstone near Bridge Mountain in the Spring Mountains of Clark County, Nevada. It is placed in the genus Ionactis (=Aster subg. Ianthe) on the basis of its crowded, multicipital crown, lack of persistent basal leaves and presence of densely arranged cauline ones, strongly carinate phyllaries, blue rays, disc style branches with linear-lanceolate appendages, asymmetric carpopodia, double pappus, and chromosome number of 2n = 9 II. A key to the four species of the genus emphasizes the distinction of the new species in its taproot, the abundant, large, glandular trichomes on its stems and leaves, and disc flowers with sterile ovaries. Ionactis is more similar to the goldenaster (Heterotheca) lineage than to Aster, with which it has been allied formerly. The core of the goldenaster genera differ from Ionactis primarily in their yellow-rayed heads, the crystal complement within cells of their disc corollas, and their primarily multinerved achenes.     

Occurrence of 28- and 27-Carbon ecdysteroids and sterols in developing worker pupae of the leaf-cutting ant acromyrmex octospinosus (reich) (hymenoptera,formicidae: Attini)

The major ecdysteroids in large worker pupae of the leaf-cutting ant Acromyrmex octospinosus were characterized at the peak ecdysteroid concentration by using high-performance liquid chromatography, enzyme immunoassay, and mass spectrometry. In decreasing amounts, they were determined to be makisterone A, an unidentified C₂₈ ecdysteroid bearing a molecular weight of 494, 20-hydroxyecdysone (ratio of 1 to 6 as compared to makisterone A), and putative but negligible ecdysone. The presence of both C₂₈ and C₂₇ ecdysteroids is discussed in relation to the content of 4-desmethylsterols determined by gas chromatography and mass spectrometry to be ergosta-5,7,24 (28)-trien-3β-ol, ergosterol, ergosta-5,7-dien-3β-ol and ergosta-7,24(28)-dien-3β-ol for the main sterols, and with a small amount of cholesterol.