New derivatives from the aerial parts of Boerhaavia diffusa L. (Nyctaginaceae)

Boerhaavia diffusa L. is used in the traditional medicine of several Asian countries. The isolation and identification of five new compounds, together with 11 known compounds, from the ethyl acetate extract of the aerial part of B. diffusa grown Vietnam is reported. The structure of the new compounds was established by 1D and 2D NMR spectroscopy, and high resolution ESI-MS analysis. New compounds are two rotenoids: 9,11-dihydroxy-6,10-dimethoxy[1]benzopyrano[3,4-b][1]benzopyran-12(6H)-one (boeravinone P, 3) and 3-[2-(β-d-glucopyranosyloxy)-3-hydroxyphenyl]-5-hydroxy-2-hydroxymethyl-7-methoxy-6-methyl-4H-1-benzopyran-4-one (boeravinone Q, 9), an atropisomeric mixture of two rotenoid glycosides (3′,5-dihydroxy-2-hydroxymethyl-7-methoxy-6-methylisoflavone 2′-O-β-d-glucopyranoside, 11), a sesquiterpene lactone (4,10-dihydroxy-8-methoxyguai-7(11)-en-8,12-olide, 5) and a new phenylpropanoid glycoside (boerhaavic acid, 15).     

Invasion of the gall mite Aceria genistae (Acari: Eriophyidae), a natural enemy of the invasive weed Cytisus scoparius,into California,U.S.A. and predictions for climate suitability in other regions using ecological niche modelling

Scotch broom (Cytisus scoparius (L.) Link) is a European shrub that has naturalised in several countries worldwide and is recognised as an invasive weed in much of western North America. The mite Aceria genistae (Nalepa) is a coevolved, gall-inducing herbivore associated with Scotch broom in its native range and has been intentionally introduced as a classical weed biological control agent of C. scoparius in Australia and New Zealand. An adventive, never intentionally introduced, population of A. genistae was discovered in Washington and Oregon, U.S.A. in 2005. Surveys for A. genistae in California resulted in the discovery of the gall mite in 11 counties, with a widely scattered distribution. Molecular and morphological assessments confirm the mites collected from galls in California are A. genistae. Whether natural or anthropogenic, the estimated rate of long range dispersal for A. genistae from Washington or Oregon to California ranges from 39 to 62?km/yr. Niche model predictions indicate that A. genistae will continue to expand its distribution throughout much of the Scotch broom-invaded lands of California but areas supporting the weed in the Eastern U.S.A. appear less suitable. Modelling evidence also indicates that portions of Chile and Argentina are suitable for colonisation by A. genistae, also suggesting that expansion of the mite is possible in areas of Tasmania, southeastern Australia, and New Zealand where the mite was released. The environmental safety of A. genistae in relation to non-target plants and the influence of herbivory on Scotch broom fitness are discussed.     

Reactions of peptidoglycan-mimetic beta-lactams with penicillin-binding proteins in vivo and in membranes.

The membrane-bound bacterial D-alanyl- D-alanine peptidases or penicillin-binding proteins (PBPs) catalyze the final transpeptidation reaction of bacterial cell wall biosynthesis and are the targets of beta-lactam antibiotics. Rather surprisingly, the substrate specificity of these enzymes is not well understood. In this paper, we present measurements of the reactivity of typical examples of these enzymes with peptidoglycan-mimetic beta-lactams under in vivo conditions. The minimum inhibitory concentrations of beta-lactams with Escherichia coli-specific side chains were determined against E. coli cells. Analogous measurements were made with Streptococcus pneumoniae R6. The reactivity of the relevant beta-lactams with E. coli PBPs in membrane preparations was also determined. The results show that under none of the above protocols were beta-lactams with peptidoglycan-mimetic side chains more reactive than generic analogues. This suggests that in vivo, as in vitro, these enzymes do not specifically recognize elements of peptidoglycan structure local to the reaction center. Substrate recognition must thus involve extended structure.     

Direct comparison of four methods to construct xylem vulnerability curves: Differences among techniques are linked to vessel network characteristics

During periods of dehydration, water transport through xylem conduits can become blocked by embolism formation. Xylem embolism compromises water supply to leaves and may lead to losses in productivity or plant death. Vulnerability curves (VCs) characterize plant losses in conductivity as xylem pressures decrease. VCs are widely used to characterize and predict plant water use at different levels of water availability. Several methodologies for constructing VCs exist and sometimes produce different results for the same plant material. We directly compared four VC construction methods on stems of black cottonwood (Populus trichocarpa), a model tree species: dehydration, centrifuge, X‐ray–computed microtomography (microCT), and optical. MicroCT VC was the most resistant, dehydration and centrifuge VCs were intermediate, and optical VC was the most vulnerable. Differences among VCs were not associated with how cavitation was induced but were related to how losses in conductivity were evaluated: measured hydraulically (dehydration and centrifuge) versus evaluated from visual information (microCT and optical). Understanding how and why methods differ in estimating vulnerability to xylem embolism is important for advancing knowledge in plant ecophysiology, interpreting literature data, and using accurate VCs in water flux models for predicting plant responses to drought.     

What constitutes fair shared decision-making in global health research collaborations?

Funders (located primarily in high-income countries) and high-income country researchers have historically dominated decision-making within global health research collaborations: from setting agendas and research design to determining how data are collected and analysed and what happens with findings and outputs. The ethical principle of shared decision-making has been proposed as a way to help address these imbalances within collaborations and to reduce semicolonial and exploitative forms of global health research. It is important to be clear about what shared decision-making means in order to ensure that it is not done in a tokenistic, shallow way. Thus far, the principle’s content has not been examined and articulated in detail. This paper aims to start the process of delineating a concept of fair shared decision-making as a minimum standard for global health research. Using two hypothetical case examples, the paper will demonstrate that global health research practice is often inconsistent with ideal shared decision-making. In such instances, it can be difficult to decide whether shared decision-making within collaborations is fair. The paper describes how the two cases do not meet criteria for unfair or non-ideal shared decision-making, despite having potentially morally troubling features. The nuances of these examples of research practice help to generate clearer ideas about how to judge fairness in shared decision-making. The paper concludes by presenting ideas about when soft power can be fairly employed between high-income-country and low- and middle-income-country partners and what fair compromise agreements may look like in shared decision-making.     

Properties of the cysteine-less Pho84 phosphate transporter of Saccharomyces cerevisiae

The murine 3T3-L1 preadipocyte cell line is well characterized for its capacity to undergo differentiation into adipocytes under appropriate hormonal stimulation. p107, a member of the retinoblastoma tumor suppressor gene family has been shown to be dramatically upregulated during the early requisite clonal expansion phase of 3T3-L1 adipogenesis; however, a functional consequence has yet to be described. A phosphorothioate antisense RNA approach was utilized to determine if inhibition of p107 expression would block or perturb adipocyte differentiation. A series of three phosphorothioate oligonucleotides in antisense orientation was generated, designated AS1, AS2, and AS3 along with a sense control oligonucleotide complementary to AS1 and added to postconfluent cells at a concentration of 20 and 50 microM throughout hormonally stimulated differentiation. Treatment of cells with either concentration of the sense, AS1, AS2, or 20 microM AS3 oligonucleotides had little effect on either Oil Red O lipid accumulation or induction of p107 protein levels. In contrast, treatment with 50 microM AS3 inhibited the increase in p107 protein levels and led to a complete block in differentiation as detected by Oil Red O lipid accumulation and inhibition of adipocyte-specific mRNA expression. In addition, treatment with AS3 led to a significant inhibition of cellular proliferation associated with clonal expansion. Combined, these results provide strong evidence supporting a functional role for p107 in 3T3-L1 adipocyte differentiation.     

Amino acids in the cytoplasmic C terminus of the parathyroid Ca2+-sensing receptor mediate efficient cell-surface expression and phospholipase C activation

The C-terminal tail of the calcium receptor (CaR) regulates the affinity of the receptor for ligand, desensitization, and membrane localization. To determine the role of specific amino acids in the bovine parathyroid CaR in mediating signal transduction and cell-surface expression, we transfected truncated and mutated CaR cDNAs into HEK-293 cells. The ability of high extracellular [Ca(2+)] ([Ca(2+)](o)) to increase total inositol phosphate (InsP) production, an index of phospholipase C (PLC) activation, was determined. Receptor expression was assessed by immunoblotting and immunocytochemistry. In cells transiently or stably expressing receptors with the C-terminal tail truncated after residue 895 (CaR-(1-895)) or 929 (CaR-(1-929)), raising [Ca(2+)](o) increased InsPs to levels comparable with those of cells expressing wild-type CaRs. There were no PLC responses to high [Ca(2+)](o) (up to 30 mm) in cells expressing CaRs with C-terminal tails of only 3 residues (CaR-(1-866)), even though these receptors were expressed in the membrane. We scanned the residues between Ser(866) and Val(895) using tandem-Ala and single-site mutagenesis. Two point mutants (His(880) --> Ala and Phe(882) --> Ala CaR) showed 50-70% reductions in high [Ca(2+)](o)-induced InsP production. The levels of expression and glycosylation of these mutants were comparable with wild-type CaRs, but both receptors were profoundly retained in intracellular organelles and co-localized with the endoplasmic reticulum marker BiP. This suggested that the signaling defects of these receptors were likely because of defective trafficking of receptors to the cell surface. Modeling of the C-terminal domain of the CaR indicated that His(880) and Phe(882) are situated in a putative alpha-helical structure of 15 amino acids between residues 877 and 891 in the C-terminal tail. Our studies support the idea that specific amino acids, and possibly a unique secondary structure in the C-terminal tail, are required for the efficient targeting of the CaR to the cell surface required for PLC activation.     

Evaluation of an in vitro coculture model for the blood-brain barrier: Comparison of human umbilical vein endothelial cells (ECV304) and rat glioma cells (C6) from two commercial sources

Summary Cocultures of human umbilical vein endothelial cells (ECV304) and rat glioma cells (C6) from two commercial sources, American Type Culture Collection and European Collection of Animal Cell Cultures, were evaluated as an in vitro model for the blood-brain barrier. Monolayers of endothelial cells grown in the presence or absence of glial cells were examined for transendothelial electrical resistance, sucrose permeability, morphology, multidrug resistance-associated protein expression, and P-glycoprotein expression and function. Coculture of glial cells with endothelial cells increased electrical resistance and decreased sucrose permeability across European endothelial cell monolayers, but had no effect on American endothelial cells. Coculture of European glial cells with endothelial cells caused cell flattening and decreased cell stacking with both European and American endothelial cells. No P-glycoprotein or multidrug resistance-associated protein was immunodetected in endothelial cells grown in glial cell-conditioned medium. Functional P-glycoprotein was demonstrated in American endothelial cells selected in vinblastine-containing medium over eight passages, but these cells did not form a tight endothelium. In conclusion, while European glial cells confer blood-brain barrier-like morphology and barrier integrity to European endothelial cells in coculture, the European endothelial-glial cell coculture model does not express P-glycoprotein, normally found at the blood-brain barrier. Further, the response of endothelial cells to glial factors was dependent on cell source, implying heterogeneity among cell populations. On the basis of these observations, the umbilical vein endothelial cell-glial cell coculture model does not appear to be a viable model for predicting blood-brain barrier penetration of drug molecules.