bluuebunny/crossref_metadata_2025 huggingface dataset:
G‐protein‐coupled receptor heteromers: function and ligand pharmacology
Authors: Franco R , Casadó V , Cortés A , Mallol J , Ciruela F , Ferré S , Lluis C , Canela E I
Published: November 2007

Almost all existing models for G‐protein‐coupled receptors (GPCRs) are based on the occurrence of monomers. Recent studies show that many GPCRs are dimers. Therefore for some receptors dimers and not monomers are the main species interacting with hormones/neurotransmitters/drugs. There are reasons for equivocal interpretations of the data fitting to receptor dimers assuming they are monomers. Fitting data using a dimer‐based model gives not only the equilibrium dissociation constants for high and low affinity binding to receptor dimers but also a ‘cooperativity index’ that reflects the molecular communication between monomers within the dimer. The dimer cooperativity index (DC) is a valuable tool that enables to interpret and quantify, for instance, the effect of allosteric regulators. For different receptors heteromerization confers a specific functional property for the receptor heteromer that can be considered as a ‘dimer fingerprint’. The occurrence of heteromers with different pharmacological and signalling properties opens a complete new field to search for novel drug targets useful to combat a variety of diseases and potentially with fewer side effects. Antagonists, which are quite common marketed drugs targeting GPCRs, display variable affinities when a given receptor is expressed with different heteromeric partners. This fact should be taken into account in the development of new drugs.

British Journal of Pharmacology (2008) 153, S90–S98; doi:10.1038/sj.bjp.0707571; published online 26 November 2007
Chlorthalidone inhibits the KvLQT1 potassium current in guinea‐pig ventricular myocytes and oocytes fromXenopus laevis
Authors: Mancilla‐Simbro C , López A , Martinez‐Morales E , Soto‐Perez‐de‐Celis E , Millan‐PerezPeña L , Tsushima R , Salinas‐Stefanon E M
Published: November 2007

Background and purpose:

Chlorthalidone is used for the treatment of hypertension as it produces a lengthening of the cardiac action potential. However, there is no experimental evidence that chlorthalidone has electrophysiological effects on the potassium currents involved in cardiac repolarization.

Experimental approach:

Ventricular myocytes and oocytes, transfected with human ionic channels that produceIK current, were exposed to different concentrations of chlorthalidone. Action potentials and potassium currents were recorded using a patch clamp technique. To determine which component of the current was affected by chlorthalidone, human channel proteins (hERG, minK and KvLQT1) were used.

Key results:

Chlorthalidone prolonged the ventricular action potential at 50 and 90% by 13 and 14%, respectively. The cardiac potassium currentsItoandIK1were not affected by chlorthalidone at any concentration, whereas the delayed rectifier potassium current,IK, was blocked in a dose‐response, voltage‐independent fashion. In our preparation, 100 μM chlorthalidone blocked the two components of the delayed rectifier potassium current with the same potency (50.1±5% forIKrand 54.6±6% forIKs) (n=7,P<0.05). The chlorthalidone‐sensitive current was slow and saturated at potentials greater than +30 mV. In our conditions only the KvLQT1 potassium current was affected by the drug, by 14%.

Conclusions and implications:

Chlorthalidone was demonstrated to have a direct effect on cardiac ventricular myocytes; it blocked the delayed rectifier potassium current (IK), specifically the KvLQT1 component of the potassium current. These results indicate that it has potential for use as an antiarrhythmic but further studies are needed.

British Journal of Pharmacology(2008)153, 448–458; doi:10.1038/sj.bjp.0707579; published online 26 November 2007
CB2receptors in the brain: role in central immune function
Authors: Cabral G A , Raborn E S , Griffin L , Dennis J , Marciano‐Cabral F
Published: November 2007

Recently, it has been recognized that the cannabinoid receptor CB2may play a functionally relevant role in the central nervous system (CNS). This role is mediated primarily through microglia, a resident population of cells in the CNS that is morphologically, phenotypically, and functionally related to macrophages. These cells also express the cannabinoid receptor CB1. The CB1receptor (CB1R) is constitutively expressed at low levels while the CB2receptor (CB2R) is expressed at higher levels and is modulated in relation to cell activation state. The relatively high levels of the CB2R correspond with microglia being in ‘responsive’ and ‘primed’ states, suggesting the existence of a ‘window’ of functional relevance during which activation of the CB2R modulates microglial activities. Signature activities of ‘responsive’ and ‘primed’ microglia are chemotaxis and antigen processing, respectively. The endocannabinoid 2‐arachidonylglycerol has been reported to stimulate a chemotactic response from these cells through the CB2R. In contrast, we have shownin vivoandin vitrothat the exogenous cannabinoids delta‐9‐tetrahydrocannabinol and CP55940 inhibit the chemotactic response of microglia toAcanthamoeba culbertsoni, an opportunistic pathogen that is the causative agent of Granulomatous Amoebic Encephalitis, through activation of the CB2R. It is postulated that these exogenous cannabinoids superimpose an inhibitory effect on pro‐chemotactic endocannabinoids that are elicited in response toAcanthamoeba. Furthermore, the collective results suggest that the CB2R plays a critical immune functional role in the CNS.

British Journal of Pharmacology(2008)153, 240–251; doi:10.1038/sj.bjp.0707584; published online 26 November 2007
Comparison of the induction profile for drug disposition proteins by typical nuclear receptor activators in human hepatic and intestinal cells
Authors: Martin P , Riley R , Back D J , Owen A
Published: November 2007

Background and purpose:

Certain nuclear receptors (NRs) such as the constitutive androstane receptor (CAR), pregnane X receptor (PXR) and farnesoid X receptor (FXR) mediate induction of some cytochrome P450 enzymes and ABC transporters but conflicting reports exist. The purpose of this study was to assess the reasons for these discrepancies and use a standardized approach to compare activators of NRs.

Experimental approach:

Dexamethasone, pregnenolone 16α‐carbonitrile, rifampicin, phenobarbital and chenodeoxycholic acid were incubated with HepG2, Caco‐2 and cryopreserved human hepatocytes prior to analysis of mRNA and protein for CYP2B6, CYP3A4, CYP3A5, ABCB1, ABCC1, ABCC2, PXR, CAR and FXR.

Key results:

Dexamethasone significantly up‐regulated PXR, CYP3A4 and ABCB1 expression in HepG2 and Caco‐2 cells. As a result, including dexamethasone as a media supplement masked the induction of these genes by pregnenolone 16α‐carbonitrile, which may explain discrepancies between previous reports. In the absence of dexamethasone, significant activator‐dependent induction was observed in all cell types. Significant correlations were observed between the fold increase in mRNA and in protein, which were, for most instances, logarithmic. Changes in mRNA expression were greater in cell lines than primary cells but for most transcripts correlations were observed between fold increases in HepG2 and hepatocytes.

Conclusions and implications:

Clearly, noin vitrosystem can imitate the physiology of a hepatocyte or intestinal cell within an intact organin vivo, but these data explain some of the discrepancies reported between laboratories and have important implications for study design.

British Journal of Pharmacology(2008)153, 805–819; doi:10.1038/sj.bjp.0707601; published online 26 November 2007
A site-renormalized molecular fluid theory
Authors: Dyer Kippi M. , Perkyns John S. , Pettitt B. Montgomery
Published: November 2007

The orientation-dependent pair distribution function for molecular fluids on site-site potentials is expanded in a topological analog of the diagrammatically proper site-site theory of liquids [D. Chandler et al., Mol. Phys. 46, 1335 (1982)]. The resulting functions are then used to diagrammatically renormalize the molecular fluid theory. A result is that the diagrammatically proper interaction site model theory is shown to be a linearized, minimal angular basis set approximation to this site-renormalized molecular theory. This framework is used to propose a new, exact, and proper closure to the diagrammatically proper interaction site model theory. The resulting equation system contains a bridge function expansion in the proper site-site theory. In addition, the construction of the theory is such that the molecular pair distribution function, in full dimensionality, is intrinsic to the theory. Furthermore, the theory is equivalent to the molecular Ornstein-Zernike treatment of site-site molecules in the basis set expansion of Blum and Torruella [J. Chem. Phys. 56, 303 (1971)]. A significant formal result of the theory is the demonstration that certain classes of diagrams which would otherwise be considered improper in the interaction site model formalism are included in the angular expansion of molecular interactions. Numerical results for several apolar homonuclear models and an apolar heteronuclear model are shown to quantitatively improve upon those of reference interaction site model and our recent proper variant with respect to simulation. Significant numerical results are that the various thermodynamic quantities obey the exact symmetries and sum rules within numerical error for the different sites in the heteronuclear case, even for the low order approximation used in this work, and the theory is independent of the so-called auxiliary site problem common to previous site-site theories.
1.58
μ
m
InGaAs quantum well laser on GaAs
Authors: Tångring I. , Ni H. Q. , Wu B. P. , Wu D. H. , Xiong Y. H. , Huang S. S. , Niu Z. C. , Wang S. M. , Lai Z. H. , Larsson A.
Published: November 2007

We demonstrate the 1.58μm emission at room temperature from a metamorphic In0.6Ga0.4As quantum well laser grown on GaAs by molecular beam epitaxy. The large lattice mismatch was accommodated through growth of a linearly graded buffer layer to create a high quality virtual In0.32Ga0.68As substrate. Careful growth optimization ensured good optical and structural qualities. For a 1250×50μm2 broad area laser, a minimum threshold current density of 490A∕cm2 was achieved under pulsed operation. This result indicates that metamorphic InGaAs quantum wells can be an alternative approach for 1.55μm GaAs-based lasers.
An efficient nonequilibrium Green’s function formalism combined with density functional theory approach for calculating electron transport properties of molecular devices with quasi-one-dimensional electrodes
Authors: Qian Zekan , Li Rui , Hou Shimin , Xue Zengquan , Sanvito Stefano
Published: November 2007

An efficient self-consistent approach combining the nonequilibrium Green’s function formalism with density functional theory is developed to calculate electron transport properties of molecular devices with quasi-one-dimensional (1D) electrodes. Two problems associated with the low dimensionality of the 1D electrodes, i.e., the nonequilibrium state and the uncertain boundary conditions for the electrostatic potential, are circumvented by introducing the reflectionless boundary conditions at the electrode-contact interfaces and the zero electric field boundary conditions at the electrode-molecule interfaces. Three prototypical systems, respectively, an ideal ballistic conductor, a high resistance tunnel junction, and a molecular device, are investigated to illustrate the accuracy and efficiency of our approach.
Circular dichroism of helical structures using semiempirical methods
Authors: Botek Edith , Champagne Benoît
Published: November 2007

A general semiempirical scheme has been elaborated to simulate circular dichroism (CD) spectra of supramolecular systems. This approach adopts the analytical method of Beck and Hohlneicher [Theor. Chem. Acc. 101, 297 (1999).] to evaluate the one- and two-center integrals over Slater atomic orbitals. The performance of the method, employing INDO/S and CNDO/S semiempirical parametrizations, has been assessed by considering (i) the effect of the size of the singly excited states manifold, (ii) the origin invariance, and (iii) comparisons with the experimental and other theoretical spectra of several helicenes as well as pyridine-pyrimidine oligomers, which can adopt helical conformations. The main results are (i) the INDO/S parametrization with rather small excitation manifolds is able to reproduce, at low computational costs, the experimental CD spectra of several helicenes as well as CD simulations performed at ab initio and time-dependent density functional theory level of approximation; (ii) in the series of homohelicenes, the rotatory strength of the lowest-energy band increases almost linearly with the size of the helix; (iii) as evidenced by the study of tetradodecyloxy helicene bisquinone, packing effects can change the sign of remarkable CD bands, which are used to assign the structure configuration.
Highly efficient red electrophosphorescence from a solution-processed zwitterionic cyclometalated iridium(III) complex
Authors: Byun Younghun , Lyu Yi-Yeol , Das Rupasree Ragini , Kwon Ohyun , Lee Tae-Woo , Park Young Ja
Published: November 2007

A mononuclear red-emitting zwitterionic iridium(III) complex, bis(1-(phenyl)isoquinolinato) iridium(III) (2,2′-bipyridine-3-ol-3′-olate), was synthesized and used as a triplet emitter doped in a polymeric host in solution-processed electrophosphorescent light-emitting diodes. We achieved a high luminous effieciency (LE) of 12.62cd∕A with fast response time in the device using the dopant unlike in the device using cationic irridium(III) phosphorescent materials. A hole transporting polymeric interlayer between the anode and the emitting layer improved the LE and decreased the exciton quenching at high electric fields.
Air stable hybrid organic-inorganic light emitting diodes using ZnO as the cathode
Authors: Bolink Henk J. , Coronado Eugenio , Repetto Diego , Sessolo Michele
Published: November 2007

An air stable hybrid organic-inorganic light emitting device is presented. This architecture makes use of metal oxides as charge injecting materials into the light emitting polymer, avoiding the use of air sensitive cathodes commonly employed in organic light emitting diode manufacturing. We report the application of zinc oxide as a cathode in an organic light emitting device. This electroluminescent device shows high brightness levels reaching 6500cd∕m2 at voltages as low as 8V. Compared to a conventional device using low workfunction metal cathodes, our device shows a lower turn-on voltage and it can operate in air.
Metastable behavior of the UV luminescence in Mg-doped GaN layers grown on quasibulk GaN templates
Authors: Pozina G. , Paskov P. P. , Bergman J. P. , Hemmingsson C. , Hultman L. , Monemar B. , Amano H. , Akasaki I. , Usui A.
Published: November 2007

Metastability of near band gap UV emissions in Mg-doped GaN layers grown by metal-organic vapor phase epitaxy on thick GaN templates grown by halide vapor phase epitaxy has been studied by cathodoluminescence (CL). The CL spectrum changes its initial shape within a few minutes under electron irradiation. The acceptor bound exciton line vanishes while the emissions related to the stacking faults (SFs) of different geometry rise significantly. The increase of the defect-related luminescence is likely caused by recombination enhanced SF formation under electron irradiation. The CL spectrum transformation is permanent at low temperatures; however, the metastable process is reversible if samples are heated to room temperature.
Efficient white-light-emitting diodes based on polyfluorene doped with fluorescent chromophores
Authors: Fan Suqin , Sun Mingliang , Wang Jian , Yang Wei , Cao Yong
Published: November 2007

Orange-red emitting small molecule chromorephores, 4,7-di-2-thienyl-2,1,3-benzothiadiazole, 4,7-(2′-diselenophenyl)-2,1,3-benzothiadiazole, and 4,7-bis(N-methylpyrrol-2-yl)-2,1,3-benzo-thiadiazole were synthesized and used for fabrication of fluorescent white-emitting device with polyfluorene (PFO) as host by solution processing. By careful controlling of dopant concentration, balanced narrow band-gap (NGB) electroluminescence (EL) emission can be obtained by solution processing due to the incomplete energy transfer from PFO to narrow band gap molecules. EL spectra of the obtained devices were very stable at a wide range of operating voltage. The best white-emitting device reached luminous efficiency of 7.54cd∕A with the CIE coordinates (0.33, 0.34) at luminance over 1000cd∕m2.
Preparation of TiO2(110)-(1×1) surface via UHV cleavage: An scanning tunneling microscopy study
Authors: Bondarchuk O. , Lyubinetsky I.
Published: November 2007

Ti O 2 ( 110 ) surface was successfully prepared in situ by UHV cleaving of a commercial TiO2 crystal. Scanning tunneling microscopy (STM) imaging revealed atomically flat more than 1μm wide terraces with (110) orientation separated by steps running in [001] direction, with very low kink density. Atomically resolved STM images show periodicity in the [001] and [11¯0] directions with the unit cell parameters measured to ∼3 and 6.5Å, respectively, which are closed to the expected values of bulk terminated (1×1) surface.
Observation of enhanced photoluminescence from silicon photonic crystal nanocavity at room temperature
Authors: Iwamoto Satoshi , Arakawa Yasuhiko , Gomyo Akiko
Published: November 2007

We fabricated air-bridge-type silicon photonic crystal (PC) nanocavities and observed significant enhancement of photoluminescence (PL) from crystalline silicon at room temperature. Cavity-resonant peaks shifted toward longer wavelengths when the period of PC was increased and their polarization dependences agree with the calculation. At a cavity mode wavelength, a 310-fold enhancement of PL intensity, compared with that of unpatterned silicon-on-insulator substrate, was demonstrated.
Tensile deformation accommodation in microscopic metallic glasses via subnanocluster reconstructions
Authors: Lekka Ch. E. , Ibenskas A. , Yavari A. R. , Evangelakis G. A.
Published: November 2007

We present results on the structure and the atomistic mechanisms for tensile deformation accommodation of the Cu46Zr54 microscopic metallic glass. At equilibrium, 23% of the atoms belong to tiny Cu-centered icosahedral clusters (Cu-ICO) and approximately 41% Zr centered slightly larger ICO-like clusters. Under deformation, the number of Cu-ICOs remains dynamically constant until yielding through a continuous cluster destruction-recreation process. Plastic deformation occurs homogeneously and is locally accommodated through the formation of rhombic dodecahedral clusters with significant (∼2%) atomic density drop. These findings explain very recent experimental results demonstrating the fundamental differences of plastic deformation mechanisms between bulk metallic and microscopic glasses.
Omnidirectional photonic band gap in polymer photonic crystal slabs
Authors: Wülbern Jan Hendrik , Schmidt Markus , Eich Manfred , Hübner Uwe , Boucher Richard , Marlow F. , Volksen W.
Published: November 2007

In this letter, we report on the experimental observation of a complete in-plane photonic band gap for transverse-electric-like polarized modes in a polymer photonic crystal slab with a triangular array of holes. We performed transmission measurements on two-dimensional photonic crystal slabs in both principal directions of the triangular lattice. For a propagation distance of 40 lattice constants, the transmission was effectively suppressed regardless of propagation direction below −15dB over a bandwidth of 65nm. The experimental results are in excellent agreement with theoretical predictions obtained from band diagram calculations and finite integration time domain techniques.
Nitride based laser diodes on substrates with patterned AlN mask
Authors: Sarzyński Marcin , Kryśko Marcin , Targowski Grzegorz , Kamler Grzegorz , Domagała Jarosław , Czernecki Robert , Libura Adam , Perlin Piotr , Leszczyński Michał
Published: November 2007

We report on electrical and optical properties of InGaN violet laser diodes, grown on high-pressure grown, almost dislocation free GaN substrates. In these structures, mechanical strain has been reduced by a partially relaxed AlN mask with stripe shaped windows. The dislocation density of the mask was 1010∕cm2. In the window areas, where we located the laser stripes, the dislocation density was below 3×106∕cm2. We fabricated three types of laser diodes with aluminum composition in the cladding of 8%, 13%, and 16%. All devices remained crack-free. The laser threshold current decreased with increasing Al composition in the cladding.
Hidden Struggles: Spaces of Power and Resistance in Informal Work in Urban Argentina
Authors: Whitson Risa
Published: November 2007

Drawing on ninety-three in-depth interviews conducted with informal workers in Buenos Aires in 2002, this paper examines how the everyday activity of informal work can be understood as a ‘hidden’ space of power and resistance in contemporary urban Argentina. Moving away from an economistic view of informal work, I argue that, while there is no single power relationship experienced by all informal workers, informal work more generally can be understood as a space in which multiple actors struggle over meaning and control through the deployment of diverse forms of power. The results presented here suggest that, while Argentines view informal work as a place of exploitation by employers and subjugation by the state, in some circumstances it can also be understood as a space of resistance, as workers attempt, through informal work, to create spaces hidden from control, to redefine the norms and rules which govern this space, and to transform the conditions of existence established by other actors. In focusing on the political function of informal work, this paper attempts to bring to light the complex relationships of power between the economy, the state, employers, and workers within the context of Argentina's economic and political crisis.
Responses of 'Pink Lady ' apple to deficit irrigation and partial rootzone drying: physiology, growth, yield, and fruit quality
Authors: O'Connell Mark G. , Goodwin Ian
Published: November 2007

Partial rootzone drying (PRD) is a new irrigation strategy whereby water is withheld from part of the rootzone while another part is well watered. A successful PRD strategy should reduce tree water use through stomatal control of transpiration and reduce vegetative growth while maintaining fruit size and yield. A field experiment examined crop water relations and production performance of PRD in a commercial apple orchard on loam soil in the Goulburn Valley, Australia. The orchard consisted of high-density (1420 trees/ha) 8-year-old ‘Pink Lady’ apple trees trained as central leader and irrigated by microjets. The effects of PRD on leaf/stem water potential, vegetative growth, yield components and fruit quality were investigated during two seasons (2001–02, Year 1 and 2002–03, Year 2). The 2-year average growing season reference crop evapotranspiration and rainfall was 954 and 168 mm, respectively. Three irrigation treatments were established: (1) deficit irrigation (DI, supplied 50% of water to a fixed side of tree); (2) PRD supplied 50% of water to alternating sides of tree; (3) and conventional irrigation (CI, supplied 100% water to both sides of tree). Irrigation inputs under the CI treatment were 334 and 529 mm for Year 1 and Year 2, respectively. In Year 1, the volume of irrigation applied to CI treatment inputs equated to the replacement of predicted crop evapotranspiration (ETc) based on a mid-season FAO-56 crop coefficient with adjustment for tree size. Vegetative growth, fruit production and water status showed both PRD and DI treatments led to a classical ‘deficit irrigation’ water stress response. Leaf water potential, leaf conductance, fruit size, shoot growth and yield were reduced on PRD and DI trees compared to the fully watered (CI) trees. In Year 2, CI inputs exceeded estimated ETc by 2-fold. Consequently, minimal or no differences between irrigation regimes were measured in stem water potential, vegetative growth, yield components and fruit quality. Fruit disorders (sunburn, russet, misshape, markings, frost damage) were not affected by irrigation regime in either season. We contend that further effort is required to determine under what circumstances or environments there is a PRD response that saves water and maintains yield and quality for apple.
An AMP nucleosidase gene knockout in
Escherichia coli
elevates intracellular ATP levels and increases cold tolerance
Authors: Morrison Brittany A , Shain Daniel H
Published: November 2007

Disparate psychrophiles (e.g. glacier ice worms, bacteria, algae and fungi) elevate steady-state intracellular ATP levels as temperatures decline, which has been interpreted as a compensatory mechanism to offset reductions in molecular motion and Gibb's free energy of ATP hydrolysis. In this study, we sought to manipulate steady-state ATP levels in the mesophilic bacterium,
Escherichia coli
, to investigate the relationship between cold temperature survivability and elevated intracellular ATP. Based on known energetic pathways and feedback loops, we targeted the AMP nucleotidase (
amn
) gene, which is thought to encode the primary AMP degradative enzyme in prokaryotes. By knocking out
amn
in wild-type
E. coli
DY330 cells using recombineering methodology, we generated a mutant (AMNk) that elevated intracellular ATP levels by more than 30% across its viable temperature range. As temperature was lowered, the relative ATP disparity between AMNk and DY330 cells increased to approximately 66% at 10°C, and was approximately 100% after storage at 0°C for 5–7 days. AMNk cells stored at 0°C for 7 days displayed approximately fivefold higher cell viability than wild-type DY330 cells treated in the same manner.
Ultrasonic signalling by a Bornean frog
Authors: Arch Victoria S , Grafe T. Ulmar , Narins Peter M
Published: November 2007

Among anuran amphibians, only two species,
Odorrana tormota
and
Huia cavitympanum
, are known to possess recessed tympanic membranes.
Odorrana tormota
is the first non-mammalian vertebrate demonstrated to communicate with ultrasonic frequencies (above 20 kHz), and the frogs' sunken tympana are hypothesized to play a key role in their high-frequency hearing sensitivity. Here we present the first data on the vocalizations of
H. cavitympanum
. We found that this species emits extraordinarily high-frequency calls, a portion of which are comprised entirely of ultrasound. This represents the first documentation of an anuran species producing purely ultrasonic signals. In addition, the vocal repertoire of
H. cavitympanum
is highly variable in frequency modulation pattern and spectral composition. The frogs' use of vocal signals with a wide range of dominant frequencies may be a strategy to maximize acoustic energy transmission to both nearby and distant receivers. The convergence of these species' call characteristics should stimulate additional, phylogenetically based studies of other lower vertebrates to provide new insight into the mechanistic and evolutionary foundations of high-frequency hearing in all vertebrate forms.
Population dynamics of defensive symbionts in aphids
Authors: Oliver Kerry M , Campos Jaime , Moran Nancy A , Hunter Martha S
Published: November 2007

Vertically transmitted micro-organisms can increase in frequency in host populations by providing net benefits to hosts. While laboratory studies have identified diverse beneficial effects conferred by inherited symbionts of insects, they have not explicitly examined the population dynamics of mutualist symbiont infection within populations. In the pea aphid,Acyrthosiphon pisum, the inherited facultative symbiont,Hamiltonella defensa, provides protection against parasitism by the wasp,Aphidius ervi. Despite a high fidelity of vertical transmission and direct benefits of infection accruing to parasitized aphids,Hamiltonellaremains only at intermediate frequencies in natural populations. Here, we conducted population cage experiments to monitor the dynamics ofHamiltonellaand of another commonA. pisumsymbiont,Serratia symbiotica, in the presence and absence of parasitism. We also conducted fitness assays ofHamiltonella-infected aphids to search for costs to infection in the absence of parasitism. In the population cages, we found that the frequency ofA. pisuminfected withHamiltonellaincreased dramatically after repeated exposure to parasitism byA. ervi, indicating that selection pressures from natural enemies can lead to the increase of particular inherited symbionts in insect populations. In our laboratory fitness assays, we did not detect a cost to infection withHamiltonella, but in the population cages not exposed to parasitism, we found a significant decline in the frequency of bothHamiltonellaandSerratia. The declining frequencies ofHamiltonella-infected aphids in population cages in the absence of parasitism indicate a probable cost to infection and may explain whyHamiltonellaremains at intermediate frequencies in natural populations.
Parental conflict in birds: comparative analyses of offspring development, ecology and mating opportunities
Authors: Olson V.A , Liker A , Freckleton R.P , Székely T
Published: November 2007

Parents often conflict over how much care to provide to their offspring. This conflict is expected to produce a negative relationship between male and female parental care, the strength of which may be mediated by both ecological and life-history variables. Previous studies have observed such trade-offs, but it is not known how generally they occur. Traditional views of sexual conflict place great importance on ecological factors in determining levels of parental care, whereas alternative views propose that the key determinant is mating opportunity. We carried out a broad-scale comparative study of parental conflict using 193 species from 41 families of birds. Using phylogenetic comparative analysis, we establish the generality of intersexual parental care conflict. We also show that parental conflict, as indicated by the disparity in care between the male and the female, depends on offspring development and mating opportunities, since in precocial species both males and females responded to increased mating opportunities. Altricial birds, however, failed to show these relationships. We also found little influence of breeding climate on parental conflict. Taken together, our results suggest that sexual conflict is a key element in the evolution of parental care systems. They also support the view that the major correlates of the intersexual conflict are mating opportunities for both sexes, rather than the breeding environment.
Construction of recombinant Lactobacillus casei efficiently surface displayed and secreted porcine parvovirus VP2 protein and comparison of the immune responses induced by oral immunization
Authors: Yigang X. U. , Yijing L. I.
Published: November 2007

Lactobacillus casei ATCC 393 was selected as a bacterial carrier for the development of mucosal vaccine against porcine parvovirus (PPV) infection. The PPV major structural polypeptide VP2 was used as the model parvovirus antigen. Two inducible expression systems, namely pPG611.1 of the cell‐surface expression system and pPG612.1 of the secretion expression system based on the xylose operon promoter were used to express the VP2 protein. The immunogenicity of recombinant strains producing VP2 protein in two cellular locations, cell‐surface exposed and secreted, was compared to each other by immunizing mice through the intragastric administration. The two types of constructs were able to induce strong specific immune responses against VP2 via intragastric administration and maximum titres of IgA and IgG were attained on days 46 post oral immunization, while the highest antibody levels were obtained with the strain producing the VP2 protein in extracellular milieu. The induced antibodies demonstrated neutralizing effects on PPV infection.
Changes in prey abundance unlikely to explain the demography of a critically endangered Central European bat
Authors: Bontadina Fabio , Schmied Sebastian F. , Beck Andres , Arlettaz Raphaël
Published: November 2007

Recognizing the factor(s) that caused a demographic crash is a prerequisite to the development of a tailored population restoration plan. While habitat destruction leaves little scope for population persistence, cryptic habitat deterioration (for example through reduction of food resources) may similarly render an area totally inhospitable, while it still appears to have a suitable habitat configuration.

Most European bat species have undergone dramatic declines over the past decades. Once among the most widespread and abundant bat species of Central Europe, the lesser horseshoe bat, Rhinolophus hipposideros (Bechstein 1800), is today extinct in many regions. Although changes in the agricultural landscape have been suggested as the major cause of decline, recent studies have shown that this bat forages almost exclusively in woodland, a habitat that has increased in area across continental Europe over the past decades. This suggests that habitat eradication per se is unlikely to be the main cause of decline. But could cryptic habitat deterioration play a harmful role?

We looked at the abundance of insect prey in woodland in the vicinity of colonial roosts with diverging demographic status (extinct, declining or recovering populations), both in the Swiss lowlands (Swiss Plateau) and in the Alps. We predicted that population size correlates positively with prey abundance.

Diet composition mirrored local insect prey abundance, confirming an opportunistic foraging strategy. Prey abundance showed marked seasonal variation, but did not differ between sites harbouring extinct, declining or recovering populations. There was also no difference in food abundance between extinct populations in the lowlands and recovering populations in the Alps.

Synthesis and applications. Cryptic habitat deterioration through a reduction in prey abundance is unlikely to preclude recolonization of abandoned areas by presently recovering populations. However, sufficient areas of natural forest should be preserved or created around potential nursery roosts. Moreover, connectivity between forest patches must be ensured (by creation of hedges and tree lines) to prevent any spatial gap in recolonization within semi‐open agricultural landscapes. Other threatened European forest bats may also benefit from these measures.
PROVIDER‐INITIATED HIV TESTING AND COUNSELING IN HEALTH FACILITIES – WHAT DOES THIS MEAN FOR THE HEALTH AND HUMAN RIGHTS OF PREGNANT WOMEN?
Authors: GRUSKIN SOFIA , AHMED SHAHIRA , FERGUSON LAURA
Published: November 2007

Since the introduction of drugs to prevent vertical transmission of HIV, the purpose of and approach to HIV testing of pregnant women has increasingly become an area of major controversy. In recent years, many strategies to increase the uptake of HIV testing have focused on offering HIV tests to women in pregnancy‐related services. New global guidance issued by the World Health Organization (WHO) and the Joint United Nations Programme on HIV/AIDS (UNAIDS) specifically notes these services as an entry point for provider‐initiated HIV testing and counseling (PITC). The guidance constitutes a useful first step towards a framework within which PITC sensitive to health, human rights and ethical concerns can be provided to pregnant women in health facilities. However, a number of issues will require further attention as implementation moves forward. It is incumbent on all those involved in the scale up of PITC to ensure that it promotes long‐term connection with relevant health services and does not result simply in increased testing with no concrete benefits being accrued by the women being tested. Within health services, this will require significant attention to informed consent, pre‐ and post‐test counseling, patient confidentiality, referrals and access to appropriate services, as well as reduction of stigma and discrimination. Beyond health services, efforts will be needed to address larger societal, legal, policy and contextual issues.

The health and human rights of pregnant women must be a primary consideration in how HIV testing is implemented; they can benefit greatly from PITC but only if it is carried out appropriately.
Some taxonomic implications of pollen and seed morphology in Mimulus hymenophyllus and M. jungermannioides and comparisons with other putative members of the M. moschatus alliance (Scrophulariaceae)
Authors: Argue Charles L.
Published: November 2007

Statistically significant differences in pollen and seed size confirm the distinctness of Mimulus hymenophyllus and M. jungermannioides and distinguish M. hymenophyllus from all other members of the M. moschatus alliance. Published descriptions of morphological differences in the seeds of M. jungermannioides, M. patulus, and M. washingtonensis are not confirmed. The pollen evidence is consistent with a segregation of M. moniliformis from M. moschatus but fails to support a previously reported difference in exine sculpturing between M. moschatus and M. inodorus. Other taxonomic implications of the pollen data are discussed. Expanded study on aperture morphology in Mimulus pollen has revealed that some species of the M. moschatus alliance and other species of section Paradanthus have predominantly unruptured colpus membranes, and the description of the pollen of this section is emended to include this aperture type.
The taxonomy of Arnica frigida and A. louiseana (Asteraceae)
Authors: Downie Stephen R. , Denford Keith E.
Published: November 2007

The systematic relationships of the Arnica frigida–louiseana complex have been evaluated. This complex has been previously recognized as one species. A. louiseana, with three infraspecific taxa: subspecies frigida, griscomii, and louiseana. Morphological, phytogeographical, and cytological data support the recognition of A. frigida ssp. frigida and the newly proposed combination A. frigida spp. griscomii. Arnica louiseana is also recognized at the specific level. All three taxa have distinct geographic distributions: A. frigida spp. frigida is found from eastern USSR, Alaska, Yukon, east to the Mackenzie River, N.W.T., with isolated populations east of the Mackenzie River and in northern British Columbia; A. frigida ssp. griscomii is extremely localized in Gaspé, Qué., and in northwest Newfoundland; and A. louiseana is restricted to high elevations in the Rocky Mountains of Alberta. The basic chromosome number for this complex is x = 19, with A. frigida ssp. frigida 2n = 38, 57, 76, and 95, A. frigida ssp. griscomii 2n = 76, and A. louiseana with chromosome complements of 2n = 76 and 95. This complex is predominantly apomictic with amphimictic phases in unglaciated Alaska. Disjunct distributions are probably the result of Pleistocene survival in refugia with apomictic phases being responsible for the recolonization of glaciated areas.
Natural poplar hybrids from southern Alberta. I. Continuous variation for foliar characteristics
Authors: Rood Stewart B. , Campbell John S. , Despins Therese
Published: November 2007

Shoot cuttings were collected from 56 poplars naturally occurring in riparian sites in southern Alberta and southeastern British Columbia and rooted in a greenhouse. Subsequently, the clones were established in a nursery plot at Lethbridge, Alta., and after two growing seasons, fully expanded late leaves from long shoots were collected. Leaf blade lengths, maximum blade widths, petiole lengths, distance from the petiole to the position of maximum width, tip angle from the midrib, margin teeth number, teeth depth, and leaf areas were measured. Petiole length, blade width, teeth number, and blade length were the most heavily weighted factors in a principal-components analysis of these leaf data. No clear disjunction was apparent from the principal-components analysis, which grouped Populus deltoides, P. balsamifera, and P. angustifolia leaf types in different regions of a two-dimensional plot. Continuous variation was observed for the hybrid leaf forms that were intermediate between the parental forms. This continuous variation for Populus leaf form indicates that the three species interbreed freely in southern Alberta, producing a single, dissectional, trispecific, hybrid swarm.
Isolation of Fomitopsis pinicola from in-flight bark beetles (Coleoptera: Scolytidae)
Authors: Pettey Thomas M. , Shaw Charles Gardner
Published: November 2007

Isolations of Hymenomycetes on a preferential medium were attempted from preflight pine engraver beetles, Ips pini, and the following in-flight bark beetles: pine engraver beetle, I. pini; western pine beetle, Dendroctonus brevicomis; mountain pine beetle, Dendroctonus ponderosae; and red turpentine beetle, Dendroctonus valens. Thirty pine engraver beetles removed from ponderosa pine slash (preflight) yielded no hymenomycete. However, Hymenomycetes were isolated from 50 of 114 beetles (all species) trapped in flight; Fomitopsis pinicola from 44, and other unidentified suspected Hymenomycetes, from 6. Cryptoporus volvatus was not isolated from any of the in-flight beetles. Since most of these isolates were without clamps (monokaryotic), the beetles may acquire basidiospores after emergence from beetle galleries in coniferous trees as hypothesized previously for the Douglas-fir beetle, Dendroctonus pseudotsugae. The isolation of F. pinicola from all species of in-flight bark beetles indicates that these beetles may be important in the dissemination of this hymenomycete.
Monoterpene emissions and cuticular lipids of loblolly and slash pines: potential bases for oviposition preference of the Nantucket pine tip moth
Authors: Ross Darrell W. , Birgersson Göran , Espelie Karl E. , Berisford C. Wayne
Published: November 2007

Monoterpene emissions from intact 5- to 29-month-old loblolly and slash pine seedlings contained α-pinene, camphene, β-pinene, myrcene, sabinene, β-phellandrene, and limonene. α-Pinene made up > 50% of the volatiles from both species. β-Pinene was significantly more abundant in slash (35.6%) than in loblolly pine (15.3%), while myrcene was significantly more abundant in loblolly (10.9%) than in slash pine (3.4%). Cuticular lipids represented 0.11 and 0.06% of the dry weight biomass of shoots from loblolly and slash pines, respectively. Species differences in cuticular lipid composition were primarily in relative proportions of a group of unidentified compounds that appear to be saturated and unsaturated diols and (or) hydroxy alcohols with chain lengths of about 18 carbons. 10-Nonacosanol made up 16.2 and 14.1% of the total lipids recovered from loblolly and slash pines, respectively. The Nantucket pine tip moth, Rhyacionia frustrana (Comstock), may use these chemical differences to distinguish the susceptible loblolly pines from the resistant slash pines. Key words: Pinus taeda, Pinus elliottii, monoterpene emissions, cuticular lipids, Rhyacionia frustrana.
Synopsis of the genusPeltigera(lichenized Ascomycetes) in British Columbia, with a key to the North American species
Authors: Goward Trevor , Goffinet Bernard , Vitikainen Orvo
Published: November 2007

Based on extensive field studies, herbarium research and thin layer chromatography, the taxonomy, distribution and ecology of 28 species of Peltigera occurring in British Columbia are discussed. Distribution maps are presented for selected species, and a key to the North American taxa is provided. Peltigera cinnamomea Goward is described as new, and the blue-green phototype of Peltigera leucophlebia (Nyl.) Gyelnik is documented for the first time. Peltigera scabrosella Holt.-Hartw. is reported as new for North America based on a collection from the Yukon Territory. Peltigera hymenina is new for British Columbia. Key words: lichens, Ascomycotina, Peltigera, Peltigeraceae, British Columbia, distribution.
Le genre Gomphoneis (Bacillariophyta) : un nouveau modèle d'organisation du cingulum
Authors: Cohu R. Le , Coste M.
Published: November 2007

The valvar structure and the cingulum arrangement of a diatom related to the Gomphoneis herculeana – Gomphoneis minuta complex were investigated in electron and light microscopy. Ultrastructural features include striae composed of double rows of areolae, apical pore fields composed of pores structurally differentiated from the areolae and the presence of an axial siliceous plate responsible for longitudinal lines visible in light microscopy. The pars interior of the valvocopula looks like a marginal lamina of silica. A new model of organization for the cingulum, quite different from the classical model, is proposed. The valvocopula is a closed band with a connective septum at both the head and the footpole. The copulae, each of them with a connective septum, are open bands, with their openings at opposite poles. All septa possess on the advalvar face a projecting lamina that fits under the pseudosepta of the valve or the septum of a girdle band. The first two copulae are directly connected with the opposite septa of the valvocopula. The third copula is attached to the first copula and the fourth to the second. Key words: Bacillariophyta, Gomphoneis, valve, model, cingulum.
Biomass and nutrient distribution in aspen, pine, and spruce stands on the same soil type in Minnesota
Authors: Alban David H. , Perala Donald A. , Schlaegel Bryce E.
Published: November 2007

Vegetation and soils were sampled in adjacent 40-year-old stands of red pine (Pinusresinosa Ait.), jack pine (Pinusbanksiana Lamb.), white spruce (Piceaglauca (Moench.) Voss), and aspen (Populustremuloides Michx., P. grandidentata Michx.) on a very fine sandy loam soil in north-central Minnesota. Total tree biomass was greatest for red pine followed by aspen, spruce, and jack pine. Nutrient weights (N, P, K, Ca, Mg) in the trees were greatest in aspen followed generally by spruce, red pine, and jack pine. Particularly large proportions of biomass and nutrients were found in aspen bark and spruce foliage and branches. Understory biomass contributed less than 1.2% of the total organic matter in the vegetation–soil complex but contributed up to 5.0% of the nutrients. Exchangeable Ca in the surface soil was much lower under aspen and spruce than under the pines. No significant soil differences between species were detected below 36 cm. Harvesting the entire aboveground portion of the tree would remove up to three times more nutrients from the site than would harvesting only the bole.
Changes in carbon content, respiration rate, ATP content, and microbial biomass in nitrogen-fertilized pine forest soils in Sweden
Authors: Nohrstedt H.-Ö. , Arnebrant K. , Bååth E. , Söderström B.
Published: November 2007

Carbon content and indices of microbial biomass and activity were determined in 1985 in different soil horizons of two nitrogen-fertilized pine forests in Sweden. The Kroksbo site was fertilized in 1974 with 150 and 600 kg N•ha−1 using NH4NO3 or urea, while the Nissafors site was fertilized in 1977 and 1984 with 150 kg NH4NO3-N•ha−1 The absolute amount of C per square metre of forest floor increased in fertilizer treatments compared with the control (by 10–26%, depending on the site or fertilizer treatment). Respiration rate, ATP content, and microbial biomass C, measured with the substrate-induced respiration technique, decreased in all horizons when expressed per gram of C. The decrease was most evident with NH4NO3, and at the highest level of fertilization. However, on an area basis there were no differences between fertilizer and control treatments. A calculated increase in litter fall in the fertilized plots could not explain all the increase in the amount of C per square metre compared with the control. Decreased microbial activity per gram of C therefore appeared to be an important factor in the increase in C content in fertilized plots.