bluuebunny/crossref_metadata_2025 huggingface dataset:
Transition between energy level alignment regimes at a low band gap polymer-electrode interfaces
Authors: Crispin Annica , Crispin Xavier , Fahlman Mats , Berggren Magnus , Salaneck William R.
Published: November 2006

The energy level alignment at interfaces between a low band gap conjugated polymer and various electrodes is investigated using ultraviolet photoemission spectroscopy. When the electrode work function is lower (higher) than the negative (positive) polaronic level of the polymer, the Fermi level is pinned to the negative (positive) polaronic level. These Fermi level pinning regimes suggest a spontaneous electron transfer from or towards the electrode resulting in an interfacial dipole of different orientation. On the contrary, when the substrate work function is intermediate, there is no charge transfer and the energy level alignment across the interface follows the Schottky-Mott limit.
Light-harvesting antennae for polymer solar cells
Authors: Doust Alexander B. , Yang Xiujuan , Dykstra Tieneke E. , Koo Kevin , Scholes Gregory D.
Published: November 2006

The authors demonstrate the incorporation of an artificial, extrinsic antenna into organic, conjugated polymer layers. This can lead to the independent optimization of spectral and spatial cross section for light absorption in organic solar devices. They report studies of three antenna layers, anthracene, 9,10-dichloroanthracene, and 9,10-diphenylanthracene, that are spin coated onto a poly[2-methoxy,5-(2methyl hexoxy)-1,4-phenylenevinylene] thin film.
Efficient flexible and thermally stable pentacene/C60 small molecule based organic solar cells
Authors: Pandey Ajay K. , Nunzi Jean-Michel
Published: November 2006

Flexible thin film solar cells based on a pentacene/C60 heterojunction on indium tin oxide coated polyethylene terephthalate (PET) substrates are described. Devices grown on PET are compared to those on glass substrates. The nature of the organic grains grown on PET and glass substrates is shown to have a significant impact on the device short circuit current. Device performance under mechanical strain and elevated temperature is reported. Devices deliver an 8.8mAcm−2 short circuit current density with a 1.6% power conversion efficiency under an AM1.5 simulated solar intensity of 80mWcm−2. The relatively low 300mV open circuit voltage appears to limit device efficiency.
Annealing effect on GaAs droplet templates in formation of self-assembled InAs quantum dots
Authors: Liang B. L. , Wang Zh. M. , Lee J. H. , Sablon K. A. , Mazur Yu. I. , Salamo G. J.
Published: November 2006

The authors report on the use of GaAs islands, formed by the droplet epitaxy growth technique, as a template for the growth of clusters of InAs quantum dots. Surface morphology measurements show that the shape and dimensions of the GaAs islands and consequently the formation of InAs quantum dots depend strongly on the annealing temperature and annealing time. This can be explained by the diffusion of gallium atom during the annealing process and the selective formation of InAs quantum dots on the misoriented GaAs island sidewalls.
Na Ta O 3 photocatalysts of different crystalline structures for water splitting into H2 and O2
Authors: Lin Wan-Hsien , Cheng Ching , Hu Che-Chia , Teng Hsisheng
Published: November 2006

Perovskite-type NaTaO3 derived from a sol-gel synthesis exhibited a larger surface area and a remarkably higher photocatalytic activity in water splitting than the solid-state synthesized NaTaO3. The sol-gel and solid-state NaTaO3 had different crystalline structures of monoclinic P2∕m and orthorhombic Pcmn, respectively. Diffuse reflectance spectra showed that the sol-gel specimen had a slightly larger band gap. The band structure analysis revealed an indirect band gap for the sol-gel NaTaO3, contrary to the direct band gap of the solid-state one. The difference in the electronic structure and surface area explained the higher photocatalytic activity of the sol-gel NaTaO3.
White polymeric light-emitting diodes with high color rendering index
Authors: Niu Xiaodi , Ma Liang , Yao Bing , Ding Junqiao , Tu Guoli , Xie Zhiyuan , Wang Lixiang
Published: November 2006

The efficient white polymeric light-emitting diodes based on a white emissive polymer doped with a red phosphorescent dopant were fabricated by spin-coating method. The emission spectrum of the device is broadened to cover the full visible region by doping the red phosphorescent dye and thereby realizes white emission with high color-rendering index (CRI). By controlling the contents of the doped electron-transporting 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole and the red phosphorescent dopant, a luminous efficiency as high as 5.3cd∕A and a power efficiency of 3lm∕W were obtained with a CRI of 92.
The role of seed in the determination of yield of grain crops
Authors: Egli D. B.
Published: November 2006

The seed is the harvested organ in grain crops and, consequently, the accumulation of dry matter by the seed is an important component of the yield production process. The growth of individual seeds, usually characterised by the rate and duration of growth, is, at least partially, controlled by the seed itself. It is this control that gives the seed a significant role in the yield production process. Genetic variation in seed growth rate, which is substantial, is not related to yield, but variation related to environmental conditions during seed filling often is. Genetic and environmental variation in seed-fill duration is usually directly related to yield. Much is now known about the regulation of seed growth and this knowledge, if applied, may help answer some of the important questions still facing crop scientists as they try to increase yields in the future.
Preliminary evaluation of diverse lucerne (Medicago sativa sspp.) germplasm to identify new material for livestock and cropping based farming systems in Australia
Authors: Humphries A. W. , Hughes S. J.
Published: November 2006

A preliminary evaluation protocol is described of Medicago sativa that enables a diverse range of germplasm from different winter-activity groups to be evaluated in the same experiment. The protocol was used to compare the seasonal growth patterns of very winter-dormant M. sativa sspp. falcata and caerulea accessions with highly winter-active M. sativa ssp. sativa accessions. Herbage production was strongly related to winter activity in the cumulative first year of growth and in second-year winter months, but completely unrelated in 3 cuts in the following spring. The vertical measurement of plant height was confirmed to be a good indicator of herbage production in winter, but neither stem height nor length were good indicators of spring production.
The preliminary evaluation protocol identified highly winter-active class 10–11 germplasm with high winter production and excellent recovery after cutting, and accessions of M. sativa sspp. caerulea and falcata (winter activity class 1) with excellent spring and summer production. These wild relatives of lucerne have great potential to increase the area of cultivated M. sativa in Australia, largely as a component in pasture mixtures. They also offer improved quality traits over winter-active Lucerne, including a higher leaf to stem ratio, and a lower stem thickness and internode length.
Gas-liquid critical properties of the cycloalkanes and their mixtures
Authors: Young CL
Published: November 2006

Gas-liquid critical
temperatures of the C5-C8 cycloalkane
mixtures and the vapour pressure and densities of cycloheptane
and cyclooctane near the critical region are
presented. Deviations of the reduced
vapour pressure and density of the cycloalkanes from
those of the inert gases have been calculated. The deviations have been found
to be similar for all four cycloalkanes. The critical temperatures
of the mixtures have been discussed in terms of the van der
Waals "one fluid" mixture theory.
Complexes of copper(II) hexanoate with t-butyl hydroperoxide and other ligands
Authors: Burchill PJ
Published: November 2006

The reaction of t-butyl
hydroperoxide with copper(11) hexanoate
in carbontetrachloride solution has been studied by electronic absorption
spectroscopy. An equilibrium system has been proposed which involves
substitution of hexanoate anions coordinated to copper by peroxy anions. In
addition the equilibria between copper(11) hexanoate and the ligands pyridine,
aniline, hexanoic acid, and ethylacetoacetate have been studied.
Equilibria between pyranoses and furanoses. II. Aldoses
Authors: Angyal SJ , Pickles VA
Published: November 2006

The proton magnetic resonance spectra of the aldopentoses and aldohexoses
were determined in deuterium oxide solution. The signals of the anomerio protons
of the two furanose and the two pyranose forms were located; the identification
of these signals is discussed. The proportions of the four forms in equilibrium
solution were determined.
Ligation of the cell surface receptor, CD46, alters T cell polarity and response to antigen presentation
Authors: Oliaro Jane , Pasam Anupama , Waterhouse Nigel J. , Browne Kylie A. , Ludford-Menting Mandy J. , Trapani Joseph A. , Russell Sarah M.
Published: November 2006

Lymphocyte function
in vivo
is dictated by multiple external cues, but the integration of different signals is not well understood. Here, we show that competition for the axis of polarization dictates functional outcomes. We investigated the effect of ligation of the immunoregulatory cell surface receptor, CD46, on lymphocyte polarity during antigen presentation and cytotoxic effector function. Ligation of CD46 on human T cells prevented recruitment of the microtubule organizing center, CD3, and perforin to the interface with the antigen-presenting cell and caused a reduction in IFN-γ production. In human NK cells, similar changes in polarity induced by CD46 ligation inhibited the recruitment of the microtubule organizing center and perforin to the interface with target cells and correlated with reduced killing. These data indicate that external signals can alter lymphocyte polarization toward antigen-presenting cells or target cells, inhibiting lymphocyte function.
Two isoforms of tissue transglutaminase mediate opposing cellular fates
Authors: Antonyak Marc A. , Jansen Jaclyn M. , Miller Allison M. , Ly Thi K. , Endo Makoto , Cerione Richard A.
Published: November 2006

Opposing cellular responses are typically regulated by distinct sets of genes. However, tissue transglutaminase (TGase) provides an interesting example of a single gene product that has been implicated both in affording protection against cellular insults as well as in promoting cell death. Here, we shed some light on how these conflicting activities might be manifested by demonstrating that alternative transcripts of TGase differentially affect cell viability. We show that although the full-length TGase protein affords strong protection against cell death signals, a shorter version of TGase that is truncated at the 3′ end, and thus called TGase-short (TGase-S), is cytotoxic. The apoptotic activity of TGase-S is not dependent on its transamidation activity because the mutation of a cysteine residue that is essential for catalyzing this reaction does not compromise the ability of TGase-S to induce cell death. Intriguingly, TGase-S undergoes inappropriate oligomer formation in cells before cell death, suggesting a novel mechanism for the apoptotic effects of this protein.
Phosphorylation and cleavage of presenilin-associated rhomboid-like protein (PARL) promotes changes in mitochondrial morphology
Authors: Jeyaraju Danny V. , Xu Liqun , Letellier Marie-Claude , Bandaru Sirisha , Zunino Rodolfo , Berg Eric A. , McBride Heidi M. , Pellegrini Luca
Published: November 2006

Remodeling of mitochondria is a dynamic process coordinated by fusion and fission of the inner and outer membranes of the organelle, mediated by a set of conserved proteins. In metazoans, the molecular mechanism behind mitochondrial morphology has been recruited to govern novel functions, such as development, calcium signaling, and apoptosis, which suggests that novel mechanisms should exist to regulate the conserved membrane fusion/fission machinery. Here we show that phosphorylation and cleavage of the vertebrate-specific Pβ domain of the mammalian presenilin-associated rhomboid-like (PARL) protease can influence mitochondrial morphology. Phosphorylation of three residues embedded in this domain, Ser-65, Thr-69, and Ser-70, impair a cleavage at position Ser
77
–Ala
78
that is required to initiate PARL-induced mitochondrial fragmentation. Our findings reveal that PARL phosphorylation and cleavage impact mitochondrial dynamics, providing a blueprint to study the molecular evolution of mitochondrial morphology.
Direct peptide-regulatable interactions between MHC class I molecules and tapasin
Authors: Rizvi Syed Monem , Raghavan Malini
Published: November 2006

Tapasin (Tpn) has been implicated in multiple steps of the MHC class I assembly pathway, but the mechanisms of function remain incompletely understood. Using purified proteins, we could demonstrate direct binding of Tpn to peptide-deficient forms of MHC class I molecules at physiological temperatures. Tpn also bound to M10.5, a pheromone receptor-associated MHC molecule that has an open and empty groove and that shares significant sequence identity with class I sequences. Two types of MHC class I–Tpn complexes were detectablein vitrodepending on the input proteins; those depleted in β2m, and those containing β2m. Both were competent for subsequent assembly with peptides, but the latter complexes assembled more rapidly. Thus, the assembly rate of Tpn-associated class I was determined by the conditions under which Tpn–MHC class I complexes were induced. Peptide loading of class I inhibited Tpn–class I-binding interactions, and peptide-depletion enhanced binding. In combination with β2m, certain peptides induced efficient dissociation of preformed Tpn–class I complexes. Together, these studies demonstrate direct Tpn–MHC class I interactions and preferential binding of empty MHC class I by Tpn, and that the Tpn–class I interaction is regulated by both β2m and peptide. In cells, Tpn is likely to be a direct mediator of peptide-regulated binding and release of MHC class I from the TAP complex.
Exploring atomistic details of pH-dependent peptide folding
Authors: Khandogin Jana , Chen Jianhan , Brooks Charles L.
Published: November 2006

Modeling pH-coupled conformational dynamics allows one to probe many important pH-dependent biological processes, ranging from ATP synthesis, enzyme catalysis, and membrane fusion to protein folding/misfolding and amyloid formation. This work illustrates the strengths and capabilities of continuous constant pH molecular dynamics in exploring pH-dependent conformational transitions in proteins by revisiting an experimentally well studied model protein fragment, the C peptide from ribonuclease A. The simulation data reveal a bell-shaped pH profile for the total helix content, in agreement with experiment, and several pairs of electrostatic interactions that control the relative populations of unfolded and partially folded states of various helical lengths. The latter information greatly complements and extends that attainable by current experimental techniques. The present work paves the way for new and exciting applications, such as the study of pH-dependent molecular mechanism in the formation of amyloid comprising peptides from Alzheimer's and Parkinson's diseases.
The root endophytic fungus
Piriformospora indica
requires host cell death for proliferation during mutualistic symbiosis with barley
Authors: Deshmukh Sachin , Hückelhoven Ralph , Schäfer Patrick , Imani Jafargholi , Sharma Monica , Weiss Michael , Waller Frank , Kogel Karl-Heinz
Published: November 2006

Fungi of the recently defined order Sebacinales (Basidiomycota) are involved in a wide spectrum of mutualistic symbioses (including mycorrhizae) with various plants, thereby exhibiting a unique potential for biocontrol strategies. The axenically cultivable root endophyte
Piriformospora indica
is a model organism of this fungal order. It is able to increase biomass and grain yield of crop plants. In barley, the endophyte induces local and systemic resistance to fungal diseases and to abiotic stress. To elucidate the lifestyle of
P. indica
, we analyzed its symbiotic interaction and endophytic development in barley roots. We found that fungal colonization increases with root tissue maturation. The root tip meristem showed no colonization, and the elongation zone showed mainly intercellular colonization. In contrast, the differentiation zone was heavily infested by inter- and intracellular hyphae and intracellular chlamydospores. The majority of hyphae were present in dead rhizodermal and cortical cells that became completely filled with chlamydospores. In some cases, hyphae penetrated cells and built a meshwork around plasmolyzed protoplasts, suggesting that the fungus either actively kills cells or senses cells undergoing endogenous programmed cell death. Seven days after inoculation, expression of barley
BAX inhibitor-1
(
HvBI-1
), a gene capable of inhibiting plant cell death, was attenuated. Consistently, fungal proliferation was strongly inhibited in transgenic barley overexpressing GFP-tagged HvBI-1, which shows that
P. indica
requires host cell death for proliferation in differentiated barley roots. We suggest that the endophyte interferes with the host cell death program to form a mutualistic interaction with plants.
Crystal structure of HIV-1 protease
in situ
product complex and observation of a low-barrier hydrogen bond between catalytic aspartates
Authors: Das Amit , Prashar Vishal , Mahale Smita , Serre L. , Ferrer J.-L. , Hosur M. V.
Published: November 2006

HIV-1 protease is an effective target for designing drugs against AIDS, and structural information about the true transition state and the correct mechanism can provide important inputs. We present here the three-dimensional structure of a bi-product complex between HIV-1 protease and the two cleavage product peptides AETF and YVDGAA. The structure, refined against synchrotron data to 1.65 Å resolution, shows the occurrence of the cleavage reaction in the crystal, with the product peptides still held in the enzyme active site. The separation between the scissile carbon and nitrogen atoms is 2.67 Å, which is shorter than a normal van der Waal separation, but it is much longer than a peptide bond length. The substrate is thus in a stage just past the G'Z intermediate described in Northrop's mechanism [Northrop DB (2001)
Acc Chem Res
34:790–797]. Because the products are generated
in situ
, the structure, by extrapolation, can give insight into the mechanism of the cleavage reaction. Both oxygens of the generated carboxyl group form hydrogen bonds with atoms at the catalytic center: one to the OD2 atom of a catalytic aspartate and the other to the scissile nitrogen atom. The latter hydrogen bond may have mediated protonation of scissile nitrogen, triggering peptide bond cleavage. The inner oxygen atoms of the catalytic aspartates in the complex are 2.30 Å apart, indicating a low-barrier hydrogen bond between them at this stage of the reaction, an observation not included in Northrop's proposal. This structure forms a template for designing mechanism-based inhibitors.
Predicted seminal astacin-like protease is required for processing of reproductive proteins in
Drosophila melanogaster
Authors: Ravi Ram Kristipati , Sirot Laura K. , Wolfner Mariana F.
Published: November 2006

During mating, males provide females with seminal fluids that include proteins affecting female physiology and, in some cases, reproductive behavior. In several species these male-derived modulators of reproduction are processed upon transfer to the female, suggesting molecular interaction between the sexes. Males could increase their reproductive success by contributing to regulation of this processing; consistent with this hypothesis, seminal fluids are rich in proteolysis regulators. However, whether these molecules carry out processing of male-derived reproductive modulators is unknown. We tested for this role using RNAi to knock down individually 11
Drosophila
seminal fluid proteases and protease inhibitors. We found that CG11864, a predicted astacin-type metalloprotease in seminal fluid, is necessary to process two other seminal proteins: the ovulation hormone ovulin (Acp26Aa) and the sperm storage protein Acp36DE. This processing occurs only after all three proteins have entered the female. Moreover, CG11864 itself is processed inside males while en route to the female and before its action in processing ovulin and Acp36DE. Thus, processing of seminal proteins is stepwise in
Drosophila
, beginning in the male after the proteins leave their site of synthesis and continuing within another organism, the mated female, and the male-donated protease CG11864 is an agent of this latter processing.
A physical linkage between cystic fibrosis airway surface dehydration and
Pseudomonas aeruginosa
biofilms
Authors: Matsui Hirotoshi , Wagner Victoria E. , Hill David B. , Schwab Ute E. , Rogers Troy D. , Button Brian , Taylor Russell M. , Superfine Richard , Rubinstein Michael , Iglewski Barbara H. , Boucher Richard C.
Published: November 2006

A vexing problem in cystic fibrosis (CF) pathogenesis has been to explain the high prevalence of
Pseudomonas aeruginosa
biofilms in CF airways. We speculated that airway surface liquid (ASL) hyperabsorption generates a concentrated airway mucus that interacts with
P. aeruginosa
to promote biofilms. To model CF vs. normal airway infections, normal (2.5% solids) and CF-like concentrated (8% solids) mucus were prepared, placed in flat chambers, and infected with an ≈5 × 10
3
strain PAO1
P. aeruginosa
. Although bacteria grew to 10
10
cfu/ml in both mucus concentrations, macrocolony formation was detected only in the CF-like (8% solids) mucus. Biophysical and functional measurements revealed that concentrated mucus exhibited properties that restrict bacterial motility and small molecule diffusion, resulting in high local bacterial densities with high autoinducer concentrations. These properties also rendered secondary forms of antimicrobial defense, e.g., lactoferrin, ineffective in preventing biofilm formation in a CF-like mucus environment. These data link airway surface liquid hyperabsorption to the high incidence of
P. aeruginosa
biofilms in CF via changes in the hydration-dependent physical–chemical properties of mucus and suggest that the thickened mucus gel model will be useful to develop therapies of
P. aeruginosa
biofilms in CF airways.
Apoptosis-inducing factor mediates poly(ADP-ribose) (PAR) polymer-induced cell death
Authors: Yu Seong-Woon , Andrabi Shaida A. , Wang Hongmin , Kim No Soo , Poirier Guy G. , Dawson Ted M. , Dawson Valina L.
Published: November 2006

Apoptosis-inducing factor (AIF), a mitochondrial oxidoreductase, is released into the cytoplasm to induce cell death in response to poly(ADP-ribose) (PAR) polymerase-1 (PARP-1) activation. How PARP-1 activation leads to AIF release is not known. Here we identify PAR polymer as a cell death signal that induces release of AIF. PAR polymer induces mitochondrial AIF release and translocation to the nucleus. PAR glycohydrolase, which degrades PAR polymer, prevents PARP-1-dependent AIF release. Cells with reduced levels of AIF are resistant to PARP-1-dependent cell death and PAR polymer cytotoxicity. These results reveal PAR polymer as an AIF-releasing factor that plays important roles in PARP-1-dependent cell death.
Effect of urea on the structural dynamics of water
Authors: Rezus Y. L. A. , Bakker H. J.
Published: November 2006

We use polarization-resolved mid-infrared pump-probe spectroscopy to study the effect of urea on the structure and dynamics of water. Surprisingly, we find that, even at high concentrations of urea (8 M), the orientational dynamics of most water molecules are the same as in pure liquid water, showing that urea has a negligible effect on the hydrogen-bond dynamics of these molecules. However, a small fraction of the water molecules (approximately one water molecule per urea molecule) turns out to be strongly immobilized by urea, displaying orientational dynamics that are more than six times slower than in bulk water. A likely explanation is that these water molecules are tightly associated with urea, forming specific urea–water complexes. We discuss these results in light of the protein denaturing ability of aqueous urea.
FAPP2, cilium formation, and compartmentalization of the apical membrane in polarized Madin–Darby canine kidney (MDCK) cells
Authors: Vieira Otilia V. , Gaus Katharina , Verkade Paul , Fullekrug Joachim , Vaz Winchil L. C. , Simons Kai
Published: November 2006

We have analyzed the role of the phosphatidylinositol-4-phosphate adaptor protein-2 (FAPP2), a component of the apical transport machinery, in cilium formation in polarized Madin–Darby canine kidney (MDCK) cells. We show that ciliogenesis is defective in FAPP2 knockdown cells. Furthermore, by using fluorescence recovery after photobleaching studies of domain connectivity and the generalized polarization spectra of Laurdan, we demonstrate that FAPP2 depletion impairs the formation of condensed apical membrane domains. Laurdan staining also revealed that the ciliary membrane has a highly condensed bilayer domain at its base that could function as a fence to separate the ciliary membrane from the surrounding apical membrane. These results indicate that the compartmentalization of the apical membrane in MDCK cells into the ciliary membrane and the surrounding membrane depends on the balance of raft and nonraft domains.
Power spectra reveal the influence of stochasticity on nonlinear population dynamics
Authors: Reuman Daniel C. , Desharnais Robert A. , Costantino Robert F. , Ahmad Omar S. , Cohen Joel E.
Published: November 2006

Stochasticity alters the nonlinear dynamics of inherently cycling populations. The power spectrum can describe and explain the impacts of stochasticity. We fitted models to short observed time series of flour beetle populations in the frequency domain, then used a well fitting stochastic mechanistic model to generate detailed predictions of population spectra. Some predicted spectral peaks represent periodic phenomena induced or modified by stochasticity and were experimentally confirmed. For one experimental treatment, linearization theory explained that these peaks represent overcompensatory decay of deviations from deterministic oscillation. In another treatment, stochasticity caused frequent directional phase shifting around a cyclic attractor. This directional phase shifting was not explained by linearization theory and modified the periodicity of the system. If field systems exhibit directional phase shifting, then changing the intensity of demographic or environmental noise while holding constant the structure of the noise can change the main frequency of population fluctuations.
Quantitative analysis of Argonaute protein reveals microRNA-dependent localization to stress granules
Authors: Leung Anthony K. L. , Calabrese J. Mauro , Sharp Phillip A.
Published: November 2006

Argonaute proteins associate with microRNAs (miRNAs) that bind mRNAs through partial base-pairings to primarily repress translation in animals. A fraction of Argonaute proteins and miRNAs biochemically cosediment with polyribosomes, yet another fraction paradoxically accumulates in ribosome-free processing bodies (PBs) in the cytoplasm. In this report, we give a quantitative account of the Argonaute protein localization and dynamics in living cells in different cellular states. We find that the majority of Argonaute is distributed diffusely in the cytoplasm, and, when cells are subjected to stress, Argonaute proteins accumulate to newly assembled structures known as stress granules (SGs) in addition to PBs. Argonaute proteins displayed distinct kinetics at different structures: exchange faster at SGs and much slower at PBs. Further, miRNAs are required for the Argonaute protein localization to SGs but not PBs. These quantitative kinetic data provide insights into miRNA-mediated repression.
Acetylation of MEK2 and IκB kinase (IKK) activation loop residues by YopJ inhibits signaling
Authors: Mittal Rohit , Peak-Chew Sew-Yeu , McMahon Harvey T.
Published: November 2006

To overcome host defenses, bacterial pathogens of the genus
Yersinia
inject specific effector proteins into colonized mammalian cells. One such virulence factor, YopJ, inhibits the host inflammatory response and induces apoptosis of immune cells by blocking multiple signaling pathways, including the MAPK and NF-κB pathways. In this study, we show that YopJ exerts its deleterious effects by catalyzing the acetylation of two serine residues in the activation loop of the MAP kinase kinase, MEK2. This covalent modification prevents the phosphorylation of these serine residues that is required for activation of MEK2 and downstream signal propagation. We also show that YopJ causes acetylation of a threonine residue in the activation loop of both the α and β subunits of the NF-κB pathway kinase, IKK. These results establish a hitherto uncharacterized mode of action for bacterial toxins and suggest the possibility that serine/threonine acetylation may occur even under nonpathogenic conditions and may be a widespread protein modification regulating protein function in eukaryotic cells.
Junctional adhesion molecule-C regulates vascular endothelial permeability by modulating VE-cadherin–mediated cell–cell contacts
Authors: Orlova Valeria V. , Economopoulou Matina , Lupu Florea , Santoso Sentot , Chavakis Triantafyllos
Published: November 2006

We recently reported that junctional adhesion molecule (JAM)-C plays a role in leukocyte transendothelial migration. Here, the role of JAM-C in vascular permeability was investigated in vitro and in vivo. As opposed to macrovascular endothelial cells that constitutively expressed JAM-C in cell–cell contacts, in quiescent microvascular endothelial cells, JAM-C localized mainly intracellularly, and was recruited to junctions upon short-term stimulation with vascular endothelial growth factor (VEGF) or histamine. Strikingly, disruption of JAM-C function decreased basal permeability and prevented the VEGF- and histamine-induced increases in human dermal microvascular endothelial cell permeability in vitro and skin permeability in mice. Permeability increases are essential in angiogenesis, and JAM-C blockade reduced hyperpermeability and neovascularization in hypoxia-induced retinal angiogenesis in mice. The underlying mechanisms of the JAM-C–mediated increase in endothelial permeability were studied. JAM-C was essential for the regulation of endothelial actomyosin, as revealed by decreased F-actin, reduced myosin light chain phosphorylation, and actin stress fiber formation due to JAM-C knockdown. Moreover, the loss of JAM-C expression resulted in stabilization of VE-cadherin–mediated interendothelial adhesion in a manner dependent on the small GTPase Rap1. Together, through modulation of endothelial contractility and VE-cadherin–mediated adhesion, JAM-C helps to regulate vascular permeability and pathologic angiogenesis.
An inflammation-induced mechanism for leukocyte transmigration across lymphatic vessel endothelium
Authors: Johnson Louise A. , Clasper Steven , Holt Andrew P. , Lalor Patricia F. , Baban Dilair , Jackson David G.
Published: November 2006

The exit of antigen-presenting cells and lymphocytes from inflamed skin to afferent lymph is vital for the initiation and maintenance of dermal immune responses. How such an exit is achieved and how cells transmigrate the distinct endothelium of lymphatic vessels are unknown. We show that inflammatory cytokines trigger activation of dermal lymphatic endothelial cells (LECs), leading to expression of the key leukocyte adhesion receptors intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and E-selectin, as well as a discrete panel of chemokines and other potential regulators of leukocyte transmigration. Furthermore, we show that both ICAM-1 and VCAM-1 are induced in the dermal lymphatic vessels of mice exposed to skin contact hypersensitivity where they mediate lymph node trafficking of dendritic cells (DCs) via afferent lymphatics. Lastly, we show that tumor necrosis factor α stimulates both DC adhesion and transmigration of dermal LEC monolayers in vitro and that the process is efficiently inhibited by ICAM-1 and VCAM-1 adhesion-blocking monoclonal antibodies. These results reveal a CAM-mediated mechanism for recruiting leukocytes to the lymph nodes in inflammation and highlight the process of lymphatic transmigration as a potential new target for antiinflammatory therapy.
Identification of a radio-resistant and cycling dermal dendritic cell population in mice and men
Authors: Bogunovic Milena , Ginhoux Florent , Wagers Amy , Loubeau Martine , Isola Luis M. , Lubrano Lauren , Najfeld Vesna , Phelps Robert G. , Grosskreutz Celia , Scigliano Eilleen , Frenette Paul S. , Merad Miriam
Published: November 2006

In this study, we explored dermal dendritic cell (DC) homeostasis in mice and humans both in the steady state and after hematopoietic cell transplantation. We discovered that dermal DCs proliferate in situ in mice and human quiescent dermis. In parabiotic mice with separate organs but shared blood circulation, the majority of dermal DCs failed to be replaced by circulating precursors for >6 mo. In lethally irradiated mice injected with donor congenic bone marrow (BM) cells, a subset of recipient DCs remained in the dermis and proliferated locally throughout life. Consistent with these findings, a large proportion of recipient dermal DCs remained in patients' skin after allogeneic hematopoietic cell transplantation, despite complete donor BM chimerism. Collectively, our results oppose the traditional view that DCs are nondividing terminally differentiated cells maintained by circulating precursors and support the new paradigm that tissue DCs have local proliferative properties that control their homeostasis in the steady state. Given the role of residual host tissue DCs in transplant immune reactions, these results suggest that dermal DC homeostasis may contribute to the development of cutaneous graft-versus-host disease in clinical transplantation.
Random migration precedes stable target cell interactions of tumor-infiltrating T cells
Authors: Mrass Paulus , Takano Hajime , Ng Lai Guan , Daxini Sachin , Lasaro Marcio O. , Iparraguirre Amaya , Cavanagh Lois L. , von Andrian Ulrich H. , Ertl Hildegund C.J. , Haydon Philip G. , Weninger Wolfgang
Published: November 2006

The tumor microenvironment is composed of an intricate mixture of tumor and host-derived cells that engage in a continuous interplay. T cells are particularly important in this context as they may recognize tumor-associated antigens and induce tumor regression. However, the precise identity of cells targeted by tumor-infiltrating T lymphocytes (TILs) as well as the kinetics and anatomy of TIL-target cell interactions within tumors are incompletely understood. Furthermore, the spatiotemporal conditions of TIL locomotion through the tumor stroma, as a prerequisite for establishing contact with target cells, have not been analyzed. These shortcomings limit the rational design of immunotherapeutic strategies that aim to overcome tumor-immune evasion. We have used two-photon microscopy to determine, in a dynamic manner, the requirements leading to tumor regression by TILs. Key observations were that TILs migrated randomly throughout the tumor microenvironment and that, in the absence of cognate antigen, they were incapable of sustaining active migration. Furthermore, TILs in regressing tumors formed long-lasting (≥30 min), cognate antigen–dependent contacts with tumor cells. Finally, TILs physically interacted with macrophages, suggesting tumor antigen cross-presentation by these cells. Our results demonstrate that recognition of cognate antigen within tumors is a critical determinant of optimal TIL migration and target cell interactions, and argue against TIL guidance by long-range chemokine gradients.
Intraluminal crawling of neutrophils to emigration sites: a molecularly distinct process from adhesion in the recruitment cascade
Authors: Phillipson Mia , Heit Bryan , Colarusso Pina , Liu Lixin , Ballantyne Christie M. , Kubes Paul
Published: November 2006

The prevailing view is that the β2-integrins Mac-1 (αMβ2, CD11b/CD18) and LFA-1 (αLβ2, CD11a/CD18) serve similar biological functions, namely adhesion, in the leukocyte recruitment cascade. Using real-time and time-lapse intravital video-microscopy and confocal microscopy within inflamed microvessels, we systematically evaluated the function of Mac-1 and LFA-1 in the recruitment paradigm. The chemokine macrophage inflammatory protein-2 induced equivalent amounts of adhesion in wild-type and Mac-1−/− mice but very little adhesion in LFA-1−/− mice. Time-lapse video-microscopy within the postcapillary venules revealed that immediately upon adhesion, there is significant intraluminal crawling of all neutrophils to distant emigration sites in wild-type mice. In dramatic contrast, very few Mac-1−/− neutrophils crawled with a 10-fold decrease in displacement and a 95% reduction in velocity. Therefore, Mac-1−/− neutrophils initiated transmigration closer to the initial site of adhesion, which in turn led to delayed transmigration due to movement through nonoptimal emigration sites. Interestingly, the few LFA-1−/− cells that did adhere crawled similarly to wild-type neutrophils. Intercellular adhesion molecule-1 but not intercellular adhesion molecule-2 mediated the Mac-1–dependent crawling. These in vivo results clearly delineate two fundamentally different molecular mechanisms for LFA-1 and Mac-1 in vivo, i.e., LFA-1–dependent adhesion followed by Mac-1–dependent crawling, and both steps ultimately contribute to efficient emigration out of the vasculature.
Insulin-induced remission in new-onset NOD mice is maintained by the PD-1–PD-L1 pathway
Authors: Fife Brian T. , Guleria Indira , Gubbels Bupp Melanie , Eagar Todd N. , Tang Qizhi , Bour-Jordan Helene , Yagita Hideo , Azuma Miyuki , Sayegh Mohamed H. , Bluestone Jeffrey A.
Published: November 2006

The past decade has seen a significant increase in the number of potentially tolerogenic therapies for treatment of new-onset diabetes. However, most treatments are antigen nonspecific, and the mechanism for the maintenance of long-term tolerance remains unclear. In this study, we developed an antigen-specific therapy, insulin-coupled antigen-presenting cells, to treat diabetes in nonobese diabetic mice after disease onset. Using this approach, we demonstrate disease remission, inhibition of pathogenic T cell proliferation, decreased cytokine production, and induction of anergy. Moreover, we show that robust long-term tolerance depends on the programmed death 1 (PD-1)–programmed death ligand (PD-L)1 pathway, not the distinct cytotoxic T lymphocyte–associated antigen 4 pathway. Anti–PD-1 and anti–PD-L1, but not anti–PD-L2, reversed tolerance weeks after tolerogenic therapy by promoting antigen-specific T cell proliferation and inflammatory cytokine production directly in infiltrated tissues. PD-1–PD-L1 blockade did not limit T regulatory cell activity, suggesting direct effects on pathogenic T cells. Finally, we describe a critical role for PD-1–PD-L1 in another powerful immunotherapy model using anti-CD3, suggesting that PD-1–PD-L1 interactions form part of a common pathway to selectively maintain tolerance within the target tissues.
Spontaneous autoimmunity prevented by thymic expression of a single self-antigen
Authors: DeVoss Jason , Hou Yafei , Johannes Kellsey , Lu Wen , Liou Gregory I. , Rinn John , Chang Howard , Caspi Rachel R. , Fong Lawrence , Anderson Mark S.
Published: November 2006

The expression of self-antigen in the thymus is believed to be responsible for the deletion of autoreactive T lymphocytes, a critical process in the maintenance of unresponsiveness to self. The Autoimmune regulator (Aire) gene, which is defective in the disorder autoimmune polyglandular syndrome type 1, has been shown to promote the thymic expression of self-antigens. A clear link, however, between specific thymic self-antigens and a single autoimmune phenotype in this model has been lacking. We show that autoimmune eye disease in aire-deficient mice develops as a result of loss of thymic expression of a single eye antigen, interphotoreceptor retinoid-binding protein (IRBP). In addition, lack of IRBP expression solely in the thymus, even in the presence of aire expression, is sufficient to trigger spontaneous eye-specific autoimmunity. These results suggest that failure of thymic expression of selective single self-antigens can be sufficient to cause organ-specific autoimmune disease, even in otherwise self-tolerant individuals.
A microsatellite linkage map of the blacklip abalone, Haliotis rubra
Authors: Baranski M. , Loughnan S. , Austin C. M. , Robinson N.
Published: November 2006

There is considerable scope for genetic improvement of cultured blacklip abalone Haliotis rubra in Australia using molecular marker‐assisted, selective‐breeding practices. Such improvement is dependent on the availability of primary genetic resources, such as a genetic linkage map. This study presents a first‐generation linkage map of H. rubra, containing 122 microsatellite markers typed in a single full‐sib family. These loci mapped to 17 and 20 linkage groups for the male and female respectively, and when aligned, the consensus map represented 18 linkage groups. The male linkage map contained 102 markers (one unlinked) covering 621 cM with an average intermarker spacing of 7.3 cM, and the female map contained 98 markers (eight unlinked) covering 766 cM with an average intermarker spacing of 9.8 cM. Analysis of markers informative in both parents showed a significantly higher recombination rate in the female parent, with an average male‐to‐female recombination ratio of 1:1.45 between linked pairs of markers. This linkage map represents a significant advancement in the genetic resource available for H. rubra and provides a framework for future quantitative trait loci mapping and eventual implementation of marker‐assisted selection.
Saving feral horse populations: does it really matter? A case study of wild horses from Doñana National Park in southern Spain
Authors: Vega‐Pla J. L. , Calderón J. , Rodríguez‐Gallardo P. P. , Martinez A. M. , Rico C.
Published: November 2006

In the 1980s, a conservation programme involving a feral horse population, the Retuertas horses from the Guadalquivir marshes, was started in the Doñana National Park. The analysis of an extensive genetic survey of this population, which now numbers 100 animals, and 10 additional European and North African breeds using DNA polymorphisms from 22 microsatellites is presented. Highly significant fixation indexes were obtained for all pairwise comparisons between the Retuertas population and other breeds. A population neighbour‐joining breed phenogram was built using different distance measures, but the Retuertas population failed to cluster with either of the two major clades of European and North African breeds, highlighting its uniqueness. In fact, the Retuertas population was positioned at the base of the trees, which were rooted using donkey samples. Furthermore, assignment tests and the individual Q‐matrices obtained with thestructureprogramme isolated the Retuertas breed from the other breeds with only fourKgroups. Interestingly, some local semi‐feral horses, known as Marismeño, also currently living in the Guadalquivir marshes, have some microsatellite genotypes that fall well within the Retuertas cluster. This raises the possibility of incorporating horses from the Marismeño population in a future conservation programme.
A 2.5‐Mb contig constructed from Angus, Longhorn and horned Hereford DNA spanning the polled interval on bovine chromosome 1
Authors: Wunderlich K. R. , Abbey C. A. , Clayton D. R. , Song Y. , Schein J. E. , Georges M. , Coppieters W. , Adelson D. L. , Taylor J. F. , Davis S. L. , Gill C. A.
Published: November 2006

The polled locus has been mapped by genetic linkage analysis to the proximal region of bovine chromosome 1. As an intermediate step in our efforts to identify the polled locus and the underlying causative mutation for the polled phenotype, we have constructed a BAC‐based physical map of the interval containing the polled locus. Clones containing genes and markers in the critical interval were isolated from the TAMBT (constructed from Angus and Longhorn genomic DNA) and CHORI‐240 (constructed from horned Hereford genomic DNA) BAC libraries and ordered based on fingerprinting and the presence or absence of 80 STS markers. A single contig spanning 2.5 Mb was assembled. Comparison of the physical order of STSs to the corresponding region of human chromosome 21 revealed the same order of genes within the polled critical interval. This contig of overlapping BAC clones from horned and polled breeds is a useful resource for SNP discovery and characterization of positional candidate genes.
Clinical risk management of herb–drug interactions
Authors: De Smet Peter A. G. M.
Published: November 2006

The concomitant use of conventional and herbal medicines can lead to clinically relevant herb–drug interactions. Clinical risk management offers a systematic approach to minimize the untoward consequences of these interactions by paying attention to: (i) risk identification and assessment; (ii) development and execution of risk reduction strategies; and (iii) evaluation of risk reduction strategies. This paper reviews which steps should be explored or taken in these domains to improve the clinical risk management of adverse herb–drug interactions.
A lesser postprandial suppression of plasma ghrelin in Prader–Willi syndrome is associated with low fasting and a blunted postprandial PYY response
Authors: Giménez‐Palop Olga , Giménez‐Pérez Gabriel , Mauricio Dídac , González‐Clemente José‐Miguel , Potau Neus , Berlanga Eugenio , Trallero Roser , Laferrère Blandine , Caixàs Assumpta
Published: November 2006

Objective  Ghrelin and polipeptide YY (PYY) are involved in the regulation of food intake. We evaluated these two peptides and their possible relationship in adult patients with Prader–Willi syndrome (PWS).

Patients  Seven patients with PWS, 16 age‐sex‐BMI matched obese and 42 age‐sex matched lean subjects.

Design and measurements  Fasting plasma PYY and ghrelin levels were measured in all subjects and, postprandially until 6 h, in seven matched subjects of each group.

Results  Fasting ghrelin levels were higher in PWS than in the other two groups. Fasting PYY levels were lower in patients with PWS than in lean subjects but similar to those in obese subjects. The postprandial decrease in ghrelin concentrations was lower in PWS as compared to the other two groups and therefore the 6‐h‐postprandial area under the curve (AUC) for ghrelin was higher in PWS than in obese subjects. PYY response after the meal was blunted in patients with PWS, but not in the other two groups that showed a peak at 60 min The AUC for PYY was lower in PWS as compared to the other two groups. Fasting PYY levels correlated negatively with fasting ghrelin levels and with ghrelin AUC and they were the only predictor for ghrelin AUC (β = −0·464, P = 0·034). The increase in PYY correlated negatively with the decrease in ghrelin at times 60 min and 120 min in PWS.

Conclusions  In PWS, the low decrease in postprandial ghrelin levels could be related to the low fasting PYY concentrations and their blunted postprandial response.