bluuebunny/crossref_metadata_2025 huggingface dataset:
Two measures of leaf capacitance: insights into the water transport pathway and hydraulic conductance in leaves
Authors: Blackman Chris J. , Brodribb Tim J.
Published: February 2011

The efficiency and stress tolerance of leaf water transport are key indicators of plant function, but our ability to assess these processes is constrained by gaps in our understanding of the water transport pathway in leaves. A major challenge is to understand how different pools of water in leaves are connected to the transpiration stream and, hence, determine leaf capacitance (Cleaf) to short- and medium-term fluctuations in transpiration. Here, we examine variation across an anatomically and phylogenetically diverse group of woody angiosperms in two measures of Cleaf assumed to represent bulk-leaf capacitance (Cbulk) and the capacitance of leaf tissues that influence dynamic changes in leaf hydration (Cdyn). Among species, Cbulk was significantly correlated with leaf mass per unit area, whereas Cdyn was independently related to leaf lignin content (%) and the saturated mass of leaf water per unit dry weight. Dynamic and steady-state measurements of leaf hydraulic conductance (Kleaf) agreed if Cdyn was used rather than Cbulk, suggesting that the leaf tissue in some species is hydraulically compartmentalised and that only a proportion of total leaf water is hydraulically well connected to the transpiration stream. These results indicate that leaf rehydration kinetics can accurately measure Kleaf with knowledge of the capacitance of the hydraulic pathway.
Chimpanzees know that others make inferences
Authors: Schmelz Martin , Call Josep , Tomasello Michael
Published: February 2011

If chimpanzees are faced with two opaque boards on a table, in the context of searching for a single piece of food, they do not choose the board lying flat (because if food was under there it would not be lying flat) but, rather, they choose the slanted one— presumably inferring that some unperceived food underneath is causing the slant. Here we demonstrate that chimpanzees know that other chimpanzees in the same situation will make a similar inference. In a back-and-forth foraging game, when their competitor had chosen before them, chimpanzees tended to avoid the slanted board on the assumption that the competitor had already chosen it. Chimpanzees can determine the inferences that a conspecific is likely to make and then adjust their competitive strategies accordingly.
Neural dysregulation of peripheral insulin action and blood pressure by brain endoplasmic reticulum stress
Authors: Purkayastha Sudarshana , Zhang Hai , Zhang Guo , Ahmed Zaghloul , Wang Yi , Cai Dongsheng
Published: February 2011

Chronic endoplasmic reticulum (ER) stress was recently revealed to affect hypothalamic neuroendocrine pathways that regulate feeding and body weight. However, it remains unexplored whether brain ER stress could use a neural route to rapidly cause the peripheral disorders that underlie the development of type 2 diabetes (T2D) and the metabolic syndrome. Using a pharmacologic model that delivered ER stress inducer thapsigargin into the brain, this study demonstrated that a short-term brain ER stress over 3 d was sufficient to induce glucose intolerance, systemic and hepatic insulin resistance, and blood pressure (BP) increase. The collection of these changes was accompanied by elevated sympathetic tone and prevented by sympathetic suppression. Molecular studies revealed that acute induction of metabolic disorders via brain ER stress was abrogated by NF-κB inhibition in the hypothalamus. Therapeutic experiments further revealed that acute inhibition of brain ER stress with tauroursodeoxycholic acid (TUDCA) partially reversed obesity-associated metabolic and blood pressure disorders. In conclusion, ER stress in the brain represents a mediator of the sympathetic disorders that underlie the development of insulin resistance syndrome and T2D.
Neuroligin-4 is localized to glycinergic postsynapses and regulates inhibition in the retina
Authors: Hoon Mrinalini , Soykan Tolga , Falkenburger Björn , Hammer Matthieu , Patrizi Annarita , Schmidt Karl-Friedrich , Sassoè-Pognetto Marco , Löwel Siegrid , Moser Tobias , Taschenberger Holger , Brose Nils , Varoqueaux Frédérique
Published: February 2011

Neuroligins (NL1–NL4) are postsynaptic adhesion proteins that control the maturation and function of synapses in the central nervous system (CNS). Loss-of-function mutations in NL4 are linked to rare forms of monogenic heritable autism, but its localization and function are unknown. Using the retina as a model system, we show that NL4 is preferentially localized to glycinergic postsynapses and that the loss of NL4 is accompanied by a reduced number of glycine receptors mediating fast glycinergic transmission. Accordingly, NL4-deficient ganglion cells exhibit slower glycinergic miniature postsynaptic currents and subtle alterations in their stimulus-coding efficacy, and inhibition within the NL4-deficient retinal network is altered as assessed by electroretinogram recordings. These data indicate that NL4 shapes network activity and information processing in the retina by modulating glycinergic inhibition. Importantly, NL4 is also targeted to inhibitory synapses in other areas of the CNS, such as the thalamus, colliculi, brainstem, and spinal cord, and forms complexes with the inhibitory postsynapse proteins gephyrin and collybistin in vivo, indicating that NL4 is an important component of glycinergic postsynapses.
Draft genome of the globally widespread and invasive Argentine ant (
Linepithema humile
)
Authors: Smith Christopher D. , Zimin Aleksey , Holt Carson , Abouheif Ehab , Benton Richard , Cash Elizabeth , Croset Vincent , Currie Cameron R. , Elhaik Eran , Elsik Christine G. , Fave Marie-Julie , Fernandes Vilaiwan , Gadau Jürgen , Gibson Joshua D. , Graur Dan , Grubbs Kirk J. , Hagen Darren E. , Helmkampf Martin , Holley Jo-Anne , Hu Hao , Viniegra Ana Sofia Ibarraran , Johnson Brian R. , Johnson Reed M. , Khila Abderrahman , Kim Jay W. , Laird Joseph , Mathis Kaitlyn A. , Moeller Joseph A. , Muñoz-Torres Monica C. , Murphy Marguerite C. , Nakamura Rin , Nigam Surabhi , Overson Rick P. , Placek Jennifer E. , Rajakumar Rajendhran , Reese Justin T. , Robertson Hugh M. , Smith Chris R. , Suarez Andrew V. , Suen Garret , Suhr Elissa L. , Tao Shu , Torres Candice W. , van Wilgenburg Ellen , Viljakainen Lumi , Walden Kimberly K. O. , Wild Alexander L. , Yandell Mark , Yorke James A. , Tsutsui Neil D.
Published: February 2011

Ants are some of the most abundant and familiar animals on Earth, and they play vital roles in most terrestrial ecosystems. Although all ants are eusocial, and display a variety of complex and fascinating behaviors, few genomic resources exist for them. Here, we report the draft genome sequence of a particularly widespread and well-studied species, the invasive Argentine ant (
Linepithema humile
), which was accomplished using a combination of 454 (Roche) and Illumina sequencing and community-based funding rather than federal grant support. Manual annotation of >1,000 genes from a variety of different gene families and functional classes reveals unique features of the Argentine ant's biology, as well as similarities to
Apis mellifera
and
Nasonia vitripennis
. Distinctive features of the Argentine ant genome include remarkable expansions of gustatory (116 genes) and odorant receptors (367 genes), an abundance of cytochrome P450 genes (>110), lineage-specific expansions of yellow/major royal jelly proteins and desaturases, and complete CpG DNA methylation and RNAi toolkits. The Argentine ant genome contains fewer immune genes than
Drosophila
and
Tribolium
, which may reflect the prominent role played by behavioral and chemical suppression of pathogens. Analysis of the ratio of observed to expected CpG nucleotides for genes in the reproductive development and apoptosis pathways suggests higher levels of methylation than in the genome overall. The resources provided by this genome sequence will offer an abundance of tools for researchers seeking to illuminate the fascinating biology of this emerging model organism.
Transgenic elimination of high-affinity antidepressant and cocaine sensitivity in the presynaptic serotonin transporter
Authors: Thompson Brent J. , Jessen Tammy , Henry L. K. , Field Julie R. , Gamble Karen L. , Gresch Paul J. , Carneiro Ana M. , Horton Rebecca E. , Chisnell Peter J. , Belova Yekaterina , McMahon Douglas G. , Daws Lynette C. , Blakely Randy D.
Published: February 2011

Serotonin [i.e., 5-hydroxytryptamine (5-HT)]–targeted antidepressants are in wide use for the treatment of mood disorders, although many patients do not show a response or experience unpleasant side effects. Psychostimulants, such as cocaine and 3,4-methylenedioxymethamphetamine (i.e., “ecstasy”), also impact 5-HT signaling. To help dissect the contribution of 5-HT signaling to the actions of these and other agents, we developed transgenic mice in which high-affinity recognition of multiple antidepressants and cocaine is eliminated. Our animals possess a modified copy of the 5-HT transporter (i.e., SERT,slc6a4) that bears a single amino acid substitution, I172M, proximal to the 5-HT binding site. Although the M172 substitution does not impact the recognition of 5-HT, this mutation disrupts high-affinity binding of many competitive antagonists in transfected cells. Here, we demonstrate that, in M172 knock-in mice, basal SERT protein levels, 5-HT transport rates, and 5-HT levels are normal. However, SERT M172 mice display a substantial loss of sensitivity to the selective 5-HT reuptake inhibitors fluoxetine and citalopram, as well as to cocaine. Through a series of biochemical, electrophysiological, and behavioral assays, we demonstrate the unique properties of this model and establish directly that SERT is the sole protein responsible for selective 5-HT reuptake inhibitor-mediated alterations in 5-HT clearance, in 5-HT1A autoreceptor modulation of raphe neuron firing, and in behaviors used to predict the utility of antidepressants.
Dishevelled is essential for neural connectivity and planar cell polarity in planarians
Authors: Almuedo-Castillo Maria , Saló Emili , Adell Teresa
Published: February 2011

The Wingless/Integrated (Wnt) signaling pathway controls multiple events during development and homeostasis. It comprises multiple branches, mainly classified according to their dependence on β-catenin activation. The Wnt/β-catenin branch is essential for the establishment of the embryonic anteroposterior (AP) body axis throughout the phylogenetic tree. It is also required for AP axis establishment during planarian regeneration. Wnt/β-catenin–independent signaling encompasses several different pathways, of which the most extensively studied is the planar cell polarity (PCP) pathway, which is responsible for planar polarization of cell structures within an epithelial sheet. Dishevelled (Dvl) is the hub of Wnt signaling because it regulates and channels the Wnt signal into every branch. Here, we analyze the role of
Schmidtea mediterranea
Dvl homologs (
Smed-dvl-1
and
Smed-dvl-2
) using gene silencing. We demonstrate that in addition to a role in AP axis specification, planarian Dvls are involved in at least two different β-catenin–independent processes. First, they are essential for neural connectivity through
Smed-wnt5
signaling. Second,
Smed-dvl-2
, together with the
S. mediterranea
homologs of Van-Gogh (Vang) and Diversin (Div), is required for apical positioning of the basal bodies of epithelial cells. These data represent evidence not only of the function of the PCP network in lophotrocozoans but of the involvement of the PCP core elements Vang and Div in apical positioning of the cilia.
Histone code pathway involving H3 S28 phosphorylation and K27 acetylation activates transcription and antagonizes polycomb silencing
Authors: Lau Priscilla Nga Ieng , Cheung Peter
Published: February 2011

Histone H3 phosphorylation is a critical step that couples signal transduction pathways to gene regulation. To specifically assess the transcriptional regulatory functions of H3 phosphorylation, we developed an in vivo targeting approach and found that the H3 kinase MSK1 is a direct and potent transcriptional activator. Targeting of this H3 kinase to the endogenous
c-fos
promoter is sufficient to activate its expression without the need of upstream signaling. Moreover, targeting MSK1 to the α-globin promoter induces H3 S28 phosphorylation and reactivates expression of this polycomb-silenced gene. Importantly, we discovered a mechanism whereby H3 S28 phosphorylation not only displaces binding of the polycomb-repressive complexes, but it also induces a methyl-acetylation switch of the adjacent K27 residue. Our findings show that signal transduction activation can directly regulate polycomb silencing through a specific histone code-mediated mechanism.
Genetic disassembly and combinatorial reassembly identify a minimal functional repertoire of type III effectors in
Pseudomonas syringae
Authors: Cunnac Sébastien , Chakravarthy Suma , Kvitko Brian H. , Russell Alistair B. , Martin Gregory B. , Collmer Alan
Published: February 2011

The virulence of
Pseudomonas syringae
and many other proteobacterial pathogens is dependent on complex repertoires of effector proteins injected into host cells by type III secretion systems. The 28 well-expressed effector genes in the repertoire of the model pathogen
P. syringae
pv.
tomato
DC3000 were deleted to produce polymutant DC3000D28E. Growth of DC3000D28E in
Nicotiana benthamiana
was symptomless and 4 logs lower than that of DC3000Δ
hopQ1-1
, which causes disease in this model plant. DC3000D28E seemed functionally effectorless but otherwise WT in diagnostic phenotypes relevant to plant interactions (for example, ability to inject the AvrPto-Cya reporter into
N. benthamiana
). Various effector genes were integrated by homologous recombination into native loci or by a programmable or random in vivo assembly shuttle (PRIVAS) system into the exchangeable effector locus in the Hrp pathogenicity island of DC3000D28E. The latter method exploited dual adapters and recombination in yeast for efficient assembly of PCR products into programmed or random combinations of multiple effector genes. Native and PRIVAS-mediated integrations were combined to identify a minimal functional repertoire of eight effector genes that restored much of the virulence of DC3000Δ
hopQ1-1
in
N. benthamiana
, revealing a hierarchy in effector function: AvrPtoB acts with priority in suppressing immunity, enabling other effectors to promote further growth (HopM1 and HopE1), chlorosis (HopG1), lesion formation (HopAM1-1), and near full growth and symptom production (AvrE, HopAA1-1, and/or HopN1 functioning synergistically with the previous effectors). DC3000D28E, the PRIVAS method, and minimal functional repertoires provide new resources for probing the plant immune system.
Involvement of ryanodine receptors in neurotrophin-induced hippocampal synaptic plasticity and spatial memory formation
Authors: Adasme Tatiana , Haeger Paola , Paula-Lima Andrea C. , Espinoza Italo , Casas-Alarcón M. Mercedes , Carrasco M. Angélica , Hidalgo Cecilia
Published: February 2011

Ryanodine receptors (RyR) amplify activity-dependent calcium influx via calcium-induced calcium release. Calcium signals trigger postsynaptic pathways in hippocampal neurons that underlie synaptic plasticity, learning, and memory. Recent evidence supports a role of the RyR2 and RyR3 isoforms in these processes. Along with calcium signals, brain-derived neurotrophic factor (BDNF) is a key signaling molecule for hippocampal synaptic plasticity and spatial memory. Upon binding to specific TrkB receptors, BDNF initiates complex signaling pathways that modify synaptic structure and function. Here, we show that BDNF-induced remodeling of hippocampal dendritic spines required functional RyR. Additionally, incubation with BDNF enhanced the expression of RyR2, RyR3, and PKMζ, an atypical protein kinase C isoform with key roles in hippocampal memory consolidation. Consistent with their increased RyR protein content, BDNF-treated neurons generated larger RyR-mediated calcium signals than controls. Selective inhibition of RyR-mediated calcium release with inhibitory ryanodine concentrations prevented the PKMζ, RyR2, and RyR3 protein content enhancement induced by BDNF. Intrahippocampal injection of BDNF or training rats in a spatial memory task enhanced PKMζ, RyR2, RyR3, and BDNF hippocampal protein content, while injection of ryanodine at concentrations that stimulate RyR-mediated calcium release improved spatial memory learning and enhanced memory consolidation. We propose that RyR-generated calcium signals are key features of the complex neuronal plasticity processes induced by BDNF, which include increased expression of RyR2, RyR3, and PKMζ and the spine remodeling required for spatial memory formation.
Intramolecular proton shuttle supports not only catalytic but also noncatalytic function of carbonic anhydrase II
Authors: Becker Holger M. , Klier Michael , Schüler Christina , McKenna Robert , Deitmer Joachim W.
Published: February 2011

Carbonic anhydrases (CAs) catalyze the reversible hydration of CO
2
to HCO
3
−
and H
+
. The rate-limiting step in this reaction is the shuttle of protons between the catalytic center of the enzyme and the bulk solution. In carbonic anhydrase II (CAII), the fastest and most wide-spread isoform, this H
+
shuttle is facilitated by the side chain of His64, whereas CA isoforms such as carbonic anhydrase III (CAIII), which lack such a shuttle, have only low catalytic activity in vitro. By using heterologous protein expression in
Xenopus
oocytes, we tested the role of this intramolecular H
+
shuttle on CA activity in an intact cell. The data revealed that CAIII, shown in vitro to have ∼1,000-fold reduced activity as compared with CAII, displays significant catalytic activity in the intact cell. Furthermore, we tested the hypothesis that the H
+
shuttle in CAII itself can facilitate transport activity of the monocarboxylate transporters 1 and 4 (MCT1/4) independent of catalytic activity. Our results show that His64 is essential for the enhancement of lactate transport via MCT1/4, because a mutation of this residue to alanine (CAII-H64A) abolishes the CAII-induced increase in MCT1/4 activity. However, injection of 4-methylimidazole, which acts as an exogenous H
+
donor/acceptor, can restore the ability of CAII-H64A to enhance transport activity of MCT1/4. These findings support the hypothesis that the H
+
shuttle in CAII not only facilitates CAII catalytic activity but also can enhance activity of acid-/base-transporting proteins such as MCT1/4 in a direct, noncatalytic manner, possibly by acting as an “H
+
-collecting antenna.”
Population genomics and local adaptation in wild isolates of a model microbial eukaryote
Authors: Ellison Christopher E. , Hall Charles , Kowbel David , Welch Juliet , Brem Rachel B. , Glass N. L. , Taylor John W.
Published: February 2011

Elucidating the connection between genotype, phenotype, and adaptation in wild populations is fundamental to the study of evolutionary biology, yet it remains an elusive goal, particularly for microscopic taxa, which comprise the majority of life. Even for microbes that can be reliably found in the wild, defining the boundaries of their populations and discovering ecologically relevant phenotypes has proved extremely difficult. Here, we have circumvented these issues in the microbial eukaryoteNeurospora crassaby using a “reverse-ecology” population genomic approach that is free of a priori assumptions about candidate adaptive alleles. We performed Illumina whole-transcriptome sequencing of 48 individuals to identify single nucleotide polymorphisms. From these data, we discovered two cryptic and recently diverged populations, one in the tropical Caribbean basin and the other endemic to subtropical Louisiana. We conducted high-resolution scans for chromosomal regions of extreme divergence between these populations and found two such genomic “islands.” Through growth-rate assays, we found that the subtropical Louisiana population has a higher fitness at low temperature (10 °C) and that several of the genes within these distinct regions have functions related to the response to cold temperature. These results suggest the divergence islands may be the result of local adaptation to the 9 °C difference in average yearly minimum temperature between these two populations. Remarkably, another of the genes identified using this unbiased, whole-genome approach is the well-known circadian oscillatorfrequency, suggesting that the 2.4°–10.6° difference in latitude between the populations may be another important environmental parameter.
Microworm optode sensors limit particle diffusion to enable in vivo measurements
Authors: Ozaydin-Ince Gozde , Dubach J. Matthew , Gleason Karen K. , Clark Heather A.
Published: February 2011

There have been a variety of nanoparticles created for in vivo uses ranging from gene and drug delivery to tumor imaging and physiological monitoring. The use of nanoparticles to measure physiological conditions while being fluorescently addressed through the skin provides an ideal method toward minimally invasive health monitoring. Here we create unique particles that have all the necessary physical characteristics to serve as in vivo reporters, but with minimized diffusion from the point of injection. These particles, called microworms, have a cylindrical shape coated with a biocompatible porous membrane that possesses a large surface-area-to-volume ratio while maintaining a large hydrodynamic radius. We use these microworms to create fluorescent sodium sensors for use as in vivo sodium concentration detectors after subcutaneous injection. However, the microworm concept has the potential to extend to the immobilization of other types of polymers for continuous physiological detection or delivery of molecules.
Successful respiratory immunization with dry powder live-attenuated measles virus vaccine in rhesus macaques
Authors: Lin Wen-Hsuan , Griffin Diane E. , Rota Paul A. , Papania Mark , Cape Stephen P. , Bennett David , Quinn Brian , Sievers Robert E. , Shermer Charles , Powell Kenneth , Adams Robert J. , Godin Steven , Winston Scott
Published: February 2011

Measles remains an important cause of childhood mortality worldwide. Sustained high vaccination coverage is the key to preventing measles deaths. Because measles vaccine is delivered by injection, hurdles to high coverage include the need for trained medical personnel and a cold chain, waste of vaccine in multidose vials and risks associated with needle use and disposal. Respiratory vaccine delivery could lower these barriers and facilitate sustained high coverage. We developed a novel single unit dose, dry powder live-attenuated measles vaccine (MVDP) for respiratory delivery without reconstitution. We tested the immunogenicity and protective efficacy in rhesus macaques of one dose of MVDP delivered either with a mask or directly intranasal with two dry powder inhalers, PuffHaler and BD Solovent. MVDP induced robust measles virus (MeV)-specific humoral and T-cell responses, without adverse effects, which completely protected the macaques from infection with wild-type MeV more than one year later. Respiratory delivery of MVDP was safe and effective and could aid in measles control.
Substantial expression of mature elastin in arterial constructs
Authors: Lee Kee-Won , Stolz Donna B. , Wang Yadong
Published: February 2011

Mature elastin synthesis is a key challenge in arterial tissue engineering. Most engineered vessels lack elastic fibers in the medial layer and those present are poorly organized. The objective of this study is to increase mature elastin synthesis in small-diameter arterial constructs. Adult primary baboon smooth muscle cells (SMCs) were seeded in the lumen of porous tubular scaffolds fabricated from a biodegradable elastomer, poly(glycerol sebacate) (PGS) and cultured in a pulsatile flow bioreactor for 3 wk. We tested the effect of pore sizes on construct properties by histological, biochemical, and mechanical evaluations. Histological analysis revealed circumferentially organized extracellular matrix proteins including elastin and the presence of multilayered SMCs expressing calponin and α-smooth muscle actin. Biochemical analysis demonstrated that the constructs contained mature elastin equivalent to 19% of the native arteries. Mechanical tests indicated that the constructs could withstand up to 200 mmHg burst pressure and exhibited compliance comparable to native arteries. These results show that nontransfected cells in PGS scaffolds in unsupplemented medium produced a substantial amount of mature elastin within 3 wk and the elastic fibers had similar orientation as those in native arteries. The 25–32 μm pore size supported cell organization and elastin synthesis more than larger pore sizes. To our knowledge, there was no prior report of the synthesis of mature and organized elastin in arterial constructs without exogenous factors or viral transduction.
Simple and elegant design of a virion egress structure in Archaea
Authors: Quax Tessa E. F. , Lucas Soizick , Reimann Julia , Pehau-Arnaudet Gerard , Prevost Marie-Christine , Forterre Patrick , Albers Sonja-Verena , Prangishvili David
Published: February 2011

Some viruses of Archaea use an unusual egress mechanism that involves the formation of virus-associated pyramids (VAPs) on the host cell surface. At the end of the infection cycle, these structures open outward and create apertures through which mature virions escape from the cell. Here we describe in detail the structure and composition of VAPs formed by the
Sulfolobus islandicus
rod-shaped virus 2 (SIRV2) in cells of its hyperthermophilic archaeal host. We show that the VAPs are stable and autonomous assemblies that can be isolated from membranes of infected cells and purified without affecting their structure. The purified VAPs are heterogeneous in size, reflecting the dynamics of VAP development in a population of infected cells; however, they have a uniform geometry, consisting of seven isosceles triangular faces forming a baseless pyramid. Biochemical and immunoelectron microscopy analyses revealed that the 10-kDa P98 protein encoded by the SIRV2 virus is the sole component of the VAPs. The VAPs were produced in
Sulfolobus acidocaldarius
and
Escherichia coli
by heterologous expression of the SIRV2-P98 gene. The results confirm that P98 is the only constituent of the VAPs and demonstrate that no other viral protein is involved in the assembly of pyramids. P98 was able to produce stable structures under conditions ranging from moderate to extremely high temperatures (80 °C) and from neutral to extremely acidic pH (pH 2), demonstrating another remarkable property of this exceptional viral protein.
Chemical storage of hydrogen in few-layer graphene
Authors: Subrahmanyam K. S. , Kumar Prashant , Maitra Urmimala , Govindaraj A. , Hembram K. P. S. S. , Waghmare Umesh V. , Rao C. N. R.
Published: February 2011

Birch reduction of few-layer graphene samples gives rise to hydrogenated samples containing up to 5 wt % of hydrogen. Spectroscopic studies reveal the presence of sp
3
C-H bonds in the hydrogenated graphenes. They, however, decompose readily on heating to 500 °C or on irradiation with UV or laser radiation releasing all the hydrogen, thereby demonstrating the possible use of few-layer graphene for chemical storage of hydrogen. First-principles calculations throw light on the mechanism of dehydrogenation that appears to involve a significant reconstruction and relaxation of the lattice.
Angiogenic sprouting into neural tissue requires Gpr124, an orphan G protein-coupled receptor
Authors: Anderson Keith D. , Pan Li , Yang Xiao-man , Hughes Virginia C. , Walls Johnathon R. , Dominguez Melissa G. , Simmons Mary V. , Burfeind Patricia , Xue Yingzi , Wei Yi , Macdonald Lynn E. , Thurston Gavin , Daly Christopher , Lin Hsin Chieh , Economides Aris N. , Valenzuela David M. , Murphy Andrew J. , Yancopoulos George D. , Gale Nicholas W.
Published: February 2011

The vasculature of the CNS is structurally and functionally distinct from that of other organ systems and is particularly prone to developmental abnormalities and hemorrhage. Although other embryonic tissues undergo primary vascularization, the developing nervous system is unique in that it is secondarily vascularized by sprouting angiogenesis from a surrounding perineural plexus. This sprouting angiogenesis requires the TGF-β and Wnt pathways because ablation of these pathways results in aberrant sprouting and hemorrhage. We have genetically deleted Gpr124, a member of the large family of long N-terminal group B G protein-coupled receptors, few members of which have identified ligands or well-defined biologic functions in mammals. We show that, in the developing CNS, Gpr124 is specifically expressed in the vasculature and is absolutely required for proper angiogenic sprouting into the developing neural tube. Embryos lacking Gpr124 exhibit vascular defects characterized by delayed vascular penetration, formation of pathological glomeruloid tufts within the CNS, and hemorrhage. In addition, they display defects in palate and lung development, two processes in which TGF-β and/or Wnt pathways also play important roles. We also show that TGF-β stimulates Gpr124 expression, and ablation of Gpr124 results in perturbed TGF-β pathway activation, suggesting roles for Gpr124 in modulating TGF-β signaling. These results represent a unique function attributed to a long N-terminal group B–type G protein-coupled receptor in a mammalian system.
Distinct progenitors for B-1 and B-2 cells are present in adult mouse spleen
Authors: Ghosn Eliver Eid Bou , Sadate-Ngatchou Patricia , Yang Yang , Herzenberg Leonard A. , Herzenberg Leonore A.
Published: February 2011

Recent studies by Dorshkind, Yoder, and colleagues show that embryonic (E9) B-cell progenitors located in the yolk sac and intraembryonic hemogenic endothelium before the initiation of circulation give rise to B-1 and marginal zone B cells but do not give rise to B-2 cells. In studies here, we confirm and extend these findings by showing that distinct progenitors for B-1 and B-2 cells are present in the adult spleen. Furthermore, we show that the splenic B-cell progenitor population (lin
–
CD19
+
/B220
lo/−
/CD43
–
) that gives rise to B-1 cells is likely to be heterogeneous because, in some recipients, it also gives rise to B cells expressing the marginal zone phenotype (B220
hi
IgM
hi
IgD
lo
CD21
hi
) and to some (CD19
–
CD5
hi
) T cells. In addition to the well-known function differences between B-1 and B-2, our studies demonstrate that substantial developmental differences separate these B-cell lineages. Thus, consistent with the known dependence of B-2 development on IL-7, all B-2 progenitors express IL-7R. However, >30% of the B-1 progenitors do not express this marker, enabling the known IL-7 independent development of B-1 cells in IL-7
−/−
mice. In addition, marker expression on cells in the early stages of the B-2 development pathway (CD19
–
/c-Kit
lo/−
/Sca-1
lo/−
) in adult bone marrow distinguish it from the early stages of B-1 development (CD19
hi
/c-Kit
+
/Sca-1
+
), which occur constitutively in neonates. In adults, in vivo inflammatory stimulation (LPS) triggers B-1 progenitors in spleen to expand and initiate development along this B-1 developmental pathway.
The death domain kinase RIP1 links the immunoregulatory CD40 receptor to apoptotic signaling in carcinomas
Authors: Knox Pauline G. , Davies Clare C. , Ioannou Marina , Eliopoulos Aristides G.
Published: February 2011

CD40, a tumor necrosis factor (TNF) receptor family member, is widely recognized for its prominent role in the antitumor immune response. The immunostimulatory effects of CD40 ligation on malignant cells can be switched to apoptosis upon disruption of survival signals transduced by the binding of the adaptor protein TRAF6 to CD40. Apoptosis induction requires a TRAF2-interacting CD40 motif but is initiated within a cytosolic death-inducing signaling complex after mobilization of receptor-bound TRAF2 to the cytoplasm. We demonstrate that receptor-interacting protein 1 (RIP1) is an integral component of this complex and is required for CD40 ligand-induced caspase-8 activation and tumor cell killing. Degradation of the RIP1 K63 ubiquitin ligases cIAP1/2 amplifies the CD40-mediated cytotoxic effect, whereas inhibition of CYLD, a RIP1 K63 deubiquitinating enzyme, reduces it. This two-step mechanism of apoptosis induction expands our appreciation of commonalities in apoptosis regulatory pathways across the TNF receptor superfamily and provides a telling example of how TNF family receptors usurp alternative programs to fulfill distinct cellular functions.
Bone marrow CD169+ macrophages promote the retention of hematopoietic stem and progenitor cells in the mesenchymal stem cell niche
Authors: Chow Andrew , Lucas Daniel , Hidalgo Andrés , Méndez-Ferrer Simón , Hashimoto Daigo , Scheiermann Christoph , Battista Michela , Leboeuf Marylene , Prophete Colette , van Rooijen Nico , Tanaka Masato , Merad Miriam , Frenette Paul S.
Published: February 2011

Hematopoietic stem cells (HSCs) reside in specialized bone marrow (BM) niches regulated by the sympathetic nervous system (SNS). Here, we have examined whether mononuclear phagocytes modulate the HSC niche. We defined three populations of BM mononuclear phagocytes that include Gr-1hi monocytes (MOs), Gr-1lo MOs, and macrophages (MΦ) based on differential expression of Gr-1, CD115, F4/80, and CD169. Using MO and MΦ conditional depletion models, we found that reductions in BM mononuclear phagocytes led to reduced BM CXCL12 levels, the selective down-regulation of HSC retention genes in Nestin+ niche cells, and egress of HSCs/progenitors to the bloodstream. Furthermore, specific depletion of CD169+ MΦ, which spares BM MOs, was sufficient to induce HSC/progenitor egress. MΦ depletion also enhanced mobilization induced by a CXCR4 antagonist or granulocyte colony-stimulating factor. These results highlight two antagonistic, tightly balanced pathways that regulate maintenance of HSCs/progenitors in the niche during homeostasis, in which MΦ cross talk with the Nestin+ niche cell promotes retention, and in contrast, SNS signals enhance egress. Thus, strategies that target BM MΦ hold the potential to augment stem cell yields in patients that mobilize HSCs/progenitors poorly.
Expression of the G-CSF receptor in monocytic cells is sufficient to mediate hematopoietic progenitor mobilization by G-CSF in mice
Authors: Christopher Matthew J. , Rao Mahil , Liu Fulu , Woloszynek Jill R. , Link Daniel C.
Published: February 2011

Granulocyte colony-stimulating factor (G-CSF), the prototypical mobilizing cytokine, induces hematopoietic stem and progenitor cell (HSPC) mobilization from the bone marrow in a cell-nonautonomous fashion. This process is mediated, in part, through suppression of osteoblasts and disruption of CXCR4/CXCL12 signaling. The cellular targets of G-CSF that initiate the mobilization cascade have not been identified. We use mixed G-CSF receptor (G-CSFR)–deficient bone marrow chimeras to show that G-CSF–induced mobilization of HSPCs correlates poorly with the number of wild-type neutrophils. We generated transgenic mice in which expression of the G-CSFR is restricted to cells of the monocytic lineage. G-CSF–induced HSPC mobilization, osteoblast suppression, and inhibition of CXCL12 expression in the bone marrow of these transgenic mice are intact, demonstrating that G-CSFR signals in monocytic cells are sufficient to induce HSPC mobilization. Moreover, G-CSF treatment of wild-type mice is associated with marked loss of monocytic cells in the bone marrow. Finally, we show that bone marrow macrophages produce factors that support the growth and/or survival of osteoblasts in vitro. Together, these data suggest a model in which G-CSFR signals in bone marrow monocytic cells inhibit the production of trophic factors required for osteoblast lineage cell maintenance, ultimately leading to HSPC mobilization.
Mitochondrial reactive oxygen species promote production of proinflammatory cytokines and are elevated in TNFR1-associated periodic syndrome (TRAPS)
Authors: Bulua Ariel C. , Simon Anna , Maddipati Ravikanth , Pelletier Martin , Park Heiyoung , Kim Kye-Young , Sack Michael N. , Kastner Daniel L. , Siegel Richard M.
Published: February 2011

Reactive oxygen species (ROS) have an established role in inflammation and host defense, as they kill intracellular bacteria and have been shown to activate the NLRP3 inflammasome. Here, we find that ROS generated by mitochondrial respiration are important for normal lipopolysaccharide (LPS)-driven production of several proinflammatory cytokines and for the enhanced responsiveness to LPS seen in cells from patients with tumor necrosis factor receptor-associated periodic syndrome (TRAPS), an autoinflammatory disorder caused by missense mutations in the type 1 TNF receptor (TNFR1). We find elevated baseline ROS in both mouse embryonic fibroblasts and human immune cells harboring TRAPS-associated TNFR1 mutations. A variety of antioxidants dampen LPS-induced MAPK phosphorylation and inflammatory cytokine production. However, gp91phox and p22phox reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits are dispensable for inflammatory cytokine production, indicating that NADPH oxidases are not the source of proinflammatory ROS. TNFR1 mutant cells exhibit altered mitochondrial function with enhanced oxidative capacity and mitochondrial ROS generation, and pharmacological blockade of mitochondrial ROS efficiently reduces inflammatory cytokine production after LPS stimulation in cells from TRAPS patients and healthy controls. These findings suggest that mitochondrial ROS may be a novel therapeutic target for TRAPS and other inflammatory diseases.
Management of Botrytis Leaf Blight of Onion: The Québec Experience of 20 Years of Continual Improvement
Authors: Carisse Odile , Tremblay David-Mathieu , McDonald Mary Ruth , Brodeur Luc , McRoberts Neil
Published: February 2011

Botrytis leaf blight (BLB) of onion (Allium cepa) is caused by Botrytis squamosa. The disease has been reported on onion crops in several of the onion production areas of the world including North and South America, Europe, Asia, and Australia, although it is not a problem in arid production regions such as the western United States. In eastern Canada, the disease is generally present every year and is especially severe on cultivars of yellow globe onion. The pathogen biology and disease epidemiology have been intensively researched. Over the last few decades, in the organic soil area of Quebec, extensive research effort has been devoted to the development and evaluation of predictive models and disease management strategies. There has been an active integrated pest management program for onions since the early 1980s, and scouting for disease has played a major role in disease management. In this article, the story of BLB management in eastern Canada over a period of two decades is summarized.
Radiation Exposure of the Anesthesiologist in the Neurointerventional Suite
Authors: Anastasian Zirka H. , Strozyk Dorothea , Meyers Philip M. , Wang Shuang , Berman Mitchell F.
Published: February 2011

Background

Scatter radiation during interventional radiology procedures can produce cataracts in participating medical personnel. Standard safety equipment for the radiologist includes eye protection. The typical configuration of fluoroscopy equipment directs radiation scatter away from the radiologist and toward the anesthesiologist. This study analyzed facial radiation exposure of the anesthesiologist during interventional neuroradiology procedures.

Methods

Radiation exposure to the forehead of the anesthesiologist and radiologist was measured during 31 adult neuroradiologic procedures involving the head or neck. Variables hypothesized to affect anesthesiologist exposure were recorded for each procedure. These included total radiation emitted by fluoroscopic equipment, radiologist exposure, number of pharmacologic interventions performed by the anesthesiologist, and other variables.

Results

Radiation exposure to the anesthesiologist's face averaged 6.5 ± 5.4 μSv per interventional procedure. This exposure was more than 6-fold greater (P < 0.0005) than for noninterventional angiographic procedures (1.0 ± 1.0) and averaged more than 3-fold the exposure of the radiologist (ratio, 3.2; 95% CI, 1.8-4.5). Multiple linear regression analysis showed that the exposure of the anesthesiologist was correlated with the number of pharmacologic interventions performed by the anesthesiologist and the total exposure of the radiologist.

Conclusions

Current guidelines for occupational radiation exposure to the eye are undergoing review and are likely to be lowered below the current 100-150 mSv/yr limit. Anesthesiologists who spend significant time in neurointerventional radiology suites may have ocular radiation exposure approaching that of a radiologist. To ensure parity with safety standards adopted by radiologists, these anesthesiologists should wear protective eyewear.
Monitoring of Vital Signs for Long-Term Survival of Mice under Anesthesia: FIGURE 1.
Authors: Ewald Andrew J. , Werb Zena , Egeblad Mikala
Published: February 2011

INTRODUCTION

Anesthesia protocols for mice have been optimized, as described here, to achieve long-term imaging (up to 40 h) and facilitate survival through careful monitoring of the mice during anesthesia. Isoflurane anesthesia is the preferred method, because it can be adjusted quickly as needed during the experiment. Critical for the long survival times under anesthesia is the use of the lowest possible dose of anesthesia, which is identified by corneal reflex and monitoring of breath and heart rate, blood-oxygenation levels, and vascular distension using an oximeter probe. It is critical that the carrier gas for isoflurane is humidified. In addition, it is essential to keep mice warm and to compensate for loss of fluid by supplementing with saline. Alternative approaches rely on injectable anesthetics, which do not require dedicated equipment or high-ventilation rates in the imaging room. However, injectable anesthetics are harder to dose for image sessions of >6-10 h.
Optical Coherence Tomography Imaging of Early Quail Embryos
Authors: Gu Shi , Jenkins Michael W. , Watanabe Michiko , Rollins Andrew M.
Published: February 2011

INTRODUCTION

Congenital heart defects (CHDs) affect thousands of newborns each year in the United States. Recent research using animal model systems indicates that the abnormal function of the early tubular heart precedes structural defects such as septal defects. Optical coherence tomography (OCT) is an imaging modality that can provide high spatial and temporal resolution to study both the structure and the function of the tubular heart. With technical advances in OCT imaging speed, especially with frequency domain OCT and image-based retrospective gating, it is now possible to image a beating avian embryonic heart in three dimensions under physiological conditions and follow morphogenesis over critical periods of developmental time. These technological advances have already revealed novel aspects of heart development. By expanding our understanding of heart development, research using OCT technology combined with other imaging modalities may eventually lead to strategies to predict, treat, and even prevent CHDs. This protocol provides some practical details for obtaining four-dimensional (4D) OCT images from beating embryonic quail hearts, with the necessary temporal and spatial resolution.
Induction of an Immune Response for Imaging Antigen-Presenting Cell/T–Cell Interactions
Authors: Matheu Melanie P. , Cahalan Michael D. , Parker Ian
Published: February 2011

INTRODUCTION

Activated dendritic cells (DCs) are the most efficient antigen-presenting cells (APCs) in the immune system. This protocol describes three different methods to activate antigen-specific CD4+ T cells using (i) bone-marrow-derived DCs, (ii) endogenous dermal DCs that drain to the local lymph node (LN), and (iii) tissue-resident APCs in a delayed-type hypersensitivity (DTH) response.
Labeling Lysosomes in Live Cells with LysoTracker
Authors: Chazotte Brad
Published: February 2011

INTRODUCTION

The LysoTracker probes (Invitrogen/Molecular Probes) are used to label lysosomes in live cells, as described in this protocol. They are more selective for acidic organelles than the classically used neutral red or acridine orange dyes. They are freely membrane permeant at neutral pH and effectively label lysosomes at nanomolar concentrations, with ~50 nM being optimal for selectivity. It has been reported that in larger acidic compartments, the staining pattern is preserved even after fixation with aldehydes. LysoTracker dyes can be visualized at different wavelengths, so they are useful when multiple fluorescent dyes are used to label cells simultaneously.
Apoplastic Alkalinization Is Instrumental for the Inhibition of Cell Elongation in the Arabidopsis Root by the Ethylene Precursor 1-Aminocyclopropane-1-Carboxylic Acid
Authors: Staal Marten , De Cnodder Tinne , Simon Damien , Vandenbussche Filip , Van Der Straeten Dominique , Verbelen Jean-Pierre , Elzenga Theo , Vissenberg Kris
Published: February 2011

In Arabidopsis (Arabidopsis thaliana; Columbia-0) roots, the so-called zone of cell elongation comprises two clearly different domains: the transition zone, a postmeristematic region (approximately 200–450 μm proximal of the root tip) with a low rate of elongation, and a fast elongation zone, the adjacent proximal region (450 μm away from the root tip up to the first root hair) with a high rate of elongation. In this study, the surface pH was measured in both zones using the microelectrode ion flux estimation technique. The surface pH is highest in the apical part of the transition zone and is lowest at the basal part of the fast elongation zone. Fast cell elongation is inhibited within minutes by the ethylene precursor 1-aminocyclopropane-1-carboxylic acid; concomitantly, apoplastic alkalinization occurs in the affected root zone. Fusicoccin, an activator of the plasma membrane H+-ATPase, can partially rescue this inhibition of cell elongation, whereas the inhibitor N,N′-dicyclohexylcarbodiimide does not further reduce the maximal cell length. Microelectrode ion flux estimation experiments with auxin mutants lead to the final conclusion that control of the activity state of plasma membrane H+-ATPases is one of the mechanisms by which ethylene, via auxin, affects the final cell length in the root.