bluuebunny/crossref_metadata_2025 huggingface dataset:
Stabilisation of a short α‐helical VIP fragment by side chain to side chain cyclisation: a comparison of common cyclisation motifs by circular dichroism
Authors: Frankiewicz Lukasz , Betti Cecilia , Guillemyn Karel , Tourwé Dirk , Jacquot Yves , Ballet Steven
Published: May 2013

A model octapeptide segment derived from vasoactive intestinal peptide (VIP) was utilised to investigate the effect of several conventional cyclisation methods on the α‐helical conformation in short peptide fragments. Three of the classical macrocyclisation techniques (i.e. lactamisation, ring‐closing metathesis and Huisgen cycloaddition) were applied, and the conformations of the resulting cyclic peptides, as well as their linear precursors, were compared by CD analysis. The visibly higher folding propensity of the triazole‐tethered peptide after azide‐alkyne CuAAC macrocyclisation illustrates that the secondary structure of a short peptide fragment can differ significantly depending on the chemical strategy used to covalently cross‐link side chain residues in a ‘helical’ fragment. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.
Conformation of gramicidin A in Triton X‐100 micelles from CD and FTIR data: a clean example of antiparallel double β5.6 helix formation
Authors: Sychev Sergei V. , Barsukov Leonid I. , Ivanov Vadim T.
Published: May 2013

The linear peptide gramicidin A (gA) forms prototypical ion channels specific for monovalent cations and has been extensively used to study the organization and dynamics of membrane channels. This polymorphic peptide can adopt two different types of structures, the helical dimer β6.3 (‘channel state’) and the double helical structure with two intertwined monomers. The structure of gA in micelles of detergent Triton X‐100 has been studied using CD, Fourier transform infrared, and fluorescence spectroscopy. The results obtained demonstrate that only one thermodynamically stable gA structure, the antiparallel left‐handed double helix β5.6, is formed in this membrane‐mimetic environment. The position of the tryptophan fluorescence maximum at 332 nm is the same as that in phospholipid membranes. The causative factors governing the double helix formation in the micellar medium are discussed on the basis of known physicochemical properties of Triton X‐100. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.
Onwards or Homewards? Complex Graduate Migration Pathways, Well‐being, and the ‘Parental Safety Net’
Authors: Sage Joanna , Evandrou Maria , Falkingham Jane
Published: May 2013

Pre‐existing literatures on post‐student migration have mainly focused on inter‐regional flows of young educated migrants, the attendant redistribution of human capital around the UK, and the impact on local and regional economies. This paper argues that the parochial focus on labour‐motivated graduate migration (usually to first employment), and the absence of data enabling individual migration histories to be traced longitudinally across the post‐student phase of the lifecourse, has masked the complexity of the patterns and processes of migration in this social group. Drawing upon recently collected primary data from a retrospective survey of the migration histories of a cohort of students who left the University of Southampton (UK) between 2001 and 2007, this paper reveals that post‐student migration trajectories are complex and precarious across the 5‐year period after leaving university. During this prolonged period of instability, the parental home (and parental support more generally) provides a crucial safety net. This begs questions about the impacts of post‐student transitions to financial and residential independence on the resources and intergenerational care exchange frameworks of contemporary mid‐life parents (terms such as ‘sandwich generation’ and ‘pivot generation’ refer to the multiple family roles and responsibilities of mid‐life parents who are caught between meeting the needs of their adult children and their ageing parents). It is suggested that the well‐being agenda in migration studies is helpful for refocusing the lens of enquiry on the impacts of return migration to the parental home on graduate migrants, their families, and the potential trade‐offs that might occur between generations. Copyright © 2013 John Wiley & Sons, Ltd.
What Makes New Grandparents Satisfied with Their Lives?
Authors: Ben Shlomo Shirley
Published: May 2013

The study examined the contribution of sociodemographic characteristics, perceived stress, and cognitive appraisals of grandparenthood to life satisfaction among new grandparents. The theoretical framework was Lazarus and Folkman's stress and coping model and the positive psychology approach. The sample consisted of 246 Israeli grandparents (aged 42–72 years) who completed a set of questionnaires 3–24 months after the birth of their first grandchild. The results showed that higher levels of life satisfaction were associated with younger age of grandparents, higher levels of physical health and economic status, and lower grandparent distress. Moreover, maternal grandparents reported higher appraisals of challenge and threat than did paternal grandparents, and grandfathers reported a higher perception of dysfunctional interaction with the grandchild than did grandmothers. Most importantly, the participants' cognitive appraisals were found to moderate the perceptions of stress generated by the birth of a first grandchild. The study highlights the need for preventive interventions aimed at promoting factors that can empower new grandparents who have difficulty coping with their new role. Copyright © 2013 John Wiley & Sons, Ltd.
Brief report: Musashi1-eGFP mice, a new tool for differential isolation of the intestinal stem cell populations
Authors: Maria Cambuli Francesca , Rezza Amélie , Nadjar Julien , Plateroti Michelina
Published: May 2013

The intestinal epithelium self-renews rapidly and continuously throughout life, due to the presence of crypt stem cells. Two pools of these cells have been identified in the small intestine, which differ in position (“+4” or the bottom of the crypts), expression of specific markers (Bmi1/mTert or Lgr5/Ascl2), and cell cycle characteristics. Interestingly, the RNA-binding protein Musashi1 is expressed in both populations and therefore a potential marker for both stem cell types. In order to locate, isolate, and study Musashi1-expressing cells within the intestinal epithelium, we generated transgenic mice expressing GFP fluorescent protein under the control of a 7-kb Msi1 promoter. The expression pattern of GFP in the intestinal crypts of both small and large intestines completely overlapped that of Musashi1, validating our model. By using fluorescence-activated cell sorting, cellular, and molecular analyses, we showed that GFP-positive Msi1-expressing cells are divided into two major pools corresponding to the Lgr5- and mTert-expressing stem cells. Interestingly, monitoring the cell cycle activity of the two sorted populations reveals that they are both actively cycling, although differences in cell cycle length were confirmed. Altogether, our new reporter mouse model based upon Musashi1 expression is a useful tool to isolate and study stem cells of the intestinal epithelium. Moreover, these mice uniquely enable the concomitant study of two pools of intestinal stem cells within the same animal model.
Somatic loss of p53 leads to stem/progenitor cell amplification in both mammary epithelial compartments, basal and luminal
Authors: Chiche Aurélie , Moumen Mejdi , Petit Valérie , Jonkers Jos , Medina Daniel , Deugnier Marie-Ange , Faraldo Marisa M. , Glukhova Marina A.
Published: May 2013

Mammary epithelium comprises a layer of luminal cells and a basal myoepithelial cell layer. Both mammary epithelial compartments, basal and luminal, contain stem and progenitor cells, but only basal cells are capable of gland regeneration upon transplantation. Aberrant expansion of stem/progenitor cell populations is considered to contribute to breast tumorigenesis. Germline deletions of p53 in humans and mice confer a predisposition to tumors, and stem cell frequency is abnormally high in the mammary epithelium of p53-deficient mice. However, it is unknown whether stem/progenitor cell amplification occurs in both, basal and luminal cell populations in p53-deficient mammary tissue. We used a conditional gene deletion approach to study the role of p53 in stem/progenitor cells residing in the mammary luminal and basal layers. Using two- and three-dimensional cell culture assays, we showed that p53 loss led to the expansion of clonogenic stem/progenitor cells in both mammary epithelial cell layers. Moreover, following p53 deletion, luminal and basal stem/progenitor cells acquired a capacity for unlimited propagation in mammosphere culture. Furthermore, limiting dilution and serial transplantation assays revealed amplification and enhanced self-renewal in the basal regenerating cell population of p53-deficient mammary epithelium. Our data suggest that the increase in stem/progenitor cell activity may be, at least, partially mediated by the Notch pathway. Taken together, these results strongly indicate that p53 restricts the propagation and self-renewal of stem/progenitor cells in both layers of the mammary epithelium providing further insight into the impact of p53 loss in breast cancerogenesis.
High throughput screening for inhibitors of REST in neural derivatives of human embryonic stem cells reveals a chemical compound that promotes expression of neuronal genes
Authors: Charbord Jérémie , Poydenot Pauline , Bonnefond Caroline , Feyeux Maxime , Casagrande Fabrice , Brinon Benjamin , Francelle Laetitia , Aurégan Gwenaelle , Guillermier Martine , Cailleret Michel , Viegas Pedro , Nicoleau Camille , Martinat Cécile , Brouillet Emmanuel , Cattaneo Elena , Peschanski Marc , Lechuga Marc , Perrier Anselme L.
Published: May 2013

Decreased expression of neuronal genes such as brain-derived neurotrophic factor (BDNF) is associated with several neurological disorders. One molecular mechanism associated with Huntington disease (HD) is a discrete increase in the nuclear activity of the transcriptional repressor REST/NRSF binding to repressor element-1 (RE1) sequences. High-throughput screening of a library of 6,984 compounds with luciferase-assay measuring REST activity in neural derivatives of human embryonic stem cells led to identify two benzoimidazole-5-carboxamide derivatives that inhibited REST silencing in a RE1-dependent manner. The most potent compound, X5050, targeted REST degradation, but neither REST expression, RNA splicing nor binding to RE1 sequence. Differential transcriptomic analysis revealed the upregulation of neuronal genes targeted by REST in wild-type neural cells treated with X5050. This activity was confirmed in neural cells produced from human induced pluripotent stem cells derived from a HD patient. Acute intraventricular delivery of X5050 increased the expressions of BDNF and several other REST-regulated genes in the prefrontal cortex of mice with quinolinate-induced striatal lesions. This study demonstrates that the use of pluripotent stem cell derivatives can represent a crucial step toward the identification of pharmacological compounds with therapeutic potential in neurological affections involving decreased expression of neuronal genes associated to increased REST activity, such as Huntington disease.
An epigenetic signature of developmental potential in neural stem cells and early neurons
Authors: Burney Matthew J. , Johnston Caroline , Wong Kee-Yew , Teng Siaw-Wei , Beglopoulos Vassilios , Stanton Lawrence W , Williams Brenda P , Bithell Angela , Buckley Noel J.
Published: May 2013

A cardinal property of neural stem cells (NSCs) is their ability to adopt multiple fates upon differentiation. The epigenome is widely seen as a read-out of cellular potential and a manifestation of this can be seen in embryonic stem cells (ESCs), where promoters of many lineage-specific regulators are marked by a bivalent epigenetic signature comprising trimethylation of both lysine 4 and lysine 27 of histone H3 (H3K4me3 and H3K27me3, respectively). Bivalency has subsequently emerged as a powerful epigenetic indicator of stem cell potential. Here, we have interrogated the epigenome during differentiation of ESC-derived NSCs to immature GABAergic interneurons. We show that developmental transitions are accompanied by loss of bivalency at many promoters in line with their increasing developmental restriction from pluripotent ESC through multipotent NSC to committed GABAergic interneuron. At the NSC stage, the promoters of genes encoding many transcriptional regulators required for differentiation of multiple neuronal subtypes and neural crest appear to be bivalent, consistent with the broad developmental potential of NSCs. Upon differentiation to GABAergic neurons, all non-GABAergic promoters resolve to H3K27me3 monovalency, whereas GABAergic promoters resolve to H3K4me3 monovalency or retain bivalency. Importantly, many of these epigenetic changes occur before any corresponding changes in gene expression. Intriguingly, another group of gene promoters gain bivalency as NSCs differentiate toward neurons, the majority of which are associated with functions connected with maturation and establishment and maintenance of connectivity. These data show that bivalency provides a dynamic epigenetic signature of developmental potential in both NSCs and in early neurons.
TNF, acting through inducibly expressed TNFR2, drives activation and cell cycle entry of c-Kit+ cardiac stem cells in ischemic heart disease
Authors: Al-Lamki Rafia S. , Lu Wanhua , Wang Jun , Yang Jun , Sargeant Timothy J. , Wells Richard , Suo Chenqu , Wright Penny , Goddard Martin , Huang Qunhua , Lebastchi Amir H. , Tellides George , Huang Yingqun , Min Wang , Pober Jordan S. , Bradley John R.
Published: May 2013

TNF, signaling through TNFR2, has been implicated in tissue repair, a process that in the heart may be mediated by activated resident cardiac stem cells (CSCs). The objective of our study is to determine whether ligation of TNFR2 can induce activation of resident CSCs in the setting of ischemic cardiac injury. We show that in human cardiac tissue affected by ischemia heart disease (IHD), TNFR2 is expressed on intrinsic CSCs, identified as c-kit+/CD45−/VEGFR2− interstitial round cells, which are activated as determined by entry to cell cycle and expression of Lin-28. Wild-type mouse heart organ cultures subjected to hypoxic conditions both increase cardiac TNF expression and show induced TNFR2 and Lin-28 expression in c-kit+ CSCs that have entered cell cycle. These CSC responses are enhanced by exogenous TNF. TNFR2−/− mouse heart organ cultures subjected to hypoxia increase cardiac TNF but fail to induce CSC activation. Similarly, c-kit+ CSCs isolated from mouse hearts exposed to hypoxia or TNF show induction of Lin-28, TNFR2, cell cycle entry, and cardiogenic marker, α-sarcomeric actin (α-SA), responses more pronounced by hypoxia in combination with TNF. Knockdown of Lin-28 by siRNA results in reduced levels of TNFR2 expression, cell cycle entry, and diminished expression of α-SA. We conclude that hypoxia-induced c-kit+ CSC activation is mediated by TNF/TNFR2/Lin-28 signaling. These observations suggest that TNFR2 signaling in resident c-kit+ CSCs induces cardiac repair, findings which provide further understanding of the unanticipated harmful effects of TNF blockade in human IHD.
Expression levels of endoglin distinctively identify hematopoietic and endothelial progeny at different stages of yolk sac hematopoiesis
Authors: Borges Luciene , Iacovino Michelina , Koyano-Nakagawa Naoko , Baik June , Garry Daniel J. , Kyba Michael , Perlingeiro Rita C. R.
Published: May 2013

Endoglin (Eng), an ancillary receptor of the transforming growth factor beta (TGFβ) signaling pathway superfamily, has been well recognized for its important function in vascular development and angiogenesis since its discovery more than a decade ago. Recent studies show that this receptor is also critical for the emergence of blood during embryonic development, and that at E7.5, endoglin together with Flk-1 identifies early mesoderm progenitors that are endowed with hematopoietic and endothelial potential. These two lineages emerge in very close association during embryogenesis, and because they share the expression of the same surface markers, it has been difficult to distinguish the earliest hematopoietic from endothelial cells. Here, we evaluated the function of endoglin in hematopoiesis as development progresses past E7.5, and found that the hematopoietic and endothelial progenitors can be distinguished by the levels of endoglin in E9.5 yolk sacs. Whereas endothelial cells are Engbright, hematopoietic activity is primarily restricted to a subset of cells that display dim expression of endoglin (Engdim). Molecular characterization of these subfractions showed that endoglin-mediated induction of hematopoiesis occurs in concert with BMP2/BMP4 signaling. This pathway is highly active in Engdim cells but significantly downregulated in the Eng knockout. Taken together, our findings show an important function for endoglin in mediating BMP2/BMP4 signaling during yolk sac hematopoietic development and suggest that the levels of this receptor modulate TGFβ versus bone morphogenetic protein (BMP) signaling.
Parallel assessment of globin lentiviral transfer in induced pluripotent stem cells and adult hematopoietic stem cells derived from the same transplanted β-thalassemia patient
Authors: Tubsuwan Alisa , Abed Soumeya , Deichmann Annette , Kardel Melanie D. , Bartholomä Cynthia , Cheung Alice , Negre Olivier , Kadri Zahra , Fucharoen Suthat , Kalle Christof , Payen Emmanuel , Chrétien Stany , Schmidt Manfred , Eaves Connie J. , Leboulch Philippe , Maouche-Chrétien Leïla
Published: May 2013

A patient with βE/β0-thalassemia major was converted to transfusion-independence 4.5 years ago by lentiviral gene transfer in hematopoietic stem cells while showing a myeloid-biased cell clone. Induced pluripotent stem cells (iPSCs) are a potential alternative source of hematopoietic stem cells. If fetal to adult globin class, switching does not occur in vivo in iPSC-derived erythroid cells, β-globin gene transfer would be unnecessary. To investigate both vector integration skewing and the potential use of iPSCs for the treatment of thalassemia, we derived iPSCs from the thalassemia gene therapy patient and compared iPSC-derived hematopoietic cells to their natural isogenic somatic counterparts. In NSG immunodeficient mice, embryonic to fetal and a partial fetal to adult globin class switching were observed, indicating that the gene transfer is likely necessary for iPSC-based therapy of the β-hemoglobinopathies. Lentivector integration occurred in regions of low and high genotoxicity. Surprisingly, common integration sites (CIS) were identified across those iPSCs and cells retrieved from isogenic and nonisogenic gene therapy patients with β-thalassemia and adrenoleukodystrophy, respectively. This suggests that CIS observed in the absence of overt tumorigenesis result from nonrandom lentiviral integration rather than oncogenic in vivo selection. These findings bring the use of iPSCs closer to practicality and further clarify our interpretation of genome-wide lentivector integration.
Polycomb group gene Ezh2 regulates mammary gland morphogenesis and maintains the luminal progenitor pool
Authors: Michalak Ewa Malgorzata , Nacerddine Karim , Pietersen Alexandra , Beuger Vincent , Pawlitzky Inka , Cornelissen-Steijger Paulien , Wientjens Ellen , Tanger Ellen , Seibler Jost , van Lohuizen Maarten , Jonkers Jos
Published: May 2013

Specification of the cellular hierarchy in the mammary gland involves complex signaling that remains poorly defined. Polycomb group proteins are known to contribute to the maintenance of stem cell identity through epigenetic modifications, leading to stable alterations in gene expression. The polycomb protein family member EZH2 is known to be important for stem cell maintenance in multiple tissues, but its role in mammary gland development and differentiation remains unknown. Our analyses show that EZH2 is predominantly expressed in luminal cells of the mouse mammary epithelium. As mammary gland development occurs mostly after birth, the analysis of EZH2 gene function in postnatal development is precluded by embryonic lethality of conventional EZH2 knockout mice. To investigate the role of EZH2 in normal mammary gland epithelium, we have generated novel transgenic mice that express doxycycline-regulatable short hairpin (sh) RNAs directed against Ezh2. Knockdown of EZH2 results in delayed outgrowth of the mammary epithelium during puberty, due to impaired terminal end bud formation and ductal elongation. Furthermore, our results demonstrate that EZH2 is required to maintain the luminal cell pool and may limit differentiation of luminal progenitors into CD61+ differentiated luminal cells, suggesting a role for EZH2 in mammary luminal cell fate determination. Consistent with this, EZH2 knockdown reduced lobuloalveolar expansion during pregnancy, suggesting EZH2 is required for the differentiation of luminal progenitors to alveolar cells.Stem Cells  2013;31:1910-1920
Lgr4 regulates mammary gland development and stem cell activity through the pluripotency transcription factor Sox2
Authors: Wang Ying , Dong Jie , Li Dali , Lai Li , Siwko Stefan , Li Yi , Liu Mingyao
Published: May 2013

The key signaling networks regulating mammary stem cells are poorly defined. The leucine-rich repeat containing G protein-coupled receptor (Lgr) family has been implicated in intestinal, gastric, and epidermal stem cell functions. We investigated whether Lgr4 functions in mammary gland development and mammary stem cells. We found that Lgr4−/− mice had delayed ductal development, fewer terminal end buds, and decreased side-branching. Crucially, the mammary stem cell repopulation capacity was severely impaired. Mammospheres from Lgr4−/− mice showed decreased Wnt signaling. Wnt3a treatment prevented the adverse effects of Lgr4 loss on organoid formation. Chromatin immunoprecipitation analysis indicated that Sox2 expression was controlled by the Lgr4/Wnt/β-catenin/Lef1 pathway. Importantly, Sox2 overexpression restored the in vivo mammary regeneration potential of Lgr4−/− mammary stem cells. Therefore, Lgr4 activates Sox2 to regulate mammary development and stem cell functions via Wnt/β-catenin/Lef1.
Isolated fetal pyelectasis and the risk of Down syndrome: a meta‐analysis
Authors: Orzechowski K. M. , Berghella V.
Published: May 2013

Objectives

We performed a meta‐analysis to examine the performance of second‐trimester (14–24 weeks' gestation) isolated fetal pyelectasis as a marker for trisomy 21 and to calculate its associated weighted pooled likelihood ratios.

Methods

PubMed, Ovid MEDLINE and Cochrane databases were searched using the terms ‘pyelectasis’ and ‘pelviectasis’. Studies were included if fetuses with isolated pyelectasis were reported separately from fetuses with other soft markers of aneuploidy and/or structural anomalies and if knowledge of the fetal karyotype was unknown at the time of ultrasound examination.

Results

Individual study statistics were pooled as weighted positive and negative likelihood ratios with 95% CIs, using a random‐effects model. Ten observational studies were included (2148 cases of isolated pyelectasis). Isolated fetal pyelectasis was defined in seven out of 10 studies as a renal pelvis anteroposterior diameter of ≥ 4 mm. Isolated fetal pyelectasis was associated with pooled positive and negative likelihood ratios of 2.78 (95% CI, 1.75–4.43) and 0.99 (95% CI, 0.98–1.00), respectively.

Conclusions

The detection of isolated fetal pyelectasis on mid‐trimester ultrasound is associated with an increased likelihood of trisomy 21. If the finding of isolated fetal pyelectasis is used to adjust the trisomy 21 risk from maternal serum screening tests, a positive likelihood ratio of 2.78 should be used in the calculation. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd.
Asymptotic analysis of multi‐branch EGC and SC over equally correlated Rician channels
Authors: Liu Shuo , Song Xuegui , Cheng Julian , Beaulieu Norman C.
Published: May 2013

Closed‐form asymptotic expressions for bit error rate and outage probability are derived for multi‐branch equal gain combining and selection combining receiver diversity over equally correlated Rician channels. Numerical results indicate that these analytical solutions can provide accurate estimation of bit error rate and outage probability in large signal‐to‐noise ratio regimes. The analytical results reveal some important insights into the performance characteristics of equal gain combining and selection combining diversity operating over equally correlated Rician fading channels. Copyright © 2013 John Wiley & Sons, Ltd.
Syntheses and Characterization of o‐Carboranes Containing Fused exo‐Polyhedral Di‐ and Triboraheterocycles
Authors: Nie Yong , Miao Jinling , Wadepohl Hubert , Pritzkow Hans , Oeser Thomas , Siebert Walter
Published: May 2013

Reaction of dilithio‐o‐carborane Li2C2B10H10 (generated in situ from o‐carborane 1 and butyllithium) with the 1, 2‐diborylbenzene derivative 1, 2‐C6H4(iPr2NBCl)2 yielded the o‐carborane compound 3 having the fused exo‐polyhedral C2B2C2 heterocycle. The analogous reactions with 1, 1‐bis(dimethylaminochloroboryl)ethane and with 1, 3‐dichloro‐1, 2,3‐tris(dimethylamino)triborane(5) afforded the o‐carborane compounds 5 and 7 containing the fused exo‐polyhedral five‐membered C2B2C and C2B3 rings, respectively. Attempts to use 1, 2‐dichloro‐1, 2‐bis(dimethylamino)diborane(4) for the synthesis of the o‐carborane compound 10 with a fused exo‐polyhedral C2B2 ring instead led to the diborane(4)yl‐o‐carborane species 9c and 9d (the latter in trace amount), which contain a diborane(4)yl moiety bonded to the o‐carborane. The molecular compositions of the new o‐carborane derivatives follow from NMR spectroscopic and mass spectrometric data as well as from X‐ray diffraction analyses of 3, 7 and 9c. The structures exhibit weak intramolecular C–H···H–B hydrogen‐hydrogen interactions.
Disproportionation of O‐Benzylhydroxylamine Catalyzed by a Ferric Bis‐Picket Fence Porphyrin Complex
Authors: McQuarters Ashley B. , Goodrich Lauren E. , Goodrich Claire M. , Lehnert Nicolai
Published: May 2013

Hydroxylamine (NH2OH) is an important molecule in biology that serves as an intermediate in the nitrogen cycle, and that can also be utilized as a nitric oxide donor in mammals under certain conditions. In light of this, the interaction of NH2OH with hemes in proteins and model systems has gained much attention recently. In this study, we use the more stable, oxygen substituted O‐benzylhydroxylamine (NH2OBn) as a model for NH2OH. Here, the reactivity of the ferric bis‐picket fence porphyrin complexes [Fe(3, 5‐Me‐BAFP)(ClO4)] (1) and [Fe(3, 5‐Me‐BAFP)(PF6)] (2) (3,5‐Me‐BAFP2– = dianion of tetra(2, 6‐bis(3,5‐dimethylphenoxy)phenyl)porphyrin)) with NH2OBn is investigated. The product of these reactions is characterized by UV/Vis and EPR spectroscopy and X‐ray crystallography. We found that addition of excess NH2OBn to our ferric porphyrin complexes results in reduction of the heme to the ferrous oxidation state. This is followed by disproportionation of additional NH2OBn to yield the ferrous complex [Fe(3,5‐Me‐BAFP)(NH3)2] (3) as the final product. The crystal structure of (3) constitutes the first structural characterization of a bis‐ammonia complex of a ferrous heme. The stability of this complex may be facilitated by the picket fences of the porphyrin ligand used here.
First‐Principles Investigations of the Structural, Vibrational and Thermochemical Properties of Barium Cerate – Another Test Case for Density‐Functional Theory
Authors: Stoffel Ralf Peter , Dronskowski Richard
Published: May 2013

The structural, vibrational and thermodynamic properties of barium cerate, BaCeO3, were investigated by means of density‐functional theory, phonon calculations based on the ab initio force‐constant method and the quasi‐harmonic approximation. Examinations of structural issues confirmed the temperature‐dependent crystal structures described in the latest literature despite arriving at somewhat lower transition temperatures. Thermochemical data such as the constant‐pressure heat capacity Cp, the entropy S and the standard enthalpy of formation ΔHf were also confirmed with only little deviation from the experiment.
RbCN3H4 and CsCN3H4: A Neutron Powder and Single‐­Crystal X‐ray Diffraction Study
Authors: Hoepfner Veronika , Jacobs Philipp , Sawinski Peter Klaus , Houben Andreas , Reim Johannes , Dronskowski Richard
Published: May 2013

Rubidium guanidinate, RbCN3H4, is the first example of a new class of compounds containing the unsubstituted guanidinate anion CN3H4–. While the first crystal‐structure determination was based on powder X‐ray diffraction, neutron powder and single‐crystal X‐ray diffraction have now been utilized to improve the previous structural model, in particular with respect to experimentally localizing the hydrogen positions, which were so far derived from density‐functional calculations. Furthermore, the molecular structure of the guanidinate anion at room temperature has been refined. All anisotropic displacement parameters, including those of the hydrogen atoms, have been derived from the neutron powder diffraction data, but no rigid‐body movement of the guanidinate anion is present. Additionally, we report the synthesis and structural data of CsCN3H4 crystallizing in the RbCN3H4 type.
Synthesis, Characterization, and X‐ray Crystal Structures of (Diphosphine)Ni(dmit) and (Diphosphine)Ni(dmio) (Diphosphine = dppv, dppb) Complexes
Authors: Li Yu‐Long , Zou Li‐Ke , Xie Bin , Lin Xiao , Zhu Sha‐Sha
Published: May 2013

Four complexes with the ligands dmit and dmio were synthesized. Reaction of (PhCO)2(dmit) and (PhCO)2(dmio) with MeONa afforded the intermediates 2‐thioxo‐1,3‐dithiole‐4,5‐dithiolate dianion and 2‐oxo‐1,3‐dithiole‐4,5‐dithiolate dianion, respectively. Reaction of the two dianions with (diphosphine)NiCl2 [diphosphine = (Z)‐1, 2‐bis(diphenylphosphanyl)ethane (dppv), 1,2‐bis(diphenylphosphanyl)benzene (dppb)] gave (dppv)Ni(dmit) (1), (dppb)Ni(dmit) (2), (dppv)Ni(dmio) (3), and (dppb)Ni(dmio) (4). This synthesis route was found to be an efficient pathway to prepare dmit and dmio ligand complexes. Complexes, 1–4 were fully characterized by elemental analysis and IR, 1H NMR, 13C NMR, and 31P NMR spectroscopy. In addition, the molecular structures of 1, 3 and 4 were established by X‐ray diffraction.
Enlargement of Nanoemulsion Region in Pseudo‐ternary Mixing Diagrams for a Drug Delivery System
Authors: Wang Ziheng , Pal Rajinder
Published: May 2013

The purpose of this research was to develop the pseudo‐ternary mixing diagrams for a potential drug delivery system consisting of vitamin E (potential drug) + soybean oil + surfactant + co‐surfactant (anhydrous glycerol) + water. The potential drug (vitamin E) was loaded in the oil phase. The effects of different surfactants (pure and mixed) on the mixing diagrams, especially on the nanoemulsion region, were investigated. The influence of the drug loading level on the mixing diagrams was also determined. The surfactants studied were polyethoxylated (20) sorbitan monolaurate, polyethoxylated (20) sorbitan monooleate, polyethoxylated (35) castor oil and their mixtures. The size (area) of the nanoemulsion region of the mixing diagrams was found to be dependent on the type of surfactant used and the loading level of the drug (vitamin E).
Enzymatic characterization of an active NDH complex from Thermosynechococcus elongatus
Authors: Hu Peng , Lv Jing , Fu Pengcheng , Hualing Mi
Published: May 2013

Although type‐1 NAD(P)H dehydrogenase (NDH) complex subunit constituents and physiological functions have been reported in plants and cyanobacteria, the biochemical properties of this enzyme are not clear. We used chromatographic isolation to purify and characterize a NADPH‐active NDH from the cyanobacterium Thermosynechococcus elongatus. Ferredoxin (Fd) and ferredoxin‐NADP+ oxidoreductase (FNR) were co‐eluted with NDH, implying the electron donation from NADPH to NDH via the interaction with FNR. We investigated the enzymatic properties of the complex. Furthermore, the activity is competitively inhibited by rotenone, suggesting that it possesses a quinone binding site, similar to mitochondria complex I.
Sexual minority status and psychotic symptoms: findings from the Netherlands Mental Health Survey and Incidence Studies (NEMESIS)
Authors: Gevonden M. J. , Selten J. P. , Myin-Germeys I. , de Graaf R. , ten Have M. , van Dorsselaer S. , van Os J. , Veling W.
Published: May 2013

Background

Ethnic minority position is associated with increased risk for psychotic outcomes, which may be mediated by experiences of social exclusion, defeat and discrimination. Sexual minorities are subject to similar stressors. The aim of this study is to examine whether sexual minorities are at increased risk for psychotic symptoms and to explore mediating pathways.

Method

A cross-sectional survey was performed assessing cumulative incidence of psychotic symptoms with the Composite International Diagnostic Interview in two separate random general population samples (NEMESIS-1 and NEMESIS-2). Participants were sexually active and aged 18–64 years (n = 5927, n = 5308). Being lesbian, gay or bisexual (LGB) was defined as having sexual relations with at least one same-sex partner during the past year. Lifetime experience of any psychotic symptom was analysed using logistic regression, adjusted for gender, educational level, urbanicity, foreign-born parents, living without a partner, cannabis use and other drug use.

Results

The rate of any psychotic symptom was elevated in the LGB population as compared with the heterosexual population both in NEMESIS-1 [odds ratio (OR) 2.56, 95% confidence interval (CI) 1.71–3.84] and NEMESIS-2 (OR 2.30, 95% CI 1.42–3.71). Childhood trauma, bullying and experience of discrimination partly mediated the association.

Conclusions

The finding that LGB orientation is associated with psychotic symptoms adds to the growing body of literature linking minority status with psychosis and other mental health problems, and suggests that exposure to minority stress represents an important mechanism.
Aurora B spatially regulates EB3 phosphorylation to coordinate daughter cell adhesion with cytokinesis
Authors: Ferreira Jorge G. , Pereira António J. , Akhmanova Anna , Maiato Helder
Published: May 2013

During mitosis, human cells round up, decreasing their adhesion to extracellular substrates. This must be quickly reestablished by poorly understood cytoskeleton remodeling mechanisms that prevent detachment from epithelia, while ensuring the successful completion of cytokinesis. Here we show that the microtubule end-binding (EB) proteins EB1 and EB3 play temporally distinct roles throughout cell division. Whereas EB1 was involved in spindle orientation before anaphase, EB3 was required for stabilization of focal adhesions and coordinated daughter cell spreading during mitotic exit. Additionally, EB3 promoted midbody microtubule stability and, consequently, midbody stabilization necessary for efficient cytokinesis. Importantly, daughter cell adhesion and cytokinesis completion were spatially regulated by distinct states of EB3 phosphorylation on serine 176 by Aurora B. This EB3 phosphorylation was enriched at the midbody and shown to control cortical microtubule growth. These findings uncover differential roles of EB proteins and explain the importance of an Aurora B phosphorylation gradient for the spatiotemporal regulation of microtubule function during mitotic exit and cytokinesis.
The interaction between CtIP and BRCA1 is not essential for resection-mediated DNA repair or tumor suppression
Authors: Reczek Colleen R. , Szabolcs Matthias , Stark Jeremy M. , Ludwig Thomas , Baer Richard
Published: May 2013

The CtIP protein facilitates homology-directed repair (HDR) of double-strand DNA breaks (DSBs) by initiating DNA resection, a process in which DSB ends are converted into 3′-ssDNA overhangs. The BRCA1 tumor suppressor, which interacts with CtIP in a phospho-dependent manner, has also been implicated in DSB repair through the HDR pathway. It was recently reported that the BRCA1–CtIP interaction is essential for HDR in chicken DT40 cells. To examine the role of this interaction in mammalian cells, we generated cells and mice that express Ctip polypeptides (Ctip-S326A) that fail to bind BRCA1. Surprisingly, isogenic lines of Ctip-S326A mutant and wild-type cells displayed comparable levels of HDR function and chromosomal stability. Although Ctip-S326A mutant cells were modestly sensitive to topoisomerase inhibitors, mice expressing Ctip-S326A polypeptides developed normally and did not exhibit a predisposition to cancer. Thus, in mammals, the phospho-dependent BRCA1–CtIP interaction is not essential for HDR-mediated DSB repair or for tumor suppression.
Alpha Yap: Cadherins hold it all together
Authors: Sedwick Caitlin
Published: May 2013

Yap is interested in how cadherins influence the cytoskeleton—and vice versa.
A model of lysosomal pH regulation
Authors: Ishida Yoichi , Nayak Smita , Mindell Joseph A. , Grabe Michael
Published: May 2013

Lysosomes must maintain an acidic luminal pH to activate hydrolytic enzymes and degrade internalized macromolecules. Acidification requires the vacuolar-type H+-ATPase to pump protons into the lumen and a counterion flux to neutralize the membrane potential created by proton accumulation. Early experiments suggested that the counterion was chloride, and more recently a pathway consistent with the ClC-7 Cl–/H+ antiporter was identified. However, reports that the steady-state luminal pH is unaffected in ClC-7 knockout mice raise questions regarding the identity of the carrier and the counterion. Here, we measure the current–voltage characteristics of a mammalian ClC-7 antiporter, and we use its transport properties, together with other key ion regulating elements, to construct a mathematical model of lysosomal pH regulation. We show that results of in vitro lysosome experiments can only be explained by the presence of ClC-7, and that ClC-7 promotes greater acidification than Cl–, K+, or Na+ channels. Our models predict strikingly different lysosomal K+ dynamics depending on the major counterion pathways. However, given the lack of experimental data concerning acidification in vivo, the model cannot definitively rule out any given mechanism, but the model does provide concrete predictions for additional experiments that would clarify the identity of the counterion and its carrier.
External pH modulates EAG superfamily K+ channels through EAG-specific acidic residues in the voltage sensor
Authors: Kazmierczak Marcin , Zhang Xiaofei , Chen Bihan , Mulkey Daniel K. , Shi Yingtang , Wagner Paul G. , Pivaroff-Ward Kendra , Sassic Jessica K. , Bayliss Douglas A. , Jegla Timothy
Published: May 2013

The Ether-a-go-go (EAG) superfamily of voltage-gated K+ channels consists of three functionally distinct gene families (Eag, Elk, and Erg) encoding a diverse set of low-threshold K+ currents that regulate excitability in neurons and muscle. Previous studies indicate that external acidification inhibits activation of three EAG superfamily K+ channels, Kv10.1 (Eag1), Kv11.1 (Erg1), and Kv12.1 (Elk1). We show here that Kv10.2, Kv12.2, and Kv12.3 are similarly inhibited by external protons, suggesting that high sensitivity to physiological pH changes is a general property of EAG superfamily channels. External acidification depolarizes the conductance–voltage (GV) curves of these channels, reducing low threshold activation. We explored the mechanism of this high pH sensitivity in Kv12.1, Kv10.2, and Kv11.1. We first examined the role of acidic voltage sensor residues that mediate divalent cation block of voltage activation in EAG superfamily channels because protons reduce the sensitivity of Kv12.1 to Zn2+. Low pH similarly reduces Mg2+ sensitivity of Kv10.1, and we found that the pH sensitivity of Kv11.1 was greatly attenuated at 1 mM Ca2+. Individual neutralizations of a pair of EAG-specific acidic residues that have previously been implicated in divalent block of diverse EAG superfamily channels greatly reduced the pH response in Kv12.1, Kv10.2, and Kv11.1. Our results therefore suggest a common mechanism for pH-sensitive voltage activation in EAG superfamily channels. The EAG-specific acidic residues may form the proton-binding site or alternatively are required to hold the voltage sensor in a pH-sensitive conformation. The high pH sensitivity of EAG superfamily channels suggests that they could contribute to pH-sensitive K+ currents observed in vivo.
Phosphoinositides alter lipid bilayer properties
Authors: Rusinova Radda , Hobart E. Ashley , Koeppe Roger E. , Andersen Olaf S.
Published: May 2013

Phosphatidylinositol-4,5-bisphosphate (PIP2), which constitutes ∼1% of the plasma membrane phospholipid, plays a key role in membrane-delimited signaling. PIP2 regulates structurally and functionally diverse membrane proteins, including voltage- and ligand-gated ion channels, inwardly rectifying ion channels, transporters, and receptors. In some cases, the regulation is known to involve specific lipid–protein interactions, but the mechanisms by which PIP2 regulates many of its various targets remain to be fully elucidated. Because many PIP2 targets are membrane-spanning proteins, we explored whether the phosphoinositides might alter bilayer physical properties such as curvature and elasticity, which would alter the equilibrium between membrane protein conformational states—and thereby protein function. Taking advantage of the gramicidin A (gA) channels’ sensitivity to changes in lipid bilayer properties, we used gA-based fluorescence quenching and single-channel assays to examine the effects of long-chain PIP2s (brain PIP2, which is predominantly 1-stearyl-2-arachidonyl-PIP2, and dioleoyl-PIP2) on bilayer properties. When premixed with dioleoyl-phosphocholine at 2 mol %, both long-chain PIP2s produced similar changes in gA channel function (bilayer properties); when applied through the aqueous solution, however, brain PIP2 was a more potent modifier than dioleoyl-PIP2. Given the widespread use of short-chain dioctanoyl-phosphoinositides, we also examined the effects of diC8-phosphoinositol (PI), PI(4,5)P2, PI(3,5)P2, PI(3,4)P2, and PI(3,4,5)P3. The diC8 phosphoinositides, except for PI(3,5)P2, altered bilayer properties with potencies that decreased with increasing head group charge. Nonphosphoinositide diC8 phospholipids generally were more potent bilayer modifiers than the polyphosphoinositides. These results show that physiological increases or decreases in plasma membrane PIP2 levels, as a result of activation of PI kinases or phosphatases, are likely to alter lipid bilayer properties, in addition to any other effects they may have. The results further show that exogenous PIP2, as well as structural analogues that differ in acyl chain length or phosphorylation state, alters lipid bilayer properties at the concentrations used in many cell physiological experiments.
Inferring subunit stoichiometry from single molecule photobleaching
Authors: Hines Keegan E.
Published: May 2013

Single molecule photobleaching is a powerful tool for determining the stoichiometry of protein complexes. By attaching fluorophores to proteins of interest, the number of associated subunits in a complex can be deduced by imaging single molecules and counting fluorophore photobleaching steps. Because some bleaching steps might be unobserved, the ensemble of steps will be binomially distributed. In this work, it is shown that inferring the true composition of a complex from such data is nontrivial because binomially distributed observations present an ill-posed inference problem. That is, a unique and optimal estimate of the relevant parameters cannot be extracted from the observations. Because of this, a method has not been firmly established to quantify confidence when using this technique. This paper presents a general inference model for interpreting such data and provides methods for accurately estimating parameter confidence. The formalization and methods presented here provide a rigorous analytical basis for this pervasive experimental tool.
Measuring technical efficiency of dairy farms with imprecise data: a fuzzy data envelopment analysis approach
Authors: Mugera Amin W.
Published: May 2013

This article integrates fuzzy set theory in the data envelopment analysis (DEA) framework to compute technical efficiency scores when input and output data are imprecise. The underlying assumption in conventional DEA is that input and output data are measured with precision. However, production agriculture takes place in an uncertain environment, and, in some situations, input and output data may be imprecise. We present an approach of measuring efficiency when data are known to lie within specified intervals and empirically illustrate this approach using a group of 29 dairy producers in Pennsylvania. Compared to the conventional DEA scores that are point estimates, the computed fuzzy efficiency scores are interval bound allowing the decision maker to trace the performance of a decision‐making unit at different possibility levels.
Influence of rice black streaked dwarf virus on the ecological fitness of non‐vector planthopper Nilaparvata lugens (Hemiptera: Delphacidae)
Authors: Xu Hong‐Xing , He Xiao‐Chan , Zheng Xu‐Song , Yang Ya‐Jun , Lu Zhong‐Xian
Published: May 2013

Rice black streak dwarf virus (RBSDV) is transmitted by the small brown planthopper (SBPH), Laodelphax striatellus (Fallen). Non‐vector rice brown planthopper (BPH), Nilaparvata lugens (Stål), shares the same host rice plants with SBPH in paddy fields. The changes in nutritional composition of rice plants infected by RBSDV and the ecological fitness of BPH feeding on the infected plants were studied under both artificial climate chamber and field conditions. Contents of 16 detected amino acids and soluble sugar in RBSDV infected rice plants were higher than those in the healthy ones. On the diseased plants BPH had significantly higher nymphal survival rates, nymphal duration of the males, weight of the female adults, as well as egg hatchability compared to BPH being fed on healthy plants. However, there was no obvious difference in female nymph duration, longevity and fecundity. Defense enzymes (superoxidase dismutase, SOD and catalase, CAT) and detoxifying enzymes (carboxylesterase, CAE and glutathione S‐transferase, GST) in BPH adults fed on diseased plants had markedly higher activities. The results indicate rice plants infected by RBSDV improved the ecological fitness of the brown planthopper, a serious pest but not a transmitter of the RBSDV virus.