This feature article introduces our recent work on understanding the roles played by citrate and poly(vinyl pyrrolidone) (PVP) as capping agents in seed-mediated syntheses of Ag nanocrystals with controlled shapes. We have demonstrated that citrate and PVP selectively bind to Ag(111) and Ag(100) surfaces, respectively, and thus favor the formation of Ag nanocrystals enclosed preferentially by {111} or {100} facets. In addition, we have quantified the coverage density of PVP adsorbed on the surface of Ag nanocubes. On the basis of the mechanistic understanding, a series of Ag nanocrystals with controlled shapes and sizes have been successfully synthesized by using different combinations of seeds and capping agents: single-crystal spherical/cubic seeds with citrate for cuboctahedrons and octahedrons or with PVP for cubes and bars and plate-like seeds with citrate for enlarged thin plates or with PVP for thickened plates.
Degeneration of the dopaminergic nigrostriatal system and of noradrenergic neurons in the locus coeruleus are important pathological features of Parkinson’s disease. There is an urgent need to develop therapies that slow down the progression of neurodegeneration in Parkinson’s disease. In the present study, we tested whether the highly specific metabotropic glutamate receptor 5 antagonist, 3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine, reduces dopaminergic and noradrenergic neuronal loss in monkeys rendered parkinsonian by chronic treatment with low doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Weekly intramuscular 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine injections (0.2–0.5 mg/kg body weight), in combination with daily administration of 3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine or vehicle, were performed until the development of parkinsonian motor symptoms in either of the two experimental groups (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine versus 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/vehicle). After 21 weeks of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine treatment, all 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/vehicle-treated animals displayed parkinsonian symptoms, whereas none of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine-treated monkeys were significantly affected. These behavioural observations were consistent with in vivo positron emission tomography dopamine transporter imaging data, and with post-mortem stereological counts of midbrain dopaminergic neurons, as well as striatal intensity measurements of dopamine transporter and tyrosine hydroxylase immunoreactivity, which were all significantly higher in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine-treated animals than in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/vehicle-treated monkeys. The 3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine treatment also had a significant effect on the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced loss of norepinephrine neurons in the locus coeruleus and adjoining A5 and A7 noradrenaline cell groups. In 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/vehicle-treated animals, almost 40% loss of tyrosine hydroxylase-positive norepinephrine neurons was found in locus coeruleus/A5/A7 noradrenaline cell groups, whereas the extent of neuronal loss was lower than 15% of control values in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine-treated monkeys. Our data demonstrate that chronic treatment with the metabotropic glutamate receptor 5 antagonist, 3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine, significantly reduces 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity towards dopaminergic and noradrenergic cell groups in non-human primates. This suggests that the use of metabotropic glutamate receptor 5 antagonists may be a useful strategy to reduce degeneration of catecholaminergic neurons in Parkinson’s disease.
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Sheng Li;
Scott W. Tighe;
Charles M. Nicolet;
Deborah Grove;
Shawn Levy;
William Farmerie;
Agnes Viale;
Chris Wright;
Peter A. Schweitzer;
Yuan Gao;
Dewey Kim;
Joe Boland;
Belynda Hicks;
Ryan Kim;
Sagar Chhangawala;
Nadereh Jafari;
Nalini Raghavachari;
Jorge Gandara;
Natalia Garcia-Reyero;
Cynthia Hendrickson;
David Roberson;
Jeffrey Rosenfeld;
Todd Smith;
Jason G. Underwood;
Dongmei Wang;
Paul Zumbo;
Don A. Baldwin;
George S. Grills;
Christopher E. Mason
High-throughput RNA sequencing (RNA-seq) greatly expands the potential for genomics discoveries, but the wide variety of platforms, protocols and performance capabilitites has created the need for comprehensive reference data. Here we describe the Association of Biomolecular Resource Facilities next-generation sequencing (ABRF-NGS) study on RNA-seq. We carried out replicate experiments across 15 laboratory sites using reference RNA standards to test four protocols (poly-A-selected, ribo-depleted, size-selected and degraded) on five sequencing platforms (Illumina HiSeq, Life Technologies PGM and Proton, Pacific Biosciences RS and Roche 454). The results show high intraplatform (Spearman rank R > 0.86) and inter-platform (R > 0.83) concordance for expression measures across the deep-count platforms, but highly variable efficiency and cost for splice junction and variant detection between all platforms. For intact RNA, gene expression profiles from rRNA-depletion and poly-A enrichment are similar. In addition, rRNA depletion enables effective analysis of degraded RNA samples. This study provides a broad foundation for cross-platform standardization, evaluation and improvement of RNA-seq.
Background: Macrophages are ubiquitous in all stages of atherosclerosis, exerting tremendous impact on lesion progression and plaque stability. Because macrophages in atherosclerotic plaques express angiotensin-converting enzyme (ACE), current dogma posits that local myeloid-mediated effects worsen the disease. In contrast, we previously reported that myeloid ACE overexpression augments macrophage resistance to various immune challenges, including tumors, bacterial infection and Alzheimer's plaque deposition. Here, we sought to assess the impact of myeloid ACE on atherosclerosis. Methods: A mouse model in which ACE is overexpressed in myelomonocytic lineage cells, called ACE10, was generated and sequentially crossed with ApoE-deficient mice to create ACE10/10ApoE−/− (ACE10/ApoE). Control mice were ACEWT/WTApoE−/− (WT/ApoE). Atherosclerosis was induced using an atherogenic diet alone, or in combination with unilateral nephrectomy plus deoxycorticosterone acetate (DOCA) salt for eight weeks. Results: With an atherogenic diet alone or in combination with DOCA, the ACE10/ApoE mice showed significantly less atherosclerotic plaques compared to their WT/ApoE counterparts (p < 0.01). When recipient ApoE−/− mice were reconstituted with ACE10/10 bone marrow, these mice showed significantly reduced lesion areas compared to recipients reconstituted with wild type bone marrow. Furthermore, transfer of ACE-deficient bone marrow had no impact on lesion area. Conclusion: Our data indicate that while myeloid ACE may not be required for atherosclerosis, enhanced ACE expression paradoxically reduced disease progression.
Cross-modal correspondences refer to associations between apparently unrelated stimulus features in different senses. For example, high and low auditory pitches are associated with high and low visual elevations, respectively. Here we examined how this crossmodal correspondence between visual elevation and auditory pitch relates to auditory elevation. We used audiovisual combinations of high- or low-frequency bursts of white noise and a visual stimulus comprising a white circle. Auditory and visual stimuli could each occur at high or low elevations. These multisensory stimuli could be congruent or incongruent for three correspondence types: cross-modal featural (auditory pitch/visual elevation), within-modal featural (auditory pitch/auditory elevation) and cross-modal spatial (auditory and visual elevation). Participants performed a 2AFC speeded classification (high or low) task while attending to auditory pitch, auditory elevation, or visual elevation. We tested for modulatory interactions between the three correspondence types. Modulatory interactions were absent when discriminating visual elevation. However, the within-modal featural correspondence affected the cross-modal featural correspondence during discrimination of auditory elevation and pitch, while the reverse modulation was observed only during discrimination of auditory pitch. The cross-modal spatial correspondence modulated the other two correspondences only when auditory elevation was being attended, was modulated by the cross-modal featural correspondence only during attention to auditory pitch, and was modulated by the within-modal featural correspondence while performing discrimination of either auditory elevation or pitch. We conclude that the cross-modal correspondence between auditory pitch and visual elevation interacts strongly with auditory elevation.
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Kento Kitada;
Steffen Daub;
Yahua Zhang;
Janet Klein;
Daisuke Nakano;
Tetyana Pedchenko;
Louise Lantier;
Lauren M. LaRocque;
Adriana Marton;
Patrick Neubert;
Agnes Schroeder;
Natalia Rakova;
Jonathan Jantsch;
Anna E. Dikalova;
Sergey I. Dikalov;
David Harrison;
Dominik N. Mueller;
Akira Nishiyama;
Manfred Rauh;
Raymond C. Harris;
Friedrich C. Luft;
David H. Wassermann;
Jeff Sands;
Jens Titze
Natriuretic regulation of extracellular fluid volume homeostasis includes suppression of the renin-angiotensin-aldosterone system, pressure natriuresis, and reduced renal nerve activity, actions that concomitantly increase urinary Na+ excretion and lead to increased urine volume. The resulting natriuresis-driven diuretic water loss is assumed to control the extracellular volume. Here, we have demonstrated that urine concentration, and therefore regulation of water conservation, is an important control system for urine formation and extracellular volume homeostasis in mice and humans across various levels of salt intake. We observed that the renal concentration mechanism couples natriuresis with correspondent renal water reabsorption, limits natriuretic osmotic diuresis, and results in concurrent extracellular volume conservation and concentration of salt excreted into urine. This water-conserving mechanism of dietary salt excretion relies on urea transporter-driven urea recycling by the kidneys and on urea production by liver and skeletal muscle. The energy-intense nature of hepatic and extrahepatic urea osmolyte production for renal water conservation requires reprioritization of energy and substrate metabolism in liver and skeletal muscle, resulting in hepatic ketogenesis and glucocorticoid-driven muscle catabolism, which are prevented by increasing food intake. This natriuretic-ureotelic, water-conserving principle relies on metabolism-driven extracellular volume control and is regulated by concerted liver, muscle, and renal actions.
L-012, a luminol-based chemiluminescent (CL) probe, is widely used in vitro and in vivo to detect NADPH oxidase (Nox)-derived superoxide (O 2-) and identify Nox inhibitors. Yet understanding of the free radical chemistry of the L-012 probe is still lacking. We report that peroxidase and H2O2 induce superoxide dismutase (SOD)-sensitive, L-012-derived CL in the presence of oxygen. O2- alone does not react with L-012 to emit luminescence. Self-generated O2- during oxidation of L-012 and luminol analogs artifactually induce CL inhibitable by SOD. These aspects make assays based on luminol analogs less than ideal for specific detection and identification of O2- and NOX inhibitors.
Single-molecule experimentation has contributed significantly to our understanding of the mechanics of nucleoprotein complexes that regulate epigenetic switches. In this minireview, we will discuss the application of the tethered-particle motion technique, magnetic tweezers, and atomic force microscopy to (i) directly visualize and thermodynamically characterize DNA loops induced by the lac, gal, and λ repressors and (ii) understand the mechanistic role of DNA-supercoiling and DNA-bending cofactors in both prokaryotic and eukaryotic systems.
In order to produce specific complex structures from a large set of similar biochemical building blocks, many biochemical systems require high sensitivity to small molecular differences. The first and most common model used to explain this high specificity is kinetic proofreading, which has been extended to a variety of systems from detection of DNA mismatch to cell signaling processes. While the specification properties of kinetic proofreading models are well known and were studied in various contexts, very little is known about their temporal behavior. In this work, we study the dynamical properties of discrete stochastic two-branch kinetic proofreading schemes. Using the Laplace transform of the corresponding chemical master equation, we obtain an analytical solution for the completion time distribution. In particular we provide expressions for the specificity as well as the mean and variance of the process completion times. We also show that, for a wide range of parameters, a process distinguishing between two different products can be reduced to a much simpler three-point process. Our results allow for the systematic study of the interplay between specificity and completion times, as well as testing the validity of the kinetic proofreading model in biological systems.
Many biological cells/tissues sense the mechanical properties of their local environments via mechanoreceptors, proteins that can respond to forces like pressure or mechanical perturbations. Mechanoreceptors detect their stimuli and transmit signals via a great diversity of mechanisms. Some of the most common roles for mechanoreceptors are in neuronal responses, like touch and pain, or hair cells which function in balance and hearing. Mechanosensation is also important for cell types which are regularly exposed to shear stress such as endothelial cells, which line blood vessels, or blood cells which experience shear in normal circulation. Viscometers are devices that detect the viscosity of fluids.
Rotational viscometers may also be used to apply a known shear force to fluids. The ability of these instruments to introduce uniform shear to fluids has been exploited to study many biological fluids including blood and plasma. Viscometry may also be used to apply shear to the cells in a solution, and to test the effects of shear on specific ligand-receptor pairs. Here, we utilize cone-plate viscometry to test the effects of endogenous levels of shear stress on platelets treated with antibodies against the platelet mechanosensory receptor complex GPIb-IX.