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1
Chang, Chiao-Yun, Huei-Min Huang, Yu-Pin Lan, Tien-Chang Lu, Hao-Chung Kuo, Shing-Chung Wang, Li-Wei Tu et Wen-Feng Hsieh. « Growth and Characteristics of a-Plane GaN/ZnO/GaN Heterostructure ». MRS Proceedings 1538 (2013) : 303–7. http://dx.doi.org/10.1557/opl.2013.550.
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AbstractThe crystal structure of a-plane GaN/ZnO heterostructures on r-plane sapphire was investigated by using the XRD and TEM measurment. It was found the formation of (220) ZnGa2O4 and crystal orientation of semipolar (10$\bar 1$3) GaN at GaN/ZnO interface. The epitaxial relation of normal surface direction are the sapphire (1$\bar 1$02) // a-GaN (11$\bar 2$0) and ZnGa2O4 (220) // semi-polar GaN (10$\bar 1$$\bar 3$). Beside, the emission peak energy of ZnO appears shift about 60 meV in the GaN/ZnO/GaN heterostructures due to the re-crystallization of ZnO layer with Ga or N atom and the formation of the localized state.
2
Sun, Haoran, Yuhui Chen, Yuhao Ben, Hongping Zhang, Yujie Zhao, Zhihao Jin, Guoqi Li et Mei Zhou. « Influence of Low-Temperature Cap Layer Thickness on Luminescence Characteristics of Green InGaN/GaN Quantum Wells ». Materials 16, no 4 (13 février 2023) : 1558. http://dx.doi.org/10.3390/ma16041558.
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GaN cap layer with different thicknesses was grown on each InGaN well layer during MOCVD growth for InGaN/GaN multiple quantum well (MQW) samples to study the influence of the cap layer on the photoluminescence (PL) characteristics of MQWs. Through the temperature-dependent (TD) PL spectra, it was found that when the cap layer was too thick, the localized states of the quantum wells were relatively non-uniform. The thicker the well layer, the worse the uniformity of the localized states. Furthermore, through micro-area fluorescence imaging tests, it was found that when the cap layer was too thick, the luminescence quality of the quantum well was worse. In summary, the uniformity of the localized states in the quantum wells and the luminescence characteristics of the quantum wells could be improved when a relatively thin cap layer of the quantum well was prepared during the growth. These results could facilitate high efficiency QW preparation, especially for green LEDs.
3
Мохов, Е. Н., А. А. Вольфсон et О. П. Казарова. « Выращивание объёмных кристаллов AlN и GaN сублимационным сандвич-методом ». Физика твердого тела 61, no 12 (2019) : 2298. http://dx.doi.org/10.21883/ftt.2019.12.48537.17ks.
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The review of the results of growth of bulk Al and Ga nitride crystals on foreign substrates by the sublimation sandwich method (SSM) is presented. The kinetics and the mechanism of sublimation and condensation nitrides depending on the growth conditions, structure of the vapor phase, crystal orientation and the distance between the source and the seed are analyzed. It is experimentally established that by joint annealing of AlN and SiC the rate of AlN sublimation significantly increases due to formation of a liquid phase on the crystal surface. Non-uniform distribution of the liquid phase localized mainly near structural and morphological defects results in the selective nature of the surface etching, and also is the reason of deterioration of the growing crystal quality. The process of bulk AlN crystals growth with simultaneous evaporation of the seed allowing to grow crystals without cracks and with the improved parameters is realized. On SiC seeds bulk AlN crystals from 0.5 to 2 inch in diameter are grown.
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Ning, X. J., F. R. Chien, P. Pirouz, J. W. Yang et M. Asif Khan. « Growth defects in GaN films on sapphire : The probable origin of threading dislocations ». Journal of Materials Research 11, no 3 (mars 1996) : 580–92. http://dx.doi.org/10.1557/jmr.1996.0071.
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Single crystal GaN films with a wurtzite structure were grown on the basal plane of sapphire. A high density of threading dislocations parallel to the c-axis crossed the film from the interface to the film surface. They were found to have a predominantly edge character with a Burgers vector. In addition, dislocation hal-loops, elongated along the c-axis of GaN, were also found on the prism planes. These dislocations had a mostly screw character with a [0001] Burgers vector. Substrate surface steps with a height of were found to be accommodated by localized elastic bending of GaN (0001)GaN planes in the vicinity of the film/substrate interface. Observations show that the region of the film, with a thickness of ∼100 nm, adjacent to the interface is highly defective. This region is thought to correspond to the low-temperature GaN “buffer” layer which is initially grown on the sapphire substrate. Based on the experimental observations, a model for the formation of the majority threading dislocations in the film is proposed. The analysis of the results leads us to conclude that the film is under residual biaxial compression.
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Wang, C. K., Y. Z. Chiou et H. J. Chang. « Investigating the Efficiency Droop of Nitride-Based Blue LEDs with Different Quantum Barrier Growth Rates ». Crystals 9, no 12 (17 décembre 2019) : 677. http://dx.doi.org/10.3390/cryst9120677.
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In this study, GaN-based blue InGaN/GaN light-emitting diodes (LEDs) with different growth rates of the quantum barriers were fabricated and investigated. The LEDs with quantum barriers grown with a higher growth rate exhibit a lower leakage current and less non-radiative recombination centers in the multiple quantum wells (MQWs). Therefore, the LED with a higher barrier growth rate achieves a better light output power by 18.4% at 120 mA, which is attributed to weaker indium fluctuation effect in the QWs. On the other hand, the localized states created by indium fluctuation lead to a higher local carrier density, and Auger recombination in the QWs. Thus, the efficiency droop ratio of the LEDs with a higher barrier growth rate was only 28.6%, which was superior to that with a lower barrier growth rate (39.3%).
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Yan, Luyi, Feng Liang, Jing Yang, Ping Chen, Desheng Jiang et Degang Zhao. « The Influence Mechanism of Quantum Well Growth and Annealing Temperature on In Migration and Stress Modulation Behavior ». Nanomaterials 14, no 8 (18 avril 2024) : 703. http://dx.doi.org/10.3390/nano14080703.
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This study explores the effects of growth temperature of InGaN/GaN quantum well (QW) layers on indium migration, structural quality, and luminescence properties. It is found that within a specific range, the growth temperature can control the efficiency of In incorporation into QWs and strain energy accumulated in the QW structure, modulating the luminescence efficiency. Temperature-dependent photoluminescence (TDPL) measurements revealed a more pronounced localized state effect in QW samples grown at higher temperatures. Moreover, a too high annealing temperature will enhance indium migration, leading to an increased density of non-radiative recombination centers and a more pronounced quantum-confined Stark effect (QCSE), thereby reducing luminescence intensity. These findings highlight the critical role of thermal management in optimizing the performance of InGaN/GaN MQWs in LEDs and other photoelectronic devices.
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El Amrani, Mohammed, Julien Buckley, Thomas Kaltsounis, David Plaza Arguello, Hala El Rammouz, Daniel Alquier et Matthew Charles. « Study of Leakage Current Transport Mechanisms in Pseudo-Vertical GaN-on-Silicon Schottky Diode Grown by Localized Epitaxy ». Crystals 14, no 6 (14 juin 2024) : 553. http://dx.doi.org/10.3390/cryst14060553.
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In this work, a GaN-on-Si quasi-vertical Schottky diode was demonstrated on a locally grown n-GaN drift layer using Selective Area Growth (SAG). The diode achieved a current density of 2.5 kA/cm2, a specific on-resistance RON,sp of 1.9 mΩ cm2 despite the current crowding effect in quasi-vertical structures, and an on/off current ratio (Ion/Ioff) of 1010. Temperature-dependent current–voltage characteristics were measured in the range of 313–433 K to investigate the mechanisms of leakage conduction in the device. At near-zero bias, thermionic emission (TE) was found to dominate. By increasing up to 10 V, electrons gained enough energy to excite into trap states, leading to the dominance of Frenkel–Poole emission (FPE). For a higher voltage range (−10 V to −40 V), the increased electric field facilitated the hopping of electrons along the continuum threading dislocations in the “bulk” GaN layers, and thus, variable range hopping became the main mechanism for the whole temperature range. This work provides an in-depth insight into the leakage conduction transport on pseudo-vertical GaN-on-Si Schottky barrier diodes (SBDs) grown by localized epitaxy.
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Savini, G., M. I. Heggie, C. P. Ewels, N. Martsinovich, R. Jones et A. T. Blumenau. « Structure and Energy of the 90° Partial Dislocations in Wurtzite-GaN ». Materials Science Forum 483-485 (mai 2005) : 1057–60. http://dx.doi.org/10.4028/www.scientific.net/msf.483-485.1057.
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90 Shockley partial dislocations in GaN are investigated by first-principles calculations. This work is focussed on the electrical properties of dislocation cores, and on investigating the electrical fields around these defects. The band structure analysis shows that both the and core partials possess a midgap state. The -core dislocations give rise to a donor level Ev +0:87 eV that might explain the absorption peak at 2.4 eV revealed by energy loss spectroscopy measurements. The acceptor level Ev + 1:11 eV localized at the -core dislocations might contribute to the yellow luminescence. These dislocations experience a substantial charge polarization along the [0001] growth axis. In addition, we show that these dislocations tend to charge in a high stress field.
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SURESH, S., V. GANESH, M. BALAJI, K. BASKAR, K. ASOKAN et D. KANJILAL. « STRUCTURAL CHARACTERISTICS OF 70 MeV Si5+ ION IRRADIATION INDUCED NANOCLUSTERS OF GALLIUM NITRIDE ». International Journal of Nanoscience 10, no 04n05 (août 2011) : 823–26. http://dx.doi.org/10.1142/s0219581x11009246.
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70 MeV Si ions irradiation at the liquid nitrogen temperature (77 K) induced nanoclustering on GaN epilayers grown by Metal Organic Chemical Vapor Deposition (MOCVD) are reported. HRXRD rocking curves show that there are no localized amorphization due to irradiation. Atomic force microscopy images reveal the formation of nanoclusters on the surface of the irradiated samples. On increasing the fluence the number of modified regions on the surface increases and resulted in three dimensional growth of nanocluster due to overlapping and coalescence. X-ray photoelectron spectroscopy (XPS) studies confirm that the surface features are composed of GaN . The variation of carrier concentration and hall mobility with respect to ion fluence are also studied. The effects of ion-beam induced modifications on the structural, surface characteristics and electrical properties of GaN are studied and possible mechanisms responsible for the modifications are discussed.
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Bassaler, Julien, Rémi Comyn, Catherine Bougerol, Yvon Cordier, Farid Medjdoub et Philippe Ferrandis. « Transport properties of a thin GaN channel formed in an Al0.9Ga0.1N/GaN heterostructure grown on AlN/sapphire template ». Journal of Applied Physics 131, no 12 (28 mars 2022) : 124501. http://dx.doi.org/10.1063/5.0077107.
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Despite a high lateral breakdown voltage above 10 kV for large contact distances and a breakdown field of 5 MV cm−1 for short contact distances, an Al0.9Ga0.1N/GaN heterostructure with an 8 nm strained GaN channel grown on an AlN/sapphire template suffers from a low and anisotropic mobility. This work deals with a material study to elucidate this issue. Threading dislocations were observed along the growth direction in transmission electron microscopy pictures and are more in number in the (11−20) plane. Steps were also detected in this plane at the GaN channel interfaces. With the help of device simulations and static characterizations, the deep level transient spectroscopy technique allowed five traps located in the GaN channel to be identified. Most of them are associated with nitrogen- or gallium-vacancy-related defects and are expected to be localized at the interfaces of GaN with the buffer and the barrier. It is likely that these electrically active defects contribute to reduce the mobility in the two-dimensional electron gas. In addition, a link was established between the mobility and the dependence of the quality of the channel interfaces on the crystallographic orientation.
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Shi, Kaiju, Chengxin Wang, Rui Li, Shangda Qu, Zonghao Wu, Jianyang Deng, Mingsheng Xu, Xiangang Xu et Ziwu Ji. « Influence of in volatilization on photoluminescence in InGaN/GaN multiple quantum wells ». Materials Express 11, no 12 (1 décembre 2021) : 2033–38. http://dx.doi.org/10.1166/mex.2021.2105.
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Two multiple quantum well (MQW) InGaN/GaN structures emitting green light, without (A) and with (B) an indium (In) volatilization suppression technique (IVST) during growth of the active region, were fabricated. The dependencies of the photoluminescence (PL) spectra upon temperature at different levels of excitation power were investigated. The results indicate that an IVST can increase the In content while suppressing the phase separation caused by volatilization of that In incorporated in the well layers. Also, compared with Structure B with IVST, which contains one phase structure, Structure A without IVST, which contains two separate phases (i.e., an In-rich phase and an In-poor phase), exhibits higher internal quantum efficiency (IQE) at low excitation power and lower IQE at high excitation power. The former is mainly attributed to the stronger In-rich phase-related localization effect of Structure A, because the In-rich phase-related emission dominates the PL spectra of Structure A at a low excitation power; the latter is mainly due to the In-poor phase-related weaker localization effect of Structure A, because the In-poor phase-related emission dominates the PL spectra of Structure A at high excitation power because localized states in this In-rich phase are saturated.
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Kocmarek, Andrea L., Moira M. Ferguson et Roy G. Danzmann. « Co-localization of growth QTL with differentially expressed candidate genes in rainbow trout ». Genome 58, no 9 (septembre 2015) : 393–403. http://dx.doi.org/10.1139/gen-2015-0047.
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We tested whether genes differentially expressed between large and small rainbow trout co-localized with familial QTL regions for body size. Eleven chromosomes, known from previous work to house QTL for weight and length in rainbow trout, were examined for QTL in half-sibling families produced in September (1 XY male and 1 XX neomale) and December (1 XY male). In previous studies, we identified 108 candidate genes for growth expressed in the liver and white muscle in a subset of the fish used in this study. These gene sequences were BLASTN aligned against the rainbow trout and stickleback genomes to determine their location (rainbow trout) and inferred location based on synteny with the stickleback genome. Across the progeny of all three males used in the study, 63.9% of the genes with differential expression appear to co-localize with the QTL regions on 6 of the 11 chromosomes tested in these males. Genes that co-localized with QTL in the mixed-sex offspring of the two XY males primarily showed up-regulation in the muscle of large fish and were related to muscle growth, metabolism, and the stress response.
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Fages, C., M. Kaksonen, T. Kinnunen, E. L. Punnonen et H. Rauvala. « Regulation of mRNA localization by transmembrane signalling : local interaction of HB-GAM (heparin-binding growth-associated molecule) with the cell surface localizes beta-actin mRNA ». Journal of Cell Science 111, no 20 (15 octobre 1998) : 3073–80. http://dx.doi.org/10.1242/jcs.111.20.3073.
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Localization of mRNAs is currently thought to be partially responsible for molecular sorting to specific compartments within the cell. In mammalian cells the best-studied example is the beta-actin mRNA that is localized to the cell processes, and its localization is necessary in migratory responses of cells. It is reasonable to assume that mRNA localization within cells is coupled to transmembrane signalling due to extracellular factors, but little is known about such putative mechanisms. We show here that HB-GAM, an extracellular matrix-associated factor that enhances migratory responses in cells, is able to localize beta-actin mRNA when locally applied to cells via microbeads. The HB-GAM-induced mRNA localization is specifically inhibited by low concentrations of heparin and by heparitinase treatment of cells, showing that cell-surface heparin-type glycans are required for the effect. The finding that soluble N-syndecan is also inhibitory suggests that the transmembrane proteoglycan N-syndecan, previously identified as an HB-GAM receptor, is involved in the mRNA-localizing effect of HB-GAM. Inhibition of the mRNA localization by the src-kinase inhibitor PP1 is compatible with an N-syndecan-mediated effect since the receptor function of N-syndecan has been recently found to depend on the src-kinase signalling pathway. The mRNA-localizing activity of N-syndecan is also suggested by the finding that affinity-purified anti-N-syndecan antibodies coated on microbeads are able to localize beta-actin mRNA.
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Fages, Carole, Marko Kaksonen, Tarja Kinnunen, Eeva-Liisa Punnonen et Heikki Rauvala. « Regulation of mRNA localization by transmembrane signalling : Local interaction of HB-GAM (heparin-binding growth-associated molecule) with the cell surface localizes β-actin mRNA ». Journal of Cell Science 111, no 20 (15 janvier 1998) : 3073–80. http://dx.doi.org/10.1242/jcs.20.111.3073.
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ABSTRACT Localization of mRNAs is currently thought to be partially responsible for molecular sorting to specific compartments within the cell. In mammalian cells the best-studied example is the β-actin mRNA that is localized to the cell processes, and its localization is necessary in migratory responses of cells. It is reasonable to assume that mRNA localization within cells is coupled to transmembrane signalling due to extracellular factors, but little is known about such putative mechanisms. We show here that HB- GAM, an extracellular matrix-associated factor that enhances migratory responses in cells, is able to localize β- actin mRNA when locally applied to cells via microbeads. The HB-GAM-induced mRNA localization is specifically inhibited by low concentrations of heparin and by heparitinase treatment of cells, showing that cell-surface heparin-type glycans are required for the effect. The finding that soluble N-syndecan is also inhibitory suggests that the transmembrane proteoglycan N-syndecan, previously identified as an HB-GAM receptor, is involved in the mRNA-localizing effect of HB-GAM. Inhibition of the mRNA localization by the src-kinase inhibitor PP1 is compatible with an N-syndecan-mediated effect since the receptor function of N-syndecan has been recently found to depend on the src-kinase signalling pathway. The mRNA- localizing activity of N-syndecan is also suggested by the finding that affinity-purified anti-N-syndecan antibodies coated on microbeads are able to localize β-actin mRNA.
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Cherubini, S., M. D. De Tullio, P. De Palma et G. Pascazio. « Transient growth in the flow past a three-dimensional smooth roughness element ». Journal of Fluid Mechanics 724 (8 mai 2013) : 642–70. http://dx.doi.org/10.1017/jfm.2013.177.
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AbstractThis work provides a global optimization analysis, looking for perturbations inducing the largest energy growth at a finite time in a boundary-layer flow in the presence of smooth three-dimensional roughness elements. Amplification mechanisms are described which can bypass the asymptotical growth of Tollmien–Schlichting waves. Smooth axisymmetric roughness elements of different height have been studied, at different Reynolds numbers. The results show that even very small roughness elements, inducing only a weak deformation of the base flow, can localize the optimal disturbance characterizing the Blasius boundary-layer flow. Moreover, for large enough bump heights and Reynolds numbers, a strong amplification mechanism has been recovered, inducing an increase of several orders of magnitude of the energy gain with respect to the Blasius case. In particular, the highest value of the energy gain is obtained for an initial varicose perturbation, differently to what found for a streaky parallel flow. Optimal varicose perturbations grow very rapidly by transporting the strong wall-normal shear of the base flow, which is localized in the wake of the bump. Such optimal disturbances are found to lead to transition for initial energies and amplitudes considerably smaller than sinuous optimal ones, inducing hairpin vortices downstream of the roughness element.
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Radin, Ivan, Ryan A. Richardson, Joshua H. Coomey, Ethan R. Weiner, Carlisle S. Bascom, Ting Li, Magdalena Bezanilla et Elizabeth S. Haswell. « Plant PIEZO homologs modulate vacuole morphology during tip growth ». Science 373, no 6554 (29 juillet 2021) : 586–90. http://dx.doi.org/10.1126/science.abe6310.
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In animals, PIEZOs are plasma membrane–localized cation channels involved in diverse mechanosensory processes. We investigated PIEZO function in tip-growing cells in the moss Physcomitrium patens and the flowering plant Arabidopsis thaliana. PpPIEZO1 and PpPIEZO2 redundantly contribute to the normal growth, size, and cytoplasmic calcium oscillations of caulonemal cells. Both PpPIEZO1 and PpPIEZO2 localized to vacuolar membranes. Loss-of-function, gain-of-function, and overexpression mutants revealed that moss PIEZO homologs promote increased complexity of vacuolar membranes through tubulation, internalization, and/or fission. Arabidopsis PIEZO1 also localized to the tonoplast and is required for vacuole tubulation in the tips of pollen tubes. We propose that in plant cells the tonoplast has more freedom of movement than the plasma membrane, making it a more effective location for mechanosensory proteins.
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Yu, Qin, et Ivan Stamenkovic. « Cell surface-localized matrix metalloproteinase-9 proteolytically activates TGF-β and promotes tumor invasion and angiogenesis ». Genes & ; Development 14, no 2 (15 janvier 2000) : 163–76. http://dx.doi.org/10.1101/gad.14.2.163.
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We have uncovered a novel functional relationship between the hyaluronan receptor CD44, the matrix metalloproteinase-9 (MMP-9) and the multifunctional cytokine TGF-β in the control of tumor-associated tissue remodeling. CD44 provides a cell surface docking receptor for proteolytically active MMP-9 and we show here that localization of MMP-9 to cell surface is required for its ability to promote tumor invasion and angiogenesis. Our observations also indicate that MMP-9, as well as MMP-2, proteolytically cleaves latent TGF-β, providing a novel and potentially important mechanism for TGF-β activation. In addition, we show that MMP-9 localization to the surface of normal keratinocytes is CD44 dependent and can activate latent TGF-β. These observations suggest that coordinated CD44, MMP-9, and TGF-β function may provide a physiological mechanism of tissue remodeling that can be adopted by malignant cells to promote tumor growth and invasion.
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Corso, Massimiliano, Fabrizio G. Doccula, J. Romário F. de Melo, Alex Costa et Nathalie Verbruggen. « Endoplasmic reticulum-localized CCX2 is required for osmotolerance by regulating ER and cytosolic Ca2+ dynamics in Arabidopsis ». Proceedings of the National Academy of Sciences 115, no 15 (26 mars 2018) : 3966–71. http://dx.doi.org/10.1073/pnas.1720422115.
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Ca2+ signals in plant cells are important for adaptive responses to environmental stresses. Here, we report that the Arabidopsis CATION/Ca2+ EXCHANGER2 (CCX2), encoding a putative cation/Ca2+ exchanger that localizes to the endoplasmic reticulum (ER), is strongly induced by salt and osmotic stresses. Compared with the WT, AtCCX2 loss-of-function mutant was less tolerant to osmotic stress and displayed the most noteworthy phenotypes (less root/shoot growth) during salt stress. Conversely, AtCCX2 gain-of-function mutants were more tolerant to osmotic stress. In addition, AtCCX2 partially suppresses the Ca2+ sensitivity of K667 yeast triple mutant, characterized by Ca2+ uptake deficiency. Remarkably, Cameleon Ca2+ sensors revealed that the absence of AtCCX2 activity results in decreased cytosolic and increased ER Ca2+ concentrations in comparison with both WT and the gain-of-function mutants. This was observed in both salt and nonsalt osmotic stress conditions. It appears that AtCCX2 is directly involved in the control of Ca2+ fluxes between the ER and the cytosol, which plays a key role in the ability of plants to cope with osmotic stresses. To our knowledge, Atccx2 is unique as a plant mutant to show a measured alteration in ER Ca2+ concentrations. In this study, we identified the ER-localized AtCCX2 as a pivotal player in the regulation of ER Ca2+ dynamics that heavily influence plant growth upon salt and osmotic stress.
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Simionescu-Bankston, Adriana, Christophe Pichavant, James P. Canner, Luciano H. Apponi, Yanru Wang, Craig Steeds, John T. Olthoff, Joseph J. Belanto, James M. Ervasti et Grace K. Pavlath. « Creatine kinase B is necessary to limit myoblast fusion during myogenesis ». American Journal of Physiology-Cell Physiology 308, no 11 (1 juin 2015) : C919—C931. http://dx.doi.org/10.1152/ajpcell.00029.2015.
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Myoblast fusion is critical for proper muscle growth and regeneration. During myoblast fusion, the localization of some molecules is spatially restricted; however, the exact reason for such localization is unknown. Creatine kinase B (CKB), which replenishes local ATP pools, localizes near the ends of cultured primary mouse myotubes. To gain insights into the function of CKB, we performed a yeast two-hybrid screen to identify CKB-interacting proteins. We identified molecules with a broad diversity of roles, including actin polymerization, intracellular protein trafficking, and alternative splicing, as well as sarcomeric components. In-depth studies of α-skeletal actin and α-cardiac actin, two predominant muscle actin isoforms, demonstrated their biochemical interaction and partial colocalization with CKB near the ends of myotubes in vitro. In contrast to other cell types, specific knockdown of CKB did not grossly affect actin polymerization in myotubes, suggesting other muscle-specific roles for CKB. Interestingly, knockdown of CKB resulted in significantly increased myoblast fusion and myotube size in vitro, whereas knockdown of creatine kinase M had no effect on these myogenic parameters. Our results suggest that localized CKB plays a key role in myotube formation by limiting myoblast fusion during myogenesis.
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Mitsiadis, T. A., M. Salmivirta, T. Muramatsu, H. Muramatsu, H. Rauvala, E. Lehtonen, M. Jalkanen et I. Thesleff. « Expression of the heparin-binding cytokines, midkine (MK) and HB-GAM (pleiotrophin) is associated with epithelial-mesenchymal interactions during fetal development and organogenesis ». Development 121, no 1 (1 janvier 1995) : 37–51. http://dx.doi.org/10.1242/dev.121.1.37.
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Midkine (MK) and heparin binding-growth associated molecule (HB-GAM or pleiotrophin), constitute a new family of heparin-binding proteins implicated in the regulation of growth and differentiation (T. Muramatsu (1993) Int. J. Dev. Biol. 37, 183–188). We used affinity-purified antibodies against MK and HB-GAM to analyze their distribution during mouse embryonic development. From 9 to 14.5 day post-coitum (dpc), both proteins were detected in central and peripheral nervous systems, facial processes, limb buds, sense organs, respiratory, digestive, urogenital, and skeletal systems. MK and HB-GAM were often localized on the surface of differentiating cells and in basement membranes of organs undergoing epithelial-mesenchymal interactions. The level of MK protein decreased considerably in the 16.5 dpc embryo, whereas HB-GAM staining persisted in many tissues. Our in situ hybridization results revealed a widespread expression of MK transcripts that was not always consistent with the distribution of MK protein in developing tissues. In many epithelio-mesenchymal organs MK and HB-GAM were codistributed with syndecan-1, a cell surface proteoglycan. In limb buds and facial processes, MK, HB-GAM, and syndecan-1 were localized to the apical epithelium and the adjacent proliferating mesenchyme. Both MK and HB-GAM bound syndecan-1 in solid-phase assays in a heparan sulfate-dependent manner. The biological effects of MK and HB-GAM on limb and facial mesenchyme were studied in vitro by application of beads preloaded with the proteins. Neither MK nor HB-GAM stimulated mesenchymal cell proliferation or induced syndecan-1 expression. Taken together these results indicate that MK and HB-GAM may play regulatory roles in differentiation and morphogenesis of the vertebrate embryo, particularly in epithelio-mesenchymal organs, and suggest molecular interactions with syndecan-1.
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Bassuk, Anna Perkins Nina. « 031 EFFECT OF BLANCHING, IBA CONCENTRATION, AND PLANT GROWTH REGULATORS ON GROWTH AND OVERWINTER SURVIVAL OF CUTTING-PROPAGATED ORNAMENTALS ». HortScience 29, no 5 (mai 1994) : 432b—432. http://dx.doi.org/10.21273/hortsci.29.5.432b.
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Budbreak inhibition and poor overwinter survival (OS) limit successful cutting propagation of Acer rubrum October Glory, A. rubrum Red Sunset, Hamamelis vernalis, H. virginiana and Stewartia pseudocamellia. Localized blanching (banding) of the cutting on the stock plant; a range of 3 IBA concentrations, and foliar spray application of: 1% silver thiosulfate(STS), STS followed ten days later by Gibberellin, GA4/7:250ppm(STS GA),50ppm thidiazuron (TDZ) and TDZ followed by GA4/7 (TDZ GA)were tested for increasing growth and overwinter survival.. Carbohydrates were analyzed in cuttings which did and didn't grow. A. rubrum October Glory*, and Hamamelis spp all had increased OS for cuttings which grew. A. rubrum Red Sunset demonstrated a similar trend. Hamamelis spp. had significant increase in carbohydrates for cuttings which grew. A. rubrum October Glory' exhibited the same trend. S. pseudocamellia did not have increased OS with growth. and showed no increases in carbohydrates with growth, but the cuttings that didn't grow had at least 93 % more carbohydrates than the other species analyzed. All species had higher OS when stored in the 3° C cooler, than in the fluctuating cold frame. Banding increased growth of A. rubrum October Glory, and H. virginiana. IBA concentration affected growth of all species. STS increased growth of H. virginiana and S. pseudocamellia. GA4/7 increased growth of all cuttings except A. rubrum October Glory.
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Duffaud, Florence, et Axel Le Cesne. « Recent advances in managing gastrointestinal stromal tumor ». F1000Research 6 (14 septembre 2017) : 1689. http://dx.doi.org/10.12688/f1000research.11118.1.
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Constitutive activating mutations inKITand platelet-derived growth factor receptor α (PDGFRα) are heavily involved in the pathobiology of gastrointestinal stromal tumors (GISTs). This disease has served as an effective “proof-of-concept” model for targeting gain-of-function kinase mutations in cancer. This review discusses the current standard of care in terms of pharmacotherapy in the management of localized and metastatic GISTs.
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Schrick, Kathrin, Ulrike Mayer, Andrea Horrichs, Christine Kuhnt, Catherine Bellini, Jeff Dangl, Jürgen Schmidt et Gerd Jürgens. « FACKEL is a sterol C-14 reductase required for organized cell division and expansion in Arabidopsis embryogenesis ». Genes & ; Development 14, no 12 (15 juin 2000) : 1471–84. http://dx.doi.org/10.1101/gad.14.12.1471.
Texte intégralRésumé :
In flowering plants, the developing embryo consists of growing populations of cells whose fates are determined in a position-dependent manner to form the adult organism. Mutations in the FACKEL(FK) gene affect body organization of theArabidopsis seedling. We report that FK is required for cell division and expansion and is involved in proper organization of the embryo. We isolated FK by positional cloning. Expression analysis in embryos revealed that FK mRNA becomes localized to meristematic zones. FK encodes a predicted integral membrane protein related to the vertebrate lamin B receptor and sterol reductases across species, including yeast sterol C-14 reductase ERG24. We provide functional evidence that FK encodes a sterol C-14 reductase by complementation of erg24. GC/MS analysis confirmed that fk mutations lead to accumulation of intermediates in the biosynthetic pathway preceding the C-14 reductase step. Although fk represents a sterol biosynthetic mutant, the phenotype was not rescued by feeding with brassinosteroids (BRs), the only plant sterol signaling molecules known so far. We propose that synthesis of sterol signals in addition to BRs is important in mediating regulated cell growth and organization during embryonic development. Our results indicate a novel role for sterols in the embryogenesis of plants.
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Wang, Luyao, Ying Gui, Bingye Yang, Wenpan Dong, Peiling Xu, Fangjie Si, Wei Yang et al. « Mitogen-Activated Protein Kinases Associated Sites of Tobacco Repression of Shoot Growth Regulates Its Localization in Plant Cells ». International Journal of Molecular Sciences 23, no 16 (11 août 2022) : 8941. http://dx.doi.org/10.3390/ijms23168941.
Texte intégralRésumé :
Plant defense and growth rely on multiple transcriptional factors (TFs). Repression of shoot growth (RSG) is a TF belonging to a bZIP family in tobacco, known to be involved in plant gibberellin feedback regulation by inducing the expression of key genes. The tobacco calcium-dependent protein kinase CDPK1 was reported to interact with RSG and manipulate its intracellular localization by phosphorylating Ser-114 of RSG previously. Here, we identified tobacco mitogen-activated protein kinase 3 (NtMPK3) as an RSG-interacting protein kinase. Moreover, the mutation of the predicted MAPK-associated phosphorylation site of RSG (Thr-30, Ser-74, and Thr-135) significantly altered the intracellular localization of the NtMPK3-RSG interaction complex. Nuclear transport of RSG and its amino acid mutants (T30A and S74A) were observed after being treated with plant defense elicitor peptide flg22 within 5 min, and the two mutated RSG swiftly re-localized in tobacco cytoplasm within 30 min. In addition, triple-point mutation of RSG (T30A/S74A/T135A) mimics constant unphosphorylated status, and is predominantly localized in tobacco cytoplasm. RSG (T30A/S74A/T135A) showed no re-localization effect under the treatments of flg22, B. cereus AR156, or GA3, and over-expression of this mutant in tobacco resulted in lower expression levels of downstream gene GA20ox1. Our results suggest that MAPK-associated phosphorylation sites of RSG regulate its localization in tobacco, and that constant unphosphorylation of RSG in Thr-30, Ser-74, and Thr-135 keeps RSG predominantly localized in cytoplasm.
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Bimberg, D., M. Grundmann et N. N. Ledentsov. « Growth, Spectroscopy, and Laser Application of Self-Ordered III-V Quantum Dots ». MRS Bulletin 23, no 2 (février 1998) : 31–34. http://dx.doi.org/10.1557/s0883769400031249.
Texte intégralRésumé :
The development and application of semiconductor light-emitting and laser diodes has been a huge success during the last 30 years in key areas of modern technology like communications, recording, and printing. Still there is ample room for improvement through combination of the atomlike properties for zero-dimensionally localized carriers in quantum dots (QDs) with state-of-the-art semiconductor-laser technology. Low, temperature-insensitive threshold current; high gain; and differential gain have been predicted since the early 1980s.In the past two decades, the fabrication of QDs has been attempted using colloidal techniques (see the article by Nozik and Mićić in this issue), patterning, etching, and layer fluctuations (see the article by Gammon in this issue). However a break-through occurred recently through the employment of self-ordering mechanisms during epitaxy of lattice-mismatched materials (see the next section) for the creation of high-density arrays of QDs that exhibit excellent optical properties, particularly high quantum efficiency, up to room temperature. The zero-dimensional carrier confinement and subsequent atomlike electronic properties have a drastic impact on optical properties (see the section on Spectroscopy). Also intimately connected is the applicability of QDs as a novel gain medium in state-of-the-art laser diodes with superior properties (see the section on Lasers).
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Emerman, Joanne T., Nancy Jones et Eveline E. Fiedler. « Glycosaminoglycan accumulation by normal and malignant human mammary epithelial cells in primary culture ». Biochemistry and Cell Biology 66, no 4 (1 avril 1988) : 309–18. http://dx.doi.org/10.1139/o88-040.
Texte intégralRésumé :
The effects of glycosaminoglycans (GAGs) on cell growth and differentiation appear to vary with cell type and stage of development. This study describes the types and distribution of GAGs accumulated by normal and malignant human mammary epithelial cells in primary culture during their exponential and stationary phases of growth. Cultures incubated with [3H]glucosamine or [35S]sulfate were separated into medium, extracellular matrix (ECM), and cell fractions. Labelled GAGs were identified by chemical and enzymatic degradations and cellulose acetate electrophoresis. Cultures of normal cells in the exponential phase of growth released the most labelled GAGs into the medium fraction, the majority of which was hyaluronic acid (HA). The increase in labelled GAG accumulation, the increase in sulfated GAGs, and the increase in GAGs localized in the ECM fraction correlated with the reduced proliferative activity and increased cell density of cells in stationary cultures. In contrast, cultures of mammary tumour cells had the same labelled GAG profile, regardless of their growth status. Although there was variation among tumours, in general, the majority of the labelled GAGs were secreted into the medium fraction and the predominant GAG was HA. The results are comparable with those obtained from studies on mammary tissue in vivo. Primary cultures of human mammary epithelial cells should be useful for determining how modulations of GAGs affect growth and differentiation of these cells.
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Basile, D. P., J. M. Rovak, D. R. Martin et M. R. Hammerman. « Increased transforming growth factor-beta 1 expression in regenerating rat renal tubules following ischemic injury ». American Journal of Physiology-Renal Physiology 270, no 3 (1 mars 1996) : F500—F509. http://dx.doi.org/10.1152/ajprenal.1996.270.3.f500.
Texte intégralRésumé :
To gain insight into the role that transforming growth factor-beta 1 (TGF-beta 1) plays in the regeneration of kidneys following acute renal failure, we characterized the expression of TGF-beta 1 mRNA and the expression of active and latent TGF-beta peptide at various times during recovery from acute ischemic injury in rat. Levels of whole kidney TGF-beta 1 mRNA were elevated significantly at 12 h postinjury (1.5-fold vs. sham-operated controls), and by 24 h postinjury were elevated by 3.6-fold. Levels remained elevated for 14 days following ischemia, but were no longer elevated at 28 days postinjury. In situ hybridization demonstrated that the elevated expression of TGF-beta 1 was localized predominantly to cells in the regenerating tubules in the outer medulla. When examined at 14 days postischemia, levels of TGF-beta 1 mRNA were elevated in the outer medulla only in tubules that appeared incompletely regenerated. Immunohistochemical staining localized active TGF-beta to the lumen of proximal tubules in control animals and in desquamated and regenerating tubular epithelial cells following ischemia. TGF-beta 1 latency-associated peptide was present intracellularly in proximal tubules of sham-operated rats and reduced following ischemia. We hypothesize that endogenous renal TGF-beta serves to promote tissue regeneration following acute injury via an autocrine or paracrine mechanism.
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Morrison, Huntly M., Julia Craft, Rafael Rivera-Lugo, Jeffery R. Johnson, Guillaume R. Golovkine, Samantha L. Bell, Claire E. Dodd et al. « Deficiency in Galectin-3, -8, and -9 impairs immunity to chronic Mycobacterium tuberculosis infection but not acute infection with multiple intracellular pathogens ». PLOS Pathogens 19, no 6 (23 juin 2023) : e1011088. http://dx.doi.org/10.1371/journal.ppat.1011088.
Texte intégralRésumé :
Macrophages employ an array of pattern recognition receptors to detect and eliminate intracellular pathogens that access the cytosol. The cytosolic carbohydrate sensors Galectin-3, -8, and -9 (Gal-3, Gal-8, and Gal-9) recognize damaged pathogen-containing phagosomes, and Gal-3 and Gal-8 are reported to restrict bacterial growth via autophagy in cultured cells. However, the contribution of these galectins to host resistance during bacterial infection in vivo remains unclear. We found that Gal-9 binds directly to Mycobacterium tuberculosis (Mtb) and Salmonella enterica serovar Typhimurium (Stm) and localizes to Mtb in macrophages. To determine the combined contribution of membrane damage-sensing galectins to immunity, we generated Gal-3, -8, and -9 triple knockout (TKO) mice. Mtb infection of primary macrophages from TKO mice resulted in defective autophagic flux but normal bacterial replication. Surprisingly, these mice had no discernable defect in resistance to acute infection with Mtb, Stm or Listeria monocytogenes, and had only modest impairments in bacterial growth restriction and CD4 T cell activation during chronic Mtb infection. Collectively, these findings indicate that while Gal-3, -8, and -9 respond to an array of intracellular pathogens, together these membrane damage-sensing galectins play a limited role in host resistance to bacterial infection.
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Bera, Smritilekha, et Dhananjoy Mondal. « Click-Chemistry-Assisted Alteration of Glycosaminoglycans for Biological Applications ». SynOpen 07, no 02 (juin 2023) : 277–89. http://dx.doi.org/10.1055/s-0040-1720072.
Texte intégralRésumé :
AbstractThis short review describes the assistance of click chemistry in the chemical modification of glycosaminoglycans. Through an alkyne-azide 1,3-dipolar cycloaddition reaction, the chemically and physiologically stable triazole unit connects glycosaminoglycans with other labelled or attached functionalities. The synthesized glycosaminoglycan (GAG) conjugates act as drug carriers, forming hydrogels or nanohydrogels for localized drug delivery or injectable GAGs and so on. These are used in research on antithrombotic agents, protein binding, and hepatocyte growth factors, as well as in mechanistic studies of glycosaminoglycans biosynthesis and wound healing.1 Introduction2 Synthetic Modification of GAGS3 Click Chemistry4 Modification of GAGS Applying Click Chemistry5 Conclusions6 Abbreviations
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Virkola, Ritva, Mirko Brummer, Heikki Rauvala, Loek van Alphen et Timo K. Korhonen. « Interaction of Fimbriae of Haemophilus influenzae Type B with Heparin-Binding Extracellular Matrix Proteins ». Infection and Immunity 68, no 10 (1 octobre 2000) : 5696–701. http://dx.doi.org/10.1128/iai.68.10.5696-5701.2000.
Texte intégralRésumé :
ABSTRACT The interaction of the fimbriae of Haemophilus influenzae type b (Hib) with two heparin-binding extracellular matrix proteins, human fibronectin (Fn) and heparin-binding growth-associated molecule (HB-GAM) from mouse, were studied. The fimbriated Hib strain 770235 fim+, as well as the recombinant strainE. coli HB101(pMH140), which expressed Hib fimbriae, adhered strongly to Fn and HB-GAM immobilized on glass. Purified Hib fimbriae bound to Fn and HB-GAM, and within the Fn molecule, the binding was localized to the N-terminal 30,000-molecular-weight (30K) and 40K fragments, which contain heparin-binding domains I and II, respectively. Fimbrial binding to Fn, HB-GAM, and the 30K and the 40K fragments was inhibited by high concentrations of heparin. The results show that fimbriae of Hib interact with heparin-binding extracellular matrix proteins. The nonfimbriated Hib strain 770235 fim− exhibited a low level of adherence to Fn but did not react with HB-GAM, indicating that Hib strains also possess a fimbria-independent mechanism to interact with Fn.
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ТАРАНЕНКО, А. В., Л. С. БАСАЛАЕВА, В. В. ФЁДОРОВ, В. С. ТУМАШЕВ et А. Г. МИЛЁХИН. « SURFACE-ENHANCED RAMAN SCATTERING FROM GAP NANOWIRES WITH A GALLIUM DROPLET ». Автометрия 60, no 4 (30 août 2024) : 93–100. http://dx.doi.org/10.15372/aut20240410.
Texte intégralRésumé :
Представлены результаты исследования структурных и оптических свойств массивов и одиночных нанопроволок (НП) GaP ориентации (111) с помощью спектроскопии комбинационного рассеяния света (КРС) и атомно-силовой микроскопии (АСМ). Массивы НП GaP были выращены на подложке Si(111) методом самокаталитического роста по механизму пар - жидкость - кристалл. Одиночные НП GaP были механически перенесены на золотую поверхность. В спектрах КРС НП GaP наблюдались моды поперечных (TO), продольных (LO) и поверхностных (SO) оптических фононов. Обнаружено поверхностно-усиленное КРС фононными модами GaP вблизи галлиевой капли, обусловленное возникающим локализованным поверхностным плазмонным резонансом в капле. Получены карты КРС НП GaP для различной геометрии рассеяния. Коэффициент усиления сигнала КРС для НП GaP диаметром 104 и 60 нм достигает значений ~11 и 6 соответственно. This paper presents the results of a study of the structural and optical properties of arrays of (111)-oriented GaP nanowires (NWs) and single NWs using Raman spectroscopy and atomic force microscopy (AFM). GaP NW arrays are grown on a (111)-Si substrate by self-catalytic growth via the vapor-liquid-crystal mechanism. Single GaP NWs are mechanically transferred onto a gold surface. Transverse (TO), longitudinal (LO), and surface (SO) optical phonon modes are observed in the Raman spectra of GaP NWs. Surface-enhanced Raman scattering by optical phonon modes in GaP NWs near a gallium droplet is detected, due to the localized surface plasmon resonance in the droplet. Raman maps for GaP NWs recorded on various scattering geometries are obtained. The Raman enhancement factor for GaP NWs with a diameter of 104 and 60 nm reaches values of ~11 and 6, respectively.
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Wishart, Tayler F. L., et Frank J. Lovicu. « Spatiotemporal Localisation of Heparan Sulphate Proteoglycans throughout Mouse Lens Morphogenesis ». Cells 12, no 10 (11 mai 2023) : 1364. http://dx.doi.org/10.3390/cells12101364.
Texte intégralRésumé :
Heparan sulphate proteoglycans (HSPGs) consist of a core protein decorated with sulphated HS-glycosaminoglycan (GAG) chains. These negatively charged HS-GAG chains rely on the activity of PAPSS synthesising enzymes for their sulfation, which allows them to bind to and regulate the activity of many positively charged HS-binding proteins. HSPGs are found on the surfaces of cells and in the pericellular matrix, where they interact with various components of the cell microenvironment, including growth factors. By binding to and regulating ocular morphogens and growth factors, HSPGs are positioned to orchestrate growth factor-mediated signalling events that are essential for lens epithelial cell proliferation, migration, and lens fibre differentiation. Previous studies have shown that HS sulfation is essential for lens development. Moreover, each of the full-time HSPGs, differentiated by thirteen different core proteins, are differentially localised in a cell-type specific manner with regional differences in the postnatal rat lens. Here, the same thirteen HSPG-associated GAGs and core proteins as well as PAPSS2, are shown to be differentially regulated throughout murine lens development in a spatiotemporal manner. These findings suggest that HS-GAG sulfation is essential for growth factor-induced cellular processes during embryogenesis, and the unique and divergent localisation of different lens HSPG core proteins indicates that different HSPGs likely play specialized roles during lens induction and morphogenesis.
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Rodriguez, Isaac A., Emily A. Growney Kalaf, Gary L. Bowlin et Scott A. Sell. « Platelet-Rich Plasma in Bone Regeneration : Engineering the Delivery for Improved Clinical Efficacy ». BioMed Research International 2014 (2014) : 1–15. http://dx.doi.org/10.1155/2014/392398.
Texte intégralRésumé :
Human bone is a tissue with a fairly remarkable inherent capacity for regeneration; however, this regenerative capacity has its limitations, and defects larger than a critical size lack the ability to spontaneously heal. As such, the development and clinical translation of effective bone regeneration modalities are paramount. One regenerative medicine approach that is beginning to gain momentum in the clinical setting is the use of platelet-rich plasma (PRP). PRP therapy is essentially a method for concentrating platelets and their intrinsic growth factors to stimulate and accelerate a healing response. While PRP has shown some efficacy in bothin vitroandin vivoscenarios, to date its use and delivery have not been optimized for bone regeneration. Issues remain with the effective delivery of the platelet-derived growth factors to a localized site of injury, the activation and temporal release of the growth factors, and the rate of growth factor clearance. This review will briefly describe the physiological principles behind PRP use and then discuss how engineering its method of delivery may ultimately impact its ability to successfully translate to widespread clinical use.
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Passaggia, Pierre-Yves, Karl R. Helfrich et Brian L. White. « Optimal transient growth in thin-interface internal solitary waves ». Journal of Fluid Mechanics 840 (12 février 2018) : 342–78. http://dx.doi.org/10.1017/jfm.2018.19.
Texte intégralRésumé :
The dynamics of perturbations to large-amplitude internal solitary waves (ISWs) in two-layered flows with thin interfaces is analysed by means of linear optimal transient growth methods. Optimal perturbations are computed through direct–adjoint iterations of the Navier–Stokes equations linearized around inviscid, steady ISWs obtained from the Dubreil-Jacotin–Long (DJL) equation. Optimal perturbations are found as a function of the ISW phase velocity $c$ (alternatively amplitude) for one representative stratification. These disturbances are found to be localized wave-like packets that originate just upstream of the ISW self-induced zone (for large enough $c$) of potentially unstable Richardson number, $Ri<0.25$. They propagate through the base wave as coherent packets whose total energy gain increases rapidly with $c$. The optimal disturbances are also shown to be relevant to DJL solitary waves that have been modified by viscosity representative of laboratory experiments. The optimal disturbances are compared to the local Wentzel–Kramers–Brillouin (WKB) approximation for spatially growing Kelvin–Helmholtz (K–H) waves through the $Ri<0.25$ zone. The WKB approach is able to capture properties (e.g. carrier frequency, wavenumber and energy gain) of the optimal disturbances except for an initial phase of non-normal growth due to the Orr mechanism. The non-normal growth can be a substantial portion of the total gain, especially for ISWs that are weakly unstable to K–H waves. The linear evolution of Gaussian packets of linear free waves with the same carrier frequency as the optimal disturbances is shown to result in less energy gain than found for either the optimal perturbations or the WKB approximation due to non-normal effects that cause absorption of disturbance energy into the leading face of the wave. Two-dimensional numerical calculations of the nonlinear evolution of optimal disturbance packets leads to the generation of large-amplitude K–H billows that can emerge on the leading face of the wave and that break down into turbulence in the lee of the wave. The nonlinear calculations are used to derive a slowly varying model of ISW decay due to repeated encounters with optimal or free wave packets. Field observations of unstable ISW by Moum et al. (J. Phys. Oceanogr., vol. 33 (10), 2003, pp. 2093–2112) are consistent with excitation by optimal disturbances.
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Basile-Borgia, Annette E., et Vassie C. Ware. « Life and death of a cardiac myocyte : principles of cellular biology ». Perfusion 16, no 3 (mai 2001) : 229–41. http://dx.doi.org/10.1177/026765910101600309.
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If the future of extracorporeal circulation is to include approaches to enhance localized or widespread distribution of cells, and/or gene transfer for augmentation of cardiac function, it is imperative that we gain an increased understanding of the mechanisms that define the cardiac myocyte phenotype. The purpose of this paper is to review the natural history of the cardiac myocyte. A variety of signals determine the cellular processes that characterize birth, growth, differentiation and death of cardiomyocytes. Examined here are primary aspects of the molecular genetics of growth and development, including signal transduction, protein phosphorylation, the cell division cycle, and transcriptional activation. This review is intended to be an update on insights into molecular aspects of the cell, with emphasis on gene expression during cardiac myogenesis and a discussion of its relevance to the field of extracorporeal circulation. In addition, the current status of research in myogenesis is presented.
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Avola, Danilo, Irene Cannistraci, Marco Cascio, Luigi Cinque, Anxhelo Diko, Alessio Fagioli, Gian Luca Foresti et al. « A Novel GAN-Based Anomaly Detection and Localization Method for Aerial Video Surveillance at Low Altitude ». Remote Sensing 14, no 16 (22 août 2022) : 4110. http://dx.doi.org/10.3390/rs14164110.
Texte intégralRésumé :
The last two decades have seen an incessant growth in the use of Unmanned Aerial Vehicles (UAVs) equipped with HD cameras for developing aerial vision-based systems to support civilian and military tasks, including land monitoring, change detection, and object classification. To perform most of these tasks, the artificial intelligence algorithms usually need to know, a priori, what to look for, identify. or recognize. Actually, in most operational scenarios, such as war zones or post-disaster situations, areas and objects of interest are not decidable a priori since their shape and visual features may have been altered by events or even intentionally disguised (e.g., improvised explosive devices (IEDs)). For these reasons, in recent years, more and more research groups are investigating the design of original anomaly detection methods, which, in short, are focused on detecting samples that differ from the others in terms of visual appearance and occurrences with respect to a given environment. In this paper, we present a novel two-branch Generative Adversarial Network (GAN)-based method for low-altitude RGB aerial video surveillance to detect and localize anomalies. We have chosen to focus on the low-altitude sequences as we are interested in complex operational scenarios where even a small object or device can represent a reason for danger or attention. The proposed model was tested on the UAV Mosaicking and Change Detection (UMCD) dataset, a one-of-a-kind collection of challenging videos whose sequences were acquired between 6 and 15 m above sea level on three types of ground (i.e., urban, dirt, and countryside). Results demonstrated the effectiveness of the model in terms of Area Under the Receiving Operating Curve (AUROC) and Structural Similarity Index (SSIM), achieving an average of 97.2% and 95.7%, respectively, thus suggesting that the system can be deployed in real-world applications.
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Park, Kiwan, Sunghee Jun, Jerry Jisang Han, Jiyoung Lee, Hwain Kim et Joonkyung Kim. « Caffé Bene Disrupts the Stagnating Korean Coffee Shop Market ». Asian Case Research Journal 19, no 01 (juin 2015) : 203–30. http://dx.doi.org/10.1142/s021892751550008x.
Texte intégralRésumé :
Caffé Bene was founded in 2007, during which the coffee shop market in Korea had been experiencing rapid growth. Caffé Bene had to compete with existing brands, including Starbucks, The Coffee Bean and Tea Leaf, and other coffee shop chains native to Korea. Sun-Kwon Kim, the founder and current CEO of Caffé Bene, tried to differentiate his brand on the basis of a new concept of European ambience mixed with Korean culture, new and localized menus, and celebrity endorsements; all of which were unheard of in the retail coffee industry at that time. This novel approach allowed Caffé Bene to gain great popularity in a short period of time. Despite its extraordinary success, however, Caffé Bene faced numerous challenges, including managerial issues caused by excessive expansion and rapid growth, dilution of differentiation as a result of new entrants that mimicked Caffé Bene's unique strategies, and an overall sluggish growth rate in the coffee shop market. In this case, the challenges that Caffé Bene faced and the strategies it employed to successfully deal with them are discussed.
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Kamikura, Darren M., Hanane Khoury, Christiane Maroun, Monica A. Naujokas et Morag Park. « Enhanced Transformation by a Plasma Membrane-Associated Met Oncoprotein : Activation of a Phosphoinositide 3′-Kinase-Dependent Autocrine Loop Involving Hyaluronic Acid and CD44 ». Molecular and Cellular Biology 20, no 10 (15 mai 2000) : 3482–96. http://dx.doi.org/10.1128/mcb.20.10.3482-3496.2000.
Texte intégralRésumé :
ABSTRACT A Met-hepatocyte growth factor receptor oncoprotein, Tpr-Met, generated by chromosomal rearrangement, fuses a protein dimerization motif with the cytoplasmic domain of the Met receptor, producing a cytosolic, constitutively activated tyrosine kinase. Although both the Met receptor and the Tpr-Met oncoprotein associate with the same substrates, activating mutations of the Met receptor in hereditary papillary renal carcinomas have different signaling requirements for transformation than Tpr-Met. This suggests differential activation of membrane-localized pathways by oncogenic forms of the membrane-bound Met receptor but not by the cytoplasmic Tpr-Met oncoprotein. To establish which pathways might be differentially regulated, we have localized the constitutively activated Tpr-Met oncoprotein to the membrane using the c-src myristoylation signal. Membrane localization enhances cellular transformation, focus formation, and anchorage-independent growth and induces tumors with a distinct myxoid phenotype. This correlates with the induction of hyaluronic acid (HA) and the presence of a distinct form of its receptor, CD44. A pharmacological inhibitor of phosphoinositide 3′ kinase (PI3′K), inhibits the production of HA, and conversely, an activated, plasma membrane-targeted form of PI3′K is sufficient to enhance HA production. Furthermore, the multisubstrate adapter protein Gab-1, which couples the Met receptor with PI3′K, enhances Met receptor-dependent HA synthesis in a PI3′K-dependent manner. These results provide a positive link to a role for HA and CD44 in Met receptor-mediated oncogenesis and implicate PI3′K in these events.
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Li, Hui, Jinbo Hu, Jing Pang, Liangtao Zhao, Bing Yang, Xinlei Kang, Aimin Wang, Tongda Xu et Zhenbiao Yang. « Rho GTPase ROP1 Interactome Analysis Reveals Novel ROP1-Associated Pathways for Pollen Tube Polar Growth in Arabidopsis ». International Journal of Molecular Sciences 21, no 19 (24 septembre 2020) : 7033. http://dx.doi.org/10.3390/ijms21197033.
Texte intégralRésumé :
ROP (Rho-like GTPases from plants) GTPases are polarly localized key regulators of polar growth in pollen tubes and other cells in plants. However, how ROP GTPases are regulated and how they control polar growth remains to be fully understood. To gain new insights into ROP-dependent mechanisms underlying polar cell growth, we characterized the interactome of ROP1 GTPase that controls Arabidopsis pollen tube (PT) tip growth, an extreme form of polar cell growth. We established an efficient method for culturing Arabidopsis pollen tubes in liquid medium, which was used for immunoprecipitation/mass spectrometry-based identification of ROP1-associated proteins. A total of 654 candidates were isolated from the ROP1 interactome in Arabidopsis pollen tubes, and GO (Gene Ontology) classification and pathway analysis revealed multiple uncharacterized ROP1-dependent processes including translation, cell wall modification, post transcriptional modification, and ion homeostasis, in addition to known ROP1-dependent pathways. The ROP1-interactome data was further supported by the co-expression of the candidate interactors in highly mature pollen with PT germination and growth defects being discovered in 25% (8/32) of the candidate mutant genes. Taken together, our work uncovers valuable information for the identification and functional elucidation of ROP-associated proteins in the regulation of polar growth, and provides a reliable reference to identify critical regulators of polar cell growth in the future.
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Pan, Jing, Jing Zhang, Andrew Hill, Peter Lapan, Steve Berasi, Brian Bates, Christopher Miller et Steven Haney. « A Kinome-Wide siRNA Screen Identifies Multiple Roles for Protein Kinases in Hypoxic Stress Adaptation, Including Roles for IRAK4 and GAK in Protection against Apoptosis in VHL−/− Renal Carcinoma Cells, Despite Activation of the NF-κB Pathway ». Journal of Biomolecular Screening 18, no 7 (16 avril 2013) : 782–96. http://dx.doi.org/10.1177/1087057113484803.
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Hypoxia induces changes to cancer cells that make them more resistant to treatment. We have looked at signaling pathways that facilitate these changes by screening the human kinome for effects on hypoxic responses in SW480 colon cancer cells. Hits identified in the screen were examined for effects on multiple molecular responses to hypoxia, including the endoplasmic reticulum stress and DNA damage responses in colon, melanoma, and renal cancer lines. To validate the hits from the small interfering RNA studies, we developed cell lines expressing stable short hairpin RNAs (shRNAs) in the A498 renal carcinoma cell line. Several lines, including those expressing shRNAs against DYRK1B, GAK, IHPK2, IRAK4, and MATK, showed an inability to form spheroid cultures. In addition, shRNAs targeting IRAK4 and GAK were incapable of 2D growth under anoxia. In the GAK shRNA-expressing line, nuclear factor–κB (NF-κB) was localized to the nucleus, but in the IRAK4 shRNA line, NF-κB levels were increased but the extent of nuclear localization was unchanged. Dominant negative mutants of IRAK4 and GAK also showed strong apoptotic effects in A498 cells under anoxia, supporting a direct link between these kinases and survival of the VHL−/− RCC line, which is typically highly resistant to hypoxic stress as a result of high and constitutive levels of Hif-1α.
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Rohan, R. M., T. G. Unterman, L. Liu et M. K. Hise. « Expression of the insulin-like growth factor system in the hypokalemic rat kidney ». American Journal of Physiology-Renal Physiology 272, no 5 (1 mai 1997) : F661—F667. http://dx.doi.org/10.1152/ajprenal.1997.272.5.f661.
Texte intégralRésumé :
We studied the renal expression of the insulin-like growth factor (IGF) system to gain a better perspective of its potential role in the hyperplastic adaptation of the distal nephron to potassium deficiency. Rats were pair fed 1% or 0.002% potassium diets for periods up to 10 days. IGF-I mRNA was diminished in potassium-deficient rats within 4 days, whereas mRNA for IGF binding protein-1 (IGFBP-1), a collecting duct-associated protein, was increased by day 7. At day 10 mRNA for IGFBP-1 in potassium-deficient animals averaged 2.07 +/- 0.53 (mean +/- SD, relative densitometry units) compared with 0.89 +/- 0.26 in control rats (n = 4, P = 0.002). Conversely, IGFBP-3, a binding protein whose mRNA has been localized to the interstitial compartment, averaged 2.40 +/- 0.02 in potassium-deficient rats and 4.77 +/- 0.05 in controls (n = 4, P < 0.03) at day 10 of treatment. Immunohistochemistry performed using a specific IGFBP-1 antibody revealed hyperplasia of distal nephron segments along with an increase in IGFBP-1 in potassium-depleted rats. These data suggest that IGFBP-1 may play an important role in the control of cellular adaptations in the hypokalemic rat kidney either directly by influencing cell migration or indirectly by localizing IGF-I to the distal nephron.
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Dini, Pouya, Mariano Carossino, Udeni B. R. Balasuriya, Hossam El-Sheikh Ali, Shavahn C. Loux, Alejandro Esteller-Vico, Kirsten E. Scoggin et al. « Paternally expressed retrotransposon Gag-like 1 gene, RTL1, is one of the crucial elements for placental angiogenesis in horses ». Biology of Reproduction 104, no 6 (8 mars 2021) : 1386–99. http://dx.doi.org/10.1093/biolre/ioab039.
Texte intégralRésumé :
Abstract RTL1 (retrotransposon Gag-like 1) is an essential gene in the development of the human and murine placenta. Several fetal and placental abnormalities such as intrauterine growth restriction (IUGR) and hydrops conditions have been associated with altered expression of this gene. However, the function of RTL1 has not been identified. RTL1 is located on a highly conserved region in eutherian mammals. Therefore, the genetic and molecular analysis in horses could hold important implications for other species, including humans. Here, we demonstrated that RTL1 is paternally expressed and is localized within the endothelial cells of the equine (Equus caballus) chorioallantois. We developed an equine placental microvasculature primary cell culture and demonstrated that RTL1 knockdown leads to loss of the sprouting ability of these endothelial cells. We further demonstrated an association between abnormal expression of RTL1 and development of hydrallantois. Our data suggest that RTL1 may be essential for placental angiogenesis, and its abnormal expression can lead to placental insufficiency. This placental insufficiency could be the reason for IUGR and hydrops conditions reported in other species, including humans.
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Bellou, Sofia, Mark A. Hink, Eleni Bagli, Ekaterini Panopoulou, Philippe I. H. Bastiaens, Carol Murphy et Theodore Fotsis. « VEGF autoregulates its proliferative and migratory ERK1/2 and p38 cascades by enhancing the expression of DUSP1 and DUSP5 phosphatases in endothelial cells ». American Journal of Physiology-Cell Physiology 297, no 6 (décembre 2009) : C1477—C1489. http://dx.doi.org/10.1152/ajpcell.00058.2009.
Texte intégralRésumé :
Vascular endothelial growth factor (VEGF) is a key angiogenic factor that regulates proliferation and migration of endothelial cells via phosphorylation of extracellular signal-regulated kinase-1/2 (ERK1/2) and p38, respectively. Here, we demonstrate that VEGF strongly induces the transcription of two dual-specificity phosphatase (DUSP) genes DUSP1 and DUSP5 in endothelial cells. Using fluorescence microscopy, fluorescence lifetime imaging (FLIM), and fluorescence cross-correlation spectroscopy (FCCS), we found that DUSP1/mitogen-activated protein kinases phosphatase-1 (MKP-1) was localized in both the nucleus and cytoplasm of endothelial cells, where it existed in complex with p38 (effective dissociation constant, KDeff, values of 294 and 197 nM, respectively), whereas DUSP5 was localized in the nucleus of endothelial cells in complex with ERK1/2 ( KDeff 345 nM). VEGF administration affected differentially the KDeff values of the DUSP1/p38 and DUSP5/ERK1/2 complexes. Gain-of-function and lack-of-function approaches revealed that DUSP1/MKP-1 dephosphorylates primarily VEGF-phosphorylated p38, thereby inhibiting endothelial cell migration, whereas DUSP5 dephosphorylates VEGF-phosphorylated ERK1/2 inhibiting proliferation of endothelial cells. Moreover, DUSP5 exhibited considerable nuclear anchoring activity on ERK1/2 in the nucleus, thereby diminishing ERK1/2 export to the cytoplasm decreasing its further availability for activation.
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Wong, Howard, Jung Soh, Paul M. K. Gordon, Tom Yu, Christoph W. Sensen, Edward Parr et Randal N. Johnston. « Genomic compartmentalization of gene families encoding core components of metazoan signaling systems ». Genome 56, no 4 (avril 2013) : 215–25. http://dx.doi.org/10.1139/gen-2013-0021.
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To investigate the role of gene localization and genome organization in cell–cell signalling and regulation, we mapped the distribution pattern of gene families that comprise core components of intercellular communication networks. Our study is centered on the distinct evolutionarily conserved metazoan signalling pathways that employ proteins in the receptor tyrosine kinase, WNT, hedgehog, NOTCH, Janus kinase/STAT, transforming growth factor beta, and nuclear hormone receptor protein families. Aberrant activity of these signalling pathways is closely associated with the promotion and maintenance of human cancers. The cataloguing and mapping of genes encoding these signalling proteins and comparisons across species has led us to propose that the genome can be subdivided into six genome-wide primary linkage groups (PLGs). PLGs are composed of assemblages of gene families that are often mutually exclusive, raising the possibility of unique functional identities for each group. Examination of the localization patterns of genes with distinct functions in signal transduction demonstrates dichotomous segregation patterns. For example, gene families of cell-surface receptors localize to genomic compartments that are distinct from the locations of their cognate ligand gene families. Additionally, genes encoding negative-acting components of signalling pathways (inhibitors and antagonists) are topologically separated from their positive regulators and other signal transducer genes. We, therefore, propose the existence of conserved genomic territories that encode key proteins required for the proper activity of metazoan signaling and regulatory systems. Disruption in this pattern of topologic genomic organization may contribute to aberrant regulation in hereditary or acquired diseases such as cancer. We further propose that long-range looping genomic regulatory interactions may provide a mechanism favouring the remarkable retention of these conserved gene clusters during chordate evolution.
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Molloy, Andrew. « Second Growth : Community Economic Development in Rural British Columbia ». Canadian Journal of Political Science 38, no 4 (décembre 2005) : 1067–68. http://dx.doi.org/10.1017/s0008423905249971.
Texte intégralRésumé :
Second Growth: Community Economic Development in Rural British Columbia, Sean Markey, John Pierce, Mark Roseland and Kelly Vodden, Vancouver: University of British Columbia Press, 2005, pp. 352.This theoretically rich, community economic development (CED) work, written by four members of the Centre for Sustainable Community Development (formerly the Community Economic Development Centre) at Simon Fraser University, is the product of a three-year participatory-action-based research project involving four “forest-based” British Columbia communities. Two Aboriginal communities and two municipalities were case studied as part of an action-learning exercise in order to gain “insight into the apparent conflict between the economic imperative and fluidity of capital versus the lived worlds of rural and small time places” (3). Through their empirical studies of the four communities, the authors argue that CED, fostered at the local level, can allow for the kind of capacity building that is needed to create diversified, sustainable economic futures for resource-based rural and small-town communities. They are careful, however, to distinguish between the use of CED as a “localized and palliative strategy” for marginalized communities caught in the throes of political and economic dependency, and the possibilities for a more robust (theoretically balanced) version of CED, which can become part and parcel of rural and small-town locally-based planning and development. While recognizing the appropriateness of CED in either situation, they argue that a host of negative economic and political factors, which are intensifying under the direction of neo-liberal ideological thinking, have resulted in a pressing need for the more robust form of community development and corresponding revitalization strategies.
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Al-Gizawiy, Mona, Robert T. Wujek, Casey J. Zoss, Ryuma Tanaka, Shama P. Mirza, Christopher R. Chitambar et Kathleen M. Schmainda. « ATRT-03. THE ORAL IRON-MIMETIC GALLIUM MALTOLATE INHIBITS ATRT IN VIVO – IMAGING AND HISTOLOGICAL CHARACTERIZATION ». Neuro-Oncology 25, Supplement_1 (1 juin 2023) : i1. http://dx.doi.org/10.1093/neuonc/noad073.003.
Texte intégralRésumé :
Abstract BACKGROUND Atypical teratoid rhabdoid tumor (ATRT) is a highly aggressive CNS tumor that is associated with poor outcome. This dire prognosis is due in part to its poor response to the limited treatment options available. Iron and iron proteins play a key role in the growth of many solid cancers, including brain tumors. Our published studies show that the ferrobiology of brain tumors can be exploited for therapeutic purposes. Here, we further demonstrate the inhibitory effects of oral gallium maltolate (GaM) in pediatric ATRT in vivo. METHODS Pediatric CHLA-266 ATRT cells were stereotactically implanted into the right striatum of male athymic rats. Advanced MR imaging at 9.4T was carried out weekly starting two weeks after implantation. Daily oral GaM (50mg/kg) or vehicle were provided on tumor confirmation. Longitudinal advanced MRI parameters were processed for enhancing tumor ROIs in OsiriX 8.5.1 (lite) with Imaging Biometrics Software (Imaging Biometrics LLC). Statistical analyses included Kaplan-Meier survival plots, linear mixed model comparisons, and t-statistic for slopes comparison (as indicator of tumor growth rate). RESULTS In concordance with our previous in vitro work, in vivo ATRT xenografts were found to be highly sensitive to oral GaM. Median overall survival was 89 days in the control group and 170 days in the treatment group (p=0.011). GaM-treated xenograft tumors grew at a significantly slower rate than control tumors (p<0.0001). On MRI, untreated ATRT xenograft tumors, as their clinical counterparts, tended to localize near the ventricle and occasionally invade it. Histologically, xenograft tumors in our rat model recapitulated the histological features of human ATRT. A significant reduction in MIB-1% and mitotic index (p<0.001 and p<0.05, respectively) was seen in the treatment group. Transferrin receptor and H-ferritin expression in GaM-treated tumors illustrated cellular iron deprivation. CONCLUSION Monotherapy with GaM profoundly inhibited ATRT growth and prolonged survival in vivo.
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Liang, Feng-Xia, Cai-Wang Ge, Teng-Fei Zhang, Wei-Jie Xie, Deng-Yue Zhang, Yi-Feng Zou, Kun Zheng et Lin-Bao Luo. « Plasmonic hollow gold nanoparticles induced high-performance Bi2S3 nanoribbon photodetector ». Nanophotonics 6, no 2 (1 mars 2017) : 494–501. http://dx.doi.org/10.1515/nanoph-2016-0024.
Texte intégralRésumé :
AbstractA high performance hollow gold nanoparticles (HGNs) decorated one-dimensional (1-D) Bi2S3nanoribbon (NR) photodetector was fabricated for green light detection (560 nm). The single crystal 1-D Bi2S3NRs with growth orientation along [001] were synthesized by a simple solvothermal approach. Optoelectronic analysis reveals that the performance of the plasmonic photodetector was greatly enhanced after decoration with HGNs. For example, the responsivity increases from 1.4 × 102to 1.09 × 103AW−1, the conductivity gain from 2.68 × 102to 2.31 × 103, and the detectivity from 2.45 × 1012to 2.78 × 1013, respectively. Such performance enhancement was attributed to the localized surface plasmon resonance (LSPR) effect caused by the HGNs according to both experiment and theoretical simulation. This study is believed to open up new opportunities for managing light and enhancing the device performance of other 1-D semiconductor nanostructures based optoelectronic devices and systems.
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Shang, Huihui, Panpan Li, Xiaobo Zhang, Xia Xu, Junyi Gong, Shihua Yang, Yuqing He et Jian-Li Wu. « The Gain-of-Function Mutation, OsSpl26, Positively Regulates Plant Immunity in Rice ». International Journal of Molecular Sciences 23, no 22 (16 novembre 2022) : 14168. http://dx.doi.org/10.3390/ijms232214168.
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Rice spotted-leaf mutants are ideal materials to study the molecular mechanism underlying programmed cell death and disease resistance in plants. LOC_Os07g04820 has previously been identified as the candidate gene responsible for the spotted-leaf phenotype in rice Spotted-leaf 26 (Spl26) mutant. Here, we cloned and validated that LOC_Os07g04820 is the locus controlling the spotted-leaf phenotype of Spl26 by reverse functional complementation and CRISPR/Cas9-mediated knockout of the mutant allele. The recessive wild-type spl26 allele (Oryza sativa spotted-leaf 26, Osspl26) is highly conservative in grass species and encodes a putative G-type lectin S-receptor-like serine/threonine protein kinase with 444 amino acid residuals. OsSPL26 localizes to the plasma membrane and can be detected constitutively in roots, stems, leaves, sheaths and panicles. The single base substitution from T to A at position 293 leads to phenylalanine/tyrosine replacement at position 98 in the encoded protein in the mutant and induces excessive accumulation of H2O2, leading to oxidative damage to cells, and finally, formation of the spotted-leaf phenotype in Spl26. The formation of lesions not only affects the growth and development of the plants but also activates the defense response and enhances the resistance to the bacterial blight pathogen, Xanthomonas oryzae pv. oryzae. Our results indicate that the gain-of-function by the mutant allele OsSpl26 positively regulates cell death and immunity in rice.
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Kong, Ping, Carlos Gonzalez-Quesada, Na Li, Michele Cavalera, Dong-Wook Lee et Nikolaos G. Frangogiannis. « Thrombospondin-1 regulates adiposity and metabolic dysfunction in diet-induced obesity enhancing adipose inflammation and stimulating adipocyte proliferation ». American Journal of Physiology-Endocrinology and Metabolism 305, no 3 (1 août 2013) : E439—E450. http://dx.doi.org/10.1152/ajpendo.00006.2013.
Texte intégralRésumé :
As a typical matricellular protein, thrombospondin (TSP)-1, binds to the structural matrix and regulates cellular behavior by modulating growth factor and cytokine signaling. Obesity and diabetes are associated with marked upregulation of TSP-1 in adipose tissue. We hypothesized that endogenous TSP-1 may play an important role in the pathogenesis of diet-induced obesity and metabolic dysfunction. Accordingly, we examined the effects of TSP-1 gene disruption on weight gain, adiposity, and adipose tissue inflammation in mice receiving a high-fat diet (HFD: 60% fat, 20% carbohydrate) or a high-carbohydrate low-fat diet (HCLFD: 10% fat, 70% carbohydrate). HFD mice had significantly higher TSP-1 expression in perigonadal adipose tissue; TSP-1 was predominantly localized in the adipose interstitium. TSP-1 loss attenuated weight gain and fat accumulation in HFD and HCLFD groups. Compared with corresponding wild-type animals, TSP-1-null mice had decreased insulin levels but exhibited elevated free fatty acid and triglyceride levels, suggesting impaired fatty acid uptake. TSP-1 loss did not affect adipocyte size and had no effect on adipose vascular density. However, TSP-1-null mice exhibited attenuated tumor necrosis factor-α mRNA expression and reduced macrophage infiltration, suggesting a role for TSP-1 in mediating obesity-associated inflammation. In vitro, TSP-1 enhanced proliferation of 3T3-L1 preadipocytes but did not modulate inflammatory cytokine and chemokine synthesis. In conclusion, TSP-1 upregulation contributes to weight gain, adipose growth, and the pathogenesis of metabolic dysfunction. The effects of TSP-1 may involve stimulation of adipocyte proliferation, activation of inflammatory signaling, and facilitated fatty acid uptake by adipocytes.
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Porco, Silvana, Aleš Pěnčík, Afaf Rashed, Ute Voß, Rubén Casanova-Sáez, Anthony Bishopp, Agata Golebiowska et al. « Dioxygenase-encoding AtDAO1 gene controls IAA oxidation and homeostasis in Arabidopsis ». Proceedings of the National Academy of Sciences 113, no 39 (20 septembre 2016) : 11016–21. http://dx.doi.org/10.1073/pnas.1604375113.
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Auxin represents a key signal in plants, regulating almost every aspect of their growth and development. Major breakthroughs have been made dissecting the molecular basis of auxin transport, perception, and response. In contrast, how plants control the metabolism and homeostasis of the major form of auxin in plants, indole-3-acetic acid (IAA), remains unclear. In this paper, we initially describe the function of the Arabidopsis thaliana gene DIOXYGENASE FOR AUXIN OXIDATION 1 (AtDAO1). Transcriptional and translational reporter lines revealed that AtDAO1 encodes a highly root-expressed, cytoplasmically localized IAA oxidase. Stable isotope-labeled IAA feeding studies of loss and gain of function AtDAO1 lines showed that this oxidase represents the major regulator of auxin degradation to 2-oxoindole-3-acetic acid (oxIAA) in Arabidopsis. Surprisingly, AtDAO1 loss and gain of function lines exhibited relatively subtle auxin-related phenotypes, such as altered root hair length. Metabolite profiling of mutant lines revealed that disrupting AtDAO1 regulation resulted in major changes in steady-state levels of oxIAA and IAA conjugates but not IAA. Hence, IAA conjugation and catabolism seem to regulate auxin levels in Arabidopsis in a highly redundant manner. We observed that transcripts of AtDOA1 IAA oxidase and GH3 IAA-conjugating enzymes are auxin-inducible, providing a molecular basis for their observed functional redundancy. We conclude that the AtDAO1 gene plays a key role regulating auxin homeostasis in Arabidopsis, acting in concert with GH3 genes, to maintain auxin concentration at optimal levels for plant growth and development.