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Transcriptional regulation of secretory capacity by bZip transcription factors

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Frontiers in Biology 2015年第1期10卷 28-51页

作者： Rebecca m. FOX Deborah j. ANDREW The Department of Cell Biology The Johns Hopkins University School of Medicine Baltimore MD 21205 USA

Cells of specialized secretory organs expand their secretory pathways to accommodate the increased protein load necessary for their function. The endoplasmic reticulum （ER）, the Golgi apparatus and the secretory vesicles, expand not only the membrane components but also the protein machinery required for increased protein production and transport. Increased protein load causes an ER stress response akin to the Unfolded Protein Response （UPR）. Recent work has implicated several bZip transcription factors in the regulation of protein components of the early secretory pathway necessary to alleviate this stress. Here, we highlight eight bZip transcription factors in regulating secretory pathway component genes. These include components of the three canonical branches of the UPR-ATF4, XBP1, and ATF6, as well as the five members of the Creb3 family of transcription factors. We review findings from both invertebrate and vertebrate model systems suggesting that all of these proteins increase secretory capacity in response to increased protein load. Finally, we propose that the Creb3 family of factors may have a dual role in secretory cell differentiation by also regulating the pathways necessary for cell cycle exit during terminal differentiation.

关键词： bZip transcription factors endoplasmic reticulum Golgi secretion secretory capacity secretory vesicles

Highly active and durable Pd-Cu catalysts for oxygen reduction in alkaline exchange membrane fuel cells

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Frontiers in Energy 2017年第3期11卷 299-309页

作者： Xiong PENG Travis j. OmASTA j.stin m. ROLLER William E. mUSTAIN Department of Chemical and Biomolecular Engineering University of Connecticut 191 Auditorium Drive Storrs CT 06269 USA

A Pd-Cu catalyst, with primary B2-type phase, supported by VulcanXC-7R carbon was synthesized via a solvothermal method. The catalysts were physically and electrochemically characterized by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, trans- mission electron microscopy （TEm） and both cyclic and linear sweep voltammetry using a rotating disk electrode （RDE）. During the RDE testing, the half-wave potential of the Pd-Cu/Vulcan catalyst was 50 mV higher compared to that of commercial Pt/C catalyst for the oxygen reduction reaction （ORR） in alkaline media. The Pd-Cu/Vulcan exhibited a specific activity of 1.27 mA/cm2 and a mass activity of 0.59 A/mgpd at 0.9 V, which were 4 and 3 times greater than that of the commercial Pt/C catalyst, respectively. The Pd-Cu/Vulcan catalyst also showed higher in-situ alkaline exchange membrane fuel cell （AEmFC） performance, with operating power densities of 1100 mW/cm2 operating on H2/O2 and 700 mW/cm2 operating on H2/Air （CO2-free）, which were markedly higher than those of the commercial Pt/C. The Pd-Cu/ Vulcan catalyst also exhibited high stability during a short-term, in-situ AEmFC durability test, with only around 11% performance loss after 30 hours of operation, an improve- ment over most AEmFCs reported in the literature to date.

关键词： alkaline exchange membrane (AEm) fuel cell Pd-Cu oxygen reduction high performance water

Roles of manganese in photosystem II dynamics to irradiations and temperatures

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Frontiers in Biology 2013年第3期8卷 312-322页

作者： Xuej.ng HOU Harvey j. m. HOU Department of Chemistry and Biochemistry University of Massachusetts Dartmouth North Dartmouth MA 02747 USA Department of Physical Sciences Alabama State University Montgomery AL 36104 USA

The most amazing chemistry is the light-driven water splitting reaction occurred in the oxygen-evolving complex of phototsystem II in higher plants, green algae, and cyanobacteria. mn, in the form of mn4CaOs cluster in photosystem II, is responsible for the catalytic water splitting reaction as well as plays roles in photosystem II dynamics to irradiation and temperatures. manganese hypothesis of UV-initiated photoinhibition as a direct target is established, and thermal inactivation of photosystem II involves the valence and structural changes of manganese. Recent progresses in understanding the roles of manganese in photoinhibition especially under UV light and in thermal inactivation including elevated temperatures using synthetic models and native PS II complexes are summarized and evaluated. Potential problems and possible solutions are discussed and presented.

关键词： photosynthesis manganese photosystem II irradiation temperature stress

The calcium sensing receptor: from calcium sensing to signaling

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Science China(Life Sciences) 2015年第1期58卷 14-27页

作者： ZHANG Chen mILLER Cassandra Lynn BROWN Edward m YANG j.nny j. Department of Chemistry Georgia State University Center for Diagnostics and Therapeutics Georgia State University Division of Endocrinology Diabetes and HypertensionDepartment of MedicineBrigham and Women's Hospital

The Ca2+-sensing receptor(the Ca SR),a G-protein-coupled receptor,regulates Ca2+ homeostasis in the body by monitoring extracellular levels of Ca2+([Ca2+]o) and responding to a diverse array of *** in the Ca2+-sensing receptor result in hypercalcemic or hypocalcemic disorders,such as familial hypocalciuric hypercalcemia,neonatal severe primary hyperparathyroidism,and autosomal dominant hypocalcemic *** evidence suggests that the Ca SR plays multiple roles extending well beyond not only regulating the level of extracellular Ca2+ in the human body,but also controlling a diverse range of biological *** this review,we focus on the structural biology of the Ca SR,the ligand interaction sites as well as their relevance to the disease associated *** systematic summary will provide a comprehensive exploration of how the Ca SR integrates extracellular Ca2+ into intracellular Ca2+ signaling.

关键词： the Ca2+-sensing receptor(the Ca SR) Ca2+ signaling extracellular domain(ECD) Ca2+-binding sites

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Control of Cell Wall Extensibility during Pollen Tube Growth

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molecular Plant 2013年第4期6卷 998-1017页

作者： Peter K. Hepler Caleb m. Rounds Lawrence j. Winship Biology Department University of Massachusetts Amherst MA 01003 USA School of Natural Science Hampshire College Amherst MA 01002 USA

In this review, we address the question of how the tip-growing pollen tube achieves its rapid rate of elongation while maintaining an intact cell wall. Although turgor is essential for growth to occur, the local expansion rate is controlled by local changes in the viscosity of the apical wall. We focus on several different structures and underly- ing processes that are thought to be maj.r participants including exocytosis, the organization and activity of the actin cytoskeleton, calcium and proton physiology, and cellular energetics. We think that the actin cytoskeleton, in particular the apical cortical actin fringe, directs the flow of vesicles to the apical domain, where they fuse with the plasma mem- brane and contribute their contents to the expanding cell wall. While pH gradients, as generated by a proton-ATPase located on the plasma membrane along the side of the clear zone, may regulate rapid actin turnover and new polymeri- zation in the fringe, the tip-focused calcium gradient biases secretion towards the polar axis. The recent data showing that exocytosis of new wall material precedes and predicts the process of cell elongation provide support for the idea that the intussusception of newly secreted pectin contributes to decreases in apical wall viscosity and to cell expansion. Other prime factors will be the localization and activity of the enzyme pectin methyl-esterase, and the chelation of calcium by pectic acids. Finally, we acknowledge a role for reactive oxygen species in the control of wall viscosity.

关键词： cell expansion cell walls cytoskeleton dynamics polarity pollen development.

Investigation of different coal types effect on the overall plant recovery

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International j.urnal of mining Science and Technology 2014年第4期24卷 447-450页

作者： Ghasemi j. Karamoozian m. Sereshki F. mining Petroleum and Geophysics Engineering Faculty Shahrood University of Technology

Coal washing plants are usually fed from various sources. Coals include different combinations which should be considered for increasing the plant proficiency. Thus different methods have been used to enrich various coal types. In this study, Alborz-Sharghi coal washing plant was investigated which is fed from five coalmines. The optimum recovery was achieved for all coal types individually through experimental design. The controllable operation parameters in the experiments were collector dosage,frother dosage, solid percent content and particle size. The other parameters such as impeller speed,pH, conditioning time and flotation time were kept constant for all experiments. The optimum combination of coals was also specified. The results show that the optimum recovery for coal blends is 91.2%which shows much improvement relative to the plant conditions.

关键词： Coal Effect Optimization Recovery

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GSTARS computer models and their applications, part I:theoretical development

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International j.urnal of Sediment Research 2008年第3期23卷 197-211页

作者： Chih Ted YANG Francisco j. m. SImES Borland Prof. of Water Resources and Director of Hydroscience and Training Center Department of Civil and Environmental Engineering Colorado State University Fort Collins CO 80523-1372 U. S. A. Research Hydrologist US Geological Survey Geomorphology and Sediment Transport Laboratory 4620 Technology Drive Suite 400 Golden CO 80403 U. S. A.

GSTARS is a series of computer models developed by the U.S. Bureau of Reclamation for alluvial river and reservoir sedimentation studies while the authors were employed by that agency. The first version of GSTARS was released in 1986 using Fortran IV for mainframe computers. GSTARS 2.0 was released in 1998 for personal computer application with most of the code in the original GSTARS revised, improved, and expanded using Fortran IV/77. GSTARS 2.1 is an improved and revised GSTARS 2.0 with graphical user interface. The unique features of all GSTARS models are the conj.nctive use of the stream tube concept and of the minimum stream power theory. The application of minimum stream power theory allows the determination of optimum channel geometry with variable channel width and cross-sectional shape. The use of the stream tube concept enables the simulation of river hydraulics using one-dimensional numerical solutions to obtain a semi-two-dimensional presentation of the hydraulic conditions along and across an alluvial channel. According to the stream tube concept, no water or sediment particles can cross the walls of stream tubes, which is valid for many natural rivers. At and near sharp bends, however, sediment particles may cross the boundaries of stream tubes. GSTARS3, based on FORTRAN 90/95, addresses this phenomenon and further expands the capabilities of GSTARS 2.1 for cohesive and non-cohesive sediment transport in rivers and reservoirs. This paper presents the concepts, methods, and techniques used to develop the GSTARS series of computer models, especially GSTARS3.

关键词： Numerical modeling Sediment transport Backwater computations Stream tubes Stream power minimization

Current Inj.ction Provokes Rapid Expansion of the Guard Cell Cytosolic Volume and Triggers Ca^2＋ Signals

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molecular Plant 2016年第3期9卷 471-480页

作者： Lena j. Voss Rainer Hedrich m. Rob G. Roelfsema molecular Plant Physiology and Biophysics Julius-von-Sachs Institute for Biosciences Biocenter Werzburg University Julius-von-Sachs-Platz 2 97082 Werzburg Germany

High-resolution microscopy opens the door for detailed single-cell studies with fluorescent reporter dyes and proteins. We used a confocal spinning disc microscope to monitor fluorescent dyes and the fluorescent protein Venus in tobacco and Arabidopsis guard cells. multi-barreled microelectrodes were used to inj.ct dyes and apply voltage pulses, which provoke transient rises in the cytosolic Ca^2＋ level. Voltage pulses also caused changes in the distribution of Lucifer Yellow and Venus, which pointed to a reversible increase of guard cell cytosolic volume. The dynamic cytosolic volume changes turned out to be provoked by current inj.ction of ions. A reduction of the clamp current, by blocking K^＋ uptake channels with Cs^＋, strongly suppressed the cytosolic volume changes. Cs^＋ not only inhibited the expansion of the cytosol, but also inhibited hyperpolarization-induced elevations of the cytosolic Ca^2＋ concentration. A complete loss of voltage-induced Ca^2＋ signals occurred when Ca^2＋-permeable plasma membrane channels were simultaneously blocked with La^3＋. This shows that two mechanisms cause hyperpolarization-induced elevation of the cytosolic Ca^2＋-concentration：（i） activation of voltage-dependent Ca^2＋-permeable channels, （ii） osmotically induced expansion of the cytosol, which leads to a release of Ca^2＋ from intracellular stores.

关键词： guard cell cytosolic Ca^2+ cytosolic volume voltage clamp current inj.ction ion channel

Validity of Amontons's law for run-in short-cut aramid fiber reinforced elastomers:The effect of epoxy coated fibers

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Friction 2020年第3期8卷 613-625页

作者： m.KHAFIDH D.j.SCHIPPER m.A.mASEN N.VLEUGELS W.K.DIERKES j.W.m.NOORDERmEER Faculty of Engineering Technology University of TwenteEnschede 7500AEThe Netherlands Dutch Polymer Institute Eindhoven 5600AXThe Netherlands Department of mechanical Engineering Universitas Islam IndonesiaYogyakarta 55584Indonesia Department of mechanical Engineering Imperial College LondonLondon SW72AZUnited Kingdom

Friction between two contacting surfaces is studied *** of the k n o w n friction theories is Amontons,law which states that the friction force is proportional to the normal ***,Amontons7 law has been found to be invalid for *** the present study,the validity of Amontons7 law for short-cut aramid fiber reinforced elastomers is *** types of fillers are used to reinforce the elastomers,namely highly dispersible silica and short-cut aramid ***-cut aramid fibers with two different surface treatments are used,namely non-reactive fibers with standard oily finish(SF-fibers)and fibers treated with an epoxy coating(EF-fibers).A pin-on-disc tribometer is used to investigate the frictional behavior of the composites in sliding contact with a granite counter *** results show that,after the run-in phase,Amontons,law is valid for those composites that are reinforced by short-cut aramid fibers(without reinforcing filler,i.e.,silica)if the contact pressure is below a threshold ***,once the contact pressure exceeds this threshold value,Amontons'law will be *** threshold contact pressure of the composites containing EF-fibers is higher than of the composites containing *** composites that are reinforced by silica and short-cut aramid fibers do not follow Amontons7 law.

关键词： Amontons's law elastomer epoxy coated fiber short-cut aramid fiber

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